JP2020063362A - Adhesive composition for wet friction material - Google Patents

Abstract

To provide an adhesive composition for wet friction material having excellent adhesive strength and excellent workability and coatability.SOLUTION: An adhesive composition for wet friction material has resol type phenol resin and polyvinyl butyral, the polyvinyl butyral having a degree of butyralation of 65 mol% or more and 95 mol% or less. In the adhesive composition for wet friction material, the polyvinyl butyral has a weight average molecular weight (Mw) of 20000 or more and 150000 or less. In the adhesive composition for wet friction material, the content of the polyvinyl butyral is 1 mass% or more and 40 mass% or less relative to the total solid content of the composition.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive composition for wet friction materials.

  Automatic transmissions such as automatic vehicles use a clutch that is installed between the engine and the transmission (transmission) and that transmits or interrupts the power of the engine to the transmission when starting, stopping, or shifting. . Friction materials, which are used for proper functioning of the clutch, are generally classified into "wet friction materials" that use oil and "dry friction materials" that do not use oil. The wet friction material can suppress an increase in friction heat by using oil. The wet friction material is manufactured by applying an adhesive to a metal called a core plate and bonding it to a member such as paper impregnated and cured with a phenol resin or the like.

  On the other hand, the resol-type phenol resin is a resin material having excellent mechanical properties, electrical properties, and adhesiveness. Therefore, the resol-type phenol resin is widely used in adhesives used in manufacturing wet friction materials such as clutches and brakes. Therefore, various studies have been conventionally performed on the resol-type phenol resin in order to improve the curing characteristics such as the adhesive strength in order to improve the friction characteristics of the wet friction material.

  Examples of resol-type phenolic resins used for wet friction materials include those described in Patent Documents 1 and 2. Patent Document 1 discloses an adhesive containing a resol-type phenol resin, a polyvinyl butyral resin, a polyvalent metal salt, and a metal salt of nitrous acid or an ester of nitrous acid in order to shorten the curing time and obtain heat resistance. Compositions are disclosed.

  Patent Document 2 discloses an adhesive for a wet friction plate containing a resol-type phenol resin, which exhibits excellent adhesive strength, and a nitrate or nitric acid.

JP, 2014-24881, A JP, 2006-83892, A

  In recent years, the demand for adhesives for wet friction materials has been increasing. For example, in order to obtain high adhesive strength, it is known to increase the molecular weight of the phenol resin, which is the main component, but when the molecular weight is increased, solvent solubility decreases and workability and coatability tend to decrease. was there. The present invention was developed to meet high demands, and provides an adhesive composition for a wet friction material, which has excellent adhesive strength and good workability and coatability.

According to the invention,
Resol type phenolic resin,
Including polyvinyl butyral,
There is provided an adhesive composition for wet friction materials, wherein the polyvinyl butyral has a degree of butyralization of 65 mol% or more and 95 mol% or less.

  According to the present invention, it is possible to provide an adhesive composition for a wet friction material, which is excellent in adhesive strength and has good workability and coatability.

  The adhesive composition for wet friction materials of the present embodiment (hereinafter, also referred to as “adhesive composition”) contains a resol-type phenol resin and polyvinyl butyral. Each component will be described below.

<Resol type phenol resin>
The resol-type phenol resin according to the present embodiment is included in the adhesive used to bond the friction material and the metal base material.

  The resol type phenol resin is obtained by reacting phenols and aldehydes in a reaction solvent by a known method under a basic catalyst.

  Specific examples of the phenols include phenol; cresols such as o-cresol, m-cresol and p-cresol; ethylphenols such as o-ethylphenol, m-ethylphenol and p-ethylphenol; isopropylphenol, Butylphenols such as butylphenol and p-tert-butylphenol; alkylphenols such as p-tert-amylphenol, p-octylphenol, p-nonylphenol and p-cumylphenol; fluorophenols, chlorophenols, bromophenols, iodophenols and the like. Halogenated phenols; monovalent phenol substitution products such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol and trinitrophenol: and 1-naphthol, -Monohydric phenols such as naphthol; and polyhydric phenols such as resorcin, alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, phloroglucin, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. . These may be used alone or in admixture of two or more.

Specific examples of the aldehydes include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butylaldehyde, caproaldehyde, allylaldehyde, benzaldehyde, croton. Examples thereof include aldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These may be used alone or in admixture of two or more.
It is also possible to use substances that are the source of these aldehydes or solutions of these aldehydes. Above all, it is preferable to use an aqueous formaldehyde solution from the viewpoint of production cost.

  Examples of the basic catalyst include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide; carbonates such as sodium carbonate and calcium carbonate; oxides such as lime; Examples thereof include sulfites such as sodium sulfite; phosphates such as sodium phosphate; ammonia, amines such as trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, hexamethylenetetramine, and pyridine.

  Water is generally used as the reaction solvent, but an organic solvent may be used. Specific examples of such organic solvents include alcohols, ketones, aromatics and the like. Specific examples of such alcohols include methanol, ethanol, propyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin and the like. Further, specific examples of the ketones include acetone and methyl ethyl ketone. Specific examples of aromatics include toluene and xylene.

  Examples of the form of the resol-type phenol resin include solid, aqueous solution, solvent solution, and aqueous dispersion. Among them, a solvent solution of methanol, ethanol, methyl ethyl ketone, and acetone is preferable from the viewpoint of good workability.

[Polyvinyl butyral]
Polyvinyl butyral is obtained by converting polyvinyl alcohol into butyral.
Although the weight average molecular weight (Mw) of polyvinyl butyral is not particularly limited, it is preferably 1.0 × 10 ^{4 to} 1.0 × 10 ⁶ and more preferably 1.5 from the viewpoint of handling property of polyvinyl butyral. × 10 ^{4 to} 5.0 × 10 ⁵ , more preferably 2.0 × 10 ^{4 to} 1.5 × 10 ⁵ . By setting such a numerical range, it becomes easy to maintain the balance between the adhesive strength and the solvent solubility.
The weight average molecular weight refers to that measured by gel permeation chromatography (GPC) in terms of polystyrene.

  The polymerization degree of polyvinyl butyral is preferably 200 to 3000. By setting the degree of polymerization to 200 or more, sufficient adhesive strength can be obtained, and by setting the degree of polymerization to 3000 or less, the viscosity of the adhesive when melted can be suppressed to be low and a good adhesive coating film can be obtained.

  The content of polyvinyl butyral is 1 to 40 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the resol-type phenol resin. By setting the content of polyvinyl butyral to the lower limit value or more, sufficient adhesive strength can be obtained, and by setting it to the upper limit value or less, the viscosity of the adhesive at the time of melting is suppressed to be a good adhesive coating film. Obtainable.

The lower limit of the degree of butyralization of polyvinyl butyral is preferably 65 mol% or more, and more preferably 70 mol% or more, from the viewpoint of obtaining good adhesive strength.
The upper limit of the degree of butyralization of polyvinyl butyral is preferably 95 mol% or less, more preferably 90 mol% or less, from the viewpoint of improving the balance between adhesive strength and solubility.
Conventionally, it has been known that high adhesive strength can be obtained by using polyvinyl butyral having a high weight average molecular weight, but when the weight average molecular weight is increased, the viscosity tends to increase and the solubility tends to decrease. On the other hand, in the adhesive composition for a wet friction material of the present embodiment, by controlling the degree of butyralization of polyvinyl butyral to be not less than 65 mol% and not more than 95 mol%, an increase in viscosity can be suppressed. It is possible to achieve both good adhesive strength and solubility in the application of the wet friction material.
The degree of butyralization of polyvinyl butyral can be measured according to JIS K6728.

The adhesive composition for wet friction materials according to the present embodiment is an elastomer such as nitrile butadiene rubber and styrene butadiene rubber, a surfactant, a flame retardant, an antioxidant, a colorant, and a silane as long as the effects of the present invention are not impaired. You may add additives, such as a coupling agent. Ingredients other than the above may be included.
The adhesive composition for wet friction materials according to the present embodiment preferably contains substantially neither nickel nor cobalt. Thereby, the environmental load can be reduced.

  The adhesive composition for a wet friction material according to the present embodiment is obtained by mixing the above-mentioned components by a known method, and may be diluted with an organic solvent from the viewpoint of easy handling. Specific examples of the organic solvent include alcohol-based organic solvents such as methanol, ethanol, isopropanol, butanol, ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, toluene, aromatic hydrocarbon solvents such as ethylbenzene, and mixtures thereof. Is mentioned.

The adhesive composition for wet friction materials according to the present embodiment preferably has a methanol tolerance (25 ° C.) of 1000% or more. By doing so, the solvent solubility becomes good, and the workability and coatability can be improved. Further, the methanol tolerance (25 ° C.) is more preferably 2000% or more from the viewpoint of further improving workability. The higher the value of methanol tolerance, the higher the solubility in methanol, and in the application of the adhesive for wet friction materials, 100% or more is required for the application of the adhesive for wet friction materials.
The methanol tolerance can be measured as follows.
First, 10 ml of the adhesive composition for a wet friction material is measured into a 500 ml graduated cylinder, and methanol is gradually added while stirring at 25 ° C. It is calculated by the following formula from the addition amount (volume) of methanol when the mixed solution of the adhesive composition for wet friction materials and methanol becomes cloudy.
Methanol tolerance (%) = (methanol addition amount (ml) / adhesive composition for wet friction material 10 ml) × 100

Moreover, the viscosity of the adhesive composition for wet friction materials according to the present embodiment is preferably 300 mPa or more and 10000 mPa or less, and more preferably 450 mPa or more and 8000 mPa or less. Within such a numerical range, while maintaining high adhesive strength, solvent solubility becomes good, and workability and coatability can be improved.
The viscosity is measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) according to JIS Z8803.

  The adhesive composition of this embodiment is suitably used for producing a wet friction plate. The wet friction plate is one in which the above-mentioned adhesive composition for wet friction materials is interposed between a friction material and a metal base material. By doing so, the resol type phenolic resin has excellent heat resistance and curability, which are the characteristics, and the adhesion between the friction material and the metal base material (steel plate or the like) can be improved. The wet friction plate according to the present embodiment is used to form friction parts such as a clutch and a brake.

  Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

  Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Synthesis of resol type phenolic resin]
To a reactor equipped with a stirrer, a reflux condenser and a thermometer, 100 parts by weight of phenol, 117 parts by weight of 37% formalin aqueous solution (F / P molar ratio = 1.2), and 4 parts by weight of 30% aqueous ammonia solution were added. The reaction was carried out for 40 minutes under reflux conditions. Then, while dehydrating under a reduced pressure of 91 kPa, when the temperature in the system reached 70 ° C., 20 parts by weight of methanol was added, and the mixture was reacted at 80 ° C. for 1 hour. Next, 80 parts by weight of methanol was added to obtain a resol-type phenol resin having a nonvolatile content of 50%.

<Example 1>
100 parts by weight of the obtained resol-type phenol resin, 12 parts by weight of polyvinyl butyral resin (PVB) shown in Table 1 and 12 parts by weight of methanol were dissolved and mixed to obtain an adhesive composition for a wet friction material.

<Example 2>
An adhesive composition for wet friction materials was obtained in the same manner as in Example 1 except that the polyvinyl butyral resin (PVB) shown in Table 1 was used.

<Example 3>
An adhesive composition for wet friction materials was obtained in the same manner as in Example 1 except that the polyvinyl butyral resin (PVB) shown in Table 1 was used.

<Example 4>
An adhesive composition for wet friction materials was obtained in the same manner as in Example 1 except that the polyvinyl butyral resin (PVB) shown in Table 1 was used.

<Comparative Example 1>
An adhesive composition for wet friction materials was obtained in the same manner as in Example 1 except that the polyvinyl butyral resin (PVB) shown in Table 1 was used.

<Comparative example 2>
An adhesive composition for wet friction materials was obtained in the same manner as in Example 1 except that the polyvinyl butyral resin (PVB) shown in Table 1 was used.

  The following evaluations were performed using the adhesive compositions for wet friction materials obtained in the examples and comparative examples.

-Methanol tolerance: First, 10 ml of the adhesive composition for wet friction materials was measured into a 500 ml graduated cylinder, and methanol was gradually added while stirring at 25 ° C. It was calculated by the following formula from the amount (volume) of addition of methanol when the mixed solution of the adhesive composition for wet friction materials and methanol became cloudy.
Methanol tolerance (%) = (methanol addition amount (ml) / adhesive composition for wet friction material 10 ml) × 100

-Viscosity: Using the adhesive composition for wet friction materials, the viscosity was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) according to JIS Z8803.

-Adhesive strength (non-peeling area ratio): An acid-washed steel sheet is coated with the obtained adhesive composition for wet friction materials, and an aramid base material is impregnated and cured with a phenol resin. The area where the adhesive surface was not peeled off when bonded at 250 ° C. and 10 MPa and bent at 90 ° C. was calculated, and the ratio (%) to the bonded area before bending was calculated.

Workability: The adhesive workability composition for wet friction materials was put in a stainless steel vat, and the cleaning workability when the stainless vat was washed with methanol was evaluated according to the following criteria.
A: Very good cleaning workability.
◯: Cleaning workability is good.
X: Adhesion was found in the stainless steel vat, and the cleaning property was poor.

Butyralization degree: Measured according to JIS K6728.

Claims (5)

Resol type phenolic resin,
Including polyvinyl butyral,
An adhesive composition for a wet friction material, wherein the butyralization degree of the polyvinyl butyral is 65 mol% or more and 95 mol% or less.   The adhesive composition for wet friction materials according to claim 1, wherein the polyvinyl butyral has a weight average molecular weight (Mw) of 20000 or more and 150,000 or less.   Content of the said polyvinyl butyral is 1 mass% or more and 40 mass% or less with respect to the whole solid content of the adhesive composition for wet friction materials, The adhesive composition for wet friction materials of Claim 1 or 2. object.   The adhesive composition for wet friction materials according to any one of claims 1 to 3, which is substantially free of nickel and cobalt.   The adhesive composition for a wet friction material according to any one of claims 1 to 4, which has a methanol tolerance (25 ° C) of 1000% or more.