Claims
- 1. An anionically-polymerized addition homopolymer or copolymer of at least one ester of methacrylic acid selected from the group consisting of (C.sub.1 -C.sub.24) alkyl esters of methacrylic acid, di(C.sub.1 -C.sub.4) alkylamino (C.sub.2 -C.sub.4) alkyl esters of methacrylic acid, (C.sub.2 -C.sub.12) alkoxyalkyl esters of methacrylic acid, (C.sub.7 -C.sub.12) aryloxyalkyl esters of methacrylic acid, (C.sub.7 -C.sub.12) aralkoxyalkyl esters of methacrylic acid, and (C.sub.7 -C.sub.10) aralkyl esters of methacrylic acid, and, in a copolymer, other anionically copolymerizable monomers, wherein n, the average chain length of the homopolymer or copolymer, is about 6to 50 mers; the polymerization being carried out, in the presence of an alcohol and a catalytic amount of an alkoxide, using controlled rates of addition of at least one of the ester, the alcohol and the alkoxide.
- 2. The polymer of claim 1 wherein at least about 85% by weight of the molecules of the polymer have chain lengths of about .sqroot.2n.sup.- to about 2n.sup.- mers.
- 3. The polymer of claim 2 wherein the average chain length is about 6 to about 25 mers.
- 4. The polymer of claim 2 wherein the polymer is a homopolymer of an ester of methacrylic acid.
- 5. The polymer of claim 4 wherein the ester is a (C.sub.1 -C.sub.24)alkyl methacrylate.
- 6. The polymer of claim 5 wherein the ester is a (C.sub.1 -C.sub.4)alkyl methacrylate.
- 7. The polymer of claim 5 wherein the ester is methyl methacrylate.
- 8. The polymer of claim 4 wherein the ester is dimethylaminoethyl methacrylate.
- 9. The polymer of claim 2 wherein the polymer is a copolymer of at least two (C.sub.1 -C.sub.24)alkyl; methacrylates.
- 10. The polymer of claim 2 wherein the polymer is a copolymer of at least one (C.sub.1 -C.sub.24)alkyl methacrylate and at least one other copolymerizable ethyleneically-unsaturated monomer.
- 11. The polymer of claim 10 wherein the copolymerizable monomer is methacrylonitrile, vinyltriethoxysilane, or dimethylaminoethyl methacrylate.
- 12. The polymer of claim 11 wherein the alkyl methacrylate is a (C.sub.1 -C.sub.4)alkyl methacrylate.
- 13. The polymer of claim 12 wherein the alkyl methacrylate is methyl methacrylate.
- 14. The polymer of claim 2 wherein the polymer comprises mers having the structure ##STR7## wherein R is a di(C.sub.1 -C.sub.4)alkylamino(C.sub.2 -C.sub.4)alkyl group, an alkoxyalkyl group having up to 8 carbon atoms, an aryloxyalkyl or aralkyloxy group having up to 10 carbon atoms, or an aralkyl group having up to 10 carbon atoms.
- 15. The polymer of claim 14 wherein the polymer also comprises mers of the structure ##STR8## wherein R.sup.1 is a (C.sub.1 -C.sub.24)alkyl group.
- 16. In a process for preparing polymers of esters of methacrylic acid, the improvement which comprises carrying out the polymerization in the presence of an alcohol and a catalytic amount of an alkoxide, using controlled rates of addition of at least one of the ester, the alcohol and the alkoxide; producing a polymer wherein n.sup.-, the average chain length of the polymer is about 6 to 50 mers.
- 17. The process of claim 16 in which at least about 85% by weight of the molecules of the polymer have chain lengths of about .sqroot.2n.sup.- to about 2n.sup.- mers.
- 18. The polymer of claim 2 represented by the formula ##STR9## wherein R'O represents the residue of the chain-regulating alcohol used in the polymerization reaction;
- R'o represents the alcohol portion of an ester of methacrylic acid;
- M represents the interspersed residue of the comonomer or comonomers; and
- n' and n" are integers of one or more, wherein the sum of n' and n" is 3 to 90.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our pending application U.S. Ser. No. 371,921, filed June 20, 1973, which is a continuation-in-part of our pending application U.S. Ser. No. 137,057, filed on Apr. 23, 1971, both now abandoned.
This invention relates to novel homopolymers and copolymers of esters of methacrylic acid, to polymer compositions which comprise these novel polymers, to methods of making the polymers, and to uses of the polymers.
Polymers having relatively low molecular weights, often referred to as oligomers, have recently become of increasing interest, in part due to their use in adhesives, plasticizers, leveling agents, and melt-index improvers, and in formulating coating compositions having very high solids content. While various alkyds, polyesters, polyethers, polyamides, and polyurethanes having molecular weights in the range of 500 to 2500 can be conveniently prepared, suitable acylic polymers in this molecular weight range have heretofore been inaccessible. Because acrylic polymers have many extremely valuable advantages, including relatively low cost, low color, good outdoor durability, high chemical resistance, and good thermal stability, and because the various non-acrylic low molecular weight polymers with functionalities greater than two are often difficult to prepare, polymer compositions comprising low molecular weight acrylic polymers would be particularly desirable.
Attempts have been made to prepare acrylic polymers having molecular weight distributions in the range of 2550 to 10000 by free radical polymerization techniques. However, these procedures are generally unacceptable, either because high temperature or high pressures are needed to carry out the polymerization reaction, because the chain transfer agent employed in the reaction has an objectionable odor or toxicity, or because the properties of the polymer produced in the polymerization reaction are adversely affected by a high incidence of initiator or chain transfer fragments in the polymer chains. Furthermore, it is difficult to control the molecular weight distribution of polymers prepared by free radical techniques. Thus, such polymers tend to have a broad molecular weight distribution, and contain significant amounts of high molecular weight polymer, which can give unattractive properties to the polymer compositions. It has now been found that novel polymer compositions free of the undesirable properties of prior art materials can be prepared by a novel anionic polymerization technique, which allows control of the polymer chain length and of the molecular weight distribution of the polymer.
According to the invention, novel polymer compositions are provided which comprise an anionically-polymerized addition homopolymer of an alkyl ester, a dialkylaminoalkyl ester, an alkoxyalkyl ester, an aryloxyalkyl ester, an aralkoxyalkyl ester, or an alkylsilylalkyl ester of methacrylic acid, an anionically-polymerized addition copolymer of at least two of these esters, or an anionically-polymerized addition copolymer of at least one of these esters with at least one other copolymerizable monomer. In the polymer compositions of the invention, the homopolymer or copolymer has an average chain length of about 6 to about 50 mers. In one preferred embodiment, the average chain length will be about 6 to about 25 mers, and in another preferred embodiment, the average chain length will be about 8 to about 20 mers.
The polymers of the invention are characterized by having not only low molecular weight, but also very narrow molecular weight distribution. Generally, at least about 85% by weight of the molecules of the homopolymer or copolymer in the polymer compositions have chain lengths falling between .sqroot.2n and 2n, where n is the average chain length of the polymer. Thus, when the average chain length of the homopolymer or copolymer is about 6 mers, at least about 85% by weight of the molecules of the homopolymer or copolymer generally have chain lengths of about 3.5 to about 12 mers, and when the average chain length of the homopolymer or copolymer is about 25 mers, at least about 85% by weight of the molecules of the homopolymer or copolymer generally have chain lengths of about 7 to about 50 mers. In a preferred embodiment of the invention, at least about 85% by weight of the molecules of the homopolymer or copolymer in the polymer compositions will have a chain length of about 4 to 40 mers. Depending upon the particular ester of methacrylic acid which is employed, and the particular comonomer which may be employed, the polymer compositions of the invention will have a molecular weight distribution (weight average molecular weight, Mw) in the range of about 400 to about 10,000, and preferably about 500 to about 2500. The dispersities (ratio of weight average molecular weight to number average molecular weight) of the polymer compositions of the invention are also quite low, generally being about 1.1 to about 3, preferably less than about 2, and most preferably less than about 1.5.
US Referenced Citations (3)
Continuation in Parts (2)
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Number |
Date |
Country |
| Parent |
371921 |
Jun 1973 |
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| Parent |
137057 |
Apr 1971 |
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Patent Grant
4056559
