JP2016069502A - Resol type phenol resin composition for wet friction material and wet friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resol type phenol resin composition for a wet friction material capable of providing a wet friction material high in porosity, excellent in oil penetrability to a fiber substrate and excellent in durability without reducing mechanical strength of the friction material.SOLUTION: There is provided a resol type phenol resin composition used for a wet friction material, having weight average molecular weight of 100 to 500 and constituted with containing a constitutional unit having no substituent with 2 to 10 carbon atoms on an aromatic ring having a phenolic hydroxyl group and a constitutional unit having a substituent with 2 to 10 carbon atoms on the aromatic ring having the phenolic hydroxyl group. There is provided a wet friction material by impregnating a fiber substrate with the resol type phenol resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a resol type phenolic resin composition for a wet friction material and a wet friction material.

  Phenol resins, which are thermosetting resins, are widely used mainly as binders to bond materials that are the base materials of molded products, and have excellent mechanical properties, electrical properties, and adhesive properties. Used in. Particularly in recent years, the amount of friction material using phenolic resin as a binder in automobiles, railway vehicles, and the like is increasing.

  Among them, a liquid resol type phenolic resin is generally used as a friction material used in an automatic transmission such as an automatic transmission vehicle called a wet friction material. In order to improve the durability of the wet friction material, it is required that the wet friction material has fine and uniform pores. The porous wet friction material can hold a large amount of automatic transmission fluid (ATF) inside. When sliding, the wet friction material causes a compression change of several μm to several tens of μm to discharge the ATF held inside, and the ATF is again absorbed along with the restoration by the release. have. Thereby, the cooling effect which lowers | hangs the temperature of the sliding surface which became high in the case of sliding and prevents internal heat storage generate | occur | produces. This cooling effect is largely related to the durability of the wet friction material. Therefore, in order to improve the durability of the wet friction material, the wet friction material is required to be more uniform and have a high porosity.

  Normally, focusing only on the porosity of the friction material, the porosity can be increased by reducing the proportion of the resin of the friction material, but the friction material strength is reduced by reducing the proportion of the resin as the binder. Therefore, there is a limit to the method for increasing the porosity by reducing the amount of resin.

  In addition, aralkyl modification and alkylbenzene modification, which are excellent in heat resistance, have been studied and some phenol resins have been put into practical use. However, when these modifications are made, the impregnation property of the resin to the base material is inferior, and uniform and high pores cannot be formed. Therefore, the cooling effect by ATF is lowered, and as a result, sufficient durability may not be exhibited.

  Therefore, as a method satisfying the above requirements, a method characterized by comprising a water-soluble phenol resin has been studied (see, for example, Patent Document 1). By using a water-soluble phenol resin, it is possible to suppress the resin migration and make the distribution of the resin existing ratio uniform in the thickness direction of the friction material. However, since the water-soluble phenolic resin has a high polarity, the wettability to the aramid fiber, which is the main component of the base material and has a low polarity, is low, and the binder reinforces the base material by bonding between the fibers. The mechanical strength tends to decrease due to a decrease in the effect, and as a result, the durability is not always satisfactory. There has been a strong demand for further improvement in the method of improving the durability of the friction material.

Japanese Patent No. 40053550

  The object of the present invention is to provide a wet friction material that has a high porosity, excellent oil permeability to a fiber substrate, and excellent durability without reducing the mechanical strength of the friction material. It is providing the resol type phenol resin composition for materials.

Such an object is achieved by the present invention described in the following items [1] to [6].
[1] A resol type phenol resin composition used for a wet friction material, having a weight average molecular weight of 100 or more and 500 or less, and a substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group For a wet friction material comprising a resol-type phenol resin comprising a structural unit having no phenol and a structural unit having a substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group Resol type phenolic resin composition.
[2] The resol-type phenol resin is a phenol having no substituent of 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group, and an aromatic ring having a phenolic hydroxyl group having 2 to 10 carbon atoms. The resol type phenol resin composition for wet friction materials according to item [1], which is a resol type phenol resin obtained from phenols having a substituent and aldehydes.
[3] The structural unit having no substituent of 2 to 10 carbon atoms in the aromatic ring having a phenolic hydroxyl group has a substituent having 1 or less carbon atoms in the aromatic ring having a phenolic hydroxyl group. Or the resol type phenol resin composition for wet friction materials as described in the item [2].
[4] Any of the items [1] to [3], wherein the aromatic ring having a phenolic hydroxyl group has 3 to 8 carbon atoms in the substituent of the structural unit having a substituent having 2 to 10 carbon atoms. The resol type phenol resin composition for wet friction materials according to claim 1.
[5] In the resol type phenol resin, the aromatic ring having a phenolic hydroxyl group has a structural unit having no substituent of 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has 2 to 10 carbon atoms. The resol type for wet friction materials according to any one of items [1] to [4], wherein the molar fraction with the structural unit having the following substituents is in the range of 95: 5 to 50:50 on average. Phenolic resin composition.
[6] A wet friction material obtained by impregnating a fiber substrate with the resol type phenol resin composition for wet friction material according to any one of items [1] to [5].

  When the resol type phenolic resin composition for wet friction materials of the present invention is used as a binder, the porosity is high, the oil permeability to the fiber base material is excellent, and the durability without reducing the mechanical strength of the friction material. Can be obtained.

The resol type phenol resin composition for wet friction material of the present invention is a resol type phenol resin composition used for a wet friction material, and has a weight average molecular weight of 100 or more and 500 or less, and an aromatic having a phenolic hydroxyl group. Resol-type phenol comprising a structural unit having no substituent of 2 to 10 carbon atoms in the aromatic ring and a structural unit having a substituent of 2 to 10 carbon atoms in the aromatic ring having a phenolic hydroxyl group A resin is included. By setting the weight average molecular weight to 100 or more and 500 or less, the impregnation property of the resol type phenol resin composition for wet friction material into the fiber base material is improved, and the resol type phenol resin composition does not decrease in mechanical strength. Even if the blending amount is increased, it is possible to obtain an effect of making the pores of the wet friction material uniform and increasing the porosity. Moreover, not only the structural unit which does not have a C2-C10 substituent in the aromatic ring which has a phenolic hydroxyl group but the structure which has a C2-C10 substituent in the aromatic ring which has a phenolic hydroxyl group By including the unit, the polarity of the resol type phenolic resin is reduced, and the wettability to the fiber base material such as aramid fiber is increased, so that the binder effect is enhanced and the durability is improved. be able to. In addition, the wet friction material of the present invention is characterized in that the fiber base material is impregnated with the resol type phenol resin composition for wet friction material of the present invention. As a result, a wet friction material having high porosity and excellent durability can be obtained without reducing the mechanical strength of the wet friction material. Below, the resol type phenol resin composition for wet friction materials of this invention and a wet friction material are demonstrated in detail.

First, the resol type phenolic resin composition for wet friction materials of this invention is demonstrated.
Conventionally, a resol type phenol resin having a weight average molecular weight of more than 500 and not more than 1200 is used in a phenol resin composition for a wet friction material. In the case of such a resol type phenolic resin having a relatively small average molecular weight, the amount of methylol groups (—CH ₂ OH) remaining in the resin is increased and the polarity is increased, so that a fiber substrate such as an aramid fiber In some cases, the wet friction material using the same cannot be applied to products that require high durability. Further, when the weight average molecular weight is larger than 1200, the impregnation property to the fiber base material is lowered, the adhesion to the fiber base material is lowered, and finally the wet friction material as a composite material has high durability. In some cases, it was not applicable to the required products.

  On the other hand, the resol type phenol resin contained in the resol type phenol resin composition for wet friction material of the present invention has a weight average molecular weight of 100 or more and 500 or less, and carbon in an aromatic ring having a phenolic hydroxyl group. A resol-type phenol resin comprising a structural unit having no substituent of 2 to 10 and a structural unit having a substituent of 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group. By making the weight average molecular weight of the resol type phenol resin smaller than that of the conventional one and not less than 100 and not more than 500, it becomes easy for the resin to penetrate into the gaps of the fiber base material. Furthermore, not only the structural unit which does not have a C2-C10 substituent in the aromatic ring which has a phenolic hydroxyl group, but the structure which has a C2-C10 substituent in the aromatic ring which has a phenolic hydroxyl group. By including the unit, the polarity of the resin is reduced, and the effect of suppressing the decrease in wettability with a fiber substrate such as an aramid fiber and improving the adhesion with the fiber substrate can be obtained.

  The weight average molecular weight of the resol type phenol resin contained in the resol type phenol resin composition for wet friction materials of the present invention is 100 or more and 500 or less, more preferably 200 or more and 400 or less. In this range, the resol type phenolic resin composition for wet friction materials is likely to penetrate into the gaps between the fibers of the fiber base material, and the effect of improving the impregnation property is obtained.

Here, the weight average molecular weight of the resol type phenol resin can be determined by, for example, GPC (gel permeation chromatography). A calibration curve prepared using a polystyrene standard substance can be used, and GPC measurement can be performed using tetrahydrofuran as an elution solvent at a flow rate of 1.0 ml / min and a column temperature of 40 ° C. The apparatus consists of a main body: HLC-8020 manufactured by Tosoh Corporation, and an analytical column: TSKgel G1000HXL 1 manufactured by Tosoh Corporation.
Book, 2 G2000HXL, 1 G3000HXL can be used.

  Structural unit and phenol having no substituent of 2 to 10 carbon atoms in the aromatic ring having a phenolic hydroxyl group in the resol type phenol resin contained in the resol type phenol resin composition for wet friction material of the present invention The molar fraction with the structural unit having a substituent having 2 or more and 10 or less carbon atoms in the aromatic ring having a functional hydroxyl group is not particularly limited, but is in the range of 95: 5 to 50:50 on average. It is preferable that the range is 90:10 to 70:30. By setting it as this range, the effect which improves the wettability with a base material, the impregnation property, and mechanical strength can be acquired.

Although the resol type phenol resin contained in the resol type phenol resin composition for wet friction materials of the present invention is not particularly limited, the aromatic ring having a phenolic hydroxyl group is substituted with 2 to 10 carbon atoms. The structural unit having no group may have a substituent having 1 or less carbon atoms on the aromatic ring having a phenolic hydroxyl group. Thereby, the effect which improves the wettability with a base material and impregnation property can be acquired.

  Moreover, substitution of the structural unit which has a C2-C10 substituent in the aromatic ring which has a phenolic hydroxyl group in the resol type phenol resin contained in the resol type phenol resin composition for wet friction materials of this invention The number of carbon atoms in the group is more preferably 3 or more and 8 or less. By setting it as this range, the effect which can implement | achieve the high-order balance with the wettability with a base material, impregnation property, and mechanical strength can be acquired.

  Although it does not specifically limit as a method of manufacturing the resol type phenol resin contained in the resol type phenol resin composition for wet friction materials of this invention, For example, it is carbon to the aromatic ring which has a phenolic hydroxyl group. Phenolic compounds having no substituents of 2 or more and 10 or less (hereinafter also referred to as “phenols” for convenience) and phenols having a substituent of 2 or more and 10 or less carbon atoms on an aromatic ring having a phenolic hydroxyl group (hereinafter referred to as “phenols”) For convenience, it is also referred to as “alkylphenols”.) And aldehydes are reacted under basic conditions. Alternatively, a method may be used in which phenols and formaldehyde are reacted in the first step, and alkylphenols are added and reacted in the second step.

  Here, in the resol type phenol resin contained in the resol type phenol resin composition for wet friction materials of the present invention, the structural unit having no substituent having 2 to 10 carbon atoms in the aromatic ring having a phenolic hydroxyl group And the molar fraction of the structural unit having a substituent having 2 or more and 10 or less carbon atoms on the aromatic ring having a phenolic hydroxyl group can be determined by, for example, NMR (nuclear magnetic resonance). Further, in a simple manner, in the above-described production method, an aromatic ring having a phenolic hydroxyl group has an aromatic ring having a phenolic hydroxyl group and a phenol having no substituent having 2 to 10 carbon atoms (phenols). It can also be calculated from the charged molar ratio with phenols (alkylphenols) having a substituent having 2 to 10 carbon atoms.

  The phenols (phenols) not having a substituent having 2 or more and 10 or less carbon atoms in the aromatic ring having a phenolic hydroxyl group used in the production of a resol type phenol resin is not particularly limited. Cresols such as phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3, Xylenols such as 5-xylenol, halogenated phenols such as fluorophenol, chlorophenol, bromophenol, iodophenol, monohydric phenol substitutes such as aminophenol, nitrophenol, dinitrophenol, trinitrophenol, and 1- Naphthol, 2-naphthol Monovalent phenols, resorcinol, catechol, hydroquinone, pyrogallol, and the like polyhydric phenols such as phloroglucinol. These can be used individually or in mixture of 2 or more types. Among these phenols, those selected from phenol and cresols are preferable. Thereby, the wettability to fiber base materials, such as an aramid fiber, can be improved in the wet friction material using the resol type phenol resin composition of this invention.

In addition, the phenols (alkylphenols) having a substituent having 2 or more and 10 or less carbon atoms in the aromatic ring having a phenolic hydroxyl group used in the production of a resol type phenol resin is not particularly limited. Ethyl phenols such as o-ethylphenol, m-ethylphenol and p-ethylphenol, propylphenols such as 1-propylphenol and isopropylphenol, butylphenols such as butylphenol and p-tert-butylphenol, p-tert- Examples thereof include alkylphenols such as amylphenol, p-octylphenol, p-nonylphenol, and p-cumylphenol. These can be used alone or in combination of two or more. Among these alkylphenols, p-tert-butylphenol is more preferable. Thereby, the effect which improves the mechanical strength of a friction material can be acquired. Moreover, when carbon number exceeds the said upper limit, since it is inferior to reactivity by a steric hindrance, a mechanical physical property may fall.

  The aldehydes used in the production of the resol type phenol resin are not particularly limited, and examples thereof include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, and furfural. , Glyoxal, n-butyraldehyde, caproaldehyde, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These can be used alone or in combination of two or more. Among these aldehydes, those selected from formaldehyde and paraformaldehyde are preferable. Thereby, in the wet friction material using the phenol resin of this invention, the wettability to fiber base materials, such as an aramid fiber, can be improved.

  The catalyst that can be used in the production of the resol type phenol resin is not particularly limited, and examples thereof include sodium hydroxide, barium hydroxide, calcium hydroxide, triethylamine, and ammonia. These can be used alone or in combination of two or more.

  In the resol type phenol resin composition for wet friction material of the present invention, an organic solvent can be used to dilute the resin. The organic solvent used for dilution is not particularly limited. For example, alcohol organic solvents such as methanol, ethanol, isopropanol and butanol, ketone organic solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, toluene, Aromatic hydrocarbon solvents such as ethylbenzene and mixtures thereof can be used. The dilution rate is not particularly limited, but it is preferable to dilute the non-volatile content of the resin composition to be about 30% to 70% from the viewpoints of handleability and change with time.

Next, the wet friction material of the present invention will be described.
The wet friction material of the present invention is obtained by impregnating a fiber base material with the resol type phenol resin composition for wet friction material of the present invention. As a result, a wet friction material having high porosity and excellent durability can be obtained without reducing the mechanical strength of the wet friction material.

  The fiber base material impregnated with the resol type phenolic resin composition for wet friction material of the present invention is not particularly limited, but natural fiber such as natural pulp fiber and linter pulp, inorganic fiber such as glass fiber, poly A base material using carbon fibers such as acrylonitrile (PAN) -based carbon fibers and pitch-based carbon fibers, or fibers such as aramid fibers and chemical fibers such as phenol fibers alone or in combination of two or more types can be used. Among these, it is preferable to use an aramid fiber as a main component for a fiber base material from the viewpoint of friction characteristics and durability. The form of the fiber is not particularly limited, and a nonwoven fabric, a woven fabric, or the like can be used.

  In the wet friction material of the present invention, a paper base material filled with a friction modifier such as cashew dust and an inorganic filler such as diatomaceous earth can be used together with the fiber base material as desired.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
“Parts” described herein indicates “parts by mass”, and “%” indicates “% by mass”.

(Manufacture of resol type phenolic resin)
Example 1
In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 800 parts of phenol as phenols (phenols) having no substituent of 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group, phenolic Addition of 200 parts of p-tert-butylphenol, 900 parts of 37% formalin aqueous solution, 30 parts of 50% sodium hydroxide aqueous solution as phenols (alkylphenols) having a substituent having 2 to 10 carbon atoms on the aromatic ring having a hydroxyl group The mixture was heated to 80 ° C. and stirred for 1 hour to react. Thereafter, dehydration was performed under reduced pressure of 91 kPa, and when the temperature in the system reached 65 ° C., 500 parts of methanol was added to obtain 1600 parts of liquid resol type phenol resin 1 having a nonvolatile content of 45%. In the liquid resol type phenol resin 1, the aromatic unit having a phenolic hydroxyl group does not have a structural unit having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 86:14 and the weight average molecular weight was 290.

(Example 2)
The same procedure as in Example 1 was carried out except that p-tert-butylphenol was changed to p-octylphenol, to obtain 1600 parts of a liquid resol type phenol resin 2 having a nonvolatile content of 45%. In the liquid resol-type phenolic resin 2, the aromatic ring having a phenolic hydroxyl group has a structural unit having no substituent of 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has a substituent of 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 90:10 and the weight average molecular weight was 350.

(Example 3)
Except for changing the phenol to cresol, the same procedure as in Example 1 was performed to obtain 1600 parts of a liquid resol type phenol resin 3 having a nonvolatile content of 45%. In the liquid resol type phenol resin 3, the aromatic unit having a phenolic hydroxyl group has a structural unit not having a substituent having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has a substituent having 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 85:15 and the weight average molecular weight was 320.
Example 4
The same procedure as in Example 1 was conducted except that 500 parts of phenol and 500 parts of p-tert-butylphenol were used, to obtain 1600 parts of a liquid resol type phenol resin 4 having a nonvolatile content of 45%. In the liquid resol type phenol resin 4, the aromatic ring having a phenolic hydroxyl group does not have a structural unit having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 61:39 and the weight average molecular weight was 280.

(Comparative Example 1)
The procedure was the same as in Example 1 except that 1000 parts of phenol was used without using p-tert-butylphenol, to obtain 1600 parts of a liquid resol type phenolic resin 5 having a nonvolatile content of 45%. In the liquid resol type phenol resin 5, the aromatic unit having a phenolic hydroxyl group has no structural unit having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 100: 0 and the weight average molecular weight was 280.

(Comparative Example 2)
The reaction was carried out in the same manner as in Example 1 except that the reaction time was 5 hours, to obtain 1600 parts of a liquid resol type phenol resin 6 having a nonvolatile content of 45%. In the liquid resol-type phenol resin 6, the aromatic ring having a phenolic hydroxyl group has a structural unit not having a substituent having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has a substituent having 2 to 10 carbon atoms. The molar fraction of the structural unit having a molecular weight of 86:14 and the weight average molecular weight was 750.

(Wet friction material test piece preparation)
Methanol was added to the resol-type phenol resin obtained from the above-mentioned Examples and Comparative Examples to prepare a resol-type phenol resin adjustment liquid in which the weight percent concentration of the resol-type phenol resin was 30%. Next, a mixture in which the respective weight percentage concentrations are 40% aramid fiber (Toray DuPont, Kevlar), 30% cellulose pulp, and 30% diatomaceous earth (Radiolite # 200, Showa Chemical Industry Co., Ltd.) is dispersed in water. The slurry liquid was prepared, the paper made using this slurry liquid was dried, and the dried paper was immersed in the resol type phenol resin adjustment liquid prepared above for 30 seconds, and then air-dried at room temperature for 30 minutes. After drying at 80 ° C. for 30 minutes, baking was performed at 200 ° C. for 30 minutes to prepare a test piece (150 mm × 80 mm × 1 mm thickness) equivalent to a paper wet friction material.

  The following evaluation was performed about the test piece equivalent to the resol type phenol resin and wet friction material obtained by each Example and the comparative example. The evaluation results are shown in Table 1.

(Evaluation method of resol type phenol resin)
(1) Weight average molecular weight The resol type phenol resin obtained by the above was dissolved in tetrahydrofuran, and GPC measurement was carried out. A calibration curve was prepared using a polystyrene standard substance, and GPC measurement was performed using tetrahydrofuran as an elution solvent under conditions of a flow rate of 1.0 ml / min and a column temperature of 40 ° C. The apparatus used was a main body: HLC-8020 manufactured by Tosoh Corporation, and an analytical column: one TSKgel G1000HXL, two G2000HXL manufactured by Tosoh, and one G3000HXL.

(Evaluation method of wet friction material)
(2) Oil permeability Automatic transmission fluid (ATF, TOYOTA genuine AUTO
(FLUID D-2GM type) 4 μl was dropped on the upper surface of the test piece corresponding to the wet friction material, and after the ATF contacted the surface of the test piece, the ATF penetrated into the test piece from the surface of the test piece. The time until the ATF droplet disappears from the surface of the test piece was measured. In addition, it is thought that the porosity of the wet friction material is higher as the oil permeation time is shorter, and the durability of the wet friction material becomes better.

(3) Tensile strength The test piece corresponding to the obtained wet friction material was measured for the tensile strength according to JIS P 8113 "Paper and paperboard-Test method for tensile properties". The tensile strength of the impregnated paper has a correlation with the durability of the wet friction material, and the higher the value, the better the durability of the wet friction material.

From the evaluation results in Table 1, the following can be understood.
In each of Examples 1 to 4, a structural unit and a phenolic hydroxyl group having a weight average molecular weight of 100 or more and 500 or less and having no substituent of 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group. And a resol type phenol resin that includes a structural unit having a substituent having 2 to 10 carbon atoms in the aromatic ring. The wet friction material produced using the resol type phenol resin is an oil. Excellent results in permeability and tensile strength were obtained.
On the other hand, although Comparative Example 1 has a weight average molecular weight of 100 or more and 500 or less, a resole-type phenol resin that does not contain a structural unit having a substituent of 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group. The tensile strength was inferior to Examples 1-4.
In Comparative Example 2, a structural unit having no substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group and a substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group are used. Although it is comprised including the structural unit which has, it is a resol type phenol resin whose molecular weight exceeds 500, and resulted in inferior oil permeability.
Therefore, by using the resol type phenolic resin composition specified in the present invention, the porosity is high, the oil permeability to the fiber base material is excellent, and the durability is excellent without reducing the mechanical strength of the friction material. It can be seen that a wet friction material can be obtained.

When the resol type phenolic resin composition for wet friction materials of the present invention is used as a binder, the porosity is high, the oil permeability to the fiber base material is excellent, and the durability without reducing the mechanical strength of the friction material. Therefore, the resol type phenolic resin composition for wet friction materials of the present invention can be suitably used for wet friction materials such as paper clutch facings.

Claims (6)

  A resol-type phenol resin composition used for a wet friction material, having a weight average molecular weight of 100 or more and 500 or less, and no aromatic group having a phenolic hydroxyl group having 2 or more and 10 or less carbon atoms. A resol type phenol for a wet friction material comprising a resol type phenol resin comprising a structural unit and a structural unit having a substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group Resin composition.   The resol-type phenol resin is a phenol having no substituents having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group, and a substituent having 2 to 10 carbon atoms in an aromatic ring having a phenolic hydroxyl group. The resol-type phenol resin composition for wet friction materials according to claim 1, which is a resol-type phenol resin obtained from phenols and aldehydes.   The structural unit which does not have a substituent having 2 to 10 carbon atoms in the aromatic ring having a phenolic hydroxyl group has a substituent having 1 or less carbon atoms in the aromatic ring having a phenolic hydroxyl group. The resol type phenolic resin composition for wet friction materials as described.   The carbon number of the substituent of the structural unit which has a C2-C10 substituent in the aromatic ring which has the said phenolic hydroxyl group is 3-8, The carbon number as described in any one of Claims 1-3. A resol type phenolic resin composition for wet friction materials.   In the resol type phenol resin, the aromatic ring having a phenolic hydroxyl group has a structural unit not having a substituent having 2 to 10 carbon atoms and the aromatic ring having a phenolic hydroxyl group has a substitution having 2 to 10 carbon atoms. The resol type phenol resin composition for wet friction materials according to any one of claims 1 to 4, wherein the molar fraction with the structural unit having a group is in the range of 95: 5 to 50:50 on average. A wet friction material obtained by impregnating a fiber substrate with the resol type phenol resin composition for wet friction material according to any one of claims 1 to 5.