JP2021195496A - Resin composition for sliding member - Google Patents

Abstract

To provide a sliding member which has exponentially improved slidability on a high-load sliding condition, and a polyamide resin composition which enables molding of the sliding member.SOLUTION: A resin composition for a sliding member includes a polyamide resin (A) having a melting point of 270-350°C, and N,N'-dialkyl benzenedicarboxylic acid amide (B) having an alkyl group having 2 to 28 carbon atoms.SELECTED DRAWING: None

Description

The present invention relates to a resin composition for a sliding member containing a polyamide resin as a main component.

Polyamide resin has excellent heat resistance and mechanical properties, and is used as a constituent material for many automobile parts. In particular, crystalline polyamide resin is used as a sliding member for gears, bearings, bearings of cams, etc. because it has good slidability in addition to mechanical properties.
In recent years, the replacement of metal materials with resin materials has been further promoted, and resin materials are required to have further improved performance. Even a sliding member using a polyamide resin is required to withstand frictional heat due to a high load and an environmental temperature such as an engine room. For example, Patent Documents 1 and 2 describe various sliding members on a polyamide resin. A method of blending a sex improver is disclosed.

Japanese Unexamined Patent Publication No. 2002-363404 Japanese Unexamined Patent Publication No. 2013-064420

However, the slidability improving agent may not have an sufficient improving effect, and a sliding member having further improved performance is required.
That is, an object of the present invention is to provide a sliding member whose slidability is dramatically improved under a high load sliding condition, and a polyamide resin composition capable of molding the sliding member.

As a result of diligent research to solve the above problems, the present inventors have found that when a specific compound is blended with a refractory polyamide resin, the slidability is improved, and the present invention has been reached.
That is, the gist of the present invention is as follows.
(1) It is characterized by containing a polyamide resin (A) having a melting point of 270 to 350 ° C. and an N, N'-dialkylbenzenedicarboxylic acid amide (B) having an alkyl group having 2 to 28 carbon atoms. Resin composition for sliding members.
(2) The resin composition for a sliding member according to (1), wherein the alkyl group in (B) has 18 carbon atoms and the benzenedicarboxylic acid is terephthalic acid.
(3) The resin composition for a sliding member according to (1) or (2), wherein the polyamide resin (A) is a semi-aromatic polyamide.
(4) The resin composition for a sliding member according to any one of (1) to (3), which further contains a slidability improving material (C).
(5) A sliding member obtained by molding the resin composition for a sliding member according to any one of (1) to (4) above.
(6) The sliding member is any one of a bearing, a gear, a cam, a mechanical seal end face material, a valve seat, a rod packing, a piston ring, a piston, an impeller, a vane, and a rotor (5). ).

According to the present invention, it is possible to provide a polyamide resin composition capable of forming a sliding member having excellent slidability while suppressing friction and wear even under high-load sliding conditions.

Hereinafter, the present invention will be described in detail.
The resin composition for a sliding member of the present invention comprises a polyamide resin (A) having a melting point of 270 to 350 ° C. and an N, N'-dialkylbenzenedicarboxylic acid amide having an alkyl group having 2 to 28 carbon atoms (A). B) is contained.

The polyamide resin (A) in the present invention needs to have a melting point of 270 to 350 ° C. Since the polyamide resin (A) has a melting point of 270 ° C. or higher, it has heat resistance, and the sliding surface of the obtained sliding member can withstand the frictional heat generated by friction. On the other hand, when the melting point of the polyamide resin (A) exceeds 350 ° C., the decomposition temperature of the amide bond is about 350 ° C., so that carbonization or decomposition may proceed during the melt processing.

Examples of the polyamide resin (A) constituting the resin composition include aliphatic polyamides, semi-aromatic polyamides, alicyclic polyamides, and copolymers thereof.
Specific examples of the aliphatic polyamide include polyamide 46 and the like.
Examples of the semi-aromatic polyamide include a polyamide composed of an aromatic dicarboxylic acid component and an aliphatic diamine component, and specific examples thereof include polyamide 4I (I: isophthalic acid), polyamide 6I, and polyamide 7T (T: terephthalic acid). ), Polyamide 8T, Polyamide 9T, Polyamide 10T, Polyamide 11T, Polyamide 12T and the like.
Specific examples of the alicyclic polyamide include polyamide 6C (C: 1,4-cyclohexanedicarboxylic acid), polyamide 7C, polyamide 8C, polyamide 9C, polyamide 10C, polyamide 11C, and polyamide 12C.
Further, as the copolymer, for example, when the number of carbon atoms of the diamine is 6, polyamide 6T / 6, polyamide 6T / 12, polyamide 6T / 66, polyamide 6T / 610, polyamide 6T / 612, polyamide 6T / 6I, polyamide 6T. / 6I / 66, Polyamide 6T / M5T (M5: Methylpentadiamine), Polyamide 6T / TM6T (TM6: 2,2,4- or 2,4,4-trimethylhexamethylenediamine), Polyamide 6T / MMCT (MMC: 4,4'-Methylenebis (2-methylcyclohexylamine)) and the like can be mentioned.
As the polyamide resin (A), these polyamides may be used alone, or a mixture of two or more kinds may be used.
In the present invention, as the polyamide resin (A), polyamide 46, polyamide 6T, polyamide 9T, polyamide 10T, and copolymers thereof are mentioned as suitable examples because of their high industrial versatility. Further, polyamide 6T, polyamide 9T, polyamide 10T, and their copolymers are more preferable because they are excellent in terms of high heat resistance and low water absorption, and polyamide 10T and its copolymer are particularly preferable.

In the present invention, the polyamide resin (A) preferably contains a monocarboxylic acid component as a constituent component. By containing the monocarboxylic acid component, the polyamide resin (A) can keep the amount of free amino groups at the ends low, and when it receives heat, the polyamide is decomposed and discolored due to thermal deterioration and oxidative deterioration. It can be suppressed. As a result, there is an effect that the mechanical properties are highly maintained.

The content of the monocarboxylic acid component is preferably 0.3 to 4.0 mol%, preferably 0.3 to 3.0 mol%, based on all the monomer components constituting the polyamide resin (A). Is more preferable, 0.3 to 2.5 mol% is more preferable, and 0.8 to 2.5 mol% is particularly preferable. By containing the monocarboxylic acid component within the above range, the polyamide resin (A) can suppress decomposition and discoloration due to thermal deterioration and oxidative deterioration when exposed to heat, and can reduce the molecular weight distribution during polymerization. In addition, the mold releasability during the molding process is improved, and the amount of gas generated during the molding process can be suppressed. On the other hand, when the content of the monocarboxylic acid component of the polyamide (A) exceeds the above range, the mechanical properties of the polyamide (A) may deteriorate. In the present invention, the content of the monocarboxylic acid component refers to the ratio of the monocarboxylic acid residue in the polyamide resin (A), that is, the monocarboxylic acid desorbed from the terminal hydroxyl group.

In the present invention, the molecular weight of the monocarboxylic acid is preferably 140 or more, more preferably 170 or more. When the molecular weight of the monocarboxylic acid (A) is 140 or more, the polyamide resin (A) suppresses decomposition and discoloration due to thermal deterioration and oxidative deterioration when exposed to heat, and improves mold releasability during molding. The amount of gas generated can be suppressed at the above temperature, and the molding fluidity can also be improved.
Examples of the monocarboxylic acid component include aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, and aromatic monocarboxylic acid, and among them, aliphatic monocarboxylic acid is preferable.
Examples of the aliphatic monocarboxylic acid having a molecular weight of 140 or more include caprylic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Of these, stearic acid is preferable because of its high versatility.
Examples of the alicyclic monocarboxylic acid having a molecular weight of 140 or more include 4-ethylcyclohexanecarboxylic acid, 4-hexylcyclohexanecarboxylic acid, and 4-laurylcyclohexanecarboxylic acid.
Examples of aromatic monocarboxylic acids having a molecular weight of 140 or more include 4-ethylbenzoic acid, 4-hexylbenzoic acid, 4-laurylbenzoic acid, 1-naphthoic acid, 2-naphthoic acid and derivatives thereof. ..
The monocarboxylic acid component may be used alone or in combination. Further, a monocarboxylic acid having a molecular weight of 140 or more and a monocarboxylic acid having a molecular weight of less than 140 may be used in combination.
In the present invention, the molecular weight of the monocarboxylic acid refers to the molecular weight of the raw material monocarboxylic acid.

In general, it is known that a polymer has a crystalline phase and an amorphous phase, and crystal characteristics such as a melting point are determined solely by the state of the crystalline phase. Since the terminal groups in the polymer are present in the amorphous phase, the melting point of the polyamide does not change depending on the presence or absence and type of the terminal groups. Since the monocarboxylic acid bonded to the end of the polyamide chain is also present in the amorphous phase, the melting point of the polyamide does not decrease due to the inclusion of the monocarboxylic acid.

The polyamide resin (A) can be produced by using a conventionally known heat polymerization method or solution polymerization method. Above all, the heat polymerization method is preferably used because it is industrially advantageous. The polymerization of the polyamide resin (A) is preferably carried out in an inert gas atmosphere by enclosing an inert gas such as nitrogen, carbon dioxide, or argon in a polymerization kettle. As a result, discoloration due to oxidative deterioration of the polyamide during polymerization can be suppressed, and at the same time, discoloration in the process after polymerization can be suppressed.

In the production of the polyamide resin (A), a polymerization catalyst may be used in order to increase the efficiency of polymerization. Examples of the polymerization catalyst include phosphoric acid, phosphorous acid, hypophosphorous acid or salts thereof, and the amount of the polymerization catalyst added is usually 2 mol% or less based on the total mol of dicarboxylic acid and diamine. Is preferable.

The resin composition for a sliding member of the present invention may be referred to as N, N'-dialkylbenzenedicarboxylic acid amide (B) (hereinafter, compound (B)) having an alkyl group having 2 to 28 carbon atoms. ) Is contained.
The alkyl group at the N-position and the N'-position of the compound (B) is a linear or branched alkyl group, and the number of carbon atoms thereof needs to be 2 to 28, preferably 10 to 24. It is more preferably 12 to 18, and particularly preferably 18.

The positional relationship between the two amide groups bonded to the benzene ring of compound (B) is not particularly limited, but when the polyamide resin (A) is a semi-aromatic polyamide, the benzene ring of the aromatic dicarboxylic acid component thereof. It is preferable that the positional relationship between the two amide groups to be bonded is the same from the viewpoint of compatibility between the compound (B) and the polyamide resin (A). That is, for example, when the polyamide resin (A) is the polyamide 10T, it is preferable that the two amide groups of the compound (B) are also in the para position. That is, the benzenedicarboxylic acid of the compound (B) is also preferably terephthalic acid, and examples of the particularly preferable compound (B) include N, N'-distearyl terephthalic acid amide.
Compound (B) may be used alone or in combination of two or more.

The compound (B) in the present invention can promote the crystallization of the polyamide resin (A). Therefore, the resin composition containing the polyamide resin (A) and the compound (B) can provide a sliding member having a high crystallinity of the polyamide resin (A) even when a molding method having a short molding cycle such as injection molding is used. Can be molded. By increasing the crystallinity of the polyamide resin (A), the slidability of the sliding member can be improved. Further, since the compound (B) can enhance the slidability of the polyamide resin (A) itself, it is also possible to exhibit the effect of combined use with the slidability improving material (C) described later.

The mass ratio of the polyamide resin (A) to the compound (B) in the resin composition for sliding members is not particularly limited, but the mass ratio (polyamide resin (A) / compound (B)) is 99/1 to 70 /. It is preferably 30, more preferably 97/3 to 80/20, and even more preferably 93/7 to 85/15. If the mass ratio deviates from the above range, the obtained sliding member may have an insufficient effect of improving slidability, or may have significantly reduced heat resistance and mechanical strength.

The resin composition for a sliding member of the present invention preferably further contains a slidability improving material (C). The slidability improving material that can be used in the present invention is not particularly limited, and for example, a polytetrafluoroethylene, a polytetrafluoroethylene / perfluoroalkoxyethylene copolymer, and a polytetrafluoroethylene / polyhexafluoropropylene copolymer are used. Fluororesin such as (high molecular weight) polyethylene, polyolefin such as polypropylene, polydimethylsiloxane, polymethylphenylsiloxane, amino-modified polydimethylsiloxane, epoxy-modified polydimethylsiloxane, alcohol-modified polydimethylsiloxane, carboxy-modified polydimethylsiloxane, fluorine Silicone such as modified polydimethylsiloxane, layered inorganic compounds such as graphite and molybdenum disulfide, glass fibers, inorganic fibers such as potassium titanate whisker, zinc oxide whisker, whisker borate, and organic fibers such as LCP fibers, aramid fibers, and carbon fibers. Inorganic particles such as fiber, alumina, talc, silica, metaphosphate, pyrophosphate, calcium phosphate, calcium hydrogen phosphate, barium phosphate, lithium phosphate, calcium metaphosphate, phosphate such as zinc pyrophosphate, spindle oil, Examples thereof include mineral oils such as turbine oils, machine oils and dynamo oils, and montanates such as calcium montanate. Among them, fluororesin, silicone, molybdenum disulfide, talc, phosphate, mineral oil, carbon fiber and montanate, which have a large effect of reducing the coefficient of friction and the amount of specific wear, are preferable. The slidability improving material (C) may be used alone or in combination.

The resin composition for a sliding member of the present invention may further contain other additives such as fillers and stabilizers, if necessary. Examples of the additive include pigments such as titanium oxide and carbon black, hindered phenolic antioxidants, sulfur-based antioxidants, light stabilizers, and antistatic agents.

A method for producing a resin composition by mixing a polyamide resin (A) and a compound (B) and, if necessary, further adding a slidability improving material (C) and other additives. The melt-kneading method is preferable, although it is not particularly limited as long as the effect of the obtained sliding member is not impaired. Examples of the melt-kneading method include a method using a batch kneader such as lavender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single-screw extruder, a twin-screw extruder and the like. The melt-kneading temperature is selected from the region where the polyamide resin (A) melts and does not decompose. If the kneading temperature is too high, not only the polyamide resin (A) but also the compound (B) may be decomposed. Therefore, with respect to the melting point (Tm) of the polyamide resin (A), (Tm-). 20 ° C.) to (Tm + 50 ° C.) is preferable.

As a method of processing the resin composition into various shapes, a method of extruding the molten mixture into a strand shape into a pellet shape, a method of hot-cutting and underwater-cutting the molten mixture into a pellet shape, and a method of extruding into a sheet shape are performed. Examples include a method of cutting and a method of extruding into a block and crushing into a powder shape.

The sliding member of the present invention is formed by molding the resin composition thus obtained.
Examples of the molding method of the sliding member of the present invention include an injection molding method, an extrusion molding method, a blow molding method, and a compression molding method, and the injection molding method is preferable from the viewpoint of mechanical properties and moldability. The injection molding machine is not particularly limited, and examples thereof include a screw in-line type injection molding machine and a plunger type injection molding machine. The resin composition heated and melted in the cylinder of the injection molding machine is weighed for each shot, injected into the mold in a molten state, cooled and solidified in a predetermined shape, and then taken out from the mold as a molded body. Is done. The resin temperature at the time of injection molding is preferably equal to or higher than the melting point (Tm) of the polyamide resin (A) and lower than (Tm + 50 ° C.).
When the resin composition is heated and melted, it is preferable to use sufficiently dried resin composition pellets. If the amount of water contained in the resin composition pellets is large, the resin composition pellets may foam in the cylinder of an injection molding machine, making it difficult to obtain an optimum molded product. The water content of the resin composition pellets used for injection molding is preferably less than 0.3 parts by mass and more preferably less than 0.1 parts by mass with respect to 100 parts by mass of the resin composition.

Since the sliding member of the present invention has excellent heat resistance and slidability, it is used for bearings of power equipment used for automobile parts and electric / electronic equipment, various gears, cams, bearings, end face materials of mechanical seals, valves of valves. It can be suitably used as a seat, a V ring, a rod packing, a piston ring, a rotating shaft / sleeve of a compressor, a piston, an impeller, a vane, a rotor, an oil seal and the like.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

1. 1. Measurement method The physical properties of the polyamide resin and resin composition were measured by the following methods.

(1) Melting point Using a differential scanning calorimeter (DSC-7 type manufactured by PerkinElmer), the temperature is raised to 360 ° C at a temperature rise rate of 20 ° C / min, held at 360 ° C for 5 minutes, and the temperature drop rate is 20 ° C / min. The temperature was lowered to 25 ° C., and after holding at 25 ° C. for 5 minutes, the top of the heat absorption peak when the temperature was raised again at a heating rate of 20 ° C./min was defined as the melting point (Tm).

(2) Specific wear amount Using an injection molding machine (J35AD manufactured by Japan Steel Works, Ltd.), the resin composition for the sliding member is used, the melting point of the polyamide resin (A) is Tm, the cylinder temperature (Tm + 25 ° C.), and the mold. Injection molding was performed under the condition of temperature (Tm-185 ° C.) to prepare a test piece of a sliding member having a size of 40 mm × 40 mm × 3 mm.
Using the obtained test piece, it is made of S45C steel with an outer diameter of 25.6 mm, an inner diameter of 20 mm, and a thickness of 15 mm by a Suzuki type friction and wear tester (EFM-III-E type manufactured by Toyo Baldwin Co., Ltd.) according to the JIS K7218 A method. The test was carried out using a cylindrical shape as a mating material under the conditions of a load of 0.05 kN, a friction distance of 3 km, and a peripheral speed of 0.5 m / s. From the difference W between the mass of the test piece before the test and the mass after the test, the specific wear amount of the test piece was calculated by the following formula. The specific wear amount is preferably 20 mm ³ / (km · kN) or less.
Specific wear amount = W / (specific weight of test piece x load x friction distance)

(3) Friction coefficient A test was conducted in the same manner as in (2) above to determine the friction coefficient.

(4) State of sliding surface The test was conducted by the same method as in (2) above, and the state of the sliding surface after the test was visually observed. The case where there is no change other than the formation of a dent due to wear on the sliding surface is marked with "○".

2. 2. Raw Materials The raw materials used in Examples and Comparative Examples are shown below.

(1) Polyamide resin (A)
-Polyamide resin (A-1, polyamide 10T)
4.70 kg of powdered terephthalic acid (TPA) as a dicarboxylic acid component, 0.32 kg of stearic acid (STA) as a monocarboxylic acid component, and 9.3 g of sodium hypophosphite monohydrate as a polymerization catalyst. The mixture was placed in a ribbon blender type reactor, sealed with nitrogen, and heated to 170 ° C. with stirring at a rotation speed of 30 rpm. Then, while keeping the temperature at 170 ° C. and the rotation speed at 30 rpm, 4.98 kg of 1,10-decanediamine (DDA) heated to 100 ° C. as a diamine component using a liquid injection device was added to 2 . Addition was made continuously (continuous liquid injection method) over 5 hours to obtain a reaction product. The molar ratio of the raw material monomer is TPA: DDA: STA = 48.5: 49.6: 1.9 (the equivalent ratio of the functional groups of the raw material monomer is TPA: DDA: STA = 49.0: 50.0). : 1.0).
Subsequently, the obtained reaction product was polymerized by heating in the same reaction apparatus at 250 ° C. and a rotation speed of 30 rpm for 8 hours in the same reaction apparatus to prepare a polyamide powder.
Then, the obtained polyamide powder was formed into strands using a twin-screw kneader, the strands were passed through a water tank to be cooled and solidified, and the strands were cut with a pelletizer to obtain polyamide resin (A-1) pellets. The melting point of the obtained pellet was 320 ° C.

-Polyamide resin (A-2, polyamide 9T)
Polyamide resin (A-2) pellets in the same manner as the polyamide resin (A-1) except that 4.57 kg of 1,9-nonanediamine (NDA) was used instead of 1,10-decanediamine (DDA). Got The melting point of the obtained pellet was 310 ° C.

-Polyamide resin (A-3)
As the polyamide resin (A-3), polyamide 6 (manufactured by Unitika Ltd., A1030BRL, melting point 225 ° C.) was used.

(2) Compound (B)
-Compound (B-1)
As compound (B-1), N, N'-distearyl terephthalic acid amide (TA-18 manufactured by Ueno Fine Chemicals Industry Co., Ltd.) was used.

-Compound (B-2, N, N'-distearyl isophthalic acid amide)
301.2 g of isophthalic acid chloride, 12 kg of tetrahydrofuran, 879.6 g of octadecylamine, and 375.4 g of triethylamine were placed in a reactor with a stirrer and heated to 60 ° C. with stirring under a nitrogen stream. Then, the temperature was maintained at 60 ° C., the mixture was stirred for 4 hours, 600 g of methanol was further added, and the mixture was stirred for 1 hour.
After the stirring was completed, the mixture was cooled to room temperature, the precipitated crystals were filtered off, and the obtained crystals were washed with 2 L of tetrahydrofuran and then 3 L of water at 60 ° C.
The obtained precipitate was placed in another reaction device with a stirrer, 10 L of chloroform was added, and the mixture was stirred at 60 ° C. for 2 hours under a nitrogen stream. After the stirring was completed, the mixture was cooled to 40 ° C., filtered off, and washed with chloroform and then with methanol to obtain compound (B-2).

(3) Sliding property improving material (C)
Polytetrafluoroethylene (manufactured by Asahi Glass Co., Ltd., L150J) was used as the slidability improving material (C).

(4) Other compounds (D)
-D-1: Ethylene bisstearic acid amide (manufactured by Mitsubishi Chemical Corporation, Slipax E)
-D-2: Butylbenzene sulfonic acid amide (manufactured by Tokyo Chemical Industry Co., Ltd.)

Example 1
97 parts by mass of the polyamide resin (A-1) and 3 parts by mass of the compound (B-1) were dry-blended and weighed using a loss-in-weight continuous quantitative feeder (CE-W-1 type manufactured by Kubota Co., Ltd.). It was supplied to the main supply port (base) of a twin-screw extruder (TEM26SS type manufactured by Toshiba Machine Co., Ltd.) having a screw diameter of 26 mm and an L / C50 in the same direction, and melt-kneaded. After the resin composition was taken into a strand shape from the die, it was cooled and solidified by passing it through a water tank, and it was cut with a pelletizer to obtain a resin composition pellet for a sliding member. The barrel temperature of the extruder was set (melting point −5 to + 15 ° C.), screw rotation speed 250 rpm, and discharge rate 25 kg / h.

Examples 2-5, Comparative Examples 1-4
The same operation as in Example 1 was carried out except that the composition of the resin composition for sliding members was changed as shown in Table 1, to obtain resin composition pellets for sliding members.

Various evaluation tests were conducted using the obtained resin composition pellets for sliding members. The results are shown in Table 1.

The resin composition of the example had a small amount of specific wear and a coefficient of friction, and the state of the sliding surface was also good. The resin composition of Example 3 is more slidable than the resin composition of Example 2 in which the compound (B) is used alone by using the compound (B) and the slidability improving material (C) in combination. It was excellent.
In the resin composition of Comparative Example 1, since the melting point of the polyamide resin (A-3) was less than 270 ° C., the sliding surface of the test piece was melted and deformed due to heat generation during the frictional wear test. Since the wear debris was melted without being detached from the test piece and pushed out of the sliding surface, the test piece had a small mass difference W before and after the test, and the specific wear amount was small.
Since the resin composition of Comparative Example 2 did not contain the compound (B), it was inferior in slidability.
In Comparative Examples 3 and 4, an amide compound such as ethylene bisstearic acid amide or butylbenzenesulfonic acid amide was used instead of the compound (B), but the slidability was not improved.

Claims (6)

A sliding member comprising a polyamide resin (A) having a melting point of 270 to 350 ° C. and an N, N'-dialkylbenzenedicarboxylic acid amide (B) having an alkyl group having 2 to 28 carbon atoms. Resin composition for. The resin composition for a sliding member according to claim 1, wherein the alkyl group in (B) has 18 carbon atoms and the benzenedicarboxylic acid is terephthalic acid. The resin composition for a sliding member according to claim 1 or 2, wherein the polyamide resin (A) is a semi-aromatic polyamide. The resin composition for a sliding member according to any one of claims 1 to 3, further comprising a slidable improving material (C). A sliding member, characterized in that the resin composition for a sliding member according to any one of claims 1 to 4 is molded. The fifth aspect of claim 5, wherein the sliding member is any one of a bearing, a gear, a cam, an end face material of a mechanical seal, a valve seat of a valve, a rod packing, a piston ring, a piston, an impeller, a vane, and a rotor. Sliding member.