WO2013017799A1

WO2013017799A1 - Soft block copolymers in the form of free-flowing granules

Info

Publication number: WO2013017799A1
Application number: PCT/FR2012/051815
Authority: WO
Inventors: Thomas Fine; Raber INOUBLI; Thierry Claude
Original assignee: Arkema France
Priority date: 2011-08-02
Filing date: 2012-08-01
Publication date: 2013-02-07
Also published as: FR2978766A1; FR2978766B1

Abstract

The invention relates to soft acrylic copolymers in the form of granules, that are surface-treated with a powder of statistical acrylic copolymers. This treatment facilitates the free flow and handling of the granules. The invention also relates to a method for treating acrylic copolymer granules, designed to limit or prevent caking and to facilitate the free flow of the granules.

Description

COPOLYMERS WITH FLEXIBLE BLOCKS IN FORM

OF FREE FLOW GRANULES

The invention relates to flexible acrylic copolymers in the form of granules, surface-treated with a powder of random acrylic copolymers. This treatment facilitates the free flow of the granules and their handling. The invention also relates to a process for treating acrylic copolymer granules for limiting or preventing caking and facilitating free flow of the granules.

The phenomenon of caking of pulverulent or granular products, occurring during transportation or storage, under the influence of changes in ambient temperature, the hydrometric degree of air or pressure, is well known. It consists of agglomeration of powders or granules, leading to the formation of blocks in the pile and / or superficial crusts, sometimes even the total mass of the entire volume stored in a storage capacity. In the case of a tank filled with powder or granules, the interactions between particles and the friction of the particles on the wall cause variations in the vertical stress, which can go as far as its cancellation at the lower end of the wall. the converging part of the tank.

There are various types of devices or processes for initiating or maintaining the flow of a powdered product or in the form of granules: mechanical, pneumatic, vibrating devices and chemical treatment processes.

These apply when the final quality of a product allows it. Indeed, it may be advantageous to apply a flow agent to the solid product in the form of powder or granules, to modify its intrinsic flow properties. The effect is obtained by coating the surface of each individual particle with an anti-caking product, which leads to significantly reducing the cohesion forces and thus to increasing the flow.

Free (or bulk) flow occurs when all of the material in the tank is in motion when the product is unloaded.

It has already been used as anti-caking agents for inorganic products in the form of powders such as technical salts, or organic products in the form of powders or granules such as fertilizers, drugs and compounds of fine chemistry, coating powder, cold-spraying liquids or hot-meltable fusible pastes, having as active organic substances (oils, glycerines, paraffins, paraffin oils, sulphonates, fatty amines, etc.) and inorganic (silica, talc, kaolin, cyanides, etc.).

In the particular case of acrylic block copolymers in the form of powder, EP 1.676.872 has been proposed as a method for preventing adhesion between the particles, the spraying of additives chosen from calcium carbonate, talc. , kaolin, silicon dioxide, fatty acid amides, fatty acid esters and metal soaps. To be effective, these additives must be added because of at least 2 parts by weight per 100 parts of block copolymer. Another anti-caking treatment described in this document consists in mixing the acrylic block copolymer with silicone oil, super-hardened oil based on beef fat, various waxes or carbon black.

In all these cases, the nature of the compound used as an anti-caking additive is different from that of the acrylic polymer granules. This can cause problems such as loss of transparency of parts made from said granules, or adhesion to various substrates, or the extension of the solubilization time of these polymers in the thermoset precursor. This last problem can be explained by a phenomenon of screening of the soluble granule by the anti-caking agent, itself insoluble.

None of these additives has yet satisfactorily solved the caking phenomenon observed in flexible acrylic copolymers in the form of granules when they are stored in bulk.

The Applicant has now found that, unexpectedly, random acrylic copolymers applied in powder form to the surface of the soft acrylic copolymers in the form of granules, make it possible to limit or prevent the caking of said acrylic copolymers and to facilitate the free flow of the granules. The invention resides in both flexible acrylic copolymers in the form of granules, surface-treated with a powder of high molecular weight random acrylic copolymers, and in the process of treating flexible acrylic copolymers in order to improve their behavior to flow.

The invention also relates to free-flowing formulations based on soft acrylic block copolymers, consisting of granules of said block copolymers, surface-treated with a powder of random acrylic copolymers.

In addition, the invention relates to the use of the treated flexible acrylic copolymers for the manufacture of adhesive or thermoset products. The invention will now be described in detail.

In the range of acrylic block copolymers manufactured by Arkema, some grades, marketed under the name Nanostrength® ^® mass have rates above 50% elastomeric phase, which gives them a character soft blocks copolymers and sometimes slightly tackant. Although these soft acrylic block copolymers are granulable by an underwater cutting process, the granules of these grades have a tendency to float. It is then difficult to run the granules which complicates the bagging operation and when empty bags in which they are stored and transported.

The object of the invention is to provide a particular surface treatment of these acrylic granules which makes it possible to obtain a free flow of the granules.

According to a first aspect, the invention relates to flexible acrylic copolymers in the form of granules, surface-treated with a powder of random acrylic copolymers.

Description of Flexible Acrylic Block Copolymers

The soft acrylic block copolymers contemplated by the present invention are any acrylic block copolymers which do not exhibit free flow under normal conditions of use, typically from 20 ° C to 50 ° C, or which tend to agglomerate under the effect of a charge.

The soft acrylic block copolymer is more particularly chosen from block copolymers of type A-B-A, A-B and A-B-C, in which:

each block is connected to the other by means of a covalent bond or an intermediate molecule connected to one of the blocks by a covalent bond and to the other block by another covalent bond,

A is a PMMA homopolymer or a copolymer of methyl methacrylate, C is either (i) a homopolymeric PMMA or a methyl methacrylate copolymer (MMA) or (ii) a polymer based on monomers or a mixture of vinyl monomers; blocks A and C may be identical;

B is incompatible or partially compatible with said resin and incompatible with the block A and the optional block C, and its glass transition temperature Tg is lower than that of the blocks A and C.

With regard to AB diblock or triblock ABA, A is a PMMA homopolymer or a copolymer of methyl methacrylate. In the case where A is a copolymer, the The comonomers used are preferably those based on alkyl methacrylate for forming a block A compatible with the thermoset resin. By way of example, mention may be made of alkyl methacrylates in which the alkyl group contains from 1 to 18 carbons: methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate methacrylate n-hexyl, cyclohexyl methacrylate, ethyl hexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate stearyl methacrylate, isobornyl methacrylate. Mention may also be made, by way of example, of all comonomers which are soluble in water, such as acrylic or methacrylic acid, amides derived from these acids, such as, for example, dimethyl acrylamide, 2-methoxyethyl acrylate or methacrylate, and acrylates. or optionally quaternized 2-aminoethyl methacrylates, (meth) acrylates of polyethylene glycol (PEG), water-soluble vinyl monomers such as N-vinyl pyrrolidone or any other monomer soluble in water. By way of example, mention may also be made of all the reactive comonomers copolymerizable with methyl methacrylate. By reactive monomer is meant a chemical group capable of reacting with the functions of the host matrices, whether the copolymer is used as an additive, or with the surface functions of a substrate, if the copolymer is used as a matrix. Block A can be formed of only one of these (meth) acrylic monomers or of several. By way of example, mention may be made of hydroxyethyl methacrylate, glycidyl methacrylate, maleic anhydride, acrylic or methacrylic acid.

Block A may be manufactured by any means of polymerization and in particular by controlled or anionic radical polymerization.

As regards block B, advantageously the Tg of B is less than 0 ° C. and preferably less than -40 ° C. By "Tg" is meant the glass transition temperature of a polymer measured by DSC according to the ASTM standard. E1356.

The monomer used to synthesize the elastomeric B block may be a diene chosen from butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 2-phenyl-1,3 butadiene. B is advantageously chosen from poly (dienes), especially poly (butadiene), poly (isoprene) and their random copolymers, or else from partially or completely hydrogenated poly (dienes). Among the polybutadienes, those with the lowest Tg are advantageously used, for example 1,4-polybutadiene of Tg (around -90 ° C.) which is lower than that of 1,2-polybutadiene (at around 0 ° C.). Blocks B can also be hydrogenated. The monomer used to synthesize block B may also be an alkyl (meth) acrylate, in which case the following Tg values are given in parentheses, following the name of the acrylate: ethyl acrylate ( -24 ° C), butyl acrylate (-54 ° C), 2-ethylhexyl acrylate (-85 ° C), hydroxyethyl acrylate (-15 ° C) and methacrylate 2 - ethylhexyl (-10 ° C). Butyl acrylate is advantageously used. Block B may also consist of a mixture of monomers. The acrylates are different from those of the block A to respect the condition of incompatibility of the blocks A and B.

In triblock A-B-C, C is either (i) a PMMA homopolymer or a methyl methacrylate copolymer as defined above (ii) a polymer based on monomers or a mixture of vinyl monomers.

The two blocks A and C of the triblock A-B-C may be identical or different. They can be different in their molar mass but consist of the same monomers. If block C contains a comonomer it may be the same or different from the comonomer of block A.

With regard to (ii) by way of example of blocks C, mention may be made of those derived from vinylaromatic compounds such as styrene, α-methyl styrene, vinyl toluene and those derived from alkyl esters of acrylic acids and / or methacrylic acid having 1 to 18 carbon atoms in the alkyl chain.

Block B consists of the same monomers and possibly comonomers as block B of diblock A-B or triblock ABA. The blocks B of the triblock A-B-C and diblock A-B may be identical or different.

Said flexible acrylic block copolymer is in the form of granules or microgranules.

These block copolymers A-B, A-B-A or A-B-C can be manufactured by any means of polymerization. Preferably, the controlled radical polymerization or anionic polymerization processes implemented using the solvent, emulsion, suspension or other method are used.

As regards the flexible nature of the acrylic block copolymer, the more the acrylic copolymer will be rich in B-block, the more flexible the copolymer will be.

In the context of the present invention, the term "flexible block copolymer" any block copolymer having the structure described above and having a flexural modulus, measured according to ISO 178, less than 500 MPa at the operating temperature. In the soft block copolymer, the Tg of one of the blocks is less than 20 ° C.

Description of the acrylic acrylic copolymers

These are random copolymers of methyl methacrylate with at least one other monomer whose homopolymer corresponds to a Tg less than 25 ° C. They are used in the form of powder, which must itself have a free flow at operating temperatures (typically from 20 to 50 ° C). The monomer concentration having a low Tg can range from 0.1 to 50%, preferably from 1 to 20% by weight of the total weight of the copolymer.

The comonomer used to synthesize the random copolymers may also be an alkyl (meth) acrylate, and in this case the following Tg values are given in parentheses, following the name of the acrylate. By way of example, mention may be made of ethyl acrylate (-24 ° C.), butyl acrylate (-54 ° C.) and 2-ethylhexyl acrylate (-85 ° C.). hydroxyethyl acrylate (-15 ° C), 2-ethylhexyl methacrylate (-10 ° C), dodecyl acrylate (-3 ° C), hexyl methacrylate (-5 ° C) and octyl methacrylate (-20 ° C).

Preferably, the invention relates to the use as an anti-caking agent of the soft acrylic block copolymers described above, random acrylic copolymers of high molecular weight, between 250,000 and 2,000,000 g / mol.

Examples of random acrylic copolymers include the range of Plastistrength ^® products manufactured by Arkema, the range of Kane Ace ^® products supplied by Dow or that of Degalan ^® products manufactured by Evonik.

According to another aspect, the invention relates to free-flowing formulations based on soft acrylic block copolymers, consisting of granules of said block copolymers, surface-treated to a height of at least 0.25 parts of acrylic copolymer powder. statistics for 100 parts of pellets. This treatment allows a regular flow of said granules.

According to yet another aspect, the invention relates to the process for treating granules of soft acrylic block copolymers described above, intended to limit or prevent caking and to facilitate free flow of the granules. Typically, this process comprises a step of coating said granules with at least one random acrylic copolymer, the proportion by weight of the latter being at least 0.25 parts by weight per 100 parts of granules. The acrylic copolymer powder is added mechanically to said granules. Caking is reduced from a dose of 0.25 parts of acrylic copolymer and completely disappears when at least 0.5 part of acrylic copolymer is added, per 100 parts of granules of flexible acrylic copolymer. The dose of acrylic copolymer in powder form to be added is between 0.25 parts and 0.8 parts, preferably from 0.4 parts to 0.6 parts per 100 parts of granules of block copolymers.

Advantageously, the granules thus treated retain their properties of transparency, adhesion and solubilization.

It would not be outside the scope of the invention if the acrylic copolymer powder was used in combination with known anti-quenching agents. Compromises of transparency of the parts made from said granules, adhesion to various substrates or solubilization of these polymers in the thermoset precursor, can then be found.

The known anti-quenching agents are chosen from calcium carbonate, talc, kaolin, silicon dioxide, fatty acid amides, fatty acid esters, silicone oil and metal soaps. The overall level of anti-caking agent used in this case (ie the random acrylic copolymer powder and the known anti-caking agent) remains below 1.5% parts per 100 parts of block copolymer granules.

In addition, the invention relates to the use of the treated flexible acrylic copolymers for the manufacture of adhesive or thermoset products.

When the acrylic soft copolymers treated according to the invention are used for the manufacture of adhesive products, it has been found that this treatment does not modify the adhesion properties of the latter.

Claims

1. Flexible acrylic block copolymer in the form of granules, surface-treated with a powder of random acrylic copolymers.

The block copolymer according to claim 1, wherein the soft acrylic block copolymer is selected from A-B-A, A-B and A-B-C block copolymers, wherein:

each block is connected to the other by means of a covalent bond or of an intermediate molecule connected to one of the blocks by a covalent bond and to the other block by another covalent bond,

A is a PMMA homopolymer or a copolymer of methyl methacrylate, C is either (i) a PMMA homopolymer or a methyl methacrylate copolymer or (ii) a monomer-based polymer or a vinyl monomer mixture, blocks A and C may be identical;

B is incompatible with the block A and the eventual block C, and its glass transition temperature Tg is lower than that of the blocks A and C.

3. Block copolymer according to one of claims 1 and 2 wherein the block A being a copolymer of MMA, the comonomer is chosen from:

alkyl methacrylates in which the alkyl group contains 1 to 18 carbons namely methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate n-hexyl methacrylate, cyclohexyl methacrylate , 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate stearyl methacrylate, isobornyl methacrylate, and water-soluble comonomers such as acrylic or methacrylic acid, amide derivatives of these acids, such as, for example, dimethyl acrylamide, 2-methoxyethyl acrylate or methacrylate, optionally quaternized 2-aminoethyl acrylates or methacrylates, polyethylene glycol (meth) acrylates (PEG), and water-soluble vinyl monomers such as N-vinyl pyrrolidone or any other monomer soluble in water.

4. Copolymer according to any preceding claim wherein wherein the Tg of the block B is less than 0 ° C, preferably less than - 40 ° C.

5. Copolymer according to any one of the preceding claims wherein the monomer used to synthesize the block B is chosen from:

dienes such as butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-phenyl-1,3-butadiene;

poly (dienes) in particular poly (butadiene), poly (isoprene) and their random copolymers;

poly (dienes) partially or totally hydrogenated;

polybutadienes, for example polybutadiene-1,4;

alkyl (meth) acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate and 2-ethylhexyl methacrylate.

6. Copolymer according to any one of the preceding claims wherein the monomer used to synthesize the block C is chosen from vinylaromatic compounds such as styrene, α-methyl styrene, vinyl toluene, or alkyl esters of acrylic acids and / or or methacrylic having from 1 to 18 carbon atoms in the alkyl chain.

7. Copolymer according to any one of the preceding claims wherein said random copolymers are copolymers of methyl methacrylate with at least one comonomer whose homopolymer corresponding to a Tg lower than 25 ° C.

The copolymer of claim 7 wherein said comonomer is selected from ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl methacrylate, and the like. dodecyl acrylate, hexyl methacrylate and octyl methacrylate.

The copolymer of any preceding claim wherein said random acrylic copolymers have a molecular weight of between 250,000 and 2,000,000 g / mol.

10. Free-flowing formulation based on soft acrylic block copolymers, consisting of granules of said block copolymers, surface-treated with a powder of random acrylic copolymers, the proportion by weight of these latter being 0.25 parts to 0 8 parts per 100 parts of block copolymers, preferably 0.4 parts to 0.6 parts per 100 parts of block copolymers.

The formulation of claim 10, wherein said soft acrylic block copolymer is according to any one of claims 2 to 6.

The formulation according to one of claims 10 or 11, wherein said random acrylic copolymers are according to any one of claims 7 to 9.

13. Use of the block copolymer according to one of claims 1 to 9 or the formulation according to one of claims 10 to 12 for the manufacture of adhesive products.

14. Use of the block copolymer according to one of claims 1 to 9 or the formulation according to one of claims 10 to 12 for the manufacture of thermosets.

15. A process for treating granules of soft acrylic block copolymers according to one of claims 2 to 6, for limiting or preventing caking and facilitating the free flow of granules, comprising a step of coating said granules with less a random acrylic copolymer, the proportion by weight of these latter ranging from 0.25 to 0.8 parts per 100 parts of block copolymers.