JPS6215330B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic resin sheet molded article and a method for molding the same. The purpose is to have excellent bulkiness,
Moreover, the object of the present invention is to propose a molded sheet having high compressive strength and suitable as a panel core material, a cushioning material, etc., and a method for molding the same. The gist of this invention is that a plurality of hollow truncated cone-shaped convex portions are provided alternately on both the front and back surfaces of a thermoplastic resin sheet, and the convex top surface is flat and the height (H) from the sheet surface to the top surface is are equal to each other, and when the unidirectional widths of the top and bottom of the protrusion are W ₁ and W ₂ , and the sheet thicknesses of the top and side walls of the protrusion are t ₁ and t ₂ , H/W ₂ <2/1, The present invention provides a thermoplastic resin sheet molded article and a method for molding the same, characterized in that the following relationships are established: W ₁ /W ₂ ≧1/3, t ₁ >t ₂ . FIGS. 1 and 2 show an example of an embodiment of the molded article according to the present invention.
2' protrude alternately from both the front and back surfaces of the thermoplastic resin sheet 1. The top surface 3 of the convex portion forms a square plane with one side W ₁ , and the top surface 3 of the sheet has a square plane, that is, the top surface 3 of the convex portion 2,
The height H from the center between the top surfaces 3, 3 of 2' is equal to each other, and the top surfaces 3, 3 of the front and back convex portions each form one plane. The bottoms of the convex portions 2 and 2' form a square with one side W ₂ , and the sheet thicknesses of the top surface 3 and side walls 4 are t ₁ and t ₂
It is becoming. The convex portion of this molded body has a height of H/W ₂ <2, that is, its height is less than twice the length of one side of the bottom W ₁ /W ₂ ≧1/3, that is, the length of one side of the top surface is less than the length of one side of the bottom. It has the shape of a truncated square pyramid, which is more than 1/3 of the length and 1/9 of the area. Further, t ₁ >t ₂ , that is, the sheet thickness of the top surface 3 of the convex portion is larger than the sheet thickness of the side wall. Since the convex portion has such a shape and dimensions, the molded article is bulky, and at the same time, the relatively wide top surfaces of the convex portion form a single plane on both the front and back surfaces, resulting in high compressive strength. For example, when used in the core material of panels, etc., the top surface of the wide convex portion comes into contact with the surface material, improving adhesive strength and compressive strength, and the formation of many independent voids separated by the convex portions makes it lightweight. The insulation properties are significantly improved. In addition, the adjacent convex portions 2 and 2' on the front and back surfaces are connected in a curved manner as shown in Fig. 1, and the curved ribs on both the front and back surfaces face each other at right angles, so that the bending strength can be improved. It is possible to plan. Furthermore, since the curved ribs are formed three-dimensionally from the convex portion of the molded body, the compressive strength of the convex portion itself is also greatly improved. The surface of the convex part of the molded body is planar as described above,
In order to increase the adhesive strength with a surface material when used as a core material of a panel or the like, or to improve the strength of the top surface of a convex portion, finer unevenness may be added. If H/W ₂ <2, that is, the height of the convex portion is more than twice the length of the bottom side, the elongation of the sheet during molding will be poor, and it will be extremely difficult to release the sheet from the mold, and at the same time In the ascending molded product, the convex portion becomes elongated and the sheet thickness on the side surface of the convex portion becomes too thin, making it easy for the convex portion to buckle during compression, resulting in a decrease in compressive strength, and W ₁ /W ₂ <1/3, i.e. When the length of one side of the top surface is less than 1/3 of the length of one side of the bottom, the ratio of the total area of the top surface of the entire molded object decreases, and the compressive strength decreases.
When used as a core material, the contact surface with the surface material is reduced, so the adhesive strength with the surface material is reduced, making it difficult to increase the bending strength of the entire panel, which is undesirable. This molded body is preferably made of hard polyvinyl chloride,
Sheets made of hard thermoplastic resins such as polystyrene, high-density polyethylene, polypropylene, nylon 6.66, polyester, and ABS resin (acrylonitrile-butadiene, styrene copolymer) are preferable, but sheets made of soft thermoplastic resins such as soft polyvinyl chloride and low-density polyethylene are preferable. A sheet of plastic resin may be used as the raw material. Those using hard resin are suitable as core materials for panels, and those using soft resin are suitable for use as cushioning materials, etc. However, its use is not limited to core materials or cushioning materials. Generally, the sheet thickness is 100μ to 1000μ, the top surface area is 0.09cm ² to 25cm ² , and the thickness between the front and back convex tops is 5mm.
~100mm. The method for molding this molded body will be explained using the drawings. In Figures 3, 4, 5, and 6, the molding device has an upper mold A and a lower mold A', each mold corresponding to every other grid intersection of the substrates 5, 5 and their surfaces. It has a plurality of protrusions 6, 6' protruding at certain positions, and the protrusions 6, 6' are in the shape of a square column (one side length W ₁ ) with flat top surfaces 7, 7'. These upper and lower molds A, A' are arranged facing each other with protrusions 6, 6' facing each other, and the protrusion 6 of one mold A is approximately at the center of the four protrusions 6' of the other mold A'. The protrusions 6, 6' of the two molds A, A' that are close to each other are positioned at grid intersections. In the close state, the distance W ₃ between the side walls of the other mold A' located on both sides of the protrusions 6 of one mold A, and the overlapping part of the protrusions 6' of the other mold that have entered between the protrusions 6 of one mold A. Penetration depth is 2H
Then, 2W ₁ /W ₃ +W ₁ ≧1/3, 2H/W ₃ +W ₁ <2
I am satisfied. When molding a sheet molded product using this device, the raw material sheet B made of thermoplastic resin is heated in advance to a temperature at which it can be fluidized and thermoformed, and this is placed between the upper and lower molds A and A'. urge On the other hand, the upper and lower molds A, A' are cooled to a temperature at which the raw material sheet B does not flow and cannot be thermoformed, and then the upper and lower molds A,
A' is brought close to the raw material sheet B so as to sandwich it therebetween. The top surfaces 7, 7' of the protrusions 6, 6' of the upper and lower molds A, A' contact the sheet B from the upper and lower surfaces of the raw material sheet B, and then approach the protrusions 6, 6' until the penetration depth reaches 2H. The sheet B is stretched in the vertical direction with the top surface 7 of the sheet B as a fixed position. Since the projections 6, 6' are at a low temperature that cannot be thermoformed, the portion of the sheet B in contact with these is cooled and solidified, and the projections 6, 6' are not stretched.
Since the sheet B between 6' does not touch the protrusions 6, 6', it is difficult to cool down and is easily stretched. As shown in FIGS. 1 and 2, the molded product formed in this manner has hollow truncated square pyramid-shaped convex portions 2 and 2' protruding alternately on both the front and back surfaces of the sheet 1.
The top surfaces 3, 3' of the convex portions 2, 2' form a square plane with a side length of W ₁ , the height of the top surface 3 from the sheet 1 surface is H, and the upper and lower top surfaces each form one plane. do. The length W ₂ of each bottom side of the protrusions 3, 3' is W ₃ +W ₁ /2, and 2W ₁ /W ₃ +W ₁ ≧1/3, so the molded protrusions 2, 2' are Similar to those shown in FIG. 1 and FIG. 2, it becomes a truncated regular square pyramid that satisfies H/W ₂ <2/1 and W ₁ /W ₂ ≧1/3. Further, the top surface 3 of the convex portion formed in contact with the top surfaces 7, 7' of the mold is not stretched, but the portion of the side wall 4 is stretched, resulting in a relationship of t ₁ >t ₂ . Furthermore, when changing the height H of the molded product, the apparatus according to the present invention does not require replacing the mold itself as in the general sheet thermoforming method, but simply replaces the upper and lower molds A as shown in FIG. Just change the spacing of A′. The raw material sheet that can be molded by this molding method is made of the above-mentioned thermoplastic resin, and those with excellent stretchability are preferred. The temperature at which the raw material sheet can flow and be molded is the temperature at which the raw resin easily undergoes plastic deformation, and is generally a temperature near the melting point of the resin. The temperature at which the resin does not flow and cannot be molded is the temperature at which plastic deformation does not easily occur, and is generally lower than the melting point or softening point of the resin. In order to keep the mold at this temperature, cooling water is sent into the mold or the protrusion during molding, or cooling air is sent between the bases of the upper and lower molds to maintain the mold, especially the protrusion, at a predetermined temperature. Measures will be taken to maintain the The shape of this molded body is not limited to the one having the above-mentioned truncated square pyramidal convex portion. By selecting the shape of the protrusion, you can freely choose a shape such as a cone, rectangular square pyramid, or polygonal pyramid. This will be explained below with reference to examples. Example 1 A brass square prism with a top side length of 5 m/m was mounted on a 10 m/m thick aluminum plate with a pitch of 2.5 m/m.
m, a plurality of them were arranged in a square grid, and the length of the square prisms was adjusted to 60 m/m. These array groups of square prisms are attached to the upper and lower sides of the press section of a radiant heating molding machine, and the square prisms of the array group attached to the upper side form a square lattice of the four prisms of the array group attached to the lower side. The array groups of square prisms are arranged alternately so that they are located at the center of the array, that is, the array group of square prisms shown in Figure 3 is on the top, the array group shown in Figure 4 is on the bottom, and the array group of square prisms is on the bottom as shown in Figure 5. did. A 0.5 m/m thick sheet of hard polyvinyl chloride was heated with radiant heat until it reached the appropriate molding temperature, and quickly sandwiched between the upper and lower arrays of square prisms, and after the sheet had cooled, it was taken out. As a result, it was possible to obtain a molded body of a hard polyvinyl chloride sheet with a thickness of 0.5 m/m having square truncated hollow protrusions with a side length of 5 m/m 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. We tried to create various thicknesses of molded bodies by adjusting the depth of the sandwiching, but we were unable to create molded bodies with thicknesses over 50 m/m because the side walls became too thin during molding. A detailed examination of the molded bodies obtained under these conditions revealed 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 ₂ was 0.4. The compressive strength of the obtained molded body was measured according to the method of JISZ0234, and 0.1 Kg/cm ² or more was evaluated as 0.

【table】

[Table] Example 2 An array group was created in which brass square prisms with a top side length of 8 m/m were attached to an aluminum plate in the same arrangement as in Example 1. I conducted an experiment. The thickness of the side wall of the molded product obtained in this experiment was also relatively thin compared to the thickness of the top surface of the hollow convex portion. Further, when the thickness of the molded product was 50 mm or more and H/W ₂ was 2.0 or more, the sheet was torn and could not be molded. W ₁ /W ₂ at this time is 0.64. Example 3 Similar to Example 1, the length of one side of the top surface is 4.2 m/m
The experiment was conducted using a square prism. At this time, W ₁ / W ₂ was set to 1/3. Similar to Examples 1 and 2, the relationship t ₁ >t ₂ was also established for the molded bodies obtained in this experiment. Similarly, the thickness of the molded body must be 50 mm or more H/W ₂
But I couldn't do anything higher than 2.0. Comparative example In a prismatic array group with the same pitch as Example 1
Square prism such that W ₁ /W ₂ <1/3 <4m/m
An experiment similar to Example 1 was conducted using the following. The molded body obtained in this experiment
Compressive strength was measured using the JISZ0234 test method, but the second
It was as shown in the table. The evaluation of compressive strength is the same as in Example 1.

【table】 [Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIGS. 1 and 2 are perspective views and longitudinal sectional views of a sheet molded product, and FIGS. 3, 4, and 5 are views of an upper mold, respectively. , a schematic plan view showing the protrusion position when the lower mold and the upper and lower molds are brought close to each other, No. 6
The figure is a longitudinal sectional view of the molding device showing the molding state. 1... Sheet, 2, 2'... Convex portion, 3... Top surface, 4, 4'... Side wall, 5... Base, 6, 6'...
Projections, 7, 7'...top surface, A, A'...upper and lower molds, B...raw material sheet.

Claims (1)

[Scope of Claims] 1. A plurality of truncated cone-shaped hollow convex portions protrude alternately from both the front and back surfaces of a thermoplastic resin sheet, and the top surfaces of the convex portions are flat, and the height from the sheet surface to the top surface (H) are equal to each other, and the width in one direction of the top and bottom of the convex portion is W ₁ ,
When W ₂ and the sheet thickness of the top surface of the convex portion and the side wall are t ₁ t ₂ , the following relationships hold: H/W ₂ <2/1, W ₁ /W ₂ ≧1/3, t ₁ >t ₂ A thermoplastic resin sheet molded article characterized by: 2. Two molds each having a plurality of protruding columnar protrusions with flat top surfaces are arranged facing each other, and a thermoplastic resin sheet heated to a temperature at which it can flow and be molded is placed between the two molds. The temperature of the molding molds is set to such a temperature that the sheet does not flow and cannot be molded, and the two molding molds are brought close to each other so that the protrusions of one are inserted into the approximately central position between the protrusions of the other, and the sheet is placed at the top of the protrusions of the two molding molds. When the surface is set as a fixed position and stretched alternately in both the front and back directions, and hollow convex portions are formed alternately on both the front and back surfaces, the distance between the side walls of the other mold protrusion located on both sides of one mold protrusion is W ₃ , when the width of the top surface of the protrusion in the side wall spacing direction is W ₁ and the depth into which the protrusion enters when the mold approaches is 2H, 2W ₁ /W ₃ +W ₁ ≧1/3, 2H/W ₃ +W ₁ <2. A method for molding a thermoplastic resin sheet molded article, characterized in that a relationship is established.