Use of hydroperoxides as regulators in polymerizations

Details Use of hydroperoxides as regulators in polymerizations Use of hydroperoxides as regulators in polymerizations

2002-01-29

2003-08-05

Pezzuto, Helen L. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S779000, C524S783000, C524S787000, C524S812000, C524S817000, C524S819000, C524S821000, C524S833000

Reexamination Certificate

active

06602951

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to the use of non-copolymerizable hydroperoxides of the general formula R—O—O—H as regulators in the free-radically initiated polymerization of ethylenically unsaturated monomers.
2. Background Art
Free-radical initiators or free-radical initiator combinations are used for initiating the polymerization of ethylenically unsaturated monomers. If the molecular weight of the resulting polymers is to be reduced to a desired value, it is usual to employ regulators in addition to the initiator. Customary regulators are, for example, mercaptans such as mercaptopropionic acid, 2-mercaptoethanol, 2-mercaptopropanol, mercaptoacetic acid, tert-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and tert-dodecyl mercaptan. Further examples of regulators are hydroxylammonium salts such as hydroxylammonium sulfate; organic solvents such as toluene, diethylbenzene and xylene; halogenated solvents such as chloroform; formic acid; sodium bisulfite; and alcohols such as methanol. A disadvantage of these regulators is that mercaptans and halogenated hydrocarbons have a strong odor and are of concern from a toxicological point of view. Furthermore, both mercaptans and halogenated hydrocarbons are difficult to remove from the polymer dispersion formed.
U.S. Pat. No. 3,800,007 describes the bulk, solution, emulsion and suspension polymerization of &agr;, &bgr;-unsaturated monomers using alkyl- or cycloalkyl-substituted cumene peroxides. The cumene peroxides are used in the temperature range of from −10° C. to 70° C. as auxiliaries for preparing peroxide-functional graft and block copolymers in a first step. In a second step, in the temperature range of from 80° C. to 150° C., the peroxide groups then decompose and initiate the graft or block copolymerization with further comonomers.
WO-A 95/30697 describes the use of organic peracids R—CO—O—O—H as regulators in polymerization reactions. The peracid is added in addition to a standard initiator in the polymerization, with the initiators being selected so that the polymerization takes place at a temperature below the decomposition temperature of the regulator.
WO-A 91/07440 discloses copolymerizable allyl hydroperoxides as regulators in polymerization processes. The objective was to provide reactive crosslinkable macromonomers for moldings and coatings. Owing to the bifunctionality of these molecules in having both an unsaturated group as well as a peroxidic group, polymers with bifunctional end groups which can subsequently be reacted by polymer-analogous reactions to provide epoxide functions are produced. The allyl hydroperoxides become fixed constituents of the polymer chain, thus altering the properties of the polymer, which is generally not desired. The copolymerizable allyl hydroperoxides also influence (slow) the polymerization behavior of the other monomers. Depending on the respective reactivities, the result can be different polymer compositions which in turn produce unique polymer properties.
SUMMARY OF THE INVENTION
It is an object of the invention to provide substances which are suitable for regulating the molecular weight in polymerizations and which can also be used without an additional initiator system, for simultaneously initiating the polymerization and regulating the molecular weight.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The invention provides for the use of non-copolymerizable hydroperoxides of the general formula R—O—O—H as regulators in the free-radically initiated polymerization of ethylenically unsaturated monomers, where R is H, a C
1
-C
18
-alkyl radical, a C
7
-C
22
-aralkyl radical or a saturated or unsaturated carbocyclic or heterocyclic ring having from 3 to 18 carbon atoms. The hydrocarbon radicals R may be substituted or unsubstituted.
The radical R may be unbranched or branched and may be substituted by one or more substituents selected from the group consisting of halogen, hydroxy, alkoxy, aryloxy, epoxy, carboxyl, ester, amido, nitrile and keto groups. Preferred radicals R are, in addition to hydrogen, isopropyl, tert-butyl, tert-pentyl, 1,1-dimethylbutyl, and 1,1-dimethylpentyl radicals, each of which may be further substituted by an OH group. A preferred aralkyl radical is the cumene radical. As carbocyclic radicals, preference is given to the menthol and pinene radicals.
Particular preference is given to hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, tert-pentyl hydroperoxide, 1,1-dimethylbutyl hydroperoxide, 1,1-dimethylpropyl hydroperoxide, 1,1-dimethyl-3-hydroxybutyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, p-menthyl hydroperoxide, pinanyl hydroperoxide, 1-methylcyclopentyl hydroperoxide, 2-hydroperoxy-2-methyltetrahydrofuran, 1-methoxycyclohexyl hydroperoxide, 1,3,4,5,6,7-hexahydro-4a(2H)-naphthalenyl hydroperoxide, &bgr;-pinene hydroperoxide, and 2,5-dihydro-2-methyl-2-furanyl hydroperoxide.
The non-copolymerizable hydroperoxides can be used as regulators in conjunction with an initiator system. In a preferred embodiment, the hydroperoxides are used simultaneously as regulator and initiator without further free-radical initiators being employed. In general, the amount of hydroperoxide is from 0.01 to 15% by weight, preferably from 0.1 to 5% by weight, particularly preferably from 0.5 to 3% by weight, in each case based on the total weight of monomers.
As monomers, it is possible to use one or more monomers selected from the group consisting of vinyl esters of unbranched and branched alkylcarboxylic acids having from 1 to 18 carbon atoms; acrylic esters and methacrylic esters of branched and unbranched alcohols and diols having from 1 to 18 carbon atoms; ethylenically unsaturated monocarboxylic and dicarboxylic acids, their amides and N-methylolamides and nitriles; ethylenically unsaturated sulfonic acids; ethylenically unsaturated heterocyclic compounds; dienes; olefins; vinylaromatics; and vinyl halides.
Suitable vinyl esters are those of carboxylic acids having from 1 to 12 carbon atoms. Preference is given to vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of &agr;-branched monocarboxylic acids having from 9 to 11 carbon atoms, for example VeoVa9
R
or VeoVa10
R
(trade names of Shell). Particular preference is given to vinyl acetate.
Suitable monomers from the group consisting of acrylic esters and methacrylic esters are esters of unbranched or branched alcohols having from 1 to 15 carbon atoms. Preferred methacrylic esters and acrylic esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, 2-ethylhexyl acrylate. Particular preference is given to methyl acrylate, methyl methacrylate, n-butyl acrylate, t-butyl acrylate and 2-ethylhexyl acrylate.
Examples of suitable ethylenically unsaturated monocarboxylic and dicarboxylic acids and their amides, N-methylolamides, and nitriles, are acrylic acid, methacrylic acid, fumaric acid, maleic acid, acrylamide, N-methylolacrylamide, N-methylolmethacrylamide, and acrylonitrile. Examples of ethylenically unsaturated sulfonic acids are vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. Suitable ethylenically unsaturated heterocyclic compounds are N-vinylpyrrolidone and N-vinylpyridine.
Preferred vinylaromatics are styrene, methylstyrene and vinyltoluene. The preferred vinyl halide is vinyl chloride. Preferred olefins are ethylene and propylene, and preferred dienes are 1,3-butadiene and isoprene.
If desired, from 0.1 to 5% by weight, based on the total weight of the monomer mixture, of auxiliary monomers can additionally be copolymerized. Preference is given to using from 0.5 to 2.5% by weight of auxiliary monomers. Examples of auxiliary monomers are ethylenically unsaturated monocarboxylic and dicarboxylic acids, preferably acrylic acid, methacryl

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