Friction material

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

[Technical Field]

[0001] The present invention relates to a friction material. [Background technology]

[0002] Friction materials are used, for example, in vehicle braking components, such as brake components and clutch components, and include, for example, a fibrous base material, a filler, a lubricant, and a binder that binds these together.

[0003] More specifically, the following friction material has been proposed. This friction material includes a binder, a fibrous base material, a filler, and a solid lubricant. The binder includes a novolac-type phenolic resin, an acetic acid-modified lignin, and a curing agent. The fibrous base material includes aramid fibers and copper fibers. The filler includes acrylonitrile butadiene rubber, cashew dust, and barium sulfate. The solid lubricant includes graphite. This friction material has excellent friction characteristics (see, for example, Patent Document 1 (Example 1)). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-179260 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to friction characteristics, friction materials are required to suppress abnormal noise (squeal) caused by friction.

[0006] The present invention provides a friction material that is excellent in friction characteristics and noise suppression. [Means for solving the problem]

[0007] The present invention [1] is a friction material containing a binder, and the binder contains a novolac type phenolic resin and lignin modified with polyethylene glycol.

[0008] The present invention [2] includes the friction material according to the above [1], in which the lignin is softwood lignin.

[0009] The present invention [3] includes the friction material according to the above [1] or [2], in which the number average molecular weight of the polyethylene glycol is 400 or more. [Effects of the Invention]

[0010] In the friction material of the present invention, the binder contains a novolac phenolic resin and lignin modified with polyethylene glycol, which provides the friction material with excellent friction characteristics and suppresses noise due to friction. DETAILED DESCRIPTION OF THE INVENTION

[0011] The friction material of the present invention contains a binder (binding agent).

[0012] The binder contains a novolac type phenolic resin and lignin modified with polyethylene glycol (hereinafter, sometimes referred to as PEG-modified lignin).

[0013] Novolac phenolic resins are, for example, reaction products of phenols and aldehydes in the presence of an acid catalyst.

[0014] Phenols include phenol and phenol derivatives (modified phenols). Examples of phenols include phenol, difunctional phenol derivatives, trifunctional phenol derivatives, and tetrafunctional phenol derivatives. Examples of difunctional phenol derivatives include o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4-xylenol, and 2,6-xylenol. Examples of trifunctional phenol derivatives include m-cresol, resorcinol, and 3,5-xylenol. Examples of tetrafunctional phenol derivatives include bisphenol A and dihydroxydiphenylmethane. Phenol derivatives also include halogenated phenols. Halogenated phenols are halides of phenol or phenol derivatives. Examples of halogens include chlorine and bromine. These phenols can be used alone or in combination of two or more. In the phenol derivatives, the timing of derivatization (modification) of phenol is not particularly limited. For example, the derivatization of phenol may be carried out before, after, or simultaneously with the reaction of the phenol with the aldehyde. As the phenol, phenol is preferably used.

[0015] Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butylaldehyde, isobutylaldehyde, furfural, glyoxal, benzaldehyde, trioxane, and tetraoxane. Furthermore, a portion 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. Preferred examples of aldehydes include formaldehyde and paraformaldehyde.

[0016] The aldehydes can be used, for example, as an aqueous solution. In such a case, the concentration of the 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.

[0017] Ketones can also be blended together with aldehydes. Examples of ketones include 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 the ketones is, on a solids basis, for example, 0.01 parts by mass or more, preferably 1 part by mass or more, and for example, 200 parts by mass or less, preferably 100 parts by mass or less, per 100 parts by mass of aldehydes.

[0018] Examples of acid catalysts include organic acids and inorganic acids. Examples of organic acids include carboxylic acid compounds, sulfonic acid compounds, and phosphoric acid compounds. Examples of carboxylic acid compounds include formic acid, acetic acid, and oxalic acid. Examples of sulfonic acid compounds include methanesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, cumenesulfonic acid, dinonylnaphthalene monosulfonic acid, and dinonylnaphthalenedisulfonic acid. Examples of phosphoric acid compounds include phosphate esters. More specifically, examples of phosphate esters include phosphate esters having an alkyl group having 1 to 18 carbon atoms. Examples of phosphoric acid compounds include trimethyl phosphate, triethyl phosphate, monobutyl phosphate, dibutyl phosphate, tributyl phosphate, and trioctyl phosphate. 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. Preferably, the acid catalyst is an organic acid, more preferably a carboxylic acid compound, and even more preferably oxalic acid.

[0019] In the reaction between phenols and aldehydes, the mixing ratio of the aldehydes relative to 100 parts by mass of the phenols is, for example, 5 parts by mass or more, or preferably 10 parts by mass or more, and for example, 35 parts by mass or less, or preferably 30 parts by mass or less.

[0020] The mixing ratio of the acid catalyst relative to 100 parts by mass of the phenols is, for example, 0.1 parts by mass or more, or preferably 0.3 parts by mass or more, and for example, 10 parts by mass or less, or preferably 5 parts by mass or less.

[0021] The timing of adding the acid catalyst is not particularly limited. For example, the acid catalyst may be added to the phenols and / or aldehydes in advance. Alternatively, the acid catalyst may be added simultaneously with the blending of the phenols and aldehydes. Furthermore, the acid catalyst may be added after the blending of the phenols and aldehydes.

[0022] Reaction conditions include atmospheric pressure. The reaction temperature is, for example, 50°C or higher, preferably 80°C or higher. The reaction temperature is, for example, 200°C or lower, preferably 180°C or lower. The reaction time is, for example, 1 hour or longer, preferably 2 hours or longer. The reaction time is, for example, 20 hours or shorter, preferably 15 hours or shorter.

[0023] This produces a novolac phenolic resin as a reaction product of the phenols and the aldehydes. Alternatively, commercially available novolac phenolic resins may be used.

[0024] In PEG-modified lignin, polyethylene glycol (PEG) modifies lignin, thereby improving the friction characteristics of the friction material and suppressing noise.

[0025] The number average molecular weight of polyethylene glycol is, for example, 100 or more, preferably 200 or more, more preferably 300 or more, even more preferably 400 or more, and particularly preferably 500 or more. The number average molecular weight of polyethylene glycol is, for example, 1000 or less, preferably 900 or less, more preferably 800 or less, and even more preferably 600 or less. When the number average molecular weight is within the above range, a friction material that satisfies both friction characteristics and noise suppression can be obtained, and the productivity of the friction material is also excellent. The number average molecular weight can be determined as a polyethylene glycol-equivalent molecular weight by a known gel permeation chromatography method.

[0026] In PEG-modified lignin, lignin is a polymeric phenolic compound. Lignin is a natural product (natural lignin) found in plants. Examples of the basic structure of lignin include guaiacyl lignin (G-type), syringyl lignin (S-type), and p-hydroxyphenyl lignin (H-type).

[0027] Lignin is industrially extracted from plant materials, such as lignocellulose. Examples of lignin include soda lignin, sulfite lignin, and kraft lignin. Methods for extracting lignin include the soda process, sulfite process, steam explosion, solvolysis, and kraft process.

[0028] More specifically, lignin includes lignin derived from woody plants and lignin derived from herbaceous plants.

[0029] Examples of woody plant-derived lignin include coniferous lignin contained in conifers (e.g., cedar) and hardwood lignin contained in hardwood. Note that 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. Furthermore, hardwood lignin has both a G-type basic skeleton and an S-type basic skeleton.

[0030] Examples of lignin derived from herbaceous plants include rice lignin, which is contained in grasses. Examples of grasses include wheat straw, rice straw, corn, and bamboo. Lignin derived from herbaceous plants has all of the basic skeletons of H-type, G-type, and S-type.

[0031] These lignins can be used alone or in combination of two or more. As the lignin, preferred is woody plant-derived lignin that does not contain an H-type basic skeleton, more preferred is coniferous lignin that does not contain an S-type basic skeleton and has a G-type basic skeleton, and particularly preferred is coniferous lignin derived from Japanese cedar. PEG-modified lignin obtained from coniferous lignin derived from Japanese cedar has excellent homogeneity.

[0032] PEG-modified lignin is produced, for example, in accordance with the method described in JP 2017-197517 A.

[0033] In this method, for example, plant material (lignocellulose), which is the raw material for lignin, is digested using polyethylene glycol.

[0034] The cooking method is not particularly limited, but for example, a plant material that is the raw material for lignin, polyethylene glycol, and an inorganic acid (for example, hydrochloric acid, sulfuric acid, etc.) as an acid catalyst are mixed and reacted.

[0035] The blending ratio of polyethylene glycol is, for example, 200 parts by mass or more, preferably 300 parts by mass or more, per 100 parts by mass of the plant material that serves as the raw material for lignin, and is, for example, 1000 parts by mass or less, preferably 600 parts by mass or less, per 100 parts by mass of the plant material that serves as the raw material for lignin.

[0036] The blending ratio of the inorganic acid (100% equivalent) relative to 100 parts by mass of polyethylene glycol is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and the blending ratio of the inorganic acid (100% equivalent) relative to 100 parts by mass of polyethylene glycol is, for example, 2 parts by mass or less, preferably 1 part by mass or less.

[0037] The reaction conditions include atmospheric pressure. The reaction temperature is, for example, 120°C or higher, preferably 130°C or higher. The reaction temperature is, for example, 180°C or lower, preferably 150°C or lower. The reaction time is, for example, 60 minutes or longer. The reaction time is, for example, 240 minutes or shorter, preferably 120 minutes or shorter.

[0038] After the reaction is complete, an alkali is added to the reaction solution in an appropriate ratio to adjust the pH. Examples of alkali include ammonia and sodium hydroxide. This allows the PEG-modified lignin to be extracted into the solution. The adjusted pH is, for example, 8 or higher, preferably 10 or higher, more preferably 10.5 or higher, and is, for example, 14 or lower.

[0039] By this method, pulp is obtained as a solid component and PEG-modified lignin is obtained as a solution component.

[0040] Next, in this method, the solid component (pulp) is separated from the reaction product by a known separation method such as filtration, pressing, or centrifugation, and the solution component is recovered.

[0041] Furthermore, in this method, if necessary, the solid component (pulp) can be washed and the solution (PEG-modified lignin) impregnated into the solid component can be recovered.

[0042] In this method, an inorganic acid (e.g., hydrochloric acid, sulfuric acid, etc.) is then added to adjust the pH to precipitate and deposit the PEG-modified lignin.

[0043] The pH after adjustment is, for example, 1.5 or higher, and for example, 5 or lower, preferably 3 or lower, and more preferably 2 or lower.

[0044] This allows the PEG-modified lignin to precipitate, and the resulting precipitate can be collected by a known method such as filtration, pressing, or centrifugation to obtain the PEG-modified lignin as a solid content.

[0045] The binder (binding agent) contains a novolac phenolic resin and a PEG-modified lignin, that is, the binder may be a mixture of a novolac phenolic resin and a PEG-modified lignin.

[0046] The blending ratio of the novolac phenolic resin and the PEG-modified lignin is, on a solids (non-volatile) basis, for 100 parts by mass of the novolac phenolic resin, for example, 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 120 parts by mass or more of the PEG-modified lignin. For 100 parts by mass of the novolac phenolic resin, the blending ratio is, for example, 300 parts by mass or less, preferably 200 parts by mass or less, more preferably 150 parts by mass or less of the PEG-modified lignin.

[0047] When the blending ratio of the novolac phenolic resin and the PEG-modified lignin is within the above range, an excessive increase in viscosity can be suppressed, excellent moldability can be ensured, and various physical properties of the resulting friction material can be improved.

[0048] The kneading method is not particularly limited, and any known kneading machine can be used, such as a single-screw extruder, a multi-screw extruder, a roll kneader, a kneader, a Henschel mixer, or a Banbury mixer.

[0049] The kneading temperature is 80°C or higher, preferably 90°C or higher, and more preferably 100°C or higher. The kneading temperature is 180°C or lower, preferably 170°C or lower, and more preferably 160°C or lower. The kneading time is, for example, 3 minutes or longer, and preferably 5 minutes or longer. The kneading time is, for example, 30 minutes or shorter, and preferably 20 minutes or shorter.

[0050] As a result, a binder (binding agent) is obtained as a resin composition containing the novolac phenolic resin and the PEG-modified lignin.

[0051] That is, the binder contains a novolac phenolic resin and a PEG-modified lignin, and therefore, the binder can achieve both excellent friction characteristics and noise suppression.

[0052] The binder may also contain a phenolic resin curing agent as needed. The binder preferably contains a novolac phenolic resin, a PEG-modified lignin, and a phenolic resin curing agent, and more preferably contains a novolac phenolic resin, a PEG-modified lignin, and a phenolic resin curing agent.

[0053] The phenolic resin curing agent is not particularly limited, and known curing agents can be used. Examples of the phenolic resin curing agent include 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 can be appropriately set depending on the purpose and application, as long as it does not impair the excellent effects of the present invention.

[0054] The binder may further contain additives. Examples of additives include known additives added to binders. Examples of additives include 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 adding the additives is not particularly limited and can be appropriately determined depending on the purpose and application. The blending ratio of the additives can be appropriately determined depending on the purpose and application, as long as it does not impair the excellent effects of the present invention.

[0055] The friction material may contain other binders as needed. The other binders are binders other than the above-mentioned resin composition (the resin composition containing the novolac-type phenolic resin and the PEG-modified lignin). Examples of the other binders include known thermosetting resins. Examples of the thermosetting resins include melamine resins, epoxy resins, and polyimide resins. These may be used alone or in combination of two or more.

[0056] When other binders are blended, the blending ratios are appropriately set within a range that does not impair the effects of the present invention. The friction material preferably does not contain other binders. That is, the friction material preferably contains only the resin composition containing the novolac-type phenolic resin and the PEG-modified lignin as the binder.

[0057] The friction material preferably contains a fibrous base material, such as organic fibers or inorganic fibers.

[0058] Examples of organic fibers include polyamide fibers and acrylic fibers. Examples of polyamide fibers include aramid fibers. Examples of acrylic fibers include flame-retardant acrylic fibers. These can be used alone or in combination of two or more types. Examples of organic fibers include preferably polyamide fibers, and more preferably aramid fibers.

[0059] Examples of inorganic fibers include metal fibers, ceramic fibers, glass fibers, and carbon fibers. Examples of metal fibers include copper fibers and brass fibers. Examples of ceramic fibers include potassium titanate fibers, Al2O3-SiO2 ceramic fibers, and biosoluble ceramic fibers. These can be used alone or in combination of two or more types. Examples of inorganic fibers include metal fibers, and more preferably copper fibers.

[0060] The fibrous substrate may be used alone or in combination of two or more kinds. Preferred examples of the fibrous substrate include organic fibers and inorganic fibers, and more preferred examples include a combination of organic fibers and inorganic fibers.

[0061] The size of the fiber substrate is appropriately set depending on the purpose and application. For example, the length (fiber length) of the fiber substrate is not particularly limited, but is, for example, 100 μm or more and 2500 μm or less. The diameter of the fiber substrate is not particularly limited, but is, for example, 3 μm or more and 600 μm or less.

[0062] The friction material preferably also contains a friction modifier, such as a filler, a solid lubricant, or an abrasive.

[0063] Examples of fillers include organic fillers and inorganic fillers.

[0064] Examples of organic fillers include wood flour, pulp, rubber powder, cashew particles (cashew dust), and melamine dust. In the rubber powder, examples of rubber include acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), and butadiene rubber (BR). These can be used alone or in combination of two or more. Preferred examples of organic fillers include rubber powder and cashew particles.

[0065] Examples of inorganic fillers include calcium carbonate, barium sulfate, calcium hydroxide, iron sulfide, copper sulfide, silicon oxide, metal powders, and minerals. In the metal powder, examples of metals include copper, aluminum, bronze, and zinc. Examples of minerals include vermiculite. These can be used alone or in combination of two or more. A preferred inorganic filler is barium sulfate.

[0066] The filler may be used alone or in combination of two or more. Preferred fillers include organic fillers and inorganic fillers, and more preferably, a combination of organic fillers and inorganic fillers.

[0067] The solid lubricant may be a known solid lubricant. More specifically, the solid lubricant may be, for example, graphite or molybdenum disulfide. These may be used alone or in combination of two or more. Preferably, the solid lubricant is graphite.

[0068] Examples of the abrasive include known abrasives. More specifically, examples of the abrasive include alumina, magnesia, and zirconia. These can be used alone or in combination of two or more.

[0069] These friction modifiers can be used alone or in combination of two or more. The friction modifier is appropriately selected depending on the required physical properties. As the friction modifier, preferred are fillers and solid lubricants, and more preferred are a combination of fillers and solid lubricants.

[0070] The size of the friction modifier is appropriately set depending on 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. The average particle size of the friction modifier is, for example, 500 μm or less, preferably 250 μm or less.

[0071] In producing the friction material, for example, first, the binder, the fibrous base material, and the friction modifier are blended and kneaded to produce a molding material (composition) for the friction material.

[0072] In the friction material molding material, the total amount of the fibrous base material and friction modifier is, for example, 250 parts by mass or more, preferably 400 parts by mass or more, per 100 parts by mass of the binder, and the total amount of the fibrous base material and friction modifier is, for example, 950 parts by mass or less, preferably 900 parts by mass or less, per 100 parts by mass of the binder.

[0073] The amount of the binder is, for example, 2 parts by mass or more, preferably 5 parts by mass or more, relative to 100 parts by mass of the total amount of the binder, fibrous base material, and friction modifier.The amount of the binder is, for example, 40 parts by mass or less, preferably 30 parts by mass or less, relative to 100 parts by mass of the total amount of the binder, fibrous base material, and friction modifier.

[0074] The amount of the fibrous base material is, for example, 1 part by mass or more, preferably 5 parts by mass or more, relative to 100 parts by mass of the total amount of the binder, fibrous base material, and friction modifier. The amount of the fibrous base material is, for example, 65 parts by mass or less, preferably 30 parts by mass or less, relative to 100 parts by mass of the total amount of the binder, fibrous base material, and friction modifier.

[0075] The amount of the friction modifier is, for example, 40 parts by mass or more, preferably 50 parts by mass or more, relative to 100 parts by mass of the total of the binder, fibrous base material, and friction modifier. The amount of the friction modifier is, for example, 95 parts by mass or less, preferably 85 parts by mass or less, relative to 100 parts by mass of the total of the binder, fibrous base material, and friction modifier.

[0076] When the friction modifier contains an abrasive, the amount of the abrasive is, for example, 1 part by mass or more, preferably 2 parts by mass or more, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined, and the amount of the abrasive is, for example, 30 parts by mass or less, preferably 25 parts by mass or less, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined.

[0077] When the friction modifier contains a filler, the amount of the filler is, for example, 30 parts by mass or more, preferably 35 parts by mass or more, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined, and is, for example, 90 parts by mass or less, preferably 85 parts by mass or less, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined.

[0078] 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, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined, and the solid lubricant is, for example, 30 parts by mass or less, preferably 25 parts by mass or less, per 100 parts by mass of the binder, fibrous base material, and friction modifier combined.

[0079] The kneading method is not particularly limited, and a known kneader can be used, such as a single-screw extruder, a multi-screw extruder, a roll kneader, a kneader, a Henschel mixer, or a Banbury mixer.

[0080] The kneading temperature is, for example, 80°C or higher, preferably 90°C or higher, and more preferably 100°C or higher. The kneading temperature is, for example, 180°C or lower, preferably 170°C or lower, and more preferably 160°C or lower. The kneading time is, for example, 3 minutes or longer, and preferably 5 minutes or longer. The kneading time is, for example, 30 minutes or shorter, and preferably 20 minutes or shorter.

[0081] The molding material for a friction material contains a mixture of the novolac phenolic resin and PEG-modified lignin as a binder, and therefore, by using the molding material for a friction material, a friction material having excellent friction characteristics and capable of suppressing noise can be obtained.

[0082] Next, in this method, the above-mentioned friction material molding material is molded by a known method, thereby obtaining a friction material.

[0083] As the molding method, a known method is adopted. More specifically, examples of the molding method include transfer molding and compression molding. The molding conditions are not particularly limited and are set appropriately depending on the purpose and application.

[0084] For example, the temperature condition is, for example, 140°C or higher, preferably 150°C or higher. The temperature condition is, for example, 200°C or lower, preferably 180°C or lower. The pressure condition is, for example, 20 MPa or higher, preferably 30 MPa or higher. The pressure condition is, for example, 100 MPa or lower, preferably 80 MPa or lower. The treatment time is, for example, 2 minutes or longer, preferably 10 minutes or longer. The treatment time is, for example, 60 minutes or shorter, preferably 30 minutes or shorter.

[0085] By molding the friction material molding material in this manner, a friction material is obtained.

[0086] The friction material may be treated by a known method, if necessary. Examples of such treatments include degreasing and primer treatment. The molded friction material may also be after-cured (thermosetting) by a known method.

[0087] The processing conditions for the after-cure are not particularly limited, but normal pressure is employed. The temperature is, for example, 10 to 100°C higher than the temperature during the molding. The temperature is, for example, 150°C or higher, preferably 160°C or higher. The temperature is, for example, 300°C or lower, preferably 200°C or lower. The processing time is, for example, 1 hour or longer, preferably 2 hours or longer. The processing time is, for example, 10 hours or shorter, preferably 8 hours or shorter. The after-cure can improve friction properties and heat resistance.

[0088] The friction material contains a binder, which contains a novolac phenolic resin and lignin modified with polyethylene glycol. As a result, the friction material has excellent friction characteristics and can suppress noise due to friction.

[0089] More specifically, the friction characteristics can usually be improved by improving the mechanical strength of the friction material. However, improving the mechanical strength of the friction material reduces the flexibility of the friction material, which makes the friction material more susceptible to vibration due to friction and therefore more susceptible to abnormal noise (squeak). In other words, improving the friction characteristics and suppressing abnormal noise are in a trade-off relationship.

[0090] In contrast, in the above-described friction material, the binder contains a novolac-type phenolic resin and lignin modified with polyethylene glycol, which improves the mechanical strength of the friction material while ensuring flexibility.

[0091] As a result, the friction characteristics of the friction material are improved, and vibration of the friction material is suppressed, thereby suppressing the occurrence of abnormal noise (squealing).

[0092] Therefore, the friction material is preferably used, for example, in braking members of vehicles. Examples of vehicles include automobiles, motorcycles, and trains. Examples of braking members include brake pads and clutch members. The friction material is particularly preferably used as brake pads for automobiles.

[0093] When the friction material is used as a brake pad for an automobile, the brake member and the above-mentioned molding material for the friction material may be integrally molded. An example of the brake member is a known pressure plate.

[0094] More specifically, for example, the above-mentioned friction material molding material is first preformed. If necessary, the preformed friction material molding material is degreased and primed. Next, the friction material molding material and the brake component are bonded together with an adhesive. After that, the friction material molding material and the brake component are thermoformed together. At the same time, the friction material molding material and the brake component are fixed together.

[0095] The processing conditions for thermoforming are not particularly limited and are set appropriately depending on the purpose and application. For example, the temperature condition is, for example, 140°C or higher and 170°C or lower. The pressure condition is, for example, 30 MPa or higher and 80 MPa or lower. The heat treatment time is, for example, 2 minutes or higher and 10 minutes or lower.

[0096] The thermoformed friction material may be subjected to after-curing and finishing treatment by known methods as needed. The after-curing conditions are not particularly limited. For example, the temperature conditions are 150°C or higher and 300°C or lower under normal pressure. The treatment time is, for example, 1 hour or higher and 4 hours or lower.

[0097] Furthermore, since the brake pad is obtained using the above-mentioned friction material, it has excellent friction characteristics and can also suppress abnormal noise (squeal) caused by friction. [Example]

[0098] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Furthermore, unless otherwise specified in the following description, "parts" and "%" are based on mass. Specific numerical values ​​of blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than" or "less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Description of the Invention."

[0099] <Synthesis of novolac-type phenolic resin> Manufacturing 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. The temperature was then raised to 110°C at a rate of 0.5°C / min and the reaction was continued at 110°C for 1.5 hours. The temperature was then raised to 120°C at a rate of 0.5°C / min and the reaction was continued at 120°C for 2 hours.

[0100] After the reaction, 2800 parts by mass of water was added, vigorously stirred, and then allowed to stand. The water was then removed by decantation to remove oxalic acid and phenol. Furthermore, the mixture was subjected to vacuum distillation at 150°C and 0.08 MPa while adding water as needed to remove residual phenol. The vacuum distillation was repeated until the residual phenol content was reduced to 1% or less.

[0101] As a result, a novolac type phenolic resin was obtained.

[0102] <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.

[0103] 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 relative to 100 parts by mass of PEG200) were placed in a reaction vessel and stirred.

[0104] Next, 46 parts by mass of bone-dry cedar wood flour was added to the reaction vessel, and the temperature was raised to 140°C under normal pressure, and the mixture was reacted for 90 minutes with stirring.

[0105] Next, the reaction vessel was cooled, and after it was confirmed that the temperature had reached 40° C. or less, 280 parts by mass of sodium hydroxide (0.2 mol / L) was added, followed by stirring for 30 minutes.

[0106] Next, the resulting solid component (pulp) was removed using a filter press, and the solution component was recovered.

[0107] Next, sulfuric acid was added to the resulting solution component to adjust the pH to 2.0, thereby obtaining a suspension of Mn200-PEG-modified lignin.

[0108] The Mn200-PEG modified lignin was then collected by centrifugation.

[0109] Production Example 3 (Mn400-PEG modified lignin) An Mn400-PEG-modified lignin was obtained in the same manner as in Production Example 2, except that polyethylene glycol having a number average molecular weight of 400 (hereinafter, Mn400-PEG) was used instead of polyethylene glycol having a number average molecular weight of 200.

[0110] Production Example 4 (Mn600-PEG modified lignin) An Mn600-PEG-modified lignin was obtained in the same manner as in Production Example 2, except that polyethylene glycol having a number average molecular weight of 600 (hereinafter, Mn600-PEG) was used instead of polyethylene glycol having a number average molecular weight of 200.

[0111] Production Example 5 (Acetic Acid Modified Lignin) 100 parts by mass of corn stover was mixed with 1,000 parts by mass of 95% acetic acid and 3 parts by mass of sulfuric acid, and the mixture was allowed to react under reflux for 4 hours. After the reaction, the mixture was filtered to remove the pulp, and the pulp waste liquid was recovered. Next, the acetic acid in the pulp waste liquid was removed using a rotary evaporator, and the mixture was concentrated to 1 / 10 of its original volume. After that, 10 times the amount (by mass) of water as the concentrated liquid was added, and the mixture was filtered to obtain acetic acid-modified lignin as a solid.

[0112] <<Friction material manufacturing>> reference Example 1 The following components were mixed in order and kneaded with two heated rolls at 100°C for 5 minutes to obtain a resin composition. 100 parts by mass (300 g) of the novolac phenolic resin of Production Example 1 50 parts by mass (150 g) of Mn200-PEG-modified lignin of Production Example 2 Hexamethylenetetramine (hardener, manufactured by Lignite) 18 parts by mass (54 g) Zinc stearate (mold release agent, manufactured by Wako Pure Chemical Industries, Ltd.) 1.5 parts by mass (4.5 g)

[0113] Next, the following components were mixed in a mixer to obtain a molding material for friction material. 20 parts by mass of the above resin composition (binder) Aramid fiber (Toray DuPont Kevlar® pulp 1F538) 5 parts by weight Copper fiber (Japan Steel Wool CCW-208) 5 parts by weight 5 parts by weight of acrylonitrile butadiene rubber (NBR) manufactured by JSR (PN30A) 10 parts by weight of cashew particles (Tohoku Kako FF-1500) Barium sulfate (Sakai Chemical Co., Ltd., elutriated barium sulfate BA) 45 parts by mass Graphite (SEC Carbon SGP-100) 10 parts by weight

[0114] The obtained friction material molding material was then compression molded at 170°C for 15 minutes to obtain a 100mmφ disk-shaped test piece. The obtained test piece was then heat-cured (after-cured) at 180°C for 4 hours to obtain a friction material.

[0115] Example 2-3, Examples 5-6, Examples 8-9, Reference Example 4, Reference Example 7, and Comparative Examples 1-2 Except for the changes in the formulation shown in Tables 1 and 2, reference In the same manner as in Example 1, a friction material was obtained.

[0116] <<Evaluation>> Each reference example, The friction materials obtained in each of the examples and comparative examples were evaluated by the following methods.

[0117] (1) Friction coefficient The friction coefficient of the friction material was determined by the following method. That is, the friction coefficient (static friction coefficient and kinetic friction coefficient) was determined using HEIDON-14 in accordance with ASTM D1894. The various conditions for determining the friction coefficient and the dimensions of the test specimen used are shown below. Test specimen: 100mm diameter, approximately 3mm thick disc test specimen Counterpart: 19mm diameter cylinder Mating material: S45C Test speed: 100 mm / min

[0118] (2) Maximum elongation (mechanical properties) The maximum elongation of the friction material was determined by the following method. That is, a three-point bending test was performed in accordance with JIS K6911 (1995) at a crosshead speed of 3 mm / min and a span of 100 mm, and the maximum elongation was measured. The maximum elongation is the strain (maximum elongation) when the material is bent until it breaks, and was calculated using the following formula.

[0119] Maximum point elongation (ε)=[6T / L 2 ] × ΔL (T: sample thickness, L: distance between supports, ΔL: bending deflection)

[0120] (3) tanδ (flexibility) The tan δ of the friction material at 200°C was determined by the following method. Specifically, solid dynamic viscoelasticity was measured using Rheogel-E4000 (manufactured by UBM) (frequency 1 Hz, temperature rise rate 2°C / min). The measurement mode was bending, and the measurement temperature range was room temperature (20°C) to 300°C. The value of tan δ at 200°C was then determined from the tan δ curve. Note that tan δ is an index of flexibility. It was determined that the larger the tan δ value, the higher the flexibility, and the better the ability to suppress vibration and abnormal noise.

[0121] [Table 1]

[0122] [Table 2]

Claims

1. A friction material containing a binder, The binder is Novolac phenolic resin, Polyethylene glycol modified lignin and Contains The friction material, wherein the polyethylene glycol has a number average molecular weight of 400 or more.

2. The friction material according to claim 1 , wherein the lignin is a softwood lignin.

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