JP2007253459A - Injection molding method of resin and manufacturing method of molded welded part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method of a resin capable of molding a large-sized injection-molded product in a fast molding cycle without deforming the same, and a manufacturing method of a molded welded part using the injection molding method. <P>SOLUTION: In the injection molding method of the resin for obtaining the injection-molded product by filling a mold, which is constituted of the cavity main body formed by a fixed mold and a movable mold and a core, with the molten resin and cooling and solidifying the charged molten resin, the core has a structure detachable with respect to the mold and the core is arranged to the outside of the molded product to inject the resin in the mold. After the resin is cooled and solidified, the core is ejected into the cavity using the ejector means provided in the mold to integrally take out the core and the molded product. Further, the manufacturing method of the molded and welded part for welding the molded product, which is integrally ejected along with the core by the injection molding method of the resin, to another part along with the core is also disclosed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection molding technique that enables a large injection-molded product made of a resin to be molded without deformation and at a fast molding cycle, and a manufacturing method for obtaining a weld-molded part of a large molded product.

  Conventionally, tank-shaped hollow molded products have been mainly molded by blow molding. When gas barrier properties and chemical resistance are required, multilayer blow with a material having excellent gas barrier properties and chemical resistance has been used.

  However, blow molding has problems such as lack of thickness uniformity, difficulty in modularization, and a long molding cycle, and a method that enables molding of a hollow molded product by injection molding has not yet been realized. It was.

  In particular, as a method for obtaining a tank-shaped hollow body by an injection molding method, generally, an upper side and a lower side are formed by hot plate welding or the like after injection molding of a box-shaped molded body on the upper side and the lower side. The method etc. which heat-seal | fuse and heat it to make an integral molded object can be considered. However, since many tank products are required to have high impact strength, it has been necessary to mold them with a material having low rigidity at high temperatures or a flexible material.

  However, when a box-shaped molded body is injection-molded with a low-rigidity material or a flexible material at high temperatures, problems such as poor mold release due to resin hugging, deformation due to an ejector, and a significant increase in molding cycle occur. It was difficult to get. In addition, there is also a problem that the molded product is deformed due to shrinkage after mold release and warpage is increased.

  On the other hand, an injection molding method using a mold having a cavity and a removable insert has been proposed (Patent Document 1).

However, this method has a drawback in that an ejecting device is required outside the mold and the molding equipment becomes complicated.
JP 2000-309040 A (Claims)

  An object of the present invention is to provide a resin injection molding method that enables a large injection molded product to be molded in a fast molding cycle without deformation, and a method for manufacturing a molded welded part using the resin injection molding method. There is to do.

  The injection molding method of the present invention that achieves the above-mentioned object comprises the following configuration (1).

(1) In a resin injection molding method for obtaining a molded product by filling a mold composed of a cavity main body and a nest formed of a fixed side mold and a movable side mold with a molten resin and solidifying by cooling. The insert has a structure that can be removed from the mold, and the insert is placed outside the molded product to be resinized. After the cooling and solidification, the insert is provided in the mold. A resin injection molding method, wherein the insert and the molded product are integrally taken out by projecting the insert into the cavity using an ejector means.

  In the resin injection molding method of the present invention, more preferably, it has the following constitution (2) or (3).

(2) The resin injection molding method as described in (1) above, wherein a mold having a concavo-convex shape portion for preventing the insert from being removed from the molded product at the time of ejector is used as the mold.

(3) The depth or height of the concavo-convex portion of the concavo-convex shape portion of the nesting is the depth or height of the concavo-convex portion = 3 mm ± (linear expansion coefficient × mold temperature × material rigidity at mold temperature / 10). The resin injection molding method according to the above (2), wherein a certain nest is used.

  Moreover, the manufacturing method of the molded welding part concerning this invention consists of the following structures (4).

  (4) Molding characterized in that a molded product taken out integrally with the insert by the resin injection molding method according to (1), (2) or (3) is welded to the other components together with the insert. Manufacturing method for welded parts.

  In the method (4), for example, a mold composed of a cavity main body and a nest formed of a fixed mold and a movable mold is filled with molten resin, and a molded product is obtained by cooling and solidifying. In the injection molding method, the insert has a structure removable from the mold, the insert is disposed outside the molded product, and the insert is placed in the cavity by ejector means provided in the mold. This is a method in which the insert and the molded product are taken out integrally by protruding, set in a welding machine in a subsequent process with the insert attached to the molded product, and welded with another molded product to obtain a product.

  In the present invention, the molded product is supported by the removable insert, and the insert portion is protruded, so that it is possible to perform molding while suppressing the deformation of the molded product and the mold release failure.

  In addition, since the insert and the molded product are integrally taken out from the mold and cooled, the insert becomes a straightening mold, and it is possible to effectively suppress warping of the molded product after the mold is taken out. When ejecting the nesting part with the ejector pin, the mold release becomes smoother if an air ejector is used in combination with the molded part.

  Nesting suppresses warping and shrinkage of the molded product, and the nested product acts as a positioning jig for the welding machine, so that the welded surface of the molded product is accurate and manufactures welded parts with high welding strength and welding reliability. Can do.

  According to the method of the present invention, a metal insert along the outer periphery of a molded product is provided in a resin mold, and the insert is protruded to form a material with low rigidity, soft material, or slow solidification at high temperatures. Even a molded product can be produced with a fast molding cycle and without deformation, and further, it is excellent in post-workability, and an inexpensive and high-quality product can be obtained.

  Hereinafter, one embodiment of the resin injection molding method of the present invention will be described with reference to FIGS. The mold used when carrying out the method of the present invention includes a fixed mold 1 and a movable mold 2 shown in FIG. 1, an ejector means 7 for removing the molded product from the cavity, and a protrusion that fits into the cavity. Nest 4 made. The insert 4 used in the present invention has a structure arranged outside the molded product.

  In the resin injection molding method of the present invention, a mold constituted by a cavity body formed by the fixed side mold 1 and the movable side mold 2 and a nest 4 is filled with molten resin, and is cooled and solidified. In this method, the insert 4 has a structure that can be removed from the mold, and the insert 4 is disposed outside the molded product. After the cooling and solidification of the product, the insert 4 and the molded product are taken out integrally by projecting the insert 4 into the cavity using the ejector means 7 provided in the mold. And

  A guide pin 5 for laterally projecting the movable die 2 is shown in FIG. 2 for positioning the insert 4 and preventing the drop when the molded product is ejected. With the movable die 2 retracted, the guide pin 5 is passed through the hole 6 formed in the insert 4 shown in FIG. 3, and the insert 4 is set in the movable die 2 or the fixed die 1 After the nesting 4 is set in the nesting groove 9 provided in, the movable mold 2 is advanced to close the mold. After the mold is closed, the injection unit 10 shown in FIG. 4 is advanced to fill the cavity with molten resin, and is cooled and solidified to form the molded product 3. The injection device at this time may be any existing device as long as it can fill the cavity with a molten resin, such as an inline screw type, a screw prepla type, a plunger type, a plunger prepla type, etc. An in-line screw type injection molding machine is particularly preferable.

  Next, as shown in FIG. 5, the molded article 3 is taken out together with the insert 4 by protruding the insert 4 into the cavity by ejector means 7 provided in the mold.

  Specifically, as the ejector means 7, various ejector means such as a pin shape or a rod shape can be favorably used.

  It is desirable that the insert 4 used in the present invention is provided with a concavo-convex shape portion as shown in FIG. Thereby, the effect that the molded product is brought into close contact with the nest by injecting the molten resin into the concavo-convex portion during the injection molding is exhibited.

The depth or height 8 of the concavo-convex portion of the nest 4 is preferably set in a range satisfying the following formula.
Concavity and convexity depth or height = 3 mm ± (linear expansion coefficient × mold temperature × material rigidity at mold temperature / 10)

  The units of linear expansion coefficient, mold temperature, and material rigidity at the mold temperature are mm / ° C., ° C., and MPa.

  An example of the manufacturing method of the welding product of this invention is demonstrated based on FIGS. The mold used in the present invention comprises a fixed mold 11, an intermediate mold 12, and a movable mold 13 shown in FIG. 11. A molded article with a metal insert is set in the intermediate mold 12 and the movable mold 13. A cavity is provided for each. With the movable mold 13 open, the molded product with a metal insert is set in the intermediate mold 12 and the movable mold 13. After setting the molded product, as shown in FIG. 12, the movable mold 13 is closed, the injection molding unit is advanced, and the molten resin is injected and injected into the secondary material inflow passage 14 provided at the welding interface of the molded product. To weld. At this time, since the metal insert serves as a correction die for the thermoplastic resin molded product and a positioning jig, the welded position of the molded product does not shift and good adhesive strength can be obtained. After cooling, the molded product welded by the ejector is ejected together with the insert, taken out from the molding machine, and a hollow molded product 15 with a metal insert shown in FIG. 13 is obtained. Thereafter, the metal insert is removed to obtain a hollow molded article 15.

  The welding method used in the present invention may be a method known per se, but hot plate welding, vibration welding, or injection welding is particularly preferable.

  Any thermoplastic resin may be used as long as it can be injection molded. For example, polyethylene, polypropylene, polystyrene, AS resin, ABS resin, methacrylic resin, polyvinyl chloride, polyamide, polycarbonate, polyethylene can be used. Terephthalate, polybutylene terephthalate, AAS resin, polyacetal, modified PPO, polyphenylene sulfide (PPS), polyimide, polyether ether ketone, ethylene-propylene copolymer, ethylene-butene copolymer, polybutene, ethylene-propylene-diene copolymer Polymers, polyolefin elastomers such as ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, polybutadiene, butadiene-acrylonitrile copolymer, polyisoprene, butene Diene elastomers such as isoprene copolymers and their hydrogenated products, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-isopropyl acrylate copolymers, ethylene-methyl methacrylate copolymers Acrylic elastomers such as copolymers, ethylene-ethyl methacrylate copolymers, polyester-based elastomers composed of aromatic dicarboxylic acids or their ester-forming derivatives and aliphatic diols and aliphatic polyethers, fats And polyamide elastomers composed of aliphatic polyamides composed of aliphatic diamines and aliphatic dicarboxylic acids and alicyclic polyamide-polyether block copolymers.

  In particular, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide (PPS), polyimide and low rigidity polyolefin elastomer, diene elastomer, acrylic elastomer, polyester, which are crystalline resins having a high molding temperature and mold temperature. A system elastomer and a polyamide elastomer are preferable.

  The present invention will be described more specifically with reference to the following examples. Each characteristic was measured by the following method.

(1) Cooling time that can be released:
The box shape having the shape shown in FIG. 7 was injection-molded, the cooling time was gradually shortened, and the shortest cooling time during which the molded product could be released was defined as the mold-releaseable cooling time.

(2) Warpage amount:
The box shape having the shape shown in FIG. 7 was injection-molded, the warpage amount of the molded product welded surface after being left for one day was measured with a three-dimensional dimension measuring machine, and the maximum value was taken as the warpage amount.

(3) Weldability:
Water was sealed in a box (having a schematic cross-sectional view shown in FIG. 13) obtained by welding two box-like shapes shown in FIG. 7 to prevent water leakage from the welded portion by applying an internal pressure of 5 MPa. The presence or absence was evaluated.

(4) Linear expansion coefficient of resin used for molding:
The linear expansion coefficient used for this invention is based on JIS-K7197, and uses the average expansion coefficient between -40 degreeC and +80 degreeC. The test piece size is obtained by cutting out a test piece having a length of 10 mm from a parallel portion of a JIS-K7139 multipurpose test piece A type obtained by injection molding.

(5) Material rigidity at the mold temperature of the resin used for molding:
A strip-shaped test piece having a length of 80 mm was cut out from a parallel portion of JIS-K7139 multipurpose test piece A type obtained by injection molding, and the bending elastic modulus measured according to ISO 178 with a bending tester with a high-temperature tank was defined as material rigidity. .

Example 1
The mold schematically shown in FIG. 1 was attached to an injection molding apparatus J350E manufactured by Nippon Steel Works, Ltd., and the cylinder temperature was set to 300 ° C. and the mold temperature was set to 130 ° C.

A PPS resin “Torelina” A670-X01 manufactured by Toray Industries, Inc. was introduced from the hopper of the molding machine, and an amount sufficient to fill the cavity was plasticized and then injected at a filling time of 9.5 sec. Thereafter, after cooling and solidifying in a 30-sec mold, mold opening was performed, and the insert was ejected by an ejector pin provided in the mold to release the mold. The PPS resin “Torelina” A670-X01 had a linear expansion coefficient of 10 × 10 ⁻⁵ (/ ° C.) and a 130 ° C. bending strength of 800 MPa.

  In such molding, there was no problem in nesting and releasability when the mold was opened, and a good molded product was obtained.

Examples 2 and 3
Molding was performed in the same manner as in Example 1 except that the dimensions of the concavo-convex portion of the nesting were as shown in Table 1. As in Example 1, there was no problem in nesting and releasability when the mold was opened, and a good molded product was obtained.

Comparative Example 1
The mold insert shown in FIG. 3 is fixed to the fixed mold with bolts, and the insert cannot be protruded into the cavity, and is molded as a normal two-sheet split mold, as in Example 1. did. Even when the cooling time was 150 sec, the protruding pin broke through the product, and the molded product could not be released.

Examples 4 and 5
Molding was performed in the same manner as in Example 1 except that the size of the concavo-convex portion of the nesting was as shown in Table 1.

  In Example 4, the nesting was released from the molded product when the mold was opened at a rate of about 1 shot per 10 shots or less, and a mold release defect occurred, but it was good in other respects. Example 5 was good in other respects although it was difficult to remove the insert from the molded product by hand after removal from the molding machine.

Examples 6-10
The molded products obtained in Examples 1 to 5 (represented as molded products 1 to 5 in Table 1, respectively) were set face-to-face with injection welding molds attached to J350E manufactured by Nippon Steel Works, Ltd. PPS resin “Torelina” A670-X01 manufactured by Toray Industries, Inc. was secondarily injected at a mold temperature of 60 ° C. and a cylinder temperature of 300 ° C. to obtain a welded hollow molded product.

  The obtained hollow molded article was filled with water, and a water pressure of 5 MPa was added to confirm the presence or absence of water leakage from the weld surface. There was no water leakage from the obtained molded product, and the weldability was good.

Comparative Example 2
The same procedure as in Examples 6 to 10 except that the molded product obtained in Comparative Example 1 (denoted as molded product 6 in Table 1) was used. Water leakage was confirmed from the welding surface of the obtained molded product, and welding failure occurred.

  The above results are shown in Tables 1 and 2.

It is the schematic sectional drawing which showed an example of the metal mold | die which can be used when implementing this invention method. It is a schematic sectional drawing of the aspect which opened one example of the metal mold | die which can be used when implementing the method of this invention. 1 is a schematic front view of a metal insert that can be used in carrying out the method of the present invention. FIG. It is a schematic sectional drawing explaining the state which, after installing the metal nest | insert which can be used in implementation of the method of this invention in a metal mold | die, an injection unit was advanced and the molten resin was filled into the cavity. It is the schematic explaining the state which filled the molten resin to the metal mold | die which can be used in implementation of the method of this invention, cooled, and opened the mold, and made the metal insert protruded by the ejector means. It is AA sectional drawing of the metal nest | insert shown in FIG. In an Example and a comparative example, it is a front view of the tank injection-molded in order to evaluate the mold release possible cooling time, the curvature amount, and weldability. FIG. 8 is a cross-sectional view taken along the line B-B of FIG. 7 of the tank shown in FIG. 7 that has been injection-molded in order to evaluate mold-releasing cooling time, warpage, and weldability in Examples and Comparative Examples. FIG. 8 is a cross-sectional view of the tank shown in FIG. 7 taken along the line C-C in FIG. 7 which is injection-molded in order to evaluate mold release possible cooling time, warpage amount, and weldability in Examples and Comparative Examples. It is an enlarged view of the welding part of the tank obtained as a result of implementing this invention method. It is sectional drawing of the injection mold which can be used for this invention method. It is the figure which showed the state which set the molded article with a metal nesting in the metal mold | die which can be used for this invention method, and was filled with the secondary material. It is sectional drawing which showed an example of the molded article obtained by injection welding by the method of this invention.

Explanation of symbols

1: Fixed side mold 2: Movable side mold 3: Molded article 4: Nest 5: Guide pin 6: Hole portion 7 formed in the nest 7: Ejector means 8: Depth or height 9 of the nest of the nest Nested groove 10: Injection unit 11: Fixed mold 12: Intermediate mold 13: Movable mold 14: Secondary material inflow path 15: Hollow molded product

Claims (4)

  In a resin injection molding method for obtaining a molded product by filling a mold composed of a cavity main body and a nest formed of a fixed side mold and a movable side mold with a molten resin and solidifying by cooling, the nest is The insert has a structure removable from the mold, and the insert is disposed outside a molded product. After the cooling and solidification, the insert is used by using an ejector provided in the mold. The resin injection molding method is characterized in that the insert and the molded product are integrally taken out by protruding into the cavity.   2. The resin injection molding method according to claim 1, wherein a mold having a concavo-convex shape portion for preventing the insert from being removed from a molded product at the time of ejector is used as the mold.   The depth or height of the concavo-convex portion of the nesting concavo-convex portion is the depth or height of the concavo-convex portion = 3 mm ± (linear expansion coefficient (mm / ° C.) × mold temperature (° C.) × mold temperature material 3. The resin injection molding method according to claim 2, wherein a nest having rigidity (MPa) / 10) is used.   A method for producing a molded welded part, comprising: welding a molded product integrally with the insert by the resin injection molding method according to claim 1, 2 or 3 to the other part together with the insert.

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