Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1991-12-11
1993-11-23
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525280, C08F29300, C08F29702
Patent
active
052645274
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to new triblock copolymers containing at least one acrylic block, and more particularly to such copolymers obtained by anionic polymerisation. The present invention also relates to a process for obtaining such copolymers, and more particularly to a process allowing their polydispersity to be controlled, and to the application of these triblock copolymers to the manufacture of elastomeric articles.
Triblock copolymers combining alkyl methacrylate blocks of different kinds are already known. Thus, Polymer Preprints 29(1), pages 343-345 describes triblock copolymers (tert-butyl methacrylate-b-2-ethylhexyl methacrylate-b-tert-butyl methacrylate) obtained by anionic polymerisation in tetrahydrofuran at -78.degree. C. in the presence of a difunctional initiator. Using this method, block copolymers are obtained which may contain up to 20% by weight of tert-butyl methacrylate but which have a relatively broad molecular weight distribution. Furthermore, the combination of different methacrylates in a triblock copolymer of this type does not appear to be capable, even after hydrolysis and/or in subsequent neutralisation of the ester functional groups, of imparting to this copolymer properties which make it suitable for a particular application. On the other hand, provided that the copolymer has a narrow molecular weight distribution, the combination of acrylate blocks and methacrylate or else vinylaromatic blocks in a triblock copolymer seems capable of providing advantageous properties in a number of types of applications, and especially for the manufacture of elastomeric articles.
U.S. Pat. No. 3,287,298 describes a class of polymers which can be converted in air at ordinary temperature, that is to say of fusible and/or soluble polymers which, on exposure to oxygen, are converted into insoluble polymers by virtue of the presence of multiple unsaturated groups in their structures. This class includes block copolymers of formula: ##STR1## in which n.sub.o is an integer equal to at least 4, m is an integer equal to at least 1 and capable of reaching up to the value of n.sub.o, ##STR2## in which R is chosen from H, CH.sub.3 and CN, and P may be, among others, an aryl radical or a group CO.sub.2 R, in which R' is chosen from aromatic, saturated aliphatic and saturated cycloaliphatic radicals containing up to 12 carbon atoms, and ##STR3## in which R is chosen from H, CH.sub.3 and CN, and Q is an unsaturated aliphatic radical containing from 16 to 24 carbon atoms.
By virtue of their property of convertibility in air, these block copolymers are particularly useful for coating applications such as varnishes, paints, and the like.
The problem which the present invention aims to solve consists in developing a polymerisation process for obtaining triblock copolymers containing at least one acrylic block and having a narrow molecular weight distribution, and capable of having properties which enable them to be employed in the manufacture of elastomeric articles. The present invention is based on the surprising discovery that this objective can be reached by combining, in the system for initiating the anionic polymerisation, the initiator with a ligand such as an alkali or alkaline-earth metal salt, by conducting the polymerisation sequentially and preferably by selecting the relative proportions of the acrylic and nonacrylic polymers which are involved.
A first subject of the present invention consists of a triblock copolymer which has a number-average molecular weight ranging approximately from 3,000 to 300,000 and a molecular weight polydispersity ranging approximately from 1.05 to 2.0, of A-B-C structure in which each of the blocks A and C denotes a monomer sequence chosen from the classes of acrylic, vinylaromatic, methacrylic and maleimide monomers, block B denotes a monomer sequence chosen from the classes of acrylic, vinylaromatic and methacrylic monomers, with the condition that at least one of the blocks A and C is chosen from a class other than that of block B.
A vinylaromatic monomer wi
REFERENCES:
patent: 3287298 (1966-11-01), D'Alelio
Chemical Abstracts; 84:136297u; Fukawa et al.
Fayt Roger
Hautekeer Jean-Paul
Teyssie Philippe
Varshney Sunil K.
Clark W. R. H.
Elf Atochem S.A.
Seidleck James J.
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