A rubber composition containing a fluoroglucinol resin for use in a tire tread of a large vehicle

Abstract

A silane-based additive, a rubber formulation containing the additive, and a tire having a tread portion made of the additive are provided, along with a method of forming those products. An uncured rubber formulation according to a preferred embodiment of the present invention comprises (1) a rubbery primary polymer or polymer blend, such as natural rubber and / or synthetic rubber; (2) a reinforcing silica filler; (3) a methylene donor compound; (4) a silane containing one or more moieties of the aforementioned network-forming polymer; and (5) a phloroglucinol resin. Networks that can be generated in situ are particularly preferred. The cured rubber formulation preferably comprises silica bonded with an interpenetrating polymer network that reinforces the load-bearing paths and is not directly bonded to the rubber chains via sulfide bonds within the rubber matrix.

Description

Technical Field

[0001] This invention generally relates to rubber compounds for use in tires of heavy vehicles such as large trucks and buses. More specifically, the present invention relates to an environmentally friendly and fuel-efficient rubber compound for use in the treads of truck and bus tires that does not contain resorcinol but unexpectedly provides excellent rolling resistance characteristics for such rubber compounds.

Background Art

[0002] There is an unmet need for further reduction in the fuel efficiency of tires due to the Corporate Average Fuel Economy (CAFE) standards, Greenhouse Gas (GHG) protocols, and other laws promulgated by the National Highway Transportation Safety Administration (NHTSA) and the Environmental Protection Agency (EPA) in the United States, regulations promulgated by Transport Canada and the Canadian Health Ministry, and the European Union Tyre Label in Europe. One way to determine fuel efficiency is to examine the rolling resistance of the rubber composition, which can be determined by various mechanical properties of the rubber composition. Simply put, the lower the rolling resistance of the rubber composition, the better the fuel economy of the tire.

[0003] Generally, it is known in the art that by adding an organosilane coupling agent containing silica or sulfur to a tire tread rubber composition, various properties such as wet traction and rolling resistance can be improved. For example, Japanese Patent No. 50-88150 shows that a tire tread for winter tires treated with a silane compound containing silica and sulfur atoms added to a rubber compound has improved skid resistance. Similarly, European Patent No. 0 299 074 proposed the use of functionalized alkoxysilanes in rubber compositions containing silica as a reinforcing filler. Similarly, U.S. Patent No. 5,227,425, the disclosure of which is incorporated herein by reference in its entirety, discloses a tire tread composition in which the rubber component is a copolymer of a conjugated diene and an aromatic compound containing vinyl prepared in solution, and the carbon black filler is partially or completely replaced with silica and a silane coupling agent added separately from the polymer during mixing.

[0004] However, these rubber compounds cannot withstand the loads required for large vehicles such as commercial medium trucks weighing more than 13,000 pounds or heavy-duty trucks weighing more than 26,000 pounds. These rubber compounds are more suitable for small tires such as those used on passenger cars and light trucks.

[0005] Attempts have been made to address the problem of providing a high-load resistant tread composition having stress-strain characteristics of a reinforced natural rubber containing silica and to provide a fuel-efficient tread for use in tires for trucks or buses. One such attempt is provided in US Patent Application Publication No. 2020 / 0140661, now US Patent No. 11,267,955, which discloses and claims a rubber compound containing natural rubber, a reinforcing filler such as reactive silica, and a special silane coupling agent such as silane functionalized with hexamethoxymethylmelamine (HMMM), and a secondary network based on resorcinol or a resorcinol-formaldehyde resin. It is noted that this patent mentions phloroglucinol as a compound containing potential active hydrogen. However, as described below, phloroglucinol is not a phloroglucinol resin. Moreover, it is noted that this patent claims in its claims a silane functionalized with reactive hexamethoxymethylmelamine and a reinforcing filler. This is considered to be the novelty of the patent, and it does not claim in its claims the use of hexamethoxymethylmelamine (HMMM) separately from the silane.

[0006] On the other hand, resorcinol-formaldehyde resin, also referred to as RF resin or resorcinol-based resin, which is formed as a reaction product of resorcinol and formaldehyde, is widely used in various applications including rubber compounding. In rubber compound formulations, solid RF resin has long been used to enhance rubber properties such as the adhesion characteristics between rubber and reinforcing materials and the mechanical properties of articles such as tires, belts, and hose products.

[0007] The problems associated with these resins are that resorcinol resins generally have 10 - 20% unreacted or free resorcinol. The amount of free resorcinol can be a very significant factor when balancing important properties and when the presence of free resorcinol can be problematic. For example, free resorcinol can potentially volatilize during rubber mixing. Such volatilization is often referred to as fuming and thus causes new problems added to the rubber mixing process. Further, the presence of free resorcinol contributes to the hygroscopicity of the resorcinol resin, which in turn causes problems in storage and handling.

[0008] Also, formaldehyde has been used for many years to make resorcinol - formaldehyde resins. Considering its widespread use, toxicity, and volatility, formaldehyde presents potential health and environmental problems. In 2011, the US National Toxicology Program described formaldehyde as a known human carcinogen. Thus, rubber compositions containing resorcinol or resorcinol - formaldehyde resin compounds are not acceptable today by new tire manufacturers.

[0009] International Publication No. WO 2021 / 141934 provides for the use of phloroglucinol resins as substitutes for resorcinol or resorcinol - formaldehyde resins, but only when silane additives are not used. That is, like many of the other patents cited above, these resins are only suitable for rubber compositions for use in tires for light - weight vehicles because no silane additives were used in those patents or tires.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Accordingly, there is a need for the development of a reinforced natural rubber stress-strain property for use in tire applications for large vehicles (e.g., medium to large trucks and buses), and a rubber compound having high load-bearing capacity with fuel efficiency of a silica-based tread.

Means for Solving the Problem

[0011] To establish a very fuel-efficient tire for heavy trucks and buses that does not contain resorcinol or formaldehyde, a rubber compound formulation consisting of natural rubber, silica, a special silane coupling agent, hexamethoxymethylmelamine (HMMM) (separate from the silane coupling agent), and phloroglucinol resin was prepared. Surprisingly and unexpectedly, these rubber formulations showed much better fuel efficiency and durability compared to compounds containing resorcinol. This invention provides a much better natural rubber-silica tread compound for trucks and buses without resorcinol or formaldehyde.

[0012] At least one aspect of the present invention can be found in a rubber composition comprising: (a) a rubbery polymer or blend of polymers; (b) at least one organosilane coupling agent; (c) at least one reinforcing filler reactive with the at least one organosilane coupling agent; (d) at least one methylene donor compound; (e) at least one phloroglucinol resin; and (f) at least one sulfur donating compound. In various embodiments, the rubber composition comprises the above components, and the rubbery component (a) ranges from about 25 to about 95 weight percent based on the total weight of the rubber composition; the organosilane coupling agent (b) ranges from 0.05 to 30 parts of organosilane coupling agent (b) per 100 parts of the rubbery polymer; the reinforcing filler (c) reactive with the organosilane coupling agent (b) ranges from 1 to 150 parts of reinforcing filler per 100 parts of the rubbery polymer; the methylene donor compound (d) ranges from 0.1 to 30 parts of methylene donor compound per 100 parts of the rubbery polymer; the phloroglucinol resin (e) ranges from 0.1 to 10 parts of phloroglucinol resin per 100 parts of the rubbery polymer; and the sulfur donating compound (f) ranges from 0.1 to 5 parts of sulfur donating compound per 100 parts of the rubbery compound.

[0013] In one or more embodiments, the rubbery polymer (a) can be selected from the group consisting of natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), various copolymers of butadiene, copolymers of isoprene, solution styrene-butadiene rubber (SSBR), emulsion styrene-butadiene rubber (ESBR), ethylene-propylene terpolymer (EPDM), acrylonitrile-butadiene rubber (NBR), and functionalized rubbers modified with at least one alkoxysilyl group, tin-containing group, amino group, hydroxyl group, carboxylic acid group, polysiloxane group, epoxy group or phthalocyanimo group. In other more specific embodiments, the rubbery polymer comprises natural rubber or a mixture of natural rubber and butadiene rubber.

[0014] In these and other embodiments, the reinforcing filler (b) can be selected from fibers, fine particles, or a sheet-like structure containing a semimetal oxide or metal oxide having a surface hydroxyl group. In the same or other embodiments, the reinforcing filler (b) contains precipitated silica.

[0015] In these and other embodiments, the methylene donor compound (d) can be selected from the group consisting of polyisocyanates, polyisocyanurates, epoxy resins, amino resins, and polyurethanes. In these and other embodiments, an amino resin is included, and 1,1,3,3 - tetramethoxymethylurea, 1,3,3 - tris - methoxymethylurea, 1,3 - bis - methoxymethylurea, 1,1 - bis - methoxymethylurea, 1,1,3,3 - tetra - ethoxymethylurea, 1,3,3 - tris - ethoxymethylurea, 1,3 - bis - ethoxymethylurea, 1,1 - bis - ethoxymethylurea, 1,1,3,3 - tetra - propoxymethylurea, 1,3,3 - tris - propoxymethylurea, 1,3 - bis - propoxymethylurea, 1,1 - bis - propoxymethylurea, 1,1,3,3 - tetra - butoxymethylurea, 1,1,3,3 - tetra - phenoxymethylurea, N-(1,3,3 - tris - ethoxymethylureidomethyl)-1,1,33 - tetra - ethoxymethylurea, N,N′ - bis-(1,1,3 - tris - ethoxymethylureidomethyl)-1,3 - bis - ethoxymethylurea, N,N′ - bis-(1,1,3 - tris - ethoxymethylureido - methoxymethyl)-1,3 - bis - ethoxymethylurea, N,N,N′,N′,N″,N″ - hexakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″,N″ - hexakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″,N″ - hexakis - propoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - propoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - propoxymethyl - [1,3,5] It may be selected from the group consisting of triazine-2,4,6-triamine, N,N,N′,N′,N″,N″-hexakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N′,N′,N″-pentakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine, and N,N,N′,N″-tetrakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine.,

[0016] In these and other embodiments, the phloroglucinol resin (e) has the formula (I):

Chemical formula

[0017] Furthermore, it can be seen that the solid phloroglucinol resin used in the rubber composition can be a reaction product of phloroglucinol and a ketone in the presence of an acid catalyst. The ketone can be selected from the group consisting of acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK).

[0018] In general, it can be seen that the sulfur donating compound (f) can be sulfur.

[0019] One or more other aspects of the present invention can be found in a method for preparing the above rubber composition.

[0020] Still other aspects of the present invention can be found in a cured rubber composition prepared from the above rubber composition. It can be seen that other aspects of the present invention can be obtained by articles such as components of a tire including this cured rubber composition.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Truck tires, and tires of other large vehicles, include a number of shrinkable bands of rubber and an expandable structure of composite material. For example, a layer above an inner liner consisting of thin woven fiber cords joined in rubber is called a carcass or casing. Carcass and casing are synonymous terms. Many tire carcasses are one or two body plies. A tire carcass can incorporate a fabric of steel, polyester, nylon or rayon cords into a carcass rubber compound. A belt system can be placed above (radially outward) the carcass portion in the tire building process. A tread slab or cap portion can be placed above (radially outward) the belt system and / or the carcass. The tread portion contacts the road and is formulated to enhance the performance characteristics and durability of the tire. Key important characteristics include handling, static friction, rolling resistance, and wear resistance.

[0022] In this specification and the claims, the following terms and expressions are to be understood as indicated.

[0023] Unless otherwise indicated in the Examples or elsewhere, all numbers expressing quantities of substances, reaction conditions, times, quantitatively determined properties of substances, etc., recited in this specification and the claims are to be understood as being modified in all instances by the term "about." Further, when a number in a table is provided in a claim, it will be understood that that number means "less than" when most or many of the other numbers in the same table for the same property, quantity, etc., are lower than the provided number. Conversely, when a number in a table is provided in a claim, it will be understood that that number means "greater than" when most or many of the other numbers in the same table for the same property, quantity, etc., are higher than the provided number.

[0024] All methods described in this specification may be performed in any suitable order, unless otherwise indicated herein or otherwise clearly precluded by the context, or unless specifically recited in the claims in a particular order. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to better illuminate the invention and does not impose a limitation on the scope of the invention unless otherwise recited in the claims.

[0025] No language in this specification should be construed as indicating that any non-recited element is essential to the practice of the invention.

[0026] The term "for instance" has the same meaning as "for example."

[0027] Any numerical range recited in this specification is to be understood to include all sub-ranges within that range and any combination of the various endpoints of such range or sub-ranges.

[0028] As used herein, integer values with subscripts in stoichiometry relate to molecular species, and non-integer values with subscripts in stoichiometry relate to mixtures of molecular species on a weight average basis, number average basis, or mole fraction basis.

[0029] In the following description, all weight percentages are based on the total weight percentage of organic substances unless otherwise stated, and all ranges given herein include all sub-ranges and all ranges and / or any combination of sub-ranges.

[0030] "Rubbery polymer", as used herein, is an organic polymer containing a backbone comprising at least two carbon-carbon double bonds and a chain of one or more carbon atoms, or a mixture thereof. In one embodiment of the present invention, the rubbery polymer can be at least one member selected from the group consisting of diene-based elastomers and rubbers. Rubber-like polymers are well known in the art and can be any of those described in numerous texts, two examples of which are incorporated herein by reference (, include The).

[0031] The term rubbery polymer does not exclude the possibility that a portion of the polymer can be temporarily or permanently in a partially or fully crystalline state. The terms used in this description are, to the extent possible, the same as those presented in Vanderbilt Rubber Handbook; R.F. Ohm, ed.; R.T. Vanderbilt Company, Inc., Norwalk, CT; 1990 and Manual For The Rubber Industry; T. Kempermann, S. Koch, J. Sumner, eds.; Bayer AG, Leverkusen, Germany; 1993.

[0032] The term primary network refers to a rubbery polymer network crosslinked by vulcanization with a crosslinking agent in a cure package.

[0033] The term interpenetrating network means the polymerization of rubber compound components within a compound without covalent interaction with the primary network.

[0034] Some representative non-limiting examples of suitable rubbery polymers that are rubber components of the composition include natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), various copolymers of butadiene, various copolymers of isoprene, solution styrene-butadiene rubber (SSBR), emulsion styrene-butadiene rubber (ESBR), ethylene-propylene terpolymer (EPDM), acrylonitrile-butadiene rubber (NBR), and combinations thereof. Natural rubber (NR) is understood to include rubbers from various natural plant sources including, but not limited to, rubber trees, dandelions, guayule rubber, and the like.

[0035] Suitable monomers for preparing the rubbery polymer in the present invention include conjugated dienes such as non-limiting examples of isoprene and 1,3-butadiene; suitable vinyl aromatic compounds such as non-limiting examples of styrene and alpha-methylstyrene; and combinations thereof. The rubbery polymer can be a sulfur-curable rubber. Dien-based elastomers or rubbers include at least one of cis-1,4-polyisoprene rubbers including natural rubber and synthetic polyisoprene rubber, more specifically natural rubber, styrene / butadiene copolymer rubber prepared by emulsion polymerization, styrene / butadiene rubber prepared by organic solution polymerization, 3,4-polyisoprene rubber, isoprene / butadiene rubber, styrene / isoprene / butadiene terpolymer rubber, cis-1,4-polybutadiene, medium vinyl polybutadiene rubber (35-50 percent vinyl), high vinyl polybutadiene rubber (50-75 percent vinyl), styrene / isoprene copolymer, styrene / butadiene / acrylonitrile terpolymer rubber prepared by emulsion polymerization, and butadiene / acrylonitrile copolymer rubber, and can be selected as such. Styrene / butadiene rubber (ESBR) derived by emulsion polymerization, for example, those having a relatively conventional styrene content of 20-28 percent bound styrene, or for some applications, ESBR having a medium to relatively high bound styrene content, i.e., a bound styrene content of 28-45 percent, is also considered a diene-based rubber used in the present invention. Styrene / butadiene / acrylonitrile terpolymer rubber prepared by emulsion polymerization containing 2-40 weight percent bound acrylonitrile in the terpolymer is also considered a diene-based rubber used in the present invention.

[0036] The rubbery polymer can also be a functionalized rubber. A functionalized rubber is a rubber modified by at least one functional group containing atoms other than carbon or hydrogen. The functional groups are typically alkoxysilyl groups, tin-containing groups, amino groups, hydroxyl groups, carboxylic acid groups, polysiloxane groups, epoxy groups, etc., or combinations of these functional groups. The functional groups can be introduced into the rubbery polymer during the preparation of the synthetic rubber by copolymerizing the monomers used to make the rubber with monomers, initiators, or end units containing the functional groups.

[0037] Alternatively, the rubber polymer can be modified with functional groups by grafting the functional groups onto an already formed rubbery polymer.

[0038] The functionalized rubbery polymer can be used in combination with other non-functionalized rubbery polymers. The mixture can contain at least about 5 to about 95 parts per hundred parts of rubber of at least one styrene-butadiene rubber functionalized with at least one group selected from phthalocyanino, tin-containing groups, hydroxyl, epoxy, carboxylate, amino, alkoxysilyl, and sulfido groups and having a styrene content of 0 to about 12 weight percent, and about 5 to about 95 parts per hundred parts of rubber of at least one additional rubbery polymer. The functionalized rubbery polymer (rubber) generally has a glass transition temperature (Tg) according to DSC of -120 to -10 °C in the unvulcanized state.

[0039] In another embodiment of the present invention, the rubbery polymer can be a diene polymer functionalized or modified with an alkoxysilane derivative. Styrene-butadiene rubber prepared by organosolution polymerization functionalized with silane and 1,4-polybutadiene rubber prepared by organosolution polymerization functionalized with silane can be used. These rubber compositions are known; see, for example, U.S. Patent No. 5,821,290, the entire contents of which are incorporated herein by reference.

[0040] In yet another embodiment of the present invention, the rubbery polymer is a diene polymer functionalized or modified with a tin derivative. A copolymer coupled with tin of styrene and butadiene can be prepared, for example, by introducing a tin coupling agent during the copolymerization reaction of styrene and 1,3-butadiene monomers in an organic solvent solution, usually at or near the end of the polymerization reaction. Such tin-coupled styrene-butadiene rubber is well known to those skilled in the art; see, for example, U.S. Patent No. 5,268,439, the entire contents of which are incorporated herein by reference. In fact, at least about 50 percent, preferably from about 60 to about 85 percent of the tin is bonded to the butadiene units of the styrene-butadiene rubber to form tin-dienyl bonds.

[0041] The properties of natural rubber (NR) are particularly useful in the manufacture of tires for large vehicles, bus tires, and truck tires. One important reason for this is due to the combination of the high cis-1,4-polyisoprene content of natural rubber, its large molecular weight, and its ability to undergo strain-induced crystallization. In one embodiment of the present invention, the rubbery polymer comprises natural rubber, or a mixture of natural rubber and synthetic rubber. Preferably, when the rubbery polymer is a mixture of rubbers, the formulation of the rubber must contain at least about 10 weight percent natural rubber, preferably about 30 weight percent natural rubber, more preferably at least about 50 weight percent natural rubber, and even more preferably at least about 70 weight percent natural rubber.

[0042] The uncured rubber composition preferably contains a reinforcing filler. The reinforcing filler should be a material having a modulus higher than that of the rubbery polymer of the rubber composition and should be able to absorb stress when the cured rubber composition is stretched. The reinforcing filler can be a material reactive with an organosilane coupling agent and can include fibers, fine particles, and sheet-like structures. They can consist of inorganic minerals, silicates, silica, clay, ceramics, and diatomaceous earth. The reinforcing filler reactive with the organosilane coupling agent can be in the form of separate particles or aggregates or agglomerates of particles. The organosilane coupling agent can be reactive with the surface of the filler. The precipitated silica of fine particles can be useful as a reinforcing filler reactive with the organosilane coupling agent, especially when the silica has a reactive surface silanol. The silica can be provided in a hydrated form or can be converted to a hydrated form by reaction with water. The reinforcing filler can be used in an amount of 1 to 150 parts of the reinforcing filler per 100 parts of the rubbery polymer, more specifically 25 to 90 parts of the reinforcing filler per 100 parts of the rubbery polymer, more specifically 40 to 80 parts of the reinforcing filler per 100 parts of the rubbery polymer.

[0043] Representative non-limiting examples of the reinforcing filler reactive with the organosilane coupling agent include at least one semi-metal oxide or metal oxide, such as calcined silica, precipitated silica, titanium dioxide, aluminosilicate, alumina, and siliceous materials including clay and talc, and combinations thereof.

[0044] In one or more embodiments of the present invention, the reinforcing filler can be silica used alone or in combination with one or more other fillers, such as organic and / or inorganic fillers that do not react with an organosilane coupling agent. Representative non-limiting examples are combinations of silica and carbon black for use as reinforcing fillers for various rubber products, including non-limiting examples of treads for tires. Alumina can be used alone or in combination with silica. As used herein, the term "alumina" means aluminum oxide or Al2O3. The use of alumina in rubber compositions is known; see, for example, U.S. Patent No. 5,116,886 and European Patent No. 631,982, both of which are incorporated herein by reference in their entirety.

[0045] The reinforcing filler reactive with the organosilane coupling agent can be used as a carrier for the organosilane coupling agent. Other fillers that can be used as carriers are non-reactive with the organosilane coupling agent. The non-reactivity of the filler is indicated by the ability of more than 50 percent of the loaded silane of the organosilane coupling agent to be extracted using an organic solvent. The extraction procedure is described in U.S. Patent No. 6,005,027, which is incorporated herein by reference in its entirety. Representative examples of non-reactive carriers include, but are not limited to, porous organic polymers and carbon black. The amount of organosilane coupling agent that can be loaded onto the carrier is preferably from 0.1 to 70 percent, more preferably from 10 to 50 percent, based on the total weight of the carrier and the organosilane coupling agent.

[0046] In one non-limiting embodiment of the present invention, other fillers that can be mixed with an organosilane coupling agent and a reactive reinforcing filler can be essentially inert to the organosilane coupling agent that is mixed in the same manner as in the case of carbon black or an organic polymer. In another embodiment, at least two reactive reinforcing fillers with an organosilane coupling agent can be mixed together and can be reactive therewith. Reinforcing fillers having a hydroxyl surface functionality of a semimetal, such as silica having a surface silanol functionality and other siliceous fine particles, can be used in combination with reinforcing fillers containing a metal hydroxyl surface functionality, such as alumina and other siliceous fillers.

[0047] In one embodiment of the present invention, precipitated silica is utilized as a reactive reinforcing filler with an organosilane coupling agent. In a preferred embodiment of the present invention, the silica filler can be characterized by having a Brunauer, Emmett, and Teller (BET) surface area in the range of about 40 to about 600 m2 / g, preferably in the range of about 50 to about 300 m2 / g, more preferably in the range of about 100 to about 220 m2 / g, as measured using nitrogen gas. The BET method for measuring the surface area described in Journal of the American Chemical Society, Volume 60, page 304 (1930) is the method used in the present invention. In yet another preferred embodiment, the silica is typically characterized by having a dibutyl phthalate (DBP) absorption value in the range of about 100 to about 350, preferably in the range of about 150 to about 300, more preferably in the range of about 200 to about 250. In other embodiments, the reactive reinforcing filler with an organosilane coupling agent can be alumina and aluminosilicate fillers and can have a CTAB surface area in the range of about 80 to about 220 m2 / g. The CTAB surface area is the external surface area determined by cetyltrimethylammonium bromide at a pH of about 9; the measurement method is described in ASTM D 3849.

[0048] The mercury porosity surface area is the specific surface area determined by mercury porosimetry. In this technique, mercury penetrates the pores of the sample after heat treatment to remove volatile substances. In a more specific embodiment, a 100 milligram sample is used under set conditions, the volatile substances are removed at 105 °C and ambient atmospheric pressure for 2 hours, and a measurement range from ambient to a pressure of 2000 bar is used. Such an evaluation can be carried out according to the method described by Winslow et al. in ASTM bulletin, page 39 (1959), or according to DIN 66133; for such an evaluation, a CARLO-ERBA Porosimeter 2000 can be used. Useful reinforcing fillers reactive with organosilanes include silicas having an average mercury porosity specific surface area in the range of about 100 to about 300 m2 / g, preferably about 150 to about 275 m2 / g, more preferably about 200 to about 250 m2 / g.

[0049] A suitable pore size distribution for reinforcing fillers reactive with organosilane coupling agents, including non-limiting examples of silica, alumina, and aluminosilicates, in accordance with such mercury porosity evaluation, in the present invention, pores having a diameter of less than 10 nm are 5 percent or less; pores having a diameter of 10 to 100 nm are about 60 to about 90 percent; pores having a diameter of 100 to 1,000 nm are about 10 to about 30 percent; and pores having a diameter greater than 1,000 nm are about 5 to about 20 percent. These reinforcing fillers can generally be expected to have an average final particle size in the range of about 0.005 to about 0.075 mm, preferably about 0.01 to about 0.05 mm, as determined by electron microscopy, although the particles can have a smaller or larger average diameter. Various commercially available silicas, such as those available under the trademark HI-SIL from PPG Industries, particularly HI-SIL 210 and 243; silicas available from Solvay, such as ZEOSIL 1165MP; silicas available from Evonik, such as VN2 and VN3, etc., and silicas available from Huber, such as HUBERSIL 8745 can be used in the present invention.

[0050] In one embodiment of the present invention, the filler can comprise a reactive reinforcing filler with an organosilane coupling agent in an amount of about 15 to about 95 weight percent of precipitated silica, alumina and / or aluminosilicate, preferably silica and correspondingly about 5 to about 85 weight percent of carbon black having a CTAB value in the range of about 80 to about 150. More preferably, the filler can comprise about 60 to about 95 weight percent of said silica, alumina and / or aluminosilicate, preferably silica and correspondingly about 40 to about 50 weight percent of carbon black. The precipitated silica, alumina and / or aluminosilicate filler and carbon black can be pre-blended or blended together during the manufacture of the vulcanized rubber. When used, the carbon black can be added in an amount in the range of 0.5 part to 10 parts of carbon black per 100 parts of the rubbery polymer.

[0051] The tire tread portion is customarily compounded with carbon black filler. Carbon black provides exceptional wear resistance to the tread portion, which leads to a high tread life, long-lasting tires. When silica is used as a filler, the dispersion of silica throughout the rubber matrix can reverse due to the high friction silica-silica and rubber-silica interactions. This friction can interfere with the properties of the tire, such as rolling resistance. Adding conventional silanes to the tire formulation can limit the internal friction of silica-silica interactions and reduce rolling resistance by immobilizing the polymer chains on the silica surface. However, without wishing to be bound by theory, it is thought that the sulfur-mediated bonding of silanes to rubber chains can increase the trans content of natural rubber, as discussed in J.I. Cuneen, Rubber Chemistry and Technology, Vol. 33, p. 445, 1960; and J.I. Cuneen and F.W. Shipley, Journal of Polymer Science, Vol. 36, p. 77, 1959. This would likely have an adverse effect on performance characteristics such as wear resistance. Also, severely restricting the chain mobility would affect the ability of natural rubber to undergo strain-induced crystallization, potentially compromising wear resistance and tear resistance.

[0052] Conventional silanes react directly with the polymer chains, deteriorating the critical properties of the primary rubber network. Standard amino resin-resorcinol systems can reinforce the primary polymer network with an interpenetrating network, but can irreversibly distort with a significant degradation of important properties. Without wishing to be bound by theory, it is believed that organosilanes react with HMMM and phloroglucinol resins to create an interpenetrating network that reinforces the transfer of load from one filler to another and reduces the friction between filler aggregates. The concentration of thermoset interpenetrating networks at the filler interface attracts thermoset resins with minimal strain.

[0053] The rolling resistance can be reduced by hydrophobating the silica. Increasing the effective filler volume promotes wear resistance and tear resistance. Further, the secondary polymer network can increase the reinforcement and stiffness under static and dynamic deformation of the resulting tread.

[0054] The polymerization of this load-bearing-path reinforcing interpenetrating network is thought to grow from the surface of the reinforcing filler reacted with an organosilane coupling agent, particularly the silica surface. These organosilane coupling agents can function as initiators or co-initiators during the rubber mixing and / or curing process. The resulting reinforcing interpenetrating network can create additional points of physical and chemical chain entanglement with respect to the rubber phase within the immediate vicinity of the filler. These entanglements, together with the resulting interpenetrating polymer network and silica, create a hierarchical structure whose modulus gradient is useful for load transfer from the rubbery polymer chains to the silica during static and dynamic deformation, thereby enhancing tear and wear resistance and reducing abrasion. The polymerization of the interpenetrating polymer network from the filler surface can create a network structure on the filler surface and increase the effective filler volume. This network structure and effective filler volume result in further reinforcement and also contribute to improved wear resistance.

[0055] Without being bound by theory, such polymer networks are believed to be formed from reinforcing interpenetrating polymer network methylene donor compounds and phloroglucinol resins. As will be understood by those skilled in the art, the interpenetrating network can also be referred to as a secondary network. Without being bound by theory, a secondary network means two separate polymer networks that are indistinguishable at the macroscale. The phloroglucinol resin forming the load-bearing-path reinforcing interpenetrating network includes, but is not limited to, phloroglucinol bonded by disubstituted methylene bonds.

[0056] In one embodiment of the present invention, the methylene donor compound is an amino resin. The amino resin can be a resin formed from the reaction of a compound containing -NH, formaldehyde, and alcohol. More preferably, the amino resin is derived from 2,4,6-triamino-1,3,5-triazine, benzoguanamine, urea, glycoluril, and poly(meth)acrylamide.

[0057] The methylene donor compound can be used in an amount of 0.1 to 30 parts, more specifically 0.2 to 15 parts, and even more specifically 0.3 to 10 parts of the methylene donor compound per 100 parts of the rubbery polymer.

[0058] Representative and non-limiting examples of methylene donor compounds are 1,1,3,3-tetra-methoxymethylurea, 1,3,3-tris-methoxymethylurea, 1,3-bis-methoxymethylurea, 1,1-bis-methoxymethylurea, 1,1,3,3-tetra-ethoxymethylurea, 1,3,3-tris-ethoxymethylurea, 1,3-bis-ethoxymethylurea, 1,1-bis-ethoxymethylurea, 1,1,3,3-tetra-propoxymethylurea, 1,3,3-tris-propoxymethylurea, 1,3-bis-propoxymethylurea, 1,1-bis-propoxymethylurea, 1,1,3,3-tetra-butoxymethylurea, 1,1,3,3-tetra-phenoxymethylurea, N-(1,3,3-tris-ethoxymethylureidomethyl)-1,1,3,3-tetra-ethoxymethylurea, N,N'-bis-(1,1,3-tris-ethoxymethylureidomethyl)-1,3-bis-ethoxymethylurea, N,N'-bis-(1,1,3-tris-ethoxymethylureido-methoxymethyl)-1,3-bis-ethoxymethylurea, N,N,N',N',N",N"-hexakis-methoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N"-pentakis-methoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N"-tetrakis-methoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N",N"-hexakis-ethoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N"-pentakis-ethoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N"-tetrakis-ethoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N",N"-hexakis-propoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N"-pentakis-propoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N"-tetrakis-propoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N",N"-hexakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N',N',N”-Pentakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine, N,N,N’,N”-tetrakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine, 1,3,4,6-tetrakis-methoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,3,4,6-tetrakis-ethoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,3,4,6-tetrakis-propoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,3,4,6-tetrakis-phenoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,3,4-tris-ethoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,4-bis-ethoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione, 1,3,4-tris-methoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione and 1,3,4-tris-phenoxymethyl-tetrahydro-imidazo[4,5-d]imidazole-2,5-dione.,

[0059] The methylene donor compound can be obtained commercially. For example, the amino resin can be commercially purchased under the trade names PERFERE, formerly INEOS Melamine GmbH, RESIMENE® 747 ULF, RESIMENE® 755, RESIMENE® 757, RESIMENE® 764, RESIMENE® CE 8824 ULF and MAPRENAL® UF 134 / 60B.,

[0060] In one example, the organosilane coupling agent has the general formula (Ia): (R 2 O)a(R 3 )3 -a Si(R 4 XH) In the formula, each R2 is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, which may optionally have at least one oxygen atom, a cycloalkyl group having 3 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably ethyl; each R3 is independently an alkyl group having 1 to 3 carbon atoms or phenyl; R4 is an alkylene group having 1 to 10 carbon atoms, which may optionally have at least one oxygen atom, a cycloalkylene group having 3 to 10 carbon atoms, an alkenylene group having 2 to 10 carbon atoms, an arylene group having 6 to 12 carbon atoms, or an aralkylene group having 7 to 14 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably propylene; X is one or more, preferably 2 to 10, and even more preferably on average 2 to 4 sulfur atoms.

[0061] Representative non-limiting examples of the silane containing the functional group of formula (Ia) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropyldimethoxyethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyldimethylethoxysilane, mercaptomethyltriethoxysilane, 4-mercapto-3,3-dimethylbutyltriethoxysilane, 3-mercaptopropylethoxy-[1,3,2]dioxasilinane, 3-mercapto-propyl-(3-hydroxy-2-methylpropoxy)-5-methyl-[1,3,2]dioxasilinane, 6-mercaptohexyltriethoxysilane, 3-aminopropyltriethoxysilane, N-ethyl-3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltriethoxysilane, N-ethyl-3,3-dimethyl-4-aminobutyltriethoxysilane, n-phenyl-3-aminopropyltriethoxysilane, 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, and mixtures thereof.

[0062] The silane coupling agent of formula (Ia) can be used in an amount of 0.05 to 30 parts, more specifically 0.5 to 15 parts, and even more specifically 1 to 10 parts of the mercaptosilane coupling agent per 100 parts of the rubbery polymer.

[0063] The organosilane of formula (Ia) is commercially available. For example, the mercaptosilane coupling agent can be commercially purchased from Momentive Performance Materials, Inc. under the trade names Si263, Usi-5301, Silquest A-189, Z-6062, KBM-803. MTMO, GENIOSIL® GF 70 and S 810.

[0064] In another example, the organosilane coupling agent is a silane having the general formula (Ib): (R 2 O) a R 3 3-a Si(R 4 )X 1 R 4 Si(R 3 3-a (R 2 O) a ) In the formula, each R2 is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, which may optionally have at least one oxygen atom, a cycloalkyl group having 3 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably ethyl; each R3 is independently an alkyl group having 1 to 3 carbon atoms or phenyl; R4 is an alkylene group having 1 to 10 carbon atoms, which may optionally have at least one oxygen atom, a cycloalkylene group having 3 to 10 carbon atoms, an alkenylene group having 2 to 10 carbon atoms, an arylene group having 6 to 12 carbon atoms, an aralkylene group having 7 to 14 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably propylene; X is one or more, preferably 2 to 10, and even more preferably on average 2 to 4 sulfur atoms.

[0065] Representative non-limiting examples of the silane containing the functional group of formula (Ib) are bis(tripropoxysilylpropyl)tetrasulfide; bis(triethoxysilylpropyl)tetrasulfide; bis(trimethoxysilylethyl)tetrasulfide; bis(trimethoxymethyl)tetrasulfide; bis(tripropoxysilylpropyl)disulfane; bis(triethoxysilylethyl)tetrasulfide; bis(triethoxysilylmethyl)tetrasulfide; bis(3-triethoxysilylpropyl)disulfane; bis[3-(triethoxysilyl)propyl]-disulfide; bis[3-(triethoxysilyl)propyl]persulfide; 3,3'-bis-(triethoxysilylpropyl)disulfide; bis[3-(triethoxysilyl)propyl]perdisulfide; bis(triethoxysilyl)-4,5-dithiooctane; bis(tripropoxysilylpropyl)disulfide; bis(triethoxysilylpropyl)disulfide; bis(trimethoxysilylethyl)disulfide; bis(triethoxysilylethyl)disulfide; bis(triethoxysilylmethyl)disulfide.

[0066] The silane coupling agent of formula (Ib) can be used in an amount of 0.05 to 30 parts, more specifically 0.5 to 15 parts, and even more specifically 1 to 10 parts of the organosilane coupling agent per 100 parts of the rubbery polymer.

[0067] The organosilane of formula (Ib) in which X1 represents four sulfur atoms on average can be obtained commercially. For example, the Si69 coupling agent can be purchased commercially from Evonik. Crosile 69 TESPT can be purchased from Guangzhou Ecopower. Z6940 can be purchased from Owen Corning Corporation. A-1289 can be purchased from Momentive Performance Materials, Inc. KBE-846 can be purchased from Shin-Etsu Co. Also, the organosilane of formula (Ib) can be purchased under the trade names Si 75, HP 1589, JH-S75, and TESPD when X1 represents two sulfur atoms on average.

[0068] In another embodiment, the organosilane covalently bonds to a hydrogen-containing compound.

[0069] The rubber composition of the present invention may further contain a phloroglucinol resin. The phloroglucinol resin can be solid under standard conditions. The solid phloroglucinol resin generally has the formula (II):

Chemical formula

[0070] Generally, the disubstituted methylene bridge is bonded to at least two C1-C10 alkyl groups extending from the methylene bridge. In another embodiment, the methylene bridge includes at least two C1-C5 alkyl groups extending therefrom. In yet another embodiment, the methylene bridge includes at least two C1-C4 alkyl groups extending therefrom. In still another embodiment, the methylene bridge includes at least two C1-C3 alkyl groups extending therefrom. In a further embodiment, the methylene bridge includes at least two C1-C2 alkyl groups extending therefrom.)

[0071] More specifically, the phloroglucinol resin of the present invention can be described as shown in formula (III). [Chemical formula] In the formula, R1 of the left - hand phloroglucinol unit is replaced by a disubstituted methylene bridge shown at the 2 - position, and R3 of the right - hand phloroglucinol unit is replaced at the 5 - position. R3 on the left - hand side and R1 on the right - hand side can also be the same disubstituted methylene bridge as shown in this specification, or can be hydrogen atoms, and R2 can be the hydrogen atom shown in this embodiment. R4 and R5 can be the same or different and are alkyl groups. In one embodiment, both R4 and R5 can be methyl groups, and the disubstituted methylene bridge formed there is an isopropylidene bridge. In another embodiment, R4 can be an ethyl group and R5 can be a methyl group, and the disubstituted methylene bridge formed there is a 2,2 - disubstituted butane bridge. In yet another embodiment, R4 can be an isopropyl group and R5 can be a methyl group, and the disubstituted methylene bridge formed there is a 2,2 - disubstituted 4 - methylpentane bridge.

[0072] The resin has a distribution of dimers, trimers, tetramers, pentamers and higher multimers, and less than 40% of the monomers can function with the resin. The phloroglucinol resin can be used in an amount of 0.1 - 15 parts, more specifically 0.5 - 10 parts, and even more specifically 1 - 5 parts of the phloroglucinol resin per 100 parts of the rubbery polymer.

[0073] Sulfur - donating compounds can also be incorporated into the rubber composition. The sulfur - donating compounds can be used to cross - link the rubbery polymer to form a cross - linked primary network. Without wishing to be bound by theory, the sulfur - donating compounds are thought to donate sulfur atoms under curing conditions. Sulfur - donating compounds generally have more than two sulfur atoms that bond to each other to form a chain of sulfur atoms. Polysulfides and elemental sulfur, preferably sulfur S8, are sulfur - donating compounds.

[0074] Vulcanization can be carried out in the presence of a sulfur - donating compound, which is often referred to as a vulcanizing agent. This reacts with a rubbery polymer containing carbon - carbon double bonds to form a cross - linked or cured rubber. Some non - limiting examples of suitable sulfur vulcanizing agents include, for example, elemental sulfur (free sulfur) or sulfur - donating compounds such as, by way of non - limiting example, aminodisulfides, polymeric polysulfides or sulfur - olefin adducts. These, along with other known and customary vulcanizing agents, are added in normal amounts during a mixing step, which is called a productive mixing step, in the method for preparing the rubber composition.

[0075] Sulfur - donating compounds are generally used in amounts of about 0.1 to about 5 phr, more preferably about 1 to about 3 phr, and even more preferably about 1.5 to about 2.5 phr.

[0076] The rubber composition can be compounded with other commonly used additive substances such as retarders and accelerators, process additives such as oils, resins such as tackifying resins, plasticizers, pigments, fatty acids, zinc oxide, waxes, antioxidants and antiozonants, mastication accelerators, etc. Depending on the intended use of the rubber composition, these and / or other rubber additives are used in conventional amounts.

[0077] If desired, a vulcanization accelerator can also be used. Non-limiting examples of vulcanization accelerators include benzothiazole, alkylthiuram disulfide, guanidine derivatives, and thiocarbamate. Other examples of such accelerators include, but are not limited to, mercaptobenzothiazole, tetramethylthiuram disulfide, tetrabenzylthiuram disulfide, benzothiazole disulfide, diphenylguanidine, zinc dithiocarbamate, alkylphenol disulfide, zinc butylxanthate, N-dicyclohexyl-2-benzothiazole sulfenamide, N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene benzothiazole-2-sulfenamide, N,N-diphenylthiourea, dithiocarbamyl sulfenamide, N,N-diisopropylbenzothiazole-2-sulfenamide, zinc-2-mercaptotolimidazole, dithiobis(N-methylpiperazine), dithiobis(N-beta-hydroxyethylpiperazine), and dithiobis(dibenzylamine). In another embodiment, other additional sulfur donors include, for example, thiuram and morpholine derivatives. In a more specific embodiment, representative examples of such donors include, but are not limited to, dimorpholine disulfide, dimorpholine tetrasulfide, tetramethylthiuram tetrasulfide, benzothiazyl-2,N-dithiomorpholide, thioplast, dipentamethylene thiuram hexasulfide, and disulfide caprolactam.

[0078] Accelerators can be used to control the time and / or temperature required for vulcanization and improve the properties of the vulcanizate. In one embodiment of the present invention, a single accelerator system, i.e., a primary accelerator, can be used. In another embodiment, conventionally and preferably, the primary accelerator is used in a total amount in the range of about 0.5 to about 4 phr, preferably about 0.8 to about 2.0 phr. In a preferred embodiment, a combination of a primary and a secondary accelerator can be used, and the secondary accelerator is used in a smaller amount, for example, about 0.05 to about 3 phr, to activate and improve the properties of the vulcanizate. In yet another embodiment, a delayed action accelerator can also be used. In still another embodiment, a vulcanization retarder can also be used. Suitable types of accelerators are, for example, amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, xanthates, and combinations thereof. In a preferred embodiment, the primary accelerator is a sulfenamide. In another embodiment, if a second accelerator is used, the secondary accelerator can be a guanidine, a dithiocarbamate, or a thiuram compound such as tetrabenzylthiuram disulfide used at a level of, for example, about 0.1 to about 0.3 phr, more preferably about 0.2 phr.

[0079] Optional tackifying resins can be used at levels of about 0.5 to about 10 phr, preferably about 1 to about 5 phr. In a preferred embodiment, the amount of processing aid ranges from about 1 to about 50 phr. Suitable processing aids include, by way of non-limiting example, aromatic, naphthenic, and / or paraffinic processing oils and combinations thereof. In yet another embodiment, the preferred amount of antioxidant is about 1 to about 5 phr. Representative antioxidants include, by way of non-limiting example, diphenyl-p-phenylenediamine and others, such as those disclosed in Vanderbilt Rubber Handbook (1978), pages 344 - 346, which is incorporated herein by reference. In yet another embodiment, the preferred amount of antiozonant ranges from about 1 to about 5 phr. The preferred amount of optional fatty acids, which can include stearic acid by way of non-limiting example, ranges from about 0.5 to about 3 phr.

[0080] The preferred amount of zinc oxide ranges from about 2 to about 5 phr. The preferred amount of wax, such as microcrystalline wax, ranges from about 1 to about 5 phr. The preferred amount of peptizer ranges from about 0.1 to about 1 phr. Suitable peptizers include, by way of non-limiting example, pentachlorothiophenol, dibenzamidodiphenyldisulfide, and combinations thereof.

[0081] In one embodiment of the present invention, the rubber composition contains a phloroglucinol resin, and the rubber composition preferably comprises (a) at least one rubbery polymer used to form a primary network, (b) at least one reinforcing filler capable of reacting with an organosilane coupling agent; (c) a methylene donor compound forming at least one load-resistant path reinforcing interpenetrating network; (d) at least one organosilane coupling agent capable of reacting with the reinforcing filler, (e) at least a phloroglucinol resin and (f) at least one sulfur donating compound, in particular sulfur (S8) or at least one sulfur donating compound, in particular sulfur (S8). The rubbery polymer may contain one or more rubber components, and the total of the rubber components is about 100 phr (parts per hundred parts of rubber). In one embodiment of the present invention, natural rubber should be about 50 to 100 phr, preferably about 75 to 100 phr of the primary polymer blend portion of the rubber composition. The reinforcing filler may comprise from about 1 to about 150 phr, preferably from about 15 to 90 phr, more preferably from about 20 to 55 phr of the rubber composition. In one embodiment of the present invention, the reinforcing filler is silica, preferably precipitated silica. The organosilane coupling agent itself and / or the material for forming the load-resistant path reinforcing interpenetrating network (the methylene donor forming the network and the phloroglucinol resin) can comprise about 6 to 50%, preferably about 8 to 25% of the weight of the reinforcing filler in the formulation, more preferably about 12 to 25% of the weight of the reinforcing filler in the formulation.

[0082] Thus, in one or more embodiments, the rubber composition comprises: (a) a rubbery polymer or blend of polymers; (b) at least one organosilane coupling agent; (c) at least one reinforcing filler reactive with the organosilane coupling agent; (d) at least one methylene donor resin; (e) at least one phloroglucinol resin; and (f) optionally, at least one sulfur donating compound including.

[0083] In another embodiment, the rubber composition comprises a rubbery component in an amount of about 25 to about 95 weight percent based on the total weight of the rubber composition, a reinforcing filler reactive with an organosilane coupling agent in an amount of about 2 to about 70 weight percent based on the total weight of the rubber composition, a methylene donor resin in an amount of about 0.2 to about 25 weight percent based on the total weight of the rubber composition, a phloroglucinol resin in an amount of about 0.2 to about 25 weight percent based on the total weight of the rubber composition, and a sulfur donating compound in an amount of about 0.2 to about 5 weight percent based on the total.

[0084] In the cured rubber composition, the primary polymeric network is formed by curing and crosslinking a rubber polymer or a polymer blend by raising the temperature of the rubber composition for a time sufficient to react a rubber polymer or a rubber polymer blend (a) with at least one sulfur donating compound.

[0085] In another embodiment of the present invention, a method for providing the rubber composition described herein includes mixing an effective amount of at least one reinforcing filler, at least one methylene donor resin, at least one organosilane coupling agent, at least one phloroglucinol resin, and optionally at least one sulfur donating compound with a rubbery component such as natural rubber. In one embodiment of the method according to the present invention, the effective amount of the organosilane coupling agent can range from about 0.2 to about 20, preferably from about 0.5 to about 15, more preferably from about 2 to about 10 weight percent based on the total weight of the rubber composition. The effective amount of the rubbery component can range from about 25 to about 95, preferably from about 50 to about 90, more preferably from about 60 to about 80 weight percent based on the total weight of the rubber composition. The effective amount of the reactive reinforcing filler and the organosilane coupling agent can range from about 2 to about 70, preferably from about 5 to about 55, more preferably from about 20 to about 50 weight percent based on the total weight of the rubber composition. The effective amount of the organic resin can range from about 0.2 to about 25 weight percent, preferably from about 2 to about 15 weight percent, more preferably from about 5 to about 10 weight percent based on the total weight of the rubber composition. The effective amount of the compound (e) containing active hydrogen can range from about 0.2 to about 25 weight percent, preferably from about 2 to about 15 weight percent, more preferably from about 5 to about 10 weight percent based on the total weight of the rubber composition. The effective amount of the sulfur donating compound can range from about 0.2 to about 5, preferably from about 0.5 to about 2.5, more preferably from about 1 to about 2 weight percent based on the total weight of the rubber composition.

[0086] In yet another embodiment of the present invention, the method for preparing the rubber composition can optionally include curing the rubber composition before, during, and / or after shaping of the rubber composition. The vulcanized rubber composition should contain a sufficient amount of load-bearing path reinforcing interpenetrating networks to contribute to a higher modulus and better wear.

[0087] In one embodiment of the present invention, the organosilane coupling agent is separately added to a process mixture containing a rubbery polymer component. It can be considered that the reinforcing filler and the organosilane coupling agent couple or react in situ to form a reinforcing filler in which the organosilane coupling agent is chemically bonded to the filler.

[0088] In one embodiment of the present invention, the method for preparing a rubber composition includes a number of steps. In non-productive step (i), a rubbery component, a reinforcing filler, a methylene donor resin, and an organosilane are mixed under reactive-mechanical-working conditions. As used herein, the expression "reactive-mechanical-working conditions" should be understood to mean the conditions of high temperature, residence time, and shear within a machining device such as an extruder, a kneading mixer, or a tangential mixer, and such conditions are sufficient to cause one or more of the following.

[0089] The reaction step of hydrolysis of the organosilane coupling agent by water present on the reinforcing filler can form alkoxymethylamino-functional silanols. The reaction step of these silanols with the reinforcing filler can form a covalent chemical bond with the filler. There can be decomposition into smaller aggregates and / or individual filler particles of the agglomerates of the reinforcing filler. When the reinforcing filler is dispersed in the rubbery polymer, it can covalently bond to the alkoxymethylamino-functional silane condensed after hydrolysis.

[0090] In non-productive step (ii), a methylene donor and a phloroglucinol resin are added to the mixture of step (i). In non-productive step (ii), all components (excluding the sulfur donating compound in this embodiment) are mixed under reactive machining conditions, where the conditions are high temperature, residence time, and shear within a machining device such as an extruder, an intermeshing mixer, or a tangential mixer, and such conditions are sufficient to cause one or more of the following. Namely, dispersion of the rubbery polymer, the reinforcing filler covalently bonded to the hydrolyzed and then condensed organosilane coupling agent of step (i), into the mixture of the methylene donor and the phloroglucinol resin; and / or reaction of the reinforcing filler covalently bonded to the hydrolyzed and then condensed organosilane coupling agent with the methylene donor and the phloroglucinol resin; and / or optionally, reaction of the methylene donor and the phloroglucinol resin to form a load-resistant path-reinforcing interpenetrating network dispersed within the primary network, providing an uncured rubber composition.

[0091] If either the methylene donor or the phloroglucinol resin is not added in step (ii), the missing component can be added in a second non-productive mixing step (ii).

[0092] In productive step (iii), a sulfur donating compound (f) is added to the mixture of step (ii).

[0093] In any of steps (i), (ii), or (iii), other components can be added to the rubber composition. Representative non-limiting examples of other components include activators, processing aids, accelerators, waxes, oils, antiozonants, and antioxidants.

[0094] The rubber composition is typically mixed in a mixing device under high shear conditions, where it heats up spontaneously as a result of the shear occurring mainly within the rubber mixture and the associated friction.

[0095] In a preferred embodiment of the present invention, the mixture of the desired amounts of the rubbery polymer, reinforcing filler, methylene donor, and organosilane coupling agent in step (i) is substantially uniformly blended under reactive machining conditions in a mixing step (i) that is carried out continuously or discontinuously. Discontinuous mixing can be used if excessive heating occurs and it becomes necessary to cool the rubber composition. Cooling of the rubber avoids or minimizes thermal decomposition of the rubbery polymer component or other components in the rubber composition. Preferably, the mixing step (i) is carried out at a temperature of 100°C to 200°C, more preferably 140°C to 180°C.

[0096] In step (iii), at least one sulfur donating compound (f) can be mixed with the rubber composition from step (ii) together with other vulcanization accelerators. The mixing should be carried out under non-reactive machining conditions. As used herein, the expression "non-reactive machining" conditions are to be understood to mean conditions of temperature, residence time, and shear within, at, or slightly above ambient temperature within a machining device such as an extruder, intermeshing mixer, tangential mixer, or roll mill, and such conditions are sufficient to cause dispersion of the sulfur donating compound, such as a vulcanizing agent, and the vulcanization accelerator into the rubber composition of step (ii) without causing significant vulcanization of the rubber composition. It is advantageous to use low temperature and low shear in step (iii).

[0097] In step (iii), the residence time can vary quite a bit and is generally chosen such that the dispersion of the vulcanizing agent is complete. The residence time can in most cases range from 0.5 to 30 minutes, preferably 5 to 20 minutes.

[0098] The temperature used in step (iii) can range from 5°C to 150°C, preferably 30°C to 120°C, more preferably 50°C to 110°C. These temperatures are lower than the temperatures utilized under reactive machining conditions in order to prevent or suppress premature curing of the sulfur-curable rubber, sometimes referred to as scorch of the rubber composition, which may occur at higher temperatures.

[0099] The rubber composition can be cooled to a temperature of 50°C or lower, for example, during or after step (iii), or between step (i) and step (ii) or between step (ii) and step (iii).

[0100] In another alternative embodiment of the present invention, when it is desired to mold and cure the rubber composition, the rubber composition is placed in a desired mold and heated at least about 130°C to about 200°C or lower for 1 to 60 minutes to cause vulcanization of the rubber.

[0101] A rubber composition preferred for forming a tire tread portion according to a preferred embodiment of the present invention comprises (a) a rubbery primary polymer or blend of polymers, (b) reinforcing silica filler particles, (c) a methylene donor capable of forming a load-resistant path-reinforcing interpenetrating network that can be generated in situ, (d) an organosilane coupling agent capable of reacting with the reinforcing filler, and / or (e) a compound containing active hydrogen, i.e., at least one phloroglucinol resin, wherein components (b), (c), (d), and (e) contribute to the aforementioned load-resistant path-reinforcing interpenetrating network.

[0102] The rubber composition of the present invention can be used for various purposes. In one embodiment of the present invention, an article is provided in which at least one element is the cured rubber composition described herein. In another embodiment of the present invention, a tire is provided in which at least one element, such as a tread, is the cured rubber composition described herein.

[0103] In yet another preferred embodiment, for example, the rubber composition can be used in the manufacture of articles such as shoe soles, hoses, seals, cable jackets, gaskets, and other industrial products. Such articles can be made, shaped, molded, and cured by various known and conventional methods that are obvious to those skilled in the art. In particular, the compositions and methods according to the present invention are particularly well-suited for the manufacture of tires, especially truck or bus tires.

Examples

[0104] To illustrate the implementation of the present invention, the following examples were prepared and tested. However, the examples should not be considered as limiting the scope of the present invention. The claims define the present invention. The abbreviation PG means "phloroglucinol".

[0105] PG resin Example 1. 440.0 g of phloroglucinol, 628.7 g of acetone and 349.3 g of an acid cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were charged into a flask and heated to 70°C. The reaction mixture was maintained at about 70°C for 24 hours. Then, 0.4 g of a 25% sodium hydroxide solution was added. Next, the solvent was removed by vacuum distillation to 155°C. When the temperature reached 155°C, the vacuum was released and the resin was discharged from the flask.

[0106] Table 1 lists the components used to prepare rubber compositions using natural rubber. The compositions contain silica coupled with bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) or a mercaptosilane coupling agent, a methylene donor compound, and resorcinol or a resorcinol resin as a control. The compositions contain a mercaptosilane coupling agent, a methylene donor compound, and a synthesized phloroglucinol resin. "Non-productive" combinations refer to combinations of materials that do not cure, and "productive" combinations are used to result in a cured composition. To illustrate the current technology of truck bus tire treads, a composition containing N121 carbon black is also prepared.

[0107] All four formulations (TESPT, mercaptosilane coupling agent, hexakis(methoxymethyl)melamine with resorcinol or Penacolite, and mercaptosilane coupling agent hexakis(methoxymethyl)melamine with phloroglucinol resin) were mixed using a mixing procedure that included three consecutive non-productive mixing steps followed by a final productive (curable) mixing in an internal rubber mixer. The silica formulations containing TESPT were heat-treated at 145 °C for 150 seconds during all three non-productive steps. The silica formulations containing the methylene donor compound with the resin were heat-treated at 155 °C for 150 seconds during the first non-productive step, at 150 °C for 150 seconds during the second non-productive step, and at 140 °C for 150 seconds during the third non-productive step. Hexakis(methoxymethyl)melamine and resorcinol, Penacolite or phloroglucinol resin for in-situ polymerization of the load-bearing pass reinforcing interpenetrating network were added in the second and third non-productive stages, respectively. The phr loading for hexakis(methoxymethyl)melamine and resorcinol was optimized to ensure that the Shore A Hardness of the cured compound was within the range typical for a truck tire formulation (Shore A Hardness of 60 - 65) and to achieve the best balance of physical and dynamic properties. The rubber compositions shown in Table 1 were cured at 160 °C for 15 minutes. The resulting dynamic and physical properties are shown in Tables 2 and 3 below, respectively.

Table 1

Table 2

Table 3

[0108] Compounds containing a mercaptosilane coupling agent, a methylene donor compound, and resorcinol or a resorcinol resin were measured using both a DIN grinder and an Angle Abrader (using a rotating grindstone as the grinding surface with slip angles of both 12° and 16° and normal loads of 61N and 123N respectively), and showed better wear and abrasion resistance compared to the TESPT compound. However, unexpectedly and surprisingly, compounds containing a mercaptosilane coupling agent, a methylene donor compound, and a phloroglucinol resin showed much better rolling resistance characteristics (tanD, 60C) when measured using dynamic mechanical analysis, Metravib, compared to others. That is, this invention not only obtained an NR / silica tread system without resorcinol but also achieved progress in improving low rolling resistance.

[0109] PG RESIN 1 unexpectedly worked well with a rolling resistance that was 48% better than carbon black control, 30% better than penacolite, 13% better than resorcinol, and 17% better than TESPT. On the other hand, it was found that the DIN wear of the compound of PG RESIN Example 1 was maintained while being 62% improved compared to TESPT, 21% improved compared to resorcinol, and equivalent to penacolite.

[0110] PG resin Example 2. 440.0 g of phloroglucinol, 628.7 g of acetone, and 349.3 g of an acidic cation exchange catalyst (DIAION PK212LH, Mitsubishi Chemical Corporation) were charged into a flask and heated to 70°C. The reaction mixture was maintained at about 70°C for 24 hours. Then, 0.4 g of a 25% sodium hydroxide solution was added. Next, the solvent was removed by vacuum distillation to 155°C. When the temperature reached 155°C, the vacuum was released and the resin was discharged from the flask.

[0111] Table 2 lists the components used to prepare the rubber compositions using natural rubber. The compositions contain silica coupled with a TESPT coupling agent, a methylene donor compound, and a phloroglucinol resin similar to that of the previous examples as a control. The compositions contain the methylene donor compound in high and low amounts, TESPT in high and low amounts, and the synthesized phloroglucinol resin in high and low amounts. "Non-productive" combinations refer to combinations of materials that do not cure, and "productive" combinations are used to produce compositions cured with low and high sulfur levels.

[0112] All three formulations (normal sulfur, high sulfur, low sulfur) were mixed in an internal rubber mixer using a mixing procedure that included three consecutive non-productive mixing steps followed by a final productive (curable) mix. All three formulations were subjected to the same process. It consisted of mixing for 3 min at 65 rpm in the first step to ensure incorporation, and then completing the additive dispensing at 80 rpm for 3 more minutes. The mixing of the first masterbatch was completed with a 2-minute silane treatment at 160 °C. In the second step, it was mixed for 2 min at 140 °C, held at 140 °C for 1.5 min, and dumped. The third mixing step was mixed for 1.5 min at 40 rpm and then held at 100 °C for 1 min. The productive step was mixed for 1.5 min and held at 100 °C for 1 min. The phr values of silane, HMMM, TESPT, resin, and sulfur were adjusted to obtain similar physical properties.

Table 4

Table 5

Table 6

Table 7

Table 8

[0113] All three experimental compounds exhibited equivalent physical properties. Without being bound by theory, high sulfur was neutralized with low levels of interpenetrating network monomers. Low sulfur compounds were neutralized by high levels of interpenetrating network components. Unexpectedly, the load resistant path interpenetrating network was able to fully neutralize the primary network over a wide range of additions.

[0114] As will be understood by those skilled in the art, hardness is a predictive material for wear performance in the DIN abrasion test.

[0115] Various modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The invention is not properly limited to the embodiments for the purposes of the description set forth herein.

Claims

1. (a) A rubbery polymer or blend of polymers; (b) At least one organosilane coupling agent; (c) At least one reinforcing filler reactive with the at least one organosilane coupling agent; (d) At least one methylene donor compound; (e) At least one phloroglucinol resin; and (f) At least one sulfur donating compound A rubber composition comprising.

2. The rubbery component (a) is in the range of about 25 to about 95 weight percent based on the total weight of the rubber composition; the organosilane coupling agent (b) is in the range of 0.05 part to 30 parts of organosilane coupling agent (b) per 100 parts of the rubbery polymer; the reinforcing filler (c) reactive with the organosilane coupling agent (b) is in the range of 1 part to 150 parts of reinforcing filler per 100 parts of the rubbery polymer; the methylene donor compound (d) is in the range of 0.1 part to 30 parts of methylene donor compound per 100 parts of the rubbery polymer; the phloroglucinol resin (e) is in the range of 0.1 part to 10 parts of phloroglucinol resin per 100 parts of the rubbery polymer; the sulfur donating compound (f) is in the range of 0.1 part to 5 parts of sulfur donating compound per 100 parts of the rubbery compound. The rubber composition according to Claim 1.

3. The rubbery polymer (a) is selected from the group consisting of natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), various copolymers of butadiene, copolymers of isoprene, solution styrene-butadiene rubber (SSBR), emulsion styrene-butadiene rubber (ESBR), ethylene-propylene terpolymer (EPDM), acrylonitrile-butadiene rubber (NBR), and functionalized rubbers modified by at least one alkoxysilyl group, tin-containing group, amino group, hydroxyl group, carboxylic acid group, polysiloxane group, epoxy group or phthalocyanimo group. The rubber composition according to Claim 2.

4. The rubbery polymer (a) comprises natural rubber or a mixture of natural rubber and butadiene rubber. The rubber composition according to Claim 2.

5. The reinforcing filler (c) is selected from fibers, fine particles or sheet-like structures containing a semi-metal oxide or metal oxide having surface hydroxyl groups. The rubber composition according to Claim 2.

6. The rubber composition according to claim 5, wherein the reinforcing filler (c) contains precipitated silica.

7. The rubber composition according to claim 2, wherein the methylene donor compound (d) is selected from the group consisting of polyisocyanates, polyisocyanurates, epoxy resins, amino resins, and polyurethanes.

8. The amino resin is 1,1,3,3 - tetra - methoxymethylurea, 1,3,3 - tris - methoxymethylurea, 1,3 - bis - methoxymethylurea, 1,1 - bis - methoxymethylurea, 1,1,3,3 - tetra - ethoxymethylurea, 1,3,3 - tris - ethoxymethylurea, 1,3 - bis - ethoxymethylurea, 1,1 - bis - ethoxymethylurea, 1,1,3,3 - tetra - propoxymethylurea, 1,3,3 - tris - propoxymethylurea, 1,3 - bis - propoxymethylurea, 1,1 - bis - propoxymethylurea, 1,1,3,3 - tetra - butoxymethylurea, 1,1,3,3 - tetra - phenoxymethylurea, N - (1,3,3 - tris - ethoxymethylureidomethyl) - 1,1,33 - tetra - ethoxymethylurea, N,N′ - bis - (1,1,3 - tris - ethoxymethylureidomethyl) - 1,3 - bis - ethoxymethylurea, N,N′ - bis - (1,1,3 - tris - ethoxymethylureido - methoxymethyl) - 1,3 - bis - ethoxymethylurea, N,N,N′,N′,N″,N″ - hexakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - methoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″,N″ - hexakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - ethoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″,N″ - hexakis - propoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″ - pentakis - propoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N″ - tetrakis - propoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,N″,N″ - hexakis - phenoxymethyl - [1,3,5]triazine - 2,4,6 - triamine, N,N,N′,N′,The rubber composition according to claim 7, selected from the group consisting of N″-pentakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine and N,N,N′,N″-tetrakis-phenoxymethyl-[1,3,5]triazine-2,4,6-triamine.,

9. The phloroglucinol resin (e) has the formula (I): 【Chemical Formula 1】 (wherein at least one of R1, R2, and R3 is bonded to a second phloroglucinol unit to form a disubstituted methylene bridge, the second of R1, R2, and R3 is a hydrogen atom or is bonded to a third phloroglucinol unit to form another disubstituted methylene bridge, and the third of R1, R2, and R3 is a hydrogen atom). The rubber composition according to claim 2.

10. The rubber composition according to claim 9, wherein the phloroglucinol resin is solid and the phloroglucinol resin has the chemical structure according to claim 9, in which the formed disubstituted methylene bridge is an isopropylidene bridge.

11. The rubber composition according to claim 9, wherein the phloroglucinol resin is solid and the phloroglucinol resin has the chemical structure according to claim 9, in which the formed disubstituted methylene bridge is a 2,2-disubstituted butane bridge.

12. The rubber composition according to claim 9, wherein the phloroglucinol resin is solid and the phloroglucinol resin has the chemical structure according to claim 9, in which the formed disubstituted methylene bridge is a 2,2-disubstituted 4-methylpentane bridge.

13. The rubber composition according to claim 2, wherein the solid phloroglucinol resin is a reaction product of phloroglucinol and a ketone in the presence of an acid catalyst.

14. The rubber composition according to claim 12, wherein the ketone in the solid phloroglucinol resin according to claim 12 is selected from the group consisting of acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK).

15. The rubber composition according to claim 2, wherein the sulfur donor compound (f) is sulfur.

16. A method for preparing the rubber composition according to claim 2.

17. A cured rubber composition prepared from the rubber composition according to claim 2.

18. An article comprising the cured rubber composition according to claim 17.

19. The article according to claim 18, wherein the article is an element of a tire.

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