JP2023070570A - friction material - Google Patents

Abstract

To provide a friction material that has sufficiently high frictional properties and sufficiently suppresses unusual noise.SOLUTION: A friction material comprises a binder, the binder comprising a novolac phenolic resin and polyethylene glycol-modified lignin. The novolac phenolic resin and polyethylene glycol-modified lignin comprised in the binder ensure that the friction material has sufficiently high frictional properties and sufficiently suppresses unusual noise (squeaks) by friction.SELECTED DRAWING: None

Description

The present invention relates to friction materials.

Friction materials are used, for example, in vehicle braking members. Braking members include, for example, brake members and clutch members. The friction material includes, for example, a fibrous base material, a filler, a lubricant, and a binder that binds them together.

More specifically, the following friction materials have been proposed. The friction material includes a binder, a fibrous base material, a filler and a solid lubricant. The binder contains a novolac-type phenolic resin, acetic acid-modified lignin and a curing agent. Fibrous substrates include aramid fibers and copper fibers. Fillers include acrylonitrile butadiene rubber, cashew dust and barium sulfate. Solid lubricants include graphite. Such a friction material has excellent friction properties (see, for example, Patent Document 1 (Example 1)).

JP 2017-179260 A

Friction materials are required to suppress abnormal noise (squeal) due to friction in addition to friction properties.

INDUSTRIAL APPLICABILITY The present invention is a friction material having excellent frictional properties and noise suppression.

The present invention [1] is a friction material containing a binder, wherein the binder contains a novolak-type phenolic resin and lignin modified with polyethylene glycol.

The present invention [2] includes the friction material according to [1] above, wherein the lignin is coniferous lignin.

The present invention [3] includes the friction material according to the above [1] or [2], wherein the polyethylene glycol has a number average molecular weight of 400 or more.

In the friction material of the present invention, the binder contains novolak-type phenolic resin and lignin modified with polyethylene glycol. Therefore, the friction material has excellent frictional properties and can suppress abnormal noise (squeal) due to friction.

The friction material of the present invention contains a binder.

The binder contains a novolak-type phenolic resin and lignin modified with polyethylene glycol (hereinafter sometimes referred to as PEG-modified lignin).

A novolak-type phenolic resin is, for example, a reaction product of a phenol and an aldehyde in the presence of an acid catalyst.

Phenols are phenol and phenol derivatives (phenol-modified products). Phenols include, for example, phenol, bifunctional phenol derivatives, trifunctional phenol derivatives and tetrafunctional phenol derivatives. Bifunctional phenol derivatives include, for example, o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4-xylenol and 2,6-xylenol. is mentioned. Trifunctional phenol derivatives include, for example, m-cresol, resorcinol, and 3,5-xylenol. Tetrafunctional phenol derivatives include, for example, bisphenol A and dihydroxydiphenylmethane. Moreover, halogenated phenols are also mentioned as a phenol derivative. Halogenated phenols are halides of phenol or phenol derivatives. Halogens include, for example, chlorine and bromine. These phenols can be used alone or in combination of two or more. In the derivative of phenol, the timing at which phenol is derivatized (denatured) is not particularly limited. For example, the derivatization of phenol may be performed before, after, or simultaneously with the reaction between phenols and aldehydes. As phenols, preferably, phenol is mentioned.

Aldehydes include, for example, formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, furfural, glyoxal, benzaldehyde, trioxane, and tetraoxane. Also, part of the aldehyde may be substituted with furfuryl alcohol or the like. These aldehydes can be used alone or in combination of two or more. Aldehydes preferably include formaldehyde and paraformaldehyde.

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

Moreover, ketones can also be mix|blended with aldehydes. Ketones include, for example, acetone, methyl ethyl ketone, diethyl ketone, acetophenone, and diphenyl ketone. These ketones can be used alone or in combination of two or more. When ketones are blended, the blending ratio of ketones is, for example, 0.01 parts by mass or more, preferably 1 part by mass or more, based on solid content, with respect to 100 parts by mass of aldehydes. 200 parts by mass or less, preferably 100 parts by mass or less.

Acid catalysts include, for example, organic acids and inorganic acids. Organic acids include, for example, carboxylic acid compounds, sulfonic acid compounds and phosphoric acid compounds. Carboxylic acid compounds include, for example, formic acid, acetic acid and oxalic acid. Sulfonic acid compounds include, for example, methanesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, cumenesulfonic acid, dinonylnaphthalenemonosulfonic acid, and dinonylnaphthalenedisulfonic acid. Phosphate compounds include, for example, phosphate esters. More specific examples of phosphate esters include phosphate esters having an alkyl group of 1 to 18 carbon atoms. Phosphate compounds include, for example, trimethyl phosphate, triethyl phosphate, monobutyl phosphate, dibutyl phosphate, tributyl phosphate, and trioctyl phosphate. Inorganic acids include, for example, phosphoric acid, hydrochloric acid, sulfuric acid and nitric acid. These acid catalysts can be used alone or in combination of two or more. Acid catalysts preferably include organic acids, more preferably carboxylic acid compounds, and even more preferably oxalic acid.

In the reaction between phenols and aldehydes, the mixing 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. Moreover, the mixing ratio of the aldehydes is, for example, 35 parts by mass or less, preferably 30 parts by mass or less with respect to 100 parts by mass of the phenols.

Moreover, 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, with respect to 100 parts by mass of the phenols. Moreover, the blending ratio of the acid catalyst is, for example, 10 parts by mass or less, preferably 5 parts by mass or less with respect to 100 parts by mass of the phenols.

The timing of addition of the acid catalyst is not particularly limited. For example, the acid catalyst may be pre-added to the phenols and/or aldehydes. Also, the acid catalyst may be added at the same time as the phenols and aldehydes are blended. Additionally, the acid catalyst may be added after the phenols and aldehydes are combined.

Reaction conditions include atmospheric pressure. Also, the reaction temperature is, for example, 50° C. or higher, preferably 80° C. or higher. Also, the reaction temperature is, for example, 200° C. or lower, preferably 180° C. or lower. Also, the reaction time is, for example, 1 hour or longer, preferably 2 hours or longer. Also, the reaction time is, for example, 20 hours or less, preferably 15 hours or less.

As a result, a novolak-type phenolic resin is obtained as a reaction product of phenols and aldehydes. Moreover, a commercial item can also be used as a novolac-type phenol resin.

In the PEG-modified lignin, polyethylene glycol (PEG) modifies the lignin to improve the frictional properties of the friction material and suppress noise suppression.

The number average molecular weight of polyethylene glycol is, for example, 100 or more, preferably 200 or more, more preferably 300 or more, still more preferably 400 or more, and particularly preferably 500 or more. Further, the number average molecular weight of polyethylene glycol is, for example, 1000 or less, preferably 900 or less, more preferably 800 or less, still more preferably 600 or less. If the number-average molecular weight is within the above range, a friction material that satisfies both friction characteristics and abnormal noise suppression can be obtained, and the productivity of the friction material is also excellent. Incidentally, the number average molecular weight can be determined as a polyethylene glycol equivalent molecular weight by a known gel permeation chromatogram method.

In PEG-modified lignin, lignin is a polymeric phenolic compound. Lignin is contained in plants in general as a natural product (natural lignin). Basic skeletons of lignin include, for example, guaiacyl lignin (G type), syringyl lignin (S type), and p-hydroxyphenyl lignin (H type).

Lignin is industrially extracted from plant material. Plant materials include, for example, lignocellulose. Lignins also include, for example, soda lignin, sulfite lignin and kraft lignin. Methods for extracting lignin include, for example, the soda method, the sulfurous acid method, the steam explosion method, the solvolysis method, and the Kraft method.

More specifically, lignin includes woody plant-derived lignin and herbaceous plant-derived lignin.

Woody plant-derived lignin includes, for example, coniferous lignin contained in conifers (eg, cedar) and broadleaf lignin contained in broadleaf trees. The woody plant-derived lignin does not contain an H-type basic skeleton. More specifically, among woody plant-derived lignins, coniferous lignin does not contain an S-type basic skeleton but has a G-type basic skeleton. In addition, hardwood lignin has a G-type basic skeleton and an S-type basic skeleton.

Herbaceous plant-derived lignins include, for example, rice lignins contained in gramineous plants. Examples of grasses include wheat straw, rice straw, corn, and bamboo. In addition, the herbaceous plant-derived lignin has all of the H-type, G-type and S-type basic skeletons.

These lignins can be used alone or in combination of two or more. The lignin preferably includes woody plant-derived lignin that does not contain an H-type basic skeleton, and more preferably includes coniferous lignin that does not contain an S-type basic skeleton and has a G-type basic skeleton. , and particularly preferably coniferous lignin derived from cedar. PEG-modified lignin obtained from coniferous lignin derived from Japanese cedar has excellent homogeneity.

PEG-modified lignin is produced, for example, according to the method described in JP-A-2017-197517.

In this method, for example, a plant material (lignocellulose) as a raw material of lignin is digested using polyethylene glycol.

The cooking method is not particularly limited, but for example, a plant material as a raw material of lignin, polyethylene glycol, and an inorganic acid (eg, hydrochloric acid, sulfuric acid, etc.) as an acid catalyst are mixed and reacted.

The blending ratio of polyethylene glycol is, for example, 200 parts by mass or more, preferably 300 parts by mass or more with respect to 100 parts by mass of the plant material that is the raw material of lignin. Moreover, the mixing ratio of polyethylene glycol is, for example, 1000 parts by mass or less, preferably 600 parts by mass or less with respect to 100 parts by mass of the plant material that is the raw material of lignin.

Moreover, the mixing ratio of the inorganic acid (converted to 100%) is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more with respect to 100 parts by mass of polyethylene glycol. Moreover, the mixing ratio of the inorganic acid (converted to 100%) is, for example, 2 parts by mass or less, preferably 1 part by mass or less with respect to 100 parts by mass of polyethylene glycol.

In addition, the reaction conditions include normal pressure. Also, the reaction temperature is, for example, 120° C. or higher, preferably 130° C. or higher. Also, the reaction temperature is, for example, 180° C. or lower, preferably 150° C. or lower. Also, the reaction time is, for example, 60 minutes or more. Also, the reaction time is, for example, 240 minutes or less, preferably 120 minutes or less.

Further, after the reaction is completed, an alkali is added to the reaction solution in an appropriate proportion to adjust the pH. Alkalis include, for example, ammonia and sodium hydroxide. This extracts the PEG-modified lignin into solution. The pH after adjustment is, for example, 8 or higher, preferably 10 or higher, more preferably 10.5 or higher, and for example, 14 or lower.

By such a method, pulp is obtained as a solid component, and PEG-modified lignin is obtained as a solution component.

Next, in this method, a solid component (pulp) is separated from the reaction product by a known separation method such as filtration, pressing, centrifugation, etc., and the solution component is recovered.

In this method, the solid component (pulp) can be washed and the solution (PEG-modified lignin) with which the solid component is impregnated can be recovered, if necessary.

Thereafter, in this method, an inorganic acid (eg, hydrochloric acid, sulfuric acid, etc.) is added and the pH is adjusted to precipitate and precipitate the PEG-modified lignin.

The pH after adjustment is, for example, 1.5 or higher, and is, for example, 5 or lower, preferably 3 or lower, and more preferably 2 or lower.

This allows the PEG-modified lignin to precipitate. Moreover, PEG-modified lignin can be obtained as a solid content by collecting the obtained precipitate by a known method such as filtration, pressing, or centrifugation.

The binder (bonding agent) contains a novolak-type phenolic resin and PEG-modified lignin. That is, the binder includes a mixture of a novolak-type phenolic resin and PEG-modified lignin.

The blending ratio of the novolak-type phenol resin and the PEG-modified lignin is based on the solid content (non-volatile content), and the PEG-modified lignin is, for example, 10 parts by mass or more, preferably 20 parts by mass with respect to 100 parts by mass of the novolak-type phenol resin. It is at least 50 parts by mass, more preferably at least 100 parts by mass, and most preferably at least 120 parts by mass. Further, the amount of PEG-modified lignin is, for example, 300 parts by mass or less, preferably 200 parts by mass or less, and more preferably 150 parts by mass or less with respect to 100 parts by mass of the novolak-type phenolic resin.

If the blending ratio of the novolak-type phenolic resin and the PEG-modified lignin is within the above range, it is possible to suppress an excessive increase in viscosity, ensure excellent moldability, and further improve various physical properties of the resulting friction material. can be improved.

Moreover, the kneading method is not particularly limited, and a known kneader is used. Kneaders include, for example, single-screw extruders, multi-screw extruders, roll kneaders, kneaders, Henschel mixers and Banbury mixers.

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

Thereby, a binder (binding agent) is obtained as a resin composition containing a novolac-type phenolic resin and PEG-modified lignin.

That is, the above binder contains a novolak-type phenolic resin and PEG-modified lignin. Therefore, according to the above binder, it is possible to achieve both excellent frictional properties and noise suppression.

The binder may also contain a phenolic resin curing agent, if desired. The binder preferably contains a novolac-type phenolic resin, PEG-modified lignin, and a phenolic resin curing agent, and more preferably consists of a novolac-type phenolic resin, PEG-modified lignin, and a phenolic resin curing agent.

The phenolic resin curing agent is not particularly limited and includes known curing agents. Phenolic resin curing agents include, for example, hexamethylenetetramine, methylolmelamine and methylolurea. These phenolic resin curing agents can be used alone or in combination of two or more. The blending ratio of the phenolic resin curing agent is appropriately set according to the purpose and application within a range that does not impair the excellent effects of the present invention.

Also, the binder can further contain additives. Additives include known additives that are added to the binder. Additives include, for example, colorants, plasticizers, stabilizers, and release agents. Examples of release agents include metal soaps, more specifically zinc stearate. These additives can be used alone or in combination of two or more. The timing of addition of the additive is not particularly limited, and is appropriately set according to the purpose and application. The blending ratio 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.

Moreover, the friction material can contain other binders as needed. Other binders are binders other than the above resin composition (resin composition containing novolac-type phenolic resin and PEG-modified lignin). Other binders include, for example, known thermosetting resins. Thermosetting resins include, for example, melamine resins, epoxy resins and polyimide resins. These 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 that does not impair the effects of the present invention. The friction material preferably contains no other binders. That is, the friction material preferably contains only the resin composition containing the novolak-type phenolic resin and PEG-modified lignin as a binder.

Also, the friction material preferably contains a fibrous base material. Fibrous substrates include, for example, organic fibers and inorganic fibers.

Organic fibers include, for example, polyamide fibers and acrylic fibers. Polyamide fibers include, for example, aramid fibers. Acrylic fibers include, for example, flame-resistant acrylic fibers. These can be used alone or in combination of two or more. The organic fibers are preferably polyamide fibers, more preferably aramid fibers.

Inorganic fibers include, for example, metal fibers, ceramic fibers, glass fibers and carbon fibers. Metal fibers include, for example, copper fibers and brass fibers. Ceramic fibers include, for example, potassium titanate fibers, Al ₂ O ₃ —SiO ₂ based ceramic fibers, and biosoluble ceramic fibers. These can be used alone or in combination of two or more. As inorganic fibers, metal fibers are preferred, and copper fibers are more preferred.

A fiber base material can be used individually or in combination of 2 or more types. The fiber substrate preferably includes organic fibers and inorganic fibers, and more preferably includes combined use of organic fibers and inorganic fibers.

In addition, the size of the fiber base material is appropriately set according to the purpose and application. For example, the length (fiber length) of the fiber base material is not particularly limited, but is, for example, 100 μm or more and 2500 μm or less. Moreover, the diameter of the fiber base material is not particularly limited, but is, for example, 3 μm or more and 600 μm or less.

Also, the friction material preferably contains a friction modifier. Friction modifiers include, for example, fillers, solid lubricants and abrasives.

Fillers include, for example, organic fillers and inorganic fillers.

Organic fillers include, for example, wood flour, pulp, rubber powder, cashew particles (cashew dust) and melamine dust. Rubber powders include, for example, acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). These can be used alone or in combination of two or more. Organic fillers preferably include rubber powder and cashew particles.

Inorganic fillers include, for example, calcium carbonate, barium sulfate, calcium hydroxide, iron sulfide, copper sulfide, silicon oxide, metal powders and minerals. In metal powders, metals include, for example, copper, aluminum, bronze and zinc. Minerals include, for example, vermiculite. These can be used alone or in combination of two or more. Barium sulfate is preferably used as the inorganic filler.

The filler can be used singly or in combination of two or more. The filler preferably includes an organic filler and an inorganic filler, and more preferably includes a combined use of an organic filler and an inorganic filler.

Solid lubricants include known solid lubricants. More specific examples of solid lubricants include graphite and molybdenum disulfide. These can be used alone or in combination of two or more. Graphite is preferably used as the solid lubricant.

A known abrasive can be used as the abrasive. Abrasives more specifically include, for example, alumina, magnesia and zirconia. These can be used alone or in combination of two or more.

These friction modifiers can be used alone or in combination of two or more. The friction modifier is appropriately selected according to the required physical properties. The friction modifier preferably includes a filler and a solid lubricant, more preferably a combination of a filler and a solid lubricant.

Note that the size of the friction modifier is appropriately set according to the purpose and application. For example, the average particle size of the friction modifier is, for example, 1 μm or more, preferably 5 μm or more. Also, the average particle size of the friction modifier is, for example, 500 μm or less, preferably 250 μm or less.

In the production of the friction material, for example, first, the binder, the fiber base material and the friction modifier are blended and kneaded to produce a molding material (composition) for the friction material.

In the molding material for friction material, the total amount of the fiber base material and the friction modifier is, for example, 250 parts by mass or more, preferably 400 parts by mass or more, with respect to 100 parts by mass of the binder. Also, the total amount of the fiber base material and the friction modifier is, for example, 950 parts by mass or less, preferably 900 parts by mass or less with respect to 100 parts by mass of the binder.

Further, the binder is, for example, 2 parts by mass or more, preferably 5 parts by mass or more with respect to 100 parts by mass as the total amount of the binder, the fiber base material and the friction modifier. Further, the binder is, for example, 40 parts by mass or less, preferably 30 parts by mass or less with respect to 100 parts by mass as the total amount of the binder, the fiber base material and the friction modifier.

In addition, the fiber base material is, for example, 1 part by mass or more, preferably 5 parts by mass or more with respect to 100 parts by mass as the total amount of the binder, the fiber base material and the friction modifier. The amount of the fiber base material is, for example, 65 parts by mass or less, preferably 30 parts by mass or less, with respect to 100 parts by mass as the total amount of the binder, the fiber base material, and the friction modifier.

Further, the friction modifier is, for example, 40 parts by mass or more, preferably 50 parts by mass or more, relative to the total amount of 100 parts by mass of the binder, fiber base material and friction modifier. Further, the friction modifier is, for example, 95 parts by mass or less, preferably 85 parts by mass or less with respect to 100 parts by mass as the total amount of the binder, the fiber base material and the friction modifier.

In addition, when the friction modifier contains an abrasive, the abrasive is, for example, 1 part by mass or more, preferably 2 parts by mass or more with respect to the total amount of 100 parts by mass of the binder, the fiber base material and the friction modifier. . The amount of the abrasive is, for example, 30 parts by mass or less, preferably 25 parts by mass or less, with respect to 100 parts by mass of the total amount of the binder, fiber base material and friction modifier.

In addition, when the friction modifier contains a filler, the filler is, for example, 30 parts by mass or more, preferably 35 parts 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. . Further, the filler is, for example, 90 parts by mass or less, preferably 85 parts by mass or less with respect to 100 parts by mass as the total amount of the binder, the fiber base material and the friction modifier.

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

The kneading method is not particularly limited, and a known kneader is used. Kneaders include, for example, single-screw extruders, multi-screw extruders, roll kneaders, kneaders, Henschel mixers and Banbury mixers.

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

Such a friction material molding material contains a mixture of the above novolac-type phenolic resin and PEG-modified lignin as a binder. Therefore, by using such a friction material molding material, a friction material having excellent frictional characteristics and capable of suppressing noise can be obtained.

Next, in this method, the friction material molding material is molded by a known method. A friction material is thus obtained.

A known method is employed as the molding method. More specific examples of molding methods include transfer molding and compression molding. Molding conditions are not particularly limited, and are appropriately set according to the purpose and application.

For example, the temperature condition is, for example, 140° C. or higher, preferably 150° C. or higher. Also, the temperature condition is, for example, 200° C. or lower, preferably 180° C. or lower. Also, the pressure condition is, for example, 20 MPa or higher, preferably 30 MPa or higher. Also, the pressure condition is, for example, 100 MPa or less, preferably 80 MPa or less. Also, the treatment time is, for example, 2 minutes or longer, preferably 10 minutes or longer. Also, the treatment time is, for example, 60 minutes or less, preferably 30 minutes or less.

A friction material is obtained by molding the friction material molding material in this manner.

Moreover, the friction material may be treated by a known method as necessary. Treatments include, for example, degreasing and primer treatments. Further, the molded friction material may be post-cured (thermally cured) by a known method.

The treatment conditions in the after-cure are not particularly limited, but normal pressure is adopted. Also, the temperature condition is, for example, 10 to 100° C. higher than the temperature at the time of molding. Temperature conditions are, for example, 150° C. or higher, preferably 160° C. or higher. Moreover, the temperature condition is, for example, 300° C. or lower, preferably 200° C. or lower. Also, the treatment time is, for example, 1 hour or more, preferably 2 hours or more. Also, the treatment time is, for example, 10 hours or less, preferably 8 hours or less. After-curing can improve frictional properties and heat resistance.

The friction material contains a binder, and the binder contains a novolak-type phenolic resin and lignin modified with polyethylene glycol. Therefore, the friction material described above has excellent frictional properties and can suppress abnormal noise (squeal) due to friction.

More specifically, generally, the friction characteristics can be improved by improving the mechanical strength of the friction material. However, if the mechanical strength of the friction material is improved, the flexibility of the friction material is reduced, so that the friction material is likely to vibrate due to friction, and noise (squeal) is likely to occur. In other words, the improvement of the frictional characteristics and the suppression of abnormal noise have a trade-off relationship.

In contrast, in the above friction material, the binder contains a novolak-type phenolic resin and lignin modified with polyethylene glycol. Therefore, flexibility can be ensured while improving the mechanical strength of the friction material.

As a result, it is possible to improve the frictional characteristics of the friction material, suppress the vibration of the friction material, and suppress the occurrence of abnormal noise (squeal).

Therefore, the friction material is preferably used, for example, in the braking member of a vehicle. Vehicles include, for example, automobiles, motorcycles, and trains. Braking members include, for example, brake pads and clutch members. Friction materials are particularly suitable for use as brake pads for automobiles.

When the friction material is used as a brake pad for an automobile, the brake member and the molding material for the friction material may be integrally formed. A well-known pressure plate is mentioned as a member for brakes, for example.

More specifically, for example, first, the friction material molding material is preformed. If necessary, the preformed friction material molding compound is degreased and primed. Next, the friction material molding material and the brake member are adhered via an adhesive. The friction molding compound and brake member are then thermoformed together. Along with this, the friction material molding material and the brake member are fixed together.

Processing conditions in thermoforming are not particularly limited, and are appropriately set according to the purpose and application. For example, the temperature condition is, for example, 140° C. or higher and 170° C. or lower. Moreover, pressure conditions are 30 MPa or more and 80 MPa or less, for example. Also, the heat treatment time is, for example, 2 minutes or more and 10 minutes or less.

The thermoformed friction material is also post-cured and finished, if desired, by known methods. Processing conditions in the after-cure are not particularly limited. For example, under normal pressure, the temperature conditions are, for example, 150° C. or higher and 300° C. or lower. Also, the processing time is, for example, 1 hour or more and 4 hours or less.

Further, since the brake pad is obtained using the friction material described above, it has excellent frictional characteristics and can suppress abnormal noise (squeal) due to friction.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited by the following examples. In the following description, "parts" and "%" are based on mass unless otherwise specified. The specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are the corresponding mixing ratios ( Content ratio), physical properties, parameters, etc. be able to.

<Synthesis of Novolac Phenolic Resin>
Production example 1
2068 parts by mass of phenol, 31.82 parts by mass of oxalic acid (acid catalyst) and 430.43 parts by mass of paraformaldehyde were placed in a flask and reacted at 95° C. for 2.5 hours. Then, the temperature was raised to 110°C at a rate of 0.5°C/min, and the reaction was carried out at 110°C for 1.5 hours. Then, the temperature was raised to 120°C at a rate of 0.5°C/min, and the reaction was carried out at 120°C for 2 hours.

After the reaction, oxalic acid and phenol were removed by adding 2,800 parts by mass of water, stirring vigorously, allowing the mixture to stand, and removing water by decantation. Furthermore, the residual phenol was removed by distillation under reduced pressure under conditions of 150° C. and 0.08 MPa while adding water appropriately. The vacuum distillation was repeated until the phenol residual rate became 1% or less.

A novolak-type phenolic resin was thus obtained.

<Synthesis of lignins>
Production Example 2 (Mn200-PEG-modified lignin)
Lignin modified with polyethylene glycol having a number average molecular weight of 200 (hereinafter referred to as Mn200-PEG-modified lignin) was produced by the following method.

That is, 230 parts by mass of commercially available polyethylene glycol (PEG200) having a number average molecular weight of 200 and 0.69 parts by mass of sulfuric acid as an acid catalyst (0.3 parts by mass with respect to 100 parts by mass of PEG200) were placed in a reaction vessel. and stirred.

Next, 46 parts by mass of absolute dry cedar wood powder was put into a reaction vessel, heated to 140° C. under normal pressure, and reacted for 90 minutes while stirring.

Next, the reaction vessel was cooled, and after confirming that the temperature had reached 40° C. or lower, 280 parts by mass of sodium hydroxide (0.2 mol/L) was added and stirred for 30 minutes.

Then, the solid component (pulp) obtained was removed by a filter press, and the solution component was recovered.

Then, sulfuric acid was added to the obtained solution components to adjust the pH to 2.0. This gave a suspension of Mn200-PEG-modified lignin.

Mn200-PEG modified lignin was then recovered by centrifugation.

Production Example 3 (Mn400-PEG-modified lignin)
Mn400-PEG-modified lignin was obtained in the same manner as in Production Example 2, except that polyethylene glycol with a number average molecular weight of 400 (hereinafter referred to as Mn400-PEG) was used instead of polyethylene glycol with a number average molecular weight of 200.

Production Example 4 (Mn600-PEG-modified lignin)
Mn600-PEG-modified lignin was obtained in the same manner as in Production Example 2, except that polyethylene glycol with a number average molecular weight of 600 (hereinafter referred to as Mn600-PEG) was used instead of polyethylene glycol with a number average molecular weight of 200.

Production Example 5 (acetic acid-modified lignin)
100 parts by weight of corn stover were mixed with 1000 parts by weight of 95% by weight acetic acid and 3 parts by weight of sulfuric acid and reacted under reflux for 4 hours. After the reaction, the pulp was removed by filtration, and pulp waste liquid was recovered. Next, acetic acid in the pulp waste liquid is removed using a rotary evaporator, and the volume is concentrated to 1/10. Acetate-modified lignin was obtained as a solid content.

<<Manufacture of friction materials>>
Example 1
The following components were sequentially blended and kneaded at 100° C. for 5 minutes with two hot rolls to obtain a resin composition.
100 parts by mass (300 g) of novolac-type phenolic resin of Production Example 1
50 parts by mass (150 g) of Mn200-PEG-modified lignin of Production Example 2
Hexamethylenetetramine (curing agent, manufactured by Lignite) 18 parts by mass (54 g)
Zinc stearate (release agent, manufactured by Wako Pure Chemical Industries) 1.5 parts by mass (4.5 g)

Next, the following components were mixed in a mixer to obtain a molding material for friction material.
The above resin composition (binder) 20 parts by mass Aramid fiber (Kevlar (R) pulp 1F538 manufactured by DuPont Toray) 5 parts by mass Copper fiber (CCW-208 manufactured by Japan Steel Wool) 5 parts by mass Acrylonitrile butadiene rubber (NBR) manufactured by JSR PN30A) 5 parts by mass Cashew particles (FF-1500, manufactured by Tohoku Kako) 10 parts by mass Barium sulfate (Etritile barium sulfate BA, manufactured by Sakai Chemical) 45 parts by mass Graphite (SGP-100, manufactured by SEC Carbon) 10 parts by mass

Thereafter, the obtained friction material molding material was compression molded at 170° C. for 15 minutes to obtain a disk-shaped test piece of 100 mmφ. Further, the obtained test piece was thermally cured (after-cured) at 180° C. for 4 hours. A friction material was thus obtained.

Examples 2-9 and Comparative Examples 1-2
A friction material was obtained in the same manner as in Example 1, except that the formulation shown in Tables 1 and 2 was changed.

<<Evaluation>>
The friction materials obtained in each example and each comparative example were evaluated by the following methods.

(1) Friction Coefficient The friction coefficient of the friction material was obtained by the following method. That is, the friction coefficient (static friction coefficient and dynamic friction coefficient) was obtained using HEIDON-14 according to ASTM D1894. Various conditions for obtaining the coefficient of friction and the dimensions of the test pieces used are shown below.
Test piece: Disc test piece with a diameter of 100 mm and a thickness of about 3 mm Mating material: Cylinder with a diameter of 19 mm Material of mating material: S45C
Test speed: 100mm/min

(2) Maximum point elongation (mechanical properties)
The maximum point elongation of the friction material was obtained by the following method. Specifically, according to JIS K6911 (1995), a three-point bending test was performed at a crosshead speed of 3 mm/min and a span of 100 mm to measure the maximum point elongation. The maximum point elongation is the strain (maximum point elongation) when bent until it breaks, and was obtained by the following formula.

Maximum point elongation (ε) = [6T/L ² ] × ΔL
(T: thickness of sample, L: distance between fulcrums, ΔL: amount of bending deflection)

(3) tan δ (flexibility)
The tan δ at 200°C of the friction material was obtained by the following method. That is, solid dynamic viscoelasticity was measured using Rheogel-E4000 (manufactured by UBM) (frequency 1 Hz, heating rate 2° C./min). The measurement mode was bending, and the measurement temperature range was room temperature (20°C) to 300°C. Then, the tan δ value at 200° C. was obtained from the tan δ curve. Note that tan δ is an index of flexibility. It was judged that the larger the value of tan δ, the higher the flexibility, the more vibrations can be suppressed, and the more noise can be suppressed.

Claims (3)

A friction material containing a binder,
The binder is
a novolak-type phenolic resin;
A friction material containing lignin modified with polyethylene glycol. The friction material according to claim 1, wherein the lignin is coniferous lignin. 3. The friction material according to claim 1, wherein said polyethylene glycol has a number average molecular weight of 400 or more.