WO2018030162A1 - Resin composition for friction materials and wet paper friction material - Google Patents

Abstract

The present invention provides: a resin composition for friction materials, which contains a resol type phenolic resin having a constituent unit represented by general formula (r1) (wherein each of R¹ and R² independently represents an optionally substituted divalent hydrocarbon group) and a constituent unit represented by general formula (r2) (wherein each of R³ and R⁴ independently represents an optionally substituted divalent hydrocarbon group), and wherein the ratio of ether groups (-R³-O-R⁴-) in the resol type phenolic resin is 0.2-1.0 mole per 1 mole of benzene rings; and the like.

Description

Resin composition for friction material and wet paper friction material

The present invention relates to a resin composition for a friction material and a wet paper friction material.
This application claims priority on August 9, 2016 based on Japanese Patent Application No. 2016-156415 filed in Japan, the contents of which are incorporated herein by reference.

Friction materials such as brake linings, disc brake pads, and clutch facings for transmission are used in automobiles, railway vehicles, and aircraft (hereinafter referred to as “automobiles”). For example, a wet paper friction material is used in an automatic transmission or continuously variable transmission of an automobile.
This wet paper friction material is generally produced by impregnating a paper base material with a resin composition containing a phenol resin and curing.
Conventionally, a phenol resin composition containing a reaction product of a specific bifunctional phenol and other phenols and aldehydes as an essential component has been proposed as the resin composition (see Patent Document 1). ). In the friction material using such a phenol resin composition, the friction characteristics are improved.

JP 7-157748 A

In recent years, in automobiles and the like, further improvement in fuel consumption and smoother transmission / cutoff of power are required. Along with this, the load on the friction material is increasing, and the friction material requires further improvement in mechanical properties (tensile strength, tensile elongation at break, etc.).
This invention is made | formed in view of the said situation, Comprising: It aims at providing the resin composition for friction materials which can improve a mechanical characteristic more, and the wet paper friction material using the same.

As a result of intensive studies, the present inventors provide the following means in order to solve the above problems. That is, the resin composition for a friction material of the present invention contains a resol type phenolic resin having a structural unit represented by the following general formula (r1) and a structural unit represented by the following general formula (r2), The ratio of the ether group (—R ³ —O—R ⁴ —) in the resol type phenol resin is 0.2 to 1.0 mol per mol of the benzene ring.

［式中、Ｒ^１～Ｒ^４は、それぞれ独立に、置換基を有してもよい２価の炭化水素基である。＊は結合手を示す。但し、式中のベンゼン環に結合する水素原子は置換基により置換されてもよい。］

[Wherein, R ¹ to R ⁴ are each independently a divalent hydrocarbon group which may have a substituent. * Indicates a bond. However, the hydrogen atom bonded to the benzene ring in the formula may be substituted with a substituent. ]

The resin composition for a friction material of the present invention may further contain a base material containing an aramid fiber.

Moreover, the wet paper friction material of this invention is a resol type phenol resin which has the base material containing an aramid fiber, the structural unit represented by the following general formula (r1), and the structural unit represented by the following general formula (r2). The resol type phenolic resin is cured in a state of impregnating the base material.

［式中、Ｒ^１～Ｒ^４は、それぞれ独立に、置換基を有してもよい２価の炭化水素基である。＊は結合手を示す。但し、式中のベンゼン環に結合する水素原子は置換基により置換されてもよい。］

[Wherein, R ¹ to R ⁴ are each independently a divalent hydrocarbon group which may have a substituent. * Indicates a bond. However, the hydrogen atom bonded to the benzene ring in the formula may be substituted with a substituent. ]

In the wet paper friction material of the present invention, the ratio of ether groups (—R ³ —O—R ⁴ —) in the resol type phenol resin is 0.2 to 1.0 mol per mol of the benzene ring. preferable.

According to the present invention, it is possible to provide a resin composition for a friction material that can further improve mechanical properties, and a wet paper friction material using the same.

(Resin composition for friction material)

The resin composition for friction material of this embodiment contains the resol type phenol resin which has a specific structural unit. Such a resin composition is suitable for a friction material, and includes both those before curing and those after curing.

<Resol type phenolic resin>

The resol type phenol resin in this embodiment has a specific structural unit, that is, a structural unit represented by the following general formula (r1) and a structural unit represented by the following general formula (r2).

［式中、Ｒ^１～Ｒ^４は、それぞれ独立に、置換基を有してもよい２価の炭化水素基である。＊は結合手を示す。但し、式中のベンゼン環に結合する水素原子は置換基により置換されてもよい。］

[Wherein, R ¹ to R ⁴ are each independently a divalent hydrocarbon group which may have a substituent. * Indicates a bond. However, the hydrogen atom bonded to the benzene ring in the formula may be substituted with a substituent. ]

R ¹ and R ² in the formula (r1), and R ³ and R ⁴ in the formula (r2) are derived from aldehydes used in the production method described later, respectively, and 2 in R ¹ to R ⁴ Examples of the valent hydrocarbon group include a chain or cyclic aliphatic hydrocarbon group, and an aromatic hydrocarbon group.
Among these, the divalent hydrocarbon group in R ¹ to R ⁴ is preferably a chain or cyclic aliphatic hydrocarbon group, and more preferably a chain aliphatic hydrocarbon group.
The chain aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group, and is preferably a saturated aliphatic hydrocarbon group.
Examples of the divalent saturated aliphatic hydrocarbon group here include —CH ₂ —, —CH (CH ₃ ) —, —CH (C ₂ H ₅ ) —, —CH (C ₃ H ₇ ) — and the like. Can be mentioned.
Examples of the divalent unsaturated aliphatic hydrocarbon group here include —CH (CH═CH ₂ ) —.

In the above formulas (r1) and (r2), the divalent hydrocarbon group represented by R ¹ to R ⁴ may have a group that substitutes a hydrogen atom constituting the hydrocarbon group, Alternatively, it may be any group that substitutes for a carbon atom constituting such a hydrocarbon group, and examples thereof include a chlorine atom (—Cl), an oxo group (═O), and an oxygen atom (—O—).

The substituent for substituting the hydrogen atom bonded to the benzene ring in the formula (r1) or the formula (r2) is derived from phenols used in the production method described later, for example, acetyl group, methyl group, tertiary butyl. Groups and the like.

Hereinafter, preferred specific examples of the structural unit represented by the general formula (r1) and the structural unit represented by the general formula (r2) are shown.

Regarding the proportion of the structural unit represented by the general formula (r2) in the resol type phenol resin, the proportion of the ether group (—R ³ —O—R ⁴ —) in the resol type phenol resin is defined as It is 0.2 to 1.0 mole per mole, preferably 0.4 to 0.9 mole.
When the base material is impregnated for the friction material, if the ratio of the ether group (—R ³ —O—R ⁴ —) is equal to or higher than the lower limit of the above range, the mechanical strength becomes higher. If it is below the upper limit value, moderate flexibility as a resin component is easily developed. These effects are particularly prominent for a substrate containing aramid fibers.

Regarding the proportion of the structural unit represented by the general formula (r1) in the resol type phenol resin, the proportion of —R ² —OH in the resol type phenol resin is 0.1 to 3.0 per mole of benzene ring. The molar ratio is preferably 0.1 to 1.0 mol, and more preferably 0.1 to 0.5 mol.
When the base material is impregnated for the friction material, if the ratio of —R ² —OH is not more than the upper limit of the above preferred range, flexibility as a resin component is easily developed, When it is at least the lower limit, the mechanical strength becomes higher.

The ratio of the ether group (—R ³ —O—R ⁴ —) and —R ² —OH in the resol type phenol resin can be measured by nuclear magnetic resonance (NMR) spectroscopy.

The weight average molecular weight (Mw) of the resol type phenol resin in the present embodiment is not particularly limited, and is preferably 100 to 2000, for example, and more preferably 150 to 1200.
In addition, the weight average molecular weight (Mw) of resin means the value of polystyrene conversion measured by gel permeation chromatography (GPC).

≪Resol type phenol resin production process≫

Examples of the method for producing a resol type phenol resin in the present embodiment include a method having a step of reacting (condensation reaction) phenols and aldehydes in the presence of a base catalyst.

Examples of the phenols include phenol, orthocresol, metacresol, paracresol, xylenol, paratertiary butylphenol, paracumylphenol, paraphenylphenol, bisphenol A, bisphenolmethane, bisphenolsulfone, bisphenol ether, resorcin, hydroquinone, and the like. Can be mentioned. Phenols may be used alone or in combination of two or more.

Examples of the aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, capronaldehyde, acrolein and the like. Aldehydes may be used alone or in combination of two or more.

Examples of the base catalyst include weak acid salts of divalent metals composed of divalent metals (for example, zinc, calcium, manganese, cobalt, nickel, lead, etc.) and weak acids (for example, acetic acid, naphthenic acid, etc.); alkali metals (for example, Lithium, sodium, potassium, etc.) hydroxides; Alkaline earth metals (eg, magnesium, calcium, barium, etc.) hydroxides; Etc. Among these, weak salts of divalent metals are preferable, and manganese acetate, calcium acetate, and zinc acetate are particularly preferable. A base catalyst may be used individually by 1 type, and may use 2 or more types together.

The reaction molar ratio of phenols to aldehydes is preferably 0.6 to 1.5 moles, more preferably 0.8 to 1.2 moles with respect to 1 mole of phenols. .
The amount of the base catalyst used is appropriately determined according to the types of phenols and aldehydes, and is preferably 10 to 100 parts by mass with respect to 1000 parts by mass of the phenols, for example.

When the phenols and aldehydes are reacted, the pH condition of the mixed solution of the phenols, aldehydes and base catalyst is preferably pH 6.0 to 8.5, more preferably pH 6.5 to 8.0. is there.
The temperature condition for reacting phenols with aldehydes is preferably 80 to 110 ° C., more preferably 90 to 100 ° C., and the reaction time is preferably 0.5 to 6 hours, more preferably 1 to 4 hours.
When reacting phenols with aldehydes, dehydration condensation is promoted by controlling the pH conditions, temperature conditions, and reaction time of the mixed solution within the above preferred ranges, and the desired resol type phenol resin is obtained. It becomes easy.
The pH condition of the mixed solution means the pH of the mixed solution at the temperature (reaction temperature) when the phenols and aldehydes are reacted.

An ether group (—R ³ —O—R ⁴ —) is generated by dehydration condensation between the phenol and the aldehyde. And the target resol type phenol resin which has a structural unit represented by general formula (r1) and a structural unit represented by general formula (r2) is obtained.

After reacting phenols and aldehydes as described above, the reaction product (resol type phenol resin) may be diluted with an organic solvent.
The organic solvent used for the dilution is not particularly limited, and examples thereof include alcohol-based organic solvents such as methanol, ethanol, isopropanol, and butanol; ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; toluene, ethylbenzene, and the like. Aromatic hydrocarbon solvents, or mixtures thereof.
Further, before the reaction product is diluted, a dehydration treatment such as decompression may be performed.

In the resin composition for friction material of the present embodiment, the resol type phenol resin may be used alone or in combination of two or more.

<Other ingredients>

The resin composition for a friction material of the present embodiment may contain, for example, a curing agent, a powder filler, a solvent, and the like, as necessary, in addition to the resol type phenol resin.

What is necessary is just to select a hardening | curing agent suitably according to the kind etc. of a resole type phenol resin, for example, hexamethylenetetramine, an isocyanate resin, an epoxy resin, hexamethoxymethylol melamine etc. are mentioned.
Examples of the powder filler include inorganic fillers such as diatomaceous earth, activated carbon, and graphite; and organic fillers such as cashew dust.

The resin composition for a friction material may use the above-mentioned resol type phenol resin as it is, or may be a mixture of the above resol type phenol resin, other components and a solvent.
This solvent can be selected as appropriate, and among them, those capable of dissolving each component are preferable. Examples of the solvent include alcohol-based organic solvents such as methanol, ethanol, isopropanol, and butanol; ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic hydrocarbon solvents such as toluene and ethylbenzene, or mixtures thereof. It is done.

The resin concentration of the resin composition for a friction material is preferably 10 to 50% by mass, more preferably 15 to 40% by mass.

Favorable examples of the resin composition for a friction material of the present embodiment include those containing a base material containing an aramid fiber in addition to the above-mentioned resol type phenol resin. Specifically, the base material containing an aramid fiber is exemplified in a state before or after curing impregnated with a resol type phenol resin.

<Base material>

The base material here is a base material containing an aramid fiber, and a fiber base material mainly composed of an aramid fiber is preferable.
An aramid fiber refers to a polyamide (aromatic polyamide) fiber having an aromatic ring in the main chain. The aramid resin constituting the aramid fiber may have either a meta-type structure (meta-type aramid) or a para-type structure (para-type aramid).
The base material containing an aramid fiber may be composed of an aramid fiber alone, or may be a mixture of an aramid fiber and other fibers. Other fibers are not particularly limited, and examples thereof include metal fibers, glass fibers, carbon fibers, natural fibers, and synthetic resin fibers. The base material may be filled with a friction modifier such as cashew dust and a filler such as diatomaceous earth in addition to the aramid fiber.

(Wet paper friction material)

The wet paper friction material of this embodiment is a resol type phenol having a base material containing the aramid fiber, a structural unit represented by the general formula (r1), and a structural unit represented by the general formula (r2). A resin, and the resol type phenolic resin is cured in a state of being impregnated into a base material containing an aramid fiber.

The wet paper friction material of the present embodiment can be produced, for example, by impregnating a base material containing aramid fibers with the above-described resin composition for friction material and curing.

The temperature condition at the time of curing is preferably 120 to 280 ° C, more preferably 150 to 250 ° C.
The curing time is preferably from 0.1 to 3 hours, more preferably from 0.25 to 1 hour.

In the resol-type phenol resin in the embodiment described above, at least a part of —R ² —OH which is a polar group in the resin is etherified by dehydration condensation. A resol type phenol resin in which at least a part of —R ² —OH is etherified has a lower polarity than a conventional product and has a high affinity with an aramid fiber. For this reason, the resol type phenol resin is easily impregnated into the aramid fiber, and the resol type phenol resin and the base material are more integrated. Therefore, the wet paper friction material in which the resin composition for a friction material of the present embodiment is cured in a state in which the base material containing aramid fibers is impregnated has higher mechanical properties (tensile strength, tensile elongation at break, etc.). ing.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.

<Manufacture of resol type phenolic resin>
[Production Example 1]

In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 1000 parts by mass of phenol, 950 parts by mass of 37% formalin aqueous solution (1.1 mol of formaldehyde with respect to 1 mol of phenol), and 20 parts by mass of zinc acetate , And the mixed solution was reacted in the range of pH 7.0 to 7.2 while stirring at 100 ° C. for 3 hours to obtain a reaction solution. The obtained reaction solution was subjected to dehydration treatment under reduced pressure of 91 kPa. When the temperature in the system reached 70 ° C., 450 parts by mass of methanol was added for dilution, and the mixture was cooled to 40 ° C. or less to obtain 1700 parts by mass of a resol type phenol resin having a nonvolatile content of 50%. The obtained resol type phenol resin had a weight average molecular weight (Mw) of 250.

[Production Example 2]

Resole having a non-volatile content of 50% was produced in the same manner as in Production Example 1 except that the blending amount of the 37% formalin aqueous solution was changed to 670 parts by mass (formaldehyde 0.8 mol relative to 1 mol of phenol) in Production Example 1. 1700 parts by mass of a type phenol resin was obtained. Mw of the obtained resol type phenol resin was 200.

[Production Example 3]

Resole having a non-volatile content of 50% was produced in the same manner as in Production Example 1 except that the blending amount of the 37% formalin aqueous solution was changed to 1190 parts by mass (formaldehyde 1.4 mol with respect to 1 mol of phenol) in Production Example 1. 1700 parts by mass of a type phenol resin was obtained. Mw of the obtained resol type phenol resin was 290.

[Production Example 4]

In a reaction apparatus equipped with a stirrer, a reflux condenser and a thermometer, 1000 parts by mass of phenol, 740 parts by mass of 37% formalin aqueous solution (1.0 mol of formaldehyde with respect to 1 mol of phenol), and 50% aqueous sodium hydroxide solution 20 parts by mass was added and reacted at 100 ° C. with stirring for 30 minutes to obtain a reaction solution.
The obtained reaction solution was subjected to dehydration treatment under reduced pressure of 91 kPa. When the temperature in the system reached 65 ° C., 1000 parts by mass of methanol was added for dilution, and the mixture was cooled to 40 ° C. or less to obtain 2100 parts by mass of a liquid resol type phenol resin having a nonvolatile content of 45%. Mw of the obtained liquid resol type phenol resin was 250.

[Production Example 5]

In a reactor equipped with a stirrer, a reflux condenser and a thermometer, phenol 1000 parts by mass, hexamethylenetetramine 370 parts by mass (0.25 mol with respect to 1 mol of phenol), methanol 100 parts by mass, and acetone 100 Part by mass and 20 parts by mass of a 50% aqueous sodium hydroxide solution were added, heated to 95 ° C. and held for 3 hours.
Thereafter, 1200 parts by mass of acetone was added and cooled to 40 ° C. or lower to obtain 2700 parts by mass of a liquid resol type phenol resin. Mw of the obtained liquid resol type phenol resin was 240.

Mw of the resol type phenol resin obtained in Production Examples 1 to 5 represents a value in terms of polystyrene measured by gel permeation chromatography (GPC).

Determination of ether group (—CH ₂ —O—CH ₂ —) and methylol group (—CH ₂ —OH): For the resol type phenol resins obtained in Production Examples 1 to 5, ether groups and methylol present in the resin Each group content was measured by NMR spectroscopy as follows. A resol type phenolic resin was acetylated by mixing with acetic anhydride to obtain a sample. For this sample, “JNM-AL300” (frequency: 300 MHz) manufactured by JEOL Ltd. was used as an NMR apparatus, and from the ¹ H-NMR spectrum, the respective contents of phenol nuclei, ether groups and methylol groups in the resin ( Mol / benzene ring 1 mol). These results are shown in Tables 1 and 2.

From the results of measurement by NMR spectroscopy, it can be confirmed that all of the resol type phenol resins obtained in Production Examples 1 to 3 have both methylol groups and ether groups in the resins.
It can be confirmed that the resol type phenolic resin obtained in Production Example 4 does not have an ether group in the resin.
It can be confirmed that the resol-type phenol resin obtained in Production Example 5 has neither a methylol group nor an ether group in the resin.

<Manufacture of wet paper friction material>

Each of the resol type phenol resins obtained in Production Examples 1 to 5 was impregnated into a base material (length 120 mm × width 10 mm × thickness 1 mm) and cured to prepare a wet paper friction material.
As the base material, the following base material (1) and base material (2) were used.
Base material (1): Aramid fiber base material Base material (2): Cellulose fiber base material

(Example 1)

The resol type phenol resin obtained in Production Example 1 and acetone were mixed to prepare a resin composition having a resin concentration of 30% by mass.
The resin composition was impregnated into the base material (1) and then cured in an oven at 190 ° C. for 30 minutes to obtain a wet paper friction material.

(Examples 2 and 3, Comparative Examples 1 and 2)

The resin composition was prepared in the same manner as in Example 1 except that the resol type phenol resin obtained in Production Example 1 was changed to the resol type phenol resin obtained in Production Examples 2 to 5. And then cured in an oven at 190 ° C. for 30 minutes to obtain a wet paper friction material.

(Reference Examples 1-5)
Except for changing the base material (1) to the base material (2), the resin composition was impregnated into the base material (2) in the same manner as in Example 1, and then cured in an oven at 190 ° C. for 30 minutes. Thus, a wet paper friction material was obtained.

<Evaluation>

About the wet paper friction material of each example, the tensile strength and the tensile elongation at break were measured by the method shown below, and mechanical characteristics were evaluated.

[Tensile strength, tensile elongation at break]

The wet paper friction material of each example was used as a test piece, and the tensile strength (MPa) and the tensile elongation at break (%) were measured in accordance with JIS P 8113 “Paper and paperboard—Test method for tensile properties”. These results are shown in Tables 1 and 2.
The higher the value of the tensile strength (MPa), the higher the mechanical strength as a paper friction material.
The higher the value of the tensile elongation at break (%), the higher the flexibility as the paper friction material.

From the results shown in Table 1, it can be confirmed that the wet paper friction materials of Examples 1 to 3 to which the present invention is applied have higher mechanical properties than the wet paper friction materials of Comparative Examples 1 and 2. .

From the results shown in Table 1 and Table 2, when the base material (1) (aramid fiber base material) is used as the base material, a remarkable effect of improving mechanical properties is obtained by applying the present invention. I can confirm. That is, it can be said that the present invention is particularly suitable when an aramid fiber substrate is used as the substrate.

Claims (6)

Containing a resol type phenolic resin having a structural unit represented by the following general formula (r1) and a structural unit represented by the following general formula (r2);
The resin composition for a friction material, wherein the ratio of ether groups (—R ³ —O—R ⁴ —) in the resol type phenol resin is 0.2 to 1.0 mol per mol of the benzene ring.

[Wherein, R ¹ to R ⁴ are each independently a divalent hydrocarbon group which may have a substituent. * Indicates a bond. However, the hydrogen atom bonded to the benzene ring in the formula may be substituted with a substituent. ] Furthermore, the resin composition for friction materials of Claim 1 containing the base material containing an aramid fiber. A base material comprising an aramid fiber, a resol type phenol resin having a structural unit represented by the following general formula (r1) and a structural unit represented by the following general formula (r2),
A wet paper friction material, wherein the resol type phenolic resin is cured in a state in which the substrate is impregnated.

[Wherein, R ¹ to R ⁴ are each independently a divalent hydrocarbon group which may have a substituent. * Indicates a bond. However, the hydrogen atom bonded to the benzene ring in the formula may be substituted with a substituent. ] 4. The wet paper friction material according to claim 3, wherein the ratio of ether groups (—R ³ —O—R ⁴ —) in the resol type phenol resin is 0.2 to 1.0 mol per mol of the benzene ring. . The manufacturing method of the resin composition for friction materials including the process of making phenols and aldehydes react in presence of a base catalyst and obtaining the resin composition for friction materials of Claim 1. A method for producing a wet paper friction material, comprising a step of curing a substrate containing aramid fibers impregnated with the resin composition for friction material according to claim 1.