Patent Application
20120125525
This invention relates to a method of protecting the innerliner of a tire from contamination during manufacture with subsequent application of a foam noise damper to the innerliner surface.
“Carcass” means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
“Innerliner” means the layer or layers of elastomer or other material that form the inside surface of a tire and that contain the inflating fluid within the tire. The “innerliner” of a tube-type tire is often called a “squeegee” to distinguish it from the innerliner of a tubeless tire.
“Pneumatic tire” means a laminated mechanical device of generally toroidal shape (usually an open torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.
“Tread” means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load, i.e., the footprint.
The terms “cure” and “vulcanize” are intended to be interchangeable terms unless otherwise noted.
The terms “green” and “uncured” are intended to be interchangeable unless otherwise noted.
“Virgin surface” means a surface, whether cured or not, that has not been subjected to a cleaning process and that has not come in contact with a release agent.
Government regulations and consumer preferences continue to compel a reduction in the acceptable noise levels produced from the tires of passenger vehicles. One source of road noise is resonance within the air chamber enclosed by the innermost surface of the tire and the rim. One type of effort to reduce tire noise is damping the sound from the air vibration in the air chamber, which efforts have focused mainly on altering the innermost surface of the tire adjacent the tire carcass. In one approach, foam material is disposed as a noise damper in the inner cavity by attaching the foam to the innerliner of the tire, which is effective in reducing noise due to tire cavity resonance at 200 to 300 Hz. However, the attachment of such a foam noise damper to a tire innerliner is problematic.
Carcasses of pneumatic green tires are built as a series of layers of flexible high modulus cords encased in a low modulus rubber. An innerliner is positioned to form the innermost surface of the tire. The green tire is cured in a curing press using a curing bladder, which forces expansion of the tire. During curing, the innerliner expands with the carcass, which is forced against the indentations in the curing mold to form the tread of the tire, and all components are co-cured so as to provide a substantially cohesive bond between one and another.
The innerliner for a pneumatic tubeless tire is typically formed from a compound containing a high proportion by weight of a halobutyl rubber due to its good barrier properties. Before the tire is cured, the entire inner surface of the innerliner and/or the outer surface of the curing bladder are coated with a release agent. The release agent is commonly referred to as a “lining cement” when used on the surface of the innerliner, and as a “bladder lube” or “bladder spray” when used on the curing bladder. The release agent facilitates removal of the curing bladder from the innerliner after curing so that the innerliner is not damaged. The innerliner (or squeegee) for a pneumatic tube-type tire is typically a thin layer of ply coat stock to protect the tube from direct contact with nylon. These innerliners normally do not contain halobutyl rubber since barrier properties are not required.
Thus, prior to bonding a foam noise damper to the cured innerliner, in prior art methods the innerliner must be cleaned to remove contaminants present on the innerliner surface from the molding operation. In particular, the release agent must be removed from the innerliner surface. Solvents have typically been used for this cleaning operation. Solvents effective for removing the release agents contain hazardous air pollutants. These solvents are thus subject to environmental regulations, which have become more stringent in the recent past. It would thus be desirable to eliminate the need for solvent cleaning of the innerliner surface in order to comply with strict environmental regulations. In addition, solvent cleaning is labor intensive and costly due to its hazardous nature, such that significant cost savings may be realized by elimination of the solvent cleaning process. Alternatively, preparation of the innerliner for application of a foam noise damper may involve buffing the innerliner to provide a surface suitable for adhesion, see for example U.S. Pat. No. 7,669,628. However, such buffing may produce dust which is undesirable due to safety considerations.
The present invention is directed to a method for making a tire having a foam noise damper, comprising the steps of: pressing a barrier layer onto an exposed virgin surface of a green tire innerliner to adhere the barrier layer to the virgin surface and thereby form a protected green innerliner; exposing the protected green innerliner to the release agent; curing the protected green innerliner; removing the barrier layer to reveal the virgin surface substantially free of the release agent; applying a foamable liquid to the virgin surface; and foaming the foamable liquid to form a foam noise damper secured to the virgin surface.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.
In accordance with the present invention, the innerliner of a tire is protected from contamination, primarily that occurring from release agents used during the curing process, by adhering a protective barrier layer to the green virgin innerliner surface. In one embodiment, the protective barrier layer is a thermoformable film adapted to stretch with the tire materials during the shaping and curing process. In one embodiment, the protective barrier layer is a thin rubber sheet. In one embodiment, the barrier layer is coated with a pressure-sensitive adhesive (PSA) that is pressed to the green virgin innerliner surface to reliably and releasably adhere the thermoformable film. The optional PSA is particularly effective in preventing movement of the barrier layer during high-pressure spraying of lining cement to the innerliner. In one embodiment, the barrier layer is exclusive of a pressure sensitive adhesive. The invention may be further understood by reference to the Figures.
Like reference numerals are used throughout the several Figures to refer to like components, and like reference numerals are used to refer to components in both the cured and uncured (green) states.
Formation of the tire assembly 10 includes assembling the innerliner 16 in a green state, i.e., an uncured state, adjacent the green tire carcass 12, and adhering the barrier layer 20 to the green virgin surface 28 of green innerliner 16, with optional PSA 22. A green tread strip 13 is assembled adjacent the outermost surface of the tire carcass 12. These layers may be assembled in any desired order. This green tire assembly 10 is then placed into a curing mold (not shown) such that the green tread strip 13 is positioned against the mold surface (not shown), and the barrier layer 20 is furthest from the mold surface so as to form the innermost layer.
In one embodiment, before all components are in place within the mold, a release agent (not shown) is applied to the green innerliner 16 over the barrier layer such that the barrier layer 20 acts as a protective barrier to prevent contact by the release agent to the virgin surface 28. The release agent, which is also referred to as lining cement, is generally applied by a high-pressure spray. Examples of lining cement-type release agent include organopolysiloxane- or silicone-based materials, such as polydimethylsiloxane with powdered mica or crystalline silica. Examples of commercially available lining cements are crystalline silica inside tire lube sold by Kalcor Coating Co. under Product Number 284-TCW, and LYNDCOAT® DV silicone-containing release agent from Rhodia Silicones. In one embodiment, a pressure sensitive adhesive (not shown) is applied between barrier layer 20 and innerliner 16 such that the high-pressure lining cement spray does not displace the barrier layer 20.
In one embodiment, no release agent is used. In this embodiment, a non-stick type of tire cure bladder may be used, for example made from silicone rubber.
After the green assembly 10 with protected innerliner 16 is placed in the mold, an expandable curing bladder (not shown) is then expanded against the protected innerliner 16 to press the green tire assembly 10 into the mold surface to press the green tread strip 13 into a tread pattern formed in the mold surface. A vulcanization temperature is applied in the mold while the tire assembly 10 is subjected to the pressure from the expanded curing bladder for a time sufficient to cure the tire assembly 10. After curing is completed, the curing bladder is deflated and stripped from the innerliner 16 protected by the barrier layer 20. Any loose lining cement may then be vacuumed from the inside of the tire assembly 10, and the barrier layer 20 is removed to reveal a cured virgin surface 28 free of release agent.
One embodiment of a method of the present invention may be described with further reference to
As shown in
In another embodiment of the method of the present invention as seen in
Another embodiment of the present invention is illustrated in
Application of the barrier layer 20 as illustrated in
In another embodiment, the barrier layer may be applied to the innerliner of an already-constructed green tire. In this embodiment, the barrier layer may be manually or automatically placed onto the innerliner of the green tire, after building of the green tire and removal of the green tire from a tire building drum. In this case, the film does not have sufficient stretch or stretch easily with less force.
The virgin innerliner surface will serve as the mounting surface for a foam noise damper. As described earlier, the green tire 110 may be fabricated with the barrier layer 120 applied during tire building as shown in
In one embodiment, the barrier layer is a thermoformable film that separates all or a part of the innerliner surface from the curing bladder surface during the shaping and curing steps to prevent contamination of the virgin surface of the innerliner in the mold. In order to expand with the innerliner during green tire building and curing, the thermoformable film should exhibit the property of necking, which refers to the ability of a material to stretch without returning back to its original shape. The film for application before cure should advantageously exhibit necking in at least one direction, and preferably in both directions, usually referred to as the machine direction (MD) and cross direction (CD). The necking force, in accordance with room temperature testing at a cross-head speed of 20 in./min, is advantageously below about 25 lbf, and more advantageously below about 20 lbf, in at least one direction, and preferably in both directions, for a 1 inch wide strip. Non-oriented films are desirable, though partially oriented films may also be used. Non-oriented films may be characterized by essentially equal necking forces in both the machine and cross directions.
Further, the thermoformable film should exhibit a melting point greater than the curing temperature of the tire assembly, which is generally in the range of about 121° C. (250° F.) to about 200° C. (392° F.). The thermoformable film should further have sufficient strength to be removed from the innerliner in a single piece for ease of manufacture. In an exemplary embodiment, the thermoformable film may be overlapped to form a pull-tab to facilitate easy removal of the film, and the overlapped portion of the film must not fuse together. In one embodiment, the thermoformable film has a thickness less than about 5 mils (127 μm), for example less than about 3 mils (76.2 μm). In another embodiment, the thermoformable film has a thickness greater than about 0.6 mil (15 μm), for example, greater than 0.75 mil (19 μm). Nylon 6 and nylon 6,6 films on the order of 0.75 mil to 2 mils thick may serve as exemplary thermoformable films in the present invention. Exemplary films include: CAPRAN® Nylon, which is a multipurpose nylon 6 film commercially available from Honeywell International; fluorinated ethylenepropylene (FEP) films, such as TEFLON® FEP fluorocarbon film from DuPont Films or A4000 from Airtech International, Inc.; 1-phenyl-3-methyl-5-pryrazolone (PMP) films, such as PMP Release Film from Honeywell; and C917 DARTEK®, which is a nylon 6,6 film available from Exopack Performance Film. Necking force, maximum tensile strength, % elongation and thickness for these exemplary films (1 inch wide) are provided below in Table 1. Exemplary thermoformable films are those that are non-oriented or only partially oriented and exhibit a necking force in both the machine direction and cross direction of less than 20 lbf.
By way of further example, nylon films are particularly useful in the method of the present invention. Examples of nylons which may be formed into film are linear polycondensates of lactams of 6 to 12 carbon atoms and conventional polycondensates of diamines and dicarboxylic acids, e.g. nylon 6; nylon 6,6; nylon 6, 66. In addition, it is possible to use polycondensates of aromatic dicarboxylic acids, e.g., isophthalic acid or terephthalic acid, with diamines, e.g., hexamethylenediamine, or octamethylenediamine, polycarbonates of aliphatic starting materials, e.g., m- and p-xylylenediamines, with adipic acid, suberic acid and sebacic acid, and polycondensates based on alicyclic starting materials, e.g., cyclohexanedicarboxylic acid, cyclohexanediacetic acid, 4,4′-diaminodicyclohexylmethane and 4,4′-diaminodicyclohexylpropane.
In one embodiment, the barrier layer is a easily moldable polyester, such as polybutylene terephthalate (PBT), for example Arnitel® from DSM.
In one embodiment, the barrier layer is a thermoformable film comprising a blend of thermoplastic resin and an elastomer.
As the thermoplastic resin, polyamide resins (for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6/N66), nylon 6/66/610 copolymer (N6/66/610), nylon MXD (MXD6), nylon 6T, nylon 6/6T copolymer, nylon 66/PP copolymer, and nylon 66/PPS copolymer) and N-alkoxyalkylates of these, for example, methoxymethylates of 6-nylon, methoxymethylates of 6-610-nylon, and methoxymethylates of 612-nylon, polyester resins (for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET/PEI copolymers, polyacrylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimid diacid/polybutyrate terephthalate copolymer, and other aromatic polyesters), polynitrile resins (for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile/styrene copolymer (AS), methacrylonitrile/styrene copolymers, methacrylonitrile/styrene/butadiene copolymers, polymethacrylate resins (for example, polymethyl methacrylate (PMMA), polyethyl methacrylate), polyvinyl resins (for example, vinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol/ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), polyvinyl/polyvinylidene chloride copolymer, polyvinylidene chloride/methyl acrylate copolymer, vinylidene chloride/acrylonitrile copolymer), cellulose resins (for example, cellulose acetate, cellulose acetobutyrate), fluororesins (for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene/ethylene copolymer), imide resins (for example, aromatic polyimides (PI)), etc. may be exemplified.
The elastomer component which may be blended with the above thermoplastic resin is not particularly limited. Examples of such an elastomer are as follows: diene rubbers and the hydrogenated products thereof (for example, NR, IR, epoxylated natural rubber, SBR, BR (high cis-BR and low-cis BR), NBR, hydrogenated NBR, hydrogenated SBR), olefin rubbers (for example, ethylene propylene rubber (EPDM, EPM), maleic acid-modified ethylene propylene rubber (M-EPM), IIR, isobutylene and aromatic vinyl or diene monomer copolymers, acryl rubbers (ACM), ionomers), halogenated rubbers (for example, Br-IIR, Cl-IIR, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), CR, chlorohydrin rubber (CHR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubbers (for example, methylvinyl silicone rubber, dimethyl silicone rubber, methylphenylvinyl silicone rubber), sulfur-containing rubber (for example, polysulfide rubber), fluororubber (for example, vinylidene fluoride rubber, fluorine-containing vinylether rubber, tetrafluoroethylene propylene rubber, fluorine-containing silicone rubber, fluorine-containing phosphazen rubber), thermoplastic elastomers (for example, styrene elastomers, olefin elastomers, ester elastomers, urethane elastomers, polyamide elastomers), etc. may be exemplified.
One method for producing the barrier layer comprising a blend of a thermoplastic and elastomer consists of melting and kneading the thermoplastic resin component and elastomer component (in the case of rubber, the unvulcanized rubber) in advance by a biaxial kneader/extruder etc. to disperse the elastomer component in the thermoplastic resin forming the continuous phase. In the case of a dynamically vulcanized alloy (DVA) composition, when vulcanizing the elastomer component, a vulcanization agent is added, while kneading, and the elastomer component is dynamically vulcanized.
Included in the category of a thermoformable film comprising a thermoplastic and an elastomer are dynamically vulcanized alloys (DVA) such as described in U.S. Pat. No. 5,938,869, and non-vulcanized blends of thermoplastic and elastomer such as described in U.S. Publication 2008/0047646.
In one embodiment, the barrier layer is an adherent, removable, inner rubber strip adhered to the innerliner of the tire.
In this embodiment, the barrier layer as a removable, rubber strip is comprised of a rubber admixture of (A) about 50 to about 100, preferably about 60 to about 90, parts by weight butyl rubber and, correspondingly, (B) about 50 to about 0, preferably about 40 to about 10, parts by weight of an ethylene/propylene/nonconjugated diene terpolymer rubber.
It is understood that the rubber strip can also contain conventional rubber compounding ingredients including processing oil, accelerators, conventional sulfur curing agents, pigments, carbon black, zinc oxide, stearic acid, tackifying resin, and plasticizer.
In the practice of this invention, it is required that the said rubber strip is covulcanized with the tire in the sense that the uncured rubber strip is built onto the innerliner as a part of the green, or uncured, tire construction. Thus, in the molding and curing operation for producing the tire, the strip and green tire cure substantially simultaneously.
In one embodiment, the cocured rubber strip barrier layer has a relatively low adhesion to the inside surface of the tire of less than about 10 lbs. per linear inch (1.8 Kg/linear cm), so that it can conveniently be pulled out by hand or by machine, and a tack value in the range of about 10 to about 30 Newtons/inch so that it will adequately adhere, or stick, to the inside surface of the green tire.
The adherent, removable, rubber strip typically has a thickness in the range of about 0.01 to about 0.1 (0.025-0.25), preferably about 0.02 to about 0.08 (0.05-0.2) inches (cm). After the tire containing the rubber strip on its innerliner has been shaped and cured, the co-cured rubber strip as the barrier layer can simply be removed by hand or by manual or automatic device. The rubber sheet can be color-coded with a pigment to contrast with the color of the tire itself so that it can be readily apparent whether it has actually been removed prior to further processing of the tire.
The butyl rubber for the rubber strip utilized in this invention is generally of the type prepared by polymerizing a mixture of isobutylene and isoprene, with the major portion being isobutylene. The butyl rubber typically has an average molecular weight in excess of 200,000, preferably in the range of about 200,000 to about 600,000 and even more preferably in the range of about 200,000 to about 400,000.
The vulcanized rubber tire itself can be of various sulfur curable rubbers such as natural rubber and synthetic rubber and their mixtures or blends. For example, it can be at least one of rubbery butadiene/styrene copolymer, butadiene/acrylonitrile copolymer, cis-1,4 polyisoprene (natural or synthetic), polybutadiene, isoprene/butadiene copolymer, butyl rubber, halogenated butyl rubber, such as chloro or bromobutyl rubber, ethylene/propylene copolymer or ethylene/propylene/diene terpolymer (EPDM). Typically the various polymers are cured or vulcanized by normal sulfur curing methods and recipes.
In particular, although other portions of the tire can be of such rubbers, the inside surface of the tire, to which the rubber strip is covulcanized, is typically and preferably comprised of a butyl-type rubber, natural rubber, or mixture thereof. Such butyl-type rubber can conveniently be selected from at least one of butyl rubber or a halobutyl rubber such as chlorobutyl or bromobutyl rubber.
The vulcanized rubber tire itself can be of various sulfur curable rubbers such as natural rubber and synthetic rubber and their mixtures or blends. For example, it can be at least one of rubbery butadiene/styrene copolymer, butadiene/acrylonitrile copolymer, cis-1,4 polyisoprene (natural or synthetic), polybutadiene, isoprene/butadiene copolymer, butyl rubber, halogenated butyl rubber, such as chloro or bromobutyl rubber, ethylene/propylene copolymer or ethylene/propylene terpolymer (EPDM). Typically the various polymers are cured or vulcanized by normal sulfur curing methods and recipes.
In particular, although other portions of the tire can be of such rubbers, the inside surface of the tire, to which the rubber strip is covulcanized, is typically and preferably comprised of a butyl-type rubber, natural rubber, or mixture thereof. Such butyl-type rubber can conveniently be selected from at least one of butyl rubber or a halobutyl rubber such as chlorobutyl or bromobutyl rubber.
An exemplary recipe for the rubber strip used as a barrier layer is shown in Table 2. The rubber strip, for this example, may be prepared according to the following recipe in which the ingredients of Table 2a are mixed in a Banbury mixer and the resultant mixture mixed on a mill with the ingredients of Table 2b.
1Ethylene/propylene/diene rubber obtained as Nordel 1320, Nordel being a trademark of the DuPont de Nemours, E.I. Co.
2Hydrocarbon derived tackifying resin of the diolefin/olefin copolymer type having a softening point in the range of about 94° C. to about 98° C.
In one embodiment, it may be desirable to include a tackifier in the recipe for the rubber composite strip as a building aid during the building of the green tire itself. In this regard, generally about 2 to about 10 parts by weight of resin tackifier for said EPDM and butyl rubbers is used. Suitable tackifiers include terpene resins and synthetic hydrocarbon-derived resins having a softening point in the range from about 50° to about 110° C.
For example, such resins can be prepared by polymerizing hydrocarbon monomers in the presence of the catalyst such as aluminum chloride or boron trifluoride or boron trifluoride etherate. Such monomers, for example, can be a mixture of diolefin and monoolefin hydrocarbons containing from 4-6 carbon atoms. For example, piperylene can be copolymerized with methyl branched α-olefin containing 5-6 carbon atoms.
The optional PSA (pressure sensitive adhesive) is a rubber-based adhesive that is compatible with the rubber of the innerliner. As is known in the adhesive art, PSA's typically comprise a polymer system, one or more tackifiers, and one or more plasticizers. In the present invention, the polymer system for the PSA is rubber-based so as to be compatible with the rubber of the innerliner. Without being bound by theory, during curing of the tire assembly, the PSA is believed to lose its status as a PSA, due to migration of the tackifier and/or other materials and/or degradation of the PSA at high temperature. When the thermoformable film is removed, all or some of the PSA, or former PSA, may be removed with the film and/or some or all may remain on or as part of the innerliner. Again, without being bound by theory, if the PSA composition is based on a rubber that is compatible with the rubber of the innerliner, then during curing, the degrading PSA may, in whole or part, migrate into the innerliner surface, thereby becoming part of the cured virgin innerliner surface. Alternatively, it may leave a cohesively-bonded surface coating, but that coating is itself an innerliner-type rubber and is free of release agent, thus being essentially the same as the cured virgin innerliner surface. Thus, in one embodiment, the PSA is curable during tire vulcanization to cohesively bond with or become a part of the tire innerliner.
In one embodiment, one side of the barrier layer is coated with a PSA that is pressed to the green virgin innerliner surface to reliably and releasably adhere the barrier layer. In another embodiment, the PSA is applied to the two edges on one side of the barrier layer.
In one embodiment of the present invention, the PSA may be a natural rubber-based, butyl rubber-based, halobutyl rubber-based or polybutadiene rubber-based adhesive, or combination thereof, since these rubbers are commonly used tire materials. By “rubber-based” is meant that the rubber is the principle component of the PSA, i.e., the component present in the greatest quantity. In a further exemplary embodiment, the PSA is a permanent grade hot-melt PSA. An exemplary PSA is commercially available from H.B. Fuller Company, Vadnais Heights, Minn., as a permanent grade, hot-melt PSA under Product Number HL2201X. Another PSA is Product Number G1110 from 3M (formerly Emtech). The PSA adheres the thermoformable film reliably to the innerliner surface, and yet allows the thermoformable film to be removed therefrom after curing the tire assembly.
The PSA may be coated onto the thermoformable film by any desirable method, such as solvent coating or hot melt extrusion coating. A film could also be purchased pre-coated. The PSA-coated film may be adhered by any pressure suitable for the particular type of adhesive. For example, hand pressure may be used to adhere to the PSA to the innerliner, or a roller, such as a 1 inch roller, may be rolled along the surface of the PSA-coated film to adhere the PSA.
The foam noise damper 45 is fixed to the inside of the innerliner radially inward of the tread, as shown in
In one embodiment, an open-cell type foam material, more specifically, polyurethane foam is used.
Depending on the environment where the tire is used, there is a possibility that the air which fills the tire cavity to inflate the tire is humid and the water makes condensation in the closed cavity. Accordingly, foam materials which are hard to be hydrolyzed such as ether based polyurethane are suitably used.
Further, in order to prevent water from penetrating into the noise damper, a water repellent treatment can be preferably made on the foam material. Also, a mildewproof treatment can be preferably made.
Furthermore, in order to avoid poison in the emission gas generated when incinerating scrap tires, it is preferred that raw materials not including halogen are used to make the foam material.
By disposing a certain volume of the foam material in the tire cavity, resonances of the air in the cavity can be controlled and vibrations of the tread portion are reduced. Therefore, noise generated from the tire during running can be reduced. In particular, reduction of noise due to tire cavity resonance measured at a frequency of 200 to 300 Hz is desirable.
The foam noise damper has a specific gravity and dimensions suitable to reduce noise level due to tire cavity resonance at 200 to 300 Hz. In one embodiment, the foam has a specific gravity greater in a range of 0.005 to 0.06 (i.e. density of 0.005 to 0.06 gm/cm3 or 5 to 60 kg/m3). In one embodiment, the foam noise damper has a thickness in the tire radial direction ranging from 10 to 50 mm. In one embodiment, the foam noise damper has a width in the axial tire direction ranging from 30 to 150 mm. In one embodiment, the foam noise damper is disposed circumferentially about the tire.
The foam noise damper 45 is formed and secured to the virgin surface of the tire innerliner by foaming in place a foamable liquid precursor material. By foaming in place, it is meant that the foamable liquid precursor is applied to the virgin surface of the tire innerliner as a liquid, and allowed to foam and cure while in contact with the virgin surface of the tire innerliner.
In so doing, the method avoids prior art methods of applying a pre-made foam to the innerliner with an adhesive or other attachment method.
Precursor foamable liquids capable of forming foams including synthetic resin foams such as ether based polyurethane foam, ester based polyurethane foam, polyethylene foam and the like; rubber foams such as chloroprene rubber foam, ethylene-propylene rubber foam, nitrile rubber foam, silicone rubber foam and the like are suitable. Foamable liquids as known in the art, including various reactive monomers, blowing agents, and curatives, are suitable.
In one embodiment, the foamable liquid is a two-part polyurethane precursor including a polyol/water and an isocyanate. So produced from the foamable liquid, in one embodiment the polyurethane foam of the foam noise damper is produced by the reaction of a long chain polyol compound containing water and an organic polyisocyanate. The final properties of the polyurethane foam will depend principally on the choice of polyethers, polyesters or other long chain polyhydroxyl compounds which are converted by the polyisocyanate into a high molecular weight polymer which is then foamed by a suitable foaming system, usually a reaction of water with the free isocyanate content of the polymer, resulting in the formation of carbon dioxide which expands the resin into the desired cellular foam.
The control of branching in the reactants permits an extremely wide range of properties in the final foam. The density of the foam is controlled to a great extent by the amount of water employed. The configuration of the cell depends principally on the equivalent weight of the long chain polyhydroxyl materials favoring the production of a closed cell structure and the higher equivalent weight polyhydroxyl materials leading to the open-cell structure. The degree of branching of the polyhydroxyl reactant also influences the cell character.
The foamable liquid may be applied to the virgin surface of the tire innerliner various methods as are known in the art, including but not limited to spraying, brushing, rolling, wiping, and the like. In one embodiment, the foamable liquid is applied to the virgin surface of the tire innerliner by spraying.
The foamable liquid may be applied to the virgin surface of the tire innerliner as a freely formed body, i.e., without constraint of a mold, or the foamable liquid may be applied with the use of a removable mold to impart a desired cross-sectional area to the resulting foam noise damper. In one embodiment, a mold in utilized to impart a rectangular cross sectional area to the foam noise damper.
The foamable liquid may be applied in one continuous circumferential motion, to avoid breaks in the foam noise damper. The continuous motion may be achieved for example during spraying by movement of a movable spray head, or by rotation of the tire on a rotating support such as a rotating table or the like.
An advantage to application of the foam noise damper from a foamable liquid is the resulting absence of a splice in the foam noise damper. Such a splice, or overlap, is typically observed in foam noise dampers applied to a tire as prefoamed solid foam. The splice may undesirably provide a source of a separation of the foam from the innerliner during use. In one embodiment, then, the solid foam noise damper is exclusive of a splice.
After the foam is applied, the surface exposed to the air cavity may include a skin that may need to be removed to expose the pores of the foam. Alternatively, the foam may be formed without skin by heating the top surface during foam formation.
The invention is further illustrated by the following non-limiting example.
In this example, the application of a foamable liquid to a rubber substrate is illustrated. A polyurethane-type foam forming spray was used (VFI 7130 from Volatile Free Inc., Brookfield, Wis.). Two components for polyurethane were mix sprayed using compressed air to form open cell foam approximate thickness ⅝ inch to the virgin surface of a sheet of cured rubber. After the application, 1″ diameter cylinder was cut out and the foam was pulled from the rubber. The foam was not separated from rubber (foam broke) thus indicating that adhesion is very good without the need of a PSA layer.
While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.
