Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-06-11
2002-04-30
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S292000
Reexamination Certificate
active
06380318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a modified acrylic rubber and more particularity to a process for producing a peroxide-crosslinkable, modified acrylic rubber.
2. Description of Related Art
Acrylic rubbers are widely used as molding materials for hoses, various seal materials, etc. due to its relative low production cost as well as good heat resistance and oil resistance, but requirements for its higher functionability and lower production cost are still now in increasing demand.
For lower production cost, it is highly desired to shorten the processing time and molding time of crosslinkable compositions, and various attempts have been so far made for that purpose. Attempts to increase the crosslinking speed, which relates to the shortening of molding time, inevidently deteriorates the scorch resistance and thus a more practical, stable crosslinking systems are in keen demand.
Systems capable of satisfying both high speed crosslinkability and scorch resistance at the same time include a peroxide-based crosslinking system, which has been so far widely studied but still has problems.
(1) A process for copolymerizing dienes, for example, 5-alkylidene-2-norbornene, etc. to introduce crosslinkable unsaturated groups into side chains (JP-A-49-87787) has such a disadvantage as poor processability, etc. of the product due to interreaction of the crosslinkable unsaturated groups during the copolymerization reaction to cause intermolecular bridging.
(2) A process for crosslinking reaction between the side chains of alkoxyalkyl acrylate in the acrylic copolymers and a bismaleimide compound used as a crosslinking aid (JP-A-5-214196) has such a disadvantage as poor compression set when subjected to vulcanization molding into O-rings.
(3) Acrylic rubber containing iodine or bromine as crosslinking sites can be crosslinked with a peroxide, but the iodine- or bromine-containing, crosslinkable monomers to be introduced into copolymers are generally expensive with failure to satisfy the requirements for lower production cost.
(4) A process for graft polymerization of monomers having a polymerizable, unsaturated group can be used as a procedure for introducing crosslinkable unsaturated groups (JP-A-3-221513), but use of an organic solvent in the reaction is with failure to satisfy the requirements for lower cost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for producing a modified acrylic rubber in the absence of a solvent, the modified acrylic rubber so produced being distinguished in the molding charactertics and O-ring compression set.
The object of the present invention can be attained by a process for producing a modified acrylic rubber, which comprises mixing an acrylic rubber having reactive functional groups with an unsaturated compound reactive with the reactive functional group with heating in the absence of a solvent.
DETAILED DESCRIPTION OF THE INVENTION
An acrylic rubber having reactive groups for use in the present invention includes, for example, acrylic copolymers obtained by copolymerizing at least one of alkyl acrylate and alkoxyalkyl acrylate as the main component with about 0.5 to about 10% by weight, preferably about 1% to about 8% by weight, on the basis of the acrylic copolymer, of a monomer having an active chlorine group, a carboxyl group, an epoxy group, an active ester group or the like.
Alkyl acrylate for use in the present invention includes, for example, alkyl acrylates having an alkyl group with 1 to 8 carbon atoms (the alkyl group may further having a substituent such as a cyano group, etc.) such as methyl acrylate, ethyl acrylate, n- or iso-propyl acrylate, n- or iso-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-cyanoethyl acrylate, etc., preferably ethyl acrylate and n-butyl acrylate, and further methyl methacrylate, ethyl methacrylate and n-butyl methacrylate.
Alkoxyalkyl acrylate for use in the present invention includes, for example, alkoxyalkyl (meth)acrylates having an alkoxyalkyl group with 2 to 8 carbon atoms such as methoxymethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, and the corresponding mathacrylates, etc., preferably 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate.
At least one of these alkyl acrylates and alkoxyalkyl acrylates can be used in a proportion of 99 to 50% by weight, preferably 98 to 70% by weight, as the main component of the acrylic copolymer, and both alkyl acrylate and alkoxyalkyl acrylate, when used together, can be generally in a ratio of the former to the latter of about 90 to about 10: about 10 to about 90% by mole.
A portions particularly up to about 20% by weight of the acrylic copolymer can be replaced with other copolymerizable monomer, followed by copolymerization of the resulting mixture. Such other copolymerizable monomer includes, for example, ethylene, propylene, vinyl chloride, vinylidene chloride, acrylonitrile, styrene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, alkyl methacrylate, alkoxyalkyl methacrylate, etc.
Monomers (vinyl monomers) having a reactive functional group, which are to be copolymerized with the main component into the acrylic rubber include, for example, monomers having an active chlorine group, a carboxyl group, an epoxy group, an active ester group, etc.
The monomers having an active chlorine group include, for example, 2-chloroethyl vinyl ether, 2-chloroethyl acrylate, vinyl monochloroacetate, chloromethylstyrene, etc. The monomers having a carboxyl group include, for example, (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid monoester, fumaric acid monoester, etc. The monomers having an epoxy group include, for example, allyl glycidyl ether, glycidyl vinyl ether, glycidyl (meth)acrylate, (meth)acrylates containing an alicyclic epoxy group, etc. The monomers having an active ester group include, for example, (meth)acrylates having a phenyl group such as phenyl (meth)acrylate, cyanophenyl (meth)acrylate, nitrophenyl (meth)acrylate, etc.
Unsaturated compounds reactive with the reactive functional group originating from these monomers copolymerized into the acrylic copolymer include the following compounds.
Unsaturated compounds reactive with the active chlorine group include, besides the above-mentioned monomers having a carboxyl group, such unsaturated compounds having a carboxyl group as:
CH
2
═CRCOOR
1
(OCOR
2
)nCOOH,
CH
2
═CRCOOR
1
OCOPhCOOH,
where R represents a hydrogen atom or a methyl group; R
1
and R
2
each represent an alkylene group having 1 to 6 carbon atoms; Ph represents a phenylene group; and n is an integer of 1 to 6,
vinyl acetic acid,
2-(meth)acryloyloxyethyl succinate,
2-(meth)acryloyloxyoxyethyl phthalate,
2-(meth)acryloyloxyethyl hexahydrophthalate; and,
(PAB-MI, trademark of a product from Mitsui Chemical Corporation, Japan).
Reaction of the unsaturated compound with the acrylic copolymer having active chlorine groups can be carried out in the presence of such an acid acceptor as calcium hydroxide, magnesium hydroxide, synthetic hydrotalcite, sodium stearate, potassium stearate, sodium 2-ethylhexanoate, etc. and typically such a quaternary onium salt as benzyltriphenylphosphonium chloride, tetrabutylammonium bromide, etc. Furthermore, unsaturated compounds containing a thiol group such as allylmercaptan, etc. can be used and also subjected to the reaction in the presence of an acid acceptor and a quaternary onium salt.
Unsaturated compounds reactive with the carboxyl group of the acrylic copolymer having carboxyl groups include, for example, unsaturated compounds having a primary amino group such as allylamine, aminostyrene, aminomethylstyrene, p-aminophenylene maleimide, etc. Reaction of the unsaturated compound with the acrylic copolymer having a carboxyl group can be carried out in the presence of a strongly basic compound such as guanidine, etc.
Unsaturated compounds reactive with the epoxy group o
Komiya Eiji
Okabe Jun
Saito Kuniyoshi
Baker & Daniels
Lipman Bernard
Nippon Mektron Limited
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