阅读说明：本技术 湿式摩擦材料用酚醛树脂、酚醛树脂组合物和湿式摩擦材料 (Phenolic resin for wet friction material, phenolic resin composition, and wet friction material ) 是由 常增卓也 国实贵夫 于 2020-02-25 设计创作，主要内容包括：本发明的湿式摩擦材料用酚醛树脂包括甲阶型酚醛树脂,上述甲阶型酚醛树脂在一个分子中包括源自具有一个酚羟基的苯酚化合物的结构单元A、和源自具有两个酚羟基的多官能苯酚化合物的结构单元B。(The phenolic resin for a wet friction material of the present invention includes a resol-type phenolic resin including, in one molecule, a structural unit a derived from a phenol compound having one phenolic hydroxyl group, and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups.)

1. A phenolic resin for a wet friction material, characterized in that,

comprising a resol-type phenol resin having, in one molecule, a structural unit A derived from a phenol compound having one phenolic hydroxyl group represented by the following general formula (A) and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups represented by the following general formula (B),

in the above general formula (A), R¹Each independently represents a substituent other than a hydroxyl group, a is an integer of 0to 3, m represents an integer of 1 to 10 inclusive,

in the above general formula (B), R²Each independently represents a substituent other than a hydroxyl group, b is an integer of 0to 2, and n is an integer of 1 to 10 inclusive.

2. The phenolic resin for a wet friction material according to claim 1, wherein,

the multifunctional phenol compound having two phenolic hydroxyl groups includes one or more selected from resorcinol, catechol, and hydroquinone.

3. The phenolic resin for a wet friction material according to claim 1 or 2,

the phenolic resin for wet friction materials has a weight average molecular weight Mw of 100 to 10000.

4. A phenolic resin composition, comprising:

the phenolic resin for a wet friction material according to any one of claims 1 to 3, and an organic solvent.

5. A wet friction material formed by impregnating the phenolic resin composition of claim 4 in a base material.

6. The wet friction material as recited in claim 5,

the content of the structural unit B in the cured product of the phenolic resin composition is 10to 90 wt% based on 100 wt% of the total of the structural unit A and the structural unit B.

Technical Field

The present invention relates to a phenol resin for a wet friction material, a phenol resin composition, and a wet friction material.

Background

A resol-type phenol resin has been variously studied as a binder for a wet friction material used for a clutch or a brake of an automatic transmission of an automobile. As such a technique, for example, a technique disclosed in patent document 1 is known. Patent document 1 describes that a binder using a maleimide-modified phenol resin obtained by modifying a resol-type phenol resin with a maleimide compound as a base material exhibits stable friction performance when used in a wet friction material, but does not mention physical durability (patent document 1, claim 1).

Disclosure of Invention

The inventors of the present invention have found that, even if a resin skeleton other than resol-type phenol resin is not used, the durability of a wet friction material using such resol-type phenol resin can be controlled by appropriately selecting a benzene ring skeleton (i.e., phenol skeleton) having a phenolic hydroxyl group in the molecular structure of the resol-type phenol resin.

Based on this finding, further intensive studies have been conducted to find that the durability of a wet friction material using a resol-type phenol resin can be improved by using a structural unit a derived from a phenol compound having one phenolic hydroxyl group and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups in combination, and the present invention has been completed.

According to the present invention, there is provided a phenolic resin for a wet friction material, comprising a resol-type phenolic resin having, in one molecule, a structural unit a derived from a phenol compound having one phenolic hydroxyl group represented by the following general formula (a) and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups represented by the following general formula (B).

(in the above general formula (A), R¹Each independently represents a substituent other than a hydroxyl group, a is an integer of 0to 3, and m is an integer of 1 to 10 inclusive. )

(in the above general formula (B), R²Each independently represents a substituent other than a hydroxyl group, b is an integer of 0to 2, and n is an integer of 1 to 10 inclusive. )

Further, according to the present invention, there is provided a phenolic resin composition comprising the above phenolic resin for a wet friction material and an organic solvent.

Further, the present invention provides a wet friction material obtained by impregnating a base material with the above phenolic resin composition.

Effects of the invention

According to the present invention, a phenol resin for a wet friction material having excellent durability, a phenol resin composition using the phenol resin, and a wet friction material are provided.

Detailed Description

The phenolic resin for a wet friction material of the present embodiment will be described in brief.

The phenolic resin for a wet friction material of the present embodiment includes a resol-type phenolic resin, and the resol-type phenolic resin has, as a structure contained in one molecule, a structural unit a derived from a phenol compound having one phenolic hydroxyl group, which is represented by the following general formula (a), and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups, which is represented by the following general formula (B).

(in the above general formula (A), R¹Each independently represents a substituent other than a hydroxyl group, a is an integer of 0to 3, and m is an integer of 1 to 10 inclusive. )

(in the above general formula (B), R²Each independently represents a substituent other than a hydroxyl group, b is an integer of 0to 2, and n is an integer of 1 to 10 inclusive. )

According to the findings of the inventors, it was found that the durability of a wet friction material using a resol-type phenol resin can be improved by using a structural unit a derived from a phenol compound having one phenolic hydroxyl group and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups in combination by appropriately selecting a phenol skeleton in the molecular structure of the resol-type phenol resin.

Although the detailed mechanism is not clear, it is considered that the adhesion of the resol resin to the base material is improved by appropriately selecting and using the molecular structure of the structural unit a derived from the phenol compound having one phenolic hydroxyl group and the structural unit B derived from the polyfunctional phenol compound having two phenolic hydroxyl groups, and therefore the durability of the wet friction material is improved.

The wet friction material of the present embodiment is formed by impregnating a base material with a phenol resin composition (resin varnish) including the phenol resin for a wet friction material and an organic solvent. Such a wet friction material can also achieve excellent durability.

The wet friction material is a friction material (clutch friction material) used for an automatic transmission of an automobile or the like. A resol-type phenol resin is generally used for the wet friction material.

In recent years, the size and weight of automatic transmissions have been reduced due to the trend toward low fuel consumption due to energy and environmental problems, and wet friction materials are also required to have a smaller diameter and a smaller number of plates. Accordingly, the conventional wet friction material has insufficient torque capacity, and therefore, in order to compensate for this, the performance required of the phenolic resin for the wet friction material has been increasing year by year. In contrast, by using the phenolic resin for a wet friction material of the present embodiment, a wet friction material having excellent durability can be realized. Therefore, the phenolic resin for a wet friction material of the present embodiment is expected to contribute to downsizing of the wet friction material.

Next, the phenolic resin for a wet friction material of the present embodiment will be described in detail.

The phenolic resin for a wet friction material of the present embodiment includes a resol-type phenolic resin including, in one molecule, a structural unit a derived from a phenol compound having one phenolic hydroxyl group and a structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups.

The method for producing the resol-type phenolic resin is not particularly limited, and the aldehyde may be reacted with the polyfunctional phenol compound B having two phenolic hydroxyl groups together with the phenol compound a having one phenolic hydroxyl group, or the obtained reaction compound may be further reacted with the polyfunctional phenol compound B having two phenolic hydroxyl groups after the phenol compound a having one phenolic hydroxyl group is reacted with the aldehyde. From the viewpoint of producing the resol-type phenolic resin, the reaction may be carried out under an alkaline condition or a weakly acidic condition. In the case of basic conditions, a basic catalyst can be used, and in the case of weakly acidic conditions, a zinc-based catalyst can be used.

The above-mentioned phenol compound a having one phenolic hydroxyl group is not particularly limited as long as it has a benzene ring having one phenolic hydroxyl group. The phenol compound a may have 1 or 2 or more substituents other than the hydroxyl group on the benzene ring having the phenolic hydroxyl group in the molecule. As the phenol compound a, a monomer compound can be used.

The substituents in the phenol compound a are independent of each other, and examples thereof include alkyl groups, aryl groups, vinyl groups, halogens, amino groups, nitro groups, and combinations thereof. Among these, non-reactive substituents are preferable, and hydrocarbon groups such as alkyl groups and aryl groups are more preferable. Among them, aryl as a substituent may be condensed with the above benzene ring to form a condensed ring.

Examples of the phenol compound a having one phenolic hydroxyl group include, but are not particularly limited to: phenol; cresols such as o-cresol, m-cresol, and p-cresol; xylenols such as 2, 3-xylenol, 2, 4-xylenol, 2, 5-xylenol, 2, 6-xylenol, 3, 5-xylenol, and the like; alkylphenols such as 2, 3, 5-trimethylphenol, 2-ethylphenol, 4-ethylphenol, 2-isopropylphenol, 4-isopropylphenol, n-butylphenol, isobutylphenol, tert-butylphenol, hexylphenol, octylphenol, nonylphenol, phenylphenol, benzylphenol, cumylphenol, allylphenol, cardanol and the like; naphthols such as 1-naphthol and 2-naphthol; a monohydric phenol substituent such as a halogenated phenol such as fluorophenol, chlorophenol, bromophenol, iodophenol, or the like, a p-phenylphenol, an aminophenol, a nitrophenol, a dinitrophenol, or a trinitrophenol; bisphenols such as bisphenol S, bisphenol F, bisphenol a, bisphenol C, bisphenol Z and bisphenol E. These may be used alone or in combination of two or more.

Among these, the phenol compound a may contain one or more selected from phenol, cresol, xylenol, alkylphenol, and bisphenol, and phenol, cresol, cardanol, butylphenol, and bisphenol a may be used from the viewpoint of low cost, and phenol, cresol, and cardanol are particularly preferably used.

The polyfunctional phenol compound B having two phenolic hydroxyl groups is not particularly limited as long as it has a benzene ring having two phenolic hydroxyl groups. The polyfunctional phenol compound B may have 1 or 2 or more substituents other than hydroxyl groups on a benzene ring having 2 phenolic hydroxyl groups in the molecule. As the polyfunctional phenol compound B, a monomer compound can be used.

The substituents in the polyfunctional phenol compound B are independent of each other, and examples thereof include alkyl groups, aryl groups, vinyl groups, halogens, amino groups, nitro groups, and combinations thereof. Among them, non-reactive substituents are preferable, and hydrocarbon groups such as alkyl groups and aryl groups are preferable. Among them, aryl as a substituent may be condensed with the above benzene ring to form a condensed ring.

Examples of the above-mentioned polyfunctional phenol compound B having two phenolic hydroxyl groups are not particularly limited, and include, for example: resorcinol, alkylresorcinol, catechol, alkylpyrocatechol, hydroquinone, alkylhydroquinone, dihydroxynaphthalene, and the like. Among these, from the viewpoint of low cost, it is preferable that the polyfunctional phenol compound B contains one or more selected from resorcinol, catechol, and hydroquinone.

In the method for producing a phenolic resin for a wet friction material, a phenol compound other than the phenol compound a and the polyfunctional phenol compound B may be used. The number of the phenol rings of the other phenol compound may be any of a mononuclear body, a binuclear body, a trinuclear body and the like, and the number of the phenolic hydroxyl groups may be one or two or more.

The phenol in the above production method includes the above phenol compound a and the multifunctional phenol compound B, and further includes another phenol compound as necessary.

The aldehydes are not particularly limited, and examples thereof include: formaldehyde such as formalin or paraformaldehyde; trioxymethylene, acetaldehyde, paraldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyl aldehyde, isobutyl aldehyde, tert-butyl aldehyde, hexyl aldehyde, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraformaldehyde, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These aldehydes may be used alone or in combination of two or more. Among them, the aldehydes may contain formaldehyde or acetaldehyde, and formalin or paraformaldehyde may be used from the viewpoint of yield and inexpensiveness.

In the step of obtaining the reaction solution, the phenol and the aldehyde can be reacted with each other using a basic catalyst under basic conditions, for example, at a pH of 7 or higher.

The basic catalyst is not particularly limited, and for example, the following can be used: alkaline substances such as alkali metal oxides and hydroxides such as sodium hydroxide, lithium hydroxide, potassium hydroxide, and sodium carbonate, and alkaline earth metal oxides and hydroxides such as carbonate, ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, methylethylamine, triethylamine, and hexamethylenetetramine, and calcium, magnesium, and barium. These may be used alone or in combination of two or more. For example, sodium hydroxide may be used.

In the step of obtaining the reaction solution, the phenol and the aldehyde can be reacted with each other using a zinc-based catalyst under a weakly acidic condition of, for example, pH4 to 6.

The zinc-based catalyst is not particularly limited as long as it is a divalent metal salt catalyst, and for example, zinc acetate, zinc formate, or the like can be used. These may be used alone or in combination of two or more. For example, a hydrate of zinc acetate may be used.

The amount of the basic catalyst or the zinc-based catalyst added may be, for example, 0.01 to 20% by weight, preferably 0.1 to 10% by weight, based on 100% by weight of the phenol.

In the present specification, "to" means including an upper limit value and a lower limit value unless otherwise specified.

The molar ratio of the phenol to the aldehyde (F/P molar ratio) may be, for example, 0.5 to 4.0 moles, preferably 1.0 to 3.0 moles, based on 1 mole of the phenol. By setting the aldehyde to the above range, as described above, the conversion of the aldehyde is improved for 1 mole of the phenol, and the remaining unreacted aldehyde can be reduced.

The reaction temperature may be, for example, 40 to 120 ℃ and preferably 60 to 100 ℃. This can suppress gelation and allow the reaction to proceed sufficiently. The reaction time is not particularly limited, and may be appropriately determined depending on the kind of the starting materials, the molar ratio of the starting materials to be used, the amount and kind of the catalyst to be used, and the reaction conditions.

As the solvent in the present embodiment, water may be used, and an organic solvent may be used. Examples of the organic solvent include: alcohols, ketones, esters, ethers, hydrocarbons. Examples of alcohols include: methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerol, and the like; examples of ketones are: acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, and the like; examples of esters include: methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, methyl lactate, ethyl lactate, butyl lactate, and the like; examples of ethers include: propyl ether, dioxane, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, methyl cellosolve acetate, ethyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate; examples of the hydrocarbons include: toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, decane, solvent naphtha, industrial gasoline, petroleum ether, petroleum volatile oil, solvent gasoline, etc. These may be used alone or in combination of two or more.

In addition, a dehydration step may be further performed. The dehydration may be performed under reduced pressure or under atmospheric pressure. For example, the degree of vacuum in the reduced-pressure dehydration may be, for example, 110torr or less, and more preferably 80 torr. This can shorten the dehydration time and obtain a stable resol-type phenolic resin with little variation in resin properties. These methods can sufficiently remove moisture, and can be combined with a step of using a known moisture removal device such as a vacuum dryer or a thin film evaporator to further remove moisture.

As described above, a resol-type phenol resin having, in the molecular structure, the structural unit a derived from a phenol compound having one phenolic hydroxyl group represented by the following general formula (a) and the structural unit B derived from a polyfunctional phenol compound having two phenolic hydroxyl groups represented by the following general formula (B) can be obtained.

In the above general formula (A), R¹Each independently represents a substituent other than a hydroxyl group, a is an integer of 0to 3, and m is an integer of 1 to 10 inclusive.

The substituents of the general formula (a) are each independently an alkyl group, an aryl group, a vinyl group, a halogen group, an amino group, a nitro group, or a combination thereof. Among them, non-reactive substituents are preferable, and hydrocarbon groups such as alkyl groups and aryl groups are preferable. Examples of the alkyl group include a linear or branched alkyl group having 1 to 10 carbon atoms.

a is 0to 3, preferably 0to 2, and more preferably 0to 1.

Wherein R of the above general formula (A)¹Preferably a hydrogen atom, methyl group, ethyl group, propyl group, butyl group, more preferably a hydrogen atom or methyl group.

In the above general formula (B), R²Each independently represents a substituent other than a hydroxyl group, b is an integer of 0to 2, and n is an integer of 1 to 10 inclusive.

The substituents of the general formula (B) are each independently an alkyl group, an aryl group, a vinyl group, a halogen group, an amino group, a nitro group, or a combination thereof. Among them, non-reactive substituents are preferable, and hydrocarbon groups such as alkyl groups and aryl groups are preferable. Examples of the alkyl group include a linear or branched alkyl group having 1 to 10 carbon atoms.

b is 0to 3, preferably 0to 2, and more preferably 0to 1.

Wherein R of the above general formula (B)²Preferably a hydrogen atom, methyl group, ethyl group, propyl group, butyl group, more preferably a hydrogen atom or methyl group.

The resol-type phenol resin obtained as described above is used for the phenol resin for a wet friction material.

The phenolic resin for a wet friction material may be composed of only a resol-type phenolic resin, or may be composed of, together with the resol-type phenolic resin, a single raw material that constitutes the structural unit a and/or the structural unit B in the resol-type phenolic resin. The phenolic resin for a wet friction material may contain, for example, several% to several tens% by mass of a raw material monomer constituting the resol-type phenolic resin in addition to the resol-type phenolic resin. The raw material monomer in the phenolic resin for a wet friction material enters the cured skeleton derived from the resol-type phenolic resin during curing in the process of producing a wet friction material described later. This can be expected to improve the strength of the wet friction material.

Next, the performance of the phenolic resin for a wet friction material of the present embodiment will be explained.

The resol-type phenol resin may be in a liquid state at room temperature of 25 ℃ and may be used in the form of a liquid phenol resin. This can improve the impregnation into the base material.

The lower limit of the content of the structural unit B in the resol-type phenolic resin is, for example, 10 wt% or more, preferably 15 wt% or more, and more preferably 20 wt% or more, based on 100 wt% of the total of the structural unit a and the structural unit B. This can improve the durability of the wet friction material. On the other hand, the upper limit of the content of the structural unit B may be, for example, 90 wt% or less, preferably 70 wt% or less, and more preferably 60 wt% or less, based on 100 wt% of the total of the structural unit a and the structural unit B. Thereby, a balance with other physical properties can be achieved.

The content ratio of the structural unit B in the resol-type phenolic resin can be measured by NMR, for example.

The phenolic resin for a wet friction material may have a viscosity at room temperature and 25 ℃ of, for example, 1 to 500 mPas, preferably 3 to 300 mPas, and more preferably 5 to 200 mPas. This can balance the impregnation properties and the fixing properties in the base material.

The weight average molecular weight Mw of the phenolic resin for a wet friction material may be, for example, 100 to 10000, preferably 120 to 5000, and more preferably 150 to 3000. This can balance the impregnation properties and the fixing properties in the base material.

In the present embodiment, the weight average molecular weight Mw can be determined by GPC (gel permeation chromatography), for example. The standard curve was prepared using polystyrene as a standard substance, and GPC measurement was performed using tetrahydrofuran as an eluting solvent under conditions of a flow rate of 1.0 ml/min and a column temperature of 40 ℃. The use of the main body: HLC-8020 from Tosoh, column for analysis: TSKgel G1000HXL 1, G2000HXL 2 and G3000HXL 1 produced by Tosoh.

Next, the wet friction material resin composition of the present embodiment will be explained.

The wet friction material resin composition (phenol resin composition) of the present embodiment may contain the above-described phenol resin for a wet friction material and an organic solvent.

The resin composition for a wet friction material is used to form a wet friction material, unlike a binder used to bond a friction material to a metal base material.

The organic solvent is not particularly limited, and for example, the following solvents can be used: alcohol organic solvents such as methanol, ethanol, isopropanol, and butanol, ketone organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, aromatic hydrocarbon solvents such as toluene and ethylbenzene, and mixtures thereof. Among these, methanol and acetone are particularly preferably contained from the viewpoint of realizing a low-cost and efficient production process, and from the viewpoint of improving the impregnation of the resin composition into the base material.

The resin composition for a wet friction material may further contain other components than the above components.

The other components are not particularly limited, and examples thereof include: phenolic resins other than resol-type phenolic resins, curing agents such as water and urotropine, elastomers, various additives, and the like. Wherein the other components do not include polyvinyl butyral as a binder component.

The nonvolatile content (solid content) of the resin composition for a wet friction material may be 10% to 90%, preferably 20% to 80%, and more preferably 30% to 70% of the total resin composition for a wet friction material. This can balance the impregnation property in the base material and the amount of resin adhering.

The resin composition for a wet friction material is particularly suitable for impregnation. The base material to be impregnated is not particularly limited, and fibers such as natural fibers, metal fibers, carbon fibers, and chemical fibers can be used. Specifically, it is possible to use: fibers such as natural fibers including natural pulp fibers and linter pulp, inorganic fibers including glass fibers, carbon fibers including Polyacrylonitrile (PAN) carbon fibers and pitch carbon fibers, and chemical fibers including aramid fibers and phenol fibers. These may be used alone or in combination of two or more. Among these, aramid fibers are preferably used as a main component for the fiber base material from the viewpoint of friction performance and durability. The form of the fibers is not particularly limited, and nonwoven fabrics, woven fabrics, and the like can be used. In this case, for example, the wet friction material can be formed by impregnating a base material made of a fiber material with the resin composition for a wet friction material, and firing and curing the impregnated base material.

(Wet Friction Material)

The wet friction material of the present embodiment is formed by impregnating the base material with the resin composition for a wet friction material (phenol resin composition).

When the resin composition for a wet friction material is used for a wet paper friction material, the wet friction material can be obtained by impregnating a paper base material filled with metal fibers, carbon fibers, chemical fibers, a friction modifier such as cashew dust, diatomaceous earth, and the like with the resin composition for a wet friction material of the present invention, and sintering and curing the impregnated paper base material.

In the wet friction material, the lower limit of the content of the structural unit B in the cured product of the phenolic resin composition is, for example, 10% by weight or more, preferably 15% by weight or more, and more preferably 20% by weight or more, based on 100% by weight of the total of the structural unit a and the structural unit B. This can improve the durability of the wet friction material. On the other hand, the upper limit of the content of the structural unit B may be, for example, 90 wt% or less, preferably 70 wt% or less, and more preferably 60 wt% or less, based on 100 wt% of the total of the structural unit a and the structural unit B. Thereby, a balance with other physical properties can be achieved.

The wet friction material obtained as described above can achieve excellent durability.

The embodiments of the present invention have been described above, but these are merely examples of the present invention, and various configurations other than the above-described configurations can be adopted. The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like are included within a range in which the object of the present invention can be achieved.