JP2905177B2 - Expanded polystyrene sheet - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] [Technical Field of the Invention The present invention relates to expanded polystyrene sheet <br/> over preparative. More specifically, a foamed polystyrene sheet having high secondary foaming ability and excellent secondary foaming moldability.
About the door. [0002] Expanded polystyrene sheets are easy to perform secondary foam molding, and the obtained molded articles are beautiful and lightweight, and have excellent heat insulating properties and are inexpensive. It is used in large quantities in tableware containers and the like. Such an expanded polystyrene sheet is generally melted and mixed with an extruder using a nucleating agent such as polystyrene, talc and calcium carbonate, and a moldability modifier such as liquid paraffin, and the foaming agent is press-fitted and then extruded from a circular die. It is manufactured by foaming into a sheet. As the foaming agent, industrial butane and dichlorodifluoromethane (hereinafter referred to as CFC-12) have been used. [0004] The expanded polystyrene sheet made by using industrial butane as the blowing agent is excellent in secondary foam moldability, but has a large dissipative property of industrial butane from the expanded polystyrene sheet. In addition, since the content of the industrial butane in the expanded polystyrene sheet is reduced and the secondary foam moldability is reduced, the period between the production of the expanded polystyrene sheet and the time when the secondary foam molding can be performed (hereinafter referred to as product life) is required. There is a problem that it is short. Also, a large amount of flammable butane gas escapes from the sheet,
Extreme care must be taken against fire and the like. On the other hand, a foamed polystyrene sheet using Freon-12 is a gas in which Freon-12 exhibits noncombustibility, and has a long product life because it escapes more slowly than a foamed polystyrene sheet, and there is no danger of handling. The secondary foam moldability is lower than foamed polystyrene sheets using industrial butane as a foaming agent, and Freon-12 is not preferred because it has problems such as decomposing ozone in the atmosphere. [0005] Accordingly, the present inventors have
A foamed polystyrene sheet having both excellent product life, which is a feature of using CFC-12 as a foaming agent of a foamed polystyrene sheet, and excellent secondary foam moldability, which is a feature of using industrial butane, As a result of intensive studies as much as possible, the present invention has been completed. Namely SUMMARY OF THE INVENTION, for the present invention is Po Li <br/> 100 parts by weight of styrene, isobutane 59 wt%
Above 7 below 0 by weight% and the Norumarubuta down 3 0 wt%
The residual amount of the blowing agent consisting of 40% by weight or less is 2.0 to
3.5 parts by weight after production of expanded polystyrene sheet
Secondary expansion ratio after lapse of 40 days is about the expanded polystyrene sheet having excellent secondary formability, characterized in that it has a foaming capacity of more than 1.71 times. DETAILED DESCRIPTION OF THE INVENTION For the expanded polystyrene <br/> sheet of the present invention will be described in detail. [0008] <br/> the manufacture of expanded polystyrene sheet of the present invention, butane isobutane 59 wt% or more 7 below 0 by weight% and Norumarubuta down 3 0 exceeding wt% 40 wt% or less as foaming agents Used. As the composition ratio of isobutane in butane increases, the life of the product centering on the secondary foaming ability increases, and if the composition ratio of isobutane in butane is 59 % by weight or more, CFC-free. 12
It is possible to maintain a product life equal to or higher than that of. Generally, some low-boiling hydrocarbons such as propane and pentane coexist as impurities in butane. In the present invention, if the composition ratio of isobutane in butane is 59 % by weight or more, these impurities are tentatively assumed. Even if coexisting in the butane, it hardly affects the physical properties such as secondary foam moldability and product life, so these impurities may be contained, but the rest of isobutane is normally butane. Is preferred. In the present invention, as a method for obtaining a foamed polystyrene sheet from polystyrene, polystyrene and an additive such as a nucleating agent are mixed and then charged into an extruder.
After the styrene resin is melted, butane is pressed in as a foaming agent and extruded. When the above method is employed, the amount of butane used must be 2.5 to 5 parts with respect to 100 parts of polystyrene (parts by weight, the same applies hereinafter). Extrusion conditions and the like are adjusted such that 2.0 to 3.5 parts of butane remain in the sheet with respect to 100 parts of the styrene resin. If the remaining amount of butane is less than 2.0 parts, the secondary foaming ability is insufficient, and a satisfactory molded product cannot be obtained. The remaining amount of the butane is 3.5
If it exceeds the part, not only the secondary foaming capacity becomes too large to control the secondary foaming ratio, but also the amount of escaped gas increases, and the risk of handling and fire increases. I will be. [0012] The secondary expansion capacity of the expanded polystyrene sheet must be 1.71 times or more in terms of secondary expansion ratio in order to obtain a satisfactory molded product. The obtained expanded polystyrene sheet usually has a thickness of 1.0 to 2.5 mm and a basis weight of 100 to 250 g / m ^2.
In general, the adjustment is made so as to be as follows, but the present invention is not limited to these conditions. Thus, the remaining amount of butane is reduced to polystyrene 1
2.0 to 3.5 parts of expanded polystyrene sheet can be obtained for 00 parts. However, when storing or shipping in a bag or the like, the bag or the like is preliminarily opened with a needle hole or the like. This is very effective because the butane gas concentration in the bag is always kept below the explosive combustion range of butane, and spontaneous ignition during storage and ignition due to static electricity during transportation and handling can be prevented beforehand. . Further, the quality of the expanded polystyrene sheet of the present invention, such as formability, strength, stiffness, surface properties, etc., is as excellent as that obtained by using industrial butane gas or Freon-12 as a conventional blowing agent. In addition, those having a high composition ratio of isobutane in the foaming agent have a small formability because the foaming agent has a small fugitive property and a large amount of the foaming agent remains in the expanded polystyrene sheet even after a long time after production. Is preferred. EXAMPLES Next, the present invention will be described in more detail with reference to Reference Examples, Examples , and Comparative Examples .
It is not limited only to the reference example, the example , and the comparative example . Reference Examples 1-3 , Example 1 and Comparative Examples 1-2 Polystyrene HH-10 manufactured by Mitsubishi Monsanto Kasei Co., Ltd.
100 parts of 5 (100 mg of polystyrene resin in 10 ml of toluene, specific viscosity at 30 ° C. 1.40) is blended with 0.1 part of talc as a nucleating agent, and the mixture is charged into a 60 mm extruder to heat the blend ( (About 100 ° C.) and melted. Then, a blowing agent gas having a composition of isobutane and normal butane shown in Table 1 was supplied to 4.4 parts of polystyrene resin by 4.4 parts.
The resin and the blowing agent gas were sufficiently mixed by pressing into the extruder in the ratio of parts. Next, the resin was cooled to a foaming temperature (about 140 to 150 ° C.) using a connected 90 mm extruder, and then extruded and foamed through a circular die to obtain a basis weight of 170 g / m 2.
^2. A foamed polystyrene sheet having a thickness of 2.0 mm and 17 to 19 cells in the thickness direction was obtained. Comparative Example 3 Foaming was carried out in the same manner as in Reference Example 1 except that 6.8 parts of Clon-12 (manufactured by Mitsui Fluorochemicals Co., Ltd.) was used instead of butane as a foaming agent and 100 parts of resin was added. I made a polystyrene sheet. The residual foaming agent content of the obtained expanded polystyrene sheet, the ability to lower the secondary expansion ratio, the secondary expansion ratio, and the moldability of the tray were examined by the following methods. Table 1 shows the results. (Amount of Remaining Foaming Agent) The foamed polystyrene sheet extruded and foamed from a circular die was calculated from the heat loss after leaving for 30 minutes in a dryer at 180 ° C. after 30 minutes. (Ability to lower secondary expansion ratio) After extruding the obtained expanded polystyrene sheet,
The secondary expansion ratio when heated at 180 ° C. for 10 seconds for up to 60 days is examined, and the relational expression between the number of days after extrusion (X) and the secondary expansion ratio (Y): Y = A−BlnX (A is a constant term) Is shown), the ability to lower the secondary expansion ratio (B) was determined. (Secondary expansion ratio and moldability of tray) Secondary expansion ratio when heated at 180 ° C. for 10 seconds 40 days after the production of the obtained expanded polystyrene sheet, and 10 cm × after heated at 180 ° C. for 10 seconds. The state of the tray when a tray having a lattice pattern of 18 cm and a depth of 2.7 cm was formed was examined. In addition, the state when the tray was formed was evaluated according to the following criteria. (Judgment Criteria) A: A molded article conforming to the shape of the mold can be obtained without any problem. The lattice pattern also appears clearly. ：: Although the lattice pattern is unclear, a molded article substantially conforming to the shape of the mold is obtained. Δ: There is a deviation from the mold shape around the corner, and no pattern appears. The molded body bottom is slightly curved. ×: Cracks occurred on the surface of the molded product, and the molded product was not obtained. [Table 1] From the above results, the ability to lower the secondary expansion ratio of the expanded polystyrene sheets obtained in Reference Examples 1 to 3 was the same as that of the conventional expanded polystyrene sheet obtained in Comparative Example 3 using CFC-12. the extent follows is excellent, also, carried out
Secondary expansion ratio of expanded polystyrene sheet obtained in Example 1
Was obtained in Comparative Example 3 using CFC-12.
Conventional foamed polystyrene sheet and it is seen almost as der Rukoto. The results of the ability to reduce the secondary expansion ratio of the expanded polystyrene sheets obtained in Example 1 and Comparative Example 1 indicate that the isobutane content is required to be 59 % by weight or more. Furthermore, the moldability of the expanded polystyrene sheets obtained in Reference Examples 1 to 3 in which the content of isobutane is 70% by weight or more is the conventional expanded polystyrene sheet obtained in Comparative Example 3 using CFC-12 as a blowing agent. And the isobutane content is 59% by weight or more.
Of the expanded polystyrene sheet obtained in Example 1
The shape was determined in Comparative Example 3 using CFC-12 as a foaming agent.
The obtained conventional foamed polystyrene sheet and it is understood that equal der Rukoto. The foamed polystyrene obtained in Comparative Examples 1 and 2 using butane (contained in an amount of 20 to 40% by weight of isobutane) as a foaming agent, which is conventionally used, has poor secondary foam retention and moldability. I understand. Next, the foamed polystyrene sheets obtained in Reference Example 2 and Comparative Example 1 were each separately used to have a width of 1 mm.
040mm, 200m long rolled product (core diameter: 25
0 mm) and placed in a polyethylene bag (length: 2,000 mm, width: 1,400 mm) provided with needle holes (hole diameter: about 0.2 mm) every 15 mm in length and width.
After storage at 10 ° C. for 10 days, the retention of butane gas in the core was examined. In the case where the expanded polystyrene sheet obtained in Reference Example 2 was used, the butane gas concentration at the core was 15 at the maximum.
In the case of using the expanded polystyrene sheet obtained in Comparative Example 1 , the butane gas concentration in the core part reached a maximum of 28,000 ppm immediately after the measurement, and the concentration of 1800, which is the lower limit of the explosion limit of butane gas, was obtained.
Periods above 0 ppm lasted 3 days. From the above, the expanded polystyrene sheet obtained in Comparative Example 1 has a risk of explosion in handling, whereas the expanded polystyrene sheet obtained in Reference Example 2 has a low risk of explosion. It can be seen that it is very easy to handle. The expanded polystyrene sheet of the present invention has almost the same or lower secondary expansion ratio lowering ability than the conventional expanded polystyrene sheet, and has the same or better moldability. Even if it is, there is little danger of explosion and the like, and it can be suitably used, for example, for food containers.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08J 9/00-9/42

Claims (1)

(57) relative to All Claims 1 port polystyrene 100 parts by weight, isobutane 5
9 wt% or more 7 below 0 by weight% and Norumarubuta down 3 0
A foaming agent having a residual amount of from 2.0 to 3.5 parts by weight, comprising more than 40 % by weight and more than 40 % by weight;
Excellent secondary moldability characterized by having a foaming capacity of 1.71 times or more after 40 days from the production of
Foamed polystyrene sheet.