JPH0853575A - Biodegradable sheet and thermoformed article made of the sheet - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic sheet for forming process capable of being decomposed as it is left in the natural world and obtainable from cellulose ester polymer. CONSTITUTION:This sheet is obtained by compounding cellulose acetate with 20-120 pts.wt. of polyoxyethylene glycol having an average molecular weight of 300-30000 base on 100 pts.wt. of the cellulose acetate and has a thickness of 10-2000mum. A thermoformed article is obtained by subjecting the sheet to a vacuum forming process and/or pressure forming process.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biodegradable sheet and a thermoformed product thereof. More specifically, it relates to a biodegradable sheet made of cellulose acetate and polyoxyethylene glycol, and a molded article obtained by subjecting this sheet to thermoforming such as vacuum forming.

[0002]

2. Description of the Related Art In recent years, as a biodegradable sheet that decomposes while being left in the natural environment, a sheet made of a mixture of starch and polyvinyl alcohol, or an aliphatic polyester sheet has been known.

However, these are not preferable because they have insufficient transparency and are difficult to thermoform.

On the other hand, cellulose acetate is usually difficult to handle as a thermoplastic resin and is used by dissolving it in a solvent such as acetone. In some cases, phthalate ester is used as a thermoplastic resin as a thermoplastic resin. Is also well known.

However, the phthalate ester used when used as a thermoplastic resin is not biodegradable, and the good biodegradability of cellulose acetate is lost.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biodegradable and transparent sheet which can be easily thermoformed, and further provides this thermoformed product. Especially.

[0007]

[Means for Solving the Problem] As a method for solving this problem, the inventors of the present invention have conducted extensive research and as a result, those obtained by adding polyoxyethylene glycol to cellulose acetate gave a transparent and biodegradable sheet. It has been found that this sheet can be easily thermoformed, and the present invention has been completed.

That is, the present invention relates to cellulose acetate 1
10 to 2000 μm in thickness, which is composed of an acetate composition containing 20 to 120 parts by weight of polyoxyethylene glycol having an average molecular weight of 300 to 30,000 per 00 parts by weight.
It is preferable to use cellulose acetate in which 60 to 95% of the hydroxyl groups of cellulose are acetylated.

The present invention also includes a thermoforming method for a biodegradable sheet, in which the above-mentioned sheet is heated to 80 to 180 ° C. and brought into close contact with a mold of less than 80 ° C. to be molded.

The cellulose acetate of the present invention is obtained by acetylating cellulose, and the amount of acetyl groups used is 60 to 95%, preferably 70 to 90%, of the hydroxyl groups of cellulose. . This is commonly called diacetate.

In the present invention, polyoxyethylene glycol is added to such cellulose acetate. The polyoxyethylene glycol is
Average molecular weight is 300 to 30,000, preferably 600 to
The one of 20,000 is used. In particular, a molded product having a molecular weight of less than 6000 is preferred for obtaining a molded product having ultrafine pores, and a product having a molecular weight of 6000 or more is preferred for preventing elution with water. This is because if the molecular weight is larger than this, the plasticizing effect is not sufficient, and if it is smaller than this, bleed-out is large and it is not preferable.

The amount of polyoxyethylene glycol to be mixed is 2 per 100 parts by weight of cellulose acetate.
It is 0 to 120 parts, preferably 40 to 100 parts by weight.

The polyoxyethylene glycol may be added by any method. For example, a method in which polyoxyethylene glycol is mixed with cellulose acetate flakes and melt-extruded to obtain a mixture is often used.
The temperature at this time is generally 170 to 230 ° C.,
180-220 degreeC is preferable. At lower temperatures,
This is because mixing is difficult, while polymer decomposition occurs at high temperatures.

As another manufacturing method, for example, a method of dissolving cellulose acetate and polyethylene glycol in a solvent such as acetone and removing the solvent can be used.

The cellulose acetate composition thus obtained is formed into a sheet by using a usual melt extrusion method. The temperature at this time is 160 to 220 ° C, preferably 170 to 210 ° C. This is because at a temperature higher than this, there is coloring due to decomposition, and at a lower temperature, the viscosity is too high and it is difficult to obtain a clean sheet.

In the sheet of the present invention, generally used inorganic fine particles such as kaolin, talc, silica and alumina may be added as a lubricant to an extent that the transparency is not impaired.

The sheet thus obtained is thermoformed if necessary. As this method, in the present invention, a method of heating the sheet and contact-molding it in a cold mold can be presented.

As this method, for example, when the sheet is indirectly heated by a heater and brought into contact with the mold, the mold is evacuated or the sheet side is pressed at about the same time,
The so-called vacuum forming and pressure forming methods for fixing the cooling shape of the sheet with a mold are generally recommended.

In these thermoforming processes, heating of the sheet is carried out at a sheet temperature of 80 to 180, preferably 100 to 15.
Adjust the heater temperature and heating time to 0 ℃,
When it is heated, it is contact-molded with a mold. The mold temperature at this time is less than 80 ° C, preferably less than 70 ° C. This is because if the mold temperature is higher than this, the molding takes time, and in some cases, it is not preferable because it adheres to the mold.

The drawing ratio in this thermoforming is 10 times or less, preferably 6 times or less in terms of area magnification.

The sheet and thermoformed product obtained by the present invention utilize biodegradability and can be used for containers, flower pots and the like.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples. In the examples, “parts” means “parts by weight”.

[Example 1] Cellulose acetate flakes (acetylation degree 86%) (100 parts) was extruded with a polyoxyethylene glycol (60 parts) having an average molecular weight of 600 at 220 ° C by an extruder and cooled to form chips. .

The chips are dried at 100 ° C. and then 200 ° C.
Was extruded with an extruder equipped with a T-die to obtain a sheet having a thickness of 200 μm.

This sheet was transparent and had a total light transmittance of 86% as measured by an integrating sphere type photometer.

The obtained sheet is set in a vacuum forming machine,
Both sides were heated with an infrared heater (15 seconds), and the mold side was depressurized with a mold at room temperature to form a tray. The molded product (having an area of 5 cm × 10 cm and a depth of 2 cm) had good traceability and was good. At this time, the temperature of the sheet immediately before molding was 125 ° C. when measured with a non-contact thermometer.

When this molded product was buried in soil and taken out 6 months later, it partially collapsed. Further, one year later, I tried to take it out, but I couldn't take it out.

[Examples 2 to 5] In Example 1, the results of the thermoformed products obtained by changing the molecular weight and the compounding amount of the polyoxyethylene glycol (PEG) used are shown in Table 1.
It was shown to.

[0029]

[Table 1]

[0030]

Industrial Applicability According to the present invention, a biodegradable thermoformable sheet having good transparency can be obtained. The present invention is easier to thermoform than other biodegradable polymer sheets.

Further, the present invention is characterized in that it is slower in degradability than other biodegradable sheets and can be used in soil for a relatively long time.

With respect to thermoforming, it is possible to take a relatively high forming temperature range and drawing ratio, and it is possible to easily perform forming using a conventional sheet thermoforming apparatus.

Claims (3)

[Claims] 1. A biodegradable sheet having a thickness of 10 to 2000 μm, which is made of an acetate composition containing 20 to 120 parts by weight of polyoxyethylene glycol having an average molecular weight of 300 to 30,000 per 100 parts by weight of cellulose acetate. 2. 60 to 95% of the hydroxyl groups of cellulose
The biodegradable sheet according to claim 1, wherein cellulose acetate in which acetyl is used is used. 3. The sheet according to claim 1 or 2 is 80 to 180.
A thermoformed product of a biodegradable sheet, which is formed by heating to 0 ° C and bringing it into close contact with a mold of less than 80 ° C.