Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Patent
1992-11-30
1995-06-06
Schofer, Joseph L.
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
210632, 528491, C08F 616
Patent
active
054222699
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the decomposition of ethylenically unsaturated carboxylic esters, in particular acrylate and methacrylate esters. It also relates to latexes treated by the process.
Methyl, ethyl, butyl and higher acrylates and methacrylates are useful monomers which can be polymerised to form plastics especially thermoplastics materials having a wide range of uses. In particular these materials find extensive applications in coating compositions, e.g. paints, varnishes and stains and in wall covering materials. The utility of acrylate and methacrylate polymers is limited to some extent because they are generally contaminated with unreacted acrylate and methacrylate monomers which, particularly in the case of ethyl and butyl acrylates, can impart an unpleasant smell to the polymer. The unreacted monomer may be present in amounts up to 1000 or 2000 ppm in some polymers and is considered quite malodorous when present in amounts above 50 ppm. Contamination with unreacted monomer is particularly a problem when the polymer is used in paints and wall coverings when the smell is especially noticeable. This problem has for some considerable time concerned manufacturers of paints and wall coverings but, to date, no fully satisfactory solution has been found. Proposed methods for removing unreacted monomers from acrylate and methacrylate polymers have suggested using chemical treatments including those disclosed in U.S. Pat. No. 4,766,173 (treatment with cysteine and lysine), European Published Patent Application 0273651A (treatment with a scavenger monomer such as vinyl acetate) and German Offenlegenschrift 3635367.
We have now found that unreacted acrylate and methacrylate monomers can be removed from polymers by treatment with suitable enzymes.
Accordingly the present invention provides a method of removing residual amounts of an ethylenically unsaturated carboxylic acid ester monomer from a dispersion in a continuous liquid phase of particles of a polymer which contains residues derived from the ester monomer, which method comprises contacting the dispersion with a hydrolytic enzyme capable of decomposing the ester monomer in the presence of the stabilized dispersed polymer, under conditions suitable for the enzyme to decompose the ester.
Further according to the present invention we provide a latex comprising a polymerised ethylenically unsaturated carboxylic ester which contains at least 0.001% by weight (based on the weight of the latex) of a hydrolytic enzyme capable of decomposing the ester monomer.
BRIEF EXPLANATION OF THE DRAWINGS
In the accompanying Figures, FIGS. 1 to 3 are graphs showing the reduction of acrylate monomer levels occurring on treatment of polymer dispersions with enzymes according to the invention.
The process of the invention is especially suitable for the decomposition of unreacted acrylate and methacrylate monomers from acrylate and methacrylate polymers. Typically, the corresponding monomers are alkyl acrylate and/or methacrylate esters and usually the alkyl groups are C.sub.1 to C.sub.10 alkyl groups including, for example, ethyl, butyl and `iso-octyl` (2-ethylhexyl) alkyl groups, together with pigments fillers and additives such as are commonly used in paint formulations. The process is also especially useful when the unreacted monomer is present in only trace amounts, say less than 2000 ppm. It can be used to treat polymers which are intended for any purpose but has particular advantages when used to treat polymers for use in wall coverings and coatings compositions e.g. paints, varnishes and stains. Treatment of the polymer with the enzyme can be carried out at any stage during its production or the treatment can be applied to the final products, e.g. the paint containing the polymer together with pigments fillers and additives such as are commonly used in paint formulations.
In the process of the invention any hydrolytic enzyme may be used which is capable of causing the decomposition of the ester monomer, especially an acrylate or methacrylate ester, t
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Carber Mark A.
Nicks Peter F.
Relton Julian M.
Imperial Chemical Industries plc
Schofer Joseph L.
Weber Tom
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