CA1321040C

CA1321040C - Cured rubber compositions of high modulus

Info

Publication number: CA1321040C
Application number: CA000538198A
Authority: CA
Inventors: Charles M. Roland
Original assignee: Firestone Tire and Rubber Co
Current assignee: Bridgestone Firestone Inc
Priority date: 1986-06-02
Filing date: 1987-05-27
Publication date: 1993-08-03
Anticipated expiration: 2010-08-03
Also published as: ZA873599B; ES2036187T3; EP0248271A1; DE3783161D1; EP0248271B1; JP2516979B2; US4720526A; DE3783161T2; JPS6322846A

Abstract

Abstract of The Disclosure Cured rubber compositions having modulii at 10%
elongation of from about 50 MPa to about 200 MPa are prepared by curing, curable rubber compositions comprising: (a) 100 parts by weight of a rubber selected from the group consisting of natural rubber, nitrile rubber, neoprene and blends thereof;
(b) from about 50 to about 100 parts by weight of a metal dimethacrylate selected from the group consisting of zinc dimethacrylate and magnesium dimethacrylate and (c) from about 1.0 to about 6.0 parts by weight of a peroxide curing agent; at temperatures ranging from about 140° to about 180°C for time periods ranging from about 10 to about 45 minutes. The curable rubber compositions may optionally and in some instances preferably contain from about 0.1 to about 2.0 parts by weight of a co-curing agent.
Cured rubber compositions of the invention may be utilized in various applications including for example conveyor belts and tire compounds.

Description

132104~

Cured Rubber Com~ositions of H~h Modulus Backqround of The_Invention The lnvention reiates to cured rubber compositions having high modulil at low ~train. More particularly, the lnvention relates to cured rubber compositions having modulii at 10% elongation of from about 50 MPa to about 200 MPa which are formed by curing, under specified temperature and time ., . . . , . _ ... _ _ . ... . .. , _ .. . . .. . . . . . .

:

132~ 040 condition~, eur~blo rubber compositlons compris~ng a rubber selected from natural rubber, nltrllo ru~ber, neoprene and blends theroof; a metal dlmethacrylate ~elact-d from zinc dimethacrylate and magnosium dimethacrylato and a peroxide curing agent and optionally, ~ co-curing agent.

Conventional cured rubber compo~ition~ normally exhibit ~xcellent flex~b~llty and extensibility having elongations at break of 200% or greater. Unfortunately, howe:ver, such compositions also normally exhibit low modulus values at low strain8. Thus, ~uch composlt~ons typically have modul U8 values at 10% elongation of less than about 10 MPa, more commonly about 5 MPa or less. On the other hand, cured polymeric compositions which exhibit high modulu~ values at 10 elongation normally have low elongations at breaX and are therefore brittle like plastics.

Cured rubber compositions having high modulil at low strain and good extensibility would have ~ignificant advantages in certa~n applications su~h as, for example, ~ire compounds.
Accordingly, a need for such compositions exists.

Curable rubber composition~ containing variou~ rubbery polymer~, metal acrylates or metal methacrylates including ba~ic zinc methacrylate and zinc dimethacrylate and peroxide çuring agent~ and certaln cured product~ formed from such compositions are Xnown in the art as illustrated by the following patents.

U.S. 4,0S6,269 to Pollitt et al. relates to molding compositions suitable for forming molded golf balls containing cis-polybutadiene or other undefined elastomers, a metal-containing crosslinXing monomer and a peroxide initiator. A
wide variety of metal-containing crosslinking monomers are disclosed in columns 2 and 3 of the patent including zinc diacrylate, zinc dimethacrylate and magnesium dimethacrylate.

~ ~ 3 ~ 132104~

The patent, ~t column 4 llnes 3-14, teache~ that the amount of the metal-contain$ng crosRllnking monomer should correspond to at least about 0.046 ~guiv~lent~ of polymerizabl~ unsaturation per molo of butadiene in th~ elastomer base, but may be as hlgh S ~8 O. 41 eguivalent~ por mole, which when converted to a parts by weight ~asis indicates a range o~ from about 9 to 90 part~
by weight of the crosslinking monomer per 100 parts by weight of cis-polybutadiene. The reference further teache~ that lf the crosslinking monomer selected is zinc dimethacrylate, the more preferable amounts are in the range of about 20 to 50 parts per 100 parts of ela~tomer. The peroxide initiator may be present in amounts of about 0.2-10% by weight of the elastomer. The reference additionally discloses that molding temperatures may range between 130 and 200C and curing time~
may range from 1 to 50 minutes.

! u.s. 4,065,537 to Miller et al. relates to a proces~
for producing molded golf balls exhibiting isometric compression which involves the use of cylindrical sl~gs about 2.5 to 3.3 $nche~ long having 6ubstantially flat or convex top and bottom surfaces during the molding process. Molding compositions for forming such slugs are disclosed which contain cis-polybutadiene or other elastomers, a metal~containing crosslinking monomer and a peroxide initiator. A wide variety of metal-containing cro~slinking monomers are disclosed including zinc dimethacrylate and magnesium dimethacrylate.
The compositions disclosed are basically the same as those described in U.S. 4,056,269 above with the exception that the preferred amounts of metal-containing crosslinking monomer, especially when said monomer i8 zinc dimethacrylate, are stated as ranging from about 15 to 60 parts per 100 parts of ci~-polybutadiene. Curing conditions disclosed are the ~ame as set forth in the aforementioned patent.

13210~

U.S. Patent 4,082,28~ to Martin et al. di~clo~es free-radic-l cro~slinkable compo~itlons contalnlng a peroxlde croRslinXablo ola~tomer, rom about 10 to about 60 parts by weight per 100 part~ by we~ght of elastomer of basic zinc S methacrylate and a peroxide curlng agent. Ihe examples of the patent lndicate that the compositlons are cured at 300F
(148.9C) for 20 minute~.
.
U.S. 4,191,671 to Kataoka et al. relates to abrasion resistant rubber composltion~ wh$ch aro prepared by curing rubber compositions comprlsing: (A) a dlene elastomer, (B) an alpha-beta ethylenlcally unsaturated carboxylic acid, wherein the ratio by weight of component (A) to component (B) i8 ~7/13 to 55/45, (C) a divalent metal compound being present in quantitie~ of 50 to 150 parts by weight per 100 parts by weight of component (B), and (D) an organic peroxide being present in quantit~es of 0.3 to 5.0 parts by weight per 100 parts by ~ weight of the combined weight o components (A~ and (B). The ; compositions may additionally conta~n an unpolymerizable carboxylic acid, carbon black in amounts of less than 50 part~
by weight per 100 parts by weight of elastomer and an amine and/or phenol compound. The patent broadly discloses curing temperatures ranging from 110-180C while the examples thereof exemplify curing temperatures ranging from 120 to 140C and curlng times Fanging from 30 minutes to 60 minutes.

U.S. 4,264,075 to Miller et al., relates to a two-piece molded gol ball consisting of a cover compri~ing an ionic ¦ copolymer and a center part formed from a molding composition j containing cis-polybutadiene or other elastomers, a metal-containing crosslinXing monomer and a peroxide initiator.
wide variety of ~uch crosslinking monomers are disclosed including zinc dimethacrylate and magnesium dimethacrylate.
The molding compositions used to form the center part of the golf ball are substantially the same as those described in U.S.
4,056,269 and 4,065,537 above with the exception that lower .
, .. . . .......... . . . . . ............ .

- ~ - . , l32io~b quantitie~ of crosslinXing monomer are preferred, l.e. from 15 to 35 parts per 100 parts o ci~-polybutadi~ne. Molding temperatures disclos~d ln th~ patant may range betwe~n 140C
and 200C, advantageously about 150 to 190C, preferably 170 S to 185~C and curinq times may range from about 50 to 1 minutes, advantageously from 30 to S minutes and preferably about 20 to 10 minute~.

U.S. 4,266,772 to Martin et al. relate~ to solid golf balls formed from a curable elastomer composition comprising a free radical crosslinkable elastomer, e~pecially a peroxide crosslinkable elastomer; from about 10 to about 60 parts by weight of a zinc oxide-methacrylic acid reaction product, preferably basic zinc methacrylate, per 100 parts by weight of elastomer and a curing agent such as a peroxide curing agent.
Curing conditions ~et forth in the example~ are 20 minutes at 300F (148.9C~.

U.S. 4,305,851 to Tominaga et al. relates to a proce~s for preparing a ~olid golf ball which comprises incorporating a microencapsulated zinc salt of an allyl group containing carboxylic acid a~ a crosslinking agent into a rubber along with a peroxide curing agent and other additives to produce a rubber composition, following which the rubber composition is molded. The patent at çolumn 5, Table I discloses æeveral polybutadiene rubber compounds containing microencapsulated zinc dimethacrylate and pe!roxide curing agent~ with the zinc dimethacrylate being present in amounts of 42 and 50 parts respectlvely. The compositions are cured for 30 minutes at 150C.

' `` 1~21~0 , U S 4,500,466 to Haye~ et al rel~t~s to a method preparlng a rlnc dim~thacryl~t~ d~uvant of high urf-c~ ar~
and to vulcanlz~bl- polymerlc compo~ltlon~ cont-lnlng the d~uvant Vuleanlzable polymerlc compo~ltlons whlch ar-S di-clo~ed comprl~e (-) rubbery polymer~ ~elected from the group con6i~tlng of natural rubber, ethylene/propylene copolymer-, ethylene/propylene/dieno terpolymers, ~tyrene/
butadiene copolymer-, nitrilè rubbers, neoprene and blend~
thereof; (b) from about 25 to bout 85 parts by wcight of a zinc dimethacrylate powder having a surface area of from about 3 7 to about 5 4 m2/g or more per lO0 part~ by welght of said rubbery polymer~; and (c) cure effective amount of a peroxide curing agent me specification discloses that the amount o peroxide generally used may range from about 0 2 to about 2 0 parts by welght Example 20 of the patent dlsclose~ a composition containlng 100 part~ of natural rubber, 60 parts of zinc dimethacrylate and l 0 parts of Vulcup R, i e , bi~-~t-butylperoxy) dil~opropyl benezene As shown in ~ablc IV, this compo~ition when cured for 15 minute~ at 160C exhibit~ a 10X
modulu~ of 3 2 MPa Example 21 di~clo~e~ a composition contalning lO0 parts of natural rubber, 70 parts of zinc dimethacrylatc and 1 0 parts of said peroxide curinq agent Thls composltlon when cured or 15 minute~ at 160C exhibit~ a 10X moduluc of 4 6 MP-, Summary of The Invention In accordance with the present lnvention, cured rubbercomposltlons having modulll at;10% elongatlon of from about 50 MPa to about 200 MP- are provided Such composltlon~ are formod by curlng, curable rubber composltlon compr$~ing (a) 100 part~ by welght of a rubber ~elected from the group con~l-tlng o natural rubber, n~trlle rubber, neoprene and blend- theroof; (b) from about 50 to about lO0 parts by weight o a metal dlmeth w rylatc ~el~cted from the group consi~tlng of zlnc dlmethacrylatc and magneslum dlmethacrylate and (c) from bout 1 0 to about 6 0 parts by wclght o a peroxide curing 13210~0 agent; at a temperature ranging from about 140 to about 180C, preferably about 160C, for a time period ~anging ~rom about 28 to about 48 minutes. The curable rubber composition may additionally contain from about 0.1 to S about 2.0 parts by weight of a co-curing agent.

The most surprising aspect of the invention is the discovery that these cured rubber compositions while having modulus value at 10% elongation as much as 40 times that of conventional rubbers also have good flexibility and extensibility and exhibit minimal permanent set. Permanent set refers to the non-recoverable deformation accompanying the elongation of a material. In addition, the rubber c~mpositions of the invention prior to curing can be processed using conventional rubber equipment and procedures.

Detailed DescriPtion of The Invention Rubbers or rubbery polymers which may be employed in the compositions of the invention include natural rubber, nitrile rubber, neoprene and blends thereof.

Metal dimethacrylates employed in the compositions of 2~ the invention are selected from zinc dimethacrylate and magnesium dimethacrylate. The preferred metal dimethacrylate is zinc dimethacrylate.

The zinc dimethacrylate and magnesium dimethacrylate may be prepared by any known method. In general, the zinc dimethacrylate may be prepared by reacting With agitatio~ zinc oxide and methacrylic acid in an amount of from about 0.5 to about 0.6 moles of zinc oxide per mole of methacrylic acid in a li~uid medium (e.g. water or a volatile organic liquid such as a liquid hydrocarbon), recovering the resulting zinc dimeth-acrylate product from the liquid medium and then drying theproduct. The magnesium dimethacrylate can be prepared in similar manner by reacting magnesium hydroxide and methacrylic acid in an amount of from about 0.5 to about 0.6 moles of ~A

.... .. . . .. . . . . ... . . .

. , , . .
; ~. . , --; . .. .

1321~0 magnesium hydroxlde per mole of methac,ylic acld in the liquld medium. If deslred, the zlnc dimethacrylate and magne~ium dimethacrylate may be finely divided to aid in dispereing the material~ into thQ rubber.

S A proferred method for preparing the zinc dimeth- :
acrylate i8 described in the above-mentioned U.S. Patent 4,500,466 to Hayes ot al. the disclosure of which ic incorporated herein by reference. The method involves reacting with agitation zinc oxide and methacrylic acid in amountfi of from about 0.5 to about 0.6 mole~ of zinc oxide per mole of methacrylic acid in a liquid aliphatic hydrocarbon (preferably an alXane, especially hexane), followed by recovery of the resultant zinc dimethacrylate from the liquid medium and drying thereof.

One important factor ~hould be noted at thi~ time.
The ~ayes et al. patent teaches that the surface area of the zinc dimethacrylate i8 an extremely important factor in the excellent properties obtained when the polymer compositions described therein are cured. In contrast, the ~urface area of the zinc dimethacrylate employed in the rubber compositions of applicants invention i~ not a critical factor in achieving the very high modulus values exhibited by applicants cured rubber compo~itions. Thus, applicant has found that zinc dimeth-acrylaSe~ having ~urface areas of 3.0 m2/g or slightly less produce desirible results'when incorporated in his compositions.
It i8 believed that the high modulus values at 10X elongation exhibited by applicants cured compositions are basically attributable to the conditions under which applicants compo~itions are cured.

Alternatively, the zinc dimethacrylate or magnesium dimethacrylate utilized in the compositions of the invention may be formed in-3itu, although thi~ method is less desirable.
Thus, the zinc dimethacrylate may be formed in-situ by - 9 - 1 321 94 ~

~eparately mlxing the zinc oxid~ and methacryllc Rcid wlth the rubber and the magnesium dimethacrylate mdy be formed ln-sltu by separately mixinq th~ magnes~um hydroxide and methacryllc ac~d with th~ rubb~r.

Amounts of metal dimethacrylate, i.e. zinc dimeth-acrylate, ~r ma~nesiu~ dimethacrylate ~mployed in the compositions of the invention may range from about 50 to about 100 parts by weight of rubber with preerred amounts ranging from about 60 to about 70 parts by weight per 100 partR by weight of rubber.

Peroxide curing agents which may be employed ln the compositions of the invention include orga~ic peroxide~ such a~
dicumyl peroxide, bi 6-( t-butyl peroxy) diisopropyl benzene, t-butyl perbenzoate, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxy hexane and the liXe. The preferred peroxide curing agents are bi~-(t-butyl peroxy) diisopropyl benzene and dicumyl peroxide.

Amounts of peroxide curing agents utilized in the composition& will depend upon the type rubber employed and may broadly be stated as cure effective amounts. In general, such amounts may range from about 1.0 to about 6.0 parts by weight - of peroxide per 100 parts by weight of rubber. Preferred amounts of peroxide curing agent may range from ab~ut 2.0 to about 5.0 parts by weight per 100 parts by weight of rubber.

Z5 As indicated above, a co-curing agent may be included in the curable rubber compo~itions from which the cured rubber composition~ of the invention are formed. In general, any co-curing agent which increases the utilization efficiency of the peroxide curing agent may be employed. Suitable co-curing agents which may be employed include N,N'-meta-phenylene-dimaleimlde, triallyl i~ocyanurate and the like. Mixtures of such co-curing agents may also be utilized.

, 1~1040 Amounts of co-curing agents omployed ln the composi-tion~ may range ~rom about 0.1 to ~bout 2.0 partn by we~ght per 100 parts by weight of rubber. Pr~ferrod amount~ may range from a~out 0.5 to about 1.0 p~rts by weight per 100 parts by weight of rubber.

The curable rubber compo~itions may option~lly contain other conventional additives which are commonly employed ln rubber compositions. Such ~ddit~ves may include small amounts of fillero ~uch as clays, silicas, calcium carbonate and the like; process and extender oils; processinS aids such as zinc stearate, sodium dodecyl ~ulfate and the like; viscosity reduction agents such as aliphatic hydrocarbon resins, anti-oxidantx, waxe~, plasticizers and the l$ke. Such additives may be utilized in amounts conventionally used in standard rubber compounds.

The curable rubber compo~itions may be mixed by any conventional mixing procedure 6uch a~, for example, by mixing the ingredient~ in an internal mixer such a~ a Banbury mixer or Brabender Plasticorder or on a mill. The rubber compositions depending on their int~nded use may be sheeted off on a rubber mill, calendared or extruded.

The conditions utilized in curing the curable rubber compositions are critical in order to obtain the very high modulus values at 10% elo~gation which are exhibited by the cured rubber compositions of the inventio~. The specific cure times and temperatures are related to the ~pecific amounts of curing agents which are employed. Thus, the curable rubber composition~ must be cured at temperatures ranging from about 140 to about 180C, preferably from 150 to 160C, for time periods ranging from about 10 to about 45 minutes, preferably from 25 to 35 minute~. It ~hould be understood that at higher curing temperatures shorter curing times are used whereas at lower curing temperatures longer curing times are required.

An important fact should be noted with regard to the above curative levels ~nd curing conditions. One skilled in the rubber compounding art would consider that ~uch curing conditions would result ln a ~lgnificant overcure of the compositions. A~ i~ well known ln the rubber compounding art, overcuring of rubber compounds normally result~ in significant degradation of phys~cal properties, particularly fitrength properties. ~owever, it was ~ûrpr$sing and unexpectsd to find that the cured rubber compositions of the invention retained excellent tensile strength propertie~ as shown by the examples which follow.

m e following examples are submitted for the purpose of further illustrating the nature of the present invention and are not to be regarded as a limitation on the scope thereof.
-Parts and percentage referred to in the examples and throughout the specificat~on are by weight unle~s otherwise indicated.

Examples 1-2 In these examples, cured rubber compositions of the invention were prepared from curable rubber compositions containing Hevea natural rubber (NR), zinc dimethacrylate and peroxide curing agent. ~The curable rubber compositions had the following formulations:

.. . . .. ... .. . .. .... . . . . . .. ... . . . .. . ..

, .
. .

.

. - 12 -1321~40 Ex. No. Part~ by welaht_ Inqrad~ent~ 1 2 ~R 100 . O 100 . O
Zinc d~methacrylato(a) 70.0 60.0 Cyrez 963 resin(b) -- 5.0 Piccopale 100 re~in(C) -- 5.0 Zinc Stearate 2.0 --Vulcup R(d) 2.0 1.5 Total 174.0 171.5 (a) prepared in accordance with the method described in U.S. 4,500,466 (b) hexamethoxymet~yl melamine resin avail~ble from American Cyanamid Company (c) aliphatic hydrocarbon resin available from Hercules, Inc.
(d) bis-(t-butylperoxy) diisopropyl benzene The above formulation~ were mixed in a Brabender Plasticorder. The m~xed formulations were then cured and tested for stres~-strain propertles. Curing conditions, te~t conditions and stress-strain properties are shown in Table I.

TABLE I
Ex. No.
_ 1 2 Cure Time (m~nutes) 28 28 Cure Temperature, C 160 160 Stress-Strain at 23C
10% modulus, MPa 78.6 58.8 Tensile, MPa 15.1 22.9 Elongation at break, % 125 135 s *MPa i8 an abbreviation for mega pascala - 13 - .
~3210~0 Example~ 3-5 These ~xample~ illu~tr~t~ cured rubber compo~ition~ of the inventlon prepared from curabl~ rubber compositions containing NR, zinc dimethacrylate, peroxide curing agent and a co-curing S agent. The curable rubber composltlons had the following forJnulations:

~art~ bY weight Ex. No. 3 4 5 Ingredients NR 100.O 100.O 100.O
Zinc dimethacrylate 70.0 70.0 90.0 sodium dodecyl ~ulfate 2.0 2.0 2.0 piccopale 100 resin -- 5.0 --Vulcup R (peroxide) 1.5 ~.0 1.5 HVA-2 (co-curing agent)* 1.5 1.5 1.5 Total 175.0 180.5 195.0 * N,N'-meta-phenylenedimaleimide The above formulations were mixed, cured and tested for stress-strain propertie~ as in Examples 1-2. Curi~g conditions, test conditions and properties are shown in Table II.

TABLE II
- Ex. No.

Cure Time, Min. 32 32 32 Cure Temp., C ~ 160C 160C 160C
Stress-Strain at 23C
10% modulu~, MPa 87.8 89 153 Ten~ile, MPa ' 16.5 16.8 16.2 Elongation at break, X 114 110 46 .

1~2i~0 Thi~ example lllu~tratos cured rubber compositions of the inventlon prepared rom a curable rubber composition containing natural rubber, magnesium dimethacrylate, peroxide S curing agent and a co-cur$ng agent. The curable rubber composition had the following formulations:

Ingredients Parts bY weight NR 100.0 Magnesuim dimethacrylate70. 0 10 Sodium dodecyl sulfate 2.0 Vulcup R 1.5 HVA-2 1.5 Total 175.0 The above formulation wa mixed, cured and tested for fitress-~train properties as in Examples 1-2. Curing - conditions, test conditions and properties are shown in Table III.

TABLE III
Cure Time, Min. 32 Cure Temp, C 160 Stres~-Strain at 23C
10% Modulus, MPa69.7 Tensile, MPa 13.0 Elongation at break, % 105 - ` 1 3 ~ 0 Examples 7-9 The~e oxamples lllustrats cured rubber composltion~ of the invention prepared from curable rubber compositionR
containing nitrll~ rubber, zinc dimethacrylate and peroxide S curing agent. Th~ curabl~ rubber compositions had the following formulation~:

Part8 bv weight Ex. No. 7 8 9 Ingredients nitrile rubber (30X ACN)~ 100.0 ~- 100.0 nitrile ru~ber (50% ACN)** -- 100.0 --Zinc dimethacrylate70.0 70.0 60.0 Vulcup R 2.0 2.0 1.5 Total 172.0 172.0 161.5 * nitrile rubber containing 30% acrylonitrile ,~nitrile rubber containing 50% acrylonitrile The above formulations were mixed, cured and tested for stress-strain properties as in Examples 1-2. Curing ,conditions, test conditions and properties are shown in Table IV.

TABLE IV
_ Ex. No.

Cure Time, Min. 48 40 48 Cure Temp., C '' 160C 160C 160C
Stress-Strain at 23C
10% Modulus, MPa ' 93 170 84 Tensile, MPa 19.4 35.3 27.4 Elongation at break, X 120 130 260 .. ... . . .

. - 16 -~321040 This example lllustrate~ curod rubbor compo~ition~ ofthe lnvent~on prepared from a curable rubber composition contain~ng natural rubber, nitrl1e rubber, zinc dimethacrylate, S peroxide curinq agent and co-curing agent. The curable rubber composition had the following formulation:

In~redients Parts bY welght NR 50.0 nitrile rubber (50X ACN) 50.0 Zinc dimethacrylate 70.0 sodium dodecyl sulfate 2.0 Vulcup ~ 1.75 HVA-2 0.75 Total 174.50 The above formulation was mixed, ~ured and tested for stress-strain properties as in Examples 1-2. Curing conditions, test conditions and properties are shown in Table V.

_ TABLE V
Cure Time, Min 32 Cure Temp, ~C 160C
Stress-strain at 23C
10% modulus, MPa 152 Tensile, MPa --Elongation at break, X 70 /

Claims

1. Cured rubber compositions having modulii at 10% elongation of from about 50 MPa to about 200 MPa formed by curing curable rubber compositions com-prising:
(a) 100 parts by weight of a rubber selected from the group consisting of natural rubber, nitrile rubber, neoprene and blends thereof;
(b) from about 50 to about 100 parts by weight of a metal dimethacrylate selected from the group consisting of zinc dimethacrylate and magnesium dimethacrylate; and (c) from about 1.0 to about 6.0 parts by weight of a peroxide curing agent;
at a temperature of about 140° to about 180°C for a time period of about 28 to about 48 minutes.

2. The cured rubber composition of claim 1 wherein said curable rubber composition further comprises from about 0.1 to about 2.0 parts by weight of a co-curing agent.

3. The cured rubber composition of claim 1 wherein the rubber of the curable rubber composition is natural rubber.

4. The cured rubber composition of claim 1 wherein the rubber of the curable rubber composition is nitrile rubber.

5. The cured rubber composition of claim 1 wherein the rubber of the curable rubber composition is a blend of natural rubber and nitrile rubber.

6. The cured rubber composition of claim 1, 2, 3, 4 or 5 wherein the metal dimethacrylate of the curable rubber composition is zinc dimethacrylate.

7. The cured rubber composition of claim 1, 2, 3, 4 or 5 wherein the peroxide curing agent of the curable rubber composition is bis-(t-butyl peroxy) diisopropyl benzene.

8. The cured rubber composition of claim 6 wherein the peroxide curing agent of the curable rubber composition is bis-(t-butyl peroxy) diiso-propyl benzene.

9. The cured rubber composition of claim 2 wherein the co-curing agent of the curable rubber composition is selected from the group consisting of N,N'-meta-phenylene dimaleimide, triallyl isocyan-urate, and mixtures thereof.

10. The cured rubber composition of claim 1, 2, 3, 4, 5, 8 or 9 wherein said temperature is about 160°C

11. The cured rubber composition of claim 6 wherein said temperature is about 160°C.

12. The cured rubber composition of claim 7 wherein said temperature is about 160°C.

13. A method for preparing a cured rubber composition having a modulus at 10% elongation of from about 50 MPa to about 200 MPa comprising the steps of:

(1) preparing a curable rubber composition which comprises:
(a) 100 parts by weight of a rubber selected from the group consisting of natural rubber, nitrile rubber, neoprene and blends thereof;
(b) from about 50 to about 100 parts by weight of a metal dimethacrylate selected from the group consisting of zinc dimeth-acrylate and magnesium dimethacrylate; and (c) from about 1.0 to about 6.0 parts by weight of a peroxide curing agent; and (2) curing said curable rubber composition at a temperature of from about 140°C to about 180°C
for a time period of from about 28 to about 48 minutes.

14. The method of claim 13 wherein the curable rubber composition prepared in step (1) further comprises from about 0.1 to about 2.0 parts by weight of a co-curing agent.

15. The method of claim 13 wherein the rubber of the curable rubber composition is natural rubber.

16. The method of claim 13 wherein the rubber of the curable rubber composition is nitrile rubber.

17. The method of claim 13 wherein the rubber of the curable rubber composition is a blend of natural rubber and nitrile rubber.

18. The method of claim 13, 14, 15, 16 or 17 wherein the metal dimethacrylate of the curable rubber composition is a zinc dimethacrylate.

19. The method of claim 13, 14, 15, 16 or 17 wherein the peroxide curing agent of the curable rubber composition is bis-(t-butyl peroxy) diiso-propyl benzene.

20. The method of claim 18 wherein the perox-ide curing agent of the curable rubber composition is bis-(t-butyl peroxy) diisopropyl benzene.

21. The method of claim 14 wherein the co-curing agent of the curable rubber composition is selected from the group consisting of N,N'-meta-phenylene dimaleimide, triallyl isocyanurate, and mixtures thereof.

22. The method of claim 13, 14, 15, 16, 17, 20 or 21 wherein said temperature is about 160°C.

23. The method of claim 18 wherein said tem-perature is about 160°C.

24. The method of claim 19 wherein said tem-perature is about 160°C.