JP5792432B2 - Adhesive composition for rubber and fiber - Google Patents

Description

  The present invention relates to an adhesive for reinforcing fibers of rubber products such as rubber belts and tires.

Reinforcing fibers such as polyester fibers and polyamide fibers are widely used as reinforcing agents for rubber products such as rubber belts and tires. These reinforcing fibers are generally put to practical use after being dipped in an aqueous dispersion mainly composed of resorcinol-formaldehyde resin and latex in order to improve adhesion to rubber. As the latex, butadiene-vinylpyridine-styrene copolymer latex (hereinafter referred to as vinylpyridine latex) is mainly used, but diene copolymer latex such as styrene-butadiene copolymer latex may be used in combination. Many.
Rubber products such as rubber belts are repeatedly subjected to bending stress, resulting in bending fatigue and performance degradation, and separation between the reinforcing fibers and the rubber matrix may occur, which is promoted by heat. Therefore, in addition to the effect of improving the adhesion between rubber and fiber, the adhesive used for the treatment of the reinforcing fiber is required to have a heat-resistant adhesive force that does not deteriorate the adhesive performance at high temperatures.
Various methods have been proposed to improve the heat-resistant adhesive force, but proposals have also been made focusing on conjugated diene copolymer latex.

In Patent Document 1, a latex composition obtained by mixing a vinylpyridine copolymer latex copolymerized with an ethylenically unsaturated carboxylic acid monomer and a diene copolymer latex using many conjugated diene monomers is used. Thus, it is disclosed that the adhesion between the reinforcing fiber and the rubber and the heat-resistant adhesive force are improved.
In Patent Document 2, as a method for bonding polyester fiber and rubber, a method is disclosed in which fiber is firstly treated with a composition comprising resorcinol-formaldehyde resin and conjugated diene copolymer rubber latex having a gel content of 80% or more. Yes.
Patent Document 3 discloses an invention in which an adhesive treatment agent for rubber / fiber formed by blending an ethylenically unsaturated acid-modified styrene / butadiene rubber latex having a Tg of 0 to 35 ° C. is used in the secondary treatment. Yes.

Japanese Patent Publication No. 7-57829 Japanese Patent Publication No. 7-21066 JP 2008-169504 A

  These patent documents are mainly aimed at improving the heat-resistant adhesive strength, but the performance degradation of rubber products such as rubber belts tends to be accelerated not only by heat but also by moisture. Therefore, an adhesive having a good water-resistant adhesive strength is strongly desired. The objective of this invention is obtaining the adhesive composition which is excellent in water-resistant adhesive force in addition to heat resistant adhesive force.

The inventors have prepared a conjugated diene copolymer latex in which the copolymerization ratio of the conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer is in a specific range and has a specific toluene insoluble content. The present inventors have found that the above problems can be solved by using the adhesive composition, and have invented an adhesive composition comprising the conjugated diene copolymer latex as a constituent material.
That is, the present invention
(1) Emulsion polymerization of 25-50 mass% conjugated diene monomer, 1-15 mass% of ethylenically unsaturated carboxylic acid monomer, and 35-74 mass% of other monomers copolymerizable therewith The diene copolymer latex (A), the vinylpyridine copolymer latex (B), and the resorcinol-formaldehyde resin (C) that are obtained by the above process and have a toluene-insoluble content of the dry film of 82 to 100% Rubber and fiber adhesive composition, characterized in that it is a material,
(2) Glass transition temperature of the dry film diene copolymer latex (A) is - characterized in that it is a 10 ~ 45 ° C., the adhesive composition according to (1),
(3) The adhesive composition according to (1) or (2), wherein the diene copolymer latex (A) contains at least one of potassium hydroxide and ammonia as a pH adjuster,
Is to provide.

  According to the present invention, an excellent heat-resistant adhesive force and water-resistant adhesive force are exhibited in the adhesion between rubber and fiber.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, In the range of the summary, various deformation | transformation can be implemented.
(Monomer composition)
In this embodiment, the composition of the monomer constituting the copolymer latex (A) is 25 to 50% by mass of the conjugated diene monomer, 1 to 15% by mass of the ethylenically unsaturated carboxylic acid monomer, and It is 74-35 mass% of other monomers copolymerizable with these.

(Conjugated diene monomer)
Examples of the conjugated diene monomer used in the present embodiment include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl- 1,3-butadiene, 1,3-pentadiene, chloroprene, 2-chloro-1,3-butadiene, cyclobutadiene and the like can be mentioned, and these can be used alone or in combination of two or more. . Among these, 1,3-butadiene can be preferably used.
The proportion of the conjugated diene monomer in the total amount of all monomers is preferably 25 to 50% by mass, more preferably 28 to 45% by mass. By setting the ratio of the conjugated diene monomer to 25% by mass or more, the adhesive strength between rubber and fiber can be increased, and by setting it to 50% by mass or less, water-resistant adhesive strength and heat-resistant adhesive strength can be maintained high. it can.

(Ethylene unsaturated carboxylic acid monomer)
Examples of the ethylenically unsaturated carboxylic acid monomer used in the present embodiment include monobasic ethylenically unsaturated carboxylic acid monomers such as acrylic acid and methacrylic acid, itaconic acid, maleic acid, and fumaric acid. And dibasic ethylenically unsaturated carboxylic acid monomers. These can be used alone or in combination of two or more.
The use ratio of the ethylenically unsaturated carboxylic acid monomer is usually 1 to 15% by mass, preferably 2 to 12% by mass, and more preferably 3 to 10% by mass. By setting the amount of the ethylenically unsaturated carboxylic acid monomer used within the above range, the adhesive force between rubber and fiber, particularly the water-resistant adhesive force, is improved. As the ethylenically unsaturated carboxylic acid, monobasic ethylenically unsaturated carboxylic acid is preferable from the viewpoint of the effect of improving the water-resistant adhesive strength, and acrylic acid is particularly preferable.

(Other copolymerizable monomers)
Preferred examples of other monomers copolymerizable with conjugated diene monomers and ethylenically unsaturated carboxylic acid monomers include aromatics such as styrene, α-methylstyrene, vinyltoluene, and p-methylstyrene. Vinyl monomers, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, Methacrylic acid alkyl esters such as methyl methacrylate and butyl methacrylate, hydroxyalkyl esters such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate, aminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate Such as Glycidyl esters such as aminoalkyl esters, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-methylol acrylamide, N-methyl acrylamide, N-methyl methacrylamide, glycidyl methacrylamide, N, N-butoxymethyl acrylamide Amides such as vinyl acetate, carboxylic acid vinyl esters such as vinyl acetate, vinyl halides such as vinyl chloride, p-styrenesulfonic acid and its sodium salt, etc., and these may be used alone or in combination of two or more. That's fine.

(Toluene insoluble matter)
In the present embodiment, the toluene insoluble content of the dry film of the diene copolymer latex (A) is usually 82% to 100%, preferably 83% to 99%. More preferably, it is 85% to 98%. By adjusting the toluene insoluble content within this range, the fiber, rubber and adhesive strength are improved, and excellent heat-resistant adhesive strength and water-resistant adhesive strength can be realized.
Toluene insoluble matter is affected by various polymerization factors such as the proportion of diene monomer used, latex particle size setting, polymerization temperature, monomer feed conditions, etc., but it is usually adjusted by the amount of chain transfer agent added. Is easy and preferable.

(Chain transfer agent)
Examples of the chain transfer agent used in the present embodiment include dimers of nucleus-substituted α-methylstyrene such as α-methylstyrene dimer, n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, and n-dodecyl. Mercaptans, mercaptans such as t-dodecyl mercaptan, disulfides such as tetramethylthiuram disulfide and tetraethylthiuram disulfide, 2-ethylhexyl thioglycolate, terpinolene, cyclopentene, cyclohexene alone or in combination of two or more Can be used in combination. Among these, mercaptans can be preferably used.

(Glass-transition temperature)
In this embodiment, the glass transition temperature of diene copolymer latex (A) becomes like this. Preferably it is -20-50 degreeC, More preferably, it is -10-45 degreeC, More preferably, it is -5-40 degreeC. By setting the glass transition temperature within this range, it is possible to obtain an adhesive having excellent adhesion between fibers and rubber, and excellent in heat-resistant adhesive force and water-resistant adhesive force.

(PH adjuster)
For adjusting the pH of the diene copolymer latex (A) in the present embodiment, commonly used ones such as sodium hydroxide, potassium hydroxide, and ammonia can be used. Either potassium hydroxide or ammonia can be used. It is preferable to include one or both. For example, after emulsion polymerization is completed, a method of adjusting the pH to 5 to 8 with potassium hydroxide and performing steam stripping, and adjusting to a predetermined range (for example, pH 6 to 10) using ammonia after the completion of steam stripping. Can be adopted. Alternatively, the pH can be adjusted using only potassium hydroxide, or the pH can be adjusted using only ammonia. By using either one or both of potassium hydroxide and ammonia, the water-resistant adhesion can be further improved. In order to obtain such a further effect of improving the water-resistant adhesive strength, neutralizing agents other than potassium hydroxide and ammonia, such as sodium hydroxide, sodium hydrogen carbonate, disodium hydrogen phosphate, monoethanolamine, triethanol When an amine or the like is used in combination, the amount used is preferably 50% or less of the total neutralizing agent.

(Particle size)
In the present embodiment, the average particle size of the diene copolymer latex (A) is preferably 80 to 500 nm, more preferably 100 to 400 nm, and further preferably 150 to 300 nm. If the average particle diameter is smaller than this range, the viscosity of the copolymer latex becomes high and it may be difficult to handle. On the other hand, if the particle diameter is large outside this range, the productivity during latex production may be reduced. The average particle diameter can be adjusted by using a method for adjusting the amount of emulsifier used in the production by emulsion polymerization or a known seed polymerization method. The composition of the latex for seed is not particularly limited, and may be the same as or different from the composition of the copolymer latex. Further, the latex for seed may be produced in the same reaction vessel or may be produced in a different other reaction vessel, and its particle size, particle size distribution, and amount used are not particularly limited. .

(Production method)
In the present embodiment, for the production method of the diene copolymer latex, for example, a method of performing polymerization with a radical initiator in the presence of an emulsifier in an aqueous medium can be employed.

(emulsifier)
As the emulsifier used here, conventionally known anionic, cationic, amphoteric and nonionic emulsifiers can be used. Examples of preferred emulsifiers include, for example, anionic emulsifiers such as aliphatic soap, rosin acid soap, alkyl sulfonate, alkyl diphenyl ether disulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate; polyoxyethylene alkyl ether Nonionic emulsifiers such as polyoxyethylene alkyl allyl ether and polyoxyethylene oxypropylene block copolymer. These can be used alone or in combination of two or more. The amount of the emulsifier used is preferably 0.1 parts by mass to 2.0 parts by mass with respect to 100 parts by mass of the monomer.
In addition, it is possible to use a reactive emulsifier having a radical polymerizable double bond such as a vinyl group, an acryloyl group or a methacryloyl group in the molecule.

(Initiator)
The radical initiator is one that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing agent, and both inorganic and organic initiators can be used. . Examples of preferred initiators include peroxodisulfate, peroxide, azobis compound and the like.
More specific examples of such initiators include, for example, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisbutyro Nitrile, cumene hydroperoxide and the like can be mentioned. These can be used alone or in combination of two or more.
In addition, a so-called redox polymerization method in which a reducing agent such as acidic sodium sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof or Rongalite is used in combination with the above-described polymerization initiator can also be used.

(Monomer addition method)
In the emulsion polymerization for obtaining the diene copolymer latex (A), a known method can be used as a method of adding the monomer mixture to the reactor, and any of batch addition, continuous addition, and divided addition can be used. I do not care. A method of continuously adding a monomer mixture having a constant composition to a reactor is general, but a method of adding several types of monomer mixtures having different compositions in multiple stages can also be used. Examples of the method of adding the monomer mixture in multiple stages include a two-stage polymerization method and a three-stage polymerization method, and any method can be used.

(Method of adding chain transfer agent)
As a method for adding a chain transfer agent, for example, a method of adding a mixture with a monomer, a method of adding a chain transfer agent alone, a method of adding a chain transfer agent continuously or intermittently, a batch of chain transfer agents Although the method of adding etc. is mentioned, there is no restriction | limiting in the addition method.

(Polymerization temperature)
The polymerization temperature for producing the copolymer latex is, for example, 40 to 100 ° C, and preferably 50 to 90 ° C. If the polymerization temperature is lower than this range, the productivity of latex production may be reduced. On the other hand, if it is higher than this range, the internal pressure of the reactor may be difficult to control during the production of latex.
It is also possible to employ a method of raising the polymerization temperature (so-called cooking step) in order to increase the polymerization conversion rate of each monomer after the addition of all the monomers in the polymerization system. The polymerization temperature in such a process is usually 80 to 100 ° C.

(Polymerized solids)
Polymerization solid content concentration in the case of producing a copolymer latex (solid content concentration when polymerization is completed. The ratio of the solid content mass obtained by drying to the mass of the original copolymer latex (including water) ) Is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, from the viewpoint of production efficiency and ease of controlling the polymerization temperature during production.

(Polymerization regulator)
In producing the copolymer latex, various known polymerization regulators can be used at the time of emulsion polymerization or at the end of emulsion polymerization, if necessary. For example, a pH adjuster, a chelating agent, etc. can be used.

(Various additives)
Various additives can be added to the diene copolymer latex of the present embodiment as necessary as long as the effect is not impaired. For example, a dispersant, an antifoaming agent, an anti-aging agent, a water resistant agent, a bactericidal agent, a thickener, a water retention agent, a crosslinking agent, and the like can be added.

(Adhesive composition)
The rubber-fiber adhesive composition in the present embodiment comprises the diene copolymer latex (A), the vinylpyridine latex (B), and the resorcinol-formaldehyde resin (C) as constituent materials. . As the resorcinol-formaldehyde resin (C) used in the present invention, those conventionally used (for example, disclosed in JP-A No. 55-142635) can be used and are not particularly limited.
As the vinylpyridine latex (B), a commonly used one can be used. For example, a vinylpyridine / styrene / butadiene ratio of 15/15/70% by mass can be used.
The use ratio of the diene copolymer latex (A) and the vinylpyridine latex (B) is 10/90 to 90/10, preferably 30/70 to 70/30, as a solid content ratio.
Note that the adhesive composition in the present embodiment is a compounded material using a diene copolymer latex different from the present invention, natural rubber latex, urethane resin latex, acrylic resin latex, etc., as long as the effect is not impaired. It can be.

In this embodiment, there is no restriction | limiting in particular about the usage method of adhesive composition, It can apply like a known resorcinol-formaldehyde polymer latex adhesive. Usually, the adhesive composition of the present embodiment is made into an aqueous solution of 10 to 30% by mass, so that fibers in a desired form are dipped, dried and heat-treated at the time of manufacturing a rubber product, and then molded together with an unvulcanized rubber compound. The fiber and rubber can be bonded by vulcanization. Moreover, it can also adhere | attach with rubber | gum using the fiber of the desired form which apply | coated the adhesive composition of this embodiment previously.
The fibers to which the adhesive composition of this embodiment can be applied are not particularly limited, and can be used for rayon fibers, polyester fibers, polyamide fibers, and the like. These fibers may be in any form such as woven fabric, cord, and thread.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.
[Production Example 1]
A pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket is charged with 70 parts by weight of ion-exchanged water, 0.50 parts by weight of seed latex having a particle size of 0.0215 μm, and 0.3 parts by weight of sodium dodecylbenzenesulfonate. The temperature was raised to 80 ° C. Subsequently, 100 parts by mass of a monomer mixture consisting of 40 parts by mass of butadiene, 50 parts by mass of styrene, 5 parts by mass of acrylic acid, and 5 parts by mass of methyl methacrylate was added in 5 hours, and 20 parts by mass of water, sodium peroxodisulfate 1 An initiator-based aqueous solution consisting of parts by weight, 0.2 parts by weight of potassium hydroxide, and 0.1 parts by weight of sodium dodecylbenzenesulfonate was added at a constant flow rate for 5.5 hours. After the addition of the monomer mixture and the initiator aqueous solution was completed, the reaction was continued at 90 ° C. for 1.5 hours to obtain a diene copolymer latex having a polymerization conversion rate of 95% or more. The copolymer latex was adjusted to pH 6.0 with potassium hydroxide and then unreacted monomers were removed by a steam stripping method. After cooling to room temperature, the pH was adjusted to 8.0 with aqueous ammonia and adjusted to a solid content of 50% by weight to finally obtain a diene copolymer latex a. For copolymer latex a, the particle size, glass transition temperature, and toluene insoluble content were measured by the following methods. The results are shown in Table 1.

(Particle size)
The particle size was determined with a light scattering particle size analyzer (Model 6000 manufactured by CNN Wood).
(Glass-transition temperature)
The obtained copolymer latex was dried at 130 ° C. for 30 minutes to form a film, and this film was subjected to a temperature increase rate of 15 ° C./min using a differential calorimeter (DSC-220C) manufactured by Seiko Denshi. Measured with
(Toluene insoluble matter)
The obtained latex was dried at 130 ° C. for 30 minutes to form a film, and a measuring test amount of 0.5 g was precisely weighed from the obtained film, immersed in 30 g of toluene, shaken for 3 hours, and then 300 mesh. It filtered with the stainless steel mesh. The undissolved matter remaining on the mesh at this time was dried, and the weight was divided by the sample weight to obtain a toluene insoluble fraction.

[Production Examples 2 to 10]
Diene copolymer latexes b to j were obtained in the same manner as in Example 1 except that the composition of the monomer mixture used was changed as shown in Table 1. The seed latex was the same as that used in Example 1, but the amount used was appropriately adjusted so that the copolymer latex had a predetermined particle size. Table 1 shows the particle size, toluene insoluble content, and glass transition temperature of the obtained diene copolymer latex.

[Production Example 11]
A copolymer latex k was obtained under the same conditions as in Production Example 1, except that sodium hydroxide was used to adjust the pH after completion of the polymerization and after completion of the steam stripping.

[Example 1]
16.6 parts of resorcinol, 14.6 parts of a formalin aqueous solution (37% concentration) and 1.3 parts of sodium hydroxide were dissolved in 333.5 parts of water and reacted at 25 ° C. for 2 hours with stirring. Next, 50 parts by mass (solid content) of a commercially available vinylpyridine-butadiene-styrene copolymer latex (vinylpyridine / styrene / butadiene = 15/15/70% by mass) and the copolymer prepared in Production Example 1 above. 50 parts by mass (solid content) of polymer latex a was added and stirred at 25 ° C. for 20 hours. Next, 30 parts of Vulkabond E (Vulnax product Vulcabondo E) was added. After adjusting this aqueous solution to a solid content concentration of 20%, a polyester tire cord (1500 D / 2) was dipped using a test single cord dipping machine. After the immersion treatment, heat treatment was performed at 240 ° C. for 1 minute. This treated polyester tire cord was pinched with a natural rubber compound produced by the compounding process shown in Table 2, and press vulcanized under predetermined conditions. The adhesion between the tire cord and rubber was evaluated by the T adhesion test method (measurement temperature 20 ° C., relative humidity 65%, 24 pull-out tests). Evaluation of adhesive force was implemented on the following three conditions.
(1) Initial adhesive strength evaluation: Evaluation was made at 150 ° C. for 30 minutes.
(2) Evaluation of heat-resistant adhesive strength: Evaluated at 170 ° C. for 90 minutes.
(3) Water-resistant adhesive strength evaluation: The adhesive strength after boiling a test piece obtained by vulcanization under the conditions of (1) for 60 minutes in water is evaluated.
The results are shown in Table 3.

[Examples 2 to 6]
As the diene copolymer latex, an adhesive composition was produced under the same conditions as in Example 1 except that b to e and k described in Table 1 were used, and the adhesive strength was measured in the same manner as in Example 1. I did it. The obtained results are shown in Table 3.

[Comparative Examples 1-5]
A water-based adhesive composition was produced under the same conditions as in Example 1 except that f to j listed in Table 1 were used as the diene copolymer latex, and the adhesive strength was measured. The obtained results are shown in Table 3.

  The adhesive of the present invention is an adhesive that bonds rubber and polyester fiber, polyamide fiber, rayon fiber, etc. to exhibit excellent heat and water resistant adhesive strength, and is used for applications using rubber products such as rubber belts and tires. there is a possibility.

Claims (3)

  Conjugated diene monomer 25 to 50% by mass, ethylenically unsaturated carboxylic acid monomer 1 to 15% by mass, aromatic vinyl monomer copolymerizable with these, vinyl cyanide monomer, acrylic Acid alkyl ester, alkyl methacrylate ester, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, aminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacryl Amide, N-methylol acrylamide, N-methyl acrylamide, N-methyl methacrylamide, glycidyl methacrylamide, N, N-butoxymethyl acrylamide, vinyl acetate, vinyl chloride, p-styrene sulfonic acid and its sodium salt group A diene copolymer latex obtained by emulsion polymerization of 35 to 74% by mass of one or more other monomers selected from the above, wherein the toluene-insoluble content of the dry film is 82 to 100% ( A rubber-fiber adhesive composition comprising A), vinylpyridine copolymer latex (B), and resorcinol-formaldehyde resin (C) as constituent materials. The glass transition temperature of the dry film diene copolymer latex (A) is - characterized in that it is a 10 ~ 45 ° C., the adhesive composition according to claim 1. The adhesive composition according to claim 1 or 2, wherein the diene copolymer latex (A) contains at least one of potassium hydroxide and ammonia as a pH adjuster.