Indian Patents. 217042:RUBBER-SILICA COMPOSITE WITH EPOXIDISED NATURAL RUBBER AS A REINFORCEMENT MODIFIER

Title of Invention	RUBBER-SILICA COMPOSITE WITH EPOXIDISED NATURAL RUBBER AS A REINFORCEMENT MODIFIER
Abstract	Epoxldlsed natural rubber could be used for Improving tt1e reinforcement of sulphur cured rubber-silica composites.

Full Text	"RUBBER SILICA COMPOSITE WITH EPOXIDISED NATURAL RUBBER AS A REINFORCEMENT MODIFIER" The present invention relents to a method for Improvement in silica reinforcement of any Rubber - Silica compositions using epoxidised natural rubber (ENR), (Nirticuiartv suited for use in tyre treads, tyre-carcass and tyre retread of a worn-out tyre; and also for any other rubber products specially requiring silica as a reinforcing agent such as paddy-dehusldng nit tow rollers In paddy-mills and printing rubber rollers in printing-press^ etc. I. BACKGROUND OF THE INVENTION :- Conventional pneumatk: tires are made by building/combining various components such as tyre tread, tyre carcass, sidewall, under tread, etc. These components are made separately from a combination of a variety of ingredients such as rubber, filler, plasticizer, curatives, anttdegradants etc. The rubber used In tyres can be eelier single or a blend of more than one. The rubbers generally being used in tires are natural rubber (NR) or synthetic cis-polyisoprene rubber, styrene butadiene rubber (SBR), polybutadiene rubber (BR) and ethylene propylene rubber (B"DM). The filler are incorporated to force the rubber. Carbon black is the most popular axe most effective reinforcing filler. Carbon black is a petroleum derivative. The second filler, which is popular, is Silica and It a more ecofriendiy material. Recently there is a global trend for a snit from carbon black to silica to use either alone or as Mend of these two. Wider use of silica instead of carbon black as a filler in tyre treads has been prompted by the need to combine high wear resistance, high wet grip and low fuel consumption, resulting from lower tyre rolling resistance. Generally hydrocarbon rubbers are being used in tyres. Carbon black can function as a reinforcing filler in hydrocarbon rubbers without the use of any modifier, while silica being a mineral filler is not compatible with such rubbers and needs modifiers for effiective reinforcement The use of modifiers, makes the silica tyres more expensive. The conventional modifiers used to Improve the silk’s reinforcement of rubbers are known as silane coupling agents. The function of the simian is to promote the bonding badwoman the silica and rubber surfaces. Typical coupling agent is living a stratum as given under: X » 0CH3 , OCzHs or oilier similar functional groups plait can Interact with silica surface groups (These groups will get converted to hydroxyl groups on hydrolysis) Y=: Functional group winch can errant with rubber. Coupling agents acts as a connecting link between silica and rubber, thereby entrances the reinforcement IX. OBJECTS OF INVENTION The main object of the present invention is related to the sputter cured rubber conrnxtsitions containing silica as the filler. Generally for such compositions, simian coupling agents are also at be used for achieving effective enforcement The present invention is that replacing a portion of tie rubber or ruttier blend being used for the said silica based compositions with epoxidised natural ruttier so tint the use of silanes coupling agents can be died easier partially or frilly. This could reduce the cost of silica filled tyres arid other products. ENR that can be used for this purpose, can leave an epoxy content In the range, 5 80 mole per cert and the selection depends on the compositions of the final product The present finding is that epoxidised natural rubber in addition to its normal function as a rubber, also serves as a coupling agent or as an interface modifier between silica and rubber. BNR can also Improve the dispersion of lawman in rubber. The structure of BNR is given under. The epoxy group can interact with the active silanes groups on the silica surfece and the unsaturatlon part with the rest of the rubber through sulphur badges, during vulcanization, thus B is functionally identical with silane coupling agents. The B0% being more polar than most of the rubbers being used for making tyres, can function also as an interface modifier between salted and rubber. The polar ENR can form a coating over the silica particles, thus reducing the filler-faller interaction, and thus an improved silica dispersion in rubbers corm be achieved. In the case of silica filled acrylonitrile butadiene rubber (NBR), in addition to the above stated functions of ENR, In the present reported Invention It was also found that these two rubbers can self crosslink, giving better technological properties to the final product, comparable with that obtained for the silane modified. The likely mechanism of cross linking of NBR and ENR is given under. ZXI. SUMHARY OF THE INVENTION The present invention relates to a sulphur cured rubber compositors are composed of, based on 100 parts by weight of rubber, m about 1 to 25 parts by weight of ENR, from about 99 to 75 parts by weight of a rubber selected from the group consisting of either natural rubber, styrene butadiene room, polybutadiene rubber, acrylonitrile butadiene rubber and mixtures thereof and wherein the sakes rubber composition further comprises 10 to 85 parts by weight of silica filler selected from the group) consisting of precipitated silica. With such a composition efficient reinforcement of rubber with silica is possible without using coupling agent. The invention in short can be put as given below. Conventional practice: (Gnarl rubber-silica composites) Ingredients Parts by weight Rubber/Rubber blend 100 Silica Variable (10 to 85 parts per hundred rubber) Silane coupling agent Variable (0-8 % based on the filter Other general rubber concentration) compounding ingredients Present Invention: Ingredients Parts by weight Rubber/Rubber blend 100-X Silica Variables (10 to 85 parts per hundred Epoxidised natural rubber rubber) Cheer general rubber X(X~ 1 to 2^ compounding Ingredients With the Incorporation of ENR, the important improvements achieved with regard to the silica reinforcement of rubbers are given below. 1. Better filler dispersion in rubber 2 Better rubber - filler Interaction 3. Better compatibility between rubber and filler 4. Better process ability 5. Faster cure 6. Better modulus and strength for the final product 7. Better tear strength and abrasion resistance to the finished product a Better aging resistance 9. Better flex resistance 10. Can avoid the use of costly coupling agents either partially or fully 11. Energy saving IZ Cost advantage IV. DESCRIPTION OF THE INVENTION The present invention relates to, sulphur cured, silica reinforced rubber compounds, which can be used for mating various rubber products and more particularly stilton reinforced rubber compounds modified with EMk, having its effects as a reirrfbrce modifier. Conventionally, for silica filled rubber compourxis, slant coupling agents are being used as reinforcement modifiers. The present invention of using BMR« in the silica filled rubber compounds that can work as a cost-effiectlve alternative to the use of sllane coupling agents In such compounds. BMR is pretended to function as an interfile modifier, diapers modifier and as a coupling agent for the rubber - silica composites. The present invention is likely to find application in tyre and non-tyre products. The details of the important components of the rubber compounds, relevant to the present Invention is given below. a) Epoxidised Natural Rubber : (ENR) Epoxidised natural rubber is a nrxxlified form of natural rubber in which some of the instauration is replaced by peroxide groups. ENR that may be used for tans particular invention may have a level of pixilation ranging from about 5 to 80 mole per cent; preferably the epoxkle level will be In the range from 25 to 60 mole percent A particularly preferred epoxide level is SO to 60 percent As known to those skilled In the art, BMR can be obtained by epoxidlstng natural rubber latex. The material is available in the form of dehydrated bales. From the observations of the present invention, it can be stated that ENR can perform as a reinforcement modifier or Interface modifier between silica and rubber in silica filled rubber compounds. It also improves the dispersion of silica in rubber and the bonding between the two. Hence on blending a limited quantity of ENR with other rubbers could enhance the silica reinforcement of such rubber The usual level of replacement of rubber with ENR ranges fine 1 to 25 parts per ICX) parts of the total rubber and more preferably form 5 to 15 parts and is decided based on the filter loading. b) Bate rubber or Rubber blend The basic concept of the invention is to blend a limited quantity of ENR as a reinforcement modifier with any of the general rubbers or blends of rubbers being used for making rubber products, which are reinforced with silica. The composition of the base rubber or rubber blend usually comprises from 99 to 75 percent by weight of the total rubber being used, and is preferably from 95 to G6 percent by weight of the total rubber and rest being ENR. The term "Base rubber or Rubber blend" is used to indicate the rubber, other than B4R. The base rubber or rubber blend is usually a single or mixture of rubbers, selected from the group consisting of either natural rubber, styrene butadiene rubber, polybutadiene rubber and acrylonitrile butadiene rubber and/or mixtures thereof. The rubber or rubber blend employed in the composition of the invention is preferably of the one chosen from the group mentioned above or a mixture of rubbers chosen fame the group. c) Silica Another important component of the sulphur cured rubber composition of the present invention is a siliceous pigment (alternatively referred herein as silica filler). The silica filler used for rubber compounding can be both phylogenic and precipitated finely divided silicas. The silica filler, however, is preferably of the type obtained by precipitation from a soluble silicate, such as sodium silicate. These precipitated hydrated silica pigments thieve a SIO2 content usually greater than 90 percent by weight of anhydrous basis. The particular silica used in the present study is the "Ultrasli VN3 a Degussa AG inflict As far as the present invention is concerned, various other commercial silicas also can attention in a similar manner. (The commercial silicas of the reinforcing category in general will have a particle si2 in the range of 50-1000 angst>ms, BET surface are in the range of 40 to 600 square meters per gram and DBP absorption number in tie range of about 220 to 3CX)). The amount of silica filter used as the reinforcing filler can vary widely. The quantity usually may range between 10 to 85 parts by weight per 100 parts by weight of total rubber used. More typically, between 40 to 60 parts by weight of silica pigment per 100 parts of rubber are used. d) Silane coupling agent Usually in the conventional practice for obtaining effective silica reinforcement of rubbers, silane coupling agents are being used. Generally it is premixed with silica before compounding. Silane coupling agents usually consists of a silane having two functional moieties, one of which will react with the silica since groups and the other with the rubber. Thus the coupling agent act as a connecting bridge between silica and the rubber and thereby enhances the reinforcement The silane group of the coupling agar apparently forms a bond to die silica surface and the rubble reactive component of the coupling agent usually the sulphur combines with the rubber. The rubber reactive component of the coupling agent combines with the rubber at the vulcanization temperature. Rare die silane-coupling agents, the usual rubber reactive functional groups can be any of mercapto, amino, vinyl, epoxy and sulphur groups, preferably a sulphur or mercapto moiety and more preferably sulphur. The silane coupling agent being used for the experiment was a bifiinctiorMil sulphur containing organosilane, Si69, a Degussa product; which is chemically Bis - (3- trietnoxysiiyi propyl; ceirasuipniae. the amount of stance coupling agent which may be used may range from 0.5 to 10 percent by weight of the filler being used. e) Other general compounding ingredients In addition to the various commoner mentioned, die sulphur cured rubber composition also contain conventional additives such as zinc oxide, stearic acid, accelerators, sulphur vulcanizing agents, antioxidants, antioxidants, process oils, etc. Representatives conventional accelerators are thiols, thturams, suiptienamides, guanidine’s etc. Typical vulcanizing agents Include elemental sulphur or sulphur donating vulcanizing agents. The amount of sulphur vulcanizing agent wilt vary depending on the type of rubber and particular type of vulcanizing agents, but generally range from 0.5 to 4 parts per hundred rubber (phr) with a range from 0.5 to Z 5 phr being preferred. Common processing oils Include naphtiienic or aromatic type for hydrocarbon rubbers and ester plasticizers for polar rubbers. Its dosage may vary from 2 to 20 phr. Conventional antidegradants used are In the range of 1 to 3 phr. The accelerator dosage can vary from 0 5 to 4 phr. for the silica composites, sulphenamide - guanidine accelerator combination is preferred. V. EXPERIMENTAL FINDINGS a) Proceesabifity studies Natural rubber - silica composites unmodified and modified with stone and ENR were prepared in the Record and the mixing energy was determined. Pnxessabiiity of the composites were evaluated using capillary remoter. Results are compared in Table 1. Lower viscosity and mixing energy exhibited by the BSiR containing mixes Indicates better dispersion of silica In the rubber phase. b) Application studies Applications of the invention The practice of this invention is further illustrated by reference to the following examples, which are Intended to be representative rather than restrictive of the scope of tiie invention. A typical silica based formulation is given below in Table Z All the experimental recipes given under were mixed in a laboratory model Intermix in a single stage mixing cycle. The order of addition also is given in Table Z Based on the formulation, the important test results relevant to the puniest, of few rubber composites used for tyre and non-tyre products, unmodified and modified with coupling agent and ENR are given below : 1. Tyre applications Tyre compounds are made from either natural or synthetic rubber. It can be used either alone or as blends. Subject to the availability from country to country and the specific requirements of the product, the blends can be either of natural rubber and synthetic rubber or of synthetic rubbers themselves. Typical formulation for various tyre compositions and the corresponding Important techologlcal properties are given In Tables 3-7. ® Ail the samples in Table 3, 4, 5, 6 and 7 also contain the ingredients 2*8 of Table Z R>r the compounds in Tables 3, 5, 6 and 7 the proceed oil used was naphthenic and for Table 4, aronrwtlc oil was used. 2. Non-tyre applications Typical application - Rice dehusldng rubber roller Test results of a typical formulation of acrylonitrile butadiene rubber (NBR) based rice dehusldng rubber rollers modified with ENR and silane-coupling agent Is given below : Tasting - Specifications followed : 1. Modulus and Tensile strength ASTM D 412 Z Tear strength ASTM D 624 3. Abrasion loss DIN 53516 4. Viscosity ASTM D 9099-93 VI. Major advantages of the present invention 1. Improved noinfbrcement of rubber-silica composites and hence better technological properties. Z Better possibility, faster cure and hence energy saving. 3. Better aging restacked. 4. BMR is a cheaper alternative to silane coupling agents and hence the cost advantage. WE CLAIM : 1. Epoxldlsed natural rubber could be used for Improvlng the reinforcement of sulphur cured rubber-silica compositas. Z The sulphur cured rubber-silica composite with epoxidised natural rubber as a reinforcement modifier as In claim 1, wherein the said ENR used has a typical structure as given below : After epoxidation, the distribution of epoxides will have a random nature. 3. Epoxidised natural rubber, identified as a silica reinforcement modifier as stated in claim 1, is derived from natural rubber, which is a renewable resource. 4. According to claim 1, the role of epoxidised natural rubber In improving the reinforcement of rubber-silica composites is identified to be due to its functions as an interface modifier, filler dispersion modifier, cure activator and/or as a coupling agent 5. The sulphur cured rubber composition of claim 1, is characterised in that the epoxidised natural rubber has a level of epoxidation in the range from 5-80 mole per cent and more particularly in the range of 50-6O mole per cent. 6. The sulphur cured rubber composition stated in clalml is characterised by, based on 100 parts by weight of rubber out of which, a) 99-75 parts by weight of a rubber is selected from the group of natural rubber, styrene butadiene rubber, polybutadlene rubber, acrylonltrlle butadiene rubber and/or selected mixtures thereof. b) 1 to 25 parts by weight of epoxidised natural rubber. c) 10 to 85 parts by weight of silica filler, preferably highly reinlforcing precipitated silica (generally having a particle size range of SO to 1000 angstroms and a BET surface area range of 40 to 600 square meters per gram) and more particularly In the 40 to 60 phr range. 7. The said claim 1, is applicable for any silica reinforced rubber product made from any rubber stated in claim 6 or for any similar rubbers. 8. The claim 1, is a cost effective and energy efficient means for improving the silica reinforcement of rubbers.

Full Text

"RUBBER SILICA COMPOSITE WITH EPOXIDISED NATURAL RUBBER AS A
REINFORCEMENT MODIFIER"
The present invention relents to a method for Improvement in silica reinforcement of any Rubber - Silica compositions using epoxidised natural rubber (ENR), (Nirticuiartv suited for use in tyre treads, tyre-carcass and tyre retread of a worn-out tyre; and also for any other rubber products specially requiring silica as a reinforcing agent such as paddy-dehusldng nit tow rollers In paddy-mills and printing rubber rollers in printing-press^ etc.
I. BACKGROUND OF THE INVENTION :-
Conventional pneumatk: tires are made by building/combining various components such as tyre tread, tyre carcass, sidewall, under tread, etc. These components are made separately from a combination of a variety of ingredients such as rubber, filler, plasticizer, curatives, anttdegradants etc. The rubber used In tyres can be eelier single or a blend of more than one. The rubbers generally being used in tires are natural rubber (NR) or synthetic cis-polyisoprene rubber, styrene butadiene rubber (SBR), polybutadiene rubber (BR) and ethylene propylene rubber (B"DM). The filler are incorporated to force the rubber. Carbon black is the most popular axe most effective reinforcing filler. Carbon black is a petroleum derivative. The second filler, which is popular, is Silica and It a more ecofriendiy material. Recently there is a global trend for a snit from carbon black to silica to use either alone or as Mend of these two. Wider use of silica instead of carbon black as a filler in tyre treads has been prompted by the need to combine high wear resistance, high wet grip and low fuel consumption, resulting from lower tyre rolling resistance. Generally hydrocarbon rubbers are being used in tyres. Carbon black can function as a reinforcing filler in hydrocarbon rubbers without the use of any modifier, while silica being a mineral filler is not compatible with such rubbers and needs modifiers for effiective reinforcement The use of modifiers, makes the silica tyres more expensive. The conventional modifiers used to Improve the silk’s reinforcement of rubbers are known as silane

coupling agents. The function of the simian is to promote the bonding badwoman the silica and rubber surfaces.
Typical coupling agent is living a stratum as given under:
X » 0CH3 , OCzHs or oilier similar functional groups plait can Interact with silica surface groups (These groups will get converted to hydroxyl groups on hydrolysis)
Y=: Functional group winch can errant with rubber.
Coupling agents acts as a connecting link between silica and rubber, thereby entrances the reinforcement
IX. OBJECTS OF INVENTION
The main object of the present invention is related to the sputter cured rubber conrnxtsitions containing silica as the filler. Generally for such compositions, simian coupling agents are also at be used for achieving effective enforcement The present invention is that replacing a portion of tie rubber or ruttier blend being used for the said silica based compositions with epoxidised natural ruttier so tint the use of silanes coupling agents can be died easier partially or frilly. This could reduce the cost of silica filled tyres arid other products. ENR that can be used for this purpose, can leave an epoxy content In the range, 5 80 mole per cert and the selection depends on the compositions of the final product The present finding is that epoxidised natural rubber in addition to its normal function as a rubber, also serves as a coupling agent or as an interface modifier between silica and rubber. BNR can also Improve the dispersion of lawman in rubber. The structure of BNR is given under.

The epoxy group can interact with the active silanes groups on the silica surfece and the unsaturatlon part with the rest of the rubber through sulphur badges, during vulcanization, thus B is functionally identical with silane coupling agents. The B0% being more polar than most of the rubbers being used for making tyres, can function also as an interface modifier between salted and rubber. The polar ENR can form a coating over the silica particles, thus reducing the filler-faller interaction, and thus an improved silica dispersion in rubbers corm be achieved.
In the case of silica filled acrylonitrile butadiene rubber (NBR), in addition to the above stated functions of ENR, In the present reported Invention It was also found that these two rubbers can self crosslink, giving better technological properties to the final product, comparable with that obtained for the silane modified. The likely mechanism of cross linking of NBR and ENR is given under.

ZXI. SUMHARY OF THE INVENTION
The present invention relates to a sulphur cured rubber compositors are composed of, based on 100 parts by weight of rubber, m about 1 to 25 parts by weight of ENR, from about 99 to 75 parts by weight of a rubber selected from the group consisting of either natural rubber, styrene butadiene room, polybutadiene rubber, acrylonitrile butadiene rubber and mixtures thereof and wherein the sakes rubber composition further comprises 10 to 85 parts by weight of silica filler selected from the group) consisting of precipitated silica. With such a

composition efficient reinforcement of rubber with silica is possible without using coupling agent.
The invention in short can be put as given below.
Conventional practice: (Gnarl rubber-silica composites)

Ingredients Parts by weight
Rubber/Rubber blend 100
Silica Variable (10 to 85 parts per hundred
rubber)
Silane coupling agent
Variable (0-8 % based on the filter
Other general rubber concentration)
compounding ingredients
Present Invention:

Ingredients Parts by weight
Rubber/Rubber blend 100-X
Silica Variables (10 to 85 parts per hundred
Epoxidised natural rubber rubber)
Cheer general rubber X(X~ 1 to 2^
compounding
Ingredients
With the Incorporation of ENR, the important improvements achieved with regard to the silica reinforcement of rubbers are given below.
1. Better filler dispersion in rubber
2 Better rubber - filler Interaction
3. Better compatibility between rubber and filler
4. Better process ability
5. Faster cure

6. Better modulus and strength for the final product
7. Better tear strength and abrasion resistance to the finished product a Better aging resistance

9. Better flex resistance
10. Can avoid the use of costly coupling agents either partially or fully
11. Energy saving IZ Cost advantage
IV. DESCRIPTION OF THE INVENTION
The present invention relates to, sulphur cured, silica reinforced rubber compounds, which can be used for mating various rubber products and more particularly stilton reinforced rubber compounds modified with EMk, having its effects as a reirrfbrce modifier. Conventionally, for silica filled rubber compourxis, slant coupling agents are being used as reinforcement modifiers. The present invention of using BMR« in the silica filled rubber compounds that can work as a cost-effiectlve alternative to the use of sllane coupling agents In such compounds. BMR is pretended to function as an interfile modifier, diapers modifier and as a coupling agent for the rubber - silica composites. The present invention is likely to find application in tyre and non-tyre products. The details of the important components of the rubber compounds, relevant to the present Invention is given below.
a) Epoxidised Natural Rubber : (ENR)
Epoxidised natural rubber is a nrxxlified form of natural rubber in which some of the instauration is replaced by peroxide groups. ENR that may be used for tans particular invention may have a level of pixilation ranging from about 5 to 80 mole per cent; preferably the epoxkle level will be In the range from 25 to 60 mole percent A particularly preferred epoxide level is SO to 60 percent As known to those skilled In the art, BMR can be obtained by epoxidlstng natural rubber latex. The material is available in the form of dehydrated bales.

From the observations of the present invention, it can be stated that ENR can perform as a reinforcement modifier or Interface modifier between silica and rubber in silica filled rubber compounds. It also improves the dispersion of silica in rubber and the bonding between the two. Hence on blending a limited quantity of ENR with other rubbers could enhance the silica reinforcement of such rubber The usual level of replacement of rubber with ENR ranges fine 1 to 25 parts per ICX) parts of the total rubber and more preferably form 5 to 15 parts and is decided based on the filter loading.
b) Bate rubber or Rubber blend
The basic concept of the invention is to blend a limited quantity of ENR as a reinforcement modifier with any of the general rubbers or blends of rubbers being used for making rubber products, which are reinforced with silica. The composition of the base rubber or rubber blend usually comprises from 99 to 75 percent by weight of the total rubber being used, and is preferably from 95 to G6 percent by weight of the total rubber and rest being ENR. The term "Base rubber or Rubber blend" is used to indicate the rubber, other than B4R. The base rubber or rubber blend is usually a single or mixture of rubbers, selected from the group consisting of either natural rubber, styrene butadiene rubber, polybutadiene rubber and acrylonitrile butadiene rubber and/or mixtures thereof.
The rubber or rubber blend employed in the composition of the invention is preferably of the one chosen from the group mentioned above or a mixture of rubbers chosen fame the group.
c) Silica
Another important component of the sulphur cured rubber composition of the present invention is a siliceous pigment (alternatively referred herein as silica filler). The silica filler used for rubber compounding can be both phylogenic and precipitated finely divided silicas. The silica filler, however, is preferably of the type obtained by precipitation from a soluble silicate, such as sodium silicate.

These precipitated hydrated silica pigments thieve a SIO2 content usually greater than 90 percent by weight of anhydrous basis.
The particular silica used in the present study is the "Ultrasli VN3 a Degussa AG inflict As far as the present invention is concerned, various other commercial silicas also can attention in a similar manner. (The commercial silicas of the reinforcing category in general will have a particle si2 in the range of 50-1000 angst>ms, BET surface are in the range of 40 to 600 square meters per gram and DBP absorption number in tie range of about 220 to 3CX)).
The amount of silica filter used as the reinforcing filler can vary widely. The quantity usually may range between 10 to 85 parts by weight per 100 parts by weight of total rubber used. More typically, between 40 to 60 parts by weight of silica pigment per 100 parts of rubber are used.
d) Silane coupling agent
Usually in the conventional practice for obtaining effective silica reinforcement of rubbers, silane coupling agents are being used. Generally it is premixed with silica before compounding. Silane coupling agents usually consists of a silane having two functional moieties, one of which will react with the silica since groups and the other with the rubber. Thus the coupling agent act as a connecting bridge between silica and the rubber and thereby enhances the reinforcement The silane group of the coupling agar apparently forms a bond to die silica surface and the rubble reactive component of the coupling agent usually the sulphur combines with the rubber. The rubber reactive component of the coupling agent combines with the rubber at the vulcanization temperature. Rare die silane-coupling agents, the usual rubber reactive functional groups can be any of mercapto, amino, vinyl, epoxy and sulphur groups, preferably a sulphur or mercapto moiety and more preferably sulphur.
The silane coupling agent being used for the experiment was a bifiinctiorMil sulphur containing organosilane, Si69, a Degussa product; which is chemically Bis -

(3- trietnoxysiiyi propyl; ceirasuipniae. the amount of stance coupling agent which may be used may range from 0.5 to 10 percent by weight of the filler being used.
e) Other general compounding ingredients
In addition to the various commoner mentioned, die sulphur cured rubber composition also contain conventional additives such as zinc oxide, stearic acid, accelerators, sulphur vulcanizing agents, antioxidants, antioxidants, process oils, etc. Representatives conventional accelerators are thiols, thturams, suiptienamides, guanidine’s etc. Typical vulcanizing agents Include elemental sulphur or sulphur donating vulcanizing agents. The amount of sulphur vulcanizing agent wilt vary depending on the type of rubber and particular type of vulcanizing agents, but generally range from 0.5 to 4 parts per hundred rubber (phr) with a range from 0.5 to Z 5 phr being preferred. Common processing oils Include naphtiienic or aromatic type for hydrocarbon rubbers and ester plasticizers for polar rubbers. Its dosage may vary from 2 to 20 phr. Conventional antidegradants used are In the range of 1 to 3 phr. The accelerator dosage can vary from 0 5 to 4 phr. for the silica composites, sulphenamide - guanidine accelerator combination is preferred.
V. EXPERIMENTAL FINDINGS
a) Proceesabifity studies
Natural rubber - silica composites unmodified and modified with stone and ENR were prepared in the Record and the mixing energy was determined. Pnxessabiiity of the composites were evaluated using capillary remoter. Results are compared in Table 1.

Lower viscosity and mixing energy exhibited by the BSiR containing mixes Indicates better dispersion of silica In the rubber phase.
b) Application studies Applications of the invention
The practice of this invention is further illustrated by reference to the following examples, which are Intended to be representative rather than restrictive of the scope of tiie invention.
A typical silica based formulation is given below in Table Z All the experimental recipes given under were mixed in a laboratory model Intermix in a single stage mixing cycle. The order of addition also is given in Table Z

Based on the formulation, the important test results relevant to the puniest, of few rubber composites used for tyre and non-tyre products, unmodified and modified with coupling agent and ENR are given below :
1. Tyre applications
Tyre compounds are made from either natural or synthetic rubber. It can be used either alone or as blends. Subject to the availability from country to country and the specific requirements of the product, the blends can be either of natural rubber and synthetic rubber or of synthetic rubbers themselves. Typical formulation for various tyre compositions and the corresponding Important techologlcal properties are given In Tables 3-7.

® Ail the samples in Table 3, 4, 5, 6 and 7 also contain the ingredients 2*8 of Table Z
R>r the compounds in Tables 3, 5, 6 and 7 the proceed oil used was naphthenic and for Table 4, aronrwtlc oil was used.
2. Non-tyre applications
Typical application - Rice dehusldng rubber roller
Test results of a typical formulation of acrylonitrile butadiene rubber (NBR) based rice dehusldng rubber rollers modified with ENR and silane-coupling agent Is given below :

Tasting - Specifications followed :
1. Modulus and Tensile strength ASTM D 412
Z Tear strength ASTM D 624
3. Abrasion loss DIN 53516
4. Viscosity ASTM D 9099-93
VI. Major advantages of the present invention
1. Improved noinfbrcement of rubber-silica composites and hence better technological properties.
Z Better possibility, faster cure and hence energy saving.
3. Better aging restacked.
4. BMR is a cheaper alternative to silane coupling agents and hence the cost advantage.

WE CLAIM :
1. Epoxldlsed natural rubber could be used for Improvlng the reinforcement of sulphur cured rubber-silica compositas.
Z The sulphur cured rubber-silica composite with epoxidised natural rubber as a reinforcement modifier as In claim 1, wherein the said ENR used has a typical structure as given below :

After epoxidation, the distribution of epoxides will have a random nature.
3. Epoxidised natural rubber, identified as a silica reinforcement modifier as stated in claim 1, is derived from natural rubber, which is a renewable resource.
4. According to claim 1, the role of epoxidised natural rubber In improving the reinforcement of rubber-silica composites is identified to be due to its functions as an interface modifier, filler dispersion modifier, cure activator and/or as a coupling agent
5. The sulphur cured rubber composition of claim 1, is characterised in that the epoxidised natural rubber has a level of epoxidation in the range from 5-80 mole per cent and more particularly in the range of 50-6O mole per cent.
6. The sulphur cured rubber composition stated in clalml is characterised by, based on 100 parts by weight of rubber out of which,

a) 99-75 parts by weight of a rubber is selected from the group of natural
rubber, styrene butadiene rubber, polybutadlene rubber, acrylonltrlle
butadiene rubber and/or selected mixtures thereof.
b) 1 to 25 parts by weight of epoxidised natural rubber.
c) 10 to 85 parts by weight of silica filler, preferably highly reinlforcing
precipitated silica (generally having a particle size range of SO to 1000
angstroms and a BET surface area range of 40 to 600 square meters per
gram) and more particularly In the 40 to 60 phr range.
7. The said claim 1, is applicable for any silica reinforced rubber product made
from any rubber stated in claim 6 or for any similar rubbers.
8. The claim 1, is a cost effective and energy efficient means for improving the
silica reinforcement of rubbers.

Documents:

« Previous Patent

Next Patent »

Patent Number

217042

Indian Patent Application Number

1109/MAS/1999

PG Journal Number

21/2008

Publication Date

23-May-2008

Grant Date

24-Mar-2008

Date of Filing

15-Nov-1999

Name of Patentee

THE RUBBER RESEARCH INSTITUTE OF INDIA

Applicant Address

RUBBER BOARD, KOTTAYAM - 686 009,

Inventors:

#	Inventor's Name	Inventor's Address
1	JACOB KONNAYIL VARKEY	RUBBER RESEARCH INSTITUTE OF INDIA, RUBBER BOARD, KOTTAYAM - 686 009,
2	SUSAMMA JOSSPH MANAKANDATHIL	RUBBER RESEARCH INSTITUTEOF INDIA, RUBBER BOARD, KOTTAYAM - 686 009,
3	MARIAMMA GEORGE KARIAPURAM	RUBBER RESEARCH INSTITUTE OF INDIA, RUBBER BOARD, KOTTAYAM - 686 009,

PCT International Classification Number

C08L 15/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA