JP2000238104A - Method and apparatus for injection-molding thermoplastic resin and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a defective appearance by the formation of a weld line, the lowering of coloring properties, and others simply and inexpensively without causing the lowering of productivity by the extension of a cooling time and others by packing a molten resin into a mold within a specified time when mold clamping is done, and the temperature of the surface of the mold is at least a specified value. SOLUTION: A mold composed of a fixed side mold 10 and a movable side mold 12 is fitted to an injection molding machine, and the nozzle of the injection molding machine is connected to the sprue 14 of the mold 10. Each medium passage 26, 28 of a temperature adjusting apparatus is formed in the molds 10, 12. A heater installs a lamp unit 20 in which a lot of halogen lamps are arranged in a lamp housing, and the unit 20 is inserted/separated between/from the molds 10, 12. With the molding opened, the surface of the mold is heated at 500 deg.C or above by the heater. After that, mold clamping is done, when the surface temperature of the mold is 80 deg.C or above, the packing of a molten resin into the mold is started, and the resin is packed within 5 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article of a thermoplastic resin having a good appearance, and an injection molding method and apparatus therefor.

[0002]

2. Description of the Related Art Thermoplastic resins are used in various fields such as exterior parts and mechanical parts of vehicles, electric appliances, equipment, miscellaneous goods, etc. due to their ease of processing. Although various processing methods are used, molding is often performed by injection molding from the viewpoint of good productivity. In particular, in appearance parts, it is required to make appearance defects as inconspicuous as possible.In general, injection molding involves the formation of weld lines due to the confluence of molten resin and the decrease in color development caused by the orientation of the resin surface layer. Appearance defects are likely to occur. In order to make such appearance defects inconspicuous, a method of increasing the temperature of a mold is generally used. However, when the temperature of the mold is increased, it is necessary to lengthen the cooling time for solidifying the molten resin, so that there is a problem that productivity is reduced. As a method of solving this problem, a method has been proposed in which the temperature of only the surface of the mold is temporarily increased to a high temperature immediately before injection molding is performed. For example, Japanese Unexamined Patent Publication No. 57-195610 discloses a method in which a high-temperature heat medium and a low-temperature heat medium are arranged in a mold through separate flow paths to raise and cool the surface temperature of the mold. However, Japanese Patent Application Laid-Open No. 62-58286 discloses a method in which an inductor of a high-frequency transmitting device is sandwiched between a fixed mold and a movable mold and the surface temperature of the mold is increased by high-frequency induction heating. 63
Japanese Unexamined Patent Publication (Kokai) No.-95919 discloses a method in which a high-frequency induction coil is embedded in a portion of a mold to be heated and the temperature is increased by induction heating.

[0003]

However, in the above-mentioned methods using two types of heat medium or high-frequency induction heating, the inside of the mold is previously worked in accordance with the shape of the cavity, or the inductor is mounted. It has to be manufactured, and there is a problem that extra cost is required every time a new mold is manufactured. As a method capable of heating the surface of the mold irrespective of the shape of the cavity or the core, Japanese Patent Publication No. Hei 7-61670 and Registered Utility Model No. 30
No. 13428 proposes a method using radiant heat of a halogen lamp. However, the publication only describes the possibility that the halogen lamp could be used for injection molding, but does not disclose any specific technology, and based on these publications, has excellent appearance. It is difficult to come up with a method or an apparatus that can actually carry out the molding of the molded article. The present invention has been made in order to solve the above problems, without accompanying a decrease in productivity due to extension of the cooling time, and simple and inexpensive,
It is an object of the present invention to provide a method or an apparatus capable of improving appearance defects due to formation of a weld line and deterioration of color development.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies with the aim of providing a method for obtaining an injection molded article having a small surface investment and excellent surface appearance. It has been clarified that the object can be achieved by performing the reaction under specific conditions, and arrived at the present invention. That is, in the method of the present invention, in injection molding of a thermoplastic resin, in a state where a mold is opened, a heating device provided with a halogen lamp, preferably, a plurality of halogen lamps are provided and the output of each halogen lamp is individually set. By heating the mold surface to 500 ° C. or more in advance by a heating device having an adjustable function, the mold is clamped, and when the surface temperature of the mold is 80 ° C. or more, the molten resin is contained in the mold. Is started, and the molten resin is filled in the mold within 5 seconds. The apparatus of the present invention is an apparatus capable of performing the method.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As the injection molding apparatus and the mold used in the present invention, various well-known injection molding apparatuses or molds can be applied as they are. For example, a general in-line screw type injection molding machine is used. Can be used, and if the mold is a general injection mold that is divided into two parts or three parts on a fixed side and a movable side and has a sprue, a runner, a gate, a cavity, a core, and the like. There is no particular limitation. Further, a metal mold, particularly an iron mold, is preferable. As used herein, the iron mold includes a mold whose surface is subjected to a surface treatment such as chromium plating or nitriding. Also, after injection filling of the molten thermoplastic resin, in order to quickly reduce the temperature to a temperature that can be cooled and solidified,
It is desirable that the fixed mold and the movable mold have cooling pipes for temperature adjustment. In the present invention, such a general-purpose mold is provided with a heating device for heating a surface in the mold, that is, a cavity and / or a core surface. As the heating device, a halogen lamp is used as a heating means. When the mold is open, the cavity and / or the core surface is heated from the vicinity thereof. A driving unit for inserting and removing the lamp unit at a predetermined position when the mold is open, a temperature control device for setting a predetermined surface temperature, and the like. It is schematically configured. As a temperature controller for measuring the temperature of the mold and driving the heating device or controlling the halogen lamp, a well-known general device can be used. As an outline of such a heating device, specifically, for example, a device described in Japanese Patent Publication No. Hei 7-61670 and Japanese Utility Model Registration No. 30134828 can be used.

[0006] The injection molding method of the present invention will be described. First,
When the mold is in the mold open state, a lamp unit is inserted between the fixed mold and the movable mold, and the cavity or core surface of the fixed mold or the cavity or core surface of the movable mold is inserted. Either one or both surfaces, or a part of the cavity or core surface of the fixed-side and / or movable-side mold is heated by radiant heat of the halogen lamp. The lamp unit used at this time can be heated in only one direction in which a lamp is mounted in one direction according to the heating surface, or can be heated in both directions by combining the two lamp units back to back. Is mentioned. In addition, the surface of one mold is usually heated by one lamp unit, but the surface of the mold may be heated by using two or more lamp units. Regarding the installation of the lamp unit, it is desirable to install the lamp unit preferably in parallel with the mold plate. For example, when the cavity and / or the core is manufactured obliquely with respect to the mold plate, When the lamp unit is installed, the lamp unit may be installed obliquely with respect to the mold plate. There is no particular limitation on the arrangement of the halogen lamps in the lamp unit, but it is preferable to arrange relatively small lamps vertically and / or horizontally because they are easy to heat evenly.

[0007] It is preferable that the output control of the halogen lamp is controlled so that it can be controlled one by one or in groups of several. With this function, it is possible to heat and raise only the required portion of the mold cavity and / or core, or to heat and raise the temperature to a different temperature depending on the location of the cavity and / or core. In particular,
If there is a location where burrs are more likely to occur when the mold is heated, it is possible to reduce the heating temperature of the location, thereby suppressing the occurrence of burrs and improving the appearance of the molded product. Can be further improved. As an example of a heating device for heating only a necessary portion of the cavity and / or the core, a lamp unit that facilitates attaching and detaching a halogen lamp so that a halogen lamp can be disposed only in a portion that requires heating, and a heating unit that does not need heating A lamp unit to which a shielding plate is attached, a lamp unit capable of locally heating such as a spotlight, and the like are also applicable.

It is desirable to start filling the molten resin into the mold when the cavity and / or core surface temperature of the mold is 80 ° C. or higher. Depending on the type, for example, ABS
90 ° C or higher for resin, 140 for PC resin
It is desirable that the temperature be not lower than ° C. When the cavity and / or core surface temperature of the mold is lower than a predetermined temperature,
Appearance defects such as poor color development caused by the weld line and the orientation of the resin surface layer generated in the molded product are not improved. In order to start filling the molten resin into the mold when the cavity and / or core surface temperature of the mold is 80 ° C. or more,
After heating with a halogen lamp, detachment of the lamp unit,
It is necessary to set the heating temperature of the mold surface in consideration of the fact that the temperature of the mold surface decreases due to heat conduction and heat radiation due to the time required for closing the mold. At this time, the temperature of the surface of the cavity and / or the core of the mold is preferably heated to 500 ° C. or more, and more preferably to 800 ° C. or more. It depends on the cooling efficiency depending on the structure and material of the mold, the time required from the end of heating by the halogen lamp to the time when the lamp unit is detached and closed to start filling the mold with the resin. If the temperature of the cavity and / or core surface of the mold is less than 500 ° C., the temperature of the surface of the mold tends to decrease to less than 80 ° C. before the filling of the resin into the mold is started. Injection-molded articles of the appearance cannot be obtained. FIG. 1 shows the change over time in the temperature of the mold cavity after heating by the halogen lamp. When the heating temperature is lower than 500 ° C., the resin must be filled in the mold within 4 seconds after heating by the halogen lamp. Mold surface temperature is 80 ℃
Therefore, the detachment of the irradiation unit and the closing of the mold must be performed within 4 seconds, which is not practical.

The temperature of the mold cavity and / or core surface heated by the halogen lamp depends on the distance between the mold cavity and / or core surface and the lamp unit, the irradiation power of the halogen lamp and the irradiation time of the halogen lamp. Changes can be adjusted and each has an optimal setting range. If the distance between the surface of the mold and the lamp unit is too long, the time required to reach a predetermined temperature will be longer, and the molding cycle time will be longer, while the distance between the surface of the mold and the lamp unit will be longer. If it is too short, it will be difficult to control the mold cavity and / or core surface to a predetermined temperature. If the irradiation output of the halogen lamp is too small, the molding cycle time becomes longer because the time required to reach the predetermined temperature becomes longer,
If the irradiation output of the halogen lamp is too large, it becomes difficult to control the surface of the mold to a predetermined temperature. The irradiation time of the halogen lamp is suitably in the range of 1 second to 15 seconds. If it exceeds 15 seconds, the molding cycle time becomes unnecessarily long, and if it is shorter than 1 second, the surface temperature of the mold decreases. The accuracy of setting the temperature to a predetermined value is deteriorated. These heating conditions vary depending on the material, surface shape, and size of the mold, and there are optimal heating conditions for each mold. An example of heating conditions is as follows. The surface of an iron mold having a cavity with a projected area of 231 cm ² and a length of 50 cm and a width of 40 cm is heated from 60 ° C. to 750 ° C. to start filling the resin into the mold. When the surface temperature of the mold is 104 ° C., the distance between the mold surface and the lamp unit is 15
mm, irradiation power is 60 kW, and irradiation time is 4 seconds.

In the injection molding method of the present invention, the thermoplastic resin is generally heated at 100 to 320 ° C., preferably at 150 to 320 ° C.
Heating and melting to a temperature of 280 ° C. is performed. The time for filling the molten thermoplastic resin into the mold is preferably within 5 seconds. The filling time referred to here is the time from when the screw of the injection molding machine starts to advance until the molten resin reaches a short shot state in which most of the cavity is occupied by the molten resin. If the filling time exceeds 5 seconds, the temperature of the surface of the mold heated by the halogen lamp decreases, and an injection-molded article having a desired molded appearance cannot be obtained. Injection molding conditions for determining the filling time include an injection pressure, an injection speed, a mold temperature adjusted by a temperature controller, and the like.
Can be within seconds. As other molding conditions,
There are a holding pressure, a cooling time, and the like, but are not particularly limited, and general conditions of the thermoplastic resin to be used are used. The temperature of the mold adjusted by the temperature controller may be adjusted to be different between the fixed mold and the movable mold in order to prevent the molded product from warping. In particular, when one of the cavity or core surface of the fixed mold or the cavity or core surface of the movable mold is heated by a halogen lamp, the molded article is taken out when the mold temperature adjusted by the temperature controller is the same. At this time, a temperature difference is generated between the cavity or core surface of the fixed mold and the cavity or core surface of the movable mold, and warpage is likely to occur. Therefore, in the mold heated by the halogen lamp, it is preferable to adjust the temperature of the mold adjusted by the temperature controller to be lower than the other.

The thermoplastic resin used in the present invention includes:
There is no particular restriction, and various general ones are used. For example, styrene-acrylonitrile copolymer (AS resin), polystyrene, high-impact polystyrene, acrylonitrile-butadiene rubber-styrene graft copolymer (ABS resin), acrylonitrile-butadiene rubber-styrene-α-methylstyrene Graft copolymer (heat-resistant ABS resin),
Graft polymer (ASA resin) composed of acrylonitrile-acrylate rubber-styrene, graft copolymer composed of acrylonitrile-ethylene propylene rubber-styrene and / or methyl methacrylate (AES resin), acrylonitrile-silicone rubber -Graft copolymer composed of styrene, acrylonitrile- (silicone-acrylic) composite rubber-graft copolymer composed of styrene, polyethylene, polypropylene, polycarbonate (PC resin), polyethylene terephthalate (PET resin), polybutylene terephthalate (PBT)
Resin), polyphenylene ether (PPE resin), polyoxymethylene (POM resin), crystalline and / or amorphous polyamide, methyl methacrylate polymer (PMMA)
Resin), polyether sulfone, polyarylate, vinyl chloride (PVC resin), maleimide compound-styrene and / or acrylonitrile and / or α-methylstyrene copolymer, rubbery polymer-maleimide compound-styrene and / or Acrylonitrile and / or α-
Graft copolymer of methylstyrene, PC resin and ABS resin and / or ASA resin or PBT resin and ABS
Examples thereof include a polymer alloy obtained by combining two or more kinds of the above resins such as a resin and / or an ASA resin, and a resin obtained by adding a filler to these.

As the filler, glass fiber, glass beads, glass flake, carbon fiber, mica, talc,
Metal coating on minerals such as wollastonite, calcium carbonate, magnesium carbonate, carbon black, ketchen black, metals such as iron, copper, zinc, and aluminum, alloys and their oxides, powders, glass fibers, and carbon fibers And the like. further,
As the thermoplastic resin used in the present invention, those to which various stabilizers such as a flame retardant, a heat stabilizer, and a light stabilizer, an antibacterial agent, an antistatic agent, and the like can be used.

[0013] The molded articles molded by the molding method of the present invention include, for example, various housings, sports products,
Products for playground equipment, products for vehicles, products for furniture, sanitary products, products for building materials, and products for kitchens. Plating, sputtering, vapor deposition, painting, laser marking, or the like can be applied to each of these molded products. More specifically, as the housing, a personal computer (including a notebook computer), a cooler box, a TV, an audio device, a printer, an FA
X, copy machine, game machine, washing machine, air conditioner,
Examples include refrigerators, vacuum cleaners, attache cases, musical instrument cases, tool boxes, containers, cameras (including video cameras, digital cameras, etc.), mobile devices (electronic notebooks, PDAs, etc.), lighting devices, phones (including mobile phones), etc. it can. Examples of sports products include swimming boards, surfboards, windsurfing, skis, snowboards, skateboards, ice hockey sticks, curling balls, gateball rackets, tennis rackets, canoes, boats, and the like. Examples of the playground equipment include a bat, a block, a building block, a fishing tackle case, and a pachinko underframe. Products for vehicles include door mirrors, door handles, front grills, air spoilers, doors, bumpers, fenders, bonnets, sunroofs, rear gates, wheel caps, instrument panels, glove boxes,
Examples include console boxes, armrests, headrests, fuel tanks, driver's seat covers, trunk tool boxes, and interior and exterior parts such as motorcycles, buses, and trucks.
Furniture products include drawers, desk tops, bed tops and bottoms, mirror frame plates, geta boxes and front doors, chair backs and bottoms, trays and trays.
A tray, an umbrella stand, a vase, a medicine box, a hanger, a cosmetic box, a storage box board, a book stand, an office desk top board, an OA desk top board, an OA rack, and the like can be exemplified. Sanitary products include shower heads, toilet seats, toilet plates, drain pans, water tank lids, vanity doors,
Bathroom doors and the like can be exemplified. Examples of building material products include handrails, ceiling boards, floor boards, wall boards, window frames, doors, benches, and the like. Examples of kitchen products include cutting boards and kitchen doors. Particularly preferable examples of the molded article formed by plating, sputtering, vapor deposition, and painting include vehicle exterior parts, electronic equipment housings, and the like. In addition, these are illustrations and can be suitably molded also with molded articles other than these.

[0014]

EXAMPLES The thermoplastic resins used in the following Examples and Comparative Examples were the following materials, each of which was colored black by adding 1.0% by weight of carbon black. -ABS resin: "Diapet" manufactured by Mitsubishi Rayon Co., Ltd.
3001M "・ ASA resin:" Diarack "manufactured by Mitsubishi Rayon Co., Ltd.
S510 "・ PBT resin:" Toughpet N "manufactured by Mitsubishi Rayon Co., Ltd.
1000 "・ PC / ABS resin:" Diaalloy TC-5 "manufactured by Mitsubishi Rayon Co., Ltd. ・ PC / ASA resin with 10% by weight of carbon fiber added:" Diaalloy FA-420CA "manufactured by Mitsubishi Rayon Co., Ltd. ・ PC resin: Novalex 70 manufactured by Mitsubishi Engineering-Plastic Corporation
22A "・ PMMA resin:“ Acripet VH ”manufactured by Mitsubishi Rayon Co., Ltd. ・ PP resin:“ Mitsubishi Polypro BC0 ”manufactured by Mitsubishi Chemical Corporation
3C "-PP resin added with 20% by weight of talc:" Mitsubishi Polypro T4430 "manufactured by Mitsubishi Chemical Corporation

Example 1 A resin molded product was molded using a mold and a heating device shown in FIG. This fixed mold 1
The fixed-side mold 10 is attached to an in-line screw type injection molding machine (not shown) (“IS-220FB” manufactured by Toshiba Machine Co., Ltd.). The nozzle (not shown) of the injection molding machine was connected to the sprue 14. In the fixed mold 10 and the movable mold 12, medium flow paths 26 and 28 of the temperature controller are formed, respectively. The mold cavity 16 is 152 mm long and 15 mm wide.
In order to obtain a flat molded product with a thickness of 2 mm and a thickness of 3 mm,
The cavity 1 has a square shape as shown in FIG.
Gates 18 and 18 ′ are formed at two places above 6. The surface of the cavity was mirror-finished. In this mold, since the gates 18 and 18 ′ are formed at two places, the weld line 30 is formed at the center of the cavity 16.
Is easy to occur. In the heating device, FIG.
As shown in FIG. 2, a lamp unit 20 in which 20 halogen lamps 24, 24,... Each having an irradiation output of 4 kW are arranged in a lamp housing 22 is provided. The irradiation output of these halogen lamps 24 is divided and controlled for each of four groups A to D of five lamps. The lamp unit 20 is inserted and removed between the fixed mold 10 and the movable mold 12 by a driving device (not shown).

Prior to molding, the temperature of the cavity surface of the mold after heating was checked with time under various heating conditions. Regarding the method of measuring the temperature of the cavity surface of the mold, a K thermocouple is attached to the cavity surface of the mold, and the temperature measurement data is stored in WAVE T
Collected using HERMO (manufactured by Keyence Corporation).
FIG. 1 shows the change over time in the temperature of the cavity surface of the mold after heating. The heating conditions were set with reference to this. Regarding the molding, with the mold open, the lamp unit 20 was inserted parallel to the surface of the mold at a distance of 15 mm from the surface of the fixed mold 10, and the irradiation output of all halogen lamps was reduced by 75% (total of 60 kW). ), The irradiation time was 4 seconds, and only the fixed mold 10 was irradiated. By this irradiation, the surface temperature of the mold cavity, which had been adjusted to 60 ° C. by the temperature controller, had risen to 750 ° C. Immediately thereafter, the lamp unit 20 was detached, and the mold was closed. At this time, the time required for detaching the lamp unit and closing the mold was 5 seconds, and the surface temperature of the mold cavity, which had risen to 750 ° C., had fallen to 104 ° C. Immediately, ABS resin melted at 200 ° C. was injected at an injection pressure of 400 kg / cm ^2.
To fill the mold. At this time, the filling time was 2 seconds. Injection molding was performed with a holding pressure of 250 kg / cm ² for 10 seconds and a cooling time of 20 seconds.

Example 2, Comparative Examples 1-2 The molding was carried out in the same manner as in Example 1, except that the irradiation time with a halogen lamp was set to the conditions shown in Table 1.

The molded articles obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for weld appearance and color development as appearance. Regarding the weld appearance, the molded product was visually observed at a position corresponding to the cavity 16 in FIG. The results were as follows: those where the weld line was conspicuous, △ where the weld line was slightly conspicuous, ○ where the weld line was not conspicuous,
The case where the weld line completely disappeared was indicated by ◎. As for the color developing property, the degree of blackness of the surface of a molded product obtained by using a thermoplastic resin colored black was evaluated. The observation position was a position corresponding to the site of the cavity 16. The degree of blackness was determined based on the value of lightness (L *) measured using a MSC type colorimeter (manufactured by Suga Test Instruments Co., Ltd.) according to a method based on JIS K7105. The smaller the value of lightness, the higher the degree of blackness. Generally, when L * is 11 or less, it is considered that the color development of black is good.

[0019]

[Table 1]

As is clear from Table 1, Examples 1 and 2
In the case of a molded product by
* Was 10 or less, indicating a good molded appearance. On the other hand, the appearance of the molded articles obtained in Comparative Example 1 in which the surface temperature of the heated mold departed from the present invention and Comparative Example 2 in which heating by a halogen lamp was not performed were poor.

Examples 3 to 4, Comparative Example 3 Except that the injection pressure and filling time of the molten resin were set to the conditions shown in Table 2,
The same operation as in Example 1 was performed.

[0022]

[Table 2]

While the appearance of the molded article obtained under the molding conditions according to the present invention was good, the appearance of the molded article obtained in Comparative Example 3 having a long filling time of the molten resin was not good.

Examples 5 to 12 The same molding was carried out using various thermoplastic resins. The operation was performed in the same manner as in Example 1, except that the heating conditions and molding conditions described in Table 3 were used.

[0025]

[Table 3]

Each of the obtained molded articles had a good appearance. In addition, PC / AS with 10% by weight of carbon fiber added
L * of the A resin could not be measured due to the influence of the fibers near the surface layer.

Example 13 Molding was performed using a mold having a cavity shape shown in FIG. That is, 152 mm in length,
In the center of a flat plate 152 mm wide and 3 mm thick, 100
It has a cavity shape capable of forming a rectangular annular molded product having an opening 36 of 100 mm in width and 100 mm in width. In this mold, the weld line 32 is easily conspicuous in the final filling portion where the resin flow distance is long and the filling pressure does not easily act, and the central opening 36 is formed by abutting against the cavity surface of the mold. Therefore, there is a feature that burrs are easily generated near the gate 34. The surface of the cavity was mirror-polished. In molding, the lamp unit 20 was inserted parallel to the surface of the mold at a distance of 15 mm from the surface of the fixed mold 10 with the mold opened. The irradiation output of the halogen lamp is 0% (0 kW) for the divided part A and 25% for the divided part B.
(5 kW), the split part C is individually set to 50% (10 kW), and the split part D is individually set to 75% (15 kW).
Irradiation was performed in seconds. By this irradiation, the surface temperature of the mold in the portion where the weld line was likely to come out had risen to 1115 ° C. Immediately thereafter, the lamp unit 20 was detached, and the mold was closed. At this time, the time required for detaching the lamp unit and closing the mold was 5 seconds, and the surface temperature of the mold cavity, which had risen to 1115 ° C., had fallen to 122 ° C. Immediately, the mold was filled with an ABS resin melted at 200 ° C. at an injection pressure of 800 kg / cm ² . At this time,
The filling time was 2 seconds. Holding pressure 250 kg / cm ²
For 10 seconds and a cooling time of 20 seconds to perform injection molding.

[Comparative Example 4, Example 14] The same operation as in Example 13 was carried out except that the irradiation output of the halogen lamp was all 0% (Comparative Example 4) and all were 75% (Example 14). When the irradiation output is all 0%, the mold temperature is 60 ° C.
Met.

With respect to the molded articles according to Examples 13 and 14 and Comparative Example 4, the weld appearance and the occurrence of burrs were evaluated as appearance. The weld appearance was visually observed at a position corresponding to the portion 3 of the cavity 16 ′ in FIG. 5 for the molded product. The occurrence of burrs was observed particularly at locations corresponding to the locations.

[0030]

[Table 4]

In the molded product obtained in Example 13, the weld line completely disappeared, and generation of burrs near the gate was not confirmed. On the other hand, in the molded article obtained in Comparative Example 4 in which the irradiation output of the halogen lamp was all 0%, the weld line was conspicuous although burrs near the gate were not confirmed. In addition, the irradiation output of all halogen lamps is 75
%, The burr was confirmed near the gate, although the weld line was completely disappeared.

[0032]

As described above, according to the present invention, without a decrease in productivity due to elongation of the cooling time, etc.
In addition, it is possible to easily and inexpensively improve poor appearance due to the formation of weld lines and a decrease in coloring. In particular, by heating the halogen lamps individually or by dividing them into a plurality of pieces, heating can be performed finely according to the shape of the molded product, etc. Appearance can be improved. Therefore, according to the present invention, it is possible to obtain a thermoplastic resin injection molded article having excellent molded appearance, and can be widely used for various uses.

[Brief description of the drawings]

FIG. 1 is a graph showing a change over time of the surface temperature of a mold due to heating by a halogen lamp in the heating device of the present invention.

FIG. 2 is a side view schematically showing a heating device and peripheral devices of the present invention.

3A and 3B schematically show a heating device, wherein FIG. 3A is a front view and FIG. 3B is a side sectional view.

FIG. 4 is a front view showing a cavity according to the first embodiment.

FIG. 5 is a front view showing a cavity according to a thirteenth embodiment.

[Explanation of symbols]

 Reference Signs List 10 fixed mold 12 movable mold 16 cavity 20 lamp unit 22 lamp housing 24 halogen lamp

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hideyuki Shigemitsu 3816 Noto, Noto, Tama-ku, Kawasaki-shi, Kanagawa F-term (reference) 4F202 AK09 AM36 AR06 AR11 AR11 CA11 CB01 CN01 CN18 CN24 4F206 AK09 AM36 AR064 AR11 JA07 JM04 JN11 JN43 JQ81

Claims (4)

[Claims] 1. A method for injection molding a thermoplastic resin, comprising:
With the mold open, the mold surface is preliminarily heated by a heater equipped with a halogen lamp, and then the mold is clamped. When the mold surface temperature is 80 ° C. or higher, the molten resin is placed in the mold. , And filling the mold with a molten resin within 5 seconds. 2. The injection molding method for a thermoplastic resin according to claim 1, wherein the mold surface is heated to 500 ° C. or higher in advance. 3. A thermoplastic resin molded article obtained by the injection molding method according to claim 1. 4. A heating apparatus provided with a plurality of halogen lamps for heating a surface in a mold, wherein the halogen lamps are controlled individually or in plurals.