Method for producing resin composition

Abstract

A method for producing a resin composition according to the present invention comprises: a management step for performing management by recovering non-standard products generated in a manufacturing process of a thermoplastic resin and classifying the products according to grades based on a design factor A; a regeneration step for obtaining regenerated products by collectively regenerating the non-standard products classified under each grade; and a compound step for screening the regenerated products obtained in the regeneration step, on the basis of a design factor B for compounded products, and carrying out compounding on the resulting products.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a resin composition. This application claims priority based on Japanese Patent Application No. 2022-081294 filed in Japan on May 18, 2022, Japanese Patent Application No. 2022-145244 filed in Japan on September 13, 2022, Japanese Patent Application No. 2022-188169 filed in Japan on November 25, 2022, and Japanese Patent Application No. 2022-188170 filed in Japan on November 25, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, various environmental measures have been implemented to realize a sustainable society. Because resins such as plastics emit carbon dioxide when burned, it is expected that the move toward carbon neutrality will further increase societal demand for avoiding the combustion of resins. In particular, polyamide 66 (PA66) emits relatively high amounts of greenhouse gases (GHG) per kilogram of resin, making it urgent to respond to the circular economy (CE). As a result, while progress is being made in replacing resins with bio-derived resources and other materials, progress is being made in recycling parts that cannot be replaced to avoid combustion.

[0003] For example, Patent Document 1 discloses a method for recycling plastic waste materials containing a plastic mixture made up of multiple types of plastics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-130885 Summary of the Invention [Problem to be solved by the invention]

[0005] During the production of resins, a certain amount of non-standard products are discarded, but physical properties such as molecular weight and moisture content vary from lot to lot, so analysis is required for each lot. Furthermore, in order to maintain consistent quality in the final product, it is difficult to increase the blending ratio of these non-standard products to virgin products.

[0006] The present invention has been made in view of the above circumstances, and provides a method for producing a resin composition having improved properties by utilizing an off-standard product. [Means for solving the problem]

[0007] That is, the present invention includes the following aspects. (1) A management process for collecting non-standard products generated in the thermoplastic resin manufacturing process, classifying them into grades based on design factor A, and managing them. a regeneration step of regenerating the non-standard products by grade to obtain regenerated products; a compounding step of selecting the recycled product obtained in the recycling step based on a design factor B of the compound product and compounding the selected recycled product; A method for producing a resin composition, comprising: (2) The method for producing a resin composition according to (1), wherein the non-standard product is converted into a masterbatch in the recycling step. (3) The method for producing a resin composition according to (1), wherein a colorant is added to the non-standard product in the recycling step. (4) The method for producing a resin composition according to any one of (1) to (3) above, wherein the thermoplastic resin is in the form of pellets. (5) The method for producing a resin composition according to any one of (1) to (4), wherein the design factor A is one or more selected from the group consisting of copper concentration, type and content of additives, amount of foreign matter mixed in, molecular weight, water content, color tone, and type and content ratio of terminal groups. (6) The method for producing a resin composition according to any one of (1) to (5), wherein the recycled product and a virgin product are mixed in the compounding step. (7) The method for producing a resin composition according to (6), wherein in the compounding step, the content of the recycled material is 0.1 mass% or more relative to the total mass of the resin composition. (8) A method for producing a resin composition according to (6) or (7), wherein the recycled product and the virgin product are in the form of pellets, and the ratio of the average diameter of the recycled product pellets to the average diameter of the virgin product pellets is 0.7 or more and 1.3 or less. (9) The method for producing a resin composition according to any one of (1) to (8) above, wherein the thermoplastic resin comprises a polyamide resin. (10) The method for producing a resin composition according to (9) above, wherein the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 6I, polyamide 66 / 6, and polyamide 66 / 6I. (11) The method for producing a resin composition according to any one of (1) to (10), wherein the non-standard product is at least one selected from the group consisting of intermediate products produced during production changeover due to a change in the type of thermoplastic resin, products containing black spots, products containing foreign matter, products not conforming to the pellet size standard, waste materials during packaging, and products not conforming to the physical properties standard. (12) The regeneration step a melt-kneading step of melt-kneading the non-standard product to obtain a molten material; a pelletizing step of pelletizing the molten material after the melt-kneading step to obtain recycled pellets; A method for producing the resin composition according to (1) or (3) above, comprising: (13) The method for producing a resin composition according to (12), further comprising a foreign matter removal step of passing the molten material through a metal mesh to remove foreign matter after the melt-kneading step and before the pelletizing step. (14) The regeneration step a melt-kneading step of melt-kneading the non-standard product to obtain a molten material; a pelletizing step of pelletizing the molten material after the melt-kneading step to obtain recycled pellets; Including, The method for producing a resin composition according to (2) above, wherein an additive containing at least one selected from the group consisting of a heat stabilizer, an antioxidant, a filler, a flame retardant, and a colorant is added in the melt-kneading step. (15) The method for producing a resin composition according to (14) above, wherein the mass ratio of the additive to the non-standard product is 10:90 to 90:10. (16) The method for producing a resin composition according to (3) above, wherein the mass ratio of the colorant to the non-standard product is 0.1:99.9 to 10:90. [Effects of the Invention]

[0008] According to the manufacturing method of the above aspect, it is possible to provide a method for manufacturing a resin composition having improved properties by utilizing a non-standard product. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a flow chart showing each step of the manufacturing method of the present embodiment. [Figure 2] FIG. 10 is a flow chart showing each step of a manufacturing method according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0011] In this specification, the term "polyamide" refers to a polymer having an amide (-NHCO-) ​​group in the main chain.

[0012] <Method for producing resin composition> The method for producing the resin composition of this embodiment (hereinafter sometimes simply referred to as "the production method of this embodiment") includes the following steps. A control process to collect non-standard products generated in the thermoplastic resin manufacturing process, classify them into grades based on design factor A, and manage them; A regeneration step of regenerating the non-standard products by grade to obtain regenerated products; and A compounding step in which the recycled products obtained in the above recycling step are selected based on the design factor B of the compound product and compounded.

[0013] The manufacturing method of this embodiment has the above-described configuration, and thus can improve the properties of the resin composition by utilizing non-standard products.

[0014] 1 is a flow chart showing each step of the manufacturing method of this embodiment. Each step of the manufacturing method of this embodiment will be described in detail below with reference to FIG.

[0015] <Management process> In the control process, non-standard products generated in the thermoplastic resin manufacturing process are collected and classified into grades based on design factor A for management. Here, "non-standard products" refers to thermoplastic resins or their intermediates that are rejected because they do not meet the conditions regarding shape, size, physical properties, etc. that are appropriately determined based on the use of the thermoplastic resin, and cannot be handled as virgin products.

[0016] The shape of the thermoplastic resin to be produced is not particularly limited, but is preferably in the form of pellets (cylindrical or non-cylindrical such as prismatic).

[0017] As shown in Figure 1, non-standard products generated in the thermoplastic resin manufacturing process are collected in the control process. The non-standard products collected in this management process are preferably at least one type selected from the group consisting of intermediate products produced during production changeover due to a change in the type of thermoplastic resin, products containing black spots, products containing foreign matter, pellet size non-standard products, packaging scraps, and physical property non-standard products.

[0018] The black speck-contaminated products and foreign matter-contaminated products may be identified using a black speck sorter (see FIG. 1) or a foreign matter sorter. When a colorant is used in the recycling process, it is preferable to exclude black speck-contaminated products and foreign matter-contaminated products from the collection targets for the recycling process. By excluding black speck-contaminated products and foreign matter-contaminated products and recycling off-specification products, it is possible to easily adjust the color of the resin composition. Note that black speck-contaminated products and foreign matter can also be removed by filtering in the recycling process described below. Examples of the black spots in the black spot-contaminated products include carbonized resins formed by heating the resin and adhering to the production line. Examples of the foreign matter in the contaminated product include crosslinked resins and gelled resins.

[0019] The pellet size out-of-standard is determined by a sieving machine.

[0020] The waste material during packaging is left as excess material when packaging is performed by a packaging machine, or is generated when the line is washed together when the type of thermoplastic resin is changed.

[0021] The non-standard physical properties are determined by an inspection machine. The physical properties that can be determined by the inspection machine include moisture content, molecular weight, color tone, and the like. The water content can be measured, for example, using a Karl Fischer moisture meter (manufactured by Mitsubishi Chemical Corporation, CA-200 / VA-200). The molecular weight can be measured, for example, using a gel permeation graph (GPC) (HLC-8020, manufactured by Tosoh Corporation, hexafluoroisopropanol solvent, converted into a PMMA (polymethyl methacrylate) standard sample (manufactured by Polymer Laboratory Co., Ltd.)). The color tone can be measured, for example, by a color difference meter (ZE-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0022] The recovered non-standard products are stored after being classified into grades based on the design factor A. Specifically, the design factor A of each recovered non-standard product is measured, and the products are classified according to the measured value and stored. Examples of design factors A include copper concentration, type and content of additives, amount of foreign matter mixed in, molecular weight, moisture content, color tone, type and content ratio of terminal groups, etc. These design factors A are used alone or in combination of two or more to classify the grade of non-standard products.

[0023] For example, in FIG. 1 , if "copper concentration" and "molecular weight" are selected as design factors A, the "copper concentration" and "molecular weight" of each recovered non-standard product are measured, and the recovered non-standard products are classified and consolidated according to the measured values. Specifically, non-standard products with a copper concentration of 0 and a small molecular weight are classified as Grade 1 and managed together. Non-standard products with a copper concentration of 0 and a large molecular weight are classified as Grade 2 and managed together. Non-standard products with a medium copper concentration and a small molecular weight are classified as Grade 3 and managed together. Non-standard products with a medium copper concentration and a large molecular weight are classified as Grade 4 and managed together. Non-standard products with a high copper concentration and a small molecular weight are classified as Grade 5 and managed together. Non-standard products with a medium copper concentration and a large molecular weight are classified as Grade 6 and managed together. Here, the "medium" and "high" copper concentrations and the "low" and "high" molecular weights are appropriately determined based on the application of the resin composition.

[0024] The copper concentration can be measured, for example, by X-ray fluorescence. The amount of foreign matter mixed in can be adjusted, for example, by whether or not black spot sorting equipment is used. The molecular weight, water content, and color can be measured as described above. The type and content of the terminal group can be measured by, for example, NMR.

[0025] <Regeneration process> In the recycling process, the non-standard products are recycled by grade to obtain recycled products. For example, in FIG. 1, out-of-standard size products, products containing black spots, products containing foreign matter, packaging scraps, and / or products with non-standard physical properties that are classified and managed as Grade 1 are mixed and recycled. Out-of-standard size products, products containing black spots, products containing foreign matter, packaging scraps, and / or products with non-standard physical properties that are classified and managed as Grade 2 are mixed and recycled. Out-of-standard size products, products containing black spots, products containing foreign matter, packaging scraps, and / or products with non-standard physical properties that are classified and managed as Grade 3 are mixed and recycled. Out-of-standard size products, products containing black spots, products containing foreign matter, packaging scraps, and / or products with non-standard physical properties that are classified and managed as Grade 4 are mixed and recycled. Out-of-standard size products, products containing black spots, products containing foreign matter, packaging scraps, and / or products with non-standard physical properties that are classified and managed as Grade 5 are mixed and recycled. It is recycled by mixing products that are classified as Grade 6 and are managed as being out of size specification, products containing black spots, products containing foreign matter, packaging scraps, and / or products that are out of physical property specification. By grouping the off-spec products classified into grades based on the setting factor A and storing them together as recycled products by grade, it becomes easier to understand the physical properties of the recycled products, and when compounding the recycled products alone in the compounding process described below or mixing the recycled products with virgin products, it becomes easier to design products with desired physical properties. Here, virgin products refer to compounds or compositions prepared from raw material monomers and do not include recycled products.

[0026] During the recycling process, colorants may be added to the off-spec product. In addition, non-standard products classified into the same grade can be collectively recycled as a masterbatch to produce recycled products. In this case, it is preferable to add at least one additive selected from the group consisting of a heat stabilizer, an antioxidant, a filler, a flame retardant, and a colorant in the recycling process.

[0027] Examples of the heat stabilizer include copper compounds, metal halides, phosphorus-based heat stabilizers, and amine-based heat stabilizers. The copper compound and metal halide may be a copper halide. The metal halide may be a halide of an alkali metal or alkaline earth metal. Among these, the heat stabilizer is preferably a copper halide.

[0028] Examples of the antioxidant include phenol-based antioxidants such as hindered phenol compounds, and phosphorus-based antioxidants, with hindered phenol compounds being preferred.

[0029] Examples of the filler include inorganic fibers such as glass fibers and carbon fibers; clay minerals, glass flakes, etc., with glass fibers being preferred.

[0030] Examples of the flame retardant include phosphorus-based flame retardants, halogen-based flame retardants, etc. The flame retardant may be a low-molecular-weight or high-molecular-weight substance as long as it can impart flame retardancy to the resin composition.

[0031] Examples of colorants include pigments and dyes, which may be organic or inorganic. Examples of the colorant color include achromatic colors such as black and white, chromatic colors such as red, blue, yellow, green, orange, brown, violet, and purple, and glossy colors such as metallic and pearlescent colors.

[0032] The mass ratio of additives added to form a masterbatch in the recycling process to the non-standard grade resin based on design factor A is preferably 10:90 to 90:10. If the proportion of additives relative to the total mass of the non-standard resin and additives is less than 10 mass%, the amount of recycled product (masterbatch) required to supply the required amount of additives to the resin composition increases, resulting in poor productivity. If the proportion of additives exceeds 90 mass%, masterbatch formation is difficult. The content of additives relative to the total mass of the recycled product is preferably 10 mass% or more and 90 mass% or less.

[0033] Although the process of collectively forming a masterbatch of non-standard products classified into the same grade is not particularly limited, it is preferable to melt-knead the non-standard thermoplastic resin after adding additives. By forming the non-standard products into a masterbatch in the recycling process and then compounding them, it is possible to achieve at least one of the following, depending on the type of additive and processing conditions: improving the properties of the resin composition, improving the homogeneity of the additive in the resin composition, and suppressing deterioration of the non-standard products in the recycling process.

[0034] For example, when a thermal stabilizer is added as an additive, deterioration of the recycled product can be suppressed, thereby suppressing deterioration of the resin composition. When an antioxidant is added as an additive, color change in the recycled product can be suppressed, thereby suppressing color change in the resin composition. In other cases, by melting and kneading the non-standard product after addition and performing a compounding process, it is possible to improve homogeneity (suppressing unopened fibers in the case of fibrous fillers).

[0035] The mass ratio of the colorant added in the recycling process to the non-standard grade resin based on design factor A is preferably 0.1:99.9 to 10:90. If the proportion of colorant relative to the total mass of the non-standard resin and colorant is less than 0.1 mass%, the resin composition is not easily colored. If the proportion of colorant exceeds 10 mass%, the amount of colorant is likely to be excessive compared to the amount required for the resin composition. The content of colorant relative to the total mass of the recycled product is preferably 0.1 mass% to 10 mass%.

[0036] In the process of recycling non-standard products into grades based on the design factor A, the process of adding a colorant to the non-standard products is not particularly limited, but it is preferable to melt-knead the non-standard thermoplastic resin after adding the colorant. By adding a colorant to the non-standard product and carrying out the recycling process, and then compounding, it is possible to easily adjust the resin composition to the desired color.

[0037] Specifically, the regeneration step preferably includes the following steps: A melt-kneading step of melt-kneading the non-standard product to obtain a molten product; and A pelletizing step in which the molten material after the melt-kneading step is pelletized to obtain recycled pellets.

[0038] [Melting and kneading process] In the melt-kneading step, the non-standard product is melt-kneaded. Non-standard products of the same grade are subjected to melt-kneading together. At this time, it is preferable to mix products containing black spots and foreign matter with non-standard products that do not contain black spots or foreign matter to form a melt. This allows the content of black spots and foreign matter to be diluted. Furthermore, since the content of black spots and foreign matter is diluted, clogging of the metal mesh by black spots and foreign matter can be more effectively suppressed when performing the foreign matter removal process described below.

[0039] As the apparatus for melt-kneading, known apparatuses, for example, melt-kneaders such as a single-screw or twin-screw extruder, a Banbury mixer, and a mixing roll, are preferably used.

[0040] When additives including at least one selected from the group consisting of a heat stabilizer, an antioxidant, a filler, a flame retardant, and a colorant are added to the non-standard thermoplastic resin to form a masterbatch, the additives are preferably added in the melt-kneading step. In this case, the non-standard thermoplastic resin may be heated and melted after the non-standard thermoplastic resin and the additives are introduced into a melt-kneader.

[0041] When a colorant is added to the non-standard product, it is also preferable to add it in the melt-kneading step. The non-standard product and the colorant may be introduced into a melt-kneader, and then the non-standard thermoplastic resin may be heated and melted.

[0042] The melt-kneading temperature is preferably about 1° C. to 100° C. higher than the melting point of the non-standard thermoplastic resin (preferably polyamide resin), more preferably about 10° C. to 50° C. higher. The shear rate in the mixer is 100 sec -1The average residence time during kneading is preferably about 0.5 minutes or more and 5 minutes or less.

[0043] [Pelletization process] In the pelletizing step, the molten material after the melt-kneading step is pelletized to obtain recycled pellets. Specifically, the molten material is preferably cooled and cut using a known device such as a pelletizer or a cutter to obtain pellets of a desired size, and more preferably the molten material is extruded as a strand, cooled (water-cooled), and cut to obtain pellets of a desired size.

[0044] The recycling step may further include the following foreign matter removal step after the melt-kneading step and before the pelletizing step. a foreign matter removal step in which the molten material is passed through a metal mesh to remove foreign matter; However, if the filler added in the regeneration step is likely to clog the metal mesh, it is preferable to omit the foreign matter removal step.

[0045] [Foreign matter removal process] In the foreign matter removal process, the molten material is passed through a metal mesh to remove foreign matter. By performing the foreign matter removal process, black spots and foreign matter contained in non-standard products can be removed, thereby further improving the quality of the obtained product. Examples of black spots and foreign matter include those exemplified as black spots and foreign matter in the above-mentioned control process.

[0046] As the metal mesh, for example, one having a mesh number of 50 or more and 500 or less can be used, and one having a mesh number of 300 or more and 400 or less can be used.

[0047] <Compounding process> In the compounding process, the recycled products obtained in the recycling process are selected based on the design factor B of the compound product and compounded.

[0048] Here, the compound product means a resin composition produced by a compounding process. The compounding step is not limited, but preferably includes a melt-kneading step of melt-kneading a virgin product or a recycled product, and a pelletizing step of pelletizing the molten product.

[0049] The design factors B of the compound product include, for example, the type of thermoplastic resin, the copper concentration, the type and content of additives, the molecular weight, the water content, the type and content ratio of terminal groups, color tone, etc. These design factors are used alone or in combination of two or more to select the recycled product.

[0050] If desired, copper or additives may be added to the selected regenerant. The additives are not particularly limited, but include heat stabilizers, antioxidants, fillers, flame retardants, colorants, flame retardant assistants, compatibilizers, rubber components, and the like. The additives added to the recycled product in the compounding step may be the same as or different from the additives added in the recycling step, but are preferably selected from a different type from the additives added in the recycling step.

[0051] The colorant may be added only in the recycling step, or may also be added in the compounding step. The colorant added to the recycled product in the compounding step may be the same or different from the colorant added in the recycling step, but is preferably selected from a different type than the colorant added in the recycling step. A colorant may be added in the compounding step, for example, a dye, in order to adjust the color of the resin composition containing the colorant added in the recycling step to a target color.

[0052] The recycled product obtained in the recycling step may be used alone for compounding, or the recycled product may be mixed with a virgin product for compounding. In particular, from the viewpoint of maintaining uniformity in the physical properties and quality of the resulting resin composition, it is preferable to mix the recycled product with a virgin product for compounding. Here, the virgin product may be a thermoplastic resin of a different type from the thermoplastic resin contained in the recycled product. When mixing masterbatched recycled products with virgin products, the concentration of additives contained in high concentrations in the recycled products can be appropriately diluted to obtain a compound product in which the additives are uniformly dispersed. By mixing the recycled product to which the colorant has been added with the virgin product, the concentration of the colorant contained in the recycled product can be appropriately diluted to obtain a compound product in which the colorant is uniformly dispersed.

[0053] For example, when selection factor B is copper concentration, in FIG. 1, to produce a resin composition in which the copper concentration of the recycled product alone is 0, recycled products recycled from non-standard products classified into grades with a copper concentration of 0 (Grades 1 and 2 in FIG. 1) are selected and compounded. When selection factor B is copper concentration and molecular weight, recycled products recycled from non-standard products classified into either Grade 1 or Grade 2 may be selected and compounded to achieve the desired molecular weight, or recycled products recycled from non-standard products classified into Grade 1 and recycled products recycled from non-standard products classified into Grade 2 may be selected and compounded by appropriately adjusting the mixing mass ratio of these.

[0054] Alternatively, for example, if selection factor B is copper concentration, to produce a resin composition having a copper concentration of 0 by mixing recycled and virgin products, a recycled product obtained from non-standard products classified as grades having a copper concentration of 0 (Grades 1 and 2 in Figure 1) is selected and mixed with a virgin product having a copper concentration of 0. If selection factor B is copper concentration and molecular weight and the molecular weight of the virgin product having a copper concentration of 0 is high, the amount of recycled product obtained from non-standard products classified as Grade 2 in Figure 1 can be increased compared to the amount of recycled product obtained from non-standard products classified as Grade 1 in Figure 1, thereby reducing the variation in molecular weight of the resulting resin composition.

[0055] Furthermore, for example, when selection factor B is copper concentration, to produce a resin composition with a high copper concentration, recycled products obtained from non-standard products classified as grades with high copper concentrations (grades 5 and 6 in Figure 1) are selected and mixed with virgin products with high copper concentrations. When selection factor B is copper concentration and molecular weight and the virgin products with high copper concentrations have a high molecular weight, the amount of recycled product obtained from non-standard products classified as grade 6 in Figure 1 can be increased compared to the amount of recycled product obtained from non-standard products classified as grade 5 in Figure 1, thereby reducing the variation in molecular weight of the resulting resin composition.

[0056] Alternatively, if selection factor B is copper concentration, a recycled product obtained from non-standard products classified as grades with a copper concentration of 0 (Grades 1 and 2 in Figure 1) or a recycled product obtained from non-standard products classified as grades with a medium copper concentration (Grades 3 and 4 in Figure 1) is selected, the required amount of copper is added, and mixed with a virgin product with a high copper concentration. If selection factor B is copper concentration and molecular weight and the virgin product with a high copper concentration has a high molecular weight, the amount of recycled product obtained from non-standard size products classified as Grades 2 or 4 in Figure 1 can be blended in greater than the amount of recycled product obtained from non-standard size products classified as Grades 1 or 3 in Figure 1, thereby reducing the variation in molecular weight of the resulting resin composition.

[0057] In the compounding step, a resin other than a thermoplastic resin may be melt-kneaded with a recycled product, and optionally a virgin product and additives, and then pelletized to form pellets of a compound product. The additives added in the recycling step may be melt-kneaded with the thermoplastic resin two or more times in total in the recycling step and the compounding step.

[0058] In the compounding step, the content of recycled materials is preferably 0.1% by mass or more relative to the total mass of the resin composition. There is no particular upper limit on the content of recycled materials, but it can be 100% by mass or less, and is preferably less than 100% by mass. Other resins and / or additives may be blended with recycled materials or with a mixture of recycled and virgin materials. When compounding recycled materials only, two or more types of recycled materials may be blended as appropriate.

[0059] Furthermore, when products containing black spots are excluded in the recycling process, the content of recycled products containing black spots in the compounding process is preferably 0.1% by mass or less relative to the total mass of the resin composition, and the content of black spots is preferably 0.01% by mass or less relative to the total mass of the resin composition. This makes it possible to further reduce the influence of black spots on the resulting resin composition and to uniform the quality of the resin composition.

[0060] In the compounding process, in order to ensure uniform quality of the resulting resin composition, the ratio of the average diameter of the recycled pellets to the average diameter of the virgin pellets is preferably 0.7 to 1.3, more preferably 0.8 to 1.2. The average diameter of the pellets refers to the average horizontal cross-sectional diameter for cylindrical pellets, the average length of the base edge for prismatic pellets, and the average diameter of the circle circumscribing the horizontal cross-section for non-cylindrical pellets (excluding prismatic). The average diameter of the pellets can be obtained, for example, by measuring the horizontal cross-sectional diameter for cylindrical pellets, the length of the base edge for prismatic pellets, and the diameter of the circle circumscribing the horizontal cross-section for non-cylindrical pellets (excluding prismatic) using a microscope for 100 pellets, and then calculating the average value based on the number of pellets.

[0061] FIG. 2 is a flow diagram showing each step of a manufacturing method according to another embodiment. FIG. 2 is similar to FIG. 1 except that the design factors A are "type of terminal group and its content ratio" and "moisture content." Therefore, the same explanation as described above with reference to FIG. 1 also applies to FIG. 2. Specifically, in FIG. 2, the specific terminal group contents A and B can be set as follows: for example, a ratio of the amount of amino terminal groups to the total molar amount of amino terminal groups and carboxy terminal groups in each off-standard product within a specific range can be set as A, and a ratio lower than the range A can be set as B. Alternatively, for example, a molar ratio (mol %) of the amount of amino terminal groups to the total molar amount of terminal groups within a specific range can be set as A, and a ratio lower than the range A can be set as B. Alternatively, for example, a molar equivalent of amino terminal groups per 1 g of off-standard product (mol equivalents / g) within a specific range can be set as A, and a ratio lower than the range A can be set as B. The specific terminal groups, the specific range of their content, and the "low" and "high" moisture content can be determined appropriately based on the intended use of the resin composition (compound product).

[0062] <Thermoplastic resin manufacturing process> The manufacturing process of the thermoplastic resin that generates the non-standard products is not particularly limited, but preferably includes, for example, a polymerization step in which raw material monomers are polymerized in a polymerization tank, and a selection and removal step in which non-standard products are selected and removed.

[0063] Examples of thermoplastic resins include polyamide resins, polyester resins, polyacetal resins, polycarbonate resins, polyacrylic resins, polyphenylene ether resins (including modified polyphenylene ethers obtained by blending or graft polymerizing polyphenylene ethers with other resins), polyarylate resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polyketone resins, polyphenylene ether ketone resins, polyimide resins, polyamideimide resins, polyetherimide resins, polyurethane resins, polyolefin resins (e.g., α-olefin (co)polymers), various ionomers, etc. Among these, polyamide resins are preferred.

[0064] [Polymerization process] The polymerization step of polymerizing raw material monomers in a polymerization tank to obtain a thermoplastic resin is not particularly limited and can be carried out by a known method. For example, when the thermoplastic resin is a polyamide resin, the step of polymerizing a dicarboxylic acid constituting a dicarboxylic acid unit, a diamine constituting a diamine unit, and, if necessary, at least one of a lactam constituting a lactam unit and an aminocarboxylic acid constituting an aminocarboxylic acid unit in a polymerization tank, or a step carried out by the method described in the following [Polyamide resin] and [Method of producing a polyamide resin] can be mentioned.

[0065] [Sorting and removal process] The sorting and removal process for sorting and removing non-standard products is not particularly limited, but it is preferable to carry out at least one process selected from the group consisting of: a process of sorting and removing pellets that do not meet the size standards using a sieving machine; a process of sorting and removing products containing black spots and / or foreign matter using a black spot sorter or a foreign matter sorter; and a process of measuring physical properties using an inspection machine and sorting and removing products that do not meet the physical property standards, and it is preferable to carry out at least one process selected from the group consisting of: a process of sorting and removing pellets that do not meet the size standards using a sieving machine; and a process of measuring physical properties using an inspection machine and sorting and removing products that do not meet the physical property standards.

[0066] Examples of inspection machines used to screen out products that do not meet the physical property standards include the following. The moisture content can be measured using, for example, a Karl Fischer moisture meter (manufactured by Mitsubishi Chemical Corporation, CA-200 / VA-200). For measuring the molecular weight, for example, a gel permeation graph (GPC) (HLC-8020 manufactured by Tosoh Corporation, hexafluoroisopropanol solvent, converted into a PMMA (polymethyl methacrylate) standard sample (manufactured by Polymer Laboratory Co., Ltd.)) is used. For measuring the color tone, for example, a color difference meter (ZE-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) is used.

[0067] [Pelletization process] Between the polymerization step and the selection and removal step, it is preferable to further carry out a pelletization step in which the polymer obtained in the polymerization step is cut using a known device such as a pelletizer or a cutter. In the pelletizing step, it is preferable that the polymer in a molten state is extruded as a strand, cooled (preferably by water cooling), and cut.

[0068] [Packaging process] In the manufacturing process of the thermoplastic resin, it is preferable to carry out a packaging process of packaging the pellets using a packaging machine between the process of sorting and removing products containing black spots and foreign matter and the process of sorting and removing products that do not meet physical property standards. Any excess material remaining in the packaging process or scraps generated during packaging when the line is washed together when the type of thermoplastic resin is changed are removed as non-standard products. For example, before or after the packaging step, during the step of sorting out and removing non-standard products, the thermoplastic resin can be stored in a stocker such as a silo.

[0069] The thermoplastic resin (sometimes referred to as a virgin product) obtained through the thermoplastic resin manufacturing process can be mixed with a recycled product in the compounding process to prepare a resin composition (compound product).

[0070] <Resin composition> The resin composition obtained by the manufacturing method of this embodiment preferably contains a thermoplastic resin as a main component. The thermoplastic resin as a main component of the resin composition may be the same or different from the thermoplastic resin that generates non-standard products during the manufacturing process, i.e., the non-standard products.

[0071] The resin composition obtained by the manufacturing method of this embodiment may contain other resins and / or additives in addition to the thermoplastic resin as the main component. The other resins may be selected from the thermoplastic resins described above. The other resins and / or additives are not particularly limited, but may include heat stabilizers, antioxidants, fillers, flame retardants, colorants, flame retardant assistants, compatibilizers, rubber components, etc.

[0072] The heat stabilizer, antioxidant, filler, flame retardant, and colorant may be the same as those described above. The flame retardant synergist is preferably used in combination with a flame retardant. Examples of the flame retardant aid include metal oxides and metal hydroxides. Examples of compatibilizers include substances that chemically or physically interact with each resin when two or more resins are mixed to improve compatibility. A modified resin in which at least one of the two or more resins is functionalized by grafting or the like may also be used as the compatibilizer. The modified resin can improve compatibility with other resins compared to unmodified resins. The rubber component may be a styrene copolymer or the like.

[0073] [Polyamide resin] Examples of polyamide resins include (a-1) polyamides obtained by ring-opening polymerization of lactams, (a-2) polyamides obtained by self-condensation of ω-aminocarboxylic acids, (a-3) polyamides obtained by condensing diamines and dicarboxylic acids, and copolymers thereof. The polyamide resins may be used alone or in combination of two or more.

[0074] (a-1) Examples of lactams used in the production of polyamide include, but are not limited to, pyrrolidone, caprolactam, undecalactam, and dodecalactam. (a-2) The ω-aminocarboxylic acid used in the production of polyamide is not limited to the following, but examples thereof include ω-amino fatty acids, which are ring-opened compounds of the above lactams with water. Furthermore, two or more kinds of the lactam or ω-aminocarboxylic acid may be used in combination and condensed.

[0075] (a-3) Diamines (monomers) used in the production of polyamides include, but are not limited to, linear aliphatic diamines, branched aliphatic diamines, alicyclic diamines, and aromatic diamines. Examples of the linear aliphatic diamine include, but are not limited to, hexamethylenediamine and pentamethylenediamine. Examples of branched aliphatic diamines include, but are not limited to, 2-methylpentanediamine and 2-ethylhexamethylenediamine. Examples of alicyclic diamines include, but are not limited to, cyclohexanediamine, cyclopentanediamine, and cyclooctanediamine. Examples of aromatic diamines include, but are not limited to, p-phenylenediamine and m-phenylenediamine. (a-3) Dicarboxylic acids (monomers) used in the production of polyamides include, but are not limited to, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, and the like. Examples of the aliphatic dicarboxylic acid include, but are not limited to, adipic acid, pimelic acid, and sebacic acid. The alicyclic dicarboxylic acid is not limited to the following, but examples thereof include cyclohexanedicarboxylic acid. Examples of aromatic dicarboxylic acids include, but are not limited to, phthalic acid and isophthalic acid. The diamines and dicarboxylic acids as the monomers may be condensed either alone or in combination of two or more.

[0076] Specific examples of polyamide resins include polyamide 4 (poly-α-pyrrolidone), polyamide 6 (polycaproamide), polyamide 11 (polyundecaneamide), polyamide 12 (polydodecanamide), polyamide 46 (polytetramethylene adipamide), polyamide 56 (polypentamethylene adipamide), polyamide 66 (polyhexamethylene adipamide), polyamide 610 (polyhexamethylene sebacamide), polyamide 612 (polyhexamethylene dodecamide), polyamide 6I (polyhexamethylene isophthalamide), polyamide 6T (polyhexamethylene terephthalamide), polyamide 9T (polynonamethylene terephthalamide), and copolymer polyamides containing these as constituent components. Among these, the polyamide resin is preferably at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 6I, polyamide 66 / 6, and polyamide 66 / 6I, and more preferably at least one selected from the group consisting of polyamide 6, polyamide 66, and polyamide 6I.

[0077] The terminals of the polyamide resin may be capped with a known terminal capping agent. Such an end-capping agent can also be added as a molecular weight regulator when producing a polyamide resin from the dicarboxylic acid, the diamine, and, if necessary, at least one of the lactam and the aminocarboxylic acid.

[0078] Examples of the end-capping agent include, but are not limited to, monocarboxylic acids, monoamines, acid anhydrides, monoisocyanates, monoacid halides, monoesters, monoalcohols, etc. Examples of the acid anhydrides include, but are not limited to, phthalic anhydride, etc. These end-capping agents may be used alone or in combination of two or more. Among these, monocarboxylic acids or monoamines are preferred as the end-capping agent. By blocking the ends of the polyamide resin with an end-capping agent, the polyamide resin tends to have better thermal stability.

[0079] The monocarboxylic acid usable as the end-capping agent may be any one that is reactive with amino groups that may be present at the terminals of the polyamide resin. Specific examples of the monocarboxylic acid include, but are not limited to, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and aromatic monocarboxylic acids. Examples of aliphatic monocarboxylic acids include, but are not limited to, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid. Examples of alicyclic monocarboxylic acids include, but are not limited to, cyclohexanecarboxylic acid. Examples of aromatic monocarboxylic acids include, but are not limited to, benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid. These monocarboxylic acids may be used alone or in combination of two or more.

[0080] The monoamine usable as the end-capping agent may be any monoamine that is reactive with a carboxyl group that may be present at the end of the polyamide resin, and specific examples of the monoamine include, but are not limited to, aliphatic monoamines, alicyclic monoamines, and aromatic monoamines. Examples of aliphatic amines include, but are not limited to, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine. Examples of alicyclic amines include, but are not limited to, cyclohexylamine and dicyclohexylamine. Examples of aromatic amines include, but are not limited to, aniline, toluidine, diphenylamine, naphthylamine, and the like. These monoamines may be used alone or in combination of two or more.

[0081] Polyamide resins end-capped with an end-capping agent tend to have better heat resistance, flowability, toughness, low water absorption, and rigidity.

[0082] [Manufacturing method of polyamide resin] The method for producing a polyamide resin includes, but is not limited to, a step of polymerizing a dicarboxylic acid constituting a dicarboxylic acid unit, a diamine constituting a diamine unit, and, if necessary, at least one of a lactam constituting a lactam unit and an aminocarboxylic acid constituting an aminocarboxylic acid unit to obtain a polymer. Preferably, the method for producing a polyamide resin further comprises a step of increasing the degree of polymerization of the polyamide resin. If necessary, a capping step of capping the ends of the resulting polymer with an end-capping agent may be included.

[0083] Specific methods for producing polyamide resins include various methods such as those exemplified in the following 1) to 4). 1) A method in which an aqueous solution of a dicarboxylic acid-diamine salt or a mixture of a dicarboxylic acid and a diamine, or an aqueous suspension of these, is heated and polymerized while maintaining the molten state (hereinafter sometimes referred to as "thermal melt polymerization"). 2) A method in which the degree of polymerization of polyamide obtained by the hot melt polymerization method is increased while maintaining the solid state at a temperature below the melting point (hereinafter sometimes referred to as "hot melt polymerization / solid state polymerization method"). 3) A method of polymerizing a dicarboxylic acid-diamine salt or a mixture of dicarboxylic acid and diamine while maintaining it in a solid state (hereinafter, sometimes referred to as "solid-state polymerization method"). 4) A method of polymerization using a dicarboxylic acid halide component equivalent to the dicarboxylic acid and a diamine component (hereinafter, sometimes referred to as the "solution method"). Among these, a specific method for producing a polyamide resin is preferably a production method including a hot melt polymerization method. When producing a polyamide resin by the hot melt polymerization method, it is preferable to maintain the molten state until the polymerization is completed. Examples of the method for maintaining the molten state include a method for producing the polyamide resin under polymerization conditions suitable for its composition. Examples of the polymerization conditions include the following conditions. First, the polymerization pressure in the hot melt polymerization method is set to 14 kg / cm. 2 More than 25kg / cm 2 Heating is continued while controlling the pressure in the vessel to atmospheric pressure (gauge pressure is 0 kg / cm 2 ), a polyamide having the desired composition can be obtained by reducing the pressure over 30 minutes or more.

[0084] In the method for producing the polyamide resin, the polymerization mode is not particularly limited, and may be a batch system or a continuous system. The polymerization apparatus used for producing the polyamide resin is not particularly limited, and any known polymerization vessel can be used, for example, an autoclave-type reactor, a tumbler-type reactor, or an extruder-type reactor such as a kneader.

[0085] Hereinafter, as a method for producing a polyamide resin, a method for producing a polyamide resin by a batch-type hot melt polymerization method will be specifically shown, but the method for producing a polyamide resin is not limited to this. First, an aqueous solution containing about 40% by mass to about 60% by mass of raw material components of a polyamide resin (dicarboxylic acid, diamine, and, as necessary, at least one of lactam and aminocarboxylic acid) is concentrated to about 65% by mass to about 90% by mass in a concentration tank operated at a temperature of 110°C to 180°C and a pressure of about 0.035 MPa to 0.6 MPa (gauge pressure) to obtain a concentrated solution. Next, the obtained concentrated solution is transferred to an autoclave, and heating is continued until the pressure in the autoclave reaches about 1.2 MPa or more and 2.2 MPa or less (gauge pressure). Thereafter, in the autoclave, the pressure is maintained at approximately 1.2 MPa to 2.2 MPa (gauge pressure) while removing at least one of the water and gas components, and when the temperature reaches approximately 220°C to 260°C, the pressure is reduced to atmospheric pressure (gauge pressure: 0 MPa). After the pressure inside the autoclave is reduced to atmospheric pressure, the pressure can be reduced as needed to effectively remove the by-produced water. The autoclave is then pressurized with an inert gas such as nitrogen, and the polyamide melt is extruded from the autoclave as a strand. The extruded strand is cooled and cut to obtain pellets of the polyamide resin.

[0086] [Polyamide resin polymer end] The polymer terminals of the polyamide resin are not particularly limited, but can be classified and defined as follows: 1) amino terminus, 2) carboxy terminus, 3) terminus with a capping agent, and 4) other terminus. 1) The amino terminal is a polymer terminal having an amino group (-NH2 group) and is derived from the diamine unit of the raw material. 2) The carboxyl end is a polymer end having a carboxyl group (-COOH group) and is derived from the dicarboxylic acid raw material. 3) The term "terminals formed by a capping agent" refers to terminals formed when a capping agent is added during polymerization. Examples of the capping agent include the above-mentioned terminal capping agents. 4) Other terminals are polymer terminals that are not classified into the above 1) to 3). Specific examples of other terminals include terminals generated by deammoniating an amino terminal, terminals generated by decarboxylating a carboxy terminal, etc. [Example]

[0087] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0088] [Examples 1 to 4] According to the flow diagram shown in Figure 1, virgin polyamide 66 was first produced. Next, non-standard products generated during the virgin polyamide 66 production process were classified into grades 1 to 4 based on design factor A (copper concentration and molecular weight). Non-standard products classified into the same grade were mixed and melt-kneaded. That is, four types of melt-kneaded products were obtained, each derived from non-standard products of grade 1 only, grade 2 only, grade 3 only, and grade 4 only. Next, the four types of melt-kneaded products were passed through a metal mesh (mesh number: 200) in order to remove foreign matter, and then pelletized to obtain four types of recycled products (recycled pellets) derived from the non-standard products of grades 1 to 4. Next, a recycled product derived from a Grade 1 non-standard product, or a recycled product derived from a Grade 2 non-standard product, selected as the recycled product based on design factor B (copper concentration and molecular weight), was melt-kneaded with the resulting virgin product (polyamide 66) or other virgin products (polyamide 6I or polyamide 6), and additives (flame retardant, flame retardant aid, compatibilizer, styrene copolymer, antioxidant, and / or filler) in the amounts shown in Table 1 below, and then pelletized (compounded) to produce a resin composition containing the recycled product and the virgin product.

[0089] [Comparative Examples 1 to 4] A resin composition was produced in the same manner as in Examples 1 to 4, except that a commercially available polyamide 66 (manufactured by Takayasu Co., Ltd., TN710L) was used as the recycled product.

[0090] [Examples 5 to 7] First, virgin polyamide 66 was produced according to the flow diagram shown in Figure 1. Next, non-standard products generated during the virgin polyamide 66 production process were classified into grades 1 to 4 based on design factor A (copper concentration and molecular weight). Non-standard products classified into the same grade were mixed, and additives (thermal stabilizer, antioxidant, or filler) for masterbatch (MB) production shown in Table 3 below were added, followed by melt-kneading. Specifically, four types of melt-kneaded products were obtained by adding additives to the non-standard mixtures of grades 1 only, 2 only, 3 only, and 4 only. Next, the melt-kneaded products derived from the non-standard products of grades 1 to 4 were pelletized to obtain four types of recycled products. Next, based on design factor B (copper concentration and molecular weight), a recycled product derived from a standard Grade 1 product or a recycled product derived from a standard Grade 2 product was selected as the recycled product. The resulting virgin polyamide 66, other virgin polyamides (polyamide 6), and fillers were melt-kneaded in the amounts shown in Table 3 below, and then pelletized (compounded) to produce a resin composition containing recycled and virgin products.

[0091] [Comparative Examples 5 to 7] A resin composition containing recycled and virgin products was produced in the same manner as in Examples 5 to 7, except that the non-standard product was melt-kneaded without adding any additives to make it into a masterbatch (MB), and the components were blended in the amounts shown in Table 3 below.

[0092] [Examples 8 to 12] First, virgin polyamide 66 was produced according to the flow diagram shown in Figure 1. Next, non-standard products generated during the virgin polyamide 66 production process were classified into grades 1 to 4 based on design factor A (copper concentration and molecular weight). Non-standard products of the same grade were mixed, a colorant was added, and melt-kneaded. That is, four types of melt-kneaded products were obtained by adding colorants to mixtures of non-standard products consisting of only grade 1, only grade 2, only grade 3, and only grade 4. Next, the melt-kneaded products were pelletized to obtain four types of recycled products derived from the non-standard products of grades 1 to 4. Next, based on design factor B (copper concentration and molecular weight), a recycled product derived from a Grade 1 standard product or a recycled product derived from a Grade 2 standard product was selected as the recycled product. The resulting virgin polyamide 66, other virgin products (polyamide 6I or polyamide 6), and additives (flame retardant, flame retardant aid, compatibilizer, styrene copolymer, antioxidant, filler, and / or colorant) were compounded in the amounts shown in Table 4 below to produce a resin composition containing the recycled product and the virgin product.

[0093] [Comparative Examples 8 to 11] A resin composition containing recycled and virgin products was produced in the same manner as in Examples 8 to 12, except that the non-standard product was melt-kneaded without adding a colorant and the components were blended in the amounts shown in Table 5 below.

[0094] <Components> [(A) Recycled products for each grade based on design factor A] A-1: Polyamide 66 recycled from non-standard products classified as Grade 1 in Figure 1 by the method described in each Example or Comparative Example. A-2: Polyamide 66 recycled from non-standard products classified as Grade 2 in Figure 1 by the method described in each Example or Comparative Example.

[0095] [(B) Recycled product] B-1: Polyamide 66 (Takayasu Co., Ltd., TN710L)

[0096] [(C) Virgin product] C-1: Polyamide 66 C-2: Polyamide 6I C-3: Polyamide 6 (BASF, Ultramid B33L) C-4: PPE (polyphenylene ether)

[0097] [(D) Flame retardant] D-1: Brominated polystyrene (BrPs: manufactured by Albemarle Corporation, SAYTEX HP-3010G) D-2: Phosphinic acid flame retardant Aluminum diethylphosphinate (Phosphinic acid AI: Clariant, Exolit OP1230)

[0098] [(E) Flame retardant synergist] E-1: Antimony trioxide (Sb2O3: manufactured by Daiichi F.R. Co., Ltd., antimony trioxide)

[0099] [(F) Compatibilizer] F-1:M PPE

[0100] [(G) Styrene-based copolymer] G-1: Styrene-acrylonitrile copolymer (AS) (manufactured by Asahi Kasei Corporation) (acrylonitrile content: 40% by mass)

[0101] [(H) Antioxidant] H-1: Hindered phenolic antioxidant (BASF, Irganox 1098)

[0102] [(I) Filler] I-1: Glass fiber (GF) (Nippon Electric Glass Co., Ltd., ECS 03T-275H) I-2: Glass fiber (GF) (manufactured by Megashi Group Co., Ltd., ECS10-03-568H) I-3: Glass fiber (GF) (Nippon Electric Glass Co., Ltd., ECS03-T297)

[0103] [(J) Heat stabilizer] J-1: Copper iodide (CuI) / potassium iodide (KI)

[0104] [(K) Colorant] K-1: Masterbatch containing black colorant (black MB) K-2: Masterbatch containing chromatic colorants (chromatic MB) K-3: Dye (adjust to the desired color)

[0105] [(L) Thermoplastic elastomer] L-1: SEBS (styrene-ethylene-butylene-styrene)

[0106] The methods for producing virgin product C-1, virgin product C-2, and compatibilizer F-1 are described in detail below. Virgin products C-1 and C-2 obtained by the following production methods were dried in a nitrogen stream to adjust the moisture content to about 0.2 mass % before being used as raw materials for the resin compositions in the above examples and comparative examples.

[0107] [Synthesis Example 1] Synthesis of virgin product C-1 (polyamide 66) The polymerization reaction of polyamide was carried out by the "hot melt polymerization method" as follows. First, 1500 g of an equimolar salt of adipic acid and hexamethylenediamine was dissolved in 1500 g of distilled water to prepare a homogeneous aqueous solution containing 50% by weight of the raw material monomers. This aqueous solution was charged into a 5.4 L autoclave and purged with nitrogen. Next, the solution was concentrated by gradually removing water vapor while stirring at a temperature of approximately 110°C to 150°C to a solution concentration of 70% by weight. The internal temperature was then raised to 220°C. The autoclave was then pressurized to 1.8 MPa. The reaction was continued for one hour while maintaining the pressure at 1.8 MPa by gradually removing water vapor until the internal temperature reached 245°C. The pressure was then reduced over one hour. The autoclave was then maintained at a reduced pressure of 650 torr (86.66 kPa) for 10 minutes using a vacuum device. The final internal temperature of the polymerization was 265°C. The mixture was then pressurized with nitrogen to form strands from the lower spinneret (nozzle), cooled with water, cut, and discharged as pellets. The pellets were then dried at 100°C under a nitrogen atmosphere for 12 hours to obtain virgin product C-1 (polyamide 66).

[0108] [Synthesis Example 2] Synthesis of virgin C-2 (Polyamide 6I) The polymerization reaction of polyamide was carried out by the "hot melt polymerization method" as follows. First, 1500 g of an equimolar salt of isophthalic acid and hexamethylenediamine, a 1.5 mol % excess of adipic acid relative to the total equimolar salt components, and 0.5 mol % of acetic acid were dissolved in 1500 g of distilled water to prepare a 50% by mass equimolar homogeneous aqueous solution of the raw material monomers. Next, the solution was concentrated by gradually removing water vapor to a solution concentration of 70% by mass while stirring at a temperature of approximately 110°C to 150°C. The internal temperature was then raised to 220°C. The autoclave was then pressurized to 1.8 MPa. The reaction was continued for 1 hour while gradually removing water vapor to maintain the pressure at 1.8 MPa until the internal temperature reached 245°C. The pressure was then reduced over 30 minutes. The autoclave was then maintained at a reduced pressure of 650 torr (86.66 kPa) for 10 minutes using a vacuum device. The final internal temperature of the polymerization was 265°C. The mixture was then pressurized with nitrogen to form strands from the lower spinneret (nozzle), cooled with water, cut, and discharged as pellets. The pellets were then dried at 100°C under a nitrogen atmosphere for 12 hours to obtain virgin product C-2 (polyamide 6I).

[0109] [Synthesis Example 3] Synthesis of compatibilizer F-1 (m-PPE) Poly(2,6-dimethyl-1,4-phenylene ether) (hereinafter sometimes abbreviated as "polyphenylene ether"), obtained by oxidative polymerization of 2,6-dimethylphenol and having a reduced viscosity of 0.52 (0.5 g / dL chloroform solution, measured at 30°C), was used in a mixture of 100 parts by mass, 0.1 parts by mass of a radical initiator, and 1.5 parts by mass of maleic anhydride as a compatibilizer. The mixture was melt-kneaded under conditions of a cylinder set temperature of 320°C, a screw rotation speed of 300 rpm, and a discharge rate of 20.15 kg / hr, and discharged as a strand. The mixture was then cooled in a strand bath. The mixture was then granulated using a cutter to obtain pellets of maleic anhydride-modified polyphenylene ether. The maleic anhydride addition rate was 0.5%.

[0110] <Physical properties and evaluation> First, pellets of the resin compositions obtained in the Examples and Comparative Examples were dried in a nitrogen stream to reduce the moisture content in the resin compositions to 500 ppm or less. Next, the pellets of each resin composition with the adjusted moisture content were used to measure and evaluate various physical properties by the following methods.

[0111] [Tensile strength] Using an injection molding machine (PS-40E, manufactured by Nissei Plastics Co., Ltd.), pellets of the resin compositions obtained in Examples 1 to 4 and 8 to 12 and Comparative Examples 1 to 4 and 8 to 11 were molded into multipurpose test specimens of type A in accordance with ISO 3167. Specific molding conditions were set as follows: injection + dwell time 25 seconds, cooling time 15 seconds, mold temperature 80°C, and molten resin temperature at the polyamide's high-temperature melting peak temperature (Tm2) + 20°C. Using the obtained molded multipurpose test piece A, a tensile test was carried out in accordance with ISO 527 at a temperature of 23°C and a pulling rate of 50 mm / min to measure the tensile yield stress, which was taken as the tensile strength. The results are shown in Tables 2 and 6.

[0112] [Sharpy] Using an "FN3000" manufactured by Nissei Kogyo Co., Ltd., pellets of the resin compositions obtained in Examples 1 to 3 and 8 to 12 and Comparative Examples 1 to 3 and 8 to 11 were molded under injection molding conditions of a cylinder temperature of 290°C, a mold temperature of 100°C, and a 10-second injection and cooling time of 10 seconds, to obtain molded articles (ISO test pieces). Charpy impact strength was measured using the obtained ISO test pieces in accordance with ISO 179. The measured value was the average of n=6.

[0113] [Izod] Pellets of the resin compositions obtained in Example 4 and Comparative Example 4 were molded using a "PS-40E" manufactured by Nissei Plastics Co., Ltd. under injection molding conditions of a cylinder temperature of 290°C, a mold temperature of 80°C, an injection time of 25 seconds, and a cooling time of 15 seconds to obtain molded pieces conforming to ASTM No. 1. The molded pieces obtained were notched, and then an impact test was carried out using an Izod impact tester (manufactured by Toyo Seiki Co., Ltd.) by the Izod method in accordance with ASTM D256 standard to measure the notched impact strength. The results are shown in Table 2.

[0114] [Flame retardant] Measurements were performed using the UL94 method (a standard established by Underwriters Laboratories Inc., USA). Test specimens (127 mm long, 12.7 mm wide, and 1.6 mm thick) were prepared by molding pellets of the resin compositions obtained in Examples 1-2 and 8-9 and Comparative Examples 1-2 and 8-9 at a cylinder temperature of 290°C using an injection molding machine (PS40E, manufactured by Nissei Kogyo Co., Ltd.) equipped with a mold for UL test specimens (mold temperature = 100°C). The injection pressure was set at +2% of the full-fill pressure used to mold the UL test specimens. Flame retardancy was evaluated according to the UL94 standard (vertical flame test) to determine whether the specimens were V-0, V-1, or V-2. The lower the grade, the higher the flame retardancy. The results are shown in Tables 2 and 6.

[0115] [Moldability] Using an injection molding machine (PS-40E: manufactured by Nissei Plastics Co., Ltd.), pellets of the resin compositions obtained in Examples 1 to 4 and 8 to 12 and Comparative Examples 1 to 4 and 8 to 11 were molded into molded articles measuring 60 mm in length, 60 mm in width, and 1.0 mm in thickness. During this molding, the injection + pressure holding time was set to 2 seconds, the cooling time to 6 seconds, the mold temperature to 130°C, and the molten resin temperature to the melting point Tm2 of the (A) polyamide + 10°C. The moldability was evaluated as follows: The ability to obtain molded products without any problems was evaluated as leading to improved productivity. ◯: Molded products were obtained without any problems. △: Sometimes sprue remained in the mold. The results are shown in Tables 2 and 6.

[0116] [Dispersibility / elimination of unopened fibers] The pellets of the resin compositions obtained in Example 5 and Comparative Example 5 were used to obtain molded articles. The evaluation of dispersibility / elimination of unopened fibers was judged as follows: Obtaining molded products without any problems was evaluated as leading to improved productivity. ◯: Unopened glass fibers were eliminated, and the dispersibility of the resin composition was excellent. ×: Unopened glass fibers were not resolved, and the dispersibility of the resin composition was poor. The results are shown in Table 3.

[0117] [Color change] The pellets of the resin compositions obtained in Example 6 and Comparative Example 6 were used to obtain molded articles. The evaluation of color change was made as follows: The fact that molded products could be obtained without any problems was evaluated as leading to improved productivity. ◯: No color change was observed. ×: A change in color was observed. The results are shown in Table 3.

[0118] [Preventing deterioration of recycled products] Molded articles were obtained using the resin compositions obtained in Example 7 and Comparative Example 7. The evaluation of deterioration prevention was made as follows: The fact that molded products could be obtained without any problems was evaluated as leading to improved productivity. Good: Deterioration of recycled pellets was suppressed. ×: Deterioration of the recycled pellets was not suppressed. The results are shown in Table 3.

[0119] [Color unevenness] Molded articles were obtained using the resin compositions obtained in Examples 8 to 12 and Comparative Examples 8 to 11. The evaluation of color unevenness was made as follows: The fact that molded products could be obtained without any problems was evaluated as leading to improved productivity. ⊚: It was very easy to adjust to the desired color. ○: It was easy to adjust to the desired color. △: It was not easy to adjust to the desired color. The results are shown in Table 6.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] [Table 4]

[0124] [Table 5]

[0125] [Table 6] [Industrial Applicability]

[0126] According to the manufacturing method of this embodiment, it is possible to provide a method for manufacturing a resin composition using non-standard products, which has improved mechanical strength, flame retardancy, moldability, and / or dispersibility, and which suppresses color unevenness, color change, and / or deterioration of recycled products.

Claims

1. a management process for collecting non-standard products generated in the thermoplastic resin manufacturing process, classifying them into grades based on design factor A, and managing them; a regeneration step of regenerating the non-standard products by grade to obtain regenerated products; a compounding step of selecting the recycled product obtained in the recycling step based on a design factor B of a compound product and compounding the selected recycled product; A method for producing a resin composition, comprising:

2. The method for producing a resin composition according to claim 1 , wherein the non-standard product is converted into a masterbatch in the recycling step.

3. The method for producing a resin composition according to claim 1 , wherein a colorant is added to the non-standard product in the recycling step.

4. The method for producing a resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin is in the form of pellets.

5. The method for producing a resin composition according to any one of claims 1 to 3, wherein the design factor A is one or more selected from the group consisting of copper concentration, type and content of additives, amount of foreign matter mixed in, molecular weight, water content, color tone, and type and content ratio of terminal groups.

6. The method for producing a resin composition according to any one of claims 1 to 3, wherein the recycled product and a virgin product are mixed in the compounding step.

7. The method for producing a resin composition according to claim 6, wherein in the compounding step, the content of the recycled product is 0.1 mass% or more with respect to the total mass of the resin composition.

8. The recycled product and the virgin product are in the form of pellets, The method for producing a resin composition according to claim 6, wherein the ratio of the average diameter of the recycled pellets to the average diameter of the virgin pellets is 0.7 or more and 1.3 or less.

9. The method for producing a resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin comprises a polyamide resin.

10. 10. The method for producing a resin composition according to claim 9, wherein the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 6I, polyamide 66 / 6, and polyamide 66 / 6I.

11. The non-standard product is at least one selected from the group consisting of intermediate products produced during production changeover due to a change in the type of thermoplastic resin, products containing black spots, products containing foreign matter, products not conforming to the size of pellets, scraps produced during packaging, and products not conforming to the physical properties. The method for producing a resin composition according to any one of claims 1 to 3.

12. The regeneration step a melt-kneading step of melt-kneading the non-standard product to obtain a molten material; a pelletizing step of pelletizing the molten material after the melt-kneading step to obtain recycled pellets; The method for producing the resin composition according to claim 1 or 3, comprising:

13. The method for producing a resin composition according to claim 12, further comprising a foreign matter removing step of passing the molten material through a metal mesh to remove foreign matter, after the melt-kneading step and before the pelletizing step.

14. The regeneration step a melt-kneading step of melt-kneading the non-standard product to obtain a molten material; a pelletizing step of pelletizing the molten material after the melt-kneading step to obtain recycled pellets; Including, The method for producing a resin composition according to claim 2, wherein an additive comprising at least one selected from the group consisting of a heat stabilizer, an antioxidant, a filler, a flame retardant, and a colorant is added in the melt-kneading step.

15. The method for producing a resin composition according to claim 14, wherein the mass ratio of the additive to the non-standard product is 10:90 to 90:

10.

16. The method for producing a resin composition according to claim 3, wherein the mass ratio of the colorant to the non-standard product is 0.1:99.9 to 10:90.

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