JPH03274127A - Apparatus and method for molding thermoplastic resin - Google Patents

Abstract

PURPOSE:To make integral mounting possible without providing a perfectly separate large-scale unit, in such a case that the molten resin in a mold is solidified while shearing force is applied to at least a part of the resin, by providing two or more hot runners communicating with a cavity to the mold and arranging pistons to the hot runners. CONSTITUTION:A molten resin is branched into hot runners 21, 21' through a sprue 20 to pass through the hot runners 22, 22' through pistons P, P' held to a heated state in the same manner and introduced into the cavity of a mold from gates 23, 23'. Compression force and reduced pressure force are cyclically applied to the pistons P, P' in usual during the period from the completion time of an injection process to pressure holding time and the molten resin in the cavity of the mold is moved or vibrated left and right as shown by an arrow. During the period when compression force and reduced pressure force in different directions are respectively applied once or more in usual, the molecular orientation of the molten resin in the cavity of the mold, the orientation of a filler and the elimination of weld are achieved and shearing force ts applied to the resin at the time of cooling and, therefore, the generation of 'sink' or 'void' is suppressed and the mold is cooled to form a solidified molded product.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thermoplastic resin molding device and its moldability, and relates to molecular orientation in a mold of a thermoplastic resin composition, particularly the orientation of a filler. This makes it possible to improve the weld strength and the appearance of the weld part, and to manufacture thick molded products with no internal voids.

[Conventional technology and its problems]

When thick thermoplastic resin molded products are manufactured using conventional injection molding methods, the surface of the molded product becomes depressed (sink marks), and voids occur inside the molded product, which significantly impairs the commercial value of the molded product. It has been known. In addition, depending on the shape of the molded product or for molded products that require two or more gates,
Welding occurs and this part has poor appearance, reduced strength,
There were problems such as deterioration of dimensional accuracy. In particular, in the case of thermoplastic resin compositions containing reinforcing materials or fillers in the form of plates or fibers, the deterioration of the weld portion was significant.

Various attempts have been made to improve these conditions by changing mold temperature, resin temperature, molding cycle, holding pressure, time, and other conditions, but the effects have been small.

As a method for solving the above-mentioned problems of conventional injection molding, Japanese Patent Application Laid-Open No. 179715/1986 discloses a method of solidifying the molten material while applying a shearing force to at least a portion of the molten material supplied to the mold cavity. A molding method,
Also disclosed is a unit for applying shear forces. Although the method disclosed in this publication is a promising method for solving the above-mentioned problems, the unit that applies the shearing force disclosed in this publication is a large-scale unit that is completely different from a conventional mold. Another problem was that it could not be installed in a general-purpose injection molding machine with a mold clamping force of 350 tons or less, for example.

[Means to solve the problem]

As a result of intensive study on a shearing force loading method that can be applied to general-purpose injection molding machines, the present inventors discovered a method of providing the shearing force loading means in a part of the mold, and completed the present invention.

That is, the present invention provides a molding device that supplies a molten thermoplastic resin to a mold and solidifies the resin while applying a shearing force to at least a portion of the molten resin in the mold, in which the device that applies the shearing force comprises: 2 in communication with the cavity within the mold.
This is a thermoplastic resin molding device characterized by a mold having a hot runner of more than 1,000 yen and a piston installed on the hot runner, and the piston is configured to act as a compressor to the sprue side runner when compressive force is applied. A thermoplastic resin molding device has a structure that doubles as a non-return pen that closes the flow path, and a thermoplastic resin molding device that supplies molten thermoplastic resin to a mold and presses the resin while applying a shearing force to at least a portion of the molten resin in the mold. In a method for molding a thermoplastic resin in which the molten resin is solidified, the shearing force applied to the molten resin during solidification is controlled by providing two or more hot runners in the mold that communicate with the mold cavity; The moldability of thermoplastic resin is characterized by applying pressure alternately to one side of each piston and reducing pressure to the other side.

The configuration of the present invention will be explained below.

First, regarding a specific example of the device used for moldability of the present invention,
This will be explained with reference to the attached drawings.

Fig. 1 is an example of a mold according to the present invention in which a piston is provided to apply shearing force to the molten resin, and Fig. 2 shows the state in which the piston moves when shearing force is applied by the apparatus shown in Fig. 1. It is something. Moreover, FIG. 3 shows a case where the type of piston that applies shearing force is changed, and FIG. 4 shows a case where four pistons that apply shearing force are used and the orientation direction can be controlled from two directions.

In Figure 1, the mold is located on the fixed side [8, 1, 2 + above the parting line [25]] and on the movable side [3°4.5
, 9: [lower than 25]], and a cavity is formed by the templates [2, 3). Fixed side [
1], hot runners [21-22.

P'] is provided. A mold cavity [23, 24, 23') is provided at the end of the hot runners 21 to 22''.This mold includes 4: a plate for the receiver, 5: a spacer block, and 6: an ejector plate. Top, 7: Lower ejector plate, 8: Fixed side mounting plate, 9: Movable side mounting plate, 11: Locate ring, 12 Varnish blue bushing, 13 Ni guide pin, 15 Ni guide bush 16:
Eject turbine, 17: Eject turbine push,
18: It naturally includes parts that are included in normal mold equipment, such as a return bin. Further, FIG. 3 shows a configuration in which a single piston for applying shear force is used to apply compression and reduced pressure. Furthermore, as shown in Fig. 4, it is possible to apply compression and vacuum pressure from two directions, so by selecting the piston that applies compression and vacuum pressure, it is possible to orient the piston in a desired direction or eliminate the orientation. It is possible.

Next, to explain the above diagram from the injection molding process, the first
In the figure, the molten resin branches through the sprue 20 to the hot runners 21 and 21', passes through the pistons P and P'' which are similarly heated, and passes through the hot runners 22 and 22'. ' is introduced into the mold cavity 24. Compression force and reduced pressure are normally applied periodically to the pistons P and P' between the end of the injection process and the time of pressure retention, and the pressure inside the mold cavity is The molten resin is moved or vibrated left and right as shown by the arrow.The instant in this state is shown in Figure 2, where the piston P moves to the right, closes the hot runner 21, and moves from the gate 23 to the cavity 24. This causes a compressive force or a movement of the molten resin, and together with this, the piston P'' similarly moves to the right, making it easier to transmit the load of reduced pressure or the compressive force of the piston P. In the next step, the pistons P and P' move in the opposite direction (to the left) and apply a force to the molten resin in the cavity 24 in the left direction. While compression and depressurization in different directions are usually applied one or more times each, molecular orientation of the molten resin in the mold cavity, orientation of the filler, and elimination of welds are caused, and shear force is generated during cooling. Because it is added, the occurrence of "sink" and "void" is suppressed, and the mold is cooled.
It is considered to be a solidified molded product. Next, the mold is opened at the parting line 25. At this time, a part of the runner is attached to the molded product in a cut state near 22.22' of the runner, and the mold is opened. The article is separated from the mold by an ejector turbine 16.

By repeating the above steps, the molded article of the present invention is manufactured.

Although the molding apparatus and molding method of the present invention have been explained above using the drawings, the present invention is not limited to the above.
As mentioned above, various measures can be taken except for providing a means for applying a shearing force within the mold. For example, in order to suitably apply compression and reduced pressure by the piston in the present invention, it is usually 50 to 1,000 kg/CJ1, taking into account the size, shape, and preferred orientation of the molded product. is suitable, and in order to apply it to various molded products, it enables stroke control and/or pressure control, for example,
In the case of the attached FIG. 1, it is preferable to use a mold formed by changing only the portions 26 to 26 below, that is, only a portion of the mold cavity.

Here, molded products that are highly effective using the molding apparatus of the present invention are ones that allow time to apply the necessary shear force until the molten resin solidifies in the mold, and usually the wall thickness of the molded product is is 1.5 or more, and it is preferable that the solidification time of the resin is extended to some extent by adding an instantaneous heating means for the molded article in the mold. In addition, resins to which the present invention is preferably applied include polyvinyl chloride; acrylic resins such as PMMA; polystyrene resins such as PS and old PS; polystyrene and acrylic esters such as ABS, AAS, MAS, and MEBS, acrylonitrile, etc. Copolymer resins with; PP, PRXTPX, and other polyolefins; Homo- to co-polyacetal resins; Nylon 6゜66.610.12, MXDA, and other crystalline to non-crystalline polyamide resins; PBT,
PET, PCTG, PCTAL, Vectra, and other crystalline, non-crystalline or liquid crystalline polyester resins; aromatic polycarbonate (PC), polyphenylene ether (PPE), polyphenylene sulfide (P)
PS), polysulfone, polyether ether ketone (PEEK), and other engineering plastics, resin compositions made by mixing two or more of these, and various thermoplastic or particulate materials as impact resistance modifiers. elastomers, various fibers,
It can also be suitably used as a composition containing fillers or reinforcing materials in various shapes such as powder, spheres, scales, plates, tetrapods, whiskers, etc.

〔Example〕

Hereinafter, a detailed explanation will be given using Examples and Comparative Examples.

Example 1 The shear force applying means is similar to that in FIG. 1, the parting line 25 is parallel to the line 26, the gate 22 is provided parallel to the parting line 25, and
Using a mold with a cavity of 12 x 130 mm, the molding method was (A) without applying shear force.

(B) Only the piston P is moved and only the runner on the piston P side is closed to form a single gate.

(C), molten resin is fed into the cavity and periodically 4
The molding of the present invention is solidified while applying a shearing force of 00 kg/cJI.

A molded article was manufactured using a polyacetal resin (manufactured by Mitsubishi Gas Chemical Company, trade name: Iupital FG25) containing 25% by weight of glass fiber. The injection molding machine is Toshiba 1.
5200B4, cylinder temperature 220°C, mold cavity surface temperature 110°C, and molding cycle 250 seconds.

The bending strength of the molded product obtained above was measured using DC320 manufactured by Shimadzu Corporation.
With the 00 type autograph, the distance between the fulcrums is 100[n[11
11 The results were measured at a bending speed of 5 mm/min and a temperature of 23° C., and the results are shown in Table 1 below.

Embodiment 2 As shown in FIG. 4, the shearing force loading means includes four pistons, the parting line 25 is parallel to the line 26, and the fan-shaped gate is provided parallel to the parting line 25. Using a mold with a thickness of 15 mm and a cavity of 100 mm angle, the molding method was (A), in which molten resin was injected from two points, the gates on the opposing piston A and B sides, and shearing force was applied. Molded without any problem.

(B), molten resin is injected from two points, the gates on the opposing piston A and B sides, and the pistons A and B are injected periodically for 500 min.
The molding of the present invention is solidified while applying a shearing force of kg/cal.

(C), molten resin is injected from two points, the gates on the opposing piston A and B sides, and the shearing force is first applied with the A and B pistons, and then the shearing force is applied with the CSD piston, which is repeated sequentially. The molding of the present invention is performed while solidifying.

A molded product was manufactured using a modified PPE resin (manufactured by Mitsubishi Gas Chemical, trade name: Iupiace Gl (30)) containing 30% by weight of glass fiber.The injection molding machine was Toshiba 15.
200B4, cylinder temperature 310°C, mold cavity surface temperature 120°C, and molding cycle 300 seconds.

From the molded product obtained above, the width in the piston CD direction, the width in the piston CD direction is 12M1, the thickness is 15mm, and the length is 100m.
A test piece of m was cut out and the bending strength was measured using DC32 manufactured by Shimadzu Corporation.
The results were measured using a 000 type autograph at a distance between fulcrums of 80 mm, a bending speed of 5 mm/mid, and a temperature of 23° C., and are shown in Table 2 below.

[Operation and effects of the invention]

As is clear from the detailed description of the invention, examples, and comparative examples, according to the apparatus and molding method of the present invention, the strength of the weld is extremely deteriorated even in the shape of the mold cavity where the weld occurs. Since the amount is small, it is possible to form a molded product with excellent strength, and even if the molded product is thick, voids will not occur. Furthermore, since the piston can be compactly attached to the mold, it is possible to control the anisotropy not only in the -axial direction but also in the biaxial direction, which has extremely industrial significance. It's expensive.

[Brief explanation of drawings]

Fig. 1 shows an example in which a piston that applies shear force to the molten resin is provided in the mold of the present invention, and Fig. 2 shows the state in which the piston moves when shear force is applied by the device shown in Fig. 1. be. Further, FIG. 3 shows a case where the type of piston that applies shearing force is changed, and FIG. 4 shows a case where four pistons that apply shearing force are used and the orientation direction can be controlled from two directions.

Claims (1)

[Claims] 1. A molding device that supplies a molten thermoplastic resin to a mold and solidifies the resin while applying a shearing force to at least a portion of the molten resin in the mold, wherein the device that applies the shearing force is ,
1. A thermoplastic resin molding apparatus, characterized in that the mold includes two or more hot runners communicating with a cavity, and a piston installed in the hot runners. 2. Claim 1, wherein the piston has a structure that doubles as a check pen that closes the flow path to the sprue side runner when compressive force is applied.
The thermoplastic resin molding apparatus described above. 3 In a thermoplastic resin molding method in which a molten thermoplastic resin is supplied to a mold and the resin is solidified while applying a shearing force to at least a portion of the molten resin in the mold, the molten resin is sheared during solidification. Two or more hot runners communicating with the mold cavity are provided in the mold, and a pressing force is applied to one side of each piston provided in the hot runners.
A thermoplastic resin molding method characterized by applying a reduced pressure to the other side alternately.