JP2016160536A - Short fiber for polyamide composite and polyamide composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short fiber for polyamide composite good in adhesiveness with a polyamide resin while maintaining high heat resistance and high Young modulus which a polyparaphenylene terephthalamide fiber originally has and capable of enhancing mechanical strength and abrasion resistance of a fiber reinforced polyamide resin (polyamide composite).SOLUTION: There are provided a short fiber for polyamide composite consisting of a polyparaphenylene terephthalamide short fiber by cutting a fiber composite obtained by penetrating a solution obtained by dissolving a resin having a functional group capable of reacting with an amide group into a hydrophilic solvent or a solution obtained by aqueous emulsifying it into a polyparaphenylene terephthalamide fiber skeleton having moisture amount adjusted to be 15 to 200 wt.% and heat treating it with a predetermined length and a polyamide composite by melting and mixing the same.SELECTED DRAWING: None

Description

  The present invention relates to a short fiber for a polyamide composite material comprising a modified polyparaphenylene terephthalamide fiber, and more particularly, to a short fiber for a polyamide composite material capable of improving the mechanical strength and wear resistance of a polyamide resin composition. It is about.

  Polyparaphenylene terephthalamide (hereinafter referred to as PPTA) fiber is formed into a highly crystallized yarn by applying concentrated sulfuric acid as a solvent for polymer dissolution at the time of spinning to a liquid crystal state, and then applying shear by a die. It is known that concentrated sulfuric acid, which is a solvent, is neutralized by washing and alkali immediately after spinning, dried and heat-treated at 200 ° C. or higher, and then wound up as a filament (Patent Document 1). .

  PPTA fiber is a synthetic fiber having both high functionality such as high strength, high elastic modulus, high heat resistance, non-conductivity, and no rust, flexibility that is unique to organic fibers, and light weight. Because of these features, they are used as rubber reinforcement materials for automobiles, motorcycles, bicycle tires, automobile toothed belts, conveyors, etc., or optical fiber cable reinforcements and ropes. Furthermore, it is also applied to bulletproof vests, protective clothing such as work gloves and work clothes that are difficult to cut against blades, and fire-fighting clothes that use incombustibility.

  However, since PPTA fiber is chemically stable, it has a problem of poor adhesion to various resins. Therefore, in order to improve the adhesion between the aramid fiber and the resin, a method in which the aramid fiber is coated with an adduct of a polyamine compound and a glycidyl ether type epoxy resin (Patent Document 2), or a carbon having a Vicat softening point of 40 ° C. or higher. A method of coating with 2 to 4 olefinic copolymers (Patent Document 3) is known.

  In addition, in order to improve adhesion between resin and aramid fiber and improve mechanical properties such as abrasion resistance, polymers with polymer chains compatible with matrix resin are modified with carboxylic acid or acid anhydride. A method (Patent Document 4) is known in which a modified polymer and an aramid fiber having an amino group on the surface are blended into a matrix resin. Aramid fiber chopped fiber is suspended in a 20% by mass sodium hydroxide aqueous solution to perform surface treatment of the aramid fiber.

US Pat. No. 3,767,756 Japanese Patent Publication No. 1-01864 JP-A-4-050377 JP 2000-292861 A

  However, the methods described in Patent Document 2 and Patent Document 3 are not a method of reacting an adduct or an olefin copolymer with an aramid fiber, but a solution of an adduct or an olefin copolymer is applied to the surface of the aramid fiber or the Since the fiber is dipped in the solution and squeezed and then dried, there is a problem that the coating is not uniform. The method described in Patent Document 4 has a problem in that aramid fibers are surface-treated with a high-concentration alkaline aqueous solution and amino groups are generated on the fiber surface, so that the physical properties of the aramid fibers are likely to deteriorate.

  The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and maintain good heat resistance and high Young's modulus inherent in polyparaphenylene terephthalamide fiber, while maintaining good adhesion with polyamide resin, and fiber reinforced polyamide resin ( An object of the present invention is to provide a short fiber for a polyamide composite capable of improving the mechanical strength and wear resistance of the polyamide composite) and a polyamide composite formed by melt-mixing the short fiber.

  In order to solve the above problems, the present invention takes the following means.

(1) A resin having a functional group capable of reacting with an amide group in a polyparaphenylene terephthalamide fiber skeleton whose water content is adjusted to 15 to 200% by drying at 100 to 160 ° C. as a hydrophilic solvent A short fiber for polyamide composite material comprising a polyparaphenylene terephthalamide short fiber obtained by infiltrating a dissolved solution or an aqueous emulsion solution and cutting the fiber composite obtained by heat treatment into a predetermined length.

(2) The short fiber for a polyamide composite material according to (1), wherein the functional group capable of reacting is a carboxylic acid group, an acid anhydride group, or an isocyanate group.

(3) The short fiber for a polyamide composite material according to the above (1) or (2), wherein the resin having a functional group capable of reacting is a radical polymerizable resin.

(4) The short fiber for a polyamide composite material according to (3), wherein the radical polymerizable resin is an olefin, styrene, or acrylic resin.

(5) The short fiber bundle for polyamide composites in which 1 to 20% by mass of the fiber sizing agent is attached to the total weight of the short fibers for polyamide composite according to any one of (1) to (4) above. .

(6) A polyamide composite obtained by melt-mixing the short fiber for a polyamide composite material according to any one of (1) to (4) or the short fiber bundle for a polyamide composite material according to (5) above into a polyamide resin. Wood.

  According to the present invention, a PPTA short fiber in which a resin having reactivity with an amide group is introduced into a PPTA fiber skeleton has excellent adhesion to a polyamide resin while maintaining the inherent high Young's modulus and heat resistance of the PPTA fiber. ing. Since the PPTA fibers are uniformly dispersed in the polyamide resin during kneading, a polyamide composite material having excellent mechanical strength and wear resistance can be provided.

  The polyparaphenylene terephthalamide (PPTA) in the present invention is a polymer obtained by polycondensation of terephthalic acid and paraphenylene diamine, but a polymer obtained by copolymerizing a small amount of dicarboxylic acid and diamine can also be used. Or, the molecular weight of the copolymer is usually preferably 20,000 to 25,000.

  PPTA fibers are made by dissolving PPTA in concentrated sulfuric acid, extruding the viscous solution from a spinneret, spinning into air or water, neutralizing with an aqueous sodium hydroxide solution, and finally Is obtained by drying and heat treatment at 120 to 500 ° C.

  The short fiber for polyamide composite of the present invention is composed of PPTA short fiber obtained by cutting a PPTA fiber composite into a predetermined length. Initially, the manufacturing method of PPTA fiber and a PPTA fiber composite is demonstrated.

As a typical example of the production method of PPTA fiber, PPTA is dissolved in concentrated sulfuric acid to obtain a viscous solution of 18 to 20% by weight, and this is discharged from a spinneret and after being spun in air for a short time. Spin into water. At this time, it is preferable to set the shear rate during discharge of the die to 25,000 to 50,000 sec ⁻¹ . Thereafter, the fiber solidified in the spinning bath is neutralized with an aqueous sodium hydroxide solution, and then dried at 100 to 160 ° C., preferably for 5 to 20 seconds. In this way, the PPTA fiber is impregnated with a resin having a functional group that can react with an amide group. Subsequently, a solution in which a resin having a functional group capable of reacting with an amide group is dissolved in a hydrophilic solvent or an aqueous emulsion solution is applied to the PPTA fiber before the impregnation treatment, and then the bobbin is wound in a winding process. Winding and water-containing PPTA fiber composite are obtained. Furthermore, the PPTA fiber composite is obtained by unwinding from the bobbin and heat-treating the moisture content to be less than 15% by weight.

  The PPTA fiber composite described above maintains the crystal size of the PPTA fiber less than 50 angstroms while changing the heat treatment conditions at a temperature of 100 to 160 ° C., and has a moisture content of 15 to 200% by weight, preferably 20 It is obtained by impregnating a solution or emulsion containing PPTA fiber that maintains a state of ˜50% by weight and containing a resin having a functional group capable of reacting with the surface functional group of PPTA fiber (resin having a reactive activity). . It is desirable that the PPTA fiber does not have a history of drying after spinning to a moisture content of less than 15% by mass.

  When the crystal size of the PPTA fiber is 50 angstroms or more, it becomes difficult to penetrate the resin having reaction activity into the fiber skeleton. Further, if the moisture content is less than 15% by weight, it becomes difficult to permeate the resin having reactive activity into the fiber skeleton, and if the moisture content exceeds 200% by weight, the process of winding the fiber becomes difficult, resulting in a cost increase. Become.

  The resin having a functional group capable of reacting with an amide group is 0.1 to 10.0% by weight, preferably 0.2 to 5.0% by weight based on the fiber weight in which the moisture content of PPTA fiber is converted to 0%. % Impregnation and penetration. If the amount of penetration is small, the effect becomes insufficient.

  Resins having functional groups capable of reacting with amide groups include olefinic, styrenic, and acrylic resins such as radical polymerizable resins such as carboxylic acid groups and acid anhydrides as functional groups capable of reacting with surface functional groups of PPTA fibers. A compound having a physical group, an isocyanate group or the like can be obtained by grafting by a known method or by modifying by a known method. Or it is obtained by copolymerizing the monomer which comprises the said radical polymerizable resin, and monomers which have functional groups, such as said carboxylic acid group, an acid anhydride group, an isocyanate group, by a well-known method. Two or more resins having reactive activity can be blended.

  Examples of the olefin radical polymerizable resin include polyethylene, polypropylene, polybutylene, copolymers of these materials, and the like. Of these, polyethylene is preferable, and any of high, medium, and low density may be used. Examples of the styrene radical polymerizable resin include polystyrene, poly-α-methylstyrene, copolymers of these materials, and styrene-butadiene copolymers. Examples of the acrylic radical polymerizable resin include polyacrylic acid alkyl ester, acrylic acid alkyl ester-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-vinyl acetate copolymer. It is done.

<Resin having carboxylic acid group or acid anhydride group>
An example of a graft is addition to a polyolefin backbone. The graft polymer can be obtained by reacting an unsaturated carboxylic acid, a carboxylic acid anhydride, or an unsaturated carboxylic acid ester with a polyolefin such as polyethylene or propylene. Preferred acids, anhydrides, and esters include acrylic acid, methacrylic acid, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diethyl maleate, monoethyl maleate, di-n-butyl maleate , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, or monoesters of the dicarboxylic acid. In particular, maleic anhydride is preferred. The proportion of the graft monomer in the graft polymer is generally about 0.01 to 20% by mass, more preferably about 0.1 to 10% by mass, and particularly preferably about 0.2 to 5% by mass.
The copolymer is a copolymer of an α-olefin having 2 to 10 carbon atoms such as ethylene, propylene, and butene and an α, β-ethylenically unsaturated carboxylic acid, ester, or anhydride having 1 or 2 carboxyl groups. Obtained by polymerization. Preferred acids, anhydrides, and esters include diethyl maleate, monoethyl maleate, di-n-butyl maleate, maleic anhydride, maleic acid, fumaric acid, itaconic acid or monoesters of the dicarboxylic acids. . The proportion of the α-olefin component in the copolymer is about 75 mol% or more, and the proportion of the monomer having a carboxyl group is about 0.2 to 25 mol%.
Among the resins having the above functional groups, polyolefins grafted with dicarboxylic acid or dicarboxylic acid derivatives such as anhydrides or esters are preferred.

<Resin having an isocyanate group>
The resin having an isocyanate group is obtained by grafting or copolymerizing an isocyanate compound having a vinyl group and an isocyanate group in the molecule to the above-mentioned radical polymerizable resin, and disclosed in JP-A-11-035642 and the like. Resin to be used. Examples of the isocyanate compound include 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate, and the like.

  The resin having a functional group capable of reacting with an amide group is infiltrated into the PPTA fiber skeleton as a solution dissolved in a hydrophilic solvent or as an aqueous emulsion solution. As the solution, an aqueous solution or a solution dissolved in a mixed solution of water and a low-boiling organic solvent is used, and an aqueous solution is particularly preferable. As for the density | concentration in the solution of the resin which has the said functional group, 5-80 mass% is preferable, More preferably, it is 15-70 mass%. The emulsified solution preferably has a small particle size and a uniform particle size.

  When a resin having a functional group capable of reacting with an amide group is allowed to penetrate into the PPTA fiber skeleton, it may be used by being included in an oil agent or may be used in a separate step from the oil agent. Examples of the oil agent include general oil agents used for PPTA fibers, such as low molecular weight fatty acid esters having 18 or less carbon atoms, polyethers, and mineral oils.

  When a resin having a functional group capable of reacting with the surface functional group of PPTA fiber is used in an oil agent, it is preferably contained in the oil agent in an amount of about 20 to 60% by weight, more preferably 30 to 50% by weight. is there.

  A solution in which a resin having a functional group capable of reacting with an amide group is dissolved or emulsified, and a method of applying an oil containing the resin to PPTA fibers is not particularly limited, and any conventionally known method may be employed. For example, it is applied to the PPTA fiber by a method such as an immersion oiling method, a spray oiling method, a roller oiling method, or a guide oiling method using a metering pump.

  A solution in which a resin having a functional group capable of reacting with an amide group is dissolved or emulsified, or an oil containing the resin is infiltrated into the PPTA fiber skeleton to form a PPTA fiber composite, and then the PPTA fiber composite. Is wound on the bobbin in the winding process.

  The wound PPTA fiber composite is unwound from the bobbin and heat-treated to make the moisture content less than 15% by weight, more preferably less than 10% by weight. The conditions for the heat treatment are not particularly limited. For example, when heat treatment is performed at 80 to 300 ° C., preferably 100 to 250 ° C., the moisture content can be less than 15% by weight. This heat treatment improves the handleability of the PPTA fiber composite.

  A PPTA fiber composite into which a resin having a functional group capable of reacting with an amide group is introduced is cut into a predetermined length to obtain a polyamide composite short fiber made of polyparaphenylene terephthalamide short fibers. Moreover, the fiber bundle which added the fiber sizing agent to said PPTA fiber composite is cut | disconnected to predetermined length, and it is good also as a short fiber bundle for polyamide composites. Examples of the method for applying the sizing agent include a method of immersing in a sizing agent solution, a method of bringing a driving roller provided with a sizing agent into contact with a traveling PPTA fiber composite, and the like.

  The cutting method is not particularly limited, and the cutting can be performed using a known guillotine cutter or rotary cutter. Although it does not specifically limit about the fiber length to cut | disconnect, It is preferable that it is the range of 0.1-5.0 mm from the reinforcement effect of resin, and the workability at the time of mixing to resin, More preferably, it is 0. .2 to 5.0 mm.

  The polyamide composite material of the present invention is prepared by mixing the short fiber for polyamide composite material of the present invention with a polyamide resin and a blender, and then using a single screw extruder, a twin screw extruder, a multi-screw extruder, a Banbury mixer, etc. It can manufacture by throwing into a melt-kneader and melt-mixing. The short fiber for polyamide composite is excellent in melt kneadability, and the fibers are uniformly dispersed and arranged in the polyamide composite. The polyamide composite material is subjected to various moldings such as injection molding, extrusion molding, hollow molding, film molding, press molding and the like, and further, a secondary product is added as necessary to obtain a molded product.

  Polyamide resins include polycaproamide (nylon 6) resin, polyhexamethylene adipamide (nylon 66) resin, polyhexamethylene sebacamide (nylon 610) resin, polyhexamethylene dodecamide (nylon 612) resin, poly Dodecanamide (nylon 12) resin, polyhexamethylene terephthalamide (nylon 6T) resin, polyhexanemethylene isophthalamide (nylon 6I) resin, polycaproamide / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T) resin, Nylon such as polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T) resin, polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I) resin Fat and nylon copolymer resin, or modified resins of these resins. A blend of these resins may also be used. Among these, nylon 6 and nylon 66 are preferable in terms of mechanical properties.

  In the polyamide composite of the present invention, it is preferable to add 5 to 50% by mass of the short fiber for polyamide composite with respect to the total amount of the composite. Although the mechanical strength and wear characteristics of the composite material can be improved with the same addition amount as that of conventional short fibers, it is more preferable to add 15% by mass or more, and still more preferable to add 20% by mass or more. Moreover, when it adds at 50 mass% or less, the fluidity required for shaping | molding will not be lost.

  In the polyamide composite material of the present invention, a plasticizer, a pigment, a filler, a foaming agent, a crystal nucleating agent, a lubricant, a processing aid, an antistatic agent, and an antioxidant are added as necessary without departing from the object of the present invention. An agent, an ultraviolet absorber, a flame retardant, an antibacterial agent, a heat stabilizer, a surfactant and the like can be blended. In addition, an adhesive may be blended in order to improve the adhesiveness between the polyamide composite short fibers and the polyamide resin as long as the object of the present invention is not impaired. Moreover, unless the object of the present invention is impaired, reinforcing fibers such as glass fiber, ceramic fiber, fluorine fiber, carbon fiber, and metal fiber may be blended.

  The polyamide resin has excellent physical properties in heat resistance, moldability, and electrical characteristics. Therefore, the molded article made of the polyamide composite material of the present invention can be suitably used for applications requiring high mechanical characteristics and wear characteristics, as well as electrical characteristics, and can be used for automobile parts, electrical insulating materials, sliding materials, etc. It is preferably used. For example, electrical / electronic parts such as connectors, plugs, arms, sockets, caps, rotors, motor parts, automobile parts, mechanical elements such as plates, bearings, gears, cams, pipes, bars, AV / OA equipment parts, bushes, washers, guides, pulleys, facings, insulators, rods, bearing cages, housings, bearings, rods, guides, gears, building parts and components, stoppers for construction equipment and building materials, guides, doors And other parts such as helmets, plastic model parts, tire core materials, fishing tackle reel parts, seals, packings, gland packings, and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only the following Examples. In addition, each measured value in an Example followed the following method.

(1) Water content About 5 g of the sample is weighed, heat-treated at 300 ° C. for 20 minutes, left at 25 ° C. and 65% RH for 5 minutes, and then weighed again. The moisture content used here is the dry base moisture content obtained by [weight before drying−weight after drying] / [weight after drying].

(2) Evaluation of tensile properties and bending properties of composite materials For test pieces cut out from molded products, the tensile strength and tensile modulus were measured by the method of ASTM D638, and the bending strength and flexural modulus were measured by the method of ASTM D790. did.

(3) Friction characteristics of composite material Using a Suzuki wear tester, the test conditions are 30 mm × 30 mm × 2 mm for the sample, S45C for the mating (ring) material, 200 mm ^{2 for} the ring area, and 0 for the test speed (circumferential speed). .15 m / sec, load 500 N, sliding distance 3 km, N = 3.
PV value: Conforms to JIS K 7218 (A method). When the PV value is obtained from the load and the peripheral speed condition, it is 375 (kPa · m / sec).
The amount of wear was the weight obtained by subtracting the weight (g) after friction from the weight (g) before friction.
The dynamic friction coefficient was calculated from the dynamic friction coefficient (μ) = friction torque (T) / load (N).

Example 1
Dissolve 1 kg of PPTA (molecular weight of about 20,000) obtained in the usual way in 4 kg of concentrated sulfuric acid and discharge from a die having 1,000 holes with a diameter of 0.1 mm to a shear rate of 30,000 sec ^−1. And after spinning in water at 4 ° C., it was neutralized with a 10 wt% aqueous sodium hydroxide solution at 10 ° C. for 15 seconds, and then dried at a low temperature of 110 ° C. for 15 seconds to obtain a moisture content. It was prepared to be 35% by weight of PPTA fiber before treatment (fineness of 1,670 dtex when converted to 0% by weight).

  An ethylene-maleic anhydride copolymer (maleic anhydride content: about 2% by mass, melting point: 108 ° C., melt flow rate: 25 g / 10 min) is used as a resin having functional groups capable of reacting with amide groups on this PPTA fiber. A water-based emulsion emulsified and dispersed in water is impregnated with 2.5% by mass (copolymer conversion) of the fiber when the moisture content is converted to 0% by weight, impregnated into PPTA fiber, and then bobbed in the winding process. A PPTA fiber composite having a moisture content of 35% by weight was wound up.

  The obtained PPTA fiber composite is unwound from a bobbin, and 2.5% by mass of a urethane fiber sizing agent is added to the fiber when converted to a moisture content of 0% by weight. A continuous fiber chop with a fiber sizing agent was obtained by continuously cutting to 0 mm.

  80 parts by mass of nylon 66 resin pellets (Zytel (R) 101, manufactured by DuPont, USA) and 20 parts by mass of short fiber chops were mixed with a tumbler mixer and then kneaded using a twin screw extruder (cylinder temperature of about 270 ° C.). The pellets were produced by extrusion molding. A test piece (polyamide composite material) was produced by an injection molding machine using the produced pellet.

(Comparative Example 1)
A test piece made of nylon 66 resin with no short fiber chop added was prepared in the same manner as in Example 1.

(Comparative Example 2)
The PPTA fiber before treatment having a moisture content of 35% by weight obtained in Example 1 was the same as Example 1 except that the resin having a functional group capable of reacting with the surface functional group of the PPTA fiber was not permeated. The PPTA fiber having a moisture content of 6.9% by weight was obtained by this method.
Similarly to Example 1, after using the obtained PPTA fiber yarn to obtain a short fiber chop provided with a sizing agent, a test piece was prepared in the same manner as in Example 1.

  Table 1 shows the characteristics of the test pieces obtained in Examples and Comparative Examples.

  From the results shown in Table 1, the composite material obtained by melt-mixing the short fiber chop of this example with nylon 66 resin is a composite in which a short fiber chop-free resin (Comparative Example 1) and a normal short fiber chop are melt-mixed. Compared to the material (Comparative Example 2), the tensile strength and bending strength were remarkably increased, and it was recognized that the wear characteristics were excellent.

  The reason why the mechanical strength and wear characteristics of the polyamide composite of the present invention are improved is not clear. However, by introducing a resin having a functional group capable of reacting with an amide group into the PPTA fiber skeleton, not only a short fiber having good adhesion to the resin can be obtained by the reaction of the amide group and the functional group. Further, it is presumed that an addition reaction or a crosslinking reaction occurs due to heat received when the short fibers are melt-mixed with the polyamide resin, and the mechanical strength of the polyamide composite is improved.

  The polyamide composite material of the present invention can be suitably used for applications such as automobile parts, portable equipment casings, sliding materials and the like.

Claims (6)

  A solution in which a resin having a functional group capable of reacting with an amide group is dissolved in a hydrophilic solvent in a polyparaphenylene terephthalamide fiber skeleton whose water content is adjusted to 15 to 200% by weight by drying at 100 to 160 ° C. Or the short fiber for polyamide composite materials which consists of the polyparaphenylene terephthalamide short fiber which cut | disconnected the fiber composite obtained by making the aqueous | water-based emulsion solution penetrate | infiltrated and heat-processing to predetermined length.   The short fiber for polyamide composite according to claim 1, wherein the functional group capable of reacting is a carboxylic acid group, an acid anhydride group, or an isocyanate group.   The short fiber for polyamide composite according to claim 1 or 2, wherein the resin having a functional group capable of reacting is a radical polymerizable resin.   The short fiber for polyamide composite according to claim 3, wherein the radical polymerizable resin is an olefin, styrene, or acrylic resin.   A short fiber bundle for polyamide composite material, wherein 1 to 20% by mass of a fiber sizing agent is attached to the total weight of the short fiber for polyamide composite material according to any one of claims 1 to 4.   A polyamide composite material obtained by melt-mixing the short fiber for a polyamide composite according to any one of claims 1 to 4 or the short fiber bundle for a polyamide composite according to claim 5 in a polyamide resin.