Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-07-24
1997-02-25
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525263, 525301, 525302, 525309, 525310, 525316, 525317, 528300, 528301, C08F26504, C08F26706, C08F25902, C08F27900
Patent
active
056059728
DESCRIPTION:
BRIEF SUMMARY
The invention relates to graft and core-shell copolymers having improved phase bonding between graft substrate and grafted-on polymer phase, peroxy-group-containing copolymers forming the basis, therefor and also processes for preparing said polymers.
Copolymerizable initiators offer interesting possibilities in the preparation of new polymer materials. They introduce potential free-radical functions into polymer chains, the so-called "macroinitiators", which function as defined anchor groups in the preparation of graft and block copolymers. One field of application is, for example, the phase coupling of incompatible polymers in core-shell latices in their preparation by the emulsion polymerization process.
Starting out from a macroinitiator, further monomers are free-radical-polymerized in grafting reactions, which monomers should be firmly anchored to the polymer backbone of the graft substrate as a result of the peroxide groups polymerized into the macroinitiator. All macroinitiators which are hitherto known in literature suffer from the disadvantage that a part of all the free radicals formed in the thermolysis of peroxide functions is not covalently bonded to the polymer backbone. This usually results in there remaining a significant amount of ungrafted polymer chains without strong bonding to the graft substrate.
Peroxycarbonates having an allylic double bond and their use as comonomer in copolymerization with further ethylenically unsaturated monomers are described in DE-A 27 26 008. DE-C 34 20 048 relates to copolymers of vinyl acetate and allyl peroxycarbonates and their use as a size for glass fibers. A disadvantage is that these allyl-functional peroxycarbonates copolymerize only very reluctantly, if at all, with other vinyl monomers.
EP-A 277 608 (U.S. Pat. No. 4,879,347) and EP-A 279 430 (U.S. Pat. No. 4,839,432) describe copolymerizable peroxycarbonates having (meth)acrylate and allyl ether functions as comonomers for improving the phase bonding in the preparation of polymer blends. The peroxycarbonate is here polymerized with vinyl monomers in the presence of an ethylene copolymer in the suspension polymerization process. On heating the mixture, coupling of the two polymer phases occurs via the peroxy functions. A method analogous to EP-A 279 430 is described in U.S. Pat. No. 4,923,956, the difference being that propylene polymers are used in place of the ethylene polymers. EP-A 307 802 relates to mixtures of polypropylene, a further polymer and a copolymer of vinyl monomer and a peroxycarbonate having an allyl ether or (meth)acrylate function, whose phase bonding is improved by heating to temperatures of from 200.degree. to 300.degree. C. EP-B 225 091 describes allyl ether-substituted peroxydicarbonates as initiators for preparing high-molecular-weight, branched VC polymers. A disadvantage of the copolymerizable peroxyesters just mentioned is, particularly in the case of the allyl compounds, their low reactivity in copolymerization with other vinyl monomers. Furthermore, the said peroxyesters can only trigger further free-radical reactions at temperatures of .gtoreq.130.degree. C. and are thus not of interest for emulsion polymerization.
The methylstyrene-based peroxy compound discussed in W. C. Endstra, Kautschuk und Gummi, Kunststoffe 42 (5), 414 (1989) has the disadvantage that it cannot be copolymerized with many vinyl monomers and further free-radical reactions are thermally triggered only at temperatures of .gtoreq.160.degree. C. The same applies to tert-butyl peroxy(p-vinylbenzoyl)benzoate (I. Gupta, S. N. Gupta, D. C. Neckers, J. Polym. Sci.: Polym. Chem. Ed. 20, 147 (1982)) which thermally triggers further free-radical reactions only at T.gtoreq.100.degree. C. and can thus not be used for grafting in the emulsion polymerization process.
Copolymerizible peroxide compounds based on free-radical-copolymerizable allyl compounds or fumaric acid derivatives are described by Yamamota Y. et al., Polymer 32, 19 (1991). A disadvantage of these compounds is their unsatisfactory copolymerizabi
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Dobler Walter
Kohlhammer Klaus
Szekely Peter A.
Wacker-Chemie GmbH
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