JP6926416B2 - Resin molded body and manufacturing method of resin molded body - Google Patents

Description

The present invention relates to a resin molded product and a method for producing the resin molded product.

Resin molded products having air bubbles inside are used in automobiles, OA equipment, and the like for the purpose of weight reduction and cost reduction by reducing the materials used. Such a resin molded body is molded, for example, by injection molding of a resin composition.

Examples of the resin composition include a composition containing a thermoplastic resin and a pyrolytic chemical foaming agent such as sodium citrate, a composition containing a thermoplastic resin and a foaming agent such as nitrogen and carbon dioxide, and the like. A composition containing a thermoplastic resin and a physical foaming agent using a heat-expandable microcapsule containing a volatile swelling agent is known.

Further, a resin composition having a rubber-reinforced styrene-based resin and a pyrolysis-type foaming agent that generates carbon dioxide gas or the like is known (see, for example, Patent Document 1). Then, a resin molded body is molded by injection molding of this resin composition. The resin molded product described in Patent Document 1 manufactured in this way has a uniform size of bubbles regardless of the portion of the resin molded product, and is excellent in mechanical performance and surface appearance.

Japanese Unexamined Patent Publication No. 2011-037925

However, the resin molded product of the resin composition described in Patent Document 1 has a problem of low flame retardancy because the surface area of the resin molded product at the time of combustion becomes large due to air bubbles. As described above, it is difficult to achieve both a high weight reduction rate and a high flame retardancy with the conventional resin molded product.

Therefore, an object of the present invention is to provide a resin molded product having both a high weight reduction rate and a high flame retardancy.

The present invention provides a resin molded product made of a thermoplastic resin and containing a plurality of bubbles, in which a flame retardant is present on the surface of the bubbles.

In the present invention, the resin composition in which the thermoplastic resin is melted by melt-kneading a resin composition containing a thermoplastic resin and a flame retardant and a thermal expansion agent containing a volatile agent contained in the flame retardant. Provided is a method for producing a resin molded body, which comprises a step of volatilizing the volatile agent in an object to generate bubbles and a step of molding the resin composition in which the bubbles are generated.

According to the present invention, it is possible to provide a resin molded product having both a high weight reduction rate and a high flame retardancy.

Hereinafter, the resin molded product according to the embodiment of the present invention will be described.

(Structure of resin molded product)
The resin molded body is made of a thermoplastic resin, contains a plurality of bubbles, and a flame retardant is present on the surface of the bubbles.

The thermoplastic resin can be appropriately selected from resins capable of containing a plurality of bubbles. Examples of thermoplastic resins include polyolefin resins (polyethylene resin, ethylene-vinyl acetate copolymer, polypropylene resin, etc.), polycarbonate resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polyamideimide resin, polyether. Etherketone resin, polyether sulfone resin, polyimide resin, polyvinyl chloride resin, polystyrene resin (polystyrene resin, syndiotactic polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile, butadiene, styrene copolymer synthetic resin (ABS resin) ), Etc.), polyamide resin, polyacetal resin, acrylic resin, cellulose resin (cellulose acetate, etc.), polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, 1,2-polybutadiene-based thermoplastic Includes elastomers, ethylene-vinyl acetate copolymer-based thermoplastic elastomers, fluororubber-based thermoplastic elastomers, chlorinated polyethylene-based thermoplastic elastomers, and the like. Such a thermoplastic resin may be used alone or in combination of two or more. The thermoplastic resin is preferably polystyrene from the viewpoint of fluidity and moldability during injection molding described later.

The thermoplastic resin may be prepared or a commercially available product may be purchased. When purchasing a thermoplastic resin, Dicstyrene XC515 (DIC Corporation; "Dickstyrene" is a registered trademark of the company) can be used as polystyrene (PS). As the ABS resin, Stylac 321 (Asahi Kasei Chemicals Co., Ltd .; "Stylac" is a registered trademark of the company) can be used. As the polycarbonate (PC), Toughlon A-1900 (Idemitsu Kosan Co., Ltd .; "Taflon" is a registered trademark of the company) can be used. As polyethylene (PE), Evaflex EV550 (Mitsui / DuPont Polychemical Co., Ltd .; "Evaflex" is a registered trademark of the company) can be used. As polyethylene (PP), Novatec BC3LS (Japan Polypropylene Corporation; "Novatec" is a registered trademark of the company) can be used. As polyethylene terephthalate (PET), Dianite MA521HD25 (Mitsubishi Rayon Co., Ltd .; "Dianite" is a registered trademark of the company) can be used.

The resin molded product contains a plurality of bubbles. Here, the "bubble" means a space formed inside and on the surface of the thermoplastic resin. The bubbles may or may not be independently present inside the thermoplastic resin. That is, a plurality of bubbles may be continuous. The bubbles may face the surface of the resin molded product. When the bubbles are located on the surface of the resin molded product, the surface of the resin molded product has slight irregularities.

The diameter of the bubbles is preferably in the range of 5 to 250 μm, more preferably in the range of 5 to 100 μm. When the diameter of the bubbles is less than 5 μm, it is necessary to include many bubbles in order to increase the weight reduction rate, and the strength of the resin molded product may decrease. On the other hand, when the diameter of the bubbles exceeds 250 μm, the proportion of bubbles in the resin molded body increases, and the strength of the resin molded body may decrease.

Further, the content of air bubbles in the resin molded product can be expressed as a weight reduction rate of the resin molded product. The weight reduction rate of the resin molded product is preferably in the range of 5 to 30%, and more preferably in the range of 20 to 30%. The weight reduction rate can be calculated by, for example, the following formula.
[Lightening rate] =
(Relative Density of Non-foamed Mold-Specific Density of Resin Mold) / Specific Density of Non-foamed Mold Here, "the specific density of the non-foamed molded product" is determined by a hydrometer (DME-220H; Shinko Denshi Co., Ltd.). Use the calculated value.
If the weight reduction rate is less than 5%, the weight reduction is not sufficient. On the other hand, if the weight reduction rate exceeds 30%, the strength may be insufficient.

In the resin molded product, a flame retardant is present on the surface of the bubbles. Here, "existing on the surface of the bubble" may be a state in which the flame retardant is present on the entire surface of the bubble, or may be a state in which the flame retardant is present on a part of the surface of the bubble. As described above, the presence of the flame retardant on at least a part of the surface of the bubbles increases the surface area of the resin molded body when the resin molded body burns, thereby imparting flame retardancy to the resin molded body. NS.

Flame retardants exhibit higher flame retardancy than thermoplastic resins. The type of flame retardant includes a polymer represented by the following general formula (1).

In the general formula (1), R ₁ and R ₂ are independently each of an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or a phenyl group. Is. When the _{number of carbon atoms of R 1} and R ₂ is 7 or more, the polymerization reaction does not proceed appropriately, so that the shell portion cannot be formed in the thermal expansion agent described later, and there is a possibility that the shell portion cannot be appropriately produced.

Further, in the general formula (1), n is an integer of 100 to 800. When n is less than 100, the polymer is in an oily state, and there is a possibility that a thermal expansion agent cannot be appropriately produced. Further, when n exceeds 800, the contained volatile agent in the thermal expansion agent may not properly generate bubbles. As a result, the weight reduction rate of the resin molded product may decrease.

The method for detecting the flame retardant in the resin molded product can be indirectly detected, for example, by detecting the silicon atom contained in the flame retardant. Specifically, the resin molded product is cut out by an ultramicrotome (Leica EM UC7; Leica) equipped with a diamond blade to prepare a flaky measurement sample. Next, the cross section of the measurement sample is subjected to EDS analysis using a field emission scanning electron microscope (JSM-7401F type; JEOL Ltd.). The elemental map analyzed by EDS can detect the localization of silicon atoms around the bubbles. As described above, the silicon atom in the resin molded product can be detected by a known technique such as elemental analysis.

(Manufacturing method of resin molded product)
In the method for producing a resin molded body, for example, a resin composition containing a thermoplastic resin and a flame retardant and a thermal expansion agent containing a volatile agent contained in the flame retardant is melt-kneaded to melt the thermoplastic resin. It includes a step of volatilizing a volatile agent in the resin composition to generate bubbles and a step of molding the resin composition in which the bubbles are generated.

In the step of generating bubbles in the resin composition, the thermoplastic resin and the thermal expansion agent are melt-kneaded to generate bubbles. As the thermoplastic resin, the above-mentioned thermoplastic resin can be used.

The thermal expansion agent expands by heating to form a region derived from the thermal expansion agent in the thermoplastic resin. In this embodiment, the thermal expansion agent has a core portion and a shell portion. The core part contains a volatile agent, the shell part contains a flame retardant, and contains the core part.

The volatile agent volatilizes when heated. The volatile agent can be appropriately selected from known volatile agents so that it can be volatilized by heating. Examples of volatile agents include low molecular weight hydrocarbons such as propene, n-butane, isobutane, butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, CCl ₃ F, CCl ₂ Includes chlorofluorocarbons such as F ₂ , _{CClF 3} , and _{CClF 2- CClF 2} , and tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. Such a volatile agent may be used alone or in combination of two or more. The volatile agent is preferably isobutane, n-butane, n-pentane, isopentane, n-hexane, or petroleum ether from the viewpoint of cost, availability, and ease of handling.

Further, the volatile agent preferably volatilizes at a temperature equal to or lower than the softening point of the thermoplastic resin. Although the details will be described later, if the volatile agent volatilizes at a temperature equal to or lower than the softening point of the thermoplastic resin, the volatile agent can be reliably volatilized in the thermoplastic resin.

As the flame retardant, the above-mentioned flame retardant can be used.

The resin composition may contain other additives as long as it can exhibit flame retardancy after being molded into a resin molded product. Examples of additives include auxiliaries, dispersants, pigments and colorants, processing aids, fillers, crystallization accelerators, clearing agents, antifoaming agents, antistatic agents, processing aids, lubricants, organics. Includes peroxides, plasticizers, photocatalysts and the like. These additives may be used alone or in combination of two or more.

Examples of auxiliaries include carbon black, silica, glass fiber, carbon fiber, cellulose fiber, aramid fiber and the like. Examples of dispersants include waxes, modified waxes, metal soaps, low molecular weight polyethylenes, low molecular weight polypropylenes and the like. Examples of waxes include paraffin wax, polyolefin wax and the like. Examples of the modified wax include waxes containing an acidic group in the molecular structure, such as maleic acid-modified wax, fumaric acid-modified wax, acrylic acid-modified wax, methacrylic acid-modified wax, and crotonic acid-modified wax. Examples of metal soaps include sodium salts, calcium salts, zinc salts, magnesium salts, aluminum salts and the like of fatty acids such as stearic acid, hydroxystearic acid, behenic acid, montanic acid, lauric acid and sebacic acid. Examples of pigments and colorants include petals, titanium oxide, cadmium red, cadmium yellow, zinc oxide, ultramarine, cobalt blue, calcium carbonate, titanium yellow, lead white, lead tan, lead yellow, dark blue and other inorganic pigments. , Cykunalidon, polyazo yellow, anthracinone yellow, polyazo red, azolake yellow, perylene, phthalocyanine blue, phthalocyanine green, isoindolinone yellow and other organic pigments are included.

The ratio of the thermoplastic resin and the thermal expansion agent in the resin composition is preferably thermoplastic resin: thermal expansion agent = 100: 1 to 100:30, and the thermoplastic resin: thermal expansion agent = 100: 5 to 100. : 20 is preferable. If the ratio of the thermoplastic resin and the thermal expansion agent in the resin composition is not within the above range, it may be difficult to achieve the above-mentioned predetermined weight reduction rate.

In the method for producing a resin molded product, first, the above-mentioned thermoplastic resin and thermal expansion agent are mixed and heated. The heating temperature is a temperature equal to or higher than the temperature at which the thermoplastic resin melts. Therefore, the heating temperature varies depending on the thermoplastic resin used. When the temperature at which the volatile agent volatilizes is the same as the softening point (temperature) of the thermoplastic resin, the softening of the thermoplastic resin and the formation of bubbles occur at the same time. Further, when the temperature exceeds the softening point of the thermoplastic resin, the shell portion of the thermal expansion agent softens. As the shell portion softens, the volatile agent contained in the core portion exudes into the thermoplastic resin and foams. At this time, a part of the volatile agent stays in the core portion and pushes out the shell portion, or the thermal expansion agent foams as it is. Further, if the volatile agent volatilizes above the softening point of the shell portion of the thermoplastic resin or the thermal expansion agent, the thermal expansion agent is crushed. Since the volatile agent volatilizes in the state where the thermal expansion agent is crushed, there is a risk that the foaming becomes non-uniform. On the other hand, when the temperature at which the volatile agent volatilizes is equal to or lower than the softening point (temperature) of the thermoplastic resin as in the present embodiment, the volatile agent volatilizes in advance, so that the internal pressure of the thermal expansion agent is higher than the internal pressure of the thermoplastic resin. It becomes high and the thermal expansion agent does not collapse. Therefore, it is preferable that the volatile agent volatilizes at a temperature equal to or lower than the softening point of the thermoplastic resin.

In the step of molding the resin composition in which bubbles are generated, the resin composition is molded into a predetermined shape to obtain a resin molded body. As a method for molding the resin composition, a known method can be appropriately selected as long as the resin composition can be molded. In the present embodiment, the method for molding the resin composition is an injection molding method.

By the above steps, it is possible to produce a resin molded product which is made of a thermoplastic resin and has a flame retardant on the surface of the bubbles.

The reason why the resin molded product as described above exhibits a high weight reduction rate and high flame retardancy is considered as follows. In the resin-formed body (resin foam), the weight is reduced by vaporizing the volatile agent contained in the thermal expansion agent and generating bubbles in the thermoplastic resin. As described above, in the resin molded product in which bubbles are generated, the flame retardancy is lowered. When the resin molded body is burned, the surface of the resin molded body is first burned. Then, the combustion that has progressed inside the resin molded product reaches the bubbles. When the combustion reaches the bubbles, the surface area of the resin molding increases by about the surface area of the bubbles. As a result, the area of combustion is dramatically increased, and it is considered that the flame retardancy of the resin molded product is reduced.

In order to improve the lowered flame retardancy, a flame retardant may be used, but when the flame retardant is added to the thermoplastic resin, the viscosity of the thermoplastic resin is lowered. As a result, the generated bubbles cannot be maintained in the thermoplastic resin, and the weight cannot be reduced. Therefore, in order to achieve both weight reduction and flame retardancy, it is necessary to reduce the amount of the flame retardant added.

Therefore, in the present embodiment, the shell portion of the thermal expansion agent is composed of a flame-retardant compound. The shell portion of the thermal expansion agent is considered to be localized on the surface of the bubbles in the resin molded product. As a result, in the resin molded product according to the present embodiment, the flame retardancy is improved by preventing the area to be burned from increasing.

As described above, in the resin molded product according to the present embodiment, since the flame retardant is present on the surface of the bubbles, the surface area of the resin composition does not increase even when burned, and the resin molded body has a high weight reduction rate and high flame retardancy. Is shown.

1. 1. Preparation of each material of the resin molded product First, a method of preparing each material of the resin molded product will be described.

(1) Preparation of Thermal Expansion Agent 1 A solution prepared by mixing the following compounds in the following compounding amounts is added to a glass bottle equipped with a stirrer, and 17.2 g of 1-pentanol as a co-surfactant is formed to form an emulsion. It was dropped into a glass bottle with stirring. As the cyclic siloxane 1, Hexamethylcyclotrisiloxane (Tokyo Chemical Industry Co., Ltd.) was used.
Cyclic siloxane 1 (flame retardant) 13.2 g
Isopentane (volatile agent) 5.0 g
22% by mass DTAB (dodecyltrimethylammonium bromide; cationic surfactant) 61.6 g

The contents of the glass bottle were transferred to a glass reaction vessel, and 1.28 g of 50 mass% sodium hydroxide solution was added for the reaction. The reaction in the container was carried out at 50 ° C. for 20 hours. The contents were neutralized with ice-cooled acetic acid and recovered by destroying the microemulsion of the reaction product using salts. The obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain a thermal expansion agent 1. The weight average molecular weight of the thermal expansion agent 1 was 22200, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 300.

(2) Preparation of Thermal Expansion Agent 2 A thermal expansion agent 2 was obtained in the same manner as the thermal expansion agent 1 except that the blending amount of the cyclic siloxane 1 was changed to 22.0 g. The weight average molecular weight of the thermal expansion agent 2 was 37,000, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 500.

(3) Preparation of Thermal Expansion Agent 3 A thermal expansion agent 3 was obtained in the same manner as the thermal expansion agent 1 except that the cyclic siloxane 1 was changed to 20.7 g of the cyclic siloxane 2. As the cyclic siloxane 2, Hexaphenylcyclotrisiloxane (Tokyo Chemical Industry Co., Ltd.) was used. The weight average molecular weight of the thermal expansion agent 3 was 29,700, the molecular weight of the repeating unit structure was 198, and the number of repetitions was 150.

(4) Preparation of Thermal Expansion Agent 4 A thermal expansion agent 4 was obtained in the same manner as the thermal expansion agent 1 except that the cyclic siloxane 1 was changed to 10.2 g of the cyclic siloxane 3. As the cyclic siloxane 3, 1,3,5-Trivinyl-1,3,5-trimethylcyclotriciloxane (Wako Pure Chemical Industries, Ltd.) was used. The weight average molecular weight of the thermal expansion agent 4 was 17,200, the molecular weight of the repeating unit structure was 86, and the number of repetitions was 200.

(5) Preparation of Thermal Expansion Agent 5 A thermal expansion agent 4 was obtained in the same manner as the thermal expansion agent 1 except that the cyclic siloxane 1 was changed to 10.5 g of the cyclic siloxane 4. As the cyclic siloxane 4, 1,3,5-Triethyl-1,3,5-trimethylcyclotriciloxane (Wako Pure Chemical Industries, Ltd.) was used. The weight average molecular weight of the thermal expansion agent 5 was 17,600, the molecular weight of the repeating unit structure was 88, and the number of repetitions was 200.

(6) Preparation of Thermal Expansion Agent 6 Cyclic siloxane 1 was 44.0 g, 22% by mass DTAB was 123.2 g, 1-pentanol was 34.4 g, and 50% by mass sodium hydroxide solution was 2.56 g. A thermal expansion agent 6 was obtained in the same manner as the thermal expansion agent 1. The weight average molecular weight of the thermal expansion agent 6 was 74,000, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 1000.

(7) Thermal expansion agent 7
As the thermal expansion agent 7, the core portion is a hydrocarbon compound and the shell portion is an acrylonitrile-based polymer. Thermal expansion microcapsules (Matsumoto Microsphere F-190D; Matsumoto Yushi Pharmaceutical Co., Ltd., "Matsumoto Micro""Sphere" used the company's registered trademark).

(8) Preparation of Thermal Expansion Agent 8 Polymerized with 100 g of styrene and 16.0 g of methyl methacrylate as a monomer, 20 g of trixylenyl phosphate as a flame retardant, and 2.5 g of azodicarboxylic acid amide as a volatile agent. A solution for oil droplets was prepared by mixing 0.5 g of azobisisobutyronitrile as an initiator. Further, 250 g of deionized water, 42.5 g of silica dispersion (solid content 20% by mass), 1.2 g of 2.5 mass% potassium dichromate aqueous solution, and diethanolamine-azipic acid condensate were 1. An aqueous medium was prepared by mixing 5 g, 90 g of sodium chloride, and 1.5 g of hydrochloric acid. The oil droplet solution and the aqueous medium were stirred and mixed for 2 minutes at a rotation speed of 8000 rpm with a homomixer (TK Robomics; Primix Corporation) to prepare a dispersion. The dispersion was transferred to a nitrogen-substituted reaction vessel, and the monomer and the cross-linking agent were reacted with stirring at 50 ° C. for 12 hours. Then, the reaction product was recovered by filtration, washed with water, and dried at room temperature to obtain a thermal expansion agent 8 containing a flame retardant and a volatile agent. The weight average molecular weight of the thermal expansion agent 8 was 40,900, the molecular weight of the repeating unit structure was 204, and the number of repetitions was 200.

(9) Preparation of Thermal Expansion Agent 9 A thermal expansion agent 9 was obtained in the same manner as the thermal expansion agent 1 except that the volatile agent was changed to 5.0 g of isobutane. The weight average molecular weight of the thermal expansion agent 9 was 22200, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 300.

(10) Preparation of Thermal Expansion Agent 10 A thermal expansion agent 10 was obtained in the same manner as the thermal expansion agent 9 except that isobutane was changed to n-hexane as a volatile agent. The weight average molecular weight of the thermal expansion agent 10 was 22200, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 300.

(11) Preparation of Thermal Expansion Agent 11 A thermal expansion agent 11 was obtained in the same manner as the thermal expansion agent 9 except that isobutane was changed to a mixture of isopentane / isobutane = 2.5 g / 2.5 g as a volatile agent. The weight average molecular weight of the thermal expansion agent 11 was 22200, the molecular weight of the repeating unit structure was 74, and the number of repetitions was 300.

The weight average molecular weights of the thermal expansion agents 1 to 11 thus prepared were determined by gel permeation chromatography (GPC) under the following conditions.
Column: Two K-804L (Showa Denko KK) connected in series were used.
Eluent: Toluene Flow rate: 1.0 mL / min
Column temperature: 40 ° C
Detector: Differential refractometer Sample concentration: 5 mg / mL
Sample amount: 100 μL
Polystyrene conversion

The number of repetitions (n) of the thermal expansion agents 1 to 11 was calculated by the following formula.
n = (weight average molecular weight) / (molecular weight of repeating unit structure)

2. Preparation of resin molded product (1) Preparation of resin molded product 100 parts by mass of polystyrene dried at 80 ° C. for 4 hours and 10 parts by mass of thermal expansion agent 1 were dry-blended, and then an injection molding machine (J55ELII; Using Japan Steel Works, Ltd.), a resin molded product 1 having a size of 100 mm × 100 mm × 1.6 mm was obtained at a cylinder set temperature of 230 ° C. and a mold temperature of 50 ° C. In addition, a resin molded product 1 having a size of 100 mm × 10 mm × 1.6 mm was also produced. Further, a resin molded product 1 having a shape conforming to JIS K7110 was also produced.

(2) Preparation of Resin Mold 2 A resin molded body 2 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 2.

(3) Preparation of Resin Molded Body 3 A resin molded body 3 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 3.

(4) Preparation of Resin Mold 4 A resin molded body 4 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 4.

(5) Preparation of Resin Molded Body 5 A resin molded body 5 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 5.

(6) Preparation of Resin Mold 6 Polystyrene is changed to acrylonitrile, butadiene, and styrene copolymer synthetic resin (ABS resin, Stylac 321; Asahi Kasei Chemicals Co., Ltd.), and the amount of the thermal expansion agent 1 is increased to 15 parts by mass. A resin molded body 6 was obtained in the same manner as the resin molded body 1 except for the modification.

(7) Preparation of resin molded product 7 Resin molding except that polystyrene is changed to polyethylene (Evaflex EV550; Mitsui DuPont Polychemical Co., Ltd.) and the blending amount of thermal expansion agent 1 is changed to 15 parts by mass. A resin molded body 7 was obtained in the same manner as the body 1.

(8) Preparation of resin molded product 8 Same as resin molded product 1 except that polystyrene is changed to polypropylene (Novatec BC3LS; Japan Polypropylene Corporation) and the amount of thermal expansion agent 1 is changed to 15 parts by mass. A resin molded product 8 was obtained.

(9) Preparation of Resin Mold 9 A resin molded body 9 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 9.

(10) Preparation of Resin Mold 10 A resin molded body 10 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 10.

(11) Preparation of Resin Mold 11 A resin molded product 11 was obtained in the same manner as the resin molded product 1 except that the heat expanding agent 1 was changed to the heat expanding agent 11.

(12) Preparation of Resin Mold 12 A resin molded body 12 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 6.

(13) Preparation of Resin Mold 13 A resin molded body 13 was obtained in the same manner as the resin molded body 1 except that the heat expanding agent 1 was changed to the heat expanding agent 7.

(14) Preparation of Resin Mold 14 A resin molded product 14 was obtained in the same manner as the resin molded product 1 except that the thermal expansion agent 1 was changed to the thermal expansion agent 8.

Table 1 shows the types and blending amounts (parts by mass) of the thermoplastic resins used in the production of the resin molded bodies 1 to 14, and the thermal expansion agent Nos. And the blending amount (parts by mass) are shown.

3. 3. Evaluation The weight reduction rate, flame retardancy, impact resistance and appearance of the produced resin molded bodies 1 to 14 were evaluated by the following methods.

(1) Evaluation of weight reduction rate For the evaluation of the weight reduction rate, resin molded bodies 1 to 14 molded into 100 mm × 100 mm × 1.6 m were used. The weight reduction rate was calculated by the following formula and evaluated by the following criteria.
[Lightening rate] =
(Specific gravity of non-foamed molded product-Specific gravity of resin molded product) / Specific density of non-foamed molded product ○: Weight reduction rate of 10% or more (passed)
Δ: Weight reduction rate 5% or more and less than 10% (passed)
×: Weight reduction rate less than 5% (failed)
As the "specific gravity of the non-foamed molded product", a value obtained by a hydrometer (DME-220H; Shinko Denshi Co., Ltd.) was used.

(2) Evaluation of flame retardancy For the evaluation of flame retardancy, resin molded bodies 1 to 14 for UL test molded into 100 mm × 10 mm × 1.6 m were used. To evaluate the flame retardancy, the resin molded products 1 to 14 were humidity-controlled in a constant temperature room at 23 ° C. and 50% humidity for 48 hours, and the UL94 test (of the equipment) specified by the Underwriters Laboratories (UL) in the United States. Combustion test of plastic material for parts) was performed. Here, the "UL94 test" is a method of evaluating flame retardancy from the residual flame time and drip property after indirect flame of a burner flame for 10 seconds on a resin molded body of a predetermined size held vertically. Then, the flame retardancy was evaluated according to the following criteria.
⊚: 5VA, 5VB, V0 (pass)
◯: V1, V2 (passed)
Δ: HB (passed)
×: Non-standard (failed)

(3) Evaluation of Impact Resistance For the evaluation of impact resistance, resin molded bodies 1 to 14 molded into a shape conforming to JIS K7110 were used. In addition, the impact resistance was evaluated by calculating the impact strength reduction rate by the following formula according to JIS K7110 and evaluating by the following criteria.
Impact strength reduction rate =
(Strength of unfoamed molded product-Strength of resin molded product) / Impact strength of unfoamed molded product of polystyrene alone ◎: Impact strength reduction rate 10% or less (passed)
◯: Impact strength reduction rate greater than 10% and 50% or less (passed)
Δ: Impact strength reduction rate greater than 50% and 90% or less (passed)
X: Impact strength reduction rate greater than 90% (failed)

(4) Evaluation of appearance The appearance is obtained by analyzing the images obtained by observing the surfaces of the resin molded products 1 to 14 using a shape analysis laser microscope (VK-X100; KEYENCE Co., Ltd.) to obtain a ten-point average roughness Rz. Calculated. The appearance was evaluated according to the following criteria.
◯: Ten-point average roughness 3 μm or less (passed)
Δ: 10-point average roughness greater than 3 um and less than 5 um (passed)
×: Ten-point average roughness larger than 5 μm (failed)

Table 2 shows the evaluation results of the weight reduction rate, flame retardancy, impact resistance and appearance of the resin molded products 1 to 14.

As shown in Table 2, the flame retardancy evaluation result of the resin molded product 13 was poor. It is considered that this is because Matsumoto Microsphere, whose shell part does not have flame retardancy, was used as a thermal expansion agent. Further, the resin molded product 14 had a poor flame retardancy evaluation result. It is considered that this is because the core portion of the thermal expansion agent contained a volatile flame retardant, so that the flame retardant could not stay in the resin molded body.

On the other hand, the resin molded bodies 1 to 12 in which the flame retardant is present on the surface of the bubbles in the resin molded body had good evaluation results in all of the weight reduction rate, flame retardancy, impact resistance and appearance.

Since the resin molded product according to the present invention has a high weight reduction rate and high flame retardancy, it is useful as an exterior material or an interior material for OA equipment that requires flame retardancy. Therefore, further diversification and further spread of OA equipment are expected. In addition, it is possible to replace it with a material that is not made of resin because it requires flame retardancy in the past, and it is expected that weight reduction and flame retardancy will be imparted in other fields.

Claims (4)

A resin molded product made of thermoplastic resin and containing a plurality of bubbles.
A flame retardant, which is a polymer of cyclic siloxane represented by the following general formula (1), is present on the surface of the bubbles.

(In the above general formula (1), R ₁ and R ₂ are independently each of an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or a phenyl group. It is a group, and n is an integer from 100 to 800.)
Resin molded body. In the resin composition in which the thermoplastic resin is melted, a resin composition containing a thermoplastic resin, a shell portion containing a flame retardant, and a thermal expansion agent containing a core portion containing a volatile agent is melt-kneaded. In the process of volatilizing the above-mentioned volatile agent to generate bubbles,
Including the step of molding the resin composition in which bubbles are generated.
The flame retardant is a polymer of cyclic siloxane represented by the following general formula (1).

(In the above general formula (1), R ₁ and R ₂ are independently each of an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or a phenyl group. It is a group, and n is an integer from 100 to 800.)
A method for manufacturing a resin molded product. The method for producing a resin molded product according to claim 2, wherein the volatile agent volatilizes at a temperature equal to or lower than the softening point of the thermoplastic resin. The method for producing a resin molded product according to claim 2 or 3, wherein the step of molding the resin composition is performed by an injection molding method.