WO2007074262A1

WO2007074262A1 - Coating of granules with nanoscale silica

Info

Publication number: WO2007074262A1
Application number: PCT/FR2006/051339
Authority: WO
Inventors: Christian Laurichesse; Martine Le Nobin
Original assignee: Arkema France
Priority date: 2005-12-20
Filing date: 2006-12-13
Publication date: 2007-07-05

Abstract

The present invention relates to granules of copolymers coated with a coating based on silica particles acting as anti-clumping agent, said copolymers being chosen from ethylene/vinyl acetate (VA) copolymers having a vinyl acetate content of greater than 25 wt% and a melt flow index within the range from 1 to 3000 g/10 min at 463 K under a load of 21.19 N, the diameter of said particles being between 5 and 50 nm and the silica particle content being between 100 and 5000 ppm. The ethylene/vinyl acetate copolymer granules coated with this anti-clumping agent have the advantage of being transparent when they are dissolved in organic solvents for appropriate application in printing inks.

Description

ENHOMGEDEGEANULEBAVIE DELA SILICON NANO MEMQUE

The invention generally provides non-stick coatings for tackifying granules of polymers or polymer blends. These polymer or polymer blend granules are advantageously granules made from ethylene / vinyl acetate copolymer comprising from 25 to 50% by weight of vinyl acetate. The invention also relates to a method of applying a release coating to tacky granules and a method for improving the storage behavior of such granules. These granules are advantageously used in printing ink applications.

As soon as there are sticky polymers or sticky polymer blends, the manufacture, transport and handling of these materials have been problematic. This is due to the agglomeration or adhesion of the granules of these polymers to each other. These polymers are solid or semi-solid at room temperature. After polymerization, mixing or formulation, the polymers are solidified in some form of granule, such as pellets, balls, pads, etc. The granules are, therefore, like any grain whatever it is. With the increase in the volume of these materials produced in the world, the need to transport them in larger quantities has also increased. The natural tendency of the polymer to adhere itself or the container is amplified by the weight of the polymer on itself and in the case of polymer bags the weight of other bags stacked on top of each other for transport and / or storage. Moreover, in hot climates, the agglomeration is aggravated. The polymer granules are then at a temperature that approaches or exceeds their softening point, so that they deform to a degree that they adhere together to form a bulky matrix or even a solid block.

However, under less stringent conditions, the polymers can be co-coated with their contact points without substantial deformations. The granules may not fuse, but their intimate contact leads them to adhere to each other which requires some type of physical disruption of adhesion to allow their handling. This leads to a substantial amount of additional work breaking down stickiness points with instruments and causing security problems. Sometimes, it is almost impossible to break the adhesion of a block of fusio ned rods. It has been known that ethylene / vinyl acetate copolymer granules having a vinyl acetate content greater than 25% by weight and a melt index of greater than 50 g / 10 min at 463 K and a load of 21.19 N, tend to to agglomerate during their manufacture as well as during the processes of transport, transhipment and storage. In order to eliminate or reduce agglomerations, separating agents or anti-caking agent, in the form of a powder, dissolved in water or in organic solvents or in the form of an aqueous dispersion, are used. Esters of methacrylic acid or modified esters of methacrylic acid, for example in the form of aqueous dispersions of a polymer, are used to coat the granulate (DE-2148224). Styrene copolymers with maleic or fumaric acid esters, reaction products of cyclohexanone with formaldehyde are sprayed as a solution onto the granulate on a vibrating screen (DE-2127416). This method, however, imposes a closed system with a complicated recovery of the solvent. Thylene polyol, low molecular weight polypropylene or mixtures of these two substances are added in finely divided form to the ethylene / vinyl acetate copolymers (DE-2206509). These products have the disadvantages that they diffuse little by little in the granule and lose in effectiveness.

Silicone oils, paraffinic hydrocarbons and copolymers of ethylene oxide and propylene oxide can be added to the granulation water (EP-0131707). The condition is that the separating agents are insoluble in water and in the copolymers and are liquid below 383K. The separation agents indicated all have the disadvantage that they tend to diffuse into the product or that they must be dissolved in solvents, thus rendering the process polluting and imposing an expensive treatment of solvents.

In EP749454, there is provided a coating with polymer particles, said coating comprising an amount in the range of 50 to 2000 ppm of an emulsifiable wax, said emulsifiable wax having a particle diameter in the range from 0.01 to 2 micrometers, characterized in that said coating comprises a non-stick additive selected from the group consisting of talc, silica, a primary amide, a secondary amide, an ethylen-bis-amide, waxes and their combinations, said anti-tack additive being present in an amount in the range of 500 ppm to 6000 ppm, preferably in the range of 1000 ppm to 4000 ppm, based on the total weight of the polymer, and said anti-tack additive adhesiveness having an average particle size of more than 1 micron up to 150 micrometers. The technical problem lies in the modification of the surface of sticky granules of polymers or polymer blends, in particular ethylene / vinyl acetate copolymers having a content of greater than 25% by weight of vinyl acetate, preferably between 28 and 50% by weight of vinyl acetate and a melt index in the range of 1 to 3000g / 10min at 463Ka load of 21.19N, preferably between 3 and 800g / 10min, so that the granules remain fit flow and that the storage properties are thus decisively improved. During this surface modification, the separating agent or anti-caking agent of the coating must not diffuse into the coated granule and must be easy to handle.

In addition, the granules must be able to be used in printing ink applications without this application being disturbed by the presence of the anti-caking agent. When dissolving the ethylene / vinyl acetate copolymer (abbreviated EVA) granules coated with fatty amide powder as anti-caking agent in solvents of the toluene, ethyl acetate, cyclohexane, methylethylether type In this application, there is a cloudiness of the solution while the solution should be transparent for a printing ink application.

The coating of the granules based on silica particles having a diameter of between 5 and 50 nm, preferably between 5 and 30 nm, still more advantageously between 7 and 20 nm, and the coated granules because coating, the invention, respond to these technical problems. In addition, the ethylene / vinyl acetate copolymer granules coated with an anti-caking agent of the silica particle type with a diameter of the order of a few nanometers, according to the invention, have the advantage of being transparent to their dissolution in the solvents mentioned above for an appropriate application in printing inks.

The silica with very fine granubmetry of the order of the dunanometer not only makes it possible to act as an anti-caking agent but also has the property of not disturbing the ink solution comprising granules coated with this agent.

Linventbna forobject a copolymer granule coated with silica particles as an anti-caking agent, the diameter of said particles being between 5 and 50 nm and the silica particles content being between 100 and 5000 ppm.

According to one embodiment, the diameter of the silica particles is between 5 and 30 nm, advantageously between 7 and 20 nm.

In one embodiment, the silica particle content is from 400 to 1500 ppm. According to one embodiment, the silica is the silica sold under the trade name AEROSIL® R972 from Degussa.

According to one embodiment, the copolymer is chosen from copolymers of ethylene and a comonomer such as an ethylenically unsaturated ester or a carboxylic acid, in which the mono-monomer is present in a copolymer. a proportion of 5 to 30 mol%, preferably 5 to 25 mol% based on the total number of moles of the copolymer, said comonomer being itself selected from the group consisting of vinyl acetate (abbreviated VA), ethyl acrylate (abbreviated as E \), methyl acrylate (abbreviated as MA), n-butyl acrylate (abbreviated as BA), isobutyl acrylate, methyl methacrylate, acrylate of 2 Xyl-thylhe (abbreviated AE2Hou EEI), acrylic acid, methacrylic acid, their derivatives or the combination of at least two of these co-monomers.

In one embodiment, the copolymer is ethylene / vinyl acetate having a content greater than 25% by weight, preferably between 28 and 51% by weight of vinyl acetate and a melt index in the range of 1 at 3000g / 10min to 463 K, a charge of 21.19N, preferably between 3 and 800g / 10min.

The invention has also been used for a solution comprising a solvent and granules as defined above.

In one embodiment, the solvent of the solution is selected from toluene, ethyl acetate, butyl acetate, cyclohexane, methylethylenethanol, methanol, methacrylate and the like. MIBK) and isopropanol

The invention has dealt with the use of granules such as de finis plus ha ut.

According to an alternative embodiment, the coating of the ethylene / vinyl acetate copolymer granules is carried out using a mixture of silica particles as described above, used as fluidizing agent, with powders. of ethylene / vinyl acetate copolymers (EVA), with a particle size of preferably between 100 and 500 μm, in EVA / silica weight ratios of between 99/1 and 1/99. In particular, the content of silica particles is between 0.1 and 10% by weight of the mixture. However, the silica particles can also be of a smaller size.

According to one embodiment, the solution is used to make a printing ink.

We have now described the invention in more detail. The polymer granules are selected from a group consisting of:

Copolymers of ethylene and a comonomer such as an ethylenically unsaturated ester or a carboxylic acid, in which the comonomer is present in a proport of 5 to 30 mol%, preferably from 5 to 25 mol% based on the total number of moles of the copolymer, said comonomer being selected from the group consisting of vinyl acetate (abbreviated VA), ethyl acrylate (abbreviated EA), methyl acrylate (abbreviated as MA), n-butyl acrylate (abbreviated as BA), isobutyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate (abbreviated as AE2H or EEI), acrylic acid, methacrylic acid or the combination of one or more of these comonomers and their derivatives;

The ethylene / (meth) acrylic ester / maleic anhydride or ethylene / (meth) acrylic ester / glycidyl methacrylate terpolymers may be mentioned. These are, for example, ethylene / butyl acrylate / maleic anhydride, ethylene / methyl acrylate / maleic anhydride, ethylene / ethyl acrylate / maleic anhydride, ethylene / methyl acrylate / glycidyl methacrylate, and also ethylene copolymers / terpolymers. glycidyl methacrylate These products are sold for example by Arkema under the trade name IOTADEBS) MAH OR ID TADEKDGMA. We can mention the LOTADER®6200, IDTADERs) 8200, LOTADEBDTX8030, IOTΑDEBD7500, IOTΑDEBD5500 ...

• Ethylene / vinyl acetate (abbreviated EVA) can be cited. These products are sold for example by Arkema under the trade name EVATANEDEVA.

Ethylene / methyl acrylate (abbreviated EMA), ethylene / butyl acrylate (abbreviated as EBA) and ethylene / 2-ethylhexyl acrylate (abbreviated EHE) copolymers may be mentioned. These products are sold, for example, by Arkema under the trade name ID TFM®EMA, IDTRYLDEBA and IDTRYLDEEI. LOTKYI®35BA320, LOTRYL®35BA175, IDTKYI®37EH550, LOTKYBs> 37EH175 may be mentioned.

Ethylene / vinyl acetate / maleic anhydride terpolymers may be mentioned. These products are sold by ARPCEMA under the name OREVAC © T

Ethylene / acrylic ester / vinyl acetate terpolymers may be mentioned. Polyethylenes, homopolymers or copolymers, grafted or polypropylenes, homopolymers or copolymers, grafted. Among the poly (ethylene copolymers), there may be mentioned as comonomers: ## STR2 ## advantageously those having from 3 to 30 carbon atoms, including propylene, 1-butene and 1-pentene, the 3- methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene, and 1-tiia co nte. These alpha-olefins can be used alone or in a mixture of two or more than two. esters of unsaturated α-carboxylic acids such as, for example, alkyl (meth) acrylates, the alkyls having up to 24 carbon atoms.

Examples of alkyl acrylate or methacrylate include methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and 2-ethyltixyl acrylate. vinyl esters of saturated carboxylic acids such as, for example, vinyl acetate acetate. the registered partners. Examples of unsaturated epoxides include: ethylene glycol esters and ethers such as glycidyl ether, vinyl glycidyl ether, glycidyl maleate and itaconate, glycidyl acrylate and methacrylate, and esters and ethers alicyclic glycidyl such as 2-hexene-1-g lycidyl ether, cyclohexene-4,5-diglycidyl carboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene-2-methyl-2-glycidyl carboxylate and the like. 'endocis-bicyclo (2,2, l) -5-heptene-2,3-diglycidyldicarboxylate. unsaturated carboxylic acids, their salts, their anhydrides. Examples of unsaturated dicarboxylic acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, hydrochloric acid anhydride, and the like.

dienes such as, for example, 1,4-hexadiene. The polyethylene copolymer may comprise several monomers.

Advantageously, the polyethylene copolymer may be a mixture of polyesters.

The polyethylene co-polymer comprises at least 51% and preferably 75% (in moles) of ethyl, or even 100% in the case of a polyethylene homopolymer. The density of the homo or copolymer polyethylene is between 0.86 and 0.98 g / cm 2 and its MH (viscosity index at 190 ° C., 2.16 kg) is advantageously between 1 and 1000 g / 10 min.

As an example of polyethylene, mention may be made of: low density polyethylene (LDPE); high density polyethylene (HDPE); linear low density polyethylene (LLDPE); very low density polyethylene (VLDPE); polyethylene obtained by metallocene catalysis, that is to say the polymers obtained by co polymerization of ethylene and hapten-fine such as propylene, butene, hexene or octene in the presence of a monosite catalyst constituted Generally, the metalbdenene catalysts are usually composed of two metaL-linked cyclopentadiene rings. These catalysts are frequently used with aluminoxanes as co-catalysts or activators. preferably methylaluminoxane (MAO). Hafnium may also be used as the metal to which cyclopentadiene is attached. Other metals may include transition metals of the groups VA, VA, and VIA. Metals of the lanthanide series can also be used. EPR (ethylene-propylene-rubber) styrene; the EPDM (ethylene-propylene-diene) ss sto mers; polyethylene blends with EPR or EPDM; alkyl ethylene-alkyl (meth) acrylate copolymers which may contain up to 60% by weight of (meth) acrylate and preferably from 2 to 40%; ethylene (meth) acrylate-maleic anhydride copolymers obtained by co-polymerization of the three monomers, the proportions of (meth) acrylate being like the above copolymers, the amount of maleic anhydride being up to 10% by weight and preferably from 0.2 to 6%. the ethylene-vinyl acetate-maleic anhydride copolymers obtained by co-polymerization of the three monomers, the proportions being the same as in the preceding copolymer.

In the case of copolymer polypropylene, mention may be made, as co-monomer, of: ## STR2 ##, advantageously those having from 3 to 30 carbon atoms. Examples of such alpha-olefins are the same as those described above for copolymer polyethylenes except to replace propylene by ethylene in the list; s diene s; The polypipolymer copolymer may also be a polypropylene block copolymer.

Advantageously, the polypropylene may be a mixture of several polymers. By way of example of polypropylene, mention may be made of polypropylene and EPDM or EPR blends

The polypropylene copolymer comprises at least 51% and preferably 75% by moles of propylene. The density of the polypropylene is between 0.86 and 0.98 g / cm 2 and the MH is advantageously between 1 and 30 g / 10 min.

Polyethylenes, homopolymers or copolymers or polypropylenes, homopolymers or copolymers are grafted with a functional monomer. By way of examples of functional monomers, mention may be made of carboxylic acids and their derivatives, acid chlorides, isocanyates, oxazolines, epoxides, amines or hydroxides.

Examples of unsaturated arboxylic acids are those having 2 to 20 carbon atoms. Functional derivatives of these acids include, for example, anhydrides, ester derivatives, amide derivatives, imide derivatives and metal salts (such as long-chain metal salts) of unsaturated caiboxylic acids.

Unsaturated arboxylic acids having 4 to 10 carbon atoms and their functional derivatives, particularly their anhydrides, are particularly preferred grafting monomers.

These grafting monomers include, for example, maleic, fumaric, itaconic, citraconic, magnesuccinic, cybhex-4-ene-1,2-dicarboxylic acid, 4-methylcyclohex-4-ene-1,2-dicarboxylic acid, bicyclo (2,2,1) hept-5-ene-2,3-dicaiboxylic acid, x-methylbicyclo (2,2,1-hept-5-ene-2,3-dicarboxylic acid), maleic, itaconic and citraconic anhydrides, Cellulose, cyclohex-4-ene-1,2-dicarboxylic acid, 4-methylenecyclohex-4-ene-1,2-dicarboxylic acid, bicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid, andx - methylbicyclo (2,2,1) hept-5-ene-2,2-dicarboxylic acid.

Examples of other grafting monomers include C-pCg alkyl esters or glycidyl ester derivatives of unsaturated carboxylic acids such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, methacrylate, and the like. butyl, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl itaconate, and diethyl itaconate; amide derivatives of unsaturated carboxylic acids such as acrylamide, methacrylamide, maleic monoamide, maleic diamide, N - monoethylamide maleic, N, N - diethylamide maleic, N - maleic monobutylamide, N, N - dibutylamide maleic, furamic monoamide, furamic diamide, N - fumethyl monoethylamide, N, N-diethylamide fumaric, N-monobutylamide fumaric and N, N-dibutylamide furamic; imide derivatives of unsaturated caiboxylic acids such as maleimide, N-butylmaleimide and N-phenylmaleimide; and metal salts of unsaturated carboxylic acids such as sodium acrylate, sodium methacrylate, potassium aciylate, and potassium methacrylate.

Various known methods can be used for grafting a grafting monomer onto polyethylenes, homopolymers or copolymers or polypropylenes, polymethylsuccinopolymers.

For example, this can be done by heating the polymer (s) to be grafted at elevated temperature, about 150 ° to about 300 ° C, in the presence or absence of a solvent with or without a radical initiator. Suitable solvents which can be used in this reaction are benzene, toluene, xylene, chlorobenzene, cumene, etc. Suitable radical initiators which can be used include t-butyl-hydro-peroxide, cumene-hydro-peroxide, di-iso-propyl-benzene hydroperoxide, di-t-butyl-peroxide, t-butyl-cumyl peroxide, (dicumyl-peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, acetyl peroxide, benzoyl peroxide, iso-butyryl-peroxide, bis-3,5,5-trimethylhexanoyl peroxide and methyl-ethyl-keto-peroxide.

In polymers, homopolymers or copolymers or polypropylenes, graft-modified homopolymers or copolymers obtained in the aforementioned manner, the amount of the grafting monomer may be suitably selected but is preferably 0.01. at 10%, more preferably 0.1 to 5%, based on the weight of graft polymer.

The amount of the grafted monomer is determined by assaying the succinic functions by MJF spectroscopy. These products are sold, for example, by Arkema under the name of REYAC®.

These copolymers and ethylene teipolymers have generally a content in the range of from 0.2 to 20 mol% based on the total number of moles of the copolymer. copolymer or terpolymer. These materials tend to be too soft, adhesive or sticky with a density of less than 0.91 g / cm 3. These copolymers and teipolymers are semi-crystalline to amorphous copolymers. High-level, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech, high-tech

> Hot melt adhesives which are mixtures of polymers and adjuvants, usually tacky resins, descends or low glass transition (Tg) materials such as oils or low molecular weight polymers; > Of its solids, it is nsib s ssio n which is so similar to its mif fusib le s, with addition of oils and other adjuvants;

Polypylene copolymers and terpolymers which generally comprise propylene / ethylene copolymers and copolymers which are preferably chosen from the group consisting of propylene / ethylene copolymers and copolymers of the same type; 1-butene, 1-hexene, lo cte, or combinations (alpha-olefin) are present in an amount in the range of 0.2 to 20 mol% on the basis of total number of moles of copolymer or terpolymer);

Polypropylene formulations comprising mixtures containing an elastomer or a low molecular weight hydrocarbon; and

> Elastomers of ethylene / propylene (EP) and ethylene / propylene / diene monomer (EPDM) polymers.

More particularly, the present invention relates to anti-caking agents which can be applied by dusting onto the polymer granules (dusting of silica alone or silica + polymer or polymer mixture as described above for the granule with up to 5% by weight of silica, eg silica + EVA) or which can be incorporated into aqueous emulsions and processes for applying the anti-caking agent to polymer granules or polymer mixtures. The coating formulation may be based on aqueous emulsion material such as those available from Eastman Chemical Co. Under the trade name Aquastab®. These materials, and processes for their preparation are described in US4898616 and US4880440. Preferably, the emulsion comprises from 2 to 10% by weight of an anti-caking agent capable of preventing adhesion or aggregation of the granules to each other. The remainder of the formulation consists of a liquid, preferably an aqueous-based mixture of a water-miscible material and water, preferably deionized water.

The anti-caking additive is a very fine silica with a diameter of between 5 and 50 nm, preferably between 5 and 30 nm, even more advantageously between 7 and 20 nm.

The anti-caking agent content (see definition below) is between 100 and 5000 ppm, ideally between 400 and 1500 ppm.

As an anti-caking agent, the silicas of Degussa can be cited as sold under the trade name: Aerosil®90, Aerosil®130, AerosiKD1δO, Aerosil®200, Aerosil®300, Aerosil®380, Aerosil®OX50, AerosilboBOO, Aerosil®MOX80, Aerosil®MOX170, Aerosil®COK84, Aerosil®R104, Aerosil®R106, Aerosil®R972, Aerosil®R974, Aerosil®R202, Aerosil®R805, Aerosil®R812, Aerosil®R812S, Aerosil®R816, AerosO®E8200, AerosO®E711, AerosO®E7200, aerosil®R972 is used.

This list is, of course, not exhaustive. The diameter of the gianules is between 1 mm and 5 mm.

In the high-pressure heat conditions usually present at the heart of the storage and handling of these polymer granules or polymer mixtures, these coatings allow the free flow of the granules.

We are now going to meet the challenge.

Emulsification of uncoated polymer granules:

The polymers, preferably the EVA copolymers, are ejected via an extruder with a granulation under water, in the granulation water, then freed, after 2 to 20 minutes, from the water which adheres.

Béalisation of application tests

1-Application of the coating

The application of the coating consists of a sprinkling of anti-caking agent on the previously manufactured EVA granules.

In a weighted weighing vessel (mO), a quantity (P) of previously manufactured granules is introduced. The amount of silica (pe) is then added to the container to effect a coating of between 500 and 1000 ppm on the granules. The vessel is shaken with a rotating rocking motion for 1 minute. The coated granules are removed from the container and the latter weighed (ml). mO, P, pe, ml are expressed in grams.

The anti-caking agent content is calculated as follows:

> Anti-caking agent content (ppm) = [pe - (ml-m0)] xlQβ / P

The coating was carried out as described above on spherical granules of EVA type at 42% by weight of vinyl acetate and melt index of 60 g / 10 min (abbreviated EVA 42-60) with agents. anti-caking.

In Table I, the anti-caking agents are of silica AERQSIL® R972 and AERO SIL® R8200 type with a content of Ile as defined in the corresponding column. These silicas are both marketed by Degussa. They are hydrophobic silicas of less than 20 nm diameter. In Table H, ELIS-type amide EBS was used as the anti-caking agent for Comparative Sample No. 6, while Comp. Sample No. 1 had no anti-caking agent.

The results of the coatings are shown in the table below.

Tkbleaul

2-Re a usa tio n of the caking test

A quantity of granules are placed in a tube of diameter 6 cm and a height of 30 cm. A mass of 2 kg is placed on the granules to simulate a pressure of about 0.07 kg / cm ² . The entire device is placed in a temperature-controlled oven for specified periods of time. After the desired period of time, the 2 kg mass is removed and the tube is lifted to allow the pellets to flow freely. The quantity of granules flowing out of the tube is noted: Pi.

An index of caking (abbreviated in) is defined which makes it possible to classify the samples No. 1 to No. 6 in relation to one another.

(Mdice of caking) = [P0Pϋ / PO The lower the flow, the better the pellet flow and the better the quality of the anti-caking agent.

Tkbleauϋ

© Sidice of caking (In) = [PO-Pl] / PO. When Sn is 0 or close to 0, the granules are easily separable and do not stick to each other. When the Sn is equal to 1, the granules are difficult to separate from one another.

< ⁴ > Pl corresponds to the weight in g of granules flowing freely from the container for 1 minute at the indicated temperature after having remained a certain period of time in h in the container.

< ^ε) PO weight in g of starting granules.

A very good result is obtained with the silica Aéiosil®R972 at a rate of 910 ppm, and with the solution (EVA plus silica), with caking at 35 ° C much lower than in the other cases.

3 -Th e tra nsp a re th e

A portion of the previously digested EVA granules are then removed to be dissolved in a proportion of 20% by weight in a toluene / ethyl acetate mixture at a ratio of 4: 1. The solutions a to f are obtained.

The granules of Test No. 7 are dissolved in the same way and give the solution.

The level of transparency of the solutions has been evaluated at the naked eye. The results are shown in Table LL Level 0: Transparent solution Level 1: Very slightly hazy solution Nive to 2: S lutio n l l l l l l l l l y Nive in the 4: so lutio n trè tro ub le

Table III

The objective being to obtain solutions whose level of transparency is less than 1, it is found that my solutions b and c comprising EVA granules coated with Aerosil®R972 give the best results. link is the same with solution g. In addition, if the fatty amides are suitable as an anti-caking agent, they do not make it possible to obtain transparent organic solutions of granules coated with fatty amide that can be used for an ink application.

Claims

KEVENDIC AΗO NS

A copolymer granule coated with silica particles as an anti-caking agent, said co polymer being selected from the copolymers of ethylene and vinyl acetate (abbreviated VA), characterized in that said copolymer has a content of greater than 25% by weight of vinyl acetate and a melt index in the range of 1 to 3000g / 10min at 463 K of a load of 21.19N, and in that the diameter of said particles is between 5 and 50 nm and the silica particle content is between 100 and 5000 ppm.

2. Granule according to claim 1, characterized in that said ethylene / vinyl acetate copolymer has a content of between 28 and 51% by weight of vinyl acetate.

3. Granule according to claims 1 and 2, characterized in that said copolymer of ethylene and vinyl acetate has a melt index of between 3 and 800g / 10min, at 463 Kusune load of 21,19N.

4. Granule according to one of the preceding claims, characterized in that the diameter of the silica particles is between 5 and 30 nm, advantageously between 7 and 20 nm.

5. Granule according to one of the preceding claims, characterized in that the silica particle content is between 400 and 1500 ppm.

6. Granule according to one of the preceding claims, characterized in that the silica is the silica sold under the trade name AEROSIKD R972 from Degussa.

7. Solution comprising a solvent and granules according to one of the preceding claims.

8. Solution according to the preceding claim, characterized in that the solvent is selected toluene, ethyl acetate, butyl acetate, cyclohexane, methyl-thythene, methylisobutyl ether. (MER and isopropanol

9. Usa tio n of a s ubb a n d in fo re n e w a nd o fth e 7 o f o f f o r m e r o f a pr ession o f f re o rm.