JPH03290451A - Degradable plastic composition - Google Patents

Abstract

PURPOSE:To obtain a degradable plastic composition having excellent utility as a material having improved degrading properties, moldability, etc., by blending specific amounts of a polyglycollide and a specific polymer substance. CONSTITUTION:(A) 5-60wt.%, preferably 10-50wt.% polyglycollide having >=500, preferably 800-1,000 number-average molecular weight is blended with (B) 95-40wt.%, preferably 90-50wt.% one or more polymer substances selected from polyolefin, polyvinyl alcohol, polyalkylene oxide and cellulose acetate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a degradable plastic composition.

(Prior art and its problems) Plastics are widely used in daily life in the form of various molded quantities such as films and containers.

However, since most plastics do not decompose in the natural environment, as the amount of plastic used increases, the problem of pollution caused by plastic waste is becoming more important. For this reason, in recent years, degradable plastics have been widely developed.

Polyglycolide is known as one of the degradable polymer compounds. Although this material has a high melting point and is excellent in heat resistance, it is not put to practical use as a plastic material because of its high crystallinity and brittleness.

(Problem of the Invention) An object of the present invention is to provide a plastic composition that is degradable and has practical use as a plastic molding material.

(Means for Solving the Problems) As a result of intensive research to solve the above problems, the present inventors have found that polyglycolide is a polymer selected from polyolefins, polyvinyl alcohols, polyalkylene oxides, and cellulose acetate. In addition to discovering that polyglycolide has excellent blending performance with other substances, they also discovered that a molten mixture of polyglycolide and these polymeric substances has excellent practicality as a plastic molding material, leading to the completion of the present invention.

Namely, according to the present invention, from a molten mixture of 5 to 60% by weight of polyglycolide and 95 to 40% by weight of at least one polymeric substance selected from polyolefins, polyvinyl alcohol, polyalkylene oxide and cellulose acetate. A degradable plastic composition is provided.

The polyglycolide used in the present invention is a crystalline polymer obtained by heating glycolic acid or its ester, sodium chloroacetate, or glycolide. In the presence of -carbon oxide and formaldehyde are reacted to produce polyglycolide, then water or a lower alcohol is added to this polyglycolide to cause a depolymerization reaction to produce glycolic acid or its lower alcohol ester, which is heated. 1 Polymerization reaction. According to this method, high molecular weight polyglycolide can be obtained in good yield using inexpensive raw materials, so it is very advantageous industrially. Further, in the present invention, it is also possible to use a relatively low molecular weight polyglycolide obtained by reacting carbon monoxide and formaldehyde in the presence of an acidic catalyst.

As the polyglycolide used in the present invention, those having a number average molecular weight of 500 or more, preferably in the range of 800 to 10,000 are advantageously used.

As the polyolefin, conventionally known polymers or copolymers mainly composed of olefins, such as polyethylene, polypropylene, polybutene, ethylene/propylene copolymer, and ethylene/vinyl acetate copolymer, are used. Commercially available polyvinyl alcohol, polyalkylene oxide (polyethylene oxide, polypropylene oxide, etc.), and cellulose acetate can be used as they are. In the present invention, other plastics such as
Even if polyvinyl chloride, polystyrene, etc. are used, blending performance is poor and it is impossible to obtain a practical plastic molding material.

The plastic composition of the present invention is prepared by melt-mixing polyglycolide and the above-mentioned polymeric substance, and molding the molten mixture into a desired shape using a conventional thermoforming machine such as an extruder. It can be made into a molded product. Furthermore, the molded product obtained by the aged molding may be an unfoamed product or a foamed product, and when a foamed product is obtained, a foaming agent is mixed into the composition. Furthermore, customary auxiliary additives such as inorganic fillers, pigments, antioxidants, etc. can be added to the composition.

The mixing ratio of polyglycolide and other polymeric substances is 5 to 60% by weight, preferably 10 to 50% by weight of polyglycolide and 95 to 40% by weight of polymeric substances, based on the total amount of polyglycolide and polymeric substances. 2, preferably 90 to 50 weight 2. If the mixing ratio of polyglycolide is smaller than the above range, the degradability of the composition will deteriorate, while if it exceeds the above range, the thermoformability of the composition will deteriorate and the mechanical properties of the molded product will be impaired. Undesirable.

(Effects of the Invention) One plastic composition of the present invention has good moldability in polyglycos having degradability (including hydrolyzability and biodegradability), and is suitable as a degradable plastic molding material. It is. Moreover, the molded product obtained by the present invention is not brittle as seen in polyglycolide, and has toughness.

Furthermore, among the compositions of the present invention, those using polyvinyl alcohol, polyalkylene oxide, or cellulose acetate as polymeric substances can be used as completely biodegradable plastic molding materials because these polymeric substances are also biodegradable. Can be used.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Trioxane 10.0 was placed in a stainless steel autoclave.
g, 30-g of dichloromethane and 4 mmol of chlorosulfonic acid were charged in a carbon monoxide atmosphere, and further 55 kg/
After one reaction in which carbon monoxide was injected until it reached aJ, the temperature was raised to 180°C while stirring, and the reaction was carried out for 2 hours.
Release unreacted carbon monoxide, wash out the contents of the autoclave with acetone, and remove 8.6 g of acetone-insoluble polymer (polyglycolide with a molecular weight of about 1200 or more) and 4 g of acetone-soluble polymer (polyglycolide with a molecular weight of about 1000 or less). .3g was obtained.

Next, 0.2 g of acetone-insoluble polymer and 0.8 g of high-density polyethylene were melt-mixed and mixed at 150°C for 5 minutes at 50 kg/kg.
It was confirmed that it could be formed into a film by applying pressure under the conditions of aJ, and that this film had sufficient flexibility.

Example 2 0.5 g of the acetone-insoluble polymer obtained in Example 1 and 0.5 g of high-density polyethylene were melt-mixed and heated at 150°C for 5
It was found that it could be formed into a film by applying pressure under the conditions of 50 kg/aJ and this film also had sufficient flexibility.

When this film was heat-treated in water at 100° C. for 1 hour, it was hydrolyzed and its weight decreased by about 20%.

Comparative Example 1 An attempt was made to form a film under the same conditions using polyvinyl chloride instead of 0.8 g of high-density polyethylene in Example 1, but the blend was extremely brittle and could not be formed into a film.

Example 3 An experiment was conducted in the same manner as in Example 1 except that 0.8 g of polypropylene was used instead of 0.8 g of high-density polyethylene, and a flexible film was also obtained in this case.

Comparative Example 2 When an experiment was conducted in the same manner as in Example 1 using 0.5 g of the acetone-insoluble polymer and 0.5 g of polystyrene, no film could be obtained.

Example 4 In Example 1, 0.5 g of acetone-insoluble polymer and 0.5 g of polyethylene oxide (molecular weight approximately 20,000)
A molten mixture was made in the same manner except that 1
A flexible film was obtained by applying pressure at 60° C., 50 kg/cd, and 5 minutes.

Example 5 ``';i'' - In Example 1, 0.5 g of acetone-insoluble polymer and
Polyvinyl alcohol (molecular weight: approximately 90,000) 0.
A molten mixture was prepared in the same manner except that 5 g was used, and this was pressurized at 130° C. for 5 minutes at 50 kg/aJ to obtain a flexible film.

Example 6 In Example 1, 0.5 g of acetone-insoluble polymer and
An experiment was conducted in the same manner except that 0.5 g of cellulose acetate (degree of polymerization: about 150) was used, and a flexible film was also obtained in this case.

Claims (1)

[Claims] (1) A degradable plastic composition consisting of a molten mixture of 5 to 60% by weight of polyglycolide and 95 to 40% by weight of at least one polymeric substance selected from polyolefin, polyvinyl alcohol, polyalkylene oxide, and cellulose acetate. thing.