Reclaimed styrene-based resin composition and shrink film

Abstract

To provide a reclaimed styrene-based resin composition and a molded product using the same, which reduce environmental load while exhibiting mechanical strength and superior appearance.SOLUTION: Provided is a reclaimed polystyrene-based resin composition comprising a polymer component (a) derived from recycled polystyrene-based resin (A); rubbery polymer particles derived from the recycled polystyrene-based resin (A); and metal-containing foreign matter containing metals derived from the recycled polystyrene-based resin (A). The metal capture rate X in the reclaimed polystyrene-based resin composition satisfies the following formula (1): X≤2 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a recycled styrene-based resin composition and a shrink film using the recycled styrene-based resin composition.

Background Art

[0002] Styrene-based resins such as polystyrene are not only odorless and suitable for food use, but also known as materials with low environmental impact because the components generated by complete combustion are carbon dioxide and water vapor. In particular, waste styrene-based resins such as inner losses generated in the production process of styrene-based resin molding factories, etc., are easy to recycle because their quality and composition are clear. However, waste styrene-based resins recovered from the market contain a large amount of various resins other than the waste styrene-based resin, or metal powders, adhesions or foreign substances. Therefore, it is difficult for molded products simply recycled from waste styrene-based resins to maintain the same mechanical properties as molded products using new styrene-based resins. For example, since members used in TV casings, partition shelves in refrigerators, or cartridges of multifunction machines contain a large amount of styrene-based resins, technologies for material recycling of these members are required. Patent Document 1 discloses a technique for suppressing a decrease in appearance designability by adsorbing dibutylhydroxytoluene molecules or dibutylhydroxytoluene dimers of resin additives, which are the causes of resin adhesion to molds during molding and yellowing over time, to zeolite by a recycled styrene-based resin composition containing a used styrene-based resin and zeolite. Further, Patent Document 2 describes a recycled polystyrene-based resin containing a used resin waste material (C) containing a polystyrene resin containing a flame retardant and a rubber component and a polystyrene resin not containing a rubber component, a styrene-based thermoplastic elastomer (D), a bromine-based flame retardant (E), and a polyfluoroolefin (F) in order to provide a polystyrene-based resin exhibiting good rigidity, impact strength, moldability, and flame retardancy equivalent to those of an unused polystyrene resin.

Prior Art Documents

Patent Documents

[0003] Patent Document 1 Japanese Patent Application Laid-Open No. 2020-007424 Patent Document 2 Japanese Patent Application Laid-Open No. 2018-087261 Summary of the Invention Problems to be Solved by the Invention

[0004] In the technologies of Patent Documents 1 and 2 above, although mechanical strength and flame retardancy have been studied, the appearance is insufficient. Therefore, the problem to be solved by the present disclosure is to provide a recycled styrene-based resin composition that reduces environmental load, has few foreign matters, and exhibits excellent appearance, and a shrink film having high transparency using the same and reduced printing defects. Means for Solving the Problems

[0005] As a result of intensive studies in view of the above problems, the present inventor has found that among foreign matters inevitably mixed in the recycled styrene-based resin composition, when the amount of metal is large, not only damage inside the mold of the molding machine during molding of the recycled styrene-based resin composition is induced, but also metal pieces or metal powders mixed in the obtained molded body as granular substances (mainly observed as black dots) are observed. And when the obtained molded body is used for a shrink film wound around a so-called PET bottle, it has been confirmed that printing defects may occur due to the presence of the metal pieces or metal powders. However, when the metal capture rate corresponding to the amount of metal inevitably mixed in the recycled styrene-based resin composition is 2% by mass or less, damage inside the mold of the molding machine and appearance defects due to the mixed metal pieces or metal powders can be reduced, and it has been found that printing defects can also be reduced when used as a shrink film, leading to the completion of the present invention. That is, the present disclosure is as follows.

[0006] [1] This disclosure relates to a recycled polystyrene-based resin composition containing a recycled polystyrene-based resin (A), which includes a polymer component containing a styrene-based polymer (a-1) derived from the recycled polystyrene-based resin (A), rubber-like polymer particles (a-2) derived from the recycled polystyrene-based resin (A), and a metal-containing foreign matter containing a metal derived from the recycled polystyrene-based resin (A). The metal capture rate X satisfies the following formula (1): [Equation 1] Formula (1): X ≤ 2% by mass (In the above formula (1), X represents the metal capture rate. After processing the recycled styrene-based resin composition into pellet bodies (X) with a major axis of 1.5 to 4.0 mm and a minor axis of 1.0 to 3.0 mm, when passing the pellet bodies (X) through a magnetic field, the magnetic field generated in the pellet bodies (X) is detected by electromagnetic induction, the metal in the pellet bodies (X) is discriminated, and by the generated magnetic field, the pellet bodies (X) are sorted into pellet bodies (1) where a magnetic field is generated and pellet bodies (2) other than the pellet bodies (1). After that, when passing each pellet body (1) through the magnetic field again, the magnetic field generated in the pellet body (1) is detected by electromagnetic induction, the metal in the pellet body (1) is discriminated, and by the generated magnetic field, the pellet body (1) is sorted into pellet bodies (3) containing metal and pellet bodies (4) other than the pellet bodies (3). The weights of the pellet bodies (2) to (4) are measured, and the metal capture rate X is calculated using the following formula (2). [Equation 2] Formula (2): X (%) = (weight of the pellet body (3) / [weight of the pellet body (2) + weight of the pellet body (3) + weight of the pellet body (4)]) × 100) The recycled polystyrene-based resin composition satisfies the above conditions.

[0007] [2] The recycled polystyrene-based resin composition according to [1], further containing a styrene-based resin (B) containing a styrene-based polymer (b-1) which is a virgin material, and the polymer component further includes the styrene-based polymer (b-1).

[0008] [3] A recycled polystyrene-based resin composition containing the polymer component, the rubber-like polymer particles (a-2), and the metal-containing foreign matter, When the recycled polystyrene-based resin composition is classified into a toluene-soluble component (1) in which the polymer component soluble in toluene is dissolved and a toluene-insoluble component (1) containing the rubber-like polymer particles (a-2) and the metal-containing foreign matter, The toluene-insoluble component (2) after the osmium tetroxide treatment obtained by subjecting the toluene-insoluble component (1) to osmium tetroxide treatment is more than 0 to 3% by mass based on the whole recycled styrene-based resin composition, The recycled polystyrene-based resin composition according to [1] or [2], wherein the toluene-insoluble component (1) before the osmium tetroxide treatment is 5 to 30% by mass.

[0009] [4] The recycled polystyrene-based resin composition according to any one of [1] to [3], wherein the content of the polymer component is more than 70% by mass based on the whole recycled styrene-based resin composition.

[0010] [5] The recycled polystyrene-based resin composition according to any one of [1] to [4], wherein the number Y of particulate matters in the disk-shaped test piece prepared from the pellet body (X) satisfies the following formula (3). [Equation 3] Formula (3): Y ≤ 10 (number / 10 g) (In the above formula (3), Y represents the number of particulate matters in the disk-shaped test piece prepared from the pellet body (X). After weighing 10 g of the recycled styrene-based resin composition and heating and compressing it to prepare a disk-shaped test piece with a thickness of 200 to 350 μm, the number of particulate matters having a maximum length of 600 μm or more in the disk-shaped test piece was measured using a 10-fold magnifying lens.)

[0011] [6] The toluene-insoluble component (1) before the osmium tetroxide treatment contains the rubber-like polymer particles (a-2), and the average particle diameter of all the rubber-like polymer particles in the recycled polystyrene-based resin composition is 2 to 4 μm. The recycled polystyrene-based resin composition according to any one of [1] to [5].

[0012] [7] The recycled polystyrene resin composition according to any one of [1] to [6], further containing an antioxidant.

[0013] [8] The recycled polystyrene resin composition according to any one of [1] to [7], wherein the styrene recycled resin is a post-industrial product.

[0014] [9] A shrink film comprising a resin layer containing the recycled polystyrene resin composition according to any one of [1] to [8] and a surface layer covering at least one surface of the resin layer. [Advantages of the Invention]

[0015] According to the present disclosure, it is possible to provide a recycled styrene resin composition that reduces the environmental load and exhibits excellent appearance. According to the present disclosure, it is possible to provide a shrink film using a recycled styrene resin composition that reduces the environmental load and printing defects and exhibits excellent appearance. [Brief Description of the Drawings]

[0016]

Figure 1

[0017] Hereinafter, embodiments of the present disclosure (hereinafter referred to as "the present embodiment") will be described in detail. However, the scope of the present disclosure is not limited to the following description, and various modifications can be made and implemented within the scope of the gist. [Recycled Styrene Resin Composition] The present disclosure relates to a recycled polystyrene-based resin composition containing a recycled polystyrene-based resin (A), which comprises a polymer component containing a styrene-based polymer (a-1) having a styrene-based monomer unit derived from the recycled polystyrene-based resin (A), rubber-like polymer particles (a-2) derived from the recycled polystyrene-based resin (A), and metal-containing foreign matter containing recycled-derived metal, and the metal capture rate X satisfies the following formula (1). [Equation 1] Formula (1): X ≤ 2% by mass (In the above formula (1), X represents the metal capture rate. After processing the recycled styrene-based resin composition into pellet bodies (X) with a major axis of 1.5 to 4.0 mm and a minor axis of 1.0 to 3.0 mm, when passing the pellet bodies (X) through a magnetic field, the magnetic field generated in the pellet bodies (X) is detected by electromagnetic induction to identify the metal in the pellet bodies (X). And by the generated magnetic field, the pellet bodies (X) are sorted (or separated) into pellet bodies (1) where a magnetic field is generated and pellet bodies (2) other than the pellet bodies (1). Then, when passing each pellet body (1) through the magnetic field again, the magnetic field generated in the pellet body (1) is detected by electromagnetic induction to identify the metal in the pellet body (1). And by the generated magnetic field, the pellet body (1) is sorted into pellet bodies (3) containing metal and pellet bodies (4) other than the pellet bodies (3). The weights of the pellet bodies (2) to (4) are measured, and the metal capture rate X is calculated using the following formula (2). [Equation 2] Formula (2): X (%) = (weight of the pellet body (3) / [weight of the pellet body (2) + weight of the pellet body (3) + weight of the pellet body (4)]) × 100) Accordingly, it is to provide a recycled styrene-based resin composition with reduced environmental impact, few foreign matters, and excellent appearance, and a shrink film having high transparency and reduced printing defects using the same. The recycled styrene-based resin composition of this embodiment may contain recycled polystyrene-based resin (A) containing metal-containing foreign matter containing metals inevitably mixed during recycling. And, if necessary, it is preferably further contained styrene-based resin (B) as virgin material. Further, the styrene-based resin (B) contains styrene-based polymer (b-1). Therefore, the polymer component may further contain the styrene-based polymer (a-1) and the styrene-based polymer (b-1). In the recycled styrene-based resin composition, it is difficult to identify whether the styrene-based polymer (a-1) having styrene-based monomer units in the recycled polystyrene-based resin (A) and the styrene-based polymer (b-1) having styrene-based monomer units in the styrene-based resin (B) which is an optionally added virgin material are derived from the recycled polystyrene-based resin (A) that has been recycled or from the styrene-based resin (B) that is a virgin material. Therefore, it is difficult to specify the respective contents of the recycled polystyrene-based resin (A) and the optionally added styrene-based resin (B) from the recycled styrene-based resin composition which is the product. Thus, in the present disclosure, the components contained in the recycled styrene-based resin composition of this embodiment are morphologically classified to specify the whole of the recycled styrene-based resin composition. That is, the recycled styrene-based resin composition of this embodiment contains a polymer component, rubber-like polymer particles, and metal-containing foreign matter containing recycling-derived metal. And, the polymer component may contain the styrene-based polymer (a-1) having styrene-based monomer units in the recycled polystyrene-based resin (A) and the styrene-based polymer (b-1) having styrene-based monomer units in the styrene-based resin (B) which is an optionally added virgin material. Hereinafter, after explaining the metal capture rate which is a characteristic of the recycled styrene-based resin composition of this embodiment, each component constituting the recycled styrene-based resin composition will be explained.

[0018] (Metal capture rate) In this embodiment, when the metal capture rate corresponding to the amount of metal inevitably mixed into the recycled styrene resin composition is 2% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less, damage inside the mold of the molding machine in injection molding and appearance defects caused by the mixed metal pieces or metal powder can be reduced, and in extrusion molding, a shrink film with reduced printing defects caused by the mixed metal pieces or metal powder can be provided. In this embodiment, the metal capture rate X corresponding to the amount of metal inevitably mixed into the recycled styrene resin composition is calculated by the following calculation means.

[0019] <Calculation means for metal capture rate X> In this embodiment, the calculation means for calculating the metal capture rate X uses a metal detection unit having a non-magnetic cylindrical body, a drive coil provided outside the cylindrical body in the radial direction, and a high-frequency current generation unit for applying a high-frequency current to the drive coil to identify the metal contained in the recycled polystyrene resin (A) or the recycled styrene resin composition, and it is preferable to select, by a sorting mechanism, a recycled styrene resin composition containing a metal amount equal to or more than a predetermined amount and a recycled styrene resin composition containing a metal amount less than the predetermined amount. As the details of the sorting mechanism, it is a device that detects metal-containing foreign substances in a pelletized recycled styrene resin composition or pelletized recycled polystyrene resin (A) (hereinafter referred to as the object to be sorted), and sorts a pellet body containing the metal-containing foreign substance and a pellet body not containing a metal-containing foreign substance with a size greater than the sorting limit capacity. It includes a passage path through which the object to be sorted passes, a drive coil arranged around the passage path that generates a magnetic field in the passage path, first and second spiral coils arranged around the passage path that receive the magnetic field generated by the drive coil and are arranged such that the difference in voltage generated in each changes when a magnetic body passes through the passage path, and a third spiral coil arranged in a planar shape substantially orthogonal to the passing direction at a distance from the first and second spiral coils around the passage path, where an impedance change occurs when a conductor passes through the passage path in a state where an oscillating current is flowing. It also includes a determination unit that determines the presence or absence of a metal-containing foreign substance in the object to be sorted based on the change in the difference in voltage generated in the first and second spiral coils and the impedance change generated in the third spiral coil. With this sorting mechanism, even when metal oxides are mixed in the object to be sorted, if the metal oxide is a magnetic body, the difference in voltage between the first and second spiral coils changes, so the determination unit can determine that there is a metal-containing foreign substance mixed in based on this voltage difference. Also, when non-ferrous metals or non-oxidized iron are mixed in the object to be sorted, the impedance of the third spiral coil changes due to eddy current loss, so the determination unit can determine that there is a metal-containing foreign substance mixed in based on this impedance change. Further, the sorting mechanism is provided with a first discharge path for discharging the pellet body not containing the metal-containing foreign substance and a second discharge path for discharging the pellet body containing the metal-containing foreign substance on the downstream side of the passage path. Until a predetermined time has elapsed after the determination unit determines that there is a metal-containing foreign substance mixed in, the discharge path of the object to be sorted is set to the first discharge path, and after a predetermined time has elapsed after the determination unit determines that there is a metal-containing foreign substance mixed in, it is provided with a switching means for switching the discharge path of the object to be sorted from the first discharge path to the second discharge path. By means of the switching means, it is possible to sort a pellet body containing the metal-containing foreign matter (pellet body (1) containing metal) and a pellet body not containing the metal foreign matter (pellet body (2) not containing metal).

[0020] Hereinafter, with reference to FIG. 1, a preferred sorting mechanism of the present embodiment will be described. FIG. 1 is a cross-sectional view of the sorting mechanism 10 of the present embodiment. That is, the sorting mechanism 10 of the present embodiment includes a housing (not shown), and above the housing (not shown), a hopper 17 with an open upper portion is provided for introducing resin pellets as an object to be inspected. Inside the housing (not shown), a detection device main body 30 shown in FIG. 1 and a circuit board (not shown) are accommodated. And a drive coil 14, a first spiral coil 12, a second spiral coil 19, a third spiral coil 21, a test coil 20, and the circuit board constitute a metal detection system of the sorting mechanism. The detection device main body 30 includes a non-magnetic cylindrical member 1 (for example, made of ceramic), and the internal space of the cylindrical member 1 forms a passage path L1 through which the object to be inspected introduced into the hopper 17 passes by natural fall. A recess 13 is formed on the outer surface of the cylindrical member 1 with a constant width over the entire circumference. And the recess 13 is provided on the hopper 17 side from the central portion of the cylindrical member 1. The drive coil 14 is wound in the recess 13. Further, a recess 13 and an annular member 15 are fixed to the outside of the cylindrical member 1. The annular member 15 is attached so as to surround the vicinity above and below the recess 13, and a convex portion 16 that fits into the recess 13 is formed on the inner surface of the annular member 15 over the entire circumference of the cylindrical member 1. The protruding length of the convex portion 16 is shorter than the depth of the recess 13 by about the thickness of the drive coil 14. A printed circuit board 11 is integrally fastened to the upper surface of the annular member 15 with the board surface along the upper surface, and a printed circuit board 18 is integrally fastened to the lower surface of the annular member 15 with the board surface along the lower surface. The printed circuit board 11 is formed of copper foil in a planar shape substantially orthogonal to the passing path L1 (passing direction) of the first spiral coil 12. Similarly, the printed circuit board 18 is formed of copper foil in a planar shape substantially orthogonal to the passing path L1 (passing direction) of the second spiral coil 19. The first and second spiral coils 12 and 19 each have signal extraction ports (not shown) at five locations near the outer peripheral side ends, and the inner peripheral side ends of the first and second spiral coils 12 and 19 are connected to each other.

[0021] Below the annular member 15 on the outer surface of the cylindrical member 1, a test coil 20 is wound around once at a distance from the annular member 15. And below the test coil 20 of the cylindrical member 1, a printed circuit board 22 is disposed around the cylindrical member 1 with its board surface facing the vertical direction at a distance from the test coil 20. On the printed circuit board 22, a third spiral coil 21 is also formed of copper foil in a planar shape substantially orthogonal to the passing path L1 (passing direction). The third spiral coil 21 is fixedly arranged so that the cylindrical member 1 (passing path L1) passes across the plane (the central portion of the spiral in the third spiral coil 21) constituted by the third spiral coil 21. Below the cylindrical member 1, a tapered cylindrical member 23a having an annular cross section with a gradually decreasing diameter toward the lower side opposite to the side where the hopper 17 is installed is disposed with its upper opening (the side where the hopper 17 is installed) facing the lower opening of the cylindrical member 1. On the side wall near the upper opening of the cylindrical member 23a, a rotatable single shaft member 24 is fixed substantially perpendicular to the side wall, and by rotating the shaft member 24, the cylindrical member 23a can rotate from the first direction state with the lower opening facing directly downward to the second direction state with the lower opening facing obliquely downward (the state of the cylindrical member 23b shown by the broken line in FIG. 1). Below the cylindrical member 1, a first discharge pipe portion (not shown) is attached at a position corresponding to the lower opening of the cylindrical member 23a in the first direction state, and a second discharge pipe portion (not shown) is attached at a position corresponding to the lower opening of the cylindrical member 23b in the second direction state. Therefore, the first discharge pipe portion serves as a path for collecting resin pellets that do not contain foreign matter, and the second discharge pipe portion serves as a discharge path for discharging resin pellets that contain foreign matter. As another form of the sorting mechanism, specifically, while applying a high-frequency current to oscillate a detection coil provided outside the non-magnetic cylindrical body in the radial direction, the recycled styrene resin composition introduced into the hopper falls by gravity and passes through the internal space of the cylindrical body. When the metal in the recycled styrene resin composition passes through the internal space, the change in impedance of the detection coil is detected to detect the metal in the recycled styrene resin composition. At this time, a sorting mechanism such as a blowing device that blows away by air blowing is used for the recycled styrene resin composition containing a metal amount equal to or more than a predetermined amount, and the recycled styrene resin composition containing a metal amount less than the predetermined amount is sorted. The blowing device is generally called an air gun and has a structure that instantaneously ejects high-pressure air from the tip of the nozzle. Since the instantaneous air blowing of the air gun operates with very high precision in units of thousandths of a second, the recycled styrene resin composition containing a metal amount equal to or more than a predetermined amount can be efficiently sorted.

[0022] (Each component of the recycled styrene resin composition) When classifying the components contained in the recycled styrenic resin composition of this embodiment morphologically, the components contained in the recycled styrenic resin composition can be classified into a polymer component composed of a styrenic polymer (including the above styrenic polymer (a-1) and, if necessary, the above styrenic polymer (b-1)), a rubber component dispersed in the polymer component (for example, in a sea-island structure) (for example, rubber-like polymer particles (a-2) and / or rubber-like polymer particles (b-2)), and contaminants derived from recycled polystyrene resin (A) (for example, other resins (for example, olefin resins such as polyethylene resin and polypropylene resin), inorganic substances (for example, metal-containing foreign substances, metal powders or silica), pigments, adherends or foreign substances). In other words, in the recycled styrenic resin composition of this embodiment, the polymer component corresponds to the polymer matrix phase in the recycled styrenic resin composition, and the rubber-like polymer particles in the recycled styrenic resin composition (for example, rubber-like polymer particles (a-2) derived from recycled polystyrene resin (A) and / or rubber-like polymer particles (b-2) derived from styrenic resin (B)) correspond to the domain phase, having a so-called sea-island structure. Therefore, in this specification, the polymer matrix phase composed of the styrenic polymer is referred to as the "polymer component", and the toluene-soluble component (toluene-soluble fraction) among the components contained in the recycled styrenic resin composition is defined as the "polymer component". On the other hand, the domain phase dispersed in the polymer matrix phase, which is the "polymer component", is rubbery polymer particles (e.g., rubbery polymer particles containing conjugated diene monomer units). Further, the metal-containing foreign matter, which is an impurity derived from the recycled polystyrene resin (A), remains insoluble in toluene even after the osmium tetroxide treatment described below, and it has been confirmed that its amount remains constant before and after the toluene dissolution treatment after the osmium tetroxide treatment. And although the rubbery polymer particles themselves are insoluble in toluene, it has been confirmed that they become soluble in toluene when the osmium tetroxide treatment described below is performed. In addition, the total of the polymer phase encapsulated in the rubbery polymer particles (e.g., the polymer phase in the rubbery polymer particles having a core-shell structure or a salami structure) and the graft polymer chain (styrenic polymer) having a styrenic monomer on the surface of the rubbery polymer particles is referred to as the "occluded component" in this specification. And for convenience in this specification, the "polymer component" is composed of a styrenic polymer and is a component soluble in toluene in the recycled styrenic resin composition before the osmium tetroxide treatment (hereinafter also referred to as toluene-soluble fraction (1)). On the other hand, the "occluded component" is composed of a styrenic polymer and is a component insoluble in toluene in the recycled styrenic resin composition before the osmium tetroxide treatment (hereinafter also referred to as toluene-insoluble fraction (1)), minus the total amount of the toluene-insoluble fraction after the osmium tetroxide treatment on the toluene-insoluble component (= the toluene-insoluble fraction after the osmium tetroxide treatment, hereinafter also referred to as toluene-insoluble fraction (2)) and the amount of the rubbery polymer (e.g., the amount of conjugated diene monomer units).In addition, the "toluene-insoluble matter after osmium tetroxide treatment (or toluene-insoluble matter (2))" in this specification means that the recycled styrene-based resin composition or recycled polystyrene-based resin (A) is subjected to toluene dissolution treatment to obtain toluene-soluble matter (1) which is a component soluble in toluene and toluene-insoluble matter (1) which is a component insoluble in toluene. After separation, the toluene-insoluble matter (1) is treated with osmium tetroxide to cleave carbon-carbon double bonds, and then further subjected to toluene dissolution treatment to obtain toluene-soluble matter (2) which is a component soluble in toluene after osmium tetroxide treatment and toluene-insoluble matter (2) which is a component insoluble in toluene after osmium tetroxide treatment. Among them, the component insoluble in toluene after osmium tetroxide treatment is referred to as "toluene-insoluble matter after osmium tetroxide treatment (or toluene-insoluble matter (2))". Note that the "toluene-insoluble matter after osmium tetroxide treatment (or toluene-insoluble matter (2))" contains, as contaminants derived from the recycled polystyrene-based resin (A), metals (such as metal-containing foreign matters), and for example, other resins (olefin resins such as polyethylene-based resins and polypropylene-based resins), inorganic substances (such as silica), pigments, adherends, or foreign matters. When the metal capture rate X corresponding to the amount of metal in the contaminants derived from the recycled polystyrene-based resin (A) shows a predetermined amount or more, it has been found that damage inside the mold of the molding machine and appearance defects caused by the mixed metal pieces or metal powder can be reduced, and printing defects can also be reduced when used as a shrink film. The relational expression of the above formula (1) is defined.

[0023] The recycled styrene-based resin composition of this embodiment preferably contains a styrene-based resin (B) as a virgin material. The styrene-based resin (B) only needs to contain a styrene-based polymer (b-1), and the styrene-based resin (B) may contain rubber-like polymer particles (b-2) and a styrene-based polymer (b-1). In other words, a styrene-based resin (B) containing rubber-like polymer particles (b-2) as a domain phase of the styrene-based resin (B) and a styrene-based polymer (b-1) as a polymer matrix phase may be blended into the recycled styrene-based resin composition as a virgin material. In addition, examples of the recycled polystyrene resin (A) include used rubber-modified polystyrene resins. Therefore, when the recycled polystyrene resin (A) is a used rubber-modified polystyrene resin, in other words, when the recycled polystyrene resin (A) contains rubber-like polymer particles (a-2), the recycled polystyrene resin (A) contains a polymer matrix part of the recycled polystyrene resin (A) and the rubber-like polymer particles (a-2). On the other hand, when the styrene resin (B) also contains rubber-like polymer particles (b-2), the styrene resin (B) can become the rubber-modified polystyrene resin (B2) described later. For convenience of explanation in this specification, the particulate rubber-like polymer contained in the recycled polystyrene resin (A) is referred to as rubber-like polymer particles (a-2), and the particulate rubber-like polymer contained in the styrene resin (B) is referred to as rubber-like polymer particles (b-2). And the particulate rubber-like polymer contained in the recycled styrene resin composition is simply referred to as rubber-like polymer particles. Therefore, the rubber-like polymer particles mean rubber-like polymer particles (a-2) and / or rubber-like polymer particles (b-2).

[0024] Hereinafter, the polymer component and the rubber-like polymer particles constituting the recycled styrene resin composition will be described. (Polymer component) The recycled styrene resin composition of this embodiment contains a polymer component as described above. And the polymer component contains a styrene polymer (a-1) which is a polymer matrix part of the recycled polystyrene resin (A) and a styrene polymer (b-1) which is a polymer matrix part of the styrene resin (B) blended as necessary. Therefore, the polymer component of the recycled styrene resin composition is composed of styrene polymers (for example, including the above-mentioned styrene polymer (a-1) and the above-mentioned styrene polymer (b-1) which is an optional component). The styrene polymer (a-1) and the above-mentioned styrene polymer (b-1) will be described later, and both have styrene monomer units and, if necessary, (meth)acrylic acid monomer units added. Examples of the monomer constituting the styrene monomer unit include styrene, α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, bromostyrene, and styrene derivatives such as indene. The monomer constituting the (meth)acrylic acid monomer unit is preferably a (meth)acrylic acid monomer and a (meth)acrylic acid ester monomer. Examples of the (meth)acrylic acid monomer include acrylic acid or methacrylic acid. Examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (n-butyl) (meth)acrylate, (t-butyl) (meth)acrylate, (isobutyl) (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, (n-octyl) (meth)acrylate, (2-ethylhexyl) (meth)acrylate, decyl (meth)acrylate, stearyl (meth)acrylate, and the like. These can be used alone or in combination. In the recycled styrene resin composition of this embodiment, the lower limit of the content of the polymer component is 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more with respect to the entire recycled styrene resin composition. On the other hand, the upper limit of the content of the polymer component is 90% by mass or less, less than 90% by mass, 87% by mass or less, 86% by mass or less, 85% by mass or less, less than 85% by mass, 84.8% by mass or less, 84% by mass or less, 83% by mass or less, 82% by mass or less, 81% by mass or less with respect to the entire recycled styrene resin composition. Incidentally, the content of the polymer component is calculated by subtracting the toluene-insoluble content (1) of the recycled styrene-based resin composition before osmium tetroxide treatment from the entire recycled styrene-based resin composition before osmium tetroxide treatment. More specifically, the recycled styrene-based resin composition before osmium tetroxide treatment is subjected to toluene dissolution treatment and divided into a component soluble in toluene (= toluene-soluble content (1)) and a component insoluble in toluene (= toluene-insoluble content (1)). Then, the mass of the component insoluble in toluene (= the toluene-insoluble content of the recycled styrene-based resin composition before osmium tetroxide treatment, which is the toluene-insoluble content (1)) is measured, and the mass of the toluene-insoluble content (1) is subtracted from the mass of the recycled styrene-based resin composition before osmium tetroxide treatment to calculate the content of the polymer component. Therefore, the content of the polymer component is synonymous with the content of the toluene-soluble content (1). Further, the polymer component of the present embodiment contains the polymer matrix part of the recycled polystyrene-based resin (A), that is, the styrene-based polymer (a-1), and the polymer matrix part of the styrene-based resin (B) blended as needed, that is, the styrene-based polymer (b-1). In the polymer component of the present embodiment, with respect to the entire polymer component, the styrene-based monomer unit is preferably 50 to 100% by mass, the (meth)acrylic acid monomer unit is preferably 0 to 20% by mass, and the (meth)acrylic acid ester monomer unit is preferably 0 to 50% by mass. More preferably, the styrene-based monomer unit is 55 to 100% by mass, the (meth)acrylic acid monomer unit is 0 to 15% by mass, and the (meth)acrylic acid ester monomer unit is 0 to 45% by mass. In the present embodiment, the weight average molecular weight (Mw) of the polymer component is preferably 120,000 to 300,000, more preferably 140,000 to 280,000, and still more preferably 150,000 to 260,000. When the weight average molecular weight of the polymer component is 120,000 to 300,000, a resin excellent in the practicality of the balance between impact strength and fluidity can be obtained. The weight average molecular weight can be measured by gel permeation chromatography in terms of polystyrene standard conversion. "Recycled polystyrene resin (A)" as used herein contains toluene-insoluble matter (2) after osmium tetroxide treatment, and the content of the toluene-insoluble matter (2) after osmium tetroxide treatment can be 5% by mass or less, preferably more than 0% to 5% by mass, more preferably more than 0% to 3% by mass, based on the whole recycled polystyrene resin (A). And the toluene-insoluble matter (2) after the osmium tetroxide treatment contains metal-containing foreign matter. "Styrenic polymer (b-1)" or virgin styrenic resin (B) as used herein substantially does not contain toluene-insoluble matter (2) after osmium tetroxide treatment, and the content of toluene-insoluble matter (2) in the polymer matrix part of the styrenic polymer (b-1) and the styrenic resin (B) can be less than 0.01% by mass, substantially below the detection limit, based on the whole polymer matrix part of the styrenic polymer (b-1) or the styrenic resin (B).

[0025] (Rubbery polymer particles) As described above, the recycled styrenic resin composition of this embodiment contains rubbery polymer particles as a rubber component. In the recycled styrenic resin composition of this embodiment, the upper limit of the content (gel %) of all rubbery polymer particles (a general term for rubbery polymer particles (a-2) and rubbery polymer particles (b-2) described later) contained in the recycled styrenic resin composition is 35% by mass or less, less than 30%, 29% by mass or less, 28% by mass or less, 27% by mass or less, 26% by mass or less, 25% by mass or less, 24% by mass or less, based on the whole recycled styrenic resin composition. On the other hand, the lower limit of the content of all rubbery polymer particles is more than 12% by mass, 13% by mass or more, 14% by mass or more, 15% by mass or more, 16% by mass or more, 17% by mass or more, 18% by mass or more, based on the whole recycled styrenic resin composition. When the content of all rubbery polymer particles is within the above range, the effect of improving mechanical properties is achieved. The content of all the rubbery polymer particles is calculated as the value obtained by subtracting [the toluene-insoluble content (2) after osmium treatment with respect to the whole recycled styrene-based resin composition (100% by mass)] from [the toluene-insoluble content (1) with respect to the whole recycled styrene-based resin composition (100% by mass)] using the calculation method of the toluene-insoluble content described below.

[0026] In this embodiment, the upper limit of the total content of the conjugated diene monomer amount in the rubbery polymer particles (a-2) and the rubbery polymer particles (b-2) before osmium tetroxide treatment is preferably 20% by mass or less, 19% by mass or less, 18% by mass or less, 17% by mass or less, 16% by mass or less, 15% by mass or less with respect to the whole recycled styrene-based resin composition (100% by mass). In this embodiment, the lower limit of the total content of the conjugated diene monomer unit amount in the rubbery polymer particles (a-2) and the conjugated diene monomer unit amount in the rubbery polymer particles (b-2) before osmium tetroxide treatment is preferably 1.7% by mass or more, 1.9% by mass or more, 2.1% by mass or more, 2.7% by mass or more, 3.0% by mass or more with respect to the whole recycled styrene-based resin composition (100% by mass). When the amount of the conjugated diene monomer is within the above range, it exhibits an excellent effect on the flexural modulus. The content of the conjugated diene monomer unit in the rubbery polymer particles is calculated as the content of butadiene by pyrolysis GC / MS described in the column of the examples below.

[0027] When the styrene-based resin (B) does not contain the rubbery polymer particles (b-2), the content of all the rubbery polymer particles in the recycled styrene-based resin composition is the content of the rubbery polymer particles (a-2). And when the recycled polystyrene-based resin (A) contains the rubbery polymer particles (a-2) and the styrene-based resin (B) contains the rubbery polymer particles (b-2), the amount of the rubber component (all the rubbery polymer particles) in the recycled styrene-based resin composition is the total amount of the rubbery polymer particles (a-2) and the rubbery polymer particles (b-2).

[0028] The average particle diameter of the entire mixture containing all rubber-like polymer particles and the contaminants (in other words, toluene-insoluble matter (2) after osmium tetroxide treatment) contained in the recycled styrene resin composition of the present embodiment is preferably 0.4 to 4.5 μm, more preferably 0.5 to 4.0 μm, still more preferably 1.2 to 3.8 μm, even more preferably 1.8 to 3.6 μm, and particularly preferably 2.5 to 3.5 μm from the viewpoint of impact resistance. In the present disclosure, the average particle diameter of the entire mixture containing all rubber-like polymer particles and the contaminants contained in the recycled styrene resin composition can be measured by the following method. An ultra-thin section with a thickness of 75 nm is prepared from the recycled styrene resin composition stained with osmium tetroxide, and a photograph is taken at a magnification of 10,000 times using an electron microscope. In the photograph, the particles stained black (mainly salami-shaped particles) are rubber-like polymer particles, and the other particles are mainly contaminants. From the photograph, the following mathematical formula (N1): [Equation N1] Average particle diameter = ΣniDri 3 / ΣniDri 2 (N1) (In the above mathematical formula (N1), ni is the number of the mixture with a particle diameter Dri, and the particle diameter Dri is the particle diameter calculated as the equivalent circle diameter from the area of the particle in the photograph.) The area average particle diameter is calculated by the above formula, and this is taken as the average particle diameter of the mixture. This measurement is carried out by capturing the photograph into a scanner at a resolution of 200 dpi and using the particle analysis software of an image analyzer IP-1000 (manufactured by Asahi Kasei Corporation). The average particle diameter of the entire rubber-like polymer particles represents the average particle diameter of all the rubber-like polymer particles contained in the recycled styrene resin composition. For example, it represents the average particle diameter of the total particles of the rubber-like polymer particles (a-2) and the rubber-like polymer particles (b-2). The balance between impact resistance and rigidity is improved when it is the average particle diameter and content of the entire mixture containing all the rubber-like polymer particles and the contaminants.

[0029] <Toluene-insoluble matter (= components insoluble in toluene)> In the recycled styrene resin composition of the present embodiment, the "toluene-insoluble content" refers to the components that remain undissolved in toluene after adding 1 g of the object to be measured, such as the recycled styrene resin composition, recycled polystyrene resin (A), or recycled styrene resin composition, to 20 ml of toluene and shaking at 23°C for 2 hours. In this specification, the toluene-insoluble content is classified into the toluene-insoluble content (1) of the recycled styrene resin composition before osmium tetroxide treatment and the toluene-insoluble content (2) of the recycled styrene resin composition after osmium tetroxide treatment. In addition, the treatment of adding 1 g of the object to be measured to 20 ml of toluene and shaking at 23°C for 2 hours is also referred to as the toluene dissolution treatment. And the "recycled styrene resin composition or recycled polystyrene resin (A) before osmium tetroxide treatment" refers to the recycled styrene resin composition or recycled polystyrene resin (A) that has not been treated with osmium tetroxide. Therefore, the toluene-insoluble content (1) present in the recycled styrene resin composition or the recycled polystyrene resin (A) before osmium tetroxide treatment includes components derived from the recycled polystyrene resin (A) (rubber components (e.g., rubber-like polymer particles (a-2) and / or rubber-like polymer particles (b-2)), metals, other resins (e.g., olefin resins such as polyethylene resin and polypropylene resin), pigments, adherents, or foreign substances), etc. On the other hand, the "recycled polystyrene resin (A) containing the toluene-insoluble content (2) after osmium tetroxide treatment" refers to the used polystyrene resin containing the toluene-insoluble content (2) remaining in the recycled polystyrene resin (A) that has been treated with osmium tetroxide, which is the recycled polystyrene resin (A) before osmium tetroxide treatment that has been treated with osmium tetroxide. The toluene-insoluble content (2) that has been treated with osmium tetroxide and is present in the recycled polystyrene resin (A) contains metal-containing foreign substances derived from recycling. However, the "recycled polystyrene resin (A) containing the toluene-insoluble content (2) after osmium tetroxide treatment" does not contain rubber-like polymer particles (a-2). In other words, the toluene-insoluble matter (2) in the recycled styrene resin composition after osmium tetroxide treatment or the recycled polystyrene resin (A) after osmium tetroxide treatment contains components derived from the recycled polystyrene resin (A) (other resins (e.g., olefin resins such as polyethylene resin and polypropylene resin), inorganic substances (e.g., metal powder, metal-containing foreign matter or silica), pigments, adherends or foreign matters), but does not contain the rubber component. After treating virgin styrene resins (e.g., styrene resin (B) which is an unused resin) containing unused styrene monomer units with osmium tetroxide and measuring the amount of toluene-insoluble matter, it was confirmed that the virgin material substantially contains no toluene-insoluble matter. Therefore, the content of toluene-insoluble matter contained in the styrene virgin material after osmium tetroxide treatment of the virgin styrene resin (B) is preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and even more preferably 0.0001% by mass or less, at or below the detection limit, based on the whole composition or virgin material.

[0030] <Method for measuring toluene-insoluble matter> In the present embodiment, the method for measuring the amount of toluene-insoluble matter in the recycled styrene resin composition, the recycled polystyrene resin (A) and the styrene resin (B) before and after osmium tetroxide treatment is as follows. Weigh 1 g (W1) of the object to be measured precisely into a precipitation tube, add 20 mL of toluene, shake at 23 °C for 2 hours, and then centrifuge at a temperature of 4 °C, a rotation speed of 20,000 rpm, and a centrifugal acceleration of 45,100 × G for 60 minutes using a centrifuge (manufactured by Sakuma Seisakusho, SS-2050A rotor: 6B-N6L). Slowly tilt the precipitation tube at about 45 degrees and decant and remove the supernatant. Add 20 mL of toluene to the Shen Dian tube again, shake at 23 °C for 2 hours, then filter using filter paper (W2) whose weight has been measured in advance. After repeatedly washing the insoluble matter on the filter paper with toluene, dry it under vacuum at 160 °C and 3 kPa or less for 1 hour. After cooling to room temperature in a desiccator, accurately weigh the mass of the filter paper (W3), obtain the mass difference W4 from the filter paper before filtration, and calculate the toluene insoluble matter using the following formula. Toluene insoluble matter (%) = W4 / W1 × 100

[0031] <Osmium tetroxide treatment> The osmium tetroxide treatment in this embodiment refers to a chemical treatment that utilizes an oxidation reaction with osmium tetroxide in which two hydroxy groups are syn-added to a carbon-carbon unsaturated bond such as an alkene group. In addition, a catalytic amount of osmium tetroxide and an oxidizing agent are added to a compound having a carbon-carbon unsaturated bond such as an alkene group (for example, rubber-like polymer particles or toluene insoluble matter (1)), converted to a diol, and then a peroxide that can be added together with osmium tetroxide can cleave the carbon-carbon unsaturated bond such as an alkene group. Therefore, when the recycled styrene resin composition or recycled polystyrene resin (A) is subjected to osmium tetroxide treatment, the conjugated diene structure contained in the recycled styrene resin composition or recycled polystyrene resin (A) is solubilized in a solvent (for example, toluene), and the recycled polystyrene resin (A) contained in the recycled styrene resin composition or recycled polystyrene resin (A) is solubilized. It was confirmed that contaminants (other resins (for example, olefin resins such as polyethylene resins and polypropylene resins), inorganic substances (for example, metal powders or silica), pigments, adherends, or foreign substances) remained. From the above, in this specification, the contaminants derived from the recycled polystyrene resin (A) mixed in when the recycled polystyrene resin (A) is recovered for reuse are defined as the toluene insoluble matter (2) after osmium tetroxide treatment. In addition, when the styrenic resin (B) described below is a rubber-modified polystyrene resin (B2), if the same osmium tetroxide treatment is performed on the rubber-modified polystyrene resin (B2), all of the rubber-like polymer particles (b-2) of the rubber-modified polystyrene resin (B2) are decomposed by the osmium tetroxide treatment, so that there is substantially no toluene-insoluble content after the osmium tetroxide treatment contained in the rubber-modified polystyrene resin (B2). The osmium tetroxide treatment in the present embodiment is not particularly limited as long as the conjugated diene structure contained in the recycled styrenic resin composition or recycled polystyrene resin (A) is solubilized in toluene. For example, it is preferably performed according to the following procedure. The osmium tetroxide treatment in the present embodiment preferably includes a step (I) of preparing an osmium tetroxide decomposing agent and a step (II) of bringing the osmium tetroxide decomposing agent into contact with the toluene-insoluble content of the recycled styrenic resin composition or recycled polystyrene resin (A). As the step (I), 30 to 500 mg of osmium (VIII) oxide (for example, 100 mg), 50 to 1,400 g (for example, 200 g) of an aqueous solution of t-butyl hydroperoxide (concentration: 40 to 80% by mass, for example, 70% by mass), and 90 to 1,500 ml (for example, 300 ml) of a lower alcohol (for example, t-butyl alcohol) are preferably mixed to obtain an osmium tetroxide decomposing agent. As the step (II), after preparing a toluene-insoluble content-containing solution in which the recovered toluene-insoluble content is dissolved in an organic solvent (for example, chloroform), the osmium tetroxide decomposing agent is added to the toluene-insoluble content-containing solution, and the osmium tetroxide decomposing agent and the toluene-insoluble content are preferably brought into contact with each other under reflux at 70 to 90 °C (for example, in a warm water bath at 90 °C) for 10 to 30 minutes (for example, 12 minutes). By the step (II), the decomposition treatment of unsaturated bonds such as alkenes contained in the toluene-insoluble content is performed. After the above step (II), a recovery step (III) for recovering the solid content and the liquid content after the decomposition treatment may be provided. As an example of the recovery step (III), after cooling the toluene-insoluble content-containing solution added with the osmium tetroxide decomposing agent, methanol is added to the solution while stirring, and a precipitation step (IV) for precipitating the methanol-insoluble content by the addition of methanol is carried out. Then, the methanol-insoluble content and the liquid content are separated by filter paper, and the recovered product, which is the methanol-insoluble content, is repeatedly washed with toluene, and it is preferable to have a washing step (V) for recovering what remains on the filter paper as the toluene-insoluble content.

[0032] In the recycled styrene-based resin composition of the present embodiment, the toluene-insoluble content (2) contained in the recycled styrene-based resin composition after the osmium tetroxide treatment is 5% by mass or less with respect to the whole recycled styrene-based resin composition, preferably 0.0001 to 4% by mass, and more preferably 0.0001 to 3% by mass. When the toluene-insoluble content (2) contained in the recycled styrene-based resin composition after the osmium tetroxide treatment is in the range of 5% by mass or less, it is preferable from the viewpoint of impact. In particular, when the toluene-insoluble content (2) contained in the recycled styrene-based resin composition after the osmium tetroxide treatment is in the range of 0.0001 to 1% by mass, it is preferable from the viewpoints of appearance and each mechanical property.

[0033] (Occluded component) The recycled styrene-based resin composition or rubber-like polymer particles of the present embodiment preferably contain an occluded component. In the present embodiment, the occluded component of all the rubber-like polymer particles (a general term for the rubber-like polymer particles (a-2) and (b-2) described later) contained in the recycled styrene-based resin composition is the polymer phase encapsulated within all the rubber-like polymer particles contained in the recycled styrene-based resin composition (for example, the polymer phase in the rubber-like polymer particles having a core-shell structure or a salami structure) and the graft polymer chains (styrene-based polymer) having styrene-based monomers on the surface of the rubber-like polymer particles. Therefore, the occluded component is composed of a styrene-based polymer and is obtained by subtracting the total amount of the insoluble component in toluene after osmium tetroxide treatment (= insoluble component in toluene after osmium tetroxide treatment (2)) and the conjugated diene amount in the rubber-like polymer particles from the component insoluble in toluene (toluene-insoluble component (1)) in the recycled styrene-based resin composition before osmium tetroxide treatment. The upper limit of the content of the occluded component in the recycled styrene-based resin composition of the present embodiment is preferably 25% by mass or less, less than 25%, 24% by mass or less, 23% by mass or less, 22% by mass or less, 21% by mass or less, 20% by mass or less with respect to the entire recycled styrene-based resin composition. On the other hand, the lower limit of the content of the occluded component is preferably 5% by mass or more, more than 5%, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, 10% by mass or more with respect to the entire recycled styrene-based resin composition. A preferred form of the rubber-like polymer particles (a-2) of the present embodiment can be encapsulated particles (including microphase separation structures, core-shell structures, and salami-type structures) in which a phase containing a polymer constituting the styrene-based polymer (a-1) is encapsulated within the rubber-like polymer (a), and surface grafted particles in which a polymer constituting the styrene-based polymer (a-1) is grafted on the surface. Also, these forms may be provided in combination. A preferred form of the rubbery polymer particles (b-2) of the present embodiment can be encapsulated particles (including microphase separation structures, core-shell structures, and salami-type structures) in which a phase containing a polymer constituting the styrenic polymer (b-1) is encapsulated within the rubbery polymer (b), and surface-grafted particles in which a polymer constituting the styrenic polymer (b-1) is grafted onto the surface. Further, these forms may be provided in combination. In the present embodiment, the upper limit of the content of the occluded component in all the rubbery polymer particles is preferably 85% by mass or less, less than 85%, 80% by mass or less, 78% by mass or less, 76% by mass or less, 74% by mass or less, 72% by mass or less with respect to the total amount of all the rubbery polymer particles. On the other hand, the lower limit of the content of the occluded component in all the rubbery polymer particles is preferably 30% by mass or more, more than 30%, 35% by mass or more, 38% by mass or more, 40% by mass or more, 42% by mass or more, 45% by mass or more with respect to the total amount of all the rubbery polymer particles.

[0034] Hereinafter, each component constituting the recycled styrenic resin composition of the present embodiment will be described. (Recycled polystyrene-based resin (A)) The recycled polystyrene-based resin (A) of the present embodiment is a used polystyrene-based resin and can be a recovered product of a so-called discarded polystyrene-based resin. More specifically, the recycled polystyrene-based resin (A) can be a material (pre-consumer material) obtained by recovering and reusing offcuts generated in the production process of products containing a styrenic resin, defective products of products containing a styrenic resin, unsold products containing a styrenic resin, styrenic resins that have passed the quality assurance period, and styrenic resins discarded before shipment, or a material (post-consumer material) obtained by recovering and reusing after being once shipped to the market and used up by consumers. And the recycled polystyrene-based resin (A) of the present embodiment contains toluene-insoluble matter (2) after osmium tetroxide treatment. The content of the toluene-insoluble matter (2) after osmium tetroxide treatment in the recycled polystyrene-based resin (A) is 10% by mass or less, preferably more than 0% by mass and 10% by mass or less, more preferably more than 0% by mass and 9% by mass or less, still more preferably more than 0% by mass and 8% by mass or less, based on the whole recycled polystyrene-based resin (A). The recycled polystyrene-based resin (A) that can be used in the present disclosure preferably contains 70% by mass or more of styrene-based monomer units based on the whole recycled polystyrene-based resin (A), and the content of the toluene-insoluble matter (2) after osmium tetroxide treatment is 5% by mass or less based on the whole recycled polystyrene-based resin (A). The recycled polystyrene-based resin (A) containing the toluene-insoluble matter (2) after osmium tetroxide treatment of the present disclosure preferably includes one or more selected from the group consisting of rubber-modified polystyrene-based resins containing a polymer matrix part composed of a styrene-based polymer (a-1) and a domain part composed of particles of a rubber-like polymer (= rubber-like polymer particles (a-2)). Note that since the physical properties and polymer composition of the rubber-modified polystyrene-based resin contained in the recycled polystyrene-based resin (A) are the same as the preferable ranges of the physical properties and polymer composition of the styrene-based polymer (B1) and the rubber-modified polystyrene-based resin (B2) described later, the preferable ranges of the physical properties and polymer composition of the above rubber-modified polystyrene-based resin can be applied.

[0035] In addition, the recycled polystyrene-based resin (A) also includes polystyrene-based resins recovered from used household appliances and the like. The polystyrene-based resin also includes those containing inorganic fillers such as known resins such as styrene-based elastomers, talc, mica, wollastonite, calcium carbonate, barium sulfate, magnesium carbonate, clay, alumina, silica, calcium sulfate, carbon fiber, glass fiber, metal fiber, cellulose, silica sand, gypsum, carbon black, titanium oxide, magnesium hydroxide, asbestos, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium hydroxide, calcium sulfite, sodium sulfate, bentonite, graphite, etc. Such recycled polystyrene-based resins (A) generally contain about 0.01 to 10 parts by weight of inorganic fillers per 100 parts by weight of the recycled polystyrene-based resin (A). In this embodiment, the weight average molecular weight (Mw) of the recycled polystyrene-based resin (A) before osmium tetroxide treatment is preferably 100,000 to 400,000, more preferably 120,000 to 380,000. When the weight average molecular weight is 150,000 to 350,000, a resin excellent in the practicality of the balance between impact strength and fluidity can be obtained. The weight average molecular weight can be measured by gel permeation chromatography in terms of polystyrene standard conversion. In this embodiment, the recycled polystyrene-based resin (A) before osmium tetroxide treatment contains rubber-like polymer particles (a-2). At this time, a resin or polystyrene-based polymer (polystyrene and / or polystyrene-(meth)acrylic acid-based) containing styrene monomer units obtained from a styrene-based monomer may be encapsulated inside the rubber-like polymer particles (a-2), and / or a resin or polystyrene-based polymer containing styrene monomer units may be grafted onto the surface of the rubber-like polymer particles (a-2). More specifically, the rubber-like polymer particles (a-2) in this embodiment may be any particulate material containing a rubber-like polymer. Therefore, the form of the rubber-like polymer particles (a-2) includes solid particles made of a rubber-like polymer, hollow particles made of the rubber-like polymer, encapsulated particles (including microphase separation structures, core-shell structures, and salami-type structures) in which a phase containing a styrene-based polymer (a-1) is encapsulated inside the rubber-like polymer, and surface-grafted particles with a styrene-based polymer (a-1) grafted onto the surface. Also, these forms may be provided in combination. The rubber-like polymer constituting the rubber-like polymer particles (a-2) of this embodiment only needs to have a conjugated diene structure. Therefore, the rubber-like polymer is a conjugated diene-based polymer having conjugated diene monomer units, and for example, rubber components such as polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer can be used.

[0036] From the viewpoint of impact resistance, the average particle diameter of the rubber-like polymer particles (a-2) contained in the recycled polystyrene-based resin (A) before osmium tetroxide treatment in this embodiment is preferably 0.1 to 4.0 μm, and more preferably 0.3 to 3.8 μm. Also, the average particle diameter of the rubber-like polymer particles (a-2) contained in the recycled polystyrene-based resin (A) before osmium tetroxide treatment can be measured by the electron micrograph described above in the same manner as the method for the average particle diameter of the rubber-like polymer particles (b-2). As a preferable form of the rubber-like polymer particles (a-2), the form of the following rubber-like polymer particles (b-2) can be applied.

[0037] <Polymer matrix part of recycled polystyrene-based resin (A)> In the recycled polystyrene-based resin (A) of the present embodiment, the recycled polystyrene-based resin (A) is preferably composed of toluene-insoluble matter (2) after osmium tetroxide treatment, a styrene-based polymer (a-1) which is a polymer matrix part, and rubber-like polymer particles (a-2). The polymer matrix part of the recycled polystyrene-based resin (A) is composed mainly of a styrene-based polymer (a-1). The styrene-based polymer (a-1) can be a styrene-based monomer homopolymer (= polystyrene), a styrene-based copolymer resin containing one or more monomer units selected from the group consisting of styrene-based monomer units and (meth)acrylic acid-based monomer units described below, or a mixture of a styrene-based monomer homopolymer and a styrene-based copolymer resin. In addition, "composed mainly of" in this specification means containing 85% by mass or more. For example, "the polymer matrix part of the recycled polystyrene-based resin (A) is composed mainly of the styrene-based polymer (a-1)" means that the styrene-based polymer (a-1) occupies 85% by mass or more of the total amount of the polymer matrix part. Examples of the monomer constituting the styrene-based monomer unit include styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, or styrene derivatives such as bromostyrene and indene. As the (meth)acrylic acid-based monomer, a (meth)acrylic acid monomer and a (meth)acrylic acid ester monomer are preferable. Examples of the (meth)acrylic acid monomer include acrylic acid or methacrylic acid. Examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (n-butyl) (meth)acrylate, (t-butyl) (meth)acrylate, (isobutyl) (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, (n-octyl) (meth)acrylate, (2-ethylhexyl) (meth)acrylate, decyl (meth)acrylate, stearyl (meth)acrylate, and the like. These can be used alone or in combination. Note that the composition of the polymer matrix part of the present embodiment varies depending on the recycled polystyrene-based resin (A) used. Generally, with respect to the entire polymer matrix part, the styrene-based monomer unit is preferably 40 to 100% by mass, the (meth)acrylic acid monomer unit is preferably 0 to 25% by mass, and the (meth)acrylic acid ester monomer unit is preferably 0 to 50% by mass. In addition, the styrene-based polymer (a-1) and / or the rubber-like polymer (a-2), which are the components constituting the recycled polystyrene-based resin (A), may be produced from monomers derived from fossil raw materials such as petroleum or coal, or may be produced from monomers derived from biomass raw materials. In other words, the recycled polystyrene-based resin (A) may be produced from monomers having radioactive carbon atoms ( 14 C).

[0038] <Toluene-insoluble matter in the recycled polystyrene-based resin (A)> In addition, the recycled polystyrene-based resin (A) of the present embodiment contains toluene-insoluble matter (1) before osmium tetroxide treatment. The content of the toluene-insoluble matter (1) includes the above-mentioned contaminants (other resins (e.g., olefin resins such as polyethylene-based resins and polypropylene-based resins), inorganic substances (e.g., metal powder or silica), pigments, adherends, or foreign substances) and rubber-like polymer particles (a-2). The content of the toluene-insoluble matter (1) in the recycled polystyrene resin (A) varies depending on the recycled polystyrene resin (A) used, but generally, it is preferably more than 0 to 35% by mass, more preferably more than 0 to 30% by mass, still more preferably more than 0 to 25% by mass, and even more preferably more than 0 to 20% by mass, based on the whole recycled polystyrene resin (A). As another form, the content of the toluene-insoluble matter (1) before the osmium tetroxide treatment is preferably 18% by mass or more and 35% by mass or less, more preferably 21% by mass or more and 32% by mass or less, and still more preferably 22% by mass or more and 28% by mass or less, based on the whole recycled polystyrene resin (A). Therefore, the content of the polymer matrix part can generally be a value obtained by removing the toluene-insoluble matter (1) before the osmium tetroxide treatment from the recycled polystyrene resin (A). The upper limit of the content of the recycled polystyrene resin (A) containing the toluene-insoluble matter (2) after the osmium tetroxide treatment in the present embodiment is not particularly limited, but it is preferably 99% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, based on the whole recycled styrene resin composition (100% by mass). When the content of the recycled polystyrene resin (A) is 70% by mass or less, more excellent impact resistance can be exhibited. On the other hand, the lower limit of the content of the recycled polystyrene resin (A) containing the toluene-insoluble matter (1) before the osmium tetroxide treatment in the present embodiment is preferably 1% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, based on the whole recycled styrene resin composition (100% by mass). When the content of the recycled polystyrene resin (A) is 30% by mass or more, more excellent reduction of environmental load can be exhibited. The upper limit and the lower limit of the content of the recycled polystyrene resin (A) can be arbitrarily combined respectively.

[0039] (Styrene resin (B)) The recycled styrene resin composition of the present disclosure may contain a styrene resin (B) as a virgin material. Further, unlike the recycled polystyrene resin (A), the styrene resin (B) substantially does not contain toluene-insoluble matter (2) after osmium tetroxide treatment. The styrene resin (B) preferably includes one or more selected from the group consisting of a styrene polymer (B1) and a rubber-modified polystyrene resin (B2) containing a polymer matrix part composed of a styrene polymer (b-1) and particles of a rubbery polymer (= rubbery polymer particles (b-2)). Hereinafter, the styrene polymer (B1) and the rubber-modified polystyrene resin (B2), which are preferred forms of the styrene resin (B), will be described.

[0040] <Styrene polymer (B1)> In the present embodiment, the styrene polymer (B1) is a homopolymer or copolymer obtained by polymerizing a styrene monomer and, if necessary, other monomers copolymerizable with the styrene monomer, and those generally available can be appropriately selected and used. Examples of the styrene monomer constituting the styrene polymer (B1) include, in addition to styrene, styrene derivatives such as α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, bromostyrene, and indene. Styrene is particularly preferred from an industrial perspective. These styrene monomers can be used alone or in combination of two or more. The styrene polymer (B1) of the present embodiment is preferably polystyrene composed of the above styrene monomer units or a styrene copolymer resin. The polystyrene may further contain monomer units other than the above styrene monomer units as long as the effects of the present invention are not impaired, but typically consists of styrene monomer units. On the one hand, the styrene-based copolymer resin is a resin containing styrene-based monomer units and other monomers copolymerizable with the styrene-based monomer (for example, (meth)acrylic acid-based monomer units). For example, when the other monomer is (meth)acrylic acid-based monomer units, in the styrene-based copolymer resin of the present embodiment, when the total content of styrene-based monomer units and (meth)acrylic acid-based monomer units is 100% by mass, the content of styrene-based monomer units is 20 to 99% by mass, more preferably 50 to 97% by mass, and even more preferably 70 to 95% by mass.

[0041] In addition, the (meth)acrylic acid-based monomer in the present embodiment includes (meth)acrylic acid monomers and (meth)acrylic acid ester monomers. When the total content of styrene-based monomer units, (meth)acrylic acid monomer units, and (meth)acrylic acid ester monomer units in the styrene-based copolymer resin is 100% by mass, the content of (meth)acrylic acid monomer units is preferably 0 to 16% by mass, more preferably 2 to 14% by mass, and even more preferably 3 to 13% by mass. In the present embodiment, when the total content of styrene-based monomer units, (meth)acrylic acid monomer units, and (meth)acrylic acid ester monomer units is 100% by mass, the content of (meth)acrylic acid ester monomer units is preferably 0 to 50% by mass, more preferably 2 to 40% by mass, and even more preferably 3 to 30% by mass. In another aspect of the content of the (meth)acrylic acid ester monomer units, it is preferably 35 to 60% by mass, more preferably 48 to 58% by mass. Also, by setting the lower limit of the content of the (meth)acrylic acid ester monomer units to 0% by mass, the heat resistance can be improved and the cost can be reduced. However, from the above viewpoints, the content of the (meth)acrylic acid ester monomer units can also be more than 0% by mass.

[0042] In this embodiment, the contents of styrenic monomer units (e.g., styrene monomer units), (meth)acrylic acid monomer units (e.g., methacrylic acid monomer units), and (meth)acrylic acid ester monomer units (e.g., methyl methacrylate monomer units) in the styrenic copolymer resin can be determined from the integration ratios of the spectra measured with a proton nuclear magnetic resonance ( 1 1H-NMR) measuring instrument.

[0043] In this embodiment, the styrenic copolymer resin is not excluded from further containing monomer units other than styrenic monomer units and (meth)acrylic acid-based monomers (e.g., (meth)acrylic acid monomer units and (meth)acrylic acid ester monomer units), which are an example of other monomers, as long as the effects of the present invention are not impaired. However, the styrenic copolymer resin in the present invention preferably consists of styrenic monomer units, (meth)acrylic acid monomer units, and / or (meth)acrylic acid ester monomer units typically.

[0044] The (meth)acrylic acid monomer constituting the styrenic copolymer resin of this embodiment is not particularly limited, and examples thereof include methacrylic acid, acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, etc. Methacrylic acid is preferred as the (meth)acrylic acid monomer because it has a great effect of improving heat resistance and is liquid at room temperature and excellent in handleability. These (meth)acrylic acid-based monomers can be used alone or in combination of two or more.

[0045] The (meth)acrylate monomers that constitute the styrene copolymer resin of this embodiment are not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. As the (meth)acrylate monomer, butyl (meth)acrylate is preferred because it has a high influence on the low-temperature shrinkage property of the shrink film. These (meth)acrylate monomers can be used alone or in combination of two or more.

[0046] Suitable styrene copolymer resins of this embodiment include styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic acid-methyl methacrylate copolymer, styrene-acrylic acid copolymer, styrene-methyl acrylate copolymer, styrene-acrylic acid-methyl acrylate copolymer, styrene-methyl methacrylate-butyl methacrylate copolymer, styrene-butyl methacrylate copolymer, or styrene-maleic anhydride copolymer, and the like.

[0047] In this embodiment, the weight average molecular weight (Mw) of the styrene polymer (B1) is preferably 100,000 to 400,000, more preferably 120,000 to 380,000, and still more preferably 160,000 to 350,000. When the weight average molecular weight (Mw) is 100,000 to 400,000, a resin with an excellent balance between mechanical strength and fluidity can be obtained, and the incorporation of gel-like substances is also less. The weight average molecular weight (Mw) is a value obtained by gel permeation chromatography in terms of standard polystyrene.

[0048] Hereinafter, an example of the polymerization method of polystyrene or styrene copolymer resin that can be used as the styrene polymer (B1) of this embodiment will be described. When polymerizing the polymerization raw materials to obtain the above-mentioned polystyrene or styrene copolymer resin, a polymerization initiator and a chain transfer agent are typically contained in the polymerization raw material composition. Examples of the polymerization initiator used for the polymerization of the above polystyrene or styrene copolymer resin include organic peroxides such as peroxyketals like 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, diacyl peroxides such as acetyl peroxide, isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxy esters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoints of decomposition rate and polymerization rate, among them, 1,1-bis(t-butylperoxy)cyclohexane is preferred.

[0049] Examples of the chain transfer agent used for the polymerization of the above polystyrene or styrene copolymer resin include, for example, α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan, and the like.

[0050] As the polymerization method of the above-mentioned polystyrene or styrene-based copolymer resin, solution polymerization using a polymerization solvent can be adopted as necessary. Examples of the polymerization solvent used include aromatic hydrocarbons such as ethylbenzene, dialkyl ketones such as methyl ethyl ketone, etc., and each of them may be used alone or in combination of two or more. Other polymerization solvents such as aliphatic hydrocarbons can be further mixed with aromatic hydrocarbons within a range that does not reduce the solubility of the polymerization product. These polymerization solvents are preferably used in a range not exceeding 25 parts by mass with respect to 100 parts by mass of all monomers. When the polymerization solvent exceeds 25 parts by mass with respect to 100 parts by mass of all monomers, the polymerization rate is significantly reduced, and the mechanical strength of the resulting resin tends to decrease significantly. It is preferable to add it at a ratio of 5 to 20 parts by mass with respect to 100 parts by mass of all monomers before polymerization, as the quality is easily homogenized and it is also preferable in terms of polymerization temperature control.

[0051] The apparatus used in the polymerization step for obtaining polystyrene or a styrene-based copolymer resin, which is an example of the styrene-based polymer (B1) of the present embodiment, is not particularly limited and may be appropriately selected according to a general polymerization method for styrene-based resins. For example, when bulk polymerization is employed, a polymerization apparatus using one or a plurality of fully mixed reactors connected in series can be used. Also, the devolatilization step is not particularly limited. When bulk polymerization is employed, polymerization is carried out until the unreacted monomer finally becomes preferably 50% by mass or less, more preferably 40% by mass or less, and the volatile components such as such unreacted monomers are removed by a known method for devolatilization treatment. More specifically, for example, ordinary devolatilization apparatuses such as a flash drum, a twin-screw devolatilizer, a thin-film evaporator, and an extruder can be used, but a devolatilization apparatus with less residence is preferred. The temperature of the devolatilization treatment is usually about 190 to 280°C. For example, in the polymerization of a styrene-based copolymer resin, from the viewpoint of suppressing the formation of a six-membered cyclic anhydride due to the adjacency of a (meth)acrylic acid monomer (for example, methacrylic acid) and a (meth)acrylic acid ester monomer (for example, methyl methacrylate), 190 to 260°C is more preferred. The pressure of the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. As the devolatilization method, for example, a method of removing volatile components by reducing the pressure under heating and a method of removing through an extruder or the like designed for the purpose of removing volatile components are desirable.

[0052] <Rubber-modified polystyrene-based resin (B2)> The rubber-modified polystyrene-based resin (B2) of the present embodiment contains rubber-like polymer particles (b-2) that constitute the domain portion and a styrene-based polymer (b-1) that constitutes the polymer matrix portion. More specifically, the rubber-modified polystyrene-based resin (B2) is so-called HIPS, in which particles of a rubber-like polymer (hereinafter referred to as rubber-like polymer particles (b-2)) are dispersed in a styrene-based polymer (b-1) as a polymer matrix phase, and it can be produced by polymerizing a styrene-based monomer in the presence of the rubber-like polymer. Further, examples of the styrene-based polymer (b-1) include the same polymers as the above-mentioned styrene-based polymer (B1) such as polystyrene-based polymers (polystyrene and / or polystyrene-(meth)acrylic acid-based polymers, etc.). Also, as the rubber-modified polystyrene-based resin (B2) of the present embodiment, a virgin material, that is, it is preferably unused.

[0053] Examples of the styrene-based monomer that constitutes the rubber-modified polystyrene-based resin (B2) of the present embodiment include, in addition to styrene, for example, styrene derivatives such as α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene or bromostyrene and indene. In particular, styrene is preferred. These styrene-based monomers can be used alone or in combination of two or more. In the present embodiment, polystyrene is a homopolymer obtained by polymerizing the above-mentioned styrene-based monomer, and a generally available one can be appropriately selected and used.

[0054] In this embodiment, the styrenic polymer (b-1) contained in a part of the styrenic polymer (b-1) or the rubber-like polymer particles (b-2) that constitute the polymer matrix phase of the rubber-modified polystyrene resin (B2) is a polymer that essentially contains styrenic monomer units composed of the above styrenic monomers. Further, the styrenic polymer (b-1) may be a copolymer of the above styrenic monomer and a (meth)acrylic acid ester monomer. Therefore, monomers constituting the styrenic polymer (b-1) contained in a part of the styrenic polymer (b-1) or the rubber-like polymer particles (b-2) that constitute the polymer matrix phase of the rubber-modified polystyrene resin (B2) include (meth)acrylic acid ester monomers in addition to the above styrenic monomers. Examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (n-butyl) (meth)acrylate, (t-butyl) (meth)acrylate, (isobutyl) (meth)acrylate, cyclohexyl (meth)acrylate, cinnamyl (meth)acrylate, (n-octyl) (meth)acrylate, (2-ethylhexyl) (meth)acrylate, decyl (meth)acrylate, stearyl (meth)acrylate, etc. These can be used alone or in combination.

[0055] The styrenic polymer (b-1) that constitutes the polymer matrix phase of the rubber-modified polystyrene resin (B2) is preferably one or more selected from the group consisting of polystyrene and styrene-(meth)acrylate copolymers.

[0056] In this embodiment, the content of styrenic monomer units in the entire rubber-modified polystyrene resin (B2) is preferably 37 to 98% by mass, more preferably 49 to 96% by mass. In this embodiment, the content of (meth)acrylic acid-based monomer units in the entire rubber-modified polystyrene resin (B2) is preferably 0 to 63% by mass, more preferably 0 to 51% by mass. In another aspect, the content of the (meth)acrylic acid monomer unit with respect to the entire rubber-modified polystyrene resin (B2) is preferably 0 to 3% by mass, more preferably 0 to 1% by mass. In the present embodiment, the content of the (meth)acrylate monomer unit with respect to the entire rubber-modified polystyrene resin (B2) is preferably 0 to 60% by mass, more preferably 0 to 50% by mass.

[0057] The rubber-like polymer particles (b-2) contained in the rubber-modified polystyrene resin (B2) of the present embodiment may, for example, encapsulate a resin or a polystyrene-based polymer containing styrene monomer units obtained from the above styrene-based monomer inside the rubber-like polymer particles (b-2), and / or may be those in which a resin or a polystyrene-based polymer containing styrene monomer units is grafted on the surface of the rubber-like polymer particles (b-2). More specifically, the rubber-like polymer particles (b-2) in the present embodiment may be any particle bodies containing a rubber-like polymer. Therefore, the form of the rubber-like polymer particles (b-2) includes solid particles made of a rubber-like polymer, hollow particles made of a rubber-like polymer, encapsulated particles (including microphase separation structures, core-shell structures, and salami-type structures) in which a phase containing a polymer constituting the styrene-based polymer (b-1) is encapsulated inside the rubber-like polymer, and surface grafted particles in which a polymer constituting the styrene-based polymer (b-1) is grafted on the surface. Further, these forms may be provided in a composite manner. In addition, the "styrene-based monomer unit" in this specification means a repeating unit that constitutes a polymer obtained by polymerizing a styrene-based monomer, and is a repeating unit (or structural unit) in which the carbon-carbon double bond in the styrene-based monomer becomes a single bond (-C-C-) by the polymerization reaction or cross-linking reaction of the styrene-based monomer. Also, other "monomer units" in this specification have the same meaning.

[0058] As the rubber-like polymer of the present embodiment (for example, the rubber-like polymer constituting the rubber-like polymer particles (b-2)), it suffices to have a conjugated diene structure. Therefore, the rubber-like polymer is a conjugated diene-based polymer having conjugated diene monomer units, and for example, rubber components such as polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer can be used. Further, the rubber-like polymer particles (b-2) containing the rubber component may include a form in which a styrene-based polymer (b-1) such as polystyrene and / or a polystyrene-(meth)acrylic acid-based polymer is encapsulated. Among them, the rubber-like polymer is preferably polybutadiene or a styrene-butadiene copolymer. For polybutadiene, both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used. Further, as the structure of the styrene-butadiene copolymer, both a random structure and a block structure can be used. These rubber-like polymers can be used singly or in combination of two or more. Also, a saturated rubber obtained by hydrogenating a butadiene-based rubber can be used. Since the rubber-like polymer constituting the rubber-like polymer particles (b-2) of the present embodiment has a conjugated diene structure, the rubber-like polymer particles (b-2) can be solubilized in an organic solvent such as toluene by the above osmium tetroxide treatment.

[0059] Examples of the rubber-modified polystyrene-based resin (B2) of the present embodiment include HIPS (high impact polystyrene), ABS resin (acrylonitrile-butadiene-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), AES resin (acrylonitrile-ethylene propylene rubber-styrene copolymer), etc., and HIPS (high impact polystyrene) is particularly preferred. In the present embodiment, when a conjugated diene polymer containing (meth)acrylonitrile such as acrylonitrile monomer units is used as the material for the rubber-like polymer particles (b-2) or the rubber-like polymer, the content of the (meth)acrylonitrile monomer units is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably 0.7% by mass or less with respect to the entire recycled styrene resin composition (100% by mass).

[0060] The content of the rubber-like polymer contained in the rubber-modified polystyrene resin (B2) of the present embodiment is preferably 1 to 20% by mass, more preferably 2 to 18% by mass, and still more preferably 3 to 15% by mass with respect to 100% by mass of the total amount of the rubber-modified polystyrene resin (B2). If the content of the rubber-like polymer is less than 1% by mass, the impact resistance of the recycled styrene resin may decrease. On the other hand, if the content of the rubber-like polymer exceeds 20% by mass, the flexural creep properties may decrease. In the present disclosure, the content of the rubber-like polymer (b) contained in the rubber-modified polystyrene resin (B2) (so-called conjugated diene amount (polybutadiene content)) is a value calculated using thermal decomposition gas chromatography.

[0061] The content of the rubber-like polymer particles (b-2) contained in the rubber-modified polystyrene resin (B2) of the present embodiment (toluene-insoluble matter in the rubber-modified polystyrene resin (B2)) is preferably 5 to 40% by mass with respect to 100% by mass of the total amount of the rubber-modified polystyrene resin (B2). In the present disclosure, the content of the rubber-like polymer particles (b-2) or all rubber-like polymer particles contained in the rubber-modified polystyrene resin (B2) or the recycled styrene resin composition corresponds to the toluene-insoluble matter of the resin (B) or the recycled styrene resin composition before osmium tetroxide treatment. Specifically, it is calculated by the following method. Weigh 1 g (W1) of the object to be measured accurately into a precipitation tube, add 20 mL of toluene, shake for 2 hours at 23 °C, and then centrifuge at 4 °C, a rotation speed of 20,000 rpm, and a centrifugal acceleration of 45,100×G for 60 minutes using a centrifuge (manufactured by Sakuma Seisakusho, model SS-2050A, rotor: 6B-N6L). Slowly tilt the precipitation tube to about 45 degrees and remove the supernatant by decantation. Weigh accurately the mass of the insoluble matter containing toluene, and denote this mass as W5. Subsequently, conduct vacuum drying for 1 hour under the conditions of 160 °C and 3 kPa or less, cool to room temperature in a desiccator, and then weigh accurately the mass of the toluene-insoluble matter, and denote this mass as W6. Then, recover the toluene-insoluble matter from inside the precipitation tube The swelling index of the toluene-insoluble matter and the toluene-insoluble matter was determined by the following formula Swelling index of toluene-insoluble matter = (W5 / W6) Toluene-insoluble matter (%) = (W6 / W1) × 100

[0062] From the perspective of impact resistance, the average particle diameter of the rubber-like polymer particles (b-2) contained in the rubber-modified polystyrene-based resin (B2) of this embodiment is preferably 0.2 to 4.0 μm, more preferably 0.8 to 2.8 μm. From another perspective, it is preferably 0.55 to 3.2 μm, and more preferably 0.65 to 2.8 μm. If the average particle diameter of the rubber-like polymer particles (b-2) is less than 0.2 μm or greater than 4.0 μm, there is a risk that the impact strength, chemical resistance, and gloss may become insufficient

[0063] In the present disclosure, the average particle diameter of the rubber-like polymer particles (b-2) contained in the rubber-modified polystyrene-based resin (B2) can be measured by the following method Prepare an ultra-thin section with a thickness of 75 nm from the rubber-modified polystyrene-based resin (B2) stained with osmium tetroxide, and take a photograph at a magnification of 10,000 times using an electron microscope. In the photograph, the black-stained particles are the rubber-like polymer particles (b-2). From the photograph, the following mathematical formula (N1): [Equation N1] Average particle diameter = ΣniDri 3 / ΣniDri 2 (N1) (In the above formula (N1), ni is the number of rubbery polymer (a) particles having a particle diameter Dri, and the particle diameter Dri is the particle diameter calculated as the equivalent circle diameter from the area of the particles in the photograph.) Calculate the average particle diameter by the above formula, and use it as the average particle diameter of the rubbery polymer particles (b-2). This measurement is carried out by taking a photograph into a scanner at a resolution of 200 dpi and using the particle analysis software of an image analyzer IP-1000 (manufactured by Asahi Kasei Corporation).

[0064] The reduced viscosity of the rubber-modified polystyrene resin (B2) (which is an index of the molecular weight of the rubber-modified polystyrene resin (B2)) is preferably in the range of 0.45 to 0.90 dL / g, more preferably in the range of 0.60 to 0.88 dL / g. If it is less than 0.45 dL / g, the impact strength may decrease, and if it exceeds 0.90 dL / g, the moldability may decrease due to the decrease in fluidity.) In the present disclosure, the reduced viscosity of the rubber-modified polystyrene resin (B2) is a value measured under the conditions of 30 °C and a concentration of 0.5 g / dL in a toluene solution.)

[0065] The method for producing the rubber-modified polystyrene resin (B2) of the present embodiment is not particularly limited, but bulk polymerization (or solution polymerization) of polymerizing a styrene monomer and an optionally added (meth)acrylate monomer (and a solvent) in the presence of a rubbery polymer (b), or bulk-suspension polymerization that shifts to suspension polymerization during the reaction, or emulsion graft polymerization of polymerizing a styrene monomer and an optionally added (meth)acrylate monomer in the presence of a rubbery polymer (b) latex. In bulk polymerization, a mixed solution obtained by adding a rubbery polymer (b), a styrene monomer, an optionally added (meth)acrylate monomer, and, if necessary, an organic solvent, an organic peroxide, and / or a chain transfer agent can be continuously supplied to a polymerization apparatus configured by connecting a complete mixing type reactor or a tank type reactor and a plurality of tank type reactors in series to produce the product.)

[0066] In addition, the styrenic polymer (b-1) and / or the rubbery polymer (b-2), which are the components constituting the styrenic resin (B) including the above-described styrenic polymer (B1) and rubber-modified polystyrene resin (B2), etc., may be produced from monomers derived from fossil raw materials such as petroleum or coal, or may be produced from monomers derived from biomass raw materials. In other words, the styrenic resin (B) may be produced from monomers having radioactive carbon atoms ( 14 C).

[0067] In the present embodiment, the melt flow rate of the rubber-modified polystyrene resin (B2) at 200 °C is preferably 0.5 to 25.0 g / 10 min, more preferably 1.0 to 20.0 g / 10 min, and still more preferably 1.2 to 10.0 g / 10 min. If the above melt flow rate is in the range of 0.5 to 25.0 g / 10 min, the miscibility with the recycled polystyrene resin (A) is good and the mechanical strength is also good. In the present disclosure, the melt flow rate is a value measured at 200 °C and a load of 49 N in accordance with ISO 1133.

[0068] In the recycled styrenic resin composition of the present embodiment, the content of the styrenic resin (B) is preferably 0 to 90% by mass, more preferably 2 to 80% by mass, still more preferably 5 to 60% by mass, even more preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass, based on the total amount of the recycled styrenic resin composition.

[0069] In the recycled styrenic resin composition of the present embodiment, the total content of the recycled polystyrene resin (A) and the styrenic resin (B) is preferably more than 70% by mass and 100% by mass or less, more preferably more than 70% by mass and less than 100% by mass, and still more preferably 75% by mass or more and 99% by mass or less, based on the total amount of the recycled styrenic resin composition. In the recycled styrene resin composition of this embodiment, the total content of the recycled polystyrene resin (A), the styrene resin (B), and the optional additive components described below is preferably 72% by mass or more and 100% by mass or less, more preferably more than 75% by mass and less than 100% by mass, and still more preferably 77% by mass or more and 95% by mass or less, based on the total amount of the recycled styrene resin composition.

[0070] In the recycled styrene resin composition of this embodiment, when the styrene polymer (B1) is used as the styrene resin (B), the total content of the recycled polystyrene resin (A), the styrene polymer (B1), and the optional additives described below in the recycled styrene resin composition preferably accounts for 95.5% by mass or more, more preferably 96% by mass or more, based on the total amount (100% by mass) of the recycled styrene resin composition. In the recycled styrene resin composition of this embodiment, when the rubber-modified polystyrene resin (B2) is used as the styrene resin (B), the total content of the recycled polystyrene resin (A), the rubber-modified polystyrene resin (B2), and the optional additives described below in the recycled styrene resin composition preferably accounts for 95.5% by mass or more, more preferably 96% by mass or more, based on the total amount (100% by mass) of the recycled styrene resin composition. Incidentally, the inevitably mixed foreign substances (including metal-containing foreign substances) corresponding to the toluene-insoluble matter (2) after osmium treatment are contained in the recycled polystyrene resin (A).

[0071] In the recycled styrene resin composition of this embodiment, the total content of the polymer component, the rubber-like polymer particles, the toluene-insoluble matter (2) after osmium tetroxide treatment, and the optional additives described below preferably accounts for 95.5% by mass or more, more preferably 96% by mass or more, based on the total amount (100% by mass) of the recycled styrene resin composition. The above are the essential components and preferred components contained in the recycled styrene resin composition of this embodiment. Hereinafter, the additive components, which are other optional components of the recycled styrene resin composition of this embodiment, will be described.

[0072] [Any additive ingredient] In this embodiment, at any stage before and after the recovery step in the production of the recycled polystyrene resin (A), the rubber-modified polystyrene resin (B2), or the recycled styrene-based resin composition, or at the stage of extrusion processing or molding processing of the recycled styrene-based resin composition, various additives may be added as necessary within the range that does not impair the object of the present invention. For example, plasticizers such as liquid paraffin, ultraviolet absorbers, light stabilizers, antioxidants such as hindered phenol-based, phosphorus-based, and sulfur-based antioxidants, lubricants, antistatic agents, flame retardants, various dyes and pigments, inorganic crystal nucleating agents (metal oxides such as titanium oxide and tin oxide), organic crystal nucleating agents, fluorescent brighteners, light diffusing agents, and selective wavelength absorbers may be added. The recycled styrene-based resin composition according to this embodiment preferably contains one or more selected from the group consisting of an antioxidant, a pigment, a flame retardant, an additive, a mineral oil, a vegetable oil, and a lubricant.

[0073] The light stabilizer of this embodiment preferably has a function of preventing the deterioration and coloring of the composition by radicals by capturing and detoxifying the photo radicals generated by the recycled styrene-based resin composition absorbing ultraviolet rays, although it does not have ultraviolet absorption ability itself. The light stabilizer can be used alone or in combination of two or more, and by using it in combination with the ultraviolet absorber and / or antioxidant described later, a higher light resistance effect can be exhibited. Examples of the light stabilizer of the present embodiment include bis(1,2,2,6-pentamethyl-4-piperidyl) sebacate, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl) butane-1,2,3,4-tetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, N'-bis(2,2,6,6-tetramethylpiperidin-4-yl) hexane-1,6-diamine, bis(1,2,2,6,6-pentamethyl-4-piperidyl) butyl(3,5-di-t-butyl-4-hydroxybenzyl) malonate, etc. Specific product names include AdekaStab LA-52, AdekaStab LA-57, AdekaStab LA-63P, AdekaStab LA-68, AdekaStab LA-72, AdekaStab LA-77Y, AdekaStab LA-77G, AdekaStab LA-81 manufactured by ADEKA Corporation, JF-90G, JF-95 manufactured by Johoku Chemical Co., Ltd., Chimassorb 2020FDL, Chimassorb 944FDL, Tinuvn 622SF manufactured by BASF Japan Ltd., etc.

[0074] The ultraviolet absorber of the present embodiment absorbs the ultraviolet rays absorbed by the recycled styrene resin composition and converts them into heat or chemical energy, thereby suppressing the generation of photo radicals due to ultraviolet absorption of the styrene resin composition and having a function of suppressing the deterioration and coloring of the resin. Preferred examples of the ultraviolet absorber of the present embodiment include benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, and benzoate-based compounds. As preferable antioxidants of the present embodiment, for example, hindered phenolic antioxidants such as octadecyl 3-(3,5-tert-butyl-4-hydroxyphenyl)propionate, 4,6-bis(octylthiomethyl)-o-cresol (for example, Irganox 1076 manufactured by BASF Japan Ltd.), and phosphorus-based processing heat stabilizers such as tris(2,4-di-tert-butylphenyl)phosphite (for example, Irgafos 168 manufactured by BASF Japan Ltd.) can be mentioned. These stabilizers may be used alone or in combination of two or more as appropriate. There is no particular limitation on the addition timing, and it may be either in the polymerization step or the devolatilization step. Also, the stabilizer can be mixed into the product using mechanical devices such as an extruder or a mixer.

[0075] Regarding the content of each of the light stabilizer, ultraviolet absorber, and antioxidant of the present embodiment, it is 0.001 to 2.0% by mass with respect to the total amount of the recycled styrene resin composition. As the upper limit value, 1.8% by mass or less, 1.6% by mass or less, 1.4% by mass or less, 1.2% by mass or less, 1.0% by mass or less, 0.8% by mass or less, 0.7% by mass or less are preferable in this order. As the lower limit value, 0.005% by mass or more, 0.010% by mass or more, 0.021% by mass or more, 0.051% by mass or more, 0.061% by mass or more, 0.071% by mass or more, 0.079% by mass or more, 0.089% by mass or more, 0.12% by mass or more, 0.17% by mass or more are preferable in this order. The content can be selected as any combination of the above upper limit value and lower limit value.

[0076] In addition, the above various additives in the recycled styrene resin composition of the present embodiment are preferably 10.0% by mass or less, more preferably 5.5% by mass or less, further preferably 2.9% by mass or less, even more preferably 1.5% by mass or less, and particularly preferably 0.9% by mass or less with respect to 100% by mass of the recycled styrene resin composition.

[0077] [Physical Properties of Recycled Styrene Resin Composition] The preferable physical properties of the recycled styrene resin composition in the present embodiment are described below. <Vicat softening temperature> In this embodiment, the Vicat softening temperature of the styrene resin composition is preferably 85°C or higher, more preferably 86°C or higher, and even more preferably 88°C or higher. By setting the Vicat softening temperature to 85°C or higher, a molded product with excellent heat resistance can be obtained. The Vicat softening temperature in this specification is measured under the conditions of a 5 kg load and a heating rate of 50°C / h in accordance with ISO 306.

[0078] <Charpy impact strength> The Charpy impact strength of the recycled styrene resin composition of this embodiment is preferably 5 kJ / m 2 or higher, more preferably 7 - 20 kJ / m 2 . If it is less than 5 kJ / m 2 , there is a concern of breakage during use. In the present disclosure, the Charpy impact strength is a value measured in accordance with ISO 179.

[0079] <Melt mass flow rate> The recycled styrene resin composition of this embodiment preferably has a melt mass flow rate of 1.5 g / 10 min or more, and more preferably 2 - 18 g / 10 min. If the melt mass flow rate is 1.5 g / 10 min or more, the moldability during extrusion molding or vacuum molding is good. The above melt mass flow rate can be achieved by adjusting the melt mass flow rates of the respective components (A) - (B) and the mixing ratio of these resins. In the present disclosure, the melt mass flow rate is a value measured at a temperature of 200°C and a load of 49 N in accordance with ISO 1133.

[0080] <Weight average molecular weight (Mw) of the matrix portion of the recycled styrene resin composition> In this embodiment, the weight average molecular weight (Mw) of the recycled styrene-based resin composition before osmium tetroxide treatment is preferably from 100,000 to 350,000, more preferably from 150,000 to 250,000. When the weight average molecular weight is from 150,000 to 250,000, a resin excellent in mechanical strength can be obtained. The weight average molecular weight can be measured by gel permeation chromatography in terms of polystyrene standard conversion.

[0081] <Calculation of the number of particulate matter> In this embodiment, the number Y of particulate matter in the disk-shaped test piece obtained from the pellet body (X) of the recycled styrene-based resin composition preferably satisfies the following formula (3), and the number Y of particulate matter in the disk-shaped test piece obtained from the pellet body (2) and the pellet body (4) of the recycled styrene-based resin composition preferably satisfies the following formula (3). [Equation 3] Formula (3): Y ≤ 10 (number / 10 g) (In the above formula (3), Y represents the number of particulate matter in the disk-shaped test piece obtained from the pellet body (X) (preferably, the pellet body (2) and the pellet body (4) of the recycled styrene-based resin composition), and the pellet body (X) (preferably, the pellet body (2) and the pellet body (4) of the recycled styrene-based resin composition) is weighed 10 g, heated and compressed to produce a disk-shaped test piece with a thickness of 200 to 350 μm, and then measured using a 10-fold magnifying lens, representing the number of particulate matter with a maximum length of 600 μm or more in the disk-shaped test piece.) When the number Y of particulate matter is 10 or less, a recycled styrene-based resin composition showing a more excellent appearance can be provided. Further, a shrink film using the composition can also further reduce printing defects and show an excellent appearance. The measuring method of the number Y of the above particulate matter is as described in the examples below. Further, the "particulate matter" is a lump (filamentous, particulate, amorphous, etc.) with a maximum length of 600 μm or more, and its color includes not only black but also lumps such as white.

[0082] [Manufacturing method of recycled styrene-based resin composition] In this embodiment, the method for producing the recycled styrene-based resin composition is not particularly limited as long as it involves blending, melting, kneading, and granulating the recycled polystyrene-based resin (A), the styrene-based resin (B), and optional components, and a method commonly used in the production of general styrene resins can be employed. For example, after blending (mixing) the above components using a drum tumbler, Henschel mixer, etc., the components are melted and kneaded using a Banbury mixer, single-screw extruder, twin-screw extruder, kneader, etc., and if necessary, a step of sieving through a screen passing through a screen mesh is performed, and the recycled styrene-based resin composition can be obtained by granulating using a rotary cutter, fan cutter, etc. The resin temperature during melting and kneading is preferably 180 to 240°C. In order to achieve the target resin temperature, the cylinder temperature of an extruder, etc. is preferably set at a temperature 10 to 20°C lower than the resin temperature. If the resin temperature is less than 180°C, mixing will be insufficient, which is not preferable. On the other hand, if the resin temperature exceeds 240°C, thermal decomposition of the resin will occur, which is not preferable.

[0083] A preferred method for producing the recycled styrene-based resin composition of this embodiment includes a purification step of purifying the recycled polystyrene-based resin (A), and a melting step of blending the purified recycled polystyrene-based resin (A) with, if necessary, the styrene-based resin (B) and optional components and melting them. Thereby, a recycled styrene-based resin composition with reduced environmental impact, few foreign substances, and excellent appearance can be obtained. The purification step is preferably one or more steps selected from the group consisting of a purification step by filtration after dissolution in a solvent, a purification step by metal detection, and a purification step by mesh. As the purification step by filtration after dissolution in a solvent, each recovered recycled polystyrene-based resin (A) is pulverized, crushed to a maximum length of about 30 mm per piece, dissolved in a solvent (methyl ethyl ketone), and then foreign substances of 0.2 mm or more are filtered off with a Millipore filter, and dried at 50 to 120°C (preferably 60°C to 90°C) for 2 to 12 hours to distill off the solvent and granulated (for example, processed into a pellet form) for use. In the purification step by metal detection, it is preferable to separate recycled styrene resin compositions containing a metal amount equal to or greater than a predetermined amount from recycled styrene resin compositions containing a metal amount less than a predetermined amount by the above-mentioned sorting mechanism. For example, after crushing each of the recycled polystyrene resins collected, the above-mentioned sorting mechanism (Metalider MC-20 manufactured by Saika Technical Research Institute) is used to remove metals, and if necessary, a known infrared sorting means is used to granulate the resins. The refining step using the mesh includes a step of washing and crushing each of the recovered recycled polystyrene resins, subjecting them to gravity separation and passing them through a mesh during granulation.

[0084] [Molded products] The recycled styrene-based resin composition according to the present invention is preferably used for injection blow molding, sheet bodies (including films), injection molding, or extrusion molding. The present disclosure may be a shrink film comprising a resin layer containing the above-mentioned recycled polystyrene-based resin composition and a surface layer covering at least one side of the resin layer. The shrink film can reduce printing defects and provide an excellent appearance.

[0085] The shrink film according to the present invention is a shrink film formed using the above-mentioned recycled styrene-based resin composition, and preferably has a multi-layer structure. The average thickness of the shrink film is not particularly limited, but is preferably 10 μm to 100 μm, more preferably 12 μm to 80 μm, and even more preferably 15 μm to 60 μm. The shrink film is preferably in the form of a multilayer film obtained by laminating the resin layer containing the above-mentioned recycled styrenic resin composition and the surface layer containing a thermoplastic resin. Examples of the thermoplastic resin include polystyrene-based polymers, polyphenylene ether-based polymers, polyethylene-based polymers, polypropylene-based polymers, polybutene-based polymers, polyvinyl chloride-based polymers, polyvinyl acetate-based polymers, polyamide-based polymers, thermoplastic polyester-based polymers, polylactic acid-based polymers, polyacrylate-based polymers (n-butyl acrylate polymer), polyphenoxy-based polymers, polyphenylene sulfide-based polymers, styrene-butadiene block copolymers, polycarbonate-based polymers, polyacetal-based polymers, polybutadiene-based polymers, thermoplastic polyurethane-based polymers, polysulfide-based polymers, and the like. The above thermoplastic resin may be used alone or in combination of two or more.

[0086] There is no particular limitation on the laminated structure of the resin layer containing the recycled polystyrene-based resin composition and the surface layer containing a thermoplastic resin, but a two-layer three-layer structure is preferable from the viewpoint of ease of manufacture. For example, a structure laminated in the order of the surface layer made of the thermoplastic resin, the resin layer containing the recycled polystyrene-based resin composition, and the layer made of the thermoplastic resin, or a structure laminated in the order of the resin layer containing the recycled polystyrene-based resin composition and the surface layer made of the thermoplastic resin can be mentioned. Known methods can be used for manufacturing such a multilayer shrink film. For example, it can be manufactured by a coextrusion method, a dry lamination method, etc. using the above-mentioned recycled polystyrene-based resin composition and other thermoplastic resins.

[0087] The shrink film of this embodiment may be printed. For example, printing of product names, illustrations, or precautions, etc. may be mentioned. The above printing may be performed only on one side of the shrink film, or may be performed on both sides. Also, the above printing may be performed on the entire surface of the shrink film, or may be performed on a part thereof. More specifically, the above printing is formed by a plurality of layers with different coloring pigments so as to have a desired design by a known printing method such as gravure printing, flexographic printing, UV printing, etc.

[0088] The shrink film of this embodiment can be used as a label or cap seal for plastic bottles, food containers, or daily sundries, an integrated packaging film, an electrical insulation coating for dry batteries, etc.

Examples

[0089] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The analysis and evaluation methods of the resins and molded products in the examples and comparative examples are as follows.

[0090] [Characteristics Evaluation of Each Resin and Resin Composition] (1) Measurement of Weight Average Molecular Weight The weight average molecular weight (Mw) of each resin and resin composition produced in the examples and comparative examples was measured under the following conditions using gel permeation chromatography (GPC). Measuring instrument: HLC-8220 manufactured by Tosoh Fractionation column: Two TSK gel Super HZM-H (inner diameter 4.6 mm) manufactured by Tosoh were connected in series Guard column: TSK guard column Super HZ-H manufactured by Tosoh Measurement solvent: Tetrahydrofuran (THF) Sample concentration: 5 mg of the measurement sample was dissolved in 10 mL of the solvent and filtered through a 0.45 μm filter. Injection volume: 10 μL Measurement temperature: 40 °C Flow rate: 0.35 mL / min Detector: Differential refractometer For the preparation of the calibration curve, 11 types of Tosoh's TSK standard polystyrenes (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) were used. The calibration curve was created using the approximate formula of a first-order straight line.

[0091] (2) Measurement of melt mass flow rate (MFR) The melt mass flow rate (g / 10 min) of each resin and resin composition produced in the examples and comparative examples was measured under the load conditions of 200 °C and 49 N in accordance with ISO 1133.

[0092] (3) Measurement of Vicat softening temperature The Vicat softening temperature of each resin and resin composition produced in the examples and comparative examples was measured in accordance with ISO 306. The load was 50 N and the heating rate was 50 °C / h.

[0093] (4) Measurement of the content of each monomer unit, the content of the polymer component and the rubber component The content of each monomer unit contained in the resin compositions prepared in the examples and comparative examples was measured by pyrolysis GC / MS under the following conditions. <Measurement conditions> Pyrolysis unit Equipment: PY-3030D manufactured by Frontier Lab Heating furnace temperature: 600 °C Boundary temperature: 300 °C GC / MS Equipment: GCMS-GP2020NX manufactured by Shimadzu Corporation Column: Ultra Alloy-5 (Length 30 m, film thickness 0.25 μm, diameter 0.250 mmφ) Column temperature: Held at 50 °C for 5 minutes, heated at 10 °C / min, Heated at 7 °C / min from 100 °C and held at 300 °C for 10 minutes. Inlet temperature: 300 °C Detector temperature: 300 °C Split ratio: 1 / 300 Carrier gas: Helium Detection method: Mass spectrometer (MSD) Sample amount: 50 μg Detection mode: Scan mode or SIM mode When detecting each monomer peak, in order to avoid peak overlap and peak intensity saturation, appropriate pretreatment such as the dilution rate of the sample, the column used, and the detection conditions may be adjusted as appropriate.

[0094] (5) Measurement of Charpy impact strength The test pieces used for measuring the Charpy impact strength were strips of specified dimensions cut from the central parallel part of ISO mold type A test pieces prepared by the method described in the section "Method for manufacturing ISO dumbbell test pieces" described below. The test was carried out in accordance with ISO 179 to measure the Charpy impact strength (kJ / m 2 ) with a notch.

[0095] (6) Measurement of tensile break elongation ISO dumbbell test pieces were prepared from each resin composition produced in the examples and comparative examples, and the tensile break elongation (%) was measured in accordance with ISO 527. The method for manufacturing the ISO dumbbell test pieces is as follows. Each resin composition produced in the examples and comparative examples was molded by an injection molding machine (EC60N, manufactured by Toshiba Machine Co., Ltd.) at a cylinder temperature of 230 °C, a mold temperature of 45 °C, an injection pressure of 80 MPa, and an injection speed of 26 mm / s to obtain test pieces of ISO mold type A.

[0096] (7) Evaluation of shrink film After producing each shrink film using the recycled polystyrene-based resin compositions of the examples and comparative examples according to the shrink film production procedure described below, the presence or absence of foreign matter was visually confirmed.

[0097] (8) Measurement of the number of particulates Using the recycled polystyrene resin compositions of the examples and comparative examples, each disc-shaped test piece was produced according to the production procedure of the disc-shaped test piece described below. Next, the particulate matter was measured using a 10-fold magnifying lens. The number Y of particulate matter (e.g., black dots or lumps) having a maximum length of 600 μm or more present in the disc-shaped test piece was visually calculated. <Production Procedure of Disc-Shaped Test Piece> 10 g of the pelletized recycled polystyrene resin compositions prepared in the examples and comparative examples was weighed, and a disc-shaped test piece with a thickness of 200 μm was produced using a compression molding machine manufactured by Soken Chemical & Engineering Co., Ltd. under the condition of a heating temperature of 200°C.

[0098] (9) Purification Process by Metal Detection or Measurement of Metal Trapping Rate (9-1) Purification Process by Metal Detection The recycled polystyrene resins of the raw materials used in each example and comparative example were extruded and pelletized to a predetermined size (e.g., major axis 1.5 - 4.0 mm, minor axis 1.0 - 3.0 mm), and then the metal was removed under the following conditions. <Conditions> Measuring Instrument: Metallider MC-20 manufactured by Zakka Gijutsu Kenkyusho Size: Major axis 2.7 mm, minor axis 2.4 mm Measurement Quantity: 2 kg each (9-2) Measurement of Metal Trapping Rate The metal capture rate X(%) of the recycled polystyrene resin compositions of the examples and comparative examples was measured under the following conditions. Specifically, after processing the recycled styrene resin compositions of the examples and comparative examples described below into pellet bodies (X) with a major axis of 2.7 mm and a minor axis of 2.4 mm, the magnetic field generated in the pellet body (X) was detected by electromagnetic induction that occurred when the pellet body (X) was passed through a magnetic field, and the metal in the pellet body (X) was discriminated. And due to the generated magnetic field, the pellet body (X) was sorted into a pellet body (X1) where a magnetic field was generated and a pellet body (X2) other than the pellet body (X1). Then, subsequently, the magnetic field generated in the pellet body (X1) was detected by electromagnetic induction that occurred when each pellet body (X1) was passed through the magnetic field again, and the metal in the pellet body (X1) was discriminated. And due to the generated magnetic field, the pellet body (X1) was sorted into a pellet body (X3) containing metal and a pellet body (X4) other than the pellet body (X3). The weights of the pellet bodies (X2) to (X4) were measured, and the metal capture rate X was calculated using the following formula (2). [Equation 2] Formula (2): X(%) = (weight of the pellet body (X3) / [weight of the pellet body (X2) + weight of the pellet body (X3) + weight of the pellet body (X4)]) × 100 <Conditions> Measuring instrument: Metallider MC-20 manufactured by Zaiga Technical Research Institute Pellet size: major axis 2.7 mm, minor axis 2.4 mm Measurement quantity: 2 kg each In addition, when sorting into a pellet body (X1) where a magnetic field is generated and a pellet body (X2) other than the pellet body (X1), since the pellet body (X2) is mixed as the pellet body (X1) where a magnetic field is generated due to the specifications of the device, two sorting operations are performed by the device of the above sorting mechanism.

[0099] (10) Measurement of flexural modulus The manufactured recycled polystyrene resin composition was injection molded into an ISO type A test piece, and the flexural modulus was measured in accordance with ISO178.

[0100] [Raw materials used in examples and comparative examples] In Table 1, the recycled polystyrene resin (A), virgin styrene resin (B), and additives used in the examples and comparative examples are as follows. (Recycled polystyrene resin (A)) Recycled polystyrene resin A: Waste polystyrene, toluene-insoluble content of 1.0% by mass after osmium decomposition treatment (toluene-insoluble content of 20.0% by mass before osmium decomposition treatment), average particle diameter of 4.4 μm, Mw of 190,000, MFR of 8.3 g / 10 min Recycled polystyrene resin B: Waste polystyrene, toluene-insoluble content of 6.0% by mass after osmium decomposition treatment (toluene-insoluble content of 23.0% by mass before osmium decomposition treatment), average particle diameter of 3.6 μm, Mw of 210,000, MFR of 5.0 g / 10 min Recycled polystyrene resin C: Waste polystyrene, toluene-insoluble content of 9.5% by mass after osmium decomposition treatment (toluene-insoluble content of 16.1% by mass before osmium decomposition treatment), average particle diameter of 4.5 μm, Mw of 190,000, MFR of 10 g / 10 min In addition, the recycled polystyrene resins A to C used as raw materials in the examples, reference examples, and comparative examples described later were used after being subjected to either of the following purification steps (1) or (2) (see Table 1). (1) Purification step by metal separation After pulverizing each recovered recycled polystyrene resin, metals were removed using a sorting device (Metalider MC-20 manufactured by Zoga Technical Research Institute), and if necessary, further sorting means using known infrared rays were applied, followed by pelletization. (2) Purification step by mesh After washing and pulverizing each recovered recycled polystyrene resin, specific gravity separation was performed, and the material passed through a mesh during pelletization was used.

[0101] In addition, when the recycled polystyrene resins B and C were granulated without subjecting them to the purification step by metal detection in the above (1) and only performing the screening step by the above (2) mesh to measure the metal capture rate, the metal capture rate of the recycled polystyrene resin B was 7.6%, and the metal capture rate of the recycled polystyrene resin C was 77%. Also, at that time, disk-shaped test pieces (average thickness 200 mm) were also produced. The number of granular substances in the disk-shaped test piece obtained from the recycled polystyrene resin B was 36, and the number of granular substances in the disk-shaped test piece obtained from the recycled polystyrene resin C was 133.

[0102] (Styrene resin (B) of virgin material) PS-1: HIPS, average particle diameter 2.1 μm, Mw 220,000 PS-2: GPPS, Mw 260,000 (Phenolic antioxidant) Stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (manufactured by BASF, Irganox 1076) (Phosphorus antioxidant) Tris(2,4-di-tert-butylphenyl)phosphite (manufactured by BASF Corporation, Irgafos 168)

[0103] <Manufacturing method of recycled polystyrene resin compositions of Examples and Comparative Examples> For the recycled polystyrene resin (A) used in the production of the recycled polystyrene resin compositions of Example 2 and Comparative Examples 1 to 3, the raw material recycled polystyrene resin (A) was prepared by performing only the screening step by mesh without performing the purification step by metal detection. On the other hand, for the recycled polystyrene resin (A) used in the production of the recycled polystyrene resin compositions of Examples other than Example 2, the raw material recycled polystyrene resin (A) was prepared by performing the purification step by metal detection and the screening step by mesh. Next, according to Table 2 below, after preparing the raw materials respectively, the weighed raw materials were blended in a drum tumbler and melt-kneaded with a twin-screw extruder (TEM-26SS manufactured by Toshiba Machine Co., Ltd.) at a cylinder set temperature of 220°C and a screw rotation speed of 100 rpm. The molten resin passed through a screen mesh provided on the upstream side of a breaker plate between the tip of the extruder screw and the die, and then was extruded as a molten strand from the die. The molten strand was cooled with water and cut with a rotary cutter to produce pellet bodies with each composition ratio. Next, according to the procedure in the column of the measurement of the above metal capture rate, the metal capture rate of each pellet body was measured to obtain a predetermined pellet-shaped recycled polystyrene-based resin composition. In addition, the first and finest mesh sizes of the above screen mesh in each Example and Comparative Example are shown in Table 2. Regarding the size of the pellet bodies in each Example and Comparative Example, by adjusting the cutting conditions of the strand, the major axis was 2.7 mm and the minor axis was 2.4 mm.

[0104] <Production of Shrink Film> Using the recycled polystyrene-based resin compositions obtained in the above Examples and Comparative Examples, a laminated film (= shrink film) in which a first outer layer and a second outer layer were formed on both main surfaces of the intermediate layer was produced under the following conditions. More specifically, the resin used for the above two outer layers and the recycled polystyrene-based resin composition described in the Example used for the intermediate layer were melt-extruded with separate extruders, merged in the die, and a sheet-shaped laminated film with a thickness of about 300 μm having a three-layer structure of the first outer layer / intermediate layer / second outer layer was produced. Next, the sheet was heated at 85°C for 3 minutes and stretched in the order of 1.1 times in the sheet extrusion direction (MD) and 5 times in the direction perpendicular to the sheet extrusion direction (TD) with a batch-type tenter (EX6-S1 manufactured by Toyo Seiki Co., Ltd.) to produce each shrink film. The characteristics of the obtained laminated film are as follows. The layer structure of the laminated film is a laminate in which a first outer layer and a second outer layer are respectively formed on both main surfaces of the intermediate layer. Average thickness ratio of the laminated film (%): First outer layer / Intermediate layer / Second outer layer = 15 / 70 / 15 For the material composition of each layer of the laminated film, as the first outer layer and the second outer layer, a rubber component styrene (S)-butadiene (B) block copolymer (S / B = 77 / 23) was used. And as the intermediate layer, a mixture of the recycled polystyrene-based resin composition described in the examples and comparative examples and the mixed resin A (mixing ratio: recycled polystyrene-based resin composition / mixed resin A = 40 / 60). Note that as the above mixed resin A, styrene / n-butyl acrylate / rubbery polymer (1) = 69 / 15 / 16 was used. Also, as the rubbery polymer (1), a styrene (S)-butadiene (B) block copolymer (S / B = 38 / 62) was used. Regarding the shrink film obtained using the recycled polystyrene-based resin composition of Example 1, when the transparency was confirmed, it was confirmed that a shrink film showing high transparency without foreign matters was obtained.

[0105]

Table 1

Claims

1. A recycled polystyrene resin composition containing a recycled polystyrene resin (A), comprising a polymer component containing a styrene-based polymer (a-1) derived from the recycled polystyrene resin (A), rubber-like polymer particles (a-2) derived from the recycled polystyrene resin (A), and a metal-containing foreign matter containing a metal derived from the recycled polystyrene resin (A), wherein the metal capture rate X in the recycled polystyrene resin composition satisfies the following formula (1): [Equation 1] Formula (1) X ≤ 2% by mass (In the above formula (1), X represents the metal capture rate. After processing the recycled styrene resin composition into pellet bodies (X) having a major axis of 1.5 to 4.0 mm and a minor axis of 1.0 to 3.0 mm, when the pellet bodies (X) are passed through a magnetic field, the magnetic field generated in the pellet bodies (X) is detected by electromagnetic induction, the metal in the pellet bodies (X) is discriminated, and by the generated magnetic field, the pellet bodies (X) are sorted into pellet bodies (1) where a magnetic field is generated and pellet bodies (2) other than the pellet bodies (1). After that, when each pellet body (1) is passed through the magnetic field again, the magnetic field generated in the pellet body (1) is detected by electromagnetic induction, the metal in the pellet body (1) is discriminated, and by the generated magnetic field, the pellet body (1) is sorted into a pellet body (3) containing metal and a pellet body (4) other than the pellet body (3). The weights of the pellet bodies (2) to (4) are measured, and the metal capture rate X is calculated using the following formula (2). [Equation 2] Formula (2): X (%) = (weight of the pellet body (3) / [weight of the pellet body (2) + weight of the pellet body (3) + weight of the pellet body (4)]) × 100 A recycled polystyrene resin composition satisfying the above.

2. Further containing a styrene resin (B) containing a styrene-based polymer (b-1) which is a virgin material, and the polymer component further containing the styrene-based polymer (b-1), the recycled polystyrene resin composition according to Claim 1.

3. A recycled polystyrene-based resin composition containing the polymer component, the rubbery polymer particles (a-2), and the metal-containing foreign matter, When the recycled polystyrene-based resin composition is classified into a toluene-soluble component (1) in which the polymer component soluble in toluene is dissolved and a toluene-insoluble component (1) containing the rubbery polymer particles (a-2) and the metal-containing foreign matter, The toluene-insoluble component (2) after the osmium tetroxide treatment obtained by subjecting the toluene-insoluble component (1) to osmium tetroxide treatment is more than 0% to 3% by mass based on the entire recycled styrene-based resin composition, The recycled polystyrene-based resin composition according to claim 1 or 2, wherein the toluene-insoluble component (1) before the osmium tetroxide treatment is 5 to 30% by mass.

4. The recycled polystyrene-based resin composition according to claim 1 or 2, wherein the content of the polymer component is more than 70% by mass based on the entire recycled styrene-based resin composition.

5. The recycled polystyrene-based resin composition according to claim 1 or 2, wherein the number Y of particulate matter in the disk-shaped test piece produced from the pellet body (X) satisfies the following formula (3). [Formula 3] Formula (3): Y ≦ 10 (number / 10 g) (In the above formula (3), Y represents the number of particulate matter in the disk-shaped test piece produced from the pellet body (X). After weighing 10 g of the pellet body (X) and heating and compressing it to produce a disk-shaped test piece with a thickness of 200 to 350 μm, the number of particulate matter having a maximum length of 600 μm or more in the disk-shaped test piece was measured using a 10-fold magnifying lens.)

6. The toluene-insoluble component (1) before the osmium tetroxide treatment contains the rubbery polymer particles (a-2), and the average particle diameter of all the rubbery polymer particles contained in the recycled polystyrene-based resin composition is 2 to 4 μm. The recycled polystyrene-based resin composition according to claim 3.

7. The recycled polystyrene resin composition according to claim 1 or 2, further containing an antioxidant.

8. The recycled polystyrene resin composition according to claim 1 or 2, wherein the styrene recycled resin is a post-industrial product.

9. A shrink film comprising a resin layer containing the recycled polystyrene resin composition according to claim 1 or 2, and a surface layer covering at least one surface of the resin layer.

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