WO2018190171A1

WO2018190171A1 - Friction material

Info

Publication number: WO2018190171A1
Application number: PCT/JP2018/014098
Authority: WO
Inventors: 康典大橋; 霖周; 麻衣子山本; 勇希谷口; 遼太郎高山; 木村　肇; 大塚　恵子; 松本　明博
Original assignee: ハリマ化成株式会社; 地方独立行政法人大阪産業技術研究所
Priority date: 2017-04-14
Filing date: 2018-04-02
Publication date: 2018-10-18
Also published as: JPWO2018190171A1

Abstract

A friction material which contains a binder, wherein the binder comprises a reaction product obtained by reactions among a lignin having aliphatic hydroxy groups in the molecule, a phenol, and an aldehyde, the lignin having an aliphatic-hydroxy-group content of 0.5-8.5 mass% with respect to the overall amount of the lignin.

Description

Friction material

The present invention relates to a friction material, and more particularly to a friction material used as a brake pad or the like.

Conventionally, friction materials have been used for brake pads and clutch members of automobiles, motorcycles, trains, and the like. Friction materials are usually manufactured by integrally forming reinforcing materials such as metal fibers and aramid fibers and additives such as fillers and lubricants through a binder (binder) such as phenol resin. Has been.

Such a friction material is required to have friction characteristics, mechanical strength, and the like, and to reduce the environmental load. Therefore, it has been proposed to use a lignin phenol resin as a binder (binder). More specifically, for example, there has been proposed a friction material containing, as a binder, a lignin phenol resin having a weight average molecular weight of 5000 or less obtained by reacting lignin, phenols and aldehydes in the presence of an acid catalyst. (See Patent Document 1).

JP 2013-199561 A

On the other hand, the friction material is required to further improve various physical properties such as friction characteristics, wear resistance, and mechanical strength.

An object of the present invention is to provide a friction material having excellent friction characteristics, wear resistance and mechanical strength.

The present invention [1] is a friction material containing a binder, wherein the binder contains a reaction product of a lignin having an aliphatic hydroxyl group in the molecule, a phenol, and an aldehyde, A friction material is included in which the content ratio of the aliphatic hydroxyl group is 0.5% by mass or more and 8.5% by mass or less based on the total amount of the lignin.

Moreover, this invention [2] contains the friction material as described in said [1] whose said lignin is said lignin is a craft lignin.

Further, the present invention [3] includes the friction material according to the above [1], wherein the lignin is lignin modified with acetic acid.

Since the friction material of the present invention contains a binder containing a reaction product of lignin having a predetermined content of aliphatic hydroxyl group, phenols, and aldehydes, friction characteristics, wear resistance, and mechanical strength Excellent.

The friction material of the present invention contains a binder (binder).

The binder (binder) contains a reaction product of lignin having an aliphatic hydroxyl group (described later) in the molecule, phenols, and aldehydes, preferably an aliphatic hydroxyl group (described later) in the molecule. It consists of a reaction product of a lignin having a phenol, a aldehyde.

Lignin is a high molecular phenolic compound having a basic skeleton such as guaiacyl lignin (G type), syringyl lignin (S type), p-hydroxyphenyl lignin (H type) and the like.

More specifically, lignin is classified according to, for example, the type of plant used as a raw material, and specific examples include woody plant-derived lignin and herbaceous plant-derived lignin.

Examples of woody plant-derived lignin include coniferous lignin contained in conifers (eg, cedar), for example, broadleaf lignin contained in broadleaf trees. Such woody plant-derived lignin does not contain lignin having H-type basic skeleton, for example, conifer lignin has G-type basic skeleton, and hardwood lignin has G-type and S-type basic skeleton. Yes.

Examples of the herbaceous plant-derived lignin include, for example, rice-based lignin contained in Gramineae plants, and more specifically, wheat straw lignin contained in wheat straw, rice straw lignin contained in rice straw, and corn. Examples include corn lignin and bamboo lignin contained in bamboo. Such herbaceous plant-derived lignin has all of H-type, G-type and S-type as the basic skeleton.

These lignins can be used alone or in combination of two or more.

The lignin is preferably a herbaceous plant-derived lignin, more preferably a herbaceous plant-derived lignin derived from straw, or a herbaceous plant-derived lignin derived from corn.

Further, as lignin, from the viewpoint of reactivity, it is preferable to contain an H-type basic skeleton in a proportion of 3% by mass or more, more preferably 9% by mass or more, and still more preferably 14% by mass or more. It is done.

Such lignin is contained in waste liquid (black liquor) discharged when pulp is produced from a plant by a known method such as an alkali method (soda method), a sulfurous acid method, or a kraft method. More specifically, the waste liquid (black liquor) discharged in the alkali method contains alkali lignin (soda lignin), and the waste liquid (black liquor) discharged in the sulfurous acid method contains sulfite lignin. The waste liquid (black liquor) discharged in the kraft process contains craft lignin.

In addition to the above, examples of lignin include acid-modified lignin obtained by modifying lignin with an acid (such as a carboxylic acid), and explosion lignin obtained by treating a plant with an explosion method.

The lignin is preferably an acid-modified lignin, more preferably a carboxylic acid-modified lignin.

In the carboxylic acid-modified lignin, examples of the carboxylic acid include a carboxylic acid having one carboxy group (hereinafter, sometimes referred to as a monofunctional carboxylic acid). Functional carboxylic acid, unsaturated aliphatic monofunctional carboxylic acid, aromatic monofunctional carboxylic acid and the like can be mentioned.

Examples of the saturated aliphatic monofunctional carboxylic acid include acetic acid, propionic acid, butyric acid, lauric acid and the like.

Examples of the unsaturated aliphatic monofunctional carboxylic acid include acrylic acid, methacrylic acid, and linoleic acid.

Examples of the aromatic monofunctional carboxylic acid include benzoic acid, 2-phenoxybenzoic acid, and 4-methylbenzoic acid.

These carboxylic acids can be used alone or in combination of two or more.

The carboxylic acid is preferably a saturated aliphatic monofunctional carboxylic acid, more preferably acetic acid (in other words, lignin modified with acetic acid is used as lignin). If the carboxylic acid is used, a carboxylic acid-modified lignin can be easily obtained, and the carboxylic acid-modified lignin obtained has a relatively high solubility in an organic solvent and has a melting temperature as described later. Since it is relatively low temperature (about 100 to 200 ° C.), it is excellent in handleability.

Also, the carboxylic acid can be prepared as an aqueous solution. In such a case, the concentration of the carboxylic acid aqueous solution is not particularly limited and is set as appropriate.

The production method of the carboxylic acid-modified lignin is not particularly limited, and can conform to a known method.

Specifically, for example, a plant material (for example, a conifer, a broadleaf tree, a gramineous plant, etc.) that is a raw material for lignin is digested with a carboxylic acid (preferably acetic acid). A carboxylic acid-modified lignin can be obtained as a pulp waste liquid by modifying with a carboxylic acid.

The cooking method is not particularly limited. For example, a plant material that is a raw material for lignin is mixed with a carboxylic acid and an inorganic acid (for example, hydrochloric acid, sulfuric acid, etc.) and reacted.

The mixing ratio of the carboxylic acid is such that the carboxylic acid (100% conversion) is, for example, 500 parts by mass or more, preferably 900 parts by mass or more, for example, 30000 with respect to 100 parts by mass of the plant material that is the raw material for lignin. It is 1 part by mass or less, preferably 15000 parts by mass or less.

The blending ratio of the inorganic acid is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more with respect to 100 parts by mass of the plant material that is the raw material for lignin. For example, it is 10 parts by mass or less, preferably 5 parts by mass or less.

As reaction conditions, under atmospheric pressure, the reaction temperature is, for example, 30 ° C. or more, preferably 50 ° C. or more, for example, 400 ° C. or less, preferably 250 ° C. or less. The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, for example, 20 hours or less, preferably 10 hours or less.

By such cooking, pulp is obtained and carboxylic acid-modified lignin is obtained as a pulp waste liquid.

Next, in this method, the pulp is separated by a known separation method such as filtration, and the filtrate (pulp waste liquid) is recovered. If necessary, the unreacted carboxylic acid is known using, for example, a rotary evaporator, vacuum distillation or the like. It is removed (distilled off) by the method. Thereafter, a large excess of water is added to precipitate the carboxylic acid-modified lignin, followed by filtration to recover the carboxylic acid-modified lignin as a solid content.

Further, the method for obtaining the carboxylic acid-modified lignin is not limited to the above. For example, lignin not modified with carboxylic acid (for example, the above alkaline lignin, the above sulfite lignin, the above kraft lignin, etc. (hereinafter referred to as unmodified lignin) ) And a carboxylic acid can be used to modify an aliphatic hydroxyl group (described later) of lignin with a carboxylic acid to obtain a carboxylic acid-modified lignin.

In such a method, the native lignin is preferably powdered native lignin.

The average particle size of the powdered unmodified lignin is, for example, 0.1 μm or more, preferably 5 μm or more, for example, 1000 μm or less, preferably 500 μm or less. In the present specification, the average particle diameter is a volume-based cumulative median diameter (D ₅₀ ) determined from a particle diameter distribution measured by a laser diffraction scattering method.

If the average particle diameter is in the above range, aggregation of the unmodified lignin can be suppressed and the unmodified lignin can be favorably dispersed in the carboxylic acid.

The powdered unmodified lignin can be obtained by drying and pulverizing the lump unmodified lignin by a known method, or a commercially available product can be used.

As a method of reacting unmodified lignin and carboxylic acid, for example, unmodified lignin, carboxylic acid and inorganic acid (for example, hydrochloric acid, sulfuric acid, etc.) are mixed and reacted.

The mixing ratio of the carboxylic acid is, for example, 300 parts by mass or more, preferably 500 parts by mass or more, for example, 15000 parts by mass or less, based on 100 parts by mass of the unmodified lignin. Preferably, it is 10000 parts by mass or less.

The blending ratio of the inorganic acid is such that the inorganic acid (100% conversion) is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more with respect to 100 parts by mass of the unmodified lignin. 10 parts by mass or less, preferably 5 parts by mass or less.

Such carboxylic acid-modified lignin is excellent in handleability.

That is, lignin that has not been modified with carboxylic acid has relatively low solubility in organic solvents and does not melt, so that it may be inferior in handleability depending on the application.

On the other hand, lignin modified with carboxylic acid as described above is an organic solvent (for example, esters such as methyl acetate, ethyl acetate, butyl acetate and isobutyl acetate, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone). For example, aliphatic alcohols such as methanol, for example, phenols such as phenol, cresol, bisphenol A, for example, ethers such as diethyl ether, tetrahydrofuran and dioxane, such as methyl cellosolve acetate, ethyl cellosolve acetate, methylcarbyl Tall acetate, ethyl carbitol acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybuty Glycol ether esters such as acetate and ethyl-3-ethoxypropionate, for example, nitriles such as acetonitrile, others, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexa Since it is relatively soluble in polar solvents such as methylphosphonilamide and can be melted at a relatively low temperature (about 100 to 200 ° C.), it is excellent in handling.

Therefore, the carboxylic acid-modified lignin can also be used as a solution of the above organic solvent. In such a case, the concentration of the carboxylic acid-modified lignin in the solution is, for example, 10% by mass or more, and preferably 30% by mass or more.

The average particle size of the carboxylic acid-modified lignin is, for example, 0.1 μm or more, preferably 5 μm or more, for example, 2 cm or less, preferably 1 cm or less.

The carboxylic acid-modified lignin is obtained as a mixture of a component (soluble component) that can be dissolved by the organic solvent (preferably ethyl acetate) and a component that cannot be dissolved by the organic solvent (insoluble component). There is a case.

In such a case, a mixture of a soluble component and an insoluble component (referred to as crude carboxylic acid-modified lignin) can be used as the carboxylic acid-modified lignin.

In addition, it is possible to separate the soluble component and the insoluble component and use only the soluble component, or it is possible to use only the insoluble component. Furthermore, the separated soluble component and insoluble component can be mixed and used.

The carboxylic acid-modified lignin is preferably a soluble component.

As a method for separating the soluble component and the insoluble component, for example, the above-described extraction method using an organic solvent is employed.

The extraction conditions are appropriately set according to the organic solvent used and the physical properties of the crude carboxylic acid-modified lignin.

Also, lignin (such as unmodified lignin and carboxylic acid-modified lignin) has an aliphatic hydroxyl group in the molecule.

An aliphatic hydroxyl group is a hydroxyl group that is not directly bonded to an aromatic ring but directly bonded to an aliphatic hydrocarbon, and is distinguished from a hydroxyl group directly bonded to an aromatic ring (aromatic hydroxyl group (phenolic hydroxyl group)).

The content ratio of the aliphatic hydroxyl group of lignin is 0.5% by mass or more, preferably 3.0% by mass or more, and 8.5% by mass or less, preferably 7.0% by mass with respect to the total amount of lignin. % Or less, more preferably 5.5% by mass or less.

If the content ratio of the aliphatic hydroxyl group of lignin is below the lower limit, the reactivity of lignin with phenols and aldehydes is inferior, and the productivity of the novolak type phenol resin is lowered.

Further, when the content of the aliphatic hydroxyl group of lignin exceeds the above upper limit, gelation easily proceeds during the reaction of lignin, phenols and aldehydes, and the obtained molded article using the novolak type phenol resin is There is a disadvantage that it is inferior to toughness (becomes brittle). In addition, since the lignin has a low crosslinking density, the physical properties of the molded product are lowered.

On the other hand, if the content ratio of the aliphatic hydroxyl group of lignin is in the above range, the production of novolac type phenolic resin is excellent because it is excellent in reactivity between lignin and phenols and aldehydes, and it is difficult to cause gelation during the reaction. In addition, the properties of the molded article using the novolac type phenol resin obtained are improved.

In addition, the content rate of an aliphatic hydroxyl group is calculated | required based on the Example mentioned later.

Further, lignin containing an aliphatic hydroxyl group in the above range is preferably kraft lignin or carboxylic acid-modified lignin. More preferably, the carboxylic acid-modified lignin includes carboxylic acid-modified lignin derived from a herbaceous plant, and more preferably an acetic acid-modified lignin derived from a herbaceous plant.

Phenols are phenols and derivatives thereof such as phenol, and further, for example, o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, Examples include 2,4- or 2,6-xylenol, m-cresol, resorcinol, 3,5-xylenol, bisphenol A, dihydroxydiphenylmethane, and the like. Further, for example, halogenated phenols substituted with halogen such as chlorine and bromine can be mentioned. These phenols can be used alone or in combination of two or more.

Phenols are preferably phenol.

Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde (n-butyraldehyde, isobutyraldehyde), furfural, glyoxal, benzaldehyde, trioxane, tetraoxane and the like. Moreover, a part of aldehyde may be substituted with furfuryl alcohol or the like. These aldehydes can be used alone or in combination of two or more.

Preferred examples of aldehydes include formaldehyde and paraformaldehyde.

Further, aldehydes can be used as an aqueous solution, for example. In such a case, the concentration of aldehydes is, for example, 10% by mass or more, preferably 20% by mass or more, for example, 99% by mass or less, preferably 95% by mass or less.

Also, ketones can be blended with aldehydes.

Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, acetophenone, diphenyl ketone, and the like. These ketones can be used alone or in combination of two or more.

When the ketones are blended, the blending ratio of the ketones is, for example, 0.01 parts by mass or more, preferably 1 part by mass or more with respect to 100 parts by mass of the aldehydes based on the solid content. 200 parts by mass or less, preferably 100 parts by mass or less.

In order to react lignin (lignin having an aliphatic hydroxyl group in the molecule) with phenols and aldehydes (and ketones blended if necessary (hereinafter the same)), the above components (lignin, phenols) And aldehydes) and heat.

In this reaction, the mixing ratio of the phenols is, for example, 30 parts by mass or more, preferably 50 parts by mass or more, more preferably 100 parts by mass or more, for example, 1000 parts by mass with respect to 100 parts by mass of lignin. Hereinafter, it is preferably 500 parts by mass or less, and more preferably 350 parts by mass or less.

The blending ratio of aldehydes is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, for example, 35 parts by mass or less, preferably 30 parts by mass or less, relative to 100 parts by mass of phenols. is there. The blending ratio of aldehydes is, for example, 1.5 parts by mass or more, preferably 3 parts by mass or more, for example, 350 parts by mass or less, preferably 300 parts by mass or less, with respect to 100 parts by mass of lignin. It is.

If the blending ratio of each component is within the above range, various physical properties such as friction characteristics, wear resistance, and mechanical strength can be improved.

In particular, from the viewpoint of improving the friction characteristics, the mixing ratio of phenols is preferably 200 parts by mass or more, more preferably 250 parts by mass or more, preferably 1000 parts by mass with respect to 100 parts by mass of lignin. Part or less, more preferably 500 parts by weight or less.

In this reaction, an acid catalyst is added. That is, each of the above components reacts under an acid catalyst.

Examples of the acid catalyst include organic acids and inorganic acids.

Examples of the organic acid include sulfonic acid compounds such as methanesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, cumenesulfonic acid, dinonylnaphthalene monosulfonic acid, dinonylnaphthalenedisulfonic acid, for example, trimethyl phosphate, Examples thereof include phosphate esters having an alkyl group having 1 to 18 carbon atoms such as triethyl phosphate, monobutyl phosphate, dibutyl phosphate, tributyl phosphate, trioctyl phosphate, and the like, for example, formic acid, acetic acid, oxalic acid and the like.

Examples of inorganic acids include phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid.

These acid catalysts can be used alone or in combination of two or more.

The acid catalyst is preferably an organic acid, more preferably oxalic acid.

The mixing ratio of the acid catalyst is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, for example, 10 parts by mass or less, preferably 100 parts by mass with respect to 100 parts by mass of phenols. 5 parts by mass or less.

The timing of addition of the acid catalyst is not particularly limited, and may be added in advance to at least one of lignin, phenols, and aldehydes, and added at the same time when lignin, phenols, and aldehydes are blended. Further, it may be added after blending lignin, phenols and aldehydes.

As reaction conditions, under atmospheric pressure, the reaction temperature is, for example, 50 ° C. or higher, preferably 80 ° C. or higher, for example, 200 ° C. or lower, preferably 180 ° C. or lower. The reaction time is, for example, 1 hour or more, preferably 2 hours or more, for example, 20 hours or less, preferably 15 hours or less.

Thereby, a binder (binder) is obtained as a novolac type phenol resin as a reaction product of lignin, phenols and aldehydes.

More specifically, a novolac type phenol resin is obtained by the reaction of phenols and aldehydes in the presence of an acid catalyst, and the novolac type phenol resin is modified with lignin.

That is, a novolak-type phenol resin modified with lignin (hereinafter sometimes referred to as a lignin-modified novolak-type phenol resin) (binder) is obtained.

According to the binder (binder) thus obtained, it is possible to obtain a friction material having excellent friction characteristics, wear resistance and mechanical strength.

In the reaction of lignin, phenols and aldehydes, as described above, the above components can be combined and reacted (collective reaction), but the above components are mixed and reacted (sequential reaction). ).

From the viewpoint of improving various physical properties such as friction characteristics, wear resistance, and mechanical strength, the above components are preferably blended and reacted sequentially.

Specifically, in the sequential reaction, first, lignin and phenols are reacted to prepare a lignin-phenol composition containing a reaction product of lignin and phenols, and then the lignin-phenol composition and aldehyde React with a kind.

In the reaction of lignin and phenols, the phenols are blended in an excess equivalent amount with respect to lignin. Specifically, the blending ratio of phenols is, for example, 30 parts by mass or more, preferably 100 parts by mass of lignin. 50 parts by mass or more, for example, 1000 parts by mass or less, preferably 500 parts by mass or less.

In this reaction, the above acid catalyst is added.

The mixing ratio of the acid catalyst is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, for example, 10 parts by mass or less, preferably 5 parts by mass with respect to 100 parts by mass of the phenols. It is as follows.

The timing of addition of the acid catalyst is not particularly limited, and may be added in advance to at least one of lignin and phenols, or may be added simultaneously with the blending of lignin and phenols. It may be added after blending lignin and phenols.

As reaction conditions, under atmospheric pressure, the reaction temperature is, for example, 60 ° C. or higher, preferably 80 ° C. or higher, for example, 250 ° C. or lower, preferably 200 ° C. or lower. The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, for example, 10 hours or less, preferably 5 hours or less.

This reaction modifies lignin with phenols. Specifically, an aliphatic hydroxyl group in the lignin molecule (when the lignin is a carboxylic acid-modified lignin, an aliphatic hydroxyl group remaining without being modified with a carboxylic acid is included), and the lignin is a carboxylic acid-modified lignin. In some cases, aliphatic hydroxyl groups (ie, esters) modified with carboxylic acids are replaced with phenols.

In the above reaction, excess phenols remain as unreacted components. Therefore, the lignin-phenol composition obtained by the above reaction contains a reaction product of lignin and phenols (lignin modified with phenols) and free phenols.

Next, in this method, the lignin-phenol composition obtained as described above (that is, lignin modified with phenols and free phenols) is reacted with aldehydes.

In this reaction, the blending ratio of aldehydes is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, with respect to 100 parts by mass of phenols (phenols used as a raw material in the above reaction). , 35 parts by mass or less, preferably 30 parts by mass or less.

In this reaction, the above acid catalyst can be added at an appropriate ratio, if necessary.

As a result, the above lignin-phenol composition reacts with aldehydes to obtain a novolak-type phenol resin modified with lignin (lignin-modified novolak-type phenol resin).

As a result, a binder is obtained as a resin composition containing a novolac type phenol resin.

In the production of a lignin-modified novolac type phenol resin, unreacted raw materials (unreacted phenols, etc.) and acid catalyst can be removed by a known method such as distillation, if necessary.

According to the binder thus obtained, a friction material having excellent friction characteristics, wear resistance and mechanical strength can be obtained.

Further, the binder (resin composition) can contain a phenol resin curing agent, if necessary.

The phenol resin curing agent is not particularly limited, and a known curing agent can be used. Specifically, for example, hexamethylenetetramine, methylolmelamine, methylolurea, phenol novolac and the like can be mentioned.

These phenolic resin curing agents can be used alone or in combination of two or more.

The blending ratio of the phenol resin curing agent is appropriately set according to the purpose and application.

In addition, the binder can further contain an additive.

As additives, known additives added to the binder, for example, fillers (wood flour, pulp, glass fibers, etc.), colorants, plasticizers, stabilizers, mold release agents (metal soaps such as zinc stearate) Etc.).

These additives can be used alone or in combination of two or more. The content of the additive is appropriately set according to the purpose and application within a range that does not impair the excellent effects of the present invention.

For example, when a filler is added, the blending ratio is, for example, 10 parts by mass or more, preferably 20 parts by mass or more with respect to 100 parts by mass of the reaction product. For example, it is 300 parts by mass or less, preferably 200 parts by mass or less.

Note that the timing of addition of the additive is not particularly limited, and is appropriately set according to the purpose and application.

Further, the friction material can contain other binders (binders excluding the above reaction products) as required in addition to the above binders.

Examples of other binders include known thermosetting resins such as melamine resins and epoxy resins.

Other binders can be used alone or in combination of two or more.

When other binders are blended, the blending ratio is appropriately set within a range not impairing the effects of the present invention. Preferably, an embodiment in which no other binder is blended (that is, an embodiment in which the friction material contains only the above reaction product as a binder) is included.

The friction material preferably contains a fiber base material and a friction modifier.

Although it does not restrict | limit especially as a fiber base material, For example, organic fibers, such as aromatic polyamide fiber (aramid fiber) and a flame-resistant acrylic fiber, For example, metal fibers, such as copper fiber and a brass fiber, For example, potassium titanate fiber, Examples thereof include inorganic fibers such as Al ₂ O ₃ —SiO ₂ ceramic fibers, biosoluble ceramic fibers, glass fibers, and carbon fibers.

These fiber base materials can be used alone or in combination of two or more.

Favorable examples of the fiber substrate include organic fibers and metal fibers, more preferably aromatic polyamide fibers (aramid fibers) and copper fibers, and still more preferably a combination thereof.

The length of the fiber base material (fiber length) is not particularly limited, but is, for example, 100 μm or more and 2500 μm or less. Further, the diameter of the fiber base material is not particularly limited, but is, for example, 3 μm or more and 600 μm or less.

The friction modifier is not particularly limited, and examples thereof include abrasives, fillers, and solid lubricants.

Examples of the abrasive include known abrasives such as alumina, magnesia, and zirconia.

These abrasives can be used alone or in combination of two or more.

Examples of the filler include inorganic fillers such as calcium carbonate, barium sulfate, calcium hydroxide, iron sulfide, copper sulfide, silicon oxide, metal powder (eg, copper, aluminum, bronze, zinc, etc.), vermiculite, etc. Examples thereof include organic fillers such as rubber (for example, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR)) powder, cashew dust, and melamine dust.

These fillers can be used alone or in combination of two or more.

The filler is preferably an inorganic filler or an organic filler, more preferably barium sulfate, rubber (especially styrene butadiene rubber (SBR)) powder, cashew dust, and more preferably, Combined use is mentioned.

Examples of the solid lubricant include known solid lubricants such as graphite and molybdenum disulfide.

These solid lubricants can be used alone or in combination of two or more.

As the solid lubricant, graphite (graphite) is preferable.

These friction modifiers can be used alone or in combination of two or more. The friction modifier is appropriately selected according to required friction characteristics, heat resistance, wear resistance, and mechanical strength.

Favorable examples of the friction modifier include fillers and solid lubricants, and more preferable combinations thereof.

Further, the average particle diameter of the friction modifier is, for example, 1 μm or more, preferably 5 μm or more, for example, 500 μm or less, preferably 250 μm or less.

The friction material is first prepared by blending and kneading the above binder, fiber base material, and friction modifier to produce a friction material molding material, and then the obtained friction material molding material is known. It can obtain by shape | molding by the method of.

In the production of the molding material for friction material, the blending ratio of each component is such that the total amount of the fiber base material and the friction modifier is, for example, 250 parts by mass or more, preferably 400 with respect to 100 parts by mass of the binder. For example, 950 parts by mass or less, preferably 900 parts by mass or less.

More specifically, the binder is, for example, 2 parts by mass or more, preferably 5 parts by mass or more, for example, 30 parts by mass or less, with respect to 100 parts by mass of the total amount of the binder, the fiber base material, and the friction modifier. The amount is preferably 20 parts by mass or less.

Further, the fiber substrate is, for example, 1 part by mass or more, preferably 5 parts by mass or more, for example, 65 parts by mass or less, preferably 100 parts by mass of the total amount of the binder, the fiber substrate, and the friction modifier. Is 30 parts by mass or less.

The friction modifier is, for example, 40 parts by mass or more, preferably 50 parts by mass or more, for example, 95 parts by mass or less, preferably 100 parts by mass of the total amount of the binder, the fiber base material, and the friction modifier. Is 85 parts by mass or less.

Further, when a grinding material is used as the friction modifier, the blending ratio thereof is, for example, 1 part by mass or more, preferably 1 part by mass or more, preferably 100 parts by mass of the binder, the fiber base material, and the friction modifier. 2 parts by mass or more, for example, 30 parts by mass or less, preferably 25 parts by mass or less.

Further, when a filler is used as the friction modifier, the blending ratio thereof is, for example, 30 parts by mass or more, preferably, relative to 100 parts by mass of the total amount of the binder, the fiber base material, and the friction modifier. , 35 parts by mass or more, for example, 90 parts by mass or less, preferably 85 parts by mass or less.

Further, when a solid lubricant is used as the friction modifier, the blending ratio thereof is, for example, 1 part by mass or more with respect to 100 parts by mass of the total amount of the binder, the fiber base material, and the friction modifier. Preferably, it is 3 parts by mass or more, for example, 30 parts by mass or less, preferably 25 parts by mass or less.

The kneading method is not particularly limited, and for example, a known kneader such as a single-screw extruder, a multi-screw extruder, a roll kneader, a kneader, Henschel mixer, or a Banbury mixer can be used.

As the kneading conditions, the kneading temperature is 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher, 180 ° C. or lower, preferably 170 ° C. or lower, more preferably 160 ° C. or lower. . The kneading time is, for example, 3 minutes or more, preferably 5 minutes or more, for example, 30 minutes or less, preferably 20 minutes or less.

Since such a molding material for friction material contains the above reaction product (resin composition) as a binder, it is possible to obtain a friction material having excellent friction characteristics, wear resistance and mechanical strength.

As a method of molding the above-mentioned molding material for friction material, for example, the molding material for friction material is molded by a known thermosetting resin molding method such as transfer molding or compression molding. The molding conditions are not particularly limited, and are appropriately set according to the purpose and application.

For example, the processing conditions in the molding are not particularly limited, but the temperature conditions are, for example, 140 ° C. or higher, preferably 150 ° C. or higher, for example, 200 ° C. or lower, preferably 180 ° C. or lower. The pressure condition is, for example, 20 MPa or more, preferably 30 MPa or more, for example, 100 MPa or less, preferably 80 MPa or less. The treatment time is, for example, 2 minutes or longer, preferably 10 minutes or longer, for example, 60 minutes or shorter, preferably 30 minutes or shorter.

In this way, the friction material is obtained by molding the molding material for the friction material.

Further, the friction material can be treated by a known method such as degreasing treatment or primer treatment, if necessary, and the molded friction material can be treated with a known method after-curing (thermosetting treatment). )can do.

The treatment conditions in after-curing are not particularly limited, but under normal pressure, the temperature conditions are preferably 10 to 100 ° C. higher than the temperature at the time of molding, specifically, for example, 150 ° C. or higher, preferably 160 ° C. For example, 300 ° C. or lower, preferably 200 ° C. or lower. The treatment time is, for example, 1 hour or more, preferably 2 hours or more, for example, 10 hours or less, preferably 8 hours or less.

By further curing the friction material in this way, it is possible to further improve the friction characteristics, wear resistance and mechanical strength.

Such a friction material contains a binder containing a reaction product of lignin having a predetermined content of aliphatic hydroxyl group, phenols, and aldehydes, so that friction characteristics, abrasion resistance and Excellent mechanical strength. Moreover, such a friction material has excellent heat resistance.

Therefore, the friction material is preferably used in a braking member such as a brake pad or a clutch member in a vehicle such as an automobile, a motorcycle, or a train.

Especially, the friction material is preferably used as a brake pad of an automobile.

When the friction material is used as an automobile brake pad, for example, the above-mentioned friction material molding material and a known member such as a pressure plate can be integrally molded.

More specifically, for example, a known member such as a pressure plate and the preformed molding material for the friction material are bonded via an adhesive and fixed by thermoforming.

Although the processing conditions in thermoforming are not particularly limited, the temperature conditions are, for example, 140 ° C. or more and 170 ° C. or less, the pressure conditions are, for example, 30 MPa or more and 80 MPa or less, and the processing time is, for example, 2 minutes or more and 10 Is less than a minute.

In such a case, if necessary, the preformed molding material for the friction material can be degreased and primed by a known method, and the thermoformed friction material can be treated by a known method. Can be after-cured and finished by the method.

The treatment conditions in after-curing are not particularly limited, but under normal pressure, the temperature conditions are, for example, 150 ° C. or more and 300 ° C. or less, and the treatment time is, for example, 1 hour or more and 4 hours or less.

The brake pad thus obtained is excellent in friction characteristics, wear resistance and mechanical strength because the friction material of the present invention is used.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. In the following description, “part” and “%” are based on mass unless otherwise specified. In addition, specific numerical values such as a blending ratio (content ratio), physical property values, and parameters used in the following description are described in the above-mentioned “Mode for Carrying Out the Invention”, and a blending ratio corresponding to them ( Substituting the upper limit value (numerical value defined as “less than” or “less than”) or the lower limit value (number defined as “greater than” or “exceeded”) such as content ratio), physical property values, parameters, etc. be able to.

<< Content ratio of aliphatic hydroxyl group >>
The content ratio of the aliphatic hydroxyl group to the total amount of lignin was measured by the following method.

That is, first, 5 mL each of pyridine and acetic anhydride was added to 500 mg of lignin, and allowed to stand at room temperature for 24 hours to acetylate the hydroxyl group. Subsequently, pyridine and acetic anhydride were removed with an evaporator while adding toluene.

Thereafter, 5 mg of acetylated lignin was dissolved in 1 g of a solvent, and proton NMR measurement was performed under the following conditions to determine the amount of protons of the acetyl group appearing at about 1.9 ppm. On the other hand, proton NMR measurement was also performed on lignin that was not acetylated under the same conditions, and the amount of protons in the acetyl group was quantified.

Then, from the peak intensity at about 1.9 ppm of acetylated lignin, the peak intensity at about 1.9 ppm of non-acetylated lignin was subtracted to obtain the peak amount due to acetylation. This was made into the amount of aliphatic hydroxyl groups.
Apparatus: Bruker Ltd. AscendTM 400 NMR apparatus _{solvent: D 2 O37.5g + NaOD12.5g + DSS} -d 6 (3- ( trimethylsilyl) -1-propane _{-1,1,2,2,3,3-d 6} - sulfonate, sodium Standard substance) 25mg
Measurement frequency: 400MHz
Measurement temperature: 25 ° C
Number of scans: 128 <Manufacturing lignin>
Preparation Example 1 (Lignin Acetate)
100 parts by mass of corn stover was mixed with 1000 parts by mass of 95% by mass acetic acid and 3 parts by mass of sulfuric acid, and reacted for 4 hours under reflux. After the reaction, the pulp was removed by filtration, and the pulp waste liquid was recovered. Next, after removing acetic acid in the pulp waste liquid using a rotary evaporator and concentrating until the volume becomes 1/10, 10 times the amount of the concentrated liquid (mass basis) is added and filtered, Acetic acid-modified lignin was obtained as a solid content.

The content of aliphatic hydroxyl groups in acetic acid-modified lignin was 5.1% by mass.

Preparation Example 2 (Craft Lignin)
Kraft lignin (manufactured by SIGMA-ALDRICH, derived from woody plant, aliphatic hydroxyl group content 4.4 mass%) was prepared.

Preparation Example 3 (Soda Lignin)
Soda lignin was obtained by neutralizing the straw pulp waste liquor (black liquor) and then filtering. Soda lignin and methanol were mixed and then filtered, and the filtrate was concentrated and dried to obtain a methanol-soluble component of soda lignin.

The content ratio of the aliphatic hydroxyl group in the methanol-soluble component of soda lignin was 8.8% by mass.

<< Manufacture of novolac-type phenolic resin >>
Synthesis Example 1 (Lignin used: Acetic acid-modified lignin (sequential reaction))
Put 493.5 parts by mass of phenol in a flask and heat to about 50 ° C. to liquefy the phenol, and then add 150 parts by mass of the soluble component (soluble acetic acid-modified lignin) of acetic acid-modified lignin obtained in Preparation Example 1. Added.

Next, 7.62 parts by mass of oxalic acid (acid catalyst) was added, and then reacted at 130 ° C. for 2.5 hours. This modified the acetic acid-modified lignin with phenol.

Then, it cooled to 80 degreeC, 117.3 mass parts of paraformaldehyde was added, and it was made to react at 95 degreeC for 2.5 hours. Next, the temperature was raised to 110 ° C. at 0.5 ° C./min and reacted at 110 ° C. for 1.5 hours. Next, the temperature was raised to 120 ° C. at 0.5 ° C./min and reacted at 120 ° C. for 2 hours.

After the reaction, 2300 parts by mass of water was added, and after stirring vigorously, the mixture was allowed to stand, and water was removed by decantation to remove oxalic acid and phenol. Furthermore, the residual phenol was removed by distillation under reduced pressure under conditions of 150 ° C. and 0.08 MPa while adding water as appropriate. The vacuum distillation was repeated until the phenol residual ratio became 1% or less.

Thereby, a novolac type phenol resin modified with phenol-modified acetic acid lignin was obtained.

Synthesis Example 2 (Lignin used: Acetic acid-modified lignin (collective reaction))
Put 493.5 parts by mass of phenol in a flask and heat to about 50 ° C. to liquefy the phenol, and then add 150 parts by mass of the soluble component (soluble acetic acid-modified lignin) of acetic acid-modified lignin obtained in Preparation Example 1. Added.

Next, 7.62 parts by mass of oxalic acid (acid catalyst) and 117.3 parts by mass of paraformaldehyde were added and reacted at 95 ° C. for 2.5 hours. Next, the temperature was raised to 110 ° C. at 0.5 ° C./min and reacted at 110 ° C. for 1.5 hours. Next, the temperature was raised to 120 ° C. at 0.5 ° C./min and reacted at 120 ° C. for 2 hours.

Thereby, a novolac type phenol resin modified with acetic acid-modified lignin was obtained.

Synthesis Example 3 (Lignin used: Acetic acid-modified lignin (sequential reaction))
A novolak type phenol resin modified with phenol-modified acetic acid lignin was obtained in the same manner as in Synthesis Example 1 except that the formulation shown in Table 1 was changed.

Synthesis Example 4 (Lignin used: Acetic acid-modified lignin (collective reaction))
A novolak-type phenol resin modified with lignin acetate was obtained in the same manner as in Synthesis Example 2 except that the formulation shown in Table 1 was changed.

Synthesis Example 5 (Lignin used: Acetic acid-modified lignin (sequential reaction))
A novolak type phenol resin modified with phenol-modified acetic acid lignin was obtained in the same manner as in Synthesis Example 1 except that the formulation shown in Table 1 was changed.

Synthesis Example 6 (Lignin used: Acetic acid-modified lignin (collective reaction))
A novolak-type phenol resin modified with lignin acetate was obtained in the same manner as in Synthesis Example 2 except that the formulation shown in Table 1 was changed.

Synthesis Example 7 (Lignin used: Kraft lignin (sequential reaction))
Instead of acetic acid-modified lignin, novolak-type phenol modified with kraft lignin modified with phenol in the same manner as in Synthesis Example 1 except that 150 parts by mass of kraft lignin of Preparation Example 2 was used. A resin was obtained.

Synthesis Example 8 (Lignin used: Kraft lignin (collective reaction))
A novolak-type phenol resin modified with kraft lignin was obtained in the same manner as in Synthesis Example 2, except that 150 parts by mass of kraft lignin of Preparation Example 2 was used instead of acetic acid-modified lignin.

Synthesis Example 9 (Lignin used: Soda lignin (sequential reaction))
Instead of acetic acid-modified lignin, soda lignin was modified with phenol in the same manner as in Synthesis Example 1 except that 150 parts by mass of the methanol-soluble component of soda lignin of Preparation Example 3 was used, and modified with the phenol-modified soda lignin. A novolac-type phenolic resin was obtained.

Synthesis Example 10 (Lignin used: Soda lignin (collective reaction))
A novolak-type phenol resin modified with soda lignin was obtained in the same manner as in Synthesis Example 2, except that 150 parts by mass of the methanol-soluble component of soda lignin of Preparation Example 3 was used instead of acetic acid-modified lignin.

<< Manufacture of friction materials >>
Example 1
100 parts (450 g) of the novolak-type phenol resin obtained in Synthesis Example 1, 12 parts (54 g) of hexamethylenetetramine (manufactured by lignite) as a phenol resin curing agent, and zinc stearate (Wako Pure Chemical Industries) as a release agent 1 part (4.5 g) (manufactured by Kogyo) was sequentially blended and kneaded with two hot rolls at 100 ° C. for 5 minutes to obtain a resin composition.

Next, 20 parts of the obtained resin composition, 5 parts of aramid fibers (Kevlar (R) pulp 1F538, manufactured by Toray DuPont), 5 parts of copper fibers (CCW-208, manufactured by Nippon Steel Wool), acrylonitrile butadiene rubber (NBR) manufactured by JSR 5 parts of PN30A, 10 parts of cashew dust (Cashew Particles FF-1500, manufactured by Tohoku Kako), 45 parts of barium sulfate (manufactured by Sakai Chemical Co., Ltd. barium sulfate BA), and 10 parts of graphite (SGP-100, manufactured by SEC Carbon) By mixing, a molding material for friction material was obtained.

Thereafter, the obtained molding material for friction material was compression molded at 170 ° C. for 15 minutes to obtain a disc-shaped test piece of 100 mmφ as the friction material. In addition, the obtained friction material was thermally cured (aftercured) at 180 ° C. for 4 hours.

Examples 2-8 and Comparative Examples 1-2
A friction material was obtained in the same manner as in Example 1 except that the formulation was changed to the formulation shown in Table 2. In addition, the obtained friction material was thermally cured (aftercured) at 180 ° C. for 4 hours.

<< Evaluation >>
The friction materials obtained in each Example and each Comparative Example were evaluated by the following methods. The results are shown in Table 2.
(1) Friction coefficient In accordance with ASTM D1894, a friction coefficient (static friction coefficient and dynamic friction coefficient) was determined using a surface property tester (Shinto Kagaku HEIDON-14S / D). Various conditions for obtaining the friction coefficient and dimensions of the test piece used are shown below.
Test piece: Disc test piece with a diameter of 100 mm and a thickness of about 3 mm Mating material: 19 mm diameter cylinder Mating material: S45C
Test speed: 100 mm / min (2) Wear test (Taber type)
The amount of wear was measured in accordance with JIS-K7204 (1999 edition), and the amount of wear was calculated in mass% to indicate how much the mass was reduced from the mass of the first sample. The conditions of the wear test and the dimensions of the test piece used are shown below.
(Wear test conditions)
Load: 10N
Rotation speed: 60rpm
Wear wheel: H-18
Number of revolutions: 1000 revolutions (test piece)
Disc test piece having a diameter of 100 mm and a thickness of about 3 mm (3) Bending strength The bending strength was measured at a crosshead speed of 1.5 mm / min and a span of 50 mm in accordance with JIS K6911 (1995 edition).

In the table, soda lignin indicates a methanol-soluble component of soda lignin.

Although the above invention has been provided as an exemplary embodiment of the present invention, this is merely an example and should not be interpreted in a limited manner. Variations of the present invention that are apparent to one of ordinary skill in the art are within the scope of the following claims.

The friction material of the present invention is suitably used in braking members such as brake pads and clutch members for vehicles such as automobiles, motorcycles, and trains.

Claims

A friction material containing a binder,
The binder is
Lignin having an aliphatic hydroxyl group in the molecule;
Phenols,
Contains reaction products with aldehydes,
The content of the aliphatic hydroxyl group in the lignin is 0.5% relative to the total amount of the lignin.
A friction material, wherein the friction material is not less than mass% and not more than 8.5 mass%.
The friction material according to claim 1, wherein the lignin is craft lignin.
The friction material according to claim 1, wherein the lignin is lignin modified with acetic acid.