JP7263922B2 - Monomer cast polyamide resin composition for sliding member and sliding member - Google Patents

Description

TECHNICAL FIELD The present invention relates to a monomer-cast polyamide resin composition for sliding members and a sliding member containing the composition.

Polyamide resins are widely used as engineering plastics because of their excellent mechanical properties, heat resistance, oil resistance, and the like. Among such polyamide resins, a polyamide resin obtained by casting a monomer such as ε-caprolactam (hereinafter also referred to as "monomer cast polyamide" or "MC polyamide") has slidability compared to other polyamide resins. It is used as a material for sliding members such as bearings because of its excellent This MC polyamide sliding member may sometimes be used without a lubricant, but there are cases where sufficient lubricity cannot be obtained from the properties of the MC polyamide itself. In such a case, it is conceivable to add a general wax such as paraffin wax as a lubricant. This is because liquid lubricants such as paraffin oil are highly likely to bleed out, and it is common to use solid lubricant waxes that are less likely to bleed out. However, it is generally not easy to disperse paraffin wax in MC polyamide to impart good lubricity. be. That is, if a small amount of raw material with a small mold is produced, by increasing the curing speed and increasing the viscosity, the wax and ε-caprolactam can be polymerized before phase separation, so that a polyamide resin molded product can be molded. However, it is difficult to prevent phase separation under mass production conditions where the mold is large. Therefore, as a remedy, it has been proposed to use a combination of various waxes and add them to a sliding member composition containing ε-caprolactam, which is a monomer of MC polyamide (Patent Documents 1 to 6).

In Patent Document 1, three kinds of paraffin wax, stearone and Fischer-Tropsch wax are added to 100 parts by weight of poly-ε-caprolactam in an amount of 1 to 6 parts by weight each and a total of 5 to 12 parts by weight. Polyamide compositions are described. By containing the three kinds of waxes in an amount within a predetermined range, which is larger than in the past, it is possible to improve lubricity without causing deterioration in mechanical strength, separation of waxes, non-uniform dispersion, etc. It is

In Patent Documents 2 and 3, poly-ε-caprolactam is mixed with polyethylene wax, polyethylene wax having a terminal or side chain with a carboxyl group, or modified polyethylene wax having a terminal and/or side chain with a hydroxyl group or an epoxy group at a predetermined ratio. Dispersed and blended polyamide compositions and the like are described. In this way, by combining polyethylene wax, which is difficult to disperse by itself, with a specific modified polyethylene wax, the polyethylene wax can be uniformly dispersed without causing a decrease in mechanical strength, improving self-lubricating properties and wear resistance. It is said that it is possible to

In Patent Document 4, Fischer-Tropsch wax, microcrystalline wax or petrolum wax, and modified polyethylene wax having hydroxyl groups or epoxy groups at terminals and/or side chains are dispersed in poly-ε-caprolactam at a predetermined ratio, A polyamide composition and the like obtained by blending are described. In this way, by combining the three specific waxes, which are difficult to disperse by themselves, with the specific modified polyethylene wax, the three specific waxes can be uniformly dispersed and self-lubricated without causing a decrease in mechanical strength. It is said that it can improve durability and wear resistance.

In Patent Documents 5 and 6, microcrystalline wax with specific properties or polyethylene wax with specific properties, modified wax modified with acid or alcohol, and graphite are dispersed and blended in a predetermined ratio in ε-caprolactam. and a polyamide composition such as the one described above. In this way, by combining a specific modified wax with a specific wax that is difficult to disperse by itself, it is possible to uniformly disperse the wax, etc., and the monomer cast nylon has excellent lubricity and does not cause stick-slip phenomena. etc. can be obtained.

Japanese Patent Publication No. 62-34269 Japanese Patent No. 3015206 Japanese Patent No. 3419975 Japanese Patent No. 3419967 JP-A-2000-143976 JP-A-2000-143977

By using the above-described conventional techniques, it is not possible to obtain an MC polyamide having a certain degree of slidability by appropriately dispersing wax, which is difficult to disperse, in a molded body of a composition containing ε-caprolactam during mass production. However, there is still room for improvement. Accordingly, an object of the present invention is to disperse wax, which is difficult to disperse, in a molded body of a composition containing ε-caprolactam even during mass production, and thereby provide a sliding surface having good lubricity. An object of the present invention is to provide a monomer-cast polyamide resin composition for members and a sliding member containing the same.

In order to solve the above-mentioned problems, the present inventors have made extensive studies. First, a wax having good compatibility with ε-caprolactam is selected, and a composition containing this wax and ε-caprolactam (hereinafter sometimes referred to as a "monomer composition") and a cured product obtained by casting the monomer. A monomer composition and its MC molded body are prepared by using a wax that is difficult to disperse (hereinafter sometimes referred to as a "difficult-to-disperse wax") in a certain molded body (hereinafter simply referred to as an "MC molded body"). An attempt was made to disperse the difficult-to-disperse wax well. As a result, when urethane waxes and various modified waxes described in prior patent documents were used, these waxes could be dispersed in the monomer composition. However, such a modified wax affects the anionic polymerization of ε-caprolactam. was found to not polymerize ε-caprolactam.

In addition, when synthetic waxes other than modified waxes and natural waxes, which have good compatibility with ε-caprolactam, were investigated, even when synthetic waxes containing alkyl groups containing 16 to 19 methylene groups were used, these The synthetic wax was dispersible in the monomer composition. However, it has been found that it is difficult to uniformly disperse the hard-to-disperse wax in the monomer composition when it is used in combination with the hard-to-disperse wax.

As a result of further investigation, it was surprisingly found that when a urethane-based wax and a synthetic wax containing an alkyl group containing 16 to 19 methylene groups were used in combination with a difficult-to-disperse wax, the urethane-based wax was present. The difficult-to-disperse wax can be well dispersed in the monomer composition and its MC molded article without hindering the anionic polymerization of ε-caprolactam, and a molded article with good sliding properties can be mass-produced. With this knowledge, the present invention has been completed.

The first aspect of the present invention is ε-caprolactam, a urethane wax (A), a synthetic wax (B) containing an alkyl group containing 16 to 19 methylene groups, and waxes other than the waxes (A) and (B). The present invention relates to a monomer-cast polyamide resin composition for sliding members, which is a cured product of a monomer composition containing the wax (C) of No.

In embodiments of the present invention, the monomer composition may contain a total of 6 to 15 weight percent of said waxes (A)-(C) in the total monomer composition. In another embodiment, the monomer composition contains 1 to 10% by weight of the wax (A), 1 to 3% by weight of the wax (B), and 2 to 2% by weight of the wax (C) in the entire monomer composition. It may contain 10% by weight.

In an embodiment of the present invention, the wax (C) may be a petroleum wax. Further, in another embodiment of the present invention, the wax (C) may contain one having a melting point of 40 to 55°C. Further, the wax (C) may contain a wax (C) having a melting point of 40 to 55°C and a wax having a melting point higher than 55°C.

Embodiments of the present invention may contain an inorganic lubricant. Also, in another embodiment of the present invention, the monomer composition may contain 0.05 to 5% by weight of inorganic lubricant in the total monomer composition.

A second aspect of the present invention relates to a sliding member containing the above monomer-cast polyamide resin composition for sliding members.

A third aspect of the present invention relates to a bearing or gear including the aforementioned sliding member.

ADVANTAGE OF THE INVENTION According to the present invention, a sliding member that contains a wax that is difficult to disperse in a cured product of a monomer composition containing ε-caprolactam in a better dispersed state than in the past, thereby having good lubricity. It is possible to mass-produce a monomer-cast polyamide resin composition for use and a sliding member containing it. Moreover, this sliding member is suitable as, for example, a bearing.

4 is a graph showing temporal changes in friction coefficient and wear height in Example 1. FIG. FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 2; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 3; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 4; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 5; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 6; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 7; FIG. 10 is a graph showing temporal changes in friction coefficient and wear height in Example 8; FIG. 10 is a graph showing changes over time in coefficient of friction and wear height in Example 9. FIG. 4 is a graph showing temporal changes in friction coefficient and wear height of Reference Example 1. FIG.

Embodiments of the present invention will be described below.

The monomer-cast polyamide resin composition for sliding members according to the embodiment of the present invention (hereinafter sometimes simply referred to as "resin composition for sliding members") comprises ε-caprolactam, urethane wax (A), A cured product of a monomer composition containing a synthetic wax (B) containing an alkyl group containing 16 to 19 methylene groups and a wax (C) other than the waxes (A) and (B). This cured product may be a molded product.

The urethane wax (A) is not particularly limited as long as it contains a component having a urethane bond. A commercially available product can be used as such a urethane wax (A). For example, Nippon Seiro Co., Ltd.: NPS-6010, HAD-5150 and the like.

Synthetic wax (B) contains alkyl groups containing 16 to 19 methylene groups. That is, it is sufficient that the compound constituting the synthetic wax contains an alkyl group containing 16 to 19 methylene groups " _--CH.sub.2-- ". Alkyl groups may be linear, branched, or cyclic. When the alkyl group has a branched chain, it may contain 16 to 19 methylene groups in total.

The other structure of the compound constituting the synthetic wax (B) is not particularly limited as long as it has at least one such alkyl group. Examples of such compounds include esters artificially synthesized from alcohols and organic acids.

The alcohol constituting the ester with an organic acid may be a monohydric alcohol or a polyhydric alcohol having a valence of 2 or more. In the case of a polyhydric alcohol, at least one hydroxyl group should be condensed with an organic acid, but the number of remaining hydroxyl groups is preferably small, and it is more preferable that all hydroxyl groups are condensed with an organic acid. The number of methylene groups in the alcohol is not particularly limited as long as the organic acid condensed with the alcohol contains an alkyl group having a predetermined range of methylene groups. Conversely, if the organic acid does not contain an alkyl group having a range of methylene groups, the alcohol has at least one alkyl group containing 16 to 19 methylene groups.

Examples of alcohols that can form such esters include sugar alcohols and fatty alcohols. Examples of sugar alcohols include glycerin; tetritols such as erythritol and pentaerythritol; pentitols such as xylitol; hexitols such as sorbitol, galactitol and mannitol; The aliphatic alcohol may be monovalent or divalent or higher. Examples thereof include alkyl alcohols having 1 or more carbon atoms, alkylene glycols having 1 or more carbon atoms, and the like. Examples of alkyl alcohols having 16 to 19 alkyl groups include 1-heptadecanol (CH ₃ (CH ₂ ) ₁₆ OH), stearyl alcohol (CH ₃ (CH ₂ ) ₁₇ OH), 1-nonadecanol ( CH ₃ (CH ₂ ) ₁₈ OH), 1-eicosanol (CH ₃ (CH ₂ ) ₁₉ OH), 1-heneicosanol (CH ₃ (CH ₂ ) ₂₀ OH), octyldodecanol (2-octyldodecan- 1-ol, CH ₃ (CH ₂ ) ₉ CH((CH ₂ ) ₇ CH ₃ )CH ₂ OH) and the like.

Examples of the organic acid that constitutes an ester of an alcohol and an organic acid include, for example, a monocarboxylic acid represented by the general formula R—COOH, where R is a saturated aliphatic hydrocarbon group having 1 or more carbon atoms; Examples thereof include unsaturated aliphatic hydrocarbon groups having 2 or more carbon atoms. The number of methylene groups in R is not particularly limited as long as the alcohol to be condensed with the organic acid contains an alkyl group having a predetermined range of methylene groups. Conversely, if the alcohol does not contain methylene groups in the range specified, then R contains an alkyl group with 16-19 methylene groups. Examples of organic acids containing alkyl groups having 16 to 19 methylene groups include stearic acid (CH ₃ (CH ₂ ) ₁₆ COOH), n-nonadecanic acid (CH ₃ (CH ₂ ) ₁₇ COOH), and arachidic acid. (CH ₃ (CH ₂ ) ₁₈ COOH), n-heneicosanoic acid (CH ₃ (CH ₂ ) ₁₉ COOH), 2-octyldodecanoic acid (CH ₃ (CH ₂ ) ₉ CH((CH ₂ ) ₇ CH ₃ ) CH ₂ COOH) and the like.

Specific examples of esters of alcohols and organic acids include stearyl stearate, ethylene glycol distearate, and pentaerythritol tetrastearate.

The wax (C) may be any wax other than the waxes (A) and (B) described above, but it is a wax capable of improving the sliding properties of the MC molded body, which is a cured product of the monomer composition. is preferred. A wax that does not affect the polymerization reaction of ε-caprolactam is more preferable. Such waxes are generally hard-to-disperse waxes that are difficult to disperse in the monomer composition and its cured MC molding. Examples of such waxes include petroleum waxes, fluorine waxes, silicone waxes, synthetic hydrocarbon waxes, and the like. One or more of these may be contained. Among these, petroleum-based waxes and fluorine-based waxes are preferred, and petroleum-based waxes are more preferred.

Examples of petroleum waxes include paraffin wax, microcrystalline wax and petrolatum defined in JIS K 2235, as well as waxes containing isoparaffin as a main component. Those having a suitable melting point can be employed as these materials depending on the application. Paraffin wax is a wax that is separated and refined from vacuum distilled oil and is solid at room temperature, and contains normal paraffin, which is a linear hydrocarbon, as a main component. Microcrystalline wax is a wax that is solid at room temperature separated and refined from residual oil or heavy distillate from vacuum distillation, and contains more isoparaffin, which is a branched hydrocarbon, and cycloparaffin, which is a saturated cyclic hydrocarbon, than paraffin wax. . Therefore, it tends to have smaller crystals, a larger molecular weight, and a higher melting point than paraffin wax. According to the JIS standard, paraffin wax and microcrystalline wax are classified according to their melting points. It is classified into 4 types between 0°C and less than 87.8°C and 1 type at 87.8°C or higher. Petrolatum is a semi-solid wax at room temperature separated and refined from vacuum distillation residue oil. The melting point of petrolatum is 45-80°C.
These waxes can be commercially available. For example, Paraffin Wax-115, 120, 125, 130, 135, 140, 145, 150, EMW-0001, 0003, Hi-Mic-2095, 1090, 1080, 1070, 2065, 1045 manufactured by Nippon Seiro Co., Ltd. , 2045, and the like.

Examples of fluorine-based wax include polyethylene/PTFE wax and PTFE-modified polyethylene wax. Such waxes tend to have similar or higher melting points than microcrystalline waxes.

Examples of silicone waxes include graft copolymers composed of acrylic polymer and dimethylpolysiloxane. The melting point of such wax can be appropriately adjusted depending on the type of acrylic polymer and the like.

Examples of synthetic hydrocarbon wax include Fischer-Tropsch wax, polyethylene wax, polypropylene wax and the like.

The wax (C) preferably contains two or more waxes having different melting points. As a result, at the initial stage of sliding, the wax having a lower melting point melts quickly, and the sliding characteristics can be maintained better. In addition, after the initial stage of sliding, the wax having the higher melting point melts, and the two waxes can maintain the sliding characteristics better. Since the wax with the higher melting point does not act at the initial stage of sliding, the lubricating action tends to be maintained over a long period of time.

When waxes with different melting points are included, the wax on the lower melting point side preferably has a melting point of 40 to 55°C, more preferably 45 to 55°C. The wax on the high melting point side preferably has a melting point higher than 55°C, more preferably 80°C or higher.

When the wax (C) is solid, the size of the wax (C) in the resin composition for the sliding member is such that the sliding member exhibits good sliding properties and maintains good toughness and surface hardness of the sliding member. From the viewpoint, the average particle size is preferably 1 μm or more and 300 μm or less, more preferably 3 μm or more and 200 μm or less, and even more preferably 5 μm or more and 100 μm or less.

In the monomer composition, the total content of waxes (A) to (C) is 6 to 15% by weight in the entire monomer composition from the viewpoint of obtaining better sliding properties. is preferred. In addition, the content of the wax (A) is 1 to 10% by weight in the entire monomer composition from the viewpoint of better dispersibility of the wax (C) and better prevention of polymerization inhibition of ε-caprolactam. and more preferably 2 to 8% by weight. The content of the wax (B) is preferably 1 to 3% by weight in the entire monomer composition from the viewpoint of obtaining better sliding properties. The content of the wax (C) is preferably 2 to 10% by weight, more preferably 3 to 8% by weight, in the entire monomer composition.

The resin composition for sliding members according to the embodiment of the present invention contains monomer cast polyamide 6 (hereinafter sometimes referred to as “MC polyamide 6”) obtained by anionic polymerization of ε-caprolactam. This polyamide resin is called monomer cast nylon 6 or monomer cast nylon 6 and is known as polyamide (nylon) 6 for sliding members. Accordingly, the monomer composition may include, in addition to ε-caprolactam, alkali metal catalysts, co-catalysts, etc. to effect anionic polymerization. Further, if necessary, a dispersant may be included for better dispersing the wax (C). Examples of alkali metal catalysts include ε-caprolactam Na salt, ε-caprolactam K salt, ε-caprolactam Li salt, ε-caprolactam MgBr salt, and ε-caprolactam MgCl salt. A promoter functions as an initiator and includes, for example, acyl lactams, acid chlorides, isocyanates, carbonates, esters, urea, and the like. Examples of isocyanates include hexamethylene diisocyanate. Examples of dispersants include cationic surfactant-type dispersants, anionic surfactant-type dispersants, amphoteric surfactant-type dispersants, polymer-type dispersants, and the like. However, it is of course possible to use one that does not affect the polymerization reaction. The amount of ε-caprolactam, alkali metal catalyst and co-catalyst to be added can be appropriately selected depending on the type of catalyst and co-catalyst in consideration of obtaining a stable polymer. For example, when the alkali metal catalyst is ε-caprolactam Na salt and the co-catalyst is hexamethylene diisocyanate, the ε-caprolactam Na salt is 0.15 to 2 mol%, hexamethylene diisocyanate per 100 mol% of ε-caprolactam. is preferably 0.1 to 1 mol %.

The resin composition for sliding members according to the embodiment of the present invention may contain an inorganic lubricant. Since the inorganic lubricant functions as a crystal nucleating agent when ε-caprolactam crystallizes, the compressive elastic modulus can be further improved, the toughness can be further improved, and the wear resistance can be further improved. can be improved. Examples of inorganic lubricants include layered silicate, boron nitride, graphite, synthetic graphite (artificial graphite), molybdenum disulfide, and tungsten disulfide. Examples of layered silicates include talc, mica, kaolinite, halloysite, chlorite, smectite (montmorillonite, hectorite, etc.). Examples of graphite include scale-like graphite, scale-like graphite, earthy graphite, and the like. Among these, graphite and artificial graphite are preferred, and graphite is particularly preferred. In particular, when graphite is included, it is considered that, in addition to interlaminar slippage of graphite, softened and melted wax is adsorbed to graphite to form a good wax-adsorbed graphite-rich transfer film on the sliding surface. Further, graphite is desirable in terms of facilitating crystallization when MC polyamide 6 melts and solidifies while maintaining the sliding properties of wax. Further, when the composition according to the embodiment of the present invention is used for bearings, gears, etc., the grease or oil applied to the bearing or the gear is adsorbed to the graphite of the composition according to the embodiment of the present invention, thereby achieving good transfer. Formation of a film can also be expected. The size of the inorganic lubricant may be any size as long as it can be uniformly dispersed in ε-caprolactam, and may be approximately 50 μm or less.

1 type of inorganic lubricants may be contained, and 2 or more types may be contained. From the viewpoint of the toughness of the resin composition for sliding members, the content of the inorganic lubricant is preferably more than 0% by weight and not more than 10% by weight, and is 0.05 to 10%. % by weight is more preferred, and 2 to 5% by weight is even more preferred. In addition, if the molded body of the resin composition for sliding members has a size that is affected by distortion due to residual stress during molding, heat treatment (annealing) may be performed to release the residual stress. . When such heat treatment is performed, the wax may be eluted. In addition, when the amount of inorganic lubricant added is small, or when wax is eluted, the color of graphite added in a small amount becomes conspicuous, and the appearance may be impaired. Therefore, from the viewpoint of preventing such elution of wax and preventing deterioration of appearance due to inorganic lubricants, the content of inorganic lubricants is 0.05 to 10% by weight in the entire monomer composition. It is more preferable to be blended, and 0.05 to 5% by weight is even more preferable.

The resin composition for sliding members according to the embodiment of the present invention may contain other additives. Such additives include heat-resistant agents, reinforcing agents, flame retardants, impact-resistant agents, coloring agents, crystal nucleating agents, and the like. In particular, when the waxes (A) to (C) are solid, the reduction in surface hardness caused by the waxes (A) to (C) can be suppressed when the crystal nucleating agent is contained. When a reinforcing agent is contained, it is possible to improve mechanical properties and wear resistance when used as a sliding member. Examples of such reinforcing agents include cloths and canvases woven from short fibers, long fibers, and continuous fibers. The type of fiber may be either artificial fiber or natural fiber, and the amount added is not particularly limited as long as the amount added does not affect the polymerization of ε-caprolactam. Examples of artificial fibers include synthetic fibers such as aramid fibers, polyvinyl alcohol fibers, nylon fibers and fluororesin fibers; inorganic fibers such as glass fibers and carbon fibers; Examples of natural fibers include cellulose (plant) fibers such as cotton, hemp and flax.

The resin composition for sliding members includes, for example, ε-caprolactam, a catalyst, a co-catalyst, waxes (A) to (C), optional additives added as necessary, and the type of each component and the environment in the atmosphere. A sliding member resin composition containing the monomer-cast polyamide 6 can be obtained by adding in an amount and under conditions in a range that does not affect depolymerization, deformation, etc. after polymerization, taking humidity into account. In addition, in the monomer casting method, a molded product having a desired shape can be obtained by polymerizing a monomer in a desired casting mold. Then, the molded body can be used as a sliding member. The sliding member can also be obtained by subjecting the obtained molding to machining such as cutting. The resin composition for sliding members obtained by the monomer casting method is a molded product.

The resin composition for sliding members can be obtained, for example, by a monomer casting method as follows.

A monomer composition containing ε-caprolactam as a monomer, an alkali metal catalyst, a co-catalyst, waxes (A) to (C) and optional additives is mixed at a temperature equal to or higher than the melting point of ε-caprolactam, and the monomer composition is When it is injected into a mold at a temperature of 160 to 180° C., it cures in about several minutes to obtain a resin composition for sliding members as a molding.

Since the polymerization of ε-caprolactam is an anionic polymerization, in order to obtain a stable polymer, substances that inhibit the reaction, especially the amount of water contained in the system and the amount of unreacted acid remaining in the added wax, must be considered. It is important to. For example, since moisture and residual unreacted acid deactivate the alkali metal catalyst, it is conceivable to add an excessive amount of the alkali metal catalyst in anticipation of this deactivation. However, if too much is added, the molecular weight of the polymerized MC polyamide 6 will be low, and the polymer may be deformed when heat treated for the purpose of relaxing internal stress and improving crystallinity. be. Therefore, considering the effect of this moisture, 0.15 to 2 mol% of ε-caprolactam Na salt as a catalyst and 0.1 to 1 mol% of hexamethylene diisocyanate as a co-catalyst are added to 100 mol% of ε-caprolactam as a monomer. is the basic compounding ratio, and it is preferable to carry out the polymerization in the range of up to 5 times the basic compounding ratio for both ε-caprolactam Na salt and hexadiisocyanate.

The method of adding ε-caprolactam, ε-caprolactam Na salt, and hexamethylene diisocyanate is not particularly limited. ε-caprolactam Na salt and hexamethylene diisocyanate may each be dissolved in ε-caprolactam at a high concentration, and the amount of ε-caprolactam added may be adjusted to a predetermined amount, or (iii) mixture A solution of ε-caprolactam Na salt and ε-caprolactam adjusted to the desired concentration when mixed with a solution of hexamethylene diisocyanate and ε-caprolactam adjusted to the desired concentration when mixed. You may In this case, the method of adding the waxes (A) to (C) and optional additives is not particularly limited. In some cases, the desired amount may be added to either ε-caprolactam solution to achieve the desired concentration when made into the monomer composition.

The temperature conditions for the polymerization reaction can be appropriately selected within the above-mentioned temperature range according to the size of the molding of the composition for sliding members produced as a result of the polymerization reaction. The heating time can be appropriately selected according to the size of the compact and temperature conditions. For example, in the case of a cylindrical shape of φ50 mm, it is preferable to heat to 140° C. and then react at 160° C. to 180° C. for 2 hours. After completion of the reaction, the mixture is cooled to room temperature. Moreover, after the completion of the reaction, it is preferable to perform a heat treatment from the viewpoint of relaxation of internal stress, improvement of crystallinity, and the like.

MC polyamide 6 is known to exhibit excellent wear resistance, a small coefficient of friction, and excellent PV value characteristics. Therefore, in the sliding member resin composition containing MC polyamide 6 and waxes (A) to (C), the hard-to-disperse wax (C) is more uniformly dispersed in MC polyamide 6 than in conventional compositions. Therefore, it has better sliding properties than conventional sliding members containing MC polyamide 6.

The resin composition for sliding members according to the embodiment of the present invention has sliding properties superior to conventional ones, and is therefore suitable as a member constituting the sliding portion of the sliding member.

The surface hardness of the molded body or sliding member of the resin composition for sliding member according to the embodiment of the present invention is preferably 75 to 85 in Shore D from the viewpoint of functioning favorably as a sliding member. Surface hardness can be measured according to JIS K7215.

Examples of sliding members according to embodiments of the present invention include bearings, gears, piston rings, seal members, air conditioner tip seals, and the like. Of these, bearings and gears are preferred.

Hereinafter, embodiments of the present invention will be described more specifically based on examples.

(Example 1)
24 g of ε-caprolactam Na salt (manufactured by Biosynth) and 400 g of ε-caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in container A while purging with nitrogen, and heated to 110°C.

Hexamethylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.): 13 g, ε-caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.): 1300 g, NPS-6010 as wax (A) (manufactured by Nippon Seiro Co., Ltd., melting point 74 ° C.): 85 g, Excepal SS (manufactured by Kao Corporation, stearyl stearate) as wax (B): 30 g, Microcrystalline wax Hi-Mic-1080 (manufactured by Nippon Seiro Co., Ltd., melting point 84 ° C.) as wax (C): 85 g, was placed in container B and heated to 140°C.

After each heating temperature is reached, the raw materials in container A are put into container B, mixed so that the raw materials are uniformly mixed (at this time, a monomer composition is obtained), and this mixture is heated to 160 ° C. It was poured into a mold (with an inner diameter of 50 mm), held at 160° C. for 1 hour, and then cooled to obtain a cylinder-shaped mold body of the monomer-cast polyamide resin composition for sliding members. The cylindrical sliding member having an outer diameter of φ5.5 mm was obtained by cutting the obtained cylindrical forming mold having an outer diameter of φ50 mm. This sliding member was used as a test piece for the following evaluations.

(Examples 2 to 9)
A sliding member was obtained in the same manner as in Example 1 except that each raw material component was adjusted so as to have the composition shown in Table 1, and this sliding member was used as a test piece for the following evaluations.

(Reference example 1: Prototype scale)
2.5 g of ε-caprolactam Na salt (manufactured by Biosynth) and 40 g of ε-caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in container A while purging with nitrogen, and heated to 150°C.

Hexamethylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.): 1.5 g, ε-caprolactam (manufactured by Wako Pure Chemical Industries, Ltd.): 130 g, microcrystalline wax Hi-Mic-1080 (Nippon Seiro Co., Ltd.) as wax (C) Product): 20 g was placed in container B and heated to 150°C.

After each heating temperature was reached, the raw materials in container A were put into container B and mixed so that the raw materials were uniformly mixed (at this time, a monomer composition was obtained). The reaction was promoted so as not to cause phase separation between ε-caprolactam and the wax (C), and the mixture was stirred until the viscosity became high. After being held at 160° C. for 1 hour, it was cooled to obtain a cylinder-shaped body of the monomer-cast polyamide resin composition for sliding members. The cylindrical sliding member having an outer diameter of φ5.5 mm was obtained by cutting the obtained cylindrical forming mold having an outer diameter of φ50 mm. This sliding member was used as a test piece for the following evaluations.

(Reference example 2: Mass production scale)
Each raw material component was adjusted so as to have the composition shown in Table 1, and heated. After each heating temperature was reached, the raw materials in container A were put into container B and stirred until the viscosity increased, and in this state the mixture was injected into a mold (inner diameter 50 mm) at 160°C. When cooled after being held at 160°C for 1 hour, phase separation occurred, and about 10% of the upper part was in a liquid state containing a wax component, and the other part was a molded body of MC polyamide. contained almost no wax.

Each component used in Examples 2 to 9 in Table 1 is as follows.

[Wax B]
Unistar H-476: manufactured by NOF Corporation, pentaerythritol tetrastearate, 16 methylene groups,
Unistar E-275: manufactured by NOF Corporation, ethylene glycol distearate, 16 methylene groups,

[Wax C]
Hi-Mic-1090: manufactured by Nippon Seiro Co., Ltd., microcrystalline wax, melting point 88°C,
EMW-001: manufactured by Nippon Seiro Co., Ltd., wax containing isoparaffin wax as a main component, melting point 49°C,
Paraffin Wax-125: manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point 53 ° C.,

[Inorganic lubricant]
Graphite CPB3: manufactured by Chuetsu Graphite Co., Ltd., flake graphite,

(evaluation)
<Wax Dispersibility>
Whether or not phase separation between the wax phase and the MC polyamide had occurred was visually confirmed from the appearance of the molded product. A case where phase separation did not occur was indicated as "◯", and a case where phase separation occurred was indicated as "x".

<Friction wear test>
Using a pin-on-disk type friction and wear tester (auto pin disk APD-101 manufactured by Starlite Industry Co., Ltd.), changes over time in the coefficient of friction of the test pieces obtained in Examples 1 to 9 and Reference Example 1 were measured. It was measured. The test conditions were room temperature, dry conditions, a load of 1 MPa, and a sliding speed of 0.15 m/s. The mating material was stainless steel (SUS440C) having a polished surface roughness Ra of 0.07 μm. Evaluation results are shown in FIGS.

As shown in Table 1, the presence of the waxes (A) to (C) does not inhibit the anionic polymerization of ε-caprolactam, and the viscosity increases to some extent like the prototype scale of Reference Example 1. Since the wax can be well dispersed in the resin composition for a sliding member without being stirred to a maximum, it is suitable for mass production. Further, as shown in FIGS. 1 to 9, the sliding members of Examples 1 to 9 have sliding characteristics equal to or higher than those of the prototype level reference example.

(Examples 10-15)
After adjusting each raw material component so that it has the composition shown in Table 2, it was injected into a mold having a cavity that yields a molded body having the shape and dimensions shown in Table 2. A molding having a predetermined shape was obtained in the same manner as in Example 1. This molded body was evaluated as a test piece. In addition, each component in Table 2 is as described above.

(evaluation)
<Wax Dispersibility>
It was evaluated in the same manner as in Example 1.

<Elution of wax by heat treatment>
A thermocouple was placed at the center of each molded body, and after the temperature at the center reached 170°C, this temperature was maintained for 3 hours and then cooled at 20°C/h. After cooling, the presence or absence of elution of wax was visually confirmed. When no elution of wax was observed, it was evaluated as "absent", and when elution was observed, it was evaluated as "yes".

<Crystallization peak temperature>
After each molded body was kept at 260° C. for 5 minutes, the crystallization peak temperature was measured by a differential scanning calorimeter (DSC6220, manufactured by SII Nanotechnology Co., Ltd.) when the temperature was lowered at 10° C./min.

Table 2 shows the evaluation results and measurement results.

As shown in Table 2, for example, the larger the cooling strain after molding, the larger the size of the molded body, and when the heat treatment is necessary, for example, by containing a predetermined amount of inorganic lubricant such as graphite, heat treatment is performed. It can be seen that the wax can be prevented from eluting due to

Claims (10)

ε-caprolactam, urethane wax (A), synthetic wax (B) containing an alkyl group containing 16 to 19 methylene groups, and wax (C) other than the above waxes (A) and (B) A cured product of a monomer composition ,
The monomer composition contains 1 to 10% by weight of the wax (A), 1 to 3% by weight of the wax (B), and 2 to 10% by weight of the wax (C) in the entire monomer composition,
A monomer-cast polyamide resin composition for a sliding member , wherein the synthetic wax (B) is an ester of an alcohol and an organic acid . 2. The monomer-cast polyamide resin composition for a sliding member according to claim 1, wherein the monomer composition contains 6 to 15% by weight of the waxes (A) to (C) in total in the monomer composition. 3. The monomer cast polyamide resin composition for sliding members according to claim 1, wherein the wax (C) is a petroleum wax. The monomer-cast polyamide resin composition for sliding members according to any one of claims 1 to 3 , wherein the wax (C) contains one having a melting point of 40 to 55°C. 5. The monomer-cast polyamide resin composition for a sliding member according to claim 4 , wherein said wax (C) contains wax (C) having a melting point of 40 to 55° C. and a wax (C) having a melting point higher than 55° C. 6. The monomer-cast polyamide resin composition for sliding members according to any one of claims 1 to 5 , which contains an inorganic lubricant. 7. The monomer-cast polyamide resin composition for sliding members according to claim 6 , wherein the monomer composition contains 0.05 to 5% by weight of the inorganic lubricant in the entire monomer composition. A sliding member comprising the monomer-cast polyamide resin composition for sliding members according to any one of claims 1 to 7 . A bearing comprising the sliding member according to claim 8 . A gear including a sliding member according to claim 8 .

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