JPH04253740A - Water-absorptive polystyrene foam and its production - Google Patents

Abstract

PURPOSE:To provide a water-absorptive foam which can absorb safely and effectively drips from fish meat or water drops condensed on fruit. CONSTITUTION:A water-absorptive polystyrene foam comprising a polystyrene foam and a highly water-absorptive polymer and a filler contained therein and a process for producing the same.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a polystyrene foam containing a superabsorbent polymer and a filler, and more particularly to a water-absorbing polystyrene foam that can effectively and safely absorb drips from fish meat and water droplets condensing on fruits. body and its manufacturing method.

0002

BACKGROUND OF THE INVENTION In recent years, in supermarkets and the like, food products are placed on foamed polystyrene trays, wrapped in plastic wrap, and displayed in food cases for the purpose of preventing food contamination and improving aesthetic appearance. However, in such a packaging form, the tray has almost no water absorbency, so excess water may accumulate between the food and the tray, causing the food to spoil. In addition, in the case of fish meat, drips come out, reducing the desire to buy it. In view of this situation, attempts have been made to insert a foam sheet or pulp sheet between the food and the tray, but this is not sufficient. Furthermore, in recent years, starch-acrylate-based superabsorbent polymers have been put on the market, and laminated sheets and the like using them have been proposed, but they are expensive and are only used in specific fields.

0003

[Problems to be solved by the invention] Foamed sheets made by adding super absorbent polymers to general-purpose plastics such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride have an extremely low diffusion permeability coefficient for water. In addition, since the water-swelling force of the water-absorbing polymer is smaller than the cohesive force of plastics, the volumetric expansion of the water-absorbing polymer is suppressed and the water-absorbing expansion is extremely small. Furthermore, when added to rubber or thermoplastic elastomer, the polymer gel absorbs water and expands, but there is a risk that the gel of the polymer that absorbs water will ooze out to the surface and come into contact with food, which may be eaten as is and enter the human body. Therefore, an object of the present invention is to provide a water-absorbing foam that can efficiently and safely absorb drips from fish meat and water droplets condensing on fruits.

0004

[Means for Solving the Problems] The above object is achieved by the following present invention. That is, the present invention is a water-absorbing polystyrene foam characterized by containing a super-absorbent polymer and a filler in the polystyrene foam, and a method for producing the same.

[0005]

[Operation] As a result of intensive research to solve the problems of the prior art, the present invention has found that a polystyrene foam to which a superabsorbent polymer and a filler are added has excellent water absorption and water retention properties, and forms a water-absorbing gel after absorbing water. The present invention was completed based on the finding that the foam remains within the internal foam cells and does not ooze out onto the surface of the foam.

[0006]

[Preferred Embodiments] Next, the present invention will be explained in more detail by citing preferred embodiments. The superabsorbent polymer used in the present invention may be any conventionally known polymer. For example, sodium salt of starch-acrylic acid graft copolymer,
Crosslinked products of acrylic acid-acrylic acid alkali metal salt copolymer, crosslinked products of alkali metal salt of isobutylene-maleic anhydride copolymer, saponified products of ethylene-vinyl ester-acrylic acid ester copolymer, crosslinked polyethylene oxide, Any conventionally known water-swellable urethane resins can be used, and one or more of them may be used in combination. The proportion used is 1 part by weight to 100 parts by weight, preferably 2 parts by weight to 50 parts by weight, per 100 parts by weight of polystyrene serving as the foam base material.

The filler used in the present invention is: Inorganic fillers that are used to promote the penetration of water into the water-absorbing polymer powder present in the polystyrene foam cells and have good wettability with water are mainly suitable for the purpose of the present invention. For example, bennite, clay, talc, zeolite, calcium carbonate, precipitated barium sulfate, barite powder, carrion,
Alumina and the like are used, and one type or a combination of two or more types thereof may be used. The proportion of its use is 5 parts by weight to 1 part by weight per 100 parts by weight of polystyrene, which is the foam base material.
00 parts by weight, preferably 10 to 50 parts by weight.

[0008] The polystyrene used as the foam base material in the present invention is one commonly used for producing foams, such as GP type polystyrene and HI type polystyrene. Expanded polystyrene beads containing low boiling point solvents, which are widely used in the manufacture of polystyrene foam products, can also be used. As a method for forming the foam of the present invention, (1) expanded polystyrene beads as described above are used. (2) A low boiling point solvent such as butane, pentane, hexane or dichlorodifluoromethane is forced into the molten resin and extruded from an extruder to cause foaming. ■ Add an inorganic chemical decomposition type blowing agent consisting of sodium bicarbonate and an organic acid such as citric acid and mold. (2) Adding an organic chemically decomposable foaming agent such as azodicarbonamide, and carrying out thermal decomposition foaming in an extruder or injection molding machine. These methods (1) to (2) may be used alone or in combination. Further, coloring agents such as dyes and pigments may be used if necessary.

The water-absorbing polystyrene foam of the present invention can be produced by conventionally known methods. For example, there are methods in which the above-mentioned super absorbent polymer, polystyrene pellets, and blowing agent are uniformly mixed in a ribbon blender, Henschel mixer, tumbler, etc., and then put into an extruder and extruded into a sheet, or The polymer, filler, or blowing agent may be made into master batch pellets, uniformly mixed with polystyrene pellets, and charged into an extrusion molding machine or an injection molding machine to produce sheets or trays. Moreover, if necessary, butane, freon, etc. may be press-fitted to increase the expansion ratio.

0010

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the text, parts or percentages are based on weight unless otherwise specified. Example 1 100 parts of GP grade polystyrene, 0.8 parts of an inorganic blowing agent with a ratio of sodium bicarbonate and monosodium citrate of 50:50, acrylic acid-sodium acrylate (ratio of 20:80) in n-hexane Using a ribbon blender, 10 parts of polyacrylate-based superabsorbent polymer powder obtained by suspension polymerization using sorbitan monostearate and 30 parts of bentonite were uniformly mixed in a ribbon blender, and the mixture was put into an extruder and passed through a T-die. A foamed sheet was obtained by extrusion. The extruder was set at a maximum temperature of 205°C, and n-butane was continuously injected. The resulting polystyrene foam sheet has a thickness of 1 m.
The foaming ratio was 15 times.

Example 2 Isobutylene-maleic anhydride copolymer was hydrolyzed in an aqueous solution of caustic soda, 1% diethylenediamine was added, evaporated to dryness, heated at 150°C for 4 hours, and then pulverized to absorb water. A super absorbent polymer with a magnification of 200 times was obtained. Pellets were prepared in advance from 100 parts of polystyrene to 30 parts of the above-mentioned superabsorbent polymer and 50 parts of clay, and 70 parts of GP grade polystyrene and an inorganic foam containing sodium bicarbonate and monosodium citrate in a ratio of 50:50 were prepared in advance. 0.8 part of the agent and the above-mentioned super absorbent polymer and polystyrene pellets of clay were mixed uniformly in a tumbler, put into an extruder, and extruded through a T-die while press-fitting n-butane to form a foam sheet. Obtained. The obtained expanded polystyrene sheet had a thickness of 1 mm and an expansion ratio of 18.
It was double that.

Comparative Example 1 100 parts of GP grade polystyrene and an inorganic blowing agent having a ratio of sodium bicarbonate and monosodium citrate of 50:50 were mixed uniformly and extrusion molded under the same conditions as in Example 1 to foam. A polystyrene sheet was obtained. Thickness is 0.9
The foaming ratio was 20 times in mm.

Example 3 Drip absorption tests were conducted on the expanded polystyrene sheets obtained in Examples 1 and 2 and Comparative Example 1. The sheets of Examples 1 and 2 and Comparative Example 1 (18.5 cm x 8.5 cm) were placed on a polystyrene foam tray (20 cm x 10 cm), and 300 g of frozen lean tuna was placed on top of the sheets, covered with saran wrap and allowed to thaw naturally. went. The sheets of Examples 1 and 2 absorbed the red drip caused by thawing and the trays did not become soiled. On the other hand, the sheet of Comparative Example 1 did not absorb drips, and when the tray was tilted, red drips ran down the corners, staining the tray surface red.

[0014]

[Effect] The water-absorbing polystyrene foam of the present invention processed into a sheet does not allow the swollen gel to escape onto the surface of the sheet after absorbing water, making it suitable for absorbing drips from fish meat and condensed water from fruits. Effective and safe. In addition, it can prevent condensation in residential or industrial piping, or can be attached to the ceiling of a container to prevent product loss during transportation due to water droplets falling from the ceiling. Furthermore, by taking advantage of the open cell feature, it can also be used to remove moisture from vegetable storage cases in refrigerators.

Claims (3)

[Claims] 1. A water-absorbing polystyrene foam, characterized in that the polystyrene foam contains a super-absorbent polymer and a filler. 2. The water-absorbing polystyrene foam according to claim 1, wherein the filler is an inorganic filler such as bennite, clay, talc, or zeolite, and has an expansion ratio of 15 to 25 times. 3. A highly water-absorbent polymer and filler are uniformly kneaded with polystyrene, and then an inorganic or organic blowing agent or a low boiling point solvent is injected under high pressure, or a combination thereof is carried out for 15 to 30 minutes.
A method for producing a water-absorbing polystyrene foam, characterized by expanding the foam 25 times.