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
2000-10-03
2002-06-11
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...
C525S217000, C525S221000, C525S222000, C525S232000, C525S238000
Reexamination Certificate
active
06403722
ABSTRACT:
TECHNICAL FIELD
This invention relates to dynamically vulcanized elastomeric blends including hydrogenated acrylonitrile-butadiene copolymers. More specifically, this invention is directed toward blends that include finely divided and well dispersed rubber particles within a matrix that includes hydrogenated acrylonitrile-butadiene copolymers. These blends can be employed as a substitute for substantially homogeneous blends of hydrogenated acrylonitrile-butadiene copolymer and are therefore economically advantageous.
BACKGROUND OF THE INVENTION
Hydrogenated acrylonitrile-butadiene copolymers, which may also be referred to as hydrogenated acrylonitrile-butadiene rubber or hydrogenated nitrile rubber, or simply HNBR, have proven to be very technologically useful. Indeed, hydrogenated nitrile rubber is distinguished by a high ultimate tensile strength, low abrasion, minimal permanent deformation after compressive and tensile stressing, high oil resistance, very high thermal stability, and excellent oxidative stability.
Unfortunately, hydrogenated nitrile rubber is expensive and therefore, although technologically useful, it is not always commercially useful. A possible solution to the economic disadvantages of using hydrogenated nitrile rubber is to blend hydrogenated nitrile rubber with other materials, such as other rubbers. In fact, elastomeric blends that include hydrogenated acrylonitrile-butadiene rubber are known. For example, U.S. Pat. No. 4,405,756 discloses a rubber composition that is co-vulcanizable with a sulfur cure system and includes 5 to 20 percent by weight of a partially hydrogenated unsaturated nitrile-conjugated diene copolymer rubber, 5 to 80 percent by weight of an ethylene-propylene-non-conjugated diene terpolymer rubber, and a required amount of at least one vulcanization accelerator selected from the group of thiuram accelerators and dithiocarbamate accelerators. These rubber compositions have the characteristics of the two rubbers that are employed including excellent oil resistance and ozone resistance and surprisingly show higher tensile strength and heat aging resistance than additively brought about by the mixing of the two rubbers.
U.S. Pat. No. 5,187,232 discloses a rubber blend that contains 20 to 60 percent by weight polychloroprene and 80 to 40 percent by weight hydrogenated nitrile rubber. Vulcanizates of this elastomeric blend demonstrate both high modulus and high dynamic stress-absorbing capacity.
European Patent Publication 0 555 781 A1 discloses a rubber composition comprising: i) partially hydrogenated unsaturated nitrile-conjugated diene copolymers having an iodine value not larger than 120, ii) an ethylenepropylene copolymer, and iii) a material selected from an ethylene-vinyl acetate copolymer, an acrylic rubber, and a hydrogenated butyl rubber. This rubber composition provides a vulcanized rubber having an improved constant-elongation fatigue performance, as well as a balanced thermal resistance, oil resistance, and other properties.
European Patent Publication 0 559 515 A1 discloses a rubber formulation comprising, based on the weight of the rubber formulation, i) 2 to 98 percent by weight of a hydrogenated nitrile rubber containing at least one functional group selected from a carboxylic acid group and an epoxy group, and ii) 98 to 2 percent by weight of an organopolysiloxane containing a functional group capable of reacting with the above-mentioned functional group. The hydrogenated nitrile rubber and the organopolysiloxane are crosslinked with and dispersed in each other.
U.S. Pat. No. 5,612,418 discloses a peroxide curable blend including a polyacrylate elastomer and a partially hydrogenated rubber. The cured product is characterized by having excellent heat and oil resistance, and is particularly suitable for making belts, hoses, gaskets and the like for use in automobile engines.
Therefore, there is a need for a material or blended material that exhibits the properties of hydrogenated nitrile rubber, and is therefore technologically useful, and that is likewise economical and therefore commercially useful.
SUMMARY OF INVENTION
It is, therefore, an object of the present invention to provide a material that exhibits the technologically useful characteristics of hydrogenated nitrile rubber.
It is another object of the present invention to provide a material that is more economical than hydrogenated nitrile rubber.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to elastomeric blends that contain hydrogenated acrylonitrile-butadiene rubber, will become apparent from the specification that follows and are accomplished by the invention as hereinafter described and claimed.
In general the present invention provides an elastomeric blend prepared by the steps comprising: dynamically vulcanizing a dynamically-vulcanizable elastomer within a mixture that comprises the dynamically-vulcanizable elastomer, a hydrogenated acrylonitrile-butadiene copolymer, and a vulcanizing agent that is specific for the dynamically-vulcanizable elastomer during dynamic vulcanization.
The present invention also includes a vulcanizate prepared by the steps comprising: dynamically vulcanizing a dynamically-vulcanizable elastomer within a mixture that comprises the dynamically-vulcanizable elastomer, a hydrogenated acrylonitrile-butadiene copolymer, and a vulcanizing agent that is specific to the dynamically-vulcanizable elastomer during dynamic vulcanization, and effecting vulcanization of the hydrogenated acrylonitrile-butadiene copolymer.
The present invention also includes an elastomeric blend comprising: from about 25 to about 75 parts by weight of total polymer in the elastomeric blend of hydrogenated acrylonitrile-butadiene copolymer; and from about 75 to about 25 parts by weight of total elastomer in the elastomeric blend of dynamically vulcanized elastomer, where said dynamically vulcanized elastomer is in the form of vulcanized particles having an average diameter below about 1.4 micrometers.
The present invention also includes a vulcanizate comprising: from about 25 to about 75 parts by weight of vulcanized acrylonitrile-butadiene copolymer; and from about 75 to about 25 parts by weight of a dynamically vulcanized elastomer, where said dynamically vulcanized elastomer is in the form of vulcanized particles having an average diameter below about 2 &mgr;m and are dispersed throughout the said vulcanized hydrogenated acrylonitrile-butadiene copolymer.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
It has now been found that certain dynamically vulcanized blends that include hydrogenated acrylonitrile-butadiene copolymers (HNBR) as the continuous phase exhibit many of the properties of substantially homogeneous compositions of HNBR. Accordingly, the dynamically vulcanized blends of this invention are technologically useful and provide many economic benefits.
The blends of this invention are dynamically vulcanized and are characterized by the presence of finely divided and well dispersed rubber particles within a matrix that includes HNBR. Those skilled in the art will appreciate that dynamic vulcanization refers to the crosslinking of at least one elastomeric polymer within a blend with at least one other non-vulcanizing polymer while both polymers are undergoing mixing or masticating at some elevated temperature, and where the mixing or masticating continues until vulcanization is essentially complete. According to this invention, a dynamically-vulcanizable elastomer is vulcanized within a blend including HNBR while the polymers are undergoing mixing or masticating at an elevated temperature. Because HNBR is likewise vulcanizable, the step of vulcanizing the vulcanizable elastomer should not likewise crosslink a significant amount of the HNBR.
The dynamically vulcanized blends of this invention, therefore, include a co-continuous phase of HNBR and at least one dynamically vulcanized elastomer that is not HNBR. The term dynamically-vulcanizable elastomer refers to those elastomeric pol
Severe Geralda
White James L.
Nutter Nathan M.
Renner Kenner Greive Bobak Taylor & Weber
The University of Akron
LandOfFree
Dynamically vulcanized elastomeric blends including... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dynamically vulcanized elastomeric blends including..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dynamically vulcanized elastomeric blends including... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2906294