JP2023066409A - Thermoplastic resin composition pellet - Google Patents

Abstract

To provide a thermoplastic resin composition pellet which enables good foam molding on a molder side without further using a foaming agent in molding.SOLUTION: A thermoplastic resin composition pellet contains 30-100 pts.mass of (A) a polybutylene terephthalate resin having intrinsic viscosity of 0.3-1.3 dl/g, 0-70 pts.mass of (B) polystyrene or rubber-reinforced polystyrene resin, and 0.5-20 pts.mass of (C) a thermally expansible microsphere having a maximum expansion temperature of 250-320°C and an average particle diameter of 10-50 μm, with respect to 100 pts.mass of the total of (A) and (B).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to thermoplastic resin composition pellets, and more particularly, thermoplastic resin composition pellets that can stably and efficiently produce pellets that can be foam-molded directly on the molder side without blending a foaming agent at the time of molding. Regarding.

Polybutylene terephthalate resin has excellent mechanical strength, chemical resistance, electrical insulation, etc., and is therefore widely used for electrical and electronic equipment parts, interior and exterior parts for automobiles, other electrical parts, mechanical parts, and the like. Polyethylene terephthalate resin is mainly used for extruded products such as bottles, fibers, sheets, and films, but polybutylene terephthalate resin is mainly used for injection molded products because it has much better moldability than polyethylene terephthalate resin. It is widely used as various parts in injection molding.
Molded articles of polybutylene terephthalate resin are often used as metal substitutes for the purpose of weight reduction, but there is a strong demand for further weight reduction. For example, in the automotive field, weight reduction is important not only for improving fuel efficiency but also for improving safety and comfort. .

As a method for obtaining a foam-molded product, there is a method of dissolving supercritical carbon dioxide or nitrogen in a resin to create minute foam cells during injection molding. Not limited to injection foam molding, it is common to dry-blend an organic or inorganic foaming agent with a raw material resin before molding, and to foam simultaneously with molding. However, when a molder in the foam molding business performs foam molding, dry-blending a foaming agent in advance forces the addition of complicated work. In addition, the foaming agent tends to be classified, and the weight and dimensions of the molded product are not stable. It is desirable for the molder to be fed from the compounder with resin composition pellets that contain the desired additives together with the blowing agent together in precise amounts so that the foam molding molder can produce a homogeneous and well-shaped polybutylene terephthalate resin. It becomes possible to manufacture a foam molded article with good productivity.

Patent Document 1 describes an invention of a resin composition containing a recycled polyethylene terephthalate resin and a dimensional stability-imparting agent, and describes that a profile extruded article excellent in dimensions can be produced by extrusion molding. However, a method of mixing the heat-expandable microspheres or a masterbatch containing the heat-expandable microspheres with the recycled polyethylene terephthalate resin is not clearly suggested, and although moistening with a liquid compound is preferable, These methods do not adequately address the risk of blowing agent classification and molding machine hopper contamination. In addition, the invention is a technology that attempts to compensate for the drawbacks of polyethylene terephthalate resin, which has a low melt viscosity and melt tension and is extremely slow to crystallize as a result of being recycled. It does not have the high rigidity and strength required for the intended use. Furthermore, since polyethylene terephthalate resin has a higher melting point than polybutylene terephthalate resin, it is difficult to obtain resin composition pellets that are suitable for molding and are not foamed even after melt-kneading.

In addition to extrusion foam molding and injection foam molding, a general method for obtaining a foam molded product is to dry-blend an organic or inorganic foaming agent with a raw material resin at the time of molding, and melt-knead the mixture to foam. However, when a molder in the foam molding business performs foam molding, dry-blending a foaming agent in advance forces the addition of complicated work. It is desirable for the molder to be fed from the compounder with resin composition pellets that contain the desired additives together with the blowing agent together in precise amounts so that the foam molding molder can produce a homogeneous and well-shaped polybutylene terephthalate resin. It becomes possible to manufacture a foam molded article with good productivity.

Polybutylene terephthalate resin composition pellets are usually produced by melt-kneading with an extruder, but the temperature during melt-kneading of the crystalline polybutylene terephthalate resin is close to the foaming temperature of the foaming agent. It has a problem that it easily foams in an extruder. In this respect, in the case of a reinforcing system in which a reinforcing filler is mixed with polybutylene terephthalate resin to improve mechanical strength and heat resistance, the hard reinforcing filler stimulates the foaming agent, and foaming and foaming are likely to occur. Therefore, it is particularly noticeable.

JP 2014-019750 A

A method for producing a good foam-molded article directly from polybutylene terephthalate resin composition pellets by injection molding without dry-blending a foaming agent or the like has not yet been known.
An object of the present invention is to solve the above-described problems and to provide a novel thermoplastic resin composition pellet that does not require the addition of a foaming agent and can be foam-molded as it is at the manufacturing site.

As a result of intensive studies to solve the above-described problems, the present inventors have found that polybutylene terephthalate resin and polystyrene or rubber-reinforced polystyrene resin having a specific intrinsic viscosity, as a foaming agent, have a thermal expansion temperature that has a maximum expansion temperature within a specific temperature range. The present inventors have found that the above-mentioned problems can be solved by compounding and pelletizing polymorphic microspheres, and arrived at the present invention.
The present invention relates to the following thermoplastic resin composition pellets.

1. (A) 30 to 100 parts by mass of polybutylene terephthalate resin having an intrinsic viscosity of 0.3 to 1.3 dl / g, (B) 0 to 70 parts by mass of polystyrene or rubber-reinforced polystyrene resin (A) and ( 0.5 to 20 parts of (C) thermally expandable microspheres having a maximum expansion temperature in the range of 250 to 320° C. and an average particle diameter in the range of 10 to 50 μm, with respect to a total of 100 parts by mass of B) A thermoplastic resin composition pellet characterized by containing parts by mass.
2. 1. The pellet according to 1 above, further comprising (D) an inorganic filler of 10 to 100 parts by mass with respect to a total of 100 parts by mass of (A) and (B).
3. (B) The pellet according to 1 or 2 above, wherein the polystyrene or rubber-reinforced polystyrene resin has a melt viscosity of 80 to 500 Pa·s at 250° C. and 912 sec ⁻¹ .
4. (D) The pellet according to 2 or 3 above, wherein the inorganic filler is a fibrous filler.
5. 4. The pellet according to any one of 1 to 4 above, further comprising 0 to 30 parts by mass of a polycarbonate resin as a compatibilizer (E) with respect to a total of 100 parts by mass of (A) and (B).
6. 6. The pellet according to any one of 1 to 5 above, which is an injection molding material.
7. A molded product obtained by foam-molding the pellet according to any one of 1 to 6 above.
8. 8. The molded product as described in 7 above, wherein the specific gravity of the foamed molded product is reduced by 15% or more relative to the specific gravity of the unfoamed molded product.
9. 9. The molded article according to 7 or 8 above, which is a molded part mounted on an automobile.

The thermoplastic resin composition pellets of the present invention can be foam-molded as they are on the molder side without further using a foaming agent during molding. A foam-molded product obtained by foam-molding the pellets has a great effect of reducing weight, has a good shape and appearance, has no problem of sink marks or warping, and is excellent in heat resistance.
In addition, the polybutylene terephthalate resin becomes a sea (matrix) with a sea-island structure or a sea with a co-continuous structure, and polystyrene resin or rubber-reinforced polystyrene resin with high melt viscosity tends to become islands, which results in high heat resistance, low warpage, and good appearance. Excellent mechanical strength and chemical resistance.
In addition, if a compatibilizer is further contained, the strength and appearance can be further improved.
In addition, when an inorganic filler is further contained, the resin phase of the polybutylene terephthalate resin becomes continuous through the inorganic filler, making it easy to form a matrix (sea). In addition, it is excellent in low warpage and appearance, as well as in mechanical strength and chemical resistance. In the case of a reinforcing system in which a reinforcing filler is mixed, the hard reinforcing filler stimulates the foaming agent and tends to cause foaming and foam breakage. It's groundbreaking when you think about it.

The thermoplastic resin composition pellets of the present invention include (A) 30 to 100 parts by mass of polybutylene terephthalate resin having an intrinsic viscosity of 0.3 to 1.3, and (B) 0 to 70 parts by mass of polystyrene or rubber-reinforced polystyrene resin. It is characterized by containing 0.5 to 20 parts by mass of (C) thermally expandable microspheres with respect to a total of 100 parts by mass of (A) and (B) containing parts.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. Although the explanations described below may be made based on embodiments and specific examples, the present invention should not be construed as being limited to such embodiments and specific examples.
In this specification, the term "~" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

[(A) Polybutylene terephthalate resin]
In the present invention, (A) polybutylene terephthalate resin having an intrinsic viscosity (IV) of 0.3 to 1.3 dl/g is used. If the IV is lower than 0.3 dl/g, the heat resistance of the polybutylene terephthalate resin is not exhibited, and the mechanical strength tends to be low. On the other hand, if it is higher than 1.3 dl/g, the flowability of the obtained resin composition pellets is poor, the moldability tends to deteriorate, and the heat-expandable microspheres tend to break due to heat generated by shearing. Sink marks are likely to occur during foam molding, making it difficult to obtain good foam molded products.
IV is preferably 0.4 dl/g or more, more preferably 0.5 dl/g or more, further 0.55 dl/g or more, more preferably 0.6 dl/g or more, and preferably 1.2 dl/g 1.1 dl/g or less, 1.0 dl/g or less, 0.9 dl/g or less, or 0.8 dl/g or less is preferable, and 0.75 dl/g or less is particularly preferable.

In the present invention, the intrinsic viscosity of (A) polybutylene terephthalate resin is a value measured at 30° C. in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.

(A) Polybutylene terephthalate resin is a polyester resin having a structure in which terephthalic acid units and 1,4-butanediol units are ester-linked, and in addition to polybutylene terephthalate resin (homopolymer), terephthalic acid units and 1 ,4-butanediol units, polybutylene terephthalate copolymers containing other copolymerization components, and mixtures of homopolymers and such copolymers.

(A) The polybutylene terephthalate resin may contain dicarboxylic acid units other than terephthalic acid. Specific examples of other dicarboxylic acids include isophthalic acid, orthophthalic acid, 1,5-naphthalene dicarboxylic acid, 2,5 -naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-3,3'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, bis(4,4'- carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4′-diphenylether dicarboxylic acid and other aromatic dicarboxylic acids; 1,4-cyclohexanedicarboxylic acid, 4,4′-dicyclohexyldicarboxylic acid and other alicyclic dicarboxylic acids; and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and dimer acid.

The diol unit may contain other diol units in addition to 1,4-butanediol, and specific examples of other diol units include aliphatic or alicyclic diols having 2 to 20 carbon atoms. , bisphenol derivatives and the like. Specific examples include ethylene glycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, decamethylene glycol, cyclohexanedimethanol, 4,4′-dicyclohexylhydroxymethane, 4,4 '-dicyclohexylhydroxypropane, ethylene oxide-added diol of bisphenol A, and the like. In addition to the above bifunctional monomers, trifunctional monomers such as trimellitic acid, trimesic acid, pyromellitic acid, pentaerythritol, and trimethylolpropane for introducing a branched structure, and fatty acids for molecular weight adjustment. A small amount of monofunctional compound can also be used together.

(A) Polybutylene terephthalate resin, as described above, is preferably a polybutylene terephthalate homopolymer obtained by polycondensation of terephthalic acid and 1,4-butanediol. A polybutylene terephthalate copolymer containing one or more dicarboxylic acids other than terephthalic acid as carboxylic acid units and/or one or more diols other than 1,4-butanediol as diol units, as long as the polybutylene terephthalate copolymer does not impair the When the (A) polybutylene terephthalate resin is a polybutylene terephthalate resin modified by copolymerization, specific preferred copolymers thereof include polyalkylene glycols, particularly polytetramethylene glycol polyester ether resin copolymerized with, dimer acid-copolymerized polybutylene terephthalate resin, and isophthalic acid-copolymerized polybutylene terephthalate resin.
In the case of these copolymers, the copolymerization amount is preferably 1 mol % or more and less than 50 mol % in all segments of the polybutylene terephthalate resin. Among them, the copolymerization amount is preferably 2 mol % or more and less than 50 mol %, more preferably 3 to 40 mol %, particularly preferably 5 to 20 mol %. By setting such a copolymerization ratio, fluidity and toughness tend to be improved, which is preferable.

(A) The polybutylene terephthalate resin preferably has a terminal carboxyl group content of 0.1 to 30 eq/ton. If it exceeds 30 eq/ton, hydrolysis resistance and alkali resistance tend to decrease, and gas tends to be generated during foam molding of the resin composition pellets. The amount of terminal carboxyl groups is more preferably 3 eq/ton or more, more preferably 5 eq/ton or more, more preferably 25 eq/ton or less, still more preferably 20 eq/ton or less.

The terminal carboxyl group content of (A) polybutylene terephthalate resin was measured by dissolving 0.5 g of polybutylene terephthalate resin in 25 mL of benzyl alcohol and titrating with a 0.01 mol/l benzyl alcohol solution of sodium hydroxide. is the value to As a method for adjusting the amount of terminal carboxyl groups, any conventionally known method may be used, such as a method of adjusting polymerization conditions such as the raw material charge ratio during polymerization, the polymerization temperature, and a decompression method, or a method of reacting a terminal blocking agent. You can do it.

(A) Polybutylene terephthalate resin is obtained by melt-polymerizing a dicarboxylic acid component or ester derivative thereof mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol in a batch or continuous manner. can be manufactured by Further, after producing a low-molecular-weight polybutylene terephthalate resin by melt polymerization, the degree of polymerization (or molecular weight) can be increased to a desired value by solid-phase polymerization under a nitrogen stream or under reduced pressure.
(A) Polybutylene terephthalate resin is obtained by a production method in which a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing 1,4-butanediol as a main component are continuously subjected to melt polycondensation. is preferred.

Catalysts used in carrying out the esterification reaction may be those conventionally known, and examples thereof include titanium compounds, tin compounds, magnesium compounds, calcium compounds, and the like. Particularly suitable among these are titanium compounds. Specific examples of the titanium compound as the esterification catalyst include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate.

[(B) Polystyrene or rubber-reinforced polystyrene resin]
In the present invention, (B) polystyrene or rubber-reinforced polystyrene resin is contained in an amount of 0 to 70 parts by mass based on a total of 100 parts by mass of (A) polybutylene terephthalate and (B) polystyrene or rubber-reinforced polystyrene resin.

(B) The polystyrene or rubber-reinforced polystyrene resin is preferably amorphous. Here, the term "amorphous" refers to a property in which a clear melting point and melting peak are not detected when a sample is measured using a differential scanning calorimeter (DSC) or the like. Conversely, crystallinity refers to the property of having a crystalline structure in which molecules are regularly arranged and having a melting point and a melting peak measured by a differential scanning calorimeter (DSC) or the like. Syndiotactic polystyrene or the like in which benzene rings are regularly arranged alternately with respect to the polymer main chain is crystalline and is preferably excluded from the (B) polystyrene or rubber-reinforced polystyrene resin.

The polystyrene resin may be a homopolymer of styrene or a copolymer obtained by copolymerizing other aromatic vinyl monomers such as α-methylstyrene, paramethylstyrene, vinyltoluene, vinylxylene, etc., in a range of 50% by mass or less. There may be.

The rubber-reinforced polystyrene resin is preferably copolymerized or blended with a butadiene-based rubber component, and the amount of the butadiene-based rubber component is usually 1% by mass or more and less than 50% by mass, preferably 3 to 40% by mass. , more preferably 5 to 30% by mass, more preferably 5 to 20% by mass. High impact polystyrene (HIPS) is particularly preferred as the rubber-reinforced polystyrene resin.

In the present invention, (B) polystyrene or rubber-reinforced polystyrene resin preferably has a melt viscosity in the range of 80 to 500 Pa·s at 250° C. and 912 sec ⁻¹ . (B) polystyrene or rubber-reinforced polystyrene resin having such a melt viscosity (η _B ), based on a total of 100 parts by mass of (A) and (B), (A) polybutylene terephthalate resin 30 to 100 parts by mass, ( By containing B) polystyrene or rubber-reinforced polystyrene resin in an amount of 0 to 70 parts by mass and further containing (C) thermally expandable microspheres, (A) polybutylene terephthalate resin becomes dominant in terms of physical properties, and its As a result, high heat resistance, low warpage, and low specific gravity can be achieved. If the melt viscosity is 80 Pa·s or more, the heat resistance can be more easily improved. Further, when the melt viscosity is 500 Pa·s or less, excellent production stability, fluidity, and foam moldability can be further improved.

(B) The content of polystyrene or rubber-reinforced polystyrene resin is 0 to 70 parts by mass, more preferably 10 parts by mass or more, more preferably 100 parts by mass in total of (A) and (B) 20 parts by mass or more, particularly preferably 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, and 55 parts by mass or more, more preferably 65 parts by mass or less.

(B) The melt viscosity (η _B ) of the polystyrene or rubber-reinforced polystyrene resin is more preferably 90 Pa·s or more, particularly preferably 100 Pa·s or more, 110 Pa·s or more, or 120 Pa·s or more. In addition, the upper limit is more preferably 400 Pa s or less, further 300 Pa s or less, especially 250 Pa s or less, 220 Pa s or less, 200 Pa s or less, 180 Pa s or less, or 160 Pa s or less. is particularly preferred.

The melt viscosity of (B) polystyrene or rubber-reinforced polystyrene resin can be measured according to ISO 11443 using a capillary rheometer and a slit die rheometer. Specifically, using an orifice with a capillary diameter of 1 mm and a capillary length of 30 mm, a furnace body with an inner diameter of 9.5 mm heated to 250 ° C. was pressed at a piston speed of 75 mm / min. Viscosity can be calculated.

[(C) Thermally expandable microspheres]
The present invention contains (C) thermally expandable microspheres having a maximum expansion temperature in the range of 250 to 320°C.

(C) Thermally expandable microspheres are microspherical foaming agents that can be foamed by heating. Microspheres, such as microcapsules, encapsulated within may be used. Such heat-expandable microspheres can be produced by any appropriate method such as coacervation, interfacial polymerization, and the like.

Substances that easily expand when heated include, for example, propane, (iso)butane, (iso)pentane, (iso)hexane, (iso)heptane, (iso)octane, (iso)nonane, (iso)decane, ( Iso) Hydrocarbons having 3 to 13 carbon atoms such as undecane, (iso) dodecane, and (iso) tridecane; Hydrocarbons having more than 13 carbon atoms and 20 or less such as (iso) hexadecane and (iso) eicosane; , hydrocarbons such as petroleum fractions such as normal paraffins and isoparaffins having an initial boiling point of 150 to 260° C. and/or a distillation range of 70 to 360° C.; their halides; fluorine-containing compounds such as hydrofluoroethers; Silane; a compound that is thermally decomposed by heating to generate a gas, and the like can be mentioned. These thermal expansion substances may be used singly or in combination of two or more. Among those mentioned above, the thermally expandable substance is preferably a linear, branched, or alicyclic hydrocarbon, more preferably an aliphatic hydrocarbon.

Examples of substances constituting the shell include nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; acrylic acid, methacrylic acid, itaconic acid, maleic acid, Carboxylic acid monomers such as fumaric acid and citraconic acid; vinylidene chloride; vinyl acetate; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) ) Acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, β-carboxyethyl acrylate (meth) acrylic esters; styrene, α-methylstyrene, styrene monomers such as chlorostyrene; acrylamide , substituted acrylamide, methacrylamide, amide monomers such as substituted methacrylamide; and the like. A polymer composed of these monomers may be a homopolymer or a copolymer. Examples of the copolymer include vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, acrylonitrile-methacrylonitrile-itaconic acid copolymer, A polymer etc. are mentioned.

(C) The heat-expandable microspheres have an average particle size in the range of 10 to 50 μm. When the average particle size of the heat-expandable microspheres is within the above range, a compact having a light weight and a good appearance can be obtained. The upper limit of the average particle size of the heat-expandable microspheres is preferably 40 µm, more preferably 30 µm. On the other hand, the lower limit of the average particle size of the heat-expandable microspheres is preferably 15 μm.

Specifically, the average particle size is preferably measured by the following method.
A Microtrac particle size distribution analyzer (model 9320-HRA) manufactured by Nikkiso Co., Ltd. is used as a measuring device, and the D50 value obtained by volume-based measurement is taken as the average particle diameter.

(C) The expansion start temperature of the thermally expandable microspheres is preferably in the range of 215 to 270°C. Examples of specific preferred measurement methods are as follows. The expansion initiation temperature is more preferably 220° C. or higher, still more preferably 225° C. or higher, more preferably 230° C. or higher, still more preferably 235° C. or higher, especially 240° C. or higher, 245° C. or higher, particularly 250° C. or higher. is preferred. Since the expansion start temperature is within the above range, it is suitable for producing a foamed molded article using the obtained resin composition pellets, and the foamed molded article has a particularly large effect of weight reduction due to foaming. It is preferable because it has excellent appearance and shape.

(C) Thermally expandable microspheres having a maximum expansion temperature in the range of 250 to 320°C are used. The maximum expansion temperature means the temperature at which the expansion of the thermally expandable microspheres reaches its maximum, and a specific example of a preferred measuring method is as follows. The maximum expansion temperature is preferably 255° C. or higher, more preferably 260° C. or higher, preferably 310° C. or lower, more preferably 300° C. or lower, especially 290° C. or lower, 285° C. or lower, particularly 280° C. or lower. preferable. Since the maximum expansion temperature is within the above range, it is suitable for producing a foam molded article using the resin composition pellets, and the foam molded article has a particularly large effect of weight reduction due to foaming, and the appearance and appearance of the foam molded article. Excellent shape.

Specifically, the expansion start temperature and the maximum expansion temperature are preferably measured by the following method.
As a measuring device, using a dynamic viscoelasticity measuring device (DMA), 0.5 mg of the sample is put in an aluminum cup with a diameter of 6.0 mm and a depth of 4.8 mm, and an aluminum lid (diameter of 5.6 mm, 0.1 mm thick) is placed on the sample, and the height of the sample is measured while a force of 0.01 N is applied to the sample from above with a pressurizer. Heat from 20°C to 300°C at a rate of 10°C/min with a force of 0.01 N applied by the presser, measure the amount of displacement in the vertical direction of the presser, and measure the displacement start temperature in the positive direction. is the expansion start temperature of the thermally expandable microspheres, and the temperature at which the maximum amount of displacement is exhibited is the maximum expansion temperature.

(C) Thermally expandable microspheres may be commercially available. Specific examples of commercially available heat-expandable microspheres include "Matsumoto Microspheres" (trade name) manufactured by Matsumoto Yushi Seiyaku Co., Ltd., "Expancel" (trade name) manufactured by Nippon Philite Co., Ltd., and Kureha Chemical Industry Co., Ltd. (trade name). "Daifoam", trade name "Advancel" manufactured by Sekisui Chemical Co., Ltd., and the like can be mentioned.

(C) The content of thermally expandable microspheres is preferably 0.5 to 20 parts by mass with respect to a total of 100 parts by mass of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. is 1 part by mass or more, more preferably 1.5 parts by mass or more, especially 2 parts by mass or more, 2.5 parts by mass or more, 3 parts by mass or more, preferably 17 parts by mass or less, more preferably 15 parts by mass or less Among them, 13 parts by weight or less, 12 parts by weight or less, 11 parts by weight or less, 10 parts by weight or less, 9 parts by weight or less, and particularly 8 parts by weight or less are preferable.
(C) The thermally expandable microspheres may be in the form of a masterbatch with a thermoplastic resin as the base resin, but the above content does not include the thermoplastic resin that is the base of the masterbatch, C) The content of the thermally expandable microspheres alone, which is the content alone in the resin composition pellets.

In the present invention, the (C) thermally expandable microspheres may be masterbatched with a thermoplastic resin as a base resin.

The base resin used for masterbatching has good compatibility with (A) polybutylene terephthalate resin, such as ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, Olefin resins such as ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polybutene, polyisobutylene, polystyrene, polyterpene; styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, etc. thermoplastic resin elastomers such as polyester elastomers, styrene elastomers and olefin elastomers; and polyester resins such as isophthalic acid copolymer polybutylene terephthalate resins. The masterbatch is preferably prepared at a temperature equal to or lower than the expansion start temperature of the heat-expandable microspheres.

The concentration of (C) the heat-expandable microspheres in the masterbatch is not particularly limited, but is preferably 20% by mass or more, more preferably 25% by mass or more, especially 30% by mass or more, 35% by mass or more, and particularly 40% by mass or more. % by mass or more, preferably 80% by mass or less, more preferably 75% by mass or less, more preferably 70% by mass or less, 65% by mass or less, and particularly preferably 60% by mass or less. If the concentration is too low or too high, the resulting thermoplastic resin composition pellets tend to exhibit poor foaming effects during foam molding.

An extruder, preferably a twin-screw extruder, is used to produce the thermoplastic resin composition pellets of the present invention. Various types of twin-screw extruders can be used, and the screw rotation system may be a co-rotating type or a counter-rotating type, but a co-meshing type twin-screw extruder is preferred. The screw length, diameter, engagement ratio, etc. of the twin-screw extruder can be set arbitrarily. Also, the twin-screw extruder may be provided with a vent port that is open to reduced pressure or the atmosphere.

(A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin are supplied from a supply port at the base of the extruder, and both resins are mixed and melted in the first kneading section. (C) The heat-expandable microspheres or a masterbatch thereof are not supplied together with (A) and (B) to the supply port at the base of the extruder, but (A) polybutylene terephthalate resin and (B) polystyrene or It is preferably side-fed after the rubber-reinforced polystyrene resin has been melted.

The components (A), (B) and (C) are melt-kneaded in the downstream second kneading section. The heating temperature during melt-kneading is preferably carried out by setting the maximum cylinder temperature to 250°C, and the resin temperature is preferably in the range of 210 to 245°C, more preferably 215°C or higher, further preferably 220°C or higher. and more preferably 235° C. or less. Under such conditions, each component can be uniformly dispersed while suppressing foaming during the production of resin composition pellets.

After melt-kneading, the strands are extruded through a nozzle of a die plate at the tip of the extruder, cooled and cut by a cutter to obtain thermoplastic resin composition pellets.

[(D) inorganic filler]
In the present invention, it is preferable to further contain (D) an inorganic filler.
In the case of reinforcing systems in which inorganic fillers are mixed with polybutylene terephthalate resin to improve its mechanical strength and heat resistance, inorganic fillers do not soften even at high temperatures, and many of them have high rigidity and hard sharp edges (C ) It is thought that the heat-expandable microspheres are likely to be damaged or lost during melt-kneading, resulting in foaming or bubble breakage. Then, as shown in the examples, such problems are solved.

(D) Inorganic fillers include fibrous and non-fibrous fillers. When the inorganic filler is fibrous, examples thereof include glass fiber, carbon fiber, silica/alumina fiber, and zirconia fiber. , boron fibers, boron nitride fibers, silicon nitride potassium titanate fibers, metal fibers, and inorganic fibers such as wollastonite, and particularly preferred are carbon fibers and glass fibers.

Carbon fibers preferably have an average fiber diameter of 1 to 25 μm, particularly 8 to 15 μm, and an average fiber length in the long axis direction of 1 to 10 mm, particularly 2 to 5 mm. If the average fiber diameter is less than 1 μm, the bulk density tends to be low, uniform dispersibility tends to decrease, and moldability tends to be impaired. On the other hand, if the average fiber diameter is larger than 25 μm, the appearance of the molded product tends to be impaired and the reinforcing effect tends to be insufficient. On the other hand, if the average fiber length is too short, the reinforcing effect is insufficient, and if the average fiber length is too long, workability during kneading and molding processability are impaired, which is not preferable.

As the glass fiber, if it is usually used for polybutylene terephthalate resin, A glass, E glass, alkali resistant glass composition containing zirconia component, chopped strand, roving glass, master of thermoplastic resin and glass fiber Any known glass fiber can be used irrespective of the form of the glass fiber at the time of blending in a batch or the like. Of these glass fibers, alkali-free glass (E-glass) is preferred for the purpose of improving the thermal stability of the thermoplastic resin composition pellets or foam-molded articles thereof.

Glass fibers and carbon fibers may be treated with a sizing agent or a surface treatment agent. In addition to the untreated glass fibers and carbon fibers, a sizing agent and a surface treatment agent may be added for surface treatment during the production of the thermoplastic resin composition pellets.

Examples of the sizing agent include resin emulsions such as vinyl acetate resins, ethylene/vinyl acetate copolymers, acrylic resins, epoxy resins, polyurethane resins and polyester resins.
Examples of surface treatment agents include aminosilane compounds such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropyltrimethoxysilane; vinyltrichlorosilane; Chlorosilane compounds such as chlorosilane, alkoxysilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxy Epoxysilane-based compounds such as silane, γ-glycidoxypropyltrimethoxysilane, acrylic compounds, isocyanate-based compounds, titanate-based compounds, and epoxy-based compounds are included.
Two or more of these sizing agents and surface treatment agents may be used in combination, and the amount used (adhesion amount) is usually 10% by mass or less, preferably 0.05 to 0.05%, based on the mass of the glass fiber or carbon fiber. 5% by mass. By setting the adhesion amount to 10% by mass or less, necessary and sufficient effects can be obtained, which is economical.

(D) Inorganic fillers other than fibrous inorganic fillers preferably include plate-shaped, granular or amorphous inorganic fillers. Examples of plate-like materials include talc, mica, wollastonite, kaolin, calcium carbonate, glass flakes, etc. Talc, mica, wollastonite, kaolin, calcium carbonate, etc. are preferred.
Other particulate or amorphous inorganic fillers include ceramic beads, asbestos, clay, zeolites, potassium titanate, barium sulfate, titanium oxide, silicon oxide, aluminum oxide, magnesium hydroxide, and the like.

The content of (D) inorganic filler is preferably 10 to 100 parts by mass, more preferably 100 parts by mass in total of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. 10 to 90 parts by mass, preferably 10 to 80 parts by mass, particularly preferably 10 to 70 parts by mass, most preferably 10 to 60 parts by mass. By containing in such a range, a high degree of heat resistance can be achieved, and the strength of the foamed molded product from the obtained resin composition pellets and the effect of reducing the shrinkage rate can be easily enhanced, and the content is 100 parts by mass. If it exceeds 10 parts by mass, the surface appearance of the molded article may deteriorate, and if it is less than 10 parts by mass, the effect of improving the strength tends to decrease.

(D) When an inorganic filler is contained, particularly in the case of a fibrous inorganic filler, it is preferable to side-feed during production with an extruder, and (A) polybutylene terephthalate resin and (B) polystyrene or rubber reinforcement It is preferable to side-feed the polystyrene resin after it is melted, and then side-feed (C) the thermally expandable microspheres or the masterbatch.

[(E) compatibilizer]
In the present invention, it is preferable to further contain (E) a compatibilizer. By containing (E) a compatibilizer, (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin, (C) thermally expandable microspheres or thermoplastic resin of masterbatch are compatibilized. Acceleration reduces the dispersed particle size of each component and increases the interfacial strength, thereby making it easier to obtain excellent mechanical strength and excellent appearance.

(E) The compatibilizing agent is not particularly limited as long as it can achieve a compatibilizing function with the resin, and from the viewpoint of heat resistance, a polymer compound-based compatibilizing agent is preferable.
As the (E) compatibilizer, a polycarbonate resin or a styrene-maleic acid copolymer is particularly preferred.

Polycarbonate resins are optionally branched thermoplastic polymers or copolymers obtained by reacting a dihydroxy compound or a small amount of a polyhydroxy compound with phosgene or a carbonic acid diester. The method for producing the polycarbonate resin is not particularly limited, and one produced by a conventionally known phosgene method (interfacial polymerization method) or melting method (transesterification method) can be used.

The raw material dihydroxy compound does not substantially contain a bromine atom, and is preferably an aromatic dihydroxy compound. Specifically, 2,2-bis(4-hydroxyphenyl)propane (that is, bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, 4,4- Examples include dihydroxydiphenyl and the like, preferably bisphenol A. A compound in which one or more tetraalkylphosphonium sulfonates are bonded to the above aromatic dihydroxy compound can also be used.

Among the polycarbonate resins mentioned above, aromatic polycarbonate resins derived from 2,2-bis(4-hydroxyphenyl)propane, or 2,2-bis(4-hydroxyphenyl)propane and other aromatic dihydroxy Aromatic polycarbonate copolymers derived from a compound are preferred. It may also be a copolymer mainly composed of an aromatic polycarbonate resin, such as a copolymer with a polymer or oligomer having a siloxane structure. Furthermore, two or more of the above polycarbonate resins may be mixed and used.

Monohydric aromatic hydroxy compounds may be used to control the molecular weight of polycarbonate resins, such as m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol, p-long chain Alkyl-substituted phenols and the like can be mentioned.

The viscosity-average molecular weight (Mv) of the polycarbonate resin is preferably 15,000 or more. If the Mv is lower than 15,000, the resulting resin composition tends to have low mechanical strength such as impact resistance. Also, Mv is preferably 60,000 or less, more preferably 40,000 or less, and even more preferably 35,000 or less. If it is higher than 60,000, the fluidity of the resin composition may deteriorate and the moldability may deteriorate.

In the present invention, the viscosity average molecular weight (Mv) of the polycarbonate resin is obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at a temperature of 25 ° C. using an Ubbelohde viscometer to determine the intrinsic viscosity [η]. shows a value calculated from the Schnell viscosity formula.
[η]=1.23×10 ⁻⁴ Mv ^0.83

The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melt method (transesterification method) can be used. Also preferred is a polycarbonate resin prepared by subjecting a polycarbonate resin produced by a melting method to a post-treatment for adjusting the amount of terminal OH groups.

The styrene-maleic acid copolymer is preferably a styrene-maleic anhydride copolymer (SMA resin), which is a copolymer of a styrene monomer and a maleic anhydride monomer. Known polymerization methods are possible.

The molecular weight and the like of the styrene-maleic acid copolymer are not particularly limited. It is preferably 80,000 or more and 350,000 or less. Here, the weight average molecular weight is the polystyrene equivalent weight average molecular weight measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

Other monomer components can be copolymerized with the styrene-maleic acid copolymer as long as the properties of the present invention are not impaired. vinyl cyanide-based monomers, unsaturated carboxylic acid alkyl ester-based monomers such as methyl methacrylate and methyl acrylate, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc. and the like, and these can be used alone or in combination of two or more.

The content of (E) compatibilizer is preferably 1 to 25 parts by mass, more preferably 3 to 100 parts by mass in total of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. 20 parts by mass, more preferably 3 to 18 parts by mass.

(E) When the compatibilizer is polycarbonate resin and/or styrene-maleic acid copolymer, the content of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin is 100 parts by mass in total. On the other hand, both alone or in total are preferably 0 to 30 parts by mass, more preferably 1 to 25 parts by mass, still more preferably 3 to 20 parts by mass, and particularly preferably 3 to 18 parts by mass.

[Stabilizer]
In the present invention, it is preferable to contain a stabilizer from the viewpoint of improving thermal stability and preventing deterioration of mechanical strength, transparency and hue. Phosphorus-based stabilizers, sulfur-based stabilizers and phenol-based stabilizers are preferred as stabilizers.

Phosphorus-based stabilizers include phosphorous acid, phosphoric acid, phosphites (phosphites), trivalent phosphates (phosphonites), pentavalent phosphates (phosphates) and the like, among which phosphites , phosphonites and phosphates are preferred.

The organic phosphate compound preferably has the following general formula:
(R ¹ O) _3-n P(=O)OH _n
(In the formula, R ¹ is an alkyl group or an aryl group, which may be the same or different. n represents an integer of 0 to 2.)
It is a compound represented by More preferably, R ¹ is a long-chain alkyl acid phosphate compound having 8 to 30 carbon atoms. Specific examples of alkyl groups having 8 to 30 carbon atoms include octyl group, 2-ethylhexyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, dodecyl group, tridecyl group, isotridecyl group, tetradecyl group, A hexadecyl group, an octadecyl group, an eicosyl group, a triacontyl group and the like can be mentioned.

Examples of long-chain alkyl acid phosphates include octyl acid phosphate, 2-ethylhexyl acid phosphate, decyl acid phosphate, lauryl acid phosphate, octadecyl acid phosphate, oleyl acid phosphate, behenyl acid phosphate, phenyl acid phosphate, nonylphenyl acid phosphate, cyclohexyl Acid phosphate, phenoxyethyl acid phosphate, alkoxypolyethylene glycol acid phosphate, bisphenol A acid phosphate, dimethyl acid phosphate, diethyl acid phosphate, dipropyl acid phosphate, diisopropyl acid phosphate, dibutyl acid phosphate, dioctyl acid phosphate, di-2-ethylhexyl acid phosphate, dioctyl acid phosphate, dilauryl acid phosphate, distearyl acid phosphate, diphenyl acid phosphate, bisnonylphenyl acid phosphate and the like. Among these, octadecyl acid phosphate is preferred, and this product is commercially available from ADEKA under the trade name "ADEKA STAB AX-71".

The organic phosphite compound preferably has the following general formula:
R ² OP(OR ³ )(OR ⁴ )
(wherein R ² , R ³ and R ⁴ are each a hydrogen atom, an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 30 carbon atoms, and among R ² , R ³ and R ⁴ is an aryl group having 6 to 30 carbon atoms.)
The compound represented by is mentioned.

Examples of organic phosphite compounds include triphenylphosphite, tris(nonylphenyl)phosphite, dilaurylhydrogenphosphite, triethylphosphite, tridecylphosphite, tris(2-ethylhexyl)phosphite, tris(tridecyl ) phosphite, tristearyl phosphite, diphenyl monodecyl phosphite, monophenyl didecyl phosphite, diphenyl mono (tridecyl) phosphite, tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra (tridecyl) pentaerythritol tetraphosphite , hydrogenated bisphenol A phenol phosphite polymer, diphenyl hydrogen phosphite, 4,4′-butylidene-bis(3-methyl-6-tert-butylphenyl di(tridecyl)phosphite), tetra(tridecyl) 4,4 '-isopropylidene diphenyl diphosphite, bis (tridecyl) pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, dilauryl pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tris(4- tert-butylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, hydrogenated bisphenol A pentaerythritol phosphite polymer, bis(2,4-di-tert-butylphenyl)pentaerythritol di Phosphites, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 2,2′-methylenebis(4,6-di-tert-butylphenyl)octylphosphite, bis( 2,4-dicumylphenyl)pentaerythritol diphosphite and the like. Among these, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite is preferred.

The organic phosphonite compound preferably has the following general formula:
R ⁵ -P(OR ⁶ )(OR ⁷ )
(wherein R ⁵ , R ⁶ and R ⁷ are each a hydrogen atom, an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 30 carbon atoms, and among R ⁵ , R ⁶ and R ⁷ is an aryl group having 6 to 30 carbon atoms.)
The compound represented by is mentioned.

Examples of organic phosphonite compounds include tetrakis(2,4-di-iso-propylphenyl)-4,4'-biphenylene diphosphonite, tetrakis(2,4-di-n-butylphenyl)-4,4'-biphenyl diphosphonite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylenediphosphonite, tetrakis(2,4-di-tert-butylphenyl)-4,3'-biphenylenediphosphonite night, tetrakis(2,4-di-tert-butylphenyl)-3,3'-biphenylenediphosphonite, tetrakis(2,6-di-iso-propylphenyl)-4,4'-biphenylenediphosphonite, Tetrakis (2,6-di-n-butylphenyl)-4,4'-biphenylene diphosphonite, tetrakis (2,6-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite, tetrakis ( 2,6-di-tert-butylphenyl)-4,3'-biphenylenediphosphonite, tetrakis(2,6-di-tert-butylphenyl)-3,3'-biphenylenediphosphonite, and the like. .

As the sulfur-based stabilizer, any conventionally known sulfur atom-containing compound can be used, and thioethers are particularly preferable. Specific examples include didodecylthiodipropionate, ditetradecylthiodipropionate, dioctadecylthiodipropionate, pentaerythritol tetrakis(3-dodecylthiopropionate), thiobis(N-phenyl-β-naphthylamine ), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropylxanthate, trilauryltrithiophosphite. Among these, pentaerythritol tetrakis(3-dodecylthiopropionate) is preferred.

Phenolic stabilizers include, for example, pentaerythritol tetrakis (3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4 -hydroxyphenyl)propionate, thiodiethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), pentaerythritol tetrakis(3-(3,5-di-neopentyl-4-hydroxyphenyl) ) propionate) and the like. Among these, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is preferred.

One stabilizer may be contained, or two or more stabilizers may be contained in any combination and ratio.

The content of the stabilizer is preferably 0.001 to 2 parts by mass with respect to a total of 100 parts by mass of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. If the content of the stabilizer is less than 0.001 part by mass, it is difficult to expect an improvement in thermal stability, and a decrease in molecular weight and deterioration in color are likely to occur when the resin composition pellets are foam-molded. If it exceeds , the amount becomes excessive, and there is a tendency that silver generation and hue deterioration tend to occur more easily. The stabilizer content is more preferably 0.01 to 1.5 parts by mass, and still more preferably 0.1 to 1 part by mass.

[Release agent]
In the present invention, it is preferable to contain a release agent. As the release agent, known release agents that are commonly used for polybutylene terephthalate resins can be used. Among them, polyolefin compounds and fatty acid ester compounds are preferred in terms of good alkali resistance, and in particular, Polyolefin compounds are preferred.

Examples of polyolefin compounds include compounds selected from paraffin waxes and polyethylene waxes. Among them, those having a weight average molecular weight of 700 to 10,000, more preferably 900 to 8,000 are preferred.

Examples of fatty acid ester compounds include saturated or unsaturated monovalent or divalent aliphatic carboxylic acid esters, fatty acid esters such as glycerol fatty acid esters, sorbitan fatty acid esters, and partially saponified products thereof. Among them, mono- or di-fatty acid esters composed of fatty acids having 11 to 28 carbon atoms, preferably 17 to 21 carbon atoms, and alcohols are preferred.

Examples of fatty acids include palmitic acid, stearic acid, caproic acid, capric acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, melicic acid, tetralyacontanoic acid, montanic acid, adipic acid, and azelaic acid. be done. Fatty acids may also be cycloaliphatic.
Alcohols may include saturated or unsaturated monohydric or polyhydric alcohols. These alcohols may have substituents such as fluorine atoms and aryl groups. Among these, monohydric or polyhydric saturated alcohols having 30 or less carbon atoms are preferred, and saturated monohydric or polyhydric alcohols having 30 or less carbon atoms are more preferred. Here, the term "aliphatic" also includes alicyclic compounds.
Specific examples of such alcohols include octanol, decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol, diethylene glycol, glycerin, pentaerythritol, 2,2-dihydroxyperfluoropropanol, neopentylene glycol, ditrimethylolpropane, dipentaerythritol, and the like. is mentioned.
The above ester compound may contain aliphatic carboxylic acid and/or alcohol as impurities, or may be a mixture of a plurality of compounds.

Specific examples of fatty acid ester compounds include glycerin monostearate, glycerin monobehenate, glycerin dibehenate, glycerin-12-hydroxy monostearate, sorbitan monobehenate, pentaerythritol monostearate, pentaerythritol di stearate, stearyl stearate, ethylene glycol montanic acid ester, and the like.

The content of the release agent is preferably 0.1 to 3 parts by mass, but 0.2 parts by mass, with respect to a total of 100 parts by mass of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. It is more preferably up to 2.5 parts by mass, still more preferably 0.3 to 2 parts by mass. If the amount is less than 0.1 part by mass, the resulting resin composition pellets are likely to be released poorly during foam molding, resulting in poor surface properties. The kneading workability at the time tends to deteriorate, and the surface of the foamed molded product tends to become cloudy.

[Carbon black]
In the present invention, it is preferable to contain carbon black.
Carbon black is not limited in its type, raw material type, and production method, and any of furnace black, channel black, acetylene black, ketjen black, etc. can be used. Although the number average particle diameter is not particularly limited, it is preferably about 5 to 60 nm.

Carbon black is preferably blended as a masterbatch premixed with a thermoplastic resin, preferably a polyalkylene terephthalate resin, particularly a polybutylene terephthalate resin.

The content of carbon black is preferably 0.1 to 4 parts by mass, more preferably 0.2 to 3 parts by mass, with respect to a total of 100 parts by mass of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin. part by mass. If it is less than 0.1 part by mass, the desired black color may not be obtained or the effect of improving weather resistance may not be sufficient, and if it exceeds 4 parts by mass, mechanical properties may deteriorate.

[Other ingredients]
In the present invention, thermoplastic resins other than those described above can be contained within a range that does not impair the effects of the present invention. Specific examples of other thermoplastic resins include polyacetal resins, polyamide resins, polyphenylene oxide resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetherimide resins, polyetherketone resins, and polyolefin resins. etc.
However, when other resins are contained, the amount is preferably 20 parts by mass or less with respect to a total of 100 parts by mass of (A) polybutylene terephthalate resin and (B) polystyrene or rubber-reinforced polystyrene resin, and 10 parts by mass. It is more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

In addition, various additives other than those described above may be contained, and such additives include flame retardants (especially brominated phthalimide, brominated polyacrylate, brominated polycarbonate, brominated epoxy, brominated polystyrene, etc.). ), flame retardant aids (especially antimony trioxide, etc.), anti-dripping agents, ultraviolet absorbers, antistatic agents, anti-fogging agents, anti-blocking agents, plasticizers, dispersants, antibacterial agents, coloring agents, dyes and pigments, etc. mentioned.

[Molded body]
The thermoplastic resin composition pellets of the present invention are not particularly limited, but any molding method generally employed for thermoplastic resin compositions can be applied. Examples include injection molding, ultra-high speed injection molding, injection compression molding, two-color molding, hollow molding such as gas assist, molding using heat insulating molds, and rapid heating molds. Molding method, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding) molding method, extrusion molding method, sheet molding method, thermoforming method, rotational molding method, laminate molding method, press molding method, A blow molding method and the like can be mentioned.
Among them, the thermoplastic resin composition pellets of the present invention are preferable as a material for injection molding, and also as a material for foam molding for producing a foam molded article.

In the thermoplastic resin composition pellets of the present invention, it is preferable that the rate of decrease (change rate) of the specific gravity of the foam-molded product relative to the specific gravity of the unfoamed product is 15% or more. The rate of decrease in specific gravity due to foaming and light weight effect is the specific gravity reduction rate (%) obtained by dividing the specific gravity (g/cm ³ ) of the resulting foamed molded product by the specific gravity (g/cm ³ ) of the unfoamed molded product. Say. The reduction rate of specific gravity, which is the effect of foaming and light weight, is more preferably 16% or more, more preferably 17% or more, particularly preferably 18% or more, preferably 60% or less, more preferably 50% or less, and further It is preferably 45% or less, particularly preferably 40% or less. An unfoamed molded article can be obtained, for example, by applying a holding pressure as high as 50% or more of the injection peak pressure during injection molding.

[Foam molding]
The method for producing a foam molded article using the thermoplastic resin composition pellets of the present invention is not particularly limited, and any molding method commonly used for thermoplastic resin compositions can be employed. , injection foam molding, press foam molding, and in-mold foam molding. Among them, the injection foam molding method is preferable because the productivity and the effect of the present invention are remarkable. As the injection foam molding method, the mold cavity is filled by injection, and (C) the short shot method in which the voids in the mold cavity are filled by the expansion pressure of the thermally expandable microspheres, or a mold with a variable mold cavity volume. A preferred example is a core-back method in which the mold cavity is filled by injection, the movable mold is retracted, and (C) the expansion pressure of the thermally expandable microspheres fills the voids in the mold cavity.

The resulting foamed molded product has a great effect of reducing weight, has a good shape, has no problems of sink marks and warping, and has excellent heat resistance. It is suitable for use as an electronic component and other electrical components.
Electrical and electronic device parts include various housing parts such as relay cases, smart meter housings, industrial breaker housings, inverter cases, mobile phone housings, warming device housings, IH cooker housings, and button cases. , grill handles, coil peripheral members, rice cooker protective frames, battery separators, battery cases, electronic component transport trays, battery transport trays, automotive charging equipment members, and the like.
Automotive parts include various housings mounted in automobiles, such as housings for engine control units (ECU), housings for head-up displays installed in automobiles, cases for batteries installed in automobiles, covers and separators. , various motor cases, sensor cases, camera cases, holder parts, air conditioner wind direction control plates, door mirror stays, door trims, automotive electrical connector parts, etc.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention should not be construed as being limited to the following examples.

(Examples 1 to 5, Comparative Examples 1 to 3)
The raw material components used are as shown in Table 1 below.

Among the components shown in Table 1 above, the components other than (C) and (D) are uniformly mixed in a tumbler mixer at the ratios shown in Table 2 below (all parts by mass), and then a twin-screw extruder ( It was supplied from the first supply port at the base of "TEM41SX" (L/D=60) manufactured by Shibaura Machine Co., Ltd. The component (C) was side-fed after the component (D) was side-fed.
The maximum cylinder set temperature is 250 ° C., the resin temperature shown in Table 2, the discharge rate is 100 kg / h, and the screw rotation speed is 170 rpm. and then pelletized using a pelletizer to obtain pellets of the thermoplastic resin composition.

[Heat resistance evaluation of pellets]
Place the pellets obtained above in an oven at a temperature of 120 ° C and dry for 6 hours. When removing the pellets, observe whether the pellets are fused together. , the heat resistance was evaluated as × when the pellets were fused to each other.

[Appearance evaluation of pellet]
20 g of the pellets obtained above were visually screened and evaluated according to the following criteria.
○: White foreign matter with a diameter of 1 mm or more was not confirmed △: Pellets with white foreign matter with a diameter of 1 mm or more were confirmed to be 5 g or less ×: Pellets with white foreign matter with a diameter of 1 mm or more were confirmed to exceed 5 g

[Injection foam molding]
The obtained pellets of the resin composition are pre-dried at 120° C. for 6 hours, and foam injection molding is performed by a short shot method using a J85AD injection molding machine manufactured by Japan Steel Works, Ltd. equipped with a shut-off nozzle. A foam-molded product of 3 mm and 40 mm long×120 mm wide was obtained. The molding conditions were a cylinder temperature of 260° C., a mold temperature of 80° C., an injection speed of 100 mm/sec and 300 mm/sec, a cooling time of 20 seconds, a back pressure of 5 MPa, and a holding pressure of 0 MPa.

[Evaluation of sink marks in foam molded product]
The presence or absence of sink marks in the foam-molded product after the foam injection molding was visually observed and judged according to the following criteria.
○: No sink marks observed △: 1 to 5 minute sink marks with a diameter of less than 3 mm ×: Large sink marks with a diameter of 3 mm or more, or 6 or more minute sink marks with a diameter of less than 3 mm

[Evaluation of Specific Gravity of Foam Molded Product and Foam Weight Reduction Effect]
The specific gravity (g/cm ³ ) of the obtained foamed molded product was measured, and this was divided by the specific gravity (g/cm ³ ) of the unfoamed molded product, and the reduction rate (%) of the specific gravity was obtained as the foaming weight reduction effect ( %) in Table 2. An unfoamed molded article can be obtained, for example, by applying a holding pressure as high as 50% or more of the injection peak pressure during injection molding. The specific gravity of each molded product was measured by the underwater gravimetric method using a Shimadzu Corporation "top-pan electronic analysis balance AW320".

[Evaluation of warpage]
Using an injection molding machine ("NEX80" manufactured by Nissei Plastic Industry Co., Ltd.), a cylinder temperature of 260°C, a mold temperature of 80°C, and an injection time of 0.5 sec were used to form a disc with a diameter of 100 mm and a thickness of 1.6 mm. The disc was shaped using a mold, the warp amount (unit: mm) of the disc was determined, and the warp property was evaluated and determined according to the following criteria. The holding pressure was 80% of the peak pressure.
◯: The amount of warp is less than 2.0 mm Δ: The amount of warp is 2.0 mm or more and 10.0 mm or less ×: The amount of warp is more than 10.0 mm The results are shown in Table 2 below.

The thermoplastic resin composition pellets of the present invention can be foam-molded directly on the molder side without using a foaming agent at the time of molding, and the produced foam-molded product has a large effect of reducing weight and has a good shape. The utility value is particularly high for foam molding of various parts to be mounted on electric and electronic equipment parts and automobiles that require weight reduction.

Claims (9)

(A) 30 to 100 parts by mass of polybutylene terephthalate resin having an intrinsic viscosity of 0.3 to 1.3 dl / g, (B) 0 to 70 parts by mass of polystyrene or rubber-reinforced polystyrene resin (A) and ( 0.5 to 20 parts of (C) thermally expandable microspheres having a maximum expansion temperature in the range of 250 to 320° C. and an average particle diameter in the range of 10 to 50 μm, with respect to a total of 100 parts by mass of B) A thermoplastic resin composition pellet characterized by containing parts by mass. The pellet according to claim 1, further comprising (D) an inorganic filler of 10 to 100 parts by mass with respect to a total of 100 parts by mass of (A) and (B). (B) The pellets according to claim 1 or 2, wherein the polystyrene or rubber-reinforced polystyrene resin has a melt viscosity of 80 to 500 Pa·s at 250°C and 912 sec ^-1 . 3. The pellet according to claim 2, wherein (D) the inorganic filler is a fibrous filler. 3. The pellet according to claim 1, further comprising 0 to 30 parts by mass of a polycarbonate resin as a compatibilizer (E) with respect to a total of 100 parts by mass of (A) and (B). 3. The pellet according to claim 1, which is an injection molding material. A molded article obtained by foam-molding the pellet according to claim 1 or 2. 8. The molded product according to claim 7, wherein the specific gravity of the foamed molded product decreases by 15% or more with respect to the specific gravity of the unfoamed molded product. The molded article according to claim 7 or 8, which is a molded part mounted on an automobile.