Screw-type injection molding machine

Abstract

To provide an injection molding machine in which breakage of fibrous filler is suppressed in injection molding that kneads plasticized thermoplastic resin and fibrous filler.SOLUTION: A screw-type injection molding machine comprises a cylinder and a screw and has a supply section that supplies thermoplastic resin, a compression section that compresses plasticized thermoplastic resin, and a metering section. In the compression section, a downstream side of a top end face of a flight of the screw is curved. It is preferable that not only in the compression section but also in the metering section, the downstream side of the top end face of the flight of the screw is curved.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a screw-type injection molding machine. [Background technology]

[0002] Fibre fillers are mixed into thermoplastic resins to improve their strength and other properties. Injection molding machines are used to mold thermoplastic resins reinforced with fibrous fillers. Patent Document 1 discloses an injection molding machine in which a kneading disc and / or a plurality of throttle rings are provided in the metering zone of the screw (single screw) of the plasticizing device. However, this injection molding machine does not sufficiently suppress breakage of the fibrous filler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-197597 Summary of the Invention [Problem to be solved by the invention]

[0004] Provided is an injection molding machine that suppresses breakage of a fibrous filler during injection molding in which a plasticized thermoplastic resin and a fibrous filler are kneaded together. [Means for solving the problem]

[0005] In the injection molding machine of the present invention, the downstream side of the top end face of the flight of the screw (and the downstream side of the end face of the disk of the screw) is curved in the compression section.

[0006] The present invention relates to the following: [1] A screw-type injection molding machine having a cylinder and a screw, and having a supply section that supplies a thermoplastic resin, a compression section that compresses the plasticized thermoplastic resin, and a metering section, A screw-type injection molding machine in which the downstream side of the top end face of the screw flight (or the downstream side of the end face of the screw disk) in the compression section is curved. [2] The injection molding machine according to [1], wherein the curved arc has a radius of curvature R of 0.4 mm or more when viewed from a direction perpendicular to the axial direction of the flight. [3] The injection molding machine according to [1] or [2], wherein the downstream side of the top end face of the flight of the screw is curved in the metering section as well as in the compression section. [4] The injection molding machine according to any one of [1] to [3], wherein the upstream side of the end face is curved in addition to the downstream side of the end face. [5] A screw for a screw-type injection molding machine in which the downstream side of the top end face of the screw flight is curved. [6] A method for producing a molded product, which comprises performing injection molding using the injection molding machine according to any one of [1] to [4]. [Effects of the Invention]

[0007] In injection molding in which a plasticized thermoplastic resin and a fibrous filler are kneaded together, breakage of the fibrous filler is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an injection molding machine of the present invention. [Figure 2] FIG. 10 is a diagram illustrating an example of a screw segment having perfectly circular corner curvatures. [Figure 3] FIG. 1 is a schematic cross-sectional view of an example of a flight of a screw segment with elliptical corner curvature. [Figure 4] FIG. 10 is a schematic cross-sectional view of another example of a flight of a screw segment having an elliptical corner curvature. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, the screw injection molding machine is preferably an in-line screw injection molding machine.

[0010] Examples of the screw include a Unimelt screw, a Dulmage screw, and a Barrier screw. The curvature may form an arc of a circle (perfect circle) or an ellipse.

[0011] The radius of curvature R of the circle may be 0.4 mm or more, 0.5 mm or more, 0.7 mm or more, 0.8 mm or more, 1 mm or more, 1.2 mm or more, or 2 mm or more, and may be 20 mm or less, 10 mm or less, or 5 mm or less.

[0012] In the ellipse, the ratio of the length of the minor axis to the length of the major axis (minor axis / major axis) may be 0.2 to 0.99, 0.3 to 0.9, or 0.4 to 0.8. The length of the major axis of the ellipse may be 0.4 mm or more, 0.5 mm or more, 0.7 mm or more, 0.8 mm or more, 1 mm or more, 1.5 mm or more, 2 mm or more, or 3 mm or more, and may be 80 mm or less, 40 mm or less, 20 mm or less, or 10 mm or less. The length of the minor axis of the ellipse may be 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, 0.8 mm or more, or 1 mm or more, and may be 20 mm or less, 10 mm or less, or 5 mm or less.

[0013] There may be curvature on the upstream side of the flight apex as well as on the downstream side of the flight apex.

[0014] The screw and cylinder of the injection molding machine may be made of metal, particularly stainless steel, and may have a chrome-plated surface, for example.

[0015] FIG. 1 is a schematic diagram (partial cross-sectional view) of an injection molding machine according to the present invention. The injection molding machine 10 has a supply section 22 that supplies the thermoplastic resin and the fibrous filler, a compression section 24 that compresses the plasticized thermoplastic resin, and a metering section 26 that meters the thermoplastic resin and the fibrous filler. The thermoplastic resin and the fibrous filler are supplied from a supply port 32.

[0016] FIG. 2 is a diagram illustrating an example of a screw segment having a perfectly circular corner. This screw segment is composed of flights. Figure 2 is a cross-sectional view of the screw segment viewed from a direction perpendicular to the axial direction of the flights. In Figure 2, a indicates the clearance between the flight and the cylinder, b indicates the cylinder, dx indicates the cylinder diameter, e indicates the lead length, c indicates the downstream side of the top end face of the flight, and d indicates the upstream side of the top end face of the flight. The downstream side c of the top of the flight is curved rather than at a right angle. The curved portion may be a circle (a perfect circle) or an elliptical arc.

[0017] The downstream side c of the top end face of the flight has an arc with a radius of curvature R of 0.4 mm or more when viewed from a direction perpendicular to the axial direction of the flight. In addition to the downstream corner of the top of the flight, there may also be curvature at the upstream corner of the top of the flight (not shown).

[0018] Figure 3 is a schematic cross-sectional view of an example of a screw segment flight with an elliptical corner curvature, with the major axis of the ellipse perpendicular to the injection direction (material flow direction) indicated by the arrow.

[0019] Figure 4 is a schematic cross-sectional view of another example of a screw segment flight with an elliptical corner curvature, with the major axis of the ellipse parallel to the injection direction (material flow direction) indicated by the arrow.

[0020] In the present invention, even in the mixing element(s) or screw element(s) having protrusions, the screw segments, like the flights, have a curved, not right-angled, side downstream of the top of the protrusion.

[0021] There are no limitations on the fibrous filler and thermoplastic resin used in the method according to this embodiment, but specific examples are shown below.

[0022] [Fiber filler] The fibrous filler is, for example, a fiber bundle formed by bundling a plurality of monofilaments with a sizing agent or the like. Fiber bundles bound with a sizing agent or the like are easy to handle during kneading. The number of monofilaments constituting the fiber bundle is not particularly limited, but may be, for example, 300 to 3,000, or 1,100 to 2,200. The fibrous filler may be formed by continuously feeding a bundle of monofilaments as rovings to a twin-screw kneading extruder, or may be fed to the twin-screw kneading extruder in the form of chopped strands obtained by cutting the rovings. Chopped strands are preferred as the fibrous filler from the viewpoints of transportation and handling.

[0023] Examples of fibrous fillers include glass fiber, carbon fiber, aramid fiber, and basalt fiber. One type of fibrous filler may be used alone, or two or more types may be used in combination.

[0024] (glass fiber) The fiber diameter of the monofilaments forming the glass fiber bundle is not particularly limited, but is preferably in the range of, for example, 6 to 20 μm, and those with diameters of 6 μm, 10 μm, and 13 μm are commonly available on the market.

[0025] The fiber diameter can be determined, for example, by cutting the fibers perpendicular to the fiber direction, measuring the diameters of the cross sections by observing them under a microscope, and calculating the number average of the diameters of 100 or more fibers.

[0026] (carbon fiber) The type of carbon fiber is not particularly limited, but examples include PAN (polyacrylonitrile)-based carbon fiber, which uses acrylonitrile as the main raw material, pitch-based carbon fiber, which uses tar pitch as the main raw material, and rayon-based carbon fiber. For example, PAN-based carbon fiber is preferred from the viewpoint of composition purity and uniformity. The method for producing carbon fiber is not particularly limited.

[0027] The fiber diameter of the monofilaments forming the carbon fiber bundle may be, for example, more than 2 μm and not more than 15 μm, 3 to 12 μm, or 4 to 10 μm. If the fiber diameter is 2 μm or less, the rigidity of the fiber tends to decrease. If the fiber diameter exceeds 15 μm, the aspect ratio of the fiber (the ratio of length (L) to thickness (D): L / D) decreases, which may result in a decrease in rigidity, heat resistance, etc.

[0028] As the PAN-based carbon fiber, for example, "Pyrofil" manufactured by Mitsubishi Rayon Co., Ltd., "Torayca" manufactured by Toray Industries, Inc., or "Besfight" manufactured by Toho Tenax Co., Ltd. can be used.

[0029] Examples of pitch-based carbon fibers that can be used include "Dialead" (trade name) manufactured by Mitsubishi Plastics, Inc., "DonaCarbo" (trade name) manufactured by Osaka Gas Chemicals, and "Kureka" (trade name) manufactured by Kureha Chemical Industry Co., Ltd.

[0030] (aramid fiber) The aramid constituting the aramid fiber is preferably meta-aramid, para-aramid, or copolymerized para-aramid, more preferably para-aramid or copolymerized para-aramid, and even more preferably copolymerized para-aramid. Here, para-aramid refers to aramid having a structure in which each benzene ring is linearly linked via an amide group (CONH).

[0031] Specific examples of aramid fibers include meta-aramid fibers such as NOMEX, a trade name of DuPont, TEIJINCONEX, a trade name of Teijin Limited, Japan, METASTAR, a trade name of Yantai Company, China, and X-FIPER, a trade name of SRO Group, China, as well as TWARON, a trade name of Teijin Limited, KEVLAR, a trade name of DuPont, KERMEL TECH, a trade name of Kermel, HERACRON, a trade name of Kolon Industries, etc.

[0032] The fiber diameter of the monofilaments forming the aramid fiber bundle may be, for example, 1 to 50 μm, 3 to 30 μm, or 5 to 15 μm, from the viewpoint of increasing the bending strength and impact resistance of the resulting resin composition.

[0033] (Basalt fiber) Basalt fiber is made by melting the mineral basalt in a melting furnace and spinning it into fibers, and is usually composed only of basalt. Basalt fiber usually contains 55-65% by mass of silicon oxide (SiO2), 15-20% by mass of aluminum oxide (Al2O3), and iron oxides (FeO, Fe2O3), etc. Because recrystallization occurs during melt spinning, it tends to have a more homogeneous crystalline structure than other rock wools.

[0034] The fiber diameter of the monofilaments forming the basalt fiber bundle may be, for example, 2 to 15 μm, 6 to 13 μm, or 9 to 13 μm.

[0035] The fibrous filler is preferably glass fiber or carbon fiber.

[0036] In order to improve dispersibility, the fibrous filler may be surface-treated with a surface treatment agent such as an organic silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zirconate coupling agent, a silicone compound, a higher fatty acid, a fatty acid metal salt, or a fatty acid ester.

[0037] There are no restrictions on the binder for bundling the fibrous filler, but for example, when the fibrous filler is an organic fiber, a polar resin or the like is preferably used.

[0038] Examples of polar resins include thermosetting resins such as unsaturated polyesters, vinyl ester resins, epoxy resins, phenolic (e.g., resol) resins, urea-melamine resins, polyimides, urethane resins, copolymers thereof, and modified products thereof; and thermoplastic resins such as saturated polyesters, polyamides, acrylic resins, copolymers thereof, modified products thereof, and acid-modified polyolefins.

[0039] [Thermoplastic resin] Examples of thermoplastic resins include polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, various polyamides (such as PA6, PA66, PA46, PA12, and semi-aromatic PA), acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, methyl methacrylate-styrene (MS) resin, polyethylene, polypropylene, polyacetal, polyamide-imide, polyethersulfone, polyimide, polyphenylene oxide, polyphenylene sulfide (PPS resin), polyphenylsulfone, polyether ether ketone, polystyrene, syndiotactic polystyrene, liquid crystalline polyester (liquid crystal polymer), thermoplastic polyurethane, polyvinyl chloride, and fluororesin, as well as mixtures thereof. These may be used alone or in combination of two or more. Thermoplastic resins may be appropriately selected based on the required properties, such as heat resistance, chemical resistance, and moldability, depending on the intended use.

[0040] The thermoplastic resin preferably contains at least one selected from the group consisting of polypropylene, polyester, polyamide, polycarbonate, polystyrene, polyphenylene ether, ABS resin, AS resin, PPS resin, and liquid crystal polymer.

[0041] [Method of supplying thermoplastic resin and fibrous filler] The thermoplastic resin and the fibrous filler may be fed together or separately from the feed port of the injection molding machine. When the thermoplastic resin and the fibrous filler are fed together, it is preferable to feed pellets in which the fibrous filler is dispersed in the thermoplastic resin from the feed port.

[0042] [Resin composition] The resin composition can be produced by a method for producing a resin composition (or a molded product) by producing a thermoplastic resin and a fibrous filler in an extruder (or an injection molding machine). The resin composition (fibrous filler reinforced thermoplastic resin composition) maintains the inherent performance of the thermoplastic resin composition while improving its mechanical strength due to the fibrous filler. The resin composition has long fibers and is excellent in mechanical strength such as flexural modulus. The resin composition can be subjected to various molding methods such as injection molding, extrusion molding, compression molding, blow molding, and injection compression molding, as needed. In particular, it is suitable for use in injection molding. The resin composition is suitable for use in, for example, plastic parts that require mechanical strength. The resin composition is particularly suitable for use in automobile parts, building materials, electrical product parts, etc. [Example]

[0043] The present invention will be described below using examples, but the present invention is not limited to these examples.

[0044] Example 1 Using an extruder, pellets consisting of 70% by weight of acrylonitrile styrene resin (AS resin) and 30% by weight of glass fiber were formed, with the glass fiber dispersed in the AS resin. The pellets were fed through the feed port of the injection molding machine shown in Figure 1 and injection molded to obtain a molded product. For injection molding, an injection molding machine having screw segments shown in Figure 2 in the compression section and metering section was used. Breakage of the glass fiber was sufficiently suppressed in the molded product. [Industrial Applicability]

[0045] By using the injection molding machine of the present invention, it is possible to obtain molded articles from a thermoplastic resin composition containing a thermoplastic resin and a fibrous filler, with little breakage of the fibrous filler and with excellent physical properties such as mechanical strength.The thermoplastic resin composition containing a fibrous filler can be used as a raw material for automobile parts, parts for electric and electronic products, etc. [Explanation of symbols]

[0046] 10 injection molding machine 22 Supply section 24 Compression section 26 Measuring section 32 Supply port

Claims

1. A screw-type injection molding machine having a cylinder and a screw, and having a supply section that supplies a thermoplastic resin, a compression section that compresses the plasticized thermoplastic resin, and a metering section, A screw-type injection molding machine in which the downstream side of the top end face of the screw flight is curved in the compression section.

2. 2. The injection molding machine according to claim 1, wherein the curved arc has a radius of curvature R of 0.4 mm or more when viewed from a direction perpendicular to the axial direction of the flight.

3. 2. The injection molding machine according to claim 1, wherein the downstream side of the top end face of the flight of the screw is curved in the metering section as well as in the compression section.

4. 2. The injection molding machine according to claim 1, wherein the upstream side of the end face is curved in addition to the downstream side of the end face.

5. A screw for a screw-type injection molding machine in which the downstream side of the top end face of the screw flight is curved.

6. A method for producing a molded product, comprising injection molding using the injection molding machine according to any one of claims 1 to 4.

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