JP2006334959A - Method and apparatus for vacuum-forming thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the oxidation degradation of a resin molding even without using an antioxidant and to exactly determine a temperature preliminarily suitable for the molding and solidification of a thermoplastic resin when the resin is molded and solidified. <P>SOLUTION: A thermoplastic resin solid material is supplied to a mold 51 to be arranged between a pair of hot press bodies 12a and 12b. The mold 51 is held in a vacuum by the hot press bodies 12a and 12b, and the material in the mold, after being heated and melted, is molded provisionally. Next, the mold 51 with the provisional molding is taken out from the hot press bodies 12a and 12b and moved between another pair of hot press bodies 13a and 13b while the vacuum is kept. The provisional molding is hot press-molded by the hot press bodies 13a and 13b while the vacuum is kept to obtain the resin molding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a thermoplastic resin vacuum molding method and apparatus for hot-pressing a thermoplastic resin solid material in a vacuum state after melting and provisional molding in a vacuum state.

In a conventional press molding machine for resin, since molding is performed in the air, the physical properties of the final molded product are likely to deteriorate due to oxidative degradation of the resin. For this reason, in most industrial processes, an antioxidant or the like is added to the resin.
As such additives, for general-purpose resins such as polyethylene and polypropylene, those having a phenol skeleton and chemical substances containing phosphorus and sulfur are used. Among them, FDA (Food and Drug Administration) approved additives are used for the production of resin for food packaging. Moreover, environmentally hazardous substances are often used in the production of products for other industrial uses. However, even if it is an FDA-approved product, considering the production volume of plastic products, a huge amount of additive is released when this product is discarded. Generally, the above additive is required to be 0.2 to 0.5% by weight based on the resin. Therefore, when calculating from the annual domestic plastic production of 12 million tons, at least 20,000 tons to 30,000 Tons of additives, that is, environmentally hazardous substances, are disposed of every year and become an environmental problem.
On the other hand, the above-mentioned additive tends to bleed out on the surface of a plastic molded product and suppresses deterioration of mechanical properties and the like, but has a problem of poor colorability and adhesiveness on the surface of the molded product. In particular, in the production process of an electrical board or the like, wiring defects occur due to the exudation of additive components, and the yield is extremely reduced. Therefore, when no additive is used, a press apparatus equipped with a vacuum mechanism must be used to prevent oxidative degradation of the resin. However, such a pressing device is very expensive, and when used for molding general-purpose resins, depreciation is difficult, and its application is limited to electronic parts with high production costs.

Conventionally, two thin thermoplastic resin material sheets are placed in a vacuum vessel and pressed under vacuum until the sheets are welded to each other and reach a temperature suitable for molding, and then adjacent to the outlet of the vacuum vessel A method and an apparatus for forming a desired shape with a forming press are disclosed (for example, see Patent Document 1).
JP-A-3-2010 Patent Claim

However, the molding method described in Patent Document 1 has a problem that it is difficult to accurately set a temperature suitable for molding a thermoplastic resin and a solidification temperature of the resin.
An object of the present invention is to prevent oxidative deterioration of a resin molded body without using an antioxidant, and to accurately determine a temperature suitable for resin molding and solidification in advance when molding and solidifying a thermoplastic resin. An object of the present invention is to provide a vacuum molding method and apparatus for thermoplastic resin that can be used.

  The invention according to claim 1 of the present application, as shown in FIGS. 4 to 7, is a step of supplying a thermoplastic resin solid material to a molding die 51 and arranging it between a pair of first hot press bodies 12 a and 12 b, A step of holding a forming die 51 by a pair of first hot press bodies 12a and 12b in a vacuum state and heating the material in the forming mold to melt and then temporarily forming a temporary formed body; and a vacuum state The step of taking out the molding die 51 containing the temporary molded body from the pair of first hot press bodies 12a and 12b and moving them between another pair of second hot press bodies 13a and 13b, And a second hot press body 13a, 13b of forming a resin molded body by hot pressing the temporary molded body.

  As shown in FIG. 1, the invention according to claim 2 of the present invention includes a pressure-resistant container 11 that can be depressurized, a vacuum pump 14 that depressurizes the pressure in the container to a predetermined pressure, and two juxtaposed in the container A pair of hot-pressed bodies 12a, 12b, 13a, 13b, a mold 51 arranged between one of these two pairs of hot-pressed bodies, and the other of these two pairs of hot-pressed bodies Mold moving tools 46 and 52 for moving the mold 51 between them, and as shown in FIGS. 4 to 7, one pair of first hot press bodies 12 a and 12 b is supplied to the mold 51. The thermoplastic resin solid material is melted and temporarily molded, and the other pair of second hot press bodies 13a and 13b is configured to heat-press the temporary molded body in the mold 51 into a resin molded body. This is a vacuum forming apparatus for thermoplastic resin.

  The invention according to claim 3 of the present application is the vacuum forming apparatus according to claim 2, wherein, as shown in FIG. 1, the pair of hot press bodies 12 a and 12 b on which the mold moving tool places the mold 51 is mounted. , 13a, 13b, and a sample moving plate 52 for moving the sample mounting plate 46.

  The invention according to claim 4 of the present application is the vacuum forming apparatus according to claim 2, wherein the temperature sensors 41a, 41b, 42a, 42b provided in the two pairs of hot press bodies 12a, 12b, 13a, 13b, respectively, The temperature adjuster 44 for setting the temperature of the heaters 12c, 12d, 13c, 13d incorporated in the heat press bodies 12a, 12b, 13a, 13b, and the set temperature of the temperature adjuster 44 and the detected temperature of the temperature sensor And a controller 43 for controlling the heaters 12c, 12d, 13c, 13d.

In the method according to claim 1 of the present application, temporary molding and resin molding are performed in separate hot press bodies in the same vacuum state, so that the oxidative deterioration of the resin molded body can be prevented without using an antioxidant. Moreover, the provisional molding conditions and the resin molding solidification conditions can be individually adjusted. Thereby, the temperature suitable for resin molding and solidification can be accurately determined in advance when molding and solidifying the thermoplastic resin.
In the apparatus according to claim 2 of the present application, inside the single container, the molded body molded by one hot press body is placed in the same mold by the mold moving tool in the same vacuum state, while the other mold is moved. It can move to a hot press body and pressurize, and resin molding can be carried out substantially in a series from temporary molding.

In the apparatus according to claim 3, by using the sample mounting plate and the sample moving shaft, the temperature of the temporary molded body is lowered from one hot press body to the other hot press body without changing the vacuum degree of the container. It is possible to move quickly without making it.
In the apparatus which concerns on Claim 4, a predetermined molding temperature can be correctly acquired by providing a temperature sensor in each hot press body.

The best mode of the present invention will be described below.
As shown in FIGS. 1 and 2, the thermoplastic resin vacuum forming apparatus 10 of this embodiment has a rectangular parallelepiped pressure-resistant container 11 that can be decompressed. The thermoplastic resin used in the present invention is a crystalline thermoplastic resin suitable for general injection molding, compression molding and the like. Examples include polyethylene, polypropylene, polyethylene terephthalate, nylon 6 (polycaprolactam), polytetrafluoroethylene, and the like. Inside the container 11, a pair of first hot press bodies 12a, 12b and a pair of second hot press bodies 13a, 13b are provided side by side. A vacuum pump 14 and a press hydraulic source 16 are provided outside the container 11. The vacuum pump 14 is connected to an exhaust port 18 of the container 11 through a pipe line 17. With this vacuum pump, the degree of vacuum of the container becomes 0.01 MPa or less.

  In the upper wall 11a of the container 11, together with the exhaust port 18, the gas introduction port 19 and the leak port 21, a vacuum gauge 22 for measuring the degree of vacuum in the container and the upper hot press bodies 12a and 13a are moved up and down respectively. A hydraulic cylinder 23 and a second hydraulic cylinder 24 are provided. The gas inlet 19 is connected to an inert gas source such as nitrogen or argon through a normally closed valve (not shown), and the leak port 21 communicates with the atmosphere via a normally closed valve (not shown). The hydraulic source 16 is connected to the two hydraulic cylinders 23 and 24 via a pipe line 26. The conduit 26 is provided with a switching valve 28 for switching the hydraulic pressure from the hydraulic gauge 27 and the hydraulic source 16 to one of the two hydraulic cylinders. In this embodiment, the first or second hot press body can be pressed by a hydraulic cylinder 23 or 24 with a maximum force of 5000 kgf (about 49000 N).

  The inside of the container 11 is partitioned by an intermediate wall 11b in the horizontal direction. The piston shaft 23a of the cylinder 23 and the piston shaft 24a of the cylinder 24 pass through the upper wall 11a and the intermediate wall 11b, respectively, and are connected to the upper hot press bodies 12a and 13a. The intermediate wall 11b is provided with bearings 31 and 32 of the piston shafts 23a and 24a and a plurality of vent holes 33. In addition, a heat shielding plate 34 that shields heat transfer between the first hot press bodies 12a and 12b and the second hot press bodies 13a and 13b is provided vertically in the center of the intermediate wall 11b.

  On the lower wall 11c of the container 11, lower heat press bodies 12b and 13b are attached via base stands 36 and 37, respectively. A moving roller 38 is provided between the base tables 36 and 37 so that a sample mounting plate 46 to be described later can smoothly move between the first hot press body and the second hot press body. Therefore, both ends of the moving roller 38 are rotatably supported by bearings 39 attached to the lower wall 11c so that the upper end of the moving roller 38 is flush with the lower heat press bodies 12d and 13d. Heaters 12c, 12d, 13c, and 13d are provided in the hot press bodies 12a, 12b, 13a, and 13b, respectively. The upper heat press bodies 12a and 13a are respectively provided with a first temperature sensor 41a and a second temperature sensor 42a, and the lower heat press bodies 12b and 13b are respectively provided with a first temperature sensor 41b and a second temperature sensor 42b. Provided. The detection outputs of these temperature sensors 41a, 41b, 42a, 42b are connected to the controller 43, and the control output of the controller 43 is connected to the heaters 12c, 12d, 13c, 13d. A heater switch and a heater temperature controller 44 (not shown) are connected to the controller 43. These heaters can be set to a predetermined temperature by manually turning on the heater switch and operating the temperature controller 44. In this embodiment, the hot press body can be heated up to 400 ° C. A sample mounting plate 46 having a flange 46a moving between the first hot press bodies 12a, 12b and the second hot press bodies 13a, 13b is disposed on the upper surface of either the lower hot press body 12b or 13b. The

As shown in FIG. 2, the front wall 11 d of the container 11 has an opening 11 e through which a thermoplastic resin material or a molded body is taken in and out, and a door 47 is provided in the opening 11 e so as to seal the opening. The door 47 has a circular view window 47a as shown by a two-dot chain line in FIG. 1, and this view window 47a is sealed with a transparent glass body 48 with a reinforcing ring.
As shown in FIGS. 1 to 3, a thermoplastic resin mold 51 is placed on the sample mounting plate 46. In this embodiment, the mold 51 includes a flat circular upper mold 51a made of stainless steel and a circular lower mold 51b having a concave mold 50 (see FIG. 3) made of stainless steel. A through hole 11g is provided in the right side wall 11f of the container 11, and the sample moving shaft 52 is inserted into the through hole 11g so as to be slidable in the longitudinal direction and rotatable about the axis. A sealing packing 11h for maintaining airtightness is attached to the outer surface of the side wall 11f. A knob 52a is attached to the right end of the sample moving shaft 52, and a hook 52b is attached to the left end. The sample moving shaft 52 and the sample mounting plate 46 described above constitute a sample moving tool.

A forming method using the vacuum forming apparatus 10 configured as described above will be described.
(a) Mold Setting and Sample Supply The door 47 on the front surface of the vacuum forming apparatus shown in FIG. 2 is opened, and the first hot press body 12a and the second hot press body 13a are moved by the first hydraulic cylinder 23 and the second hydraulic cylinder 24. Ascend and hold at a predetermined height. Subsequently, as shown in FIG. 4, the sample mounting board 46 is arrange | positioned on the 1st hot press body 12b. Next, after putting the powdery thermoplastic resin material into the concave mold of the lower mold 51b having the concave mold 50, the lower mold 51b is placed on the sample mounting plate 46, and this same A disk-shaped upper mold 51a having an outer diameter is overlapped. Subsequently, as shown in FIG. 5, the piston shaft 23a of the first hydraulic cylinder 23 is pushed down by the hydraulic pressure of the hydraulic source 16, and the upper and lower molds 51a and 51b are held by the pair of hot press bodies 12a and 12b. The pressing of the piston shaft 23a at this time is to fix the molds 51a and 51b by a pair of hot press bodies 12a and 12b.

(b) Temperature setting of the first and second hot press bodies Next, the door 47 is closed and locked, and the pressure-resistant container 11 is sealed. The inside of the container is evacuated by the vacuum pump 14, and the pressure is reduced to a predetermined pressure. An inert gas is introduced from the gas inlet 19 as needed during decompression to replace the internal air. Thereby, the inside of a container can be made into a non-oxidizing atmosphere. Subsequently, a heater switch and a temperature controller (not shown) are operated to energize the heaters 12c, 12d, 13c, and 13d via the controller 43, and the first hot press bodies 12a and 12b are respectively melted by the thermoplastic resin material. Heat to the temperature of. The lower limit value of the predetermined temperature is a temperature at which the thermoplastic resin starts to soften, and the upper limit value is a temperature about 200 ° C. higher than the softening start temperature.

(c) Temporary molding by the first hot press body Thermoplasticity is maintained by maintaining the upper and lower molds 51a and 51b by the pair of hot press bodies 12a and 12b at the predetermined temperature for 1 minute to 12 hours. The resin material is melted and softened. Next, as shown in FIG. 5, the piston shaft 23a of the first hydraulic cylinder 23 is further pushed down, and the upper and lower molding dies 51a and 51b are pressurized by the pair of hot press bodies 12a and 12b to temporarily mold the thermoplastic resin. The applied pressure at this time is 1 to 100 MPa. If the pressure is less than the lower limit value, the resin is not temporarily molded into a predetermined mold shape, and even if the pressure exceeds the upper limit value, the degree of temporary molding does not change, so the above range is selected.

(d) Sample movement from the first hot press body to the second hot press body After the temporary molding is finished, the upper hot press body 12a is pushed up by the piston shaft 23a to release the pressure. As shown in FIG. 5, after turning the knob 52a of the sample moving shaft 52 so that the hook 52b faces upward, the knob 52a is pushed into the container and turned again as shown in FIGS. 1 and 2, and the sample mounting plate 46 is turned. As shown in FIG. 6, the sample moving shaft 52 is pulled out from the container, and the sample mounting plate 46 is quickly moved onto the lower second hot press body 13b. As the moving roller 38 rotates, the sample mounting plate 46 on which the forming die 51 is placed moves smoothly.

(e) Solidification of sample by the second hot press body After the sample mounting plate 46 is moved onto the hot press body 13b, the heaters 12c, 12d of the first hot press bodies 12a, 12b are turned off. Further, as shown in FIG. 7, the upper hot press body 13a is pushed down by the piston shaft 24a to pressurize the forming die 51. The molding conditions at this time set temperature, pressure, and time in order to crystallize the thermoplastic resin isothermally. The temperature, pressure and time vary depending on the type of thermoplastic resin, the size and shape of the mold. For example, 100 to 250 ° C., 1 to 100 MPa, 1 minute to 12 hours for polyethylene, 100 to 250 ° C., 1 to 100 MPa, 1 minute to 12 hours for polypropylene, 200 to 300 ° C. for polyethylene terephthalate, 1 ~ 100 MPa, 1 minute to 12 hours, 200 to 300 ° C, 1 to 100 MPa, 1 minute to 12 hours for nylon 6 (polycaprolactam), 300 to 400 ° C, 1 to 100 MPa for polytetrafluoroethylene, 1 Molding conditions of minutes to 12 hours are set.

(f) Removing the sample from the container With the molding die 51 being pressurized at a predetermined pressure by the second hot press bodies 13a and 13b, the heaters 13c and 13d are turned off, and the second hot press bodies 13a and 13b are brought to room temperature. Leave until. Thereafter, the vacuum pump 14 is stopped, the valve is opened, and the atmosphere is introduced into the container 11 from the leak port 21. Subsequently, the upper hot press body 13a is raised by the piston shaft 24a at room temperature, the door 47 is opened, and the molding die 51 is taken out.

Next, examples of the present invention will be described.
<Example 1>
[Mold set and sample supply]
As shown in FIG. 1 and FIG. 2, the door 47 on the front side of the vacuum forming apparatus is opened, and the upper first hot press body 12a and the second hot press body 13a are moved up to lower the hot press bodies 12b and 13b. A gap of 5 cm was set between them. Next, as shown in FIG. 4, the sample mounting plate 46 was disposed on the first hot press body 12b. Next, a desired lower mold 51b having a rectangular concave mold 50 (FIG. 3) of 40 mm (vertical) × 70 mm (horizontal) × 0.3 mm (depth) was placed on the sample mounting plate (FIG. 3). 4). 3 g of powdered polyethylene resin was placed in the rectangular concave mold, and a flat circular upper mold 51b was placed thereon. Next, the first hot press body 12a was pushed down by the hydraulic piston shaft 23a, and the mold 51b was pressed with a pressure of 1 MPa.

[Temperature setting of first and second hot press bodies]
After holding the mold and the sample between the first hot press bodies 12a and 12b in this way, the door 47 is closed and locked, and the vacuum pump 14 is driven to evacuate the inside of the container 11, and the inside of the container is set to 0. 0. The pressure was reduced to 01 Pa or less. Next, the heater switch was turned on, and the temperature controller 44 was operated to set the temperatures of the first hot press body and the second hot press body to 180 ° C. and 100 ° C., respectively.

[Temporary molding by the first hot press body]
By maintaining the temperature of the first hot press body at 180 ° C. for 1 minute, the polyethylene resin powder of the sample is melted, and then the piston shaft 23a is pushed down to increase the pressure of the first hot press body to 50 MPa. Then, the sample was temporarily formed into a desired rectangle.

[Sample movement from the first hot press body to the second hot press body]
After the temporary molding is completed, the upper first hot press body is lifted by the piston shaft 23a to release the pressure, and the sample mounting plate 52 is moved by the sample moving shaft 52 as shown in FIGS. The mold 51 on 46 was quickly moved from the first hot press body to the second hot press body. At this time, since the first hot press body is not used, the heaters 12c and 12d are turned off.

[Sample solidification by second hot press body]
After the sample movement was finished, the piston shaft 24a was pushed down, and the second hot press body maintained at 100 ° C. was pressurized at 50 MPa. This temperature was maintained for 1 day to allow isothermal crystallization of the sample polyethylene resin.

[Sample removal]
After maintaining for 1 day, the heaters 13c and 13d were turned off and left at 50 MPa until the second hot press body reached room temperature. Thereafter, the upper hot press body 13a was raised by the piston shaft 24a at room temperature. After the vacuum pump 14 was stopped and the inside of the chamber was easily brought to atmospheric pressure, the door 47 was opened, and the mold 51 was taken out from the second hot press body to the outside of the container. When this mold was opened, a polyethylene resin sheet was molded in a rectangular concave mold of 40 mm (length) × 70 mm (width) × 0.3 mm (depth). This sheet had no defects such as bubbles, and had a very uniform shape.

FIG. 1 is a cross-sectional configuration diagram of a main part of a thermoplastic resin vacuum forming apparatus of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a perspective view of a lower mold before supplying a resin sample placed on the sample mounting plate and an upper mold superimposed on the lower mold. FIG. 4 is a view showing a state before pressurizing the mold with the first hot press body. FIG. 5 is a view showing a state in which the mold is pressed by the first hot press body. FIG. 6 is a view showing a state in which the mold is moved to the second hot press body after pressurizing the mold with the first hot press body. FIG. 7 is a view showing a state in which the forming die is being pressed by the second hot press body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vacuum forming apparatus 11 Pressure-resistant container 12a, 12b A pair of 1st heat press body 12c, 12d Heater 13a, 13b A pair of 2nd heat press body 13c, 13d Heater 14 Vacuum pump 41a, 41b 1st temperature sensor 42a, 42b 1st 2 Temperature sensor 43 Controller 44 Heater temperature controller 46 Sample mounting plate 51 Mold 52 Sample moving axis

Claims (4)

  Supplying a thermoplastic resin solid material to the mold (51) and disposing it between the pair of first hot press bodies (12a, 12b), and the pair of first hot press bodies (12a, 12b) in a vacuum state ) Holding the mold (51) and heating the material in the mold to melt and then temporarily forming a temporary molded body, and the pair of first heats in a vacuum state Removing the molding die (51) containing the temporary molded body from the press body (12a, 12b) and moving it between another pair of second hot press bodies (13a, 13b); A method of vacuum forming a thermoplastic resin, comprising: hot pressing the temporary molded body into a resin molded body by a pair of second hot press bodies (13a, 13b). A pressure-resistant container (11) capable of depressurization, a vacuum pump (14) for depressurizing the pressure in the container to a predetermined pressure, and two pairs of hot press bodies (12a, 12b, 13a) arranged in parallel in the container 13b), a mold (51) disposed between any one of the two pairs of hot press bodies, and the mold (51) between either one of the two pairs of hot press bodies. A mold moving tool (46, 52) to be moved,
One pair of first hot press bodies (12a, 12b) melts and temporarily molds the thermoplastic resin solid material supplied to the mold (51), and the other pair of second hot press bodies (13a, 13b). ) Is a thermoplastic resin vacuum molding apparatus configured to hot-press the temporary molded body in the mold (51) into a resin molded body.   The mold moving tool includes a sample mounting plate (46) that can move between two pairs of hot press bodies (12a, 12b, 13a, 13b) on which the mold (51) is placed, and the sample mounting plate ( The vacuum molding apparatus for thermoplastic resin according to claim 2, further comprising a sample moving shaft (52) for moving 46). Temperature sensors (41a, 41b, 42a, 42b) provided in the two pairs of hot press bodies (12a, 12b, 13a, 13b) respectively, and built in the hot press bodies (12a, 12b, 13a, 13b) A temperature controller (44) for setting the temperature of the heater (12c, 12d, 13c, 13d), and the heater (12c, 12d, according to the set temperature of the temperature controller (44) and the detected temperature of the temperature sensor The vacuum molding apparatus for thermoplastic resin according to claim 2, further comprising a controller (43) for controlling 13c, 13d).

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