Impact additive of the core/shell type for thermoplastic polymers

Abstract

The invention relates to an impact additive of the core/shell type for thermoplastic polymers.This impact additive comprises a crosslinked elastomeric core based on n-alkyl acrylate and a shell made of poly(alkyl methacrylate) grafted onto the said core.

We claim:  
     
       1. Impact additive of the core/shell type composed of a core based on alkyl acrylate or on a polyorganosiloxane rubber and a shell based on poly(alkyl methacrylate), or on a styrene-acrylonitrile copolymer, characterized in that the said impact additive comprises from: 
       a) 70% to 90% by weight of a crosslinked elastomeric core which is composed:  
       1) of 20% to less than 100%by weight of a nucleus composed of a copolymer (I) of n-alkyl acrylate, the alkyl group of which has a carbon number ranging from 5 to 12, of a polyfunctional crosslinking agent possessing unsaturated groups in its molecule, at least one of which is of a vinyl group, and optionally of a polyfunctional grafting agent possessing unsaturated groups in its molecule, at least one of which is an allyl group,  
       2) of more than 0 and  to 80% by weight, of a covering composed of a copolymer (II) of n-alkyl acrylate, the alkyl group of which has a carbon number ranging from 4 to 12, or  and of a grafting agent possessing allyl groups, the said covering containing a molar amount of grafting agent ranging from 0.05% to 2.5%, said grafting agent having only allyl functional groups, all having the same reactivity,  
       b) 30% to 10% by weight of a shell grafted onto the said core composed of a polymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, or alternatively of a statistical copolymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, and of an alkyl acrylate, the alkyl group of which has a carbon number ranging from 1 to 8, containing a molar amount of alkyl acrylate ranging from 5% to 40%, or alternatively composed of a styrene-acrylonitrile copolymer.  
     
     
       2. An additive for improving impact resistance, said additive comprising: 
       a) 70-90% by weight of a cross linked elastomeric core compound of  
       1) 20-90% by weight of a nucleus comprising a copolymer of n-octyl acrylate and 1,4-butanediol diacrylate, and  
       2) surrounding said nucleus, 80-90%  more than 0 to 80% by weight of a covering comprising a copolymer of n-octyl acrylate and diallyl maleate, said covering containing a molar amount of diallyl maleate from  0 . 05 %  to  2 . 5   % and  
       b) surrounding said core, 30-10% by weight of a shell grafted on to the said core, said shell composed of a polymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, or alternatively of a statistical copolymer of an alkyl methacrylate, the alkyl group of which has a carbon number ranging from 1 to 4, and of an alkyl acrylate, the alkyl group of which has a carbon number ranging from 1 to 8, containing a molar amount of alkyl acrylate ranging from 5% to 40%, or alternatively composed of a styrene-acrylonitrile copolymer.  
     
     
       3. An additive according to  claim 2 , wherein said nucleus is about 90% by weight of said core and, said covering is about 10% by weight. 
     
     
       4. An additive according to  claim 3 , wherein said shell consists essentially of poly(methyl methacrylate). 
     
     
       5. An impact resistance additive according to  claim 2 , wherein said impact additive comprises from: 
       a) 75% to 85% of said crosslinked elastomeric core,  
       b) 25% to 15% of said shell grafted onto the said core.  
     
     
       6. An impact additive according to  claim 2 , wherein the covering of the crosslinked core has a molar amount of grafting agent of between 0.5% and 1.5%. 
     
     
       7. An impact additive according to  claim 2 , characterized in that the alkyl methacrylate used to form the shell is methyl methacrylate.