Manufacturing method of alloy resin and manufacturing method of molded product

Abstract

To provide a method for manufacturing an alloy resin and a method for manufacturing a molded article which enable manufacture of a molded article that is excellent in transparency and scratch resistance.SOLUTION: Manufacture of an alloy resin using a twin screw extruder 10 feeds a methyl methacrylate-based resin from a main hopper 14 on the upstream side of a cylinder 12, side feeds a powdery vinyl chloride-based resin from a side feeder 16, adds the vinyl chloride-based resin to the methyl methacrylate-based resin in a molten state, and melt-kneads the mixture. A molded article is obtained by molding an alloy resin melt-kneaded by the method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an alloy resin and a method for producing a molded article. [Background technology]

[0002] Rigid polyvinyl chloride resins are generally excellent in flame retardancy and chemical resistance, and are therefore widely used in applications such as pipes, general building materials, etc. In addition, for the purpose of improving the properties of rigid polyvinyl chloride resins, it is known to add acrylic resins, ABS resins, etc. to polyvinyl chloride resins as alloys and mold them by injection molding or the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 61-014246 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional methods such as that described in Patent Document 1, it is difficult to produce a molded article that is both excellent in transparency and excellent in scratch resistance.

[0005] An object of the present invention is to provide a method for producing an alloy resin capable of producing a molded article having excellent transparency and excellent scratch resistance, and a method for producing the molded article. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A method for producing an alloy resin, comprising adding a powdered vinyl chloride resin to a molten methyl methacrylate resin and melt-kneading the mixture to obtain an alloy resin. [2] A method for producing an alloy resin according to [1], comprising using a twin-screw extruder, feeding the methyl methacrylate resin from a main hopper on the upstream side of a cylinder, and side-feeding the powdered vinyl chloride resin to melt-knead it with the molten methyl methacrylate resin. [3] The method for producing an alloy resin according to [2], wherein the temperature of the part of the cylinder of the twin-screw extruder through which the vinyl chloride resin is side-fed is 160°C or higher and 190°C or lower. [4] A method for producing a molded article, comprising molding an alloy resin produced by the method for producing an alloy resin according to any one of [1] to [3] to obtain a molded article. Effect of the Invention

[0007] According to the present invention, there can be provided a method for producing an alloy resin capable of producing a molded article having excellent transparency and excellent scratch resistance, and a method for producing the molded article. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of a twin-screw extruder used in the production method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Manufacturing method of alloy resin] The method for producing an alloy resin of the present invention is a method in which a powdered polyvinyl chloride resin (hereinafter referred to as "PVC resin") is added to a molten methyl methacrylate resin (hereinafter referred to as "MMA resin") and melt-kneaded to obtain an alloy resin.

[0010] By melt-kneading the powdered PVC resin with the molten MMA resin, the PVC resin can be efficiently kneaded. This shortens the thermal history of the PVC resin, thereby suppressing yellowing of the PVC resin. Therefore, by using the alloy resin produced by the production method of the present invention for molding, a molded product with excellent transparency can be obtained. In addition, since the MMA resin and the PVC resin are sufficiently melt-kneaded, a molded product with excellent scratch resistance can be obtained.

[0011] A twin-screw extruder can be used for melt-kneading the MMA resin and the PVC resin. For example, a method using a twin-screw extruder 10 as illustrated in Fig. 1 can be exemplified. Note that the dimensions and the like of the figures illustrated in the following description are merely examples, and the present invention is not necessarily limited thereto, and can be appropriately modified and carried out within the scope of the present invention.

[0012] The twin-screw extruder 10 includes a cylinder 12 having a screw (not shown) therein, a main hopper 14 provided upstream of the cylinder 12, and a side feeder 16 provided midway in the axial direction of the cylinder 12.

[0013] In the method using the twin-screw extruder 10, MMA-based resin is fed from the main hopper 14 to the upstream portion of the cylinder 12. The fed MMA-based resin is heated in the cylinder 12 and becomes molten by the time it reaches the portion where the side feeder 16 is provided. In addition, powdered PVC-based resin is side-fed from the side feeder 16 to the middle portion of the cylinder 12. This allows the powdered PVC-based resin to be added to the molten MMA-based resin. On the downstream side of the side feeder 16 of the cylinder 12, the molten MMA-based resin and the powdered PVC-based resin are melt-kneaded by the screw, and the alloy resin is extruded from the tip of the cylinder 12.

[0014] It is preferable to provide a high-temperature region in the cylinder 12 upstream of the side feeder 16 in order to sufficiently melt the MMA-based resin. The temperature of the high-temperature region upstream of the side feeder 16 of the cylinder 12 is preferably 190°C or higher, and more preferably 190°C or higher and 210°C or lower. If the temperature of the high-temperature region is equal to or higher than the lower limit of the above range, the MMA-based resin is easily sufficiently melted. If the temperature of the high-temperature region is equal to or lower than the upper limit of the above range, thermal degradation of the MMA-based resin is easily suppressed.

[0015] The temperature of the side feed portion of the cylinder 12 where the side feeder 16 is provided, i.e., the portion through which the PVC-based resin is side-fed, is preferably 160°C to 190°C, more preferably 170°C to 180°C. If the temperature of the side feed portion of the cylinder 12 is equal to or higher than the lower limit of the aforementioned range, melt-kneading of the MMA-based resin and the PVC-based resin becomes easy. If the temperature of the side feed portion of the cylinder 12 is equal to or lower than the upper limit of the aforementioned range, thermal degradation of the PVC-based resin is easily suppressed.

[0016] The temperature of the portion of the cylinder 12 on the tip side of the side feed portion is preferably 160°C to 190°C, and more preferably 170°C to 180°C, similar to the side feed portion. If the temperature of the portion of the cylinder 12 on the tip side of the side feed portion is equal to or higher than the lower limit of the above range, melt-kneading of the MMA-based resin and the PVC-based resin becomes easy, and good dispersibility and transparency can be obtained. If the temperature of the cylinder 12 on the tip side of the side feed portion is equal to or lower than the upper limit of the above range, heat generation of the alloy resin is suppressed, and thermal degradation of the PVC-based resin can be suppressed.

[0017] The position where the side feeder 16 is provided in the cylinder 12 of the twin-screw extruder 10 is preferably a position where the distance from the rear end of the cylinder 12 to the tip is 1 / 2 or more, that is, closer to the tip than the halfway point, when the length from the rear end (upstream end) of the cylinder 12 to the tip is taken as 1. This makes it possible to further shorten the thermal history of the PVC-based resin, making it easier to suppress yellowing of the PVC-based resin and to obtain a molded product with excellent transparency.

[0018] In terms of facilitating sufficient melt-kneading of the MMA-based resin and the PVC-based resin, the position at which the side feeder 16 is provided in the cylinder 12 of the twin-screw extruder 10 is preferably such that, when the length from the rear end of the cylinder 12 to the front end is taken as 1, the distance from the rear end of the cylinder 12 is in the range of 1 / 2.5 to 1 / 3.

[0019] A PVC-based resin is a polymer in which the proportion of repeating units derived from vinyl chloride (hereinafter also referred to as "vinyl chloride units") exceeds 50% by mass relative to the total repeating units. The PVC-based resin may be a homopolymer of vinyl chloride, or a copolymer of vinyl chloride and a vinyl-based monomer copolymerizable with vinyl chloride. When the PVC-based resin is a copolymer, it may be a random copolymer, a block copolymer, or a graft copolymer. The PVC-based resin contained in the alloy resin may be one type, or two or more types.

[0020] The proportion of vinyl chloride units in the PVC resin is preferably 75 mass % or more, more preferably 80 mass % or more, further preferably 85 mass % or more, and particularly preferably 98 mass % or more, based on all repeating units.

[0021] The vinyl monomer copolymerizable with vinyl chloride is not particularly limited, and examples thereof include fatty acid vinyl esters, acrylates, methacrylates, vinyl cyanide, vinyl ethers, α-olefins, unsaturated carboxylic acids or their acid anhydrides, vinylidene chloride, vinyl bromide, and various urethanes.

[0022] Examples of fatty acid vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate. Examples of acrylates include methyl acrylate, ethyl acrylate, and butyl acrylate. Examples of methacrylates include methyl methacrylate and ethyl methacrylate. Examples of vinyl cyanides include acrylonitrile and methacrylonitrile. Examples of vinyl ethers include vinyl methyl ether, vinyl butyl ether, and vinyl octyl ether. Examples of α-olefins include ethylene, propylene, and butylene. Examples of unsaturated carboxylic acids or acid anhydrides thereof include acrylic acid, methacrylic acid, and maleic anhydride. The vinyl monomers copolymerizable with vinyl chloride may be used alone or in combination of two or more.

[0023] The average degree of polymerization of the PVC resin is preferably 400 to 1200, more preferably 500 to 800, and even more preferably 550 to 700. When the average degree of polymerization of the PVC resin is equal to or higher than the lower limit of the above range, the pencil hardness is improved. When the average degree of polymerization of the PVC resin is equal to or lower than the upper limit of the above range, the molding processability is improved. The average degree of polymerization is measured in accordance with JIS K 6720-2.

[0024] The PVC resin may be either a hard vinyl chloride resin or a soft vinyl chloride resin, but the hard vinyl chloride resin is preferred because it provides a molded product with high surface hardness and excellent scratch resistance.

[0025] The MMA-based resin is a polymer in which the proportion of repeating units derived from methyl methacrylate (MMA) (hereinafter also referred to as "MMA units") is 80% by mass or more relative to the total repeating units. The MMA-based resin may be a homopolymer of MMA, or a copolymer of MMA and a (meth)acrylate other than MMA. Incidentally, (meth)acrylate is a general term for methacrylate and acrylate. When the MMA-based resin is a copolymer, it may be a random copolymer or a block copolymer. The MMA-based resin contained in the alloy resin may be one type or two or more types.

[0026] The proportion of MMA units in the MMA-based resin is preferably 80% by mass or more, more preferably 90% by mass or more, based on all repeating units. When the proportion of MMA units is equal to or more than the lower limit of the above range, moldability is improved.

[0027] Examples of (meth)acrylates other than MMA include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and 2-ethylhexyl methacrylate. The (meth)acrylates other than MMA used in the MMA-based resin may be one type or two or more types.

[0028] The weight average molecular weight of the MMA resin is preferably 10,000 to 600,000, more preferably 20,000 to 400,000. When the weight average molecular weight of the MMA resin is equal to or higher than the lower limit of the above range, the pencil hardness is improved. When the weight average molecular weight of the MMA resin is equal to or lower than the upper limit of the above range, the strength is improved.

[0029] The number average molecular weight of the MMA resin is preferably 5,000 to 300,000, more preferably 10,000 to 200,000. When the number average molecular weight of the MMA resin is equal to or higher than the lower limit of the above range, the pencil hardness is improved. When the number average molecular weight of the MMA resin is equal to or lower than the upper limit of the above range, the strength is improved. The weight average molecular weight and number average molecular weight are average molecular weights measured using gel permeation chromatography in terms of polystyrene.

[0030] The melt flow rate (MFR) of the MMA resin is preferably 1.0 g / 10 min or more and 20 g / 10 min or less, more preferably 2.0 g / 10 min or more and 15 g / 10 min or less. If the MFR of the MMA resin is equal to or more than the lower limit of the above range, the processability is good. If the MFR of the MMA resin is equal to or less than the upper limit of the above range, the pencil hardness is improved. The MFR is measured in accordance with JIS K 7210 under conditions of a load of 37.3 N and a temperature of 230°C.

[0031] The total proportion of the PVC resin and the MMA resin in the alloy resin is preferably 80 mass % or more, more preferably 85 mass % or more, and even more preferably 90 mass % or more, based on the total mass of the alloy resin.

[0032] The mass ratio of the PVC resin to the MMA resin to be melt-kneaded is preferably 20:80 to 90:10, more preferably 50:50 to 80:20. The higher the ratio of the PVC resin, the more improved the solvent resistance. The higher the ratio of the MMA resin, the more improved the scratch resistance.

[0033] The alloy resin produced in the present invention may contain additives such as heat stabilizers, light stabilizers, lubricants, and fillers, if necessary, within the range that does not impair the effects of the present invention. The form of the alloy resin to be produced is not particularly limited, and may be, for example, a pellet form. For example, the alloy resin may be extruded in a strand form from the tip of the twin-screw extruder 10, and cut into pellets while being cooled by pouring water on it.

[0034] [Method of manufacturing molded products] The method for producing a molded article of the present invention is a method for obtaining a molded article by molding an alloy resin produced by the method for producing an alloy resin of the present invention. The method for producing a molded article of the present invention can adopt a known embodiment except that the alloy resin produced by the method for producing an alloy resin of the present invention is used. In the present invention, a pellet-shaped alloy resin produced by the method for producing an alloy resin of the present invention may be used, or a die may be provided downstream of the twin-screw extruder, and molding may be performed continuously after melt kneading.

[0035] The pencil hardness of the surface of the molded article is preferably F or more, more preferably H or more. When the pencil hardness is equal to or more than the lower limit, the surface of the molded article has excellent scratch resistance. The pencil hardness of the surface of the molded article is measured in accordance with JIS K5600-5-4.

[0036] As described above, in the present invention, a powdered PVC resin is added to a molten MMA resin and melt-kneaded. This allows the PVC resin to be sufficiently melt-kneaded into the MMA resin while suppressing yellowing of the PVC resin with a short thermal history. Therefore, a molded product with excellent transparency and scratch resistance can be produced. The uses of the molded article of the present invention are not particularly limited, and examples thereof include vehicles, building materials, and home appliances. EXAMPLES

[0037] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0038] [Transparency] The molded products produced in each example were visually inspected and rated according to the following criteria. ○: No yellowing was observed on the molded product. ×: Yellowish discoloration was observed on the molded product.

[0039] [Pencil hardness] The pencil hardness was measured in accordance with JIS K5600-5-4.

[0040] [Example 1] A die was installed downstream of the twin-screw extruder 10 shown in Figure 1, and the resin was extruded in the form of strands, which were then cut into pellets while being cooled by pouring water over them. The molded pellets were fed into an injection molding machine to produce plate-shaped molded products. When the length from the rear end to the front end of the cylinder 12 is taken as 1, the main hopper 14 was positioned 1 / 4 from the rear end of the cylinder 12, and the side feeder 16 was positioned 1 / 2.7 from the rear end of the cylinder 12. As the MMA-based resin, acrylic pellets VH-001 (trade name, manufactured by Mitsubishi Chemical Corporation, proportion of MMA units: 90 mass%, weight average molecular weight: 90,000, number average molecular weight: 50,000, MFR: 2.0 g / 10 min) were fed from the main hopper 14, and as the PVC-based resin, powder-like TJZ-2310 (trade name, manufactured by Shin-Etsu Polymer Co., Ltd., proportion of vinyl chloride units: 87 mass%, average degree of polymerization: 700) was side-fed from the side feeder. The mass ratio of the PVC-based resin to the MMA-based resin was 70:30. The temperature of the high temperature region upstream of the side feeder 16 of the cylinder 12 was set to 190 to 200°C. The temperature of the side feed portion of the cylinder 12 where the side feeder 16 was provided was set to 170 to 180°C. The temperature of the portion of the cylinder 12 on the tip side of the side feed portion was set to 170 to 180°C.

[0041] [Example 2] Molded articles were produced in the same manner as in Example 1, except that the mass ratio of the PVC-based resin to the MMA-based resin was changed as shown in Table 1.

[0042] [Comparative Example 1] Molded articles were produced in the same manner as in Example 1, except that the mass ratio of the PVC-based resin to the MMA-based resin was changed as shown in Table 1 and both the PVC-based resin and the MMA-based resin were fed from the main hopper 14.

[0043] The production conditions and evaluation results of each example are shown in Table 1.

[0044] [Table 1]

[0045] As shown in Table 1, the molded articles of Examples 1 and 2, in which powdered PVC resin was side-fed into molten MMA resin, had excellent transparency, high pencil hardness, and excellent scratch resistance. On the other hand, the molded product of Comparative Example 1 in which both the PVC resin and the MMA resin were fed from the main hopper was inferior in transparency, had low pencil hardness, and was also inferior in scratch resistance. [Explanation of symbols]

[0046] 10: twin-screw extruder, 12: cylinder, 14: main hopper, 16: side feeder.

Claims

1. A method for producing an alloy resin, comprising adding a powdered vinyl chloride resin to a molten methyl methacrylate resin (excluding those in which an ethylene copolymer is mixed and melted), and melt-kneading the mixture to obtain an alloy resin, comprising the steps of: A method for producing an alloy resin, comprising: using a twin-screw extruder, feeding the methyl methacrylate resin from a main hopper on the upstream side of a cylinder; and side-feeding the powdered vinyl chloride resin to melt-knead it with the molten methyl methacrylate resin.

2. 2. The method for producing an alloy resin according to claim 1, wherein a temperature of a portion of a cylinder of the twin-screw extruder through which the vinyl chloride resin is side-fed is 160°C or higher and 190°C or lower.

3. A method for producing a molded article, comprising molding an alloy resin produced by the method for producing an alloy resin according to claim 1 or 2 to obtain a molded article.

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