Method for producing resin molding

Abstract

To provide a resin molding that is streak-free and does not cause stringiness during production.SOLUTION: In a method for producing a resin molding, a molten resin ejected from an injection nozzle is molded using a mold equipped with a sprue bush and runners. In injection molding, a partition wall of the sprue bush and the runners are arranged so that they are not parallel to each other.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a resin molded product.

Background Art

[0002] As one of the ways to manufacture a resin molded product, there is injection molding. In injection molding, a molded product is obtained by injecting molten resin into a mold provided with a cavity having a desired shape. More specifically, molten resin is injected from the nozzle of an injection molding machine, and the molten resin is passed through members respectively called a sprue bush and a runner in this order, and the cavity of the mold is filled to obtain a molded product. Then, after the resin is solidified in the cavity, the mold is opened to take out the molded product and also extract the resin solidified in the sprue bush. At this time, if the cooling of the resin remaining in the sprue bush becomes insufficient, the resin may be stretched and a so-called stringing phenomenon may occur.

[0003] Conventionally, various proposals have been made regarding the sprue bush for the purpose of reducing such a stringing phenomenon. For example, Patent Document 1 discloses a joining structure of a nozzle and a sprue bush of an injection molding machine that can prevent stringing with a simple structure and can also prevent clogging in the passage of molten resin. Specifically, it is disclosed that a special structure adapter for preventing stringing of molten resin is provided between the nozzle and the sprue bush. Such an adapter is a passage through which molten resin passes, and is characterized in that the inlet side opening of the molten resin is smaller than the outlet side opening of the supply hole of the nozzle, and the inlet side opening is sized such that the molten resin hardens when the molding die is demolded.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in recent years, for resin molded products, in addition to no stringing occurring during manufacturing, further quality improvement has been demanded. Specifically, it has been demanded to provide a resin molded product without streaks. However, in the above-mentioned conventional technology, there has been room for further improvement, particularly in the appearance surface of resin molded products.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a resin molded product that provides a resin molded product without streaks without causing stringing during manufacturing.

Means for Solving the Problems

[0007] This invention aims to advantageously solve the above problems. [1] The method for manufacturing a resin molded product of the present invention is a method for manufacturing a resin molded product in which molten resin ejected from an injection molding nozzle is molded with a mold provided with a sprue bushing. The mold includes the sprue bushing and at least one cavity communicating with the sprue bushing via a runner. The sprue bushing has a nozzle touch portion that abuts against the injection molding nozzle and a sprue hole connected to the nozzle touch portion. The nozzle touch portion has at least one through hole through which the molten resin ejected from the injection molding nozzle passes and at least one partition wall partitioning the through hole. When the partition wall and the runner are projected onto a plane A perpendicular to the axis of the sprue hole during the manufacture of the resin molded product, they are arranged so as not to be parallel to each other. A melt of an alicyclic structure-containing resin composition containing an alicyclic structure-containing resin and a rubbery polymer is ejected from the injection molding nozzle and filled into the cavity through the sprue bushing and the runner.

[0008] [2] Further, in the method for manufacturing the resin molded product of [1] above, when manufacturing the resin molded product, on the plane A, for each of the partition wall and the runner, when an axis is set, it is preferable to include setting the angle formed by the two to be 5° or more.

Advantages of the Invention

[0009] According to the present invention, a resin molded product without streaks can be provided without causing wire drawing during manufacturing.

Brief Description of the Drawings

[0010]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

Figure 7

Figure 8

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, components denoted by the same reference numerals represent the same components. Each figure is merely a schematic diagram, and the specific dimensions of each component are not limited to those shown. Here, the method for manufacturing a resin molded product of the present invention is not particularly limited, and for example, it can be suitably used when manufacturing an optical lens.

[0012] The method for manufacturing a resin molded product of the present invention is a method for manufacturing a resin molded product in which molten resin injected from an injection molding nozzle is molded by a mold provided with a sprue bush. As a prerequisite, the mold includes a sprue bush and at least one cavity communicating with the sprue bush via a runner. Further, the sprue bush has a nozzle touch portion that abuts against the injection molding nozzle and a sprue hole connected to the nozzle touch portion. Furthermore, the nozzle touch portion has at least one through hole through which the molten resin injected from the injection molding nozzle passes and at least one partition wall partitioning the through hole. In the manufacturing method of the present invention, when the partition wall and the runner are projected onto a plane A perpendicular to the axis of the sprue hole during the manufacture of the resin molded product, they are arranged so as not to be parallel to each other, and an alicyclic structure-containing resin composition containing an alicyclic structure-containing resin and a rubbery polymer is injected from the injection molding nozzle, and the sprue bush and the runner are passed through and filled into the cavity. According to such a manufacturing method, a resin molded product without streaks can be provided without causing stringing during manufacture. Specifically, a defect in which the lightness of the resin in a part of the molded product (for example, the inside of the molded product) is different from that of the surrounding resin, and the streak-like defect is an example of a streak.

[0013] (Mold with sprue bush) FIG. 1A is a schematic plan view for explaining the partition wall and runner arrangement relationship of the nozzle touch part in the mold used in the manufacturing method of the present invention. The mold 100 includes a mold forming part 10 and a sprue bush 20. The mold forming part 10 is an inner wall surface of the mold that forms the molded product and the runner, and includes a cavity 1 for obtaining a molded product of the target shape, a gate 2 that serves as an inlet when filling the cavity with molten resin, and a runner 3 that allows the molten resin to reach the gate. The sprue bush 20 has a sprue hole (not shown in FIG. 1A) that communicates with the runner 3, and a partition wall 22 included in the nozzle touch part 21 and a through hole 23 partitioned by the partition wall 22. As shown in FIG. 1A, the partition wall 22 and the runner 3 are arranged so as not to be parallel to each other in the projection plane A of FIG. 1A, which is perpendicular to the axis of the sprue hole. Although the "axis of the sprue hole" is not shown, it is a hole that penetrates the center of the sprue bush in the longitudinal direction, and is an axis in the direction that coincides with the Z-axis direction with the projection plane of FIG. 1A as the XY plane. By arranging the partition wall 22 and the runner 3 in the manner shown in FIG. 1A, it is possible to effectively suppress the occurrence of stringing during manufacturing and the occurrence of streaks in the obtained molded product. As a result, it becomes possible to shorten the cycle time in the manufacture of resin molded products.

[0014] FIG. 1B shows a cross-sectional view taken along line A-A' of FIG. 1A. As shown in FIG. 1B, the mold forming portion 10 includes a fixed mold 11 and a movable mold 12. The molding is performed by filling the cavity 1 formed at the joining portion with molten resin in a state where the movable mold 12 is joined to the fixed mold 11. The filling of the resin into the cavity 1 is performed by injecting the resin into the sprue hole 25 which is a resin introduction path provided in the fixed mold 11. Although the structure of the sprue bush 20 will be described later with reference to FIG. 3, the molten resin flowing in from the sprue hole 25 passes through the nozzle touch portion 21 having the partition wall 22 and is introduced into each cavity 1 through the branched runners 3 and further through each gate 2 connected to the end of each runner. The molten resin introduced into the cavity 1 is cooled and solidified by the mold forming portion 10. After being solidified, the movable mold 12 is separated from the fixed mold 11, and the molded product is pushed out and taken out of the cavity 1. Note that the sprue hole 25 is mounted as a replaceable part in the form of the sprue bush 20 when wear and deformation occur. Also, in FIG. 1B, the sprue hole 25 is shown shortened from the viewpoint of clarity of illustration, but the relative dimensions between the sprue hole 25 and the nozzle touch portion 21 can be as shown in FIG. 3.

[0015] Here, as shown in FIG. 1A, when the partition wall 22 and the runner 3 are arranged so as not to be parallel to each other in the plane A, it is preferable that the angle formed between the two is 5° or more. If the angle between the partition wall 22 and the runner 3 is 5° or more, the generation of streaks in the obtained molded product can be more effectively suppressed. Specifically, it will be described with reference to FIG. 2.

[0016] Figure 2 is a partially enlarged view of Figure 1A. In Figure 2, the axes on the plane A of the runner 3 are shown as L3 and L3', and the axis on the plane A of the partition wall 22 is shown as L22. Let the angle formed by the axis L22 of the partition wall 22 and the axis L3 of the runner 3 be θ, and the angle formed by the axis L22 of the partition wall 22 and the axis L3' of the runner 3 be θ'. As is clear from Figure 2, the angle θ is smaller than the angle θ'. Thus, in the arrangement relationship between a certain partition wall and a runner, when a plurality of axes of the partition wall and the runner can be respectively assumed, it is preferable that the minimum angle among the angles formed between them is 5° or more. In other words, referring to Figure 2, it is preferable that the angle θ, which is the minimum angle among the angles between the partition wall and the runner that can be defined in the arrangement relationship shown in Figure 2, is 5° or more. Note that the upper limit of the angle between the axis of the partition wall and the axis of the runner depends on the number and shape of the partition walls and runners. As described above, the upper limit of such an angle is not particularly limited as long as the minimum angle is 5° or more.

[0017] Figure 3 shows a cross-sectional view for explaining a schematic structure of an example of a sprue bush provided in a mold used in the manufacturing method of the present invention. The sprue bush 20 shown in Figure 3 includes a nozzle touch portion 21 and a body 24. A sprue hole 25 exists inside the body 24. Although not shown in Figure 3, the sprue hole 25 communicates with the runner, and the molten resin can reach the cavity of the mold through the runner, gate, etc. An injection molding nozzle for injecting the molten resin injects the molten resin while being pressed against the recess of the nozzle touch portion 21, so that the molten resin passes through the through-hole 23 partitioned by the partition wall 22 and the sprue hole 25 and reaches a runner (not shown). Note that the nozzle touch portion 21 shown in Figure 3 includes one partition wall 22. Specifically, the planar shape of such a partition wall 22 can be as shown in Figure 4A.

[0018] FIG. 4A is a plan view showing an example of a nozzle contact portion of a sprue bush. The nozzle contact portion 21 includes two through holes 23 partitioned by one partition wall 22. In the illustrated embodiment, the partition wall 22 has a structure in which it is thin at the central portion and its thickness increases toward the end portion, but the shape of the partition wall that can be provided in the nozzle contact portion of the sprue bush is not limited to this. According to such a nozzle contact portion 21 having a structure including two through holes 23 partitioned by one partition wall 22, it is possible to effectively achieve both the effect of suppressing yarn pulling and the ease of flow of the molten resin.

[0019] FIG. 4B is a plan view showing another example of a nozzle contact portion of a sprue bush. The nozzle contact portion 21B includes three through holes 23B partitioned by a bifurcated partition wall 22B. In the illustrated embodiment, the partition wall 22B has a structure in which it is thin at the central portion and its thickness increases toward the end portion, similar to FIG. 4A, but the shape of the partition wall that can be provided in the nozzle contact portion of the sprue bush is not limited to this.

[0020] FIG. 4C is a plan view showing another example of a nozzle contact portion of a sprue bush. The nozzle contact portion 21C includes four through holes 23C partitioned by a cross-shaped partition wall 22C. In the illustrated embodiment, the partition wall 22C has a structure in which it is thin at the central portion and its thickness increases toward the end portion, similar to FIG. 4A, but the shape of the partition wall that can be provided in the nozzle contact portion of the sprue bush is not limited to this.

[0021] Note that the number of partition walls provided in the nozzle contact portion of the sprue bush is not limited to the above embodiment, and for example, it may be five or more.

[0022] Among the partition walls 22, 22B, 22C illustrated in FIGS. 4A to 4C and the nozzle touch part having five or more partition walls, from the viewpoint of the balance between the effect of suppressing yarn drawing and the ease of flow of the molten resin, it is most preferable to use the nozzle touch part having the partition wall 22 shown in FIG. 4A. For example, in a mold provided with two runners arranged such that the angle formed by their respective axes is 180°, in other words, in a so-called "two-up" mold, FIG. 5 illustrates an embodiment in which a sprue bush having the partition walls of the shapes shown in FIGS. 3 and 4A is adopted.

[0023] FIG. 5 is a schematic plan view for explaining an example of the relationship between the partition wall of the nozzle touch part and the runner arrangement. In FIG. 5, for the sake of clarity of the entire drawing, only the through hole 23 and the partition wall 22 are shown for the nozzle touch part. And in a two-up mold having two runners 3A whose axes form an angle of 180°, in other words, the axes coincide, and two cavities 1A connected to each runner 3A via gates (not shown), a sprue bush provided with the through hole 23 and the partition wall 22 is adopted. When the projection plane of FIG. 5 is plane A, the partition wall 22 and the runner 3A are arranged so as not to be parallel to each other. Therefore, it is possible to effectively suppress the occurrence of streaks in the molded product formed in the cavity 1A.

[0024] FIG. 6 is a schematic plan view for explaining another example of the partition wall of the nozzle touch part and the runner arrangement relationship. In FIG. 6, a sprue bush having a partition wall of the shape shown in FIGS. 3 and 4A is attached to a mold provided with two runners 3B. In the mold, in the connection region between the sprue bush and the runner, the two runners 3B are arranged such that the angle formed by their respective axes is 180°. And in other parts other than the vicinity of the connection region, each runner 3B has a U-shaped curved flow path for reasons such as mold area saving. Each runner 3B is connected to the cavity 1B via the gate 2B. Further, in FIG. 6, only the through hole 23 and the partition wall 22 are shown for the nozzle touch part for the sake of clarity of the whole drawing. As is clear from FIG. 6, the axis L3B of the runner and the axis L22 of the partition wall 22 are arranged so as not to be parallel to each other at least in the connection region between the sprue bush and the runner. For this reason, it is possible to effectively suppress the occurrence of streaks in the molded product formed in the cavity 1A.

[0025] Note that the number of runners provided in the mold is not limited to the above-described aspect, and can be, for example, 1 or more and 8 or less. Further, the runner may be branched at one or a plurality of locations. Also, the thickness of the runner is not particularly limited, and it is preferable that the thickness of the portion where the thickness is maximum, that is, the maximum thickness is 1 mm or more. The upper limit of the maximum thickness of the runner is not particularly limited, but can be, for example, 10 mm or less. Also, the cavity provided in the mold may have a maximum thickness of 1 mm or more, or 2 mm or more. The upper limit of the maximum thickness of the cavity is not particularly limited, but can be, for example, 30 mm or less. Note that the maximum thickness of the cavity may correspond to the maximum thickness of the obtained molded product.

[0026] (Nozzle for injection molding) The nozzle for injection molding is not particularly limited, and a nozzle provided in an injection molding machine according to the application can be used.

[0027] (Alicyclic structure-containing resin composition) The alicyclic structure-containing resin composition used in the production method of the present invention contains an alicyclic structure-containing resin and a rubbery polymer. By using a composition containing an alicyclic structure-containing resin and a rubbery polymer, a molded article excellent in transparency and strength can be provided.

[0028] <alicyclic structure-containing resin> The alicyclic structure-containing resin is a resin having an alicyclic structure in the main chain and / or side chain. Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure, an unsaturated cyclic hydrocarbon (cycloalkene, cycloalkyne) structure, etc. From the viewpoints of mechanical strength, heat resistance, etc., a cycloalkane structure or a cycloalkene structure is preferable, and among them, a cycloalkane structure is most preferable. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but when it is usually in the range of 4 to 30, preferably 5 to 20, more preferably 5 to 15, the characteristics of mechanical strength, heat resistance, and moldability of the pixel device are highly balanced and suitable.

[0029] Specific examples of the alicyclic structure-containing resin include (1) Ring-opening polymers of norbornene-based monomers and ring-opening copolymers of norbornene-based monomers and other monomers copolymerizable therewith by ring-opening, and hydrogenated products thereof, addition polymers of norbornene-based monomers and addition copolymers of norbornene-based monomers and other monomers copolymerizable therewith, etc., norbornene-based polymers, (2) Monocyclic cyclic olefin-based polymers and hydrogenated products thereof, (3) Cyclic conjugated diene-based polymers and hydrogenated products thereof, (4) Polymers of vinyl alicyclic hydrocarbon-based monomers and copolymers of vinyl alicyclic hydrocarbon-based monomers and other monomers copolymerizable therewith, and hydrogenated products thereof, hydrogenated products of aromatic rings of polymers of vinyl aromatic-based monomers and hydrogenated products of aromatic rings of copolymers of vinyl aromatic monomers and other monomers copolymerizable therewith, etc., vinyl alicyclic hydrocarbon-based polymers, etc. Among these, from the viewpoints of heat resistance, mechanical strength, etc., alicyclic structure-containing polymers are particularly preferable. Specific examples of such alicyclic structure-containing polymers include the ring-opening polymers and their hydrogenated products described in JP-A-5-279554, polymers obtained by subjecting norbornene derivatives having methacryl groups in the side chains, described in JP-A-2004-067985, to ring-opening polymerization with a metallocene catalyst or the like and then hydrogenating them, and copolymers of ethylene and cyclic olefins described in JP-A-2001-26693.

[0030] Specific examples of the alicyclic structure-containing resin include ZEONEX (registered trademark) manufactured by Nippon Zeon Co., Ltd., APEL (registered trademark) manufactured by Mitsui Chemicals, Inc., ARTON (registered trademark) manufactured by JSR Corporation, and TOPAS (registered trademark) manufactured by Polyplastics Co., Ltd.

[0031] <Rubbery polymer> The rubbery polymer used in the present invention is not particularly limited as long as it is incompatible with the alicyclic structure-containing resin and can form microdomains and disperse in the alicyclic structure-containing resin. However, an organic polymer compound is preferable, and a rubbery polymer having a glass transition temperature of 40°C or lower is particularly preferable. In the case of a block copolymerized rubbery polymer or the like having two or more glass transition temperatures, if the lowest glass transition temperature is 40°C or lower, it can be used as the rubbery polymer having a glass transition temperature of 40°C or lower in the present invention.

[0032] Examples of the rubbery polymer used in the present invention include randomly or block styrene-butadiene copolymers such as emulsion-polymerized or solution-polymerized styrene-butadiene rubber and high styrene rubber, and hydrogenated products thereof; isoprene rubber and hydrogenated products thereof; chloroprene rubber and hydrogenated products thereof; saturated polyolefin rubbers such as ethylene-propylene copolymers, ethylene-α-olefin copolymers, and propylene-α-olefin copolymers; diene polymers such as ethylene-propylene-diene copolymers, α-olefin-diene copolymers, diene copolymers, isobutylene-isoprene copolymers, and isobutylene-diene copolymers, and halogenated products thereof, hydrogenated products of diene polymers or halogenated products thereof; acrylonitrile-butadiene copolymers and hydrogenated products thereof; fluorine rubbers such as vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and propylene-tetrafluoroethylene copolymer; special rubbers such as urethane rubber, silicone rubber, polyether rubber, acrylic rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, propylene oxide rubber, and ethylene acrylic rubber; rubbery polymers containing an alicyclic structure that are incompatible with the alicyclic structure-containing resin that is the main component of the resin composition, such as copolymers of alicyclic structure-containing monomers and ethylene or α-olefin, terpolymers of alicyclic structure-containing monomers, ethylene, and α-olefin, ring-opening polymers of alicyclic structure-containing monomers, and hydrogenated products of ring-opening polymers of alicyclic structure-containing monomers; random copolymers of aromatic vinyl monomers and conjugated dienes such as styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber, and styrene-ethylene-butadiene-styrene rubber, and hydrogenated products thereof; linear or radial block copolymers of aromatic vinyl monomers and conjugated dienes such as styrene-butadiene-styrene rubber, styrene-isoprene-styrene rubber, and styrene-ethylene-butadiene-styrene rubber, and hydrogenated products thereof, styrene-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, 1,2-polybutadiene-based thermoplastic Examples of the thermoplastic elastomers include plastic elastomers, vinyl chloride-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers.

[0033] Among these, copolymers of aromatic vinyl-based monomers and conjugated diene-based monomers, and hydrogenated products thereof, have good dispersibility with the alicyclic structure-containing resin and are preferred. The copolymer of aromatic vinyl-based monomers and conjugated diene-based monomers may be a block copolymer or a random copolymer. Those in which parts other than the aromatic ring are hydrogenated are more preferred from the viewpoint of weather resistance. Specifically, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, and hydrogenated products thereof, styrene-butadiene random copolymer, etc. are mentioned.

[0034] In addition, the rubbery polymer preferably has a refractive index such that the difference from the refractive index of the alicyclic structure-containing resin to which it is added is 0.02 or less, more preferably 0.015 or less, and particularly preferably 0.01 or less. When those with a large difference in refractive index are mixed, they tend to become opaque when added in a large amount. Although the refractive index varies depending on the type of the alicyclic structure-containing resin, for example, the rubbery polymer can continuously change the refractive index by changing the ratio of the monomers or changing the number of unsaturated bonds in the main chain by hydrogenation or the like. It is preferable to select a rubbery polymer having an appropriate refractive index according to the refractive index of the alicyclic structure-containing resin to be used.

[0035] The blending amount of the rubbery polymer in the alicyclic structure-containing resin composition is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, preferably 1.0 part by mass or less, and more preferably 0.3 part by mass or less with respect to 100 parts by mass of the alicyclic structure-containing resin. If the blending amount of the rubbery polymer is at least the above lower limit value, the strength of the obtained molded product can be increased. If the blending amount of the rubbery polymer is at most the above upper limit value, the transparency of the obtained molded product can be increased.

[0036] <Other components> Furthermore, in addition to the rubbery polymer, the alicyclic structure-containing resin composition can contain other additives. Examples of the other additives include antioxidants, light stabilizers, heat stabilizers, antistatic agents, lubricants, and the like. There are no particular restrictions on the method of blending the rubbery polymer and other additives with the alicyclic structure-containing resin. For example, a method of mixing the alicyclic structure-containing resin and the additives while kneading with a kneader such as a roll, a kneader, an extrusion kneader, a Banbury mixer, or a feeder extruder; a method of dissolving the alicyclic structure-containing resin in an appropriate solvent, blending and mixing the additives therein, and then removing the solvent; and the like can be mentioned. The alicyclic structure-containing resin with additives blended therein as required is usually pelletized and then molded. There are no particular restrictions on the method of producing the pellets. However, after mixing the alicyclic structure-containing resin and the additives blended as required using a mixer such as a twin-screw kneader, extruding it in a strand shape, and finely cutting it with a pelletizer or the like, pellets can be obtained.

[0037] (Melt resin) In the production method of the present invention, the melt resin used in injection molding is the melt of the above-described alicyclic structure-containing resin composition. The method of preparing the melt resin is not particularly limited. For example, it can be obtained by introducing the above-described pellets into the cylinder through the hopper of an injection molding machine and melting them in the cylinder.

[0038] (Injection molding) In injection molding, with respect to the mold, as described above, when the partition wall of the sprue bush and the runner are projected onto a plane A perpendicular to the axis of the sprue hole of the sprue bush, it is necessary to arrange them so that they are not parallel to each other. After such an arrangement, the molten resin obtained above is injected into the sprue bush through the injection molding nozzle. The injection conditions and the like at this time are not particularly limited and can follow the conventional methods. Then, the molten resin passing through the sprue bush and the runner is filled and solidified in the cavity, thereby obtaining a molded product. In such a manufacturing method, stringing is less likely to occur during manufacturing, and the occurrence of streaks in the obtained molded product can be effectively suppressed. As a result, it becomes possible to shorten the cycle time and improve productivity in the production of resin molded products.

Examples

[0039] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, “%” and “parts” representing amounts are based on mass unless otherwise specified. In the examples and comparative examples, the stringing of the resin during manufacturing and the occurrence of streaks in the molded product were evaluated using the following methods, respectively.

[0040] (Stringing) The presence or absence of resin stringing was visually confirmed by appearance evaluation. When stringing of 20 mm or more was confirmed, it was determined that stringing occurred, and in other cases, it was determined that stringing did not occur.

[0041] (Occurrence of streaks) For 20 molded products obtained in each of the examples and comparative examples, light was incident and visual observation was carried out to confirm whether transparent streaks occurred.

[0042] (Alicyclic structure-containing resin) The following were used as the alicyclic structure-containing resin. Resin A: Hydrogenated ring-opening polymer of norbornene-based monomer (manufactured by Nippon Zeon Co., Ltd., product name "ZEONEX (registered trademark) T62R", glass transition temperature 154 °C) Resin B: Hydrogenated ring-opening polymer of norbornene-based monomer (manufactured by Nippon Zeon Co., Ltd., product name "ZEONEX (registered trademark) 330R", glass transition temperature 123 °C) Resin C: Addition copolymer of norbornene-based monomer and olefin (manufactured by Mitsui Chemicals, Inc., product name "APEL (registered trademark) 5014XH", glass transition temperature 135 °C)

[0043] (Examples 1 to 9, Comparative Examples 1 to 9) Pellets were obtained by blending 0.05 parts by mass of a hydrogenated styrene-butadiene-styrene block copolymer (SEBS manufactured by Asahi Kasei Chemicals Corporation, product name "Tuftec (registered trademark) H1051") with 100 parts by mass of an alicyclic structure-containing resin (Resins A to C). An injection molding machine (Fanuc Corporation, product name "ROBOSHOT (registered trademark) S-2000i100A", screw configuration: screw diameter = 32 mm, compression ratio = 2.0) was used with the resin temperature set as shown in Table 1 (resin temperature, injection speed, mold temperature, cooling time) to obtain a rectangular molded body with a thickness of 3 mm and a length and width of 65 mm. The type of sprue bush used in each example and comparative example, the number of runners provided in the mold, and the angle formed by the partition wall of the sprue bush and the runner (referred to as the partition wall angle) were as shown in Table 2. In Table 2, when the number of runners was two, the arrangement was such that the axes of the two runners coincided in plane A as shown in FIG. 5. Also, when the number of runners was four, as shown in FIGS. 1A and 4, two runners were arranged in alignment vertically and horizontally in plane A, and the common axes of the two upper runners and the common axes of the two lower runners were perpendicular to each other. Further, the partition wall denoted as partition wall shape I had the shape shown in FIG. 4A. In Comparative Examples 4 to 9, a normal sprue bush without a partition wall and without anti-drawing processing was used. The structure of the nozzle touch part of the sprue bush used in Comparative Examples 4 to 9 is shown in FIG. 8. As shown in FIG. 8, since the through hole 23D of the nozzle touch part 21D does not have a partition wall, it is in a state without anti-drawing processing. Then, for the molded product thus obtained, each evaluation was carried out according to the above. The results are shown in Table 2.

[0044]

Table 1

[0045]

Table 2

[0046] According to Table 2, in the mold, when the partition wall of the sprue bush and the runner are arranged so as not to be parallel to each other, in other words, when the partition wall angle is not 0°, injection molding is performed, it can be seen that the stringing during manufacturing can be effectively suppressed, and the occurrence of transparent streaks in the obtained molded product can be effectively suppressed. On the other hand, in Comparative Examples 1 to 3 in which the partition wall of the sprue bush and the runner are arranged in parallel in the mold, and in Comparative Examples 4 to 9 using a normal sprue bush without a partition wall having a stringing prevention effect, it can be seen that the stringing suppression effect and the generation suppression effect of transparent streaks cannot be achieved simultaneously.

[0047] Here, as an example, the generation mode of the transparent streaks will be described with reference to FIG. 7. FIG. 7 is a schematic plan view for explaining the arrangement relationship when the number of runners is four and two of their axes are arranged parallel to the partition wall. In the mode shown in FIG. 7, although a mold having the same structure as in FIG. 1A is used, the partition wall 22 and the runner 3C arranged in the left-right direction in the drawing are arranged parallel to each other. Therefore, as shown in the figure, transparent streaks S have occurred in the molded products formed in the cavities 1CL and 1CR respectively connected to the left and right runners 3C.

Industrial Applicability

[0048] According to the present invention, a resin molded product without streaks can be provided without causing stringing during manufacturing.

Explanation of Reference Numerals

[0049] 1, 1A, 1B, 1CL, 1CR cavities 2, 2B, 2C gates 3, 3A, 3B, 3C runners 10, 10C die forming parts 11 fixed die 12 movable die 20 sprue bush 21, 21B, 21C nozzle touch parts 22, 22B, 22C partitions 23, 23B through holes 24 body 25 sprue holes 100 die Axes of runners L3, L3’, L3B Axis of partition L22 S transparent streaks

Claims

Claim 1 A method for manufacturing a resin molded product by molding a molten resin ejected from a nozzle for injection molding with a mold having a sprue bush, wherein the mold includes the sprue bush and at least one cavity communicating with the sprue bush via a runner, the sprue bush has a nozzle touch portion that contacts the injection molding nozzle and a sprue hole connected to the nozzle touch portion, the nozzle touch portion has at least one through hole through which the molten resin ejected from the injection molding nozzle passes and at least one partition wall partitioning the through hole, when manufacturing the resin molded product, the partition wall and the runner are arranged so as not to be parallel to each other when projected onto a plane A perpendicular to the axis of the sprue hole, including ejecting a melt of an alicyclic structure-containing resin composition containing an alicyclic structure-containing resin and a rubbery polymer from the injection molding nozzle and filling the cavity through the sprue bush and the runner, A method for manufacturing a resin molded product. Claim 2 When manufacturing the resin molded product, including making the angle formed by the two be 5° or more when axes are set for each of the partition wall and the runner on the plane A, the method for manufacturing a resin molded product according to Claim 1.

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