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
1998-12-04
2001-03-06
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C180S300000, C248S638000
Reexamination Certificate
active
06197885
ABSTRACT:
TECHNICAL FIELD
The present invention relates to vulcanized rubber parts useful to dampen and/or isolate vibrations generated by mechanical devices.
BACKGROUND
Machines such as automobile, truck or jet engines, compressors and industrial air conditioners, automotive exhaust systems and like dynamic devices generate significant vibration during operation. This vibration will be transmitted directly to support structures with which the dynamic devices is mounted or associated, e.g., an automobile or aircraft frame, a compressor frame, or a floor or rooftop. In order to minimize transfer of vibration from the operating dynamic device to the associated support structure, i.e., isolate the vibrations, it is common to interpose vibration damping and/or isolation means between the dynamic device and the associated support structure. Examples of such vibration damping and/or isolation means would be vibration-absorbing, elastomeric automobile or truck engine mounts placed between the brackets which are used to bolt the engine to the associated auto or truck frame, exhaust hangers, pads interposed between an air conditioner or compressor and a frame or floor and the like.
Vibration damping and/or isolation materials known in the art include vulcanized shapes, e.g., squares, rectangles or cylindrical shapes prepared from vulcanized rubber. These dampening and/or isolation devices can be solid rubber, foamed rubber or solid rubber enclosing a fluid-containing cavity. Suitable rubbers which have heretofore been used in such applications include halogenated and non-halogenated butyl rubber (copolymer of isobutylene with up to 10 wt % isoprene), natural rubber and synthetic elastomeric polymers and copolymers of butadiene.
In addition, EPA 0533746 discloses vibration damping materials based on a vulcanized mixture containing a halogenated copolymer of a C
4
to C
7
isomonoolefin and para-alkystyrene, carbon black, a plasticizer oil and a curing system.
Although natural rubber is an elastomer of choice in some applications because of its superior dynamic properties, i.e., good tensile, modulus and spring rate (stress/strain) properties, the aging and high temperature resistance of cured parts based on natural rubber vulcanizates are poor, thereby limiting the effective life of such parts. For example, engine mounts associated with modern engines must be able to withstand temperatures as high as 150° C. for periods in the range of 1,000 to 5,000 hours without significant loss of dynamic properties, in order to meet current and anticipated automotive standards.
SUMMARY
The present invention provides shaped rubber parts, either solid, foamed, or fluid filled useful to isolating vibrations and dampening vibrations generated by mechanical devices. More particularly, the invention provides mechanical devices comprising a dynamic means which generates heat and/or vibrations, e.g., an automotive engine, an electric motor, and a static structure which supports said dynamic means, e.g., an automotive frame, and which is connected to said dynamic means, e.g., by bolting together brackets attached to the frame and engine, and having a vulcanized rubber vibration, isolation, and/or damping part interposed between said dynamic means and said static structure at said point of connection, e.g., one or more disc-shaped rubber parts sandwiched between the engine and frame brackets. The improvement provided by the invention comprises the utilization as said rubber part of a shaped, vulcanized composition comprising a mixture of:
1. An elastomeric olefin polymer or copolymer,
2. an elastomeric, halogen-containing copolymer of a C
4
to C
7
isomonoolefin and a para-alkylstyrene, said halogen-containing copolymer comprising from 10 to 35 wt % of the elastomer content of the mixture;
3. a particulate filler; and
4. a curing system for said composition.
The elastomeric olefin polymer or copolymer can be derived from monoolefins or diolefins. Molded or shaped parts prepared from the vulcanized composition exhibit both excellent isolation and vibration damping properties at high and low temperatures and enhanced heat aging resistance, thereby rendering them particularly suitable for applications involving prolonged exposure to high temperatures.
DESCRIPTION
The halogen-containing elastomer present in the curable composition of this invention is a chlorinated or brominated interpolymer of a C
4
to C
7
isomonolefin and a para-alkylstyrene.
Halogenated interpolymers based on a C
4
to C
7
isomonoolefin, such as isobutylene, and a para-alkylstryrene, such as para-methylstyrene, are known in the art as evidenced by U.S. Pat. No. 5,162,445, the complete disclosure of which is incorporated herein by reference.
Preferred materials are the halogenation product of a random copolymer of a C
4
to C
7
isomonoolefin, such as isobutylene, and a para-alkylstyrene comonomer wherein at least some of the alkyl substituent groups present in the styrene monomer units contain halogen. Preferred materials may be characterized as isobutylene interpolymers containing the following monomer units randomly spaced along the polymer chains:
wherein at least about 5% of the comonomer units present in the polymer chain are of the structure of formula 2, R and R′ are independently hydrogen or C
1
to C
4
alkyl, R″ is independently hydrogen, C
1
to C
4
alkyl or X, and X is bromine or chlorine, and wherein the interpolymer is otherwise substantially free of any halogen in the polymer backbone chain.
With reference isobutylene as the isoolefin comonomer, these interpolymers are inclusive of:
1. copolymers consisting of isobutylene and a monomer having the structure of formula 2 wherein R″ is hydrogen or C
1
to C
4
alkyl, eg, copolymers of isobutylene and a monohalo-substituted para-alkylstyrene;
2. terpolymers comprising isobutylene and a mixture of monomers having the structure of formulas 1 and 2 wherein R″ is hydrogen or C
1
to C
4
alkyl, eg, terpolymers of isobutylene, a para-alkylstyrene and a monohalo-substituted para-alkylstyrene;
3. terpolymers comprising isobutylene and a mixture of monomers having the structure of formula 2 wherein, with respect to a major proportion of the formula 2 monomer, R″ is hydrogen or C
1
to C
4
alkyl and, with respect to a minor proportion of said formula 2 monomer, R″ is bromine or chlorine, eg, terpolymers of isobutylene, a mono-halo substituted para-alkylstyrene and a di-halo substituted para-alkylstyrene; and
4. tetrapolymers comprising isobutylene and a mixture of monomers having the structure of formulas 1 and 2 wherein, with respect to major proportion of the formula 2 monomer, R″ is hydrogen or C
1
to C
4
alkyl and, with respect to a minor proportion of said formula 2 monomer, R″ is bromine or chlorine, eg, tetrapolymers of isobutylene, a para-alkylstyrene, a monohalo-substituted para-alkylstyrene and a dihalo-substituted para-alkylstyrene.
As stated above, these halogenated interpolymers are prepared using a copolymer of a C
4
to C
7
isoolefin and a para-alkylstyrene as the halogenation substrate. Interpolymers having the composition (a), (b), (c) or (d) above will be produced as a function of the severity of the halogenation reaction. For example, mild halogenation will tend to yield interpolymers of the characteristics of (b), stronger halogenation will yield interpolymers of the characteristics of (a) or (d) and the strongest halogenation will yield terpolymers having the characteristics of (c).
The most preferred elastomers used in the compositions of the present invention are random elastomeric brominated terpolymers comprising isobutylene and para-methylstyrene (PMS) containing from about 0.5 to about 20 wt % PMS, more preferably from about 2 to about 15 wt % PMS, wherein up to about 65% of the PMS monomer units contain a mono-bromomethyl group. These elastomeric copolymers generally exhibit a number average molecular weight in the range of from about 50,000 to about 250,000, more preferably from about 80,000 to about 180,000. From
McElrath, Jr. Kenneth Odell
Yamashita Shinichiro
Exxon Chemical Patents Inc.
Kurtzman Myron B.
Nutter Nathan M.
Peebles Brent M.
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