JP2020002318A - Phenolic resin composition for wet friction material and wet friction material - Google Patents

Abstract

To provide a technique about a phenolic resin composition for a wet friction material that is useful for preparing a wet friction material to stably exhibit high friction ability by improving durability while maintaining flexibility.SOLUTION: A phenolic resin composition for a wet friction material according to an embodiment has a modified resol type phenol resin, and a polymer containing a structural unit represented by the following formula (1) (where, Rx, Ry independently represent hydrogen or a C1-3 organic group).SELECTED DRAWING: None

Description

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

  Phenolic resin, which is a thermosetting resin, has been widely used as a binder for bonding materials that are base materials of molded articles, and has excellent mechanical properties, electrical properties, and adhesiveness. Used in various fields. In recent years, development of a technique using a phenol resin as a binder for a wet friction material such as a brake has been advanced.

  However, although a cured product of a phenol resin is generally excellent in mechanical properties, it is known that it is hard and brittle. In view of these circumstances, various studies have been reported on phenol resins used as binders for wet friction materials in order to improve the friction performance of cured products thereof (for example, Patent Document 1).

JP-A-9-59599

  However, the demand level of the conventional phenolic resin used as a binder for wet friction materials, that is, the conventional phenolic resin for wet friction materials, tends to be higher. The present inventors have found the following problems with respect to a conventional phenol resin for a wet friction material.

  When using a cured product of phenolic resin for wet friction materials as a wet friction material, in addition to exhibiting a stable high coefficient of friction and exhibiting good friction performance, the friction performance does not decrease even after long use. Is required. From the findings so far, it has been found that it is important to improve the flexibility of the cured product in order to obtain good friction performance. However, when the flexibility of the cured product of the conventional wet friction material phenolic resin is improved, the curability of the cured product is reduced, and as a result, the durability of the wet friction material containing the cured product is also reduced. As a result, the friction performance cannot be maintained for a long time. On the other hand, when the curability of a cured product of a conventional wet friction material phenolic resin is improved, the durability of the wet friction material containing the cured product is improved, but the flexibility of the cured product is reduced. As a result, the friction performance of the wet friction material containing the cured product is reduced. As described above, the present inventors have attempted to improve the friction performance of a wet friction material using a cured product of a phenolic resin for a wet friction material. It has been found that a trade-off relationship is established between durability and durability.

  Therefore, the present invention relates to a technique relating to a phenolic resin composition for a wet friction material, which is useful for producing a wet friction material stably exhibiting high friction performance by improving durability while maintaining flexibility. I will provide a.

（式（１）中、Ｒｘ、Ｒｙは、それぞれ独立して水素または炭素数１〜３の有機基を表す。） According to the present invention, there is provided a phenolic resin composition for a wet friction material, comprising a modified resol type phenolic resin and a polymer containing a structural unit represented by the following formula (1).

(In the formula (1), Rx and Ry each independently represent hydrogen or an organic group having 1 to 3 carbon atoms.)

  Further, according to the present invention, there is provided a wet friction material including a cured product of the phenolic resin composition for a wet friction material.

  According to the present invention, a technique relating to a phenolic resin composition for a wet friction material useful for producing a wet friction material stably exhibiting high friction performance by improving durability while maintaining flexibility. Can be provided.

It is the graph which plotted the result of each example and each comparative example, making a horizontal axis a tensile elongation at break (%) and a vertical axis | shaft as Rockwell hardness (HRD).

  Hereinafter, embodiments of the present invention will be described in detail. In the present specification, the notation “ab” in the description of the numerical range indicates that the number is a or more and b or less unless otherwise specified.

<Phenolic resin composition for wet friction materials>
The phenolic resin composition for a wet friction material according to the present embodiment (hereinafter, also referred to as the present resin composition) comprises a modified resol type phenolic resin and a polymer containing a structural unit represented by the following formula (1). Including.

（式（１）中、Ｒｘ、Ｒｙは、それぞれ独立して水素または炭素数１〜３の有機基を示す。）

(In the formula (1), Rx and Ry each independently represent hydrogen or an organic group having 1 to 3 carbon atoms.)

According to the present resin composition, the curability of the phenolic resin composition for wet friction materials can be improved while maintaining the flexibility of the cured product. As a result, it is possible to produce a wet friction material that is excellent in balance between durability and flexibility and that stably exhibits high friction performance for a long time.
The reason for this is not clear, but for example, the present resin composition contains a modified resol type phenol resin and a polymer containing the structural unit represented by the above formula (1). It is conceivable that the hydroxyl group of the type phenol resin acts on the structural unit represented by the formula (1), and as a result, the polymer and the modified resol type phenol resin take a linked structure.

  Hereinafter, each component constituting the present resin composition will be described.

(Modified resol type phenol resin)
First, the modified resol type phenol resin contained in the present resin composition will be described.
As the modified resol-type phenol resin contained in the present resin composition, a conventionally known resin obtained by reacting a phenol, a modifier, and an aldehyde can be used. Further, the modified resol-type phenol resin can be obtained by reacting a phenol with an aldehyde to prepare a phenol resin, and then reacting the obtained phenol resin with a modifier. In the modified resol-type phenol resin, the modifying agent may be incorporated into the main skeleton, or may be incorporated into one end or both ends.

As modified resol type phenol resins, unsaturated alkyl phenol modified resole type phenol resins, alkyl phenol modified resole type phenol resins, unsaturated fatty acid modified resole type phenol resins, epoxy modified resole type phenol resins, xylene modified resole type phenol resins, polyamide modified resole type One or more resins selected from the group consisting of phenolic resins, polyester-modified resole-type phenolic resins, and aralkyl ether-modified resole-type phenolic resins are preferably used.
Examples of the unsaturated alkylphenol-modified resol-type phenol resin include a cashew oil-modified resol-type phenol resin using a cashew oil containing cardanol or cardol having an unsaturated double bond in a side chain as a modifier. In addition, examples of the unsaturated alkylphenol-modified resol-type phenol resin include an unsaturated alkylphenol-modified resol-type phenol resin having a denaturant of urushi extract, cardanol, curdle, methyl curdle, anacardic acid, urushiol, laccol, and thiol. .
Examples of the alkylphenol-modified resol-type phenol resin include an alkylphenol-modified resol-type phenol resin using alkylphenols such as cresol and p-tert-butylphenol as a modifier.
Examples of the unsaturated fatty acid-modified resol-type phenol resin include a modified resol-type phenol resin using an unsaturated fatty acid such as soybean oil, tung oil, linseed oil, tall oil or the like as a modifier.
Examples of the epoxy-modified resol-type phenol resin include an epoxy-modified resol-type phenol resin using various conventionally known epoxy resins such as bisphenol A-type epoxy resin as a modifier.
Examples of the xylene-modified resol-type phenol resin include a para-xylene-modified resol-type phenol resin.
Examples of the polyamide-modified resol-type phenol resin include a polyamide-modified resol-type phenol resin using a polyamide such as polyamide 6 or polyamide 66 as a modifier.
Examples of the polyester-modified resol-type phenol resin include a polyester-modified resol-type phenol resin using polyethylene terephthalate as a modifier.
Examples of the aralkyl ether-modified resol type phenol resin include α, α′-dimethoxy-p-xylene (PXDM), α, α′-diethoxy-p-xylene, α, α′-dimethoxy-m-xylene, α, α And aralkyl ether-modified resol-type phenol resins using aralkyl ethers such as α, -trimethoxy-p-xylene as modifiers.

  As the modified resol type phenol resin, one of the above resins may be used alone, or two or more having different weight average molecular weights may be used in combination, and one or two or more thereof and their prepolymers may be used. May be used in combination.

  Among the modified resol-type phenolic resins, more preferable resins from the viewpoint of stably obtaining good friction performance include cashew oil-modified resole-type phenolic resins and tung oil-modified resole-type phenolic resins.

The modified resol-type phenol resin can be appropriately selected according to the use as long as it is a resin obtained by reacting a phenol, a modifier, and an aldehyde in the presence of a basic catalyst.
The modified resol type phenol resin is usually obtained by controlling the molar ratio of aldehydes to phenols (aldehydes / phenols) to be 1.3 or more and 1.7 or less and then reacting. Can be.

Specific examples of phenols used in preparing this modified resol type phenol resin include phenol, o-cresol, m-cresol, p-cresol, xylenol, alkylphenols, catechol, resorcinol, and the like.
In addition, you may use these phenols individually or in mixture of 2 or more types.

  Further, specific examples of aldehydes used when preparing the modified resol type phenol resin include aldehyde compounds such as formaldehyde, paraformaldehyde, and benzaldehyde, and substances that are sources of these aldehyde compounds, or these aldehyde compounds. And the like can be used. These aldehydes may be used alone or in combination of two or more.

  Specific examples of the basic catalyst used when preparing the modified resol-type phenol resin include hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide, and alkali metals such as calcium, magnesium and barium. Examples include earth metal oxides and hydroxides, sodium carbonate, aqueous ammonia, amines such as triethylamine and hexamethylenetetramine, and divalent metal salts such as magnesium acetate and zinc acetate. These may be used alone or in combination of two or more.

The molecular weight of the modified resol-type phenol resin is, for example, preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more as a weight average molecular weight (Mw). When the weight average molecular weight (Mw) is equal to or more than the lower limit, the mechanical strength and the heat resistance of the present resin composition and the resin film obtained from the present resin composition can be improved.
The molecular weight of the modified resol-type phenol resin is, for example, preferably 100,000 or less, more preferably 50,000 or less, and still more preferably 20,000 or less, as a weight average molecular weight (Mw). When the weight average molecular weight (Mw) is equal to or less than the upper limit, the workability in producing the present resin composition and the impregnation property in obtaining an impregnated paper from the present resin composition can be improved. it can.
The weight average molecular weight can be calculated by gel permeation chromatography (GPC) based on a calibration curve prepared using a polystyrene standard substance, similarly to a polymer described later.

(polymer)
The polymer contained in the present resin composition contains the structural unit represented by the above formula (1). That is, the polymer contained in the present resin composition is a polymer containing a unit derived from an unsaturated carboxylic anhydride having a cyclic structure in the molecule, for example, a polymer of unsaturated carboxylic anhydride and another monomer It is a copolymer. In this embodiment, the unsaturated carboxylic anhydride having a cyclic structure in the molecule may be selected from a group including maleic anhydride, citraconic anhydride, dimethyl maleic anhydride or a derivative thereof, and maleic anhydride, It may be selected from the group consisting of citraconic anhydride and dimethyl maleic anhydride. These may be used alone or in combination of two or more.

（式（１）中、Ｒ_Ｘ、Ｒ_Ｙは、それぞれ独立して水素または炭素数１〜３の有機基である。）

Examples of the unit derived from the unsaturated carboxylic anhydride having a cyclic structure in the molecule of the polymer contained in the resin composition include, for example, an unsaturated carboxylic acid having a cyclic structure in the molecule represented by the following formula (1). A unit derived from an acid anhydride may be used, and a unit derived from maleic anhydride represented by the following formula (2) may be used.

(In the formula (1), R _X and R _Y are each independently hydrogen or an organic group having 1 to 3 carbon atoms.)

In the present embodiment, in the above formula (1), R _X and R _Y are preferably, for example, each independently hydrogen or an organic group having 1 to 3 carbon atoms, and are each independently hydrogen or 1 carbon atoms. It is more preferable that R _X is hydrogen and R _Y is hydrogen or an organic group having 1 carbon atom, and it is even more preferable that R _X and R _Y are hydrogen.

In the present embodiment, in the above formula (1), examples of the organic group constituting R _X and R _Y include an alkyl group, an alkenyl group, an alkynyl group, an alkylidene group, a cycloalkyl group, and a heterocyclic group.
Examples of the alkyl group include a methyl group, an ethyl group, and an n-propyl group. Examples of the alkenyl group include an allyl group and a vinyl group. Examples of the alkynyl group include an ethynyl group. Examples of the alkylidene group include a methylidene group and an ethylidene group. Examples of the cycloalkyl group include a cyclopropyl group. Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

（式（ａ）中、Ｒ_Ｘ，Ｒ_Ｙは、それぞれ独立して水素または炭素数１〜３の有機基であり、Ｗ、Ｚは、それぞれ独立して水素または炭素数１〜３０の有機基である。） Further, the polymer according to the present embodiment is represented by the following general formula (a), which is derived from a first esterified product obtained by opening an acid anhydride ring of an unsaturated carboxylic anhydride having a cyclic structure in a molecule with an alcohol. It may include a structural unit.

(In the formula (a), R _{X and} R _Y are each independently hydrogen or an organic group having 1 to 3 carbon atoms, and W and Z are each independently hydrogen or an organic group having 1 to 30 carbon atoms. Is.)

In the above formula (a), R _{X and} R _Y are the same as those in the above (1). In the above formula (a), one or both of W and Z are hydrogen or an organic group having 1 to 30 carbon atoms, and can include a structure derived from alcohol.

  In the present embodiment, the alcohol is, for example, preferably an alcohol having 1 to 30 carbon atoms, more preferably an alcohol having 1 to 15 carbon atoms, and an alcohol having 1 to 10 carbon atoms. Is more preferable, and an alcohol having 1 to 7 carbon atoms is more preferable.

  Examples of the above-mentioned alcohol include aliphatic alcohols such as methanol, ethanol, n-propanol, isopropanol, butanol, t-butanol, hexanol, pentanol, neopentanol and dodecanol; benzyl alcohol, phenol, 2,6-di- aromatic alcohols such as i-propylphenol and 4-t-octylphenol; and alicyclic alcohols such as cyclohexanol and 5-norbornene-2-methanol. These may be used alone or in combination of two or more.

The other monomer to be copolymerized with the unsaturated carboxylic anhydride having a cyclic structure in the molecule described above can be appropriately selected according to the application to which the resin composition is applied.
More specific examples include norbornene, norbornadiene, bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene), 5-methyl-2-norbornene, and 5-ethyl-2-norbornene. , 5-butyl-2-norbornene, 5-hexyl-2-norbornene, 5-decyl-2-norbornene, 5-allyl-2-norbornene, 5- (2-propenyl) -2-norbornene, 5- (1- Norbornene-based monomers such as methyl-4-pentenyl) -2-norbornene, 5-ethynyl-2-norbornene, 5-benzyl-2-norbornene, 5-phenethyl-2-norbornene; indene, 2-methylindene, 3-methyl Indene monomers such as indene; 1,5,9-cyclododecatriene, cis-trans-trans-1,5 9-cyclododecatriene, trans-trans-trans-1,5,9-cyclododecatriene, trans-cis-cis-1,5,9-cyclododecatriene, cis-cis-cis-1,5,9- Alicyclic monomers such as cyclododecatriene; styrene monomers such as styrene, vinyltoluene and α-methylstyrene; vinyl monomers such as vinyl chloride and vinylidene chloride; fluorine such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride Vinyl-containing monomers; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; nitrile-group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; amide-group-containing vinyl monomers such as acrylamide and methacrylamide; acetic acid Vinyl, propio Vinyl esters such as vinyl phosphate, vinyl pivalate, vinyl benzoate and vinyl cinnamate; alkenes such as ethylene and propylene; conjugated dienes such as butadiene and isoprene; allyl monomers such as allyl chloride and allyl alcohol; N-alkylmaleimides such as N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, Nt-butylmaleimide; N-cyclohexylmaleimide; N-cycloalkylmaleimides such as -cyclopentylmaleimide, N-norbornylmaleimide, N-cyclohexylmethylmaleimide, N-cyclopentylmethylmaleimide; N-phenylmaleimide, N-chlorophenylmaleimide, N-methyl N-arylmaleimides such as ruphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide; N-alkylmaleimide, N-cycloalkylmaleimide, In addition to N-arylmaleimide, maleimide-based monomers such as N-hydroxymaleimide; One of these may be used alone, or two or more different types may be used in combination.

As the other monomer, preferably, among alicyclic monomers, norbornene-type monomers, styrene-type monomers, indene-type monomers, and maleimide-type monomers can be used. That is, the polymer of the present embodiment is:
A structural unit derived from a norbornene-type monomer represented by the following formula (3):
A structural unit derived from a styrene-based monomer represented by the following formula (4):
A structural unit derived from an indene-based monomer represented by the following formula (5):
A structural unit derived from a maleimide-based monomer represented by the following formula (6):
It is preferable to further include at least one or more structural units selected from the group consisting of: These may include one unit alone, or may include two or more different units.
When the polymer contains at least one of these units, the durability of the wet friction material containing the cured product of the present resin composition can be improved.

（式（３）中、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４はそれぞれ独立して水素または炭素数１〜３０の有機基である。ｎは０、１または２である。）

(In the formula (3), R ₁ , R ₂ , R _3, and R ₄ are each independently hydrogen or an organic group having 1 to 30 carbon atoms. N is 0, 1, or 2.)

（式（４）中、Ｒ_ａはそれぞれ独立して炭素数１〜３０の有機基である。ｋは０以上５以下の整数である。）

(In the formula (4), _Ra is each independently an organic group having 1 to 30 carbon atoms. K is an integer of 0 or more and 5 or less.)

（式（５）中、Ｒ_５からＲ_１１はそれぞれ独立して水素または炭素数１〜３の有機基である。）

(In the formula (5), R ₅ to R ₁₁ are each independently hydrogen or an organic group having 1 to 3 carbon atoms.)

（式（６）中、Ｒ_１２は水素または炭素数１〜１０の有機基である。）

(In the formula (6), R ₁₂ is hydrogen or an organic group having 1 to 10 carbon atoms.)

In the embodiment, in the above formula (3), R _{1 to} R ₄ are, for example, each independently hydrogen or an organic group having 1 to 30 carbon atoms, and each independently represents hydrogen or an organic group having 1 to 10 carbon atoms. It is preferably an organic group, more preferably each independently hydrogen or an organic group having 1 to 3 carbon atoms, and even more preferably each independently hydrogen or an organic group having 1 carbon atom. In the above formula (3), n is, for example, 0, 1, or 2, preferably 0 or 1, and more preferably 0.

In the present embodiment, in the above formula (4), _Ra is, for example, each independently hydrogen or an organic group having 1 to 30 carbon atoms, and each independently represents hydrogen or an organic group having 1 to 10 carbon atoms. It is preferable that each is independently hydrogen or an organic group having 1 to 3 carbon atoms, and it is further preferable that each is independently hydrogen or an organic group having 1 carbon atom. In the above formula (4), k is, for example, an integer of 0 or more and 5 or less, preferably an integer of 0 or more and 3 or less, and more preferably an integer of 0 or more and 1 or less.

In the present embodiment, in the above formula (5), R _{5 to} R ₁₁ are, for example, each independently hydrogen or an organic group having 1 to 3 carbon atoms, and each is independently hydrogen or an organic group having 1 carbon atom. And more preferably each independently hydrogen.

In the embodiment, in the above formula (6), R ₁₂ is, for example, hydrogen or an organic group having 1 to 10 carbon atoms, preferably hydrogen or an organic group having 1 to 5 carbon atoms, and It is more preferably an organic group having the number of 1 to 3, more preferably hydrogen or an organic group having 1 carbon atom.

The organic group having 1 to 30 carbon atoms constituting the _{R 1} ~R _4, R _a is, O in their structure, N, S, may contain one or more atoms selected from P and Si. Further, the organic group having 1 to 3 carbon atoms constituting R _{5 to} R ₁₁ may include one or more atoms selected from O, N, S, P and Si in its structure. The organic group having 1 to 10 carbon atoms constituting the R ₁₂ is, O in their structure, N, S, may contain one or more atoms selected from P and Si. Further, the organic groups constituting R _{1 to} R ₄ , R _a , R _{5 to} R ₁₁ and R ₁₂ may not have any acidic functional group. Thereby, control of the acid value in the polymer can be facilitated.

In the present embodiment, the organic group constituting _R 1 ~R _4, R _a, for example, an alkyl group, an alkenyl group, an alkynyl group, an alkylidene group, an aryl group, an aralkyl group, an alkaryl group, a cycloalkyl group, and heterocyclic Groups.
Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, Octyl, nonyl, and decyl. Alkenyl groups include, for example, allyl, pentenyl, and vinyl. Examples of the alkynyl group include an ethynyl group. Examples of the alkylidene group include a methylidene group and an ethylidene group. Examples of the aryl group include a tolyl group, a xylyl group, a phenyl group, a naphthyl group, and an anthracenyl group. Examples of the aralkyl group include a benzyl group and a phenethyl group. Examples of the cycloalkyl group include an adamantyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

In the present embodiment, examples of the organic group constituting R _{5 to} R ₁₁ include an alkyl group, an alkenyl group, an alkynyl group, an alkylidene group, a cycloalkyl group, and a heterocyclic group.
Examples of the alkyl group include a methyl group, an ethyl group, and an n-propyl group. Examples of the alkenyl group include an allyl group and a vinyl group. Examples of the alkynyl group include an ethynyl group. Examples of the alkylidene group include a methylidene group and an ethylidene group. Examples of the cycloalkyl group include a cyclopropyl group. Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

In the present _embodiment, the organic group constituting _{R 12,} for example, hydrogen and, among the exemplified organic groups in the above _R 1 _~R 4, _{R a,} may be used an organic group having 1 to 10 carbon atoms .

Furthermore, the alkyl group, alkenyl group, alkynyl group, alkylidene group, aryl group, aralkyl group, alkaryl group, cycloalkyl group, and heterocyclic ring constituting R _{1 to} R ₄ , R _a , R _{5 to} R _11, and R _12. The groups may have one or more hydrogen atoms replaced by halogen atoms. Halogen atoms include fluorine, chlorine, bromine, and iodine. Of these, a haloalkyl group in which at least one hydrogen atom of an alkyl group is substituted with a halogen atom is preferable. By making at least one of R _{1 to} R ₄ , R _a , R _{5 to} R ₁₁ and R ₁₂ a haloalkyl group, the hardness of the wet friction material including the cured product of the present resin composition is improved. The balance between durability and flexibility can be improved. Further, by using a haloalkyl alcohol group, the hardness of a wet friction material containing a cured product of the present resin composition can be improved while maintaining flexibility.
From the viewpoint of enhancing the flexibility of the wet friction material containing the cured product of the present resin composition, it is preferable that any one of R _{1 to} R ₄ , R _a , R _{5 to} R ₁₁ and R ₁₂ is hydrogen. For example, when employing the structural unit of the formula (3), it is preferable that all of R _{1 to} R ₄ are hydrogen. For example, in the case of employing the structural units of formula (4), it is preferred that R _a is hydrogen. For example, when employing the structural unit of the formula (5), it is preferable that R _{5 to} R ₁₁ be hydrogen.

（式（７）中、ｌ、ｐおよびｍは、ポリマー中におけるモル含有率を示し、かつ、ｌ＋ｐ＋ｍ≦１、０≦ｌ＜１、０≦ｐ＜１、および０＜ｍ＜１の条件を満たし、ｎおよびｑはそれぞれ独立して０、１または２であり、Ｒ_１〜Ｒ_４およびＲ_１３〜Ｒ_１６はそれぞれ独立して水素または炭素数１〜３０の有機基であり、Ｒ_１３、Ｒ_１４、Ｒ_１５およびＲ_１６から選択される１または２以上がアルコール性水酸基を有する有機基であり、Ａは下記式（２ａ）、（２ｂ）、（２ｃ）または（２ｄ）により示される構造単位であり、複数のＡのうち、下記式（２ｃ）により示される構造単位を１以上含む。）

（式（２ａ）および式（２ｂ）中、Ｒ_１７、Ｒ_１８およびＲ_１９は、それぞれ独立して炭素数１〜３０の有機基である。） When the polymer has the structural unit of the formula (1), the polymer is preferably composed of a copolymer having a structure represented by the following formula (7).

(In the formula (7), l, p and m indicate the molar content in the polymer and satisfy the conditions of 1 + p + m ≦ 1, 0 ≦ l <1, 0 ≦ p <1, and 0 <m <1) And n and q are each independently 0, 1 or 2, R _{1 to} R ₄ and R _{13 to} R ₁₆ are each independently hydrogen or an organic group having 1 to 30 carbon atoms, and R ₁₃ , One or more selected from R ₁₄ , R ₁₅ and R ₁₆ is an organic group having an alcoholic hydroxyl group, and A is a structure represented by the following formula (2a), (2b), (2c) or (2d) (A is a unit and includes one or more structural units represented by the following formula (2c) among a plurality of A.)

(In the formulas (2a) and (2b), R ₁₇ , R ₁₈ and R ₁₉ are each independently an organic group having 1 to 30 carbon atoms.)

In the present resin composition, the content of the modified resol-type phenol resin described above is preferably 1 part by mass or more, more preferably 10 parts by mass or more, and more preferably 50 parts by mass, based on 100 parts by mass of the polymer. More preferably, it is more preferably 100 parts by mass or more.
Further, in the present resin composition, the content of the modified resol-type phenol resin described above is preferably 10,000 parts by mass or less, more preferably 5000 parts by mass or less, and more preferably 2500 parts by mass, based on 100 parts by mass of the polymer. It is more preferably at most 1,000 parts by mass, particularly preferably at most 1,000 parts by mass.
By setting the content of the modified resol-type phenol resin to the polymer in such a range, an appropriate interaction between the polymer and the modified resol-type phenol resin is brought about, which can further contribute to the improvement of durability.

  A chain transfer agent can be appropriately used to adjust the molecular weight of the polymer. Examples of the chain transfer agent include stearyl-3-mercaptopropionate, pentaerythritol tetrakis (3-mercaptopropionate), β-mercaptopropionic acid, methoxybutyl-3-mercaptopropionate, and stearyl-3-mercapto. Β-mercaptopropionic acids such as propionate, trimethylolpropane tris (3-mercaptopropionate), tris-[(3-mercaptopropionyloxy) -ethyl] -isocyanurate; 2-hydroxy-1,4-naphthoquinone And naphthoquinones such as 1,4-naphthoquinone; mercaptans such as n-hexylmercaptan, n-octylmercaptan, n-dodecylmercaptan, tert-dodecylmercaptan, thioglycolic acid and mercaptopropionic acid Xanthogens such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; and other examples include triethoxysilane, terpinolene, and α-methylstyrene dimer.

In the molecular weight distribution curve obtained by, for example, GPC (Gel Permeation Chromatography), the above-mentioned polymer in the stage before reacting with the modified resol-type phenol resin in this embodiment may have a peak area at a molecular weight of 1,000 or less, 3% or less of the whole. , May be 2% or less.
By setting the ratio of the peak area at a molecular weight of 1000 or less in the molecular weight distribution curve obtained by GPC to the above range, the durability of the wet friction material containing the cured product of the present resin composition in terms of hardness is obtained. And the flexibility can be improved.
In addition, the lower limit of the amount of the low molecular weight component in the polymer is not particularly limited. However, the polymer in the present embodiment allows a case where the peak area at a molecular weight of 1,000 or less in the molecular weight distribution curve obtained by GPC is 0.01% or more of the whole.

  In the present embodiment, the polymer before reacting with the modified resol-type phenol resin preferably has, for example, Mw (weight average molecular weight) / Mn (number average molecular weight) of 1.4 or more and 4.0 or less. By doing so, the durability of the wet friction material containing the cured product of the present resin composition during use can be improved. Note that Mw / Mn is a degree of dispersion indicating the width of the molecular weight distribution. Further, the above-mentioned effects are particularly remarkable when the low-molecular-weight components of the polymer are simultaneously reduced as described above. The Mw (weight average molecular weight) of the polymer is, for example, from 1500 to 30,000.

For the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn), values in terms of polystyrene obtained from, for example, a calibration curve of standard polystyrene (PS) obtained by GPC measurement are used. The measurement conditions are, for example, as follows.
Tosoh Gel Permeation Chromatography System HLC-8320GPC
Column: TSK-GEL Supermultipore HZ-M manufactured by Tosoh Corporation
Detector: RI detector for liquid chromatogram Measurement temperature: 40 ° C
Solvent: THF
Sample concentration: 2.0 mg / milliliter The amount of low molecular weight components in the polymer is determined by, for example, the total area of components having a molecular weight of 1000 or less in the entire area of the molecular weight distribution based on data on molecular weight obtained by GPC measurement. Is calculated from the ratio of

(Method for producing polymer)
The polymer according to the present embodiment can be obtained by copolymerizing an unsaturated carboxylic anhydride having a cyclic structure in the molecule with another monomer. As this manufacturing method, a conventionally known method may be used. Hereinafter, a method for producing a polymer containing the structural unit represented by the above formula (3) will be described as an example.

(Polymerization step (Process S1))
First, a norbornene-type monomer represented by the following formula (3a) and maleic anhydride as a monomer are prepared. In the norbornene-type monomer represented by the formula (3a), n and R _{1 to} R ₄ can be the same as those in the formula (3).

Specific examples of the norbornene-type monomer represented by the formula (3a) include bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene), and further have an alkyl group. As those having an alkenyl group, such as 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, and 5-decyl-2-norbornene Are 5-ethynyl such as 5-allyl-2-norbornene, 5- (2-propenyl) -2-norbornene and 5- (1-methyl-4-pentenyl) -2-norbornene. Examples of those having an aralkyl group such as -2-norbornene include 5-benzyl-2-norbornene and 5-phenethyl-2-norbornene. Such as emissions, and the like.
Other examples of the norbornene-type monomer include a functional group such as a crosslinkable group or a group containing a halogen atom such as fluorine in the structure of R ₁ , R ₂ , R ₃ and R _{4 in} the formula (3a). Can be adopted.
As the norbornene-type monomer, any one or more of these can be used. Among them, it is preferable to use bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene) from the viewpoint of controlling the reactivity between the polymer and the phenol resin.

Specific examples of the norbornene-type monomer represented by the formula (3a) include bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene), and further have an alkyl group. As those having an alkenyl group, such as 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-hexyl-2-norbornene, and 5-decyl-2-norbornene Is a compound having an alkynyl group such as 5-allyl-2-norbornene, 5- (2-propenyl) -2-norbornene, 5- (1-methyl-4-pentenyl) -2-norbornene, Examples of those having an aralkyl group such as -2-norbornene include 5-benzyl-2-norbornene and 5-phenethyl-2-norbornene. Such as emissions, and the like.
Other examples of the norbornene-type monomer include a functional group such as a crosslinkable group or a group containing a halogen atom such as fluorine in the structure of R ₁ , R ₂ , R ₃ and R _{4 in} the formula (3a). Can be adopted.
As the norbornene-type monomer, any one or more of these can be used. Among them, it is preferable to use bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene) from the viewpoint of controlling the reactivity between the polymer and the phenol resin.

Next, the norbornene-type monomer represented by the formula (3a) is subjected to addition polymerization with maleic anhydride. Here, a copolymer (copolymer 1) of the norbornene-type monomer represented by the formula (3a) and maleic anhydride is formed by radical polymerization.
The molar ratio of the norbornene-type monomer represented by the formula (3a) to maleic anhydride (the number of moles of the compound represented by the formula (3a): the number of moles of maleic anhydride) is 0.5: 1 to 1: 0. .5. Among them, from the viewpoint of controlling the molecular structure, it is preferable that the molar number of the norbornene-type monomer represented by the formula (3a): the molar number of the maleic anhydride = 0.8: 1 to 1: 0.8.
In addition, at the time of this addition polymerization, a monomer that can be copolymerized other than the above-mentioned norbornene-type monomer and maleic anhydride may be added. Examples of such a monomer include a compound containing a group having an ethylenic double bond in the molecule. Here, specific examples of the group having an ethylenic double bond include an allyl group, an acryl group, a methacryl group, a maleimide group, and an aromatic vinyl group such as a styryl group and an indenyl group.
Instead of the maleic anhydride, another unsaturated carboxylic anhydride having a cyclic structure in the molecule may be used.

  For example, by dissolving a norbornene-type monomer represented by the formula (3a), maleic anhydride, and a polymerization initiator in a solvent, and then heating for a predetermined time, the norbornene-type monomer represented by the formula (3a): Solution polymerization with maleic anhydride. The heating temperature is, for example, 50 to 80 ° C., and the heating time is 10 to 20 hours.

  As the solvent used for the polymerization, for example, any one or more of diethyl ether, tetrahydrofuran, toluene, methyl ethyl ketone, ethyl acetate and the like can be used.

As the radical polymerization initiator, any one or more of an azo compound and an organic peroxide can be used.
Examples of the azo compound include azobisisobutyronitrile (AIBN), dimethyl 2,2′-azobis (2-methylpropionate), and 1,1′-azobis (cyclohexanecarbonitrile) (ABCN). Any one or more of these can be used. Examples of the organic peroxide include hydrogen peroxide, di-tert-butyl peroxide (DTBP), benzoyl peroxide (benzoyl peroxide, BPO), and methyl ethyl ketone peroxide (MEKP). , Any one or more of which can be used.

  The amount (molar number) of the radical polymerization initiator is preferably 1% to 10% of the total mole number of the norbornene-type monomer represented by the formula (3a) and maleic anhydride. The weight average molecular weight (Mw) of the obtained polymer is adjusted to an appropriate range by appropriately setting the amount of the polymerization initiator within the above range, and appropriately setting the reaction temperature, the reaction time, and the amount of the chain transfer agent. can do.

By this polymerization step (processing S1), the copolymer 1 having the structural unit represented by the above formula (1) and the structural unit represented by the above formula (3) can be polymerized.
However, in the copolymer 1, R _{1 in} the structure of the formula (3) is preferably common to a plurality of structural units, but may be different for each structural unit. The same applies to R _{2 to} R ₄ .

（式（８）において、ｎ、Ｒ_１〜Ｒ_４は、上記式（３）と同じである。すなわち、ｎは０、１、２のいずれかである。Ｒ_１〜Ｒ_４は、水素または炭素数１〜３０の有機基である。Ｒ_１〜Ｒ_４は、同一のものであっても異なっていてもよい。また、ｂは１０以上、２００以下の整数である。） In the copolymer 1, the structural unit represented by the formula (1) and the structural unit represented by the formula (3) may be randomly arranged, or may be alternately arranged. There may be. Further, a norbornene-type monomer represented by the formula (3a) and maleic anhydride may be subjected to block copolymerization. However, from the viewpoint of controlling the balance between flexibility and durability of the cured product of the resin composition using the polymer produced in the present embodiment so as to be in a good state, the structure represented by the formula (1) is used. It is preferable that the unit and the structural unit represented by the formula (3) are arranged alternately. That is, for example, when the norbornene-type monomer and maleic anhydride are copolymerized, the copolymer 1 preferably has a structural unit represented by the following formula (8).

(In the formula (8), n and R _{1 to} R ₄ are the same as the formula (3). That is, n is any one of 0, 1, and 2. R _{1 to} R ₄ are hydrogen or It is an organic group having 1 to 30 carbon atoms. R _{1 to} R ₄ may be the same or different. Also, b is an integer of 10 or more and 200 or less.)

Here, R _{1 in} the structure of the formula (8) is preferably common to a plurality of structural units, but may be different for each structural unit. The same applies to R _{2 to} R ₄ .

(Low molecular weight component removal step (processing S2))
Next, if necessary, a large amount of a poor solvent, for example, hexane or methanol, is added to the organic layer containing the copolymer 1 and low molecular weight components such as residual monomers and oligomers to obtain a copolymer. The polymer containing coalescing 1 is coagulated and precipitated. Here, the low molecular weight component includes residual monomers and oligomers, and further includes a polymerization initiator and the like. Next, filtration is performed, and the obtained coagulated product is dried. Thereby, a polymer having the copolymer 1 from which the low molecular weight component has been removed as a main component (main product) can be obtained.

（式（５ａ）中、Ｒ_５〜Ｒ_１１は式（５）と同じである。） Further, for example, when the above-mentioned polymer contains the structural unit represented by the above formula (5), the structural unit of the formula (3) can be obtained by using an indene-based monomer represented by the following formula (5a). It can be produced in the same manner as the monomer and polymer containing.

(In the formula (5a), R _{5 to} R ₁₁ are the same as the formula (5).)

  The resin composition contains the above-mentioned modified resol-type phenol resin and a polymer. The polymer has a structural unit represented by the above-mentioned formula (2) (that is, a maleic anhydride unit (an acid anhydride site)). It is preferable to include a compound (ester compound) in which a hydroxyl group provided in the modified resol-type phenol resin is bonded via an ester bond.

（式（９）中、Ｒは変性レゾール型フェノール樹脂に由来する原子団である。） In the present resin composition, it is conceivable that the hydroxyl group of the modified resol type phenol resin is added to maleic anhydride to give a half ester as represented by the following formula (9). Due to the ester bond in the formula (9), the cured product of the resin composition of the present embodiment can further improve the durability.
Instead of the maleic anhydride, another unsaturated carboxylic anhydride having a cyclic structure in the molecule may be used.

(In the formula (9), R is an atomic group derived from a modified resol-type phenol resin.)

Note that, as described above, the resin composition of the present embodiment may provide a half ester as represented by the formula (9). Since effects such as heat resistance are thereby exhibited, the content ratio of the above-mentioned half ester can be increased by heating the resin composition before providing the resin composition to various uses.
The conditions for this heating are, for example, in the range of 50 to 100 ° C.
Further, for example, in the case of using for an application that undergoes a heating step in the process, the above-mentioned modified resol-type phenol resin and the polymer can be mixed at room temperature and used without heating.
In this heating, a catalyst can be appropriately added from the viewpoint of accelerating the reaction, and for example, a base catalyst or an acid catalyst can be added.
Examples of the base catalyst include hydroxy compounds such as sodium hydroxide and potassium hydroxide, pyridine, alkylamines such as triethylamine, amine compounds such as dimethylaniline, urotropin and dimethylaminopyridine, metal salts such as sodium acetate, and ammonia. be able to. One of these may be used alone, or two or more base catalysts may be combined to further increase the reactivity.
As the acid catalyst, a mineral acid such as sulfuric acid or hydrochloric acid, an organic acid such as paratoluenesulfonic acid, a Lewis acid such as boron fluoride etherate, or the like can be used.
Instead of the maleic anhydride, another unsaturated carboxylic anhydride having a cyclic structure in the molecule may be used.

  Further, the present resin composition contains an ester compound in which an acid anhydride site of a polymer containing the structural unit represented by the above formula (1) and a hydroxyl group provided in the modified resol-type phenol resin form an ester bond. It may be. In this case, in the present resin composition, all of the acid anhydride (for example, maleic anhydride) of the polymer may be ring-opened, and / or all of the hydroxyl groups provided in the modified resol-type phenol resin may be used. It may have an ester bond. This makes it possible to improve the durability of the cured product of the present resin composition in terms of hardness.

In addition, the present resin composition may contain an inorganic filler from the viewpoint of improving hardness while maintaining flexibility of the cured product. Specific examples of such inorganic fillers include talc, calcined clay, unfired clay, silicates such as mica, oxides such as titanium oxide, alumina, silica, fused silica, calcium carbonate, magnesium carbonate, hydrotalcite, and the like. Carbonates, hydroxides such as aluminum hydroxide, magnesium hydroxide and calcium hydroxide, sulfates or sulfites such as barium sulfate, calcium sulfate and calcium sulfite, zinc borate, barium metaborate, aluminum borate and borate Borates such as calcium oxide and sodium borate; nitrides such as aluminum nitride, boron nitride and silicon nitride; glass fibers; These may be used alone or in combination of two or more.
In addition, the content of the inorganic filler is preferably 35% by mass or more and 65% by mass or less, more preferably 40% by mass or more and 60% by mass, based on the total amount of the present resin composition, from the viewpoint of improving workability. It is as follows.

  Further, the present resin composition may contain additives such as a lubricant, a curing aid, and a pigment as long as the object of the present invention is not impaired.

<Wet friction material>
The wet friction material according to this embodiment includes a cured product of the above resin composition. The wet friction material according to the present embodiment is suitably used as a wet friction material such as a clutch.

  The wet friction material according to the present embodiment is generally manufactured by impregnating or coating a base material with the present resin composition mixed with an organic solvent, followed by firing and curing. Specific examples of the base material include natural fibers, metal fibers, carbon fibers, and chemical fibers. These may contain one kind alone or may be a mixture of two or more kinds. Further, specific examples of the organic solvent include methanol, ethanol, isopropanol, alcoholic organic solvents such as butanol, acetone, methyl ethyl ketone, ketone organic solvents such as methyl isobutyl ketone, toluene, aromatic hydrocarbon solvents such as ethylbenzene and the like. These mixtures are mentioned.

  Further, when the wet friction material according to the present embodiment is a wet paper friction material, such a wet friction material is generally prepared by mixing the present resin composition mixed with an organic solvent with metal fibers, carbon fibers and chemical fibers, and cashew dust. It is manufactured by impregnating a paper base material filled with a friction modifier such as a diatomaceous earth or the like, followed by firing and curing.

  It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.

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

<Preparation of unmodified resol type phenol resin A>
In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 740 parts by mass of a formalin aqueous solution (formalin content: 37 parts by mass) such that the molar ratio of 1000 parts by mass of phenol to the phenol becomes 1 %) And 20 parts by mass of triethylamine were added and reacted at 100 ° C. with stirring for 30 minutes. Next, while dehydration was performed under a reduced pressure of 91 kPa, when the temperature in the system reached 65 ° C., 1000 parts by mass of methyl ethyl ketone (MEK) was added to dissolve the reaction product, followed by cooling. In this way, 2100 parts by mass of a liquid unmodified resol-type phenolic resin A (non-volatile content (solid content) content: 45% by mass) was obtained.
The weight average molecular weight (Mw) of the obtained liquid unmodified resol type phenol resin A was 200, and the degree of dispersion (Mw / Mn) was 2.5.

<Preparation of unmodified resol type phenolic resin B>
In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 1480 parts by mass of a formalin aqueous solution (formalin content: 37 parts by mass) such that the molar ratio of 1000 parts by mass of phenol to the phenol becomes 2 %) And 20 parts by mass of triethylamine were added and reacted at 100 ° C. with stirring for 30 minutes. Next, while dehydrating under a reduced pressure of 91 kPa, when the temperature in the system reached 65 ° C., 1000 parts by mass of methanol was added to dissolve the reaction product, and then cooled. In this way, 2100 parts by mass of a liquid non-modified resol type phenolic resin B having a high crosslinking density (non-volatile content (solid content) content: 45% by mass) was obtained.
The weight average molecular weight (Mw) of the obtained liquid unmodified resol type phenol resin B was 230, and the degree of dispersion (Mw / Mn) was 2.5.

<Preparation of tung oil-modified resole type phenolic resin C>
In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 1000 parts by mass of phenol, 540 parts by mass of tung oil and 1 part by mass of p-toluenesulfonic acid were added, and the mixture was added at 60 ° C. for 30 minutes. The reaction was carried out with stirring. Next, 770 parts by mass of an aqueous solution of formalin (formalin content: 37% by mass), 1 part by mass of triethanolamine, and 20 parts by mass of an aqueous ammonia solution so that the molar ratio with the phenol becomes 1.2. (Ammonia content: 25% by mass), and reacted while stirring at 100 ° C. for 2 hours. Next, when the temperature in the system reached 70 ° C. while dehydrating under a reduced pressure of 91 kPa, 280 parts by mass of toluene and 670 parts by mass of methanol were added to dissolve the reactants, and then cooled. . Thus, 2100 parts by mass of a liquid tung oil-modified (oil-modified) resol-type phenolic resin C (non-volatile content (solid content) content: 45% by mass) was obtained.
The weight-average molecular weight (Mw) of the obtained liquid tung oil-modified resol phenolic resin C was 300, and the degree of dispersion (Mw / Mn) was 3.0.

<Preparation of cashew-modified resol-type phenolic resin D>
1000 parts by mass of cardanol and 15 parts by mass of paratoluenesulfonic acid were added to a reactor equipped with a stirrer, a reflux condenser, and a thermometer, and heated to 140 ° C., and reacted while stirring for 1 hour. After neutralization by adding 5 parts by mass of triethylamine, 300 parts by mass of phenol, 535 parts by mass of a 37% formalin aqueous solution (molar ratio to the total of the cardanol reactant and phenol 1.0), and 24 parts by mass of triethylamine were added. The mixture was heated to 90 ° C. and reacted while stirring for 2 hours. Thereafter, while dehydrating at a reduced pressure of 91 kPa, when the temperature in the system reached 65 ° C., 280 parts by mass of toluene and 630 parts by mass of methanol were added to dissolve and cool. In this way, 2,100 parts by mass of a liquid cashew-modified resol-type phenol resin D having a nonvolatile content of 45% was obtained. The weight average molecular weight (Mw) of the obtained cashew-modified resol-type phenol resin D was 1,000, and the degree of dispersion (Mw / Mn) was 3.0.

<Polymer A: Preparation of norbornene-maleic anhydride copolymer>
In a reactor equipped with a stirrer, reflux condenser and thermometer, 706 g of 2-norbornene (7.5 mol) and 69 g of dimethyl-2,2′-azobis (2-methylpropionate, 0.3 mol ) Was dissolved in methyl ethyl ketone. Next, dissolved oxygen in the system was removed by performing nitrogen bubbling on the obtained solution. Then, after reaching 80 ° C. with stirring, a solution of maleic anhydride (735 g, 7.5 mol) in methyl ethyl ketone and a solution of n-dodecyl mercaptan (243.2 g, 1.20 mol) in methyl ethyl ketone were sequentially added from each mouth over 1 hour. . Thereafter, a heat treatment was further performed for 8 hours. The weight average molecular weight (Mw) of the obtained norbornene-maleic anhydride copolymer was 3,200, and the degree of dispersion (Mw / Mn) was 1.5.

<Polymer B: preparation of norbornene-maleic anhydride copolymer>
In a reactor equipped with a stirrer, reflux condenser and thermometer, 706 g of 2-norbornene (7.5 mol), 735 g of maleic anhydride (7.5 mol) and 69 g of dimethyl-2,2′- Azobis (2-methylpropionate, 0.3 mol) was weighed and dissolved in methyl ethyl ketone and toluene. Next, the dissolved solution obtained was subjected to nitrogen bubbling to remove dissolved oxygen in the system, and then heat-treated at 60 ° C. for 15 hours.
The weight average molecular weight (Mw) of the obtained norbornene-maleic anhydride copolymer was 10,000, and the degree of dispersion (Mw / Mn) was 2.1.

<Polymer C: Styrene-maleic anhydride copolymer>
As a styrene-maleic anhydride copolymer, SMA-1000-P manufactured by Cray Valley USA, LLC was prepared.
The weight average molecular weight (Mw) of the styrene-maleic anhydride copolymer was 3,600, and the degree of dispersion (Mw / Mn) was 2.3.

<Polymer D: Preparation of indene 25% by mass modified novolak type phenol resin>
750 parts by mass of a novolak-type phenol resin and 250 parts by mass of an indene-maleic anhydride copolymer are added to 250 parts by mass of a methyl ethyl ketone solution, and then methyl ethyl ketone and 5 parts by mass of pyridine are added. The content of the resin component was adjusted to 50% by mass, and after heating at 70 ° C. for 2 days, the solvent and pyridine were removed and the mixture was filtered with a filter to obtain a desired indene 25% by mass modified novolak-type phenol resin. Got.

<Polymer E: Preparation of indene 75% by mass modified novolak type phenol resin>
By adding 250 parts by mass of a novolak type phenol resin and 750 parts by mass of an indene-maleic anhydride copolymer to a 750 parts by mass of methyl ethyl ketone solution, and then adding methyl ethyl ketone and 5 parts by mass of pyridine. The content of the resin component was adjusted to 50% by mass, and after heating at 70 ° C. for 2 days, the solvent and pyridine were removed, followed by filtration with a filter to obtain the desired indene 75% by mass modified novolak-type phenol resin. Got.

<Preparation of phenolic resin composition for wet friction material>
Each component was blended according to the blending amounts shown in Table 1 below to obtain phenolic resin compositions for wet friction materials according to each of Examples and Comparative Examples.

<Preparation of wet friction material>
A resin varnish obtained by adjusting the obtained phenol resin compositions for wet friction materials of Examples 1 to 5 and Comparative Examples 1 to 10 with methyl ethyl ketone so that the content of the resin component was 30% by mass was 120 mm × 10 mm × thickness. A 1 mm thick aramid fiber base material was impregnated, and then dried and cured in an oven at 190 ° C. for 30 minutes to obtain a wet friction material (impregnated paper) as a test piece.

  The following evaluations and measurements were performed using the obtained test pieces of the wet friction material. The evaluation results are shown in Table 1 below. Further, in FIG. 1, the results of Examples and Comparative Examples are plotted on the assumption that the horizontal axis indicates tensile elongation at break (%) and the vertical axis indicates Rockwell hardness (HRD).

-Tensile rupture elongation: The tensile rupture elongation of a test piece of the obtained wet friction material was measured by a method in accordance with JIS P 8113. The unit is%. The measurement conditions were a precision universal testing machine AG-IS 5 kN (manufactured by Shimadzu Corporation) and a test speed of 1 mm / min under normal temperature and normal pressure. The numerical value of the tensile elongation at break indicates that the higher the value, the better the flexibility of the test piece.

Rockwell hardness (HRD): The hardness of a test piece of the obtained wet friction material was measured on an M scale according to a method based on JIS Z 2245. The higher the value of Rockwell hardness (HRD), the higher the durability of the test piece.

  As shown in Table 1 and FIG. 1, all of the wet friction materials of Examples 1 to 5 are more excellent in the balance between flexibility and durability than the wet friction materials of Comparative Examples 1 to 10, It was confirmed that good friction performance can be stably exhibited for a long time.

Claims (8)

A modified resol type phenolic resin,
A polymer containing a structural unit represented by the following formula (1):
A phenolic resin composition for a wet friction material, comprising:

(In the formula (1), Rx and Ry each independently represent hydrogen or an organic group having 1 to 3 carbon atoms.)   The modified resol-type phenolic resin is an unsaturated alkylphenol-modified resole-type phenolic resin, an alkylphenol-modified resole-type phenolic resin, an unsaturated fatty acid-modified resole-type phenolic resin, an epoxy-modified resole-type phenolic resin, a xylene-modified resole-type phenolic resin, or a polyamide-modified resole. The phenolic resin composition for a wet friction material according to claim 1, which is at least one resin selected from the group consisting of a phenolic resin, a polyester-modified resole-type phenolic resin, and an aralkyl ether-modified resole-type phenolic resin. The phenolic resin composition for a wet friction material according to claim 1 or 2, wherein the polymer is composed of a copolymer having a structure represented by the following formula (7).

(In the formula (7), l, p and m indicate the molar content in the polymer and satisfy the conditions of 1 + p + m ≦ 1, 0 ≦ l <1, 0 ≦ p <1, and 0 <m <1) Fill,
n and q are each independently 0, 1 or 2;
R _{1 to} R ₄ and R _{13 to} R ₁₆ are each independently hydrogen or an organic group having 1 to 30 carbon atoms;
One or more selected from R ₁₃ , R ₁₄ , R ₁₅ and R ₁₆ is an organic group having an alcoholic hydroxyl group, and A is represented by the following formula (2a), (2b), (2c) or (2d) And one or more structural units represented by the following formula (2c) among a plurality of A's. )

(In the formulas (2a) and (2b), R ₁₇ , R ₁₈ and R ₁₉ are each independently an organic group having 1 to 30 carbon atoms.)   The phenolic resin composition for a wet friction material according to any one of claims 1 to 3, wherein the content of the modified resol-type phenolic resin is 1 part by mass or more and 10,000 parts by mass or less based on 100 parts by mass of the polymer. object.   The phenolic resin composition for a wet friction material according to any one of claims 1 to 4, wherein the modified resol-type phenol resin has a weight average molecular weight of 100 or more and 100,000 or less.   The phenolic resin composition for a wet friction material according to any one of claims 1 to 5, wherein the degree of dispersion (Mw / Mn) of the polymer is 1.4 or more and 4.0 or less.   7. The composition according to claim 1, further comprising a compound in which an acid anhydride moiety provided in the structural unit represented by the formula (1) and a hydroxyl group provided in the modified resol-type phenol resin are bonded via an ester bond. The phenolic resin composition for a wet friction material according to claim 1 or 2.   A wet friction material comprising a cured product of the phenolic resin composition for a wet friction material according to any one of claims 1 to 7.

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