JPS6213898B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a molding device for plastically deforming a thermoplastic resin sheet to form a sheet molded body. The purpose is to propose a molding device that can efficiently mold a molded article in which truncated cone-shaped hollow convex portions alternately protrude on both sides of a sheet. Conventionally, when forming hollow convex parts in a thermoplastic resin sheet (hereinafter simply referred to as a sheet), a mold matching the dimensions of the convex part was prepared, and the raw material sheet was brought into contact with this mold and plastically deformed. It was being molded. Therefore, one mold is required for one type of convex shape, which increases the cost of the mold. In particular, in the case of a molded product having a large number of hollow convex portions on both sides of the sheet, the mold shape is complicated and the cost of the mold is even greater. This invention was made in view of the above circumstances, and its gist is that two molds each having a plurality of protruding columnar protrusions with flat top surfaces face each other, and the protrusions of one mold are arranged between the protrusions of the other mold. At least one of the molds is arranged so as to be movable in the height direction of the protrusion so as to fit into the center, and at least the top of the protrusion of the two molds substantially prevents the thermoplastic resin sheet to be molded from flowing. When one protrusion is inserted between the other protrusions, the distance between the sides of the other protrusion located on both sides of one protrusion becomes
W ₂ , the width of the top surface of the protrusion in the side-to-side distance direction is W ₁ , and the depth into which the protrusion enters is 2H, then 2W ₁ /W ₁ +W ₂ ≧1/3, 2H/W ₁ +W
The present invention is a molding apparatus for a thermoplastic resin sheet molded body, characterized in that the relationship ₂ < 2 holds true. FIG. 1 shows an example of an embodiment of this device, which has an upper mold A and a lower mold A', each mold having a substrate 1 and its surface as shown in FIGS. 2 and 3. It has a plurality of protrusions 2, 2' at positions corresponding to every other grid intersection. The projections 2, 2' are columnar bodies whose top surfaces 3, 3' are square planes (one side length W ₁ ). These upper and lower molds A, A' have protrusions 2,
As shown in Fig. 4, one mold A has its protrusion 2 facing the other mold.
At least one of the molds A is disposed so as to be movable in the height direction of the projections 2 so as to fit into the approximately central position of the four projections 2' of A'. In addition, upper and lower molds A,
Cooling water pipes (not shown) are embedded in the protrusions 2, 2' of A', and at least the tops of the protrusions 2, 2' are kept at a temperature at which the sheet to be formed does not substantially flow. It's becoming like that. When the two molds A and A' are close together,
Both protrusions 2, 2' alternately occupy grid intersection positions, and the distance W 2 between the side surfaces 4', 4' of the other protrusions 2', _2' located on both sides of one protrusion 2, Determine the depth of the penetration between the other protrusions 2' and 2'.
When 2H, 2W ₁ /W ₁ +W ₂ ≧1/3 and 2H/W ₁ +W ₂ <2 are satisfied. When molding a sheet molded product using this device, the raw material sheet B made of thermoplastic resin is heated in advance to make it fluid and thermoformable, and as shown in FIG. 5, upper and lower molds A, A' Send it in between. In this state, the upper and lower molds A and A' are brought close to each other so as to sandwich the sheet B. First, the top surfaces 3, 3' of the protrusions 2, 2' contact the sheet B, but since the temperature at the top surface is such that the sheet B does not substantially flow, the portions of the sheet in contact with the top surfaces 3, 3' B solidifies on cooling and ceases to flow. Therefore, when the molds A and A' are brought closer together and the protrusion 2 of one is inserted between the protrusions 2' of the other, the sheet B fixes the top surfaces of the protrusions 2 and 2', and The sheet is stretched in the vertical direction without contacting the side surfaces of the projections 2, 2'. In this way, mold A until the penetration depth is 2H.
The molded products obtained by molding A' in close proximity and cooling are shown in FIGS. 6 and 7. That is,
Hollow truncated quadrangular pyramidal convex portions 5, 5' protrude alternately on both the front and back surfaces of the sheet B, and the top surfaces 6, 5' of the convex portions 5, 5' protrude alternately.
6' forms a square plane with a side length W ₁ , the heights of the top surfaces 6 and 6' from the sheet B surface are each H, and the upper and lower top surfaces 6 and 6' are aligned on one plane. Convex portion 5,
The length W ₃ of the bottom side of 5' is W ₁ +W ₂ /2, and 2W ₁ /W ₁ +W ₂ ≧1/3, 2H/W ₁ +W ₂ <2, so the convex part of the sheet molded product 5 and 5' are truncated regular square pyramids with W ₁ /W ₃ ≧1/3 and H/W ₃ <2. In addition, the convex portions 5, 5'
The top surfaces 6, 6' of the mold projections 2, 2' are the top surfaces 3, 3' of the mold protrusions 2, 2'.
Since it is in contact with and is not stretched, its thickness t ₁ becomes t ₁ /t ₂ compared to the thickness t ₂ of the stretched convex side surfaces 7 and 7'. This sheet molded product is bulky and at the same time has relatively wide top surfaces on both the front and back surfaces, so it can have high compressive strength. For example, when used as a core material for panels, etc., it can be bonded to the surface material with a wide top surface, forming a panel with high adhesive strength and compressive strength.In addition, it has many independent voids separated by convex parts, is lightweight, and has good heat insulation performance. is excellent. In addition, the convex portions 5 and 5' adjacent to each other on both the front and back sides are the sixth
As shown in the figure, the ribs are curved in a row, and the curved ribs on both the front and back sides face each other at right angles, so it is possible to improve the bending strength. Furthermore, since the curved ribs are formed in a three-dimensional direction from the convex portion 5 of the molded body, the compressive strength of the convex portion itself is increased. Note that fine irregularities are provided on the flat projection top surfaces 3 and 3' of the molds A and A', and the projections 5 and 3 of the resulting sheet molded body are
It is also possible to form thin irregularities on the top surfaces 6, 6' of 5' to improve the adhesive strength. When the protrusions 2, 2' of the forming device are 2H/W ₁ +W ₂ ≧2, the protrusions 5, 5' of the resulting sheet molded product are H/W 1 +W 2 ≧2.
W ₃ ≦2, that is, the height of the convex portions 5, 5' is more than twice the length of one side of the bottom, the elongation during molding becomes poor, and it becomes extremely difficult to release the mold from the molded product. At the same time, the convex portions of the sheet molded product obtained are elongated and thin, and the side surfaces are thin, making it easy to buckle and lowering the compressive strength, which is undesirable. Further, when the protrusions 2, 2' are 2W ₁ /W ₁ +W ₂ <1/3, the convex portions 5, 5' of the sheet molded product obtained are W ₁ /W ₃ <1/3, that is, the length of one side of the top surface. is less than 1/3 of the length of one side of the bottom, and the ratio of the total area of the top surface to the entire surface of the molded body decreases. When used as a panel core material or cushioning material, the compressive strength and adhesive area with the surface material decreases, which is preferable. do not have. Normally, the area of the top surfaces 3, 3' of the projections is 0.09 cm ² to 25 cm ² , and the depth 2H of the projections is about 5 to 100 mm. Sheets that can be molded using this molding device are preferably hard vinyl chloride, polystyrene, high density polyethylene, polypropylene, nylon 6,
66. It is made of hard thermoplastic resin such as polyester, ABS resin (acrylonitrile, butadiene, styrene copolymer), etc., but sheets of soft thermoplastic resin such as soft polyvinyl chloride and low density polyethylene can be used as raw materials. You can also do it. The hard resin sheet molding is suitable for use as a panel core material, and the soft resin sheet molding is suitable for use as a cushioning material. However, its uses are not limited to the above-mentioned uses. The thickness of the raw material sheet is 100 to 1000μ. The mold projections of the forming apparatus must be cooled, at least at the top, to a temperature at which the sheet to be formed will not substantially flow. This temperature is generally below the melting or softening point of the sheet.
In order to cool the mold to this temperature, in addition to embedding a water cooling tube in the protrusion, conventional means such as cooling the mold by blowing cooling air onto the mold are employed. The shape of the protrusions can be freely set to include a cylinder, a polygonal prism, etc. in addition to the above-mentioned regular square prism, and a sheet molded body in which hollow convex portions such as a truncated cone shape and a truncated polygonal pyramid are alternately protruded can be formed. The present invention is as described above, and a sheet molded body having hollow convex portions protruding from both the front and back sides can be molded using two molds having a large number of protruding columnar protrusions. Therefore, compared to conventional molding that uses a mold that matches the shape of the convex part, the structure is simpler and the mold cost is lower, and the depth of the convex part can be adjusted by adjusting the penetration depth of the two molds. Since the height can be freely selected and a wide variety of molded objects can be molded, mold costs are further reduced. Furthermore, the resulting sheet molded product can have increased compressive strength and adhesive strength, and is suitable for use as a panel core material, cushioning material, etc. Example 1 Two molds in which a plurality of square prism protrusions made of brass having a square top surface of 5 mm on a side and a height of 60 mm were protruded from a 10 mm thick aluminum plate at a pitch of 25 mm, arranged in grid intersections. were placed facing each other on the upper and lower sides of the press section of the radiation heating molding machine. Place the mold protrusion group attached on the upper side at the center of the four adjacent protrusions of the protrusion group attached on the lower side, that is, the protrusion group shown in Fig. 2 is on the upper side, and the protrusion group shown in Fig. 3 is on the lower side. As shown in Fig. 4, the upper and lower protrusions are positioned so that they alternately occupy grid intersection points, and at the same time, in order to prevent the protrusions from heating up to 20°C or higher,
A molding device was constructed by embedding a water cooling pipe for circulating cooling water inside the protrusion. On the other hand, a 0.5 mm thick sheet of hard polyvinyl chloride is heated with radiant heat to the appropriate molding temperature and quickly fed between the upper and lower molds to bring them closer together.
After the sheet was molded by being inserted between the upper and lower protrusions and cooled, the upper and lower molds were separated and the sheet molded product was taken out.
As a result, a 0.5 mm thick hard polyvinyl chloride sheet could be molded with square truncated hollow protrusions each side having a length of 5 mm on both the front and back sides. Also, the speed at which the sheet is inserted is 20
Molding was possible at mm/sec or higher. I tried adjusting the depth of the sandwiching to create molded bodies of various thicknesses, but I was unable to create anything over 50mm because the side walls became too thin during molding. When the molded bodies obtained under these conditions were examined in detail, it was found that the thickness of the top surface of the hollow convex portion was relatively thicker than the thickness of the side wall in each case. Similarly, similar results were obtained for impact-resistant polystyrene sheets and polypropylene sheets, as shown in Table 1, but W ₁ /W ₃ was 0.4. The compressive strength of the obtained molded product was measured according to the method of JIS Z 0234, and 1.0 Kg/cm ² or more was evaluated as ○.

【table】

[Table] Comparative example In a molding device similar to Example 1, only the protrusions
An experiment similar to that of the example was conducted using a regular square prism (4 mm or less on each side) where W ₁ /W ₃ <1/3. The compressive strength was measured by the test method and was as shown in Table 2. The evaluation of compressive strength is the same as in Example 1.

【table】

【table】 [Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a longitudinal cross-sectional view of the mold part of this device, and Figs. 2, 3, and 4 show an upper mold and a lower mold, respectively. FIG. 5 is a vertical sectional view showing the state of sheet molding by this device, and FIGS. 6 and 7 are respectively the obtained sheet molded bodies. FIG. 2 is a perspective view and a vertical cross-sectional view. A... Upper mold, A'... Lower mold, B... Sheet, 1... Substrate, 2, 2'... Protrusion, 3, 3'...
...Top surface, 4,4'...Side surface, 5,5'...Protrusion,
6, 6'...Top surface of the protrusion, 7,7'...Side surface of the protrusion,
W ₁ ...Top width of protrusions and protrusions, W ₃ ...Bottom width of protrusions, W ₂ ...Protrusion side spacing, H...
Protrusion penetration depth/2, t ₁ , t ₂ ...thickness of the top and side surfaces of the protrusion.

Claims (1)

[Claims] 1. Two molds each having a plurality of protruding columnar projections each having a flat top surface face each other, and the projections of one mold fit into the approximately central position between the projections of the other mold. , at least one of the molds is disposed so as to be movable in the height direction of the protrusion, and the two molds are cooled to a temperature at which at least the top of the protrusion does not substantially flow the thermoplastic resin sheet to be molded. When one protrusion is inserted between the other protrusions, the distance between the sides of the other protrusion located on both sides of one protrusion is W ₂ ,
If the width of the top surface of the protrusion in the direction of the side spacing is W ₁ and the depth into which the protrusion enters is 2H, then 2W ₁ /W ₁ +W ₂ ≧1/3, 2H/W ₁ +W
A molding device for a thermoplastic resin sheet molded article, characterized in that a relationship of ₂ < 2 holds true.