JP6498966B2 - Polyamide-based resin composition for injection foaming and injection-foamed molded article - Google Patents

Description

  The present invention relates to a polyamide-based resin composition having excellent foam moldability by injection molding.

Polyamide resins have excellent properties such as mechanical properties, chemical resistance, heat resistance, and moldability, and have been widely used for automobile parts, electronic parts, and the like. As means for reducing the weight by utilizing these characteristics, a polyamide resin foam formed by adding a foaming agent to a polyamide resin has been proposed. For example, Patent Documents 1 to 3 describe a resin composition in which a fibrous reinforcing material and a foaming agent are blended in a resin such as polyamide, and a foam made of the same. However, in order to obtain a practical level of strength and rigidity, the amount of the reinforcing material is increased, so that the weight reduction effect is poor and the surface smoothness is not excellent.
Further, as a technique for increasing the weight reduction, for example, Patent Document 4 discloses a polyamide resin composed of a swellable fluorinated mica and a foaming agent, but the expansion ratio cannot be increased, which is insufficient as a weight reduction. .

JP-A-5-214141 JP-A-7-216126 JP 58-76431 A Japanese Patent No. 3535919

  An object of the present invention is to provide a polyamide-based resin composition for injection foaming that can obtain an injection foamed molded article having high foaming ratio, uniform cells and excellent impact resistance, with good moldability.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polyamide-based resin composition in which a polytetrafluoroethylene-containing resin is added to a polyamide resin so as to have a strain hardening coefficient within a specific range, The present invention has been found.

That is, the gist of the present invention is as follows.
(1) Polyamide resin (A) and polytetrafluoroethylene-containing resin having a relative viscosity determined in the range of 2.0 to 4.0 using 96% sulfuric acid as a solvent at a temperature of 25 ° C. and a concentration of 1 g / 100 ml. (B) is a resin composition in which the content of the polytetrafluoroethylene-containing resin (B) is 0.05 to 3 parts by mass with respect to 100 parts by weight of the polyamide resin, the melting point of the resin composition being plus A polyamide-based resin composition for injection foaming, having a strain hardening coefficient measured at 10 ° C. of 1.05 to 10.
(2) Furthermore, the inorganic filler (C) is contained in an amount of 5 to 100 parts by mass with respect to 100 parts by weight of the polyamide resin, and the polyamide-based resin composition for injection foaming according to (1) object.
(3) The injection-foaming polyamide resin composition according to (2) , wherein the inorganic filler (C) is at least one selected from talc, silica, and glass fiber.
(4) Further, 0.1 to 5 parts by mass of at least one selected from acrylonitrile butadiene styrene copolymer, ethylene-α olefin copolymer and these acid-modified products is contained with respect to 100 parts by weight of polyamide resin. The polyamide-based resin composition for injection foaming according to any one of (1) to (3), wherein
(5) An injection foam molded article formed from the polyamide resin composition for injection foam according to any one of (1) to (4).

The polyamide resin composition for injection foaming of the present invention is a foamed molded product having uniform cells, and can obtain a foamed molded product excellent in surface smoothness and impact resistance at high foaming ratio and good moldability. .
The injection-foamed molded article of the present invention has a low density and excellent surface smoothness and impact resistance, and can be widely used for automobile parts, electronic electrical parts and the like.

FIG. 6 is a schematic diagram of elongation time and elongation viscosity when determining the ratio (a2 / a1, strain hardening coefficient) of the slope a1 of the linear region at the initial stage of elongation until the inflection point appears and the slope a2 of the later stage of elongation after the inflection point. .

Hereinafter, the present invention will be described in detail. First, the polyamide resin (A) will be described.
The polyamide resin (A) used in the present invention means a polymer having an amide bond formed from an amino acid, a lactam or a diamine and a dicarboxylic acid. Examples of monomers that form such a polyamide resin include the following.

  Examples of amino acids include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and paraaminomethylbenzoic acid.

  Examples of the lactam include ε-caprolactam and ω-laurolactam.

  Examples of the diamine include tetramethylene diamine, hexamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4-trimethylhexamethylene diamine, 5-methylnonamethylene diamine, 2,4-dimethyloctamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 3, 8-bis (aminomethyl) tricyclodecane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminopropyl) ) Piperazine, aminoethylpi Rajin, and the like.

  Examples of dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5 -Sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, diglycolic acid and the like.

  As the polyamide resin (A) used in the present invention, polycaproamide (nylon 6), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebaca Mido (nylon 610), polyhexamethylene dodecane (nylon 612), polyundecane methylene adipamide (nylon 116), polyundecanamide (nylon 11), polydodecanamide (nylon 12), polytrimethylhexamethylene terephthalamide (Nylon TMHT), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide / isophthalamide (nylon 6T / 6I), polybis (1-aminocyclohexyl) methane dodecamide (nylon PACM1 ), Polybis (3-methyl-4-aminocyclohexyl) methane dodecamide (nylon dimethyl PACM12), polymetaxylylene adipamide (nylon MXD6), polydecamethylene terephthalamide (nylon 10T), polyundecamethylene terephthalamide ( Nylon 11T), polyundecamethylenehexahydroterephthalamide (nylon 11T (H)), and their copolyamides and mixed polyamides. Of these, nylon 6, nylon 46, nylon 66, nylon 11, nylon 12 and their copolyamides and mixed polyamides are particularly preferable. Among these, nylon 6 and nylon 66 are particularly preferable from the viewpoint of excellent heat resistance and easy molding.

  The polyamide resin (A) used here is usually produced by a known melt polymerization method or by further using a solid phase polymerization method.

  The polyamide resin (A) used in the present invention must be 96% sulfuric acid as a solvent and have a relative viscosity of 2.0 to 4.0 determined under conditions of a temperature of 25 ° C. and a concentration of 1 g / 100 ml. In particular, the range of 2.5 to 3.4 is preferable. When the relative viscosity is less than 2.0, it is not preferable when foam molding is performed because uniform foam cells are hardly generated and foamability is lowered, and mechanical properties of the obtained foam are also lowered. On the other hand, if the relative viscosity is more than 4.0, the flowability of the resulting polyamide resin composition for injection foaming is lowered, and foam moldability is lowered.

  Next, the polytetrafluoroethylene-containing resin (B) will be described. The polytetrafluoroethylene-containing resin (B) used in the present invention is a polymer obtained by homopolymerizing or copolymerizing a tetrafluoroethylene monomer. Examples of monomers that can be copolymerized include fluorine-containing olefins such as hexafluoropropylene, chlorotrifluoroethylene, fluoroalkylethylene, and perfluoroalkyl vinyl ether, and fluorine-containing alkyl (meth) acrylates such as perfluoroalkyl (meth) acrylate. Can be mentioned. The content of the copolymer component is preferably 10% by mass or less with respect to tetrafluoroethylene.

  It is necessary that the polytetrafluoroethylene-containing resin (B) is contained in an amount of 0.05 to 3 parts by mass with respect to 100 parts by weight of the polyamide resin (A), and in particular, 0.1 to 2 parts by mass is contained. It is preferable. When the polytetrafluoroethylene-containing resin (B) is less than 0.05 parts by mass, it is difficult to make the strain hardening coefficient of the resin composition 1.05 or more, and injection foam molding cannot be performed satisfactorily. It becomes. On the other hand, if the polytetrafluoroethylene-containing resin (B) exceeds 3 parts by mass, the strain curability becomes too large, and the foaming ratio of the resulting foam cannot be increased, and the impact resistance is reduced. The surface appearance deteriorates.

  Examples of the polytetrafluoroethylene-containing resin (B) include, for example, trade names “Metablene A-3000”, “A-3700”, “A-3750”, “A-3800”, and General, manufactured by Mitsubishi Rayon Co., Ltd. A product name “Blendex 869” manufactured by Electric Specialty Chemicals may be mentioned. These polytetrafluoroethylene-containing resins (B) can be used alone or in combination of two or more.

  The polyamide resin composition for injection foaming of the present invention has rheological properties suitable for the foam molding process, and is obtained by time-elongation obtained by measuring an extensional viscosity at a temperature 10 ° C. higher than the melting point of the resin composition. In the viscosity curve (see FIG. 1), the strain hardening coefficient expressed by the ratio (a2 / a1) of the slope a1 of the linear region at the initial stage of elongation until the inflection point appears and the slope a2 of the later stage of elongation after the inflection point is 1 0.05 to 10 is required, and 1.2 to 8 is particularly preferable, and 1.5 to 6.0 is more preferable.

  By satisfying such a strain hardening coefficient, the polyamide resin composition of the present invention is particularly suitable for a foam molding process when obtaining an injection foam molded article, and has a high foaming ratio and uniform cells. An injection foam molded article excellent in surface smoothness can be obtained with good operability.

  When the strain hardening coefficient is less than 1.05, foam breakage occurs during injection foam molding, resulting in a foam molded article having a large average cell diameter and poor surface smoothness. On the other hand, when the strain hardening coefficient exceeds 10, the fluidity is greatly lowered and the expansion ratio cannot be increased. Moreover, the obtained foam tends to be inferior in impact resistance, and the surface appearance is also deteriorated.

  By including the inorganic filler (C), the polyamide resin composition for injection foaming of the present invention has excellent dimensional stability and high rigidity. Moreover, since the foaming molding obtained is excellent in heat resistance by containing an inorganic filler (C), it is preferable practically.

  The content of the inorganic filler (C) can exert the effects as described above, and in consideration of the balance of appearance, fluidity and mechanical properties during molding, with respect to 100 parts by mass of the polyamide resin (A), It is preferably 5 to 30 parts by mass, and more preferably 8 to 25 parts by mass. When the amount is less than 5 parts by mass, the effect of adding the inorganic filler cannot be achieved. On the other hand, when it exceeds 30 parts by mass, not only the appearance is deteriorated, but also the specific gravity is increased and it is difficult to reduce the weight.

  As the inorganic filler (C) used in the present invention, a fibrous material can be used in addition to a non-fibrous material such as powder, plate, scaly, granular, indefinite shape, and crushed product.

  Non-fibrous inorganic fillers include mica, talc, kaolin, silica, calcium carbonate, layered silicate, barium sulfate, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, wollastonite, calcium polyphosphate Metal oxides (alumina, zinc oxide, titanium oxide, magnesium oxide, etc.), metal nitrides (boron nitride, aluminum nitride), carbon powder, graphite, carbon flakes, scaly carbon, carbon nanotubes, etc. can be used. Of these, talc or silica is preferably selected from the viewpoints of dimensional stability and foamability.

  Glass fiber, carbon fiber, basalt fiber, cellulose fiber, gypsum fiber, ceramic fiber, zirconia fiber, alumina fiber, silica fiber, titanium oxide fiber, silicon carbide fiber, zinc oxide whisker etc. should be used as the fibrous filler Can do. Among these, glass fibers are preferably selected because they are generally known for improving mechanical strength and heat resistance and are inexpensive.

  The cross-sectional shape of the fibrous inorganic filler (C) is preferably a flat cross-sectional shape in addition to a general circular shape. Specific cross-sectional shapes include an oval, a pair of eyebrows, an ellipse, a semicircle, a rectangle, a square, other polygons, a star, and a single fiber or multiple pairs of fibers. Be mentioned

  In addition, the inorganic filler (C) used in the present invention may have a surface pretreated with a coupling agent such as a silane coupling agent or a titanate coupling agent or other surface treatment agent.

  The foamed polyamide resin composition for injection foaming of the present invention is preferably prepared by adding a foaming agent (D) during foam molding. Such a foaming agent (D) is a component that can substantially foam the polyamide-based resin composition for injection foaming of the present invention.

  Examples of the blowing agent (D) include pyrolytic organic compounds such as azo, N-nitroso, heterocyclic nitrogen-containing and decomposable groups such as sulfonyl hydrazide groups, ammonium carbonate, sodium hydrogen carbonate, etc. Inorganic compounds can be mentioned.

  Specific examples thereof include azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, diazoaminobenzene, dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide, benzenesulfonyl Hydrazide, 4,4′-oxy-bis (benzenesulfonyl) hydrazide, diphenylsulfone-3,3′-disulfonylhydrazide, 4-toluenesulfonyl hydrazide, 4,4′-oxy-bis (benzenesulfonyl) semicarbazide, 4- Toluenesulfonyl semicarbazide, barium azodicarboxylate, 5-phenyltetrazole, trihydrazinotriazine, 4-toluenesulfonyl azide, 4,4′-diphenyldisulfonyl azide and the like.

  Further, as the foaming agent (D), a gaseous material such as gaseous fluorocarbon, nitrogen, carbon dioxide, air, helium, and argon at room temperature, or a liquid material such as liquid fluorocarbon and pentane at room temperature can be used. When the gas or liquid foaming agent is used, nitrogen or carbon dioxide is preferably selected from the viewpoint of foamability and hygiene.

  0.05-2 mass parts is preferable with respect to 100 mass parts of polyamide resins (A), and, as for the compounding quantity of a foaming agent (D), 0.1-1.5 mass parts is more preferable. If the blending amount is less than 0.05 parts by mass, the amount of gas to be foamed is small, the expansion ratio when foaming the polyamide resin composition for injection foaming of the present invention is not increased, and the mass reduction effect may not be obtained. . On the other hand, if it exceeds 2 parts by mass, the resulting foamed molded article may be deteriorated in strength, or may have a poor appearance such as silver streak.

  The polyamide resin composition for injection foaming of the present invention preferably contains the following thermoplastic resin (E) in order to further improve impact resistance. As the thermoplastic resin (E), polyethylene (PE), polystyrene (PS), polypropylene (PP), acrylonitrile butadiene styrene copolymer (ABS), acrylonitrile styrene copolymer (AS), polylactic acid (PLA), polyamide (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyarylate (PAR), styrene-ethylene-butadiene-styrene copolymer (SEBS), ethylene-α olefin copolymer and These modified products such as maleic anhydride, ethylene-propylene-diene rubber (EPDM) and the like are preferably used. Especially, it is preferable to use at least 1 sort (s) chosen from ABS, an ethylene-alpha olefin copolymer, and these acid-modified products.

  The thermoplastic resin (E) is preferably added in an amount of 0.1 to 5 parts by weight, more preferably 1 to 4.5 parts by weight, with respect to 100 parts by weight of the polyamide resin. If it is less than 0.1 parts by mass, the effect of improving impact resistance is poor. On the other hand, when it exceeds 5 mass parts, heat resistance may fall.

  In the polyamide resin composition for injection foaming of the present invention, when the above-mentioned pyrolytic foaming agent is used as the foaming agent (D), a foaming agent master pellet form in which the foaming agent (D) and a thermoplastic resin are mixed. More preferably. By using the foaming agent master pellet, the polyamide resin composition for injection foaming of the present invention and the foaming agent master pellet are melted together, the foaming agent is easily dispersed, and foaming is efficiently performed in the melted polyamide resin composition. Since gas is generated, foamability is improved.

  Specific examples of the foaming agent master pellets are melt-kneaded into a thermoplastic resin having a melting point lower than the decomposition start temperature of the foaming agent, pelletized, and the thermoplastic resin granules and the foaming agent powder are mixed. And those obtained by compressing and granulating into pellets and those obtained by mixing and adhering a foaming agent to the surface of the thermoplastic resin pellets.

  At this time, it is preferable to use the above-described thermoplastic resin (E) as the thermoplastic resin used for the foaming agent master pellet.

  Moreover, it is preferable that 3-50 mass% of foaming agents (D) are mix | blended with such a foaming agent master pellet, and 5-30 mass% is more preferable. When the foaming agent (D) is less than 3% by mass, it is necessary to increase the blending amount of the foaming agent master pellet when used together with the polyamide resin composition, so that the strength of the obtained foamed molded product may be lowered. On the other hand, if the foaming agent (D) exceeds 50% by mass, the blending amount of the foaming agent master pellet is reduced when used with the polyamide resin composition, and therefore the dispersion of the foaming agent (D) in the polyamide resin composition Unevenness may occur, and foamability may be reduced.

  Next, the manufacturing method of the polyamide-type resin composition for injection foaming of this invention is demonstrated. The polyamide-based resin composition for injection foaming according to the present invention includes each component constituting the resin composition in the extruder [polyamide resin (A), polytetrafluoroethylene-containing resin (B), inorganic filler (C), etc. ] Can be obtained by melt kneading.

  In melt kneading, a general kneader such as a single screw extruder, a twin screw extruder, a roll kneader, or a Brabender can be used. From the viewpoint of improving mixing uniformity and dispersibility, it is preferable to use a twin screw extruder.

  The polyamide resin composition for injection foaming of the present invention is a biaxial extrusion of a polyamide resin (A) and a polytetrafluoroethylene-containing resin (B), if necessary, an inorganic filler (C) as described above. After melt-kneading with a machine, pelletized or granulated, mixed (dry blend) with foaming agent (D) or master pellets containing foaming agent (D) and thermoplastic resin (E), and then this mixture (A foamable polyamide-based resin composition) can be supplied into a molding machine, melted, and injection molded to obtain a foamed molded article.

  In order to improve the strength, surface smoothness, and appearance of the foam molded article, the injection foam molded article of the present invention has a form in which the core part where the foam cells are present is covered with the skin part where the foam cells are not present. It is preferable. Such a foam-molded product can be obtained by, for example, an injection core back type injection molding method in an injection molding machine.

  Specifically, this is a method performed under the following conditions in an injection molding machine. The molten foamable polyamide-based resin composition is injected into the mold cavity and no holding pressure is applied, or when the molten resin reaches the vicinity of the flow end, it is between 0.2 and 2.0. A holding pressure of 100 MPa is applied. Next, the mold core portion (movable mold) constituting the mold cavity is retracted at a speed of 10 to 100 mm / s in a direction in which the thickness of the mold cavity expands.

Here, a value obtained using the following equation from the retreat distance of the die plate and the initial depth of the mold cavity is defined as a set foaming ratio (X).
Set foaming ratio (X) = (initial depth + retract distance of die plate) / (initial depth)
And the real magnification (Y) of foaming of the injection foaming molding at this time is represented by (actual thickness of foam) / (initial depth).

  In the injection-foamed molded article of the present invention, the actual expansion ratio is preferably 1.15 to 4.00, and more preferably 1.25 to 3.50. If the actual foaming ratio is less than 1.15, the foamed molded article is not sufficiently foamed, and the lightening effect is insufficient. On the other hand, when it exceeds 4.00, the foam cell of the core part may be coarsened in the foamed molded product, or the skin part may be thinned, and the strength and surface smoothness of the foamed molded product are lowered.

When the injection-foamed molded article of the present invention has a form in which the core part in which the foam cells are present is covered with the skin part in which the foam cells are not present, the average cell diameter of the foam cells in the core part increases the surface smoothness. 200 μm or less, more preferably 150 μm or less, and even more preferably 120 μm or less. When the average cell diameter exceeds 200 μm, the surface smoothness of the foamed molded product may decrease, and the strength of the foamed molded product may decrease.
Further, the thickness of the skin part is preferably 50 μm or more, and more preferably 100 μm. If the thickness of the skin part is less than 50 μm, the strength of the foamed molded product may be lowered.

  The polyamide resin composition for injection foaming of the present invention has a heat stabilizer, an antioxidant, a pigment, an anti-coloring agent, a weathering agent, a flame retardant, a plasticizer, a crystal nucleating agent, as long as the properties are not significantly impaired. A mold release stabilizer, impact resistance improver, etc. may be added.

In addition, the injection-foamed molded article of the present invention is suitably used in the electrical / electronic equipment field, the automobile field, the machine field, and the like because of its low specific gravity and excellent impact resistance and surface smoothness.
Among them, taking advantage of excellent impact resistance while having a low specific gravity, it can be used for durable consumer goods and can be suitably used for automobile parts and electrical / electronic parts.

In automotive parts applications, engine covers, air intake manifolds, throttle bodies, air intake pipes, radiator tanks, radiator supports, radiator hoses, radiator grills, timing belt covers, water pump renlets, water pump outlets, cooling fans, fan shrouds Engine peripheral parts such as, wire harness, relay block, sensor housing, encapsulation, ignition coil, distributor, thermostat housing, quick connector, lamp reflector, lamp housing, lamp extension, lamp socket, etc. Spoiler, wheel cover, wheel cap, cowl vent grill, air outlet Louvers, air scoop, hood bulges, fenders, back door, a shift lever housing, window regulator, door lock, door handle, can be suitably used in various interior and exterior parts such as outside door mirror stay, and the like.
In electrical / electronic component applications, connectors, LED reflectors, switches, sensors, sockets, capacitors, jacks, fuse holders, relays, coil bobbins, resistors, ICs, LED housings, and the like can be given.

Hereinafter, the present invention will be described specifically by way of examples. The raw materials used in Examples and Comparative Examples are shown.

[Polyamide resin]
A-1: Polyamide 6 resin (“A1030BRF” manufactured by Unitika), relative viscosity 3.1, specific gravity 1.13
A-2: Polyamide 66 resin ("E2000" manufactured by Unitika Ltd.), relative viscosity 2.7, specific gravity 1.14
A-3: Polyamide 11 resin (“Rilsan KNO” manufactured by Arkema), relative viscosity 2.7, specific gravity 1.14
A-4: Layered silicate-containing polyamide 6 resin (obtained according to Production Example 1 below), relative viscosity 3.1, specific gravity 1.14
A-5: Polyamide 6 resin (obtained by Production Example 2 below), relative viscosity 3.5, specific gravity 1.13

[Production Example 1]
To 100 parts by mass of ε-caprolactam, 0.2 part by mass of phosphorous acid, 2.8 parts by mass of layered silicate (ME-100 manufactured by Co-op Chemical Co., Ltd.) and 5 parts by mass of water are blended, and 1 at 80 ° C. After stirring for 1 hour, stirring at 260 ° C. and 0.7 MPa for 1 hour, then stirring at 260 ° C. and normal pressure for 1 hour, polymerization is performed, and the reaction product is discharged in a strand form from a 4 mm diameter × 2 hole die. And cut into pellets. Next, the pellets were refined with hot water at 95 ° C. for 8 hours, and then dried at a temperature of 100 ° C. for 8 hours in a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Kagaku Co., Ltd.). A salt-containing polyamide 6 resin (A-4) was obtained. The ash content of the obtained layered silicate-containing polyamide 6 resin (A-4) was 3% by mass.

[Production Example 2]
100 parts by mass of polyamide resin (A-1) and 0.5 parts by mass of trimethylolpropane polyglycidyl ether (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., SR-TMP) are dry blended, and a loss-in-weight continuous quantitative supply device CE manufactured by Kubota Corporation. It measured using -W-1 and supplied to the main supply port of the same direction twin screw extruder (Toshiba Machine Co., Ltd. TEM37BS) of screw diameter 37mm and L / D40. The barrel temperature of the extruder was 250 ° C. to 270 ° C., the screw rotation speed was 250 rpm, and the discharge rate was 25 kg / h, and melt kneading was performed to obtain polyamide 6 resin (A-5). After melt-kneading, a strand is extruded from a 4 mm diameter × 3 hole die, cut into a pellet, and is heated at a temperature of 100 ° C. with a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Scientific Co., Ltd.). It was time-dried and made into pellets.

[Polytetrafluoroethylene-containing resin]
B-1: Metabrene A-3000 (Mitsubishi Rayon Co., Ltd.)
[Inorganic filler]
C-1: Talc (“MW-HST” manufactured by Hayashi Kasei Co., Ltd.), average particle size: 2.7 μm
C-2: Glass fiber (“MAFT692” manufactured by Owens Corning), fiber diameter: 13 μm

[Foaming agent master pellet]
M-1: Master pellet of ADCA (azodicarbonamide: D-1) using ABS (acrylonitrile-butadiene-styrene copolymer) [thermoplastic resin (E-1)] as a carrier resin (manufactured by Eiwa Kasei Kogyo Co., Ltd.) EB-106 ")
M-2: Master pellet of sodium hydrogen carbonate (D-2) using polystyrene [thermoplastic resin (E-2)] as a carrier resin (“ES275” manufactured by Eiwa Kasei Kogyo Co., Ltd.)
ADC-3 (azodicarbonamide: D-1) using M-3: ethylene-α-olefin copolymer (mass ratio of Tuffmer DE 7350 and Tuffmer M7010 as 3/7) [thermoplastic resin (E-3)] as a carrier resin. ) Master pellets (obtained in Production Example 3 below)

Production Example 3
30 parts by mass of Tafmer DF7350 (E-3a) and 11 parts by mass of ADCA (D-1) were dry blended, weighed using a loss-in-weight continuous quantitative feeder CE-W-1 manufactured by Kubota Corporation, and the screw diameter It was supplied to the main supply port of a 37 mm, L / D40 co-directional twin screw extruder (TEM37BS manufactured by Toshiba Machine Co., Ltd.). The barrel temperature setting of the extruder is 120 ° C. to 150 ° C., the screw rotation speed is 150 rpm, the discharge rate is 35 kg / h, and melt kneading while supplying 70 parts by mass of Toughmer M7010 (E-3b) from the middle of the cylinder with the side feeder. Went. After melt-kneading, a strand is extruded from a 4 mm diameter × 3 hole die, cut into a pellet shape, and 36 ° C. at a temperature of 60 ° C. in a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Kagaku Co., Ltd.). After drying for a time, master batch pellets (M-3) were obtained.

Next, measurement methods and evaluation methods of various characteristic values in the examples were performed as follows.
(1) Relative viscosity The obtained polyamide resin composition pellets were dissolved in 96% by mass sulfuric acid so as to have a concentration of 1 g / dl, filtered through a G-3 glass filter, and subjected to measurement. The measurement was performed in an atmosphere of 25 ° C. using an Ubbelohde viscometer.
(2) Elongation Viscosity A 10 mm × 18 mm × 0.7 mm test piece was prepared from the obtained polyamide resin composition pellets using an elongation viscosity measuring device RME (manufactured by Rheometric). After fixing both ends of the test piece with a metal jig, it is rotated at a strain rate of 0.1 sec-1 at a temperature 10 ° C higher than the melting point of the resin composition, and the measurement sample is stretched and deformed. The elongational viscosity was determined by detecting.

(3) Strain hardening coefficient (see Fig. 1)
In the logarithmic plot of the extension time and extension viscosity in (2), the ratio (a2 / a1) between the slope a1 of the linear region at the initial stage of elongation until the inflection point appears and the slope a2 of the later stage of elongation after the inflection point was calculated. . However, the strain hardening coefficient when the bending point was not observed was 1.
(4) Actual magnification of foaming (Y)
The actual thickness of the obtained injection-foamed molded article was measured and calculated according to the following formula.
Actual magnification of foaming (Y) = (actual thickness of injection foam molded article) / (initial depth)

(5) Impact absorption energy of foamed molded product Using the obtained injection foamed molded product (vertical 50mm x 50mm wide plate-shaped foamed molded product), the impact at the time of breakage with a graphic impact tester (manufactured by Toyo Seiki Seisakusho) Absorbed energy was measured. The impact absorption energy is preferably 1.0 J or more.
(6) Average cell diameter of the foam molded body core section A cross-sectional photograph of an injection foam molded body obtained by a scanning electron microscope was taken, and the equivalent circle diameters of at least 100 adjacent cells were measured. The average value was obtained.

(7) Surface smoothness of foam molded article The surface of the foam molded article was observed, and it was visually determined whether the surface had a uniform thickness due to expansion due to foaming. When the foaming property is poor, the thickness is not uniform with the surface being wavy.
If the thickness is uniform and surface smoothness is high, ◎
If the thickness is uniform but somewhat uneven, ○
When the thickness was not uniform, it was set as x.

Example 1
100 parts by mass of the polyamide resin (A-1) and 0.2 parts by mass of the polytetrafluoroethylene-containing resin (B-1) are dry blended, and a loss-in-weight continuous quantitative supply device CE-W-1 manufactured by Kubota Corporation is used. Were measured and supplied to the main supply port of a twin screw extruder (TEM37BS manufactured by Toshiba Machine Co., Ltd.) having a screw diameter of 37 mm and L / D40. The barrel temperature of the extruder was 270 ° C. to 290 ° C., the screw rotation speed was 250 rpm, and the discharge rate was 35 kg / h. After melt-kneading, a strand is extruded from a 4 mm diameter × 3 hole die, cut into a pellet, and is heated at a temperature of 100 ° C. with a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Scientific Co., Ltd.). After drying for a time, a polyamide resin composition pellet was obtained.
Next, 3 parts by mass of a blowing agent (C-1) is dry blended with 100 parts by mass of the polyamide resin composition pellets, and the mixture is put into an injection molding machine (S-2000i manufactured by FANUC) equipped with a shut-off nozzle. Then, injection molding was performed under conditions of a cylinder temperature of 280 ° C. and a mold temperature of 80 ° C.
At this time, it filled to the flow end of the test piece in 1.2 seconds, and immediately after that, the die plate of the injection molding machine was retracted so that the set foaming ratio was doubled to obtain an injection foam molded article.

Examples 2-9, Comparative Examples 1-5
A polyamide resin composition was obtained in the same manner as in Example 1 except that the type of polyamide resin, the blending amount of the polytetrafluoroethylene-containing resin, and the type of foaming agent were changed as shown in Table 1.
Subsequently, an injection foamed molded article was obtained in the same manner as in Example 1 except that the obtained polyamide-based resin composition was used and the set foaming ratio was changed as shown in Table 1.

Examples 10 to 16, Comparative Example 6
A polyamide-based resin composition was obtained in the same manner as in Example 1 except that the inorganic fillers of the types and amounts shown in Table 1 were supplied from the side feeder of the twin screw extruder and melt kneaded.
Subsequently, an injection foamed molded article was obtained in the same manner as in Example 1 except that the obtained polyamide-based resin composition was used and the set foaming ratio was changed as shown in Table 1.

Example 17, Comparative Example 7
A polyamide-based resin composition was obtained in the same manner as in Example 1 except that the type of polyamide resin, the blending amount of the polytetrafluoroethylene-containing resin, and the foaming agent were changed as shown in Table 1.
Subsequently, an injection foamed molded article was obtained in the same manner as in Example 1 except that the obtained polyamide-based resin composition was used and the set foaming ratio was changed as shown in Table 1.

  Table 1 shows the characteristic values and evaluations of the polyamide resin compositions and the injection-foamed molded articles obtained in Examples 1 to 17 and Comparative Examples 1 to 7.

As is apparent from Table 1, the polyamide resin compositions obtained in Examples 1 to 17 satisfy the compositions specified in the present invention and have a strain hardening coefficient within the optimum range. The injection-foamed molded article was a foamed molded article that sufficiently foamed and had many fine cells, and was excellent in surface smoothness and impact resistance.
On the other hand, since the polyamide resin compositions obtained in Comparative Examples 1, 3, and 7 did not contain the polytetrafluoroethylene-containing resin (B), the polyamide resin compositions obtained in Comparative Example 2 were Since the polytetrafluoroethylene-containing resin (B) was less than 0.05 parts by mass, both the strain hardening coefficient was less than 1.05, the actual foaming ratio was smaller than the set foaming ratio, and the obtained injection foaming The molded product had a large bubble diameter, and was inferior in surface smoothness and impact resistance.
The polyamide-based resin composition obtained in Comparative Example 4 was obtained because the polytetrafluoroethylene-containing resin (B) was too much, the strain hardening coefficient exceeded 10, and the actual foaming ratio was smaller than the set foaming ratio. The injection foam molded article was inferior in surface smoothness and impact resistance.
Since the polyamide resin composition obtained in Comparative Example 5 had a strain hardening coefficient exceeding 10, the actual foaming ratio was smaller than the set foaming ratio, and the resulting injection-foamed molded article had surface smoothness. It was inferior.
Since the polyamide-based resin composition obtained in Comparative Example 6 did not contain the polytetrafluoroethylene-containing resin (B), the strain hardening coefficient was less than 1.05, and the actual foaming ratio was higher than the set foaming ratio. The obtained injection foamed molded product had a large cell diameter and was inferior in surface smoothness.

Example 18
100 parts by mass of the polyamide resin (A-1) and 0.5 parts by mass of the polytetrafluoroethylene-containing resin (B-1) are dry blended, and a loss-in-weight continuous quantitative supply device CE-W-1 manufactured by Kubota Corporation is used. Were measured and supplied to the main supply port of a twin screw extruder (TEM37BS manufactured by Toshiba Machine Co., Ltd.) having a screw diameter of 37 mm and L / D40. The barrel temperature of the extruder was 270 ° C. to 290 ° C., the screw rotation speed was 250 rpm, and the discharge rate was 35 kg / h. After melt-kneading, a strand is extruded from a 4 mm diameter × 3 hole die, cut into a pellet, and is heated at a temperature of 100 ° C. with a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Scientific Co., Ltd.). After drying for a time, a polyamide resin composition pellet was obtained.
Subsequently, the obtained polyamide resin composition pellets were put into an injection molding machine equipped with a supercritical fluid injection device (JJ35ELIII-F manufactured by Nippon Steel), cylinder temperature 250 ° C., mold temperature 60 ° C., Nitrogen supercritical fluid (pressure 24 MPa, flow rate 0.06 kg / h) was injection-molded under conditions of 0.2 s injection. At this time, it filled to the flow end of the test piece in 1.2 seconds, and immediately after that, the die plate of the injection molding machine was retracted so that the set foaming ratio was doubled to obtain an injection foam molded article.

Example 19
A polyamide-based resin composition was obtained in the same manner as in Example 18 except that the inorganic fillers of the types and amounts shown in Table 1 were supplied from the side feeder of the twin screw extruder and melt kneaded.
Subsequently, an injection foamed molded article was obtained in the same manner as in Example 18 except that the obtained polyamide-based resin composition was used and the set foaming ratio was changed as shown in Table 1.

Comparative Example 8
A polyamide-based resin composition was obtained in the same manner as in Example 18 except that the polytetrafluoroethylene-containing resin was not added.
Then, it performed by the method similar to Example 18 using the obtained polyamide-type resin composition, and obtained the injection-foaming molding.

Comparative Example 9
A polyamide-based resin composition was obtained in the same manner as in Example 19 except that the polytetrafluoroethylene-containing resin was not added.
Then, it carried out by the method similar to Example 19 using the obtained polyamide-type resin composition, and obtained the injection-foaming molding.

  Table 2 shows the characteristic values and evaluations of the polyamide resin compositions and the injection-foamed molded articles obtained in Examples 18 to 19 and Comparative Examples 8 to 9.

As is apparent from Table 2, the polyamide resin compositions obtained in Examples 18 and 19 satisfy the compositions specified in the present invention, and the strain hardening coefficient is within the optimum range. The injection-foamed molded article was a foamed molded article that sufficiently foamed and had many fine cells, and was excellent in surface smoothness and impact resistance.
On the other hand, since the polyamide resin compositions obtained in Comparative Examples 8 and 9 did not contain the polytetrafluoroethylene-containing resin (B), the strain hardening coefficient was less than 1.05, and the actual foaming ratio was set. It became smaller than the expansion ratio. For this reason, the injection-foamed molded article obtained in Comparative Example 8 had a large cell diameter, and was inferior in surface smoothness and impact resistance. The injection foam molded article obtained in Comparative Example 9 was inferior in surface smoothness.

Claims (5)

Polyamide resin (A) and polytetrafluoroethylene-containing resin (B) having a relative viscosity determined in the range of 2.0 to 4.0 using 96% sulfuric acid as a solvent at a temperature of 25 ° C. and a concentration of 1 g / 100 ml. A resin composition in which the content of the polytetrafluoroethylene-containing resin (B) is 0.05 to 3 parts by mass with respect to 100 parts by weight of the polyamide resin (A), the melting point of the resin composition plus A polyamide-based resin composition for injection foaming, having a strain hardening coefficient measured at 10 ° C. of 1.05 to 10. Furthermore, 5-100 mass parts of inorganic fillers (C) are contained with respect to 100 weight part of polyamide resins, The polyamide-type resin composition for injection foaming of Claim 1 characterized by the above-mentioned. The polyamide resin composition for injection foaming according to claim 2 , wherein the inorganic filler (C) is at least one selected from talc, silica, and glass fiber. Furthermore, 0.1-5 mass parts of at least 1 sort (s) chosen from an acrylonitrile butadiene styrene copolymer, an ethylene-alpha olefin copolymer, and these acid-modified products are contained with respect to 100 weight part of polyamide resins. The polyamide resin composition for injection foaming according to any one of claims 1 to 3, wherein: An injection-foamed molded article formed from the polyamide-based resin composition for injection foaming according to any one of claims 1 to 4.

Images