JP2001129865A - Manufacturing method for thermoplastic resin foamed sheet using sheet fixing tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method for a thermoplastic resin foam, by which a maturing period can be shortened. SOLUTION: In this manufacturing method for a thermoplastic resin foamed sheet, the mixture of a thermoplastic resin and a foaming agent is heated and kneaded in an extruder so as to be extended in a form of a sheet and then wound up in a roll on a sheet fixing tool having a roll core material and a side surface part provided at least at one side of the roll core material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed thermoplastic resin sheet, and an object of the invention is to provide a sheet having improved handleability of a product and a shortened aging period.

[0002]

2. Description of the Related Art In recent years, a container formed by heating and molding a thermoplastic resin foam sheet has been used as a container for storing various instant foods, snack foods and the like. The thermoplastic resin foam sheet has advantages such as being lightweight and inexpensive, and having good heat insulating properties. As a method for producing a thermoplastic resin foam sheet, an extrusion foam molding method which has features such as a simple molding process and stable quality of the thermoplastic resin foam sheet has been widely adopted.

In this extrusion foam molding method, a resin composition melt-kneaded together with a foaming agent or the like is discharged into the atmosphere from an annular die orifice to form a tubular resin foam, and then the tubular foam is formed. The surface is cooled by contact with a cooling drum, and then one end or two ends of the tubular foam are cut open to produce a thermoplastic resin foam sheet.

[0004] By the way, such a thermoplastic resin foam sheet is usually discharged immediately after being extruded using a circular die or the like, and then the gasified foaming agent escapes from the sheet and the atmospheric gas flows into the sheet. Begins, which is known as the aging phenomenon. Immediately after being extruded into a sheet, the secondary foaming formability of the sheet is increased, and the period from when the sheet satisfies a favorable foaming state is referred to as an aging period. In a normal case, the aging period has elapsed. It is later subjected to secondary foam molding.

However, the above-mentioned aging phenomenon is a phenomenon of gas permeation through a thermoplastic resin. In addition, since the raw material is a rolled body of a foamed sheet, the outflow and inflow of the gas become slow, Especially in the sheet near the outermost periphery of the sheet and the sheet near the middle layer of the sheet, there is a difference in the ripening state,
It has been considered that a certain aging period is necessary and inevitable for the secondary foam moldability to be uniform in the raw material.

[0006] Here, the longer the period required for aging, the more space is required for storing and managing the foamed resin sheet wound up in a roll shape, which has been a major problem in terms of storage space and cost.

In order to shorten the time required for ripening, Japanese Patent Application Laid-Open Nos. 4-138239 and 5-7
No. 7304 and JP-A-9-48030. In Japanese Patent Application Laid-Open No. 4-138239, a method is adopted in which the winding of the sheet is loosened by lowering the winding tension when the sheet is wound. Although the aging period can be shortened to some extent by this method, if the winding of the sheet is loosened in order to further shorten the aging period, there is a drawback that the winding will be lost and the workability will be deteriorated. Also, Japanese Patent Application Laid-Open No.
In Japanese Patent Application Publication No. 4 (1999) -1992, a method is adopted in which irregularities of a specific height that do not remain during thermoforming are provided on the sheet surface, and the sheet is wound up in a roll shape to shorten the aging period. In this method, there is a limit to the depth of the unevenness in order to eliminate the unevenness on the sheet surface during the thermoforming, and it was not possible to expect a drastic shortening of the aging period.

[0008]

SUMMARY OF THE INVENTION Therefore, Japanese Patent Application Laid-Open No. 9-48 is disclosed.
Japanese Patent Publication No. 030 discloses a method in which these are combined, the sheet winding is loosened, and an uneven portion having a specific height which does not remain during thermoforming is provided on the sheet surface. However, in this method too, if the winding is too loose, the winding will be lost and the workability will deteriorate, so that a drastic shortening of the aging period cannot be expected.

The present inventors have conducted intensive studies on shortening the aging period of the thermoplastic resin foam sheet, and as a result,
The present invention has been found that the use of a sheet fixing device having a core and a side portion on at least one side when winding a thermoplastic resin foam sheet does not cause winding collapse and has good workability and can greatly shorten the aging period. Reached.

[0010]

That is, when a mixture of a thermoplastic resin and a foaming agent is heated and kneaded in an extruder and extruded into a sheet and wound into a roll, the roll core material and at least one side surface are provided at one side. The above problem can be solved by winding the sheet around the sheet fixing device.

The thermoplastic resin foam sheet that can be used in the present invention is a foam sheet obtained by a generally used extrusion foam molding method. Although the resin is not particularly limited, for example, general-purpose polystyrene resin, high-impact polystyrene resin, styrene-ethylene copolymer resin, styrene-acrylonitrile copolymer resin, styrene-methyl methacrylate copolymer resin, styrene-acrylate copolymer Polymer resins, styrene-based resins such as styrene-maleic anhydride copolymer resins and mixtures thereof,
Polyolefin resins such as polypropylene and polyethylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; polyamide resins; and the like can be appropriately selected from single substances or mixtures thereof.

An inorganic substance such as talc and calcium carbonate, a plasticizer and a stabilizer can be added to these thermoplastic resins according to a desired substance. The foaming agent can be appropriately selected from physical foaming agents and chemical foaming agents known as thermoplastic resin 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, 1,1-dichloro-2,2,2-trifluoroethane, methyl chloride,
Examples thereof include halogenated hydrocarbons such as 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.

[0013] The material of the sheet fixing device is not particularly limited. For example, metals such as iron, aluminum and brass; paper; thermoplastic resins such as vinyl chloride resin and polyethylene; and thermosetting resins such as phenol resin. These may be combined, if necessary. In particular, a lightweight and durable material is suitable for improving workability, and a vinyl chloride resin is suitable from the viewpoint of cost.

The shape of the sheet fixing device is prepared according to the shape of the winding machine used when extruding the sheet. The structure of the sheet fixing device includes a tubular core for winding the sheet, and a side surface portion attached to at least one end of the core tube in a diameter direction of the core tube. The shape of the side portion is not particularly limited, and for example, the shape shown in FIG. Further, the side portion may be fixed to the core or detachable. When there are side portions on both sides, the detachable type is preferable.

The core of the sheet fixing device is preferably a circular tube, and its diameter is determined by the winding roll of the sheet winding machine. Usually, the diameter of the winding roll of the winding machine is variable by air pressure. The core of the sheet fixing device is set to match the maximum diameter of the take-up roll so as not to cause slippage between the take-up roll and the take-up roll.

Next, a method for producing a thermoplastic resin foam sheet of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram of a winder used in the manufacturing method of the present invention.

In the figure, a take-up roll 22 takes up a thermoplastic resin foam sheet 21 with low tension. 25
Take-up roll is prepared for winding the next sheet. After the 24 sheet fixing devices are mounted with the diameter of the 25 winding rolls being minimized, the diameter of the 25 winding rolls is increased to fix the sheet fixing device. At this time, one or two side portions of the seat fixture may be removed. After a predetermined sheet length has been wound on the winding roll 22, the sheet is started to be wound on the winding roll 25. The roll-shaped thermoplastic resin foam sheet wound around the winding roll 22 is removed from the winding roll 22 together with the sheet fixing tool 24 and stored in a warehouse as needed. The winding method of the thermoplastic resin foam sheet may be loosened by hand. By loosening by hand, the thermoplastic resin foam sheet can be further loosely wound.

According to the present invention, when the side portion of the sheet fixing member is formed in a mesh disk shape or a cross shape as shown in FIG. 2, the effect of further shortening the aging period can be obtained. Usually, after a roll of a thermoplastic resin foam sheet is placed on a pallet, the pallet is stored in a warehouse in two or more stages to save space. At this time, since the winding roll is suppressed by the pallet from above and below, the inflow and outflow of air and the blowing agent gas from the gap between the sheets are hindered. However, if a mesh disk or cross-shaped side surface is used in the manufacturing method of the present invention, a gap is formed between the pallet and the sheet, so that air and blowing agent gas can easily flow in and out of the sheet gap, and aging. There was an effect that the period was shortened.

[0019]

Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The parts shown below are parts by weight.

The secondary expansion ratio, which indicates the secondary foam moldability, was defined as follows. The thermoplastic foam sheet was held in an atmosphere at 150 ° C. for 15 seconds, the thickness before heating and the thickness after heating were measured, and the value obtained by the following equation was defined as the secondary expansion ratio.
The point at which the secondary expansion ratio becomes the maximum is defined as the aging period.

[0021]

(Equation 1)

[0022]

EXAMPLES Example 1 1.0 part of talc as a nucleating agent was blended with 100 parts of a polystyrene resin, and the mixture was charged into a first extruder and melted and kneaded. Thereafter, 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. After cooling the resin to the foaming temperature, the resin was extruded through a circular die and had a thickness of 2.
A foam sheet of 2 mm, basis weight of 250 g / m ² and length of 250 m was obtained. The foamed sheet was wound under a tension of 2 kg by a winder equipped with a sheet fixture having the material and structure shown in Table 1, and as a result, a roll having an outer diameter of 895 mm and a core diameter of 258 mm was obtained. The roll was aged in a storage warehouse maintained at a temperature of 25 ° C. FIG. 4 shows the change over time in the secondary expansion ratio of the obtained roll.
It was shown to. The aging period ended in 10 days. Since the treatment is usually completed in about 21 days, a significant effect of shortening the ripening period has been recognized.

(Example 2) In the same manner as in Example 1, the wound roll was loosened by hand to obtain a roll having an outer diameter of 950 mm and a core diameter of 240 mm. As a result of using the side part of the seat fixture as a working part, the obtained rewind can be moved without any problem.
Workability was good. FIG. 4 shows the change over time in the secondary expansion ratio of the obtained roll. The aging period ended in 7 days. (Example 3) An outer diameter of 89 was obtained in the same manner as in Example 1 except that the sheet fixing device was a mesh disk type fixing device shown in FIG.
5 mm and a rewind having a core diameter of 258 mm were obtained. As for this rewind, as in Example 1, the side portion of the sheet fixing tool was used as a working portion. As a result, the obtained rewind could be moved without any problem, and workability was good. FIG. 4 shows the change over time in the secondary expansion ratio of the obtained roll. The ripening period ended in 8 days.

Comparative Example 1 An outer diameter of 895 was obtained in the same manner as in Example 1 except that the sheet fixing device was not used at the time of winding.
mm and a winding core having a core diameter of 258 mm were obtained. An attempt was made to transport this roll to a storage warehouse, but if a part of the roll was held, the shape of the roll was deformed and stable transport was not possible.

(Comparative Example 2) A rewind having an outer diameter of 888 mm and a core diameter of 258 mm was obtained in the same manner as in Example 1, except that the sheet fixing device was not used at the time of winding and the winding tension was 10 kg. The transfer to the storage warehouse was performed without any problem, and the workability was good. FIG. 4 shows the change over time in the secondary expansion ratio of the obtained roll. The aging period ended in 21 days.

[0026]

According to the present invention, when a mixture of a thermoplastic resin and a foaming agent is heated and kneaded in an extruder, and extruded into a sheet and wound into a roll, a sheet having a roll core material and at least one side surface on one side is provided. This is a method for producing a thermoplastic resin foam sheet, which is wound around a fixture. The ripening period can be significantly reduced by using this sheet fixing device.

[Brief description of the drawings]

FIG. 1 is a schematic view of a seat fixture according to the present invention.

FIG. 2 is a schematic view of a side view of a seat fixing device according to the present invention.

FIG. 3 is a schematic view of a sheet winding machine used in the present invention.

FIG. 4 is a graph showing the change over time in the secondary expansion ratio of a roll in Examples and Comparative Examples.

[Explanation of symbols]

 1. Seat fixing device 2. Rewind 3 Disc-shaped side part 4. Core 5. 5. Perforated double disk type side part Air holes 7. 7. Mesh disk type side part Cross-shaped side part 9. One side part 10. 10. Side part with support rod Support rod 21. Thermoplastic foam sheet 22, 25. Core roll 23. Rewind 24. Seat fixture

Claims (2)

[Claims] 1. A mixture of a thermoplastic resin and a foaming agent is heated and kneaded in an extruder, extruded into a sheet and wound into a roll, and wound around a roll core material and a sheet fixture having at least one side surface on one side. A method for producing a foamed thermoplastic resin sheet. 2. The method for producing a foamed thermoplastic resin sheet according to claim 1, wherein the foamed thermoplastic resin sheet is a polystyrene resin foam sheet.