Injection molding method, molding resin composition, and molded article

Abstract

To provide an injection molding method for obtaining a molded product having a structure in which a core part and a shell part are formed of different resins by one injection molding of a resin composition.SOLUTION: In an injection molding method, a resin composition for molding containing at least two resins having different apparent viscosity at 230°C and at least one compatibility accelerator is used as a raw material for injection molding.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an injection molding method, a molding resin composition, and a molded article. [Background technology]

[0002] Injection molding is a molding method that uses a mold. Materials such as resin are heated and melted, then fed into a mold and cooled to form the desired shape. Injection molding is used in a wide range of fields because it allows for the rapid, continuous mass production of articles of desired shapes.

[0003] For example, Patent Document 1 discloses a molded article having excellent impact resistance, which is obtained by injection molding a resin composition containing a styrene-based resin, polylactic acid, and a copolymer of butadiene and an ethylenically unsaturated carboxylic acid ester. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-199654 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventionally, to produce a molded body using different resins to form a core part and a shell part covering the core part, it has not been possible to perform a single injection molding process, but has required multiple processes such as two-color molding or painting. Patent Document 1 also does not consider the production of a molded body having a structure including a core part and a shell part.

[0006] The present disclosure has been made in view of the above, and an object of the present disclosure is to provide an injection molding method by which a molded article having a structure in which a core portion and a shell portion are formed of different resins can be obtained by injection molding a resin composition in a single step, a molding resin composition to be used in the method, and a molded article obtained by the method. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects. <1> An injection molding method in which a molding resin composition containing at least two resins having different apparent viscosities at 230°C and at least one compatibilizer is injection molded as a raw material. <2> The resins include at least two types of resins, namely, resin A and resin B, the difference in apparent viscosity between which is smallest at 230°C is 1000 Pa·s to 50000 Pa·s. <1> 1. The injection molding method according to claim 1. <3> The apparent viscosity (η A ) to the apparent viscosity (η B ) ratio (η B / η A ) is 0.01 to 0.4, <2> 1. The injection molding method according to claim 1. <4> The compatibilizer includes a first compatibilizer compatible with the resin A and a second compatibilizer compatible with the resin B. <2> or <3> 1. The injection molding method according to claim 1. <5> With respect to the total mass of the molding resin composition, the resin A is 40% by mass to 99% by mass, the resin B is 0.1% by mass to 40% by mass, the first compatibilizer is 0.1% by mass to 20% by mass, and the second compatibilizer is 0.1% by mass to 20% by mass. <4> 1. The injection molding method according to claim 1. <6> The first compatibilizer and the second compatibilizer are both organic compounds. <4> or <5> 1. The injection molding method according to claim 1. <7> The resin A is a resin containing a structural unit derived from an aromatic hydrocarbon, and the resin B is a resin containing a structural unit derived from an unsaturated aliphatic hydrocarbon. <4> ~ <6> 10. The injection molding method according to claim 9, wherein the molding step is carried out in a manner similar to that described above. <8> the first compatibilizer and the second compatibilizer are copolymers; the content of aromatic hydrocarbon-derived structural units in the first compatibilizer exceeds 50 mass% based on the total structural units of the first compatibilizer; the content of structural units derived from unsaturated aliphatic hydrocarbons in the second compatibilizer exceeds 50 mass% based on the total structural units of the second compatibilizer; The aforementioned <7> 1. The injection molding method according to claim 1. <9> at least two resins and at least one compatibilizer; The resin is a molding resin composition comprising at least two resins, Resin A and Resin B, which have the smallest apparent viscosity difference at 230°C between them, and the difference in apparent viscosity between the two resins is 1000 Pa·s to 50000 Pa·s. <10> The apparent viscosity (η A ) to the apparent viscosity (η B ) ratio (η B / η A ) is 0.01 to 0.4, <9> The molding resin composition according to claim 1. <11> The compatibilizer includes a first compatibilizer compatible with the resin A and a second compatibilizer compatible with the resin B. <9> or <10> The molding resin composition according to claim 1. <12> The first compatibilizer and the second compatibilizer are both organic compounds. <11> The molding resin composition according to claim 1. <13> The resin A is a resin containing a structural unit derived from an aromatic hydrocarbon, and the resin B is a resin containing a structural unit derived from an unsaturated aliphatic hydrocarbon. <11> or <12> The molding resin composition according to claim 1. <14> the first compatibilizer and the second compatibilizer are copolymers; the content of aromatic hydrocarbon-derived structural units in the first compatibilizer exceeds 50 mass% based on the total structural units of the first compatibilizer; the content of structural units derived from unsaturated aliphatic hydrocarbons in the second compatibilizer exceeds 50 mass% based on the total structural units of the second compatibilizer; The aforementioned <13> The molding resin composition according to claim 1. <15> a core portion including a cured product of resin A; a shell portion containing a cured product of resin B and covering at least a portion of the core portion; an intermediate portion located between the core portion and the shell portion and containing a cured product of at least one compatibilizer; A molded article, wherein the concentrations of the resin A and the resin B each have a distribution that changes continuously from the core portion to the shell portion. <16> The compatibilizer is at least two types. <15> The molded article according to claim 1. <17> The thickness of the shell portion is 300 μm or less. <15> or <16> The molded article according to claim 1. [Effects of the Invention]

[0008] According to the present disclosure, there are provided an injection molding method by which a molded article having a structure in which a core portion and a shell portion are formed of different resins can be obtained by injection molding a resin composition in a single step, a molding resin composition used in the method, and a molded article obtained by the method. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram showing the flow of a molten molding resin composition when the molding resin composition is injection molded. [Figure 2] FIG. 2 is a schematic diagram showing a cross section of a molded body. [Figure 3] FIG. 2 is an enlarged view of a cross section of a molded body. [Figure 4] 1 is a micrograph showing a cross section of a molded body before and after acetone vapor etching. [Figure 5] 1 is a micrograph showing a cross section of a molded body before and after acetone vapor etching. [Figure 6] 1 is a micrograph showing the structure of a molded body. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiment. In the following disclosure, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure. In the present disclosure, the term "process" includes not only a process that is independent of other processes, but also a process that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the present disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit of the numerical range may be replaced with the value shown in the examples. In the present disclosure, when a composition contains multiple substances corresponding to each component, the content of each component in the composition means the total content of the multiple substances present in the composition, unless otherwise specified.

[0011] ≪Injection molding method≫ The injection molding method of the present disclosure involves injection molding using as a raw material a molding resin composition containing at least two resins with different apparent viscosities at 230°C and at least one compatibilizer.

[0012] When a molding resin composition containing at least two resins with different apparent viscosities at 230°C and at least one compatibilizer is injection molded as a raw material, a molded article having a structure in which the core and shell are formed from different resins can be obtained by injection molding the resin composition once.

[0013] The action of the injection molding method of the present disclosure is not clear, but is presumed to be as follows. FIG. 1 shows a schematic diagram of a molding resin composition containing at least two resins with different apparent viscosities at 230°C melted and injection-molded. The molten molding resin composition flows through a mold 5 in the direction 1 of the flow of the molten molding resin composition. Based on the fountain flow principle, the molten low-viscosity resin 3 flows through the mold 5 more quickly than the molten high-viscosity resin 2, rapidly moving toward the surface of the mold 5 along the flow indicated by the dotted arrows in FIG. 1 . Meanwhile, the molten high-viscosity resin 2 flows through the mold 5 later than the molten low-viscosity resin 3, making it less likely to move toward the surface of the mold and remaining in the center of the mold. These resins then naturally cool and solidify within the mold, forming a molded article with a core and shell structure, as shown in FIG. 2 . Note that when the high-viscosity resin 2 has a higher viscosity and the difference in apparent viscosity between the high-viscosity resin 2 and the low-viscosity resin 3 is greater, a molded article with a core and shell structure is more likely to be formed. Furthermore, since the molding resin composition of the present disclosure contains at least one compatibilizer, the presence of the compatibilizer between the at least two resins allows the at least two resins to adhere to each other without phase separation, thereby forming a single molded body. That is, according to the injection molding method of the present disclosure, a molded article having a structure in which the core portion and the shell portion are formed of different resins can be obtained by injection molding a resin composition in a single operation. It should be noted that the present disclosure is in no way limited to the above-mentioned presumed mechanism.

[0014] <Molding resin composition> (resin) In the injection molding method of the present disclosure, the at least two resins having different apparent viscosities at 230°C preferably include resin A and resin B having the smallest apparent viscosity difference at 230°C of 1,000 Pa·s to 50,000 Pa·s, more preferably resin A and resin B having the smallest apparent viscosity difference at 230°C of 3,000 Pa·s to 50,000 Pa·s, from the viewpoint that a molded article having a structure in which the core and shell are formed of different resins can be easily obtained by injection molding a resin composition in a single process. Resins A and B preferably have the smallest apparent viscosity difference at 230°C of 1,000 Pa·s to 50,000 Pa·s, more preferably resin A and resin B having the smallest apparent viscosity difference at 230°C of 5,000 Pa·s to 50,000 Pa·s. The "two resins having the smallest apparent viscosity difference at 230°C" can respectively constitute the core or shell of the molded article by having the above-described apparent viscosity difference. In the injection molding method of the present disclosure, for example, when two types of resins with different apparent viscosities at 230°C are used, the "difference in apparent viscosity at 230°C" refers to the difference in apparent viscosity between the two types of resins, and the preferred difference in apparent viscosity is the same as above. The two types of resins can each constitute a core portion or a shell portion in the molded product. In the injection molding method of the present disclosure, the "at least two resins with different apparent viscosities at 230°C" does not include the "compatibilizer" described below.

[0015] In the injection molding method of the present disclosure, at least two types of resins having different apparent viscosities at 230°C are selected from the group consisting of resin A and resin B, which have the smallest difference in apparent viscosity at 230°C among the at least two types of resins, from the viewpoint that a molded article having a structure in which the core portion and the shell portion are formed of different resins can be easily obtained by injection molding a resin composition once. A ) to the apparent viscosity (η B ) ratio (η B / η A) is preferably 0.01 to 0.4, more preferably 0.01 to 0.3, and even more preferably 0.01 to 0.2. The "resin A and resin B having the smallest difference in apparent viscosity at 230°C among the at least two resins" can respectively constitute the core and shell of the molded product by having the above-mentioned apparent viscosity ratio. In the injection molding method of the present disclosure, when two resins having different apparent viscosities at 230°C are used, the ratio (η B / η A ) is the ratio of the two resins (η B / η A ) and the preferred ratio (η B / η A ) are the same as above, and the two resins can respectively constitute the core portion and the shell portion in the molded product.

[0016] In this disclosure, the apparent viscosity of a resin at 230°C is measured as follows. Specifically, the melt volume rate (MVR) is measured based on Appendix C of JIS K7210. Next, the flow value Q (cm 3 / s) is calculated using the MVR value, and the apparent viscosity (Pa·s) is calculated.

[0017] The type of the resin is not particularly limited, and may be a homopolymer or a copolymer. When the resin is a copolymer, the resin may be a random copolymer, a block copolymer, or a graft copolymer. The resin is preferably a thermoplastic resin, and may be a thermoplastic elastomer (TPE). Examples of the resin include acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene resin (PS resin), polyamide resin (PA resin, such as nylon 6T, nylon 6I, or nylon 9T), polybutylene terephthalate resin (PBT resin), polyethylene terephthalate resin (PET resin), polycarbonate resin (PC resin), polyphenylene sulfide resin (PPS resin), polyphenylene ether resin (PPE resin), polyimide resin (PI resin), polyether ether ketone resin (PEEK resin), liquid crystal polymer resin (LCP resin), high impact polystyrene (HIPS resin), and styrene. Examples of suitable resins include ethylene butadiene rubber (SBR resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), methyl methacrylate-butadiene rubber-styrene copolymer (MBS resin), acrylonitrile-styrene copolymer (AS resin), methyl methacrylate-styrene copolymer (MS resin), polypropylene resin (PP resin), polyethylene resin (PE resin), polymethyl methacrylate resin (PMMA resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), and polyoxymethylene resin (POM resin).

[0018] In the injection molding method of the present disclosure, the types of the at least two resins having different apparent viscosities at 230°C are not particularly limited. However, when using two types of resins, namely, resin A and resin B, which have the smallest difference in apparent viscosity at 230°C among the at least two resins, it is preferable that resin A is a resin containing structural units derived from aromatic hydrocarbons, and further, it is preferable that resin B is a resin containing structural units derived from unsaturated aliphatic hydrocarbons.

[0019] -Resin A- In Resin A of the present disclosure, the type of aromatic hydrocarbon-derived structural unit is not particularly limited, and examples include structural units derived from styrene, α-methylstyrene, (o-, m-, p-)methylstyrene, 1,3-dimethylstyrene, vinylnaphthalene, vinylanthracene, (o-, m-, p-)phthalic acid, bisphenol A, dihalogenated benzenes, xylenol, pyromellitic anhydride, hydroquinone, 4,4′-difluorobenzophenone, ethylene terephthalate, p-hydroxybenzoic acid, and 6-hydroxy-2-naphthoic acid.

[0020] Resin A of the present disclosure may be a homopolymer or a copolymer. When Resin A is a copolymer, Resin A may be a random copolymer, a block copolymer, or a graft copolymer.

[0021] Resin A of the present disclosure is preferably a thermoplastic resin, and may be a thermoplastic elastomer (TPE). Examples of Resin A include acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene resin (PS resin), polyamide resin (PA resin, such as nylon 6T, nylon 6I, or nylon 9T), polybutylene terephthalate resin (PBT resin), polyethylene terephthalate resin (PET resin), polycarbonate resin (PC resin), polyphenylene sulfide resin (PPS resin), polyphenylene ether resin (PPE resin), polyimide resin (PI resin), polyether ether, etc. Examples include polyetherketone resin (PEEK resin), liquid crystal polymer resin (LCP resin), high impact polystyrene (HIPS resin), styrene butadiene rubber (SBR resin), acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin), acrylonitrile-acrylic rubber-styrene copolymer (AAS resin), methyl methacrylate-butadiene rubber-styrene copolymer (MBS resin), acrylonitrile-styrene copolymer (AS resin), and methyl methacrylate-styrene copolymer (MS resin).

[0022] The apparent viscosity of Resin A of the present disclosure at 230°C is preferably 2000 Pa·s to 100,000 Pa·s, more preferably 5,000 Pa·s to 70,000 Pa·s, and even more preferably 10,000 Pa·s to 50,000 Pa·s, from the viewpoint of facilitating the production of a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition. Note that in the present disclosure, the apparent viscosity at 230°C is a value calculated based on JIS K7210 Appendix C and JIS K7210 Appendix JA.8 Results Expression Method (Formula No. JA.4), as described above.

[0023] The melt flow rate (MFR) of Resin A of the present disclosure is not particularly limited, but from the viewpoint of easily obtaining a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition, it is preferably 0.01 g / 10 min to 20 g / 10 min, and more preferably 0.01 g / 10 min to 10 g / 10 min. In the present disclosure, the melt flow rate (MFR) is a value measured in accordance with JIS K7210:1999 under conditions of 230°C and a load of 21.18 N.

[0024] The tensile strength of Resin A of the present disclosure is not particularly limited, but from the viewpoint of easily obtaining a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition, it is preferably 20 MPa to 300 MPa, and more preferably 30 MPa to 300 MPa. In the present disclosure, the tensile strength is a value measured in accordance with ISO 527.

[0025] The deflection temperature under load of Resin A of the present disclosure is not particularly limited, but from the viewpoint of easily obtaining a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition, it is preferably 80° C. to 150° C. at a bending stress of 1.8 MPa, and more preferably 90° C. to 120° C. In the present disclosure, the deflection temperature under load is a value measured in accordance with JIS K7191-1 using the flatwise method at a bending stress of 1.8 MPa.

[0026] -Resin B- In Resin B of the present disclosure, the type of structural unit derived from an unsaturated aliphatic hydrocarbon is not particularly limited, but examples include structural units derived from propylene, ethylene, methyl acrylate, methyl methacrylate, butadiene, and the like.

[0027] Resin B of the present disclosure may be a homopolymer or a copolymer. When Resin B is a copolymer, Resin B may be a random copolymer, a block copolymer, or a graft copolymer.

[0028] Resin B of the present disclosure is preferably a thermoplastic resin and may be a thermoplastic elastomer (TPE). Examples of Resin B include polypropylene resin (PP resin), polyethylene resin (PE resin), polymethyl methacrylate resin (PMMA resin), and acrylonitrile-butadiene-styrene copolymer (ABS resin).

[0029] The apparent viscosity of Resin B of the present disclosure at 230°C is preferably 100 Pa·s to 50,000 Pa·s, and more preferably 100 Pa·s to 10,000 Pa·s, from the viewpoint of facilitating the production of a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition. Note that in the present disclosure, the apparent viscosity at 230°C is a value calculated based on JIS K7210 Annex C and JIS K7210 Annex JA.8 Results Expression Method (Formula No. JA.4), as described above.

[0030] The melt flow rate (MFR) of Resin B of the present disclosure is not particularly limited, but is preferably 0.1 g / 10 min to 50 g / 10 min, and more preferably 0.5 g / 10 min to 50 g / 10 min, from the viewpoint of easily obtaining a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition. Note that, in the present disclosure, the melt flow rate (MFR) is a value measured at 230°C and a load of 21.18 N in accordance with JIS K7210:1999, as described above.

[0031] The tensile strength of Resin B of the present disclosure is not particularly limited, but from the viewpoint of easily obtaining a molded article having a structure in which the core and shell are formed of different resins by a single injection molding of the resin composition, it is preferably 1 MPa to 300 MPa, more preferably 1 MPa to 300 MPa. Note that in the present disclosure, the tensile strength is a value measured in accordance with ISO 527, as described above.

[0032] (Compatibilizer) The compatibilizer in the molding resin composition used in the injection molding method of the present disclosure preferably contains a first compatibilizer that is compatible with resin A and a second compatibilizer that is compatible with resin B. By containing the first compatibilizer that is compatible with resin A and the second compatibilizer that is compatible with resin B in the molding resin composition used in the injection molding method of the present disclosure, a molded article molded by the injection molding method has a structure that, from the surface side of the molded article toward the interior side of the molded article, successively includes a portion mainly containing resin B, a portion mainly containing resin B and the second compatibilizer, a portion mainly containing the second compatibilizer and the first compatibilizer, a portion mainly containing the first compatibilizer and resin A, and a portion mainly containing resin A. In this case, the portion of the portion mainly containing resin B that mainly contains resin B and the second compatibilizer is referred to as the "shell portion," the portion mainly containing the second compatibilizer and the first compatibilizer is referred to as the "intermediate portion," and the portion of the portion mainly containing the first compatibilizer and resin A that mainly contains resin A is referred to as the "core portion." That is, a single injection molding of the resin composition can produce a molded article having a structure in which the core portion and shell portion are formed of different resins. Note that the concentrations of the resin A, resin B, first compatibilizer, and second compatibilizer are all continuously distributed in the molded article, so although the terms "portion" (or "portion"), such as the shell portion, intermediate portion, or core portion, do not exist between the portions (portions). Note that a "portion mainly containing component X" means that the portion contains more than 50 mass% of component X.

[0033] For example, if the molding resin composition contains resin A, resin B, and a first compatibilizer but does not contain a second compatibilizer, the molded article molded by injection molding will have a structure consisting of, successively from the surface side of the molded article toward the interior side of the molded article, a portion mainly containing resin B, a portion mainly containing resin B and the first compatibilizer, a portion mainly containing the first compatibilizer, a portion mainly containing the first compatibilizer and resin A, and a portion mainly containing resin A. In this case, the portion extending from the portion mainly containing resin B to mainly containing resin B and the first compatibilizer is referred to as the "shell portion," the portion mainly containing the first compatibilizer is referred to as the "intermediate portion," and the portion extending from the portion mainly containing the first compatibilizer and resin A to mainly containing resin A is referred to as the "core portion." In other words, a molded article having a structure in which the core portion and shell portion are formed of different resins can be obtained by injection molding the resin composition once. The concentrations of the resin A, resin B, and first compatibilizer are all continuously distributed in the molded body, and therefore although they are expressed as "parts" (or "portions") such as the shell part, intermediate part, or core part, there are no interfaces between the parts (portions).

[0034] For example, when the molding resin composition contains three or more resins with different apparent viscosities at 230° C., it is preferable to contain four or more compatibilizers. For example, when the molding resin composition contains four or more resins with different apparent viscosities at 230° C., it is preferable to contain six or more compatibilizers. In other words, it is preferable to design the number of types of resins and the number of types of compatibilizers so that the compatibilizer is present between each cured product of each resin in a molded article obtained by injection molding the molding resin composition.

[0035] Although the type of the compatibilizer of the present disclosure is not particularly limited, it is preferable that all of the compatibilizers of the present disclosure are organic compounds. For example, it is preferable that both the first compatibilizer and the second compatibilizer of the present disclosure are organic compounds.

[0036] In the injection molding method of the present disclosure, the first compatibilizer and the second compatibilizer are copolymers, and the content of aromatic hydrocarbon-derived structural units in the first compatibilizer is preferably greater than 50% by mass relative to all structural units of the first compatibilizer, and the content of unsaturated aliphatic hydrocarbon-derived structural units in the second compatibilizer is preferably greater than 50% by mass relative to all structural units of the second compatibilizer.From the viewpoint of easily obtaining a molded article having a core and a shell formed of different resins by a single injection molding of a resin composition, it is more preferable that the content of aromatic hydrocarbon-derived structural units in the first compatibilizer is greater than 60% by mass relative to all structural units of the first compatibilizer, and the content of unsaturated aliphatic hydrocarbon-derived structural units in the second compatibilizer is greater than 60% by mass relative to all structural units of the second compatibilizer.

[0037] The description regarding the type of aromatic hydrocarbon-derived structural unit in the first compatibilizer is the same as the description regarding the type of aromatic hydrocarbon-derived structural unit in Resin A of the present disclosure. The description regarding the unsaturated aliphatic hydrocarbon-derived structural unit in the second compatibilizer is the same as the description regarding the type of unsaturated aliphatic hydrocarbon-derived structural unit in Resin B of the present disclosure.

[0038] When the first compatibilizer contains structural units derived from aromatic hydrocarbons and when the resin A of the present disclosure contains structural units derived from aromatic hydrocarbons, the first compatibilizer and resin A become more compatible with each other. Furthermore, when the content of structural units derived from aromatic hydrocarbons in the first compatibilizer is high relative to the total structural units of the first compatibilizer, the first compatibilizer and resin A become more compatible with each other. Similarly, when the second compatibilizer contains structural units derived from unsaturated aliphatic hydrocarbons and when the resin B of the present disclosure contains structural units derived from unsaturated aliphatic hydrocarbons, the second compatibilizer and resin B become more compatible with each other. Furthermore, when the content of structural units derived from unsaturated aliphatic hydrocarbons in the second compatibilizer is high relative to the total structural units of the second compatibilizer, the second compatibilizer and resin B become more compatible with each other.

[0039] The compatibilizer may be a reactive or non-reactive compatibilizer. A reactive compatibilizer is a polymer compound having a reactive group. Examples of the reactive group include a maleic anhydride group, a (meth)acrylic acid having a carboxylic acid, an epoxy (glycidyl) group, and an oxazoline group. Furthermore, a random copolymer, a block copolymer, or a graft copolymer may be used as a non-reactive compatibilizer to adjust compatibility. Examples of the non-reactive compatibilizer include a styrene-ethylene-styrene copolymer, a styrene-ethylenebutylene-styrene copolymer, and modified products thereof. More specifically, examples of the compatibilizer include hydrogenated styrene-based thermoplastic elastomers (SEBS). Examples of the hydrogenated styrene-based thermoplastic elastomers (SEBS) include polymers in which the double bonds of a block copolymer consisting of styrene and butadiene are hydrogenated.

[0040] (ratio) In the molding resin composition used in the injection molding method of the present disclosure, it is preferable that, relative to the total mass of the molding resin composition, the resin A is 40% to 99% by mass, the resin B is 0.1% to 40% by mass, the first compatibilizer is 0.1% to 20% by mass, and the second compatibilizer is 0.1% to 20% by mass. From the viewpoint of easily obtaining a molded article having a structure in which the core portion and the shell portion are formed of different resins by a single injection molding of the resin composition, it is even more preferable that, relative to the total mass of the molding resin composition, the resin A is 60% to 98% by mass, the resin B is 1% to 30% by mass, the first compatibilizer is 0.3% to 10% by mass, and the second compatibilizer is 0.3% to 10% by mass.

[0041] (Other ingredients) The molding resin composition used in the injection molding method of the present disclosure may contain other components within the scope of the present disclosure. The other components may be mixed in advance with the resin A, or may be mixed in advance with the resin B. For example, by mixing the resin B and the other components in advance, preparing a molding resin composition, and then injection-molding the molding resin composition, a molded article can be produced in which the concentration of the components is high in the shell portion but low in the core portion.

[0042] <Injection molding method> The injection molding method of the present disclosure is not particularly limited. The runner used in injection molding may be a cold runner system or a hot runner system. The gate used in injection molding may be a single gate or multiple gates.

[0043] The detailed conditions for injection molding are not particularly limited, but conditions such as molding temperature, nozzle temperature, mold temperature, weighing value, weighing speed, injection speed (IS), injection speed (VP), filling dwell pressure, filling dwell time, cooling time, and injection peak pressure can be appropriately set by a person skilled in the art.

[0044] ≪Resin composition for molding≫ The molding resin composition of the present disclosure includes at least two resins and at least one compatibilizer, and the resins include Resin A and Resin B, which have the smallest apparent viscosity difference at 230°C between the at least two resins, and have an apparent viscosity difference of 1000 Pa·s to 50000 Pa·s.

[0045] As described above, a molded article having a core and a shell is formed based on the fountain flow principle due to the difference in apparent viscosity between resin A and resin B. Furthermore, by including at least one compatibilizer, the at least two resins are bonded to each other without phase separation, thereby forming a single molded article. That is, according to the molding resin composition of the present disclosure, a molded article having a structure in which the core portion and the shell portion are formed of different resins can be obtained by a single injection molding of the resin composition.

[0046] (resin) In the molding resin composition of the present disclosure, the difference in apparent viscosity between Resin A and Resin B at 230°C is preferably 1000 Pa·s to 50000 Pa·s, more preferably 3000 Pa·s to 50000 Pa·s, and even more preferably 5000 Pa·s to 50000 Pa·s, from the viewpoint that a molded article having a structure in which the core portion and the shell portion are formed of different resins can be easily obtained by injection molding a single resin composition. Note that, in the molding resin composition of the present disclosure, when, for example, two resins with different apparent viscosities at 230°C are used, the "difference in apparent viscosity at 230°C" refers to the difference in apparent viscosity between the two resins, and the preferred difference in apparent viscosity is the same as above. In the molding resin composition of the present disclosure, the "at least two types of resins" does not include the "compatibilizer" described below.

[0047] In the molding resin composition of the present disclosure, Resin A and Resin B are selected from the viewpoint that a molded article having a structure in which the core portion and the shell portion are formed of different resins can be easily obtained by injection molding a single resin composition, and therefore Resin A has an apparent viscosity at 230°C (η A ) to the apparent viscosity (η B ) ratio (η B / η A ) is preferably 0.01 to 0.4, more preferably 0.01 to 0.3, and even more preferably 0.01 to 0.2. In the molding resin composition of the present disclosure, when two resins having different apparent viscosities at 230°C are used, for example, the "ratio (η B / η A ) is the ratio of the two resins (η B / η A ) and the preferred ratio (η B / η A ) is the same as above.

[0048] In the present disclosure, the apparent viscosity of a resin at 230°C is measured as described above by calculation based on the results shown in JIS K7210 Appendix C and JIS K7210 Appendix JA.8 (Formula No. JA.4).

[0049] The type of the resin is not particularly limited, and the description of the resin in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., is the same as the description of the resin in the injection molding method of the present disclosure.

[0050] The types of resin A and resin B in the molding resin composition of the present disclosure are not particularly limited, but it is preferable that resin A is a resin containing structural units derived from aromatic hydrocarbons, and further, it is preferable that resin B is a resin containing structural units derived from unsaturated aliphatic hydrocarbons.

[0051] -Resin A- The description of resin A in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., is the same as the description of resin A in the injection molding method of the present disclosure.

[0052] -Resin B- The description of resin B in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., is the same as the description of resin B in the injection molding method of the present disclosure.

[0053] (Compatibilizer) The description of the compatibilizer in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., is the same as the description of the compatibilizer in the injection molding method of the present disclosure.

[0054] (ratio) The explanation of the ratios in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., is the same as the explanation of the ratios in the injection molding method of the present disclosure.

[0055] (Other ingredients) The descriptions of the other components in the molding resin composition of the present disclosure, including definitions, examples, preferred embodiments, etc., are the same as the descriptions of the other components in the injection molding method of the present disclosure.

[0056] <Method for preparing molding resin composition> The molding resin composition of the present disclosure can be prepared by any known method without any particular limitation. For example, the molding resin composition can be prepared by premixing various raw materials using a mixing device such as a mixer, a V-blender, or a tumbler mixer, and then melt-kneading the mixture. The melt-kneading device is also not particularly limited, and examples thereof include a Banbury mixer, a kneader, a roll, a single-screw extruder, a special single-screw extruder, and a twin-screw extruder.

[0057] The molding resin composition of the present disclosure may be molded into a known form by a known method. For example, the molding resin composition of the present disclosure may be molded into pellets using a pelletizer, or may be molded into flakes using a known device, or may be molded into a pulverized product thereof.

[0058] When the molding resin composition of the present disclosure, or a cured product of the molding resin composition formed into, for example, pellets, is injection molded, a molded article having a core-shell structure can be produced due to the difference in viscosity between Resin A and Resin B.

[0059] <Molded body> The molded article of the present disclosure has a core portion containing a cured product of resin A, a shell portion containing a cured product of resin B and covering at least a portion of the core portion, and an intermediate portion located between the core portion and the shell portion and containing a cured product of at least one type of compatibilizer, and the concentrations of resin A and resin B each have a distribution that changes continuously from the core portion to the shell portion.

[0060] Figure 3 is an enlarged view of the area enclosed by the dotted square frame in the cross-sectional view of Figure 2. As shown in Figure 3, the molded body of the present disclosure has a shell portion 4, an intermediate portion 7, and a core portion 6 that change in a gradational manner from the surface 8 side of the molded body toward the interior side of the molded body.

[0061] In the molded article of the present disclosure, the core portion containing a cured product of resin A may contain a cured product of resin B, i.e., resin B may be finely dispersed in the core portion. Furthermore, in the molded article of the present disclosure, the shell portion containing a cured product of resin B may contain a cured product of resin A, i.e., resin A may be finely dispersed in the shell portion. In other words, the molded article of the present disclosure may have a gradational transition from the shell portion to the intermediate portion and then to the core portion.

[0062] In the molded article of the present disclosure, it is preferable that there are at least two types of compatibilizers.

[0063] In the molded article of the present disclosure, the thickness of the shell portion is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. Conventionally, when a molded article having a core portion and a shell portion is produced by, for example, two-color molding, the thickness of the shell portion ends up being 1 mm or more. Therefore, compared to conventional molded articles having a core portion and a shell portion, the molded article of the present disclosure has a very thin shell portion.

[0064] In the molded article of the present disclosure, the shell portion may cover at least a portion of the core portion, or may cover the entire core portion.

[0065] The cross-sectional structure of the molded article of the present disclosure can be identified, for example, by cutting a thin section from the molded article of the present disclosure with a microtome and observing the thin section with a microscope.

[0066] In the molded article of the present disclosure, the concentrations of the resin A and the resin B each have a distribution that changes continuously from the core portion to the shell portion. More specifically, in the molded article, the concentration of the resin A has a distribution that decreases continuously from the core portion to the shell portion, and the concentration of the resin B has a distribution that increases continuously from the core portion to the shell portion.

[0067] The resin concentrations in the molded article of the present disclosure can be determined, for example, by cutting a thin section from the molded article of the present disclosure using a microtome and analyzing the thin section using infrared spectroscopy (IR). Alternatively, the fact that the concentrations of Resin A and Resin B each have a distribution that changes continuously from the core to the shell can be confirmed, for example, by cutting a thin section from the molded article of the present disclosure and analyzing the thin section using a transmission electron microscope (TEM). [Example]

[0068] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure. Unless otherwise specified, "parts" are based on mass. "%" is also based on mass.

[0069] <Examples 1 to 3 and Comparative Examples 1 to 5> (Preparation of test samples) For Examples 1 to 3 and Comparative Examples 1 to 5, resin compositions for injection molding were prepared using the blending ratios of the components shown in Table 1 below. Specifically, the components were kneaded using a kneading extruder under the following conditions: nozzle temperature 230°C to 245°C, intermediate temperature (kneading zone temperature) 230°C to 245°C, hopper temperature 160°C to 180°C, screw rotation speed 60 rpm, and feed rate 3.0 g / min to 4.0 g / min to prepare the resin compositions for injection molding. Furthermore, the resin compositions for injection molding were dried at 80°C for 12 hours to produce pellets of the resin composition for injection molding.

[0070] [Table 1]

[0071] Details of the compounds and abbreviations listed in Table 1 are shown below. ABS(a): Resin A of the present disclosure Acrylonitrile-butadiene-styrene copolymer Apparent viscosity 2500 Pa·s MFR (230℃, 21.18N load) 3g / 10min Tensile strength 51MPa Deflection temperature under load (1.8 MPa) 95℃ ABS(b): Resin A of the present disclosure Acrylonitrile-butadiene-styrene copolymer Apparent viscosity 10730 Pa·s MFR (230℃, 21.18N load) 0.7g / 10min Tensile strength 50MPa Deflection temperature under load (1.8 MPa) 101°C PP(a): Resin B of the present disclosure Polypropylene resin Apparent viscosity 2500 Pa·s MFR (230℃, 21.18N load) 3g / 10min Tensile strength 37MPa homopolymer PP(b): Resin B of the present disclosure Polypropylene resin Apparent viscosity 840 Pa·s MFR (230℃, 21.18N load) 9g / 10min Tensile strength 29MPa Copolymer Compatibilizer (a): the first compatibilizer of the present disclosure Hydrogenated styrenic thermoplastic elastomer (SEBS) Styrene / ethylene / butylene mass ratio 67 / 33 Compatibilizer (b): the second compatibilizer of the present disclosure Hydrogenated styrenic thermoplastic elastomer (SEBS) Styrene / ethylene / butylene mass ratio 20 / 80 Apparent viscosity difference: The difference in apparent viscosity between Resin A and Resin B at 230°C. η B / η A : Apparent viscosity of resin A at 230 ° C (η A ) to the apparent viscosity (η B ) ratio. -: The substance is not blended into the resin composition for injection molding.

[0072] The pellet-shaped resin composition for injection molding was injection molded under the following conditions: molding temperature 250°C, nozzle temperature 250°C, mold temperature 70°C, metering value 13.5 mm, metering speed 2 mm, injection speed (IS) 30 mm / s, injection speed (VP) 5.2 mm, filling dwell pressure 90%, filling dwell time 15 seconds, cooling time 15 seconds, and injection peak pressure 111% to 118%.

[0073] By the injection molding, strip-shaped test samples each having a length of 50 mm, a width of 5 mm, and a thickness of 2 mm were prepared.

[0074] (chloroform immersion) Test pieces measuring 15 mm in length, 5 mm in width, and 2 mm in thickness were cut from each strip of test sample. Each test piece was immersed in a chloroform solution containing 99% or more by mass at 25±5°C for 120 hours. When the test samples of Comparative Examples 1 and 2 were immersed in chloroform, the ABS dissolved, causing the chloroform solution to change from transparent to black. In contrast, in Comparative Example 5 and Example 3, the ABS did not dissolve, and the chloroform solution remained transparent. This is because ABS is easily soluble in chloroform, while PP is poorly soluble in chloroform. That is, when the apparent viscosities of Resin A and Resin B at 230°C are different, as in Comparative Example 5 and Example 3, a molded product with a core-shell structure was obtained, with PP predominantly present in the shell and ABS predominantly present in the core.

[0075] (Cross-section acetone vapor etching) After embedding in epoxy resin and polishing the cross sections, the longitudinal center of each rectangular test sample was observed at 50x or 200x magnification using ring or incident light. After observation, the test sample was placed in a container filled with acetone, with the cross section facing the acetone. Care was taken to avoid direct contact of the acetone with the test sample. After etching with acetone vapor for 60 seconds at 25±5°C, the cross sections were again observed at 50x or 200x magnification using ring or incident light. A microscope was used for cross-sectional observation. The cross-sectional observation results are shown in Figures 4 and 5. In Figures 4 and 5, the 200x magnification results are enlarged versions of the area enclosed by the dotted square in the upper right corner of each cross section observed at 50x magnification.

[0076] When the cross sections of the test samples before acetone vapor etching were observed, a 100 μm thick shell portion (a portion mainly containing PP) was confirmed on the surface side of the test samples (i.e., the outer side of the cross section of the test samples) in Examples 1 to 3 and Comparative Examples 3 to 5. When the cross sections of the test samples after acetone vapor etching were observed, differences in color intensity between the shell and core portions were confirmed in Comparative Examples 1, 3, 4, and 5, which did not contain a compatibilizer, and the boundary between the shell and core portions was clear. This is because ABS is not acetone-resistant, so the core portion (the portion mainly containing ABS) was etched by acetone vapor, and cracks in the ABS appeared white. Furthermore, because PP is acetone-resistant, the shell portion (the portion mainly containing PP) was not easily etched by acetone vapor and remained black. On the other hand, in Comparative Example 2 and Examples 1 to 3, which contained a compatibilizer, the difference in color intensity between the shell and core was unclear, and the boundary between the shell and core was unclear. This is because the compatibilizer caused PP to mix with the core (the portion mainly containing ABS), improving the acetone resistance of the core. Furthermore, in Comparative Examples 1 and 2 in particular, an incomplete core-shell structure was formed in which the thickness of the shell portion (the portion mainly containing PP) was too small, whereas a core-shell structure with a thick shell portion was formed in Comparative Example 5 and Example 3 in particular. That is, when the apparent viscosities at 230°C of Resin A and Resin B differed greatly, a molded article with a core-shell structure was obtained in which PP was mainly present in the shell portion and ABS was mainly present in the core portion.

[0077] From the above, in Examples 1 to 3, it was possible to provide an injection molding method that can obtain a molded article having a structure in which the core portion and the shell portion are formed of different resins by injection molding a resin composition in a single operation, a molding resin composition used in the method, and a molded article obtained by the method. In Examples 1 to 3, two types of compatibilizers (compatibilizer (a) and compatibilizer (b)) were used. The styrene / ethylene-butylene ratio (mass ratio) of compatibilizer (a) was 67 / 33, which means that the styrene ratio was high, i.e., the ratio of structural units derived from aromatic hydrocarbons was high. Therefore, compatibilizer (a) was easily compatible with ABS, which has structural units derived from aromatic hydrocarbons (styrene). On the other hand, the styrene / ethylene-butylene ratio (mass ratio) of compatibilizer (b) was 20 / 80, which means that the ethylene-butylene ratio was high, i.e., the ratio of structural units derived from unsaturated aliphatic hydrocarbons was high. Therefore, compatibilizer (b) was easily compatible with PP, which has structural units derived from unsaturated aliphatic hydrocarbons (propylene). That is, the structures of the molded bodies produced in Examples 1 to 3 were, from the surface side of the molded body toward the interior side of the molded body, successively consisting of a portion mainly containing PP, a portion mainly containing PP and compatibilizer (b), a portion mainly containing compatibilizer (b) and compatibilizer (a), a portion mainly containing compatibilizer (a) and ABS, and a portion mainly containing ABS.

[0078] (Transmission electron microscope (TEM) analysis of molded body) A thin section was cut from a test piece 10 mm long, 5 mm wide, and 2 mm thick prepared under the conditions of Example 3. A transmission electron microscope (TEM) was used to observe the dispersion distribution of Resin A and Resin B in the test piece from the core portion toward the shell portion. Observation was performed at a total of four locations (the outermost surface of the test piece, and depths of approximately 50 μm, approximately 100 μm, and approximately 150 μm from the outermost surface).

[0079] The observation results are shown in Figure 6. The length of each scale bar shown in the lower right of the figure is 2.0 μm. The phase believed to be an aliphatic hydrocarbon-based material was amorphous, and its size tended to increase with increasing depth from the outermost surface. Meanwhile, the total amount of aliphatic hydrocarbon-based material in the entire observation field tended to increase from the inner side toward the outermost surface. A layer-separated structure (i.e., a core-shell structure) was observed within the phase, with two types of dispersed island phases: amorphous island phases with lamellar structures and circular island phases. Furthermore, a region believed to contain a higher amount of compatibilizer than the inner and outermost surfaces was observed between the inner and outermost surfaces. That is, in the test sample (i.e., the molded article of the present disclosure), resin A and resin B each had a distribution that changed continuously from the core portion (inner side) to the shell portion (outermost surface side). Furthermore, the test sample had an intermediate portion located between the core portion and the shell portion and containing a relatively large amount of compatibilizer, and it was confirmed that the molded article was as shown in Figure 3. Therefore, it was confirmed that resin A was compatible with the first compatibilizer, and resin B was compatible with the second compatibilizer.

[0080] <Examples 3 to 5 and Comparative Examples 6 and 7> (Preparation of test samples) In addition to the above-mentioned Example 3, in Examples 4 and 5, resin compositions for injection molding were prepared using the compounding ratios of the components shown in Table 2 below in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 5, and pellets of the resin compositions for injection molding were then produced. In Comparative Examples 6 and 7, resin compositions for injection molding were prepared using the components shown in Table 2 below. Details of the compounds and abbreviations listed in Table 2 are the same as those in Table 1.

[0081] For Examples 3 to 5, the pellets were injection molded from the pellet-shaped resin compositions for injection molding under the conditions shown in Table 2. For Comparative Examples 6 and 7, the resin compositions for injection molding were injection molded under the conditions shown in Table 2. By the above operations, ISO multipurpose test pieces (Test Samples 1 to 6) were each produced.

[0082] [Table 2]

[0083] (Polishing of test specimen) Test samples 1 to 6 were used to further prepare "unpolished test specimens" and "polished test specimens." Specifically, the "unpolished test specimens" were the ends (excluding the gate side) of the Charpy impact test specimens taken out of the test samples between the gauge lines. The cut surfaces were sealed with PP (b) to prevent chloroform from adhering to and dissolving from the cut surfaces. On the other hand, the "polished test specimens" were prepared by polishing one side of the test sample by 1 mm (grain size #120) to remove the shell portion. The cut surfaces of the polished test specimens were not sealed.

[0084] (chloroform immersion) 10 ml of chloroform solution of 99% by mass or more was placed in a screw tube bottle (50 ml capacity), and the unpolished or polished test specimens were immersed with the cut surface facing upward at 25 ± 5°C for 24 hours. The condition of each test solution (chloroform solution) and each test specimen was observed at regular intervals, and the results are shown in Table 3.

[0085] [Table 3]

[0086] In Table 3, the condition of each test solution (chloroform solution) and each test piece was evaluated on a 5-point scale (5, 4, 3, 2, or 0 points) according to the following criteria. 5 points: The test solution was highly transparent and no black turbidity was observed. 4 points: The test solution was highly transparent, but a slight black turbidity was observed. 3 points: The test solution was not very transparent and the entire solution was black and cloudy. The shape of the test piece was maintained. 2 points: The test solution was dark and turbid, and dissolution was observed to the extent that the shape of the test specimen was partially distorted (swelling was not included). 0 points: The test solution was dark and turbid, and the shape of the test piece was not maintained (swelling is not included).

[0087] In Table 3, "Difference" indicates the difference between the total score for the unpolished test piece and the total score for the polished test piece. "-" indicates that the difference was not calculated.

[0088] This chloroform immersion test can confirm whether a molded product has a core-shell structure by confirming its chloroform resistance. For example, in this example, if a molded product has a layer-separated structure (i.e., a core-shell structure), the core exists on the outermost surface (i.e., the outermost surface is primarily PP, which is less soluble in chloroform), and therefore the molded product has chloroform resistance. However, if the surface of a molded product with a layer-separated structure is polished and the outermost surface (i.e., PP) is removed, the ABS, which is more soluble in chloroform, is exposed, reducing the molded product's chloroform resistance. Therefore, a molded product with a large difference between the unpolished (i.e., "unpolished test piece") and polished (i.e., "polished test piece") was determined to have a layer-separated structure. For Test Sample 6 (a molded product consisting of ABS alone), the difference between the unpolished and polished test pieces was 4 points. This was used as the score for the change in chloroform resistance due to changes in plate thickness and volume. If the difference in the molded product was greater than 4 points, the molded product was determined to have a layer-separated structure (i.e., a core-shell structure).

[0089] That is, in test samples 1 to 4, molded bodies having a better core-shell structure were obtained. [Explanation of symbols]

[0090] 1. Flow direction of molten molding resin composition 2. Molten high-viscosity resin 3. Molten low-viscosity resin 4 Shell part 5. Mold 6 Core 7 Middle section 8. Surface of the molded body

Claims

1. a core portion including a cured product of resin A; a shell portion containing a cured product of resin B and covering at least a portion of the core portion; an intermediate portion located between the core portion and the shell portion and containing a cured product of at least one compatibilizer; the ratio (η B / η A ) of the apparent viscosity (η B ) of the resin B at 230° C. to the apparent viscosity (η A ) of the resin A at 230° C. is 0.01 to 0.4; A molded article, wherein the concentrations of the resin A and the resin B each have a distribution that changes continuously from the core portion toward the shell portion.

2. The molded article according to claim 1 , wherein the compatibilizer is at least two types.

3. The molded article according to claim 1 or 2, wherein the shell portion has a thickness of 300 μm or less.

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