Method for producing alloy resin and method for producing molded article

Abstract

To provide a method for producing an alloy resin in a more simple and rapid manner, and a method for producing a molded article.SOLUTION: There is provided a method for producing an alloy resin, in which a non-molten methyl methacrylate-based resin, a non-molten vinyl chloride-based resin independent of the methyl methacrylate-based resin, and other optional materials are mixed in a hopper of an injection molding machine, and then melted in a cylinder and injection-molded to obtain an alloy resin, wherein the non-molten methyl methacrylate-based resin is preferably in a pellet form and the non-molten vinyl chloride-based resin is preferably in a powder form.SELECTED DRAWING: None

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 vinyl chloride resins generally have excellent flame retardancy and chemical resistance, and are therefore widely used in applications such as pipes, general building materials, etc. It is also known that, in order to improve the properties of rigid vinyl chloride resins, acrylic resins, ABS resins, etc. are added to vinyl chloride resins as alloys, and the alloys are molded by injection molding or the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-053913 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a method for producing an alloy resin using a twin-screw extruder. Specifically, a methyl methacrylate resin is fed from a main hopper upstream of the cylinder of the twin-screw extruder, a powdered vinyl chloride resin is side-fed from a side feeder, and the vinyl chloride resin is added to the molten methyl methacrylate resin, followed by melt-kneading. As a result, an alloy resin suitable for producing molded articles with excellent transparency and scratch resistance is obtained.

[0005] A typical method for evaluating alloy resin materials, such as those described in Patent Document 1, involves thoroughly kneading the material using a twin-screw extruder, molding it into pellets, and then remelting the pellets in an injection molding machine to create dumbbell pieces or plates, and evaluating their performance. To obtain molded products from alloy resins that are a mixture of acrylic resin and vinyl chloride resin, the gold standard was to thoroughly knead the material using a twin-screw extruder before molding it.

[0006] However, while the inventors were studying and improving the physical properties of alloy resins through trial and error using various materials, they keenly felt the need for a simpler and faster method for producing alloy resins. Therefore, they abandoned the conventional method of kneading materials using a twin-screw extruder, which was considered to be the gold standard, and instead diligently investigated a simpler and faster method for producing alloy resins, which led to the completion of the present invention.

[0007] The present invention provides a method for producing an alloy resin and a method for producing a molded article in a simpler and faster manner. [Means for solving the problem]

[0008] The present invention has the following aspects. [1] A method for producing an alloy resin, in which a non-molten methyl methacrylate resin, a non-molten vinyl chloride resin independent of the methyl methacrylate resin, and other optional materials are mixed in the hopper of an injection molding machine, and then the mixture is melted in the cylinder and injection molded to obtain an alloy resin. [2] The method for producing an alloy resin according to [1], wherein the non-molten methyl methacrylate resin is in the form of pellets, and the non-molten vinyl chloride resin is in the form of powder. [3] The method for producing an alloy resin according to [1] or [2], further comprising mixing a non-molten polycarbonate resin as the optional material. [4] The method for producing an alloy resin according to any one of [1] to [3], wherein the alloy resin is opaque or cloudy. [5] The method for producing an alloy resin according to any one of [1] to [4], wherein a plurality of glass transition points are observed in the melting curve of the alloy resin. [6] A method for producing a molded article, comprising obtaining a molded article made of an alloy resin produced by the method for producing an alloy resin according to any one of [1] to [5]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a simpler and faster method for producing an alloy resin and a method for producing a molded article. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a graph showing a DSC curve of an evaluation sample of Example 1 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Alloy resin manufacturing method> A first aspect of the present invention is a method for producing an alloy resin, in which a non-molten methyl methacrylate resin (hereinafter referred to as "MMA-based resin"), a non-molten vinyl chloride resin (hereinafter referred to as "PVC-based resin") that is independent of the methyl methacrylate-based resin, and other optional materials are mixed in a hopper of an injection molding machine, and then the mixture is melted in a cylinder and injection-molded to obtain an alloy resin.

[0012] In this embodiment, there is no need to melt-knead the MMA resin and the PVC resin in advance using a twin-screw extruder or the like before feeding them into an injection molding machine. The MMA resin and the PVC resin are mixed in the hopper of the injection molding machine, and then melted in the cylinder and injection-molded, thereby making it possible to obtain the desired alloy resin more simply and quickly than conventional methods.

[0013] It is preferable that the MMA resin be fed into the hopper of the injection molding machine in pellet form, and the PVC resin be fed into the same hopper in powder form. In this way, when the size of the MMA resin is larger than that of the PVC resin, mixing in the hopper of the injection molding machine is improved, and an alloy resin with good physical properties can be more easily obtained.

[0014] The diameter (maximum diameter across) of the MMA resin pellets is preferably 1 mm or more, more preferably 2 mm to 10 mm, and even more preferably 3 mm to 8 mm. Here, the diameter of the MMA resin can be measured by known means such as vernier calipers or image analysis, and is the average value of 20 or more randomly selected pellets. When the diameter is within the above preferred range, mixing in the hopper of the injection molding machine is improved, making it easier to obtain an alloy resin with good physical properties.

[0015] The size (diameter) of each particle constituting the PVC resin powder is preferably less than 500 μm, more preferably 1 to 200 μm, and even more preferably 1 to 100 μm. Here, the diameter of the PVC resin is the average particle size measured on a mass basis using a known laser diffraction method. When the diameter is within the above preferred range, mixing in the hopper of the injection molding machine is improved, making it easier to obtain an alloy resin with good physical properties.

[0016] 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 mass% of all 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.

[0017] The proportion of vinyl chloride units in the PVC resin is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and particularly preferably 98% by mass or more, based on all repeating units.

[0018] 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.

[0019] 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 monomer copolymerizable with vinyl chloride may be used alone or in combination of two or more.

[0020] 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 greater 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 less than the upper limit of the above range, the molding processability is improved. The average degree of polymerization is measured according to JIS K 6720-2.

[0021] The PVC resin may be either a hard vinyl chloride resin or a soft vinyl chloride resin, but a hard vinyl chloride resin is preferred because it provides a molded product with high surface hardness and excellent scratch resistance.

[0022] 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 mass % or more of 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. (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.

[0023] 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 at least the lower limit of the above range, moldability is improved.

[0024] 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.

[0025] The weight-average molecular weight of the MMA resin is preferably 10,000 or more and 600,000 or less, and more preferably 20,000 or more and 400,000 or less. When the weight-average molecular weight of the MMA resin is equal to or more 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 less than the upper limit of the above range, the strength is improved.

[0026] The number-average molecular weight of the MMA resin is preferably 5,000 or more and 300,000 or less, and more preferably 10,000 or more and 200,000 or less. When the number-average molecular weight of the MMA resin is equal to or greater 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 less 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.

[0027] 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, and more preferably 2.0 g / 10 min or more and 15 g / 10 min or less. When the MFR of the MMA resin is equal to or greater than the lower limit of the above range, the processability is good. When 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.

[0028] The total proportion of the PVC resin and the MMA resin in the alloy resin is preferably 60% by mass or more, more preferably 70% by mass or more, 80% by mass or more, or even 90% by mass or more, based on the total mass of the alloy resin. This proportion makes it easy to obtain an alloy resin with good bending strength and impact strength.

[0029] The content of the MMA resin in the alloy resin relative to 100 parts by mass of the PVC resin is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass. The above ratios make it easy to obtain an alloy resin with good bending strength and impact strength.

[0030] When the MMA resin and the PVC resin are charged into the hopper of the injection molding machine, a non-molten polycarbonate resin may also be charged and mixed.

[0031] The polycarbonate resin to be fed into the hopper of the injection molding machine is preferably in the form of pellets. When the size of the polycarbonate resin is larger than that of the PVC resin, mixing in the hopper of the injection molding machine is improved, and an alloy resin with good physical properties can be more easily obtained.

[0032] The diameter (maximum diameter across) of the polycarbonate resin pellets is preferably 1 mm or more, more preferably 2 mm to 10 mm, and even more preferably 3 mm to 8 mm. Here, the diameter of the polycarbonate resin can be measured by known means such as a vernier caliper or image analysis, and is the average value of 20 or more randomly selected pellets. When the diameter is within the above preferred range, mixing in the hopper of the injection molding machine is good, and an alloy resin with good physical properties can be easily obtained.

[0033] The polycarbonate resin is not particularly limited, and examples thereof include aromatic polycarbonate resins and aliphatic polycarbonate resins, with aromatic polycarbonate resins being preferred. Specifically, an aromatic polycarbonate resin obtained by reacting an aromatic dihydroxy compound such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) with phosgene can be exemplified. The polycarbonate resin contained in the alloy resin may be one type or two or more types.

[0034] The MFR of the polycarbonate-based resin, measured according to ISO 1133 at a temperature of 300°C and a load of 1.2 kg, is preferably 10 g / 10 min or more, more preferably 15 g / 10 min or more, and even more preferably 25 g / 10 min or more. If the MFR of the polycarbonate-based resin is above the lower limit, the heat resistance temperature of the alloy resin is high and the strength of the molded product is high. The MFR of the polycarbonate-based resin is preferably 40 g / 10 min or less, more preferably 35 g / 10 min or less, and even more preferably 30 g / 10 min or less. If the MFR of the polycarbonate-based resin is below the upper limit, the dispersibility in the alloy resin is good and the impact strength is high. The preferred lower and upper limits of the MFR (unit omitted) of the polycarbonate resin can be arbitrarily combined. For example, 10-40 is preferred, 15-35 is more preferred, and 25-30 is even more preferred.

[0035] The content of the polycarbonate resin in the alloy resin relative to 100 parts by mass of the PVC resin is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass. With this ratio, an alloy resin with excellent impact strength is likely to be obtained.

[0036] The content of the polycarbonate resin in the alloy resin relative to 100 parts by mass of the MMA resin is preferably 70 to 130 parts by mass, more preferably 80 to 120 parts by mass, and even more preferably 90 to 110 parts by mass. The above ratios make it easy to obtain an alloy resin with excellent impact strength.

[0037] The alloy resin produced by the method of this embodiment may be blended with any other materials as needed, provided that the blending does not impair the spirit of the present invention. Examples of other materials include those commonly added to MMA-based resins and PVC-based resins, such as heat stabilizers, light stabilizers, lubricants, processing aids, impact modifiers, compatibilizers, and fillers.

[0038] The form of the alloy resin produced by the method of this embodiment is not particularly limited, and any form known as the form of an injection molded product can be exemplified.

[0039] The injection molding machine used in the manufacturing method of this embodiment is not particularly limited, and any commonly used commercially available injection molding machine can be used as long as it is equipped with a hopper upstream of the cylinder. However, injection molding machines equipped with a twin-screw extruder upstream of the cylinder are not common, and as far as the inventors know, there are no commercially available machines with such a configuration, and therefore they do not conform to the spirit of the present invention.

[0040] In this embodiment, the performance and operating conditions of the injection molding machine are not particularly limited as long as heating conditions and injection pressure suitable for melting the MMA-based resin and PVC-based resin can be achieved.

[0041] <Molded product manufacturing method> A second aspect of the present invention is a method for producing a molded article, which produces a molded article made of an alloy resin produced by the method for producing an alloy resin of the first aspect. The molded article of this aspect is obtained by the method of the first aspect. The uses of the molded article of this aspect are not particularly limited, and examples thereof include vehicles, building materials, and home appliances. [Example]

[0042] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0043] [Example 1] As an MMA-based resin, acrylic pellets VH-001 (trade name, manufactured by Mitsubishi Chemical Corporation, MMA unit ratio: 90% by mass, weight-average molecular weight: 90,000, number-average molecular weight: 50,000, MFR: 2.0 g / 10 min) in pellet form (size: 5 mm) were prepared. As the PVC-based resin, powdered TK-700 (straight polymer, manufactured by Shin-Etsu Chemical Co., Ltd., vinyl chloride unit ratio: 87% by mass, average degree of polymerization: 700) was prepared. The PVC-based resin was previously blended with a stabilizer, lubricant, and processing aid, which will be described later, in predetermined proportions. The pellets and powder prepared above were mixed with other materials in the weight parts listed in Table 1 and placed in the hopper of an injection molding machine. While blending in the hopper, the mixture was melted and mixed at 220-170°C and injection molded to obtain a thin plate as an evaluation sample. The injection molding conditions were an injection speed of 20-10 mm / sec, an injection pressure of 120-150 MPa, a holding pressure of 80 MPa, and a holding time of 5 seconds.

[0044] The other materials are as follows: "Stabilizer": Methyltin mercapto compound "Lubricant": Stearyl stearate "Processing aid": High molecular weight acrylic polymer "Impact modifier": High molecular weight acrylic polymer "Compatibilizer": Terpene resin (YS Resin PX1250, manufactured by Yasuhara Chemical Co., Ltd.)

[0045] [Example 2] An evaluation sample was obtained in the same manner as in Example 1, except that ACRYPET VRL40-001 (trade name, manufactured by Mitsubishi Chemical Corporation) in pellet form (size: 5 mm) was used as the MMA-based resin.

[0046] [Example 3] An evaluation sample was obtained in the same manner as in Example 1, except that the impact modifier was placed in the hopper together with the other materials.

[0047] [Example 4] An evaluation sample was obtained in the same manner as in Example 3, except that the amount of impact modifier added was increased.

[0048] [Example 5] An evaluation sample was obtained in the same manner as in Example 4, except that the compatibilizer and SD Polycarbonate 301-30 (manufactured by Sumika Polycarbonate Co., Ltd.) in pellet form (size: 3 mm) as the polycarbonate resin were placed in the hopper together with the other materials.

[0049] [Comparative Examples 1 to 5] Evaluation samples were obtained in the same manner as in Examples 1 to 5, except that each material was thoroughly mixed and pelletized in a twin-screw extruder before being placed in the hopper of the injection molding machine, and then the mixed pellets were placed in the hopper of the injection molding machine.

[0050] [Flexural strength (bending strength)] The flexural strength (unit: MPa) of the evaluation sample for each example was measured in accordance with JIS K7171.

[0051] [Charpy impact strength] The evaluation samples in each example were measured for Charpy impact strength (kJ / m 2 ) was measured.

[0052] [exterior] The evaluation sample for each example was visually inspected and evaluated according to the following criteria. Opaque: The evaluation sample was opaque enough that the opposite side could not be seen through it. Cloudiness: The evaluation sample was cloudy to the extent that the opposite side was visible through the sample. Transparency: The evaluation sample was transparent enough that the opposite side could be clearly seen through it.

[0053] [Table 1]

[0054] As shown in Table 1, molded articles made from alloy resins of Examples in which pelletized MMA-based resin and powdered PVC-based resin were mixed in the hopper of an injection molding machine were generally equivalent in flexural strength and impact strength to Comparative Examples in which the resins were thoroughly mixed and pelletized in advance in a twin-screw extruder, although their appearances were different. These results demonstrate that the production method of the present invention can produce alloy resins that exhibit physical properties sufficient for use as molded articles in applications where transparency is not a requirement. Furthermore, since it is not necessary to pelletize each material in advance using a twin-screw extruder, the method for producing the alloy resin according to the present invention is simpler and faster.

[0055] The evaluation sample of Example 1 was finely pulverized in a mortar and 10 mg was weighed into an aluminum pan to serve as a sample. The sample was then subjected to a first heating cycle under conditions of a starting temperature of 30°C, a measurement temperature range of 30 to 220°C, and a heating rate of 10°C / min. It was then cooled to 30°C at a temperature drop rate of 10°C / min. Subsequently, a second heating cycle was performed under conditions of a starting temperature of 30°C, a measurement temperature range of 30 to 220°C, and a heating rate of 10°C / min. Differential scanning calorimetry was then performed. A differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Corporation) was used for the measurement. As shown in FIG. 1, multiple glass transition points were observed in the resulting melting curve (DSC curve) (circled positions in the figure).

Claims

1. A method for producing an alloy resin, comprising mixing a non-molten methyl methacrylate resin, a non-molten vinyl chloride resin independent of the methyl methacrylate resin, and other optional materials in a hopper of an injection molding machine, and then melting and injection molding the mixture in a cylinder to obtain an alloy resin.

2. 2. The method for producing an alloy resin according to claim 1, wherein the non-molten methyl methacrylate resin is in the form of pellets, and the non-molten vinyl chloride resin is in the form of powder.

3. The method for producing an alloy resin according to claim 1 , wherein a non-molten polycarbonate resin is further mixed as the optional material.

4. The method for producing an alloy resin according to claim 1, wherein the alloy resin is opaque or cloudy.

5. The method for producing an alloy resin according to claim 1, wherein a plurality of glass transition points are observed in the melting curve of the alloy resin.

6. A method for producing a molded article, comprising obtaining a molded article made of an alloy resin produced by the method for producing an alloy resin according to any one of claims 1 to 5.

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