Low rolling resistant inner liner composition

Abstract

To provide an inner liner which improves rolling resistance performance of a tire while maintaining air retention to be satisfied.SOLUTION: There is provided a rubber composition for an inner liner (30). The rubber composition contains 100 phr of an elastomer containing at least 60 phr of a butyl rubber and 0 to 40 phr of a diene-based rubber, 35 to 70 phr of a filler for reinforcement, and a curing system for curing the elastomer. There is provided an inner liner (30) which is composed of 25 to 35 phr of natural rubber, 65 to 75 phr of a halobutyl rubber, 45 to 60 phr of calcium carbonate, 2 to 12 phr of a carbon black, optionally, at least one of oil, a plasticizer and a tackifier resin, a sulfur-based curing agent, at least 1 phr of zinc oxide, and a curing accelerator, or is formed of them.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] Exemplary embodiments relate to a rubber composition suitable for forming an innerliner for a tire, and methods of forming the composition, the innerliner, and the tire. [Background technology]

[0002] The inner surface of a pneumatic tire is typically formed of an elastomeric composition designed to prevent or retard the permeation of air and moisture from the tire's internal air chamber into the carcass. The thin layer of material that defines the inner surface is commonly referred to as the innerliner. Rubbers such as halobutyl rubber and blends of butyl and halobutyl rubbers are relatively impermeable to air and are often used as the main portion of the innerliner.

[0003] Innerliners are generally prepared by calendaring or milling techniques to form strips of uncured compounded rubber of suitable width, sometimes referred to as gum strips. Typically, the gum strip is the first element of the tire that is applied to the tire building drum, over and around which the remainder of the tire is built. When the tire is cured, the innerliner becomes an integral part of the co-cured tire. To improve properties such as air retention, tire innerliners may incorporate various additives. As a result, innerliners have traditionally been relatively stiff.

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

[0005] [Patent Document 1] U.S. Patent No. 8,220,511B2 [Patent Document 2] U.S. Patent Application Publication No. 20110146870A1 [Patent Document 3] U.S. Patent No. 7,506,677B2 [Patent Document 4] U.S. Patent No. 6,765,063B2 [Patent Document 5] U.S. Patent No. 5,587,416A [Patent Document 6] U.S. Patent No. 5,708,069A [Patent Document 7] U.S. Patent No. 9,359,215B2 [Patent Document 8] U.S. Patent Application Publication No. 20020081247A1 [Patent Document 9] U.S. Patent Application Publication No. 20050032965A1 [Non-patent literature]

[0006] [Non-Patent Document 1] The Vanderbilt Rubber Handbook (1978), pp. 344-347 Summary of the Invention [Problem to be solved by the invention]

[0007] To provide an inner liner which improves the rolling resistance performance of a tire while maintaining satisfactory air retention. [Means for solving the problem]

[0008] According to one exemplary embodiment, the rubber composition for the innerliner comprises 100 phr of an elastomer, the elastomer comprising at least 60 phr of butyl rubber and up to 40 phr of a diene-based rubber, the rubber composition further comprising 35 to 70 phr of a reinforcing filler, and a curing system.

[0009] In various aspects of this embodiment: The butyl rubber may be at least 65 phr, or not more than 80 phr, or not more than 75 phr. The butyl rubber may include a halobutyl rubber selected from bromobutyl rubber, chlorobutyl rubber, and mixtures thereof.

[0010] The diene based rubber may be at least 20 phr, or up to 35 phr. The diene based rubber may include at least one polyisoprene, such as natural rubber and / or synthetic polyisoprene.

[0011] In the rubber composition, elastomers other than butyl rubber and polyisoprene are preferably present at not more than 10 phr, or not more than 5 phr.

[0012] The curing system may include at least one of a sulfur-based curing agent and zinc oxide.

[0013] The rubber composition may further include at least one curing aid selected from organic cure activators, cure accelerators, cure retarders, and combinations thereof.

[0014] The reinforcing filler may comprise 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 35-70 phr or 45-60 phr.

[0015] The reinforcing filler may comprise rubber reinforcing carbon black at 1 to 20 phr, or up to 12 phr, or up to 10 phr.

[0016] The reinforcing filler may comprise calcium carbonate and rubber reinforcing carbon black in a weight ratio of at least 4:1, or at least 5:1 and / or up to 30:1.

[0017] The rubber composition may further comprise at least one processing aid selected from oils, plasticizers, tackifier resins, and mixtures thereof.

[0018] In another aspect, an innerliner is formed by curing the rubber composition of any of the above aspects.

[0019] In another aspect, a pneumatic tire includes an innerliner formed by curing the rubber composition of any of the above aspects.

[0020] According to another exemplary embodiment, a method of forming an innerliner for a tire includes forming a mixture including 100 phr of an elastomer including at least 60 phr of butyl rubber and up to 40 phr of a diene based rubber, 35 to 70 phr of a reinforcing filler including calcium carbonate and carbon black, and at least one of a sulfur based curative and zinc oxide. The method further includes shaping the mixture to form a gum strip, and curing the gum strip to form the innerliner for the tire.

[0021] In various aspects of this embodiment: The mixture formed preferably has a Mooney viscosity in the range of 10 to 26 M.U. or 18 to 23 M.U.

[0022] Upon curing, the innerliner preferably becomes an integral part of the tire.

[0023] According to another exemplary embodiment, the innerliner is composed of or formed from 20-35 phr natural rubber, 65-80 phr halobutyl rubber, 45-60 phr calcium carbonate, 2-12 phr carbon black, at least 1 phr zinc oxide, a sulfur-based curative, a cure accelerator, and optionally at least one of an oil, a plasticizer, and a tackifier resin. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view of a passenger vehicle tire according to one embodiment. [Diagram 2] 1 is a graph showing plots of air diffusion vs G″ for innerliner samples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In an exemplary embodiment, a pneumatic rubber tire has an integral innerliner formed from the cured rubber composition. The innerliner has good air retention, as well as low stiffness and hysteresis, which imparts low rolling resistance to the tire. The innerliner's contribution to rolling resistance is strain control with a low loss modulus G", which indicates low rolling resistance.

[0026] Exemplary rubber compositions have a low filler content (e.g., including or consisting of at least one of calcium carbonate and magnesium carbonate, and optionally carbon black). The butyl rubber content of the rubber composition may be relatively high, e.g., at least 60 phr.

[0027] In another aspect of the exemplary embodiment, the rubber composition with lower stiffness and higher butyl levels passes standard air diffusion tests and shows improvement in rolling resistance.

[0028] In the description of this invention, the term "phr" refers to parts by weight of a particular component per 100 parts by weight of uncured rubber contained in the rubber composition. The terms "rubber" and "elastomer" are used interchangeably unless otherwise indicated. The terms "cure" and "vulcanize" are used interchangeably unless otherwise indicated.

[0029] As used herein, unless otherwise indicated, the term "butyl rubber" refers to butyl rubber (a copolymer of isobutylene and isoprene) and also to halobutyl rubbers such as chlorobutyl rubber and bromobutyl rubber (chlorinated and brominated butyl rubber, respectively).

[0030] 1, a pneumatic tire 10 includes a tire tread 12 that defines the tire's contact patch. Two sidewalls 14 and 16 extend from the tread to respective bead areas 18 and 20. Each bead area includes a bead(s) 22 and 24 that may be held in place by respective bead filler apexes 26 and 28. An innerliner 30 defines the innermost surface of the tire and is joined at each end to the respective sidewalls 14 and 16.

[0031] The tire may also include a set of belt plies 32 and carcass plies 36 that are internal to the belt plies. The illustrated carcass ply 36 includes a pair of axially opposed ends 38 and 40, each of which connects to a respective one of the beads 22 and 24. Each axial end 38 and 40 of the carcass ply 36 may be turned and redirected to a position that secures the respective bead. The carcass ply turnups 38 and 40 may engage the axially outer surfaces of the respective flippers 42 and 44 and the axially inner surfaces of the respective chippers 46 and 48. The illustrated tread 10 has circumferential grooves (four in the illustrated embodiment), each groove defining a U-shaped depression in the tread 10. The tread 12, sidewalls, and carcass may be formed of one or more rubber-based compositions. The illustrated tire is suitable, for example, for mounting on the rims of a vehicle, for example a truck or automobile. As will be recognized, the overall structure of tire 10 may differ from that shown in FIG. 1 and may include fewer or more components.

[0032] The present innerliner may be used as a unitary innerliner 30 in a pneumatic tire, as shown in Figure 1. However, it should be recognized that the tire may have a configuration different from that shown. The innerliner is comprised of, on a parts by weight per 100 parts by weight of whole rubber (phr), (A)(1) At least 60 phr of butyl rubber; and (2) Diene rubber up to 40 phr 100 phr of a vulcanizable elastomer comprising (B) 35-70 phr of reinforcing fillers, such as: (1) one or more inorganic fillers, such as calcium carbonate and / or magnesium carbonate, and (2) Carbon black for rubber reinforcement, not exceeding 20 phr and, (C) optionally, one or more processing aids, such as one or more of oils, plasticizers, and tackifier resins; (D) optionally, one or more antidegradants, such as one or more of an antiozonant and an antioxidant; (E) a curing system including at least one of a sulfur-based curing agent and zinc oxide; (F) optionally, one or more curing aids other than zinc oxide, such as one or more of an organic curing activator, a curing accelerator, and a curing retarder; The rubber composition may be formed from a cured rubber composition comprising:

[0033] A: Elastomer 1.Butyl rubber Butyl rubber is a copolymer of isobutylene and isoprene. The butyl rubber may be non-halogenated butyl rubber and / or halobutyl rubber, such as bromobutyl rubber, chlorobutyl rubber, partially polymerized bromobutyl rubber, partially polymerized chlorobutylbutyl rubber, and partially polymerized butyl rubber, and mixtures thereof.

[0034] In one embodiment, the butyl rubber includes bromobutyl rubber. Butyl rubber is the major component of the elastomer in the rubber composition and may be up to 100 phr (i.e., no other elastomers). The butyl rubber may be at least 60 phr, or at least 65 phr, or up to 80 phr, or up to 75 phr, for example 65-75 phr.

[0035] 2. Diene-based elastomers The diene-based elastomer may be selected from at least one polymer of isoprene and 1,3-butadiene, copolymers of styrene and at least one of isoprene and 1,3-butadiene, derivatives thereof, and mixtures thereof. For example, the diene-based elastomer may be selected from polyisoprene, such as natural rubber (mainly cis-1,4-polyisoprene) and synthetic cis-1,4-polyisoprene, methylbutadiene, dimethylbutadiene, pentadiene, and mixtures thereof.

[0036] 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 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 modified synthetic polyisoprene rubber, such as deproteinized, epoxidized, hydrogenated and / or grafted synthetic cis-1,4-polyisoprene, or mixtures thereof.

[0037] The term "natural rubber" as used herein means rubber that is naturally occurring, e.g., that may be harvested from sources, e.g., Hevea rubber trees and non-Hevea sources (e.g., guayule shrubs and dandelions, e.g., TKS). In other words, the term "natural rubber" should be interpreted to exclude synthetic polyisoprene. Natural rubber produced from field-grade coagulum (cup lumps) from Hevea brasiliensis trees is a common form of natural rubber. For example, Technically Graded Block Rubber (TSR) is natural rubber available from Indonesia, which may be referred to as Standard Indonesian Rubber (SIR), Standard Malaysian Rubber (SMR) and Standard Thai Rubber (STR). It is available in several grades, including TSR 10 and TSR 20, with the TSR 10 grade being of higher purity.

[0038] In one embodiment natural rubber comprises the majority (highest phr) of the diene based rubber used in the composition.

[0039] 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.

[0040] 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 diene-based elastomer, such as natural rubber. The diene-based elastomer, such as natural rubber, may be at least 25 phr, or up to 40 phr, or up to 35 phr in the rubber composition.

[0041] Apart from the conjugated diene based elastomers and natural rubber present in the rubber composition, other suitable vulcanizable elastomers that can be used in minor amounts (e.g., less than 10 phr, or up to 5 phr, or up to 2 phr) are 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; terpolymers formed from ethylene monomer, propylene monomer and / or ethylene propylene diene monomer (EPDM);Isoprene-based block copolymers, butadiene-based block copolymers, styrene block copolymers, styrene-butadiene-styrene block copolymers (SBS), styrene-ethylene / butylene-styrene block copolymers (SEBS), styrene-[ethylene-(ethylene / propylene)]-styrene block copolymers (SEEPS), styrene-isoprene-styrene block copolymers (SIS), random styrene copolymers, hydrogenated styrene block copolymers, styrene butadiene copolymers, polyisobutylene, ethylene vinyl acetate (EVA) polymers, polyolefins, amorphous polyolefins, semi-crystalline polyolefins, alpha-polyolefins, reactor-ready polyolefins, acrylates, metallocene-catalyzed polyolefin polymers and elastomers, reactor-made thermoplastic polyolefins elastomers, olefin block copolymers, copolyester block copolymers, polyurethane block copolymers, polyamide block copolymers, thermoplastic polyolefins, thermoplastic vulcanizates, ethylene vinyl acetate copolymers, ethylene n-butyl acrylate copolymers, ethylene methyl acrylate copolymers, neoprene, acrylics, urethanes, poly(acrylates), ethylene acrylic acid copolymers, polyether ether ketones, polyamides, 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-butylene terpolymers; propylene, ethylene, C; 4 ~C 10Copolymers made from alpha-olefin monomers; polypropylene polymers, maleated polyolefins, polyester copolymers, copolyester polymers, ethylene acrylic acid copolymers, and / or polyvinyl acetate, and mixtures thereof, and / or said polymers have functional groups at the polymer chain ends or at pendant positions within the polymer, and / or are modified with functional groups selected from one or more of hydroxyl groups, ethoxy groups, epoxy groups, siloxane groups, amine groups, amine siloxane groups, carboxy groups, phthalocyanine groups, and silane-sulfide groups.

[0042] B Reinforcing filler The rubber composition may contain a total of at least 35 phr of filler, or at least 40 phr, or at least 50 phr, or up to 90 phr, or up to 80 phr, or up to 70 phr, or up to 60 phr, or up to 50 phr of filler. The filler may be selected from inorganic fillers, carbon black, and mixtures thereof.

[0043] (1) Inorganic filler Examples of inorganic 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.

[0044] In one embodiment, the inorganic filler is calcium carbonate (CaCO 3 In one particular embodiment, calcium carbonate is the only inorganic filler used.

[0045] The rubber composition may contain at least 35 phr of calcium carbonate, or at least 40 phr, or at least 45 phr, or up to 70 phr, or up to 65 phr, or up to 60 phr of calcium carbonate.

[0046] In one embodiment, calcium carbonate is present in an amount of 60 parts by weight per 100 parts of filler (phf) or more, such as at least 70 phf, or at least 80 phf, or at least 90 phf, or up to 100 phf, the total amount of filler including all carbon-based fillers and all inorganic fillers present.

[0047] In other embodiments, all or a portion of the calcium carbonate may be replaced with magnesium carbonate.

[0048] In one embodiment, the rubber composition may also contain silica, for example at least 1 phr of silica, or at least 3 phr, or at least 5 phr, or up to 40 phr, or up to 30 phr, or up to 20 phr, or up to 8 phr, or up to 6 phr of silica. In another embodiment, silica may be excluded from the rubber composition or may be present at 1 phr or less.

[0049] Silica can be amorphous (e.g., precipitated) silica and / or crystalline silica. The term "silica" refers to silicon dioxide, SiO 2(which may contain small amounts, generally less than 1 wt.%, of impurities resulting from the process in which the silica is formed). The term "precipitated silica" is used herein to refer to synthetic amorphous silica, typically obtained by a process in which silicates are precipitated with an acidifying agent. Precipitated silica may be prepared, for example, by digesting amorphous silica found in rice husks or other biological waste with sodium hydroxide to form sodium silicate, and precipitating silica from the sodium silicate by reaction with an acidifying agent, for example sulfuric acid or carbon dioxide. Alternatively, silica may be produced from silica gel, for example, by hydrophobating silica hydrogel with organomercaptosilanes and alkylsilanes, and drying the product. Methods for preparing precipitated silica are disclosed, for example, in U.S. Patent Nos. 5,587,416A, 5,708,069A and 9,359,215B2, and U.S. Patent Application Publication Nos. 20020081247A1 and 20050032965A1.

[0050] Silica used as a reinforcing filler must be at least 20m2 in accordance with ASTM D6845-20 "Standard Test Method for Silica, Precipitated, Hydrated-CTAB (Cetyltrimethylammonium Bromide) Surface Area". 2 / g, or at least 120m 2 / g, or at least 140m 2 / g, and / or 500m 2 / g or 400m 2 / g or 300m 2 / g.

[0051] In one embodiment, the silica may be surface treated, for example, with a coupling agent and / or a polyalkylene oxide, such as polyethylene glycol, before incorporating the pretreated silica into the rubber composition. The pretreatment may function to improve the dispersion and / or adhesion of the silica to the elastomer. In another embodiment, the silica may be treated with the coupling agent and / or polyalkylene oxide in situ, within the rubber composition, generally prior to the addition of the curative.

[0052] Representative coupling agents include bis(3-trialkoxysilylpropyl) polysulfides, in which at least two, and optionally all three, of the alkoxy groups are ethoxy groups, the polysulfide bridges having an average of at least two linked sulfur atoms, e.g., up to four, or up to two linked sulfur atoms, and alkoxyorganomercaptosilanes, which may optionally have mercapto moieties blocked with a suitable blocking agent during mixing with the rubber composition. The alkoxy groups may be, for example, ethoxy groups.

[0053] The rubber composition may also contain, for example, at least one of talc, clay and mica, and mixtures thereof, in the range of, for example, about 2 to 25 phr, or up to 5 phr, depending on various physical properties desired in the innerliner composition.

[0054] (2) Carbon black In one embodiment, the rubber composition includes carbon black, for example, at least 1 phr of carbon black, or at least 2 phr, or at least 3 phr, or up to 20 phr, or up to 12 phr, or up to 10 phr of carbon black. In another embodiment, carbon black may be excluded from the rubber composition.

[0055] The carbon black, when present in the rubber composition, may be a single reinforcing carbon black or may include two or more different types of carbon black.

[0056] Carbon black useful in the rubber composition has a surface area of ​​15 mm or less, as determined in accordance with ASTM D6556-21, "Standard Test Method for Carbon Black-Total and External Surface Area by Nitrogen Adsorption." 2 / g~300m 2 / g, or at least 40m 2 Exemplary carbon blacks include the 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 designated by ASTM D1765-21, "Standard Classification System for Carbon Blacks Used in Rubber Products."

[0057] In one embodiment, the carbon black is pretreated prior to forming the rubber composition, for example with silicon. An example silicon treated carbon black is available from Cabot Corporation as CRX™ 2000 ECOBLACK®.

[0058] In one embodiment, the reinforcing filler may comprise or consist of calcium carbonate and carbon black in a weight ratio of calcium carbonate to rubber reinforcing carbon black of at least 4:1, or at least 4.5:1, or at least 5:1 and / or up to 30:1.

[0059] C. Processing aids Processing aids may be used in a total amount of 0 to 10.0 phr in the rubber composition, 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 tackifier resins.

[0060] (1) Processing oil Processing oils are oils used in the non-productive stages of rubber composition formation and aid in composition processing and may also impart beneficial properties to the cured rubber composition. Processing oils are liquid at room temperature (i.e., liquid at 25°C or higher and at atmospheric pressure). Generally, oils and other liquid plasticizers have a Tg below 0°C, generally well below, e.g., below -30°C, or below -40°C, or below -50°C, e.g., between 0°C and -100°C. The Tg of the oil(s) used may be between -40°C and -100°C. The glass transition temperature (Tg) of elastomers or oils is determined according to DIN 53445 "Torsion Pendulum Test, Testing of Polymer Materials" (1986) at a heating rate of 1°C per minute unless otherwise specified.

[0061] The rubber composition may contain at least 0.5 phr, or at least 1 phr, or up to 5 phr, or up to 4 phr, or up to 3 phr, or up to 2 phr of processing oil. In another embodiment, processing oil may be excluded from the rubber composition.

[0062] Exemplary processing oils include petroleum-based, vegetable-based oils, and mixtures thereof. Petroleum-based oils may include aromatic, naphthenic, low polycyclic aromatic (PCA) oils, and mixtures thereof. Vegetable-based oils may include oils and their derivatives, such as triglycerides and esterified alkoxylated polyols, derived from vegetables, nuts, and seeds. Exemplary processing oils may include or consist of blends of vegetable-based triglyceride oils and esterified alkoxylated polyols, which may also be vegetable-based. Other processing oils are also contemplated.

[0063] (2) Plasticizers Examples of plasticizers for the rubber composition include alkylated and aromatic hydrocarbon resins. The rubber composition may include at least 0.2 phr, or at least 0.5 phr, or up to 4 phr, or up to 3 phr, or up to 2 phr of plasticizer. In another embodiment, such plasticizers may be excluded from the rubber composition.

[0064] Exemplary hydrocarbon resins may have a Tg of at least 30° C., or up to 50° C. The Tg of the hydrocarbon resin may be determined by DSC following the procedure described above for measuring the Tg of elastomers. The hydrocarbon resin may have a softening point of at least 70° C., or up to 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 Tg, the lower the softening point.

[0065] Examples of aliphatic resins include C5 fraction homopolymer and copolymer resins. Examples of cycloaliphatic resins include cyclopentadiene ("CPD") homopolymer or copolymer resins, dicyclopentadiene ("DCPD") homopolymer or copolymer resins, and combinations thereof.

[0066] Examples of aromatic resins include aromatic homopolymer resins and aromatic copolymer resins, which refers to a hydrocarbon resin that includes one or more aromatic monomers in combination with one or more other (non-aromatic) monomers, where the majority by weight of all monomers is generally aromatic.

[0067] Specific examples of aromatic resins include coumarone-indene resins, alkyl-phenol resins, and vinyl aromatic homopolymer or copolymer resins. Examples of alkyl-phenol resins include alkylphenol-acetylene resins, such as p-tert-butylphenol-acetylene resins, alkylphenol-formaldehyde resins (e.g., those with low degrees of polymerization). Vinyl aromatic resins may include one or more of the following monomers: alpha-methylstyrene, styrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene, and the like. Examples of vinyl aromatic copolymer resins include vinyl aromatic / terpene copolymer resins (e.g., limonene / styrene copolymer resins), vinyl aromatic / C5 fraction resins (e.g., C5 fraction / styrene copolymer resins), vinyl aromatic / aliphatic copolymer resins (e.g., CPD / styrene copolymer resins, and DCPD / styrene copolymer resins).

[0068] In the case of aromatic resins based on one or more of the vinyl aromatic monomers mentioned above (e.g., styrene, alpha-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.

[0069] (3) Tackifier resin Tackifier resins are added to rubber compounds to help bind the different parts of the tire together until they cure and to provide adhesion between layers of the rubber compound during the processing stage. Tackifier resins are generally solid at room temperature. Examples of tackifier resins that can be used in the rubber composition include non-reactive phenol formaldehyde resins, aromatic modified terpene resins, aromatic modified terpene phenolic resins, and resins prepared by polymerizing 2-methyl-2-butene and piperylene with additional unsaturated hydrocarbons containing 4 to 18 carbon atoms.

[0070] In one embodiment, such a tackifier resin may be absent from the rubber composition, hi another embodiment, the rubber composition may include at least 0.1 phr, or at least 0.2 phr, or up to 2 phr, or up to 1 phr of a tackifier resin.

[0071] (4) Wax Suitable waxes, particularly microcrystalline waxes, may be of the type set forth in The Vanderbilt Rubber Handbook (1978), pages 346 and 347. Exemplary waxes include C 2 , which may be branched or unbranched. 22 ~C 60 saturated hydrocarbons, and mixtures thereof. Waxes, if used, may be present in the rubber composition at 1 to 5 phr. In other embodiments, waxes are not included in the rubber composition.

[0072] In addition to one or more of the above processing aids, the rubber composition may include a peptizer, such as pentachlorothiophenol, dibenzamidodiphenyl disulfide, or mixtures thereof. Typical amounts of peptizers, if used, may be from 0.1 phr to 1 phr.

[0073] D. Antidegradants (antioxidants, antiozonants) In some embodiments, especially when the elastomer comprises natural rubber, the rubber composition may include one or more anti-degradants, such as antiozonants and / or antioxidants. These compounds help protect the tire from oxidation and ozonation. Representative anti-degradants include amine-based antioxidants, such as monophenols, bisphenols, thiobisphenols, polyphenols, polymeric hindered phenols, hydroquinone derivatives, phosphites, phosphate blends, thioesters, naphthylamines, diphenolamines, and other diarylamine derivatives, para-phenylenediamines (PPDs), quinolines, and blended amines. Examples of amine-based antioxidants include diphenyl-p-phenylenediamines, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamines (6PPDs), oligomerized 2,2,4-trimethyl-quinolines (TMQs), and other amine-based antioxidants, 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 included in the rubber composition.

[0074] Examples of antiozonants include physical protection materials, such as waxes. Suitable waxes include paraffin waxes and microcrystalline waxes, which may be of the type described in The Vanderbilt Rubber Handbook (1978), pages 346 and 347. The waxes may be present at 0.1 phr or more, such as at least 0.3 phr, or at least 0.5 phr, or up to 5 phr, or up to 2 phr. In another embodiment, no antiozonants are included in the rubber composition.

[0075] E. Curing system Examples of cure systems can include sulfur-based curatives 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.

[0076] Sulfur based vulcanizing agents may be used in an amount of 0.1 to 10 phr in the rubber composition, 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.

[0077] In other embodiments, for example when polyisoprene is not present in the rubber composition, the sulfur based vulcanizing agent may be omitted.

[0078] Zinc oxide (ZnO), when present, serves as a crosslinking (i.e., curing) agent for the halobutyl rubber while also serving as an activator for the sulfur-based curatives that cure the diene elastomer. Zinc oxide may be present in an amount of at least 1 phr, e.g., at least 2 phr, or at least 3 phr, or up to 10 phr, or up to 8 phr, or up to 7 phr, or up to 5 phr.

[0079] F. Organic cure activators, cure accelerators and cure retarders (1)Organic curing activator Cure activators are additives used to support vulcanization. Cure activators include both inorganic cure activators (such as zinc oxide mentioned above) and organic cure activators.

[0080] Organic cure activators include stearic acid, palmitic acid, lauric acid, mixtures thereof, the zinc salts of each of the foregoing, and thiourea compounds such as thioureas, and dihydrocarbylthioureas, 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-dithiobiurea, guanylthiourea, 1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, and o-tolylthiourea. One commonly used organic cure activator is a blend of stearic acid, palmitic acid, and oleic acid, with stearic acid being the major component of the blend.

[0081] The total amount of organic cure activators, if used, can be from 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 activators are excluded from the rubber composition.

[0082] (2) Curing accelerator The cure accelerator acts as a catalyst for the sulfur-based curing agent. Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanizate. A single accelerator system, i.e., a primary accelerator, may be used in amounts ranging from about 0.5 to 8.0 phr. Alternatively, a combination of two or more accelerators may be used, which may consist of a primary accelerator, generally used in higher amounts (0.3 to 3.0 phr), and a secondary accelerator, generally used in lower amounts (0.05 to 1.0 phr), to activate and improve the properties of the vulcanizate.

[0083] 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'-dithiobis(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).

[0084] Examples of other accelerators that may be used are 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)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, tellurium diethyldithiocarbamate (TDEC), dibenzyldithiocarbamate, Examples of suitable xanthate derivatives include zinc diisononyldithiocarbamate (ZBED), zinc diisononyldithiocarbamate, zinc pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate (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 phosphorodithioate (ZDT / S) and mixtures thereof.

[0085] In some cases, combinations are used with one accelerator acting faster than the other. These accelerator combinations are known to produce a synergistic effect in the final properties, the final properties of which are somewhat better than those produced by either accelerator alone. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures. Disulfides or sulfenamides may be used as primary accelerators.

[0086] The accelerator may be incorporated into the rubber composition at 0.1 to 10 phr, or at least 0.5 phr, or at least 1 phr, or at least 1.5 phr, or up to 8 phr, or up to 7 phr, or up to 6 phr. The amount of accelerator may be selected to provide an acceptable cure time, for example, less than 90 minutes.

[0087] 3) Hardening retarder Cure retarders can be used to control the curing process and generally slow or inhibit curing until a desired time and / or temperature is reached. Examples of cure retarders include cyclohexylthiophthalimide.

[0088] The amount of set retarder, if used, can be at least 0.1 phr, or up to 3 phr, or up to 2 phr. In one embodiment, cure retarders are excluded from the rubber composition.

[0089] Preparation of Rubber Composition The rubber composition may be prepared by mixing the elastomer, inorganic filler and carbon black, as well as other rubber compounding ingredients not including the cure system (sulfur-based vulcanizing agent and / or zinc oxide), under high shear rubber mixing conditions to elevated temperatures in at least one successive mix stage, usually referred to as the "non-productive" mix stage(s), with at least one mechanical mixer, followed by a final "productive" mix stage, in which the cure package, e.g., sulfur-based vulcanizing agent, zinc oxide, and one or more cure accelerators, are added to the mix and mixed at a lower mix temperature to avoid unnecessarily pre-curing the rubber mix during the productive mix stage.

[0090] The ingredients may be mixed in a non-productive mix stage(s) for about 2-3 minutes at a temperature of 130°C to 200°C, for example, about 140°C to 160°C. Two or more non-productive stages may be used in some embodiments. Once the curing package (including the sulfur-based curative (e.g., soluble sulfur), accelerator, and any remaining activators) has been added, the subsequent productive mix step may be carried out at a temperature below the vulcanization (cure) temperature, for example, below 120°C, for example at least 40°C, or at least 60°C, for example, at a temperature of 105-115°C for 2 minutes to avoid undesirable pre-curing of the rubber composition. Mixing may be carried out, for example, in a Banbury mixer or by kneading the ingredients together on a milled roll. The rubber composition may be cooled to a temperature below 40°C between each of the mixing stages. For example, the rubber composition may be dropped from the mixer or sheeted out of an open mill after each mixing step and cooled to below 40°C after each mixing step.

[0091] The resulting mixture may have a Mooney viscosity of 10 to 26 M.U. or 18 to 23 M.U. As used herein, Mooney viscosity (ML1+4) is measured in MU at 100° C. according to ASTM D1646-19a “Standard Test Methods for Rubber—Viscosity, Stress Relaxation, and Pre-Vulcanization Characteristics (Mooney Viscometer).”

[0092] The innerliner rubber composition thus formed is formed into what is commonly referred to as a gum strip. The rubber gum strip may have a thickness ranging from 0.4 to 10 mm, or 0.5 to 5 mm, depending on the type, size and intended use of the tire. The gum strip may be produced by pressing or passing the rubber compound through a mill, calendar, multi-head extruder or other suitable forming means. The uncured gum strip is then constructed as the interior surface (exposed inner surface) of the uncured rubber tire structure, also known as the carcass. The innerliner is then co-cured with the tire carcass under conditions of heat and pressure during the tire curing operation.

[0093] Vulcanization of the tire may be carried out, for example, at a temperature of from 100° C. to 200° C., such as from 110° C. to 180° C. Any of the conventional vulcanization processes may be used, such as heating in a press or mold, heating with superheated steam or hot salt, or heating in a salt bath.

[0094] As a result of this vulcanization, the innerliner becomes an integral part of the tire by being co-cured with the tire. Thus, the innerliner may be initially constructed as a compounded rubber gum strip that defines the interior surface of the uncured rubber tire and then co-cured with the tire during the tire curing operation.

[0095] The pneumatic tire having an integral innerliner may be constructed in the form of a passenger tire, truck tire, or other type of bias or radial construction pneumatic tire. The rubber composition is not limited to use in tires, but may also find application in rubber gloves, surgical instruments, and the like.

[0096] Table 1 shows examples of inner liner rubber compositions.

[0097] [Table 1]

[0098] The following examples illustrate exemplary rubber compositions, innerliners, the preparation of tires including innerliners, and properties thereof, without intending to limit the scope of the exemplary embodiments. EXAMPLES

[0099] Butyl rubber type rubber compositions A to H are prepared using the components shown in Table 2. In the non-productive phase, the natural rubber, halobutyl rubber, calcium carbonate, carbon black (if used), fatty acids and processing aids, if used, are combined in an electric mixer, mixed for 2-3 minutes and then dripped from the mixer at a temperature of about 140° C. In the productive phase, the sulfur, zinc oxide and accelerators are added to the mixture, mixed for about 2 minutes and then dripped from the mixer at a temperature of about 110° C. The mixture is formed into gum strips and cured at 170°C for approximately 23 minutes.

[0100] [Table 2]

[0101] Evaluation of rubber compositions Compound Testing The following tests are performed on the innerliner samples: G' (storage modulus) and G" (loss modulus) are determined in MPa using a rubber process analyzer. Results are obtained at 100°C, 1%, 10% and 50% strain, and a frequency of 1 Hertz. Tan δ, the ratio of G" to G' (G":G'), is determined on samples at 10% strain, 100°C and 1 Hertz. Lower values ​​of G" are considered better.

[0102] Air diffusion testing is performed on cured samples having a length of approximately 150 mm and a thickness of 1.27 mm ± 20%. For the test, an air diffusion device designed by Cooper Tire & Rubber Company, Findlay, Ohio, is used to diaphragm the sample at 3.45 bar (approximately 3.52 kg / cm 2) air pressure and a temperature of 70°C.

[0103] The results are shown in Table 3. Conventional innerliners for passenger vehicle tires, represented by Reference Examples 1-3, are also evaluated.

[0104] [Table 3]

[0105] Examples A, B and C are generally seen to be softer materials than the reference sample (conventional innerliner) as evidenced by the loss modulus G'' results.

[0106] Tire Testing Air diffusion testing is performed on passenger tires having integral innerliners formed from some of the compositions shown in Table 2. The innerliners have a thickness of 1.2 mm in the uncured state. Passenger tires represented in Reference Examples 1-3 are also evaluated with the same innerliner thickness. A temperature of 45±2° C. for 15 days and a temperature of 21±3° C. for 60 days were used for the accelerated air retention and air diffusion measurements, respectively.

[0107] Rolling resistance is determined 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 the methods for measuring rolling resistance under controlled laboratory conditions for new pneumatic tires designed primarily for use in passenger cars, trucks and buses. The test used passenger car tire test conditions at 80% load, inflation 2.1SL / 2.5XL, 25°C, and a speed of 80 km / h after 3 hours of conditioning at test room temperature and 30 minutes of warm-up (tested with 205 / 55R16 tires). The results are shown in Table 4.

[0108] [Table 4]

[0109] As shown in Table 4, tires 4, 5 and 6 with the example innerliners have a lower rolling resistance coefficient (<5 kg / t) than tires 1-3 with conventional innerliners. The increase in rolling resistance over the conventional innerliner is 2-7%, while the air permeability is kept within the range of the conventional innerliner. Overall, the example innerliners provide a better compromise between rolling resistance and air permeability.

[0110] Overall, the example innerliners exhibit the benefits of reduced rolling resistance while maintaining good air retention in the tire.

[0111] The innerliner of the embodiment has controlled strain and a lower G″ (loss modulus), resulting in lower rolling resistance.

[0112] FIG. 2 illustrates that Examples A, B and C are all within the target range for both low G″ and low air diffusion.

[0113] Other physical tests performed on the innerliner compositions which have advantages over those of conventional innerliners are not included here.

[0114] The soft innerliner disclosed herein provides consumer tires with low rolling resistance and good air retention. Another advantage is that calcium carbonate and less carbon black can be used to form the tire innerliner, reducing the overall cost of the innerliner when compared to the reference tire.

[0115] Unless otherwise indicated, each chemical or composition referred to herein should be construed as a commercial grade material that may contain isomers, by-products, derivatives and other such materials that are normally understood to be present in commercial grades. However, the amount of each chemical component does not include any solvent or diluent oil that may be conventionally present in commercial materials unless otherwise indicated. It should be understood that the amounts, upper and lower range limits and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the present invention may be used with the ranges or amounts for any other elements.

Claims

1. A rubber composition for an innerliner (30), comprising: 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; a cure system for curing the elastomer; A rubber composition comprising:

2. 10. The rubber composition of claim 1 comprising at least 65 phr of butyl rubber and / or up to 80 phr of butyl rubber.

3. 10. The rubber composition of claim 1 comprising at least 20 phr of the diene based rubber and / or up to 35 phr of the diene based rubber.

4. The rubber composition of 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. 2. 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 up to 30:

1.

7. An inner liner formed by curing the rubber composition according to any one of claims 1 to 6.

8. 25 to 35 phr of natural rubber; 65 to 75 phr of halobutyl 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 tackifier resin; A sulfur-based curing agent; at least 1 phr of zinc oxide; A curing accelerator; An inner liner consisting of or formed from:

9. A pneumatic tire comprising an innerliner (30) according to claim 7 or 8.

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

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