JP2001138383A - Polystyrene resin foam sheet and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrene resin foamed sheet which has its aging period shortened and secondary foaming properties showing uniformity in the width direction as well as a method for manufacturing the polystyrene resin foamed sheet. SOLUTION: The polystyrene resin foamed sheet is obtained by extrusion- molding a polystyrene resin and a foaming agent and has the end part in the width direction molded thicker than the average thickness in the width direction. Further, the polystyrene resin foamed sheet is rolled and then is aged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polystyrene resin foam sheet and a method for producing the same. More specifically, the present invention relates to a polystyrene resin foam sheet capable of shortening the aging period after extrusion molding and having uniform secondary foam moldability in the width direction of the sheet, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a container formed by heating and molding a polystyrene resin foam sheet has been used as a container for storing various instant foods, snack foods, and the like. Such a polystyrene resin foam sheet is lightweight and inexpensive,
It has advantages such as good heat insulation.

[0003] As a method for producing a polystyrene resin foam sheet, an extrusion foam molding method having features such as a simple molding step and stable quality of the polystyrene resin foam sheet has been widely adopted. In most cases, the obtained foamed polystyrene resin sheet is commercialized as a wound layer body obtained by winding the sheet into a roll. The diameter of the sheet generally varies depending on the thickness and length of the sheet.
It is about 5 to 1.0 m.

[0004] Immediately after extrusion, the foaming agent is gasified and dissipated from the sheet-like foam, and the atmospheric gas starts to flow into the foam, so-called aging occurs. The aging period is defined as the period until the extruded foam increases the secondary foaming formability and satisfies a favorable foaming state. In the case of wound layers, this aging period is usually required for 2 to 3 weeks. It has been.

[0005] As a method of shortening the aging period, a fine gap is formed between the foamed sheet layers of the wound body. This method includes JP-A-4-138239,
JP-A-5-77304 and JP-A-9-480
There is a method described in Japanese Patent Publication No. 30-300. JP-A-4-1
In the method disclosed in Japanese Patent No. 38239, the thickness of the end portion in the sheet width direction is formed smaller than the average thickness in the width direction, and the winding tension at the time of winding is reduced. Also, Japanese Patent Application Laid-Open No.
In the method described in Japanese Patent Application Laid-Open No. 4 (1999) -1995, after providing irregularities of a specific height that do not remain during thermoforming on the sheet surface, the sheet is wound up in a roll shape. Furthermore, in the method described in JP-A-9-48030, a method has been proposed in which the sheet winding is loosened and irregularities having a specific height that do not remain during thermoforming are provided on the sheet surface.

[0006]

However, aging proceeds when air flows into the center from the end in the sheet width direction, and at the same time, the blowing agent in the foamed sheet diffuses into the atmosphere from the end in the sheet width direction. Therefore, in any of the above methods, a difference occurs in the aging state between the end portion and the center portion, and a foamed sheet having uniform secondary formability in the sheet width direction cannot be obtained. Therefore, the present inventors have conducted intensive studies, and as a result, by defining the shape of the polystyrene resin foam sheet before winding, it is possible to shorten the aging period after extrusion foam molding, and furthermore, to reduce the secondary time in the sheet width direction. The present inventors have found that a polystyrene resin foam sheet having uniform foaming moldability can be obtained, and have reached the present invention.

[0007]

That is, the polystyrene resin foam sheet of the present invention is a resin foam sheet made of a polystyrene resin and wound in a roll shape, and has an end portion in the width direction of the sheet. The thickness is formed to be thicker than the average thickness in the width direction.

In such a polystyrene resin foam sheet, the maximum thickness within a range of 10 cm from both ends in the width direction of the sheet is 0.1 mm from the average thickness in a range excluding each 10 cm from both ends in the width direction of the sheet.
It is thicker than that.

Further, in the polystyrene resin foam sheet, the polystyrene resin is a polystyrene homopolymer resin or a copolymer resin of a polystyrene and a monomer copolymerizable with polystyrene.

[0010] Next, the gist of the method for producing a foamed polystyrene resin sheet according to the present invention is to extrude a polystyrene resin together with a foaming agent to produce a sheet-like foam and, at the same time, to produce a sheet-like foam. Processing to make the thickness of the end portion larger than the average thickness in the width direction.

Another aspect of the method for producing a polystyrene resin foam sheet according to the present invention includes a step of extruding a polystyrene resin together with a foaming agent to produce a sheet-like foam, and Processing the foam-like foam to adjust the thickness of the end portion in the width direction to be greater than the average thickness in the width direction.

In the method for producing a polystyrene-based resin foam sheet, the sheet-like foam is processed by molding one or both sides of the foam into a concave shape in a width direction by a pressing roll.

Further, in the method for producing a polystyrene resin foam sheet, the concave shape is formed within a range that does not destroy the cell structure of the sheet foam.

Further, in the method for producing a foamed polystyrene resin sheet, the maximum thickness within a range of 10 cm from both ends in the width direction of the sheet-like foam may be less than 10 cm from both ends in the width direction of the sheet. The thickness is adjusted to be 0.1 mm or more than the average thickness in the range.

Further, in the method for producing a foamed polystyrene resin sheet, the polystyrene resin may be:
It is a polystyrene homopolymer resin or a copolymer resin of a polystyrene and a monomer copolymerizable with polystyrene.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The polystyrene resin as a raw material of the foamed polystyrene resin sheet of the present invention is a homopolymer resin of polystyrene or a copolymer resin of a monomer mainly composed of polystyrene and copolymerizable with polystyrene.

The foaming agent used as a raw material of the polystyrene resin foam sheet of the present invention is not particularly limited, and can be appropriately selected from known physical foaming agents and chemical foaming agents. Examples of the physical foaming agent include hydrocarbon compounds such as propane, butane, hexane, heptane, cyclobutane and cyclopentane, trichlorofluoromethane, dichlorodifluoromethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane. , 1-chloro-1,1-difluoroethane, 1,1-difluoroethane,
Examples thereof include halogenated hydrocarbons such as 1,1-dichloro-2,2,2-trifluoroethane, methyl chloride, ethyl chloride, and ethylene chloride, carbon dioxide, nitrogen, air, water, and mixtures thereof. . Examples of the chemical foaming agent include an organic thermal decomposition type foaming agent such as azodicarbonamide, and a combination of bicarbonate and an organic acid such as citric acid.

Further, a cell regulator can be added to the raw material of the polystyrene resin foam sheet of the present invention.
Examples of such a cell regulator include inorganic substances such as talc and calcium carbonate. Further, a plasticizer, a stabilizer, a colorant, and the like can be added to the raw material of the polystyrene resin foam sheet of the present invention as needed.

In the production of the polystyrene resin foam sheet of the present invention, first, a raw material comprising a polystyrene resin, a foaming agent, and other additives is melted and kneaded in an extruder, and then a temperature and pressure suitable for foaming are obtained. A sheet-like foam is formed by extruding the kneaded material from a slit die or a circular die adjusted to a predetermined temperature. When a circular die is used, a sheet-like foam is obtained by extruding once into a cylindrical shape and then cutting along an arbitrary line. As the extruder, any equipment generally used in the art can be used.

In the method for producing a foamed polystyrene resin sheet of the present invention, the thickness of both ends of the extruded sheet-like foam itself is adjusted by adjusting the shape of the die at the time of extrusion molding, so as to be greater than the average thickness in the width direction. Process to be thick. This makes it possible to directly obtain the polystyrene resin foam sheet according to the present invention.

More generally, the sheet-like foam obtained by extrusion molding is processed so that the thickness of the end of the foam in the width direction is larger than the average thickness in the width direction. The processed polystyrene resin foam sheet is wound into a roll. As a processing method, after extrusion molding, a method of heating the end portion of the sheet-like foam before winding up to increase the thickness of only the end portion, or simultaneously with extrusion molding or sheet-like foaming before winding up after extrusion molding Examples thereof include a method of laminating a thermoplastic resin on a body end portion, and a method of forming one or both sides of a sheet-like foam after extrusion molding and before winding into a concave shape in a width direction by a pressing roll. In particular, a method of forming a concave shape in the width direction using a pressing roll is preferable because the structure of the processing apparatus is simple and the thickness of the foam is easily adjusted.

The structure of the pressing roll is not particularly limited. 1
As one embodiment, there is a structure in which two rolls are set to be shorter than the thickness of the sheet-like foam to be processed, and the sheet-like foam is pressed by passing between the rolls.

In this case, as shown in FIG. 1, for example, the width of the upper roll 1 is shorter than the width of the sheet-like foam 3, and the width of the lower roll 2 is greater than the width of the sheet-like foam 3. As a result, a polystyrene resin foam sheet 20 formed in a concave shape as shown in FIG. 2 is obtained. Alternatively, by setting both of the upper and lower rolls shorter than the width of the sheet-like foam 3, a polystyrene resin foam sheet 22 having both ends protruding as shown in FIG. 3 can be obtained. Further, as shown in FIG. 4, the sheet-like foam 3 is formed by forming a roll 25 having a small outer diameter at both ends of the upper roll 24 and forming a notch 26 in the roll 25. It is preferable to press. When the upper roll 24 makes one rotation, the grooves 27 are repeatedly formed in the thick portions at both ends of the polystyrene resin foam sheet 28,
It becomes an air conduction part.

In the method for producing a foamed polystyrene resin sheet of the present invention, when both ends in the width direction are formed to be thicker than the average thickness of the other portions by using a pressing roll, the cell structure of the foamed sheet obtained is To the extent that it does not destroy Specifically, the amount of pressing is 30% or less, preferably 10% or less of the thickness of the sheet foam before pressing. Here, the pressing amount is the difference between the thickness of the sheet foam before pressing and the thickness of the foam sheet after pressing.

Regardless of which method is used for processing, the obtained polystyrene resin foam sheet of the present invention has a maximum thickness within a range of 10 cm from both ends in the width direction, and a maximum thickness of 10 cm from both ends in the width direction of the sheet.
It is preferable that the thickness is 0.1 mm or more than the average thickness in a range excluding cm. The width of the polystyrene resin foam sheet is preferably 50 cm or more.

Alternatively, the polystyrene-based resin foam sheet of the present invention is not particularly limited, but the production steps can be performed separately, but it can also be produced continuously by an apparatus as shown in FIG. That is, in this embodiment, a kneaded product obtained by melt-kneading a polystyrene-based resin with a foaming agent and other additives is extruded from an extruder 4 through a circular die 5. The extruded cylindrical foam is formed into a cylindrical shape having a substantially constant thickness by a mandrel 6, cut at a line in the feed direction where the mandrel 6 exits, and formed into a sheet-like foam 3. This sheet-like foam 3 is taken up by a take-up roll 7.
Then, it is pressed by the upper pressing roll 1 and the lower pressing roll 2 to produce a polystyrene resin foam sheet. Thereafter, the produced polystyrene-based resin foam sheet is wound by a winder 8 to obtain a foam sheet wound layer body 9.

In the polystyrene resin foam sheet according to the present invention, after winding, a gap is formed between the central portions in the width direction of the sheet, and a space containing air is formed therein, so that the aging period can be shortened. Furthermore, this space extends from the center in the width direction to the vicinity of the end, and aging proceeds simultaneously in the width direction, so that uniform secondary foaming properties can be obtained.

[0028]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. All parts shown below are parts by weight.

Example 1 A polystyrene resin and 1.0 part of talc as a nucleating agent were blended and charged into a first extruder to be melted and kneaded. Thereafter, butane as a foaming agent was pressed into the extruder, and the resin and the foaming agent were mixed.

Next, the resin temperature was lowered to 150 ° C. by a connected second extruder, and the kneaded material was extruded into a cylindrical shape through a circular die, and then cut to have an average thickness of 2.25.
mm, a width of 1050 mm, and a basis weight of 250 g / m ² were obtained. The average thickness is 10 m in the sheet width direction.
It is the arithmetic mean of the thickness measured at m intervals.

The obtained sheet-like foam was sequentially passed through a pressing roll shown in FIG. 1, and one side of the sheet was formed into a concave shape in the width direction. In the polystyrene resin foam sheet after the press molding, the maximum thickness in a range of 10 cm from both ends in the width direction is 2.28 mm, and the average thickness in a range excluding each 10 cm from both ends in the width direction of the sheet is 2.15 mm. there were.

Thereafter, a length of 315 m was continuously wound to obtain a roll-shaped rolled body having a core diameter of 258 mm, an outer diameter of 990 mm, and 160 turns. This wound layer body was aged at room temperature, and the secondary foamability was evaluated by the following method.

The 80th round from the outermost periphery of the wound layer body during aging was sampled, and a 10 cm square test piece cut at intervals of 20 cm from the center in the sheet width direction was fixed at its periphery to prevent heat shrinkage. The mixture was heated in an oven maintained at a temperature of 15 ° C for 15 seconds to cause secondary foaming. The thickness ratio before and after heating, that is, (thickness after heating / thickness before heating) is defined as the secondary expansion ratio. The point at which the secondary expansion ratio becomes the maximum is defined as the aging.

Table 1 shows the measurement results. In the table, A is the measurement result at the center position in the width direction of the foam sheet, B is the measurement result at a position 20 cm away from the center, and C is the measurement result at the position 40 cm away from the center. According to this example, the secondary expansion ratio reached the maximum on the seventh day of ripening, and then gradually decreased. Therefore, the aging period was 7 days. The temporary thickness, secondary thickness, and secondary expansion ratio in the width direction are almost the same, and it can be seen that ripening in the sheet width direction is proceeding simultaneously.

[0035]

[Table 1]

(Example 2) The sheet-like foam obtained in the same manner as in Example 1 was sequentially passed through a pressing roll having a smaller roll interval than in Example 1, and one surface of the sheet was formed into a concave shape in the width direction. Molded. The thickness of the foamed sheet after pressing is 2.28 mm in the range of 10 cm from both ends in the width direction, and 10 c each from both ends in the width direction of the sheet.
The average thickness in the range excluding m was 2.00 mm.

Thereafter, winding was performed in the same manner as in Example 1 to obtain a roll-shaped wound layer body. This wound body was aged at room temperature in the same manner as in Example 1 and measured. Table 2 shows the measurement results. The aging period was 5 days, and the temporary thickness, secondary thickness, and secondary expansion ratio in the sheet width direction were almost the same as in Example 1.

[0038]

[Table 2]

(Comparative Example 1) The sheet-like foam obtained in the same manner as in Example 1 was continuously wound into a length of 315 m without passing through a pressing roll.
A roll-shaped layered body having a diameter of 58 mm, an outer diameter of 995 mm, and 160 turns was obtained. This wound body was aged at room temperature in the same manner as in Example 1 and measured. Table 3 shows the measurement results.

[0040]

[Table 3]

Aging took 14 days or more. The secondary foaming properties differed in the sheet width direction, and ripening was fast at point C near the end in the width direction, and point A in the center was slowest. further,
Even in the results after 60 days, variation in the secondary foaming property was observed.
The point was the slowest.

(Comparative Example 2) The foamed sheet obtained in the same manner as in Example 1 was successively passed through a pressing roll having a smaller roll interval than in Example 2, and one side of the sheet was formed into a concave shape in the width direction. did. The thickness of the foam sheet after pressing is
The maximum thickness within a range of 10 cm from both ends in the width direction is 2.28 mm, and the maximum thickness is 10 mm from both ends in the width direction of the sheet.
The average thickness in the range excluding cm was 1.50 mm. The cell structure of this foam sheet was broken, and it was not possible to obtain a sufficient secondary foaming property even after aging.

[0043]

As described above, the foamed polystyrene resin sheet according to the present invention has a space containing air between the sheets of the wound body as compared with the conventional foamed polystyrene resin sheet. Polystyrene that communicates from the center in the width direction to the vicinity of the end, and ripening proceeds simultaneously in the width direction, so that the aging period after extrusion foaming can be shortened and the secondary foamability in the sheet width direction is uniform. There is an effect that a resin foam sheet can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of one embodiment of a pressing roll that can be used for producing a polystyrene resin foam sheet of the present invention.

FIG. 2 is a cross-sectional view of one embodiment of the polystyrene resin foam sheet of the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the polystyrene resin foam sheet of the present invention.

FIG. 4 is a schematic perspective view of a main part of another embodiment of a pressing roll and a foamed sheet which can be used for producing a polystyrene resin foamed sheet of the present invention.

FIG. 5 is a schematic view of a manufacturing apparatus for continuously manufacturing a polystyrene resin foam sheet of the present invention.

[Explanation of symbols]

 1: Upper pressing roll 2: Lower pressing roll 3: Sheet-like foam 20, 30: Polystyrene resin foam sheet 4: Extruder 5: Die 6: Mandrel 7: Take-up roll 8: Winder 9: Polystyrene resin foam Sheet winding body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 04 B29K 105: 04 B29L 7:00 B29L 7:00 C08L 25:04 C08L 25:04 F term ( 4F074 AA32 BA13 BA32 BA33 BA34 BA36 BA37 BA40 BA42 CA22 DA34 4F207 AA13E AB02 AB08 AE02 AG01 AG20 AH55 AH56 AH58 AR12 KA01 KA11 KA19 KL84 KL88 KW26 KW42

Claims (9)

[Claims] 1. A resin foam sheet made of a polystyrene resin and wound into a roll, wherein a thickness of an end portion in a width direction of the sheet is formed to be larger than an average thickness in a width direction. Characterized by polystyrene resin foam sheet. 2. 10c from both ends in the width direction of the sheet.
2. The polystyrene resin foam sheet according to claim 1, wherein a maximum thickness in a range of m is 0.1 mm or more than an average thickness in a range excluding 10 cm from both ends in a width direction of the sheet. 3. The polystyrene resin according to claim 1, wherein the polystyrene resin is a polystyrene homopolymer resin or a copolymer resin of a monomer copolymerizable with polystyrene and polystyrene. Foam sheet. 4. A step of extruding a polystyrene resin together with a foaming agent to produce a sheet-like foam while simultaneously processing the end portion in the width direction so as to have a thickness greater than the average thickness in the width direction. A method for producing a polystyrene-based resin foam sheet, comprising: 5. A step of extruding a polystyrene-based resin together with a foaming agent to produce a sheet-like foam, and processing the sheet-like foam so that the thickness of an end in the width direction is an average thickness in the width direction. A method for producing a polystyrene resin foam sheet, comprising a step of adjusting the thickness of the polystyrene resin foam sheet to be larger. 6. The polystyrene system according to claim 5, wherein the processing of the sheet-like foam is performed by forming one or both sides of the foam into a concave shape in a width direction by a pressing roll. A method for producing a resin foam sheet. 7. The method for producing a polystyrene resin foam sheet according to claim 6, wherein the molding into the concave shape is performed within a range that does not destroy the cell structure of the sheet foam. 8. In the processing of the sheet-like foam, the maximum thickness within a range of 10 cm from both ends in the width direction is 0.1 mm or more than the average thickness in a range excluding each 10 cm from both ends in the width direction of the sheet. The method for producing a polystyrene-based resin foam sheet according to any one of claims 4 to 7, wherein adjustment is performed so as to be as follows. 9. The method according to claim 4, wherein the polystyrene resin is a polystyrene homopolymer resin or a copolymer resin of a polystyrene and a monomer copolymerizable with polystyrene. Of producing a polystyrene resin foam sheet.