Lining composition with low rolling resistance

Abstract

The invention relates to a low rolling resistance lining composition. A rubber composition for an inner liner (30) is disclosed. The rubber composition comprises 100 phr of an elastomer comprising at least 60 phr of a butyl rubber and 0 to 40 phr of a diene-based rubber; 35 to 70 phr of a reinforcing filler; and a curing system for curing the elastomer. Also disclosed is an inner liner (30) comprising or formed from: 25 to 35 phr of natural rubber; 65 to 75 phr of a halogenated butyl rubber; 45 to 60 phr of calcium carbonate; from 2 to 12 phr of carbon black; optionally, at least one of an oil, a plasticizer, and a tackifying resin; a sulfur-based curing agent; at least 1 phr of zinc oxide; and a curing accelerator.

Description

Technical Field

[0001] Exemplary embodiments relate to rubber compositions suitable for forming tire innerliners and methods of forming the compositions, innerliners, and tires. Background Art

[0002] The inner surface of a pneumatic tire is typically formed of an elastomeric composition designed to prevent or slow the penetration of air and moisture from the inner air chamber of the tire into the carcass. The thin layer of material defining the inner surface is typically referred to as an innerliner. Relatively impermeable rubbers, such as halogenated butyl rubber and blends of butyl rubber and halogenated butyl rubber, are typically used as the major portion of the innerliner.

[0003] Innerliners are usually prepared by calendaring or grinding techniques to form strips of uncured composite rubber of appropriate width, which are sometimes called gumstrips. Typically, gumstrips are the first element of a tire applied to a tire building drum, on and around which the rest of the tire is built. When the tire is cured, the innerliner becomes an integral co-cured portion of the tire. In order to improve their properties, such as air tightness, tire innerliners may include various additives. Therefore, innerliners are conventionally relatively hard.

[0004] For example, U.S. Patent No. 8,220,511 B2 describes an inner liner rubber composition containing an ethylene-vinyl alcohol polymer dispersed in an elastomer selected from bromobutyl rubber and chlorobutyl rubber. U.S. Patent Publication No. 20110146870A1 describes a tire having an inner liner containing slate powder. U.S. Patent No. 7,506,677 B2 describes a pneumatic tire having an inner liner formed from a dispersion of butyl rubber and precured diene rubber. U.S. Patent No. 6,765,063 B2 describes a pneumatic tire having an inner liner of a rubber composition containing a low molecular weight trans-1,4-polybutadiene rubber.

[0005] An innerliner is described herein that improves the rolling resistance performance of a tire while maintaining satisfactory airtight properties. Summary of the invention

[0006] According to an exemplary embodiment, a rubber composition for an inner liner includes 100 phr of an elastomer, the elastomer including at least 60 phr of butyl rubber and at most 40 phr of diene rubber. The rubber composition further includes 35 to 70 phr of a reinforcing filler and a curing system.

[0007] In various aspects of this embodiment:

[0008] The butyl rubber may be at least 65 phr, or at most 80 phr, or at most 75 phr.

[0009] The butyl rubber may include a halogenated butyl rubber selected from the group consisting of bromobutyl rubber, chlorobutyl rubber, and mixtures thereof.

[0010] The diene based rubber may be present at least 20 phr or at most 35 phr.

[0011] The diene-based rubber may include at least one polyisoprene, such as natural rubber and / or synthetic polyisoprene.

[0012] In the rubber composition, the elastomer other than butyl rubber and polyisoprene is preferably present in an amount of at most 10 phr or at most 5 phr.

[0013] The curing system may include at least one of a sulfur-based curing agent and zinc oxide.

[0014] The rubber composition may further include at least one vulcanization aid selected from the group consisting of an organic curing activator, a curing accelerator, a curing retarder, and combinations thereof.

[0015] The reinforcing filler may include or consist of at least one of calcium carbonate and magnesium carbonate. The calcium carbonate and / or magnesium carbonate may be present in the rubber composition at 35 to 70 phr or 45 to 60 phr.

[0016] The reinforcing filler may include 1 to 20 phr, or up to 12 phr, or up to 10 phr of rubber reinforcing carbon black.

[0017] The reinforcing filler may include calcium carbonate and rubber reinforcing carbon black in a weight ratio of at least 4:1, or at least 5:1 and / or at most 30:1.

[0018] The rubber composition may further include at least one processing aid selected from the group consisting of oils, plasticizers, tackifying resins, and mixtures thereof.

[0019] In another aspect, an inner liner is formed by curing the rubber composition of any of the above aspects.

[0020] In another aspect, a pneumatic tire includes an inner liner formed by curing the rubber composition of any of the above aspects.

[0021] According to another exemplary embodiment, a method of forming an inner liner of a tire includes forming a mixture comprising: 100 phr of an elastomer, the elastomer including at least 60 phr of butyl rubber and up to 40 phr of diene rubber, 35 to 70 phr of a reinforcing filler including calcium carbonate and carbon black, and at least one of a sulfur-based curing agent and zinc oxide. The method further includes shaping the mixture to form a strip, and curing the strip to form the inner liner of the tire.

[0022] In various aspects of this embodiment:

[0023] The resulting mixture preferably has a Mooney viscosity of from 10 to 26 M.U. or from 18 to 23 M.U.

[0024] During curing, the innerliner preferably becomes an integral component of the tire.

[0025] According to another exemplary embodiment, the liner comprises or is formed of the following components: 20 to 35 phr of natural rubber; 65 to 80 phr of halogenated butyl rubber; 45 to 60 phr of calcium carbonate; 2 to 12 phr of carbon black; at least 1 phr of zinc oxide; a sulfur-based curing agent; and a curing accelerator; and optionally, at least one of an oil, a plasticizer, and a tackifying resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic cross-sectional view of a passenger vehicle tire according to one embodiment; and

[0027] Figure 2 is a graph of air diffusion vs G” for the lined sample. DETAILED DESCRIPTION

[0028] In an exemplary embodiment, the pneumatic rubber tire has an integral inner liner formed from a cured rubber composition. The inner liner has good air tightness and relatively low stiffness and hysteresis, which provides low rolling resistance for the tire. The rolling resistance contribution of the inner liner is strain controlled, and a lower loss modulus G" indicates a lower rolling resistance.

[0029] Exemplary rubber compositions have low filler content (e.g., include or consist of at least one of calcium carbonate and magnesium carbonate and optionally carbon black). The butyl rubber content of the rubber composition can be relatively high, such as at least 60 phr.

[0030] In another aspect of this exemplary embodiment, a rubber composition having low stiffness and high butyl levels satisfies a standard air diffusion test and exhibits an improvement in rolling resistance.

[0031] In the description of the present invention, the term "phr" refers to parts by weight of a specific ingredient per 100 parts by weight of uncured rubber contained in the rubber composition.

[0032] Unless otherwise specified, the terms "rubber" and "elastomer" are used interchangeably.

[0033] Unless otherwise indicated, the terms "cure" and "vulcanize" are used interchangeably.

[0034] Unless otherwise indicated, the term "butyl rubber" is used herein to refer to butyl rubber (a copolymer of isobutylene and isoprene) and also to halogenated butyl rubbers such as chlorobutyl rubber and bromobutyl rubber (chlorinated and brominated butyl rubbers, respectively).

[0035] refer to Figure 1 , a pneumatic tire 10 includes a tire tread 12, which defines the road contacting surface of the tire. Two sidewalls 14, 16 extend from the tread to respective bead areas 18, 20. Each bead area includes one or more beads 22, 24, which may be secured in place by respective bead filler apexes 26, 28. An inner liner 30 defines the innermost surface of the tire and is connected at each end to the respective sidewalls 14, 16.

[0036] The tire may also include a set of belt layers 32 and a carcass ply 36 located inside the belt layers. The carcass ply 36 shown includes a pair of axially opposite end portions 38, 40, each of which is engaged with a corresponding one of the beads 22, 24. Each axial end portion 38, 40 of the carcass ply 36 can be turned up and surround a respective bead until a position anchoring each axial end portion. The turned-up portions 38, 40 of the carcass ply can engage the axially outer surface of the respective tread core wrappers (flippers) 42, 44 and the axial inner surface of the respective chippers (chippers) 46, 48. The exemplary tread 10 has circumferential grooves (four in the illustrated embodiment), each groove substantially defining a U-shaped depression in the tread 10. The tread 12, sidewalls and carcass can be formed from one or more rubber-based compositions. The exemplary tire is suitable, for example, for mounting on a rim of a vehicle, such as a truck or a passenger car. It will be appreciated that the overall construction of the tire 10 may differ from Figure 1 The configuration shown in , and may include fewer or more components.

[0037] This lining can be used as Figure 1 The integral innerliner 30 in the pneumatic tire shown in FIG. However, it is to be appreciated that the tire may have a configuration different from that shown. The innerliner may be formed from a cured rubber composition comprising, based on parts by weight per 100 parts by weight of total rubber (phr):

[0038] (A) 100 phr of a vulcanizable elastomer comprising:

[0039] (1) At least 60 phr of butyl rubber; and

[0040] (2) up to 40 phr of diene rubber;

[0041] (B) 35 to 70 phr of reinforcing fillers, such as:

[0042] (1) one or more mineral fillers, such as calcium carbonate and / or magnesium carbonate; and

[0043] (2) Not more than 20 phr of rubber reinforcing carbon black;

[0044] (C) optionally, one or more processing aids, such as one or more of oils, plasticizers, and tackifying resins; and

[0045] (D) optionally, one or more antidegradants, such as one or more of an antiozonant and an antioxidant;

[0046] (E) a curing system comprising at least one of a sulfur-based curing agent and zinc oxide; and

[0047] (F) Optionally, one or more non-zinc oxide vulcanization aids, such as one or more of an organic curing activator, a curing accelerator and a curing retarder.

[0048] A: Elastomer

[0049] 1. Butyl rubber

[0050] Butyl rubber is a copolymer of isobutylene and isoprene. Butyl rubber can be non-halogenated butyl rubber and / or halogenated butyl rubber, such as bromobutyl rubber, chlorobutyl rubber, partially depolymerized bromobutyl rubber, partially depolymerized chlorobutyl rubber and partially depolymerized butyl rubber, and mixtures thereof.

[0051] In one embodiment, the butyl rubber comprises bromobutyl rubber.

[0052] Butyl rubber is the main component of the elastomer in the rubber composition and may be up to 100 phr (ie, no other elastomers).Butyl rubber may be at least 60 phr, or at least 65 phr, or up to 80 phr, or up to 75 phr, such as 65-75 phr.

[0053] 2. Diene-based elastomer

[0054] The diene-based elastomer may be selected from polymers of at least one of isoprene and 1,3-butadiene, copolymers of styrene with at least one of isoprene and 1,3-butadiene, derivatives thereof, and mixtures thereof. For example, the diene-based elastomer may be selected from polyisoprenes, such as natural rubber (mainly cis-1,4-polyisoprene) and synthetic cis-1,4-polyisoprene; methylbutadiene; dimethylbutadiene; pentadiene; and mixtures thereof.

[0055] In one embodiment, the diene-based elastomer comprises or consists of a polyisoprene selected from natural rubber and synthetic polyisoprene. In some embodiments, the natural rubber may comprise or consist of a modified natural rubber, such as deproteinized natural rubber (DPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, or mixtures thereof. In some embodiments, the synthetic polyisoprene rubber may comprise or consist of a modified synthetic polyisoprene rubber, such as deproteinized, epoxidized, hydrogenated, and / or grafted synthetic cis-1,4-polyisoprene, or mixtures thereof.

[0056] As used herein, the term "natural rubber" refers to naturally occurring rubber, such as can be harvested from sources such as Hevea rubber trees and non-Hevea (such as guayule shrubs and dandelions such as TKS). In other words, the term "natural rubber" should be interpreted as excluding synthetic polyisoprene. Natural rubber produced from garden-grade condensate (cuplump) from Hevea brasiliensis tree (Hevea brasiliensis tree) is a common form of natural rubber. For example, technically specified rubber or block rubber (TSR) is a natural rubber available from Indonesia, where it can be referred to as Standard Indonesian Rubber (SIR), Malaysia (SMR) and Thailand (STR). It can be obtained in many grades, including TSR 10 and TSR20, wherein the TSR 10 grade has a higher purity.

[0057] In one embodiment, natural rubber is the major portion (highest phr) of the diene based rubber used in the composition.

[0058] Other diene-based elastomers that may be used include styrene-butadiene rubber, styrene / isoprene / butadiene rubber, alkoxy-silyl end-functionalized solution-polymerized polymers (SBR, PBR, IBR, and SIBR), and silicon-coupled and tin-coupled star-branched polymers.

[0059] The rubber composition may be free of diene-based elastomers as described herein. In another embodiment, the rubber composition includes at least 10 phr of a diene-based elastomer, such as natural rubber. The diene-based elastomer, such as natural rubber, may be present in the rubber composition at least 25 phr, or at most 40 phr, or at most 35 phr.

[0060] In addition to the conjugated diene-based elastomer and natural rubber present in the rubber composition, other suitable vulcanizable elastomers that can be used in small amounts (e.g., less than 10 phr, or up to 5 phr, or up to 2 phr) can be selected from nitrile rubber, liquid rubber, polynorbornene copolymer, ethylene-propylene-diene rubber, chloroprene rubber, acrylate rubber, fluororubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrated acrylonitrile butadiene rubber, isoprene-butadiene copolymer, butyl rubber, hydrogenated styrene-butadiene rubber, Butadiene acrylonitrile rubber, terpolymer formed by ethylene monomer, propylene monomer and / or ethylene propylene diene monomer (EPDM), isoprene-based block copolymer, butadiene-based block copolymer, styrene-based block copolymer, styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-[ethylene-(ethylene / propylene)]-styrene block copolymer (SEEPS), styrene-isoprene-styrene block copolymer (SIS), random styrene-based copolymer, hydrogenated styrene-based block copolymer polyolefins, amorphous polyolefins, semi-crystalline polyolefins, alpha-polyolefins, reactor-ready polyolefins, acrylates, metallocene-catalyzed polyolefin polymers and elastomers, reactor-made thermoplastic polyolefin elastomers, olefin block copolymers, copolyester block copolymers, polyurethane block copolymers, polyamide block copolymers, thermoplastic polyolefins, thermoplastic vulcanizates, ethylene acetate Ethylene ester copolymers, ethylene n-butyl acrylate copolymers, ethylene methyl acrylate copolymers, chloroprene rubber, acrylic acid, urethane, poly (acrylate), ethylene acrylic acid copolymer, polyetheretherketone, polyamide, atactic polypropylene, polyethylene including atactic polypropylene, ethylene-propylene polymers, propylene-hexene polymers, ethylene-butene polymers, ethylene-octene polymers, propylene-butene polymers, propylene-octene polymers, metallocene-catalyzed polypropylene polymers, metallocene-catalyzed polyethylene polymers, ethylene-propylene-butene terpolymers, propylene, ethylene, C4-C 10 Copolymers made from α-olefin monomers, polypropylene polymers, maleated polyolefins, polyester copolymers, copolyester polymers, ethylene acrylic acid copolymers and / or polyvinyl acetate, and / or wherein the polymers are optionally modified and / or functionalized at the polymer chain ends or side chain positions within the polymer to include one or more selected from hydroxyl groups, ethoxy groups, epoxy groups, siloxane groups, amine groups, aminosiloxane groups, carboxyl groups, phthalocyanine groups and silane-sulfide groups, and mixtures thereof.

[0061] B Reinforcement filler

[0062] The rubber composition may include a total of at least 35 phr of filler, or at least 40 phr, or at least 50 phr, or at most 90 phr, or at most 80 phr, or at most 70 phr, or at most 60 phr or at most 50 phr of filler. The filler may be selected from mineral fillers, carbon black and mixtures thereof.

[0063] (1) Mineral fillers

[0064] Examples of mineral fillers that may be used in the rubber composition include calcium carbonate, magnesium carbonate, silica, talc, clay, mica, alumina, aluminum hydroxide, magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, and mixtures thereof.

[0065] In one embodiment, the mineral filler comprises calcium carbonate (CaCO3). In a specific embodiment, calcium carbonate is the only mineral filler used.

[0066] The rubber composition may include at least 35 phr of calcium carbonate, or at least 40 phr, or at least 45 phr, or at most 70 phr, or at most 65 phr, or at most 60 phr of calcium carbonate.

[0067] In one embodiment, the calcium carbonate is present at 60 parts per hundred parts of filler by weight (phf) or more, such as at least 70 phf, or at least 80 phf, or at least 90 phf, or up to 100 phf, wherein the total amount of filler includes all carbon-based fillers and all mineral fillers present.

[0068] In other embodiments, all or a portion of the calcium carbonate may be replaced with magnesium carbonate.

[0069] In one embodiment, the rubber composition may further include silica, for example, at least 1 phr of silica, or at least 3 phr, or at least 5 phr, or at most 40 phr, or at most 30 phr, or at most 20 phr, or at most 8 phr, or at most 6 phr of silica. In another embodiment, silica may be omitted from the rubber composition or present at 1 phr or less.

[0070] The silica may be amorphous (e.g. precipitated) silica and / or crystalline silica. The term "silica" is used herein to refer to silicon dioxide SiO2 (which may contain small amounts of impurities, typically less than 1% by weight, from the silica formation process). The term "precipitated silica" is used to refer to synthetic amorphous silica, typically obtained by a process of precipitating silicates with an acidulant. Precipitated silica may be prepared by digesting amorphous silica (e.g. present in rice husks or other biowaste) with sodium hydroxide to form sodium silicate, and precipitating silica from the sodium silicate by reaction with an acidulant such as sulphuric acid or carbon dioxide. Alternatively, silica may be made from silica gel, for example by hydrophobizing a silica hydrogel with, for example, organomercaptosilanes and alkylsilanes and drying the product. Methods for preparing precipitated silica are disclosed, for example, in U.S. Pat. Nos. 5,587,416A, 5,708,069A, and 9,359,215B2 and U.S. Publication Nos. 20020081247A1 and 20050032965A1.

[0071] The silica used in the reinforcing filler may have a thickness of at least 20 m 2 / g, or at least 120m 2 / g, or at least 140m 2 / g, and / or up to 500m 2 / g, or up to 400m 2 / g, or up to 300m 2 / g of CTAB specific surface area according to ASTM D6845-20, "Standard Test Method for Silica, Precipitated, Hydrated—CTAB (Cetyltrimethylammonium Bromide) Surface Area".

[0072] In one embodiment, the silica may have been surface treated, for example, with a coupling agent and / or polyalkylene oxide, such as polyethylene glycol, before the pretreated silica is incorporated into the rubber composition. The pretreatment may be used to enhance dispersion and / or adhesion of the silica to the elastomer. In another embodiment, the silica may be in the rubber composition, typically treated in situ with a coupling agent and / or polyalkylene oxide, prior to the addition of a vulcanizing agent.

[0073] Representative coupling agents include bis(3-trialkoxysilylpropyl)polysulfides, wherein at least two, optionally all three, of the alkoxy groups are ethoxy groups, and the polysulfide bridges have an average of at least 2 connected sulfur atoms, such as up to 4, or up to 2 connected sulfur atoms, and alkoxyorganomercaptosilanes, the mercapto moieties of which may be optionally blocked with a suitable blocking agent during mixing with the rubber composition. The alkoxy group may be, for example, an ethoxy group.

[0074] The rubber composition may also contain, for example, at least one of talc, clay, mica, and mixtures thereof, in a range of, for example, about 2 to 25 phr, or up to 5 phr, depending on various physical properties desired for the inner liner composition.

[0075] (2) Carbon Black

[0076] In one embodiment, the rubber composition includes carbon black, such as at least 1 phr of carbon black, or at least 2 phr, or at least 3 phr, or at most 20 phr, or at most 12 phr, or at most 10 phr of carbon black. In another embodiment, carbon black can be omitted from the rubber composition.

[0077] When present in the rubber composition, the carbon black may be a single reinforcing carbon black or may include two or more different types of carbon black.

[0078] The carbon black that can be used in the rubber composition may have a 15 m 2 / g to 300m 2 / g, or at least 40m 2 The nitrogen surface area (NSA) of carbon black is measured according to ASTM D6556-21, "Standard Test Method for Carbon Black—Total and External Surface Area by Nitrogen Adsorption". Exemplary carbon blacks include ASTM designations N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N774, N787, N907, N908, N990, and N991 as specified in ASTM D1765-21, "Standard Classification System for Carbon Blacks Used in Rubber Products."

[0079] In one embodiment, the carbon black is pretreated, for example with silicon, prior to forming the rubber composition. An exemplary silicon-treated carbon black may be used as CRX TM 2000 Available from Cabot Corporation.

[0080] In one embodiment, the reinforcing filler comprises or consists of calcium carbonate and carbon black, wherein the weight ratio of calcium carbonate to rubber reinforcing carbon black is at least 4:1, or at least 4.5:1, or at least 5:1, and / or at most 30:1.

[0081] C. Processing Aids

[0082] Processing aids may be used in the rubber composition in a total of 0 to 10.0 phr, or at least 0.5 phr, or at least 1 phr, or up to 6 phr, or up to 2 phr, and may include one or more of processing oils, plasticizers such as hydrocarbon resins, waxes, and tackifying resins.

[0083] (1) Processing oil

[0084] Processing oil is the oil used in the non-productive stage of forming rubber composition, and helps to process the composition, and in some cases, provides useful properties for curing rubber composition.Processing oil is liquid at room temperature (that is, more than 25 ℃, liquid at atmospheric pressure).Usually, oil and other liquid plasticizers have lower than 0 ℃, usually far below 0 ℃, such as lower than -30 ℃ or lower than -40 ℃ or lower than -50 ℃ Tg, such as 0 ℃ to -100 ℃ Tg.The Tg of oil used can be -40 ℃ to -100 ℃.Unless otherwise stated, the glass transition temperature (Tg) of elastomer or oil is measured at a heating rate of 1 ℃ / minute according to DIN 53445, " Torsion Pendulum Test, Testing of Polymer Materials " (1986).

[0085] The rubber composition may include at least 0.5 phr, or at least 1 phr, or at most 5 phr, or at most 4 phr, or at most 3 phr, or at most 2 phr of processing oil. In another embodiment, processing oil may be omitted from the rubber composition.

[0086] Exemplary processing oils include petroleum, plant-based oils and mixtures thereof. Petroleum-based oils may include aromatic oils, naphthenic oils, low polycyclic aromatic hydrocarbons (PCA) oils and mixtures thereof. Plant-based oils may include oils and derivatives thereof obtained from vegetables, nuts, seeds, such as triglycerides and esterified alkoxylated polyols. Exemplary processing oils include blends of plant-based triglyceride oils and esterified alkoxylated polyols, or are composed of blends of plant-based triglyceride oils and esterified alkoxylated polyols, which may also be plant-based. Other processing oils are also contemplated.

[0087] (2) Plasticizers

[0088] Examples of plasticizers for the rubber composition include alkylated and aromatic resins. The rubber composition may include at least 0.2 phr, or at least 0.5 phr, or at most 4 phr, or at most 3 phr, or at most 2 phr of plasticizer. In another embodiment, such plasticizer may be omitted from the rubber composition.

[0089] Exemplary hydrocarbon resins may have a Tg of at least 30°C or at most 50°C. The Tg of a hydrocarbon resin may be determined by DSC according to the procedure discussed above for measuring Tg of an elastomer. A hydrocarbon resin may have a softening point of at least 70°C or at most 100°C. The softening point of a hydrocarbon resin is generally related to the Tg. The Tg is generally lower than its softening point, and the lower the softening point, the lower the Tg.

[0090] Examples of aliphatic resins include C5 fraction homopolymer and copolymer resins.Examples of alicyclic resins include cyclopentadiene ("CPD") homopolymer or copolymer resins, dicyclopentadiene ("DCPD") homopolymer or copolymer resins, and combinations thereof.

[0091] Examples of aromatic resins include aromatic homopolymer resins and aromatic copolymer resins.Aromatic copolymer resins refer to hydrocarbon resins comprising one or more aromatic monomers in combination with one or more other (non-aromatic) monomers, wherein a majority by weight of all monomers are typically aromatic.

[0092] The specific example of aromatic resin includes coumarone-indene resin, alkylphenol resin and vinyl aromatic homopolymer or copolymer resin. The example of alkylphenol resin includes alkylphenol-acetylene resin, such as p-tert-butylphenol-acetylene resin, alkylphenol-formaldehyde resin (such as those with low polymerization degree). Vinyl aromatic resin can include one or more of the following monomers: alpha-methylstyrene, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinyl mesitylene, divinylbenzene, vinylnaphthalene etc. The example of vinyl aromatic copolymer resin includes vinyl aromatic / terpene copolymer resin (for example, limonene / styrene copolymer resin), vinyl aromatic / C5 fraction resin (for example, C5 fraction / styrene copolymer resin), vinyl aromatic / aliphatic copolymer resin (for example, CPD / styrene copolymer resin and DCPD / styrene copolymer resin).

[0093] In the case of an aromatic resin based on one or more of the above-mentioned vinyl aromatic monomers (e.g. styrene, α-methylstyrene), at least 80% by weight, or at least 85% by weight, or at least 90% by weight, or at least 95% by weight, or up to 100% by weight of the monomers in the aromatic resin may be aromatic monomers.

[0094] (3) Tackifying resin

[0095] Tackifying resins are added to the rubber compound to help bond the different parts of the tire together until they solidify, and to provide tack between the layers of the rubber compound during the processing stage. Tackifying resins are generally solid at room temperature. Examples of tackifying resins that can be used for the rubber composition include non-reactive phenol formaldehyde resins, aromatic modified terpene resins, aromatic modified terpene phenol resins, and resins prepared by polymerizing 2-methyl-2-butene and piperylene with other unsaturated hydrocarbons containing 4 to 18 carbon atoms.

[0096] In one embodiment, such tackifying resins may not be present in the rubber composition.In another embodiment, the rubber composition may include at least 0.1 phr, or at least 0.2 phr, or at most 2 phr, or at most 1 phr of a tackifying resin.

[0097] (4) Wax

[0098] Suitable waxes, particularly microcrystalline waxes, may be of the type shown in The Vanderbilt Rubber Handbook (1978), pages 346 and 347. Examples of waxes include C 22 -C 60Saturated hydrocarbons, which may be branched or unbranched, and mixtures thereof. When wax is used, it may be present in the rubber composition at 1 to 5 phr. In other embodiments, wax is not present in the rubber composition.

[0099] In addition to one or more of the above processing aids, the rubber composition may also include a peptizer, such as pentachlorothiophenol, dibenzamidodiphenyl disulfide, or mixtures thereof. If a peptizer is used, a typical amount thereof may be 0.1 phr to 1 phr.

[0100] D. Antidegradants (antioxidants, antiozonants)

[0101] In some embodiments, particularly when the elastomer includes natural rubber, the rubber composition may include one or more antidegradants, such as antiozonants and / or antioxidants. These compounds help protect the tire from oxidation and ozonation. Representative antidegradants include amine antioxidants, such as monophenols, bisphenols, thiobisphenols, polyphenols, polymerized hindered phenols, hydroquinone derivatives, phosphites, phosphate blends, thioesters, naphthylamines, diphenolamines and other diarylamine derivatives, p-phenylenediamine (PPD), quinoline and blended amines. Exemplary amine antioxidants include diphenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), oligomeric 2,2,4-trimethyl-quinoline (TMQ), etc., such as those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344-347. The antioxidant may be at least 0.1 phr, or at least 0.3 phr, or at least 1 phr, or at least 2 phr, or up to 10 phr, or up to 5 phr of the rubber composition. In another embodiment, no antioxidant is present in the rubber composition.

[0102] Exemplary antiozonants include physical protectants, such as waxes. Suitable waxes include paraffin wax and microcrystalline wax, which can be the type described in The Vanderbilt Rubber Handbook (1978), pages 346 and 347. Wax can be present in an amount of more than 0.1 phr, such as at least 0.3 phr, or at least 0.5 phr, or at most 5 phr, or at most 2 phr. In another embodiment, there is no antiozonant in the rubber composition.

[0103] E. Curing system

[0104] Exemplary curing systems may include sulfur-based curing agents such as elemental sulfur (free sulfur), insoluble polymeric sulfur, soluble sulfur, and sulfur donating vulcanizing agents, such as amine disulfides, polymeric polysulfides, or sulfur olefin adducts, and mixtures thereof.

[0105] Sulfur-based curing agents may be used in the rubber composition in amounts of 0.1 to 10 phr, such as at least 0.3 phr, or at least 0.4 phr, or at least 0.6 phr, or up to 2 phr, or up to 1.5 phr, or up to 1 phr, or up to 0.8 phr.

[0106] In other embodiments, such as when polyisoprene is not present in the rubber composition, the sulfur-based curative may be omitted.

[0107] Zinc oxide (ZnO), when present, acts as a crosslinking (i.e., curing) agent for the halogenated butyl rubber, while also acting as an activator for the sulfur-based curing agent that cures the diene elastomer. Zinc oxide may be present in an amount of at least 1 phr, such as at least 2 phr, or at least 3 phr, or at most 10 phr, or at most 8 phr, or at most 7 phr, or at most 5 phr.

[0108] F. Organic curing activators, curing accelerators and curing retarders

[0109] (1) Organic curing activator

[0110] The curing activator is an additive used to assist vulcanization. The curing activator includes an inorganic curing activator (such as the above-mentioned zinc oxide) and an organic curing activator.

[0111] Organic curing activators include stearic acid, palmitic acid, lauric acid, mixtures thereof, zinc salts of each of the above, and thiourea compounds, such as thiourea, and dialkylthioureas, such as dialkylthioureas and diarylthioureas, and mixtures thereof. Specific thiourea compounds include N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea (DEU), N,N'-dimethylthiourea, N,N'-dibutylthiourea, ethylenethiourea, N,N'-diisopropylthiourea, N,N'-dicyclohexylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1,1-diphenyl-2-thiourea, 2,5-dithiodiurea, guanylthiourea, 1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, and o-tolylthiourea. One commonly used organic curing activator is a blend of stearic acid, palmitic acid, and oleic acid, with stearic acid being the major component of the blend.

[0112] When used, the total amount of organic cure activator may be 0.1 to 10 phr, such as at least 0.5 phr, or at least 2 phr, or at least 3 phr, or up to 8 phr.In another embodiment, organic cure activator is omitted from the rubber composition.

[0113] (2) Curing accelerator

[0114] Curing accelerator serves as the catalyst of the curing agent based on sulfur.Accelerator is used to control the time and / or temperature required for vulcanization, and improves the property of vulcanized rubber.Single accelerator system can be used, i.e. main accelerator, and its amount is about 0.5 to 8.0phr.Or, the combination of two or more accelerators can be used, which can be composed of the main accelerator used with a larger amount (0.3 to 3.0phr) and the auxiliary accelerator used with a smaller amount (0.05 to 1.0phr), to activate and improve the property of vulcanized rubber.

[0115] Suitable curing accelerators include amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, xanthates and mixtures thereof. Examples of disulfides include alkylphenol disulfide polymers, such as poly-tert-butylphenol disulfide. Examples of thiazole curing accelerators include 2-mercaptobenzothiazole and 2,2'-disulfide bis(benzothiazole) (MBTS). Examples of sulfenamide curing accelerators include benzothiazole sulfenamides, such as N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and N-tert-butyl-2-benzothiazole-sulfenamide (TBBS). Guanidine curing accelerators include diphenylguanidine (DPG).

[0116] Other examples of accelerators that can be used include 1,6-bis(N,N'-dibenzylthiocarbamoyldisulfide)hexane (BDBZTH), tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyldithiocarbamate (ZDBC), zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, diethyldithiocarbamate, and the like. Tellurium thiocarbamate (TDEC), zinc dibenzyl dithiocarbamate (ZBED), zinc diisononyl dithiocarbamate, zinc pentamethylene dithiocarbamate, zinc dibenzyl dithiocarbamate (ZBEC), zinc isopropyl xanthate (ZIX), zinc butyl xanthate (ZBX), sodium ethyl xanthate (SEX), sodium isobutyl xanthate (SIBX), sodium isopropyl xanthate (SIPX), sodium n-butyl xanthate (SNBX), sodium amyl xanthate (SAX), potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX), zinc 2-ethylhexyl dithiophosphate (ZDT / S), and mixtures thereof.

[0117] In some cases, a combination of accelerators is used, one of which works faster than the other. These combinations of accelerators are known to produce a synergistic effect on the final properties, and are slightly better than those produced by using either accelerator alone. In addition, delayed-acting accelerators can be used, which are not affected by normal processing temperatures but produce satisfactory cure at ordinary vulcanization temperatures. As primary accelerators, disulfides or sulfenamides can be used.

[0118] The curing accelerator can be incorporated into the rubber composition with 0.1 to 10 phr, or at least 0.5 phr, or at least 1 phr, or at least 1.5 phr, or at most 8 phr, or at most 7 phr, or at most 6 phr. The amount of the curing accelerator can be selected to provide an acceptable curing time, such as 90 minutes or less.

[0119] 3) Curing retardants

[0120] Cure retarders can be used to control the curing process and typically delay or inhibit curing until the desired time and / or temperature is reached. Examples of cure retarders include cyclohexylthiophthalimide.

[0121] When used, the amount of cure retarders may be at least 0.1 phr, or at most 3 phr, or at most 2 phr.

[0122] In one embodiment, cure retarders are omitted from the rubber composition.

[0123] Preparation of rubber composition

[0124] The rubber composition can be prepared by mixing the elastomer, mineral filler and carbon black, and other rubber compounding ingredients excluding the cure system (sulfur-based curative and / or zinc oxide) to elevated temperatures in at least one sequential mixing stage with at least one mechanical mixer (commonly referred to as a "non-productive" mixing stage), under high shear rubber mixing conditions, followed by a final "productive" mixing stage, wherein a cure package, such as a sulfur-based curative, zinc oxide and one or more cure accelerators, is added to the mixture and mixed at a lower mixing temperature to avoid unnecessary pre-curing of the rubber mixture during the productive mixing stage.

[0125] These ingredients can be mixed in a non-productive mixing stage for about 2-3 minutes to 130°C to 200°C, such as a temperature of about 140°C to 160°C. Two or more non-productive stages can be used in some embodiments. Once a curing package (including a sulfur-based curing agent (such as soluble sulfur), an accelerator, and any remaining activator) is added, a subsequent productive mixing step can be carried out at a temperature lower than the vulcanization (curing) temperature to avoid the undesired pre-curing of the rubber composition, such as not higher than 120°C, such as at least 40°C or at least 60°C, such as at a temperature of 105-115°C for 2 minutes. It can be mixed, for example, by kneading the ingredients together in a Banbury mixer or on a milled roll. The rubber composition can be cooled to a temperature lower than 40°C between each mixing stage. For example, the rubber composition can be poured out from a mixer after each mixing step, sheeted out from an open mill, and cooled to less than 40°C after each mixing step.

[0126] The resulting mixture may have a Mooney viscosity of 10-26 M.U. or 18-23 M.U. As used herein, Mooney viscosity (ML1+4) is measured in MU units at 100°C according to ASTM D1646-19a, "Standard Test Methods for Rubber—Viscosity, Stress Relaxation, and Pre-Vulcanization Characteristics (Mooney Viscometer)".

[0127] The liner rubber composition thus formed is shaped as a so-called gum strip (gum strip) usually. The thickness of the rubber strip can be 0.4 to 10mm or 0.5 to 5mm, which depends on the type, size and intended use of the tire. The strip can be produced by a press or by making the rubber compound pass through a grinding machine, a calender, a multi-head extruder or other suitable molding devices. The uncured strip is then constructed as the inner surface (exposed inner surface) of an unvulcanized rubber tire structure (also referred to as a carcass). The inner liner is then co-cured with the tire carcass under heat and pressure conditions during the tire curing operation.

[0128] Vulcanization of the tire may be carried out, for example, at a temperature of 100 to 200° C., such as 110 to 180° C. Any conventional vulcanization method may be used, such as heating in a press or mold, heating with superheated steam or hot air or in a salt bath.

[0129] Due to this vulcanization, the innerliner becomes an integral part of the tire by being co-cured with the tire. The innerliner can thus first be constructed as a composite rubber strip defining the inner surface of an uncured rubber tire and then co-cured with the tire during the tire curing operation.

[0130] The pneumatic tire with an integral inner liner can be constructed in the form of a passenger tire, a truck tire or other types of bias or radial pneumatic tires. The rubber composition is not limited to use in tires, but can also be applied to rubber gloves, surgical instruments, etc.

[0131] Table 1 shows exemplary inner liner rubber compositions.

[0132] Table 1: Ranges of exemplary liner compositions (expressed in phr)

[0133]

[0134] Without intending to limit the scope of the exemplary embodiments, the following examples illustrate the preparation of exemplary rubber compositions, innerliners, tires including the innerliners, and properties thereof.

[0135] Example

[0136] Using the ingredients shown in Table 2, butyl rubber type rubber compositions AH were prepared.

[0137] In the non-productive stage, natural rubber, halogenated butyl rubber, calcium carbonate, carbon black (when used), fatty acids and processing aids (when used) are combined in an electric mixer and mixed for 2-3 minutes before being dosed from the mixer at a temperature of about 140° C. In the productive stage, sulfur, zinc oxide and accelerators are added to the mixture and mixed for about two minutes before being dosed from the mixer at a temperature of about 110° C.

[0138] The mixture was formed into a bead and cured at 170°C for approximately 23 minutes.

[0139] Table 2: Liner composition (in phr)

[0140] Ex.A Ex.B ExC Ref.1 Ref.2 Ref.3 Natural rubber 35 25 30 0 25 20 Bromobutyl rubber 65 75 70 100 75 68 SBR 0 0 0 0 0 16.5 Calcium carbonate 45 45 55 0 0 40 <![CDATA[Carbon black 1 > 10 7 2 64 64 41 <![CDATA[Fatty acid 2 > 4 4 4 2 1.1 2 <![CDATA[Oil 3 > 2 2 2 10.8 12 9 <![CDATA[Plasticizer 4 > 2 2 2 8 0 8 <![CDATA[Adhesive]] 5 > - - - 1 4 2.2 <![CDATA[Sulfur 6 > 0.7 0.7 0.7 0.5 0.3 1.5 Zinc Oxide 4 4 4 1 4. 4.3 Accelerator <![CDATA[5.5 8 ]]> <![CDATA[5.5 8 ]]> <![CDATA[5.5 8 ]]> 0.4 1.5 1.2 Total number of copies 173.2 170.2 175.2 187.7 187.4 213.4

[0141] 1 Carbon black, ASTM grade N660.

[0142] 2 Fatty acid mixture, mainly stearic acid

[0143] 3 Mixture of naphthenic and paraffinic oils

[0144] 4 Mixture of alkylated hydrocarbons and aromatic resins

[0145] 5 Phenol formaldehyde resin

[0146] 6 Elemental sulfur

[0147] 7 2,2'-Bis(benzothiazole)dithioate (MBTS)

[0148] 8 A mixture of MBTS, N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and poly-tert-butylphenol disulfide accelerator

[0149] Evaluation of rubber compositions

[0150] Compound testing

[0151] The following tests were performed on the lining samples:

[0152] G' (storage modulus) and G" (loss modulus) in MPa were measured using a rubber process analyzer. Results were obtained at 100°C, 1%, 10% and 50% strain and a frequency of 1 Hz. Tan δ, the ratio of G" to G', was measured for the samples at 10% strain, 100°C and 1 Hz. Lower G" values ​​are considered better.

[0153] The air diffusion test was performed on cured samples having a length of about 150 mm and a thickness of 1.27 mm ± 20%. The test used an air diffusion apparatus designed by Cooper Tire & Rubber Company, Findlay, Ohio, at 3.45 bar (-3.52 kg / cm 2 ) under air pressure and at a temperature of 70°C.

[0154] The results are shown in Table 3. Conventional innerliners for passenger car tires, identified as Refs 1-3, were also evaluated.

[0155] Table 3: Lining results

[0156]

[0157] Table 3: Lining Results (Continued)

[0158]

[0159]

[0160] It can be seen that, in general, Examples A, B, and C are softer materials than the reference sample (conventional liner), as evidenced by the loss modulus G" results.

[0161] Tire testing

[0162] Air diffusion tests were performed on passenger car tires having integral innerliners formed from some of the compositions shown in Table 2. The innerliner had a thickness of 1.2 mm in the uncured state. Passenger car tires labeled Refs 1-3 were also evaluated at the same innerliner thickness. A temperature of 45±2°C for 15 days and a temperature of 21°C±3°C for 60 days were used to measure accelerated air tightness and air diffusion, respectively.

[0163] Rolling resistance is measured according to ISO 28580:2009, "Passenger Car, Truck and Bus Tyres-Methods Of Measuring Rolling Resistance-Single Point Test and Correlation Of Measurement Results". ISO 28580:2009 specifies a method for measuring rolling resistance under controlled laboratory conditions for new pneumatic tires designed primarily for passenger cars, trucks and buses. The test uses passenger car tire test conditions: load 80%, inflation 2.1 SL / 2.5 XL, at 25°C, speed 80 km / hr (tested on 205 / 55R16 tires), after conditioning for 3 hours at test room temperature and 30 minutes of preheating. The results are shown in Table 4.

[0164] Table 4: Tire performance results

[0165]

[0166] As shown in Table 4, the rolling resistance coefficients (<5 kg / t) of tires 4, 5, and 6 with the exemplary innerliners are lower than those of tires 1-3 with conventional innerliners. The rolling resistance gain compared to conventional innerliners is 2-7%, while the air permeability is kept within the range of conventional innerliners. Overall, the exemplary innerliners provide a better compromise between rolling resistance and air permeability.

[0167] Overall, the exemplary innerliner exhibits the benefit of low rolling resistance while maintaining good airtightness of the tire.

[0168] The exemplary liner is strain controlled so that lower G" (loss modulus) results in lower rolling resistance.

[0169] Figure 2 It is shown that Examples A, B and C all fall within the target area of ​​low G" and low air diffusion.

[0170] Other physical tests performed on the liner composition compared favorably with conventional liners and are not included here.

[0171] The soft innerliner disclosed herein provides low rolling resistance and good airtightness in consumer tires.Another advantage is that the use of calcium carbonate and a lower amount of carbon black to form the innerliner of the tire can reduce the overall cost of the innerliner compared to a reference tire.

[0172] Each document mentioned above is incorporated herein by reference.Except in the embodiments or otherwise indicated, all numerical values ​​of the amount of material, reaction conditions, molecular weight, carbon number, etc., specified in this specification should be understood to be modified by the word "about".Unless otherwise stated, each chemical or composition mentioned herein should be interpreted as a commercial grade material, which may contain isomers, by-products, derivatives and other such materials generally understood to be present in the commercial grade.But, unless otherwise stated, the amount of each chemical component stated does not include any solvent or diluent oil that may be conventionally present in commercial materials.It is to be understood that the upper and lower limits, scopes and ratio limits listed herein can be independently combined.Similarly, the scope and amount of each key element of the present invention can be used together with the scope or amount of any other key element.

Claims

1. A rubber composition for an inner liner (30), the rubber composition comprising: 100 phr of an elastomer comprising at least 60 phr of butyl rubber and 0 to 40 phr of diene rubber; 35 to 70 phr of reinforcing filler; and A cure system for curing the elastomer.

2. The rubber composition according to claim 1, wherein the rubber composition comprises at least 65 phr of butyl rubber and / or at most 80 phr of butyl rubber. 3 . The rubber composition according to claim 1 , wherein the rubber composition comprises at least 20 phr of diene-based rubber and / or at most 35 phr of diene-based rubber. 4 . The rubber composition according to claim 1 , wherein the diene-based rubber comprises polyisoprene. 5 . The rubber composition according to claim 1 , wherein the reinforcing filler comprises at least one of calcium carbonate and magnesium carbonate.

6. The rubber composition of claim 1, wherein the reinforcing filler comprises calcium carbonate and rubber reinforcing carbon black in a weight ratio of at least 4:1, or at least 5:1 and / or at most 30:

1.

7. Forming an inner liner by curing the rubber composition of any one of the preceding claims.

8. Linings comprising or formed from the following components: 25 to 35 phr of natural rubber; 65 to 75 phr of halogenated butyl rubber; 45 to 60 phr of calcium carbonate; 2 to 12 phr of carbon black; Optionally, at least one of an oil, a plasticizer, and a tackifying resin; Sulfur-based curing agents; At least 1 phr of zinc oxide; and Curing accelerator.

9. A pneumatic tire comprising the inner liner (30) according to claim 7 or 8.

10. A method of forming an inner liner (30) of a tire (10), the method comprising: forming a mixture comprising: 100 phr of an elastomer comprising at least 60 phr of butyl rubber and up to 40 phr of polyisoprene; 35 to 70 phr of a reinforcing filler comprising calcium carbonate and carbon black; and at least one of zinc oxide and a sulfur-based curing agent; shaping the mixture to form a strip; and The strip is cured to form an inner liner (30) of a tire (10).

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