Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-03-16
2001-04-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S209000, C526S318200, C524S418000, C524S419000, C528S497000
Reexamination Certificate
active
06211318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to copolymers of maleic anhydride and a C
1
-C
4
alkyl vinyl ether, and, more particularly, to copolymers which are substantially free of poly(alkyl vinyl ether) homopolymers therein.
2. Description of the Prior Art
Copolymers of maleic anhydride (MAN) and a C
1
-C
4
alkyl vinyl ether (AVE) have been described extensively in the art. However, such copolymer products invariably include homopolymers of poly(alkyl vinyl ether) as an impurity as a result of homopolymerization of excess alkyl vinyl ether present in the reaction mixture. The presence of this poly(alkyl vinyl ether) impurity adversely affects the performance of any hydrolyzed copolymer product made therefrom, in personal and oral care compositions. Particularly, this impurity imparts objectionable color and haze to such compositions.
Accordingly, it is an object of the present invention to provide solvent-free, fine white powders of a copolymer of maleic anhydride and a C
1
-C
4
alkyl vinyl ether free of poly(alkyl vinyl ether) homopolymer to the extent of the detection limit of NMR analysis, which is <1 molar % of the homopolymer.
Another object of the invention is to provide a solvent-free process for making such high purity copolymers.
A feature of the invention is the inclusion of a suppressor agent in the reaction mixture of maleic anhydride and excess alkyl vinyl ether and radical initiator. The suppressor agent is present therein in an amount sufficient to prevent cationic homopolymerization of alkyl vinyl ether monomer during the radical copolymerization of these monomers.
Another feature of the invention is to provide hydrolyzed copolymers of maleic anhydride and alkyl vinyl ether free of homopolymers of alkyl vinyl ether which are without color or haze.
SUMMARY OF THE INVENTION
What is described herein are solvent-free, fine white powders of a copolymer of maleic anhydride and a C
1
-C
4
alkyl vinyl ether which is substantially free of poly(alkyl vinyl ether) homopolymer.
A feature of the invention is the provision of the copolymer which is free of said homopolymer to the extent of the detection limit of NMR analysis.
Preferably the suppressor agent is present in an amount of about 500 to 5000 ppm by weight of the alkyl vinyl ether monomer used in the process.
Suitable suppressor agents to preclude cationic homopolymerization of alkyl vinyl ether include water, alcohols, ammonia, amines, hydroxyamines, amides or carboxylic acids, trialkyl- or triaryl- phosphines, thiophenes and esters. Water is preferred.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, there is provided a solvent-free process for making solvent-free, fine white powders of copolymers of maleic anhydride and a C
1-
C
4
alkyl vinyl ether, preferably methyl vinyl ether, MVE, which are substantially free of homopolymers of alkyl vinyl ether monomer, i.e. poly(alkyl vinyl ether) homopolymers. These homopolymers ordinarily are produced by homopolymerization of excess alkyl vinyl ether present in the reaction mixture.
In this invention, an alkyl vinyl ether homopolymerization suppressor agent is included in the reaction mixture which thwarts cationic homopolymerization of the alkyl vinyl ether monomer while the desired free radical copolymerization of maleic anhydride and alkyl vinyl ether monomers can occur readily.
Suitable suppressor agents for use herein include water, alcohols, ammonia, amines, hydroxyamines, amides, phosphines, thiophene, carboxylic acids and esters. Water is most preferred.
Preferably water as the suppressor agent is present in a sufficient amount of about 500 to 5000 ppm by weight of the alkyl vinyl ether. Of course, an amount in excess of sufficient may be used, if desired.
Suitably the MAN:MVE mole ratio is at least 3, preferably 25:1 to 5:1, and, most preferably 12:1 to 7:1. The % solids level during polymerization is about 10-40%.
The free radical initiator concentration is about 0.01 to 0.2%, preferably 0.05 to 0.1%, by weight, based on the copolymer obtained.
Usually, varying concentrations of homopolymer are found in the copolymer product. The use of suppressor agent during copolymerization reduces this amount to a level under the detection limit for NMR analysis of the copolymer, i.e. <1 molar % of homopolymer.
After polymerization is complete, the excess MVE is stripped off and the copolymer is dried at about 40-100° C. under vacuum.
The invention will now be described with reference to the following examples, in which:
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patent: 2782181 (1957-02-01), Verburg et al.
patent: 3003988 (1961-10-01), Germann et al.
patent: 3868432 (1975-02-01), Keegan et al.
patent: 4962185 (1990-10-01), Tazi et al.
patent: 5147963 (1992-09-01), Plochocka et al.
patent: 5214089 (1993-05-01), Login et al.
patent: 5369145 (1994-11-01), Gasman et al.
patent: 5449715 (1995-09-01), Plochocka et al.
patent: 5939506 (1999-08-01), Plochocka
“Polymer Handbook”, 2-d edition, J. Brandrup, J. Willey & Sons, NY, pp. 11-391-98, 1974.
Davis William J.
ISP Investments Inc.
Katz Walter
Maue Marilyn J.
Wu David W.
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