JP2014113802A - Polyamide resin composition for water assist injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin composition in which poor appearances such as a shrinkage cavity and a flow mark are not hardly generated by water assist injection molding, and further a formed part in which coating excellent in adhesion can be performed can be obtained without priming.SOLUTION: A polyamide resin composition for water assist injection molding includes: 97-70 mass% of a polyamide and ABS resin composition (C) in which a blending ratio of a crystalline aliphatic polyamide resin (A) in which a relative viscosity measured at 25°C, 1 g/dl is 1.8-3.3 using 96 mass% of concentrated sulfuric acid as a solvent, to an ABS resin (B) is 90/10-50/50 (mass ratio) or a polyamide and ABS resin mixture (C') in which a mix proportion of the crystalline aliphatic polyamide resin (A) to a modification ABS resin (B') is 90/10-50/50 (mass ratio); and 3-30 mass% of a non-crystalline polyamide resin (D), wherein the ABS resin (B) or the modification ABS resin (B') is performed by fine dispersion by an average grain diameter of at most 2 μm.

Description

  The present invention relates to a polyamide resin composition which is easy to be hollow-molded by water-assisted injection molding, has an excellent molded appearance, and has excellent primer-less paintability.

Conventionally, in the field of automobiles, examination of weight reduction has been promoted in consideration of environmental aspects. Gas assist injection molding is known as a weight reduction technique by hollow molding of a resin material (for example, Patent Documents 1 and 2). In gas-assisted injection molding, a high-pressure gas is injected immediately after the resin is injected into the mold in the injection molding, and the mold surface is transferred by the pressure of an inert gas instead of holding pressure to obtain a hollow molded product. It is a technique. In this method, since the pressure holding process is performed with gas pressure, there is a problem that the absolute pressure is insufficient and the transferability of the mold surface is reduced, or the thickness of the hollow molded product is likely to fluctuate. An improvement method for this problem has also been proposed (Patent Document 3). However, since the inert gas easily rises in temperature and hardly exhibits a cooling effect on the molten resin, there is a drawback that the cooling rate of the molten resin is slow and the cycle time becomes very long. In recent years, water-assisted injection molding that can shorten the cycle time and can also mold a large-diameter or long hollow molded product has attracted more attention (Patent Document 4).
Therefore, the use of molding materials used in gas-assisted injection molding for water-assisted injection molding has been studied. However, appearance defects such as sink marks and flow marks are likely to occur, making molding suitable for water-assisted injection molding. There is a need for materials.

JP 11-99533 A JP 2004-352737 A JP 2011-201991 A JP 2006-213041 A

  An object of the present invention is to provide a polyamide resin composition capable of obtaining a molded product that is less likely to cause appearance defects such as sink marks and flow marks by water-assisted injection molding and that can be coated with excellent adhesion without being subjected to primer treatment. Is to provide things.

As a result of diligent research to solve the above-mentioned problems, the present inventors have found that a water-assisted injection molding can provide a molded product having a short molding cycle time, excellent molding appearance, and excellent paintability. . The present invention employs the following configuration.
(1) A crystalline aliphatic polyamide resin (A) having a relative viscosity of 1.8 to 3.3 measured at 25 ° C. and 1 g / dl using 96% by mass concentrated sulfuric acid as a solvent, and an ABS resin (B) The mixing ratio of the polyamide / ABS resin composition (C) having a blending ratio of 90/10 to 50/50 (mass ratio) or the crystalline aliphatic polyamide resin (A) and the modified ABS resin (B ′) is The ABS-based resin containing 97 to 70% by mass of a polyamide / ABS resin mixture (C ′) of 90/10 to 50/50 (mass ratio) and 3 to 30% by mass of an amorphous polyamide resin (D) A polyamide resin composition for water-assisted injection molding, wherein (B) or the modified ABS resin (B ′) is finely dispersed with an average particle size of 2 μm or less.
(2) The polyamide resin composition for water-assisted injection molding according to (1), wherein the crystalline aliphatic polyamide resin (A) is a nanocomposite polyamide resin in which a layered silicate is dispersed at a molecular level in the resin.
(3) The polyamide resin composition for water-assisted injection molding according to (1) or (2), further comprising 2 to 15% by mass of a reinforcing material.
(4) The polyamide resin composition for water-assisted injection molding according to (3), wherein the reinforcing material is magnesium sulfate whisker.
(5) The polyamide resin composition for water-assisted injection molding according to any one of (1) to (4), further containing 0.5 to 5% by mass of a terpene phenol-based resin.

  By using the polyamide resin composition for water-assisted injection molding of the present invention for water-assisted injection molding, appearance defects such as sink marks and flow marks can be suppressed, and coating with excellent adhesion is possible without primer treatment. Can be obtained.

The present invention will be specifically described below.
The crystalline aliphatic polyamide resin (A) used in the present invention (hereinafter sometimes simply referred to as “aliphatic polyamide resin (A)”) is an aliphatic polyamide resin having an acid amide bond (—CONH—) in the molecule. Have a crystalline melting point. Specifically, polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polytetramethylene adipamide (polyamide 46), polyhexamethylene sebamide (polyamide 610), polyhexamethylene dodeca Examples include, but are not limited to, amide (polyamide 610), polylauryl lactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), and copolymers and blends thereof. . From the viewpoint of availability, polyamide 6 and polyamide 66 are preferably used, and polyamide 6 is particularly preferable.

These crystalline aliphatic polyamide resins are preferably nanocomposite polyamide resins obtained by dispersing layered silicates at the molecular level in the resin. The layered silicate is preferably contained in the resin in an amount of 0.1 to 6% by mass. The layered silicate is preferably dispersed at a molecular level of 100 nm or less. Since the strength and rigidity are improved by dispersing the layered silicate in the polyamide resin at the nano level, the amount of reinforcing material added for obtaining the strength and rigidity necessary for the molded product can be lowered.
Examples of the layered silicate include phyllosilicate, smectite clay mineral, vermiculite clay mineral, and mica. Examples of smectite clay minerals include montmorillonite, nontronite, beidellite, vorconite, hectorite, stevensite, pyroloysite, supportite, soconite, magadiaite, kenyanite, and montmorillonite is preferred.

These crystalline aliphatic polyamide resins have a relative viscosity of 1.8 to 3.3 as measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent.
In order to obtain an aliphatic polyamide resin having a relative viscosity of 1.8 to 3.3, the production conditions are adjusted to polymerize a polyamide resin having a relative viscosity of 1.8 to 3.3, or a relative viscosity of 3.3. There is a method of cleaving a polyamide molecular chain using a viscosity reducing agent after producing a super polyamide resin. As the viscosity reducer, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, etc. are effective. Specifically, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, terephthalic acid, etc. Can be mentioned. The addition amount can be obtained by blending around 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyamide resin and melt kneading.

  When an aliphatic polyamide resin having a relative viscosity exceeding 3.3 is used, the fluidity of the resin is lowered, so that it is difficult to obtain a uniform hollow thickness by water pressure, and at the same time, the mold transfer is caused by the low fluidity. It also becomes difficult to obtain a good molded appearance. When an aliphatic polyamide resin having a relative viscosity of less than 1.8 is used, the difference in viscosity between the aliphatic polyamide and the ABS resin increases, and the dispersed particle size of the ABS resin increases, resulting in mechanical strength and impact resistance. Decrease, and paintability also decreases. Furthermore, the viscosity becomes too low, and hollow rupture occurs during water-assisted molding. The relative viscosity of the aliphatic polyamide resin is preferably 2.0 to 3.3, more preferably 2.5 to 3.2.

  As the ABS resin (B) used in the present invention, a commercially available ABS resin can be used. An ABS resin is a graft copolymer obtained by polymerizing two or more compounds selected from a vinyl cyanide compound, an aromatic vinyl compound and an unsaturated carboxylic acid alkyl ester compound in the presence of a conjugated diene rubber. (A). Moreover, the copolymer (b) obtained by superposing | polymerizing 2 or more types of compounds selected from the vinyl cyanide compound, the aromatic vinyl compound, and the unsaturated carboxylic acid alkylester compound as needed can be contained. The composition ratio of the conjugated diene rubber and the above compound in the graft copolymer (a) is not particularly limited, but a composition ratio of 5 to 80% by mass of the conjugated diene rubber and 95 to 20% by mass of the above compound is preferable. . Moreover, it is preferable that the composition ratio of the above-mentioned compound is 0-30 mass% of vinyl cyanide compounds, 30-80 mass% of aromatic vinyl compounds, and 0-70 mass% of unsaturated carboxylic acid alkyl ester compounds. The particle diameter of the conjugated diene rubber is not particularly limited, but is preferably 0.05 to 1 μm. The composition ratio of the above-mentioned compound of the copolymer (b) is 0 to 30% by mass of the vinyl cyanide compound, 50 to 90% by mass of the aromatic vinyl compound, and 0 to 40% by mass of the unsaturated carboxylic acid alkyl ester compound. preferable. The intrinsic viscosity [30 ° C., dimethylformamide (DMF)] of the copolymer (b) is not particularly limited, but is preferably 0.25 to 1.0 dl / g.

  Examples of the conjugated diene rubber include polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, and the like. Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, and chlorostyrene. Examples of unsaturated carboxylic acid alkyl ester compounds include methyl. Examples include acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and hydroxyethyl acrylate. Examples of the production method of the ABS resin include an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, and an emulsion-suspension polymerization method.

  Moreover, as the modified ABS resin (B ′) used in the present invention, the ABS resin (B) is further acid-modified with an acid anhydride such as maleic anhydride, acrylic acid or methacrylic acid. The modified ABS resin (B ′) is more compatible with the crystalline aliphatic polyamide resin (A) than the ABS resin (B). For this reason, the dispersibility is better than that of the ABS resin (B), and it is possible to obtain a desired dispersion state simply by dry blending and kneading with the pellets of the crystalline aliphatic polyamide resin (A). .

The ABS resin (B) or modified ABS resin (B ′) used in the present invention has a content of 10 in the polyamide / ABS resin composition (C) or the polyamide / ABS resin mixture (C ′) of the present invention. It is -50 mass%, Preferably it is 15-45 mass%, More preferably, it is 20-40 mass%. When the content exceeds 50% by mass, the appearance of the molded product is deteriorated. When the content is less than 10% by mass, the effect of improving the paintability tends to be hardly exhibited.
The ABS resin (B) or the modified ABS resin (B ′) must be finely dispersed in the polyamide resin composition of the present invention with an average particle diameter of 2 μm or less. Preferably it is 0.5 micrometer or less. When the average particle diameter exceeds 2 μm, mechanical strength and impact resistance tend to be inferior, and paintability tends to be inferior.
The average particle size of the ABS resin (B) or the modified ABS resin (B ′) is obtained by enlarging the average particle size by 500 times or more with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). . At this time, it can be determined more clearly by selectively dyeing the polyamide component with osmium oxide or the like.

  In the present invention, the polyamide / ABS resin composition (C) or the polyamide / ABS resin mixture (C ′) is contained in an amount of 97 to 70% by mass in the polyamide resin composition. If the content exceeds 97% by mass, the amount of ABS is too small, so that a sufficient coating improvement effect can be obtained, and further, the impact resistance and toughness cannot be improved. If it is less than 70% by mass, the amount of the polyamide resin is reduced, and sufficient mechanical strength and rigidity cannot be obtained. The content of the polyamide / ABS resin composition (C) or the polyamide / ABS resin mixture (C ′) is preferably 95 to 70% by mass, and more preferably 92 to 72% by mass.

The average particle diameter of the ABS resin (B) or the modified ABS resin (B ′) is required to be 2 μm or less in the polyamide resin composition of the present invention. In the polyamide / ABS resin composition to be used, it is preferable that the average particle diameter is already 0.5 μm or less.
In order to make the average particle diameter of the ABS resin (B) 2 μm or less, it is preferable to use a compatibilizing agent. The compatibilizer is selected from carboxylic acid-modified AS resin, carboxylic acid-modified acrylic resin, carboxylic acid anhydride-modified maleimide resin, carboxylic acid-modified ABS resin, carboxylic acid anhydride-modified SEBS resin, and carboxylic acid anhydride-modified EPDM. Can be used. Examples of the carboxylic acids or anhydrides thereof include maleic acid or anhydrides thereof, acrylic acid or methacrylic acid.
The mixing ratio of the compatibilizing agent is 0.1 to 20% by mass, preferably 0.1 to 10% by mass in the polyamide / ABS resin composition.
Moreover, the method of acid-modifying ABS resin using maleic acid or its anhydride, acrylic acid, or methacrylic acid is also mentioned.
In addition, as a polyamide / ABS resin composition having an average particle diameter of 0.5 μm or less, NE6080 and NE6060 manufactured by Nanopolymer Composites Corporation are commercially available and can be used.

  The amorphous polyamide resin (D) used in the present invention does not show a clear melting point when measured with a differential scanning calorimeter (DSC) according to JIS K7121, and is a crystalline aliphatic polyamide resin (A). Difference in SP value ([SP value of amorphous polyamide resin (D)] − [SP value of crystalline aliphatic polyamide resin (A)]) is in the range of −1.0 to 1.0. Some are preferred, and a range of 0 to 1.0 is more preferred.

  Specific examples of the monomer constituting the amorphous polyamide resin (D) include bis (4-amino-cyclohexyl) methane (may be abbreviated as PACM), bis (3-amino-cyclohexyl) methane, bis (3 -Methyl-4-amino-cyclohexyl) methane (may be abbreviated as MACM), 2,2-bis (4-amino-cyclohexyl) propane, isophoronediamine, ε-caprolactam, ω-laurolactam (LL), etc. Lactams, 6-aminocaproic acid, 11-aminoundecanoic acid, aminocarboxylic acid such as 12-aminododecanoic acid, tetramethylenediamine, hexamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4 / 2 4,4-trimethylhexamethylenediamine (TMD), 5-methyl Lunonamethylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 3-aminocyclohexyl-4-aminocyclohexylmethane, 1-amino-3-aminomethyl-3,5 Diamines such as adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecane, and diamines such as 1,5-trimethylcyclohexane, bis (aminopropyl) piperazine, and bis (aminoethyl) piperazine Aliphatic dicarboxylic acids having a linear or alkyl side chain having 4 to 36 carbon atoms such as diacid (sometimes abbreviated as 12), tridecanedioic acid, tetradecanedioic acid (sometimes abbreviated as 14) Terftal acid (sometimes abbreviated as T), isophthalic acid (I Sometimes abbreviated) and an aromatic dicarboxylic acids such as.

Preferred examples of the monomer combination include bis (4-amino-cyclohexyl) methane (PACM), bis (3-amino-cyclohexyl) methane, bis (3-methyl-4-amino-cyclohexyl) methane (MACM), Specific examples include combinations of alicyclic diamines such as 2,2-bis (4-amino-cyclohexyl) propane and dicarboxylic acids such as undecanedioic acid, dodecanedioic acid, tridecanedioic acid, and tetradecanedioic acid. Examples include, but are not limited to, polymers or copolymers or blends of 12MACM, 14MACM, 10MACM / 11, 12MACM / I, I / MACM / LL, T / TMD, 6T6I, etc. .
For example, when the crystalline aliphatic polyamide resin (A) is polyamide 6 (SP value 12.3), 6T6I (SP value 12.9) is preferable.

The content rate in the polyamide resin composition of this invention of an amorphous polyamide resin (D) is 3-30 mass%. When the amount of the amorphous polyamide resin (D) is less than 3% by mass, the cooling and solidification rate in the mold becomes too fast, the thickness after water-assisted molding is uneven, the filler floats, the flow mark, etc. The appearance defect becomes severe and can be visually confirmed even after painting.
On the other hand, when the blending amount of the amorphous polyamide resin (D) exceeds 30% by mass, the cooling and solidifying rate becomes too slow and the releasability is deteriorated, and the mold cannot be released due to close contact with the mold. Release wrinkles appear on the surface. Further, the crystallinity may be deteriorated so that the mechanical strength and impact strength may be lowered. 3-20 mass% is preferable and, as for the content rate of an amorphous polyamide resin (D), 5-15 mass% is more preferable.

  In the present invention, the reason is not clear, but the compatibility of the amorphous polyamide resin (D) is good, and the ABS resin (B) which is an amorphous resin is finely dispersed to 2 μm or less. It is considered that this has a synergistic effect, the cooling and solidification rate is appropriately controlled, and molding with excellent appearance can be achieved by water-assisted molding.

  The terpene phenol-based resin used in the present invention is compatible with the amorphous polyamide resin used in the present invention, can lower the apparent glass transition temperature of the amorphous polyamide resin, and can increase the melt fluidity. . Compared to the case where no terpene phenolic resin is blended, it is difficult to cause a problem in filling even if the molding temperature and mold temperature are lowered, so the cooling time can be shortened and the molding condition range can be widened. . Moreover, the paintability without a primer can be improved.

Because terpene phenolic resins have many hydroxyl groups, they are incorporated into the amide groups of polyamides by hydrogen bonding. As a result, the glass transition temperature of polyamides can be apparently lowered, and adhesion to paint resins can be achieved. Since the property is good, the paint adhesion can be improved.
The terpene phenolic resin used in the present invention is obtained by copolymerizing a monomer component composed of a terpene monomer and a phenolic monomer in an organic solvent in the presence of a Friedel-Craft type catalyst, or further hydrogenating after copolymerization. It means a part of the reaction mixture or the whole composition.

The terpene monomer is a hydrocarbon compound represented by the molecular formula of (C ₅ H ₈ ) n or an oxygen-containing compound derived therefrom. For example, monoterpenes (when n = 2, myrcene, osymene, pinene, limonene) , Citronole, borneol, menthol, camphor, etc.), sesquiterpenes (when n = 3, curcumen, etc.), diterpenes (when n = 4, camphorene, hinokiol, etc.), tetraterpenes (when n = 8) , Carotenoids, etc.) and polyterpenes (natural rubber). Preferred terpenes are monoterpenes, particularly pinene and limonene.

  The phenolic monomer is a compound having at least one hydroxyl group on an aromatic ring such as a benzene ring or a naphthalene ring, and may have a substituent (for example, a halogen atom, an alkyl group) on the aromatic ring. For example, phenol, cresol, xylenol, naphthol, catechol, resorcin, hydroquinone, pyrogallol and the like can be mentioned.

A preferred terpene phenol resin in terms of resistance to discoloration is a copolymer of monoterpenes and phenol. Copolymers of monoterpenes such as α-pinene and limonene and phenol are industrially easy to produce and more preferable.
The hydroxyl value (KOHmg / g) of the terpene phenol resin used in the present invention is usually preferably 150 or more, and more preferably 200 or more from the viewpoint of the effect of suppressing dimensional change due to water absorption.

  The degree of polymerization of the terpene phenol resin used in the present invention is preferably a number average molecular weight of about 500 to 10,000. If it is less than 500, the low molecular weight component may emit smoke upon heating and workability may be deteriorated. If it exceeds 10,000, it becomes a brittle material, which may affect the stickiness and compatibility. Specifically, there are, for example, YS polyster series and Mighty Ace series manufactured by Yashara Chemical Co., Ltd.

  It is preferable that the compounding quantity of the terpene phenol-type resin in this invention is 0.5-5 mass% with respect to a polyamide resin composition, More preferably, it is 1-4 mass%. If the amount is less than 0.5% by mass, almost no expression of the blending effect is observed, and if it exceeds 5% by mass, the mechanical strength is lowered or the terpene phenol deposited on the surface is peeled off.

In order to increase the strength and rigidity of the resin composition of the present invention, it is preferable to contain a needle-like or fibrous reinforcing material, a non-fiber reinforcing material, or the like. Examples of the acicular reinforcing material that can be used in the present invention include potassium titanate whisker, aluminum borate whisker, zinc oxide whisker, calcium carbonate whisker, magnesium sulfate whisker, and wollastonite. In particular, when a reinforcing material having an aspect ratio (fiber length / fiber diameter) of 10 or more is used, the mechanical strength tends to increase. Among them, magnesium sulfate whisker is a preferable reinforcing material in that it has few defects such as poor appearance of a molded product and reduced paintability.
In the present invention, the reinforcing material is preferably contained in the polyamide resin composition in an amount of 2 to 15% by mass. When the content exceeds 15% by mass, the reinforcing material floats on the surface of the molded product, the surface appearance is deteriorated, and at the same time, the coating appearance is also deteriorated. Furthermore, the fluidity of the resin is lowered, and it becomes difficult to obtain uniform hollowness. Moreover, since sufficient intensity | strength and rigidity cannot be obtained if it is less than 2 mass%, as for the content rate of a reinforcing material, 5-15 mass% is more preferable.

  Examples of the fibrous reinforcing material include glass fiber, carbon fiber, boron fiber, ceramic fiber, silicon carbide fiber, stone koji fiber, and metal fiber, and the glass fiber has a length of 0.1 mm to 100 mm. It is possible to use chopped strands or continuous filament fibers. As the cross-sectional shape of the glass fiber, a glass fiber having a circular cross section and a non-circular cross section can be used. The diameter of the circular cross-section glass fiber is 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less. Moreover, the glass fiber of a non-circular cross section is preferable in terms of physical properties and fluidity. Non-circular cross-sectional glass fibers include those that are substantially oval, substantially oval, and substantially bowl-shaped in a cross section perpendicular to the length direction of the fiber length, and have a flatness of 1.5 to 8. It is preferable. Here, the flatness is assumed to be a rectangle with the smallest area circumscribing a cross section perpendicular to the longitudinal direction of the glass fiber, the length of the long side of the rectangle is the major axis, and the length of the short side is the minor axis. It is the ratio of major axis / minor axis. The thickness of the glass fiber is not particularly limited, but the minor axis is about 1 to 20 μm and the major axis is about 2 to 100 μm. Moreover, the glass fiber becomes a fiber bundle, and the thing of the chopped strand shape cut | disconnected by about 1-20 mm of fiber length can use it preferably.

  Examples of non-fiber reinforcing materials include silicates such as wollastonite, zeolite, sericite, talc, kaolin, mica, clay, pyrophyllite, bentonite, and alumina silicate, alumina, silicon oxide, magnesium oxide, zirconium oxide, and titanium oxide. , Metal oxides such as iron oxide, carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as magnesium hydroxide, calcium hydroxide and aluminum hydroxide, milled glass Examples thereof include fibers, glass flakes, glass beads, ceramic beads, boron nitride, and silicon carbide. These reinforcing materials may be hollow, and a plurality of types may be used in combination. In addition, these reinforcing materials are combined with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, and an epoxy compound at the same time as the compounding with the polyamide resin, or processed into a reinforcing material in advance. Is preferable in terms of obtaining better mechanical properties and appearance.

  In addition, in the polymyad resin composition of the present invention, carbon black, zinc sulfide, zinc oxide, iron oxide, chromium compound, nickel compound, which are generally used for polyamide resins within a range not impairing the object of the present invention, Additives such as pigments such as cobalt, cobalt compounds and titanium compounds, organic dyes such as nigrosine, antioxidants, UV absorbers, plasticizers, lubricants, antistatic agents, flame retardants, release agents, etc. can do. These are preferably 5% by mass or less, and more preferably 2% by mass or less, in total in the polymiad resin composition.

The method for producing the polyamide resin composition of the present invention is not particularly limited, and a general single-screw extruder, twin-screw extruder, pressure kneader, or the like can be used as a kneading apparatus. A twin screw extruder is particularly preferred.
As one embodiment, crystalline aliphatic polyamide resin (A), ABS-based resin (B), amorphous polyamide resin (D), and reinforcing materials, pigments, dyes, additives, etc., if necessary, are mixed, A polyamide resin composition can be produced by charging into a twin-screw extruder and uniformly kneading and kneading.
Also, the ABS resin (B) is melt-kneaded with the crystalline aliphatic polyamide resin (A) in advance and dispersed in the crystalline aliphatic polyamide resin (A). It is suitable for the fine dispersion of (B). The kneading temperature is preferably 230 to 320 ° C. and the kneading time is preferably about 0.3 to 10 minutes.

In the present invention, water-assisted molding refers to injection of high-pressure water immediately after a resin is injected into a mold in injection molding, and transfer of the mold surface by water pressure (holding pressure) to form a hollow molded product. Examples of the process include a short shot process, a melt pushback process, a side cavity process, and a core tension process. The cylinder temperature at the time of molding is 220 to 320 ° C, preferably 230 to 290 ° C.
The degree of hollowness of the water-assisted molding obtained in the present invention can be expressed by the uneven thickness that can be observed when the water-assisted molded product is cut at the center. Specifically, the ratio of the thickness of the thickest portion of the cross section to the thickness of the thinnest portion can be made uneven. For example, if the thickness of the thickest part is 4.0 mm and the thickness of the thinnest part is 2.0 mm, the uneven thickness is 2.0 (= 4.0 mm / 2.0 mm). It is. The preferred thickness unevenness in the present invention is 1.0 to 4.0, more preferably 1.0 to 3.0. When the uneven thickness exceeds 4.0, the thickness of the thinnest part is too thin, and the hollow burst during molding or the strength of the molded product is reduced.

  In order to achieve a high hollow ratio, it is preferable to appropriately provide a spillover cavity in the mold cavity in the case where a hollow molded article is molded from the polyamide resin composition of the present invention by a water-assisted molding method. From the viewpoint of improving the utilization efficiency of the polyamide resin composition, at least a part of the spillover cavity can be used as a mold cavity for producing a single molded product.

When water-assisted molding is performed with the polyamide resin composition obtained in the present invention, a molded product having an even wall thickness and a high strength of the molded product and a good appearance after molding can be obtained. In addition, since a wide range of molding conditions can be taken, a good product can be obtained stably.
The molded product obtained by the present invention is suitable for exterior parts of automobiles, electricity, and mechanical parts, and is most suitable for large-diameter and long hollow molded products. In particular, a molded product obtained by water-assisted molding of the resin composition of the present invention is approximately 50 hollow molded products that are thinner, lighter, and have a better molded appearance than molded products obtained by gas injection molding. % Can be mass-produced stably at low cost with a short cycle time.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.
The raw materials used in Examples and Comparative Examples of the present invention are as follows.

[Crystalline aliphatic polyamide resin (A1)]
・ Polyamide 6:
Polyamide resin T-820 manufactured by Toyobo Co., Ltd., relative viscosity 3.2, melting point 224 ° C., SP value: 12.3
[Crystalline aliphatic polyamide resin (A2)]
・ Polyamide 6:
Polyamide resin T-850 manufactured by Toyobo Co., Ltd., relative viscosity 3.5, melting point 224 ° C., SP value: 12.3

[ABS resin (B1)]:
UMG ABS Co., Ltd. 3001M
[Modified ABS resin (B2)]:
UMG ABS Co., Ltd. Acid-modified by passing 3001M with maleic anhydride through a twin screw extruder. Acid modification was carried out by melt-kneading 100 mass% of 3001M with 0.4 mass% of perhexine 25B-40 from Nippon Oil & Fats Co., Ltd. and 0.5 mass% of maleic anhydride as a cross-linking agent using a twin screw extruder.

[Nanocon polyamide 6 / ABS resin master pellet C1]:
NE6080 (Nanocon PA6 / ABS = 60/40 (mass ratio)) manufactured by Nanopolymer Composites Corporation, PA6 relative viscosity 3.0, and 4.0 mass% of layered silicate in PA6 [Nanocon polyamide 6 / ABS resin master Pellet C2]:
NE 6060 (Nanocon PA6 / ABS = 70/30 (mass ratio)) manufactured by Nanopolymer Composites Corporation, PA6 relative viscosity 3.0, and PA6 contains 4.0% by mass of layered silicate.

[Amorphous polyamide resin (D)]
Hexamethylene terephthalate / hexamethylene isophthalate copolymer (6T / 6I): Grivory G21 manufactured by EMS, Tg 135 ° C., SP value: 12.9

[Needle reinforcement E1]
Magnesium sulfate whisker: manufactured by Ube Materials, Mosheidi A-1, aspect ratio 30
[Needle reinforcement E2]
Wollastonite: NYCO Materials Inc. MYGLOS8, aspect ratio 17

[Terpene phenol resin F]:
YS Polystar S145 manufactured by Hayakawa Chemical Co., Ltd.

  Kneading was performed using a twin screw extruder. After pre-mixing with the compositions of Examples and Comparative Examples described in Tables 1 and 2, they were put into a hopper of a twin screw extruder and melt kneaded. The setting conditions of the twin screw extruder were a cylinder temperature of 240 to 280 ° C. and a kneading time of 0.5 to 3 minutes.

  After drying the pellets of Examples and Comparative Examples, water-assisted molding of hollow molded articles (door handles) was performed with an injection molding machine equipped with a water-based hollow article molding apparatus. The mold used was that whose surface was textured (TH-112). Cylinder temperature is 260 ° C and mold temperature is 80 ° C. The cooling time was 25 seconds.

The molded products of Examples and Comparative Examples were evaluated by the following methods.
(B) Melting point, Tc2
A DSC measuring device (EXSTAR6000, manufactured by Seiko Instruments Inc.) was used. It is a numerical value measured by raising the temperature to 300 ° C. at a rate of temperature increase of 20 ° C./min under a nitrogen stream, holding the temperature for 5 minutes, and then decreasing the temperature to 50 ° C. at a rate of 10 ° C./min . The melting point was the peak top of the endothermic peak when the temperature was raised. Similarly, Tc2 is the peak top of the exothermic peak when the temperature is lowered. The DSC measurement sample was cut out from the vicinity of the center of a 100 × 100 × 1 mm flat plate. The flat plate was formed by using Toshiba Machine Co., Ltd. injection molding machine IS-80G at a cylinder temperature of 240 ° C., a mold temperature of 80 ° C., and an injection pressure of 100 MPa.

(B) Measuring method of ABS resin dispersed particle size A cross section of a 100 × 100 × 1 mmt flat plate is allowed to stand under osmium oxide vapor, and then magnified 1000 times with a scanning electron microscope, and 100 or more ABS resins are measured. The particle diameter was measured and the average value was determined.

(C) Uneven thickness The ratio of the wall thickness of the thinnest part to the wall thickness of the thinnest section of the water-assisted hollow molded product cut at the center.
(D) Releasability It was evaluated whether the water-assisted hollow molded product could be released smoothly.
○: The mold could be released smoothly.
Δ: Mold release wrinkles appeared on the surface of the molded product.
X: The mold could not be released.

(E) Paint appearance Urethane paint was applied with a spray gun so that the paint film thickness was about 30 μm. The baking temperature was 100 ° C. × 30 minutes.
◎: Good glossy appearance of paint ○: Level at which the flow mark and filler float are not visible after painting ×: Level at which the flow mark and filler float can be confirmed even after painting

(F) Paint adhesion strength:
The strength of adhesion is 10mm long and 30mm long cylindrical metal jig with a hook on one side. Aron Alpha 101 is used to bond the metal jig to the coated product, and the hook part is pulled with a push-pull gauge. Asked.
A: The peel strength exceeds 200 N, and the broken base material is attached to the peeled paint.
○: Peeling force is 150N or more and 200N or less.
X: Peeling force is less than 150N.

(G) Flexural strength, flexural modulus, deflection rate A multipurpose specimen A type was molded according to JIS K7152. The cylinder temperature at this time is 260 ° C., and the mold temperature is 280 ° C. Thereafter, bending strength, flexural modulus, and deflection rate were determined in accordance with JIS K7171. When the deflection rate exceeded 12%, it was determined as NB.
(H) Charpy A multi-purpose test piece A shaped according to JIS K7152 was notched according to JIS K7141, and then a Charpy impact test was performed according to JIS K7111.

  Various evaluations are shown in Tables 1 and 2.

  In Examples 1 and 2, polyamide 6 having RV = 3.2 and a modified ABS resin are used. The dispersed particle diameter of ABS became 2 μm or less, and good coating strength could be obtained. Further, due to the effect of the amorphous polyamide resin, appearance defects such as flow marks and filler floating became inconspicuous and could be concealed by painting. On the other hand, in Comparative Example 1 using polyamide 6 with RV = 3.5, the flowability at the time of molding is low and the thickness of the hollow becomes uneven, and at the same time, the flow mark and the filler float are conspicuous and are visually observed after coating. It became a level that can be confirmed with. Also. In Comparative Example 2 using unmodified ABS, the dispersed particle size of ABS increased, the deflection rate and Charpy decreased, and at the same time the coating appearance deteriorated and the coating strength also decreased.

Examples 3 to 5 are cases where a master batch of nano PA6 / ABS was used. Since the ABS particle size was dispersed to 0.5 μm or less, Charpy was high and excellent coating strength could be exhibited. Also, the appearance of the coating is excellent due to the effect of the amorphous polyamide resin. The same excellent results were obtained in Example 6 in which the fiber reinforcement was wollastonite.
Although the result which was excellent also in Example 7 which excluded the terpene phenol resin from the composition was compared with Example 4 which added terpene phenol, the coating strength became low.
On the other hand, in Comparative Example 3 in which the amount of ABS added was low, the ABS component was insufficient, so that sufficient coating strength could not be obtained.

When the addition amount of the amorphous polyamide resin was reduced, the coating appearance and coating strength were almost excellent in Example 8, but the coating appearance was inferior to that of Example 6. Further, in Comparative Example 4 containing no amorphous polyamide resin, the flow marks and the filler floated out clearly, and even when painted, the level was visually recognized.
On the contrary, when the amount of the amorphous polyamide resin was increased (the amount of the polyamide / ABS resin composition was decreased), in the comparative example 5, the releasability deteriorated and the release wrinkles remained on the appearance, and even after coating In Comparative Example 6 in which the amount of the amorphous polyamide resin was increased so that the release wrinkles could be recognized, it was stuck to the mold and could not be released.

  By using the polyamide resin composition for water-assisted injection molding of the present invention for water-assisted injection molding, occurrence of poor appearance such as sink marks and flow marks can be suppressed, and coating with excellent adhesion without primer treatment is possible. A molded product can be obtained. Therefore, it is most suitable for exterior members in the electric and electronic fields and automobile fields, especially for automobile door handles, which are lightweight and have high design.

Claims (5)

  The blending ratio of the crystalline aliphatic polyamide resin (A) and the ABS resin (B) having a relative viscosity of 1.8 to 3.3 measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent is 90/10 to 50/50 (mass ratio) of the polyamide / ABS resin composition (C) or the mixing ratio of the crystalline aliphatic polyamide resin (A) and the modified ABS resin (B ′) is 90/10. 50 to 50 (mass ratio) of polyamide / ABS resin mixture (C ′) 97 to 70% by mass and amorphous polyamide resin (D) 3 to 30% by mass, the ABS resin (B) Alternatively, the polyamide resin composition for water-assisted injection molding, wherein the modified ABS resin (B ′) is finely dispersed with an average particle size of 2 μm or less.   2. The polyamide resin composition for water-assisted injection molding according to claim 1, wherein the crystalline aliphatic polyamide resin (A) is a nanocomposite polyamide resin in which a layered silicate is dispersed in a resin at a molecular level.   The polyamide resin composition for water-assisted injection molding according to claim 1 or 2, further comprising 2 to 15% by mass of a reinforcing material.   The polyamide resin composition for water-assisted injection molding according to claim 3, wherein the reinforcing material is magnesium sulfate whisker. Furthermore, the polyamide resin composition for water assist injection molding in any one of Claims 1-4 formed by containing 0.5-5 mass% of terpene phenol-type resin.