ITTO20100174A1 - CYCLODESTRINIC NANOSPUGNE BY APPLICATION IN THE FIELD OF DELAY TO THE FLAME OF POLYMERIC MATERIALS - Google Patents

Description

"Cyclodextrin nanosponges for application in the flame retardant sector of polymeric materials"

DESCRIPTION

The present invention relates to flame retardant compositions with intumescent behavior and their use in polymeric matrices to give such matrices self-extinguishing properties.

The drawbacks related to the use of halogenated flame retardants have motivated a considerable effort in the study of alternative systems, capable of intervening early on the combustion cycle by acting on that part of the cycle that occurs in the condensed phase, in order to slow down and / or interrupt the process of degradation of the polymer that produces the volatile products.

The systems with intumescent behavior, developed as a valid alternative to the use of halogenated flame retardants, form for heating an expanded carbonized phase with a multicellular structure, thermally stable that isolates the underlying material from the action of the flame; this flame retardant mechanism limits the formation of volatile products by minimizing the negative side effects typical of halogenated systems, such as the formation of darkening, corrosive and toxic fumes. In addition, the carbonized phase which adheres to the surface of the burning material prevents the dripping of burning polymer particles which can contribute to the spread of the fire.

Typically, additives with intumescent behavior comprise a compound capable of providing the carbonized phase (carbonic) and a swelling agent to give it the cellular structure (spumific). To obtain these functions, the use of:

a) a polyhydric organic compound, rich in carbon, such as, for example, dextrins, sorbitol, pentaerythritol, phenol-formaldehyde resins;

b) an organic acid both free and obtained in situ by thermal decomposition of a precursor compound, such as:

- acids, such as phosphoric, sulfuric, boric acid; - ammonium salts such as phosphates, polyphosphates, sulphates, halides;

- amine / amide phosphates such as urea, melamine, reaction products between ammonia and P2O5;

- organophosphorus compounds such as tricresyl phosphate, alkyl phosphates;

c) amines / amides such as urea, urea / formaldehyde resins, melamine and polyamides.

More recent developments have aimed at reducing the complexity of the multicomponent intumescent system, trying for example to synthesize compounds (in particular nitrogen compounds) which also act as a carbon source, so that the flame retardant was made up of only two components: the precursor of the acid and the nitrogenous compound.

The desired maximum simplification requires condensing into a single compound the multiple functions considered necessary to obtain intumescence. A commercial example of this approach was a phosphate of pentaerythritol and melamine which, however, showed how having fixed in this way the proportions between the chemical structures responsible for acting respectively as a source of acid, carbon and expanding gas, does not guarantee to obtain the maximum possible efficiency.

It is therefore desirable to develop new additives by suitably combining different compounds and to use the results obtained from the optimization to synthesize a compound which contains the various structures in the desired ratio.

The general purpose of the present invention is therefore to provide new flame retardant compositions with intumescent behavior for polymeric materials.

Another object of the invention is to provide new flame retardant compositions with improved characteristics of environmental compatibility and less risky / harmful than the traditional additives currently used.

Another object of the invention is to provide flame retardant compositions having improved intumescent behavior.

In view of these purposes, the subject of the invention are compositions of flame retardants having the characteristics defined in the following claims.

Also the subject of the invention are polymeric compositions, with self-extinguishing behavior, with the addition of the aforementioned flame retardant compositions.

Another object of the invention, also defined in the following claims, is the use of cyclodextrin nanosponges for the preparation of flame retardant compositions with an intumescent effect.

The flame retardant compositions according to the invention comprise cyclodextrin nanosponges and at least one precursor compound of phosphoric, sulfuric, sulphonic or boric acid, and / or extinguishing gas.

Cyclodextrin nanosponges are cross-linked cyclodextrin polymers with different chemical bonds, which have found use in various applications including environmental decontamination and the preparation of controlled release forms of drugs.

The cyclodextrin nanosponges, used in the context of the invention, can be prepared by methods known in the state of the art. In particular, nanosponges obtained by crosslinking cyclodextrins with molecules containing activated carbonyl groups such as dimethylcarbonate, diphenycarbonate and carbonyldiimidazole can be used, as described for example in WO03085002, using for example a molar ratio of carbonyl crosslinker to cyclodextrin between 2 and 16. The cyclodextrin nanosponges can also be prepared by the process described in WO2006002814, ie by reaction of cyclodextrins with organic carbonates in the absence of a solvent and under sonication conditions.

The nanosponges can also be produced through the reaction of cyclodextrins with organic anhydrides such as pyromellitic anhydride according to the procedure reported in the patent application MI2004A000614

The cyclodextrins used can be natural, preferably (beta) -cyclodextrins or partially chemically modified cyclodextrins, such as methyl (beta) -cyclodextrins or alkyloxycarbonylcyclodextrins or even secondarily modified nanosponges.

The nanosponges obtained by means of the processes described in the aforementioned patents contain cross-linked cyclodextrins with carbonate group which are insoluble in water and in all organic solvents, do not swell significantly, are non-toxic, are porous and stable above 300 ° C.

Moreover, nanosponges obtainable by reaction of cyclodextrins with multifunctional crosslinkers of polyisocyanates, as described for example in WO98 / 22197, can be used.

In a preferred embodiment, the flame retardant compositions comprise at least one acid precursor compound, capable of forming the acid at a temperature lower than the decomposition or evaporation temperature of the cyclodextrin nanosponges used.

The term acid precursor refers to a compound which, following combustion, is capable of generating the corresponding acid.

Organic or inorganic phosphorus compounds are preferred. For phosphorus compounds, the following are cited in particular:

- organic phosphates and phosphates OP (OR) 3 in which the groups R are the same or different and are selected from hydrogen, alkyl, cycloalkyl, phenyl, optionally substituted;

- organic polyphosphates having from 2 to 15 phosphate groups, in particular compounds of formula

in which the groups R have the above mentioned meaning and n is between 1 and 15, preferably between 1 and 5,

- organic phosphites and phosphites P (OR) 3, in which the groups R are the same or different and are selected from hydrogen, alkyl, cycloalkyl and phenyl, optionally substituted;

- organic phosphonates RPO (OR) 2, in which the R groups are the same or different and are selected from an optionally substituted alkyl, cycloalkyl, phenyl group (by way of example, aliphatic and aromatic phosphates and phosphites are mentioned such as: trimethylphosphate , triethylphosphate, triphenylphosphate, triphenylphosphate);

- compounds derived from phosphorus including ammonium, amine or amide groups such as for example ammonium polyphosphate, dibasic ammonium phosphate, diethylphosphoramidate, melamine phosphate and polyphosphate, phosphorus-based amides.

They can also be used:

- precursor compounds of sulfuric and / or sulphonic acid, such as organic sulphonates and sulphates, sulphites. - boric acid precursor compounds, such as organic borates, in particular, melamine borate.

Among the compounds mentioned above, compounds whose molecular size is such that they are able to be incorporated as inclusion compounds in the cavity of the cyclodextrins are generally preferable, forming complexes; however, the invention is not intended to be limited to this solution and the use of mixtures of the nanosponges with the compounds mentioned above falls within the scope of the invention.

The above compounds can be mixed or incorporated into the nanosponges, typically in quantities from 5 to 50% referred to the weight of the nanosponges.

Optionally, the flame retardant compositions can further comprise nitrogen compounds such as urea, melamine and their derivatives (for example melamine cyanurate), amines and amides, polyamides, urea-formaldehyde resins; when used these compounds can be added to the nanosponges in quantities from 5 to 50% by weight referred to the weight of the nanosponges.

The process for the preparation of the nanosponges loaded with the aforementioned compounds is carried out following known technologies, described in the patent literature relating to the use of cyclodextrin nanosponges as a vehicle for pharmaceutical compounds.

These include the formation of complexes in solution, in suspension, through â € œkneadingâ € and fusion.

For example, if the acid precursor molecule is a liquid, the nanosponges can be placed in contact with the liquid, preferably in a glass / pyrex vessel and subjected to mechanical agitation for sufficient time to cause physical adsorption, for example for about 24 hours. In this way the nanosponges physically adsorb the additive molecule so as to obtain a combined system which as a whole represents the flame retardant. In some cases it is also possible to proceed by suspending the nanosponges and the additive molecule in an organic solvent preferably low boiling which is able to increase the interaction surface and with which both systems are compatible. Both polar solvents such as for example acetone or methanol, ethanol and non-polar solvents such as hydrocarbons such as pentane or hexane can be used.

Adsorption can be assisted by sonication by means of an immersion probe or sonicator bath, possibly at temperature.

If the precursor molecule is a solid, it can be done by mechanical mixing in a mortar, mill or similar.

Flame retardant compositions in which the nanosponges comprise an extinguishing gas, such as, in particular, carbon dioxide, fall within the scope of the invention. In this case, the preparatory process comprises the exposure of the nanosponges to a flow of the extinguishing gas used to cause adsorption, preferably preceded by a heat treatment, suitable for eliminating the water absorbed by the nanosponges.

In an example of preparation, the nanosponges are treated at about 120 ° C up to constant weight to eliminate the physisorbed water present therein (for example 5 mg out of 127 mg); a flow of 10 ml / minute of CO2 at 30 ° C at atmospheric pressure is then sent onto the nanosponges sample and proceeds until a constant weight of the sample is obtained.

The flame retardant compositions object of the invention can be used to impart self-extinguishing properties to various polymeric matrices. Polymeric matrices include olefin polymers and copolymers, in particular, polyethylene, polypropylene and their copolymers, polyethylene vinyl acetate, polystyrene, polyamide polymers, epoxy resins, polyurethanes, thermoplastic polyurethanes, saturated and unsaturated polyesters, poly (vinyl chloride), rubber.

Preferably, the flame retardant compositions can be added to the polymer, by mechanical action, for example in an amount ranging from 5 to 40% by weight referred to the weight of the polymer matrix, preferably from 10 to 25% by weight, more preferably from 15 to 25% by weight.

The tests carried out to verify the properties of flame retardants in polymeric matrices have shown that the use of cyclodextrin nanosponges as a carbon source of the flame retardant system with intumescent behavior is particularly advantageous as it allows to limit the quantity of flame retardant. added to the polymeric matrix which in the intumescent behavior systems currently used is of the order of 25-30%, in order to obtain the required protection, a quantity that can seriously damage the properties of the polymeric material.

In the case of use of nanosponges, the carbon source is in direct contact with the acid source and this allows to reach the necessary level of protection of the polymeric matrices with smaller quantities of overall additive and therefore with less negative effect on the properties of the material. Thanks to the intimate contact between the carbon source (nanosponges) and the acid precursor and / or, optionally, the nitrogen compound and also thanks to the better contact with the polymeric matrix, the speed of carbon formation is increased, therefore efficiency. of the entire flame retardant system.

Furthermore, nanosponges are clearly advantageous in terms of eco-compatibility and health safety in relation to their handling.

Further advantages and properties of the flame retardant compositions object of the invention will result from the following events which are not to be construed as limiting the scope of the invention.

In the accompanying drawings:

- Figure 1 is a diagram illustrating the trend of the HRR (Heat Release Rate) parameter determined in the combustion test by cone calorimetry, in relation to a polymeric matrix of polyethylene vinyl acetate (EVA) with additive with different concentrations of retardant compositions flame according to the invention;

- figure 2 is a diagram illustrating the trend of the THR (Total Heat Release Rate) parameter determined by the test of figure 1 for the same polymer matrix;

Example 1: preparation of nanosponges

The nanosponges were prepared following the procedure described in example 1 of WO2006002814 using beta-cyclodextrins and diphenylcarbonate as crosslinking agent.

The nanosponges (hereinafter NS) thus obtained consist of beta-type cyclodextrins linked together by carbonate bridges.

Example 2: preparation of the flame retardant compositions: nanosponges with additive with phosphoric compounds

The nanosponges obtained by the preparation of Example 1 were additives with various phosphoric compounds, in particular with: triethylphosphite (TEP), triphenylphosphite (TPP), ammonium polyphosphate (APP), dibasic ammonium phosphate (APb), diethylphosphoramidate (PhEt).

The preparation was carried out by simple mechanical mixing in a ceramic mortar, being solid phosphoric compounds. A quantity of phosphoric compound equal to 1: 1 or 1: 2 by weight referred to the weight of the nanosponges was used for all the preparations.

Example 3: flammability tests

A UL94 test was developed as a flammability test based on the ASTM D3801-00 standard. The specimens used had the shape of a parallelepiped with dimensions 127x12.7x3.2 mm.

Table 1 shows the classification results according to the UL94 test and the general test data of the samples in relation to a polyethylene vinyl acetate (EVA) matrix loaded with the flame retardant compositions of components identified in example 2.

As can be seen from table 1, the V2 classification is already achievable for concentrations of 5% by weight with the use of nanosponges loaded with triethylphosphate.

Table 1

Samples Classes Single weight Single weight- Material- t1 t2 [s] Presen- (series of 5) first specimen test the [s] but of the test after the cyiate drops [g] test [g] [% ]

EVA n.c. 2.4 0.0 100 91 <Turns on and> completely burns out EVA + 5% NS n.c. 2.3 0.0 100 106 <Turns on and> burns completely EVA + 5% NSTEP V2 2.0 1.6 3.2 15 4 yes EVA + 10% NSTEP V2 2.3 2.0 13 16 <Does not burn> yes EVA + 15% NSTEP V2 2.0 2.0 1 71 <Do not burn EVA + 15% NSAPP V2 2.2 1.5 30 15 1 <yes> EVA + 15% NSAPb V2 2.3 2.2 4 23 <Do not burn

E- V2 2.3 2.2 5 1 7 <si> VA + 15% NSPhEt

t1 = the time during which the sample burns

after the first application of the flame of 10 seconds

t2 = the time during which the sample burns

after the second 10 second flame application

The flammability test according to UL94 was

also repeated with polymeric matrices of polypropylene and polyethylene.

The results obtained at the end of UL94 classification are shown in table 2.

Table 2

Samples Classes Weight Weight Material t1 t2 [s] Presence (series of 5) single single burned [s] of drops specimen specimen [%]

before after

of the test

test [g]

[g]

<PP n.c.> 4.3 0.0 100 282 <Ignites and> burns completely <PP + 10% NS n.c.> 4.3 0.0 100 244 <Ignites and> burns completely <PP + 10% NSTEP V2> 4.5 0.0 100 38 193 yes PE n.c. 4.5 0.0 100 386 <Ignites and> burns completely PE + 10% NS n.c. 3.7 0.0 100 251 <Turns on and> burns completely PE + 10% NSTEP V2 4.6 0.0 100 257 <Turns on and> burns completely

As can be seen from the tabulated values, the V2 classification is applied in relation to concentrations of nanosponges loaded with triethylphosphite of

10% by weight in the case of polypropylene as well as in

polyethylene case.

Example 4: combustion test by cone calorimetry

The calorimetric cone combustion test provides useful information relating to the forced combustion of materials following the regulations

ISO 5660. The specimens used are tiles with dimensions of 50x50x3 mm. Through this test, information on the combustion process is obtained;

below are cited and reported in table 3 i

values considered main such as pkHRR (Pick Heat Release Rate) and THR (Total Heat Release Rate); the trend of these parameters, with respect to time, is shown in the graphs of figures 1 and 2.

Table 3

Samples pk HRR ∠† pk HRR THR ∠† THR

<2 2>

(series of 3) [kW / m] [%] [MJ / m] [%] EVA 1520 - 101 -EVA + 5% NS 1178 -22 100 -1 <EVA + 5% NSTPP> 1354 -11 94 -7 EVA + 5% NSTEP 1694 11 99 -2 EVA + 10% NSTEP 349 -77 26 -74 EVA + 15% NSTEP 211 -86 23 -77 EVA + 15% NSTEP 211 -86 23 -77 EVA + 15% NSAPP 239 - 84 23 -77 EVA + 15% NSAPb 310 -79 25 -75 EVA + 15% NSPhEt 257 -83 23 -77 As can be seen from table 3, the pkHRR registers a significant variation in the samples with additives at 10-15% by weight , with a 75-85% decrease in this value compared to the pure EVA polymeric matrix; the same trend is also observed in the case of THR with a decrease of 75% compared to the pure EVA polymer matrix.

Table 4 shows the pkHRR value determined by calorimetric cone analysis with polypropylene, polyethylene and polyamide 6 matrices in which, in the samples added with 15 and 20%, a decrease of the pkHRR value of 40 is observed. % compared to pure polymeric matrices (without additives).

Table 4

Pk HRR samples ∠† pk HRR

(series of 3) [kW / m <2>

] [%]

<PP> 1545 - <PP + 15% NSTEP> 922 -40 <PP + 15% NSAPP> 938 -39

PA6 1242 -PA6 + 10% NS 1374 11 PA6 + 20% NSTEP 777 -37

Claims (11)

CLAIMS 1. Intumescent flame retardant composition for polymeric materials characterized in that it comprises cyclodextrin nanosponges and at least one precursor compound or derivative of phosphoric, boric, sulfuric or sulphonic acid, or an extinguishing gas or a mixture of such compounds. 2. Flame retardant composition, according to claim 1, characterized in that it comprises a phosphoric acid precursor selected from the group consisting of: - organic phosphates and phosphates OP (OR) 3 in which the groups R are the same or different and are selected from hydrogen, alkyl, cycloalkyl, phenyl, optionally substituted; - organic polyphosphates having from 2 to 15 phosphate groups; - organic phosphites and phosphites P (OR) 3, in which the groups R are the same or different and are selected from hydrogen, alkyl, cycloalkyl and phenyl, optionally substituted; - organic phosphonates RPO (OR) 2, in which the R groups are the same or different and are selected from possibly substituted alkyl, cycloalkyl, phenyl. - a phosphorus derivative containing amino or amide groups or one or more ammonium groups; - and their mixtures. 3. A flame retardant composition according to claim 1 or 2, comprising a sulfuric acid precursor, selected from organic sulfates or sulfates, organic sulfonates, organic sulphites and sulphites. 4. Flame retardant composition according to any one of claims 1 to 3, comprising a boric acid precursor, particularly borates and organic borates. 5. Flame retardant composition according to any one of claims 1 to 4, further comprising a nitrogenous compound selected from urea, melamine, urea-formaldehyde resin, polyamides and their mixtures. 6. Flame retardant composition according to any one of claims 1 to 5, characterized in that said cyclodextrin nanosponges comprise nanosponges cross-linked with carbonate groups. 7. Use of cyclodextrin nanosponges for the preparation of flame retardant compositions with an intumescent effect, for polymeric materials. 8. Self-extinguishing polymeric composition, comprising a flame retardant composition according to any one of claims 1 to 6. 9. Polymeric composition according to claim 8, characterized in that it comprises said flame retardant composition in quantities from 5 to 40% by weight, preferably from 15 to 25% by weight, based on the weight of the polymeric material. 10. Polymeric composition according to claims 8 or 9, wherein the polymeric material is selected from the group consisting of olefin polymers or copolymers, polyamides, epoxy resins, polyurethanes, thermoplastic polyurethanes, saturated and unsaturated polyesters, poly (vinyl chloride) and tires. 11. Process for the preparation of self-extinguishing polymeric compositions, characterized in that it comprises the addition to a polymeric material of a flame retardant composition according to any one of claims 1 to 6.