JPH08302317A - Adhesive composition for bonding between fiber and rubber and cord-rubber composite material obtained using the same - Google Patents

Abstract

PURPOSE: To obtain an adhesive compsn. capable of bonding between hardly bondable fiber such as a polyester fiber or an aramid fiber and rubber with an excellent adhesion by one-bath treatment. CONSTITUTION: This compsn. comprises (i) an aq. mixture of a resorcinol- formaldehyde precondensate and a rubber latex, and (ii) a substantially org. solvent-free aq. dispersion of an epoxy resin which is solid at ordinary temp., has an epoxy equivalent of at most 300, and is substantially insoluble in water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition of a fiber and a rubber necessary for producing a composite product of a rubber and a fiber such as a tire, a conveyor belt and a hose, and a cord / rubber composite obtained by using the same. Regarding the body

[0002]

2. Description of the Related Art Adhesion between rubber and difficult-to-adhere fibers such as polyester fibers and aramid fibers is conventionally performed by previously treating the fibers with epoxy or blocked isocyanate, and then further mixing resorcinol / formaldehyde precondensate and rubber latex in an aqueous system. Liquid (RFL) or the like, or p-chlorophenol-resorcinol-formaldehyde condensate (for example, Denabond (trademark) manufactured by Nagase Kasei Co., Ltd.)
Or after treatment with an aqueous solution containing allyl hydroxyphenyl ether / resorcinol / formaldehyde condensate,
A so-called two-bath treatment such as an RFL treatment is applied, but such an adhesion method has a problem that productivity is low and adhesive strength is not necessarily high.

From the viewpoint of productivity, the above-mentioned p-chlorophenol / resorcin / formaldehyde condensate or allyl hydroxyphenyl ether / resorcin / formaldehyde condensate is an aqueous mixture (RFL) of a resorcin / formaldehyde initial condensate and a rubber latex. There is also a method in which the condensate is an aqueous ammonia solution, and there is a problem in the working environment such as an odor problem, and there is a problem that the adhesive strength is low.

Further, in the case of polyester fiber or aramid fiber, in the process of spinning the fiber, an epoxy resin is added to the fiber oil agent, and the epoxy resin is attached to the fiber to give the adhesive activity in advance. There is so-called easy-adhesion thread. If this is used, it is possible to bond the rubber to the rubber by one bath treatment of RFL after forming the fiber into a cord shape or a woven shape. However, there is a problem in that it is not preferable in the work environment in terms of smoke generation in the oil agent adhesion step, and a problem that sufficient adhesion cannot be obtained only by RFL treatment.

[0005]

Therefore, the present invention has heretofore been difficult to adhere to fibers such as polyester fibers and aramid fibers which have been required to undergo a two-bath treatment for adhesion to rubber because of their difficulty in adhering. It is an object of the present invention to provide an adhesive composition capable of excellent adhesion to the rubber by the one-bath treatment without using the above-mentioned easily adhesive thread.

Further, the present invention is a cord / rubber in which the heat treatment is simplified, the energy is saved, the productivity is high and the working environment is improved without using ammonia water or the like unlike the conventional method. The purpose is to provide a complex.

[0007]

According to the present invention, (i)
Aqueous mixture of resorcinol / formaldehyde initial condensate and rubber latex, and (ii) Water dispersion of epoxy resin which is solid at room temperature and has an epoxy equivalent of 300 or less and which is substantially insoluble in water and does not contain organic solvent. Provided is a fiber-rubber adhesive composition for use in a one-bath treatment comprising a liquid.

According to the present invention, a cord / rubber composite obtained by further impregnating and coating fibers with the above-mentioned adhesive composition, then subjecting it to a dry heat treatment and embedding it in an unvulcanized rubber composition and vulcanizing and integrating it. Will be provided.

According to the present invention, an epoxy resin which is water-insoluble in a water-based mixture of resorcin / formaldehyde precondensate and rubber latex (hereinafter referred to as "RFL") and solid at room temperature is dissolved in water without using an organic solvent. Provided is an adhesive composition obtained by adding and mixing an aqueous dispersion of an epoxy resin obtained by dispersing, impregnating and adhering the adhesive composition to polyester fibers, aramid fibers, and other hardly-adhesive fibers, followed by a dry heat treatment, By embedding in a vulcanized rubber and vulcanizing it to integrate it, a cord-rubber composite having excellent adhesiveness can be obtained with high productivity.

The resorcin-formaldehyde initial condensate used for RFL has already been widely used. Resorcin and an aqueous formalin solution are dissolved in water and reacted with an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide as a catalyst. There are a resol type and a novolak type which are reacted under an acidic catalyst such as oxalic acid and hydrochloric acid, but any of them can be used in the present invention. As the novolac type initial condensate, Sumikanol 700 manufactured by Sumitomo Chemical Co., Ltd. and Adha-R manufactured by Hodogaya Chemical Co., Ltd.
F and the like are commercially available. When these novolac type RF resins are used, it is necessary to add a small amount of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide in order to dissolve them in water. When these novolac type RF resins are used, it is usually necessary to add an aqueous formalin solution afterwards.

The rubber latex is appropriately selected according to the type of unvulcanized rubber, but for general rubbers such as natural rubber, SBR, IR, BR, vinyl pyridine / styrene / butadiene terpolymer latex and SBR latex. ,
Natural rubber latex is preferably used, and vinylpyridine / styrene / butadiene terpolymer latex is particularly preferably used from the viewpoint of adhesiveness, and SBR latex or natural rubber latex can be appropriately mixed and used. If the adhered rubber is CR or NBR,
It is preferable to use CR latex, NBR latex, or a mixture of these with vinyl pyridine / styrene / butadiene terpolymer latex. The type of latex can be appropriately selected according to the use. The compounding ratio of the resorcinol-formaldehyde initial condensate and the rubber latex used in the present invention is preferably 5: 100 to 50: 100 in terms of solid content weight ratio.

The epoxy resin used in the present invention is
Epoxy resin that is solid at room temperature, has an epoxy equivalent of 300 or less, and is substantially insoluble in water, and is usually used for the adhesive treatment between fibers and rubber. For example, a water-soluble epoxy resin obtained from the reaction of a polyol and epichlorohydrin (for example,
Denacol EX313, EX6 manufactured by Nagase Kasei Co., Ltd.
14, EX512, etc.) are RFL due to their water solubility.
If added to the epoxy resin, the epoxy reacts with the RF resin, causing gelation of the adhesive and deterioration of the adhesiveness, which is not preferable. Here, “substantially insoluble in water” means that the water solubility is 10% or less when 10 parts by weight of the epoxy resin is dissolved in 90 parts by weight of water at room temperature. Even in the case of a water-insoluble epoxy resin, an epoxy resin that is liquid at room temperature or liquid at a room temperature with a melting point of less than 40 ° C cannot be used in the present invention. Further, the epoxy resin used in the present invention must have an epoxy equivalent of 300 or less.

The epoxy resin used in the present invention is required to be solid at room temperature and preferably have a melting point of 40 ° C. or higher. The reason is that the adhesive composition of the present invention is usually
It is used at room temperature and exposed to an environment of 5 to 40 ° C. Epoxy, which is liquid under the temperature atmosphere at the time of use, is not preferable because it is reacted with RF resin when left mixed with RFL in the study by the present inventors, causing gelation of the adhesive and deterioration of adhesion. It is presumed that this is because when the RF resin is dissolved in water and the epoxy resin is dispersed in a liquid state, the reaction becomes easier than when the epoxy resin is dispersed in a solid state. Therefore, it is essential to select an epoxy resin that does not cause liquefaction due to thermal softening at a normal use environment temperature, for example, below 40 ° C.

The epoxy equivalent of the epoxy resin used in the present invention must be 300 or less.
The “epoxy equivalent” is the molecular weight per epoxy group of the epoxy resin, and the epoxy equivalent is 30.
When it is 0 or more, sufficient adhesive force cannot be obtained because the number of epoxy groups that react with the fiber is substantially small. From the viewpoint of adhesiveness, the epoxy equivalent is more preferably 250 or less. Examples of such epoxy resin include polyphenol type epoxy resins, phenol novolac type, cresol novolac type, hydroquinone type, brominated novolac type, xylene modified novolac type, phenol glyoxal type, trisoxyphenylmethane type,
Examples include trisphenol PA type and bisphenol A novolac type epoxy resins. A cresol novolac type epoxy resin is particularly preferable in terms of adhesiveness and versatility.

Further, in the present invention, it is necessary that the aqueous dispersion of the epoxy resin contains substantially no organic solvent. Usually, in order to disperse these epoxy resins in water, a method of once dissolving the epoxy resin in an organic solvent such as toluene and dispersing it in water using an appropriate dispersant is performed. However, as described above, when dispersed in water in a liquid state, a reaction with the RF resin is likely to occur, and there is a problem that the adhesive force is reduced. Further, when mixed with RFL, the epoxy resin is apt to cause cohesive precipitation.

In the present invention, a known method can be used to obtain a water dispersion containing substantially no organic solvent. For example, an epoxy resin which is solid at room temperature is heated to a temperature higher than the heat softening temperature to bring it into a molten state, hot water and a dispersant are mixed and stirred, and passed through a colloid mill for further miniaturization, and the average particle size is, for example, 5 μm or less. To This method can be applied to epoxy resins that melt below the boiling point of water. When using an epoxy resin with a higher thermal softening temperature, use an organic solvent in which the epoxy resin is soluble, dissolve the epoxy resin, add water and a dispersant, and add it to a stirrer with high shearing force. Mix and stir to a predetermined degree of dispersion,
Furthermore, in order to remove the organic solvent, vacuum distillation is carried out to obtain an aqueous dispersion of the epoxy resin substantially free of the organic solvent.

As the dispersant used here, a known nonionic dispersant or anionic dispersant is used. Although it is possible to use a cationic dispersant, it is not so preferable because it may cause gelation when added to RFL.

The average dispersed particle size of the epoxy resin in the aqueous dispersion of the epoxy resin according to the present invention is preferably 5 μm or less, more preferably 0.1 to 4 μm. If this average particle diameter exceeds 5 μm, the dispersion stability of the aqueous dispersion is poor, and the epoxy resin tends to settle when an adhesive is used, and sufficient adhesive strength may not be obtained. Therefore, in order to obtain more stable adhesion, the average particle size is preferably 5 μm or less.

Polyester fibers such as polyethylene terephthalate fiber, polyethylene-2, 6-naphthalate fiber are the most effective fibers to which the adhesive composition of the present invention is applied, but aramid fibers (for example, Kevlar manufactured by DuPont) ), Teijin Technora Co., Ltd.), polyarylate fibers (eg, Vectran manufactured by Kuraray Co., Ltd.), aromatic ring-containing aromatic polymer fibers (eg poly-p-phenylenebenzbisoxazole fibers, poly-p-phenylenebenzbisthiazole). It can also be applied to fibers). The present invention is not limited to these, and can be applied to difficultly-adhesive fibers that require treatment with RFL after previously treating the fibers with an epoxy resin or isocyanate.

The solid content ratio of RFL to epoxy resin is preferably in the range of 100: 15 to 100: 120 by weight. If the epoxy resin is less than 15 parts with respect to 100 parts of RFL (parts by weight, the same applies hereinafter), good adhesion may not be obtained. Further, when the epoxy resin exceeds 120 parts, the adhesive force may be reduced, and the cord may be hardened to reduce fatigue and workability.
The solid content ratio is more preferably 100: 20 to 100: 100 from the viewpoint of adhesiveness and workability.

In the adhesive composition of the present invention, it is more preferable that the alkali metal hydroxide contained in the adhesive composition is 0.05 to 1.0% by weight based on the total solid content of the adhesive. . Usually, when an RFL is prepared, an alkali metal hydroxide is used, but when the alkali metal hydroxide finally contained in the adhesive composition exceeds 1.0% by weight, the adhesion with the polyester fiber is particularly increased. In this case, the alkali metal hydroxide serves as a catalyst to easily cause hydrolysis of the polyester fiber, and as a result, the heat-resistant adhesiveness may be deteriorated, which is not preferable. On the other hand, when the content of the alkali metal hydroxide is less than 0.05% by weight, the novolac-type resorcinol-formaldehyde initial condensate tends to be difficult to dissolve in water, and the aging of RFL takes a long time. Is required, and productivity tends to decrease, which is not preferable.

The temperature of the dry heat treatment after applying the adhesive composition according to the present invention to the fibers is preferably 220 ° C. or higher, more preferably 230 ° C. or higher. This heat treatment temperature is 22
If the temperature is lower than 0 ° C, the adhesion tends to decrease, which is not preferable.

[0023]

EXAMPLES The present invention will be further described below with reference to examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Example 1 An orthocresol novolac type epoxy resin (epoxy equivalent: 230, melting point: 85 ° C.) was used to obtain an organic resin-free epoxy resin aqueous dispersion A by a known method. The solid content of this aqueous dispersion A was 40% by weight, and the average particle size of the dispersed particles measured by the light scattering method was 4 μm. In contrast, the same cresol novolac type epoxy resin was previously dissolved in toluene, and water and a dispersant were added in the same manner as above to prepare an aqueous dispersion B. The solid content and particle size of the water dispersion B are the same as those of the water dispersion A, but this dispersion B contains 8 parts of toluene.
Contains% by weight. Further, glycerol diglycidyl ether (Denacol EX313 epoxy equivalent 1 manufactured by Nagase Kasei Co., Ltd.) is usually used as the water-soluble epoxy resin C used for bonding polyester fibers and aramid fibers.
41) was prepared. This epoxy resin C is a liquid at room temperature. Further, an aqueous dispersion D was prepared by water-dispersing a bisphenol F type epoxy resin (epoxy equivalent 160), which is a water-insoluble but liquid epoxy resin at room temperature, without using an organic solvent. The solid content and particle size of this aqueous dispersion D are the same as those of the above epoxy resin aqueous dispersion. Further, as the water-insoluble solid epoxy resin having a large epoxy equivalent at room temperature, a bisphenol A type epoxy resin (epoxy equivalent 700 melting point 84 ° C.) and a biphenyl type epoxy resin (epoxy equivalent 370 melting point 105 ° C.) are respectively used as organic resins. Aqueous dispersions E and F were prepared without using a solvent. The solid content and particle size of the water-acid solutions E and F are the same as those of the above epoxy resin dispersion liquid. Furthermore, as an adhesive G which is usually used in the two-bath treatment of polyester fibers, a condensate of p-chlorophenol / resorcinol / formaldehyde (Denabond manufactured by Nagase Kasei Co., Ltd.) was prepared.

On the other hand, the RFL used in this example had the formulation shown in Table I below.

Table I: RFL formulation (parts by weight) Soft water 52.3 10% sodium hydroxide aqueous solution 2.3 Sumicanol 700 ^{* 1} 4.9 37% formalin aqueous solution 3.7 Nipol 2518FS ^{* 2} 36.8 Total 100.0 (Solid content 20.0% by weight)

Table I Footnotes ^{* 1} Resorcin-formaldehyde initial condensate manufactured by Sumitomo Chemical Co., Ltd. Solid content 75% by weight (novolac type RF resin) ^{* 2} Vinyl pyridine / styrene / butadiene terpolymer latex solid manufactured by Nippon Zeon Co., Ltd. 40% by weight

The following formulations were used as the one-bath treatment method in the examples. a) Treating fibers only with RFL shown in Table I (comparative example) b) RFL of Table I and epoxy resin aqueous dispersion A are mixed so that the solid content ratio (weight ratio) is 100: 20. The fiber was treated with a 20% by weight one-bath solution (Example of the present invention) c) RFL of Table I and epoxy resin aqueous dispersion B were mixed so that the solid content ratio (weight ratio) was 100: 20. Fiber is treated with one bath liquid having a solid content of 20% by weight (comparative example) d) RFL of Table I and water-soluble epoxy resin C are mixed so that the solid content ratio (weight ratio) is 100: 20. Fiber is treated with 20% by weight of one-bath liquid (comparative example) e) RFL of Table I and epoxy resin aqueous dispersion D are mixed so that the solid content ratio (weight ratio) is 100: 20. 20% by weight of one-bath solution (comparative example) f) The RFL of Table I and the epoxy resin aqueous dispersion E are solidified One bath liquid with a solid content of 20% by weight mixed so that the ratio (weight ratio) was 100: 20 (comparative example) g) The solid content ratio (weight) of RFL in Table I and epoxy resin aqueous dispersion F (A ratio) of 100: 20 mixed in one bath liquid with a solid content of 20% by weight (comparative example) h) RFL and Denabond in Table I were mixed in a solid content ratio (weight ratio) of 100: 100. Solid content of 20
Fiber treated with 1% by weight of one-bath solution (comparative example)

The following formulation was used as the two-bath treatment method. i) One bath liquid having a solid content of 20% by weight, which was prepared by mixing RFL of Table I and Denabond at a solid content ratio (weight ratio) of 1: 1 and RFL of Table 1 was used as a second bath liquid to prepare fibers. Treatment (comparative example)

As the fiber, 1500 D / 2 40 × 4
0 (times / 10 cm) untreated polyethylene terephthalate fiber not pre-treated with epoxy or the like was used. The treatment is performed by immersing the fibers in the adhesive composition, adjusting the amount of adhesion to be 5% by weight, drying at 100 ° C. for 1 minute, and then heat-treating at 240 ° C. for 2 minutes. A bending hardness test was conducted.

For the two-bath treatment, one bath contains 3% by weight, and 2
The amount of adhesive was adjusted to be 2% by weight in the bath and 5% by weight in total. Further, after soaking in one bath liquid, drying at 100 ° C. for 1 minute, heat treatment at 240 ° C. for 1 minute, further soaking in two bath liquid, drying at 100 ° C. for 1 minute, heat treatment at 240 ° C. for 1 minute, An adhesion test and a bending hardness test of the cord were performed. After these adhesive solutions were prepared, they were left for 24 hours and then treated. In addition, the state of gelation of the adhesive liquid was confirmed when performing the treatment.

For the adhesion test with rubber, unvulcanized rubber compositions shown in Table 2 below were used, and the vulcanization conditions were 148 ° C. × 30 minutes. For the adhesion test, the treated cords are packed in parallel on a rubber sheet with a thickness of 2 mm in a close-packed manner over a width of 25 mm, a rubber sheet with a thickness of 1 mm is laid on top of it, and the treated cords are packed in the same manner. Then, a so-called two-ply laminated sample was prepared by aligning the rubber sheet with a width of 25 mm over a width of 25 mm, and a rubber sheet having a thickness of 2 mm was again laid on the sample, and the peeling force between the plies and the state of breakage (rubber coverage) were observed. The state of failure is 100% when the cohesive failure of rubber occurs on the entire surface,
The case where the interface breakage of the fiber cord occurred on the entire surface was indicated as 0%. Good adhesion is 100% rubber fracture and high adhesion.

Table II: Unvulcanized rubber composition (parts by weight) NR 60 SBR 40 ZnO 4 Stearic acid 1.5 Anti-aging agent 1 Carbon black 60 Aromatic oil 8 Sulfur 3 Vulcanization accelerator 1.5 ─── ─────────────

The hardness of the treated cord is JIS L1096.
The hardness of two cords was measured in accordance with the Gurley bending test method of. If the bending hardness is high, the workability of molding tires, hoses, and the like will be problematic, so the smaller the value, the better. The above results are shown in Table III.

[0035]

[Table 1]

As is clear from the above results, an aqueous dispersion of a water-insoluble epoxy resin which is liquid at room temperature, an epoxy resin aqueous dispersion containing an organic solvent or a water-soluble epoxy resin which is solid at room temperature is used as an RFL. The one-bath treatment did not give good adhesion in the mixture. In addition, these materials did not withstand practical use because aggregates and gel components were generated when the adhesive solution was left standing. On the other hand, an aqueous dispersion of a substantially water-insoluble epoxy resin, which is solid at room temperature and contains substantially no organic solvent, contains p-chlorophenol.
Not only does it give much better adhesion than the one-bath treatment using the resorcinol-formaldehyde condensate, but, of course, it shows better performance than the conventional two-bath treatment and also has a small bending hardness. Further, it is understood that those having an epoxy equivalent of more than 300 are solid at room temperature and have poor reactivity even when used as an aqueous dispersion containing no organic solvent, and no improvement in adhesion is observed.

Example 2 An epoxy resin aqueous dispersion A of Example 1 having the same composition and solid content but an average particle size of 10 μm was prepared, and the same experiment as in Example 1b was carried out. did. As a result, the peeling force was 20.5 Kgf / 25 mm and the rubber coverage was 90%. Although the same adhesion as the conventional two-bath treatment can be obtained, the adhesion is lower than that of the experimental example b of Example 1. It is considered that this is because dispersed particles settled when the adhesive composition was allowed to stand. Therefore, the average particle diameter is more preferably 5 μm or less.

Example 3 Using the epoxy resin aqueous dispersion A of Example 1, the mixing ratio with RFL was changed. Others were tested under the same conditions. For the adhesion test, the vulcanization time was set to 148
Two conditions of ℃ × 30 minutes and 170 ℃ × 60 minutes were evaluated, and the initial adhesion and heat resistant adhesion were measured. Moreover, the bending hardness of the treated cord was measured.

Table IV: Test results ─────────────────────────────────── RFL / A 100/10 100 / 15 100/20 100/50 100/100 100/120 100/140 Solid content ratio ─────────────────────────────── ───── Peeling force (initial) 21.0 23.5 24.0 26.5 25.5 23.5 21.0 (Kgf / 25mm) Rubber coverage (%) 85 95 100 100 100 95 85 Peeling force (heat resistance) 9.5 12.5 14.5 17.0 18.5 18.0 16.5 (Kgf / 20mm) Rubber coverage (%) 25 40 50 65 75 70 65 ──────────────────────────────────── Bending hardness (mg) 410 415 420 460 560 610 780 ────────────────────────────────────

From the results of Table IV, it can be seen that the solid content ratio of RFL to epoxy resin is in the range of 100: 15 to 100: 120 from the viewpoint of bending hardness of the heat resistant adhesive cord. When the solid content ratio of the epoxy resin is less than 15 parts, the heat-resistant adhesion tends to decrease, while when it exceeds 120 parts, the bending hardness of the cord remarkably increases, and the fatigue property and workability may decrease. I know there is something.

Example 4 As an epoxy resin, a phenol glyoxal type epoxy resin (epoxy equivalent: 200, melting point: 75 ° C.) and a phenolvolac type epoxy resin (epoxy equivalent: 190,
A melting point of 65 ° C.) was used to obtain an aqueous dispersion containing no organic solvent. Both solid content and average particle size are 40%, 4 μm
Is. Adhesion test was conducted by mixing these with RFL in the same manner as in Example 1. The former has a peeling force of 22.0Kgf / 25m
m, 90% rubber coverage, while the latter has a peel force of 21.5 Kgf
/ 25 mm, rubber coverage was 85%. From the above, with the epoxy resin used in the present invention (similar to the result shown in Example 1), if the epoxy equivalent is at least 300 or less, the same adhesion as the two-bath treatment of Example 1 (comparative example) is obtained, and It can be seen that, although it gives clearer adhesion than the one-bath treatment of the comparative example, the cresol novolac type epoxy resin shown in Example 1b gives higher adhesion and is more preferable.

Example 5 RFL varying the amount of sodium hydroxide used for RFL
(J) to (m) were created. Table V shows the formulation. This R
An adhesion test was carried out in the same manner as in Example 1 except that an adhesive solution was prepared by mixing FL and the aqueous dispersion A of the epoxy resin A of Example 1 in such a manner that the solid content weight ratio was 100/20. However, the vulcanization condition of the adhesion test sample is 170 ° C ×
It was 60 minutes. The results are shown in Table VI.

Table V: RFL formulation (parts by weight) ─────────────────────────────────── RFL composition ( j) (k) (l) (m) ─────────────────────────────────── Soft water 51.6 52.6 53.6 53.9 10% NaOH water 3.0 2.0 2.0 1.0 0.2 Sumicanol 700 4.9 4.9 4.9 4.9 37% formalin aqueous solution 3.7 3.7 3 .7 3.7 Nipol 2518FS 36.8 36.8 36.8 36.8 ──────────────────────────────── ──── Total 100.0 100.0 100.0 100.0 Solid content (%) 20 20 20 20 ──────────────────────── ───────── ─

Table VI: Adhesion results ─────────────────────────────────── RFL / Epoxy A RFL RFL RFL RFL = 100/20 (j) (k) (l) (m) ────────────────────────────────── ────────────────────────────────────────────────────────────────────────────────────────────── ───────── Peeling force (kgf / 25mm) 11.0 14.5 16.5 16.0 Rubber coverage (%) 35 50 65 60 60 ──────────── ───────────────────────

As shown in Table VI, it is understood that the weight% of the alkali metal hydroxide in the solid content of the adhesive is 1.0% or less, which is more preferable for the heat resistant adhesion. On the other hand, if less than 0.1%, RF
In the process of preparing L, an insoluble portion of the resorcinol formalin initial condensate was generated. (RFL (k) formulation in Table V) Also no further improvement in adhesion is obtained. Therefore, it is understood that the alkali metal hydroxide is more preferably 1.0 to 0.1%.

Example 6 The heat treatment temperature was changed using the adhesive of Experimental Example b) of Example 1. Other conditions were the same as in Example 1. The results of the adhesion test are shown in Table VII.

Table VII ────────────────────────────── Treatment temperature (℃) 210 220 220 230 ──────── ─────────────────────── Peeling force (kgf / 25mm) 21.5 23.5 24.5 Adhesion rate (%) 85 95 95 100 ── ──────────────────────────── Above Even at 210 ° C, adhesion similar to conventional two-bath treatment can be obtained, but at 220 ° C or above It can be seen that the heat treatment gives better adhesion.

Example 7 1500D / 2 35 × 35 aramid fiber (Kevlar (trademark) manufactured by DuPont) was used. Here, as a conventional method, aramid fibers were immersed in an epoxy resin aqueous solution having a composition shown in Table VIII, dried at 100 ° C. for 1 minute, then heat-treated at 240 ° C. for half, and further immersed in RFL shown in Table I and then at 100 ° C. for 1 minute. Minute drying and heat treatment at 240 ° C. for 1 minute were performed. On the other hand, as the method of the present invention, the same one-bath treatment as in Example 1b was performed. Similar peel adhesion tests were carried out using these treated cords. The conventional method is 19.5 kgf / 25 mm with rubber 7
20.0 kgf / 2 in the one-bath treatment method of the present invention with respect to 5%
Adhesion equivalent to 5 mm 80% was shown.

[0049]

[0050]

EFFECTS OF THE INVENTION According to the present invention, the adhesive treatment between the hardly-adhesive fiber and the rubber, which conventionally required the two-bath treatment, can be performed by the one-bath treatment, and further, the productivity can be improved and the energy can be saved. It was Further, in the present invention, since the aqueous ammonia solution or the like is not used, it is possible to perform the treatment without any problem in the working environment. Further, higher adhesive strength can be obtained as compared with the conventional two-bath treatment method. Thus, the present invention improves the durability of rubber / fiber composites such as tires, conveyor belts and hoses.

Claims (8)

[Claims] 1. (i) A water-based mixture of a resorcinol / formaldehyde initial condensate and a rubber latex, and (ii) a substantially water-insoluble epoxy resin which is solid at room temperature and has an epoxy equivalent of 300 or less. An adhesive composition of fibers and rubber used for one-bath treatment, which comprises an aqueous dispersion containing no organic solvent. 2. The adhesive composition according to claim 1, wherein the dispersed particle diameter of the epoxy resin in the aqueous dispersion of epoxy resin is 5 μm or less. 3. The mixing ratio of the solid content of the aqueous mixture of resorcinol-formaldehyde precondensate and the rubber latex and the solid content of the epoxy resin aqueous dispersion is 100: by weight.
The adhesive composition according to claim 1 or 2, which is 15 to 100: 120. 4. The adhesive composition according to claim 1, wherein the epoxy resin is a cresol novolac type epoxy resin. 5. The content of the alkali metal hydroxide in the adhesive composition is from 0.05 to 0.05 based on the total solid content of the adhesive.
The adhesive composition according to any one of claims 1 to 4, which is 1.0% by weight. 6. A fiber is impregnated with the adhesive composition according to any one of claims 1 to 5 and then dried and heat-treated to be embedded in an unvulcanized rubber composition for vulcanization and integration. The resulting cord-rubber composite. 7. The cord / rubber composite according to claim 6, wherein the fiber is a polyester fiber, an aramid fiber, a polyarylate fiber, or a heterocycle-containing aromatic polymer fiber. 8. The cord / rubber composite according to claim 6, wherein the drying heat treatment temperature is 220 ° C. or higher.