Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-10-17
2002-06-04
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C558S261000
Reexamination Certificate
active
06399728
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to compositions classified in the art of chemistry as dialkyl peroxydicarbonates, more specifically to new and novel thermally-stabilized initiator compositions comprising dialkyl peroxydicarbonates stabilized by the addition thereto of a stabilizing effective amount of at least one stabilizing compound selected from the group consisting of diesters of unsaturated dicarboxylic acids. The invention further relates to the use of such novel compositions as initiators of polymerization or cure of ethylenically unsaturated monomers, oligomers and polymers. The invention still further relates to the stabilization of dialkyl peroxydicarbonates during their manufacture by the inclusion of stabilizing effective amount of at least one stabilizing compound selected from the group consisting of non-hydrolyzable diesters of unsaturated dicarboxylic acids in the mixture of reactants from which a dialkyl peroxydicarbonate is to be prepared prior to, at the commencement of, or during the preparative reaction.
DESCRIPTION OF PRIOR ART
Generally, dialkyl peroxydicarbonates which are in liquid form (molten or in solution) above ca. 10. degree. c. are very hazardous owing to auto-accelerated decomposition attributed to induced decomposition of the dialkyl peroxydicarbonate.
Strain, et al. (J. Am. Chem. Soc., 1950, 72, 1254-1263) found that auto-accelerated decomposition of diisopropyl peroxydicarbonate (IPP) at room temperature could be largely suppressed by incorporating small quantities of additives such as iodine (1%) phenol (1%), hydroquinone (1%), resorcinol (1%), pyrogallol (1%), tetralin (1%), ethyl acetoacetate (1%), acetanilide (1%), trinitrobenzene (1%), 30% hydrogen peroxide (1%) and several other additives. However, when such stabilizing compositions are used to polymerize vinyl chloride monomer (VCM), there is potential for contamination of the resulting PVC resin by the additives. This contamination is undesirable, both for the PVC resin as well as for the environment. Because the thermally stabilized dialkyl peroxydicarbonate compositions of the instant invention contain olefinic unsaturation, the diluent is copolymerized with VCM at very low levels and, thus, does not contaminate the PVC resin or the effluent from the polymerization process.
U.S. Pat. No. 5,155,192 discloses stabilized peroxydicarbonate compositions containing small amounts (0.03 to 3.0 equivalent percent) of compounds containing hydroperoxy groups. Such compositions are claimed to reduce sensitivity to auto-accelerative decompositions, increase safe storage temperatures and increase self-accelerating decomposition temperatures (SADTs). However, polymer producers such as PVC producers do not like to employ initiators containing significant levels of hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide since these impurities are free-radical chain-transfer agents and can become incorporated into the resin molecular chains as peroxy end groups. Such labile end groups can adversely affect the thermal and color stability of the resin. In addition, the lower molecular weight t-alkyl hydroperoxides such as t-butyl and t-amyl hydroperoxides are sufficiently volatile to cause problems during recycle of vinyl chloride and other monomers.
The thermally stabilized dialkyl peroxydicarbonate compositions of the instant invention, which contain compounds having olefinic unsaturation advance the peroxide art and the polymerization art since they do not cause the above resin stability problems or monomer recycle problems.
U.S. Pat. Nos. 5,541,151 and 5,548,046 disclose stabilized peroxydicarbonate solutions containing small amounts (0.05 to 1.4 equivalent percent) of compounds having an ethylenically unsaturated functional group conjugated with an acetylenic or nitrile functional group. Such compositions are stated to enhance safety for manufacture, storage, handling and use of pure liquid dialkyl peroxydicarbonates. Polymer producers, such as polyvinylchloride manufacturers prefer not to use initiators stabilized with compounds having ethylenic unsaturation conjugated with acetylenic or nitrile groups, such as acrylonitrile or methacrylonitrile due to toxicity and waste water concerns. These compounds are toxic and/or carcinogenic and would require special waste water handling and permits.
U.S. Pat. No 5,654,463 discloses the use of &agr;-hydroxyalkyl peroxide compounds to retard the rate of decomposition of organic peroxides such as peroxydicarbonates. However, the addition of such higher half-life peroxides can cause problems during the recycle of vinyl chloride or other monomers and can cause gel formation during stripping of the resin.
U.S. Pat. No. 5,654,464 discloses the use of cyclic &agr;-diketone compounds to retard the rate of decomposition of organic peroxides, such as peroxydicarbonates. U.S. Pat. No. 5,714,626 discloses the use of &bgr;-dicarbonyl compounds to retard the rate of decomposition of organic peroxides, such as peroxydicarbonates. U.S. Pat. No. 5,719,304 discloses the use of phosphomolybdic acid to retard the rate of decomposition of organic peroxides, such as peroxydicarbonates. However, polymer producers, including polyvinylchloride manufacturers do not like to employ peroxides stabilized using these materials since their use introduces impurities which can cause toxicity and quality problems in the final resin.
U.S. Pat. Nos. 4,131,728 and 4,178,263 disclose shock desensitized peroxide compositions which comprise a mixture of shock sensitive peroxide and a diluent. The diluent is a monomeric material containing olefinic unsaturation which does not readily homopolymerize. Peroxydicarbonates are not included in the types of peroxides which are illustrated as suitable for use in the invention of these patents. The stabilization by the various monomeric materials is for the express purpose of reducing the shock sensitivity of the peroxides being stabilized and the monomeric materials are also stated to not adversely affect the heat distortion temperatures of the final resin. There is no known correlation between the ability to reduce shock sensitivity and the ability to reduce auto-accelerated decomposition, increase safe storage temperatures or raise SADTs.
The lack of correlation can be seeing using the data in the following tables.
Peroxide
Diluent
Time to Decomposition
1,1-dimethyl-3-hydroxybutyl
OMS
33 hours
peroxyneodecanoate
1,1-dimethyl-3-hydroxybutyl
Dibutyl
31 hours
peroxyneodecanoate
Maleate
&agr;-cumyl peroxyneodecanoate
OMS
27 hours
&agr;-cumyl peroxyneodecanoate
Dibutyl
22 hours
Maleate
% Assay Loss during Storage
t-Butyl Peroxyneodecanoate (75%) in OMS
O° C.
5° C.
10° C.
4 weeks
1.4
4.3
10.3
8 weeks
3.4
8.9
19.3
12 weeks
5.7
13.0
27.2
t-Butyl Peroxyneodecanoate (75%) in Dibutyl Maleate
O° C.
5° C.
10° C.
4 weeks
2.0
3.9
6.5
8 weeks
4.9
13.7
15.3
12 weeks
12.4
20.2
30.0
The dibutyl maleate will have decreased the shock sensitivity as mentioned in the two aforementioned patents, but did not increase the safety characteristics of the peroxyesters. Quite unexpectedly, the safety characteristics of peroxydicarbonates are increased with the practice of the instant invention (Tables I, II, III, IV).
The above two patents also disclose that any solvent will reduce shock sensitivity but that some will also have a deleterious effect on properties of the polymer produced. Among the monomeric diluents disclosed as suitable for the invention of these patents are many that cannot be used during the manufacturing process of organic peroxides. Solid diluents may interfere with aqueous separations and many of the proposed compounds will hydrolyze under peroxide production conditions leaving pure unstabilized peroxide in the reactor at elevated temperatures; an extremely dangerous and undesirable state. Furthermore, the organic peroxides disclosed in these patents are no longer considered shock sensitive by today's standard test methods.
It is generally known to organic peroxide producers, see the Strain reference cited abov
Brennan Joseph M.
Callais Peter A.
Mendolia Michael S.
Myers Terry N.
Stainbrook Barbara L.
ATOFINA Chemicals, Inc.
Henderson Christopher
Mitchell William D.
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