Recycled styrene resin composition and molded body

Abstract

Provided are: a regenerated-styrene-based resin composition which has a high recycled-material content, excellent impact resistance, and excellent thin-wall creep resistance and which has such safety that the flammability meets UL94HB; and a molded object comprising the resin composition.　The regenerated-styrene-based resin composition includes a styrene-based recycled material (A) and a styrene-based virgin material (B), the content of the styrene-based recycled material (A) being 40-90 mass% with respect to the sum of the (A) and the (B), which is taken as 100 mass%, and has a rubbery-polymer content of 5.0-7.0 mass%, a toluene insoluble content of 21 mass% or less, and a bending strength, as measured in accordance with JIS K7171, of 47 MPa or greater.

Description

[Technical Field]

[0001] The present invention relates to a recycled styrene-based resin composition with a high recycled content, excellent impact resistance, excellent creep resistance even at thin walls, and safety with flammability conforming to UL94HB, and to a molded article made from the resin composition. [Background technology]

[0002] In recent years, with growing awareness of environmental issues, there has been a growing trend to use recycled materials in plastic parts for home appliances and office equipment. However, it has been difficult to stabilize the strength and combustibility of plastic parts because the physical properties of recycled materials can be reduced due to deterioration, dirt, and foreign matter, and the types and amounts of discarded equipment are not consistent. The following are technologies related to the use of polystyrene-based recycled materials. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-149768 [Patent Document 2] Japanese Patent Publication No. 2020-7424 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a recycled styrene-based resin composition that has a high recycled material content, excellent impact resistance, excellent creep resistance even at thin walls, and safety with flammability conforming to UL94HB, and a molded article made from the resin composition. [Means for solving the problem]

[0005] The present invention is as follows.

[0006] 1. A recycled styrene-based resin composition containing at least (A) a styrene-based recycled material and (B) a styrene-based virgin material, wherein, when the total amount of the (A) styrene-based recycled material and the (B) styrene-based virgin material is taken as 100% by mass, the content of the (A) styrene-based recycled material is 40% by mass or more and 90% by mass or less, and the content of the (B) styrene-based virgin material is 10% by mass or more and 60% by mass or less, A recycled styrene-based resin composition characterized by having a rubbery polymer content of 5.0% by mass or more and 7.0% by mass or less, a toluene-insoluble matter content of 21% by mass or less, and a flexural strength of 47 MPa or more as measured in accordance with JIS K7171.

[0007] 2. The recycled styrene resin composition according to item 1 above, wherein the (A) styrene recycled material is a post-consumer material.

[0008] 3. A recycled styrene resin composition according to 1 or 2 above, characterized in that the chlorine (Cl) content determined by a fluorescent X-ray method is 900 ppm or less, the bromine (Br) content is 900 ppm or less, and the sum of the chlorine (Cl) content and the bromine (Br) content is 1500 ppm or less.

[0009] 4. A recycled styrene resin composition according to any one of 1 to 3 above, characterized in that the total content of iron (Fe) and copper (Cu) determined by fluorescent X-ray analysis is 150 ppm or less.

[0010] 5. A molded article comprising the recycled styrene-based resin composition according to any one of 1 to 4 above.

[0011] 6. The molded article according to item 5 above, which is a container for a toner cartridge. [Effects of the Invention]

[0012] The present invention provides a molded article made of a recycled styrene-based resin composition that has a high recycled material content and is excellent in impact resistance, creep resistance, and safety. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is a recycled styrene-based resin composition containing at least (A) a styrene-based recycled material and (B) a styrene-based virgin material.

[0014] The (A) styrene-based recycled material in the present invention refers to a recycled material containing a styrene-based resin, and either pre-consumer or post-consumer material may be used. Pre-consumer material refers to materials recovered and reused from scraps and defective products generated during the production process of styrene-based resin products, as well as from styrene-based resin products that are unsold or have exceeded their quality guarantee period and discarded before shipping. Post-consumer material refers to materials that have been shipped to the market and then recovered and reused after consumer use. In the present invention, from the perspective of producing products with low environmental impact and promoting green purchasing and improving recycling rates, the styrene-based recycled material is preferably post-consumer material. Specific examples of styrene-based resins suitable as post-consumer material include polystyrene foam, extruded sheets, containers, packaging materials, cases for recording media such as CDs and MDs, miscellaneous goods such as bobbins and hangers, and plastic parts for electrical equipment and office automation equipment. Among these, rubber-modified polystyrene recovered from plastic parts of home appliances such as televisions and air conditioners, or plastic parts of office equipment such as copiers, is particularly preferred because it can increase the impact resistance of recycled styrene-based resin compositions.

[0015] From the viewpoints of impact resistance, flammability, and environmental impact, it is preferable to reduce as much as possible the content of metals such as iron (Fe) and copper (Cu), other resins such as olefin-based resins, and halogen-containing substances such as chlorine (Cl) and bromine (Br) in the (A) styrene-based recycled material of the present invention. Known techniques can be applied to remove these substances. Examples include manual sorting, sorting using magnetic force or eddy currents, sorting using differences in specific gravity, sorting using the electrostatic charge of plastics, sorting using near-infrared rays, sorting using X-rays, sorting using a color sensor, and removal using a screen mesh in an extruder.

[0016] The (B) virgin styrene resin in the present invention refers to an unused styrene resin that has not undergone the production process of a styrene resin product. The styrene resins described below may be used alone or in combination of two or more. Among these, polystyrene and rubber-modified polystyrene are particularly preferred.

[0017] The styrene-based resin in the present invention is obtained by polymerizing an aromatic vinyl compound, and may be rubber-modified by adding a conjugated diene rubber-like polymer, if necessary. Known polymerization methods include bulk polymerization, two-stage bulk / suspension polymerization, and solution polymerization, and resins produced by any of these methods can be used. Examples of aromatic vinyl compound-based monomers include known ones such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene, with styrene being preferred. Furthermore, copolymers of styrene-based monomers with acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, etc., which are copolymerizable with these aromatic vinyl compound-based monomers, may also be used. Furthermore, copolymers obtained by adding a crosslinking agent such as divinylbenzene to a styrene-based monomer and polymerizing them are also included.

[0018] Conjugated diene rubbery polymers used for rubber modification of styrene resins include polybutadiene, styrene-butadiene random or block copolymers, polyisoprene, polychloroprene, styrene-isoprene random, block or graft copolymers, ethylene-propylene rubber, ethylene-propylene-diene rubber, etc., with polybutadiene and styrene-butadiene random, block or graft copolymers being particularly preferred. These may also be partially hydrogenated.

[0019] Examples of such styrene-based resins include polystyrene (GPPS), rubber-modified polystyrene (HIPS), ABS resin (acrylonitrile-butadiene-styrene copolymer), AS resin (acrylonitrile-styrene copolymer), MS resin (methyl methacrylate-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), and AES resin (acrylonitrile-ethylene propylene-styrene copolymer).

[0020] The styrene-based resin in the present invention may contain additives other than the styrene-based resin, such as a flame retardant, a dye or pigment, a coloring inhibitor, a lubricant, an antioxidant, an antiaging agent, a light stabilizer, an antistatic agent, a filler, a crystallization nucleating agent, a compatibilizer, and a colorant such as titanium oxide or carbon black.

[0021] In the recycled styrene-based resin composition of the present invention, the blending ratio of (A) styrene-based recycled material to (B) styrene-based virgin material is 40% by mass or more and 90% by mass or less, when the total amount of both is 100% by mass. Therefore, the amount of (B) styrene-based virgin material is 10% by mass or more and 60% by mass or less. More preferably, the amount of (A) styrene-based recycled material is 45% by mass or more and 85% by mass or less, and the amount of (B) styrene-based virgin material is 15% by mass or more and 55% by mass or less. Even more preferably, the amount of (A) styrene-based recycled material is 50% by mass or more and 80% by mass or less, and the amount of (B) styrene-based virgin material is 20% by mass or more and 50% by mass or less. Within these ranges, a recycled material content is high, and a recycled styrene-based resin composition with good combustibility even at a thin thickness can be obtained.

[0022] Because the physical properties of (A) styrene-based recycled material are unstable, it is difficult to limit the physical properties of (B) styrene-based virgin material to be combined. Therefore, in the present invention, by specifying the content of rubber-like polymer, toluene-insoluble matter, and flexural strength in the recycled styrene-based resin composition after mixing (A) styrene-based recycled material and (B) styrene-based virgin material, a recycled styrene-based resin composition excellent in impact resistance, creep resistance, and flammability can be obtained.

[0023] The content of the rubber-like polymer in the recycled styrene-based resin composition is 5.0% by mass or more and 7.0% by mass or less, more preferably 5.0% by mass or more and 6.8% by mass or less, and even more preferably 5.2% by mass or more and 6.5% by mass or less. Within this range, a recycled styrene-based resin composition with good impact resistance and creep resistance can be obtained.

[0024] The toluene-insoluble matter in the recycled styrene-based resin composition of the present invention includes the rubbery polymer phase contained in the styrene-based resin and other resins that are poorly soluble or insoluble in toluene, but the toluene-insoluble matter in the recycled styrene-based resin composition of the present invention is 21% by mass or less. If the toluene-insoluble matter is 21% by mass or less, a recycled styrene-based resin composition with good flammability at thin thicknesses can be obtained.

[0025] The flexural strength of the recycled styrene resin composition determined in accordance with JIS K 7171 is 47 MPa or more. If the flexural strength is within this range, a recycled styrene resin composition with good creep resistance at thin thickness can be obtained.

[0026] In the present invention, from the viewpoint of environmental impact, it is preferable that the chlorine (Cl) content in the recycled styrene-based resin composition determined by fluorescent X-ray analysis be 900 ppm or less, the bromine (Br) content be 900 ppm or less, and the total of the chlorine (Cl) content and the bromine (Br) content be 1500 ppm or less. Within these ranges, the generation of harmful gases during combustion is suppressed, and the material is generally treated as a halogen-free material. More preferably, both chlorine (Cl) and bromine (Br) are 700 ppm or less, and even more preferably, both chlorine (Cl) and bromine (Br) are 500 ppm or less.

[0027] From the viewpoint of flammability, the total content of iron (Fe) and copper (Cu) in the recycled styrene resin composition determined by fluorescent X-ray analysis is preferably 150 ppm or less.

[0028] The recycled styrene resin composition of the present invention can contain other additives as long as they do not impair the effects of the present invention. Examples of such additives include phenolic antioxidants, phosphorus-based antioxidants, metal deactivators, acid catchers, UV absorbers, light stabilizers, and other stabilizers; fatty acid-based lubricants, aliphatic amide-based lubricants, and metal soap-based lubricants; fillers such as talc, mica, and silica; reinforcing agents such as glass fiber; colorants such as pigments and dyes; flame retardants such as bromine-based flame retardants, phosphorus-based flame retardants, and nitrogen-based flame retardants; flame retardant aids such as antimony trioxide; anti-dripping agents such as polytetrafluoroethylene (PTFE); antistatic agents such as nonionic surfactants and cationic surfactants; and compatibilizers such as oxazoline-based compatibilizers, maleic anhydride-based compatibilizers, and elastomer-based compatibilizers.

[0029] In the present invention, known mixing techniques can be applied to the method of mixing the styrene-based recycled material and the styrene-based virgin material. For example, a mixture premixed in a mixing device such as a mixer-type mixer, a V-type blender, or a tumbler-type mixer can be further melt-kneaded to obtain a homogeneous resin composition. There are no particular limitations on the melt-kneading method, and known melting techniques can be applied. Suitable melt-kneading devices include a single-screw extruder, a special single-screw extruder, and a twin-screw extruder. Another method for obtaining a resin composition involves feeding each component into a melt-kneading device such as an extruder using a metering feeder.

[0030] The molded article made from the recycled styrene-based resin composition of the present invention can be formed using known techniques, such as injection molding, press molding, extrusion molding, and blow molding.

[0031] Specific examples of molded articles made from the recycled styrene-based resin composition of the present invention are not particularly limited, but for example, they can be suitably used as toner cartridge containers. [Example]

[0032] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0033] <Measurement of rubber polymer content> A styrene resin or resin composition was dissolved in chloroform, a certain amount of iodine monochloride / carbon tetrachloride solution was added, and the mixture was left in a dark place for approximately 1 hour. After that, a 15% by mass potassium iodide solution and 50 ml of pure water were added, and the excess iodine monochloride was titrated with a 0.1 N sodium thiosulfate / ethanol aqueous solution, and the concentration was calculated from the amount of iodine monochloride added.

[0034] <Measurement of reduced viscosity (ηsp / C)> A mixed solvent of 17.5 ml of methyl ethyl ketone and 17.5 ml of acetone was added to 1 g of styrene-based resin and the mixture was dissolved by shaking at 25°C for 2 hours. The insoluble matter was then precipitated by centrifugation, the supernatant was removed by decantation, 250 ml of methanol was added to precipitate the resin, and the insoluble matter was filtered and dried. The resin obtained by this procedure was dissolved in toluene to prepare a sample solution with a polymer concentration of 0.4% (mass / volume). The time it took for this sample solution and pure toluene to flow down in seconds was measured using an Ubbelohde viscometer at a constant temperature of 30°C, and the viscosity was calculated using the following formula.

[0035] ηsp / C=(t1 / t0-1) / C t0: Number of seconds for pure toluene to flow t1: Number of seconds for sample solution to flow C: polymer concentration

[0036] <(A) Styrene-based recycled material> A-1: Rubber-modified polystyrene recovered from home appliances Post-consumer material content: 100% by mass, rubber polymer content: 5.7% by mass A-2: Rubber-modified polystyrene recovered from home appliances Post-consumer material content: 100% by mass, rubber polymer content: 6.2% by mass A-3: Rubber-modified polystyrene recovered from miscellaneous goods Post-consumer material content: 100% by mass, rubber polymer content: 3.3% by mass

[0037] <(B) Virgin styrene material> B-1: Rubber-modified polystyrene Reduced viscosity (ηsp / C) 0.75 dl / g, rubbery polymer content 9.2% by mass B-2: Polystyrene Reduced viscosity (ηsp / C) 0.70 dl / g B-3: Rubber-modified polystyrene Reduced viscosity (ηsp / C) 0.72 dl / g, rubber polymer content 5.1% by mass

[0038] <Preparation of Recycled Styrene-Based Resin Composition> The raw materials (A) styrene-based recycled material and (B) styrene-based virgin material) in the amounts shown in Table 1 were charged into a mixer and pre-blended. The blend was fed into a twin-screw extruder (Toshiba Corporation's "TEM26SS:14 barrel") using a metering feeder and melt-kneaded and extruded under extrusion conditions of a cylinder temperature of 220°C, a total feed rate of 30 kg / hour, and a screw rotation speed of 300 rpm. The extruded strands were water-cooled and then introduced into a pelletizer to obtain pellets of the resin composition. However, in Comparative Example 1 and Reference Example, the raw material pellets were used as they were. The obtained resin compositions were evaluated using the following methods, and the results are shown in Table 1.

[0039] <Toluene insolubles> The resin composition was added to toluene at a ratio of 2.5% by mass, and the mixture was dissolved by shaking at 25°C for 2 hours. The insoluble matter (gel content) was then precipitated by centrifugation (rotation speed: 10,000 rpm to 14,000 rpm, separation time: 30 minutes), and the supernatant was removed by decantation to obtain a gel. The swollen gel was then pre-dried at 100°C for 2 hours, and then dried in a vacuum dryer at 120°C for 1 hour. The gel was then cooled to room temperature in a desiccator, precisely weighed, and calculated using the formula below.

[0040] Insoluble content (%) = ((ba) / S) x 100 a: Weight of the centrifugal sedimentation tube b: Weight of dry gel + centrifuge tube S: sample weight

[0041] <Bending strength> The resin composition pellets were dried by heating at 70°C for 3 hours, and then molded into A-type test pieces (dumbbells) according to JIS K7139 using an injection molding machine ("J100E-P" manufactured by The Japan Steel Works, Ltd.) at a cylinder temperature of 220°C and a mold temperature of 45°C. Using test pieces cut out from the center of the above dumbbell pieces, bending strength was measured according to JIS K7171.

[0042] <Impact resistance> Impact resistance was evaluated by Charpy impact value. Pellets of the resin composition were dried by heating at 70°C for 3 hours, and then molded into A-type test pieces (dumbbells) according to JIS K 7139 using an injection molding machine (manufactured by The Japan Steel Works, Ltd., "J100E-P") at a cylinder temperature of 220°C and a mold temperature of 45°C. Test pieces cut from the center of the dumbbells were notched (type A, r = 0.25 mm) by cutting, and the impact resistance was measured according to JIS K 7111-1.

[0043] <Flammability> Pellets of the resin composition were dried by heating at 70°C for 3 hours, and then an injection molding machine (manufactured by The Japan Steel Works, Ltd., "J100E-P") was used to mold combustion test specimens measuring 127 mm in length, 12.7 mm in width, and 0.8 mm in thickness at a cylinder temperature of 200°C and a mold temperature of 45°C. A combustion test was conducted based on the horizontal combustion test method (UL94) of Underwriters Laboratories, Inc., USA, Subject 94. Test specimens that did not meet the HB standard using this test method were rated "NG."

[0044] <Creep resistance> Pellets of the resin composition were dried by heating at 70°C for 3 hours. Then, using an injection molding machine (Japan Steel Works, Ltd., "J100E-P"), molded specimens measuring 127 mm long, 127 mm wide, and 0.8 mm thick were obtained at a cylinder temperature of 240°C and a mold temperature of 45°C. The resulting molded specimens were cut into 127 mm long, 12.7 mm wide, and 0.8 mm thick specimens with the short sides parallel to the flow direction. The resulting specimens were annealed at 60°C for 24 hours, after which a load was applied to the center of both ends supported (30 mm distance between supports) in a 50°C atmosphere. The initial deflection and the deflection after 1 hour of standing were measured using a microgauge, and the difference from the initial value was calculated. Smaller values ​​indicate better creep resistance; 5.0 mm or less was rated "A," and greater than 5.0 mm was rated "B."

[0045] <Chlorine (Cl), Bromine (Br), Iron (Fe), Copper (Cu) Content> The molded bodies, 127 mm long x 127 mm wide x 0.8 mm thick, obtained in the same manner as in the creep resistance test were analyzed using a fluorescent X-ray analyzer ("EDXL300" manufactured by Rigaku Corporation) to quantify the contents of each element. "ND" in the table means not detected.

[0046] [Table 1]

[0047] Table 1 shows that the recycled styrene resin composition of the present invention boasts a high recycled material content, yet has excellent impact resistance, and even in thin-walled molded products, has excellent creep resistance and safety that meets UL94HB standards.

[0048] The rubber polymer content (measured value) of the recycled styrene-based resin composition shown in Table 1 may not match the calculated value calculated from the respective contents (measured value) of the styrene-based recycled material and the styrene-based virgin material. This is thought to be due to large variations within lots of the styrene-based recycled material.

Claims

1. A recycled styrene-based resin composition containing at least (A) a styrene-based recycled material and (B) a styrene-based virgin material, wherein when the total amount of the (A) styrene-based recycled material and the (B) styrene-based virgin material is taken as 100% by mass, the content of the (A) styrene-based recycled material is 40% by mass or more and 90% by mass or less, and the content of the (B) styrene-based virgin material is 10% by mass or more and 60% by mass or less, A recycled styrene-based resin composition characterized by having a rubber-like polymer content of 5.0% by mass or more and 7.0% by mass or less, a toluene-insoluble content of 21% by mass or less, and a flexural strength of 47 MPa or more as measured in accordance with JIS K7171.

2. 2. The recycled styrene-based resin composition according to claim 1, wherein the styrene-based recycled material (A) is a post-consumer material.

3. The recycled styrene-based resin composition according to claim 1 or 2, characterized in that the chlorine (Cl) content determined by a fluorescent X-ray method is 900 ppm or less, the bromine (Br) content is 900 ppm or less, and the sum of the chlorine (Cl) content and the bromine (Br) content is 1500 ppm or less.

4. 4. The recycled styrene-based resin composition according to claim 1, wherein the total content of iron (Fe) and copper (Cu) determined by a fluorescent X-ray method is 150 ppm or less.

5. A molded article comprising the recycled styrene-based resin composition according to any one of claims 1 to 4.

6. 6. The molded article according to claim 5, which is a container for a toner cartridge.

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