JP2001011221A - Biodegradable resin foam and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin foam excellent in safety, water resistance, denseness, processability and biodegradability and free from an offensive smell such as a smack of acetic acid or the like, and to provide a method for preparing the same. SOLUTION: In a biodegradable resin foam composed mainly of a cellulose acetate, 5-149 pts.wt. of a starch and 1-20 pts.wt. of a modifier material, each based on 100 pts.wt. of the cellulose acetate, are contained. The introduction of the starch and the modifier into the foam mainly composed of the cellulose acetate gives a foam excellent in water resistance, denseness and processability. Further, the mixing of the modifier material enables to remove a smack of acetic acid. The foam is excellent in water resistance, denseness, processability and biodegradability and therefore suitable for being processed into a vessel for a cup noodle and a food tray.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable resin foam and a method for producing the same, and more particularly to a biodegradable resin foam which can be used for food containers such as trays and cup noodle containers, and a method for producing the same. .

[0002]

2. Description of the Related Art Conventionally, natural materials such as straw and rice hulls have been used as they are as cushioning materials for packing and transporting fruits and ceramics such as apples, and some natural materials such as cotton and old newspaper have been processed. And was using. Later, with the development of the synthetic resin industry, polystyrene foam was developed.Polystyrene foam was used not only in cushioning materials for home appliances such as mechanical parts and electrical parts, but also in trays for fresh food and containers for cup noodles. Until it was used. However, polystyrene has begun to be suspected to be one of the environmental hormones that has been a problem in recent years. In addition, synthetic resin products used in the packaging of other foodstuffs, daily necessities / furniture, etc., including these polystyrene foams, are disposed of as garbage after use. However, if dumped in landfills, unlike natural products such as straw and cotton, they will not be decomposed by microorganisms and will remain bulky forever, hindering the growth of local plants. In addition, problems such as impairing the stability of the ground, and sometimes being eaten incorrectly by birds, wild animals, fish, etc., impairing the health of these animals have occurred.

Therefore, in recent years, development of biodegradable plastics that are environmentally friendly and do not affect the human body has been promoted. A number of inventions have been made on biodegradable plastics so far, one of which is a plastic in which corn or other starch is mixed with polyethylene, polypropylene, or the like, for example, disclosed in JP-A-7-258453. Biodegradable plastics comprising a thermoplastic starch and a thermoplastic polymer are exemplified. When such starch-containing plastics are disposed of in soil, only the contaminated starch is decomposed by microorganisms, which makes the plastic porous and increases its surface area.
Thereby, the synthetic resin component is considered to be susceptible to weathering and the like, and in a narrow sense, is called a biodegradable resin.

[0004] However, all of the conventional starch-containing plastics have a disadvantage that they are poor in water resistance and moisture resistance. Therefore, when it is used as a cushioning foam for packing, it is necessary to use it in a moisture-proof bag made of polyethylene film, etc. And troublesome work such as disposal of bags after use. Even when there is no danger of the package being wet at all, if the foam for cushioning is used as it is for packaging home appliances and machine parts, it absorbs the humidity in the air, and the foam may fall off or be removed from the stored goods. There is a problem that a gap is formed between them and the function as a cushioning material is impaired. Furthermore, when used for packing fruits and vegetables, there arises a problem that the moisture of the fruits and vegetables is absorbed, the foam is muddy, and the function as a cushioning material is completely lost.

On the other hand, Japanese Patent Application Laid-Open No. Hei 10-72535 discloses a moisture-resistant biodegradable resin foam made of starch, polyvinyl alcohol, and aliphatic polyester or polypropylene. However, this biodegradable resin foam has a problem that water resistance is remarkably inferior and elasticity and compression resistance are inferior to conventional polystyrene resin foam.

[0006] In order to solve the above-mentioned problems, the present inventors have focused on biodegradable cellulose acetate, and have tried to produce a foam by mixing cellulose acetate and starch. In a biodegradable resin foam, a resin foam mixed with a synthetic resin such as polypropylene has no biodegradability in a normal state, so it only has biodegradability, and is not necessarily complete. Not biodegradable. However, if cellulose acetate is used in place of the conventional synthetic resin, only biodegradable materials are used to demonstrate complete biodegradability, while at the same time having high elasticity and high compression resistance, A highly safe biodegradable resin foam without hormonal anxiety can be obtained.

[0007]

However, in order to use a cellulose acetate-based biodegradable resin foam for cup noodle containers or food trays, not only safety but also water resistance, denseness and processability are required. It is hoped that it is good. It is also important not to give off odor such as acetic acid odor. However, according to the conventional technology, a biodegradable resin foam excellent in water resistance, denseness, and processability cannot be obtained, and acetic acid odor cannot be removed.

[0008] Therefore, a main object of the present invention is to provide a biodegradable resin foam excellent in safety, water resistance, denseness, processability, and biodegradability and free of an odor such as acetic acid odor, and a method for producing the same. To provide.

[0009]

The biodegradable resin foam according to the present invention is a biodegradable resin foam containing cellulose acetate as a main component, and 5-149 parts by weight of starch with respect to 100 parts by weight of cellulose acetate. And 1 to 20 parts by weight of a modifier. By mixing starch and a modifier with cellulose acetate as a main component, a foam excellent in water resistance, denseness and processability can be obtained. By increasing the mixing ratio of cellulose acetate as the main component, the water resistance is mainly improved, by mixing starch, the elasticity and compression resistance are mainly improved, and by mixing the modifier, the denseness and processing are mainly improved. The performance is improved. In addition, the denseness means that the foaming is dense and uniform, and is an aptitude that contributes to the smoothness of the surface of the processed product and printability. Further, the odor of acetic acid can be eliminated by mixing the modifier. It is desirable that talc, eggshell, and the like be contained alone or in combination as the modifying material. The biodegradable resin foam according to the present invention is excellent in water resistance, denseness, and processability, and thus is suitable for processing cup noodles into containers and food trays. Therefore, it can be expected to replace foamed polystyrene, which is currently widely used for cup noodle containers, food trays, and the like, and can eliminate anxiety about environmental hormones. The amount of starch was 5 parts per 100 parts by weight of cellulose acetate.
When the amount is less than the weight part, the processability is deteriorated, and when the amount is too much, the water resistance is lowered. If the amount of the modifier such as talc or eggshell is less than 1 part by weight per 100 parts by weight of cellulose acetate, it affects the compactness, processability and off-flavor. In addition, a commercially available acetate flake can be generally used for cellulose acetate, but is not necessarily limited thereto. Further, as the starch, naturally used natural starch such as corn starch, wheat flour, potato starch, kudzu starch, tapioca starch can be used as it is. Further, as the eggshell powder, generally available eggshell powder can be used.

Further, the biodegradable resin foam according to the present invention preferably contains not more than 20 parts by weight of polyethylene glycol and / or polypropylene glycol based on 100 parts by weight of the biodegradable resin foam. By containing 20 parts by weight or less of either polyethylene glycol or polypropylene glycol, or a mixture of both, flexibility is improved and workability can be further improved. However, if the amount exceeds 20 parts by weight, bleeding out is not preferred. If the molecular weight of polyethylene glycol or polypropylene glycol is too large, it does not penetrate into the cellulose acetate molecules and flows out during molding and does not exhibit a plasticizing effect. Therefore, the molecular weight is preferably 400 or less.

Further, the biodegradable resin foam according to the present invention may be in the form of a sheet. By forming the biodegradable resin foam into a sheet, secondary processing into a container or the like becomes easy, and application to various uses can be expected.

Further, the method for producing a biodegradable resin foam according to the present invention is based on 100 parts by weight of cellulose acetate.
A method for producing a biodegradable resin foam, characterized in that water is previously mixed in an amount of 5 to 25 parts by weight, another composition is mixed, raw materials are adjusted, and then foaming is performed. According to this production method, water acts as a foaming agent without using a conventional foaming agent, and a desired foam can be produced by adding only water. However, if the amount of water is too small, the foaming property is affected. Conversely, if the amount is too large, a foam having a desired quality cannot be obtained. Therefore, the appropriate amount of water is 5 to 25 parts by weight based on 100 parts by weight of cellulose acetate.

In the method for producing a biodegradable resin foam according to the present invention, the biodegradable resin foam may be foamed into a desired shape using an extruder. This extruder may be single-screw or twin-screw, but twin-screw is more preferable because the materials can be more uniformly mixed and a high-quality product can be obtained. By changing the shape of the die of the extruder, foam products having various shapes including a sheet shape can be manufactured.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the drawings.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) To 4.75 kg of cellulose acetate (manufactured by Teijin Limited), 712.5 g of water was added and mixed.
It was left for 30 minutes to be sufficiently impregnated with water. This is because the molding temperature can be lowered by water and the gas foaming effect by water vapor can be obtained. 4.75 corn starch
kg and 0.5 kg of talc were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 shown in FIG. 1 by a screw feeder. Twin screw extruder 10 is L / D
= 24, D = 50mm, and the barrel temperature is 100 ° C in the first barrel, 180 ° C in the second barrel,
The third barrel is 220 ° C, and the maximum discharge rate per hour is 4
0 kg. While foaming the raw material inside the twin-screw extruder 10, the contents were extruded from a die for producing a sheet-like material. As a result, a uniform sheet-like foam could be formed very well in a stable state at all times. In this example, a flexible sheet-like foam having a thickness of 1 mm, a width of 340 mm and a length of 50 m was completely smooth and flexible. The change before and after immersing the 10 square cm test piece of the obtained sheet-like foam in room temperature water and 60 ° C. hot water was examined.
No change in shape or physical properties was observed. Further, when the cross section of the sheet-like foam was observed with an electron microscope, the foam was uniformly and stably dispersed, and was excellent in denseness.
Also, no acetic acid odor was emitted. When biodegradability was examined by a soil burial test under natural conditions, the weight was reduced by 51% in 25 weeks and completely decomposed in 40 weeks.

Example 2 To 4.9 kg of cellulose acetate (manufactured by Teijin Limited), 735 g of water was added and mixed.
Let stand for minutes. To this, 4.9 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform. The mixture is fed to a twin-screw extruder 1 by a screw feeder.
0 and foamed and extruded under the same conditions as in Example 1. As a result, the same sheet-like foam as in Example 1 was successfully molded. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability.
Also, no acetic acid odor was emitted.

(Example 3) 735 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited), and mixed.
Let stand for minutes. To this, 0.25 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform.
This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, the same sheet-like foam as in Example 1 was successfully molded. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability.
Also, no acetic acid odor was emitted.

(Comparative Example 1) 735 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Let stand for minutes. 7.5 kg of corn starch and 0.2 kg of eggshell powder were added thereto and mixed until uniform. The mixture is fed to a twin-screw extruder 1 by a screw feeder.
0 and foamed and extruded under the same conditions as in Example 1. As a result, a sheet-like foam was obtained. However, when the obtained sheet-like foam was immersed in water for 30 minutes, it became soft and brittle.

Comparative Example 2 735 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Let stand for minutes. To this, 0.2 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform. The mixture is fed to a twin-screw extruder 1 by a screw feeder.
0 and foamed and extruded under the same conditions as in Example 1. As a result, a sheet-like foam was obtained,
The sheet foam was hard and brittle and had poor workability.

Example 4 To 4.9 kg of cellulose acetate (manufactured by Teijin Limited), 735 g of water was added and mixed.
Let stand for minutes. To this, 4.9 kg of corn starch and 0.049 kg of eggshell powder were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, the same sheet-like foam as in Example 1 was successfully molded. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability. Also, no acetic acid odor was emitted.

Example 5 To 4.9 kg of cellulose acetate (manufactured by Teijin Limited), 735 g of water was added and mixed.
Let stand for minutes. To this, 4.9 kg of corn starch and 0.98 kg of eggshell powder were added and mixed until uniform.
This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, the same sheet-like foam as in Example 1 was successfully molded. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability.
Also, no acetic acid odor was emitted.

Comparative Example 3 735 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Let stand for minutes. To this was added 5.0 kg of corn starch and 25 g of eggshell powder, and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, a sheet-like foam could be obtained, but the foaming ratio became very large and the odor of acetic acid became strong, so that it could not be used.

(Example 6) 570 g of water was added to 3.8 kg of cellulose acetate (manufactured by Teijin Limited), and mixed.
It was left to stand for a minute and was sufficiently impregnated with water. This has a molecular weight of 400
Add 200 g of the following polyethylene glycol and add 2
Leave for 0 minutes to fully impregnate. Next, 5.4 kg of corn starch, 500 g of talc, and 200 g of eggshell powder were added and mixed until uniform. This mixture was supplied to a twin-screw extruder 10 by a screw feeder, and Example 1 was used.
The mixture was foamed and extruded under the same conditions as described above. As a result, the same sheet-like foam as in Example 1 was successfully molded. When the cross section of the obtained foam was checked with an electron microscope, it was confirmed that the foam was densely and uniformly foamed,
The foaming rate was significantly reduced. Also, the acetic acid odor was completely eliminated, and the flexibility related to processability was considerably improved. Water resistance has also been greatly improved. Biodegradability was the same as in Example 1.

(Example 7) 750 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
It was left to stand for a minute and was sufficiently impregnated with water. This has a molecular weight of 400
The following 100 g of polyethylene glycol and 100 g of polypropylene glycol were added, and the mixture was allowed to stand for further 20 minutes to be sufficiently impregnated. Next, 5.0 kg of corn starch
And 500 g of talc and 200 g of eggshell powder were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, the same sheet-like foam as in Example 1 was successfully molded. When the cross section of the obtained sheet-like foam was checked with an electron microscope, it was confirmed that the foam was densely and uniformly foamed, and the foaming rate could be significantly suppressed. Also, the acetic acid odor was completely eliminated, and the flexibility related to processability was considerably improved.
Water resistance has also been greatly improved. Biodegradability was the same as in Example 1.

Example 8 570 g of water was added to 3.8 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Let stand for minutes. 200 g of polyethylene glycol having a molecular weight of 400 or less was added thereto, and the mixture was allowed to stand for further 20 minutes to be sufficiently impregnated. Next, 5.4 kg of corn starch, 500 g of talc, and 200 g of eggshell powder were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, the same sheet-like foam as in Example 1 was successfully molded. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability. Also, no acetic acid odor was emitted.

Comparative Example 4 Water (570 g) was added to 3.8 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
It was left to stand for a minute and was sufficiently impregnated with water. This has a molecular weight of 400
2.5 kg of polyethylene glycol
Allowed to stand for minutes to fully impregnate. Next, 5.4 kg of corn starch, 500 g of talc, and 200 g of eggshell powder were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, a sheet-like foam could be obtained, but the polyethylene glycol bleed out and was not usable.

(Comparative Example 5) 570 g of water was added to 3.8 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
It was left to stand for a minute and was sufficiently impregnated with water. It has a molecular weight of 100
0 to 200 g of polyethylene glycol and add another 20 g
After standing for minutes, the polyethylene glycol did not impregnate.

Example 9 To 5.0 kg of cellulose acetate (manufactured by Teijin Limited), 1.25 kg of water was added and mixed.
Left for 20 minutes. To this, 5.0 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform. This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, a sheet-like foam similar to that of Example 1 could be obtained. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability. Also,
There was no acetic acid odor.

Example 10 250 g of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Left for 0 minutes. To this, 5.0 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform.
This mixture was supplied to the twin-screw extruder 10 by a screw feeder, foamed under the same conditions as in Example 1, and extruded. As a result, a sheet-like foam similar to that of Example 1 could be obtained. The obtained sheet-like foam had flexibility, and was excellent in water resistance, denseness, and biodegradability. Also, no acetic acid odor was emitted.

Comparative Example 6 3.0 kg of water was added to 5.0 kg of cellulose acetate (manufactured by Teijin Limited) and mixed.
Left for 0 minutes. To this, 5.0 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform.
This mixture was supplied to the twin-screw extruder 10 by a screw feeder and extruded under the same conditions as in Example 1. As a result, a sheet-like foam could not be obtained.

Comparative Example 7 To 5.0 kg of cellulose acetate (manufactured by Teijin Limited), 200 g of water was added and mixed.
Let stand for minutes. To this, 5.0 kg of corn starch and 0.2 kg of eggshell powder were added and mixed until uniform. The mixture is fed to a twin-screw extruder 1 by a screw feeder.
0 and extruded under the same conditions as in Example 1. As a result, the foamability was poor and the product was burnt, so that a sheet-like molded product could not be obtained.

[0032]

According to the present invention, it is possible to obtain a biodegradable resin foam excellent in safety, water resistance, denseness, processability, and biodegradability, and having no unpleasant odor such as acetic acid odor, and a method for producing the same. Can be. By processing the obtained biodegradable resin foam, it can be used for food containers such as trays and cup noodle containers.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of an extruder used for producing a biodegradable resin foam according to the present invention.

[Explanation of symbols]

 10 Extruder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 3:02 71:02) B29K 1:00 (72) Inventor Hiroshi Miyakawa 1-6 Edobori, Nishi-ku, Osaka-shi 14 Kobe Steel, Ltd. (72) Inventor Kiyohiko Sawa 1-1-1, Wakihama Kaigandori, Chuo-ku, Kobe Kobe Steel Techno Co., Ltd. (72) Michio Hayashi 2-1 Takasu-cho, Nishinomiya-shi, Hyogo 29-816 F-term (reference) 4F071 AA08 AA09 AA51 AB26 AF52 AH04 AH05 BB06 BC01 BC04 BC17 4F074 AA02 AA03 AA76 AA98 AC26 AC31 AC32 BA34 CA22 CC04Y CC10X CC22X CC32Y CC34Y DA24 DA34 4F201 AA01 AG12 BC01 AG01 BC BD05 BM06 BM11 4J002 AB02W AB04X CH023 DE027 DE236 DH046 DJ046 FD016 FD327 GG01

Claims (6)

[Claims] 1. A biodegradable resin foam containing cellulose acetate as a main component, characterized by containing 5-149 parts by weight of starch and 1-20 parts by weight of a modifier based on 100 parts by weight of cellulose acetate. A biodegradable resin foam. 2. The biodegradable resin foam according to claim 1, wherein talc and / or eggshell powder is used as the modifier. 3. A biodegradable resin characterized by containing polyethylene glycol and / or polypropylene glycol in an amount of 20 parts by weight or less based on 100 parts by weight of the biodegradable resin foam according to claim 1 or 2. Resin foam. 4. A biodegradable resin foam sheet, wherein the biodegradable resin foam according to claim 1 is formed into a sheet. 5. The method for producing a biodegradable resin foam according to claim 1, wherein 5 to 25 parts by weight of water is previously mixed with 100 parts by weight of cellulose acetate. A method for producing a biodegradable resin foam, characterized in that a raw material is prepared by mixing other compositions and then foamed. 6. The method for producing a biodegradable resin foam according to claim 5, wherein foaming is performed using an extruder.