JPH04356538A - Biodegradable foamed polyolefin resin molding - Google Patents

Abstract

PURPOSE:To obtain a foamed molding which is biodegradable, has weak caloric force when burnt and excels in breath-ability, hygroscopicity and heat insulation by mixing a powder of a natural cellulosic substance with a biodegradable foamed polyolefin resin molding. CONSTITUTION:A biodegradable foamed polyolefin resin molding containing 30-80wt.% powder of a natural cellulosic substance. Examples of the natural cellulosic substances include wood flour, straws, rice hulls, bagasses and banana fibers. The formed molding is decomposed by the enzyme produced by the contained natural cellulosic substance and is spontaneously degraded when it is placed in surroundings such as soil where bacteria are active, so that it can be easily subjected to waste disposal. Because the powder of the natural cellulosic substance contains usually about 7wt.% water, when a mixture prepared by adding it in an amount of 30-80wt.% to a polyolefin resin is expansion- molded by heating, the water can act as a blowing agent to give a foamed resin molding. When the water content of the natural cellulosic substance is low, or a high expansion ratio is desired, a blowing agent is combinedly used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to so-called biodegradable foamed polyolefin resin moldings that can be decomposed by enzymes generated by bacteria or the like.

0002

BACKGROUND OF THE INVENTION Foamed resin molded products, such as foamed polystyrene resin molded products, are widely used in various applications such as packaging materials due to their good cushioning and heat insulation properties. These foamed resin molded products pose problems when disposed of when they are no longer needed. That is, when it is burned, it tends to damage the incinerator due to its strong firepower, and it also has the disadvantage that it remains intact without rotting even if buried underground.

[0003] An object of the present invention is to provide a foamed resin product that is biodegradable, has low thermal power during combustion, and has excellent breathability, hygroscopicity, and heat insulation properties.

0004

[Means for Solving the Problems] The present inventor paid attention to the fact that cellulose is easily decomposed by enzymes, and foam-molded the powder of natural cellulose by mixing it with various resins. As a result of studies from various viewpoints such as moldability and biodegradability, it was found that polyolefin resins were suitable as the resin, and the present invention was completed.

That is, the present invention is a biodegradable foamed polyolefin resin molding containing 30 to 80% by weight of natural cellulose material powder.

[0006] As the polyolefin resin, low density polyethylene, high density polyethylene, polyethylene resin such as ethylene-vinyl acetate copolymer, polypropylene, propylene copolymer, etc. are used. However, when foam molding is performed by adding powder of natural cellulose-based substances to polyvinyl chloride, molding is extremely difficult, and when polystyrene resin is used, physical properties such as strength are significantly reduced, making it difficult to achieve satisfactory foaming. A molded product cannot be obtained, and even when impact-resistant styrene resin is used, two natural cellulose material powders are used.
When more than 0% by weight was added, the foamed molded product became extremely brittle and unusable, but this drawback was overcome when polyolefin resin was used.

[0007] Natural cellulose materials include wood powder, straw,
Rice hulls, bagasse, banana fibers, etc. are used. These contain a large amount of short fibrous cellulose, as well as pentosan, lignin, ash, etc. Natural cellulose materials are used after being ground to 50 mesh or less. These may be used after being bleached.

[0008] The amount of the powder of the natural cellulose material added to the polyolefin resin is 30 to 80% by weight. 30
Addition of less than 8% by weight may result in insufficient biodegradability;
If it is added in an amount of 0% by weight or more, the physical properties of the foamed molded product will deteriorate and a practically usable foamed molded product cannot be obtained.

[0009] Powders of natural cellulosic materials usually contain about 7% water. Therefore, when 30 to 80% by weight of it is added to a polyolefin resin and heat foam molded, this water becomes a foaming agent and a foamed resin molded product is obtained. When the moisture content of the powder of natural cellulose material is low or when it is desired to increase the foaming ratio, a foaming agent is used in combination. Butane, pentane, hexane, N2, CO2, etc. are used as the blowing agent.

[0010] Foam molding is carried out by extrusion molding, blow molding, injection molding, etc. The expansion ratio is preferably 1.2 to 5.0 times.

Enzymes that decompose natural cellulose substances include cellulase, pectolyase, acerozyme, and the like.

[0012] In the foamed product of the present invention, the natural cellulosic substance contained therein is decomposed by enzymes produced by bacteria, so if it is placed in an environment where bacteria are likely to be active, such as underground, the foamed product will naturally decompose. Since it disintegrates, disposal is easy. Also, since it contains natural cellulose substances, it does not generate too much firepower when burned, and does not damage incinerators when burned as waste. Furthermore, since natural cellulosic substances have the property of absorbing or releasing air or water depending on the atmosphere, the foamed resin molded product of the present invention is highly breathable and has good hygroscopicity. Of course, since it is foamable, it also has excellent heat insulation properties.

[0013]

EXAMPLES A circular die was attached to an extruder having a screw diameter of 40 mm, and a foamed sheet was extruded as follows. 30 parts of ethylene-vinyl acetate copolymer resin pellets, 70 parts of rice hull powder, and 0.0 parts of azodicarboxylic acid amide.
5 parts were mixed and fed to the extruder to obtain an expansion ratio of 2.
A foamed sheet with a thickness of 1.5 mm and a thickness of 0 times was produced.

Next, a 1 g sample of this foamed sheet was placed in a porous nylon film bag with an opening of 64 μm. On the other hand, the bag was added to 40 ml of a 0.1 M sodium citrate buffer solution containing 1% pectolyase and 4% cellulase, and the bag was shaken at 25 DEG C. for 96 hours. Then, the bag was taken out, and the weight of the sample was measured after washing with water and drying, and the weight was 0.87 g. This means that rice hull powder was decomposed by about 13%.

[0015]

[Effects of the Invention] The foamed polyolefin resin molded product of the present invention has natural cellulose powder mixed therein, so it is biodegradable, and since the firepower during combustion is weak, it is easy to dispose of. . Furthermore, this molded product has good breathability against air and water and excellent heat insulation properties, so it is extremely useful for various uses such as packaging materials.

Claims (1)

[Claims] 1. A biodegradable foamed polyolefin resin molding containing 30 to 80% by weight of powder of a natural cellulose material.