JP2502421B2 - Thermoplastic polyester resin foam sheet having water absorbency and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polyester resin (hereinafter referred to as PAT) foamed sheet, and more particularly to a PAT sheet having excellent water absorption performance.

[0002]

2. Description of the Related Art A thermoplastic resin foam sheet manufactured conventionally has water repellency because it is formed of closed cells. Therefore, when the PAT foam sheet is used as a leather sheet as described in Japanese Patent Application No. 1-294306, the appearance is similar to leather, but the water absorption and air permeability are far from the leather. Met. Also PA
When the T foam sheet is used as a heat insulating material for an oil tank, the application is limited because the oil flows out of the tank when the oil leaks.

Various chemicals are kneaded and molded to improve the surface quality of synthetic resin.
Since the foamed sheet made of AT is a closed-cell body as described above, the drug is trapped inside the cells, and the improvement effect cannot be sufficiently expressed. Therefore, it has been practiced to directly apply the drug to the surface of the PAT foam sheet, but this method still cannot obtain a sufficient effect because the application area of the drug is limited.

[0004]

PROBLEM TO BE SOLVED BY THE INVENTION To form open cells of a PAT foam sheet to give water absorption to the PAT foam sheet and to sufficiently exert its effect when surface quality is improved by a chemical agent. Is.

[0005]

We have a thickness of 0.5.
It has been found that the above problems can be solved by immersing a PAT foam sheet having a density of at least mm and a density of 0.7 g / cc or less in a strong alkaline solution. That is, by the extremely simple means of immersing the PAT foam sheet in a strong alkaline solution, P
A fibrous portion in which cells are broken is formed on the surface of the AT foam sheet, and a PAT foam sheet having excellent water absorption having open cells having an open cell ratio of 40% or more can be manufactured.

The PAT which can be used in the present invention is a high molecular weight chain polyester obtained by reacting an aromatic dicarboxylic acid with a dihydric alcohol. Although terephthalic acid is most often used as the dicarboxylic acid, isophthalic acid or 2,6-naphthalenedicarboxylic acid may also be used. In addition, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxy dicarboxylic acid may be used. On the other hand, as dihydric alcohol, ethylene glycol is mainly used, but trimethylene glycol,
Tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane,
Some use 4,4′-bis (β-hydroxyethoxy) diphenyl sulfone and diethylene glycol.
Such PAT is commercially available. In the present invention, commercially available PAT can be used.

Among the above-mentioned PATs, polyethylene terephthalate, polybutylene terephthalate elastomer, amorphous polyester, polycyclohexane terephthalate, etc. are suitable for use in the present invention. These resins can be used alone or as a mixture. If another resin is mixed, the amount of the other resin needs to be smaller than that of PAT.

The alkaline solution in which the resin is dipped in the present invention includes hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide, carbonates such as calcium carbonate and sodium carbonate, sodium phosphate and phosphoric acid. Examples thereof include phosphates such as potassium. The alkaline solution is preferably a solution having a pH of 12.5 or higher. 80 ℃ ~ 10
When heated to 0 ° C., the open cell ratio becomes 45% to 80% after 20 to 30 minutes of immersion.

In the present invention, the PAT foam sheet is defined as having a thickness of 0.5 mm or more and a density of 0.7 g / cc or less because the sheet has a heat insulating property (especially as a heat insulating material for an oil tank used at high temperature). In this case, a thickness of 0.5 mm or more is required to fully exert the cushioning property, and the sheet has sufficient heat insulating properties (especially when used as an insulating material for oil tanks used at high temperatures). Since it is necessary to have a density of 0.7 g / cc or less to exert the effect, and in order to attack the bubble wall with an alkaline solution, it is more effective to make the cell wall thinner with a density of 0.7 g / cc or less. Is.

The foamed thermoplastic polyester-based resin sheet having an open cell ratio of 40% or more obtained in the present invention has good absorption of water droplets and is soft, so that its feel is similar to that of a leather sheet.

[0011]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

[0012]

Example 1 A polyethylene terephthalate foam sheet having a thickness of 1.1 mm and a density of 0.30 g / cc was immersed in a sodium hydroxide aqueous solution (30% by weight aqueous solution) at 80 ° C. for 30 minutes. The foamed sheet thus obtained had an open cell rate of 48% and a water absorption rate of 54%. It was found from the magnified photograph that there were fibrous portions in which bubbles were broken on the surface.

[0013]

Example 2 A sheet was produced in the same manner as in Example 1 except that the time of immersion in 100 ° C. sodium hydroxide was 20 minutes. The resulting foamed sheet had an open cell rate of 76% and a water absorption rate of 134%.

[0014]

Example 3 A polyethylene terephthalate foam sheet having a thickness of 1.1 mm and a density of 0.50 g / cc was immersed in an aqueous calcium carbonate solution (30% by weight aqueous solution) at 80 ° C. for 30 minutes.
The foamed sheet thus obtained had an open cell rate of 42% and a water absorption rate of 4
4%.

[0015]

Example 4 A polyethylene terephthalate foam sheet having a thickness of 1.1 mm and a density of 0.30 g / cc was dipped in an aqueous sodium phosphate solution (30% by weight aqueous solution) at 80 ° C. for 30 minutes,
Similarly, a foamed sheet was obtained. [Comparative Example 1] A polyethylene terephthalate foam sheet having a thickness of 1.1 mm and a density of 0.30 g / cc was not treated, but the open cell rate was 4% and the water absorption rate was 0.7%.

In the above examples, the water absorption rate is JIS K7.
It was based on the method A (determined from the ratio of the original mass of the test piece and the mass increase before and after water absorption). Moreover, the open cell rate was based on ASTM D2856.

[0017]

From the above, it can be seen that the foamed sheet of the present invention has an open cell ratio of 40% or more and excellent water absorption. Further, in the case of surface treatment with a chemical, when the sheet is used at a high temperature (100 ° C.), the chemical melts and loses its effect each time the chemical is used, but the sheet obtained by the present invention does not have such a defect.

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Claims (2)

(57) [Claims] 1. A thermoplastic polyester resin foam sheet having a thickness of 0.5 mm or more and a density of 0.7 g / cc or less, in which fibrous portions in which bubbles are broken are present on the surface, and the open cell ratio of the foam sheet is A thermoplastic polyester-based resin foam sheet having water absorption, which is 40% or more. 2. The thermoplastic polyester resin according to claim 1, wherein a foamed thermoplastic polyester resin sheet having a thickness of 0.5 mm or more and a density of 0.7 g / cc or less is immersed in a strong alkaline solution. A method for producing a resin foam sheet.