JP7700440B2 - Silicone Dispersants and Filler Dispersions - Google Patents

Description

The present invention relates to a dispersant capable of imparting excellent filler dispersibility in a liquid medium, and a filler dispersion containing the same.

Products using liquid media such as hydrocarbons, alkanols, alkenols, fatty acids, unsaturated fatty acids, esters of fatty acids and hydroxyl-containing compounds, esters of unsaturated fatty acids and hydroxyl-containing compounds, silicone oil, acrylic resins, epoxy resins, and urethane resins include cosmetics, liquid toners, oil-based inkjet inks, weak solvent paints, lubricants, cleaning agents, thermally conductive materials, conductive materials, and optical materials. In addition, by dispersing fillers such as pigments in these liquid media, functions according to the application can be imparted.

For example, in recent years, with the increasing density and integration of printed circuit boards and hybrid ICs mounted with electronic components such as transistors, ICs, and memory elements, and the increasing capacity of secondary batteries (cell type), thermally conductive silicone compositions consisting of organopolysiloxanes and thermally conductive fillers such as aluminum oxide powder and zinc oxide powder are widely used as thermal conductive materials to efficiently dissipate heat generated from electronic and electrical devices such as electronic components and batteries. In particular, thermally conductive silicone compositions filled with a large amount of thermally conductive filler have been proposed to deal with high heat dissipation. However, even if the filling rate of the thermally conductive filler filled in the thermal grease, thermal dissipation sheet, etc. is increased to reduce the thermal resistance or improve the thermal conductivity, the viscosity of the resin composition used in the thermal grease, thermal dissipation sheet, etc. increases, making it difficult to discharge the resin composition. For this reason, various studies have been conducted on combinations of thermally conductive fillers to be filled in order to reduce the thermal resistance or increase the thermal conductivity of thermal greases and thermal sheets (see Patent Document 1, Patent Document 2, or Patent Document 3). However, the combinations of thermally conductive fillers that have been studied so far have been insufficient in terms of thermal conductivity, or have high viscosity even if they have high thermal conductivity, and there has been no combination that achieves both of these.

To solve this problem, Patent Document 4 describes that in a thermally conductive silicone composition filled with a thermally conductive filler, an organopolysiloxane having trimethoxysilyl at one end plays a role in reducing the viscosity of the composition and imparting fluidity. With regard to the effect of the molecular weight of the organopolysiloxane having trimethoxysilyl on viscosity reduction and imparting fluidity, it describes that a larger molecular weight is preferable, but the examples do not describe a specific example of using an organopolysiloxane having trimethoxysilyl at one end and a molecular weight of 5,000 or more.

JP 2005-054099 A JP 2004-091743 A JP 2000-063873 A JP 2020-066678 A

The present invention relates to a dispersant capable of imparting excellent filler dispersibility in a liquid medium, and a filler dispersion containing the same. An object of the present invention is to provide a dispersant capable of imparting excellent filler dispersibility in a liquid medium. A further object of the present invention is to provide a filler dispersion obtained by using the above dispersant, in which the filler is stably dispersed.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that organopolysiloxanes having an alkoxysilyl group at one end and a number average molecular weight (Mn) of 13,000 or more are useful as dispersants, and thus completed the present invention.

式（１）中、Ｒ^１は独立して、炭素数１～１２の１価飽和炭化水素基、または炭素数６～１２の１価芳香族炭化水素基であり、Ｒ^２は独立して、炭素数１～１２の１価飽和炭化水素基であり、Ｘは、酸素、または炭素数２～８の２価炭化水素基であり、ｎは１以上の整数であり、ａは１～３の整数である。 That is, according to the present invention, there is provided the following dispersant.
Item 1. A silicone-based dispersant which is a compound represented by formula (1), has an alkoxysilyl group at one end, and is composed of an organopolysiloxane having a number average molecular weight (Mn) of 13,000 or more.

In formula (1), R ¹ is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms; R ² is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms; X is oxygen or a divalent hydrocarbon group having 2 to 8 carbon atoms; n is an integer of 1 or more; and a is an integer of 1 to 3.

According to the present invention, there is also provided a filler dispersion as shown below.
Item 2. A filler dispersion comprising a filler, a liquid medium, and the silicone-based dispersant according to Item 1.
Item 3. The filler dispersion according to item 2, wherein the content of the liquid medium is 4 to 50 parts by mass and the content of the silicone-based dispersant is 0.1 to 20 parts by mass, relative to 100 parts by mass of the filler.

The present invention provides a dispersant that can stably disperse a filler in a liquid medium.

Furthermore, according to the present invention, a filler dispersion obtained by using the above-mentioned dispersant can be provided in which the filler is stably dispersed. The filler dispersion of the present invention is useful, for example, as cosmetics, liquid developers, oil-based inkjet inks, UV-curable inkjet inks, weak solvent-based paints, offset inks, lubricants, cleaning agents, insecticides, release agents, adhesives, heat-conducting materials, conductive materials, optical materials, etc.

1 is a graph plotting the change in shear viscosity versus shear rate for the dispersants of Example 1 and Comparative Examples 1 to 3.

The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment.

<Silicone-based dispersant>
The dispersant of the present invention is an organopolysiloxane having an alkoxysilyl group at one end, which is used for dispersing a filler in a liquid medium and has a number average molecular weight (Mn) of at least 13000. The dispersant of the present invention is a silicone-based dispersant which is an organopolysiloxane having an alkoxysilyl group at one end, which is represented by formula (1), and has a number average molecular weight (Mn) of at least 13000.

式（１）中、Ｒ^１は独立して、炭素数１～１２の１価飽和炭化水素基、または炭素数６～１２の１価芳香族炭化水素基であり、Ｒ^２は独立して、炭素数１～１２の１価飽和炭化水素基であり、Ｘは、酸素、または炭素数２～８の２価炭化水素基であり、ｎは１以上の整数であり、ａは１～３の整数である。

In formula (1), R ¹ is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms; R ² is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms; X is oxygen or a divalent hydrocarbon group having 2 to 8 carbon atoms; n is an integer of 1 or more; and a is an integer of 1 to 3.

Examples of alkoxysilyl include trimethoxysilyl, triethoxysilyl, tripropoxysilyl, methyldimethoxysilyl, methyldiethoxysilyl, ethyldimethoxysilyl, ethyldiethoxysilyl, propyldimethoxysilyl, propyldiethoxysilyl, dimethylmethoxysilyl, dimethylethoxysilyl, diethylmethoxysilyl, diethylethoxysilyl, dipropylmethoxysilyl, dipropylethoxysilyl, etc. Among these, trimethoxysilyl is preferred from the viewpoints of affinity with fillers, ease of availability of manufacturing raw materials, etc.

The polystyrene-equivalent number average molecular weight (Mn) of the dispersant measured by gel permeation chromatography (GPC) is 13,000 or more. If the number average molecular weight is less than 13,000, the molecular weight is too small, so that steric repulsion is not exerted when the filler is dispersed, and a stable dispersion cannot be obtained.

The dispersant of the present invention is used to disperse a filler in a liquid medium. Examples of liquid media include hydrocarbons, alkanols, alkenols, fatty acids, unsaturated fatty acids, esters of fatty acids and hydroxyl-containing compounds, esters of unsaturated fatty acids and hydroxyl-containing compounds, silicone oils, acrylic resins, epoxy resins, and urethane resins. These liquid media can be used alone or in combination of two or more. A liquid medium suitable for use as a thermally conductive material is silicone oil.

Hydrocarbons include hexane, hexene, 2-ethylhexane, heptane, heptene, cyclohexane, cyclohexaneheptane, octane, octene, 2-ethylhexane, nonane, decane, isodecane, dodecane, isododecane, tridecane, undecane, octadecane, C8-20 isoparaffin, squalane, petrolatum, microcrystalline wax, hydrogenated polyisobutene, 1-octene, 2-octene, 1-nonene, 2-nonene, 1-decene Examples of cyclohexane include cyclohexane, 2-decene, 1-undecene, 2-undecene, 1-dodecene, 2-dodecene, 1-tridecene, 2-tridecene, 1-tetradecene, 2-tetradecene, 1-pentadecene, 2-pentadecene, 1-hexadecene, 2-hexadecene, 1-heptadecene, 2-heptadecene, 1-octadecene, 2-octadecene, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, and propylcyclohexane.

Examples of alkanols or alkenols include octanol, 2-ethylhexanol, nonanol, decanol, isodecanol, dodecanol, cetyl alcohol, stearyl alcohol, arachyl alcohol, behenyl alcohol, hexyldecanol, octyldodecanol, isocetyl alcohol, isostearyl alcohol, and oleyl alcohol.

Examples of saturated or unsaturated fatty acids include octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tridecanoic acid, stearic acid, oleic acid, 1,2-hydroxystearic acid, ricinoleic acid, ricinoleic acid, undecylenic acid, isononanoic acid, myristic acid, palmitic acid, myristic acid, and 2-ethylhexanoic acid.

Examples of esters of saturated fatty acids and hydroxyl group-containing compounds, or esters of unsaturated fatty acids and hydroxyl group-containing compounds, include methyl laurate, heptyl undecylenate, isononyl isononanoate, ethyl oleate, isopropyl myristate, isopropyl palmitate, butyl stearate, cetyl palmitate, myristyl myristate, octyldodecyl myristate, isopropyl isostearate, ethyl isostearate, cetyl 2-ethylhexanoate, hexyl isostearate, ethylene glycol di-2-ethylhexanoate, and ethyl dioleate. Examples of the fatty acids include propylene glycol, dicapryl/caprate, propylene glycol dioleate, trimethylolpropane triisostearate, pentaerythritol tetra 2-ethylhexanoate, neopentyl glycol diheptanoate, isocetyl isostearate, 2-octyldodecyl dimethyloctanoate, myristyl lactate, trioctyldodecyl citrate, diisostearyl malate, di 2-ethylhexyl succinate, diisopropyl adipate, diisobutyl adipate, and cholesteryl stearate.Further examples include triesters with glycerin such as almond oil, avocado oil, olive oil, shea butter, shea butter oil, evening primrose oil, passionflower seed oil, camellia oil, babassu oil, peanut oil, and rosehip oil; waxes such as beeswax, Japan wax, jojoba oil, candelilla wax, and carnauba wax; and the like.

Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxy-modified silicone oil, carbinol-modified silicone oil, polyether-modified silicone oil, alkyl-modified silicone oil, and fluorine-modified silicone oil.

Examples of acrylic resins include monofunctional (meth)acrylates, bifunctional (meth)acrylates, trifunctional or higher polyfunctional (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, and bifunctional or higher polyester (meth)acrylates.

Epoxy resins include combinations of a base agent, such as phenol-based glycidyl ethers such as bisphenol A, bisphenol F, and phenol novolac, and alcohol-based glycidyl ethers such as polypropylene glycol, and a curing agent. Examples of the curing agent include amine compounds such as aliphatic polyamines, modified aliphatic polyamines, polyamidoamines, polyamides, alicyclic polyamines, modified alicyclic polyamines, modified aromatic polyamines, and tertiary amines. These curing agents may be used alone or in a mixture of two or more. A reaction accelerator that accelerates the reaction between the base agent and the curing agent may also be used. Examples of reaction accelerators include phenol, p-t-butylphenol, di-t-butylphenol, cresol, triphenyl phosphite, salicylic acid, and triethanolamine. These reaction accelerators may be used alone or in a mixture of two or more.

Examples of urethane resins include reaction products of hydroxyl group-containing compounds and polyisocyanate compounds, such as polyurethanes obtained by reacting short-chain glycols or short-chain ethers with isocyanate compounds as hard segments, and linear multi-block copolymers of polyurethanes obtained by reacting long-chain glycols or long-chain ethers with isocyanate compounds as soft segments. Other examples include reaction products (cured products) of urethane prepolymers and polyisocyanate compounds.

Examples of fillers include inorganic pigments, organic pigments, extender pigments, bulking agents, inorganic fine particles, diamond, graphene, graphite, carbon black, carbon nanotubes, clay, conductive fillers, thermally conductive agents, carbon fibers, glass fibers, cellulose, and cellulose nanofibers. These fillers are particulate, powdery, or fibrous substances that are added to plastics, rubber, paints, inks, and the like to improve strength and functionality and reduce costs. There are no particular limitations on the crystal form, particle size, surface condition, or presence or absence of surface treatment of the filler. The filler (thermally conductive agent) of the thermally conductive material is preferably aluminum oxide, zinc oxide, aluminum nitride, or boron nitride, and more preferably aluminum oxide.

<Filler dispersion>
The filler dispersion of the present invention contains a filler, a liquid medium, and a dispersant that disperses the filler in the liquid medium. The dispersant is the above-mentioned silicone-based dispersant. The above-mentioned liquid medium is used as the liquid medium. Among them, it is preferable to use silicone oil. In addition to the liquid medium, for example, various organic solvents, monomers, liquid oligomers, etc. can also be used.

As the filler, the above-mentioned fillers are used. Among them, aluminum oxide, zinc oxide, aluminum nitride, or boron nitride is preferable, and aluminum oxide is more preferable.

The filler dispersion preferably contains 4 to 50 parts by mass of the liquid medium, more preferably 5 to 30 parts by mass, per 100 parts by mass of the filler. The filler dispersion preferably contains 0.1 to 20 parts by mass of the silicone-based dispersant, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the filler. If the silicone-based dispersant content per 100 parts by mass of the filler is less than 0.1 parts by mass, it may be difficult to stably disperse the filler. On the other hand, if the silicone-based dispersant content per 100 parts by mass of the filler exceeds 10 parts by mass, an excess of silicone-based dispersant that does not contribute to the dispersion of the filler will be included.

The filler dispersion of the present invention can contain various additives such as other surfactants, plasticizers, and defoamers, to the extent that the purpose of the dispersion is not impaired.

The filler dispersion of the present invention can be produced in accordance with known methods for producing filler dispersions. Examples include a method in which a filler is added to a liquid medium to which a silicone-based dispersant has been added, followed by stirring and mixing, and a method in which a liquid medium and a silicone-based dispersant are added to a filler, followed by stirring and mixing. Known dispersing machines can be used as dispersing equipment for stirring, mixing, or dispersion. Examples include roll mills, ball mills, bead mills, sand mills, homogenizers, dispersers, and rotation-revolution mixers. Dispersion treatment can also be performed in an ultrasonic bath.

The present invention will be described in more detail below. In the examples, "parts" and "%" are all based on mass (parts by mass, % by mass) unless otherwise specified. The present invention is not limited in any way by these examples.

<Measurement of molecular weight>
The molecular weight of the organopolysiloxane was measured by gel permeation chromatography (GPC), and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was defined as the molecular weight distribution index (Mw/Mn). Polystyrene was used as a standard sample to measure the molecular weight in terms of polystyrene.
The measurement of the molecular weight in terms of polystyrene by the GPC method is carried out under the following measurement conditions.
a) Measuring instrument: JASCO HPLC LC-2000Plus series
b) Column: Shodex KF-804L x 2 c) Oven temperature: 40°C
d) Eluent: toluene 0.7 mL/min
e) Standard sample: polystyrene f) Injection volume: 20 μL
g) Concentration: 0.05g/10mL
h) Sample preparation: Toluene was used as a solvent and the sample was dissolved by stirring at room temperature.

Synthesis Example 1: Synthesis of organopolysiloxane having an alkoxysilyl group at one end and a number average molecular weight of 17,000
In a 1000 ml four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 697 g of polydimethylsiloxane having hydrosilyl at one end (number average molecular weight (Mn) = 17100) and 14 g of vinyltrimethoxysilane (S210 manufactured by JNC, molecular weight = 148.2) were weighed and heated to 70 ° C. under a nitrogen atmosphere with stirring. After reaching 70 ° C., 81 μL of Pt-VTSC-3.0X manufactured by Umicore Japan was added as a Karstedt catalyst and stirred at 70 ° C. for 1 hour. The mixture was cooled to room temperature and the reflux condenser was replaced with a distillation head with a collection flask. Next, the product was heated at 120° C. for 1 hour under reduced pressure of 0.3 kPaA using a vacuum pump to distill off any volatile substances remaining in the product, obtaining 703 g of polydimethylsiloxane having trimethoxysilyl at one end (number average molecular weight (Mn) = 16,900, weight average molecular weight (Mw) = 17,600, molecular weight distribution index (Mw/Mn) = 1.04).

Synthesis Example 2: Synthesis of organopolysiloxane having an alkoxysilyl group at one end and a number average molecular weight of 1,500
In a 500 ml four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 300 g of polydimethylsiloxane (number average molecular weight (Mn) = 1300) having a hydrosilyl group at one end and 55 g of vinyltrimethoxysilane (S210 manufactured by JNC, molecular weight = 148.2) were weighed and heated to 70 ° C. under a nitrogen atmosphere with stirring. After reaching 70 ° C., 4 μL of Pt-VTSC-3.0X manufactured by Umicore Japan was added as a Karstedt catalyst and stirred at 70 ° C. for 1 hour. The mixture was cooled to room temperature and the reflux condenser was replaced with a distillation head with a collection flask. Next, the product was heated at 150° C. for 1 hour under reduced pressure conditions of 5 kPaA using a vacuum pump, and then further heated at 150° C. for 2 hours under reduced pressure conditions of 0.1 kPaA to distill off any volatile substances remaining in the product, thereby obtaining 338 g of polydimethylsiloxane having trimethoxysilyl at one end (number average molecular weight (Mn) = 1500, weight average molecular weight (Mw) = 1700, molecular weight distribution index (Mw/Mn) = 1.14).

Synthesis Example 3: Synthesis of organopolysiloxane having an alkoxysilyl group at one end and a number average molecular weight of 6,500
In a 2000 ml four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 1000 g of polydimethylsiloxane (number average molecular weight (Mn) = 5000) having a hydrosilyl group at one end and 45 g of vinyltrimethoxysilane (S210 manufactured by JNC, molecular weight = 148.2) were weighed and heated to 70 ° C. under a nitrogen atmosphere with stirring. After reaching 70 ° C., 12 μL of Pt-VTSC-3.0X manufactured by Umicore Japan was added as a Karstedt catalyst and stirred at 70 ° C. for 1 hour. The mixture was cooled to room temperature and the reflux condenser was replaced with a distillation head with a collection flask. Next, the product was heated at 150° C. for 1 hour under reduced pressure conditions of 5 kPaA using a vacuum pump, and then further heated at 150° C. for 2 hours under reduced pressure conditions of 0.1 kPaA to distill off any volatile substances remaining in the product, thereby obtaining 1,010 g of polydimethylsiloxane having trimethoxysilyl at one end (number average molecular weight (Mn) = 6,500, weight average molecular weight (Mw) = 6,900, molecular weight distribution index (Mw/Mn) = 1.05).

Synthesis Example 4: Synthesis of organopolysiloxane having an alkoxysilyl group at one end and a number average molecular weight of 12,000
In a 1000 ml four-neck flask equipped with a stirrer, a thermometer, and a reflux condenser, 659 g of polydimethylsiloxane having hydrosilyl at one end (number average molecular weight (Mn) = 11100) and 20 g of vinyltrimethoxysilane (S210 manufactured by JNC, molecular weight = 148.2) were weighed and heated to 70 ° C. under a nitrogen atmosphere with stirring. After reaching 70 ° C., 76 μL of Pt-VTSC-3.0X manufactured by Umicore Japan was added as a Karstedt catalyst and stirred at 70 ° C. for 1 hour. The mixture was cooled to room temperature and the reflux condenser was replaced with a distillation head with a collection flask. Next, the product was heated at 120° C. for 1 hour under reduced pressure of 0.3 kPaA using a vacuum pump to distill off any volatile substances remaining in the product, thereby obtaining 663 g of polydimethylsiloxane having trimethoxysilyl at one end (number average molecular weight (Mn) = 11,600, weight average molecular weight (Mw) = 17,600, molecular weight distribution index (Mw/Mn) = 1.04).

As shown in Tables 1 to 4, Example 1 and Comparative Examples 1 to 3 were evaluated by the following method using the organopolysiloxanes having alkoxysilyl at one end synthesized in Synthesis Examples 1 to 4. The results are shown in Tables 1 to 4 and Figure 1.

<Preparation of Samples for Dispersibility Evaluation>
Into an ointment jar container, 2.6 g of polydimethylsiloxane (KF-96-1000CS manufactured by Shin-Etsu Chemical Co., Ltd.) which is a silicone oil was weighed as a liquid medium, and 0.1 g of organopolysiloxane having trimethoxysilyl at one end, which was synthesized in Synthesis Examples 1 to 4, was weighed as a silicone-based dispersant. Furthermore, 10 g of alumina (DAW-10 manufactured by Denka Co., Ltd.) having an average diameter of 13 μm was weighed as a dispersoid, and stirred with a spatula. Next, using a Thinky Corporation Awatori Rentaro Vacuum Type (Model: ARV-310), the mixture was kneaded at 2000 rpm for 1 minute under normal pressure conditions and at 2000 rpm for 1 minute under reduced pressure conditions to prepare a sample for dispersibility evaluation.

<Dispersibility evaluation>
The dispersibility of the dispersibility evaluation sample prepared as described above was evaluated by measuring the shear viscosity at different shear rates under the following conditions using a rheometer (MCR302, manufactured by Anton Paar).
a) Plate shape: circular flat plate 25 mm diameter
b) Sample thickness: 1 mm
c) Temperature: 25±1℃
d) Shear rate: 0.001 to 1 ^S

Table 1. Dispersibility evaluation results 1

Table 2. Dispersibility evaluation results 2

Table 3. Dispersibility evaluation results 3

Table 4. Dispersibility evaluation results 4

The organopolysiloxane of the present invention having a number average molecular weight (Mn) of 13,000 or more and trimethoxysilyl at one end was found to be a good dispersant because the shear viscosity at each shear rate was lower in the dispersibility evaluation compared to an organopolysiloxane having an alkoxysilyl at one end and a number average molecular weight (Mn) of less than 13,000.

The silicone-based dispersant of the present invention can be used as a dispersant for stably dispersing fillers in liquid media in fields such as cosmetics, liquid developers, oil-based inkjet inks, UV-curable inkjet inks, weak solvent paints, offset inks, lubricants, cleaning agents, insecticides, release agents, adhesives, thermally conductive materials, conductive materials, and optical materials.

Claims (4)

1. A filler dispersion for use as a liquid developer, lubricant, cleaning agent, insecticide, release agent, adhesive, thermally conductive material, electrically conductive material, or optical material, comprising:
Contains a filler, a liquid medium, and a silicone-based dispersant ,
the liquid medium is polydimethylsiloxane ;
The silicone-based dispersant is represented by formula (1) and contains an organopolysiloxane having a number average molecular weight (Mn) of 13,000 or more.
In formula (1), R ¹ is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms; R ² is independently a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms; X is oxygen or a divalent hydrocarbon group having 2 to 8 carbon atoms; n is an integer of 1 or more; and a is an integer of 1 to 3. The filler dispersion according to claim 1, wherein the content of the liquid medium is 4 to 50 parts by mass and the content of the silicone-based dispersant is 0.1 to 20 parts by mass relative to 100 parts by mass of the filler. The filler dispersion according to claim 1 or 2, wherein the filler is aluminum oxide. A filler dispersion according to any one of claims 1 to 3 for use as a heat conducting material.

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