Processability of silica-filled rubber stocks

TECHNICAL FIELD

The present invention relates to the processing and vulcanization of diene polymer and copolymer elastomer-containing rubber stocks. More particularly, the present invention relates to the processing and vulcanization of diene polymer and copolymer elastomer-containing, silica-filled rubber stocks using processing aids selected from the group consisting of alkyl alkoxysilane, fatty acid esters of hydrogenated and non-hydrogenated sugars and the polyoxyethylene derivatives thereof, and combinations and mixtures of these processing aids, with or without other reinforcing fillers, e.g., carbon black, or non-reinforcing fillers, e.g., mineral fillers. The present invention further relates to the processing and vulcanization of diene polymer and copolymer elastomer-containing, silica-filled rubber stocks using the above processing aids supported on the silica filler or other reinforcing or non-reinforcing fillers prior to mixing with the elastomer.

BACKGROUND OF THE INVENTION

In the art it is desirable to produce elastomeric compounds exhibiting reduced hysteresis when properly compounded with other ingredients such as reinforcing agents, followed by vulcanization. Such elastomers, when compounded, fabricated and vulcanized into components for constructing articles such as tires, power belts, and the like, will manifest properties of increased rebound, decreased rolling resistance and less heat-build up when subjected to mechanical stress during normal use.

The hysteresis of an elastomer refers to the difference between the energy applied to deform an article made from the elastomer and the energy released as the elastomer returns to its initial, undeformed state. In pneumatic tires, lowered hysteresis properties are associated with reduced rolling resistance and heat build-up during operation of the tire. These properties, in turn, result in lower fuel consumption for vehicles using such tires.

In such contexts, the property of lowered hysteresis of compounded, vulcanizable elastomer compositions is particularly significant. Examples of such compounded elastomer systems are known to the art and typically include at least one elastomer (that is, a natural or synthetic polymer exhibiting elastomeric properties, such as a rubber), a reinforcing (or non-reinforcing) filler agent (such as finely divided carbon black, thermal black, or mineral fillers such as clay and the like) and a vulcanizing system such as a sulfur-containing vulcanizing (i.e., curing) system.

Recently, precipitated silica has been increasingly used as a reinforcing particulate filler in carbon black-filled rubber components of tires and mechanical goods. While providing excellent properties, including reduced hysteresis, to the rubber stocks, these silica-loaded rubber stocks are unfortunately not easily produced, exhibiting relatively poor processability characteristics.

Previous attempts at preparing readily processable, vulcanizable, silica-filled rubber stocks containing natural rubber or diene polymer and copolymer elastomers have focused upon the sequence of adding ingredients during mixing (Bomal, et al., Influence of Mixing procedures on the Properties of a Silica Reinforced Agricultural Tire Tread, May 1992), the addition of de-agglomeration agents such as zinc methacrylate and zinc octoate, or SBR-silica coupling agents such as mercapto propyl trimethoxy silane (Hewitt, Processing Technology of Silica Reinforced SBR, Elastomerics, pp 33-37, March 1981), and the use of bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69) processing aid (Degussa, PPG).

The use of Si69 processing aid in the formulation of silica-filled rubber stocks has been successful in providing more readily processable rubber stocks. Disadvantageously, however, is the fact that, in order to obtain the desired processing results, a relatively large amount of the processing additive, on the order of at least 10 percent by weight based on the weight of silica, is required in order to be effective.

Thus, it is believed highly desirable to provide formulations for the processing and vulcanization of diene polymer and copolymer elastomer-containing, silica-filled rubber stocks which include processing aids other than Si69 that are effective in improving the processability and properties of the resulting silica-filled products. To that end, the present invention provides alkyl alkoxysilanes, fatty acid esters of hydrogenated and non-hydrogenated sugars, and mixtures thereof, for use as processing aids for silica-filled rubber stocks, which greatly improves the processability and properties of the formulations and the resulting vulcanized product, particularly where these processing aids are supported on silica or another reinforcing or non-reinforcing filler prior to being mixed with the elastomer. In addition, it has been found that mineral fillers as used in silica-filled elastomeric rubber stocks further improving tear strength and lower hysteresis, and can also be supported on silica or another filler.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide processing aids which improve the processability of formulations of diene polymer elastomers reinforced with silica filler.

It is another object of the present invention to provide formulations of diene polymer elastomers reinforced with silica filler having improved processability with decreased levels of bis[34triethoxysilyl)propyl]tetrasulfide (Si69).

It is still another object of the present invention to provide mineral and non-mineral fillers which improve the processability of formulations of diene polymer elastomers reinforced with silica filler.

It is a further object of the present invention to provide silica-supported, carbon black-supported or mineral filler-supported processing aids which improve the processability of formulations of diene polymer elastomers reinforced with silica filler.

It is still a further object of the present invention to provide reinforcing filler-supported additives, such as a mineral fillers, capable of improving the processability of the formulations of diene polymer elastomers reinforced with silica filler.

It is yet a further object of the present invention to provide a process for improving the processability of formulations of diene polymer elastomers reinforced with silica filler.

It is still a further object of the present invention to provide a process for reducing the viscosity of silica-filled elastomeric vulcanizable compounds.

It is yet a further object of the present invention to provide a process for decreasing the level of bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69) in silica-filled elastomeric vulcanizable compounds.

It is still a further object of the present invention to provide vulcanizable silica-filled elastomeric compounds having enhanced physical properties, including decreased hysteresis and increased tear strength.

At least one or more of the foregoing objects, together with the advantages thereof over the existing art, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.

The present invention provides a process for the preparation of a silica-filled, vulcanized elastomeric compound comprising the steps of mixing an elastomer with from about 1 to about 100 parts by weight of an amorphous silica filler, from 0 to about 20 percent by weight, based on said silica filler, of bis[3-(triethoxysilyl)propyl]tetrasulfide, from about 0.1 to about 150 percent by weight, based on said silica filler, of an alkyl alkoxysilane, and a cure agent; and, effecting vulcanization. Preferably, the elastomer is a diene monomer homopolymer or a copolymer of a diene monomer and a monovinyl aromatic monomer.

The present invention further provides a vulcanizable silica-filled compound comprising an elastomer, a silica filler, from 0 to about 20 percent by weight, based on said silica filler, of bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69), from about 0.1 to about 150 percent by weight, based on said silica filler, of an alkyl alkoxysilane, and a cure agent. Preferably, the elastomer is styrene butadiene rubber, and the compound may optionally contain an additional filler, e.g., carbon black.

The present invention further provides a process for the preparation of a silica-filled, vulcanized elastomeric compound comprising mixing an elastomer with from about 5 to about 100 parts by weight of a reinforcing filler per 100 parts of elastomer, wherein the reinforcing filler is selected from the group consisting of silica filler and mixtures of silica filler and carbon black; from 0 to about 20 percent by weight, based upon the weight of the silica filler, of a bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69); from about 0.1 to about 150 percent by weight, based upon the weight of the silica filler, of a processing aid selected from the group consisting of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars; polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars and mixtures thereof; from about 0 to about 40 parts by weight of an additional filler other than silica or carbon black, with the provisos that if the processing aid is sorbitan monooleate, then at least one of the polyoxyethylene derivatives or additional fillers is also present and, that the minimal amount for each processing aid and additional filler, if present, is about one part by weight per 100 parts elastomer; and a cure agent; and, effecting vulcanization.

The present invention further provides a vulcanizable silica-filled compound comprising 100 parts by weight of an elastomer; from about 5 to about 100 parts by weight of a reinforcing filler per 100 parts of elastomer, wherein the reinforcing fillers are selected from the group consisting of silica filler and mixtures of silica filler and carbon black; from 0 to about 20 percent by weight, based upon the weight of the silica filler, of bis[3-triethoxysilyl)propyl]tetrasulfide (Si69); from about 0.1 to about 150 percent by weight, based upon the weight of the silica filler, of a processing aid selected from the group consisting of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars; polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars and mixtures thereof; from about 0 to about 40 parts by weight of an additional filler other than silica or carbon black, with the provisos that if the processing aid is sorbitan monooleate, then at least one of the polyoxyethylene derivatives or additional fillers is also present and, that the minimal amount for each processing aid and additional filler, if present, is about one part by weight; and a cure agent.

The present invention further provides a process for the preparation of a silica-filled, vulcanized elastomeric compound comprising mixing 100 parts by weight of an elastomer with from about 5 to about 100 parts by weight of a reinforcing filler selected from the group consisting of silica filler or mixtures thereof with carbon black, per 100 parts of the elastomer; from about 0.1 to about 150 percent by weight, based on the silica filler, of a processing aid selected from the group consisting of alkylalkoxysilanes, fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars; polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars and mixtures thereof; from 0 to about 40 parts by weight of a non-reinforcing filler, per 100 parts elastomer; and a cure agent; wherein the processing aid is first mixed with and supported on at least some of either the reinforcing filler or non-reinforcing filler prior to mixing with the elastomer; and effecting vulcanization.

The present invention further provides a silica-filled, vulcanized elastomeric compound comprising 100 parts by weight of an elastomer; about 5 to about 100 parts by weight of a reinforcing filler selected from the group consisting of silica filler or mixtures thereof with carbon black, per 100 parts of the elastomer; from about 0.1 to about 150 percent by weight, based on the silica filler, of a processing aid selected from the group consisting of alkylalkoxysilanes, fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars; polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars and mixtures thereof; from 0 to about 40 parts by weight of a non-reinforcing filler, per 100 parts elastomer; and a cure agent; wherein the processing aid is supported on at least some of either the reinforcing filler or non-reinforcing filler.

The present invention further provides a pneumatic tire employing tread stock manufactured from the vulcanizable silica-filled compounds of the present invention.

BRIEF DESCRIPTION OF THE DRAWING

The drawing FIGURE is a graph of Beta, an inverse measure of filler association or crosslink density, as a function of mix energy.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, the present invention provides a means to reduce the level of Si69 needed to obtain good physical properties in a cured elastomeric stock containing silica as a filler. In addition, the present invention further provides maintenance of the processability of the compounded stock, as measured by Mooney viscosity, at the same level as achieved with high levels of Si69.

In one embodiment of the present invention, an alkyl alkoxysilane is utilized as a silica hydrophobating agent, such that minimal amounts of Si69 are needed to obtain good processability, and yet still give good physical properties. According to the invention, therefore, a less costly silane can be substituted for the majority or all of the Si69 that would be normally used without any loss of processability or properties. Additionally, remilling can be eliminated, and the cure of the rubber stock is not dependent on the high sulfur level present in the Si69.

The silica-hydrophobating agents useful according to the present invention include those alkyl alkoxysilanes of the formula (R

1

)

2

Si(OR

2

)

2

or R

1

Si(OR

2

)

3

, wherein the alkoxy groups are the same or are different; each R

1

independently comprising C1 to about C18 aliphatic, about C5 to about C12 cyclo-aliphatic, or about C6 to about C18 aromatic, preferably C1 to about C10 aliphatic, about C6 to about C10 cyclo-aliphatic, or about C6 to about C12 aromatic; and each R

2

independently containing from one to about 6 carbon atoms. Representative examples include octyltriethoxy silane, octyltrimethyloxy silane, (3-glycidoxypropyl)trimethoxy silane, (3-glycidoxypropyl)triethoxy silane, hexyltrimethoxy silane, ethyltrimethyoxy silane, propyltriethoxy silane, phenyltrimethoxy silane, cyclohexyltrimethoxy silane, cyclohexyltriethyoxy silane, dimethyldimethyoxy silane, 3-chloropropyltriethoxy silane, methacryoltrimethoxy silane, i-butyltriethoxy silane, and the like. Of these, octyltriethoxysilane is preferred.

Preferably, from about 0.1 to about 150 percent by weight of an alkyl alkoxysilane is used in the present invention. Thus, given the amount of silica filler typically preferred in the subject composition, up to about 150 parts by weight of the processing aid, per 100 parts elastomer, may be used, representing a 60/40 ratio of processing aid to silica.

According to the present invention, the polymerized elastomer, e.g., polybutadiene, polyisoprene and the like, and copolymers thereof with monovinyl aromatics such as styrene, alpha methyl styrene and the like, or trienes such as myrcene, is compounded to-form the rubber stock. Thus, the elastomers include diene homopolymers, A, and copolymers thereof with monovinyl aromatic polymers, B. Exemplary diene homopolymers are those prepared from diolefin monomers having from 4 to about 12 carbon atoms. Exemplary vinyl aromatic polymers are those prepared from monomers having from 8 to about 20 carbon atoms. Examples of conjugated diene monomers and the like useful in the present invention include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and 1,3-hexadiene, and aromatic vinyl monomers include styrene, α-methylstyrene, p-methylstyrene, vinyltoluenes and vinylnaphthalenes. The conjugated diene monomer and aromatic vinyl monomer are normally used at the weight ratios of about 90:10 to about 55:45, preferably about 80:20 to about 65:35.

Preferred elastomers include diene homopolymers such as polybutadiene and polyisoprene and copolymers such as styrene butadiene rubber (SBR). Copolymers can comprise from about 99 to 55 percent by weight of diene units and from about 1 to about 45 percent by weight of monovinyl aromatic or triene units, totaling 100 percent. The polymers and copolymers of the present invention may have 1,2-microstructure contents ranging from about 10 to about 80 percent, with the preferred polymers or copolymers having 1,2-microstructure contents of from about 25 to 65 percent, based upon the diene content. The molecular weight of the polymer that is produced according to the present invention, is preferably such that a proton-quenched sample will exhibit a gum Mooney viscosity (ML

4

/212° F.) of from about 2 to about 150. The copolymers are preferably random copolymers which result from simultaneous copolymerization of the monomers, as is known in the art. Also included are non-functionalized cis-polybutadiene, ethylene-propylene-diene monomer (EPDM), emulsion styrene butadiene rubber, and natural rubber.

Initiators known in the art such as an organolithium initiator, preferably an alkyllithium initiator, can be employed to prepare the elastomer. More particularly, the initiators used in the present invention include N-lithio-hexamethyleneimine, organolithium compounds such as n-butyllithium, tributyltin lithium, dialkylaminolithium compounds such as dimethylaminolithium, diethylaminolithium, dipropylaminolithium, dibutylaminolithium and the like, dialkylaminoalkyllithium compounds such as diethylaminopropyllithium and the like, and trialkyl stanyl lithium, wherein the alkyl group contains 1 to about 12 carbon atoms, preferably 1 to about 4 carbon atoms.

Polymerization is usually conducted in a conventional solvent for anionic polymerizations such as the various cyclic and acyclic hexanes, heptanes, octanes, pentanes, their alkylated derivatives, and mixtures thereof. Other techniques for polymerization, such as semi-batch and continuous polymerization may be employed. In order to promote randomization in copolymerization and to increase vinyl content, a coordinator may optionally be added to the polymerization ingredients. Amounts range between 0 to 90 or more equivalents per equivalent of lithium. The amount depends upon the amount of vinyl desired, the level of styrene employed and the temperature of the polymerizations, as well as the nature of the specific polar coordinator employed.

Compounds useful as coordinators are organic and include those having an oxygen or nitrogen hetero-atom and a non-bonded pair of electrons. Examples include dialkyl ethers of mono and oligo alkylene glycols; “crown” ethers; tertiary amines such as tetramethylethylene diamine (TMEDA); THF; THF oligomers; linear and cyclic oligomeric oxolanyl alkanes, such as 2-2′-di(tetrahydrofuryl) propane, dipiperidyl ethane, hexamethylphosphoramide, N-N′-dimethylpiperazine, diazabicyclooctane, diethyl ether, tributylamine and the like. Details of linear and cyclic oligomeric oxolanyl coordinators can be found in U.S. Pat. No. 4,429,091, owned by the Assignee of record, the subject matter of which is incorporated herein by reference.

Polymerization is usually begun by charging a blend of the monomer(s) and solvent to a suitable reaction vessel, followed by the addition of the coordinator and the initiator solution previously described. Alternatively, the monomer and coordinator can be added to the initiator. The procedure is carried out under anhydrous, anaerobic conditions. The reactants are heated to a temperature of from about 10° C. to about 150° C. and are agitated for about 0.1 to about 24 hours. After polymerization is complete, the product is removed from the heat and terminated in one or more ways. To terminate the polymerization, a terminating agent, coupling agent or linking agent may be employed, all of these agents being collectively referred to herein as “terminating agents”. Certain of these agents may provide the resulting polymer with a multifunctionality. That is, the polymers of the present invention, can carry at least one amine functional group as discussed hereinabove, and may also carry a second functional group selected and derived from the group consisting of terminating agents, coupling agents and linking agents. Generally, the amount of terminating agent that is employed ranges from about 0.3 and one mole per mole of initiator, with from about 0.5 to about 0.8 moles per mole of initiator being preferred.

Examples of terminating agents according to the present invention include those commonly employed in the art, including hydrogen, water, steam, an alcohol such as isopropanol, 1,3-dimethyl-2-imidazolidinone (DMI), carbodiimides, N-methylpyrrolidine, cyclic amides, cyclic ureas, isocyanates, Schiff bases, 4,4′-bis(diethylamino)benzophenone, and the like. Other useful terminating agents may include those of the structural formula (R

1

)

a

ZX

b

, wherein Z is tin or silicon. It is preferred that Z is tin. R

1

is an alkyl having from about 1 to about 20 carbon atoms; a cycloalkyl having from about 3 to about 20 carbon atoms; an aryl having from about 6 to about 20 carbon atoms; or, an aralkyl having from about 7 to about 20 carbon atoms. For example, R

1

may include methyl, ethyl, n-butyl, neophyl, phenyl, cyclohexyl or the like. X is a halogen, such as chlorine or bromine, or alkoxy (—OR

1

), “a” is from 0 to 3, and “b” is from about 1 to 4; where a+b=4. Examples of such terminating agents include tin tetrachloride, (R

1

)

3

SnCl,(R

1

)

2

SnCl

2

, R

1

SnCl

3

, and R

1

SiCl

3

as well as tetraethoxysilane (Si(OEt)

4

) and methyltriphenoxysilane (MeSi(OPh)

3

).

When mineral fillers, in addition to silica, are to be used in the vulcanizable compound, it is preferred that the polymer contain a silane functionality, such as residual terminal silylethoxy or methylsilylphenoxy groups obtained by the use of a tetraethoxysilane or methyltriphenoxysilane terminator, respectively.

The terminating agent is added to the reaction vessel, and the vessel is agitated for about 1 to about 1000 minutes. As a result, an elastomer is produced having an even greater affinity for silica compounding materials, and hence, even further reduced hysteresis. Additional examples of terminating agents include those found in U.S. Pat. No. 4,616,069 which is herein incorporated by reference. It is to be understood that practice of the present invention is not limited solely to these terminators inasmuch as other compounds that are reactive with the polymer bound lithium moiety can be selected to provide a desired functional group.

Quenching is usually conducted by stirring the polymer and quenching agent for about 0.05 to about 2 hours at temperatures of from about 30° to 150° C. to ensure complete reaction. Polymers terminated with a functional group as discussed hereinabove, are subsequently quenched with alcohol or other quenching agent as described hereinabove.

Lastly, the solvent is removed from the polymer by conventional techniques such as drum drying, extruder drying vacuum drying or the like, which may be combined with coagulation with water, alcohol or steam, thermal desolventization, or any other suitable method. If coagulation with water or steam is used, oven drying may be desirable.

The elastomeric polymers can be utilized as 100 parts of the rubber in the treadstock compound or, they can be blended with any conventionally employed treadstock rubber which includes natural rubber, synthetic rubber and blends thereof. Such rubbers are well known to those skilled in the art and include synthetic polyisoprene rubber, styrene/butadiene rubber (SBR), including emulsion SBR's, polybutadiene, butyl rubber, neoprene, ethylene/propylene rubber, ethylene/propylene/diene rubber (EPDM), acrylonitrile/butadiene rubber (NBR), silicone rubber, the fluoroelastomers, ethylene acrylic rubber, ethylene vinyl acetate copolymer (EVA), epichlorohydrin rubbers, chlorinated polyethylene rubbers, chlorosulfonated polyethylene rubbers, hydrogenated nitrile rubber, tetrafluoroethylene/propylene rubber and the like. When the functionalized polymers are blended with conventional rubbers, the amounts can vary widely within a range comprising about 5 to about 99 percent by weight of the total rubber, with the conventional rubber or rubbers making up the balance of the total rubber (100 parts). It is to be appreciated that the minimum amount will depend primarily upon the degree of reduced hysteresis that is desired.

According to the present invention, amorphous silica (silicon dioxide) is utilized as a filler for the diene polymer or copolymer elastomer-containing vulcanizable compound. Silicas are generally classed as wet-process, hydrated silicas because they are produced by a chemical reaction in water, from which they are precipitated as ultrafine, spherical particles.

These primary particles strongly associate into aggregates, which in turn combine less strongly into agglomerates. The surface area, as measured by the BET method gives the best measure of the reinforcing character of different silicas. For silicas of interest for the present invention, the surface area should be about 32 to about 400 m

2

/g, with the range of about 100 to about 250 m

2

/g being preferred, and the range of about 150 to about 220 m

2

/g being most preferred. The pH of the silica filler is generally about 5.5 to about 7 or slightly over, preferably about 5.5 to about 6.8.

Silica can be employed in the amount of about 1 part to about 100 parts by weight per 100 parts of polymer (phr), preferably in an amount from about 5 to about 80 phr. The useful upper range is limited by the high viscosity imparted by fillers of this type. Some of the commercially available silicas which may be used include: Hi-Sil® 215, Hi-Sil® 233, and Hi-Sil® 190, produced by PPG Industries. Also, a number of useful commercial grades of different silicas are available from De Gussa Corporation, Rhone Poulenc, and J. M. Huber Corporation.

Although the vulcanizable elastomeric compounds of the present invention are primarily silica-filled, the polymers can be optionally compounded with all forms of carbon black in amounts ranging from 0 to about 50 parts by weight, per 100 parts of rubber (phr), with about 5 to about 40 phr being preferred. When carbon is present, with silica, the amount of silica can be decreased to as low as about one phr, otherwise it too is present alone in at least 5 phr. As is known to those skilled in the art, elastomeric compounds as are discussed herein are typically filled to a volume fraction of about 25 percent which is the total volume of filler(s) added divided by the total volume of the elastomeric stock. Accordingly, while the minimum amounts expressed herein are operable, a useful range of reinforcing fillers i.e., silica and carbon black, is about 30 to 100 phr.

The carbon blacks may include any of the commonly available, commercially-produced carbon blacks but those having a surface area (EMSA) of at least 20 m

2

/gram and more preferably at least 35 m

2

/gram up to 200 m

2

/gram or higher are preferred. Surface area values used in this application are those determined by ASTM test D-1765 using the cetyltrimethyl-ammonium bromide (CTAB) technique. Among the useful carbon blacks are furnace black, channel blacks and lamp blacks. More specifically, examples of the carbon blacks include super abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF) blacks, medium processing channel blacks, hard processing channel blacks and conducting channel blacks. Other carbon blacks which may be utilized include acetylene blacks. Mixtures of two or more of the above blacks can be used in preparing the carbon black products of the invention. Typical values for surface areas of usable carbon blacks are summarized in TABLE I hereinbelow.

TABLE I

Carbon Blacks

ASTM Designation

Surface Area (m

2

/g)

(D-1 765-82a)

(D-3765)

N-110

126

N-220

111

N-339

95

N-330

83

N-351

74

N-550

42

N-660

35

The carbon blacks utilized-in the preparation of the rubber compounds of the invention may be in pelletized form or an unpelletized flocculent mass. Preferably, for more uniform mixing, unpelletized carbon black is preferred.

Recognizing that carbon black may be used as an additional reinforcing filler with silica, the total amount of reinforcing filler(s) in the vulcanizable elastomeric compounds of the present invention ranges between about 30 to 100 phr, all of which can comprise silica or, mixtures with carbon black within the foregoing ranges. It is to be appreciated that as the amount of silica decreases, lower amounts of the processing aids of the present invention, plus silane, if any, can be employed.

When silica is employed as a reinforcing filler, it is customary to add bis[3-(triethoxysilyl)propyl]tetrasulfide to obtain good physical properties in a cured rubber stock containing silica as a filler. In general, the present invention provides a means to reduce or eliminate the level of this compound. This material is commonly added to silica filled rubber formulations and will be referred to throughout this specification by its industry recognized designation, Si69. In addition, the present invention further provides maintenance of the processability of the compounded stock, as measured by Mooney viscosity, at the same level as achieved with high levels of Si69. This replacement of Si69 results in reduced cost and provides a material that is stable for storage and is easily added to rubber compounds. In addition, the use of vulcanizable elastomeric compounds according to the present invention provides the same or better physical properties upon curing. Generally, the amount of Si69 that is added ranges between about 4 and 20 percent by weight, based upon the weight of silica filler present in the elastomeric compound. By practice of the present invention, it is possible to reduce the amount of Si69 down to about 5 percent, more preferably, 3 to 1 percent and most preferably, to eliminate its presence totally i.e., 0 percent. It may also be desirable to increase processability of the silica filled elastomer compounds without any decrease in the silane content which can be accomplished by the addition of a processing aid or filler according to the present invention as is described hereinafter.

Thus, in another embodiment, the present invention provides a silica-filled, vulcanizable elastomeric compound useful as tread stocks for pneumatic tires that employs a processing aid as a replacement for Si69, wherein the processing aid is selected from the group consisting of alkyl alkoxysilanes, fatty acid esters of hydrogenated and non-hydrogenated sugars, ethoxylated derivatives of fatty acid esters of hydrogenated and non-hydrogenated sugars, and mixtures thereof and wherein the processing aid is supported on the silica filler or other filler, e.g., either another reinforcing filler such as carbon black, or a non-reinforcing filler such as one of a number of mineral fillers or the like.

A mixture of a filler and a filler-supported processing aid selected from the group consisting of alkyl alkoxysilanes, fatty acid esters of hydrogenated and non-hydrogenated sugars, ethoxylated derivatives of fatty acid esters of hydrogenated and non-hydrogenated sugars, and mixtures thereof, is preferably added to the elastomer in an amount of about 5 to about 100 parts by weight per 100 parts of the elastomer. It should be stressed that when a silica-supported or carbon black-supported processing aid is used, the non-reinforcing fillers, including mineral fillers or other processing aids are not required in the elastomeric formulation. However, it will be appreciated that if mineral fillers are used, they may be used to support the processing aid(s).

Preferably, the processing aid is added to the silica or other filler in a mixture ratio of from about 1:99 to about 60:40, with a 50:50 mixture being most preferred.

The present invention utilizes the presence of one or more processing aids to replace the silane (Si69) to give equal processability of the vulcanizable compound, and better hot tear strength and lower hysteresis of the vulcanized rubber stock, without loss of the other measured physical properties. The processing aids are air stable and do not decompose. They are lower in cost and more storage stable than Si69, and when used with silica filled elastomers, give similar reduction of ML

4

, and tan δ with an increase in tear strength.

In order to demonstrate the preparation and properties of silica-filled, diene elastomer containing rubber stocks prepared according to the present invention, styrene butadiene rubber (SBR) polymers were prepared and were compounded using the formulations set forth in Tables II and III below.

Test results for the Control, C-A, using the Si69 processing aid only, and Examples 1-3, using silane processing aids according to the invention in Formulation A, are reported in Table II.

TABLE II

Formulation A for the Partial Replacement of Si69

and Physical Test Results

Material

Amount (phr)

Example No.

C-A

1

2

3

SBR

100

100

100

100

Oil

20

20

20

20

Silica

60

60

60

60

Carbon Black

6

6

6

6

Stearic Acid

2

2

2

2

Wax

0.75

0.75

0.75

0.75

Si-69

5.4

0.6

0.6

0.6

Silane (Type)

—

Octyl

Methacroyl

Dimethyl

Tri-

Trimethoxy

Di-

meth-

methoxy

oxy

Silane (Amount)

0

4.71

4.99

3.62

Tackifier

3.5

3.5

3.5

3.5

Antioxidant

0.95

0.95

0.95

0.95

Sulfur

1.4

1.4

1.4

1.4

Accelerators

2.4

2.4

2.4

2.4

Zinc Oxide

3

3

3

3

Physical Properties

ML

1+4

@ 100° C.

93.7

84.7

93.3

88.8

Tensile(psi) @ 23° C.

2913

2216

2476

2834

Tensile(psi) @ 100° C

1239

954

1122

1294

% Elong. at break, 23° C.

444

603

504

551

% Elong. at break, 100 ° C.

262

407

342

365

Ring Tear (lb/in) @ 100° C.

191

198

179

223

Dispersion Index, %

72.9

76.1

84

84.3

Test results for the Control, C-B, using the Si69 processing aid only, and Examples 4-7, using silane processing aids according to the invention in Formulation B, are reported in Table III.

TABLE III

Formulation B for the Partial Replacement of Si69

and Physical Test Results

Material

Amount (phr)

Example No.

C-B

4

5

6

7

SBR

75

75

75

75

75

BR

25

25

25

25

25

Oil

41.25

41.25

41.25

41.25

41.25

Silica

80

80

80

80

80

Carbon Black

8

8

8

8

8

Stearic Acid

1

1

1

1

1

Wax

1.5

1.5

1.5

1.5

1.5

Si-69

7.2

0.8

0.8

0.8

0.8

Silane (Type)

—

Propyl

3-

Octyl

i-Butyl

Tri-

Chloropropyl

Triethoxy

Tri-

ethoxy

Triethoxy

ethoxy

Silane (Amount)

0

5.5

6.42

7.39

5.88

Tackifier

3

3

3

3

3

Antioxidant

1.17

1.17

1.17

1.17

1.17

Sulfur

2.8

2.8

2.8

2.8

2.8

Accelerators

2.4

2.4

2.4

2.4

2.4

Zinc Oxide

1.7

1.7

1.7

1.7

1.7

Physical Properties

ML

1+4

@ 100° C.

64.8

69.2

96.1

53.8

93.9

Tensile(psi) @

2497

2268

2566

2400

2513

23° C.

Tensile(psi) @

1453

1278

1693

1280

1379

100° C.

% Elong. at break,

487

614

544

612

649

23° C.

% Elong. at break,

386

486

487

467

499

100° C.

Ring Tear (lb/in) @

190

270

245

262

298

100° C.

Dispersion Index,

93.1

80.5

95.7

87.9

93.3

%

A series of tests were conducted, in which the Si69 processing aid was omitted and insoluble sulfur was added, while processing Formulation B with 2 phr octyl-triethoxy silane, and 4 phr sorbitan oleate. Test conditions and results are reported for Examples 8-17 and the Control (no added insoluble sulfur), C-C, in Table IV, below. As illustrated in Table IV, the degree of cure of the composition, expressed as the 300% Modulus (psi) and/or the molecular weight between crosslinks M

c

, g/mol), improved as the amount of additional sulfur (and total sulfur) increased until the 300% Modulus and/or the M

c

were approximately equal to that of the satisfactorily cured control (C-C) composition containing Si69 and no added sulfur. Both the 300% Modulus and the M

c

are well known in the art to be indicators of the state of cure of a vulcanize elastomeric composition.

TABLE IV

Physical Properties of Formulation B with 2 phr Octyl-Triethoxy Silane, 4 phr Sorbitan Monooleate, and

Insoluble Sulfur without Si69

Sample

8

9

10

11

12

13

14

15

16

17

C-C

Insoluble S (phr)

1.4

1.7

2

2.3

2.6

2.9

3.3

3.7

4.1

4.5

0

Total S (phr)

2.8

3.1

3.4

3.7

4

4.3

4.7

5.1

5.5

5.9

1.4

Physical Test Results

ML

1+4

/100° C.

84

81.9

80.7

78.9

78.9

103.6

101.8

99.5

99.8

101.7

75.7

Monsanto Cure @ 171° C.

ML

13.6

14.7

13.4

13

12.8

18

18.2

18

17.8

18.2

11.6

MH

33.4

34.8

37.1

37

38.3

46.5

48.3

50.6

50.8

53.9

37.37

ts2

2:54

2:48

2:41

2:47

2:44

2:42

2:34

2:30

2:28

2:29

2:30

tc90

10:51

9:50

9:42

9:28

9:15

12:05

11:36

11:11

10:29

11:11

10:01

Ring Tensile @ 24° C.

100% Modulus, psi

188

184

209

194

227

212

267

256

284

326

318

300% Modulus, psi

494

485

592

556

667

670

792

765

872

988

1150

Tensile str, psi

1798

1550

1814

1548

1769

1842

2120

1757

1925

2076

2809

% Elongation

724

657

641

613

594

601

591

538

527

510

556

Break energy, lbs/in

2

5273

4203

4835

4000

4445

4569

5196

4034

4343

4580

6596

Ring Tensile @ 100° C.

100% Modulus, psi

131

151

191

215

187

210

231

255

286

292

268

300% Modulus, psi

333

381

519

566

532

621

656

730

846

833

661

Tensile str, psi

905

1062

1233

1162

983

1156

1017

878

1079

1042

1263

% Elongation

649

652

592

529

500

500

441

340

375

364

364

Break Energy, lbs/in

2

2612

3070

3306

2850

2310

2849

2172

1565

1984

1906

2092

Ring Tear @ 171° C., ppi

250

217

228

230

201

247

216

201

192

221

276

Pendulum Rebound 65° C.

33.6

35

32.4

37.6

40.2

37.2

40.2

37.6

41.2

41.4

53.6

Wet Stanley London,(#/std)

56/53

54/53

56/53

53/53

57/53

60/54

62/54

63/54

64/54

63/54

Shore A @ 24° C.

68

67

68

68

69

71

71

73

73

72

65

Dispersion Index #1

85.6

85.5

86.5

87.1

88

59.4

Specific Gravity

1.184

1.186

1.189

1.188

1.189

1.195

1.197

1.199

1.199

1.21

1.202

Rheometries @ 7% strain

tan δ @ 65° C.

.1978

.1924

.1807

.1858

.1789

.1697

.1662

.158

.1583

.1503

.1839

ΔG′ @ 65° C., MPa

4.884

6.201

6.133

5.937

6.117

7.747

8.845

9.295

9.552

10.041

6.88

Tensile Retraction

Mc × 10

−3

g/mol

20.9

20.0

17.5

17.4

16.3

15.4

13.2

12.3

12.2

A further series of tests were conducted, in which Formulation B, described in Table III, was processed with added sulfur and a processing aid comprising 1.5 phr octyl-triethoxy silane, 0.5 phr Si69, and 4 phr sorbitan oleate. Test conditions and results are reported for Examples 18-22 in Table V, below. Table V illustrates a progressive improvement in the degree of cure of the composition, expressed as the 300% Modulus (psi) and/or the molecular weight between crosslinks (M

c

, g/mol), as the total amount of added sulfur is progressively increased.

TABLE V

Physical Properties of Formulation B with 1.5 phr Octyl-triethoxysilane,

4 phr Sorbitan, 0.5 Si69 and Insoluble Sulfur

Sample

18

19

20

21

22

Insoluble S (phr)

2.8

3.2

3.6

4

4.4

Total S (phr)

4.2

4.6

5

5.4

5.8

Physical Test Results

ML

1+4

/100° C.

81.9

83.6

84.2

86.3

80.8

Monsanto Cure @ 171° C.

ML

13.15

13.2

13.15

13.82

12.48

MH

41.84

44.62

44.62

46.58

46.98

ts2

2:50

2:44

2:43

2:35

2:38

tc90

10:15

10:12

9:12

9:24

8:59

Ring Tensile @ 24° C.

100% Modulus, psi

273

291

326

341

408

300% Modulus, psi

935

994

1112

1158

1452

Tensile str, psi

2323

2183

2112

2012

2497

% Elongation

582

537

483

461

460

Break Energy, lbs/in

2

5760

5099

4545

4164

5130

Ring Tensile @ 100° C.

100% Modulus, psi

251

251

287

307

311

300% Modulus, psi

826

798

933

1030

998

Tensile str, psi

1326

1215

1255

1229

1113

% Elongation

444

428

388

350

329

Break Energy, lbs/in

2

2720

2439

2306

2069

1800

Ring Tear @ 171° C., psi

240

230

201

219

206

Pendulum Rebound 65° C.

37.2

39

42.8

39.4

42.4

Wet Stanley London

64/53

61/53

64/53

65/53

65/53

(#/std)

Shore A, @ RT

72

71

72

74

73

Specific Gravity

1.195

1.196

1.197

1.197

1.202

Rheometries @ 7% strain

tan δ @ 65° C.

0.1577

0.1528

0.1444

0.1384

0.1533

Δ G′ @ 65° C., MPa

6.89

6.798

6.676

6.285

7.789

Tensile Retraction

12.6

12.4

11.1

10.4

9.7

Mc, × 10

−3

g/mol

The present invention can thus further utilize the presence of an ester of a fatty acid or an ester of a polyol as a processing aid to replace the silane Si69 to give equal processability of the vulcanizable compound, and better hot tear strength and lower hysteresis of the vulcanized rubber stock, without loss of the other measured physical properties.

The further processing aid, such as the preferred sorbitan oleate, is air stable and does not decompose. The sorbitan oleate is lower in cost and more storage stable than Si69, and when used with a silica filler and a silane terminated polymer, gives similar reduction of ML

4

, and tan δ with an increase in tear strength.

The additional processing aids useful according to the present invention include esters of fatty acids or esters of polyols. Representative examples include the sorbitan oleates, such as sorbitan monooleate, dioleate, trioleate and sesquioleate, as well as sorbitan esters of laurate, palmitate and stearate fatty acids, and the polyoxyethylene derivatives of each, and other polyols, including glycols such as polyhydroxy compounds and the like. Of these, sorbitan monooleate is preferred.

In yet another embodiment of the present invention, fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars e.g., sorbitose, mannitose and arabinose, can be used as the processing aid in replacement of Si69. These compounds have at least three hydroxyl groups and from one to 3.5 ester groups (sesqui esters). Also useful are the polyoxyethylene derivatives thereof. The esterified hydrogenated and non-hydrogenated sugars can be described generally by the following formula using sorbitol as the representative ester

where R is derived from C

10

to C

22

saturated and unsaturated fatty acids, for example, stearic, lauric, palmitic, oleic and the like.

Representative examples include the sorbitan oleates, including monooleate, dioleate, trioleate and sesquioleate, as well as sorbitan esters of laurate, palmitate and stearate fatty acids, and polyoxyethylene derivatives thereof, and other polyols and, more particularly, glycols, such as polyhydroxy compounds, and the like. Of these, sorbitan oleates are preferred, with sorbitan monooleate being most preferred. In similar fashion, other esters can be formed with mannitose and arabinose. Generally, the amount of this processing aid that is employed ranges from 0 to about 20 parts by weight, phr, with from about one to about 10 phr being preferred. These processing aids are commercially available from ICI Specialty Chemicals under the tradename SPAN, which is a registered trademark of ICI. Several useful products include SPAN 60 (sorbitan stearate); SPAN 80 (sorbitan oleate) and SPAN 85 (sorbitan tri-oleate). Other commercially available sorbitans can be used for example, the sorbitan monooleates known as Alkamuls SMO; Capmul O; Glycomul O; Arlacel 80; Emsorb 2500 and, S-Maz 80. Similar products of other esters are likewise available.

The polyoxyethylene derivatives of the foregoing processing aids according to the present invention also include fatty acid esters of hydrogenated and non-hydrogenated C

5

and C

6

sugars e.g., sorbitose, mannitose and arabinose, and have at least three hydroxyl groups and from one to 3.5 ester groups (sesqui esters). The polyoxyethylene derived esterified hydrogenated and non-hydrogenated sugars can be described generally by the following formula again, using sorbitol as the representative ester:

where R is derived from C

10

to C

22

saturated and unsaturated fatty acids, for example, stearic, lauric, palmitic, oleic and the like and the sum of w+x+y+z equals 20.

The Polyoxyethylene derivatives of these processing aids, sometimes referred to as polysorbates and polyoxyethylene sorbitan esters, are analogous to the fatty acid esters of hydrogenated and non-hydrogenated sugars noted above (sorbitans) except that ethylene oxide units are placed on each of the hydroxyl groups. Representative examples of the polysorbates include POE (20) sorbitan monooleate; Polysorbate 80; Tween 80; Emsorb 6900; Liposorb O-20; T-Maz 80 and the like. The TWEENS are commercially available from ICI Specialty Chemicals, the tradename TWEEN being a registered trademark of ICI. Several useful products include TWEEN 60 [POE (20) sorbitan stearate]; TWEEN 80 [POE (20) sorbitan oleate]; TWEEN 85 [POE (20) sorbitan tri-oleate]; POE (20) sorbitan sesquioleate; POE (20) sorbitan laurate; POE (20) sorbitan palmitate as well as TWEEN 20, TWEEN 21, TWEEN 60K, TWEEN 65, TWEEN 65K and TWEEN 81. Generally, the amount of this processing aid that is employed ranges from 0 to about 20 parts by weight, phr, with from about one to about 10 phr being preferred.

Finally, certain additional fillers can be utilized according to the present invention as processing aids which include, but are not limited to, mineral fillers, such as clay (hydrous aluminum silicate), talc (hydrous magnesium silicate), and mica as well as non-mineral fillers such as urea and sodium sulfate. Preferred micas contain principally alumina, silica and potash, although other variants are also useful, as set forth below. The additional fillers are also optional and can be utilized in the amount of from 0 parts to about 40 parts per 100 parts of polymer (phr), preferably in an amount from about 1 to about 20 phr. It will be understood that these mineral fillers can also be used as non-reinforcing fillers to support the processing aids of the present invention.

The selection of processing aid(s) and relative amounts for practice of the present invention includes the use of any one of the foregoing materials, as well as mixtures thereof, as noted hereinabove. Accordingly, various embodiments are possible as follows.

a) The use of fatty acid esters of hydrogenated and non-hydrogenated sugars alone, in amounts of up to 20 phr. These esters include all of the esterified sugars, but not sorbitan monooleate.

b) The use of polyoxyethylene derivatives of the fatty acid esters of hydrogenated and non-hydrogenated sugars alone, in amounts of up to 20 phr.

c) The use of a mineral or non-mineral filler alone or mixtures thereof, in amounts of up to 40 phr. It is to be understood that reference to these mineral and non-mineral fillers does not include the reinforcing fillers disclosed herein—carbon black and silica.

d) Mixtures of fatty acid esters of hydrogenated and non-hydrogenated sugars with the polyoxyethylene derivatives thereof, in an amount of up to 20 total phr, with a minimum of at least about one phr of either processing aid. When such mixtures are utilized, sorbitan monooleate can be employed.

e) Mixtures of fatty acid esters of hydrogenated and non-hydrogenated sugars with a mineral or non-mineral filler, as above, in an amount of up to 30 total phr, with a minimum of at least about one phr of the processing aid. When such mixtures are utilized, sorbitan monooleate can be employed.

f) Mixtures of polyoxyethylene derivatives of the fatty acid esters of hydrogenated and non-hydrogenated sugars with a mineral or non-mineral filler, as above, in an amount of up to 30 total phr, with a minimum of at least about one phr of the processing aid. When such mixtures are utilized, sorbitan monooleate can be employed.

g) Mixtures of fatty acid esters of hydrogenated and non-hydrogenated sugars with the polyoxyethylene derivatives thereof and with a mineral or non-mineral filler, as above, in an amount of up to 30 total phr, with a minimum of at least about one phr of either processing aid. When such mixtures are utilized, sorbitan monooleate can be employed.

While practice of the present invention includes the addition of at least one type of processing aid or an additional filler or combinations thereof, to be effective, preferably at least one part by weight of each type that is selected should be employed. Where only a processing aid or mixtures thereof are added, the upper limit is about 20 phr as contrasted with the use of an additional filler at an upper limit of about 40 phr. When a processing aid(s) is present with an additional filler, the upper limit total of these additives is about 30 phr. Irrespective of the upper limit amounts stated herein, it is to be appreciated that the combined total filler, that is, reinforcing fillers (silica and carbon black) plus additional fillers (other than silica and carbon black) will generally not exceed about 25 percent volume fraction. Accordingly, for an elastomeric stock containing additional fillers at the upper range of about 40 phr, the amount of reinforcing fillers will be lower than where additional fillers have not been added. Unexpectedly, we have found herein that physical properties do not fall off where additional filler or fillers are added and the amount of reinforcing fillers are lowered.

The reinforced rubber compounds can be cured in a conventional manner with known vulcanizing agents at about 0.2 to about 5 phr. For example, sulfur or peroxide-based curing systems may be employed. For a general disclosure of suitable vulcanizing agents one can refer to Kirk-Othmer,

Encyclopedia of Chemical Technology,

3rd ed., Wiley lnterscience, N.Y. 1982, Vol. 20, pp. 365-468, particularly “Vulcanization Agents and Auxiliary Materials”pp. 390-402. Vulcanizing agents can be used alone or in combination.

Vulcanizable elastomeric compositions of the invention can be prepared by compounding or mixing the elastomeric polymer with silica, optionally carbon black, as noted above, and one or more of the processing aids and optionally additional filler(s) according to the present invention, as well as other conventional rubber additives including for example, plasticizers, antioxidants, curing agents and the like, using standard rubber mixing equipment and procedures.

The present invention was demonstrated by comparing tread formulations as shown in TABLE VI in which 3 parts per hundred rubber (phr) Si69 (control, C-F) were replaced with 7.5 phr of either an aromatic oil (C-D) or naphthenic oil (C-E). This replacement was further compared to a stock prepared according to the present invention with 3 phr of sorbitan monooleate and 4.5 phr aromatic oil (Sample 23).

TABLE VI

Rubber Formulations to Evaluate Silica Modification

and Physical Properties Obtained

Materials

Amount (parts per hundred rubber)

Sample

C-D

C-E

C-F

23

SBR

75

75

75

75

Natural Rubber

25

25

25

25

Silica

30

30

30

30

Carbon Black

35

35

35

35

Wax

1

1

1

1

Stearic Acid

1.5

1.5

1.5

1.5

Zinc Oxide

3

3

3

3

Accelerators

2

2

2

2

Antioxidant

0.95

0.95

0.95

0.95

Retarder

0.25

0.25

0.25

0.25

Varied Materials

Si69 Processing Aid

0

0

3

0

Sulfur

2.7

2.7

1.7

2.7

Aromatic Oil

7.5

0

0

4.5

Naphthenic Oil

15

22.5

15

15

Sorbitan Oleate

0

0

0

3

ML

4

@ 130° C.

72

74

59

59

M50 @ 25° C. (psi)

271

295

236

241

M300 @ 25° C. (psi)

1750

1990

1970

1670

Tensile @ 25° C. (psi)

2380

2520

2410

2570

% Elongation @ 25° C.

383

361

349

419

M200 @ 100° C. (psi)

817

959

921

860

Tensile @ 100° C. (psi)

1270

1410

1300

1400

% Elongation @ 100° C.

280

266

256

290

Tear Strength @ 171° C.

98

95

99

120

(lb/in)

Tan δ 50° C.

0.123

0.105

0.132

0.105

As can be seen in TABLE VI, Sample 23 had better tear strength. The ML

4

@ 130° C. of Sample 23 has been reduced to the level of the control, C-F, and the 50° C. tan δ is lower than the. Samples C-F or C-D and similar to that of Sample C-E.

A Mooney viscosity reduction of the vulcanizable compound by the sorbitan monooleate (Sor. Oleate) in a high silica containing formulation was also demonstrated with the addition of other ML

4

reducing co-agents, summarized in TABLE VII hereinbelow.

TABLE VII

Rubber Formulations to Evaluate Mooney Reduction

and Test Results Thereof

Material

Amount (parts per hundred rubber)

SBR

75

PBD

25

Silica

80

Carbon Black

8

Modifier

Variable (see below)

Stearic Acid

1

Naphthenic Oil

41.25

Wax

1.5

Resins

1.5

Stabilizers

1.17

Zinc Oxide

1.7

Curatives

2.4

Sulfur

2

Modifier Added (in phr) and ML

4

/100° C.

Sample

Si69 (phr)

Modifier 1

phr

Modifier 2

phr

ML

4

/100° C.

C-G

0

None

0

None

0

161

C-H

8

None

0

None

0

84

24

0.8

Sor. Oleate

4

None

0

129

25

0.8

Sor. Oleate

8

None

0

104

C-I

0.8

PEG

4

None

0

148

C-J

0.8

PEG

8

None

0

124

C-K

0.8

Sorbitol

4

None

0

146

C-L

0.8

Sorbitol

8

None

0

136

26

0

Sor. Oleate

4

OTES

3

73

27

0

Sor. Oleate

4

OTES

2

79

28

0

Sor. Oleate

4

OTES/

3/2

72

Talc

29

0

Sor. Oleate

4

OTES/

3/2

70

Urea

C-M

0.8

None

0

Mica

15

122

30

0.8

Sor. Oleate

4

Mica

15

93

31

0.8

Sor. Oleate

8

Mica

15

77

Cured at 171° C. for 20 minutes

OTES = Octyltriethoxysilane

As is demonstrated in TABLE VII, the sorbitan oleate processing aid was more effective in reducing ML

4

at 100° C. than PEG or sorbitol (Samples C-I to C-L). The addition of a small amount of another silane such as Si69 or OTES gave an even greater ML

4

reduction (Samples 24-27). Co-agents like urea, talc and mica also had a large effect on ML

4

reduction, especially when used with the sorbitan oleate (Samples 28-31). In fact, there is an effect on ML

4

reduction even when a low level of silane is used along with the sorbitan oleate and mica (compare Samples 30-31 with Sample C-M). These results clearly demonstrate the advantage of using a processing aid such as sorbitan oleate to reduce ML

4

in silica filled rubber stocks.

We have therefore found that mineral fillers inhibit re-agglomeration of the silica in silica-filled vulcanizable elastomer formulations and maintain the dispersion of the silica, thereby reducing the mixing required and aiding in the processability of the compound through a diminished Mooney viscosity. This is demonstrated by the compounding of the following formulation to screen silica filled, vulcanizable elastomeric compound properties described below in TABLE VIII.

TABLE VIII

Screening Formulation

Material

Silica

Carbon Black

Polymer

100

100

Silica

40

Carbon Black

8

45

Si-69

1

Dicyclohexylamine

1

1

Antioxidant

1

1

Stearic Acid

2

2

Sulfur

1.4

1.4

Accelerators

2.4

2.4

Zinc Oxide

3

3

Totals

159.8

155.8

In this basic formulation, without oil, five parts (by weight) of the silica were replaced with five parts of either mica, talc, or clay and compounded with a rubber specifically terminated to interact with filler through residual terminal methylsilylphenoxy groups. The rubber had been terminated with methyltriphenoxysilane (MeSi(OPh)

3

). Both a silica and carbon black filled stock were used as controls in these examples, as set forth in TABLE IX.

TABLE IX

Partial Silica Replacement with Mineral Fillers

Sample

C-K

32

33

34

C-O

Additive

Talc

Mica

Clay

Carbon

Black

Silica

40

35

35

35

Carbon Black

8

8

8

8

45

Talc

5

Mica

5

Clay

5

The properties of the compounds and the cured stocks are presented in TABLE IX. The uncured compound ML

1+4

at 100° C. of the stocks containing talc and mica were significantly lower than the all silica control. Moreover, the minimum torques (ML) by Monsanto Rheometer were also lower, indicative of a more processable stock. The hardness and MH of the talc and mica stocks indicated a slightly lower state of cure, although only slight differences were shown in the tensile properties, as reported in Table X, below.

TABLE X

Physical Test Results

Initial Partial Silica Replacement with Mineral Fillers

Sample

C-N

32

33

34

C-O

Cpd ML

1+4

100° C.

107.8

96.7

97.5

102.7

88.1

Monsanto Rheometer

ML

9.55

8.06

8.40

8.78

6.53

TS

2

3′37″

3′42″

3′46″

3′39″

1′32″

TC

90

12′39″

10′24″

10′31″

10′42″

3′17″

MH

43.39

41.27

41.47

42.38

34.60

Shore A

69

65

66

67

67

Pendulum Rebound

69.8

71.2

71.8

71.2

63.6

65° C.

Ring Tensile 24° C.

100% Mod.

598

589

550

558

569

Max. Stress (psi)

2177

2186

2090

1885

2636

Max. Strain (%)

298

309

302

289

311

Ring Tensile 100° C.

100% Mod.

473

471

443

494

370

Max. Stress (psi)

1002

933

918

948

1712

Max. Strain (%)

190

184

188

182

272

Ring Tear 171° C. lb/in

82

68

65

62

95

65° C.

Tan δ (@ 7%

0.070

0.063

0.064

0.074

0.121

Elongation)

G′, MPa

3.131

3.004

3.041

3.163

2.752

ΔG′, MPa

0.586

0.349

0.534

0.655

0.811

Wet Skid

45

47

44

43

37

Further testing of silica-filled vulcanizable elastomeric compounds was conducted to determine the effect of additional mineral fillers and the use of sorbitan oleate as a processing aid in the stock formulations. These examples are described in TABLES XI, XII, XIV and XVI, and results of the tests reported in TABLES XIII, XV, XVII and XVIII.

Compound properties displayed in TABLE XII indicated a lower raw compound ML

1+4

at 100° C. with lower T80, and lower minimum torque, ML indicative of an easier processing stock. Tensile properties of the cured stocks were not adversely affected by the mica or talc at these levels and neither was the hardness or state of cure. Further, hot ring tear was improved compared to the control. Rebound and Tan δ were indicative of lower rolling resistance stocks.

TABLE XI

Basic Formulation (C-M)

Parts

Masterbatch Material

SBR

90.75

BR

25

Silica

80

Mica

Variable

Talc

Variable

Sorbitan Monooleate

Variable

Si69, Neat

Variable

Carbon Black

8

Oil

25.5

Stearic Acid

1

Wax Blend

1.5

Resin

3

Final Mixing Material

Masterbatch

(as above)

Processing Aid

0.95

Antiozonant

0.22

Zinc Oxide

1.7

Resin

2.5

Accelerators

2.4

Sulfur

Variable

TABLE XII

Partial Silica Replacement with Talc or Mica

Sample

C-P

35

36

37

38

39

Silica (phr)

80

78.5

76.4

72.7

76.6

73.3

Talc (phr)

0

2

5

10

0

0

Mica (phr)

0

0

0

0

5

10

Accelerator (phr)

2.4

2.4

2.4

2.4

2.4

2.4

Sulfur (phr)

1.6

1.6

1.6

1.6

1.6

1.6

Si69 (phr)

8

8

8

8

8

8

TABLE XIII

Physical Test Results

Partial Replacement of Silica with Talc or Mica

Sample

C-P

35

36

37

38

39

Mooney Viscometer

ML

1+4

(100° C.)

82.0

80.3

77.9

71.0

76.7

71.7

T

80

(seconds)

44.3

42.9

34.7

24.5

33.7

26.5

Monsanto Cure (170° C.)

ML

12.14

12.04

11.46

10.37

11.41

10.47

TS

2

2′31″

2′30″

2′29″

2′32″

2′37″

2′30″

TC

90

13′52″

13′08″

12′11″

11′37″

12′22″

11′56″

MH

35.38

35.95

35.69

33.97

35.48

34.60

Ring Tensile @ 23° C.

100% Modulus

281

294

335

323

319

315

Max. Stress (psi)

2434

2449

2601

2709

2634

2510

Max. % Strain

436

430

425

417

436

413

Ring Tensile @ 100%

100% Modulus

314

258

283

253

274

305

Max. Stress (psi)

1580

1405

1447

1264

1471

1485

Max. % Strain

436

430

425

417

436

413

Ring Tear Strength @ 170° C.

189

239

238

215

256

227

(lb/in)

Pendulum Rebound 65° C.

50.6

51.6

52.2

54.4

52.6

53.2

Shore “A” Hardness

66.0

70.0

69.0

65.0

65.0

67.0

Rheometrics @ 65° C.

Tan δ @ 7% Strain

0.1871

0.1825

0.1866

0.1730

0.1694

0.1740

ΔG′, MPa

6.201

7.237

6.825

4.949

6.033

5.498

TABLE XIV lists variations in order to maintain a constant volume fraction filler in the basic formulation, provided in TABLE XI. Among these variations were included two types of mica to replace some silica and replacement of Si69 with sorbitan monooleate and silica with a non reinforcing carbon black, N880. The mica utilized contained 16% Mg and is considered to be the mineral biotite, whereas C-3000 (available from KMG Minerals Inc, Kings Mountain, N.C.) is muscovite and contains very little magnesium. Properties for these formulations are displayed in TABLE XV.

A least squares estimate of the ML

1+4

at 100° C. and 0.8 parts Si69 was 137 in the all silica formulation. Addition of up to 15 parts mica caused a significant decrease in the observed value which was enhanced by the addition of sorbitan monooleate. There was an unexpected synergism of these additives on reduction of ML

1+4

, t80, and ML. MH, tensile, and hardness, all indicative of a lower state of cure, were reduced by the sorbitan monooleate. These effects were also reflected in the tensile retraction data as well.

Adjustment of curatives compensated for the lower cure rate. Even at the lower state of cure, these stocks had lower Tan δ values indicative of lower rolling resistance and increased fuel efficiency. This was further enhanced with a tighter cure.

TABLE XIV

Partial Silica Replacement with Mica

Sample

C-Q

C-R

C-S

C-T

C-U

C-V

40

41

42

43

44

45

C-W

C-X

46

Silica (phr)

80

80

80

80

80

80

80

80

72.8

69.2

69.2

69.2

73.3

73.3

69.2

Mica (phr)

0

0

0

0

0

0

0

0

10

15

15

15

0

0

15

Mica Type

—

—

—

—

—

—

—

—

B

B

B

M

—

—

M

N880 (phr)

0

0

0

0

0

0

0

0

0

0

0

0

0

6.21

0

Sorbitan

0

0

0

0

0

0

4

8

0

0

4

8

0

0

0

Monooleate

Accelerator

1.6

1.9

2.2

2.5

2.2

2.2

2.2

2.2

2.2

2.2

2.5

2.2

1.6

1.6

2.2

1 (phr)

Sulfur (phr)

1.6

1.5

1.4

1.3

1.6

1.2

1.8

1.8

1.8

1.8

1.7

1.9

1.6

1.6

1.8

Si69 (phr)

8

8

8

8

4

12

0.8

0.8

0.8

0.8

0.8

0

8

8

0.8

Accelerator

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

2 (phr)

B = BIOTITE

M = MUSCOVITE

TABLE XV

Physical Test Results

Partial Replacement of Silica with Mica

Sample

C-Q

C-R

C-S

C-T

C-U

C-V

40

Mooney Viscometer

ML

1+4

@ 100° C.

82.9

78.4

79.8

81.3

119.7

68.1

129.1

T

80

38.8

31.3

34.7

35

1154

17

730

Monsanto Cure @ 170° C.

ML

12.81

12.46

12.08

12.46

19.82

10.03

24.59

TS

2

2′29″

2′29″

2′34″

2′31″

2′07″

2′18″

2′17″

TC

90

13′16″

11′36″

9′29″

7′37″

17′43″

11′03″

17′52″

MH

36.91

36.71

35.45

36.68

42.95

38.12

44.36

Ring Tensile @ 23° C.

100% Modulus

362

327

343

351

294

390

236

Max. Stress (psi)

2793

2537

2798

2760

2479

2521

2216

Max. % Strain

511

504

525

518

557

457

729

Ring Tensile @ 100° C.

100% Modulus

353

293

285

326

294

355

183

Max. Stress (psi)

1555

1464

1418

1538

1470

1386

1444

Max. % Strain

363

394

386

379

411

333

739

Ring Tear @ 170° C.

245

257

243

237

233

280

176

Strength (lb/in)

Pendulum Rebound 65° C.

51.8

51.8

52.0

52.8

52.2

54.8

49.0

Shore “A” Hardness

72.0

69.0

70.0

70.0

72.0

70.0

68.0

Rheometric @ 65 ° C.

Tan δ @ 7% Strain

0.1815

0.1834

0.1904

0.19

.01707

0.1751

0.1837

ΔG′, MPa

8.329

8.247

8.754

9.227

9.267

7.488

9.762

Tensile Retraction

M

0

(×10

−4

), g/mol

1.23

1.15

1.25

1.14

1.26

1.05

1.43

Slope (×10

−3

), g/mol

3.06

3.07

3.16

3.09

3.73

2.86

4.95

β (×10

−3

), g/mol

5.70

5.91

5.99

5.11

4.06

5.55

3.90

Sample

41

42

43

44

45

C-V

C-W

46

Mooney Viscometer

ML

1+4

@ 100° C.

103.5

135.7

122.0

92.7

76.6

69.8

73.6

123.6

T

80

300

1510

592

109.5

27.2

18.7

21.4

1316.6

Monsanto Cure @

170° C.

ML

19.28

26.83

23.03

16.46

13.63

10.03

10.37

22.59

TS

2

2′39″

1′53″

1′57″

2′30″

3′13″

2′27″

2′20″

1′49″

TC

90

15′24″

18′45″

18′24″

13′16″

12′10″

12′06″

10′49″

18′45″

MH

39.24

47.72

44.36

37.25

31.80

33.35

34.57

43.14

Ring Tensile @ 23° C.

100% Modulus

191

273

258

205

166

237

265

271

Max. Stress (psi)

1916

2389

2281

2123

1559

2551

2796

2283

Max. % Strain

768

665

675

782

831

616

618

678

Ring Tensile @ 100° C.

100% Modulus

151

208

231

176

134

268

287

280

Max. Stress (psi)

1296

1311

1402

1399

959

1392

1381

1242

Max. % Strain

821

585

584

745

826

433

414

530

Ring Tear @ 170° C.

278

272

247

267

212

260

246

237

Strength (lb/in)

Pendulum Rebound

46.8

51.8

53.0

51.4

47.6

53

52.8

51.6

65° C.

Shore “A” Hardness

66.0

75.0

70.0

65.0

62.0

67.0

69.0

75.0

Rheometric @ 65 ° C.

Tan δ @ 7% Strain

0.1935

0.1791

0.1798

0.1819

0.1932

0.1851

0.1792

0.1701

ΔG′, MPa

8.351

9.676

8.826

7.022

5.185

5.749

5.656

10.165

Tensile Retraction

M

0

(×10

−4

), g′mol

1.6

1.26

1.29

1.59

1.87

1.10

1.10

1.26

Slope (×10

−3

), g/mol

5.63

4.69

5.12

5.53

7.03

2.93

2.98

4.94

β (×10

−3

), g/mol

4.07

3.42

4.35

5.61

7.95

6.35

6.72

4.02

TABLE XVI describes additional variations in formulation as well as including other types of mica. The particular mica was unimportant in the ML

4

reduction which ranged from about 12 to 14 points at 15 parts mica per 100 rubber, shown in TABLE XVII. Nor, were there significant effects of mica type on ML or T

80

reductions. The mica stocks showed higher rebound and reduced tan δ values at comparable states of cure as judged from tensile properties. Hardness values indicated a lower state of cure for the mica stocks; however, a change of filler type may not allow direct comparison of hardness to judge state of cure.

TABLE XVI

Partial Silica Replacement with Mica

Change of Cure System

Sample

C-X

C-Y

C-Z

C-AA

47

48

49

50

51

C-BB

Recipe Per

C-P

C-P

C-P

C-P

C-P

C-P

C-P

C-P

C-P

C-P

Previous Stock

ZnO (phr)

1.70

2.40

3.00

3.00

1.70

1.70

1.70

3.00

3.00

1.70

Stearic Acid

1.00

1.00

1.00

2.00

1.00

1.00

1.00

1.00

1.00

1.00

(phr)

Silica (phr)

80

80

80

80

69.2

69.2

69.2

69.2

69.2

80

Mica Muscovite

0

0

0

0

15

0

0

0

0

0

(phr)

Water Ground

0

0

0

0

0

15

0

0

0

0

325 Mesh Mica

Muscovite (phr)

C3000-SM-M

0

0

0

0

0

0

15

15

15

0

(phr) Silane

Treated

Si69/CB Mixture

16

16

16

16

16

16

16

16

0(*)

16

(1:1) (phr)

Sulfur (phr)

1.40

1.40

1.40

1.40

2.20

2.20

2.20

2.20

2.20

2.20

(*) Add 8.0 phr N330 Carbon Black to Compensate for that in 16.00 phr

TABLE XVII

Physical Test Results

Effect of Presence of Mica, Type of Mica and of Cure System

Variations at Constant Mixing Energy Input (238.4 w-hrs/lb)

Sample

C-X

C-Y

C-Z

C-AA

47

48

49

50

51

C-BB

Mooney Viscometer

ML

1+4

100° C.

75.7

73.4

74.5

71.5

58.7

60.1

60.4

60.2

125.1

72.7

T

80

24.1

22.7

24.1

22.4

19.7

15.9

15.6

14.6

>300.6

26.1

Monsanto Cure (170° C.)

ML

11.6

11.17

11.36

10.59

8.94

8.85

9.38

8.60

25.86

10.97

TS

2

2′30″

2′31″

2′36″

2′42″

2′19″

2′21″

2′18″

2′27″

2′11″

2′12″

TC

90

10′01″

9′43″

10′11″

8′49″

11′01″

10′49″

11′07″

11′53″

20′49″

12′55″

MH

37.37

37.08

37.70

35.43

39.44

39.16

40.70

38.43

48.24

41.52

Ring Tensile @ 23° C.

100% Modulus

318

333

327

301

393

430

387

368

256

368

MAX. Stress (psi)

2809

3107

2927

2819

2604

2766

2681

2452

1886

2714

Energy To Break (psi)

6596

7435

7132

7038

5540

5977

5989

5212

5293

5399

Ring Tensile @ 100° C.

100% Modulus

<268

276

281

248

321

347

366

341

220

366

Max. Stress (psi)

1263

1631

1503

1483

1093

1255

1376

1436

1212

1811

Max. % Strain

364

439

417

451

324

334

341

368

671

361

Ring Tear @ 170° C. Tear

276

307

305

322

253

253

261

246

240

253

Strength (lb/in)

Pendulum Rebound

53.6(*)

53.0(*)

54.8

53.6

59.6

58.8

58.8

58.6

51.2

55.8

65° C.

Shore “A” Hardness

65.0

67.0

67.0

68.0

68.0

68.0

67.0

68.0

72.0

70.0

Rheometrics @ 65° C.

Tan δ @ 7% Strain

0.1839

0.1868

0.1764

0.1855

0.1436

0.1458

0.1471

0.1480

0.1679

0.1875

ΔG′, MPa

6.881

6.167

5.950

5.290

4.745

5.146

5.063

4.792

10.08

5.831

(*) Samples not well molded

TABLE XVIII lists the results of controlled mix studies into which a known energy input was applied to a mix after the Si69 was added in the presence of mica, talc, and/or sorbitan monooleate. It has been established that β, an inverse measure of filler association or crosslink density, as determined by tensile retraction, can be increased by more mixing energy. This effect can be calculated from the slope of 33.99 g/mol mix energy, and intercept, 1349 g/mol, (see drawing FIGURE) and applied to the mix energy supplied to the samples.

The data in TABLE XVIII have been sorted by increasing Si69, Mica, and Talc in that order. The Δβ value, the increase in β over that expected, increased with Si69 and the Mica and Talc level and have thusly been grouped. The two exceptions were the combination of Mica (15 parts) with sorbitan monooleate (8 parts) and the sorbitan monooleate alone (8 parts) which showed much higher β than expected from mix energy calculations alone.

TABLE XVIII

Tensile Retraction of Controlled Energy Mixes

Energy After Si69 was Added to a 280 g Brabender

Mr

S

β

Energy

Si69

Sulfur

Sample

g/mol

g/mol

S/Mr

g/mol

W/H

phr

phr

45

16700

7034

0.421

7947

112.17

0

1.9

42

109.13

4910

0.450

2057

72.73

0.8

2

40

14270

4945

0.347

3899

106.13

0.8

1.8

52

16040

5626

0.351

4069

103.83

0.8

1.8

41

11387

2686

0.236

5811

75.40

0.8

2

42

12630

4690

0.371

3415

101.44

0.8

1.8

53

12640

4944

0.391

4022

104.93

0.8

1.8

46

12930

5122

0.396

4354

113.16

0.8

1.8

44

15875

5532

0.348

5615

123.10

0.8

1.7

39

10475

2547

0.243

5697

147.00

8

2.2

47

12184

3247

0.268

6668

147.00

8

1.4

C-Y

10980

2928

0.267

6346

117.05

8

1.6

C-X

12304

3061

0.249

5702

93.51

8

1.6

48

12890

3010

0.234

5579

80.37

8

1.8

C-W

11040

2980

0.270

6716

109.72

8

1.6

C-P

12656

3130

0.247

6058

87.65

8

1.6

35

12398

3352

0.270

6835

88.70

8

1.6

36

12690

3443

0.271

7380

96.59

8

1.6

37

12491

3270

0.262

6706

89.88

8

1.6

38

12579

3423

0.272

7880

92.61

8

1.6

54

9111

3098

0.340

8289

147.00

8

2.2

C-BB

9299

3082

0.331

8309

147.00

8

2.2

48

9348

3155

0.338

8630

147.00

8

2.2

49

9849

3141

0.319

8708

147.00

8

2.2

ACC

MICA

TALC

SO

CALC β

ΔB

Sample

phr

phr

phr

phr

g/mol

g/mol

45

3.0

15

0

8

5161

2786

42

2.4

0

0

0

3820

−1763

40

3.0

0

0

4

4956

−1057

52

3.0

0

0

8

4878

−809

41

2.4

0

0

8

3912

1899

42

3.0

10

0

0

4796

−1381

53

3.0

15

0

0

4915

−893

46

3.0

15

0

0

5195

−841

44

3.0

15

0

4

5533

82

39

2.4

0

0

0

6345

−648

47

3.0

0

0

0

6345

323

C-V

2.4

0

0

0

5327

1019

C-X

2.4

0

0

0

4527

1175

48

3.0

0

0

0

4080

1499

C-W

2.4

0

0

0

5078

1638

C-P

2.4

0

2

0

4328

1730

35

2.4

0

5

0

4363

2472

36

2.4

0

10

0

4632

2748

37

2.4

5

0

0

4403

2303

38

2.4

10

0

0

4496

3384

54

2.4

15

0

0

6345

1944

C-BB

2.4

15

0

0

6345

1964

48

2.4

15

0

0

6345

2285

49

2.4

15

0

0

6345

2363

It is therefore unexpected that mica and talc should decrease the filler interaction and increase β as their levels were increased. Further, sorbitan monooleate, alone and in concert with mica, acted to increase the observed β and thus reduce filler interaction.

Further testing of silica-filled vulcanizable elastomeric compounds was conducted to determine the effect of mineral fillers and the use of polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated sugars as processing aids in the stock formulations. These examples are described in TABLE XIX with the results of the tests conducted to evaluate and compare physical properties. As a Control, Sample C-F was prepared as above, without any fatty acid ester additives. The ethoxylated species (Tweens) are presented as Samples 52, 54, 55 and 59 and are compared against analogous sorbitans (Spans, non-ethoxylated), Samples 53, 56, 57 and 58. The Samples contained carbon black 35 phr, 30 phr of silica and 3 parts by weight of Si69 (10 percent per weight of silica) and were prepared with the formulation as set forth in Table VI, Sample C-F, to which the processing aids of Table XIX were added. The processing aids included Spans (fatty acid esters) and Tweens (polyoxyethylene fatty acid esters).

TABLE XIX

Physical Test Results

Effect of Partial Replacement of Silica with Sorbitan Esters

Sample

C-F

52

53

54

55

56

57

58

59

Additive

—

Tween 80

Span 80

Tween 60

Tween 85

Span 60

Span 85

Span 80

Tween 80

Level, phr

—

3

3

3

3

3

3

1.5

1.5

Mooney Viscosity

ML

1+4

100° C.

60.3

52

50.2

53.8

50.5

49.5

52.3

53.5

56.7

T

80

7.8

6.7

6.7

6.7

5.3

5.4

5.7

5.7

6

Monsanto Cure (165° C.)

ML*

2.56

2.34

1.87

2.43

7.25

8.52

7.25

7.44

8.17

TS

2

2′58″

3′27″

3′30″

3′33″

4′47″

4′41″

4′27″

4′22″

4′38″

TC

90

9′43″

11′46′

11′29″

11′56″

14′38″

13′34″

12′16″

12′25″

11′56″

MH*

15.69

16.42

14.68

17.94

40.36

37.88

37.88

38.55

41.67

Ring Tensile @ 24° C.

100% Modulus

465

485

600

472

363

446

393

383

394

MAX. Stress (psi)

2278

2264

3595

2218

3274

2956

2961

2706

2466

Energy To Break (in-

3374

3398

6380

3384

4169

5403

5705

4965

4319

lbs/in

3

)

Ring Tensile @ 100° C.

100% Modulus

371

387

379

375

329

298

315

338

346

Max. Stress (psi)

1228

1255

1268

1272

1492

1216

1417

1437

1389

Max. % Strain

257

251

260

263

311

288

313

304

286

Ring Tear @ 171° C.

—

—

—

—

112

148

123

124

118

Tear Strength (lb/in)

Pendulum Rebound

51.4

53

52

53

50.2

50

51.8

50.6

50.8

65° C.

Rheometrics

Tan δ @ 7% Strain

0.138

0.1207

0.1232

0.1088

0.1155

0.1214

0.1209

0.1319

0.1266

9

ΔG′, MPa at 65° C.

2.752

2.922

2.243

2.551

2.417

2.475

2.144

2.45

2.697

(*)ML and MH values for Samples C-F and 52-54 were measured on a Monsanto MDR 2000 rheometer and ML and MH values for Samples 55-59 were measured on a Monsanto ODR rheometer.

As is apparent from the physical properties reported in Table XIX, the ethoxylated sorbitans (Tweens) provided improved properties over the Control and generally performed as well as the sorbitans (Spans). All aids were fairly well equivalent, showing reduced Mooney viscosity and torque while desired physical properties remained. Unexpectedly, the need for adjacent hydroxyls in the sorbitan molecule, as taught by Canadian Pat. No. 2,184,932 to Semerit, was found to be unfounded as the use of tri-oleates, which contain only a single hydroxyl, were effective in producing processability as was equally true for the polysorbates which are polyethoxylated and thus, contain no adjacent hydroxyls.

Further testing of silica-filled vulcanizable elastomeric compounds was conducted to determine the effect silica-supported and carbon black-supported alkyl alkoxysilanes and polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated sugars as processing aids in the elastomeric stock formulations. The basic formulation, C-CC, of the elastomeric stock formulation is shown and described in Table XX below.

The physical properties of the Example Nos. 60-65 and the control, C-DD, are shown and described in Table XXI, below. Example Nos. 61-65 indicated a Mooney viscosities (ML 1+4/100° C.) comparable to the control, C-DD, with 3 phr of Si69 processing aid. Tensile properties of the cured elastomeric stocks, containing processing aids comprising octyl triethoxy silane and sorbitan oleate supported on silica are comparable to the tensile properties of the control elastomeric stock formulation, C-DD, containing 3 phr of Si69 processing aid. Curing at 171° C. for 20 minutes was used to obtain the physical properties set forth below.

TABLE XX

Basic Formulation of Elastomeric Stock (C-CC)

Component

Parts

SBR

75

NR

25

Oil

15

carbon black

35

silica

VARIABLE

stearic acid

1.5

wax

1.0

process aid

VARIABLE

antioxidant

0.95

sulfur

1.7

CBS

1.5

DPG

0.5

Zinc oxide

2.5

Final Elastomeric Stock Formulations

C-

Component

DD

60

61

62

63

64

65

46% SO on Silica

a

—

3.3

3.3

—

—

—

—

47% SO on Silica

b

—

1.5

2.5

—

—

—

—

5% SO/3.8% OS on Silica

c

—

—

—

32.9

—

—

—

5% SO/3.8% OS on Silica

d

—

—

—

—

32.9

—

—

Sorbitan Oleate (SO)

—

—

—

—

—

1.65

1.6

5

Octyl triethoxysilane (OS)

—

—

—

—

—

1.25

1.2

5

a

Flogard SP (712-090)

b

Flogard SP (712-091)

c

Flogard SP (712-097)

d

HiSil (712-098)

TABLE XXI

Physical Properties of Elastomeric Formulations

Example

C-DD

60

61

62

63

64

65

Mooney Viscosity

ML 1 + 4/100° C.

77.6

132.4

75.2

77.9

80.8

64.6

72.9

T80

9.7

43.5

7.5

8.5

9.3

6.5

7.4

MDR Monsanto Cure at 165° C.

ML

11.01

3.86

3.48

3.7

3.75

3.13

3.32

MH

35.37

20.42

19.39

19.67

20.28

18.89

19.1

ts2

2:36

2:08

2:16

2:26

2:16

2:22

2:24

tc90

17:06

13:55

11:14

10:37

11:14

10:41

10:02

tan δ at MH

—

0.144

0.145

0.158

0.15

0.134

0.135

Ring Tensile at 24° C.

50% Modulus, psi

221

256

230

209

219

207

227

100% Modulus, psi

322

403

360

331

356

331

360

200% Modulus, psi

615

819

766

678

739

697

765

300% Modulus, psi

1008

1407

1338

1177

1279

1234

1335

Tensile Strength, psi

1852

2082

1899

1726

1959

1840

1886

% Elongation

474

400

386

392

407

395

381

Break energy,

4012

3762

3229

3013

3549

3156

3166

in-lbs/in

2

Ring Tensile at 100° C.

50% Modulus, psi

189

229

208

212

196

193

190

100% Modulus, psi

263

350

323

312

303

296

300

200% Modulus, psi

518

685

654

632

607

614

604

300% Modulus, psi

869

1140

1107

1022

1025

1070

1023

Tensile Strength, psi

1299

1248

1227

1203

1075

1097

1148

% Elongation

412

322

322

327

310

308

326

Break energy,

2496

1894

1837

1813

1557

1552

1761

in-lbs/in

2

Ring Tear at 171° C., psi

184.9

175.

140.8

152.2

108.2

118.4

154

6

Wet Stanley

59/53

57/5

57/52

58/52

58/52

57/52

57/52

London(#/std)

2

Shore A, at RT

—

72

70

67

67

67

66

Shore A at 50° C.

—

67

67

65

67

66

65

Rheometrics at 7% Strain

tan C at 24° C.

0.193

0.195

0.169

0.173

0.175

0.166

G.180

δ G′ × 10

−7

at 24° C.

4.239

4.506

4.879

5.267

4.718

3.94

4.712

24° C. G′ × 10

−7

at 14.5%

3.006

3.138

3.261

3.01

3.127

2.856

3.422

tan δ at 65° C.

0.152

0.153

0.155

0.143

0.145

0.138

0.149

5 G′ × 10

−7

at 65° C.

2.689

3.779

5.667

3.939

4.554

4.172

3.836

50° C. G′ × 10

−7

at 14.5%

2.42

2.736

2.77

2.731

2.992

2.509

2.6

Mr, g/mol from

13680

10440

—

11320

—

—

—

Tensile Retraction

Further testing of silica-filled vulcanizable elastomeric stock formulations was conducted to determine the effects of the silica and carbon black-supported processing aids on the physical properties and processability of the elastomeric formulations after six months of ambient storage.

The elastomeric stock formulations were prepared according to Table XXII, below, and the physical properties were evaluated after curing at 170° C. for 20 minutes, followed by six months of ambient aging. The data for the physical properties and processability of the elastomeric formulations for the ambient aging study are shown in Table XXIII, below.

TABLE XXII

Basic Formulation of Elastomeric Stock (C-CC)

Component

Parts

SBR

75

NR

25

Oil

15

carbon black

35

silica

VARIABLE

stearic acid

1.5

wax

1.0

process aid

VARIABLE

antioxidant

0.95

sulfur

1.7

CBS

1.5

DPG

0.5

Final Elastomeric Stock Formulations

Example

66

67

68

69

70

71

46% SO on Silica

a

3.3

3.3

—

—

—

—

47% SO on Silica

b

—

2.5

—

—

—

—

5% SO 13.8% OS on

—

—

32.9

—

—

—

Silica

c

5% SO/3.8% 05 on Silica

d

—

—

—

32.9

—

—

Sorbitan Oleate (SO)

—

—

—

—

1.65

1.65

Octyl triethoxysilane (OS)

1.25

—

—

—

1.25

1.25

TABLE XXIII

Physical Properties of Elastomeric Formulations

After Ambient aging for 6 months

66

67

68

69

70

71

Mooney Viscosity

ML 1 +4/100° C.

77

80.8

78.9

78.9

74.8

78.1

MDR Monsanto Cure at

165° C.

ML

2.97

3.62

3.5

3.69

3.29

3.47

MH

16.12

19.65

19.02

19.62

18.72

16.49

ts2

2:52

2:42

3:04

3:05

2:49

2:54

tc90

14:27

10:47

9:37

9:11

9:41

14:00

tan δ at MH

0.2

0.093

0.102

0.103

0.091

0.189

Ring Tensile at 24° C.

50% Modulus, psi

181

159

172

166

171

165

100% Modulus, psi

333

286

316

296

310

294

200% Modulus, psi

778

676

754

691

740

696

300% Modulus, psi

1415

1242

1389

1273

1375

1288

Tensile Strength,

2551

2233

2442

2298

2548

2438

psi

% Elongation

448

445

441

447

454

461

Break energy,

4735

4088

4521

4235

4731

4605

in-lbs/in

2

Physical Properties of Elastomeric Formulations-aging

Example

66

67

68

69

70

71

Ring Tensile at

100° C.

50% Modulus,

131

131

146

153

146

139

psi

100% Modulus,

244

240

267

274

266

250

psi

200% Modulus,

541

532

596

596

590

546

psi

300% Modulus,

973

963

1073

1076

1069

982

psi

Tensile

1285

1400

1356

1433

1430

1396

Strength, psi

% Elongation

367

394

356

369

371

388

Break energy,

2024

2353

2069

2266

2270

2330

in-lbs/in

2

New Lambourn

179

181

157

147

158

149

at 65%, g lost

New Lambourn

0.145

0.148

0.1456

0.1506

0.1454

0.1481

at 65%,

INDEX

Ring Tear at

0.97

0.95

0.96

0.93

0.96

0.95

171° C., psi

Wet Stanley

53/48.5

57/48.5

53/48.5

53/48.5

56/48.5

53/48

London(#/std)

Shore A, at RT

66.4

67

67.7

67.5

65.8

64.1

Shore A at

63.6

64.3

64.8

64.9

63.9

64.1

50° C.

Rheometrics at

7% Strain

tan δ at 24° C.

0.1779

0.169

0.181

0.1843

0.159

0.1724

24° C. G′ ×

0.628

0.605

0.657

0.739

0.491

0.577

10

−7

at 7%

δ G′ ×

4.772

4.224

5.233

5.909

3.13

4.087

10

−7

at 24° C.

24° C. G′ ×

2.652

2.779

2.779

3.009

2.48

2.572

10

−7

at 14.5%

tan δ at 50° C.

0.15

0.1391

0.1524

0.1544

0.1417

0.1412

50° C. G′ ×

0.462

0.441

0.482

0.521

0.38

0.401

10

−7

at 7%

δ G′ ×

3.648

3.374

3.941

4.428

2.829

2.995

10

−7

at 50° C.

50° C. G′ ×

2.417

2.536

2.477

2.644

2.151

2.281

10

−7

at 14.5%

It is apparent from the data contained in Table XXIII, above, that elastomeric formulations containing a silica-supported or carbon black-supported processing aid selected from the group consisting of an alkyl alkoxysilane, fatty acid ester of hydrogenated or non-hydrogenated C

5

and C

6

sugars, e.g., sorbitan, and ethoxylated derivatives of fatty acid esters of these sugars provide physical properties, after six months of ambient aging, comparable to the control elastomeric formulation containing 3 phr of Si69 as a processing aid (C-DD).

Thus, it should be evident that the process of the present invention is useful in improving the processability of formulations of diene polymer elastomers containing silica filler by reducing the viscosity of silica-filled elastomeric vulcanizable compounds. It is further demonstrated that the present invention provides vulcanizable silica-filled elastomeric compounds having enhanced physical properties. Practice of the present invention allows a reduction of Si69 which is added to vulcanizable rubber compositions containing silica fillers. The reduction can be effected by the addition of the processing aids described herein, mineral and non-mineral fillers as well as combinations of more than one.

It will be appreciated that the processing aids and additional fillers exemplified herein have been provided to demonstrate practice of the invention and are otherwise not to be construed as a limitation on practice of the present invention. Moreover, the processing aids and mineral fillers disclosed herein have been provided for purposes of exemplification only and thus, it is to be appreciated that other materials can be substituted without falling outside of the scope of this invention. Those skilled in the art can readily determine suitable additives and the appropriate manner of formulating elastomeric compositions containing silica fillers. Furthermore, practice of the present invention is not limited to a specific formulation of elastomers.

Based upon the foregoing disclosure, it should now be apparent that the process and related components described herein will carry out the objects set forth hereinabove. It is, therefore, to be understood that any variations evident fall within the scope of the claimed invention and thus, the selection of specific component elements can be determined without departing from the spirit of the invention herein disclosed and described. Thus, the scope of the invention shall include all modifications and variations that may fall within the scope of the attached claims.

Number	Name	Date	Kind
3627723	Kealy et al.	Dec 1971	A
3717600	Dalhuisen et al.	Feb 1973	A
3737334	Doran	Jun 1973	A
3768537	Hess et al.	Oct 1973	A
3873489	Thurn	Mar 1975	A
3881536	Doran, Jr. et al.	May 1975	A
3884285	Russell et al.	May 1975	A
3923712	Vickery	Dec 1975	A
3938574	Burmester et al.	Feb 1976	A
3978103	Meyer-Simon et al.	Aug 1976	A
4029513	Vessey et al.	Jun 1977	A
4076550	Thurn et al.	Feb 1978	A
4143027	Sollman et al.	Mar 1979	A
4179537	Rykowski	Dec 1979	A
4201698	Itoh et al.	May 1980	A
4229333	Wolff et al.	Oct 1980	A
4297145	Wolff et al.	Oct 1981	A
4431755	Weber et al.	Feb 1984	A
4433013	Pühringer	Feb 1984	A
4436847	Wagner	Mar 1984	A
4463120	Collins et al.	Jul 1984	A
4474908	Wagner	Oct 1984	A
4482657	Fischer et al.	Nov 1984	A
4623414	Collins et al.	Nov 1986	A
4629758	Kawaguchi et al.	Dec 1986	A
4906680	Umeda et al.	Mar 1990	A
4937104	Pühringer	Jun 1990	A
5057601	Schiessl et al.	Oct 1991	A
5066721	Hamada et al.	Nov 1991	A
5159009	Wolff et al.	Oct 1992	A
5178676	Lackey et al.	Jan 1993	A
5227425	Rauline	Jul 1993	A
5227431	Lawson et al.	Jul 1993	A
5328949	Sandstrom et al.	Jul 1994	A
5336730	Sandstrom et al.	Aug 1994	A
5426136	Waddell et al.	Jun 1995	A
5502131	Antkowiak et al.	Mar 1996	A
5508333	Shimizu	Apr 1996	A
5514756	Hsu et al.	May 1996	A
5521309	Antkowiak et al.	May 1996	A
5552473	Lawson et al.	Sep 1996	A
5569697	Ferrandino et al.	Oct 1996	A
5574109	Lawson et al.	Nov 1996	A
5580919	Agostini et al.	Dec 1996	A
5591794	Fukumoto et al.	Jan 1997	A
5610221	Waddell et al.	Mar 1997	A
5610227	Antkowiak et al.	Mar 1997	A
5610237	Lawson et al.	Mar 1997	A
5616655	D'Sidocky et al.	Apr 1997	A
5659056	Hergenrother et al.	Aug 1997	A
5674932	Agostini et al.	Oct 1997	A
5679728	Kawazura et al.	Oct 1997	A
5686523	Chen et al.	Nov 1997	A
5708053	Jalics et al.	Jan 1998	A
5717022	Beckmann et al.	Feb 1998	A
5719207	Cohen et al.	Feb 1998	A
5723531	Visel et al.	Mar 1998	A
5741858	Brann et al.	Apr 1998	A
5763388	Lightsey et al.	Jun 1998	A
5777013	Gardiner et al.	Jul 1998	A
5780537	Smith et al.	Jul 1998	A
5780538	Cohen et al.	Jul 1998	A
5798419	Quiteria et al.	Aug 1998	A
5804636	Nahmias et al.	Sep 1998	A
5804645	Matsuo	Sep 1998	A
5866650	Lawson et al.	Feb 1999	A
5872171	Detrano	Feb 1999	A
5872176	Hergenrother et al.	Feb 1999	A
5872178	Kansupada et al.	Feb 1999	A
5872179	Hubbell	Feb 1999	A
5877249	Lambotte	Mar 1999	A
5883179	Kawazoe et al.	Mar 1999	A
5886074	Sandstrom et al.	Mar 1999	A
5886086	Hubbell et al.	Mar 1999	A
5898047	Howland et al.	Apr 1999	A
5912374	Agostini eet al.	Jun 1999	A
5914364	Cohen et al.	Jun 1999	A
5916951	Nahmias et al.	Jun 1999	A
5916961	Hergenrother et al.	Jun 1999	A
5916973	Zimmer et al.	Jun 1999	A
5929149	Matsuo et al.	Jul 1999	A
6008295	Takeichi et al.	Dec 1999	A
6022922	Bergh et al.	Feb 2000	A
6046266	Sandstrom et al.	Apr 2000	A
6053226	Agostini	Apr 2000	A
6080809	Stuhldreher	Jun 2000	A

Number	Date	Country
2177095	May 1996	CA
2184932	Mar 1997	CA
2242310	Jan 1999	CA
2242383	Jan 1999	CA
2242783	Jan 1999	CA
2242797	Jan 1999	CA
2242800	Jan 1999	CA
2242801	Jan 1999	CA
2243091	Jan 1999	CA
299373	Aug 1954	CH
29 05 977	Aug 1979	DE
0 447 066	Sep 1991	EP
0 510 410	Oct 1992	EP
0 754 710	Jan 1997	EP
0 765 904	Apr 1997	EP
0 767 179	Apr 1997	EP
0 890 580	Jan 1999	EP
0 890 587	Jan 1999	EP
0 890 588	Jan 1999	EP
0 890 602	Jan 1999	EP
0 890 603	Jan 1999	EP
0 890 606	Jan 1999	EP
0 908 586	Jan 1999	EP
63-213536	Sep 1988	JP
5-51484	Mar 1993	JP
WO 9902601	Jan 1999	WO

	Number	Date	Country
Parent	08/985859	Dec 1997	US
Child	09/203438		US
Parent	08/893864	Jul 1997	US
Child	08/985859		US
Parent	08/893875	Jul 1997	US
Child	08/893864		US

Processability of silica-filled rubber stocks

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

CROSS-REFERENCE TO RELATED APPLICATIONS

US Referenced Citations (86)

Foreign Referenced Citations (26)

Continuation in Parts (3)