DE102024121360A1 - Adhesive - Google Patents

Abstract

An adhesive with good chemical resistance and high internal strength under static load in the z-direction should be provided. This can be achieved with an adhesive that...
- one or more poly(meth)acrylates; and
- one or more acrylonitrile butadiene rubbers
contains and is characterized in that the adhesive compound contains one or more vinyl aromatic block copolymers.
The application also relates to an adhesive tape comprising a layer of an adhesive compound according to the invention and to the use of the adhesive compound for bonding components of electronic devices or components in automobiles.

Description

The present invention relates to the technical field of pressure-sensitive adhesives, which are used in many areas of technology, particularly as components of adhesive tapes, for the temporary or permanent joining of components. More specifically, the invention relates to a pressure-sensitive adhesive containing one or more poly(meth)acrylates and one or more acrylonitrile butadiene rubbers, and to which one or more vinyl aromatic block copolymers are additionally added. Furthermore, the invention relates to an adhesive tape comprising at least one layer of a pressure-sensitive adhesive according to the invention, as well as the use of a pressure-sensitive adhesive according to the invention for bonding components of electronic devices or components in automobiles.

Pressure-sensitive adhesives based on poly(meth)acrylates and synthetic rubbers have long been used for bonding various materials. Different adhesive properties can be specifically tailored by selecting the individual components of the blend. Both the choice of individual components and their relative weights are crucial for the adhesive's property profile. The (meth)acrylate polymer predominantly forms the matrix in which the synthetic rubber domains, present as a dispersed phase, can be embedded in various morphologies.

Although such dispersed phases usually represent a minority component of the pressure-sensitive adhesive in terms of weight, the properties of the adhesive can be controlled to a considerable extent by them.

For many applications of pressure-sensitive adhesives and adhesive tapes, as well as for a variety of industrial processes, it is essential that the adhesives exhibit high resistance to as many chemicals as possible. This often significantly limits the selection of components for manufacturing the adhesives.

Adhesive systems based on acrylates and synthetic rubbers are generally known in the prior art.

• - eines Blends aus zumindest einem Nitrilkautschuk S1 und zumindest einem Nitrilkautschuk S2, wobei der zumindest eine Nitrilkautschuk S1 einen Acrylnitrilanteil von nicht mehr als 25 Gew.-% und der zumindest eine Nitrilkautschuk S2 einen Acrylnitrilanteil von nicht weniger als 30 Gew.-% sowie
• - zumindest eines Reaktivharzes

aufweist.Outside the field of pressure-sensitive adhesives, for example, WO 2006/128629 A1 an adhesive film that uses a heat-activated adhesive compound

• - a blend of at least one nitrile rubber S1 and at least one nitrile rubber S2, wherein the at least one nitrile rubber S1 has an acrylonitrile content of not more than 25 wt.% and the at least one nitrile rubber S2 has an acrylonitrile content of not less than 30 wt.% as well as
• - at least one reactive resin

exhibits.

In the field of pressure-sensitive adhesives, for example, EP 2 832 811 A1 Pressure-sensitive adhesives based on poly(meth)acrylates with at least one synthetic rubber and at least one tackifier compatible with the poly(meth)acrylate(s). However, such pressure-sensitive adhesives exhibit low chemical resistance, for example to oleic acid.

Pressure-sensitive adhesives based on acrylonitrile butadiene rubber and exhibiting chemical resistance are described, for example, in WO 2017/025492 A1. However, such pressure-sensitive adhesives exhibit low cohesion.

DE 10 2022 100 562 A1 describes an adhesive compound containing at least one poly(meth)acrylate and at least one acrylonitrile butadiene rubber, wherein the at least one acrylonitrile butadiene rubber is present in 1 to 49% by weight, based on the total weight of the adhesive compound.

As has been shown, pressure-sensitive adhesives based on poly(meth)acrylate and nitrile butadiene rubber often exhibit good shock resistance and good adhesive strength, but only lower internal strength under static load in the z-direction.

One object of the present invention was therefore to provide an adhesive compound with good chemical resistance that exhibits high internal strength under static load in the z-direction.

Another objective of the invention was to provide such an adhesive compound that generally exhibits good adhesive properties.

An additional task was to equip the adhesive compound in such a way that it also exhibits good shear strength against stress in the x-y direction.

The solution to the problems is based on the basic idea of the invention, to add a vinyl aromatic block copolymer as a complementary component to an adhesive compound based on poly(meth)acrylate and nitrile butadiene rubber.

The aforementioned problems are solved accordingly by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments also referred to as preferred. Combinations of two or more of the embodiments hereinafter referred to as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment, referred to as preferred to any degree, is combined with one or more further features of other embodiments, which are referred to as preferred to any degree. Features of preferred uses result from the features of preferred adhesive compounds or adhesive tapes.

Insofar as specific quantities or proportions of an element as well as preferred embodiments of the element are disclosed below, the specific quantities or proportions of the preferably embodiments are also disclosed. Furthermore, it is disclosed that, among the corresponding specific total quantities or proportions of the elements, at least some of the elements may be preferably embodiments, and in particular, that preferably embodiments may, in turn, be present within the specific total quantities or proportions.

• - ein oder mehrere Poly(meth)acrylate; und
• - einen oder mehrere Acrylnitril-Butadien-Kautschuke enthält und

dadurch gekennzeichnet ist, dass die Haftklebmasse ein oder mehrere Vinylaromat-Blockcopolymere enthält.A first and general object of the invention is an adhesive compound which

• - one or more poly(meth)acrylates; and
• - contains one or more acrylonitrile butadiene rubbers and

characterized by the fact that the adhesive compound contains one or more vinyl aromatic block copolymers.

According to the invention, an adhesive compound or pressure-sensitive adhesive is understood, as is common in general usage, to be a substance that is permanently sticky and adhesive, at least at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and adheres there, whereby the pressure to be applied and the duration of this pressure are not defined in detail. Generally, however, depending on the exact type of pressure-sensitive adhesive and the substrate, as well as the temperature and humidity, the application of a short-term, minimal pressure, not exceeding a light touch for a brief moment, is sufficient to achieve the adhesive effect; in other cases, a longer duration of higher pressure may be necessary.

Pressure-sensitive adhesives possess special, characteristic viscoelastic properties that result in their permanent tackiness and bonding strength. A defining characteristic is that when mechanically deformed, both viscous flow processes and the development of elastic restoring forces occur. The relative proportions of these two processes depend on the precise composition, structure, and degree of cross-linking of the pressure-sensitive adhesive, as well as the rate and duration of deformation and the temperature.

The proportion of viscous flow is necessary to achieve adhesion. Only the viscous components, often caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high tack (also known as surface tack) and thus often also to high adhesion. Highly cross-linked systems, crystalline or glassy polymers, are generally not tacky or at least only slightly tacky due to a lack of flowable components.

The elastic restoring forces are necessary to achieve cohesion. They are generated, for example, by very long-chain and highly entangled macromolecules, as well as by physically or chemically cross-linked macromolecules, and enable the transmission of forces acting on an adhesive bond. This allows an adhesive bond to withstand a sustained load, such as continuous shear stress, to a sufficient degree over an extended period.

To describe and quantify the degree of elastic and viscous components, as well as their ratio, the storage modulus (G') and loss modulus (G''), which can be determined by Dynamic Mechanical Analysis (DMA), are used. G' is a measure of the elastic component, and G'' is a measure of the viscous component of a material. Both quantities depend on the deformation frequency and the temperature.

The parameters can be determined using a rheometer. The material under investigation is subjected, for example, to a sinusoidally oscillating shear stress in a plate-plate arrangement. In shear-stress controlled devices, the deformation is measured as a function of time, along with the time lag of this deformation relative to the application of the shear stress. This time lag is called the phase angle δ.

The storage modulus G' is defined as follows: G' = (τ/γ)·cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between the shear stress and deformation vectors). The definition of the loss modulus G'' is: G'' = (τ/γ) · sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between the shear stress and deformation vectors).

A mass is considered to be an adhesive mass and is defined as such in the sense of the invention, in particular, if at 23 °C in the deformation frequency range of 10 ⁰ to 10 ¹ rad/sec both G' and G" are at least partially in the range of 10 ³ to 10 ⁷ Pa.

A “poly(meth)acrylate” is understood to be a polymer obtainable by radical polymerization of acrylic and/or methacrylic monomers and optionally other copolymerizable monomers. In particular, a “poly(meth)acrylate” is understood to be a polymer whose monomer base consists of at least 50 wt.% acrylic acid, methacrylic acid, acrylic esters and/or methacrylic esters, wherein acrylic esters and/or methacrylic esters are present at least proportionally, preferably at least 30 wt.%, based on the total monomer base of the polymer in question.

Preferably, the pressure-sensitive adhesive composition according to the invention contains one or more poly(meth)acrylates in a total amount of ≥ 45 wt.%, more preferably in a total amount of 45 to 85 wt.%, and in particular in a total amount of 48 to 70 wt.%, in each case based on the total weight of the pressure-sensitive adhesive composition. It may contain one (single) poly(meth)acrylate or several poly(meth)acrylates, and the expression "in a total amount..." does not, of course, preclude the possibility that the pressure-sensitive adhesive composition may contain only a single poly(meth)acrylate; rather, "in total" refers to the case where the pressure-sensitive adhesive composition contains several poly(meth)acrylates. Where the plural term "poly(meth)acrylates" is used below, this term also includes the case where the pressure-sensitive adhesive composition contains only a single poly(meth)acrylate.

The glass transition temperature of the poly(meth)acrylate or poly(meth)acrylates of an adhesive compound according to the invention is preferably < 0 °C, more preferably between -5 and -50 °C. The glass transition temperature is determined as described below.

Preferably, the poly(meth)acrylate(s) of an adhesive compound according to the invention contains at least one partially polymerized functional monomer, particularly preferably one that is reactive with epoxy groups forming a covalent bond. Most preferably, the partially polymerized functional monomer contains at least one functional group. Selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxy groups, and amino groups; in particular, it contains at least one carboxylic acid group. Most preferably, the poly(meth)acrylate(s) of an adhesive compound according to the invention contains partially polymerized acrylic acid and/or methacrylic acid. All of the aforementioned groups exhibit reactivity with epoxy groups or other suitable crosslinking agents, thereby advantageously making the poly(meth)acrylate amenable to thermal crosslinking, for example, with incorporated epoxides.

1. a) mindestens ein Acrylsäureester und/oder Methacrylsäureester der folgenden Formel (1) CH₂=C(R^I)(COOR^II) (1), worin R^I = H oder CH₃ und R^II ein Alkylrest mit 4 bis 18 C-Atomen ist
2. b) mindestens ein olefinisch ungesättigtes Monomer mit mindestens einer funktionellen Gruppe ausgewählt aus der Gruppe bestehend aus Carbonsäuregruppen, Sulfonsäuregruppen, Phosphonsäuregruppen, Hydroxygruppen, Säureanhydridgruppen, Epoxidgruppen und Aminogruppen;
3. c) optional weitere Acrylsäureester und/oder Methacrylsäureester und/oder olefinisch ungesättigte Monomere, die mit der Komponente (a) copolymerisierbar sind.

The poly(meth)acrylates of an adhesive compound according to the invention can preferably be traced back to the following monomer composition:

1. a) at least one acrylic acid ester and/or methacrylic acid ester of the following formula (1) CH ₂ =C(R ^I )(COOR ^II ) (1), where R ^I = H or CH ₃ and R ^II is an alkyl group with 4 to 18 C atoms
2. b) at least one olefinically unsaturated monomer with at least one functional group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxide groups and amino groups;
3. c) optionally further acrylic acid esters and/or methacrylic acid esters and/or olefinically unsaturated monomers that can be copolymerized with component (a).

• - Monomere der Komponente a) zu insgesamt 45 bis 99 Gew.-%,
• - Monomere der Komponente b) zu insgesamt 1 bis 15 Gew.-% und
• - Monomere der Komponente c) zu insgesamt 0 bis 40 Gew.-%,

jeweils bezogen auf das Gesamtgewicht der Monomerenzusammensetzung.Preferably, the respective monomer composition to which the poly(meth)acrylates of an adhesive compound according to the invention can be traced contains

• - Monomers of component a) to a total of 45 to 99 wt.%,
• - Monomers of component b) to a total of 1 to 15 wt.% and
• - Monomers of component c) to a total of 0 to 40 wt.%,

each based on the total weight of the monomer composition.

The monomers of component a) are preferably generally plasticizing, rather nonpolar monomers. R ^II in monomers a) is particularly preferably an alkyl group with 4 to 10 carbon atoms, 2-propylheptyl acrylate, or 2-propylheptyl methacrylate. The monomers of formula (1) are in particular selected from the group consisting of n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, 2-propylheptyl acrylate and 2-propylheptyl methacrylate.

The monomers of component b) are particularly preferably selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acrylic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, hydroxyethyl acrylate, in particular 2-hydroxyethyl acrylate, hydroxypropyl acrylate, in particular 3-hydroxypropyl acrylate, hydroxybutyl acrylate, in particular 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, in particular 6-hydroxyhexyl acrylate, hydroxyethyl methacrylate, in particular 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, in particular 3-hydroxypropyl methacrylate, hydroxybutyl methacrylate, in particular 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, in particular 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate.

• Methylacrylat, Ethylacrylat, Propylacrylat, Methylmethacrylat, Ethylmethacrylat, Benzylacrylat, Benzylmethacrylat, sec-Butylacrylat, tert-Butylacrylat, Phenylacrylat, Phenylmethacrylat, Isobornylacrylat, Isobornylmethacrylat, tert-Butylphenylacrylat, tert-Butylphenylmethacrylat, Dodecylmethacrylat, Isodecylacrylat, Laurylacrylat, n-Undecylacrylat, Stearylacrylat, Tridecylacrylat, Behenylacrylat, Cyclohexylmethacrylat, Cyclopentylmethacrylat, Phenoxyethylacrylat, Phenoxyethylmethacrylat, 2-Butoxyethylmethacrylat, 2-Butoxyethylacrylat, 3,3,5-Trimethylcyclohexylacrylat, 3,5-Dimethyladamantylacrylat, 4-Cumylphenylmethacrylat, Cyanoethylacrylat, Cyanoethylmethacrylat, 4-Biphenylacrylat, 4-Biphenylmethacrylat, 2-Naphthylacrylat, 2-Naphthylmethacrylat, Tetrahydrofufurylacrylat, Diethylaminoethylacrylat, Diethylaminoethylmethacrylat, Dimethylaminoethylacrylat, Dimethylaminoethylmethacrylat, 3-Methoxyacrylsäuremethylester, 3-Methoxybutylacrylat, 2-Phenoxyethylmethacrylat, Butyldiglykolmethacrylat, Ethylenglycolacrylat, Ethylenglycolmonomethylacrylat, Methoxypolyethylenglykolmethacrylat 350, Methoxypolyethylenglykolmethacrylat 500, Propylenglycolmonomethacrylat, Butoxydiethylenglykolmethacrylat, Ethoxytriethylenglykolmethacrylat, Octafluoropentylacrylat, Octafluoropentylmethacrylat, 2,2,2-Trifluorethylmethacrylat, 1,1,1,3,3,3-Hexafluoroisopropylacrylat, 1,1,1,3,3,3-Hexafluoroisopropylmethacrylat, 2,2,3,3,3-Pentafluoropropylmethacrylat, 2,2,3,4,4,4-Hexafluorobutylmethacrylat, 2,2,3,3,4,4,4-Heptafluorobutylacrylat, 2,2,3,3,4,4,4-Heptafluorobutylmethacrylat, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctylmethacrylat, Dimethylaminopropylacrylamid, Dimethylaminopropylmethacrylamid, N-(1-Methylundecyl)acrylamid, N-(n-Butoxymethyl)acrylamid, N-(Butoxymethyl)methacrylamid, N-(Ethoxymethyl)acrylamid, N-(n-Octadecyl)acrylamid; N,N-Dialkyl-substituierte Amide wie beispielsweise N,N-Dimethylacrylamid und N,N-Dimethylmethacrylamid; N-Benzylacrylamid, N-Isopropylacrylamid, N-tert-Butylacrylamid, N-tert-Octylacrylamid, N-Methylolacrylamid, N-Methylolmethacrylamid, Acrylnitril, Methacrylnitril; Vinylether wie Vinylmethylether, Ethylvinylether, Vinylisobutylether; Vinylester wie Vinylacetat; Vinylhalogenide, Vinylidenhalogenide, Vinylpyridin, 4-Vinylpyridin, N-Vinylphthalimid, N-Vinyllactam, N-Vinylpyrrolidon, Styrol, α- und p-Methylstyrol, α-Butylstyrol, 4-n-Butylstyrol, 4-n-Decylstyrol, 3,4-Dimethoxystyrol; Makromonomere wie 2-Polystyrolethylmethacrylat (gewichtsmittleres Molekulargewicht Mw, bestimmt mittels GPC, von 4000 bis 13000 g/mol), Poly(methylmethacrylat)ethylmethacrylat (Mw von 2000 bis 8000 g/mol).

Examples of monomers of component c) are:

• Methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butyl acrylate, tert-butyl acrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, isobornyl methacrylate, tert-butyl phenyl acrylate, tert-butyl phenyl methacrylate, dodecyl methacrylate, Isodecyl acrylate, lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecyl acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-Dimethyladamantyl acrylate, 4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, 4-Biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofufuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoe thyl methacrylate, 3-methoxyacrylic acid methyl ester, 3-methoxybutyl acrylate, 2-phenoxyethyl methacrylate, butyl diglycol methacrylate, ethylene glycol acrylate, ethylene glycol monomethyl acrylate, methoxypolyethylene glycol methacrylate 350, methoxypolyethylene glycol methacrylate 500, propylene glycol monomethacrylate, Butoxydiethylene glycol methacrylate, Ethoxytriethylene glycol methacrylate, Octafluoropentyl acrylate, Octafluoropentyl methacrylate, 2,2,2-Trifluoroethyl methacrylate, 1,1,1,3,3,3-Hexafluoroisopropyl acrylate, 1,1,1,3,3,3-Hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctylmethacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N-(1-methylundecyl)acrylamide, N-(n-butoxymethyl)acrylamide, N-(butoxymethyl)methacrylamide, N-(ethoxymethyl)acrylamide, N-(n-octadecyl)acrylamide; N,N-dialkyl-substituted amides such as N,N-dimethylacrylamide and N,N-dimethylmethacrylamide; N-benzylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-tert-octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylonitrile, methacrylonitrile; vinyl ethers such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether; vinyl esters such as vinyl acetate; vinyl halides, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3,4-dimethoxystyrene; Macromonomers such as 2-polystyrene ethyl methacrylate (weight-mean molecular weight Mw, determined by GPC, from 4000 to 13000 g/mol), poly(methyl methacrylate) ethyl methacrylate (Mw from 2000 to 8000 g/mol).

Monomers of component c) can advantageously be selected to contain functional groups that support radiation-chemical crosslinking (e.g., by electron beams, UV). Suitable copolymerizable photoinitiators include, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers that support crosslinking by electron irradiation include, for example, tetrahydrofurfuryl acrylate, N-tert-butylacrylamide, and allyl acrylate.

The poly(meth)acrylates are preferably produced by conventional radical polymerization or controlled radical polymerization. The poly(meth)acrylates can be prepared by copolymerization of the monomers using conventional polymerization initiators and, optionally, regulators, with polymerization taking place at normal temperatures in the solid form, in an emulsion (e.g., in water or liquid hydrocarbons), or in solution.

The poly(meth)acrylates are preferably produced by copolymerization of the monomers in solvents, particularly preferably in solvents with a boiling range of 50 to 150 °C, in particular of 60 to 120 °C, using 0.01 to 5 wt.%, in particular of 0.1 to 2 wt.%, in each case based on the total weight of the monomers, of polymerization initiators.

In principle, all common initiators are suitable. Examples of radical sources include peroxides, hydroperoxides, and azo compounds, such as dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, and benzopinacol. Preferred radical initiators are 2,2'-azobis(2-methylbutyronitrile) (DuPont Vazo® 67) or 2,2'-azobis(2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN; DuPont Vazo® 64).

Preferred solvents for the production of the poly(meth)acrylates are alcohols such as methanol, ethanol, n- and isopropanol, n- and isobutanol, in particular isopropanol and/or isobutanol; hydrocarbons such as toluene and in particular gasoline with a boiling range of 60 to 120°C; ketones, in particular acetone, methyl ethyl ketone, methyl isobutyl ketone; esters such as ethyl acetate; and mixtures of the aforementioned solvents. Particularly preferred solvents are mixtures containing isopropanol in amounts of 2 to 15 wt.%, in particular 3 to 10 wt.%, based on the solvent mixture used.

Preferably, after the production (polymerization) of the poly(meth)acrylates, a concentration step is carried out, and further processing of the poly(meth)acrylates is essentially solvent-free. The concentration of the polymer can take place in the absence of crosslinking agents and accelerators. However, it is also possible to add one of these additives to the polymer prior to concentration, so that the concentration then occurs in the presence of this substance(s).

After the concentration step, the polymers can be transferred to a compounder. If necessary, the concentration and compounding can also take place in the same reactor.

The weight-average molecular weights M _{_w} of the polyacrylates are preferably 20,000 to 2,000,000 g/mol; very preferably 100,000 to 1,500,000 g/mol; and most preferably 150,000 to 1,000,000 g/mol. It may be advantageous to carry out the polymerization in the presence of suitable polymerization regulators such as thiols, halogen compounds, and/or alcohols to achieve the desired weight-average molecular weight.

The figures for number-average molar mass M _{_n} and weight-average molar mass M _{_w} in this document refer to the determination by gel permeation chromatography (GPC), which is known per se and described later herein.

The poly(meth)acrylates preferably have a K-value of 30 to 90, particularly preferably of 40 to 70, measured in toluene (1% solution, 21 °C). The Fikentscher K-value is a measure of the molecular weight and viscosity of polymers and is determined according to the method described below.

Preferably, the poly(meth)acrylates of an adhesive compound according to the invention exhibit a polydispersity PD < 4 and thus a relatively narrow molecular weight distribution. Compounds based on this have particularly good shear strength after crosslinking, despite their relatively low molecular weight. Furthermore, the lower polydispersity facilitates easier processing from the melt, as the flow viscosity is lower compared to a more broadly distributed poly(meth)acrylate, while maintaining largely the same application properties. Narrowly distributed poly(meth)acrylates can advantageously be produced by anionic polymerization or by controlled radical polymerization methods, the latter being particularly suitable. Corresponding poly(meth)acrylates can also be produced via N-oxyles. Furthermore, atom transfer radical polymerization (ATRP) can be advantageously used for the synthesis of tightly divided poly(meth)acrylates, wherein monofunctional or difunctional secondary or tertiary halides are preferably used as initiators and Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag, or Au complexes are used for abstraction of the halides. RAFT polymerization is also suitable.

• - sowohl eine ausreichend lange Verarbeitungszeit gewährleisten, sodass es nicht zu einer Vergelung während des Verarbeitungsprozesses, insbesondere während eines Extrusionsprozesses, kommt,
• - als auch zu einer schnellen Nachvernetzung der Polymere bis zum gewünschten Vernetzungsgrad bei niedrigeren Temperaturen als der Verarbeitungstemperatur, insbesondere bei Raumtemperatur, führen.

The poly(meth)acrylates of an adhesive compound according to the invention are preferably crosslinked by crosslinking reactions – in particular in the sense of addition or substitution reactions – of functional groups contained therein with thermal crosslinkers. All thermal crosslinkers can be used which

• - ensure a sufficiently long processing time so that no retardation occurs during the processing, especially during an extrusion process,
• - as well as leading to rapid re-crosslinking of the polymers to the desired degree of crosslinking at temperatures lower than the processing temperature, especially at room temperature.

Thermal crosslinkers are preferably used at a rate of 0.1 to 5 wt.%, in particular at a rate of 0.2 to 1 wt.%, based on the total amount of polymers to be crosslinked.

Crosslinking via complexing agents, also known as chelates, is also possible as a supplementary or alternative. Aluminum acetylacetonate is, for example, a preferred complexing agent.

Preferably, the poly(meth)acrylates of an adhesive compound according to the invention are cross-linked by means of epoxy(s) or by means of one or more substances containing epoxy groups.

The substances containing epoxide groups are primarily multifunctional epoxides, meaning those with at least two epoxide groups; accordingly, there is an indirect linkage of the building blocks of the poly(meth)acrylates that bear the functional groups. The substances containing epoxide groups can be both aromatic and aliphatic compounds.

Excellent multifunctional epoxides are oligomers of epichlorohydrin, epoxy ethers of polyhydric alcohols, especially ethylene, propylene, and butylene glycols, polyglycols, thiodiglycols, glycerol, pentaerythritol, sorbitol, polyvinyl alcohol, polyallyl alcohol and similar compounds; Epoxy ethers of polyhydric phenols, in particular resorcinol, hydroquinone, bis-(4-hydroxyphenyl)methane, bis-(4-hydroxy-3-methylphenyl)methane, bis-(4-hydroxy-3,5-dibromophenyl)methane, bis-(4-hydroxy-3,5-difluorophenyl)methane, 1,1-bis-(4-hydroxyphenyl)ethane, 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(4-hydroxy-3-methylphenyl)propane, 2,2-bis-(4-hydroxy-3-chlorophenyl)propane, 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)propane, bis-(4-hydroxyphenyl)phenylmethane, bis-(4-hydroxyphenyl)phenylmethane, bis-(4- hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)-4'-methylphenylmethane, 1,1-bis(4-hydroxyphenyl)-2,2,2-trichloroethane, bis(4-hydroxyphenyl)-(4-chlorophenyl)methane, 1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)cyclohexylmethane, 4,4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylsulfone and their hydroxyethyl ethers; phenol-formaldehyde condensation products such as phenol alcohols and phenolaldehyde resins; sulfur- and nitrogen-containing epoxides, for example N,N-diglycidylaniline and N,N'-dimethyldiglycidyl-4,4-diaminodiphenylmethane; as well as epoxides which have been prepared by conventional methods from polyunsaturated carboxylic acids or monounsaturated carboxylic acid esters of unsaturated alcohols; glycidyl esters; polyglycidyl esters which can be obtained by polymerization or copolymerization of glycidyl esters of unsaturated acids or which are available from other acidic compounds, for example from cyanuric acid, diglycidyl sulfide or cyclic trimethylene trisulfone or its derivatives.

Very suitable ethers include, for example, 1,4-butanediol diglycid ether, polyglycerol 3-glycid ether, cyclohexanedimethyl ethanol diglycid ether, glycerol triglycid ether, neopentyl glycol diglycid ether, pentaerythritol triglycid ether, 1,6-hexanediol diglycid ether, polypropylene glycol diglycid ether, trimethylolpropane triglycid ether, pentaerythritol triglycid ether, bisphenol A diglycid ether and bisphenol F diglycid ether.

Other preferred epoxides are cycloaliphatic epoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (UVACure1500).

Other preferred epoxides are epoxy-functional organoalkoxysilanes, and in particular cycloaliphatic epoxysilanes selected from the group consisting of (3-glycidyloxypropyl)trimethoxysilane (CAS No. 2530-83-8, e.g., Dynasylan® GLYMO, Evonik), (3-glycidyloxypropyl)triethoxysilane (CAS No. 2602-34-8, e.g., Dynasylan® GLYEO, Evonik), (3-glycidyloxypropyl)methyldimethoxysilane (CAS No. 65799-47-5, e.g., Gelest Inc.), (3-glycidyloxypropyl)methyldiethoxysilane (CAS No. 2897-60-1, e.g., Gelest Inc.), 5,6-epoxyhexyltriethoxysilane (CAS No. 86138-01-4, e.g., Gelest Inc.), 2-(3,4-Epoxycyclohexyl)ethyl]trimethoxysilane (CAS No. 3388-04-3, e.g., Sigma-Aldrich), 2-(3,4-Epoxycyclohexyl)ethyl]triethoxysilane (CAS No. 10217-34-2, e.g., ABCR GmbH), Triethoxy[3-[(3-ethyl-3-oxetanyl)methoxy]propyl]silane (CAS No. 220520-33-2, e.g., Aron Oxetane OXT-610, Toagosei Co., Ltd.). 2-(3,4-Epoxycyclohexyl)ethyl]triethoxysilane is particularly preferred.

The poly(meth)acrylates are preferably crosslinked using a crosslinker-accelerator system ("crosslinking system") to obtain better control over the processing time, crosslinking kinetics, and degree of crosslinking. The crosslinker-accelerator system preferably comprises at least one epoxy-containing substance as a crosslinker and at least one accelerator substance that accelerates crosslinking reactions using epoxy-containing compounds at temperatures below the melting temperature of the polymer to be crosslinked.

According to the invention, one or more substances selected from the group consisting of amines, amino alcohols, pyridine, imidazoles, phosphines, phosphonium compounds and ammonium compounds are particularly preferably used as accelerators.

The pressure-sensitive adhesive composition according to the invention further comprises one or more acrylonitrile butadiene rubbers. Preferably, the pressure-sensitive adhesive composition according to the invention contains the one or more acrylonitrile butadiene rubbers in a total of 8 to 30 wt.%, more preferably in a total of 9 to 28 wt.%, and in particular in a total of 9.5 to 26 wt.%, in each case based on the total weight of the pressure-sensitive adhesive composition. It may contain one (single) acrylonitrile butadiene rubber or several acrylonitrile butadiene rubbers, and the expression "in a total of..." does not, of course, preclude the fact that the pressure-sensitive adhesive composition may contain only a single acrylonitrile butadiene rubber; rather, "in total" refers to the case in which the pressure-sensitive adhesive composition contains several acrylonitrile butadiene rubbers. Where the plural term "acrylonitrile butadiene rubbers" is used below, this term also includes the case where the adhesive compound contains only a single acrylonitrile butadiene rubber.

Acrylonitrile butadiene rubber (NBR), derived from "nitrile butadiene rubber," is a synthetic rubber produced by the copolymerization of acrylonitrile and buta-1,3-diene in mass ratios of approximately 52:48 to 10:90. It is manufactured almost exclusively in aqueous emulsions. The resulting emulsions are used as such (NBR latex) or processed into solid rubber.

In principle, polymerization is divided into so-called cold and hot polymerization. Cold polymerization usually takes place at temperatures of 5 to 15 °C and, in contrast to hot polymerization, which is usually carried out at 30 to 40 °C, results in a smaller number of chain branches.

Carboxylated NBR types are produced by the terpolymerization of acrylonitrile and butadiene with small amounts of (meth)acrylic acid in an emulsion. Selective hydrogenation of the C,C double bond of NBR leads to hydrogenated nitrile rubbers (H-NBR). Vulcanization is achieved using conventional sulfur crosslinkers, peroxides, or high-energy radiation.

Preferably, one or more acrylonitrile butadiene rubbers of an adhesive compound according to the invention are hydrogenated or partially hydrogenated acrylonitrile butadiene rubbers.

It is also preferred that one or more acrylonitrile butadiene rubbers of an adhesive compound according to the invention are carboxylated.

Particularly preferred is the one or more acrylonitrile butadiene rubbers of an adhesive compound according to the invention, carboxylated as well as hydrogenated or partially hydrogenated acrylonitrile butadiene rubbers.

Besides carboxylated and/or hydrogenated NBRs, which are usually solid, there are also liquid NBRs. These are limited in their molecular weight during polymerization by the addition of polymerization regulators and are therefore obtained as liquid rubbers.

Preferably, an adhesive compound according to the invention comprises at least one solid acrylonitrile butadiene rubber. In addition to the at least one solid acrylonitrile butadiene rubber, an adhesive compound according to the invention may also contain at least one liquid acrylonitrile butadiene rubber. The proportion of the one or more liquid acrylonitrile butadiene rubbers is preferably up to 20% by weight, more preferably 1 to 15% by weight, and in particular 2 to 10% by weight, in each case based on the total weight of the acrylonitrile butadiene rubbers.

Liquid NBR differs from solid NBR in that it has a softening point of < 40 °C. The softening point (TE _{_E}) values given here for oligomeric and polymeric compounds refer to the ring-ball method according to [reference to relevant method]. DIN EN 1427:2007 with appropriate application of the provisions (examination of the oligomer or polymer sample instead of bitumen while otherwise maintaining the same procedure); the measurements are carried out in a glycerol bath.

Preferably, one or more acrylonitrile butadiene rubbers of an adhesive compound according to the invention have an acrylonitrile content of 10 to 60 wt.%, more preferably 15 to 50 wt.%, based on the total weight of the acrylonitrile butadiene rubbers.

Preferably, one or more acrylonitrile butadiene rubbers of an adhesive compound according to the invention have a Mooney viscosity, measured according to DIN 53523-2:1991-05, of at least 19, preferably of 20 to 100, at 100°C.

An adhesive compound according to the invention further comprises one or more vinyl aromatic block copolymers. Accordingly, it can contain one (single) vinyl aromatic block copolymer or several vinyl aromatic block copolymers. Preferably, an adhesive compound according to the invention contains the one or more vinyl aromatic block copolymers in a total of 8 to 25 wt.%, more preferably in a total of 8.5 to 23 wt.%, and particularly preferably in a total of 9 to 21 wt.%, in each case based on the total weight of the adhesive compound. The expression "in a total of..." does not, of course, contradict the fact that the adhesive compound may contain only a single vinyl aromatic block copolymer; rather, "in total" refers to the case where the adhesive compound contains several vinyl aromatic block copolymers. Where the plural expression "vinyl aromatic block copolymers" is used below, this expression also includes the case where the adhesive compound contains only a single vinyl aromatic block copolymer.

• - A bzw. A' ein Polymer, gebildet durch Polymerisation eines Vinylaromaten, wie beispielweise Styrol oder α-Methylstyrol, ist;
• - B bzw. B' ein Polymer aus einem Isopren, Butadien, einem Farnesen-Isomer oder einem Gemisch aus Butadien und Isopren oder einem Gemisch aus Butadien und Styrol, oder enthaltend vollständig oder teilweise Ethylen, Propylen, Butylen und/oder Isobutylen, ist;
• - X eine optionale Verknüpfungsgruppe (z. B. ein Rest eines Kopplungsreagenzes oder Intiators) ist;
• - n eine ganze Zahl zwischen 1 und 4 ist;
• - (A'-B')_n über A' (Struktur 3a) oder B' (Struktur 3b) mit X bzw. mit (A-B) verknüpft sein kann, bevorzugt über B';
• - A hinsichtlich der Zusammensetzung und/oder Molmasse = A' sein kann und B hinsichtlich der Zusammensetzung und/oder Molmasse = B' sein kann.

Preferably, the vinyl aromatic block copolymers are thermoplastic block copolymers whose structure can be represented by one of the following formulas: $$\text{A}-\text{B}$$ $$\text{A}-\text{B}-\text{X}{\left(\text{A}\text{'}-\text{B}\text{'}\right)}_{\text{n}}$$
where

• - A or A' is a polymer formed by polymerization of a vinyl aromatic, such as styrene or α-methylstyrene;
• - B or B' is a polymer consisting of an isoprene, butadiene, a farnesene isomer or a mixture of butadiene and isoprene or a mixture of butadiene and styrene, or containing wholly or partly ethylene, propylene, butylene and/or isobutylene;
• - X is an optional coupling group (e.g., a residue of a coupling reagent or intiator);
• - n is an integer between 1 and 4;
• - (A'-B') _n can be linked to X or to (AB) via A' (structure 3a) or B' (structure 3b), preferably via B';
• - A can be A' with respect to composition and/or molar mass and B can be B' with respect to composition and/or molar mass.

Suitable vinyl aromatic block copolymers comprise one or more rubber-like blocks B or B' (soft blocks, elastomer blocks) and one or more glass-like blocks A or A'. In some embodiments, the block copolymer comprises at least one glass-like block. In some further embodiments, the block copolymer comprises one to five glass-like blocks.

In some advantageous embodiments, in addition to or exclusively using structures 2, 3a and/or 3b, a block copolymer is employed, which is a multi-arm block copolymer. This is described by the general formula $${\text{Q}}_{\text{m}}-\text{Y}$$ described, wherein Q represents an arm of the multi-arm block copolymer and m represents the number of arms, where m is an integer of at least 3. Y is the residue of a multifunctional linking reagent, which originates, for example, from a coupling reagent or a multifunctional initiator. Preferably, each arm Q independently has the formula A*-B*, where A* and B* are each chosen independently of the other arms according to the preceding definitions for A and A', respectively, and B and B', respectively, such that, analogous to structures 2, 3a, and 3b, A* represents a glassy block and B* a soft block. Of course, it is also possible to choose identical A* and/or identical B* for several arms Q or for all arms Q.

Blocks A, A', and A* will henceforth be referred to collectively as A-blocks. Blocks B, B', and B* will henceforth be referred to collectively as B-blocks.

A-blocks are generally glass-like blocks, each with a glass transition temperature T_{_g} (DSC, see below) that is above room temperature (room temperature is understood to be 23 °C in the context of this invention). In some advantageous embodiments, the T_{_g} of the glass-like block is at least 40 °C, preferably at least 60 °C, more preferably at least 80 °C, or very preferably at least 100 °C.

The vinyl aromatic block copolymer generally comprises one or more rubber-like B-blocks (soft blocks or elastomer blocks) with a T_{_g} of less than room temperature. In some embodiments, the T_{_g} of the soft block is less than -30 °C or even less than -60 °C.

In addition to the preferred monomers for the B-blocks mentioned for formulas 2 and 3a/3b and 4, further advantageous embodiments comprise a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or a combination thereof. In some embodiments, the conjugated dienes comprise 4 to 18 carbon atoms. Examples of further advantageous conjugated dienes for the rubbery B-blocks include ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene, and dimethylbutadiene, wherein the polymerized conjugated dienes can be present as a homopolymer or as a copolymer.

The proportion of A-blocks relative to the total number of block copolymers is preferably 10 - 40 wt.%, more preferably 15 - 33 wt.%.

Polystyrene is preferred as the polymer for A-blocks. Polybutadiene, polyisoprene, polyfarnesene, and their partially or fully hydrogenated derivatives, such as polyethylene butylene, polyethylene propylene, polyethylene ethylene propylene, polybutylene butadiene, or polyisobutylene, are preferred as polymers for B-blocks. Polybutadiene is particularly preferred.

Mixtures of different block copolymers can be used. Triblock copolymers ABA and/or diblock copolymers AB are preferred.

The block copolymers can be linear, radial or star-shaped (multiarm), also independently of structures 2 and 3.

Preferably, the vinyl aromatic block copolymers of an adhesive compound according to the invention are styrene block copolymers and preferably have a styrene content of at least 25 wt.%, particularly preferably at least 28 wt.%, and especially at least 30 wt.%. According to the findings obtained within the scope of the invention, this has an advantageous effect on the internal strength (cohesion) of the adhesive compound.

Preferably, the vinyl aromatic block copolymers of an adhesive compound according to the invention have a diblock content of > 50%, particularly preferably > 65%, and especially > 75%. High diblock contents have proven advantageous for the adhesive properties of the adhesive compound.

Preferably, both the one or more acrylonitrile butadiene rubbers and the one or more vinyl aromatic block copolymers are dispersed in the one or more poly(meth)acrylates of an adhesive compound according to the invention. Accordingly, the poly(meth)acrylates, acrylonitrile butadiene rubbers, and vinyl aromatic block copolymers are preferably homogeneous phases. The poly(meth)acrylates, acrylonitrile butadiene rubbers, and vinyl aromatic block copolymers of an adhesive compound according to the invention are preferably not miscible to homogeneity at 23 °C. Thus, an adhesive compound according to the invention preferably exists in at least a three-phase morphology, at least microscopically and at least at room temperature. Particularly preferred are poly(meth)acrylate(s), acrylonitrile butadiene rubber(s) and vinyl aromatic block copolymer(s) that are not homogeneously miscible with each other in a temperature range of 0 °C to 50 °C, especially from -30 °C to 80 °C, so that the pressure-sensitive adhesive is at least microscopically present in these temperature ranges as being at least three-phase.

For the purposes of this document, components are defined as "not homogeneously miscible" if, even after thorough mixing, the formation of at least two stable phases can be demonstrated physically and/or chemically, at least microscopically, with one phase being rich in one component and the other phase being rich in the other component. The presence of negligible amounts of one component in the other, which does not preclude the formation of multiphases, is considered irrelevant. Thus, small amounts of acrylonitrile butadiene rubber and/or small amounts of a poly(meth)acrylate component may be present in a poly(meth)acrylate phase and/or in an acrylonitrile butadiene rubber phase, provided that these are not significant amounts that affect phase separation.

Phase separation can be achieved, in particular, by having discrete regions (“domains”) rich in acrylonitrile butadiene rubber or vinyl aromatic block copolymer—i.e., essentially composed of acrylonitrile butadiene rubber or vinyl aromatic block copolymer, respectively—within a continuous matrix rich in poly(meth)acrylate—i.e., essentially composed of poly(meth)acrylate. Scanning electron microscopy is, for example, a suitable analytical system for phase separation. Phase separation can also be demonstrated, for example, by the fact that the different phases exhibit two independent glass transition temperatures when analyzed by differential scanning calorimetry (DSC) or dynamic mechanical analysis (DMA). According to the invention, phase separation is present if it can be unambiguously demonstrated by at least one of the analytical methods.

An adhesive compound according to the invention preferably further comprises at least one, in particular with the poly(meth)acrylates and/or the acrylonitrile butadiene rubbers and/or the vinyl aromatic block compounds. A polymer-compatible tackifier, which can also be referred to as an adhesive strength enhancer or adhesive resin. According to the general understanding of those skilled in the art, a "tackifier" is understood to be an oligomeric or polymeric resin that increases the adhesion (sticky strength) of the pressure-sensitive adhesive compared to an otherwise identical pressure-sensitive adhesive without a tackifier. A pressure-sensitive adhesive according to the invention particularly preferably contains at least one tackifier compatible with the poly(meth)acrylates.

A "tackifier compatible with poly(meth)acrylates" is defined as a tackifier that alters the glass transition temperature of the system obtained after thorough mixing of poly(meth)acrylates and the tackifier compared to the pure poly(meth)acrylates, whereby only one glass transition temperature (Tg) can be assigned to the mixture of poly(meth)acrylates and tackifier. A tackifier incompatible with poly(meth)acrylates would lead to at least two Tgs in the system obtained after thorough mixing of poly(meth)acrylates and the tackifier, one or more of which would be attributable to the poly(meth)acrylate or poly(meth)acrylates, and another to the resin domains. In this context, the Tg is determined calorimetrically using DSC (differential scanning calorimetry).

The tackifier compatible with the poly(meth)acrylates preferably has a DACP value of less than -30 °C, more preferably of at most -70 °C, most preferably of less than -50 °C, and/or preferably an MMAP value of less than 40 °C, very preferably of at most 30 °C, in particular of 24 to 28 °C. DACP and MMAP values are determined according to... C. Donker, PSTC Annual Technical Seminar, Proceedings, pp. 149-164, May 2001 referred.

A tackifier compatible with poly(meth)acrylates is particularly preferred if selected from the group consisting of (meth)acrylate resins, rosin derivatives, and aromatic-containing, particularly aromatic-rich, hydrocarbon resins; especially from the group consisting of (meth)acrylate resins and aromatic hydrocarbon resins. A (meth)acrylate resin is particularly preferred as the tackifier compatible with poly(meth)acrylates. This improves adhesion, especially to polar substrates. An adhesive compound according to the invention may also contain mixtures of several tackifiers. Among the rosin derivatives, rosin esters are preferred.

Preferably, an adhesive compound according to the invention contains tackifiers compatible with the poly(meth)acrylates in a total of 5 to 25 wt.%, particularly preferably in a total of 8 to 18 wt.%, in each case based on the total weight of the adhesive compound.

• insgesamt 40 - 70 Gew.-% eines oder mehrerer Poly(meth)acrylate,
• insgesamt 5 - 30 Gew.-% eines oder mehrerer Acrylnitril-Butadien-Kautschuke,
• insgesamt 5 - 30 Gew.-% eines oder mehrerer Vinylaromat-Blockcopolymere; und
• insgesamt 5 - 25 Gew.-% eines oder mehrerer Tackifier,

jeweils bezogen auf das Gesamtgewicht der Haftklebmasse. Besonders bevorzugt beträgt die Summe der Gewichtsanteile der Poly(meth)acrylat und der Tackifier mindestens 55 Gew.-%, insbesondere mindestens 60 Gew.-%, jeweils bezogen auf das Gesamtgewicht der Haftklebmasse.Preferably, an adhesive compound according to the invention contains

• A total of 40-70 wt% of one or more poly(meth)acrylates,
• A total of 5 - 30 wt% of one or more acrylonitrile butadiene rubbers,
• a total of 5–30 wt% of one or more vinyl aromatic block copolymers; and
• A total of 5-25% by weight of one or more tackifiers,

each based on the total weight of the pressure-sensitive adhesive. Particularly preferably, the sum of the weight fractions of the poly(meth)acrylate and the tackifier is at least 55 wt.%, in particular at least 60 wt.%, each based on the total weight of the pressure-sensitive adhesive.

• Insbesondere enthält eine erfindungsgemäße Haftklebmasse
• insgesamt 48 - 60 Gew.-% eines oder mehrerer Poly(meth)acrylate,
• insgesamt 10 bis 25 Gew.-% eines oder mehrerer Acrylnitril-Butadien-Kautschuke,
• insgesamt 10 - 25 Gew.-% eines oder mehrerer Vinylaromat-Blockcopolymere; und 10 bis 20 Gew.-% eines oder mehrerer Tackifier,

jeweils bezogen auf das Gesamtgewicht der Haftklebmasse.

• In particular, an adhesive compound according to the invention contains
• A total of 48-60 wt% of one or more poly(meth)acrylates,
• a total of 10 to 25 wt.% of one or more acrylonitrile butadiene rubbers,
• a total of 10–25 wt.% of one or more vinyl aromatic block copolymers; and 10–20 wt.% of one or more tackifiers,

each based on the total weight of the adhesive compound.

Depending on the application and desired properties of an adhesive compound according to the invention, it may contain further components and/or additives, either alone or in combination with one or more other additives or components. Preferred embodiments are described below.

An adhesive compound according to the invention can further contain at least one polyurethane- and/or silicone-based filler. In general, all polyurethane- and silicone-based fillers known in the field are suitable; however, an adhesive compound according to the invention preferably contains at least one polyurethane- and/or silicone-based filler in the form of solid polymer spheres, in particular those with a diameter of 4 to 30 µm. Such solid polymer spheres can be used in the production of the adhesive compound, for example, as an approximately 50% masterbatch in a dispersion medium such as EVA.

Alternatively or additionally, an adhesive compound according to the invention may, for example, contain powder and granular fillers, in particular also abrasive and reinforcing fillers, which are different from the polyurethane and/or silicone-based filler, dyes and pigments such as chalks ( _CaCO3 ), titanium dioxide, zinc oxides and/or carbon blacks.

Suitable additives for the adhesive compound according to the invention are also - selected independently of other additives - non-expandable polymer hollow spheres or polymer solid spheres, glass hollow spheres, glass solid spheres, ceramic hollow spheres, ceramic solid spheres and/or carbon solid spheres ("Carbon Micro Balloons").

In a preferred embodiment, an adhesive compound according to the invention is foamed. The foaming is preferably achieved by introducing and subsequently expanding microballoons. In a further preferred embodiment, an adhesive compound according to the invention comprises at least one tackifier and/or a plurality of expanded microballoons; more preferably, an adhesive compound according to the invention comprises a plurality of microballoons.

The term "microballoons" refers to elastic, and therefore expandable in their ground state, microhollow spheres with a thermoplastic polymer shell. These spheres are filled with low-boiling liquids or liquefied gas. Polyacrylonitrile, PVDC, PVC, or polyacrylates are particularly suitable shell materials. Low-boiling liquids such as isobutane or isopentane, which are contained as a liquefied gas under pressure within the polymer shell, are especially suitable.

When the microballoons are subjected to stress, particularly heat, the outer polymer shell softens. Simultaneously, the liquid propellant inside the shell transitions into a gaseous state. This causes the microballoons to expand irreversibly and three-dimensionally. The expansion ceases when the internal and external pressures equalize. Because the polymer shell remains intact, this process results in a closed-cell foam.

A wide variety of microballoon types are commercially available, which differ mainly in their size (6 to 45 µm diameter in the unexpanded state) and their starting temperatures required for expansion (75 to 220 °C).

Unexpanded microballoon types are also available as aqueous dispersions with a solids or microballoon content of approximately 40 to 45 wt.%, and also as polymer-bound microballoons (masterbatches), for example in ethyl vinyl acetate with a microballoon concentration of approximately 65 wt.%.

A foamed adhesive compound according to the invention can also be produced using so-called pre-expanded microballoons. In this group, the expansion takes place before the microballoons are mixed into the polymer matrix.

In the embodiment described here, preferably at least 90% of all cavities formed by microballoons have a maximum diameter of 10 to 200 µm, more preferably 15 to 200 µm. The "maximum diameter" is understood to be the maximum extent of a microballoon in any spatial direction. The diameters are determined using a cryogenic fracture edge in a scanning electron microscope (SEM) at 500x magnification. The diameter of each individual microballoon is determined graphically.

The proportion of microballoons in an adhesive compound according to the invention is preferably 0.1 wt.% to 10 wt.%, in particular 0.25 wt.% to 5 wt.%, and most preferably 0.5 wt.%, in each case based on the total weight of the adhesive compound.

The absolute density of a foamed adhesive compound according to the invention is preferably 350 to 1200 kg/m ³ , more preferably 600 to 1000 kg/m ³ , in particular 750 to 950 kg/m ³ .

The relative density describes the ratio of the density of the foamed adhesive compound according to the invention to the density of the formula-identical, non-foamed adhesive compound according to the invention. The relative density of a foamed adhesive compound according to the invention is preferably 0.35 to 0.99, more preferably 0.45 to 0.97, and particularly 0.50 to 0.90.

Furthermore, an adhesive compound according to the invention may contain flame-retardant fillers, for example ammonium polyphosphate; electrically conductive fillers, for example conductive carbon black, carbon fibers and/or silver-coated spheres; thermally conductive materials, for example boron nitride, aluminum oxide, silicon carbide; ferromagnetic additives, for example iron(III) oxides; organic, renewable raw materials, for example wood flour; organic and/or inorganic nanoparticles; fibers, compounding agents, antioxidants, light stabilizers and/or ozone stabilizers.

Optionally, an adhesive compound according to the invention contains one or more plasticizers. Examples of plasticizers that can be added include (meth)acrylate oligomers, phthalates, hydrocarbon oils, cyclohexanedicarboxylic acid esters, water-soluble plasticizers, soft resins, phosphates, or polyphosphates.

A pressure-sensitive adhesive composition according to the invention preferably contains silicas, particularly preferably precipitated silica, especially precipitated silica surface-modified with dimethyldichlorosilane. Advantageously, the thermal shear strength of the pressure-sensitive adhesive composition can be adjusted with this additive.

An adhesive compound according to the invention is preferably in the form of a sheet of material, particularly as a layer in the structure of an adhesive tape. The thickness of a sheet-like adhesive compound according to the invention is preferably 50 to 1500 µm, particularly preferably 70 to 1200 µm, and in particular 100 to 800 µm, for example 150 µm to 500 µm or 200 µm to 400 µm.

The coating of an adhesive compound according to the invention, for example onto a temporary carrier material or onto the carrier material of an adhesive tape, can in principle be carried out using all conventional methods known to those skilled in the art. For example, the adhesive compound, including the additives, dissolved in a suitable solvent, can be coated onto a carrier or release film by anilox roller application, doctor blade coating, multi-roller coating, or in a printing process, and the solvent is then removed in a drying tunnel or oven. Alternatively, the coating of the carrier or release film can also be carried out using a solvent-free process. For this purpose, the acrylonitrile butadiene rubbers, the vinyl aromatic block copolymers, and the poly(meth)acrylates are heated and melted, for example, in an extruder. Further process steps, such as mixing with the described additives, filtration, or degassing, can take place in the extruder. The melt is then coated onto the carrier or release film, for example, by means of a calender.

A further aspect of the invention is the use of an adhesive compound according to the invention for bonding components of electronic devices, in particular displays, or components in or on automobiles, in particular for bonding electronic components in automobiles and for bonding trim strips or emblems to clear coats of automobiles. Bonding using adhesive compounds according to the invention can be carried out both manually and automatically.

Finally, another object of the present invention is an adhesive tape comprising at least one layer of an adhesive compound according to the invention.

Examples

Measurement and testing methods

Method 1: Determination of molecular weight

The weight-mean molar masses M _{_w} and number-mean molar masses M_{_n} given in this document refer to the well-established determination by gel permeation chromatography (GPC). The determination is performed on 100 µl of clear-filtered sample (sample concentration 3 g/L). Tetrahydrofuran is used as the eluent. The measurement is carried out at 35 °C.

A PSS-SDV column, 5 µm, 8.0 mm × 50 mm (specifications here and below in the order: type, particle size, porosity, inner diameter × length; 1 Å = ^10⁻¹⁰ m) is used as a guard column. For separation, a combination of PSS SDV columns, 5 µm, ^10³ Å, ^10⁵ Å, and ^10⁶ Å, each 8.0 mm × 300 mm (columns from Polymer Standards Service), is used; detection is performed using a PSS SECcurity ² differential refractometer. The flow rate is 1.0 ml per minute. Calibration is performed using the commercially available ReadyCal kit Poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz, Germany. The results are universally converted to polymethyl methacrylate (PMMA) using the Mark-Houwink parameters K and alpha, so that the data are given in PMMA mass equivalents.

Method 2: K-value according to Fikentscher

The K-value according to Fikentscher is a measure of the molecular weight and viscosity of polymers.

The principle of the method is based on the capillary viscometric determination of the relative solution viscosity. For this purpose, the test substance is dissolved in toluene by shaking for thirty minutes to obtain a 1% solution. The flow time is measured in a Vogel-Ossag viscometer at 25 °C, and the relative viscosity of the sample solution is determined from this with respect to the viscosity of the pure solvent. According to Fikentscher [ PE Hinkamp, Polymer, 1967, 8, 381 ] the K-value can be read (K = 1000 k).

Method 3: Glass transition temperature

The glass transition temperature of polymers or polymer blocks in block copolymers is determined according to the invention using dynamic scanning calorimetry (DSC). For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 µl) and sealed with a perforated lid. A Netzsch DSC 204 F1 is used for the measurement. The instrument is operated under nitrogen for inerting. The sample is first cooled to -150 °C, then heated to +150 °C at a rate of 10 K/min and cooled again to -50 °C. The subsequent second heating cycle is again performed at 10 K/min, and the change in heat capacity is recorded. Glass transitions are identified as steps in the thermogram.

• Der jeweils linear verlaufende Bereich der Messkurve vor und nach der Stufe wird in Richtung steigender (Bereich vor der Stufe) bzw. fallender (Bereich nach der Stufe) Temperaturen verlängert (Verlängerungsgeraden ① und ②). Im Bereich der Stufe wird eine Ausgleichsgerade ⑤ parallel zur Ordinate so gelegt, dass sie die beiden Verlängerungslinien schneidet, und zwar so, dass zwei Flächen ③ und ④ (zwischen der jeweils einen Verlängerungslinie, der Ausgleichsgeraden und der Messkurve) gleichen Inhalts entstehen. Der Schnittpunkt der so positionierten Ausgleichsgeraden mit der Messkurve ergibt die Glasübergangstemperatur.

The glass transition temperature is obtained as follows (see 1 ):

• The linear portions of the measurement curve before and after the step are extended in the direction of increasing (before the step) and decreasing (after the step) temperatures, respectively (extension lines ① and ②). Within the step, a regression line ⑤ is placed parallel to the ordinate such that it intersects the two extension lines, creating two areas ③ and ④ (between the respective extension lines, the regression line, and the measurement curve) of equal area. The intersection of this regression line with the measurement curve yields the glass transition temperature.

Method 4: Static load test (stretching in z-direction)

The static load test method serves to determine both the holding power and the deflection of the adhesive tape in the z-direction.

A square, frame-shaped sample is cut from the adhesive tape to be examined (area 180 ^mm² ; web width 2.0 mm).

This sample is glued to a steel frame cleaned with acetone. A steel window, also cleaned with acetone, is glued to the other side of the adhesive tape. The steel frame, the frame made of adhesive tape, and the steel window are glued together so that their geometric centers and diagonals are aligned (corner-to-corner). The bond is pressed with 62 N for 10 seconds and then conditioned for 72 hours at 23 °C and 50% relative humidity.

On the side of the steel window opposite the bonded area, a so-called T-block with base dimensions of 20 x 20 mm, made of steel, is applied across its entire surface using suitable adhesive tape. The resulting test specimen is then suspended in a frame with the T-block pointing downwards. The test specimen rests on the frame of the steel window frame, and the window, with the T-block attached, is thus suspended downwards without contact with the frame. A 1000 g weight is attached to the T-block to start the test. The window is hung. Immediately afterwards, the deflection of the adhesive tape is determined as a starting value. For this, the distance between the outside of the steel frame and the inside of the window (i.e., the material thickness of the steel frame plus the adhesive) is measured at all four corners using calipers. This measurement is repeated after 2 h, 5 h, 24 h, 48 h, 72 h, 144 h, and 168 h.

The mean of the four measurement points is used to determine the extent to which the deflection of the adhesive bond has changed and whether the bond is still intact.

The results include recording both the holding time and the deflection of three test specimens each. The deflection is only determined for samples that withstood a holding time of up to 168 hours.

Good results are a holding time > 72 h (> 168 h is considered very good) and a deflection < 0.5 mm.

Method 5: Drop tower test method (penetration strength)

A square, frame-shaped sample was cut from the adhesive tape to be examined (area 180 ^mm² ; web width 2.0 mm).

This sample was glued to a steel frame cleaned with acetone. A steel window, also cleaned with acetone, was glued to the other side of the adhesive tape.

The steel frame, adhesive tape frame, and steel window were bonded in such a way that the geometric centers and diagonals were aligned (corner-to-corner). The bond was pressed with 62 N for 10 seconds and then conditioned for 24 hours at 23 °C and 50% relative humidity.

The test specimen was positioned in the specimen holder of an instrumented drop tester such that the assembly was horizontal with the steel window facing downwards. The measurement was performed instrumentally and automatically using a 5 kg load weight and a drop height of 20 cm. The kinetic energy of the load weight caused the adhesive bond between the window and frame to break, with the force being recorded by a piezoelectric sensor at microsecond intervals. The associated software then generated a graph of the force-time curve, from which the maximum force, F _{_max} , could be determined. Shortly before the rectangular impact geometry struck the window, the velocity of the falling weight was measured using two light barriers. Assuming that the energy applied was large compared to the impact strength of the adhesive, the work done by the adhesive bond until complete detachment—i.e., the detachment work—was calculated from the force curve, the time required for detachment, and the velocity of the falling weight. Five test specimens of each sample were examined; the final result of the impact strength consists of the mean value of the work of removal (J) of these five samples.

A release energy of > 0.5 J is considered a good value.

Method 6: Static shear test at 70 °C

A 13 × 20 mm transfer tape was applied to a steel plate cleaned with acetone, ensuring no air bubbles were present. The back of the tape was covered with aluminum foil. The adhesive was rolled a total of four times at a speed of 10 m/min using a 2 kg steel roller. The test specimen was then suspended in a shear test rig combined with a heating cabinet.

The load was applied at 5 N, and the time until bond failure was measured. The test was considered complete when the bond failed or the specified test time had elapsed. The result is given in minutes and is the median of three individual measurements. Table 1: NBR Characterization ACN content (%) Mooney viscosity ML at 100°C (MU) Nipol® DN401 L 17-20 60-70 Perbunan® 1846F 18 45

General experiment description: Production of the pressure-sensitive adhesives

Production of polyacrylate:

A conventional reactor for radical polymerizations was filled with 72.0 kg of 2-ethylhexyl acrylate, 20.0 kg of methyl acrylate, 8.0 kg of acrylic acid, and 66.6 kg of acetone/isopropanol (94:6). After 45 minutes of nitrogen gas purging with stirring, the reactor was heated to 58 °C and 50 g of AIBN dissolved in 500 g of acetone was added. The external heating bath was then heated to 75 °C, and the reaction was carried out at this constant temperature. After 1 h, another 50 g of AIBN dissolved in 500 g of acetone was added, and after 4 h, the mixture was diluted with 10 kg of acetone/isopropanol (94:6).

After 5 h and again after 7 h, the reaction was restarted with 150 g of bis-(4-tert-butylcyclohexyl)peroxydicarbonate dissolved in 500 g of acetone. After 22 h of reaction time, the polymerization was stopped and the mixture cooled to room temperature. The product had a solids content of 55.8% and was dried.

• In einem Planetwalzenextruder wurden über einen Feststoffdosierer der Acrylnitrilkautschuk (siehe Tabelle 2) und das Vinylaromat-Blockcopolymer (SBS, Calprene® 7318, Dynasol) als Granulat aufgeschmolzen. Nachfolgend wurden das in einem Einschneckenextruder aufkonzentrierte und vorgeschmolzene Polyacrylat, der Tackifier(Paraloid® DM55 bzw. Dertophene® T105, siehe Tabelle 2) und die Mikroballons (Expancel® 920DU40 bzw. Expancel® 920DU80)zugegeben. Der Mischung wurden zudem ein Vernetzer (Uvacure® 1500, 0,1 Gew.-%) und eine Rußpaste (Levanyl® Black, 1.5 Gew.-%), zugesetzt. Die Schmelze wurde durchmischt und über einen Zweiwalzenkalander zwischen zwei Trennfolien (silikonisierte PET-Folie) zu einer Schicht mit einer Dicke von 200 µm ausgeformt.

General manufacturing process for the pressure-sensitive adhesives:

• In a planetary roller extruder, acrylonitrile rubber (see Table 2) and vinyl aromatic block copolymer (SBS, Calprene® 7318, Dynasol) were melted as granules via a solids feeder. Subsequently, the polyacrylate, concentrated and pre-melted in a single-screw extruder, the tackifier (Paraloid® DM55 or Dertophene® T105, see Table 2), and the microballoons (Expancel® 920DU40 or Expancel® 920DU80) were added. A crosslinker (Uvacure® 1500, 0.1 wt%) and a carbon black paste (Levanyl® Black, 1.5 wt%) were also added to the mixture. The melt was thoroughly mixed and formed into a 200 µm thick layer between two release films (siliconized PET film) using a two-roll calender.

The composition of the resulting pressure-sensitive adhesive layers is given in Table 2. Table 2: Composition of the pressure-sensitive adhesive layers No. Percentage of polyacrylate (wt%) NBR share (weight %) Share of SBS (Weight %) Tackifier / Proportion (wt.%), Paraloid® DM55/ Dertophene® T105 Percentage of microballoons (wt%) 1 53.8 19.3 9.7 7.25/7.25 1.1 2 53.8 14.5 14.5 14.5/-- 1.1 3 53.8 14.5 14.5 7.25/7.25 1.1 4 53.8 9.7 19.3 14.5/-- 1.1 5 53.8 9.7 19.3 7.25/7.25 1.1 6(cf.) 50.5 34 - --/13.5 0.4 7(Cf.) 49.8 34 - --/13.5 1.1 8(cf.) 57.5 24 - 15.5/-- 1.4 9 (See above) 58.0 24 - 15.5/-- 0.9 NBR - Examples 1-6, 8, 9: Perbunan® 1846F, Example 7: Nipol® DN401 L Microballoons - Examples 1-8: Expancel® 920DU40, Example 9: Expancel® 920DU80

The test results are given in Table 3. Table 3: Test results No. Density (kg/ ^m³ ) Static load (h/mm) Droptower (J) Static shear test (min) 1 880 > 72, < 168 / ne 0.856 10000 2 894 > 168 / 0.23 0.837 10000 3 882 > 168 / 0.06 0.838 10000 4 896 > 168 / 0.05 0.751 10000 5 871 > 72, < 168 / ne 0.832 10000 6(cf.) 968 < 5/ne 1,396 1961 7(Cf.) 924 < 48 / ne 0.816 10000 8(cf.) 809 < 24/ ne 0.605 10000 9 (See above) 893 < 24/ ne 0.926 5308 no - not determined

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2006/128629 A1 [0006]
• EP 2 832 811 A1 [0007]
• DE 10 2022 100 562 A1 [0009]

Cited non-patent literature

• DIN EN 1427:2007 [0067]
• C. Donker, PSTC Annual Technical Seminar, Proceedings, pp. 149-164, May 2001 [0089]
• P. E. Hinkamp, Polymer, 1967, 8, 381 [0117]

Claims (11)

Pressure-sensitive adhesive containing - one or more poly(meth)acrylates; and - one or more acrylonitrile butadiene rubbers; characterized in that the pressure-sensitive adhesive contains one or more vinyl aromatic block copolymers. Adhesive compound according to Claim 1 , characterized in that the adhesive compound contains one or more poly(meth)acrylates in a total of ≥ 45 wt.%. Adhesive compound according to one of the Claims 1 and 2 , characterized in that the adhesive compound contains one or more acrylonitrile butadiene rubbers in a total of 8 to 30 wt.%. Adhesive compound according to one of the preceding claims, characterized in that one or more acrylonitrile butadiene rubbers each have an acrylonitrile content of 10 to 60 wt.%. Adhesive compound according to one of the preceding claims, characterized in that one or more acrylonitrile butadiene rubbers are each hydrogenated or partially hydrogenated acrylonitrile butadiene rubbers. Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the pressure-sensitive adhesive contains one or more vinyl aromatic block copolymers in a total of 8 to 25 wt.%. Adhesive compound according to one of the preceding claims, characterized in that the adhesive compound is a foamed adhesive compound. Adhesive compound according to one of the preceding claims, characterized in that the adhesive compound contains at least one tackifier. Adhesive compound according to one of the preceding claims, characterized in that the adhesive compound contains a plurality of microballoons. Adhesive tape comprising at least one layer of an adhesive compound according to one of the preceding claims. Use of an adhesive compound according to one of the Claims 1 until 8 For bonding components of electronic devices or components in automobiles.