WO2002036367A1

WO2002036367A1 - Pneumatic tire with cords adhered directly to inner liner

Info

Publication number: WO2002036367A1
Application number: PCT/US2001/045253
Authority: WO
Inventors: Gerald Huber; Victor M. Monroy; Frank P. Papp
Original assignee: Continental Automotive Licensing Corp.
Priority date: 2000-10-31
Filing date: 2001-10-31
Publication date: 2002-05-10
Also published as: WO2002036367A9; AU2002220023A1; WO2002036367A8

Abstract

A pneumatic tire has reinforcement cord (24) adhered directly to, or embedded within, a low air-permeable inner-liner layer (22) which results in a pneumatic tire has a reduced cross-section thickness and/or reduced weight.

Description

PNEUMATIC TIRE WITH CORDS ADHERED DIRECTLY TO INNER LINER

FIELD OF THE INVENTION

This invention relates to a pneumatic tire and a process of making a pneumatic tire. More specifically, the invention relates to a pneumatic tire that includes reinforcement cords and has an inner-liner for prevention of air permeation.

BACKGROUND OF THE INVENTION

Pneumatic tires are constructed using the combination of flexible rubber or rubberlike polymers and high strength reinforcement materials such as known fabrics or cords. A tire is assembled by placing a variety of rubber or polymer sheet layers, reinforcement beads and belt components on a tire drum. The sheet layers, which can be reinforced with fabric or cord, are produced in a calendering operation in which softened rubber or polymer is squeezed between two rollers spaced apart to achieve a desired sheet thickness. The tire components are assembled on the tire drum, starting with the innermost portion of the tire, typically the inner-liner layer, and followed by one or more body-ply layers, reinforcement beads and sidewall layers. This combination of components is generally referred to as a tire carcass. The tire carcass may be further shaped into the toroidal shape of a tire by a known "second stage" forming machine. Then, steel belts and the exterior tread layer are added to form a "green tire" which is then placed in a curing press that vulcanizes or cures the tire into the final tire shape and tread pattern. The inner-liner layer of the tire seals in the air and enables the air pressure to be held constant without the use of an inner tube. The inner-liner layer is made of a rubber or polymer that has low gas-permeability compared to the rubbers or polymers used to make the other sheet layers within the tire. For example, halogenated butyl rubbers have low gas- permeability and are commonly present in compounds that make up the imier-liner layer. The adjacent body-ply layer, supports the sidewall and tread layers and is typically reinforced with fabric or cord. The fabric or cord is totally embedded into the softened body- ply rubber or polymer during the calendering operation. More specifically, a top and a bottom body ply skim encapsulate the cords in a one or two-step calendering operation thereby producing a reinforced body-ply layer, typically in sheet layer form. The inner-liner layer and the body-ply layer are subsequently plied together when they are placed on the tire drum, in sequence with the other tire components. The inner-liner layer and body ply layer are bonded together during vulcanization.

In order for tires to withstand long term static and dynamic stresses, high demands are made on the bonding between the rubber or polymer layers within the tire and also the bonding between the reinforcing cord and the surrounding ply-body rubber or polymer. The inner-liner, which is often made of a butyl rubber, is known by those skilled in the art to have low chemical reactivity and can be difficult to adhere to the body ply during vulcanization. The halobutyl rubbers, which have slightly higher reactivity among the butyl rubbers, are commonly employed for the inner-liner to help overcome the adhesion problems. The reinforcement cord which can be made of polyester, rayon, polyethylene, aramid, polyamide and polyethylene naphthanate, for example, is difficult to adhere to the surrounding body-ply rubber or polymer. In automotive applications, for example, most tire cords are made of polyester because it is characterized by its good combination of tensile strength, flexibility and modulus. However, polyester is relatively chemically inert and is, therefore, difficult to adhere to many rubbers and polymer compositions. Nevertheless, many developments have been made to improve the adhesion between body-plies and tire cords embedded within them. Adhesion promoters have been formulated that are either applied to the cord or compounded in the rubber to improve the adhesion between the cord and the various rubber compounds that make up the body ply.

Another ongoing challenge in the design of pneumatic tires is the reduction of cross- section thickness and weight. An obvious advantage of a reduction in thickness or weight of tire components and tires is the cost savings in the materials used to manufacture the tire. Another advantage of a tire having reduced cross-section or weight is improved rolling resistance resulting in improved vehicle fuel economy. The effect of rolling resistance on fuel efficiency is demonstrated in "Low Rolling Resistance Tire Devices for Electric Vehicles", Giuliana Ghilardi and Alessandro Nolpi, Third International Conference Innovation, and Reliability in Automotive Design and Testing, Firenze, Italy, April 1992, page 878. It is therefore desirable to produce a pneumatic tire having a reduced cross-section thickness and weight and which also possesses excellent adhesion between the reinforcement cords and the surrounding rubber or polymer compositions that contact the surface of the cords. It is further desirable to achieve a process for making pneumatic tires that has a fewer number of processing steps and tire components and, thus, is less labor intensive. SUMMARY OF THE LNNENTION

The present invention provides for a pneumatic tire having reduced cross-section and weight. A thinner cross-section and reduced weight is achieved because a portion of the body-ply layer can be eliminated or the entire body-ply layer can be eliminated. The reinforcement cord, rather than being disposed entirely within the body-ply layer made of a body-ply compound, is at least partially adhered directly to the inner-liner layer made of an inner-liner compound. The inner-liner layer of the present invention is comprised of any known low gas-permeable compound. The coefficient of permeability of the inner-liner compound is lower than the coefficient of permeability of the body-ply layer.

In one embodiment of the invention, the pneumatic tire comprises reinforcement cord that is adhered directly to both a low gas-permeable, inner-liner layer made of a inner-liner compound and a body-ply layer made of a body-ply compound. A portion of the longitudinal surface of the cord is adhered to the inner-liner layer and a portion of the longitudinal surface of the cord is adhered to the body-ply layer. The pneumatic tire also comprises sidewalls, beads, a belt structure and a tread layer. The tire has a reduced cross-section thickness because the reinforcement cord is not fully surrounded by the body-ply, and as such, the tire contains less body-ply compound.

In another embodiment of the invention the pneumatic tire comprises a cord that is adhered directly to the inner-liner layer made of an inner-liner compound such that the surface of the cord adheres to and is surrounded by the inner-liner layer. In this embodiment the inner-liner layer, reinforced with cord, can support the sidewall layers, beads, belts and tread components of the tire. The cord is adhered to the inner-liner layer rather than both the inner-liner layer and the body-ply layer, and thus, the pneumatic tire has a thinner cross- section and reduced weight.

In another embodiment of the invention, the pneumatic tire comprises an adhesion promoter compound. In one embodiment, the adhesion promoter compound is present on the surface of the cord. In another embodiment the adhesion promoter compound is present in the body-ply compound that makes up the body-ply layer, or in the inner-liner compound that makes up the inner-liner layer, or on the cord or combinations thereof.

In another embodiment of the invention, the method of making a pneumatic tire comprises adhering a portion of the reinforcement cord to an inner-liner compound that makes up the inner-liner layer and adhering a portion of the cord to a body-ply compound to produce an inrer-liner/cord/body-ply composite layer. The cord can be adhered to both the inner-liner and body-ply compounds in a one-step calendering operation, for example. In another embodiment, the method of the present invention further comprises applying an adhesion promoter compound to the surface of the cord prior to adhering the cord to the inner-liner and body-ply layers. In another embodiment of the invention the invention further comprises treating the inner-liner compound or the body-ply compound with adhesion promoter compound prior to adhering the cord to the inner-liner and body-ply layers. Alternatively, the cord or the inner-liner compound or the body-ply compound or combinations thereof are treated with adhesion promoter compound prior to adhering the cord to the inner-liner and body-ply layers. Once the inner-liner/cord/body-ply composite layer is cut to size, it is wrapped around the tire drum along with the sidewalls, the beads, the belts and the tread components to form an uncured or "green tire" which is then vulcanized to the final tire shape.

In yet another embodiment of the invention the method comprises adhering the reinforcement cord exclusively to the inner-liner compound to produce an inner- liner/cord/inner-liner composite layer. In another embodiment of the invention the method further comprises applying an adhesion promoter to the cord prior to adhering the cord to the inner-liner compound. In another embodiment the method comprises treating the inner-liner compound with adhesion promoter compound, or additionally, applying an adhesion promoter compound to the cord prior to adhering the cord to the inner-liner compound. The inner-liner/cord/composite layer can likewise be wrapped around the tire drum followed by the addition of the sidewalls, the beads, the belts and the tread components to form an uncured or "green tire" which is then vulcanized to the final tire shape.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a pneumatic tire according to the prior art; FIG. 2 is a cross-sectional view of the inner-liner layer and the body-ply layer of the pneumatic tire of FIG. 1 according to the prior art;

FIG. 3 is a partial cross-sectional view of a tire showing the inner liner and body ply layers according to one embodiment of the present invention; and

FIG. 4 is a partial cross-sectional view of a tire showing the inner-liner layer according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

A typical pneumatic tire construction of the prior art is illustrated in FIG. 1. The construction of the tire from the inside surface to the outermost surface includes a low gas- permeable inner-liner layer 1, a body-ply layer 2, at least one reinforcement cord (not shown in FIG. 1) embedded within the body-ply layer, a second body-ply layer 3, a side-wall layer 4, a bead core 5 having bead reinforcements 6, a belt structure 7 and a tread 8. Typically, a plurality of reinforcement cords run in parallel within the body-ply 2 and between bead reinforcements 6. Depending on the type of cord that is used, the cord may be pretreated with an adhesion promoter so that the cord suitably adheres to the body-ply composition. FIG. 2 is a cross-sectional view of inner-liner layer 1 and body-ply layer 2 of the pneumatic tire shown in FIG. 1 according to the prior art. Body-ply layer 2 having a thickness X can be made in a one-step calendering operation during which top body-ply skim 12 and bottom body-ply skim 14 adhere to and surround reinforcement cord 10. FIG. 2 illustrates cord 10 as being completely embedded within body-ply layer 2 and cord 10 does not come in contact with inner-liner layer 1. Inner-liner layer 1 having a thickness Y is typically produced as separate sheet layer in a separate calendering operation. Inner-liner layer 1 and body-ply layer 2 are placed on a tire drum and adhered to one another during vulcanization. The total thickness T of inner-liner layer 1 and body-ply layer 2 in a vulcanized pneumatic tire used on automobiles, for example, generally ranges from about 66 mils to about 110 mils. In automotive applications, the thickness Y of inner-liner layer 1 generally ranges froni about 30 mils to about 60 mils to effectively maintain the air pressure of the tire for an extended period of time, and the thickness X of body-ply layer 2 generally ranges from about 36 mils to about 50 mils to adequately encapsulate cord 10.

PNEUMATIC TLRE CONSTRUCTIONS

achieved when the cord is adhered directly to the inner-liner layer. As a result, a portion, or all of the body-ply layer made of a body-ply compound can be eliminated.

According to one embodiment of the present invention, FIG. 3 illustrates a cross- section of the inner-liner and body-ply portion 20 of the pneumatic tire in which cord 24 is adhered directly to inner-liner 22 made of inner-liner compound and to body-play layer 26 made of body-ply compound. The cord is adhered to inner-liner layer 22 having thickness Y and body-ply layer 26 having thickness X , which together have a total thickness T . In comparing FIG. 3 to the prior art shown in FIG. 2, the thickness X of body-ply layer 26 is substantially less than the thickness X of body-ply layer 2. As a result of the cord adhering directly to inner-liner layer 22, the total thickness T of the inner-liner and body-ply layers within the tire is substantially less than the thickness T of the layers of conventional tires. A pneumatic tire constructed according to the present invention used in automobiles, for example, can have an inner-liner layer thickness Y that ranges from about 30 mils to about 60 mils. A pneumatic tire herein having the combined inner-liner and body-ply portion 20 and embedded cord 24 has a total cross-sectional thickness T that is from about 85 mils or less, and preferably about 48 mils or less. In addition, the pneumatic tire of the present invention has reinforcement beads, sidewall layers, a belt structure and a tread layer in addition to the combined inner-liner and body-ply portion 20 with the embedded cord.

FIG 4. is a partial cross-sectional view illustrating the inner-liner portion 30 of a pneumatic tire according to another embodiment of the invention. The inner-liner portion 30 of the pneumatic tire comprises cord 24 that is adhered directly to top inner-liner skim 32 and bottom inner-liner skim 34. The total thickness T of inner-liner portion 30 is preferably the same thickness as conventional tires of the prior art, however, where the cord is embedded within the inner-liner layer, a body-ply layer is not needed. Where the body-ply layer is eliminated, the remaining tire components, namely the reinforcement beads, sidewall layers, belt structure and tread layer, can be supported by the inner-liner layer.

The inner-liner layer is distinct from the body ply layer and other tire components in that it is made of a low gas-permeable compound that enables the air pressure within the tire to be held nearly constant over a prolonged period of time. For example, in automotive tires the inner-liner layer has a coefficient of permeability that is typically less than about 14, preferably, less than about 11, and more preferably, less than about 9 at 65 °C as measured in a permeability test in accordance with permeability data disclosed in "Exxon Bromobutyl Rubber Compounding and Applications," Exxon Chemical, Exxon Corporation, April 1993, page 10-3. The body-ply layer, or other rubber or polymers layers in the tire such as the sidewall layer, have a coefficient of permeability of about 20.5 or greater at 65°C as measured by the same test. The inner-liner layer is made up of any known low gas- permeable compounds and can include, but are not limited to, rubber halobutyl polymers, such as, halogenated isoprene-isobutylene copolymer and polychloroprene rubber, epichlorohydrin, and styrene butadiene rubber (SBR). The inner-liner layer preferably comprises from about 50 to about 90 parts per 100 parts of rubber halobutyl polymer of either chlorobutyl or bromobutyl.

A body-ply layer can be made of any rubber or polymer compound known in the art. The body-ply compound can be prepared from mixtures containing as the polymer components, but is not limited to, natural rubber, polybutadiene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, isoprene-butadiene copolymer, synthetic polyiosoprene, isoprene-isobutylene copolymer, ethylene-propylene-diene rubber, ethylenepropylene rubber, ethylene-vinyl acetate rubber, polypropylene or polyethylene and mixtures thereof. However, other polymers known from the related art can also be used. In addition, the body-ply compound usually contains at least one crosslinking substance, such as sulfur, sulfur donors or peroxide, as well as other conventional additives such as filler, vulcanization accelerators, plasticizers, anti-aging agents, coupling agents and processing aids.

The cord can be made of any known polymers including, but not limited to, polyester, rayon, polyethylene, aramid, polyamide and polyethylene naphthanate, for example. Examples of polyesters include, but are not limited to, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene isophthalate (PEI). PET/PEI copolymers, polybutylene napthtalate (PBN), and polyester elastomers.

ADHESION PROMOTER COMPOUND

In another embodiment of the invention the pneumatic tire comprises an adhesion promoter compound. It has been discovered that the use of known adhesion promoter compounds that are applied to the cord or the body-ply layer in order to adhere the cord to body-ply compound, surprisingly, results in excellent adhesion between the cord and the inner-liner layer. Thus, any known adhesive promoter compound that can be used to adhere reinforcement cord to the body-ply layer made of body-ply compound can be used in the present invention. The adhesion promoter compound can be applied to the cord, the inner- liner compound, the body-ply compound or combinations thereof. The reinforcement cord can be treated with the application of one or more adhesion promoter substances of liquid or solution form by dipping, spraying, painting or roller methods, for example. The cord can be treated with an adhesive promoter compound at the time of its production, in which case the cord is said to have an "active finish", or the cord can be treated with one or more adhesion promoter compound in the tire manufacturing plant before it is adhered to the inner-liner and/or the body-ply layers. Alternatively, a treated cord having "active finish" can be further treated one or more additional adhesive promoter compounds in the tire manufacturing plant.

Any adhesive promoter compound that is known to adhere reinforcement cord to the body-ply layer made of body-ply compound can be used Well-known adhesion promoter compounds that have been used to improve the adhesion of reinforcement cord to body-ply layers can be applied to the cord in one or multiple steps. See "Polyester Fiberes", J.E. Mclntyre, Handbook of Fiber Chemistry, 2nd ed., page 59. For example, a well-known adhesion promoter compound contains resorcinol-formaldehyde-latex impregnating solutions (RFL). RFL is traditionally used with cellulosic and nylon tire cords. It is known, however, that polyester, does not generally adhere well to rubbers and polymers if treated only with a standard RFL dip. Hence, two-treatment systems had been developed, for example, a first treatment with blocked isocyanates of the phenyl urethane or aminimide type or resorcinol/p- chlorophenol/formaldehyde precondensate of the Novolak type, and a second treatment with RFL. Furthermore, adhesion promoter compounds that are surface activating systems, for example, epoxy or isocyanate resin precursors that are applied during production of the cord at the fiber producer, can also be used. These cords, having an "active finish," can be further treated with RFL.

As an alternative to treatment of the cord, the inner-liner layer or body-ply layer, or both, can include adhesion promoter compound. The adhesion promoter compound can be compounded into the inner-liner and/or body-ply compounds, or the adhesion promoter compound can be applied directly to the inner-liner layer or body-ply layers by means in which the adhesion promoter compound is applied to reinforcement cord, such as by spraying, brushing, or dipping, for example. The adhesion promoter compound can be compounded into the unvulcanized inner-liner or body-ply compounds in addition to, or in lieu of being applied to the cord. If more than one adhesion promoter compound is used, they may be applied in succession or they may be mixed together in advance and applied jointly in one step. Any adhesive promoter compound that is known to adhere reinforcement cord to the body-ply layer made of body-ply compound can be used. Excellent adhesion between reinforcement cord and the inner-liner layer is achieved, according to the present invention, when the adhesion promoter compound comprises any one or more compounds of the following structures:

X-R^ or X-R^Y^-X where the X moieties in the molecule may be the same or different, and X is selected from the group consisting of:

R² R² R³

Si ^■ R Si ^•R^J and Si R

R³ R³ R³

where R is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl

2 group with 5 to 8 carbons or a phenyl group, where the R moieties in one molecule may be the same or different, and wherein R³ is a branched or unbranched alkoxy group with 1 to 20 carbons, a cycloalkoxy group with 5 to 8 carbons or a phenoxy group, where the R³ moieties in a molecule may be the same or different,

R¹ is a substituted or unsubstituted, optionally unsaturated, optionally cyclic, alkylene group with a total of 1 to 18 carbons, optionally having heteroatoms selected from nitrogen, sulfur, oxygen and phosphorus in the chain, or R¹ may be a substituted or unsubstituted arylene group with a total of 6 to 18 carbons, and the R¹ moieties in a molecule may be the same or different,

Y¹ is selected from the group: -SH, -NH₂, NHR⁴, -NR⁴ ₂,

substituted or unsubstituted,

substituted or unsubstituted, where R⁴ is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R⁴ moieties in a molecule may be the same or different, where Y² is a sulfur chain -S_x- where x=2-8; or a functionalized polymer which has the functionalities Z and is compatible and copolymerizable, covulcanizable or cross-linkable with the unvulcanized inner layer and ply layer, and where the Z functionalities in a molecule may be the same or different and are selected from the group also given for X, as well as -COOH, -SO₂OH, -NH₂, -NHR⁴ and - NR⁴ ₂, these functionalities being in terminal position and/or bound to the main chain and/or side chains, and/or the Z functionalities are epoxy groups, these epoxy groups being incorporated into the main polymer chain and/or side chain and/or being in termmal position and/or bound to the main chain and/or side chains.

In another embodiment of the invention, the pneumatic tire comprises an adhesion promoter compound that comprises 3-aminopropyl triethoxysilane; bis-3- triethoxysilylpropyl-tetrasulfϊde; polybutadiene functionalized with the group

CH,

Si OC₂H₅ with a degree of modification of 1% to 80%, preferably, 15% to 30%; epoxy- terminated acrylonitrile-butadiene copolymer; epoxidized natural rubber with a degree of epoxidation of 1% to 80%, preferably 20% to 50%, or mixtures thereof.

The adhesion between polyester cord and rubber or polymer compounds used in pneumatic tires was tested in Examples 1 through 17 of the Working Examples below, in accordance with the "H-test" set forth in ASTM D 4776. Several "H-bodies" were prepared in which each end of a cord was adhered to a % inch inner-liner layer and a ^lA inch body-ply layer in accordance with FIG. 3 or the cord was adhered to two VΛ inch inner-liner layers in accordance with FIG. 4. The cord was adhered to the layers via vulcanization. Also, "H- bodies" in which the cord was adhered to both the inner-liner layer and the body-ply layer, in accordance with FIG. 3, were made using two different body-ply compounds, body-ply compound A and body-ply compound B which are listed in Tables 2 and 3, respectively. Body-ply compound A and body-ply compound B had substantially the same material ingredients except that body-ply compound B included an adhesion promoter compound, namely, hexamethoxymethyl melamine resin (HMMM).

The force necessary to pull the cord away from the inner-liner or body-ply layers of the "H-bodies" was measured. Although adhesion measurements obtained in an "H-test" are likely to be different than the actual adhesion of reinforcement cord to a finished vulcanized tire, the results obtained can be correlated by those of ordinary skill in the art to aid in determining the adhesive strength in an actual pneumatic tire. For example, pneumatic tires that are used in automotive applications should have an "H-test" measurement of at least 30 Newtons (N), preferably at least 45 N, more preferably at least 60 N and even more preferably, at least 80 N. The results of the "H-tests" listed in Table 4 show that excellent adhesion is achieved between the cord and the inner-liner layer. In one embodiment of the invention the pneumatic tire comprises a cord in which a portion of its longitudinal surface is adhered to the inner-liner layer and a portion of its longitudinal surface is adhered to the body-ply layer, in accordance with FIG. 3 and the cord is treated with an adhesion promoter compound. Optionally, the body-ply layer contains an adhesion promoter compound. In Example 8, cord which was supplied by KoSa of Houston, Texas and cord which was supplied by Honeywell of Morristown, New Jersey, each having been treated with an adhesion promoter compound, also known as "active finish," was found to adhere well to the inner-liner body-ply composite. Surprisingly, there was no RFL or adhesion promoter compound other than the active finish on the cord. In another embodiment of the invention, the cord is treated with two or more adhesive promoter compounds. For example, a reinforcement cord can be treated with "active finish" and also a second adhesion promoter compound. Example 11 shows that good adhesion results were obtained where only the cord was treated with adhesion promoter compound and neither the inner-liner nor the body-ply layers contained adhesion promoter compound. In another embodiment of the invention the pneumatic tire comprises a cord that is adhered to and embedded within the inner-liner layer, in accordance with FIG. 4 and the cord is treated with an adhesion promoter compound, "active finish", and a second adhesive promoter compound. In example 9, polyester cord having an active finish was additionally treated with resorcinol-formaldehyde-latex (RFL) and tested for adhesion. It was previously believed that the cord, treated with known adhesion promoter compounds, would not adhere well to inner-liner compounds, however, it has been discovered, herein, that excellent adhesion can be achieved between the cord and the inner-liner layer when known adhesion promoter compounds are used.

In example 13 adhesion between polyester cord, that was treated with 3-aminopropyl- triethoxy-silane, and inner-liner compound was tested. The treated cord was place between two layers of inner-liner compound and vulcanized. Table 4 shows that the average pull strength was at least 3 IN. In examples 14 through 17 the cord was treated with two adhesive promoter compounds. In each example the cord was first dipped in 3-aminopropyl-triethoxy- silane and was then dried, and then dipped in the following rubber or polymer solutions or blends: an inner-liner compound dissolved in toluene; a solution of toluene and a vulcanizable rubber blend based on epoxidized natural rubber; a solution of toluene and polybutadiene and 3-aminopropyl-triethoxy-silane mixture; and a solution of hexane and bis- 3-triethoxysilylpropyl-tetrasulfide mixture. Table 4 shows that the adhesion results are improved when a second adhesion promoter is applied to a cord that is first treated with 3- aminopropyl-triethoxy-silane.

METHOD OF MAKING A PNEUMATIC TIRE

A further advantage of the present invention is that the method of fabricating a pneumatic tire requires fewer steps. In one embodiment of the present invention, the method of making a pneumatic tire comprises adhering reinforcement cord to an inner-liner compound and to a body-ply compound to produce an inner-liner/cord/body-ply composite layer. Preferably, the longitudinal axis of the cord is partially embedded to in the inner-liner compound and partially embedded in the body-ply compound. The method of the present invention preferably comprises applying an adhesion promoter to at least the cord, the inner- liner compound or the body-ply compound, or combinations thereof, prior to adhering the cord to either of the inner-liner or body-ply compounds. The cord can be adhered to the inner-liner and body-ply compounds in a one-step calendering operation. Once the inner- liner/cord/body-ply composite layer is cut to size, it is wrapped around the tire drum along with the sidewall layer, the beads, the belts and the tread components to form an uncured or "green tire" which is then vulcanized to the final tire shape.

In yet another embodiment of the invention, the method of making a pneumatic tire comprises adhering a reinforcement cord to the an inner-liner compound to produce an inner- liner layer having an embedded cord therein, placing the inner-liner layer with embedded cord, a tread layer, a belt structure, sidwall layers, and beads on a tire drum to produce a green tire, and vulcanizing the green tire to produce a cured pneumatic tire. As with the above embodiments the cord or inner-liner compound or both can be treated with any one or more adhesive promoter compounds described above.

WORKING EXAMPLES In order to more fully and clearly describe the present invention so that those skilled in the art may better understand how to practice the present invention, the following examples are given. These examples are intended to illustrate the invention and should not be construed as limiting the invention disclosed and claimed herein in any manner.

In the following examples 1 through 17, the adhesive strength between polyester cord and various inner-liner and body-ply compounds was tested according to the "H test" set forth in ASTM D 4776. Various adhesion promoter compounds were applied to the cord and to the body-ply compounds, hi each example, both ends of a tire cord that is 6 mm wide and 152 mm long are placed between two VA inch thick sheet layers of various inner-liner and body-ply compound combinations described below, and vulcanized at 177 °C for 14 minutes. The test bodies thus obtained had tire cord sections vulcanized in rubber at both ends and no rubber in the center section of the cord (H form). The force required to pull each polyester cord out of each rubber composite was determined and the results are listed in Table 4 below.

Inner-liner and Body-ply Compounds Tables 1, 2 and 3 list the material ingredients of the inner-liner compound and two different body-ply compounds used to make sheet layers for the adhesion tests. The range amounts of material ingredients are listed in terms of parts per hundred parts of rubber (phr). Body-ply compound A and body-ply compound B have substantially overlapping ingredients, however, body-ply compound B additionally contains an adhesion promoter compound, namely, resorcinol formaldehyde resin (RF), hexamethoxymethyl melamine resin (HMMM) or mixtures thereof.

Table 1

Inner-Liner phr

Halobutyl polymer of either chlorobutyl or bromobutyl 50-90

Natural rubber 10-50

Styrene butadiene copolymer 0-15

Carbon black 20-65

Clay or calcium carbonate 0-60

Softeners of the mineral oil type, either aromatic or naphthenic 4-20

Processing aids of the phenolic or hydrocarbon resin type and fatty acid type 2-14

Activators and curatives, including zinc oxide, stearic acid, accelerators and sulfur 4-9

Table 2

Body-Ply Compound A phr

Natural rubber 50-80

Styrene butadiene copolymer 0-50

Butadiene copolymer 0-50

Carbon black 50-60

Softeners of the mineral oil type, either aromatic or naphthenic 8-23

Processing aids of the phenolic or hydrocarbon resin type and fatty acid type 1-4

Chemical protectant (trimethylquinoline type) 1-4

Activators and curatives, including zinc oxide, stearic acid, accelerators and sulfur 6-9

Table 3

Body-Ply Compound B phr

Natural rubber 50-80

Styrene butadiene copolymer 0-50

Butadiene copolymer 0-50

Carbon black 50-60

Softeners of the mineral oil type, either aromatic or naphthenic 8-23

Chemical protectant (trimethylquinoline type) 1-4

Resin adhesive: resorcinol formaldehyde resin (RF) and/or hexamethoxymethyl melamine resin (HMMM)) 2.5-3.5 Cord Treatment and H-Body Constructions

All cords used are made of polyethylene terephthalate, PET, with a gauge of 1670 dtex and with two folds (type 1670 dtex/2) available from Honeywell of Morristown, New Jersey and KoSa of Houston, Texas.

Examples 1-4:

The adhesion pull tests were conducted using blank, i.e. untreated, polyester tire cord disposed between the following H-body constructions and vulcanized:

Example 1 : inner-liner/inner-liner; Example 2 : body-ply A/body-ply A;

Example 3: inner-liner/body-ply A;

Example 4: inner-liner/body-ply B

Examples 5-8 The adhesion pull tests were conducted using polyester tire cord that was treated with an adhesive promoter compound. Polyester cords treated with adhesive promoter compounds made of proprietary active finishes are available as KoSa's D793 and Allied's 1x53. The H- body constructions used in examples 5 through 8 were of the same arrangement as in examples 1-4, respectively.

Examples 9-12

The adhesion pull tests were conducted using active finish cords in examples 5-8 and which were additionally treated with resorcinol formaldehyde latex (RFL) by dipping the cord in RFL. The H body constructions used in examples 9 through 12 were of the same arrangement as in examples 1-4, respectively.

Example 13

Blank cord was treated with 3-ammopropyl-triethoxy-silane ("silane") in a sealed jar for two hours at 100°C. Next, the excess silane was poured out and the cord was washed three times with water by adding water to the jar and shaking the jar for a time period that ranged from about 1 minute to 24 hours. The wet cord was then dried at room temperature. This cord was placed between two sheets of Compound A (inner-liner) and vulcanized as described below. Example 14

Blank cord was treated with 3-aminopropyl-triethoxy-silane, the same as in Example

13. Compound C (Table 3) was dissolved in toluene to produce a 1:5 by volume Compound

C: toluene solution. The treated (silane) cord was then dipped in the Compound C toluene solution for a short period of 0J to 5 seconds and dried at room temperature. The cord was then placed between two sheets of Compound A (inner-layer) and vulcanized.

Example 15

Blank cord was treated with 3-aminopropyl-triethoxy-silane under the conditions discussed in Example 13 and dried at room temperature. A vulcanizable rubber blend was prepared using epoxidized natural rubber, ENR 50, with a 50% degree of epoxidation (i.e., an average of one out of two monomer building block is epoxidized). The vulcanizable rubber blend was made using: 100 phr ENR 50, 50 phr carbon black, 11 phr oil, 2 phr phenolic resins, 0.075 phr antiaging additive, 3 phr zinc oxide, 0.35 phr stearic acid, 0.92 phr vulcanization accelerator, and 3 phr sulfur. Toluene was added to the rubber blend at a concentration of 100 grams/liter and the ENR 50 rubber/toluene solution was placed in a closed container and shaken for 20 hours at room temperature.

The cord that was treated in silane was dipped in the ENR 50 rubber/toluene solution for a period of 0J to 5 seconds and dried at room temperature. The cord was then placed between two sheets of Compound A (inner-layer) and vulcanized.

Example 16

Blank cord was treated with 3-aminopropyl-triethoxy-silane under the conditions discussed in Example 13 and dried at room temperature.

A 50% by volume solution of toluene and polybutadiene that is 25% functionalized with Si(Me)(OMe)₂ groups was mixed with 3-aminopropyl-triethoxy-silane in a 1:1 by volume polybutadiene and silane mixture. After the mixture was stirred, the mixture was left to stand in a sealed container for at least 20 hours at room temperature.

The cord was then dipped in the silane-polybutadiene mixture for a short period of 0J to 5 seconds and dried at room temperature.

Example 17 Blank cord was treated with 3-aminopropyl-triethoxy-silane under the conditions discussed in Example 13 and dried at room temperature. Bis-3-triethoxysilylpropyl-tetrasulfide (Si69) was mixed with 3-aminopropyl- triethoxy-silane to produce a 1:1 by volume silane-tetrasulfid mixture. Next, hexane was added to the mixture to produce a solution containing 10% by volume hexane. The solution was placed in a sealed container.

The cord was then dipped in the silane-tetrasulfid mixture for a short period of 0J to 5 seconds and dried at room temperature.

Adhesion Pull Tests

Table 4 lists the results of the measured force values of the pull test in Newtons. The force needed to pull the cord out of the rubber was determined at room temperature using an Instron testing device for measuring tensile strength in Newtons. Every value listed is an average of eight measurements taken for eight pull tests samples in which one cord was used to make eight H-bodies. Where two adhesive values are listed, each value represents an average of eight pull tests for each of two cords, treated alike, and each of which was used to make eight H-bodies.

Table 4

All such modifications and variations of the present invention are possible in light of the above teachings. For example, in test bodies where an adhesion promoter compound was present, the adhesion promoter compound was applied only to the cord, however, the adhesive promoter compound could alternatively or additionally be applied to the inner-liner or body-ply compounds. These and other modifications can be made without departing from the spirit and scope of the invention.

Claims

IN THE CLAIMS

WE CLAIM:

L A pneumatic tire having a tread layer, beads and sidewalls, and comprising: an inner-liner layer made of an inner-liner compound; and a reinforcement cord adhered directly to the inner-liner layer.

2. The pneumatic tire of claim 1 wherein the longitudinal surface of the reinforcement cord is fully embedded within the inner-liner layer.

3. The pneumatic tire of claim 1 further comprising: a body-ply layer made of a body-ply compound which is adhered directly to the inner-liner layer and the reinforcement cord.

4. The pneumatic tire of claim 1 further comprising: a body-ply layer made of a body-ply compound and the reinforcement cord is disposed between the body-ply layer and the inner-liner layer, a portion of the longitudinal surface of the reinforcement cord is embedded within the body-ply layer and a portion of the longitudinal surface of the reinforcement cord is embedded within the inner-liner layer.

5. The pneumatic tire of claim 3 wherein the inner-liner compound has a coefficient of permeability that is lower than the coefficient of permeability of the body-ply compound.

6. The pneumatic tire of claim 5 wherein the coefficient of permeability of the inner-liner compound has a maximum of about 9.

7. The pneumatic tire of claim 1 wherein the inner-liner compound comprises halogenated butyl polymer.

8. The pneumatic tire of claim 1 wherein the reinforcement cord is made from a material selected from the group consisting of: of polyester, rayon, polyethylene, aramid, polyamide and polyethylene naphthanate, and blends thereof.

9. The pneumatic tire of claim 3 wherein the body-ply comprises a polymer selected from the group consisting of: natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, isoprene-butadiene copolymer, synthetic polyiosoprene, isoprene-isobutylene copolymer, ethylene-propylene-diene rubber, ethylenepropylene rubber, ethylene- vinyl acetate rubber, polypropylene or polyethylene and mixtures thereof.

10. The pneumatic tire of claim 1 wherein the reinforcement cord or the inner- liner compound, or both, comprise an adhesion promoter compound.

11. The pneumatic tire of claim 10 wherein the reinforcement cord contains an adhesion promoter compound.

12. The pneumatic tire of claim 11 wherein the adhesion promoter compound is selected from the group consisting of: resorcinol-formaldehyde-latex; active finish; a polymer that has the following structure:

X-R^Y¹ or X-R^Y^R^X

where the X moieties in the molecule may be the same or different, and X is selected from the group consisting of:

where R is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R² moieties in one molecule may be the same or different, and wherein R³ is a branched or unbranched alkoxy group with 1 to 20 carbons, a cycloalkoxy group with 5 to 8 carbons or a phenoxy group, where the R³ moieties in a molecule may be the same or different, R¹ is a substituted or unsubstituted, optionally unsaturated, optionally cyclic, alkylene group with a total of 1 to 18 carbons, optionally having heteroatoms selected from nitrogen, sulfur, oxygen and phosphorus in the chain, or R may be a substituted or unsubstituted arylene group with a total of 6 to 18 carbons, and the R¹ moieties in a molecule may be the same or different,

Y¹ is selected from the group: -SH, -NH₂, NHR⁴, -NR⁴ ₂,

substituted or unsubstituted,

substituted or unsubstituted, where R⁴ is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R⁴ moieties in a molecule may be the same or different, where Y is a sulfur chain -S_x-where x=2-8;

a functionalized polymer which has the functionalities Z and is compatible and copolymerizable, covulcanizable or cross-linkable with the unvulcanized inner layer and body-ply layer, and where the Z functionalities in a molecule may be the same or different and are selected from the group also given for X, as well as -COOH, -SO₂OH, -NH₂, -NHR⁴ and -NR⁴ ₂, these functionalities being in terminal position and/or bound to the main chain and/or side chains, and/or the Z functionalities are epoxy groups, these epoxy groups being incorporated into the main polymer chain and/or side chain and/or being in terminal position and/or bound to the main chain and/or side chains; and mixtures thereof.

13. The pneumatic tire of claim 10, wherein the adhesion promoter is selected from the group consisting of: 3-aminopropyl-triethoxy-silane; bis-3-triethoxysilylpropyl- tetrasulfide; polybutadiene functionalized with the group

CH,

Si OC₂H₅

OC₂H₅

with a degree of modification of 1% to 80%; epoxy-terminated acrylonitrile-butadiene copolymer; epoxidized natural rubber with a degree of epoxidation of 1% to 80%; and mixtures thereof.

14. The pneumatic tire of claim 4 wherein the reinforcement cord or the body-ply material or both comprise an adliesive promoter compound and the reinforcement cord is polyester.

15. The pneumatic tire of claim 14 wherein the reinforcement cord comprises an active finish and no other adhesion promoter compound is present on the cord.

16. A pneumatic tire with a tread layer, beads and sidewalls, and comprising: an inner-liner layer made of an inner-liner compound; a body-ply layer made of a body-ply compound; a reinforcement cord adhered to inner-liner layer and body-ply layer; the reinforcement cord is treated with an adhesion promoter compound or the adjacent inner-liner compound or body-ply compound comprises an adhesion promoter compound; and the adhesion promoter compound comprises: a) a polymer that has the following structure: X-R^ or X-R^Y^-X where the X moieties in the molecule may be the same or different, and X is selected from the group consisting of:

R² R² R³

/ / / Si R² Si R³ and Si R³

R³ R³ R³

where R² is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R moieties in one molecule may be the same or different, and where R³ is a branched or unbranched alkoxy group with 1 to 20 carbons, a cycloalkoxy group with 5 to 8 carbons or a phenoxy group, where the R moieties in a molecule may be the same or different,

R¹ is a substituted or unsubstituted, optionally unsaturated, optionally cyclic alkylene group with a total of 1 to 18 carbons, optionally having heteroatoms selected from nitrogen, sulfur, oxygen and phosphorus in the chain, or R¹ may be a substituted or unsubstituted arylene group with a total of 6 to 18 carbons, and the R¹ moieties in a molecule may be the same or different, Y¹ is selected from the group: -SH, -NH₂, NHR⁴, -NR⁴ ₂,

substituted or unsubstituted,

substituted or unsubstituted, where R⁴ is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R⁴ moieties in a molecule may be the same or different, where Y² is a sulfur chain -S_x- where x=2-8; or b) a functionalized polymer which has the functionalities Z and is compatible and copolymerizable, covulcanizable or cross-linkable with the unvulcanized inner layer and body-ply layer, and where the Z functionalities in a molecule may be the same or different and are selected from the group also given for X, as well as -COOH, -SO₂OH, -NH₂, -NHR⁴ and - NR ₂, these functionalities being in terminal position and/or bound to the main chain and/or side chains, and/or the Z functionalities are epoxy groups, these epoxy groups being incorporated into the main polymer chain and or side chain and/or being in terminal position and/or bound to the main chain and/or side chains.

17. The pneumatic tire of claim 16 wherein the inner-liner layer and body-ply layer have a total thickness that is about 48 mils or less.

18. The pneumatic tire of claim 16 wherein the reinforcement cord comprises polyester and the adhesion promoter compound comprises 3-aminopropyl-triethoxy-silane.

19. A method of making a pneumatic tire comprising: adhering a reinforcement cord to an inner-liner layer and a body-ply layer so that the longitudinal axis of the cord is partially embedded in the inner-liner layer and partially embedded in the body-ply layer to produce a inner-liner/body-ply composite layer; assembling the inner-liner/body-ply composite layer, a tread layer, sidewall layers, and beads to produce a "green tire"; and vulcanizing the green tire.

20. The method of claim 19 wherein the reinforcement cord is adhered to the inner-liner compound and the body-ply compound via a calendering operation.

21. The method of claim 19 further comprising: treating the cord or the inner-liner compound or the body-ply compound with an adhesion promoter compound prior to adhering the cord to the inner-liner compound and the body-ply compound.

22. The method of claim 21 wherein the reinforcement cord is treated with an adhesion promoter compound and the adhesion promoter compound is active finish.

23. The method of claim 21 wherein the reinforcement cord is treated with and adhesion promoter compound and the adhesion promoter compound comprises: a) a polymer that has the following structure:

X-R^Y' or X-R^Y^-X where the X moieties in the molecule may be the same or different, and X is selected from the group consisting of:

R² R² R³

/ / / Si R² Si R³ and Si R³

\ ' \ \

R³ R³ R³ where R is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R² moieties in one molecule may be the same or different, and wherein R³ is a branched or unbranched alkoxy group with 1 to 20 carbons, a cycloalkoxy group with 5 to 8 carbons or a phenoxy group, where the R³ moieties in a molecule may be the same or different,

R¹ is a substituted or unsubstituted, optionally unsaturated, optionally cyclic alkylene group with a total of 1 to 18 carbons, optionally having heteroatoms selected from nitrogen, sulfur, oxygen and phosphorus in the chain, or R¹ may be a substituted or unsubstituted arylene group with a total of 6 to 18 carbons, and the R¹ moieties in a molecule may be the same or different,

Y¹ is selected from the group: -SH, -NH₂, NHR⁴, -NR⁴ ₂,

substituted or unsubstituted,

substituted or unsubstituted, where R⁴ is a branched or unbranched alkyl group with 1 to 20 carbons, a cycloalkyl group with 5 to 8 carbons or a phenyl group, where the R⁴ moieties in a molecule may be the same or different, where Y² is a sulfur chain -S_x-where x=2-8; or b) a functionalized polymer which has the functionalities Z and is compatible and copolymerizable, covulcanizable or cross-linkable with the unvulcanized imier layer and ply layer, and where the Z functionalities in a molecule may be the same or different and are selected from the group also given for X, as well as -COOH, -SO₂OH, -NH , -NHR⁴ and - NR ₂, these functionalities being in terminal position and/or bound to the main chain and/or side chains, and/or the Z functionalities are epoxy groups, these epoxy groups being incorporated into the main polymer chain and/or side chain and/or being in terminal position and/or bound to the main chain and/or side chains.

^■ π -