CA2134833A1 - Sulfur cured rubber composition containing expoxidized natural rubber and carboxylated nitrile rubber - Google Patents
Sulfur cured rubber composition containing expoxidized natural rubber and carboxylated nitrile rubberInfo
- Publication number
- CA2134833A1 CA2134833A1 CA002134833A CA2134833A CA2134833A1 CA 2134833 A1 CA2134833 A1 CA 2134833A1 CA 002134833 A CA002134833 A CA 002134833A CA 2134833 A CA2134833 A CA 2134833A CA 2134833 A1 CA2134833 A1 CA 2134833A1
- Authority
- CA
- Canada
- Prior art keywords
- rubber
- weight
- parts
- silica
- styrene
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
- B60C1/0016—Compositions of the tread
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L21/00—Compositions of unspecified rubbers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S152/00—Resilient tires and wheels
- Y10S152/905—Tread composition
Abstract
The present invention relates to a sulfur cured rubber composition particularly suited for use in tire treads. The sulfur cured rubber composition is composed of, based on 100 parts by weight of rubber, from about 1.0 to 15 parts by weight of epoxidized rubber; from about 1.0 to 15 parts by weight of a carboxylated nitrile rubber; and 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
Description
~134833 SULFUR CURED RUBBER COMPOSITION
CONTAINING EPOXIDIZED NATURAL RUBBER
AND CARBOXYLATED NITRILE RUBBER
Background of the Invention A pneumatic tire is a polymeric composite and is a complex system of interacting components, each with specific properties for maximum effectiveness. One of the more important components of a tire is the tread.
Since the tread of a tire comes into contact with the road, it is particularly compounded for abrasion and tear resistance. For example, abrasion resistance can correlate to tread wear and tear resistance can correlate to the tread's ability to resist chunking or tearing of the ground contacting tread elements. With the ever present need to improve the performance of tires, there is a continuous need for a rubber composition which improves both abrasion resistance and tear values.
Summary of the Invention The present invention relates to a sulfur cured rubber composition particularly suited for the tread of a pneumatic tire. The sulfur cured rubber composition is composed of, based on 100 parts by weight of rubber, 1.0 to 15 parts by weight of epoxidized rubber; 1.0 to 15 parts by weight of a carboxylated nitrile rubber; and 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis 1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
~13~833 Detailed Description of the Invention In accordance with one embodiment of the present invention, there is disclosed a pneumatic tire having an outer circumferential tread wherein said tread is a sulfur cured composition composed of, based on 100 parts by weight of rubber (phr) (a) 1.0 to 15 parts by weight of a epoxidized natural rubber; (b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber and 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis 1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
As known to those skilled in the art, epoxidizednatural rubber is a modified form of natural rubber in which some of the unsaturation is replaced by epoxidized groups. Epoxidized natural rubber which may be used in the present invention may have a level of epoxidized modification ranging from about 15 to 85 mole percent. Preferably, the epoxidized level will be in the range of from about 20 to 50 percent. A
particularly preferred epoxidized level is 25 percent.
As known to those skilled in the art, epoxidized natural rubber can be obtained by epoxidizing natural rubber latex. This material is commercially available from Malaysian rubber producers under the designation ENR 50 (50 percent epoxidized level) and ENR 25 (25 percent epoxidized level) in the form of dehydrated bales.
Based on 100 parts by weight of the total rubber in the sulfur-cured rubber composition, from 1.0 to 15 phr, is the epoxidized rubber. Preferably, from 2.5 to 10 parts by weight is the epoxidized rubber.
213~833 The second component contained in the present invention is a carboxylated nitrile rubber. Based on 100 parts by weight of the total rubber in the sulfur-cured rubber composition, from 1.0 to 15 parts by weight, is the carboxylated nitrile rubber.
Preferably, from 2.5 to 10 parts by weight is the carboxylated nitrile rubber.
The carboxylated nitrile rubbers (elastomers) contain chain linkages derived from unsaturated carboxylic acids of the acrylic acid type (unsaturated carboxylic acid monomers). Some representative examples of unsaturated carboxylic acids of the acrylic acid type include acrylic acid, methacrylic acid, sorbic acid, ~-acryloxypropanoic acid, ethacrylic acid, 2-ethyl-3-propyl acrylic acid, vinyl acrylic acid, c' nn~ml C acid, maleic acid, fumaric acid and the like. Carboxylated nitrile rubbers generally contain from about 0.75 percent to 15 percent by weight chain linkages (repeat units) which are derived from unsaturated carboxylic acid monomers.
The carboxylic nitrile rubbers can be synthesized using any conventional polymerization technique.
Emulsion polymerization of carboxylated nitrile elastomers is generally preferred and is used almost exclusively in industrial production. This type of a synthesis generally utilizes a charge composition comprising water, monomers, an initiator and an emulsifier (soap). Such polymerizations can be run over a very wide temperature range from about 0C to as high as 100C. It is more preferred for these polymerizations to be run at a temperature from about 5C to 60C.
The amount of carboxylic acid monomer (unsaturated carboxylic acid of the acrylic acid type) incorporated in a carboxylated nitrite rubber may be varied over a wide range. The monomer charge ratio ,, 213~833 between the carboxylic monomer and the comonomers employed in a polymerization may also be varied over a very wide range. Generally, the charge composition used in the synthesis of carboxylated nitrile rubbers will contain 60 percent to 75 percent by weight butadiene, 15 percent to 35 percent by weight of acrylonitrile and 1 percent to 15 percent by weight methacrylic acid, based upon the total monomer charge.
A typical charge composition for a carboxylated nitrile rubber will contain 65 to 69 weight butadiene, 24 to 28 weight percent acrylonitrile and 5 to 9 weight percent methacrylic acid.
The emulsifiers used in the polymerization of such polymers may be charged at the outset of the polymerization or may be added incrementally or by proportioning as the reaction proceeds. Generally, anionic emulsifier systems provide good results;
however, any of the general types of anionic, cationic or nonionic emulsifiers may be employed in the polymerization.
Among the anionic emulsifiers that can be employed in emulsion polymerizations are fatty acids and their alkali metal soaps such as caprylic acid, capric acid, pelargonic acid, lauric acid, undecylic acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid and the like; amine soaps of fatty acids such as those formed from ammonia, mono- and dialkyl amines, substituted hydrazines, guanidine and various low molecular weight diamines;
chain-substituted derivatives of fatty acids such as those having alkyl substituents; naphthenic acids and their soaps and the like; sulfuric esters and their salts, such as the tallow alcohol sulfates, coconut alcohol sulfates, fatty alcohol sulfates, such as oleyl sulfate, sodium lauryl sulfate and the like;
sterol sulfates; sulfates of alkylcyclohexanols, ~1348~3 sulfation products of lower polymers of ethylene as C10 to C20.straight chain olefins, and other hydrocarbon mixtures, sulfuric esters of aliphatic and aromatic alcohols having intermediate linkages, such as ether, ester or amide groups such as alkylbenzyl (polyethyleneoxy) alcohols, the sodium salt or tridecyl ether sulfate; alkane sulfonates, esters and salts, such as alkylchlorosulfonates with the general formula RS02Cl, wherein R is an alkyl group having from 1 to 20 carbon atoms, and alkylsulfonates with the general formula RS02-OH, wherein R is an alkyl group having from 1 to 20 carbon atoms; sulfonates with intermediate linkages such as ester and ester-linked sulfonates such as those having the formula RCOOC2H4S03H and ROOC-CH2-S03H, wherein R is an alkyl group having from 1 to 20 carbon atoms such as dialkyl sulfosuccinates; ester salts with the general formula:
/='\ 1 O
~ SO3Na wherein R is an alkyl group having from 1 to 20 carbon atoms; alkaryl sulfonates in which the alkyl groups contain preferably from 10 to 20 carbon atoms, e.g.
dodecylbenzenesulfonates, such as sodium dodecylbenzenesulfonate; alkyl phenol sulfonates;
sulfonic acids and their salts such as acids with the formula RS03Na, wherein R is an alkyl and the like;
sulfonamides, sulfamido methylenesulfonic acids; rosin acids and their soaps; sulfonated derivatives of rosin and rosin oil; and lignin sulfonates and the like.
Rosin acid soap has been used with good success at a concentration of about 5 percent by weight in the initial charge composition used in the synthesis of carboxylated elastomers. Of rosin acids, about 90 ~134~33 percent are isomeric with abietic acid and the other 10 percent is a mixture of dehydro abietic acid and dihydro abietic acid.
The polymerization of these carboxylated nitrile rubbers may be initiated using free radical catalysts, ultraviolet light or radiation. To ensure a satisfactory polymerization rate, uniformity and a controllable polymerization, free radical initiators are generally used with good results. Free radical initiators which are commonly used include the various peroxygen compounds such as potassium persulfate, ammonium persulfate, benzoyl peroxide, hydrogen peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, decanoyl peroxide, lauroyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, t-butylhydroperoxide, acetyl acetone peroxide, methyl ethyl ketone peroxide, succinic acid peroxide, dicetyl peroxydicarbonate, t-butyl peroxyacetate, t-butyl peroxymaleic acid, t-butyl peroxybenzoate, acetyl cyclohexyl sulfonyl peroxide and the like; the various azo compounds such as 2-t-butylazo-2-cyanopropane, dimethyl azodiisobutyrate, azodiisobutyronitrile, 2-t-butylazo-1-cyanocyclohexane, 1-t-amylazo-1-cyanocyclohexane and the like; the various alkyl perketals, such as 2,2-bis-(t-butylperoxy)butane, ethyl 3,3-bis(t-butylperoxy)butyrate, 1,1-di-(t-butylperoxy)cyclohexane and the like. Cumene hydroperoxide can be used as an initiator to obtain very good results in the polymerization of carboxylated nitrile rubber.
The emulsion polymerization system used in the synthesis of carboxylated nitrile rubbers can be treated at the desired degree of conversion with shortstopping agents, such as hydroquinone. Typical shortstopping agents will not interfere with the ~13483~
action of the succinic acid derivative salts as scorch inhibitors. Typical stabilizing agents and standard antioxidants can also be added to the emulsion of a carboxylated nitrile rubber.
After the emulsion polymerization has been completed, most conventional coagulating techniques for carboxylated nitrile rubbers can be employed. A
review of coagulation techniques for nitrile rubbers is presented in Hofmann, Werner "Nitrile Rubber,"
Rubber Chemistry and Technology, vol. 37, no. 2, part 2 (April-June 1964), pp. 94-96, which is incorporated herein by reference. Normally such latexes are coagulated with reagents which ensure the preservation of the carboxyl groups of the elastomers as acidic moieties. Coagulation with acid or blends of salts with acids is usually very satisfactory. For example, sulfuric acid, hydrochloric acid, blends of sodium chloride with sulfuric acid and blends of hydrochloric acids with methanol are very effective as coagulating agents for carboxylated rubber emulsions. Calcium chloride solutions which are free of calcium hydroxide have also been used as coagulants with great success.
After coagulation, washing may be employed to remove excess soap and/or electrolyte from the carboxylated rubber. Sometimes washing is also useful in adjusting the pH of the carboxylated elastomer that has been synthesized. After washing, if it is desired, the elastomer can be dewatered. If it is desirable to do so, the carboyxlated rubber can also be dried and baled after dewatering using conventional techniques.
Example of commercially available carboxylated nitrile rubber are HYCAR~ 1072 (Bd/ACN=65/34, with 1 percent carboxylic acid) marketed by BF Goodrich and CHEMIGUM~ NX-775 (Bd/ACN-55/38 with 7 percent - 8 - 21 3~83 3 carboxylic acid) marketed by The Goodyear Tire ~
Rubber Company. These carboxylated copolymers contain approximately 0.5-10 percent by weight terminal carboxyl groups.
The sulfur cured rubber composition also contains a natural or synthetic diene derived rubber.
Representative of the rubbers include medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
Preferably, the rubber is natural rubber, styrene-butadiene rubber or cis-polybutadiene. This rubber, other than the epoxidized natural rubber and carboxylated nitrile rubber, may be used in amounts ranging from 98 to 70 parts by weight based on 100 parts by weight of total rubber. Preferably, this rubber is used in amounts ranging from about 95 to about 80 parts by weight based on 100 parts by weight of total rubber.
The compositions of the present invention may be compounded by conventional means including a Banbury~, mill, extruder, etc. It has been found to be preferred to add the carboxylated nitrile rubber at a separate stage than the epoxidized rubber.
In addition to the above-identified and required components of the sulfur cured rubber compositions of the present invention, one may also use a siliceous pigment (alternatively referred to herein as silica filler). The silica filler that can be used include both pyrogenic and precipitated finely-divided silicas of the type heretofore employed for rubber compounding. The silica filler, however, is preferably of the type obtained by precipitation from 213~833 a soluble silicate, such as sodium silicate. For example, silica fillers produced according to the method described in U.S. Patent No. 2,940,830 can be used. These precipitated, hydrated silica pigments have a SiO2 content of at least 50~ and usually greater than 80~ by weight on anhydrous basis. The silica filler may have an ultimate particle size in the range of from about 50 to 10,000 angstroms, preferably between 50 and 400 and, more preferably, between 100 and 300 angstroms. The silica may be expected to have an average ultimate particle size in a range of about 0.01 to 0.05 microns as determined by electron microscope, although the silica particles may even be smaller in size. The BET surface area of the filler as measured using nitrogen gas is preferably in the range of 40 to 600 square meters per gram, usually 50 to 300 square meters per gram. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Vol. 60, page 304 (1930). The silica also has a dibutyl (DBP) absorption value in a range of about 200 to about 400, with a range of from about 220 to 300 being preferred.
Various commercially available silicas may be considered, for example, silicas commercially available from PPG Industries under the Hi-Sil trademark such as, for example, those with designations 210, 243, etc.; silicas available from Rhone-Poulenc, with designations of Z1165MP and Z165GR
and silicas available from Degussa AG with designations VN2 and VN3, etc. The Rhone-Poulenc Z1165MP silica is a preferred silica which is reportedly characterized by having a BET surface area of about 160-170 and by a DBP value of about 250-290 and by having a substantially spherical shape.
The amount of silica filler used as the reinforcing filler can vary widely. Generally ~13~833 speaking, the amount may range between about 5 and about 85 parts by weight of siliceous pigment per 100 parts by weight of total rubber are used. More typically, between about 10 and 50 parts by weight of siliceous pigment per 100 parts of rubber are used.
In compounding a silica filled rubber composition, one generally uses a coupling agent.
Such coupling agents, for example, may be premixed, or pre-reacted, with the silica particles or added to the rubber mix during the rubber/silica processing, or mixing, stage. If the coupling agent and silica are added separately to the rubber mix during the rubber/silica mixing, or processing stage, it is considered that the coupling agent then combines in situ with the silica.
In particular, such coupling agents are generally composed of a silane which has a constituent component, or moiety, (the silane portion) capable of reacting with the silica surface and, also, a constituent component, or moiety, capable of reacting with the rubber, particularly a sulfur vulcanizable rubber which contains carbon-to-carbon double bonds, or unsaturation. In this manner, then the coupler acts as a connecting bridge between the silica and the rubber and thereby enhances the rubber reinforcement aspect of the silica.
The silane of the coupling agent apparently forms a bond to the silica surface, possibly through hydrolysis, and the rubber reactive component of the coupling agent combines with the rubber itself.
Usually the rubber reactive component of the coupler is temperature sensitive and tends to combine with the rubber during the final and higher temperature sulfur vulcanization stage and, thus, subsequent to the rubber/silica/coupler mixing stage and, therefore, after the silane group of the coupler has combined - 11- 213~833 with the silica. However, partly because of typical temperature sensitivity of the coupler, some degree of combination, or bonding, may occur between the rubber-reactive component of the coupler and the rubber during an initial rubber/silica/coupler mixing stages and, thus, prior to a subsequent vulcanization stage.
The rubber-reactive group component of the coupler may be, for example, one or more of groups such as mercapto, amino, vinyl, epoxy, and sulfur groups, preferably a sulfur or mercapto moiety and more preferably sulfur.
A representative coupling agent may be, for example, a bifunctional sulfur containing organosilane such as, for example, bis-(3-triethoxy-silylpropyl)tetrasulfide, bis-(3-trimethoxy-silylpropyl)tetrasulfide and bis(3-triethoxy-silylpropyl)tetrasulfide grafted silica from DeGussa, A.G. The amount of silica coupling agent which may be used may range from about 0.5 to about 8.5 parts by weight per 100 parts by weight of total rubber used.
Preferably, the amount of silica coupler ranges from about 1.0 to about 5.0 parts by weight per 100 parts by weight of rubber used.
The sulfur cured rubber composition may also contain conventional additives including reinforcing agents, fillers, peptizing agents, pigments, stearic acid, accelerators, sulfur w lcanizing agents, antiozonants, antioxidants, processing oils, activators, initiators, plasticizers, waxes, prevulcanization inhibitors, extender oils and the like. Representative of reinforcing agents include carbon black, which is typically added in amounts ranging from about 5 to 100 parts by weight based on 100 parts by weight of total rubber (phr).
Preferably, carbon black is used in amounts ranging from about 15 to 85 phr. Typical carbon blacks that ~1 3~833 are used include N110, N121, N220, N231, N234, N242, N293, N299, N326, N330, M332, N339, N343, N347, N351, N358, N375, N472, N539, N550, N660, N683, N754, and N765. Depending on the particular use of the compound, the appropriate carbon black may be selected. Representative of conventional accelerators are amines, guanidines, thioureas, thiols, thiurams, sulfenamides, dithiocarbamates and xanthates which are typically added in amounts of from about 0.2 to about 5 phr. Representative of sulfur w lcanizing agents include element sulfur (free sulfur) or sulfur donating w lcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. The amount of sulfur w lcanizing agent will vary depending on the type of rubber and particular type of sulfur wlcanizing agent but generally range from about 0.1 phr to about 5 phr with a range of from about 0.5 phr to about 2 phr being preferred.
Representative of the antidegradants which may be in the rubber composition include monophenols, bisphenols, thiobisphenols, polyphenols, hydroquinone derivatives, phosphites, phosphate blends, thioesters, naphthylamines, diphenol amines as well as other diaryl amine derivatives, para-phenylene diamines, quinolines and blended amines. Antidegradants are generally used in an amount ranging from about 0.1 phr to about 10 phr with a range of from about 2 to 6 phr being preferred. Representative of a peptizing agent that may be used is pentachlorophenol which may be used in an amount ranging from about 0.1 phr to 0.4 phr with a range of from about 0.2 to 0.3 phr being preferred. Representative of processing oils which may be used in the rubber composition of the present invention include aliphatic-naphthenic aromatic resins, polyethylene glycol, petroleum oils, ester plasticizers, vulcanized vegetable oils, pine tar, 213~833 phenolic resins, petroleum resins, polymeric esters and rosins. These processing oils may be used in a conventional amount ranging from about 0 to about 50 phr with a range of from about 5 to 35 phr being preferred. Representative of an initiator that may be used is stearic acid. Initiators are generally used in a conventional amount ranging from about 1 to 4 phr with a range of from about 2 to 3 phr being preferred.
Accelerators may be used in a conventional amount. In cases where only a primary accelerator is used, the amounts range from about 0.5 to 2.5 phr. In cases where combinations of two or more accelerators are used, the primary accelerator is generally used in amounts ranging from 0.5 to 2.0 phr and a secondary accelerator is used in amounts ranging from about 0.1 to 0.5 phr. Combinations of accelerators have been known to produce a synergistic effect. Suitable types of conventional accelerators are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
Preferably, the primary accelerator is a sulfenamide.
If a secondary accelerator is used, it is preferably a guanidine, dithiocarbamate or thiuram compound.
Pneumatic tires are conventionally comprised of a generally toroidal shaped carcass with an outer circumferential tread adapted to the ground contacting space beads and sidewalls extending radially from and connecting said tread to said beads. The tread may be built, shaped, molded and cured by various methods which will be readily apparent to those skilled in the art.
The sulfur cured rubber composition may be used to form a tread rubber which can then be applied in the building of a green tire in which the uncured, shaped tread is built unto the carcass following which the green tire is shaped and cured. Alternatively, ~I39833 the tread can be applied to a cured tire carcass from which the previously tread has been buffed or abraded away and the tread cured thereon as a retread.
The practice of this invention is further illustrated by reference to the following examples which are intended to be representative rather than restrictivé of the scope of the invention. Unless otherwise indicated, all parts and percentages are by weight.
Example 1 Rubber compositions containing the materials set out in Table I were prepared in a BR Banbury~ using three separate stages of addition. Table I also sets out the cure behavior and w lcanizate properties for the control compound A and also compounds B, C and control D which contain polyisoprene, epoxidized natural rubber and carboxylated nitrile rubber.
SampleControl Control A D C D
1st Non-Productive Polyisoprenel 100 90 80 60 Epoxidized NR2 0 5 10 20 Carbon Black 35 35 35 35 Zinc Oxide 5 5 5 5 Processing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2nd Non-Productive Carbon Black 15 15 15 15 Carboxylated Nitrile3 0 5 10 20 Productive Sulfur ¦ 1.4 ¦1.4 ¦1.4 ¦1.4 Accelerator ¦1.0 ¦ 1.0 ¦ 1.0 ¦1.0 Rheometer, 150C
Max Torque 40.0 40.3 38.0 37.0 Min Torque 6.7 8.0 8.4 12.0 ~ Torque 33.3 32.3 29.6 25.0 T90 (min) 13.3 13.0 14.5 14.0 Stress-Strain Tensile Strength (MPa) 21.1 19.6 14.7 8.4 Elongation ~ Brk (~) 528 523 428 229 M100 (MPa) 2.0 2.6 3.1 4.5 M300 (MPa) 11.0 10.6 10.6 --Hardness Room Temperature 61 68 69 74 Rebound Room Temperature 48 35 30 23 Strebler to Self (N) 111 169 73 6 DIN Abrasion (~ Standard) 108 62 87 142 INatsyn~ 2200 obtained from The Goodyear Tire h Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer's Research Association 3Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the above data, use of 5 and 10 parts of carboxylated nitrile rubber and epoxidized nitrile rubber results in improved (lower) DIN
abrasion in comparison to the controls.
At the 5 phr level of carboxylated nitrile rubber and epoxidized nitrile rubber, one gets superior (higher) tear properties (Peel Adhesion) versus the controls.
~134833 Example 2 Silica-filled rubber compositions containing the materials set out in Table I were prepared in a BR
Banbury~ using three separate stages of addition.
Table II also sets out the cure behavior and vulcanizate properties for control compound E, control compound F and compounds G and H.
TAP~E II
Sample Control Control E F G H
1st Non-Productive Polyi60prenel 100 100 80 80 Epoxidized NR2 0 0 10 10 Carbon Black 35 35 35 35 Zinc Oxide 5 5 5 5 Processing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2nd Non-Productive Silica3 15 15 15 15 Carboxylated Nitrile4 0 0 10 10 Organo6ilane Coupling 0 3 0 3 AgentS
Productive Sulfur 1.4 1.4 1.4 1.4 Sulfenamide Accelerator 1.0 1.0 1.0 1.0 Rheometer, 150C
Max Torque 26.4 31.5 27.7 30.7 Min Torque 6.7 7.7 12.3 11.0 ~ Torque 19.7 23.8 15.4 19.7 T90 (min) 22.3 18.5 22.0 20.0 Stre66-Strain Ten6ile Strength (MPa) ¦14.1 ¦18.2 ¦5.7 ¦ 7.5 2l34833 Elongation ~ Brk (~) 528 229 414 382 M100 (NPa) 0.96 1.53 2.05 2.60 M300 (MPa) 3.98 7.14 4.46 6.66 Hardness Room Temperature 46.6 54.3 66.0 68.7 100C 42.2 50.6 53.1 57.1 Rebound Room Temperature 42.1 45.1 27.6 27.8 100C 51.0 56.2 44.1 43.5 DIN Abrasion 290 181 175 151 (~ of Standard) 1Nat6yn~ 2200 obtained from The Goodyear Tire & Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer'6 Reæearch As60ciation 3Hil Sil~ 210 obtained from PPG
4Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company 5Si69 obtained from Degu66a As can be seen from the above data, Samples G and H have improved modulus and DIN abrasion values versus the corresponding Control E and Control F.
Example 3 Silica-filled rubber compositions containing the materials set out in Table III were prepared in a BR
Banbury~ using three separate stages of addition.
o Table III also sets out the cure behavior and vulcanizate properties for control compound I, compound J, control compound K and compound L.
TABLE III
Sample Control Control I J K L
1st Non-Productive E-SBRI 68.7568.7568.75 68.75 Polybutadiene215.00 15.0015.0015.00 Polyisoprene335.00 30.0035.0015.00 Epoxidized NR40.00 2.50.0010.00 Silicas 40.00 40.0040.0040.00 Carbon Black 10.00 10.0010.00110.00 Zinc Oxide 3.00 3.003.00 3.00 Fatty Acid 3.00 3.003.00 3.00 Organosilane Coupling 0.000.00 2.00 2.00 Agent6 Antioxidant 2.00 2.002.00 2.00 2nd Non-Productive Silicas 30.00 30.0030.0030.00 Carboxylated Nitrile7 0.002.50 0.00 10.00 Organosilane Coupling 0.000.00 1.50 1.50 Agent6 Productive Sulfur 3.50 3.501.40 1.40 Accelerator 3.50 3.501.80 1.80 Secondary Accelerator 2.002.00 1.50 1.50 Rheometer, 150C
Max Torque 58.5 59.046.0 52.7 Min Torque 15.8 17.39.0 19.5 ~ Torque 42.7 41.737.0 33.2 T90 (min) 16.3 14.818.5 19.0 Stress-Strain Tensile Strength ~MPa)7.759.89 15.4 15.2 Elongation ~ Brk (~) 261257 384 382 M100 (MPa) 2.77 3.573.48 4.81 DIN Abrasion 170 137112 103 (~ of Standard) - 19 - ~13~833 IPlioflex~ 1712 obtained from The Goodyear Tire & Rubber Company 2Budene~ 1207 obtained from The Goodyear Tire & Rubber Company 3Natsyn~ 2200 obtained from The Goodyear Tire & Rubber Company 4ENR-25 obtained from The Malaysian Rubber Producer' 8 Research As~ociation 5Zl165 MP obtained from Rhene-Poulenc 6Si69 obtained from Degu6æa 7Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the above data, the present invention provides improved DIN abrasion values for silica containing compounds both with and without the presence of a silica coupler.
Example 4 Rubber compositions containing the materials set out in Table IV were prepared in a BR Banbury~ using three separate stages of addition. Table IV also sets out the cure behavior and vulcanizate properties for control compound M, control compound N, control compound O and compound P.
TABLE IV
Sample Control Control Control M N O P
l~t Non-Productive Polyi~oprenel 100 95 95 90 Epoxidized NR2 0 5 0 5 Carbon Black 50 50 50 50 Zinc Oxide 5 5 5 5 Proce~ing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2 5 2nd Non-Productive Carboxylated Nitrile3¦ 0 ¦ 0¦ 5 ¦ 5 Productive Sulfur ¦1.4 ¦1.4 ¦1.4 ¦ 1.4 213~833 Accelerator ¦1.0 ¦1.0 ¦1.0 ¦1.0 Rheometer, 150C
Max Torque 40.0 39.3 39.0 39.0 Min Torque 9.7 9.9 10.3 11.3 ~ Torque 30.3 29.4 28.7 27.7 T90 (min) 13.3 13.5 13.5 13.5 Stre6s-Strain Ten~ile Strength (MPa) 21.1 20.8 19.1 18.5 Elongation ~ Brk (~) 506 518 495 485 M100 (MPa) 2.36 2.46 2.79 3.03 Peel Adhe6ion to Self (N) 106 118 152 157 DIN Abrasion 108 101 93 76 (~ of Standard) 15 INat~yn~ 2200 obtained from The Goodyear Tire & Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer's Re6earch As~ociation 3Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the data in Table IV, there is a synergistic effect from the presence of both epoxidized rubber and carboxylated nitrile versus the presence of each component alone.
CONTAINING EPOXIDIZED NATURAL RUBBER
AND CARBOXYLATED NITRILE RUBBER
Background of the Invention A pneumatic tire is a polymeric composite and is a complex system of interacting components, each with specific properties for maximum effectiveness. One of the more important components of a tire is the tread.
Since the tread of a tire comes into contact with the road, it is particularly compounded for abrasion and tear resistance. For example, abrasion resistance can correlate to tread wear and tear resistance can correlate to the tread's ability to resist chunking or tearing of the ground contacting tread elements. With the ever present need to improve the performance of tires, there is a continuous need for a rubber composition which improves both abrasion resistance and tear values.
Summary of the Invention The present invention relates to a sulfur cured rubber composition particularly suited for the tread of a pneumatic tire. The sulfur cured rubber composition is composed of, based on 100 parts by weight of rubber, 1.0 to 15 parts by weight of epoxidized rubber; 1.0 to 15 parts by weight of a carboxylated nitrile rubber; and 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis 1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
~13~833 Detailed Description of the Invention In accordance with one embodiment of the present invention, there is disclosed a pneumatic tire having an outer circumferential tread wherein said tread is a sulfur cured composition composed of, based on 100 parts by weight of rubber (phr) (a) 1.0 to 15 parts by weight of a epoxidized natural rubber; (b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber and 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis 1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
As known to those skilled in the art, epoxidizednatural rubber is a modified form of natural rubber in which some of the unsaturation is replaced by epoxidized groups. Epoxidized natural rubber which may be used in the present invention may have a level of epoxidized modification ranging from about 15 to 85 mole percent. Preferably, the epoxidized level will be in the range of from about 20 to 50 percent. A
particularly preferred epoxidized level is 25 percent.
As known to those skilled in the art, epoxidized natural rubber can be obtained by epoxidizing natural rubber latex. This material is commercially available from Malaysian rubber producers under the designation ENR 50 (50 percent epoxidized level) and ENR 25 (25 percent epoxidized level) in the form of dehydrated bales.
Based on 100 parts by weight of the total rubber in the sulfur-cured rubber composition, from 1.0 to 15 phr, is the epoxidized rubber. Preferably, from 2.5 to 10 parts by weight is the epoxidized rubber.
213~833 The second component contained in the present invention is a carboxylated nitrile rubber. Based on 100 parts by weight of the total rubber in the sulfur-cured rubber composition, from 1.0 to 15 parts by weight, is the carboxylated nitrile rubber.
Preferably, from 2.5 to 10 parts by weight is the carboxylated nitrile rubber.
The carboxylated nitrile rubbers (elastomers) contain chain linkages derived from unsaturated carboxylic acids of the acrylic acid type (unsaturated carboxylic acid monomers). Some representative examples of unsaturated carboxylic acids of the acrylic acid type include acrylic acid, methacrylic acid, sorbic acid, ~-acryloxypropanoic acid, ethacrylic acid, 2-ethyl-3-propyl acrylic acid, vinyl acrylic acid, c' nn~ml C acid, maleic acid, fumaric acid and the like. Carboxylated nitrile rubbers generally contain from about 0.75 percent to 15 percent by weight chain linkages (repeat units) which are derived from unsaturated carboxylic acid monomers.
The carboxylic nitrile rubbers can be synthesized using any conventional polymerization technique.
Emulsion polymerization of carboxylated nitrile elastomers is generally preferred and is used almost exclusively in industrial production. This type of a synthesis generally utilizes a charge composition comprising water, monomers, an initiator and an emulsifier (soap). Such polymerizations can be run over a very wide temperature range from about 0C to as high as 100C. It is more preferred for these polymerizations to be run at a temperature from about 5C to 60C.
The amount of carboxylic acid monomer (unsaturated carboxylic acid of the acrylic acid type) incorporated in a carboxylated nitrite rubber may be varied over a wide range. The monomer charge ratio ,, 213~833 between the carboxylic monomer and the comonomers employed in a polymerization may also be varied over a very wide range. Generally, the charge composition used in the synthesis of carboxylated nitrile rubbers will contain 60 percent to 75 percent by weight butadiene, 15 percent to 35 percent by weight of acrylonitrile and 1 percent to 15 percent by weight methacrylic acid, based upon the total monomer charge.
A typical charge composition for a carboxylated nitrile rubber will contain 65 to 69 weight butadiene, 24 to 28 weight percent acrylonitrile and 5 to 9 weight percent methacrylic acid.
The emulsifiers used in the polymerization of such polymers may be charged at the outset of the polymerization or may be added incrementally or by proportioning as the reaction proceeds. Generally, anionic emulsifier systems provide good results;
however, any of the general types of anionic, cationic or nonionic emulsifiers may be employed in the polymerization.
Among the anionic emulsifiers that can be employed in emulsion polymerizations are fatty acids and their alkali metal soaps such as caprylic acid, capric acid, pelargonic acid, lauric acid, undecylic acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid and the like; amine soaps of fatty acids such as those formed from ammonia, mono- and dialkyl amines, substituted hydrazines, guanidine and various low molecular weight diamines;
chain-substituted derivatives of fatty acids such as those having alkyl substituents; naphthenic acids and their soaps and the like; sulfuric esters and their salts, such as the tallow alcohol sulfates, coconut alcohol sulfates, fatty alcohol sulfates, such as oleyl sulfate, sodium lauryl sulfate and the like;
sterol sulfates; sulfates of alkylcyclohexanols, ~1348~3 sulfation products of lower polymers of ethylene as C10 to C20.straight chain olefins, and other hydrocarbon mixtures, sulfuric esters of aliphatic and aromatic alcohols having intermediate linkages, such as ether, ester or amide groups such as alkylbenzyl (polyethyleneoxy) alcohols, the sodium salt or tridecyl ether sulfate; alkane sulfonates, esters and salts, such as alkylchlorosulfonates with the general formula RS02Cl, wherein R is an alkyl group having from 1 to 20 carbon atoms, and alkylsulfonates with the general formula RS02-OH, wherein R is an alkyl group having from 1 to 20 carbon atoms; sulfonates with intermediate linkages such as ester and ester-linked sulfonates such as those having the formula RCOOC2H4S03H and ROOC-CH2-S03H, wherein R is an alkyl group having from 1 to 20 carbon atoms such as dialkyl sulfosuccinates; ester salts with the general formula:
/='\ 1 O
~ SO3Na wherein R is an alkyl group having from 1 to 20 carbon atoms; alkaryl sulfonates in which the alkyl groups contain preferably from 10 to 20 carbon atoms, e.g.
dodecylbenzenesulfonates, such as sodium dodecylbenzenesulfonate; alkyl phenol sulfonates;
sulfonic acids and their salts such as acids with the formula RS03Na, wherein R is an alkyl and the like;
sulfonamides, sulfamido methylenesulfonic acids; rosin acids and their soaps; sulfonated derivatives of rosin and rosin oil; and lignin sulfonates and the like.
Rosin acid soap has been used with good success at a concentration of about 5 percent by weight in the initial charge composition used in the synthesis of carboxylated elastomers. Of rosin acids, about 90 ~134~33 percent are isomeric with abietic acid and the other 10 percent is a mixture of dehydro abietic acid and dihydro abietic acid.
The polymerization of these carboxylated nitrile rubbers may be initiated using free radical catalysts, ultraviolet light or radiation. To ensure a satisfactory polymerization rate, uniformity and a controllable polymerization, free radical initiators are generally used with good results. Free radical initiators which are commonly used include the various peroxygen compounds such as potassium persulfate, ammonium persulfate, benzoyl peroxide, hydrogen peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, decanoyl peroxide, lauroyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, t-butylhydroperoxide, acetyl acetone peroxide, methyl ethyl ketone peroxide, succinic acid peroxide, dicetyl peroxydicarbonate, t-butyl peroxyacetate, t-butyl peroxymaleic acid, t-butyl peroxybenzoate, acetyl cyclohexyl sulfonyl peroxide and the like; the various azo compounds such as 2-t-butylazo-2-cyanopropane, dimethyl azodiisobutyrate, azodiisobutyronitrile, 2-t-butylazo-1-cyanocyclohexane, 1-t-amylazo-1-cyanocyclohexane and the like; the various alkyl perketals, such as 2,2-bis-(t-butylperoxy)butane, ethyl 3,3-bis(t-butylperoxy)butyrate, 1,1-di-(t-butylperoxy)cyclohexane and the like. Cumene hydroperoxide can be used as an initiator to obtain very good results in the polymerization of carboxylated nitrile rubber.
The emulsion polymerization system used in the synthesis of carboxylated nitrile rubbers can be treated at the desired degree of conversion with shortstopping agents, such as hydroquinone. Typical shortstopping agents will not interfere with the ~13483~
action of the succinic acid derivative salts as scorch inhibitors. Typical stabilizing agents and standard antioxidants can also be added to the emulsion of a carboxylated nitrile rubber.
After the emulsion polymerization has been completed, most conventional coagulating techniques for carboxylated nitrile rubbers can be employed. A
review of coagulation techniques for nitrile rubbers is presented in Hofmann, Werner "Nitrile Rubber,"
Rubber Chemistry and Technology, vol. 37, no. 2, part 2 (April-June 1964), pp. 94-96, which is incorporated herein by reference. Normally such latexes are coagulated with reagents which ensure the preservation of the carboxyl groups of the elastomers as acidic moieties. Coagulation with acid or blends of salts with acids is usually very satisfactory. For example, sulfuric acid, hydrochloric acid, blends of sodium chloride with sulfuric acid and blends of hydrochloric acids with methanol are very effective as coagulating agents for carboxylated rubber emulsions. Calcium chloride solutions which are free of calcium hydroxide have also been used as coagulants with great success.
After coagulation, washing may be employed to remove excess soap and/or electrolyte from the carboxylated rubber. Sometimes washing is also useful in adjusting the pH of the carboxylated elastomer that has been synthesized. After washing, if it is desired, the elastomer can be dewatered. If it is desirable to do so, the carboyxlated rubber can also be dried and baled after dewatering using conventional techniques.
Example of commercially available carboxylated nitrile rubber are HYCAR~ 1072 (Bd/ACN=65/34, with 1 percent carboxylic acid) marketed by BF Goodrich and CHEMIGUM~ NX-775 (Bd/ACN-55/38 with 7 percent - 8 - 21 3~83 3 carboxylic acid) marketed by The Goodyear Tire ~
Rubber Company. These carboxylated copolymers contain approximately 0.5-10 percent by weight terminal carboxyl groups.
The sulfur cured rubber composition also contains a natural or synthetic diene derived rubber.
Representative of the rubbers include medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
Preferably, the rubber is natural rubber, styrene-butadiene rubber or cis-polybutadiene. This rubber, other than the epoxidized natural rubber and carboxylated nitrile rubber, may be used in amounts ranging from 98 to 70 parts by weight based on 100 parts by weight of total rubber. Preferably, this rubber is used in amounts ranging from about 95 to about 80 parts by weight based on 100 parts by weight of total rubber.
The compositions of the present invention may be compounded by conventional means including a Banbury~, mill, extruder, etc. It has been found to be preferred to add the carboxylated nitrile rubber at a separate stage than the epoxidized rubber.
In addition to the above-identified and required components of the sulfur cured rubber compositions of the present invention, one may also use a siliceous pigment (alternatively referred to herein as silica filler). The silica filler that can be used include both pyrogenic and precipitated finely-divided silicas of the type heretofore employed for rubber compounding. The silica filler, however, is preferably of the type obtained by precipitation from 213~833 a soluble silicate, such as sodium silicate. For example, silica fillers produced according to the method described in U.S. Patent No. 2,940,830 can be used. These precipitated, hydrated silica pigments have a SiO2 content of at least 50~ and usually greater than 80~ by weight on anhydrous basis. The silica filler may have an ultimate particle size in the range of from about 50 to 10,000 angstroms, preferably between 50 and 400 and, more preferably, between 100 and 300 angstroms. The silica may be expected to have an average ultimate particle size in a range of about 0.01 to 0.05 microns as determined by electron microscope, although the silica particles may even be smaller in size. The BET surface area of the filler as measured using nitrogen gas is preferably in the range of 40 to 600 square meters per gram, usually 50 to 300 square meters per gram. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Vol. 60, page 304 (1930). The silica also has a dibutyl (DBP) absorption value in a range of about 200 to about 400, with a range of from about 220 to 300 being preferred.
Various commercially available silicas may be considered, for example, silicas commercially available from PPG Industries under the Hi-Sil trademark such as, for example, those with designations 210, 243, etc.; silicas available from Rhone-Poulenc, with designations of Z1165MP and Z165GR
and silicas available from Degussa AG with designations VN2 and VN3, etc. The Rhone-Poulenc Z1165MP silica is a preferred silica which is reportedly characterized by having a BET surface area of about 160-170 and by a DBP value of about 250-290 and by having a substantially spherical shape.
The amount of silica filler used as the reinforcing filler can vary widely. Generally ~13~833 speaking, the amount may range between about 5 and about 85 parts by weight of siliceous pigment per 100 parts by weight of total rubber are used. More typically, between about 10 and 50 parts by weight of siliceous pigment per 100 parts of rubber are used.
In compounding a silica filled rubber composition, one generally uses a coupling agent.
Such coupling agents, for example, may be premixed, or pre-reacted, with the silica particles or added to the rubber mix during the rubber/silica processing, or mixing, stage. If the coupling agent and silica are added separately to the rubber mix during the rubber/silica mixing, or processing stage, it is considered that the coupling agent then combines in situ with the silica.
In particular, such coupling agents are generally composed of a silane which has a constituent component, or moiety, (the silane portion) capable of reacting with the silica surface and, also, a constituent component, or moiety, capable of reacting with the rubber, particularly a sulfur vulcanizable rubber which contains carbon-to-carbon double bonds, or unsaturation. In this manner, then the coupler acts as a connecting bridge between the silica and the rubber and thereby enhances the rubber reinforcement aspect of the silica.
The silane of the coupling agent apparently forms a bond to the silica surface, possibly through hydrolysis, and the rubber reactive component of the coupling agent combines with the rubber itself.
Usually the rubber reactive component of the coupler is temperature sensitive and tends to combine with the rubber during the final and higher temperature sulfur vulcanization stage and, thus, subsequent to the rubber/silica/coupler mixing stage and, therefore, after the silane group of the coupler has combined - 11- 213~833 with the silica. However, partly because of typical temperature sensitivity of the coupler, some degree of combination, or bonding, may occur between the rubber-reactive component of the coupler and the rubber during an initial rubber/silica/coupler mixing stages and, thus, prior to a subsequent vulcanization stage.
The rubber-reactive group component of the coupler may be, for example, one or more of groups such as mercapto, amino, vinyl, epoxy, and sulfur groups, preferably a sulfur or mercapto moiety and more preferably sulfur.
A representative coupling agent may be, for example, a bifunctional sulfur containing organosilane such as, for example, bis-(3-triethoxy-silylpropyl)tetrasulfide, bis-(3-trimethoxy-silylpropyl)tetrasulfide and bis(3-triethoxy-silylpropyl)tetrasulfide grafted silica from DeGussa, A.G. The amount of silica coupling agent which may be used may range from about 0.5 to about 8.5 parts by weight per 100 parts by weight of total rubber used.
Preferably, the amount of silica coupler ranges from about 1.0 to about 5.0 parts by weight per 100 parts by weight of rubber used.
The sulfur cured rubber composition may also contain conventional additives including reinforcing agents, fillers, peptizing agents, pigments, stearic acid, accelerators, sulfur w lcanizing agents, antiozonants, antioxidants, processing oils, activators, initiators, plasticizers, waxes, prevulcanization inhibitors, extender oils and the like. Representative of reinforcing agents include carbon black, which is typically added in amounts ranging from about 5 to 100 parts by weight based on 100 parts by weight of total rubber (phr).
Preferably, carbon black is used in amounts ranging from about 15 to 85 phr. Typical carbon blacks that ~1 3~833 are used include N110, N121, N220, N231, N234, N242, N293, N299, N326, N330, M332, N339, N343, N347, N351, N358, N375, N472, N539, N550, N660, N683, N754, and N765. Depending on the particular use of the compound, the appropriate carbon black may be selected. Representative of conventional accelerators are amines, guanidines, thioureas, thiols, thiurams, sulfenamides, dithiocarbamates and xanthates which are typically added in amounts of from about 0.2 to about 5 phr. Representative of sulfur w lcanizing agents include element sulfur (free sulfur) or sulfur donating w lcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. The amount of sulfur w lcanizing agent will vary depending on the type of rubber and particular type of sulfur wlcanizing agent but generally range from about 0.1 phr to about 5 phr with a range of from about 0.5 phr to about 2 phr being preferred.
Representative of the antidegradants which may be in the rubber composition include monophenols, bisphenols, thiobisphenols, polyphenols, hydroquinone derivatives, phosphites, phosphate blends, thioesters, naphthylamines, diphenol amines as well as other diaryl amine derivatives, para-phenylene diamines, quinolines and blended amines. Antidegradants are generally used in an amount ranging from about 0.1 phr to about 10 phr with a range of from about 2 to 6 phr being preferred. Representative of a peptizing agent that may be used is pentachlorophenol which may be used in an amount ranging from about 0.1 phr to 0.4 phr with a range of from about 0.2 to 0.3 phr being preferred. Representative of processing oils which may be used in the rubber composition of the present invention include aliphatic-naphthenic aromatic resins, polyethylene glycol, petroleum oils, ester plasticizers, vulcanized vegetable oils, pine tar, 213~833 phenolic resins, petroleum resins, polymeric esters and rosins. These processing oils may be used in a conventional amount ranging from about 0 to about 50 phr with a range of from about 5 to 35 phr being preferred. Representative of an initiator that may be used is stearic acid. Initiators are generally used in a conventional amount ranging from about 1 to 4 phr with a range of from about 2 to 3 phr being preferred.
Accelerators may be used in a conventional amount. In cases where only a primary accelerator is used, the amounts range from about 0.5 to 2.5 phr. In cases where combinations of two or more accelerators are used, the primary accelerator is generally used in amounts ranging from 0.5 to 2.0 phr and a secondary accelerator is used in amounts ranging from about 0.1 to 0.5 phr. Combinations of accelerators have been known to produce a synergistic effect. Suitable types of conventional accelerators are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
Preferably, the primary accelerator is a sulfenamide.
If a secondary accelerator is used, it is preferably a guanidine, dithiocarbamate or thiuram compound.
Pneumatic tires are conventionally comprised of a generally toroidal shaped carcass with an outer circumferential tread adapted to the ground contacting space beads and sidewalls extending radially from and connecting said tread to said beads. The tread may be built, shaped, molded and cured by various methods which will be readily apparent to those skilled in the art.
The sulfur cured rubber composition may be used to form a tread rubber which can then be applied in the building of a green tire in which the uncured, shaped tread is built unto the carcass following which the green tire is shaped and cured. Alternatively, ~I39833 the tread can be applied to a cured tire carcass from which the previously tread has been buffed or abraded away and the tread cured thereon as a retread.
The practice of this invention is further illustrated by reference to the following examples which are intended to be representative rather than restrictivé of the scope of the invention. Unless otherwise indicated, all parts and percentages are by weight.
Example 1 Rubber compositions containing the materials set out in Table I were prepared in a BR Banbury~ using three separate stages of addition. Table I also sets out the cure behavior and w lcanizate properties for the control compound A and also compounds B, C and control D which contain polyisoprene, epoxidized natural rubber and carboxylated nitrile rubber.
SampleControl Control A D C D
1st Non-Productive Polyisoprenel 100 90 80 60 Epoxidized NR2 0 5 10 20 Carbon Black 35 35 35 35 Zinc Oxide 5 5 5 5 Processing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2nd Non-Productive Carbon Black 15 15 15 15 Carboxylated Nitrile3 0 5 10 20 Productive Sulfur ¦ 1.4 ¦1.4 ¦1.4 ¦1.4 Accelerator ¦1.0 ¦ 1.0 ¦ 1.0 ¦1.0 Rheometer, 150C
Max Torque 40.0 40.3 38.0 37.0 Min Torque 6.7 8.0 8.4 12.0 ~ Torque 33.3 32.3 29.6 25.0 T90 (min) 13.3 13.0 14.5 14.0 Stress-Strain Tensile Strength (MPa) 21.1 19.6 14.7 8.4 Elongation ~ Brk (~) 528 523 428 229 M100 (MPa) 2.0 2.6 3.1 4.5 M300 (MPa) 11.0 10.6 10.6 --Hardness Room Temperature 61 68 69 74 Rebound Room Temperature 48 35 30 23 Strebler to Self (N) 111 169 73 6 DIN Abrasion (~ Standard) 108 62 87 142 INatsyn~ 2200 obtained from The Goodyear Tire h Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer's Research Association 3Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the above data, use of 5 and 10 parts of carboxylated nitrile rubber and epoxidized nitrile rubber results in improved (lower) DIN
abrasion in comparison to the controls.
At the 5 phr level of carboxylated nitrile rubber and epoxidized nitrile rubber, one gets superior (higher) tear properties (Peel Adhesion) versus the controls.
~134833 Example 2 Silica-filled rubber compositions containing the materials set out in Table I were prepared in a BR
Banbury~ using three separate stages of addition.
Table II also sets out the cure behavior and vulcanizate properties for control compound E, control compound F and compounds G and H.
TAP~E II
Sample Control Control E F G H
1st Non-Productive Polyi60prenel 100 100 80 80 Epoxidized NR2 0 0 10 10 Carbon Black 35 35 35 35 Zinc Oxide 5 5 5 5 Processing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2nd Non-Productive Silica3 15 15 15 15 Carboxylated Nitrile4 0 0 10 10 Organo6ilane Coupling 0 3 0 3 AgentS
Productive Sulfur 1.4 1.4 1.4 1.4 Sulfenamide Accelerator 1.0 1.0 1.0 1.0 Rheometer, 150C
Max Torque 26.4 31.5 27.7 30.7 Min Torque 6.7 7.7 12.3 11.0 ~ Torque 19.7 23.8 15.4 19.7 T90 (min) 22.3 18.5 22.0 20.0 Stre66-Strain Ten6ile Strength (MPa) ¦14.1 ¦18.2 ¦5.7 ¦ 7.5 2l34833 Elongation ~ Brk (~) 528 229 414 382 M100 (NPa) 0.96 1.53 2.05 2.60 M300 (MPa) 3.98 7.14 4.46 6.66 Hardness Room Temperature 46.6 54.3 66.0 68.7 100C 42.2 50.6 53.1 57.1 Rebound Room Temperature 42.1 45.1 27.6 27.8 100C 51.0 56.2 44.1 43.5 DIN Abrasion 290 181 175 151 (~ of Standard) 1Nat6yn~ 2200 obtained from The Goodyear Tire & Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer'6 Reæearch As60ciation 3Hil Sil~ 210 obtained from PPG
4Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company 5Si69 obtained from Degu66a As can be seen from the above data, Samples G and H have improved modulus and DIN abrasion values versus the corresponding Control E and Control F.
Example 3 Silica-filled rubber compositions containing the materials set out in Table III were prepared in a BR
Banbury~ using three separate stages of addition.
o Table III also sets out the cure behavior and vulcanizate properties for control compound I, compound J, control compound K and compound L.
TABLE III
Sample Control Control I J K L
1st Non-Productive E-SBRI 68.7568.7568.75 68.75 Polybutadiene215.00 15.0015.0015.00 Polyisoprene335.00 30.0035.0015.00 Epoxidized NR40.00 2.50.0010.00 Silicas 40.00 40.0040.0040.00 Carbon Black 10.00 10.0010.00110.00 Zinc Oxide 3.00 3.003.00 3.00 Fatty Acid 3.00 3.003.00 3.00 Organosilane Coupling 0.000.00 2.00 2.00 Agent6 Antioxidant 2.00 2.002.00 2.00 2nd Non-Productive Silicas 30.00 30.0030.0030.00 Carboxylated Nitrile7 0.002.50 0.00 10.00 Organosilane Coupling 0.000.00 1.50 1.50 Agent6 Productive Sulfur 3.50 3.501.40 1.40 Accelerator 3.50 3.501.80 1.80 Secondary Accelerator 2.002.00 1.50 1.50 Rheometer, 150C
Max Torque 58.5 59.046.0 52.7 Min Torque 15.8 17.39.0 19.5 ~ Torque 42.7 41.737.0 33.2 T90 (min) 16.3 14.818.5 19.0 Stress-Strain Tensile Strength ~MPa)7.759.89 15.4 15.2 Elongation ~ Brk (~) 261257 384 382 M100 (MPa) 2.77 3.573.48 4.81 DIN Abrasion 170 137112 103 (~ of Standard) - 19 - ~13~833 IPlioflex~ 1712 obtained from The Goodyear Tire & Rubber Company 2Budene~ 1207 obtained from The Goodyear Tire & Rubber Company 3Natsyn~ 2200 obtained from The Goodyear Tire & Rubber Company 4ENR-25 obtained from The Malaysian Rubber Producer' 8 Research As~ociation 5Zl165 MP obtained from Rhene-Poulenc 6Si69 obtained from Degu6æa 7Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the above data, the present invention provides improved DIN abrasion values for silica containing compounds both with and without the presence of a silica coupler.
Example 4 Rubber compositions containing the materials set out in Table IV were prepared in a BR Banbury~ using three separate stages of addition. Table IV also sets out the cure behavior and vulcanizate properties for control compound M, control compound N, control compound O and compound P.
TABLE IV
Sample Control Control Control M N O P
l~t Non-Productive Polyi~oprenel 100 95 95 90 Epoxidized NR2 0 5 0 5 Carbon Black 50 50 50 50 Zinc Oxide 5 5 5 5 Proce~ing Oil 5 5 5 5 Fatty Acid 2 2 2 2 Antioxidant 2 2 2 2 2 5 2nd Non-Productive Carboxylated Nitrile3¦ 0 ¦ 0¦ 5 ¦ 5 Productive Sulfur ¦1.4 ¦1.4 ¦1.4 ¦ 1.4 213~833 Accelerator ¦1.0 ¦1.0 ¦1.0 ¦1.0 Rheometer, 150C
Max Torque 40.0 39.3 39.0 39.0 Min Torque 9.7 9.9 10.3 11.3 ~ Torque 30.3 29.4 28.7 27.7 T90 (min) 13.3 13.5 13.5 13.5 Stre6s-Strain Ten~ile Strength (MPa) 21.1 20.8 19.1 18.5 Elongation ~ Brk (~) 506 518 495 485 M100 (MPa) 2.36 2.46 2.79 3.03 Peel Adhe6ion to Self (N) 106 118 152 157 DIN Abrasion 108 101 93 76 (~ of Standard) 15 INat~yn~ 2200 obtained from The Goodyear Tire & Rubber Company 2ENR-25 obtained from The Malaysian Rubber Producer's Re6earch As~ociation 3Chemigum~ NX775 obtained from The Goodyear Tire & Rubber Company As can be seen from the data in Table IV, there is a synergistic effect from the presence of both epoxidized rubber and carboxylated nitrile versus the presence of each component alone.
Claims (19)
1. A sulfur cured rubber composition composed of, based on 100 parts by weight of rubber (phr);
(a) 1.0 to 15 parts by weight of epoxidized natural rubber;
(b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber; and (c) 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
(a) 1.0 to 15 parts by weight of epoxidized natural rubber;
(b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber; and (c) 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
2. The sulfur cured rubber composition of claim 1 wherein the epoxidized rubber has a level of epoxidized modification in the range of from about 15 to 85 mole percent.
3. The sulfur cured rubber composition of claim 1 wherein from 0.75 percent to 15 percent by weight chain linkages are derived from an unsaturated carboxylic acid monomer.
4. The sulfur cured rubber composition of claim 1 wherein said composition additionally comprises 5 to 85 parts by weight of a silica filler.
5. The sulfur cured rubber composition of claim 4 wherein said composition additionally comprises 0.5 to 8.5 parts by weight of a silica coupling agent.
6. The sulfur cured rubber composition of claim 4 wherein the silica is selected from the group consisting of pyrogenic and precipitated silicas.
7. The sulfur cured rubber composition of claim 6 wherein the silica has an ultimate particle size in a range of from about 50 to 1,000 angstroms and a BET
surface area in the range of from about 40 to 600.
surface area in the range of from about 40 to 600.
8. The sulfur cured rubber composition of claim 5 wherein the silica coupling agent is a bifunctional sulfur containing organosilane.
9. The sulfur cured rubber composition of claim 8 wherein the coupling agent is selected from the group consisting of bis-(3-triethoxy-silylpropyl)tetrasulfide, bis-(3-trimethoxy-silylpropyl)tetrasulfide and bis(3-triethoxy-silylpropyl)tetrasulfide grafted silica.
10. The sulfur cured rubber composition of claim 1 comprising, based on 100 parts by weight of rubber (phr);
(a) 2.5 to 10 parts by weight of epoxidized natural rubber;
(b) 2.5 to 10 parts by weight of a carboxylated nitrile rubber;
(c) 98 to 70 parts by weight of a rubber selected from a group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
(a) 2.5 to 10 parts by weight of epoxidized natural rubber;
(b) 2.5 to 10 parts by weight of a carboxylated nitrile rubber;
(c) 98 to 70 parts by weight of a rubber selected from a group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
11. A pneumatic tire having an outer circumferential tread wherein said tread comprises a sulfur cured rubber composition composed of, based on 100 parts by weight of rubber (phr);
(a) 1.0 to 15 parts by weight of epoxidized natural rubber;
(b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber;
(c) 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
(a) 1.0 to 15 parts by weight of epoxidized natural rubber;
(b) 1.0 to 15 parts by weight of a carboxylated nitrile rubber;
(c) 98 to 70 parts by weight of a rubber selected from the group consisting of medium vinyl polybutadiene, styrene-butadiene rubber, synthetic cis-1,4-polyisoprene, synthetic 3,4-polyisoprene, natural rubber, cis-polybutadiene, styrene-isoprene rubber, styrene-isoprene-butadiene rubber, acrylonitrile-butadiene rubber and mixtures thereof.
12. The pneumatic tire of claim 11 wherein the epoxidized rubber has a level of epoxidized modification in the range of from about 15 to 85 mole percent.
13. The pneumatic tire of claim 11 wherein from 0.75 percent to 15 percent by weight chain linkages are derived from an unsaturated carboxylic acid monomer.
14. The pneumatic tire of claim 11 wherein said composition additionally comprises 5 to 85 parts by weight of a silica filler.
15. The pneumatic tire of claim 14 wherein the silica is selected from the group consisting of pyrogenic and precipitated silicas.
16. The pneumatic tire of claim 15 wherein said composition additionally comprises 0.5 to 8.5 parts by weight of a silica coupling agent.
17. The pneumatic tire of claim 16 wherein the silica has an ultimate particle size in a range of from about 50 to 1,000 angstroms and a BET surface area in the range of from about 40 to 600.
18. The pneumatic tire of claim 16 wherein the silica coupling agent is a bifunctional sulfur containing organosilane.
19. The pneumatic tire of claim 18 wherein the coupling agent is selected from the group consisting of bis-(3-triethoxy-silylpropyl)tetrasulfide, bis-(3-trimethoxy-silylpropyl)tetrasulfide and bis(3-triethoxy-silylpropyl)tetrasulfide grafted silica.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/313,954 | 1994-09-28 | ||
| US08/313,954 US5462979A (en) | 1994-09-28 | 1994-09-28 | Sulfur cured rubber composition containing epoxidized natural rubber and carboxylated nitrile rubber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2134833A1 true CA2134833A1 (en) | 1996-03-29 |
Family
ID=23217904
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002134833A Abandoned CA2134833A1 (en) | 1994-09-28 | 1994-11-01 | Sulfur cured rubber composition containing expoxidized natural rubber and carboxylated nitrile rubber |
Country Status (5)
| Country | Link |
|---|---|
| US (4) | US5462979A (en) |
| EP (1) | EP0704481B1 (en) |
| CA (1) | CA2134833A1 (en) |
| DE (1) | DE69501303T2 (en) |
| ES (1) | ES2113152T3 (en) |
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| US5708053A (en) * | 1996-08-15 | 1998-01-13 | The Goodyear Tire & Rubber Company | Silica-filled rubber compositions and the processing thereof |
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| EP0972799A1 (en) * | 1998-07-15 | 2000-01-19 | PIRELLI PNEUMATICI Società per Azioni | Vulcanizable rubber composition for treads of vehicle tires |
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| US10179479B2 (en) | 2015-05-19 | 2019-01-15 | Bridgestone Americas Tire Operations, Llc | Plant oil-containing rubber compositions, tread thereof and race tires containing the tread |
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| US11555102B2 (en) * | 2017-11-22 | 2023-01-17 | Bridgestone Europe Nv/Sa | Rubber compound for portions of pneumatic tyres |
| CN110684253B (en) * | 2018-07-06 | 2022-01-04 | 中国石油天然气股份有限公司 | Amidated vulcanized carboxyl nitrile rubber and preparation method thereof |
| CN110684252B (en) * | 2018-07-06 | 2022-01-04 | 中国石油天然气股份有限公司 | Carboxyl nitrile rubber and preparation method thereof |
| WO2020227459A1 (en) | 2019-05-07 | 2020-11-12 | Cooper Tire & Rubber Company | Electrically conductive tread chimney compound |
| CN114992595A (en) * | 2022-03-01 | 2022-09-02 | 上海英众信息科技有限公司 | Anti-seismic street lamp tower pole |
| CN116970229B (en) * | 2023-09-23 | 2023-12-05 | 河北华密新材科技股份有限公司 | Pressure-resistant shrinkage rubber sealing gasket and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4585826A (en) * | 1985-01-28 | 1986-04-29 | The Firestone Tire & Rubber Company | Natural rubber containing compositions with increased tear strength |
| US5023301A (en) * | 1990-03-05 | 1991-06-11 | The Goodyear Tire & Rubber Company | Polypropylene reinforced rubber |
| US5225479A (en) * | 1991-10-17 | 1993-07-06 | The Goodyear Tire & Rubber Company | Polymers derived from a conjugated diolefin, a vinyl-substituted aromatic compound, and olefinically unsaturated nitrile |
| JPH06220254A (en) * | 1993-01-22 | 1994-08-09 | Yokohama Rubber Co Ltd:The | Rubber composition for tire tread |
| US5396940A (en) * | 1993-09-17 | 1995-03-14 | The Goodyear Tire & Rubber Company | Sulfur cured rubber composition containing epoxidized natural rubber and silica filler |
-
1994
- 1994-09-28 US US08/313,954 patent/US5462979A/en not_active Expired - Fee Related
- 1994-11-01 CA CA002134833A patent/CA2134833A1/en not_active Abandoned
-
1995
- 1995-05-30 US US08/452,745 patent/US5489628A/en not_active Expired - Fee Related
- 1995-05-30 US US08/452,744 patent/US5489627A/en not_active Expired - Lifetime
- 1995-05-30 US US08/452,929 patent/US5488077A/en not_active Expired - Fee Related
- 1995-09-19 EP EP95202522A patent/EP0704481B1/en not_active Expired - Lifetime
- 1995-09-19 DE DE69501303T patent/DE69501303T2/en not_active Expired - Fee Related
- 1995-09-19 ES ES95202522T patent/ES2113152T3/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US5489627A (en) | 1996-02-06 |
| ES2113152T3 (en) | 1998-04-16 |
| EP0704481B1 (en) | 1997-12-29 |
| US5462979A (en) | 1995-10-31 |
| US5489628A (en) | 1996-02-06 |
| DE69501303D1 (en) | 1998-02-05 |
| DE69501303T2 (en) | 1998-07-09 |
| US5488077A (en) | 1996-01-30 |
| EP0704481A1 (en) | 1996-04-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |