JP4461357B2 - Polyamide resin molded product with excellent slidability and heat resistance - Google Patents

Description

  The present invention retains the excellent strength, impact resistance and chemical resistance of polyamide resin molded products, has extremely excellent slidability and heat resistance, and has a coefficient of friction even after repeated sliding over a long period of time. The present invention relates to a polyamide-based resin molded product having excellent slidability and heat resistance.

Polyamide resins have high slidability due to their high crystallinity, but many studies have been made for a long time to obtain even better sliding properties. Solid lubricants such as molybdenum disulfide, graphite, and fluororesins Liquid lubricants such as oils, lubricating oils, and silicone oils are being investigated as major sliding improvers. (For example, plastic course [16] polyamide resin Nikkan Kogyo Shimbun (1970))
Plastic course [16] "Polyamide resin", Nikkan Kogyo Shimbun (1970)

  Of these sliding modifiers, solid lubricants are resins that have inherently excellent sliding properties, such as polyamide resins, and in order to further improve the sliding properties, it is necessary to add a large amount of solid lubricant. As a result, the toughness of the resulting polyamide resin is remarkably lowered, and the evaluation standard of molded articles for automobiles such as heat cycle cannot be satisfied. Moreover, since a large amount of expensive solid lubricant is blended, it is not economically preferable.

  On the other hand, liquid lubricants can impart highly effective slidability to resins such as engineering plastics in relatively small amounts, but in many cases, the compatibility with the base resin is poor, and the surface of the molded product has these liquid lubricants. In many cases, the resin products whose sliding properties have been improved with these liquid lubricants have limited applications. In particular, it is not preferable that the surface of the molded product is contaminated with oil or the like for use in contact with humans. For example, the solitary parameter (SP value) of nylon 66 resin is 12.7, and the SP value of silicone oil generally used as a liquid lubricant is 7.3. Thus, if the SP values of the two are greatly different, the compatibility is very poor, and it is not preferable that the silicone resin molded product is contaminated by silicone oil.

Further, when repeatedly sliding or sliding with a high load, the heat generated on the sliding surface is large, and the temperature may rise to nearly 200 to 300 ° C. In such high-temperature sliding, studies have been made to improve the limit PV value by adding glass fibers or carbon fibers to polyamide resin. (For example, Toray Technical Data “Torayca Pellet” Improvement of limit PV value by adding carbon fiber)
Toray technical data "Torayca pellet" (improvement of limit PV value by adding carbon fiber)

  However, there is a limit to increasing the slidability at high temperature by adding glass fiber or carbon fiber. When the heat generated during sliding approaches the melting point of the polyamide resin, the friction coefficient increases rapidly and the slidability deteriorates. And the material melts locally.

  The present invention was made against the background of the problems of the prior art and has extremely excellent heat resistance and sliding property while maintaining the excellent strength, impact resistance and chemical resistance of polyamide-based resin molded products. Also, it is an object to produce a polyamide resin molded product having low slidability and heat resistance that does not change the coefficient of friction even if the surface of the molded product is not polluted with oil etc. It is.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is (1) nylon 6 or nylon 66 as a polyamide resin having a melting point of 280 ° C. or less, a maleic acid-modified polyethylene resin as a compatibilizer, triallyl isocyanurate as a crosslinking aid, and a silicone structure as a silicone compound of 30% by weight. A molded article comprising a resin composition containing LDPE that has been graft polymerized or ether-modified silicone having a polyoxyalkylene structure introduced at the side chain or terminal, and at least the surface layer is formed by irradiating the molded part with an electron beam. A molded article having excellent sliding properties and heat resistance, characterized in that the part is crosslinked and the dynamic elastic modulus E ′ at 280 ° C. measured by dynamic viscoelasticity of the molded part is 0.1 MPa or more. is there.

  The polyamide resin molded product with excellent heat resistance and slidability according to the present invention has a very stable coefficient of friction when repeatedly slid, and has a stable coefficient of friction without melting of the molded item even when sliding at high loads. Is obtained. In addition, since the excellent toughness of polyamide resin is not impaired without contamination with oil, etc., parts such as various gears, guides and reels are used in the home appliance, AV equipment and office supplies fields, and gears and cams are used in the machinery and automobile fields. It can be used in a wide range of fields such as bearings, rollers, door check levers, sash guides, shoulder adjusters, etc., and contributes to the industry.

Hereinafter, the present invention will be described in detail.
The polyamide-based resin in the present invention has an acid amide bond (—CONH—) in the molecule. Specifically, ε-caprolactam, 6-aminocaproic acid, ω-enantolactam, 7-aminoheptanoic acid, Polymers or copolymers or blends obtained from 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone, etc., hexamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, meta Examples include polymers or copolymers or blends obtained by polycondensation of diamines such as xylylenediamine and dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. It is not limited.

The melting point (melting peak temperature determined in accordance with JIS K 7121) of the polyamide-based resin in the present invention is 280 ° C. or lower. In order to obtain a molded article having excellent slidability, the polyamide resin needs to be a crystalline polyamide resin having a melting point. The melting point is 280 ° C. or lower. When the melting point exceeds 280 ° C., it is necessary to mold at an extremely high temperature, and a special molding machine or the like is required. Further, the resin itself is not preferable because it is expensive. The lower limit of the melting point is not particularly limited as long as the elastic modulus at 280 ° C. measured by dynamic viscoelasticity measurement of the molded product is 0.1 MPa or more. Since processing requires a long time, 100 or more is preferable. In this respect, a polyamide-based resin having nylon 6, nylon 66, and nylon MXD6 as main constituent components is particularly preferable.
In the present invention, the polyamide resin preferably has a number average molecular weight of 7,000 to 30,000. A number average molecular weight of 7,000 or less is not preferable because the toughness is lowered. Moreover, if it is 30000 or more, fluidity | liquidity falls and it is not preferable.

  In the present invention, reinforcing polyamides can be blended with the polyamide-based resin. Reinforcing inorganic materials include fiber reinforcing materials such as glass fibers, carbon fibers, ceramic fibers and various whiskers, and powdery inorganic reinforcing materials such as silica, alumina, talc, kaolin, quartz, powdered glass, mica, and graphite. Can be mentioned. These reinforcing inorganic materials may be treated with a silane coupling agent as a surface treatment agent.

Examples of the various silicone compounds contained in the polyamide resin composition in the present invention include (1) to (4).
(1) A silicone compound having polyoxyalkylene introduced in the side chain or terminal. Specific examples include silicone compounds represented by the chemical formulas shown below.

(2) A silicone compound having a polyoxyalkylene introduced into the side chain or terminal and having an OH group (also referred to as a hydroxy group) at the terminal of the polyoxyalkylene. Specific examples include silicone compounds in which the alkyl group R ₂ in the chemical formulas [Chemical Formula 1] and [Chemical Formula 2] has an OH group.

  (3) A silicone graft thermoplastic resin in which a silicone structure is introduced into the thermoplastic resin by graft polymerization in an amount of 30% by weight or more. Specifically, it can be obtained by graft polymerization of a reactive polyorganosiloxane onto a thermoplastic resin. As the thermoplastic resin, various polyethylene resins, ethylene / olefin resins and the like are preferable, but the thermoplastic resin is not limited thereto.

  (4) A silicone compound having a functional group that reacts with a polyamide resin. Specifically, it is a silicone compound in which a part of the methyl group of polyorganosiloxane is substituted with a functional group such as an amino group, a hydroxyl group, a carboxyl group, an acid anhydride group or an epoxy group that reacts with the polyamide resin. The group is not limited to this.

  The compounding quantity of these silicone compounds is 0.1-10 weight part as a silicone compound single-piece | unit with respect to 100 weight part of polyamide-type resin compositions, Preferably it is 0.2-8 weight part.

  In the present invention, a compatibilizing agent may be added in order to improve the compatibility between the thermoplastic resin grafted with the silicone compound and the polyamide resin. When the thermoplastic resin is a polyethylene resin, it is preferable to add a maleic acid-modified polyethylene resin.

  The molded product comprising the polyamide-based resin composition in the present invention needs to crosslink at least the surface layer portion of the molded product by irradiating an electron beam. In order to promote the crosslinking of the molded product upon irradiation with an electron beam, a crosslinking aid can be added to the polyamide-based resin composition. Specific examples of the crosslinking aid include triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylallyl isocyanurate (TMAIC), trimethylolpropane trimethacrylate (TMPTA), trishydroxyethyl. Although polyfunctional compounds, such as isocyanuric acrylate (THEICA) and N, N'-m-phenylene bismaleimide (MPBM), can be illustrated, it is not limited to these. These crosslinking assistants can be used alone or in combination of two or more. The amount of the crosslinking aid is 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, based on 100 parts by weight of the polyamide-based composition. If it is 0.01 parts by weight or less, the crosslinking does not proceed and the crosslinking degree is lowered. On the other hand, if it is 10 parts by weight or more, not only the efficiency as a crosslinking aid is deteriorated, but also the physical properties of the polyamide-based resin are lowered, which is not preferable.

  A heat stabilizer can be blended in the polyamide resin composition of the present invention. The heat stabilizer is blended mainly for the purpose of preventing thermal deterioration of a compound having relatively poor thermal stability, such as a crosslinking aid, when kneading a polyamide resin, a crosslinking aid and other compounding agents. The hindered phenol-based heat stabilizer is not particularly limited.

  Specifically, 2,6-di-t-butyl-4-methylphenol (BHT), tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] Methane (manufactured by Ciba Geigy, Irganox (R) 1010), triethylene glycol-bis- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (manufactured by Ciba Geigy, Irganox (R) ) 245) and the like can be exemplified, but not limited thereto. These heat stabilizers can be used alone or in combination of two or more. The blending amount of the heat stabilizer is 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the polyamide-based composition. If it is 0.05 parts by weight or less, there is no effect as a heat stabilizer, and if it is 5 parts by weight or more, the efficiency as a heat stabilizer is poor and it is not economical.

  The composition molded into the molded article of the present invention includes a polyamide-based resin composition, a crosslinking aid and a stabilizer for promoting electron beam crosslinking, and a weather resistance improver used for ordinary polyamide resin compositions. Carbon black, copper oxide and / or alkali metal halide, and light or heat stabilizers such as phenolic antioxidants, phosphorus compounds, flame retardants, antistatic agents, pigments and dyes may be added.

  In the present invention, the molded product is excellent in heat resistance and slidability. The polyamide resin is a polyamide resin in which a silicone compound and, if necessary, additives such as reinforcing inorganics, crosslinking aids and heat stabilizers are blended. It is obtained by melt-kneading the composition. As the melting and kneading apparatus, there are a single screw extruder, a twin screw extruder, a pressure kneader and the like, and a twin screw extruder is particularly preferable.

  A molded product comprising the polyamide-based resin composition of the present invention is obtained by crosslinking at least the surface layer of the molded product by electron beam irradiation. The dose of electron beam irradiation varies depending on the type of the polyamide-based resin composition and the shape of the molded product, but is generally 30 to 400 kGy, and the minimum dose at which the desired molded product can be obtained is particularly preferable.

  The molded article made of the polyamide resin composition of the present invention is remarkably improved in heat resistance against heat generation during sliding due to crosslinking by electron beam irradiation. The degree of cross-linking of the molded product can be evaluated by the elastic modulus above the melting point. The degree of crosslinking of the molded product is such that the dynamic elastic modulus E ′ at 280 ° C. measured by a dynamic viscoelasticity measuring apparatus is 0.1 MPa or more, preferably 1 MPa or more. Since the molded product has a melting point of 280 ° C. or lower, the uncrosslinked molded product has a dynamic elastic modulus E ′ that suddenly drops near the melting point, eventually flows, and the dynamic elastic modulus E ′ cannot be measured. It becomes possible. Further, when the degree of crosslinking of the molded product is insufficient, the dynamic elastic modulus E ′ at 280 ° C. is reduced to 0.1 MPa or less.

  In general, the cross-linking by electron beam irradiation is most advanced in the surface layer portion of the molded product directly hit by the electron beam, and the degree of cross-linking gradually decreases in the inner layer portion and the back surface. For this reason, in the molded product, it is necessary to irradiate an electron beam onto a sliding portion to crosslink, or to irradiate with a dose necessary to sufficiently crosslink the entire molded product.

  The present invention retains the excellent strength, impact resistance and chemical resistance of polyamide resin molded products, and has excellent sliding properties at high temperatures, and the molded product surface is not contaminated with oil or the like for a long time. Thus, a polyamide-based resin molded product in which the friction coefficient does not fluctuate even when repeatedly sliding is obtained.

EXAMPLES Next, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited to these.
(Evaluation methods)
1. Melting point The polyamide resin sample was subjected to DSC measurement under the following conditions, and the melting point (melting peak temperature Tpm) was determined according to JIS K7121.
Device name: MacScience DSC3100
Bread: Aluminum bread (non-hermetic)
Sample weight: 4mmg
Measurement start temperature: 30 ° C
Temperature increase rate: 20 ° C./min.
Atmosphere: Argon

2. Tensile strength and tensile elongation Tensile strength and tensile elongation were measured according to ASTM D638.
3. Izod impact strength Izod impact strength was measured according to ASTM D256.

4). Coefficient of friction Evaluation of the coefficient of friction by repeated sliding was performed under the following conditions using the apparatus of FIG.
Evaluation sample: 2 mm flat plate Mating material: Delrin (R) 100 manufactured by DuPont
Mating material shape: 1/2 inch spherical molded product Total load: 500 gf
Sliding distance: 40 mm repetition 1000 times reciprocating speed: 30 cm / min
Measurement temperature: room temperature (25 ° C., 65% RH)
The coefficient of friction was evaluated by the average value of the coefficient of friction every 100 times in 1000 reciprocating slides.

5. Heat resistance Evaluation of heat resistance is done by placing an evaluation sample with a thickness of 3 mm on a hot plate at 280 ° C, placing a load of 630 gf from the top, taking out the sample after 1 minute, observing the molten state of the contact surface, and the appearance of melting Was evaluated in the following four stages.
◎: No surface melting, no change in surface state ○: Very little surface melting, almost no change in surface state ×: With surface melting, large change in surface state XX: There is considerable surface melting, drastic change in surface state Dynamic elastic modulus E '
The dynamic viscoelastic modulus E ′ was measured with a test piece obtained by cutting a test piece having a width of 4.0 mm and a thickness of 0.5 mm from a 2 mm-thick flat plate product using “Rheogel-E4000” manufactured by Toyo Sangyo Co., Ltd. The measurement was performed under the following test conditions. FIG. 2 shows a graph of (temperature) versus (dynamic viscoelastic modulus E ′) of the measurement example.
Frequency: 1Hz
Temperature rising rate: 3 ° C./min.
Temperature range; 30 ° C to 300 ° C

(Examples 1-2, Comparative Examples 1-3)
<Raw materials used>
NY6 (manufactured by Toyobo Co., Ltd., Toyobo Nylon T-850) and NY66 (manufactured by Asahi Kasei Co., Ltd., Leona 1700) as a polyamide resin, and a master pellet which is a thermoplastic resin in which a silicone structure is graft-polymerized as a silicone compound SP-350 (resin is LDPE, manufactured by Multibase Asia Co., Ltd.), ether-modified silicone that is a silicone compound having a polyoxyalkylene structure introduced in the side chain or terminal (manufactured by Dow Corning Asia Co., Ltd., Paintad (R)) 54), maleic acid-modified polyethylene resin (manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., MME001) as a compatibilizer, triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd., also referred to as TAIC) as a crosslinking aid, and heat stabilizer Hindered phenol heat stabilizer (Ciba Geigy Co., Ltd.) was used Irganox (R) B1171).

<Manufacture of evaluation samples>
In the production of the evaluation sample, each raw material was weighed at a ratio shown in Table 1, mixed with a tumbler, kneaded at a temperature of 270 to 290 ° C. with a twin screw extruder, pelletized, and then 2 mm or 3 mm with an injection molding machine. Evaluation samples such as ASTM dumbbells were molded. The cylinder temperature of the injection molding machine was 270 to 300 ° C., and the mold temperature was 60 ° C. About the evaluation sample with electron beam irradiation, the injection-molded molded article was irradiated on the following electron beam irradiation conditions.

<Electron beam irradiation conditions>
Electron beam irradiation was performed under the following conditions.
Electron beam irradiation device: manufactured by RDI, Dynamitron-type 5 MeV electron accelerator Irradiation conditions: voltage = 4.6 MeV, current = 20 mA
Irradiation dose: 60 kGy
The results are shown in Table 1.

  Comparative Example 1 has a high coefficient of friction at room temperature and no heat resistance. In Comparative Example 2, the coefficient of friction is significantly high. In Comparative Examples 3 and 4, the friction coefficient at normal temperature is good and low by blending a specific silicone compound. However, at a high temperature of 280 ° C., the molded product does not melt and retain its shape as indicated by the dynamic elastic modulus E ′ of 280 ° C. Therefore, when used at a high temperature, it is not used as a sliding part. On the other hand, in Examples 1 and 3, the coefficient of friction at room temperature is also excellent, and the dynamic elastic modulus E ′ at 280 ° C. becomes 2.2 to 2.3 MPa due to crosslinking of the surface layer portion of the molded product by electron beam irradiation. However, since it does not lose its shape by flowing due to melting, it can be used as a sliding part having high heat resistance. Further, a stable friction coefficient can be obtained even after 1000 times of sliding, and there is no contamination of the surface of the molded product with oil or the like. Example 2 uses nylon 66, while examples 1 and 3 use nylon 6, but as in examples 1 and 3, it can be used as a sliding part with high heat resistance. it can.

  The molded article made of the polyamide resin composition of the present invention has excellent sliding properties from room temperature to high temperature while maintaining excellent strength, impact resistance and chemical resistance. It can be used in a wide range of application fields, from “light sliding parts” to high use in machines and automobiles and “heavy sliding parts” that generate large amounts of sliding heat. It is.

Schematic diagram of a friction coefficient evaluation device by repeated sliding Example of measurement result of dynamic elastic modulus E '

Explanation of symbols

1. Load 2. Sliding material 3: Evaluation target material

Claims (1)

Nylon 6 or nylon 66 as a polyamide resin having a melting point of 280 ° C. or less, a maleic acid-modified polyethylene resin as a compatibilizing agent, triallyl isocyanurate as a crosslinking aid, and LDPE having a silicone structure of 30% by weight or more as a silicone compound. Or a molded article made of a resin composition containing an ether-modified silicone having a polyoxyalkylene structure introduced in the side chain or terminal, wherein at least the surface layer portion is crosslinked by irradiating the electron beam with the molded part, and the molded article A molded article excellent in slidability and heat resistance, wherein a dynamic elastic modulus E ′ at 280 ° C. measured by dynamic viscoelasticity of the part is 0.1 MPa or more.

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