JP5262469B2 - Method for producing molded thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thermoplastic resin molding with excellent appearance, restraining a ring mark from generating. <P>SOLUTION: The method for manufacturing the molding includes: a supply process for bringing a pair of molding dies 10, having a cavity face 31 for forming a cavity 40, into an open state, and for supplying a thermoplastic resin 51 into the cavity; and a die clamping process for clamping the molding die by starting clamping of the molding die before finishing the supply of the thermoplastic resin. An electric motor serves as a driving source for a drive unit for opening and clamping the molding die, and acceleration of a mold clamping speed of the unit is 35 mm/sec<SP>2</SP>or less, at the start time of the die clamping process. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a thermoplastic resin molded body.

  Thermoplastic resin moldings made of thermoplastic resins are widely used in the fields of automobile interior parts, exterior parts, home appliances, housing equipment-related products, etc. because of their economy, light weight, and good formability.

It is known that such a thermoplastic resin molded body is manufactured by a molding method such as injection molding or compression molding. For example, the mold clamping operation is stopped or decelerated in the middle to supply the molten resin to the cavity space, and the molten resin is supplied at a thickness of the corresponding part of the molded product when the distance between the main parts of the bottom surface of the mold is 50 mm or less. When the molten resin supply is completed, the clamping is resumed or re-accelerated immediately before or after the completion of the molten resin supply, and the supply port is closed immediately after the molten resin supply is completed. A method for producing a molded product characterized by press molding is disclosed (see Patent Document 1).
JP-A-61-222917

According to the above method, a molded article having a good appearance can be obtained at a low pressure, but a ring mark may be formed depending on molding conditions. Therefore, it is required to suppress the generation of this ring mark.
In view of the above-described problems, an object of the present invention is to provide a method for producing a thermoplastic resin molded article that suppresses the generation of ring marks and has a good appearance.

The present inventors have found that the object of the present invention can be achieved by adopting the following configuration, and have completed the present invention.
The present invention includes a step of opening a pair of molds having cavity surfaces that form cavities, supplying a thermoplastic resin to the cavities, and the mold until the supply of the thermoplastic resin is completed. A mold manufacturing method including a mold clamping process for starting mold clamping and clamping the mold, wherein a drive source of a driving device that performs mold opening and clamping of the mold is an electric motor, and the mold clamping is performed The acceleration of the mold clamping speed of the apparatus at the start of the process provides a method for producing a thermoplastic resin molded body of 35 mm / sec ² or less.
In the present invention, “clamping” means that a pair of molds are relatively brought close to each other until a cavity having a predetermined dimension is formed by the cavity surface of each mold, or the dimension of the formed cavity does not change. This means holding the mold. “Die opening” means that a pair of molds are relatively separated from each other.

  According to the present invention, it is possible to provide a thermoplastic resin molded article that suppresses the generation of ring marks and has a good appearance.

  Hereinafter, it demonstrates in detail using figures. In addition, the same code | symbol shows the same member and the description is abbreviate | omitted.

〔Mold〕
First, the metal mold | die used in the manufacturing method of the thermoplastic resin molded object (henceforth a molded object only) based on this invention is demonstrated. The shape of the mold is not particularly limited as long as it is a mold used for normal injection molding or press molding.

  FIG. 1 is a view showing a mold preferably used in the present invention. The mold 10 is composed of a male and female pair of a female mold 20 and a male mold 30, and a cavity 40 is formed inside the female mold 20 and the male mold 30 in a closed state.

  The male mold 30 is provided with a plurality of temperature control passages 310 for heating or cooling the cavity surface 31 on the surface opposite to the cavity surface 31 forming the cavity 40. A heat exchange medium supply device (not shown) is connected. The cavity surface 31 is provided with at least one resin supply gate 320 for supplying the molten thermoplastic resin into the cavity 40. The resin supply gate 320 communicates with a resin supply passage 32 formed in the male mold 30. The resin supply passage 32 is connected to an injection nozzle of an injection device 50 that can melt and inject a predetermined amount of the thermoplastic resin, thereby supplying the molten thermoplastic resin into the cavity 40. it can.

  Similarly, in the female mold 20, a plurality of temperature control passages 220 for heating or cooling the cavity surface 21 are formed on the surface opposite to the cavity surface 21 forming the cavity 40. Is connected to a heat exchange medium supply device (not shown).

  In the pair of molds 10 including the female mold 20 and the male mold 30 described above, the male mold 30 is fixed to a stationary platen of a press device (not shown), the female die 20 is fixed to a movable platen, and is movable by a driving device. The mold 10 can be opened and clamped by moving the board in the direction of the fixed board. The female mold 20 may be fixed to the stationary platen, and the male mold 30 may be fixed to the movable platen, or both the female mold 20 and the male die 30 can be moved by changing the fixed platen to the movable platen. It may be. The drive source of the drive device that performs mold opening and mold clamping of the mold 10 is an electric motor.

[Supply process]
Subsequently, the manufacturing method of the molded object which concerns on this invention is demonstrated.
FIG. 2 shows the molten thermoplastic resin 51 from a resin supply gate 320 through a resin supply passage 32 formed in the male mold 30 in a cavity 40 formed by a pair of male and female molds 10 in an open state. It shows where the supply started. By using the mold in the open state as described above, the pressure applied to the mold can be reduced.

The mold cavity clearance at this time is not particularly limited as long as it is larger than the product thickness C ₄ as shown by C ₁ in FIG. 3, but if the skin material is not used, the product thickness is set to 20 mm or less. From the viewpoint of the appearance of the product.
The supply process in the present invention includes a case where the mold cavity clearance is set to a desired value in advance and the supply of the thermoplastic resin is started, and a case where the mold is once closed to a predetermined position and the thermoplastic resin is opened while the mold is opened. It may be either of the case where the supply of is started.

Note that the supply rate of the molten thermoplastic resin is preferably 600 cc / sec or more, more preferably 800 cc / sec or more. You may change this supply speed on the way. By setting the supply rate to 600 cc / sec or more, it is possible to prevent a decrease in the flow rate when flowing on the mold cavity surface, and to reduce the difference from the flow rate during mold clamping. For this reason, it is possible to prevent the transfer unevenness from occurring due to the difference in the transfer state on the mold surface.
The “feed rate” of the molten thermoplastic resin in the present invention refers to the injection capacity per unit time calculated from the resin capacity injected from the injection apparatus and the injection time.

[Clamping process]
After starting the supply of the molten thermoplastic resin, before the supply of the total resin amount is completed, the mold clamping is started, and after the supply of the molten thermoplastic resin is completed (see FIG. 3C ₃ ), the mold clamping is completed. (see Fig. 3C _4).
By starting the mold clamping before the supply of the thermoplastic resin is completed, shaping can be performed without stopping the flow of the molten thermoplastic resin, and the generation of ring marks can be suppressed. Further, by completing the mold clamping after the supply of the molten thermoplastic resin is completed, the resin can be supplied at a low pressure. The timing for starting the mold clamping is not particularly limited as long as the supply of the molten thermoplastic resin is completed.
The clamping speed when clamping the male and female dies is not particularly limited, but the maximum value is preferably more than 30 mm / sec and preferably not more than 300 mm / sec. By exceeding 30 mm / sec, the force required for mold clamping can be reduced. Moreover, it becomes possible to reduce the impact which concerns on a metal mold | die at the time of mold clamping by setting it as 300 mm / sec or less.

The acceleration of the mold clamping speed of the apparatus when starting the mold clamping needs to be 35 mm / sec ² or less, and more preferably 30 mm / sec ² or less.
By setting the acceleration to 35 mm / sec ² or less, it is possible to suppress a rapid change in the flow rate when the molten thermoplastic resin flows on the mold cavity surface, and the transfer state of the mold cavity surface can be suppressed. The difference can be made inconspicuous. As a result, it is possible to suppress the generation of ring marks in the molded body and provide a molded body having a good appearance. In particular, it has a concave and convex shape such as a grain on its surface, and a molded product having a groove depth of 50 μm or less has a great effect of suppressing a ring mark, and a molded product without a concave and convex shape such as a grain is more effective in suppressing a ring mark large.
In the present invention, “acceleration” refers to a value obtained by dividing the mold clamping speed by the time required for the mold to reach a predetermined mold clamping speed from a stopped state.

Although the mold clamping speed may be changed in the middle, it is preferable that the acceleration is 35 mm / sec ² or less when the speed is increased and the deceleration is 25 mm / sec ² or less when the speed is reduced.
This makes it possible to minimize the rapid change in the flow velocity flowing on the mold cavity surface and suppress the generation of ring marks.

[Cooling process]
In this invention, you may have a cooling process which cools the thermoplastic resin supplied after the clamping process.
As a specific cooling method for each of the cavity surfaces 21, 31, for example, water is provided in the temperature adjustment passage 220 provided in the female mold 20 shown in FIG. A method of cooling the cavity surfaces 21 and 31 by circulating a cooling medium such as
In addition, as cooling time, it is preferable that it is the temperature which does not deform | transform, when a molded object is taken out. Specifically, it is preferably 1 second to 60 seconds, and more preferably 1 second to 40 seconds. By setting the cooling time within the above range, it is possible to prevent a decrease in productivity.

After the above steps, the movable platen of the apparatus is moved, the cavity is opened, and the molded body obtained from the inside is taken out.
The molded body according to the present invention can be obtained by the above steps.
In the figure, 1 and 2 show an example of clamping in the vertical direction, but the clamping direction may be the vertical direction or the horizontal direction.

  Here, examples of the thermoplastic resin that can be used in the production method according to the present invention include thermoplastic resins that are usually used in compression molding, injection molding, extrusion molding, and the like. Examples of such resins include general polypropylene, polyethylene, acrylonitrile-styrene-butadiene block copolymers, polyamides such as polystyrene and nylon, polyvinyl chloride, polycarbonate, acrylic resins, styrene-butadiene block copolymers, and the like. And thermoplastic elastomers, thermoplastic elastomers such as ethylene / propylene rubber (EPM, EPDM), mixtures thereof, and polymer alloys using these.

  Moreover, these thermoplastic resins may contain fillers, such as an inorganic and organic filler normally used as needed. Moreover, you may contain various additives, such as various pigments normally used, a lubricant, an antistatic agent, and a stabilizer.

  Moreover, in the production method according to the present invention, a skin material is supplied in advance between a pair of male and female dies, and a molded body in which the skin material is bonded can be obtained. Examples thereof include woven and knitted fabrics such as moquettes and tricots, nonwoven fabrics such as needle punch carpets, metal foils, sheets and films of thermoplastic resins and thermoplastic elastomers, and the like.

Examples of the fibers constituting the nonwoven fabric include natural fibers such as cotton, wool, silk, and hemp, and synthetic fibers such as polyamide, polyester, and nylon. The nonwoven fabric may be composed of a single type of fiber or may be composed of two or more types of fibers.
Synthetic resin sheets and films include, for example, thermoplastic resins such as polypropylene and polyethylene, and polyolefin thermoplastic elastomer sheets and films. Good fusion with thermoplastic resins used as base resins. Are preferably used.

These skin materials may be multilayer skin materials having a foam layer or a backing layer.
Examples of the foam layer include polyolefin foams such as polypropylene and polyethylene, polyvinyl chloride foams, soft or semi-rigid polyurethane foams, and the like. Moreover, as a backing layer, a nonwoven fabric, a synthetic resin sheet, a film, etc. are mentioned, for example.
These multi-layer skin materials have good heat-fusibility with a thermoplastic resin from the viewpoint of adhesion to a base material portion made of a thermoplastic resin, or a molten thermoplastic resin is impregnated on the back surface of a skin material. Thus, those capable of bonding with the base resin are preferably used.

  The molded body obtained by the method according to the present invention is suitably used for interior parts and exterior parts such as automobile door trims and instrument panels, interior and exterior parts of household electrical appliances, and housing-related parts such as bathroom panels and floors. It is possible.

[Example 1]
400 × using the product name SLIM1016 (manufactured by Sato Iron Works, mold clamping force 980 kN, injection capacity 1600 cc) as the molding device, and the product name Sumitomo Noblen (manufactured by Sumitomo Chemical Co., Ltd., MFR = 30 g / 10 min) as the thermoplastic resin. A molded body having dimensions of 600 mm and a thickness of 2.5 mm was molded. Table 1 shows the results of visual confirmation of the ring mark generation state of the obtained molded body. In the table, ◯ indicates that the generation of the ring mark could not be visually confirmed, and x indicates that the generation of the ring mark could be visually confirmed.
<Molding conditions>
Resin temperature: 230 ° C
Mold temperature: 50 ℃
Cavity clearance to start supplying molten thermoplastic resin: 20mm
Clamping speed: 30mm / sec
Cavity clearance for supplying molten thermoplastic resin: 5mm
Acceleration time setting value when starting mold clamping: 5 sec
Pressurized surface pressure: 4 MPa
Cooling time: 30 sec

[Example 2]
Molding was performed in the same manner as in Example 1 except that the mold clamping speed was set to 50 mm / sec and the acceleration time set value for starting mold clamping was set to 5 sec.

[Comparative Example 1]
Molding was performed in the same manner as in Example 1 except that the acceleration time set value at the start of mold clamping was 3 sec.

[Comparative Example 2]
Molding was performed in the same manner as in Example 2 except that the acceleration time set value for starting mold clamping was 3 sec.

It is the figure which showed the cross section of the metal mold | die preferably used with the manufacturing method of the molded object which concerns on this invention. It is the figure which showed the supply process in the manufacturing method of the molded object which concerns on this invention. It is the figure which showed the relationship between a mold cavity clearance and supply time in a supply process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mold 20 Female mold 21, 31 Cavity surface 30 Male mold 32 Resin supply passage 220, 310 Temperature control passage 320 Resin supply gate 40 Cavity 50 Injection device 51 Thermoplastic resin

Claims (3)

A supply step of opening a pair of molds having a cavity surface forming a cavity and supplying thermoplastic resin to the cavity;
Before the supply of the thermoplastic resin is completed, the mold starts to be clamped and a mold manufacturing method including a mold clamping step of clamping the mold,
The drive source of the drive device that performs mold opening and clamping of the mold is an electric motor,
The method for producing a thermoplastic resin molded body, wherein an acceleration of a mold clamping speed of the apparatus at the start of the mold clamping process is 35 mm / sec ² or less. The method for producing a thermoplastic resin molded article according to claim 1, wherein the maximum clamping speed of the apparatus in the clamping process is 30 mm / sec or more and 300 mm / sec or less.   The method for producing a thermoplastic resin molded article according to claim 1 or 2, wherein a supply speed of the thermoplastic resin in the supplying step is 600 cc / sec or more.

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