JP2006045413A - Polyamide resin composition excellent in slidability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding material having excellent mechanical strength and sliding characteristics, particularly excellent friction and wear characteristics represented by a high limit PV value.
(A) A polyamide resin obtained from a mixed xylylenediamine composed of 15 to 45 mol% of paraxylylenediamine and 85 to 55 mol% of metaxylylenediamine and an α, ω-linear aliphatic dibasic acid, (B) contains a fibrous reinforcing material and (C) a solid lubricant, and (B) is 8 to 65% by weight, and (C) is based on the total weight of (A) + (B) + (C). A polyamide resin composition having an excellent sliding property of 8 to 30% by weight.
[Selection figure] None

Description

  The present invention relates to a polyamide resin composition having excellent slidability. Specifically, a polyamide resin composition having a high limit PV value, which is made of a thermoplastic resin material that has a relatively low melting point and is easy to mold, and is suitable for parts such as bearings, gears, and worms that require sliding resistance. Related to things.

In general, a highly slidable material made of a thermoplastic resin is preferably a material having a high melting point and high crystallinity so that melting due to frictional heat hardly occurs. In this sense, polyether ether ketone (PEEK), polyamide resin (9T nylon, 46 nylon), polyphenylene sulfide (PPS), polyacetal (POM) and the like are known as excellent thermoplastic resins for highly slidable materials. . Furthermore, it is also known to add a solid lubricant such as fluorine-based resin, graphite, or MoS ₂ to these resins to enhance their sliding performance.
However, when a fluorine-based resin and carbon fiber are added to the PPS resin, the wear resistance is improved, but there is a possibility of damaging a soft metal such as an aluminum alloy. A heat-resistant sliding bearing for a fixing device composed of a resin composition formulated with a polyamide resin is proposed, and the polyamide resin is selected from nylon 6, nylon 66, nylon 46, nylon 6T, polyamide MXD, and nylon 6 / 6T. In addition, it is described that a filler such as carbon fiber can be further added to the resin composition, but the blending amount of the filler is not described, and the effect thereof is specifically described. The composition shown is only a composition in which polytetrafluoroethylene (PTFE), which is a solid lubricant, is blended with the above polyamide resin. A composition in which a fibrous reinforcing material is further blended with a polyamide resin, for example, a polyamide MXD resin, shown in Reference 1, can reduce the friction coefficient when PTFE is blended as a solid lubricant, but the effect of improving the limit PV value is Small, sufficient sliding resistance was not obtained, and a resin material having a particularly high limit PV value was not obtained.

  Thermosetting resins and thermoplastic resins such as PEEK, polyimide (PI), and polyamideimide (PAI) are used as materials having a high limit PV value, but thermosetting resins have problems such as recyclability. Yes, it may not be preferable in consideration of environmental problems. PI resin cannot be molded by itself and is used like an organic filler. Avoiding the use of thermosetting resins, thermoplastic resins having a high melting point are required to have high heat resistance as a material to be added.

  On the other hand, in Patent Document 2 (Japanese Patent Laid-Open No. 7-41669), mixed xylylenediamine composed of 25 to 45 mol% of paraxylylenediamine and 75 to 55 mol% of metaxylylenediamine and α, ω-linear aliphatic are disclosed. A molding polyamide resin composition in which 0.1 to 10 parts by weight of talc as a nucleating agent or 10 to 150 parts by weight of a fibrous filler is blended with 100 parts by weight of a polyamide resin obtained from dibasic acid. Proposed. According to Patent Document 2, the polyamide MXD (polyamide resin obtained from metaxylylenediamine and α, ω-linear aliphatic dibasic acid) used in Patent Document 1 is compared with other polyamide resins. It exhibits high mechanical strength and elastic modulus, and also has a low water absorption, but has the disadvantage that the crystallization speed is slow and the molding cycle is long, and when polyamide 66 is kneaded to improve the crystallization speed of polyamide MXD, Inconveniences such as an increase in rate and a decrease in mechanical strength occur. The invention of Patent Document 2 aims to increase the crystallization speed of xylylene adipamide and improve moldability without causing such inconvenience. There is no description about slidability.

JP-A-9-177765 Japanese Patent Laid-Open No. 7-41669

  An object of the present invention is to provide a molding material having excellent mechanical strength and sliding characteristics, particularly excellent friction and wear characteristics represented by a high limit PV value.

  The present inventor has repeatedly studied to achieve the above object, and when a solid lubricant is added to a base resin using a mixed amine of metaxylylenediamine and paraxylylenediamine, the skin melting which is the first stage limit PV value Exceeds the friction coefficient, drastically decreases, maintains good slidability even when high load and high speed conditions are applied without further melting, and polyamide MXD, a similar material, is used as the base resin. As a result, the present invention has been achieved by finding a phenomenon that dramatically improves the limit PV value to 2 to 4 times that of the above case. That is, the gist of the present invention is obtained from (A) a mixed xylylenediamine composed of 15 to 45 mol% of paraxylylenediamine and 85 to 55 mol% of metaxylylenediamine and an α, ω-linear aliphatic dibasic acid. It contains a polyamide resin, (B) a fibrous reinforcing material, and (C) a solid lubricant, and (B) is 8 to 65% by weight based on the total weight of (A) + (B) + (C). C) is a polyamide resin composition having an excellent sliding property of 8 to 30% by weight.

  The composition of the present invention is excellent in mechanical properties such as strength and elastic modulus, and has excellent sliding properties represented by a high limit PV value. The composition of the present invention using a polyamide resin obtained from mixed xylylenediamine as a base resin has a high limit PV value and a low final friction coefficient that cannot be achieved by a composition using a polyamide MXD resin as a base resin. Can be achieved.

Hereinafter, the present invention will be described in detail.
The (A) polyamide resin used as the base of the composition of the present invention is a polyamide resin using a mixed diamine of paraxylylenediamine and metaxylylenediamine and an α, ω-linear aliphatic dibasic acid as raw materials. The mixing ratio is selected from the range of 15 to 45 mol% of paraxylylenediamine (P): 85 to 55 mol% of metaxylylenediamine (M), preferably in the range of P: M = 15: 85 to 36:64. It is.
Examples of the α, ω-linear aliphatic dibasic acid to be reacted with the mixed diamine include adipic acid, sebacic acid, suberic acid, dodecanedioic acid and the like, and preferably adipic acid.
The (A) polyamide resin used in the present invention preferably has a relative viscosity in the range of 2.0 to 4.0, more preferably 2.0 to 2.7. If the relative viscosity is too low (too low molecular weight), the physical properties of the resin are insufficient. On the other hand, if the relative viscosity is too high, molding is difficult, and it is difficult to produce a polyamide resin having a relative viscosity of more than 4.0. In the present specification, the relative viscosity of the polyamide resin is a viscosity measured using 96% sulfuric acid as a solvent and a solution having a resin concentration of 1 g / 100 ml.
The polyamide resin of the present invention may be mixed with other polyamide resins as long as the gist of the invention is not changed. Further, other thermoplastic resins may be mixed to form a polymer alloy. For example, it is preferable to mix with a nylon resin having a high melting point such as polyamide 46, 66, 66 / 6T, 9T, 66 or the like because the PV value is not lowered. Even if the resin has a low melting point, it may be alloyed with a modified polypropylene resin, polyethylene resin, or polyamide 12 for other purposes, for example, to improve chemical resistance, or polyamide 6, polyamide 6/66 or 66 for improving the surface appearance. / 6I, 6 / 6T6I alloy.

The (B) fibrous reinforcing material used in the present invention can be selected from a wide range of fibrous fillers known as resin reinforcing materials, preferably glass fibers, carbon fibers, wholly aromatic polyamides. Fibers, cellulose fibers, metal fibers, inorganic compound whiskers. The carbon fibers may be either PAN-based or pitch-based, and examples of the wholly aromatic polyamide fibers include aramid fibers. Examples of the metal fibers include metal fibers such as steel, SUS, brass and copper. Chopped strands and milled fibers are suitable for the shape, but in the case of reinforcing long fibers, these roving fibers may be used. Examples of the inorganic compound whisker include various inorganic compound whiskers such as potassium titanate, aluminum borate, gypsum, calcium carbonate, magnesium sulfate, sepiolite, zonolite, wollastonite, and needle-like ones.
In addition to these fibrous reinforcements, mica, talc, glass flakes, montmorillonite, swellable fluoromica minerals, calcium carbonate, barium sulfate, aluminum borate, kaolin, clay, plaster, etc. It is also possible to use a filler that is low and has no reinforcing effect for molding accuracy and surface smoothness.
(B) The fiber reinforcing material is particularly preferably glass fiber, carbon fiber, or aluminum borate whisker.
The glass fiber preferably has a fiber diameter of 3 to 27 μm, and the carbon fiber preferably has a fiber diameter of 5 to 15 μm.
(B) The fibrous reinforcing material may be subjected to a surface treatment for improving adhesion to the resin, or a convergence or sizing agent treatment for improving handling properties.
The blending amount of the (B) fibrous reinforcing material is 8% by weight or more and 65% by weight in the total composition (that is, the total weight of (A) the polyamide resin, (B) the fibrous reinforcing material and (C) the solid lubricant). It is as follows. If the blending amount of the fibrous reinforcing material is less than 8%, the reinforcing effect is small and the strength is insufficient, and if it is 65% or more, compounding becomes difficult, or the fluidity at the time of molding may be inferior and molding may be difficult.

As the solid lubricant (C) used in the composition of the present invention, all aromatic polyamide fibers such as fluorine resin, polyethylene and other polyolefin resins, graphite, carbon black, molybdenum disulfide, molybdenum trioxide, aramid resin, etc. , Silicone, copper-lead alloy, tungsten disulfide, calcium sulfate, magnesium sulfate, boron nitride powder, etc., especially fluorine-based resins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer, etc. Graphite, molybdenum disulfide, conductive or granular carbon black for pigment, aramid resin, boron nitride, and the like are preferable, and fluorine resin, conductive or pigment carbon black, graphite, and the like are more preferable.
The blending amount of (C) solid lubricant varies depending on the type of lubricant used, but the total weight of the entire composition (that is, (A) polyamide resin, (B) fibrous reinforcing material and (C) solid lubricant. 8) to 30% by weight, more preferably 9% to 30% by weight. When the blending amount of the solid lubricant is less than 8%, there is no effect of improving the limit PV value even though there is an effect of reducing the friction coefficient, and when it exceeds 30%, physical properties such as the strength of the entire composition are lowered, There exists a possibility that the performance of the molded article obtained from this invention composition may fall.

The composition of the present invention is required to contain the components (A), (B), and (C) described above, but other additives are added within a range that does not impair the characteristics of the composition of the present invention. Can do.
Specifically, it is preferable to add a nucleating agent to the composition of the present invention in order to increase the crystallization rate and improve the moldability. Examples of the nucleating agent include inorganic nucleating agents such as talc and boron nitride, but an organic nucleating agent may be added. The addition amount of the nucleating agent is 0.01 to 6 parts by weight, preferably 0.03 to 1 part by weight in the case of the organic nucleating agent or boron nitride with respect to 100 parts by weight of the (A) polyamide resin. When using a nucleating agent, it is 0.5-8 weight part, Preferably it is 1-4 weight part.
In addition, a release agent is preferably added to the composition of the present invention in order to improve releasability at the time of molding, and it is preferable to add a relatively large amount so as to have an effect of improving slidability. Specific examples of the release agent include long-chain aliphatic carboxylic acids having 14 or more carbon atoms such as stearic acid and palmitic acid and derivatives thereof (for example, esters, metal salts, amides, etc.), and higher aliphatic alcohols such as stearyl alcohol. And waxes such as low molecular weight polyethylene wax, silicone oil, silicone gum and the like.
In addition to the above, various additives generally used in polyamide resin compositions, for example, flame retardants, stabilizers, pigments, dyes, weather resistance improvers, and the like can be appropriately added as necessary.

  The method for producing the polyamide resin composition of the present invention is not particularly limited. Usually, a predetermined amount of the above-mentioned components (A) to (C) and other additives added as necessary are blended, and melt-kneaded. It is manufactured by doing. The melt kneading method may be any known method. For example, using a single-screw or twin-screw extruder, a Banbury mixer, or a similar device, all the materials may be put together from the root of the extruder and melt kneaded. Pellets can also be produced by a method of kneading with a fibrous reinforcing material that is side-feeded while being melted. Moreover, after pelletizing different types of compounds, pellet blending or a method of separately blending some powder components and liquid components may be used.

The present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.
The materials used in the following examples are as follows.
<Material>
* MXD6: Polyamide resin, trade name “Polyamide MXD6 # 6000”, manufactured by Mitsubishi Gas Chemical Co., Inc., a polyamide resin produced from metaxylylenediamine and adipic acid, melting point 243 ° C., relative viscosity 2.14.
* PA66: Polyamide resin, trade name “Zytel 101”, manufactured by DuPont, relative viscosity 3.0.
* MP mixed PA: polyamide resin, polycondensate of mixed xylylenediamine and adipic acid produced according to Production Example 1.

* Glass fiber: Trade name “CS03JAFT2”, product of Asahi Fiber Glass, chopped strand, fiber diameter 10 μm.
* PAN-based CF: carbon fiber, trade name “Pyrofil TR03NB”, manufactured by Mitsubishi Rayon Co., Ltd., fiber diameter 7 μm.
* Aluminum borate whisker: Trade name “Arborex D”, manufactured by Shikoku Kasei Kogyo Co., Ltd.

* PTFE: Polytetrafluoroethylene, trade name “Lublon L5F”, manufactured by Daikin Industries, Ltd.
* Graphite: Natural scaly graphite, manufactured by Nippon Graphite Co., Ltd., “Special CP”.
Conductive carbon; Furnace Black, trade name “Vulcan XC-72”, manufactured by Cabot Corporation.
* Talc: Nucleating agent, trade name “Micron White 5000A”, manufactured by Hayashi Kasei Co., Ltd.

[Production Example 1]
730 g of adipic acid was charged into a 3 liter flask equipped with a stirrer, thermometer, reflux condenser, raw material dripping device, heating device, etc., and the temperature inside the flask was raised to 160 ° C. in a nitrogen atmosphere. The acid was melted. Into the flask, 680 g of mixed xylylenediamine containing 30 mol% of paraxylylenediamine and 70 mol% of metaxylylenediamine was successively added dropwise over about 2.5 hours. During this period, the reaction was continued while maintaining the internal temperature always above the melting point of the product with stirring, and the temperature was raised to 270 ° C. at the end of the reaction. Water generated by the reaction was discharged out of the reaction system by a partial condenser. After completion of the dropwise addition, the reaction was continued for 1 hour at a temperature of 275 ° C. with stirring to complete the reaction. The product was removed from the flask, cooled with water and pelletized. The obtained aromatic polyamide (hereinafter referred to as “MP mixed PA”) has a melting point of 258 ° C., a crystallization temperature of 216 ° C., and a relative viscosity (resin concentration of 1 g / 100 ml in a 96% sulfuric acid solution) of 2. 0.08.

[Examples 1 to 4 and Comparative Examples 1 to 6]
Each component is weighed so that the composition shown in Table-1 is measured, and the components excluding the fibrous reinforcing material are blended with a tumbler and charged from the base of a twin-screw extruder manufactured by Toshiba Machine Co., Ltd. (trade name: TEM35B). After melting, glass fibers were side fed to form resin pellets. The temperature setting of the extruder was 280 ° C. up to the side feed part and 260 ° C. from the side feed part.
Using the resulting pellets, a sliding test ring having the shape shown in FIG. 1 was molded under the following conditions, and the slidability was evaluated by the following method.
1 has an outer diameter (L ₁ ) of 26 mm, an inner diameter (L ₂ ) of 20 mm, a thickness (t ₁ ) of 3 mm, a height (h ₁ ) of 15.3 mm, and a gate position (11 ) And an opening (13) having a height (h ₂ ) of 5 mm and a width (w ₁ ) of 6.3 mm at the lower end of the ring 90 ° along the circumference from the weld portion (12). Has been.

<Molding conditions>
* Molding machine: NS40 manufactured by Nissei Plastic Industry.
* Mold temperature controller: Cisco pressurized water type TARBO TD-u4 131H
* Cylinder temperature setting: 280 ° C uniformly, mold temperature controller setting: 130 ° C.
* Holding pressure: 12 seconds at 600 kgf / cm.
* Injection speed, injection pressure: 50% of equipment capacity.

<Slidability evaluation>
A sliding test was performed with a ring-to-ring using a Suzuki-type sliding tester. The counterpart material S45C (steel material) has the same shape as the ring, and the sliding surface was polished with Emery # 1200 and set on the lower side of the apparatus. The contact area of the ring is approximately 2 cm ² . The maximum load is 500 kgf. The rotation speed starts at 10 cm / sec. If there is no problem at the maximum load of 500 kgf (surface pressure: 250 kgf / cm ² ), the rotation speed is increased at this surface pressure until the melting is performed. The limit PV value was obtained by multiplying the condition speed and the surface pressure. The case where it did not melt for 2 minutes or more during the test was passed to a more severe condition.
The coefficient of friction is not stable at the initial light load and shows a high value, but becomes stable when the load is increased to some extent, and shows a low value while being stable near the limit PV value. Therefore, the coefficient of friction immediately before the limit PV value was measured and used as the “final coefficient of friction”.

  Moreover, the ISO tensile test piece was shape | molded using the pellet of each resin composition, and the tensile strength, the tensile elongation, and the tensile elasticity modulus were measured according to ISO527-112. The results are shown in Table-1.

  Comparing Comparative Examples 4 and 5, in a general glass fiber reinforced composition in which a reinforcing material is blended with a resin, depending on whether the base resin is MXD or MP mixed PA, the limit PV value and the final coefficient of friction are reached. It is clear that there is almost no influence. However, when Example 1 and Comparative Example 2 are compared with Example 2 and Comparative Example 3, respectively, in the case of a composition containing a solid lubricant, an example using MP mixed PA obtained from mixed xylylenediamine is used. Compared to the comparative example composition using polyamide MXD, the limit PV value is dramatically improved by 3 to 4 times, and the coefficient of friction near the final load is also halved, respectively. I understand. The compositions of Examples 3 and 4 using a solid lubricant other than PTFE also show sliding properties equivalent to those of Examples 1 and 2. In addition, the glass fiber reinforced polyamide resin composition of Comparative Example 6 in which an amount of talc that functions as a nucleating agent described in Patent Document 2 is blended is not improved in sliding characteristics.

  The polyamide resin composition of the present invention has excellent mechanical properties and a high limit PV value, is a material having a relatively low melting point and can be easily molded, and requires resin bearings, gears, worms and other sliding properties. It is suitable as a material for a molded product.

External view of the slidability test ring used in the examples

Explanation of symbols

11: Gate position 12: Weld part 13: Opening

Claims (7)

  (A) Polyamide resin obtained from mixed xylylenediamine and 15-45 mol% paraxylylenediamine and 85-55 mol% metaxylylenediamine and α, ω-linear aliphatic dibasic acid, (B) fiber And (C) a solid lubricant, and (B) is 8 to 65% by weight and (C) is 8 to 30% by weight based on the total weight of (A) + (B) + (C) % Polyamide resin composition excellent in slidability.   (A) The polyamide resin composition according to claim 1, wherein the α, ω-linear aliphatic dibasic acid of the polyamide resin raw material is adipic acid.   (B) The fibrous reinforcing material is at least one selected from glass fiber, carbon fiber, wholly aromatic polyamide fiber, cellulose fiber, metal fiber, and inorganic compound whisker. Polyamide resin composition.   (B) Whisker of at least one inorganic compound selected from glass fiber, carbon fiber and potassium titanate, aluminum borate, gypsum, calcium carbonate, magnesium sulfate, sepiolite, zonotlite and wollastonite The polyamide resin composition according to claim 3, wherein the polyamide resin composition is selected from needle-like crystals.   (C) Solid lubricant is fluorine resin, polyolefin resin, graphite, carbon black, molybdenum disulfide, molybdenum trioxide, wholly aromatic polyamide resin, silicone, copper lead alloy, tungsten disulfide, calcium sulfate, magnesium sulfate The polyamide resin composition according to claim 1, wherein the polyamide resin composition is at least one selected from boron nitride.   (C) The polyamide resin composition according to claim 5, wherein the solid lubricant is at least one selected from fluorine-based resin, carbon black, and graphite.   The polyamide resin composition according to claim 6, wherein the fluororesin is polytetrafluoroethylene.

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