JPH073038A - Method for achieving improved bonding strength of unvulcanized rubber to vulcanized rubber - Google Patents

Abstract

PURPOSE:To achieve an improved bonding strength between an unvulcanized rubber component and an at least partially vulcanized rubber component. CONSTITUTION:This method for improving the bonding strength is to select two unvulcanized rubber components for producing an unvulcanized rubber article, treat either of the components under conditions for achieving a lower cross-linking density gradient than the cross-linking concentration in the surface, apply the other rubber component to the surface and simultaneously vulcanize the respective components. In this method, at least either of both the components contains a cross-linking agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention provides a method for improving or achieving good bond strength between layers of vulcanized rubber or partially vulcanized rubber and unvulcanized rubber, or between laminates. One application of the method is that of a rubber article having a plurality of laminates, one layer being vulcanized, ie pre-cured, and the other being unvulcanized with at least two adjacent layers. Manufacturing.

Several manufacturing processes, including the processing of tires, require or will benefit from the assembly of pre-cured and uncured rubber components and subsequent co-vulcanization. For example, in tire tread recycling, in some cases a pre-cured tread is applied over a buffed used carcass with the aid of a thin uncured rubber layer. Radiation precuring of certain tire components has also become a well accepted commercial processing technique for matching precured and uncured rubber components.

[0003]

BACKGROUND OF THE INVENTION Tires, conveyor belts, and reinforced high pressure hoses are typical but few examples of articles to which hardened and uncured components may be applied adjacently. In general,
The manufacture of these articles involves the assembly of multiple layers of well-mixed rubber that have been reinforced with carbon black or the like. A more specific example tire includes components such as beads, sidewalls, carcasses, treads and belts. In some cases it may be desirable to cure one or more of these individual components ex situ, prior to tire building and vulcanization. The advantage of pre-curing is that it imparts integrity to the components of the rubber substrate to resist distortion during subsequent building and assembly operations, thus providing a more accurate alignment of components, greater accuracy during construction and at the end of assembly. , And to provide an improved tire. Also, because the base components of the beads and tread are not constant in thickness, some of these structural components can be pre-cured to reduce the curing time of the final product. In addition, the ability to bond the base components of the cured rubber and the uncured rubber is a tire that uses one or more "standard" components or elements that can bind various elements such as treads. Would allow the manufacture of various articles such as

Therefore, it has been desired to partially or completely pre-cure or vulcanize certain components before assembling the whole to produce the final product. Unfortunately, however, one of them was vulcanized and the bonding interface between adjacent components where one was not vulcanized was unacceptable. One approach to improving adhesion required mechanical buffing of the surface of the vulcanized rubber component, which is an extra step and cannot always be used.

The major obstacles to the wider application of this technology of using pre-cured components with uncured components are:
It was a decrease in the adhesive force between the pre-cured component and the uncured component observed after the simultaneous vulcanization. The art was intended to provide for the development or improvement of the bond between adjacent rubber layers, but was not always successful when the layers were cured and uncured.

US Pat. No. 1,274,091, for example, comprises a sheet of washed and dried uncured rubber, one of which is broken when passing through a roll and which contains a vulcanizing agent, while the other contains Disclosed is a vulcanized rubber composite sheet that is neither destroyed nor contains a vulcanizing agent. The two uncured sheets are finally simultaneously vulcanized.

US Pat. No. 1,402,872 discloses a method of intercalating a layer of rubber that does not contain sulfur therein and then co-vulcanizing this multilayer body to coalesce the body of vulcanizable rubber. Are offered.

US Pat. No. 1,434,892 combines one layer containing sulfur with a second layer containing accelerator,
Thereafter, a method is provided for simultaneously vulcanizing this multilayer sheet to form a rubber sheet.

US Pat. No. 1,478,576 is directed to sheet rubber patch materials for repairing intumescent rubber articles. This material comprises a composite including a rubber layer containing a non-migratory accelerator and a rubber layer containing sulfur.

Other US patents suggesting simultaneous vulcanization of uncured rubber sheets, each containing a different vulcanizing agent and / or different amounts, include US Pat. Nos. 1,537,865, 1,5.
37,866, 1,569,662, 1,777,960,
And No. 2,206,441.

While others have co-vulcanized rubber sheets containing various vulcanizing agents in various amounts, the art has
It does not provide a way to obtain good adhesion between adjacent rubber articles or rubber components, one of which is vulcanized and the other of which is unvulcanized. More specifically, the art has hitherto not recognized the presence of a graded crosslink density at the interface between the cured and uncured rubbers, and therefore
It was not possible to provide good adhesion between them.

The use of radiation to cause the partial cure of at least some of the tire components other than the tread, and the subsequent normal cure of the tire is described in US Pat. No. 4,16.
No. 6,883, and 4,221,253 and 4,851,063, which are each divided. These prior patents do not suggest the use of the interphase layer according to the invention.

[0013]

DISCLOSURE OF THE INVENTION Accordingly, sheets of rubber or other rubber-based components, one of which is at least partially vulcanized and the other of which is unvulcanized, are bonded together and covulcanized, It is an aim of the present invention to provide a method of improving the bond strength in between.

It is another object of the present invention to provide a method of bonding the components of a rubber or other rubber substrate to one another, including the use of an interphase layer, to improve the bond strength therebetween.

Providing a method for bonding sheets of rubber or other rubber-based component to one another, which involves the use of an interphase layer that is free of cross-linking agents such as sulfur, sulfur donors, peroxides and the like, It is another goal of the invention.

A method is provided for bonding sheets of rubber or other rubber-based components, one of which is at least partially vulcanized and has a gradient of crosslink density, the other being unvulcanized. That is another goal of the present invention.

Mechanical buffing of the vulcanized rubber, one of which is at least partially vulcanized, the other of which is used to bond the sheet to the unvulcanized rubber or other rubber-based component. It is another aim of the present invention to provide a process-free method.

It is another object of the present invention to provide a method for bonding sheets of rubber or other rubber-based component to each other, including the use of at least one chemical cure inhibitor.

It is another goal of the present invention to provide a method of bonding sheets of rubber or other rubber-based component to each other, including the use of radiation to provide a crosslink density gradient.

At least one or more of the above objectives, as well as advantages over known methods which will become apparent from the specification below, are described and claimed herein below. Achieved by the invention.

The present invention generally selects two initially unvulcanized rubber components, the improvement of which is for the production of vulcanized rubber articles; one of the above components having a higher crosslinking concentration at the surface. Treated under conditions that achieve a low crosslink density gradient to adhere to the other components; apply the other rubber component to the surface under conditions where at least one of the above components contains a crosslinking agent; Providing an improved method for achieving improved bond strength between both unvulcanized rubber and at least partially vulcanized rubber, including the steps of co-vulcanizing both components of To do.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 to 3 diagrammatically show the simultaneous vulcanization of two rubber base components, one of which has been prevulcanized, as described in the prior art.

FIG. 4 is a sectional view of one layer of the unvulcanized rubber base material component.

FIG. 5 shows that both were subjected to prevulcanization, FIG.
FIG. 3 is a cross-sectional view of the components shown in FIG. 1 and the interphase layer applied thereon according to the present invention.

FIG. 6 is a cross-sectional view of the layer shown in FIG. 5, in which a second unvulcanized layer of a rubber base material is applied to the above-mentioned interphase layer, and finally this is simultaneously vulcanized. is there.

FIG. 7 is a cross-sectional view of one layer of an unvulcanized rubber substrate component having an interphase layer applied thereon, both subject to radiation curing according to another method described in this invention.

FIG. 8 is a cross-sectional view of the layer shown in FIG. 7, in which a second unvulcanized layer of the rubber base material is applied to the above-mentioned interphase layer and this is finally covulcanized. is there.

FIG. 9 is a cross-sectional view of one layer of a rubber substrate component having a chemical cure inhibitor applied on its surface according to the method of the present invention.

FIG. 10 is a cross-sectional view of the layer shown in FIG. 9 in which a second unvulcanized layer of the rubber substrate component was applied to the surface-treated layer and this was finally covulcanized. is there.

FIGS. 11 to 13 are the same as those shown in FIGS.
1 schematically illustrates simultaneous vulcanization of various rubber substrate components and an interphase.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the practice of the present invention is directed to achieving improved bond strength of rubber, vulcanizates of the same or different chemical composition, and in dissimilar states. Allows for easy coupling. The method is useful in the manufacture of rubber products from component laminates or equivalents where it is desirable or necessary to combine one unvulcanized component with another that is at least partially vulcanized. is there.

Vulcanization involves the crosslinking of the rubber molecules in the composition at a concentration of crosslink density which governs the physical properties of the vulcanizate. Partial vulcanization means that the components are partially crosslinked and can be sufficiently crosslinked to the desired level to achieve full vulcanization. Partial vulcanization is useful when the fabric strength is too low and will provide enhanced physical properties to withstand subsequent manufacturing operations.
Also, thicker rubber substrate components such as bead areas or tread foundations for tire building can be partially vulcanized to reduce the final cure time of the fully assembled product. Partial vulcanization is also useful when a particular rubber-based component is selected from a number of different components of this type and can be further mixed with "standard" components to assemble the final product. For example, in the manufacture of tires, standard carcasses could be constructed and prevulcanized for the construction of various tires with different performance characteristics. Replacing the tread base will allow the production of different tires with the same standard carcass.

Since the rubber is in any case pre-vulcanized, the problem that arises during the subsequent simultaneous vulcanization of the components is that the at least partially vulcanized component is over-crosslinked at the interface. That is, when the vulcanization is completed, good bonding does not occur at the interface, and the rubber actually becomes brittle at the interface.

The method according to the invention solves these problems and gives good bond strength at the rubber layer or at the interface of the rubber components. The method provides the vulcanized component with a crosslink density gradient that results in a lower degree of cure at the surface that will bond with an adjacent layer of unvulcanized rubber component during final covulcanization of the two components. By doing this,

In one embodiment of the present invention, a thin layer of rubber material, referred to herein as the interphase layer, is combined with a layer or component of unvulcanized rubber and a layer or component of rubber that is at least partially vulcanized. Apply between and. This interphase layer is first applied to the unvulcanized rubber base component and both are subjected to prevulcanization. In another aspect of the invention, the unvulcanized rubber substrate component is subjected to radiation curing under conditions that produce a crosslink density gradient. Means of this type include, for example, high-energy electron beams, and are useful because the crosslink density can be changed depending on the thickness of the component.

In a third aspect of the invention, a cure inhibitor is first applied to one surface of the rubber substrate component to be at least partially crosslinked to produce the desired crosslink density gradient. This inhibitor is applied to the unvulcanized rubber component,
It may then be subjected to sufficient curing conditions to provide at least partial crosslinking, but only slight curing occurs at the surface and curing proceeds within the thick component. Alternatively, the inhibitor can be applied to the surface of the rubber component, followed by prevulcanization. In each case, when subsequently contacting the second unvulcanized rubber substrate component with the surface of the previously treated first component, simultaneous co-addition as a result of the crosslink density gradient provided by the cure inhibitor. A good bond develops between the two components during sulfurization.

For compatibility, the composition of the interphase layer is preferably substantially the same as the composition of the first rubber substrate component. The interphase layer composition should also be compatible with the composition of the second rubber substrate component. Preferably, this will include a mixture of the two rubbers used in the first rubber substrate component and the second rubber substrate component. The interphase layer is preferably miscible without the use of any cross-linking agents such as sulfur, sulfur donors, peroxides, etc., but the accelerator is optionally about 0.1 to 4 parts per 100 parts of rubber unless it is elemental sulfur. (Ph
There is an amount in the range r). Although any of the conventional rubber accelerators such as thiuram, thiazole, dithiocarbamic acid ester, sulfenamide and guanidine can be used, these accelerators are merely illustrative and practice of the invention does not It is understood that the accelerator is also not necessarily limited, and its presence is optional.

Rubbers that can be mixed according to the present invention include natural rubbers and synthetic rubbers. Synthetic rubbers are well known and include ethylene / propylene copolymers, ethylene / propylene / diene terpolymers, halogenated rubbers, copolymers of conjugated dienes with at least one monoolefin, and conjugated diene homopolymers. And mixtures of these with or without natural rubber. Natural rubber / synthetic rubber mixtures containing about 5 to 95 parts by weight of natural rubber can also be used.

Examples of suitable halogenated polymers include chloroprene, (2-chloro-1,3-butadiene or neoprene), chlorosulfonated polyethylene, chlorobutyl rubber and bromobutyl rubber. Neoprene generally falls into the G-, W- and T-type categories, all well known to those skilled in the art.

The above copolymers are conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene- (isoprene), 2,3-dimethyl-1,3-butadiene, 1,2.
-Pentadiene, 1,3-hexadiene, etc., as well as mixtures of the above dienes. The preferred conjugated diene is 1,3-butadiene. With respect to monoolefinic monomers, this includes vinyl aromatic monomers having 8 to about 20 carbon atoms, such as styrene, α-methylstyrene, vinylnaphthalene, vinylpyridine, etc., and optionally 1 With one or more halogen substituents; alkyl acrylates or alkyl methacrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, etc .; unsaturated nitriles, such as acrylonitrile, Included are methacrylonitrile and the like; vinyl halides such as vinyl chloride, vinylidene chloride and the like; and aliphatic monoolefins such as isobutene; and mixtures of the above monoolefins. The copolymer can contain up to 50 weight percent monoolefin, based on the total weight of the copolymer. Preferred copolymers are styrene-butadiene rubber (SBR), conjugated dienes, especially copolymers of butadiene and vinyl aromatic hydrocarbons, especially styrene.

Copolymers of the above conjugated dienes and methods for making them are well known in the rubber and polymer arts. Many polymers and copolymers are commercially available.
It should be understood that the practice of the present invention is not limited to any particular rubber, including those mentioned above or excluded. This rubber should be useful as a tire component, although rubber compositions for other rubber products can be selected.

Include the same rubber, eg natural rubber, in natural rubber, or SBR in SBR, or a different rubber, eg natural rubber in SBR, either of which is unvulcanized at the time of final covulcanization. It is possible to mix and combine the components, which may be sulfur. According to one embodiment of the present invention, a thin interphase layer is used when one of the rubber components should be at least partially vulcanized prior to contact with the second rubber substrate component. This layer is substantially free of cross-linking agents other than the use of an accelerating agent, so this layer does not contain sulfur and, in some cases, accelerating agents in adjacent rubber components (previously unvulcanized). Accept from diffusion) In this manner a crosslink density gradient is achieved, as discussed below in connection with the drawings. Subsequently, if the at least partially vulcanized component is combined with the other unvulcanized rubber base component, it will not be combined with the at least partially vulcanized rubber base component as before. Much greater bond strength occurs than when co-vulcanized with the vulcanizing components without the interphase layer.

As noted above, the interphase layer containing no crosslinker is preferably composed of the same rubber as the two rubber base components, with a certain amount of accelerator optionally present. The interphase layer may also include a block copolymer that is compatible with the two rubber base components or another compatible polymer. Generally, the composition and thickness of the interphase layer can be optimized for intercalation between the two rubber substrate components. However, thicknesses of at least 0.010 inches to about 0.080 inches are considered practical, although other thicknesses are not necessarily excluded.

The preferred method of practicing the present invention is to prevulcanize one unvulcanized rubber substrate component and the interphase layer together, followed by a second unvulcanized rubber substrate component and prevulcanized rubber. The product is brought into contact with the interphase layer of the product and subjected to simultaneous vulcanization.
Pre-vulcanization of the interphase layer with the first rubber substrate component causes or causes the development of physical properties up to some of the optimum conditions reached during complete vulcanization. For sufficient time and temperature. This part is usually in the range of 10% to 100% or less of the optimum condition, but is not limited to this range.

Curing conditions will vary depending on the composition of the rubber, its thickness and degree of vulcanization, as well as pre- and post-treatments, and therefore the purpose of specifying the range of these types of conditions is no matter what. It should also be understood that this would not be useful, nor is there any particular need for this kind. This is also true when the preferred method uses irradiation, as discussed below.

The interphase layer is not necessary if the use of inhibitors such as set retarders or set deactivators is desired.
Alternatively, a cure inhibitor is applied to the surface of the rubber substrate component that is or is at least partially vulcanized. Typical cure retarders are well known to those skilled in the art, for example salicylic acid, phthalic anhydride, benzoic acid, N- (cyclohexylthio) phthalimide, N-nitrosodiphenylamine, and others known to those skilled in the art. Things are included. Typical cure deactivators include mineral acids.
One method of surface coating is to form a solution of the inhibitor in a solvent that can be subsequently applied to the rubber substrate component by any suitable technique including, but not limited to, dipping, spraying, roller coating, etc. It is to let. Implementation of the present invention
It should be understood that the invention is not limited to any of the specific cure inhibitors disclosed herein, nor to the method of application. Similarly, the amount used is not limited, but an amount of about 0.1 to about 10 phr may be effective.

FIGS. 1 to 3 show one of two rubber components, one pre-vulcanized, one unvulcanized and subsequently co-vulcanized together according to the prior art. Figure 3 schematically shows a cross-linking agent and the concentration profile of the cross-links formed therein. In FIG. 1, component 10 is pre-vulcanized and component 12 is unvulcanized. Component 12 has an accelerator concentration 13 and a sulfur concentration 14. Component 10 has been prevulcanized with sulfur and an accelerator,
It has a crosslink density of 15. During the simultaneous vulcanization shown in FIG. 2, from component 12 to sulfur and accelerator 10 (region 1
6) diffuses in and contributes to the subsequent cross-linking of that region. As shown in FIG. 3, after simultaneous vulcanization, the crosslink density 19 of component 12 is lower near the interface 17 between the two components. In contrast, the presence of new crosslinks (region 18) formed in component 10 during co-vulcanization, in addition to the crosslink density 15 formed during prevulcanization, results in a crosslink density near the interface of component 10. It is a cause of increasing 19 significantly. This region of overvulcanization and brittleness 20 is responsible for the loss of adhesion and possibly the premature failure of articles containing components 10 and 12.

Implementations of the three embodiments of the present invention are illustrated in FIGS. 4-10. In FIG. 4, a layer 10 of unvulcanized rubber substrate components is shown, which is shown diagrammatically. In FIG. 5, component 10 is applied to the interphase layer 11. First these two layers were vulcanized, followed by the unvulcanized layer
Apply 12. In FIG. 6, the three layers are covulcanized together to form the product 21. In FIG. 7, the layer 10 of the unvulcanized rubber base material component shown schematically is also the interphase layer 1.
1, both of which are first subjected to irradiation through suitable means 22 to produce a crosslink concentration gradient, followed by a second application of the unvulcanized rubber matrix component 12. . The interphase layer 11 is optionally one or more radiation blocking agents, such as 2-naphthylamine; 6-phenyl-
2,2,4-trimethyl-1,2-dihydroquinone and N,
N'-Dioctyl-p-phenylenediamine may be included in effective amounts known to those skilled in the art. This amount ranges, for example, from about 0.1 phr to about 10 phr. In Figure 8, two layers were simultaneously vulcanized together to produce product 2
5 is formed.

An implementation of the third aspect is shown in FIGS. 9 and 10. The first layer of unvulcanized rubber substrate component 10 is treated by means 30 of applying a coating of cure inhibitor 31 to surface 32 of component 10. Component 10 is then prevulcanized to an extent sufficient to cause at least partial vulcanization. A second unvulcanized layer 12 of rubber component is then applied to the above surface 32 and the two components are covulcanized together as shown in FIG. 9 to form the product 35.

11 to 13 show the concentration profile of the crosslinker and the crosslinks formed in the rubber component obtained by carrying out the process according to the invention described in connection with FIGS. 4 to 6. FIG. 11 also shows two rubber component layers 10 and 12 having a crosslinker-free interphase layer 11 inserted therebetween prior to simultaneous vulcanization.
Component 12 has an accelerator concentration 13 and a sulfur concentration 14. It will be noted that although component 10 has been pre-vulcanized with interphase layer 11, its crosslink density 40 has decreased at the interface 41 between the two layers and continues to decrease through interphase layer 11. Therefore, a diffusion density gradient across the layer 11 is achieved due to the diffusion of sulfur and accelerator during prevulcanization, giving the surface 43 a low crosslinking density. In FIG. 12, the two components 10 and 12 are co-vulcanized, but the sulfur from component 12 and the accelerator are diffused into the interphase layer 11 and into component 10 (region 45), whereupon It will be noted that it contributes to the crosslinking. In FIG. 13, the crosslinks 40 formed during prevulcanization, along with crosslinks formed as a result of the diffusion of sulfur that occurs during covulcanization (region 47), together with a more average crosslink distribution 46 throughout the composite. It is clear that there is also no excessive vulcanization in the vicinity of the interface region of the prior art (FIG. 3).

In order to show the effectiveness of the present invention, natural rubber component (NR); styrene-butadiene rubber admixture (SB
R); and three rubber blends including SBR rubber and including an interphase layer (IPL) containing one accelerator. The composition of these layers is given in Tables I-III. All numerical values represent the number of parts per 100 parts of rubber, and are based on 100 parts of the total amount of rubber.

Table I Type of Natural Rubber Composition Base Material: NR Natural Rubber 100.00 Carbon Black 62.00 ZnO 7.50 Stearic Acid 0.50 Adhesion Promoter 0.88 Paraphenylenediamine Antioxidant 2.00 Antioxidant 1.00 Primary Sulfenamide Accelerator 0.50 Second Grade Sulfenamide accelerator 0.30 Sulfur mixed in oil 6.25 Phthalamide retarder 0.20 Total 181.13 Table II SBR composition Base material type: SBR SBR 100.00 Process oil 27.6 Carbon black 4.00 ZnO 2.00 Stearic acid 2.00 Wax 0.75 Polymerized petroleum resin 3.50 Paraphenylene Diamine Antioxidant 0.95 Sulfur 2.25 Sulfenamide Accelerator 0.60 Sulfur Donor 0.60 Total 194.25 Table III Interphase Layer Base Material with Accelerator Type: SBR + Major Accelerator SBR 100.00 Process Oil 27.60 Carbon Black 54.00 ZnO 2.00 Stearic Acid 2.00 Wax 0.75 Polymerized petroleum resin 3.50 Diamine antioxidant Agent 0.95 Sulfur 0.00 Sulfenamide accelerator 0.60 Total 191.40 N, including those with and without interphase IPL
Peel adhesion studies were performed using R and SBR blends. Several combinations of unvulcanized and vulcanized base materials were combined in the following manner.

For testing purposes, the rubber substrates to be bonded together were first milled to a thickness of 0.050 inch and cut into 6 inch squares. A rubber backing material reinforced with polyester cord was also made to the same dimensions. First lined
Layers of lay on a flat surface with cords running horizontally. To this was applied a second layer of lining with a cord running vertically. One layer of test base material was then applied to the above double backing layer to complete one half of the adhesive test pad. A second similar laminate was prepared for a second test base intended for pre-cure, which also covered a 6 inch square section of the interphase base. The thickness of the interphase layer is from 0.010 inch to 0.080 inch, the composition of which is described above.
The interphase layer was then coated with a 6 inch square section of 0.006 inch polyester film. The film had a smooth or rough surface finish as noted below. (When the test was to check the adhesion between two unvulcanized test substrates, the interphase layer, polyester film and prevulcanization step were omitted.) The second laminate with the interphase layer , About 278p
Prevulcanization was performed in a pressure mold of si at a time and temperature that resulted in a prevulcanization in the range of 50 to 100 percent of optimum cure as measured by shear rheometer. After prevulcanization, the laminate was removed from the mold and the film was removed. Typical prevulcanization conditions for the SBR / interlayer laminate were 11 minutes at 165 ° C.

A 2 ″ × 6 ″ polyester separator film was placed on one end of the test base material in the first laminate and placed perpendicular to the cord in the second backing layer closest to the test base material. . The prevulcanized laminate with this interphase was then faced to the top of the first laminate and laid parallel to the lined cord closest to the test base. Then, the assembled pad is about 278p.
In pressure molds of si, with temperature and time varying directly proportional to the thickness of the interphase layer, but always below the optimum cure time for the test base material in the first laminate as measured by the rheometer cure curve. Simultaneous vulcanization for at least 5 minutes longer. Typical co-vulcanization conditions for SBR / interphase / NR laminate were 165 ° C. for 10 minutes. After removing the mold, the 1 "x 6" test strip was die cut from the bond pad in such a manner that the cord closest to the test substrate was parallel to the long axis of the test strip. The separator film was then removed and the test piece was peeled 180 ° and loaded into an Instron device for testing.

Peel adhesion values (pounds per inch) were measured for each of the bonded and covulcanized laminates as follows: 6 inch x 1 inch strips were typically clamped at 2 inches per minute. Tested at speed.
The strength of the adhesive bond is the width of the sample (typically 1 inch) 1
Measured in pounds per inch. The strength to initiate tearing at the adhesive interface reached a maximum at the beginning of the test, followed by a rapid sequence of smaller maxima and minima over the rest of the test. The first maximum at the beginning of the test was taken as the peak value and the smaller maxima and minima were mathematically averaged to reach a flat value. Two or more strips from each pad were tested and individual peak and flat values were averaged to reach the final peak / flat value.

The measurements were carried out at 20 ° C. and 100 ° C. and the results are reported in Table IV for the 10 individual examples below. Examples 1 to 10 contained SBR as the unvulcanized rubber component layer or the pre-vulcanized rubber component layer, and contained SBR and the natural rubber (NR) as the unvulcanized rubber component layer. The SBR, NR and interphase were made from the compositions given in Tables I-III. The thickness was varied according to a reasonable adjustment of cure time.

[0057]

【Example】

Example 1 Two SBR layers of the composition shown in Table II were individually laminated to two polyester cord reinforced backing layers, then bonded together and covulcanized at 165 ° C for 18 minutes.

Example 2 S laminated to two reinforced backing layers on one side and a smooth polyester film 0.006 inch thick on the other side.
The BR layer was pre-cured at 165 ° C for 11 minutes. Then,
The polyester film was removed, the newly exposed rubber surface was bonded and then covulcanized at a temperature of 165 ° C. for 16 minutes with a laminate containing an unvulcanized SBR layer and two reinforced backing layers.

Example 3 SB laminated to two reinforcing backing layers on one side and a 0.006 inch thick rough polyester film on the other side
The R layer was pre-cured at 165 ° C for 13 minutes. The polyester film was then removed, the newly exposed rubber surface was bonded, and then co-vulcanized with a laminate containing an unvulcanized SBR layer and two reinforced backing layers at a temperature of 165 ° C. for 16 minutes.

Example 4 Two reinforced backing layers on one side and an SBR layer laminated on a smooth polyester film on the other side at 165 ° C.
Precured for a minute. The polyester film was then removed and the newly exposed surface first buffed and cleaned, followed by bonding, with a laminate containing an unvulcanized SBR layer and two reinforced backing layers at a temperature of 165 ° C. Were simultaneously vulcanized for 16 minutes.

Example 5 An SBR layer laminated on one side with two reinforcing backing layers and on the other side with a 0.045 inch thick interphase layer of the composition listed in Table III was precured at 165 ° C. for 13 minutes. It was The polyester film coated on one side of this interphase layer is then removed, the newly exposed surface is bonded, and then at a temperature of 165 ° C. with a laminate comprising an unvulcanized SBR layer and two reinforcing backing layers. Simultaneous vulcanization for minutes.

Example 6 SBR layer having the composition shown in Table II and NR having the composition shown in Table I
The layers were individually laminated to two polyester cord backing reinforcement layers. The two laminates were then bonded together and covulcanized at a temperature of 165 ° C. for 11 minutes.

Example 7 S laminated to two reinforced backing layers on one side and a smooth polyester film 0.006 inch thick on the other side.
The BR layer was pre-cured at 165 ° C for 11 minutes. Then,
The polyester film was removed, the newly exposed rubber surface was bonded, and then simultaneously with a laminate containing an unvulcanized NR layer of the composition shown in Table I and two reinforcing backing layers at a temperature of 165 ° C. for 10 minutes. Vulcanized

Example 8 SB laminated to two reinforcing backing layers on one side and a 0.006 inch thick rough polyester film on the other side
The R layer was pre-cured at 165 ° C for 13 minutes. The polyester film was then removed, the newly exposed rubber surface was bonded, and then 10% at a temperature of 165 ° C. with a laminate containing an unvulcanized NR layer of the composition shown in Table I and two reinforcing backing layers. Simultaneous vulcanization for minutes.

EXAMPLE 9 Two reinforced backing layers on one side and an SBR layer laminated on a smooth polyester film on the other side at 165 ° C. 11
Pre-cured for minutes. The polyester film is then removed and the newly exposed surface is first buffed and cleaned, followed by bonding, containing an unvulcanized NR layer of the composition shown in Table I and two reinforced backing layers. Simultaneous vulcanization was performed with the laminate for 10 minutes at a temperature of 165 ° C.

Example 10 An SBR layer laminated on one side with two reinforcing backing layers and on the other side with a 0.045 inch thick interphase layer of the composition listed in Table III was precured at 165 ° C. for 13 minutes. . The polyester film coated on one side of this interphase layer is then removed, the newly exposed surface is bonded, and then a laminate comprising an unvulcanized NR layer of the composition shown in Table I and two reinforcing backing layers. Simultaneous vulcanization was performed at 165 ° C. for 11 minutes.

[0067]

[Table 1]

As is apparent from Table IV, Examples 5 and 10 according to the method of the present invention use Examples 2 and 10 that do not use any interphase or any technique involving the use of smooth, rough and buffed surfaces. Much improved adhesion values were obtained above 7. The flatness values for Examples 1 and 9 were reported as (>) values greater than the stated values because tearing on the backing occurred rather than tearing at the bond interface. Therefore, the bond strength at the interface between the base materials was not measured, but is believed to be greater than the bond strength between the base material and the reinforced backing.

On the basis of the above description, it must now be clear that the use of the methods described herein achieves the goals set out above. The method according to the invention is also practiced to achieve improved adhesion between various rubber layers and components used in the manufacture of tires and other laminates or articles constructed from various components. It should be clear to those skilled in the art that this is possible. The time, temperature and pressure for vulcanization would also be readily determinable by one of ordinary skill in the art.

Therefore, any process variants are clearly within the scope of the claimed invention, and therefore the specific rubber composition for the unvulcanized rubber substrate layer or its components, as well as the composition and thickness of the interphase layer. The choice can be determined without departing from the spirit of the invention disclosed and described herein. Moreover, the scope of the invention shall include all modifications and variations that fall within the scope of the appended claims.

The main features and aspects of the present invention are as follows.

1. The improvement is for the production of vulcanized rubber articles
The initially unvulcanized rubber component of the seed is selected; one of the above components is treated under conditions that achieve a lower crosslinking concentration gradient at the surface;
The other of the above rubber components is applied to the above surface in a condition that the species contains a cross-linking agent; at least partially vulcanized with the components of the unvulcanized rubber, including the steps of simultaneously vulcanizing both of the above components. Improved method for achieving enhanced bond strength between rubber components.

2. The processing steps are: applying an interphase of a rubber material that does not contain a cross-linking agent to at least one of the above components; both the layers and the above components together until at least partially vulcanized. Improved process according to claim 1, characterized in that it comprises pre-vulcanizing steps; providing said surface with said interphase layer.

3. 3. The method according to 2, wherein the unvulcanized rubber is selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

4. 4. The method according to 3, wherein the interphase layer contains one or more selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

5. 5. The method according to 4, wherein the rubber of the interphase layer is substantially the same as or is miscible with the rubber of the unvulcanized rubber component and the vulcanized rubber component.

6. A process according to claim 1, characterized in that the crosslinking agent is selected from the group consisting of peroxides, sulfur, sulfur donors and accelerators for natural and synthetic rubbers. 7. 7. The method according to 6, which also comprises the additional step of incorporating in said interphase layer at least a portion of at least one of the accelerators present in said unvulcanized rubber component.

8. The above treatment steps include: coating at least one surface of each of the above components with a cure inhibitor; subjecting the above surface coated components to vulcanization sufficient to impart a graded crosslink density to the above components. The improved method of claim 1, further comprising the step of applying.

9. 9. The method according to claim 8, wherein the curing inhibitor is selected from the group consisting of a curing retarder and a curing deactivator.

10. 9. The method according to 8, wherein the unvulcanized rubber is selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

11. Improved process according to claim 1, characterized in that said treatment steps also include: subjecting said components to a prevulcanization; a continuous step of coating the surface thereof with a curing inhibitor.

12. 12. The method according to 11, wherein the curing inhibitor is selected from the group consisting of a curing retarder and a curing deactivator.

13. 13. The method according to 12, wherein the unvulcanized rubber is selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

14. The processing steps include: applying an interphase of a rubber material that does not contain a crosslinker to at least one of the above ingredients; until both the interphase and the above ingredients are at least partially vulcanized. An improved method according to claim 1, characterized in that it also comprises the step of exposing to a radiation source; providing said surface with said interphase layer.

15. 15. The method of 14, which also comprises the additional step of incorporating an effective amount of a radiation blocking agent into the interphase.

16. 15. The method of 14, wherein the unvulcanized rubber is selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

17. 17. The method according to 16, wherein the interphase layer contains one or more rubbers selected from the group consisting of natural rubber and synthetic rubber, and mixtures thereof.

18. 18. The method according to 17, wherein the rubber of the interphase layer is substantially the same as or miscible with the rubber of the unvulcanized rubber component and the vulcanized rubber component.

19. 19. The method according to 18, which also comprises the additional step of incorporating in the interphase layer at least a portion of at least one of the accelerators present in the unvulcanized rubber component.

[Brief description of drawings]

FIG. 1 is an illustration schematically showing simultaneous vulcanization of two rubber base components, one of which has been prevulcanized, as described in one of the prior art.

FIG. 2 is an illustration schematically showing simultaneous vulcanization of two rubber base components, one of which is prevulcanized, as described in one of the prior art.

FIG. 3 is an illustration schematically showing simultaneous vulcanization of two rubber base components, one of which has been prevulcanized, as described in the prior art.

FIG. 4 is a cross-sectional view of one layer of unvulcanized rubber base component.

FIG. 5 is a cross-sectional view of the components shown in FIG. 4 and an interphase layer applied thereon in accordance with the present invention, both prevulcanized.

FIG. 6 is a cross-sectional view of the layer shown in FIG. 5, in which a second unvulcanized layer of a rubber base material is applied to the above-mentioned interphase layer, and this is simultaneously vulcanized.

FIG. 7 is a cross-sectional view of an unvulcanized, one layer of a rubber substrate component that has both applied an interphase layer and both have been radiation cured.

FIG. 8 is a cross-sectional view of the layer shown in FIG. 7, in which a second unvulcanized layer of a rubber base component is applied to the above interphase layer, and this is finally simultaneously vulcanized.

FIG. 9 is a cross-sectional view of one layer of a rubber substrate component having a chemical cure inhibitor applied on its surface according to the method of the present invention.

FIG. 10 shows the second part of the rubber base material for the surface-treated layer.
FIG. 10 is a cross-sectional view of the layer shown in FIG. 9, in which the unvulcanized layer of No. 1 was applied and finally co-vulcanized.

FIG. 11 is one of the explanatory diagrams schematically showing simultaneous vulcanization of the two types of rubber base components and the interphase layer shown in FIGS. 4 to 6.

FIG. 12 is one of the explanatory views schematically showing simultaneous vulcanization of the two types of rubber base components and the interphase layer shown in FIGS. 4 to 6.

FIG. 13 is one of the explanatory views schematically showing simultaneous vulcanization of the two types of rubber base components and the interphase layer shown in FIGS. 4 to 6.

Claims (1)

[Claims] 1. A method, the improvement of which selects two initially unvulcanized rubber components for the production of vulcanized rubber articles; one of the above components achieving a crosslinking density gradient with a lower crosslinking concentration at the surface. Applying the other of the above rubber components to the above surface under the condition that at least one of the above two components contains a cross-linking agent; and including the steps of simultaneous vulcanization of both of the above components. , An improved method for achieving enhanced bond strength between an unvulcanized rubber component and an at least partially vulcanized rubber component.