JP5918585B2 - Friction material manufacturing method - Google Patents

Description

  The present invention relates to a friction material having a low environmental load using a carbon-neutral plant-derived material as a raw material. is there.

  Friction materials used for brakes, clutches, etc. include, for example, a fiber base material that provides reinforcement, a friction adjustment material that imparts friction and adjusts its friction performance, and a binding material that integrates these components. Made of material.

  In recent years, the global warming problem due to an increase in the concentration of carbon dioxide in the atmosphere is becoming a global problem, and technologies for reducing carbon dioxide emissions are being developed in various industrial fields. Also in the field of friction materials, from the viewpoint of environmental protection, consideration is also required for the environmental load caused by the abrasion powder generated from the friction material and the discarded friction material. In such circumstances, the use of carbon-neutral plant-derived materials has attracted attention. For example, lignin, which is a polyphenol contained in a large amount in wood and the like, is produced as a by-product when cellulose is produced during pulp production, so attempts have been made to effectively use this.

  Here, in Patent Document 1, about 1 to 30% by weight of the phenol resin which is a binder component in the friction material composition is substituted with organosolv lignin having substantially no sulfur content and low water solubility. Thus, it is described that noise, wear and sulfur odor can be reduced.

  Patent Document 2 describes a lignin-modified novolak-type phenolic resin and a method for producing the same.

Japanese National Patent Publication No. 11-513726 JP 2008-156601 A

  However, in the binder resin composition described in Patent Document 1, organosolv lignin powder is simply blended as a raw material for the friction material, and is hardly compatible with the phenol resin. For this reason, there is a limit to the amount of lignin substitution, and further, there is room for improvement such as poor heat fluidity during molding, resulting in poor moldability. Further, Patent Document 2 does not describe the use of the friction material as a binder.

  The present invention solves the above-mentioned problem, that is, a friction material with improved friction performance (fade resistance) without reducing the environmental load while increasing the biomass content and without reducing the strength. The purpose is to provide.

As a result of various studies, the present inventors have found that the above problem can be solved by using a friction material having the following configuration. That is, the present invention is as follows.
<1> A friction material containing a lignin phenol resin having a weight average molecular weight of 5000 or less as a binder.
<2> The friction material according to <1>, wherein the lignin phenol resin has a softening point of 50 to 150 ° C.
<3> The friction material according to <1> or <2>, wherein the lignin phenol resin is obtained by reacting lignin, phenols, and aldehydes in the presence of an acid catalyst.
<4> The friction material according to <3>, wherein the lignin is at least one selected from the group consisting of softwood lignin, hardwood lignin, and herbaceous lignin.
<5> A method for producing the friction material according to <1>, wherein lignin having a weight average molecular weight of 5000 or less, phenols, and aldehydes are reacted in the presence of an acid catalyst. A method for producing a friction material, including a step of obtaining a resin.
<6> A step of purifying lignin with one or more solvents selected from the group consisting of methanol, ethanol, acetone, and tetrahydrofuran to obtain lignin having a weight average molecular weight of 5000 or less, and the purified lignin and phenols The method for producing a friction material according to <5>, further comprising a step of reacting aldehydes with an aldehyde in the presence of an acid catalyst to obtain a lignin phenol resin.

  ADVANTAGE OF THE INVENTION According to this invention, even if plant-derived material is used, the friction material which can improve friction performance (fade resistance) without impairing intensity | strength can be provided.

The friction material according to the present invention is a friction material having a low environmental load by replacing the phenol resin, which is a conventional binder component, with a lignin phenol resin.
The lignin phenol resin in the present invention can be obtained by mixing and reacting lignin, phenols and aldehydes. Since phenol and lignin are reacted at a molecular level to form an integral resin, the thermal fluidity at the time of forming the friction material is good, and the content of lignin can be improved as compared with Patent Document 1.

  Lignin is a major component of the plant cell wall that is present in plants such as wood along with cellulose, hemicellulose, etc., and is a polymer compound polymerized in an amorphous form with phenylpropane as a basic unit. Lignin can be separated and extracted from the plant body by various methods, but it is usually difficult to extract lignin present in the plant body as it is, and it is extracted as a lignin derivative.

In the present invention, the plant body and extraction method for extracting lignin are not limited.
The plant body may be wood and herbs that contain lignin and have a woody part. Coniferous trees such as cedar, pine and cypress, broad-leaved trees such as beech and zelkova, rice plants such as rice, wheat, corn and bamboo. (Herbaceous). Thus, lignin is roughly classified into conifer lignin, hardwood lignin, and herbaceous lignin depending on the plant body from which it is derived, and one or more of these can be used in the present invention.

  Further, as shown in the following formula, the basic skeleton of lignin has a guaiacyl type (G type) represented by the formula (G) depending on the number of methoxyl groups that are characteristic functional groups in addition to the phenylpropane structure as a basic unit. ), Syringyl type (S type) represented by formula (S), p-hydroxyphenyl type (H type) represented by formula (H), and the like are known. The basic skeleton of lignin varies depending on the plant from which it is derived, and it is known that conifer lignin is composed of G type, hardwood lignin is composed of G type and S type, and herbaceous lignin is composed of G type, S type and H type. Yes.

  Extraction methods are roughly classified into two methods: a method of hydrolyzing cellulose and hemicellulose in a plant body and leaving lignin as an insoluble residue, and a method of dissolving and eluting lignin. The former includes, for example, an acid hydrolysis method in which concentrated sulfuric acid is allowed to act on a piece of wood to separate lignin from the remaining portion. Examples of the latter include soda cooking method that separates lignin with sodium hydroxide, phase separation system conversion system that uses phenols as a solvent, solvent method that uses organic solvents, supercritical and subcritical fluids Extraction methods and the like.

  The plant body and the lignin extraction method can be appropriately combined.

  Moreover, the molecular weight (weight average molecular weight) of the lignin used for the raw material of lignin phenol resin becomes like this. Preferably it is 5000 or less, More preferably, it is 4000 or less. If the molecular weight of lignin is within such a range, it is preferable because the heat fluidity during molding of the synthesized lignin phenol resin is good.

  Moreover, the lignin used as a raw material of the lignin phenol resin in the present invention preferably has a softening point of 70 ° C to 180 ° C, more preferably 80 ° C to 160 ° C, and still more preferably 90 to 130 ° C. If the softening point is in such a range, it is preferable because the heat fluidity during molding of the synthesized lignin phenol resin is good. The softening point is a value measured by a thermomechanical measuring device.

In order to make the molecular weight (weight average molecular weight) and softening point of lignin within the above range, a method of purifying lignin soluble in a solvent such as methanol, ethanol, acetone, tetrahydrofuran, etc., from the crude lignin extract can be mentioned. Lignin soluble in such a solvent has a relatively low molecular weight and satisfies the above softening point range. For example, when the lignin extracted from a gramineous plant by soda digestion (manufactured by Harima Kasei Co., Ltd., product name: high-purity lignin) was purified with the following organic solvents, the lignin softening point was measured. : 126 ° C., ethanol: 109 ° C., acetone: 107 ° C., tetrahydrofuran: 101 ° C. From this result, it was found that by selecting an appropriate organic solvent, it is possible to obtain a lignin phenol resin having a softening point exhibiting an appropriate heat fluidity necessary for forming a friction material. However, when the crude extract itself already satisfies the molecular weight (weight average molecular weight) and the softening point range, the purification operation is unnecessary.
In addition, lignin can be used individually by 1 type or in combination of 2 or more types.

The phenol used in the present invention refers to phenol or a phenol derivative. The phenol derivative is not particularly limited as long as it has a phenol skeleton, and may have an arbitrary substituent on the benzene ring. Examples of the substituent include an alkyl group, a halogen atom, an amino group, a nitro group, and a carboxy group. Specific examples of phenols include phenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol, hydroquinone, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2 , 6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, p-tert-butylphenol, bisphenol A, o-fluorophenol, m-fluorophenol, p-fluorophenol, o-chlorophenol, m -Chlorophenol, p-chlorophenol, o-bromophenol, m-bromophenol, p-bromophenol, o-iodophenol, m-iodophenol, p-iodophenol, o-aminophenol, m-aminophenol, p Aminophenol, o- nitrophenol, m- nitrophenol, p- nitrophenol, 2,4-dinitrophenol, 2,4,6-nitrophenol, salicylic, p- hydroxybenzoic acid, and the like. Of these, phenol and cresol are particularly preferable.
The said phenols can be used 1 type or in combination of 2 or more types.

  Examples of aldehydes used in the present invention include formaldehyde, paraformaldehyde, acetaldehyde, n-butyraldehyde, isobutyraldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, and n-butyraldehyde. , Caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, paraxylene dimethyl ether and the like. Preferred are formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, and paraxylene dimethyl ether. These may be used alone or in combination of two or more, and formaldehyde is particularly preferred.

  Examples of the acid catalyst used in the present invention include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, phosphoric acid, tartaric acid, and citric acid. Of these, organic acids such as oxalic acid and p-toluenesulfonic acid are preferred.

  As for the synthesis conditions of lignin phenol resin, it is preferable that phenols are 20-200 mass parts with respect to 100 mass parts of lignin, and it is more preferable that it is 40-150 mass parts. Thereby, the softening point of the lignin phenol resin obtained can be made into the preferable range mentioned later.

  Moreover, it is preferable that the mixture ratio of aldehydes is 1-80 mass parts with respect to 100 mass parts of lignin. Thereby, the softening point of the lignin phenol resin obtained can be made into the preferable range mentioned later.

  It is preferable that an acid catalyst is 0.1-10 mass parts with respect to phenols.

  In addition, it is preferable that the lignin content rate in the lignin phenol resin after a synthesis | combination is 20-90 mass% from the point of the heat fluidity at the time of friction material shaping | molding, More preferably, it is 40-85 mass%. Here, the lignin content can be calculated by (Lignin charge) / (Lignin phenol resin yield) × 100, assuming that the mass of lignin does not change before and after synthesis. If the content of lignin is within such a range, the friction material can be molded, which is preferable because it exhibits a friction coefficient equal to or higher than that of the conventional one.

The lignin phenol resin in the present invention is obtained by reacting lignin, phenols, and aldehydes in the presence of an acid catalyst. Although the mixing method of phenols and lignin is not specifically limited, It is preferable to stir at 80-120 degreeC for 30 minutes-2 hours. Furthermore, the polymerization reaction after addition of the catalyst is preferably 70 to 130 ° C, more preferably 80 to 120 ° C. The reaction time is preferably 10 minutes to 6 hours, more preferably 30 minutes to 3 hours.
Subsequently, although water and unreacted phenol are distilled off from the obtained reaction mixture, atmospheric distillation and / or vacuum distillation are preferable, and distillation under reduced pressure at 120 to 200 ° C. is particularly preferable.

  The lignin phenol resin obtained by the above method has a molecular weight (weight average molecular weight) of 5000 or less, more preferably 4000 or less. If the molecular weight of the lignin phenol resin is within such a range, it is preferable because the heat fluidity at the time of forming the friction material is good. In addition, in order to make molecular weight into the said range, using the lignin whose weight average molecular weight is 5000 or less is mentioned.

  And the lignin phenol resin in this invention becomes like this. Preferably a softening point is 50-150 degreeC, More preferably, it is 50-130 degreeC. If the softening point of the lignin phenol resin is within such a range, it is preferable because the resin flows heat before the resin curing reaction starts. In order to bring the softening point of the resin into the above range, for example, lignin is purified with a solvent as necessary, and lignin in the above preferred softening point range is used as a raw material.

  The friction material of the present invention includes a fiber base material, a friction modifier, and a binder, and the lignin phenol resin is blended as a binder.

  In addition, it is preferable that the lignin content rate in a binder is 50-90 mass% from the point of reduction of an environmental load and a moldability, More preferably, it is 60-85 mass%.

The fiber base material used in the present invention is not particularly limited, and those usually used in this field are used. For example, organic fibers such as aromatic polyamide fibers and flame-resistant acrylic fibers; metal fibers such as copper fibers and brass fibers; potassium titanate fibers, Al ₂ O ₃ —SiO ₂ ceramic fibers, biosoluble ceramic fibers, glass fibers Inorganic fibers such as carbon fiber can be used, and one of these can be used alone or in combination of two or more. The length of the fiber substrate is preferably 100 to 2500 μm and the diameter is preferably 3 to 600 μm.
The blending amount of the fiber base is preferably 1 to 30% by mass, more preferably 5 to 15% by mass with respect to the entire friction material.

  The blending amount of the binder in the friction material of the present invention is not particularly limited, but is preferably 5 to 20% by mass, more preferably 5 to 10% by mass with respect to the entire friction material.

  In addition to the above lignin phenolic resin, the friction material of the present invention can be used in combination with a known material that is usually used for a binding material for a friction material, if necessary. For example, thermosetting resins, such as a melamine resin, an epoxy resin, and a polyimide resin, are mentioned, These 1 type can be used individually or in combination of 2 or more types.

  In the present invention, various friction adjusting materials can be used according to various purposes as a friction adjusting material for imparting a frictional action and adjusting the friction performance. Various solid powder materials called materials, solid lubricants and the like can be used.

For example, calcium carbonate, barium sulfate, calcium hydroxide, iron sulfide, copper sulfide, silicon oxide, metal powder (copper, aluminum, bronze, zinc, etc.), inorganic fillers such as vermiculite, mica, alumina, magnesia, zirconia, etc. Examples thereof include abrasives, various rubber powders (such as rubber dust and tire powder), organic fillers such as cashew dust and melamine dust, and solid lubricants such as graphite and molybdenum disulfide. These can be blended singly or in combination of two or more according to the friction characteristics required for the product, for example, the coefficient of friction, wear resistance, vibration characteristics, squeal characteristics, and the like.
The blending amount of these friction modifiers is preferably 50 to 90% by mass and more preferably 70 to 90% by mass with respect to the entire friction material.

  In order to produce the friction material of the present invention, predetermined amounts of the above-mentioned fiber base material, friction modifier and binder are blended, and the blend is preformed according to a normal production method, such as thermoforming, heating, and polishing It can manufacture by processing.

  The brake pad provided with the friction material is molded into a predetermined shape by a sheet metal press, subjected to a degreasing process and a primer process, and a pressure plate coated with an adhesive, and a friction material preform, In the molding process, thermoforming is performed for 2 to 10 minutes at a molding temperature of 140 to 170 ° C. and a molding pressure of 30 to 80 MPa, and both members are fixed together, and the resulting molded product is aftercured for 1 to 4 hours at a temperature of 150 to 300 ° C. It can manufacture by the process of performing and finally finishing.

  Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Production of lignin phenolic resin>
Lignin extracted from a grass family plant by soda cooking (product of Harima Chemicals, product name: high-purity lignin, softening point: 165 ° C) is purified with methanol, and lignin (weight average molecular weight: 1600) with a softening point of 126 ° C is obtained. Obtained. A method for measuring the softening point will be described later.
The purified lignin and phenol (manufactured by Wako Pure Chemical Industries, Ltd.) were added to the three-necked flask at the ratio shown in Table 1, and the mixture was stirred at 80 ° C. for 30 minutes. Thereafter, a 37% aqueous formaldehyde solution and oxalic acid (1.5 mol%) were added, and the mixture was stirred at 100 ° C. for 1 hour. Next, vacuum distillation was performed while raising the temperature to 180 ° C., and water and unreacted phenol were distilled off to obtain lignin phenol resins A to C.

  Various physical properties of the lignin phenol resins A to C were evaluated and compared with a commercially available phenol resin D (manufactured by Sumitomo Bakelite, random novolak, weight average molecular weight: 7200). For evaluation of thermal fluidity, heat resistance, and bending strength, a sample obtained by adding 10 phr of hexamethylenetetramine (manufactured by Wako Pure Chemical Industries, Ltd.) to the resin and curing it was used.

<Heat fluidity evaluation (Pressure flow measurement)>
A sample (0.3 g) was placed between two steel plates heated to 150 ° C., and a load of 5000 kgf was applied and held for 4 minutes. The load was released, and the flat area of the sample that spread and solidified in a circle was measured.

<Heat resistance test>
Hold at 150 ° C. for 1 hour, further heat cure at 250 ° C. for 3 hours, take 10 mg of resin in an alumina container, heat up at 10 ° C./min, up to 30-1000 ° C. under nitrogen atmosphere The temperature was raised and the temperature at which the weight decreased by 5% from the initial weight (Td5) was measured.

<Measurement of softening point>
A 3 mg sample was taken in an aluminum container and measured using a thermomechanical measuring device (TMA-60: manufactured by Shimadzu Corporation), and the tangent intersection at the inflection point was defined as the softening point. The measurement conditions were 30 to 250 ° C., a heating rate of 5 ° C./min, a load of 1 kgf, and a nitrogen atmosphere.

<Measurement of bending strength>
20 volume% resin and 80 volume% calcium carbonate were mixed and cured to produce a molded body, and the bending strength was measured in accordance with JIS-K7171.
Table 2 shows the results of various physical property evaluations. Here, the lignin content is a value represented by (Lignin charge) / (Yield of lignin phenol resin) × 100.

  From the measurement results, it can be seen that the lignin phenolic resin in the present invention has a bending strength equal to or higher than that of the conventional phenolic resin, and the heat resistance is improved as compared with the conventional phenolic resin. The reason why the heat resistance is improved is considered that carbonization of the lignin phenol resin progressed more than the phenol resin.

<Production of friction material>
Resins A, B, and D obtained above were mixed with other materials at a blending ratio shown in Table 3 with a mixer to prepare a raw material mixture. This raw material mixture was thermoformed at a forming pressure of 50 MPa and a forming temperature of 150 ° C., and further subjected to a heat treatment at 250 ° C. for 3 hours to obtain the friction materials of Examples 1 and 2 and Comparative Example 1.

<Frictional property test>
A specimen of 13 mm × 35 mm × 10 mm was cut out from each of the produced friction materials, and a friction characteristic test was conducted with a 1/10 scale brake dynamometer in accordance with JASO-C406 (Examples 1 and 2 and Comparative Example 1). . Table 4 shows the measurement results of the minimum friction coefficient (minμ) and the second and third efficacy (130 km / h, 0.6 G) of the first fade.

  From the measurement results, the friction materials of Examples 1 and 2 were improved in comparison with the friction material of Comparative Example 1 in the lowest friction coefficient of the first fade, so that the conventional phenol resin was used by using lignin phenol resin as a binder. It can be seen that a friction material superior in friction performance (fading resistance) can be obtained as compared with the case where is used.

Claims (5)

A method for producing a friction material comprising a lignin phenol resin having a weight average molecular weight of 5000 or less as a binder,
Purifying lignin with one or more solvents selected from the group consisting of methanol, ethanol, acetone, and tetrahydrofuran to obtain lignin having a weight average molecular weight of 5000 or less, and the purified lignin, phenols, and aldehyde s and a step of manufacturing method of including friction Kosuzai be reacted to obtain a lignin phenol resin in the presence of an acid catalyst. The method for producing a friction material according to claim 1, wherein 20 to 200 parts by mass of the phenols and 1 to 80 parts by mass of the aldehydes are used with respect to 100 parts by mass of the purified lignin. The method for producing a friction material according to claim 1 or 2, wherein the lignin is at least one selected from the group consisting of coniferous lignin, hardwood lignin and herbaceous lignin. The manufacturing method of the friction material of any one of Claims 1-3 which contains 5-20 mass% of said binding materials with respect to the whole friction material. The manufacturing method of the friction material of any one of Claims 1-4 whose lignin content rate in the said binding material is 50-90 mass%.