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...
Reexamination Certificate
2002-08-15
2003-11-04
Teskin, Fred (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...
C524S760000, C525S025000, C525S042000, C525S043000, C525S168000, C525S538000, C526S079000, C526S086000, C526S219000
Reexamination Certificate
active
06642306
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
This application claims benefit to International Application No. PCT/FR00/02401 (corresponding to publication number WO 01/21665), filed Mar. 29, 2001, which claims benefit of priority from French Application No. 99.11834, filed Sep. 22, 1999. The present invention relates to a process for preparing low-viscosity stable dispersions, that are free of toxic initiator residue, of (co)polymers in a polyol. More particularly, the invention relates to the in situ polymerization of an ethylenically unsaturated monomer or mixture of monomers in a polyol, in the presence of a particular azo initiator.
(ii) Description of Related Art
Dispersions of grafted copolymers prepared by the in situ polymerization of an ethylenically unsaturated monomer or mixture of monomers in a polyol in the presence of a free-radical initiator are known, as emerges from patents U.S. Pat. No. 3,652,659, U.S. Pat. No. 3,875,258 and U.S. Pat. No. 3,950,317. Among the various methods for preparing dispersions of grafted copolymers disclosed in these patents, the one that is particularly preferred consists in injecting at constant speed, into a reactor containing polyol, simultaneously monomer and initiator dispersed in a fraction of the polyol. According to the abovementioned patents, although numerous initiators may be suitable, it is nevertheless preferable to use azobis(isobutyronitrile) AIBN.
Although AIBN is the preferred initiator for the polymerization, it nevertheless has the drawback of being solid at room temperature and of being very sparingly soluble in the polyol, thus making it necessary for the initiator dispersion to be stirred constantly so that the amount of AIBN injected into the reactor is constant over time. In addition, the decomposition of AIBN during the reaction leads to the formation of side products, such as tetramethylsuccinonitrile, that are highly toxic and whose removal from the copolymer dispersion would be extremely difficult, if not impossible.
Moreover, patent U.S. Pat. No. 4,161,468 describes a process for preparing dispersions of grafted copolymers by in situ polymerization of an ethylenically unsaturated monomer or mixture of monomers in a polyol, in the presence of an asymmetrically substituted liquid azo compound with a half-life at a temperature of between 55 and 100° C. of 10 hours. The liquid azo compound defined in the said document is represented by formula (I):
in which R is an alkyl radical with a carbon number of between 1 and 6, R
1
is chosen from the group formed by an alkyl radical with a carbon number of between 1 and 20, a phenylalkyl radical containing from 7 to 12 carbon atoms and a cycloalkyl radical containing from 3 to 12 carbon atoms; R
2
is an alkyl radical with a carbon number of between 1 and 6 or a phenyl radical; and Z is either a hydrogen atom or a C≡N group.
SUMMARY OF THE INVENTION
The Applicant has now developed a process for preparing stable dispersions of (co)polymers in a polyol by in situ polymerization of an ethylenically unsaturated monomer or mixture of monomers in the presence of a novel family of azo initiator.
This novel family is represented by the azocarboxylic acid esters of formula (II)
in which:
R
1
, R
2
, R
3
and R
4
, which may be identical or different, are independently selected from the group consisting of
linear or branched alkyls containing from 1 to 9 carbon atoms and preferably from 1 to 4 carbon atoms, optionally substituted with one or more substituents selected from hydroxyl, C
1
to C
6
alkoxy and halogen substituents;
C
3
to C
12
cycloalkyls, optionally substituted with one or more substituents selected from C
1
to C
6
alkyl, C
1
to C
6
alkoxy, hydroxyl and halo groups;
aralkyls optionally substituted with one or more C
1
to C
6
alkyl, C
1
to C
6
alkoxy, hydroxyl and halo groups;
aryls optionally substituted with one or more substituents selected from C
1
to C
6
alkyl, C
1
to C
6
alkoxy, hydroxyl and halo groups; with at least one of the combinations R
1
-R
2
and R
3
-R
4
possibly forming an aliphatic ring; R″ and R′ are identical or different and are independently selected from the group consisting of linear or branched C
1
to C
10
and preferably C
1
to C
4
aliphatic radicals.
The advantage of these azocarboxylic acid esters is their low melting point, which is generally less than 27° C. The preferred azocarboxylic acid esters are those in which R″ and R′ represent methyl or ethyl and in which R
1
, R
2
, R
3
and R
4
advantageously represent C
1
to C
4
alkyl groups.
The azocarboxylic acid ester that is particularly preferred is diethyl 2,2′-azobisiso-butyrate, that is to say with R
1
, R
2
, R
3
and R
4
representing methyl and R′ and R″ representing ethyl. A mixture of diethyl 2,2′-azobisisobutyrate (DEAB) and dimethyl 2,2′-azobisisobutyrate (DMAB) with a content by mass of DEAB preferably of greater than 50% gives very advantageous results. Mixtures of DEAB, DMAB and 2-methyl ethyl 2′-azobisisobutyrate, preferably with a COOMe/COOEt molar ratio ≦10, may be suitable.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The azocarboxylic acid esters of formula (II) may be prepared by a conventional two-step process comprising a first step of converting the azonitrile, by reaction with an alcohol, in the presence of HCl, according to the Pinner reaction, leading to the corresponding azo imino ether hydrochloride, and a second step of hydrolysis in the presence of the hydrochloride thus obtained. They may also be prepared by improved processes as described in documents DE 2 254 472, EP 80 275 and EP 230 586.
In addition, these esters may be prepared by reacting an azonitrile with an alcohol and hydrochloric acid in an aromatic solvent, with an HCl/azonitrile molar ratio >2 when the alcohol is methanol and >3 when the alcohol is ethanol or a higher alcohol.
The amount of azocarboxylic acid esters used in the process according to the present invention represents about 0.1% to 6% by weight of the ethylenically unsaturated monomer(s) used, and preferably 0.5% to 4% by weight.
The ethylenically-unsaturated monomers that may be used in the process of the invention are, for example, butadiene, isoprene, 1,4-pentadiene, 1,6-hexadiene, 1,7-octadiene, styrene, &agr;-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, methylstyrene, cyclohexylstyrene, benzylstyrene, etc.; other substituted styrenes, for instance chlorostyrene, 2,5-dichlorostyrene, bromostyrene, fluorostyrene, trifluoromethylstyrene, iodostyrene, cyanostyrene, nitrostyrene, N,N-dimethylaminostyrene, acetoxystyrene, methyl 4-vinylbenzoate, phenoxystyrene, p-vinylphenyl phenyl sulphide, p-vinylphenyl phenyl oxide, etc.; acrylic and substituted acrylic monomers, for instance acrylonitrile, acrylic acid, methacrylic acid, methyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, isopropyl methacrylate, octyl methacrylate, methacrylonitrile, methyl &agr;-chloroacrylate, ethyl &agr;-ethoxyacrylate, methyl &agr;-acetaminoacrylate, butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, phenyl methacrylate, &agr;-chloroacrylonitrile, N,N-dimethylacrylamide, N,N-dibenzylacrylamide, N-butylacrylamide, methacrylylformamide, etc.; vinyl esters, vinyl ethers, vinyl ketones, etc., for instance vinyl acetate, vinyl chloroacetate, vinyl alcohol, vinyl butyrate, isopropenyl acetate, vinyl formate, vinylidene chloride, vinyl methoxyacetate, vinyl benzoate, vinyl chloride, vinyl iodide, vinyltoluene, vinylnaphthalene, vinyl bromide, vinyl fluoride, vinylidene bromide, 1-chloro-1-fluoroethylene, vinylidene fluoride, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ethers, butyl vinyl ethers, 2-ethylhexyl vinyl ether, phenyl vinyl ether, 2-methoxyethyl vinyl ether, methoxybutadiene, 2-butoxyethyl vinyl ether, 3,4-dihydro-1,2-pyran, 2-butoxy-2′-vinyloxyethyl ethyl ether, 2-ethylme
Cerf Martine
Wnuk Mieczyslaw
Atofina
Hunton & Williams LLP
Teskin Fred
LandOfFree
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