JP3038368B2 - Polystyrene resin foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene resin foam sheet (hereinafter abbreviated as PSFS).

[0002]

2. Description of the Related Art PSFS is easy to perform secondary foam molding, and the resulting molded product is clean and lightweight, and has excellent heat insulation properties and is inexpensive. Used in This PSFS is
Generally, a nucleating agent such as polystyrene resin and talc is melt-kneaded using an extruder, and a foaming agent such as butane is press-fitted, then extruded and foamed from a circular die, expanded to a predetermined sheet width, and cooled to form a sheet. It is manufactured by. The PSFS thus manufactured is heated by a vacuum forming machine or the like, softened, secondary-foamed, and then shaped by a mold to form a predetermined molded product. By the way, in the secondary foam molding step, if the secondary foaming property in the thickness direction of the sheet is low, the thickness of the obtained molded body becomes thin, and the molded body has low strength. In addition, if the sheet has a small elongation at the time of softening and secondary foaming, the sheet will break when being shaped by a mold. For this reason, it has been practiced to obtain a predetermined thickness at the time of secondary foaming and a predetermined sheet elongation by increasing the amount of heating in the molding machine.
However, if the heating time in the molding machine is increased to increase the amount of heating in the molding machine, the molding speed decreases, and
When the heater temperature of the molding machine is increased, the heat energy loss increases, and the molding efficiency is significantly reduced. Further, when the heating amount in the molding machine is excessively increased, there is a problem that bubbles on the sheet surface are defoamed before a predetermined secondary foaming occurs, resulting in a molded article having a poor appearance.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems found in conventional polystyrene resin foam sheets, has a high secondary foaming property in the sheet thickness direction, and has an excellent sheet elongation during molding. It is an object of the present invention to provide a foamed polystyrene resin sheet which provides a secondary foam molded article having a large appearance and excellent appearance and strength.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have solved the above-mentioned problems by making the cell structure of the polystyrene resin foam sheet specific. It was found that the present invention was obtained, and the present invention was completed.

That is, according to the present invention, the extruder is continuously extruded and foamed through a circular die in a low-pressure region, and is then cut open to obtain a thickness of 1.0 to 5.0 m.
m, in a foamed polystyrene resin sheet having a basis weight of 100 to 300 g / m ² , the average number of cells in a straight line in the thickness direction included in a portion 300 μm thick from at least one side is 5 or less, and the thickness of the foamed sheet Is tmm, 2t / 5 to 3t / 5mm in the thickness direction from the sheet surface
The average cell diameter in the vertical section in the extrusion direction of the bubbles present in the range of the above and the average cell diameter in the vertical section in the width direction orthogonal to the extrusion direction are represented by the following formulas (1) and (2): 1.05 ≦ X / Z ≦ 1 .5 (1) 1.5 ≦ Y / Z (2) (X: average cell diameter in the extrusion direction of the foam sheet Y: average cell diameter in the width direction of the foam sheet Z: average cell diameter in the thickness direction of the foam sheet) The polystyrene resin foam sheet characterized by satisfying the following is provided.

Hereinafter, the PSFS of the present invention will be described in detail. The appearance (whiteness) of a molded product obtained by molding PSFS is determined by the number of cells in the thickness direction.
The number of bubbles in the thickness direction of the SFS is generally arbitrarily determined in the range of 10 to 30 and manufactured. In addition, conventional PS
The FS depends on the type of the molded body, but generally ranges from 1 to 2.
The sheet is formed into a sheet with a thickness of 5 mm, and is subjected to secondary foaming in the thickness direction by a factor of 2 to 3 in the heating section of the molding machine to be molded. As described above, the number of bubbles and the thickness in the thickness direction are determined arbitrarily.
In SFS, at least one sheet surface is 3
If the average number of cells in the thickness direction included in the sheet thickness portion of 00 μm is more than 5, the secondary foaming property is significantly reduced, the elongation is not good, and the heating amount of the molding machine is increased in order to increase the secondary foaming. If the height is increased, the air bubbles on the sheet surface are easily defoamed, the elongation of the sheet during molding is reduced, the sheet is easily broken when being shaped, and further, in the case of shallow drawing, Although the sheet does not break, it is difficult to obtain the shape of the molded article according to the mold. Although the causes are unknown, when the number of bubbles near the sheet surface increases, most of the width radiant heat received by the sheet passes through the bubble film near the sheet surface when the sheet is heated by the molding machine. Since the heat is converted into heat near the surface, the temperature of the sheet surface becomes excessively high, and the air bubbles in the same portion are easily defoamed. On the other hand, the temperature of the bubble film near the center in the sheet thickness direction is increased. It is considered that the secondary foaming property and the elongation of the sheet hardly increase.

The PSFS of the present invention has solved the above-mentioned problems. In the PSFS of the present invention,
When X / Z in the formulas (1) and (2) is smaller than 1.05 and Y / Z is smaller than 1.5, when the sheet undergoes secondary foaming in the heating section of the molding machine, the thickness direction is reduced. The sheet flow direction and / or
Alternatively, secondary foam expands in the width direction of the sheet, and the sheet hangs down in the molding machine due to its own weight due to softening, making it difficult to pass the sheet through the molding machine. The reason for this is that the distortion of the bubbles in the flow direction or the width direction of the sheet is too small, and at the same time as the sheet undergoes secondary foaming in the heating section of the molding machine, the distortion of the resulting bubbles is too small, and the distortion of the bubbles is recovered. It is thought to be smaller. On the other hand, X / Z is 1.5
If it is larger than the above, the distortion of the bubbles in the sheet flow direction is too large, and the sheet flow direction shrinkage in the heating part of the molding machine becomes large, so it is shaped in the shaping part and not yet sufficiently cooled The contracted force acts on the compact in the state, and the compact is deformed.

[0008] As a method for obtaining PSFS of the present invention, a generally used polystyrene resin is impregnated with a foaming agent, and then additives such as a nucleating agent are mixed, and the mixture is charged into an extruder. There is a method of extruding after mixing the polystyrene resin and additives such as a nucleating agent into the extruder after melting the polystyrene resin and extruding by pressing the blowing agent after melting the polystyrene resin, It is not limited to these methods. The cell structure of the PSFS shown in the present invention is characterized in that, in the above-described method for producing a foam, the expansion ratio from the diameter of the circular die to the sheet width, the extrusion temperature, the sheet cooling conditions after being discharged from the circular die, and the nucleation. It can be obtained by adjusting the addition amount of the agent. In the present invention, as shown in FIG. 1, in a cylindrical extruded foam sheet 2 obtained from a circular die 1, a desired ring is formed by bringing a resistance ring 4 into contact with and pressing the outer peripheral surface of the foam sheet immediately after the extrusion. The structure can be easily obtained. That is, in this way, when the resistance ring is provided near the exit of the circular die, and the sheet is pressed in the sheet thickness direction, (a) the bubbles near the surface gather at the time of contact with the resistance ring, and the number of bubbles is reduced. (B) The resistance ring acts on the sheet in the sheet flow direction to cause resistance, so that bubbles near the center in the sheet thickness direction are distorted in the sheet flow direction. (C) Foaming occurs at the time of contact with the resistance ring. Since the sheet moves in the thickness direction, the sheet of the present invention can be more effectively obtained because the sheet is distorted in the width direction when the sheet is developed in the width direction with the resistance ring as a base point. In FIG. 1, reference numeral 3 denotes a cooling drum. As the polystyrene resin in the present invention, styrene or a styrene derivative having its benzene nucleus substituted with a substituent such as an alkyl group, an alkoxy group, or a halogen is used. As the foaming agent and the nucleating agent, conventionally known ones are used, and their types are not particularly limited. In the PSFS of the present invention, the thickness is usually 1.0 to
It is about 2.5 mm, and its basis weight is 100 to 250 g /
m ² .

[0009]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. The parts shown below are parts by weight.

Example 1 As a polystyrene resin, polystyrene stylon 685 manufactured by Asahi Kasei Corporation was blended with 0.15 part of talc as a nucleating agent for 100 parts thereof, and the mixture was charged into a 90 mm extruder and melted. After kneading, butane as a foaming agent was pressed into the extruder at a ratio of 3.0 parts to mix the resin and the foaming agent. Next, the resin was cooled to a resin temperature of 150 ° C. by a connected 120 mm extruder, and then cooled to a resin diameter of 110 mm.
It is extruded and foamed through a circular die controlled at 0 ° C., and has a basis weight of 190 g /
m ² , thickness 2.2 mm, total number of bubbles in the thickness direction 19 to 21
PSFS were obtained.

Example 2 An experiment was conducted in the same manner as in Example 1 except that the amount of talc added was 0.1 part and the resin temperature was 153 ° C.
A PSFS having a basis weight of 190 g / m ² , a thickness of 2.2 mm, and a total of 16 to 18 bubbles in the thickness direction was obtained.

Example 3 An experiment was conducted in the same manner as in Example 1 except that the foaming agent was changed to 3.5 parts and the temperature of the circulator die was set to 130 ° C., and the basis weight was 190 g / m ² and the thickness was 190 g / m ² . 2.2 mm,
PSFS having a total of 19 to 21 bubbles in the thickness direction was obtained.

Comparative Example 1 In Example 1, butane was used instead of using a resistance ring.
The experiment was conducted in the same manner as in Example 1 except that the temperature of the circular die was 130 ° C. and the basis weight was 190 g /
m ² , thickness 2.2 mm, total number of bubbles in thickness direction 23 to 25
PSFS were obtained.

Comparative Example 2 In Example 1, butane was used instead of using a resistance ring.
The experiment was conducted in the same manner except that the resin temperature was set to 156 ° C. and 0 parts, to obtain PSFS having a basis weight of 190 g / m ² , a thickness of 2.2 mm, and a total of 18 to 20 bubbles in the thickness direction.

Comparative Example 3 An experiment was conducted in the same manner as in Example 2 except that the diameter of the circular die was set to 130 mm and the resin temperature was set to 155 ° C. without using the resistance ring, and the basis weight was 190 g / m ² and the thickness was 2 .
A 2 mm PSFS having a total of 14 to 16 bubbles in the thickness direction was obtained.

Next, the results obtained in the above Examples and Comparative Examples were obtained.
The cell structure of PSFS was measured as follows. Number of bubbles on the surface PSFS is sliced in the cross-sectional direction to a thickness of about 50 μm,
A cross-sectional photograph was taken with a microscope of 50 magnification. Using this photograph, a parallel line was drawn at a position of 300 μm from the surface of the sheet with respect to the sheet surface. Next, a perpendicular line was drawn on the sheet surface, and the number of bubbles that collided with the perpendicular line was measured up to the point where the perpendicular line intersects with the above-described parallel line. Table 1 shows the average number of bubbles thus measured. Measurement of Bubble Size PSFS was sliced to a thickness of about 50 μm in the cross-sectional direction in the flow direction and the width direction, and each cross-sectional photograph was taken with a microscope of 50 magnification. Using this photograph, the thickness of the sheet (tmm)
Is measured, 2t / 5 mm and 3 from the one surface of the sheet.
Two lines parallel to the sheet surface were drawn at a position of t / 5 mm. Next, two perpendicular lines were drawn at intervals corresponding to 2 mm from the sheet surface. With respect to the bubbles including the entirety of the bubbles in these four straight lines, the bubble size in the thickness direction (Zmm), the bubble size in the sheet flow direction (Xmm), and the bubble size in the sheet width direction (Ymm) were measured. The average cell size determined in this way is shown in Table 1.

Next, with respect to the PSFS obtained in the above Examples and Comparative Examples, the amount of the residual foaming agent with respect to the number of days elapsed after extrusion was measured, and when the amount of the residual foaming agent became 2.8 to 2.9 wt%. The secondary foaming moldability of each PSFS was evaluated using a vacuum forming machine as follows. (1) Secondary Foaming Property The heater thickness of the molding machine was set to 250 ° C., and the sheet thickness after secondary foaming when heated in a heating section for 5 seconds was measured. At this point, the evaluation was interrupted for the sheet which sagged in the heating section and could not be passed through the molding machine. (2) Elongation of sheet Under the heating conditions shown in (1), a tray having a size of 10 cm × 19 cm and a depth of 3.0 cm was formed, and whether or not a molded article according to the shape of a mold was obtained, and whether the sheet was broken. Examined. ：: A molded article conforming to the shape of the mold can be obtained at all locations. ：: There is a difference from the mold shape mainly at the outer periphery. ×: The molded article is cracked and the molded article cannot be obtained.

[0018]

[Table 1]

A: Outer surface of circular die B: Inner surface of circular die

From the above results, the PSFS of the present invention is 2
It can be seen that the secondary foamability and the elongation of the sheet during the next foam molding are excellent.

[0021]

The foamed polystyrene resin sheet of the present invention is excellent in the secondary foaming property and the elongation of the sheet during the secondary foam molding, so that the molding efficiency is remarkably improved.

[Brief description of the drawings]

FIG. 1 is a system diagram 1 for obtaining a PSFS of the present invention.
Here is an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circular die 2 Extruded foam sheet 3 Cooling drum

Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29L 7:00 C08L 25:00

Claims (1)

(57) [Claims] 1. A continuous extrusion foaming from an extruder through a circular die to a low pressure region, followed by cutting and opening, a thickness of 1.0 to 5.0 mm and a basis weight of 100 to 300.
g / m ² of a polystyrene resin foam sheet, the average number of cells in a straight line in the thickness direction included in a thickness portion of at least 300 μm from one side is 5 or less, and the thickness of the foam sheet is tmm, The average cell diameter in the vertical section in the extrusion direction of bubbles existing in the range of 2 t / 5 to 3 t / 5 mm in the thickness direction from the sheet surface and the average cell diameter in the vertical section in the width direction orthogonal to the extrusion direction are represented by the following formula (1). )
And (2) 1.05 ≦ X / Z ≦ 1.5 (1) 1.5 ≦ Y / Z (2) (X: average cell diameter in the extrusion direction of the foam sheet Y: average cell in the width direction of the foam sheet (Z: average cell diameter in the thickness direction of the foamed sheet).