JP2007231211A - Polyamide-based resin foam-molded product and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyamide-based resin foam-molded product remarkably improved in melt tension of the polyamide-based resin and dispersibility of polytetrafluoroethylene-containing powder, excellent in a foaming expansion rate with good moldability in foam molding, and the polyamide-based resin foam-molded product produced by the method. <P>SOLUTION: The polyamide-based resin foam-molded product is produced by preparing a mixture comprising 100 pts.mass (A) polyamide-based resin with 0.5-10 pts.mass (B) polytetrafluoroethylene-containing mixed powder containing polytetrafluoroethylene particles and an organic polymer and 0.1-10 pts.mass (C) foaming agent, feeding the mixture into an extruder, melting, kneading and foam-extruding the mixture. The polyamide-based resin foam-molded product produced by the method is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a polyamide-based resin foam molded article having improved foam moldability, and a foam molded article obtained by this production method.

Polyamide resins are widely used as engineering plastics due to their excellent physical properties, but most of them are used for injection molding. In order to obtain a wider variety of polyamide resin molded products, application to molding by blow molding, extrusion molding, foam molding or the like is desired. However, the polyamide resin generally has a low melt tension, which is most important in applying these molding methods. For this reason, it is difficult to obtain a molded product having a desired shape by a molding method other than injection molding, such as that drawdown is severe during blow molding or extrusion molding, and uniform cells cannot be obtained by foam molding.
As this improved method, a method using a high polymerization degree polyamide resin having a high intrinsic viscosity, a method using a branched polyamide resin, a method of blending with another thermoplastic resin, a method of adding a filler, etc. have been proposed. , Both have little improvement effect.

Patent Document 1 proposes that polytetrafluoroethylene is blended with a thermoplastic resin such as a polyamide resin to improve moldability. However, polytetrafluoroethylene is not dispersible with respect to general thermoplastic resins containing no halogen atom, and this method requires a large amount of polytetrafluoroethylene to improve moldability and There was a drawback that the surface appearance of the molded article was impaired.
Patent Document 2 proposes improving the melt tension and improving the blow moldability by blending a polytetrafluoroethylene-containing powder having a specific structure with a polyamide resin. However, this document only describes blow moldability, and does not disclose effects on other molding methods.
On the other hand, in recent years, molding in which a foaming agent is added for the purpose of reducing the weight of the material has attracted attention. However, conventional polyamide resin foam molding is mainly performed by injection molding, and technical development by other molding methods is desired.
Japanese Patent Laid-Open No. 3-183524 JP 2000-290497 A

  An object of the present invention is to provide a polyamide-based resin foam molded article having significantly improved melt tension of the polyamide-based resin and dispersibility of the polytetrafluoroethylene-containing powder, good moldability in foam molding, and excellent foaming ratio. It is to provide a manufacturing method. Another object of the present invention is to obtain a foamed molded article having an excellent foaming ratio.

  The present invention relates to polytetrafluoroethylene-containing mixed powder (B) 0.5 to 10 parts by mass containing polytetrafluoroethylene particles and an organic polymer with respect to 100 parts by mass of the polyamide-based resin (A), and This is a method for producing a polyamide-based resin foam molded article in which a mixture containing 0.1 to 10 parts by mass of a foaming agent (C) is supplied into an extruder, melt-kneaded, and foam-extruded. Moreover, this invention is a polyamide-type resin foaming molding obtained by this manufacturing method.

According to the present invention, the melt tension of a polyamide resin and the dispersibility of a polytetrafluoroethylene-containing powder are remarkably improved, the moldability in foam molding is good, and the production of a polyamide resin foam molded article having an excellent expansion ratio is achieved. It is possible to obtain a foamed molded article having excellent foaming ratio.
In addition, the polyamide-based resin foam molded article of the present invention has a low specific gravity, and is excellent in surface properties of the obtained molded product and can be reduced in weight. Therefore, it is used for various applications such as automobiles.

Examples of the polyamide resin (A) used in the present invention include all melt-moldable polymers composed of amino acid lactam or diamine and dicarboxylic acid. Specifically, the following resins (1) to (3) can be exemplified.
(1) A polycondensate of an organic dicarboxylic acid having 4 to 12 carbon atoms and an organic diamine having 2 to 13 carbon atoms, for example, polyhexamethylene adipamide, which is a polycondensate of hexamethylenediamine and adipic acid ( 6,6 nylon), polyhexamethylene azelamide (6,9 nylon) which is a polycondensate of hexamethylene diamine and azelaic acid, polyhexamethylene sebacamide which is a polycondensate of hexamethylene diamine and sebacic acid (6,10 nylon), polyhexamethylene dodecanoamide (6,12 nylon) which is a polycondensate of hexamethylenediamine and dodecanedioic acid, polycondensate of bis-P-aminocyclohexylmethane and dodecanedioic acid Polybis (4-aminocyclohexyl) methane dodecane.
(2) Polyundecanamide (11 nylon) which is a polycondensate of ω-amino acid, for example, a polycondensate of ω-aminoundecanoic acid.
(3) A ring-opening polymer of lactam, such as polycapramide (6 nylon) which is a ring-opening polymer of ε-aminocaprolactam, polylauric lactam (12 nylon) of ε-aminolaurolactam.

Among the above, 6,6 nylon, 6,9 nylon and 6 nylon are preferably used.
In the present invention, for example, a polyamide-based resin produced from adipic acid or isophthalic acid and hexamethylenediamine can also be used. Furthermore, the thing which mixed 2 or more types of polyamide-type resin like the mixture of 6 nylon and 6, 6 nylon can also be used.
The polyamide-based resin (1) can be produced, for example, by polycondensing an organic dicarboxylic acid having 4 to 12 carbon atoms and an organic diamine having 2 to 13 carbon atoms in an equimolar amount.
Specific examples of the organic dicarboxylic acid include adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid and the like. Specific examples of the organic diamine include hexamethylene diamine and octamethylene diamine.
Further, the polyamide-based resin (1) can also be produced from a derivative capable of producing a carboxylic acid such as an ester or an acid chloride and a derivative capable of producing an amine such as an amine salt in the same manner as the above method. .
The polyamide-based resin (2) can be produced, for example, by heating and polycondensing an ω-amino acid in the presence of a small amount of water. A small amount of a viscosity stabilizer such as acetic acid may be added during polycondensation.
The polyamide-based resin (3) can be produced, for example, by heating lactam in the presence of a small amount of water to cause ring-opening polymerization. In this case, a small amount of a viscosity stabilizer such as acetic acid may be added.

The polytetrafluoroethylene (hereinafter referred to as “PTFE”)-containing mixed powder (B) of the present invention contains PTFE particles and an organic polymer.
The blending amount of the PTFE particles in the PTFE-containing mixed powder (B) is preferably 0.05 to 7 parts by mass with respect to 100 parts by mass of the polyamide resin (A). More preferably, it is 0.2-5 mass parts. When the PTFE particles are 0.05 parts by mass or more, the effect of improving the melt tension appears at the time of foam molding, the mold retainability with the sizing die does not deteriorate, and a good foam molded product is obtained. Moreover, when the PTFE particles are 7 parts by mass or less, no blisters occur when the polyamide resin (A) is foam-molded, and the appearance is unlikely to be poor. Moreover, the rough surface of the foamed molded product does not occur, the impact strength does not decrease, and the fluidity does not decrease significantly.

In the present invention, it is preferable to use PTFE particles in the form of an aqueous dispersion in order to improve the dispersibility in the obtained polyamide resin foamed molded article. In this case, the mass average particle diameter of the PTFE particles is preferably 0.05 to 1.0 μm in order to obtain good powder characteristics. Further, as a method for obtaining an aqueous dispersion of PTFE particles, a method of emulsion polymerization of a tetrafluoroethylene monomer using a fluorine-containing surfactant is preferable. The molecular weight of PTFE is preferably 1 million to 30 million. The PTFE molecular weight is a value obtained by conversion from the standard specific gravity measured according to STM D-4895.
As PTFE particles, fluorine-containing olefins such as hexafluoropropylene, chlorotrifluoroethylene, fluoroalkylethylene and perfluoroalkyl vinyl ether, and fluorine-containing materials such as perfluoroalkyl (meth) acrylate, as long as the properties of PTFE particles are not impaired. A copolymer having an alkyl (meth) acrylate as a copolymerization component can be used. In this case, the content of the copolymer component as a raw material is preferably 10% by mass or less with respect to tetrafluoroethylene.

As an aqueous dispersion of PTFE particles, Asahi Glass Fluoropolymers Co., Ltd. full-on AD-1, AD-936, AD-911, AD-938, Daikin Industries Co., Ltd. polyflon D-1, D-2, Commercially available products such as D-3, D-2E, D-3E, and Teflon 30J manufactured by Mitsui DuPont Fluorochemical Co., Ltd. are representative examples.
Ordinary PTFE particles become aggregates of 100 μm or more in the step of recovering as powder from the state of an aqueous dispersion, and thus it is difficult to uniformly disperse them in a thermoplastic resin such as a polyamide-based resin. On the other hand, since the PTFE-containing mixed powder (B) of the present invention contains PTFE particles and an organic polymer, it does not form a domain having a mass average particle diameter of more than 10 μm, and is therefore dispersible with respect to a polyamide-based resin. Is very good. As a result, the polyamide resin foam molded article of the present invention has PTFE particles efficiently dispersed (fine fibers) in the polyamide resin (A), has excellent moldability and excellent surface appearance. .

The organic polymer is preferably one having a high affinity with the polyamide resin (A) from the viewpoint of dispersibility when blended with the polyamide resin (A).
Specific examples of monomers used as raw materials for organic polymers include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, t-butylstyrene, o-ethylstyrene, p-chlorostyrene, o -Aromatic vinyl monomers such as chlorostyrene, 2,4-dichlorostyrene, p-methoxystyrene, o-methoxystyrene, 2,4-dimethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate (Meth) such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate Acrylic acid ester monomers; Vinyl cyanide monomers such as (meth) acrylonitrile; Maleic anhydride, etc. α, β-unsaturated carboxylic acid; maleimide monomers such as N-phenylmaleimide, N-methylmaleimide and N-cyclohexylmaleimide; epoxy group-containing monomers such as glycidyl methacrylate; vinyl methyl ether, vinyl ethyl ether Vinyl ester monomers such as vinyl acetate, vinyl ester monomers such as vinyl butyrate; olefin monomers such as ethylene, propylene and isobutylene; and diene monomers such as butadiene, isoprene and dimethylbutadiene be able to. These monomers can be used alone or in admixture of two or more.
Among these monomers, aromatic vinyl monomers, (meth) acrylic acid ester monomers and vinyl cyanide monomers are preferable from the viewpoint of affinity with the polyamide resin (A). 20 to 99.9% by mass of one or more monomers selected from the group consisting of isomers, and from the group consisting of α, β-unsaturated carboxylic acids, maleimide monomers and epoxy group-containing monomers A monomer mixture containing 0.1 to 20% by mass of one or more selected monomers can be exemplified.
Particularly preferred is a maleic anhydride containing 20 to 99.9% by mass of one or more monomers selected from the group consisting of styrene, methyl methacrylate, 2-ethylhexyl methacrylate, butyl acrylate, dodecyl acrylate and acrylonitrile. A monomer mixture containing 0.1 to 20% by mass of one or more monomers selected from the group consisting of acid, N-phenylmaleimide and glycidyl methacrylate can be given.

The organic polymer is preferably used in the form of an aqueous dispersion as in the case of PTFE particles.
PTFE containing mixed powder (B) is mix | blended 0.5-10 mass parts with respect to 100 mass parts of polyamide-type resin (A). When the PTFE-containing mixed powder (B) is 0.5 parts by mass or more, the effect of improving the melt tension at the time of foam molding of the polyamide-based resin (A) is large, and a good foam molded product is obtained. In addition, when the PTFE-containing mixed powder (B) is 10 parts by mass or less, the polyamide-based resin (A) is less likely to cause blistering and hardly deteriorate in appearance.
The PTFE-containing mixed powder (B) is obtained, for example, by pulverization by a method of mixing an aqueous dispersion of PTFE particles and an aqueous dispersion of organic polymer particles and coagulating them, or by a spray drying method. It can also be obtained by polymerizing a monomer as a raw material of the organic polymer in the presence of an aqueous dispersion of PTFE particles and then pulverizing it by a coagulation method or a spray drying method. Furthermore, after emulsion polymerization of a monomer having an ethylenically unsaturated bond in a dispersion obtained by mixing an aqueous dispersion of PTFE particles and an aqueous dispersion of organic polymer particles, the coagulation method or spray drying method is used. It can also be obtained by powdering.

The PTFE content in the PTFE-containing mixed powder (B) is preferably 0.1 to 90% by mass. More preferably, it is 10-70 mass%. An effect of improving the melt tension can be obtained at 0.1% by mass or more, a molding appearance defect due to outgassing of the foaming agent hardly occurs, a good sizing die mold retainability, and a good foam can be obtained. Further, when the content is 90% by mass or less, the aggregation of the powder particles hardly occurs, and problems such as poor dispersion such as generation of defects at the time of molding hardly occur.
The PTFE-containing mixed powder (B) is prepared by pouring the aqueous dispersion into hot water in which a metal salt such as calcium acetate, calcium chloride, or magnesium sulfate is dissolved, salting out and solidifying, and then drying to powder. It can be pulverized by spray drying. Among these, a method of salting out with a salt compound containing an alkaline earth metal, solidifying and recovering is particularly preferable, and a method of salting out with a calcium salt compound, solidifying and recovering is more preferable. It is preferable to solidify and recover the PTFE-containing mixed powder (B) with a salt compound containing an alkaline earth metal because there is no fear of decomposing the polyamide-based resin.

The amount of the foaming agent (C) added is 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the polyamide-based resin (A) as the pure part of the foaming agent (C). A foam can be obtained at 0.1 parts by mass or more, and the melt tension improvement effect by the PTFE mixed powder can be obtained without greatly reducing the melt tension of the polyamide resin (A) at 10 parts by mass or less. The magnification increases.
As the foaming agent (C), an inorganic foaming agent, a volatile foaming agent, a decomposable foaming agent, or the like is used. Carbon dioxide, air, nitrogen or the like is used as the inorganic foaming agent. Volatile blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, pentane and hexane, halogenated carbonization such as trichlorofluoromethane, dichlorofluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride. Hydrogen or the like is used.
As the decomposable foaming agent, azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate, or the like is used. These foaming agents can be appropriately mixed and used. Moreover, the masterbatch goods which mix | blended the diluent dispersant with the foaming agent can also be used.
Examples of commercially available foaming agents include Polyslen EE206-5 and Polyslen EE204, which are foaming agent master batch products of Eiwa Kasei Co., Ltd.
The mass ratio of PTFE to the foaming agent (C) is preferably PTFE / foaming agent (C) = 1/25 to 25/1 from the viewpoint of foam moldability (balance between resin swelling and melt tension).

A mixture comprising the polyamide-based resin (A), the PTFE-containing mixed powder (B), and the foaming agent (C) is supplied into the extruder, melt-kneaded, and foam-extruded to obtain a polyamide-based resin molded body.
Examples of the method for extruding the polyamide resin foam molded body include the following method 1 and method 2.
Method 1 includes a method in which the polyamide-based resin (A), the PTFE-containing mixed powder (B), and the foaming agent (C) are supplied to an extruder and subjected to foam extrusion.
As the method 2, the polyamide-based resin (A) and the PTFE-containing mixed powder (B) are melt-kneaded in an extruder or the like to form pellets, and the pellets and the foaming agent (C) are supplied to the extruder and subjected to foam extrusion. A method is mentioned.
Part of the polyamide resin (A) and the PTFE-containing mixed powder (B) are melted and kneaded into pellets, and the pellets, the remainder of the polyamide resin (A), and the foaming agent (C) are supplied to the extruder. It is also possible to perform foam extrusion.
When Method 1 is used, it is necessary to improve the dispersibility of the PTFE-containing mixed powder (B). Therefore, in order to increase the residence time in the cylinder of the extruder or to facilitate kneading, the device such as the screw shape is improved. is required. Therefore, a method such as Method 2 using pellets is preferable.
The extruder barrel temperature at the time of melt-kneading and pelletizing the polyamide-based resin (A) and the PTFE-containing mixed powder (B) is preferably 210 to 260 ° C.

As for the cylinder temperature under the supply hopper of the extruder at the time of foam molding, 230-240 degreeC is preferable. If it is 230 degreeC or more, since it will not become the melting | fusing point vicinity of a polyamide-type resin (A), the torque load of an extruder does not become large easily. Also, since the decomposition temperature of the decomposable foaming agent usually exceeds 240 ° C, if it is 240 ° C or less, the foaming agent will not be decomposed there, so that the foaming gas from the vent port will not be emitted, and the foaming efficiency Is less likely to occur.
The cylinder temperature near the die is preferably 250 to 260 ° C. It is preferable in terms of foaming efficiency to promote foaming, volatilization or decomposition of the foaming agent within this temperature range, and it is preferable because it improves the dispersibility of the PTFE-containing mixed powder (B). The die temperature is preferably 230 to 240 ° C. When the temperature of the die part is 230 ° C. or higher, uniform foamed cells can be easily obtained, and when the temperature is 240 ° C. or lower, the melt tension does not decrease, so that the mold can be easily held with a sizing die.
As the die, an atypical (L-shaped) die is preferable.
The polyamide resin foam molded article of the present invention thus obtained has a low specific gravity and excellent cell uniformity. Further, there is no large aggregate of PTFE, and the surface state of the foamed molded article is excellent.

In the present invention, a cell regulator may be further added to the mixture of the polyamide resin (A), the PTFE-containing mixed powder (B), and the foaming agent (C). Examples of the air conditioner include inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, and reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate.
When adding a bubble regulator, 13 mass parts or less are preferable with respect to 100 mass parts of polyamide-type resin (A).
The polyamide resin foam molded article of the present invention has a reinforcing agent and filler such as pigments, dyes, glass fibers, metal fibers, metal flakes, carbon fibers, and the like, as long as the original purpose is not impaired. Phenolic antioxidants such as -4-methylphenol and 4,4'-butylidene-bis (3-methyl-6-t-butylphenol), tris (mono, di-nonylphenyl) phosphite, diphenylisodecyl phosphite Such as phosphite antioxidants such as dilauryl thiodipropionate, dimyristyl thiodipropionate, diastereyl thiodipropionate, 2-hydroxy-4-octoxybenzophenone, 2- ( Benzotriazole ultraviolet absorbers such as 2-hydroxy-5-methylphenyl) benzotriazole, bis (2, , 6,6-tetramethyl-4-piperidinyl) and other light stabilizers, hydroxylalkylamines, antistatic agents such as sulfonates, lubricants such as ethylenebisstearylamide, metal soaps, and tetrabromophenol A, decabromo Various additives such as flame retardants such as phenol oxide, TBA epoxy oligomer, TBA polycarbonate oligomer, and antimony trioxide can be appropriately blended. As a blending method, it is preferable to add at the time of melt-kneading the polyamide-based resin (A) and the PTFE-containing mixed powder (B).

Hereinafter, the present invention will be described by way of examples.
The following “parts” represent parts by mass, “%” represents mass%, and various physical properties were measured by the following methods.

(1) Solid content concentration It calculated | required by putting 2 g of aqueous dispersion liquids in a container, and drying for 30 minutes at 170 degreeC.
Solid content concentration (%) = ((mass after drying) / (mass before drying)) × 100

(2) Particle size distribution and mass average particle size Measured by a dynamic light scattering method (ELS800, manufactured by Otsuka Electronics Co., Ltd., temperature 25 ° C., scattering angle 90 °) using an aqueous dispersion diluted with water as a sample solution. did.

(3) Melt tension Using a capillary rheometer (Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd.), the resin composition is discharged at a resin temperature of 240 ° C., an orifice L / D = 16 mm / 1 mm, and a piston lowering speed of 5 mm / min. The load at the time of taking off at a take-up speed of 4 m / min was measured with a load cell.

(4) Drawdown resistance The time required to reach a parison length of 110 cm at a molding temperature of 250 ° C. was measured.

(5) Foam molding appearance The appearance at the time of foam molding was visually observed and judged according to the following criteria.
○: The molded product is glossy and held in the shape of a die.
Δ: The molded product is glossy but not held in the shape of a die.
X: The surface of the molded product was confirmed to be rough and was not held in the shape of a die.

(6) Foam specific gravity The specific gravity of the foam molded product was measured using Shimadzu specific gravity measuring device SGM-300P.

[Reference Example 1] Production of PTFE-containing mixed powder (B-1) 190 parts of distilled water, 1.5 parts of sodium dodecylbenzenesulfonate in a separable flask equipped with a stirring blade, a condenser, a thermocouple and a nitrogen inlet, 100 parts of styrene and 0.5 part of cumene hydroperoxide were charged, and the temperature was raised to 40 ° C. under a nitrogen stream.
Next, a mixed solution of 0.001 part of ferrous sulfate, 0.003 part of ethylenediaminetetraacetic acid disodium salt, 0.24 part of Rongalite salt and 10 parts of distilled water was added to initiate radical polymerization. After completion of heat generation, the temperature in the system was maintained at 40 ° C. for 1 hour to complete the polymerization, and an aqueous dispersion of polystyrene particles (hereinafter referred to as “P-1”) was obtained as an organic polymer.
The solid content concentration of P-1 was 33.3%, the particle size distribution showed a single peak, and the mass average particle size was 96 nm.
On the other hand, Fullon AD936 manufactured by Asahi Glass Fluoropolymers Co., Ltd. was used as PTFE particles. The solid content concentration of AD936 is 63.0%, and contains 5 parts of polyoxyethylene alkylphenyl ether with respect to 100 parts of PTFE. The particle size distribution of AD936 showed a single peak, and the mass average particle size was 290 nm.
1167 parts of distilled water was added to 833 parts of AD936 to obtain an aqueous dispersion (hereinafter referred to as “F-1”) of PTFE particles having a solid content concentration of 26.2%. F-1 contains 25% PTFE particles and 1.2% polyoxyethylene nonylphenyl ether.
160 parts of F-1 (40 parts as PTFE particles) and 181.8 parts of P-1 (60 parts as polystyrene) were charged into a separable flask similar to the above and stirred at room temperature for 1 hour in a nitrogen stream. . Thereafter, the system was heated to 80 ° C. and held for 1 hour. Solid separation was not observed through a series of operations. This mixed aqueous dispersion had a solid content concentration of 29.3%, a particle size distribution that was relatively broad, and a mass average particle size of 168 nm.
341.8 parts of this mixed aqueous dispersion was put into 700 parts of hot water at 85 ° C. containing 5 parts of calcium acetate, the solid matter was separated, filtered, washed and dried to obtain a PTFE-containing mixed powder (B- 1) 98 parts were obtained.
The PTFE-containing mixed powder (B-1) was shaped into a strip (length 50 mm x width 3 mm x thickness 2 mm) with a press molding machine at 250 ° C, and then passed through an ultrathin section with a microtome without staining. Observed with a scanning electron microscope. Although PTFE particles were observed as dark parts, aggregates of PTFE particles exceeding 10 μm were not observed.

[Reference Example 2] Production of PTFE-containing mixed powder (B-2) 160 parts of F-1 used in Reference Example 1 in a separable flask equipped with a stirring blade, a condenser, a thermocouple, a nitrogen inlet and a dropping funnel (40 parts as PTFE particles), 1.0 part of dodecylbenzenesulfonic acid and 70 parts of distilled water were charged, and the temperature was raised to 80 ° C. under a nitrogen stream.
Next, after adding a mixed liquid of 0.001 part of ferrous sulfate, 0.003 part of ethylenediaminetetraacetic acid disodium salt, 0.24 part of Rongalite salt and 10 parts of distilled water, 20 parts of n-butyl acrylate, 35 of styrene Part, 5 parts of maleic anhydride and 0.3 part of t-butyl peroxide were added dropwise over 90 minutes from the dropping funnel. After completion of the dropwise addition, the internal temperature was maintained at 80 ° C. for 1 hour to complete radical polymerization. Solid separation was not observed through a series of operations. The solid content concentration of the aqueous dispersion was 33.2%, the particle size distribution was relatively broad, and the mass average particle size was 252 nm.
301.5 parts of this aqueous dispersion was put into 700 parts of hot water at 85 ° C. containing 5 parts of calcium acetate, the solid matter was separated, filtered, washed and dried to obtain a mixed powder containing PTFE (B-2 ) 97 parts were obtained.
When the PTFE-containing mixed powder (B-2) was observed in the same manner as in Reference Example 1, aggregates of PTFE particles exceeding 10 μm were not observed.

[Reference Example 3] Production of PTFE-containing mixed powder (B-3) 0.12 part of 2,2'-azobis (2,4-dimethylvaleronitrile) was added to a mixed liquid of 70 parts of dodecyl methacrylate and 30 parts of methyl methacrylate. Dissolved. To this was added a mixed solution of 2.0 parts of sodium dodecylbenzenesulfonate and 300 parts of distilled water, stirred for 4 minutes at 10000 rpm with a homomixer, and then passed twice through a homogenizer at a pressure of 30 MPa. Got. This was placed in a separable flask similar to that in Reference Example 1, and the internal temperature was raised to 80 ° C. under a nitrogen stream and stirred for 3 hours to effect radical polymerization. As an organic polymer, both dodecyl methacrylate / methyl methacrylate were used. An aqueous dispersion of polymer particles (hereinafter referred to as “P-2”) was obtained.
The solid content concentration of P-2 was 25.1%, the particle size distribution showed a single peak, and the mass average particle size was 190 nm.
80 parts of F-1 (20 parts as PTFE particles) and 239.0 parts of P-2 (60 parts as dodecyl methacrylate / methyl methacrylate copolymer) similar to those used in Reference Example 1 were used as Reference Example 2. The same separable flask as in the above was charged and stirred at room temperature for 1 hour under a nitrogen stream. Thereafter, the system was heated to 80 ° C., and after adding a mixed liquid of 0.001 part of ferrous sulfate, 0.003 part of disodium ethylenediaminetetraacetate, 0.24 part of Rongalite salt and 10 parts of distilled water, A mixed solution of 18 parts of methyl methacrylate, 2 parts of glycidyl methacrylate and 0.1 part of t-butyl peroxide was added dropwise over 30 minutes. After completion of dropping, the internal temperature was maintained at 80 ° C. for 1 hour to complete radical polymerization. Solid separation was not observed through a series of operations. The solid content concentration of the aqueous dispersion was 28.6%, the particle size distribution was relatively broad, and the mass average particle size was 221 nm.
349.7 parts of this aqueous dispersion was put into 600 parts of 75 ° C. hot water containing 5 parts of calcium chloride, the solid matter was separated, filtered, washed and dried to obtain a PTFE-containing mixed powder (B-3). ) 98 parts were obtained.
The aggregated state of PTFE particles was observed in the same manner as in Reference Example 1 except that the PTFE-containing mixed powder (B-3) was shaped into a strip shape by a press molding machine at 220 ° C. Aggregates of PTFE particles exceeding 10 μm were not observed.

[Reference Example 4] Production of PTFE-containing mixed powder (B-4) 0.3 part of cumene hydroperoxide was dissolved in a mixed solution of 60 parts of dodecyl methacrylate, 35 parts of methyl methacrylate and 5 parts of methyl acrylate. To this was added a mixed solution of 2.0 parts of sodium dodecylbenzenesulfonate and 300 parts of distilled water, stirred for 5 minutes at 10,000 rpm with a homomixer, and then passed twice through a homogenizer at a pressure of 20 MPa to obtain a stable reserve. A dispersion was obtained. This was charged into the same flask as in Reference Example 2 and heated to 70 ° C. under a nitrogen stream. A mixture of 0.0004 parts ferrous sulfate, 0.0012 parts ethylenediaminetetraacetic acid disodium salt and 0.2 parts Rongalite salt in 5 parts distilled water is added to the flask to initiate polymerization and hold for 3 hours As a result, an aqueous dispersion (hereinafter referred to as “P-3”) of methyl methacrylate / methyl acrylate copolymer particles was obtained. The solid content concentration of P-3 was 25.2%, the particle size distribution showed a single peak, and the mass average particle size was 180 nm.
120 parts of F-1 (30 parts as PTFE particles) and 199.2 parts of P-3 (50 parts as methyl methacrylate / methyl acrylate copolymer) similar to those used in Reference Example 1 were used as reference examples. The same separable flask as in 1 was charged and stirred for 1 hour under a nitrogen stream. Thereafter, the system was heated to 80 ° C. and stirred for 1 hour, and then 0.001 part of ferrous sulfate, 0.003 part of ethylenediaminetetraacetic acid disodium salt, 0.24 part of Rongalite salt and 60.8 distilled water. A mixture of 19 parts of methyl methacrylate, 1 part of methyl acrylate and 0.4 part of t-butyl peroxide was added dropwise over 1 hour. After completion of dropping, the internal temperature was maintained at 80 ° C. for 1 hour to complete radical polymerization. Solid separation was not observed through a series of operations. This aqueous dispersion was poured into 400 parts of 90 ° C. hot water containing 5 parts of calcium acetate, the solid matter was separated, filtered, washed and dried to obtain 99 parts of PTFE-containing mixed powder (B-4). .
When the PTFE-containing mixed powder (B-4) was observed for the aggregated state of PTFE particles in the same manner as in Reference Example 3, no aggregates of PTFE particles exceeding 10 μm were observed.

[Examples 1-7 and Comparative Examples 1-5]
Polyamide resins (A-1) and (A-2) and the PTFE-containing mixed powders (B-1) to (B-4) obtained in Reference Examples 1 to 4 were blended in the proportions shown in Table 1, Extruded at a barrel temperature of 230 to 250 ° C. and a screw rotation speed of 150 rpm by a shaft extruder (PCM-30 manufactured by Ikegai Seisakusho Co., Ltd.) to pelletize the mixture of polyamide resin (A) and PTFE-containing mixed powder (B) did. This pellet was used to measure melt tension and resistance to drawdown, and then a mixture of the foaming agent in the ratio shown in Table 1 was mixed with this pellet to a single-screw extruder equipped with an L-shaped profile die ( GM Engineering Co., Ltd.), melt kneading and foam extrusion at a cylinder temperature of 230 ° C. under the hopper, a cylinder temperature of 250 ° C. near the die, a die temperature of 230 ° C., and a screw speed of 30 rpm, and foam molding Got the body. The evaluation results are shown in Table 1.
For comparison, those extruded without adding PTFE-containing mixed powder (B) and those added with PTFE-containing mixed powder (B) deviated from the scope of the present invention (Comparative Examples 1 to 3) , PTFE fine powder (Asahi Glass Fluoropolymers Co., Ltd. CD123) added (Comparative Example 4) and acrylic polymer processing aid (Mitsubishi Rayon Co., Ltd. Metabrene P530A) (Comparative Example 5) Were similarly evaluated. The results are shown in Table 1.

Claims (8)

  0.5 to 10 parts by mass of a polytetrafluoroethylene-containing mixed powder (B) containing polytetrafluoroethylene particles and an organic polymer with respect to 100 parts by mass of the polyamide-based resin (A), and a foaming agent (C ) A method for producing a polyamide-based resin foam molded article in which a mixture containing 0.1 to 10 parts by mass is supplied into an extruder, melt-kneaded, and foam-extruded.   A foaming agent (C) is added to a mixture obtained by melting and kneading a polytetrafluoroethylene-containing mixed powder (B) containing a polyamide-based resin (A) and polytetrafluoroethylene particles and an organic polymer. The method according to claim 1, which is a mixture.   The polytetrafluoroethylene-containing mixed powder (B) is solidified by mixing an aqueous dispersion of polytetrafluoroethylene particles having a mass average particle diameter of 0.05 to 1.0 μm and an aqueous dispersion of organic polymer particles. Alternatively, the method according to claim 1 or 2, wherein the method is obtained by pulverization after spray drying.   The polytetrafluoroethylene-containing mixed powder (B) polymerizes monomers as raw materials for organic polymers in the presence of an aqueous dispersion of polytetrafluoroethylene particles having a mass average particle diameter of 0.05 to 1.0 μm. The method according to claim 1 or 2, wherein the method is obtained by solidification or spray drying and then pulverizing.   Dispersion obtained by mixing polytetrafluoroethylene-containing mixed powder (B) with an aqueous dispersion of polytetrafluoroethylene particles having a mass average particle diameter of 0.05 to 1.0 μm and an aqueous dispersion of organic polymer particles The method according to claim 1 or 2, wherein the monomer is obtained by emulsion polymerization of a monomer having an ethylenically unsaturated bond, solidification or spray drying, and then pulverization.   The method according to any one of claims 1 to 5, wherein the polytetrafluoroethylene-containing mixed powder (B) is coagulated with a salt compound containing an alkaline earth metal.   The mass ratio of polytetrafluoroethylene and the foaming agent (C) in the polytetrafluoroethylene-containing mixed powder (B) is polytetrafluoroethylene / foaming agent (C) = 1/25 to 25/1. The method as described in any one of 1-6.   A polyamide-based resin foam molded article obtained by the method according to claim 1.