JP2000072906A - Biodegradable resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a perfectly biodegradable, highly elastic and highly compression-resistant foam by using a composition mainly consisting of acetylcellulose and starch in a specified ratio. SOLUTION: This foam is made from a composition containing as the main components 20-40 pts.wt. acetylcellulose and 60-80 pts.wt. starch and containing as an optical component 1-5 pts.wt. shell powder. This is produced by adding 6-15 pts.wt. water to a mixture comprising 20-40 pts.wt. acetylcellulose and, optionally, 1-5 pts.wt. shell powder to fully swell the mixture, adding 60-80 pts.wt. starch, etc., to the swollen mixture, and foaming the resulting mixture by extrusion from an extruder. Alternatively, the foam is made from a mixture mainly consisting of 5-20 pts.wt. acetylcellulose, 5-20 pts.wt. PVA, 60-80 pts.wt. starch, and 1-5 pts.wt. shell powder. This is produced by adding 2-7 pts.wt. water to a mixture comprising 5-20 pts.wt. acetylcellulose and 1-5 pts.wt. shell powder to fully swell the mixture, adding 5-20 pts.wt. PVA to the swollen mixture, further adding 60-80 pts.wt. starch thereto, and foaming the final mixture in a similar manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new, highly biodegradable resin foam having complete biodegradability. Conventionally, resin foams such as expanded polystyrene,
It has been used as a buffer for fresh food trays, containers for cup noodles, home electric appliances and the like. However, synthetic resin products such as polystyrene have been converted to biodegradable resin foams because of problems in processing such as incineration and burying after use. As one of the methods, development of a resin foam mainly containing biodegradable starch has been promoted. However, these materials do not have moisture resistance, absorb moisture, have poor elasticity, or have only starch decomposed, leaving the synthetic resin tattered, resulting in environmental problems. The present invention relates to a new completely biodegradable, highly elastic, biodegradable resin foam which has improved such disadvantages.

[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 natural materials such as cotton and old newspaper have been somewhat processed. I have used things. Later, with the development of the synthetic resin industry, polystyrene foam was developed.Polystyrene foam was used not only in cushioning materials for mechanical parts, electrical parts and home appliances, but also in trays for fresh food and containers for cup noodles. Until it was used. However, 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, unlike natural products such as straw and cotton, if they are dumped in landfills, they will not be decomposed by microorganisms,
It will remain bulky for a long time, hindering the growth of the local plants, impairing the stability of the ground,
Occasionally, birds, wild animals, fish, and the like have inadvertently eaten the food, causing problems such as impairing the health of these animals. Therefore, development of biodegradable plastics has been promoted.

Under such circumstances, many inventions have been made on biodegradable plastics. One of them is a plastic in which corn or the like is mixed with polyethylene or polypropylene, such as a biodegradable plastic comprising a thermoplastic starch and a thermoplastic polymer disclosed in JP-A-7-258453. Is raised. When such starch-containing plastics are discarded in soil, only the portion of the contaminated starch is decomposed by microorganisms, thereby making the plastic porous and increasing its surface area. It is considered that the resin is susceptible to the like, and in a narrow sense, is called a biodegradable resin.

[0004] However, the above-mentioned starch-containing plastics are all poor in water resistance and moisture resistance, and when used as a buffer foam for packing, they are put in a moisture-proof bag made of polyethylene film or the like. It is necessary to insert and insert into the bag, pay attention to and check for tearing of the bag,
There was troublesome work such as disposal of bags after use. In addition, even if 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,
If the foam absorbs the humidity in the air, the foam will fall off, and a gap will be created between the stored articles, impairing the function as a cushioning material, or if used for packing fruits and vegetables, fruits and vegetables This causes the foam to become muddy due to the absorption of water, and the function as a cushioning material is completely lost. In order to solve such a problem, the present applicant has disclosed in
No. 2,535 discloses a moisture-resistant biodegradable resin foam made of starch, polyvinyl alcohol and aliphatic polyester, and a moisture-resistant biodegradable resin foam made of starch, polyvinyl alcohol and polypropylene. However, these resin foams have some problems in elasticity and compression resistance as compared with conventional polystyrene resin foams. Then, the present applicant further disclosed in Japanese Patent Application No. 10-214718 that mainly 20 to 40 parts by weight of polypropylene and 60 to 8 parts of starch.
0 parts by weight, and a titanate-based crosslinking agent 0.05 to 5.0.
A biodegradable resin foam excellent in elasticity and compression resistance characterized by being composed of parts by weight has been disclosed.

[0005]

In the above-mentioned biodegradable resin foam, a resin foam mixed with a synthetic resin such as polypropylene for improving the elasticity and compression resistance is formed by using such a synthetic resin. In the state, it does not have biodegradability, so it has only biodegradability and does not necessarily have complete biodegradability. The problem to be solved by the present invention is to provide a biodegradable resin foam having high elasticity and high compression resistance while exhibiting full biodegradability using only a biodegradable material. It is in. Further, as a secondary problem of the present invention, when producing such a biodegradable resin foam, effective utilization of waste is also mentioned.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors focused on biodegradable acetylcellulose and tried to produce a foam by mixing acetylcellulose and starch. However, according to the conventional method, carbonization of starch was started when the melting temperature of acetylcellulose was reached, and a high-quality foam could not be produced. However, as a result of intensive research, it was easy to swell acetylcellulose in advance with water. In another method, it was found that the melting temperature of acetyl cellulose could be lowered, and further, it was found that shell powder could be used instead of calcium carbonate, which had been used as a foaming aid, and the present invention was reached. is there. The present inventors have found that a biodegradable resin foam (hereinafter, referred to as “first invention”) mainly comprising 20 to 40 parts by weight of acetylcellulose and 60 to 80 parts by weight of starch, mainly acetyl 20 to 40 parts by weight of cellulose, 60 to 80 parts by weight of starch, and 1 to 5 parts by weight of shell powder (hereinafter referred to as "second invention"), and mainly A biodegradable resin foam comprising 5 to 20 parts by weight of acetylcellulose, 5 to 20 parts by weight of polyvinyl alcohol, 60 to 80 parts by weight of starch, and 1 to 5 parts by weight of shell powder (hereinafter referred to as "No. 3 invention "), and adding 20 to 40 parts by weight of acetyl cellulose to 6 to 15 parts of water.
2. A method for producing a biodegradable resin foam according to claim 1, further comprising extruding a mixture obtained by adding 60 to 80 parts by weight of starch, etc., from an extruder and foaming the mixture after adding parts by weight to sufficiently swell. Method (hereinafter referred to as “fourth invention”),
20-40 parts by weight of acetylcellulose and shell powder 1-5
3. A mixture comprising 6 to 15 parts by weight of water and a sufficient amount of water added to the mixture with 60 to 80 parts by weight of starch, and extruded from an extruder to foam. The method for producing a biodegradable resin foam according to the above (hereinafter referred to as “fifth invention”), and after adding 2 to 7 parts by weight of water to 5 to 20 parts by weight of acetylcellulose and sufficiently swelling, or 2 to 7 parts by weight of water is added to a mixture of 5 to 20 parts by weight of cellulose and 1 to 5 parts by weight of shell powder to sufficiently swell, and then 5 to 20 parts by weight of polyvinyl alcohol is mixed. A method for producing a biodegradable resin foam according to claim 3 (hereinafter referred to as a "sixth invention"), characterized in that a mixture of about 80 parts by weight or the like is extruded from an extruder and foamed.

The biodegradable resin foam according to the first invention comprises:
It is mainly composed of 20 to 40 parts by weight of acetylcellulose and 60 to 80 parts by weight of starch. Usually, commercially available acetate flakes are used for the acetylcellulose, but are not necessarily limited thereto. Further, as the starch, naturally used natural starch such as corn starch, wheat flour, potato starch, kudzu starch and tapioca starch can be used as it is. If the amount of acetylcellulose is less than 20 parts by weight with respect to 80 parts by weight of starch, elasticity and compression resistance are not sufficient, and if it exceeds 40 parts by weight with respect to 60 parts by weight of starch, compression resistance becomes insufficient. It will be higher than necessary. What is contained besides this acetylcellulose and starch is decomposition products and unreacted products of foaming agents such as calcium carbonate added to the raw materials, and there is residual moisture, and stearic acid and polypropylene are used as additives such as softeners. When glycol or the like is added, the residue is included, and when pigment is added, the pigment is included.

[0008] The biodegradable resin foam according to the second invention comprises:
It is mainly characterized by comprising 20 to 40 parts by weight of acetylcellulose, 60 to 80 parts by weight of starch, and 1 to 5 parts by weight of shell powder. Acetylcellulose and starch in the second invention are the same as in the first invention, and their composition ratios have the same significance as in the first invention. After removing the contents from the cultured scallop,
Scallop shell powder, which is commercially available as a soil conditioner by converting shells that had previously been discarded on the shore into powder, will be used.In the future, if oyster shells become commercially available, oyster shell powder will be used. It is also considered to be used. These shell powders contain calcium carbonate as a main component, but also hard proteins such as conchiolin and polysaccharides such as chitin and lamiranan as minor components.
Note that these trace components have biodegradability and are finely dispersed in the shell, so that the biodegradability of the shell is also enhanced. This shell powder is not only used as a substitute for calcium carbonate as a foaming aid, but also has the effect of smoothing and stiffening the foam surface as if the foam were covered with a thin film Things. The shell powder is composed of 40 parts by weight of acetylcellulose and 80 parts of starch.
If the amount is less than 1 part by weight, the effect of the shell powder described above is not exhibited. If the amount exceeds 5 parts by weight with respect to 20 parts by weight of acetylcellulose and 60 parts by weight of starch, the feel of the foam becomes poor. . However, more may be added as needed. The components contained in addition to acetyl cellulose, starch and shell powder are the same as those in the first invention.

The biodegradable resin foam according to the third invention comprises:
Acetyl cellulose 5-20 parts by weight, polyvinyl alcohol 5-20 parts by weight, starch 60-80 parts by weight, and
It is characterized by comprising 1 to 5 parts by weight of shell powder.
The acetylcellulose and the starch in the third invention are the same as those in the first invention.
It is the same as the invention, and the composition ratio has the same significance as the first invention. The shell according to the third aspect is the same as that of the second aspect. Polyvinyl alcohol has been conventionally recognized as biodegradable. The reason why not only acetylcellulose but also polyvinyl alcohol is added is that it is expected to improve the elasticity in addition to the compression resistance of the foam.

The method for producing a biodegradable resin foam according to the fourth invention is characterized in that 20 to 40 parts by weight of acetyl cellulose is added to water 6
After adding １５15 parts by weight and swelling sufficiently, starch 60６０
The biodegradable resin foam according to the first aspect of the present invention is characterized in that the product to which 80 parts by weight or the like are added is extruded from an extruder and foamed to produce the biodegradable resin foam according to the first invention. The point of this production method is to add acetylcellulose to water in advance to sufficiently swell. If starch is mixed with acetyl cellulose and water is added to the extruder as before, the starch absorbs water and becomes muddy, and carbonization starts before acetyl cellulose is melted. A good quality foam cannot be produced. By adding water to acetylcellulose in advance and sufficiently swelling, not only such a problem can be avoided, but also the melting temperature of acetylcellulose can be lowered, and a high-quality foam can be manufactured.

The amount of water added to acetylcellulose is
Generally, it is about 1/4 to 1/3 of acetylcellulose, but when the amount of starch is large, it is larger than this.
If the amount of starch is small, lower it. The temperature of the water added to the acetylcellulose is preferably somewhat warm in order to shorten the swelling time. However, heat is generated at the time of swelling, so it is better not to use hot water that is too hot. In view of this exothermic phenomenon and the fact that acetylcellulose generally improves thermoplasticity with a decrease in the degree of acetylation, some chemical change such as elimination of some acetic acid groups occurs during this swelling, and It is considered that the melting temperature of cellulose decreases. The addition of the starch after swelling is preferably performed after the temperature of the swelled acetylcellulose is lowered, in order to avoid the starch from being hygroscopically gelatinized. The starch or the like added after swelling usually refers to a mixture of starch and a foaming agent such as calcium carbonate, a softening agent, a pigment, or the like. The body can be manufactured.

The method for producing a biodegradable resin foam according to the fifth invention is characterized in that a mixture of 20 to 40 parts by weight of acetylcellulose and 1 to 5 parts by weight of shell powder is added with 6 to 15 parts by weight of water to swell sufficiently. After that, a product to which 60 to 80 parts by weight of starch is added is extruded from an extruder and foamed to produce a biodegradable resin foam according to the second invention. The point of this production method is that in the fourth invention, calcium carbonate as a foaming aid is added to starch after swelling with acetyl cellulose in water. Is mixed with acetylcellulose and water is added together.

As described above, adding water to a mixture of acetylcellulose and shell powder not only swells acetylcellulose but also swells shell powder to promote further micronization. It is in. Shells are formed by the biochemical action of shellfish and, unlike simple crystals of calcium carbonate, have a fine structure containing proteins, chitin, polysaccharides, etc., and these substances absorb water. It is also conceivable that acetic acid released during swelling of acetylcellulose promotes swelling of the shell powder. The term "starch or the like added after swelling" generally refers to a mixture of starch and various additives such as a softener and a pigment, which are added as needed.

The method for producing a biodegradable resin foam according to the sixth invention is characterized in that 5 to 20 parts by weight of acetyl cellulose is added to
After adding 7 parts by weight and sufficiently swelling, or after adding 2 to 7 parts by weight of water to a mixture of 5 to 20 parts by weight of acetylcellulose and 1 to 5 parts by weight of shell powder, the mixture is sufficiently swelled. Mix vinyl alcohol and add starch 60-80
It is characterized in that a product to which parts by weight and the like are added is extruded from an extruder and foamed to produce a biodegradable resin foam according to the third invention. The point of this production method is to mix polyvinyl alcohol after swelling acetyl cellulose with water.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Confirmation of acetylcellulose swelling effect [Comparative Example 1] 8 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) in order to produce a foam of polypropylene and starch, which had been replaced with acetylcellulose. Then, 39 kg of corn starch and 1 kg of calcium carbonate were mixed with 2 kg of polyethylene glycol (molecular weight 3000) dissolved and mixed in warm water to make the ratio of acetylcellulose and starch about 2/8, and 5 kg of water was added. It is supplied to a twin screw extruder (φ46 mm, L / D 21.5), and the cylinder temperature is C ₁ 80 ° C., C ₂ 90 ° C., C ₃ 140 ° C.
_{C 4 200 ℃, C 5 230} ℃, die temperature _D 1 200
Extruded from a 2.7mm nozzle at 2.7 ° C and foamed.
cm to obtain a foam (hereinafter referred to as “foam A”). The foam A has a specific gravity of 0.0150 g / cm
^In No. ³ , a part was carbonized, the air bubbles were medium, and the bubbles were small, and were not usable.

[Comparative Example 2] A mixture of 9 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) in 1 kg of polyethylene glycol (molecular weight 3000) dissolved in warm water and having a higher ratio of acetylcellulose than in Comparative Example 1 7.5 kg, 15 kg of corn starch and 2.5 kg of calcium carbonate were mixed to make the ratio of acetylcellulose and starch about 3/7, and 2.5 kg of water was further added. The cylinder temperature C ₁ 80 ° C., C ₂ 90 ° C., C ₃ 140 ° C.
_{C 4 200 ℃, C 5 230} ℃, die temperature _D 1 200 ° C.
Although extruded, since the product can not be obtained, the cylinder temperature _{C 1 80 ℃, C 2 90} ℃, C 3 150 ℃, C 4 23
0 ° C., C _{5 to} 270 ° C., and the die temperature to D ₁ 210
C. and extruded to produce a foam (hereinafter referred to as "foam B". Foam B was partially carbonized in order to raise the cylinder temperature, and the foam was irregular and did not withstand use.

Example 1 As a result of various studies, it was found that if acetyl cellulose was swelled in advance with water, the melting temperature was lowered, and the method was carried out. First, 1 kg of water is added to 3 kg of acetylcellulose (“Acetate Flake” manufactured by Teijin Limited) and swelled for about 30 minutes. Then, 7 kg of corn starch and 150 g of calcium carbonate are mixed, and the ratio of acetylcellulose to starch is 3/7. In the same manner as in Comparative Example 1, the mixture was supplied to a twin-screw extruder, and cylinder temperatures C ₁ 80 ° C., C ₂ 90 ° C., C ₃ 160 ° C., C ₄ 2
It was extruded at 00 ° C., C ₅ 230 ° C., and die temperature D ₁ 210 ° C. to produce a foam (hereinafter referred to as “foam 1”. Foam 1
Had a specific gravity of 0.0138 g / cm ³ and some fine bubbles, but could withstand use sufficiently.

Example 2 The ratio of acetylcellulose was increased from that of Example 1, and 1 kg of water was added to 4 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) to swell for about 30 minutes, followed by 6 kg of corn starch. And 150 g of calcium carbonate to give a ratio of acetylcellulose to starch of 4/6. The mixture was supplied to a twin-screw extruder in the same manner as in Comparative Example 1, and the cylinder temperature was C ₁ 80 ° C., C ₂ 90
_{℃, C 3 160 ℃, C} 4 200 ℃, C 5 230 ℃, foam extrusion at a die temperature of _D 1 210 ° C. (to produce a "foam 2" or less. Foam 2 has a specific gravity 0.0150G /
cm ³ , the compression resistance was slightly improved, and the material was sufficiently usable.

2. Confirmation of foaming property of swollen acetylcellulose [Comparative Example 3] 7.5 kg of a mixture of 9.5 kg of acetylcellulose (“Acetate Flake” manufactured by Teijin Limited) not swollen with water and 0.5 kg of polypropylene glycol
17 kg of corn starch and 0.1 kg of calcium carbonate.
By mixing 5KgN 0.05 kg of stearic acid, the ratio of acetyl cellulose and starch and about 3/7, in the same manner as in Comparative Example 1, was fed to a twin screw extruder at a cylinder temperature of _C 1 80
_{℃, C 2 90 ℃, C} 3 150 ℃, C 4 230 ℃, C 5 2
70 ° C., the foam extruded at a die temperature of _D 1 210 ° C. (to produce a "foam C" below. Foams C has a specific gravity at 0.0143g / cm ^3, were those have hard and light.

Example 3 Water was added to 3.95 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) in water.
After swelling for 30 minutes, 0.05 kg of polypropylene glycol is mixed. Without mixing calcium carbonate, a mixture of 6 kg of corn starch and 0.05 kg of stearic acid is mixed, and acetyl cellulose and starch are mixed. the ratio was about 4/6, as in Comparative example 1, was fed to a twin screw extruder at a cylinder temperature of C ₁ 80 ° C.,
C ₂ 90 ° C., C ₃ 160 ° C., C ₄ 170 ° C., C ₅ 180
° C., the foam extruded at a die temperature of _D 1 180 ° C. (to produce a "foam 3" or less. The foam 3 has a specific gravity 0.01
At 50 g / cm ³ , the bubbles were fine, but it was confirmed that if acetylcellulose was swollen with water in advance, foaming could be performed without adding calcium carbonate as a foaming aid.

3. Production of foam according to the first invention [Example 4] 1 kg of water was added to 3.5 kg of acetylcellulose ("Acetate flake" manufactured by Teijin Ltd.), and
After swelling for 0 minutes, 0.05 kg of calcium carbonate was mixed, 6.5 kg of corn starch was further mixed, and the ratio of acetylcellulose to starch was 35/65.
Similar to, and fed to a twin screw extruder at a cylinder temperature of C ₁ 8
0 ° C., C ₂ 90 ° C., C ₃ 170 ° C., C ₄ 170 ° C., C ₅
It was extruded at 180 ° C. and a die temperature D _{1 of} 160 ° C. to produce a foam (hereinafter referred to as “foam 4”. The foam 4 had a specific gravity of 0.0114 g / cm ³ .

Example 5 3.5 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) was added to 1 kg of water.
After swelling for about 30 minutes was added g, by mixing those advance calcium carbonate 100g was mixed with corn starch 6.5 kg, in the same manner as in Comparative Example 1, was fed to a twin screw extruder at a cylinder temperature of C ₁ 80 ° C, C ₂ 90 ° C, C ₃ 1
70 ° C., C ₄ 170 ° C., C ₅ 180 ° C., Die temperature D ₁
An extruded foam (hereinafter referred to as “foam 5”) was produced at 160 ° C. The foam 5 had a specific gravity of 0.0118 g / cm ³ .

Example 6 3.5 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) was added to 1 kg of water.
After swelling for about 30 minutes was added g, by mixing those advance calcium carbonate 150g was mixed with corn starch 6.5 kg, in the same manner as in Comparative Example 1, was fed to a twin screw extruder at a cylinder temperature of C ₁ 80 ° C, C ₂ 90 ° C, C ₃ 1
60 ° C., C ₄ 170 ° C., C ₅ 180 ° C., Die temperature D ₁
An extruded foam (hereinafter referred to as “foam 6”) was produced at 160 ° C. The foam 6 had a specific gravity of 0.0120 g / cm ³ .

Example 7 3.5 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) was added to 1 kg of water.
After swelling for about 30 minutes was added g, by mixing those advance calcium carbonate 200g was mixed with corn starch 6.5 kg, in the same manner as in Comparative Example 1, was fed to a twin screw extruder at a cylinder temperature of C ₁ 80 ° C, C ₂ 90 ° C, C ₃ 1
70 ° C., C ₄ 180 ° C., C ₅ 190 ° C., Die temperature D ₁
An extruded foam (hereinafter referred to as “foam 7”) was produced at 180 ° C. The foam 7 had a specific gravity of 0.0128 g / cm ³ .

The foams 4 to 4 obtained in the above Examples 4 to 7
No. 7 had excellent compression resistance as a cushioning material. In addition, as shown in Examples 4 to 7, by swelling acetylcellulose with water, it is possible to lower the cylinder temperature of the twin-screw extruder and to prevent deterioration of products such as carbonization of starch due to heat. It was also found that by simply adjusting the amount of calcium carbonate, a biodegradable resin foam having an arbitrary cell rate (reciprocal of specific gravity) and compression resistance can be obtained.

4. Example 8: Production of foam according to the second invention [Example 8] 3.5 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) was added to scallop shell powder (manufactured by Teijin Limited).
Changqing Scallop Gala Industrial “Shell Power”) 0.20kg
Is reacted by adding water 1kg to a mixture of, by mixing the reaction was completed after cornstarch 6.5 kg, in the same manner as in Comparative Example 1, was fed to a twin screw extruder at a cylinder temperature of C ₁ 80
_{℃, C 2 90 ℃, C} 3 170 ℃, C 4 180 ℃, C 5 1
An extruded foam (hereinafter referred to as “foam 8”) was manufactured at 90 ° C. and a die temperature D _{1 of} 180 ° C. The foam 8 had a specific gravity of 0.0
120 g / cm ³ , and despite the fact that calcium carbonate was not added as a foaming aid, the scallop shell powder worked as a foaming aid, or foamed very well.
Also, the surface had a smooth and durable surface layer as if covered with a thin film.

5. Example 9 Production of a Foam According to the Third Invention Example 9 1 kg of water was added to 1.5 kg of acetylcellulose ("Acetate Flake" manufactured by Teijin Limited) and allowed to swell for about 30 minutes. 5
The mixture was mixed with 7.4 kg of cornstarch and 0.10 kg of scallop shell powder (“Shell Power” manufactured by Changkei Scallop Gala Industry Co., Ltd.), and mixed similarly to Comparative Example 1. Feed to extruder, cylinder temperature C ₁
80 ° C., C ₂ 90 ° C., C ₃ 160 ° C., C ₄ 170 ° C., C
₅ Extruded foam at 180 ° C. and die temperature D ₁ 180 ° C. (hereinafter referred to as “foam 9”. Foam 9 has a specific gravity of 0.0125 g / cm ³ and a very high elasticity of compression resistance. It is a certain foam, because the shell powder does not participate in the reaction between acetylcellulose and water on the surface,
A smoother and more durable surface layer was formed than in Example 8.

6. Compression resistance test The foam 6 produced in Example 6 and
A biodegradable resin foam ("TOYO PLUST Ecosoft" manufactured by Toyo Plast Co., Ltd .; hereinafter, referred to as "foam D") mainly composed of starch and polyvinyl alcohol disclosed in Japanese Patent No.
The bottom placed in a room with a temperature of 85 ° C and humidity of 85% is 50x50cm
In each of the two tubes 50 cm high and 50 c
m, a plate was placed on top of it, and a load of 7 kg was applied, and the state of compression was observed.
Although the foam 6 was compressed to 46 cm after 4 hours, 45 cm after 36 hours, and 35 cm after 120 hours, the foam 6 was compressed to 49 cm after 24 hours, 49 cm after 36 hours, and only 28 cm after 120 hours. It has been found that the biodegradable resin foam according to the present invention has excellent compression resistance.

[0029]

The biodegradable resin foam according to the present invention comprises:
As described above, it is a complete biodegradable resin foam using only a biodegradable material, has excellent compression resistance, and replaces calcium carbonate as a foaming aid. In addition, those using shell powder using shells as waste not only contribute to saving of raw materials and effective use of wastes, but also have improved surface characteristics. In addition, the method for producing a biodegradable resin foam according to the present invention prevents carbonization of starch, which cannot be avoided by a general production method, and enables the production of a high-quality biodegradable resin foam for the first time. It was made. Therefore, the present invention makes a great contribution to eliminate the waste plastic pollution which is now a major social problem.

[Procedure amendment]

[Submission date] November 13, 1998 (1998.11.
13)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors focused on biodegradable acetylcellulose and tried to produce a foam by mixing acetylcellulose and starch. However, according to the conventional method, carbonization of starch was started when the melting temperature of acetylcellulose was reached, and a high-quality foam could not be produced. However, as a result of intensive research, it was easy to swell acetylcellulose in advance with water. In addition, they found that the melting temperature of acetylcellulose could be lowered, and found that shell powder could be used instead of calcium carbonate, which had been used as a foaming aid, and reached the present invention. is there. The present inventors have found that a biodegradable resin foam (hereinafter, referred to as “first invention”) mainly comprising 20 to 40 parts by weight of acetylcellulose and 60 to 80 parts by weight of starch, mainly acetyl 20 to 40 parts by weight of cellulose, 60 to 80 parts by weight of starch, and 1 to 5 parts by weight of shell powder (hereinafter referred to as "second invention"), and mainly A biodegradable resin foam comprising 5 to 20 parts by weight of acetyl cellulose, 5 to 20 parts by weight of polyvinyl alcohol, and 60 to 80 parts by weight of starch, or 1 to 5 parts by weight of shell powder. (Hereinafter referred to as "third invention"), swelled sufficiently by adding 6 to 15 parts by weight of water to 20 to 40 parts by weight of acetylcellulose, and then adding 60 to 80 parts by weight of starch and the like. , Claim 1, wherein the foaming extruded from an extruder
The method for producing a biodegradable resin foam according to the above (hereinafter referred to as "the fourth invention"), by adding 6 to 15 parts by weight of water to a mixture of 20 to 40 parts by weight of acetyl cellulose and 1 to 5 parts by weight of shell powder. 3. The method for producing a biodegradable resin foam according to claim 2, wherein the swelled product obtained by adding 60 to 80 parts by weight of starch is extruded from an extruder and foamed. Invention "), and
After adding 2 to 7 parts by weight of water to 5 to 20 parts by weight of acetyl cellulose and sufficiently swelling, or adding 2 to 7 parts by weight of water to a mixture of 5 to 20 parts by weight of acetyl cellulose and 1 to 5 parts by weight of shell powder. After adding 5 parts by weight of polyvinyl alcohol, the mixture was mixed with 5 to 20 parts by weight of polyvinyl alcohol.
A method for producing a biodegradable resin foam according to claim 3 (hereinafter referred to as a "sixth invention"), characterized in that a mixture of about 80 parts by weight or the like is extruded from an extruder and foamed.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

The biodegradable resin foam according to the third invention comprises:
Mainly, 5 to 20 parts by weight of acetyl cellulose, 5 to 20 parts by weight of polyvinyl alcohol, and 60 to 8 parts of starch
0 parts by weight or mainly acetylcellulo
5-20 parts by weight, polyvinyl alcohol 5-20
Parts by weight, starch 60 to 80 parts by weight, and shell powder 1 to 5
It is characterized by consisting of parts by weight. Acetyl cellulose and starch in the third invention is the same as the first invention, also set formed ratio with the same significance as the first invention.
The shell according to the third aspect is the same as that of the second aspect. Polyvinyl alcohol has been conventionally recognized as biodegradable. The reason why not only acetylcellulose but also polyvinyl alcohol is added is that it is expected to improve the elasticity in addition to the compression resistance of the foam.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

6. Compression resistance test The foam 6 produced in Example 6 and
A biodegradable resin foam ("TOYO PLUST Ecosoft" manufactured by Toyo Plast Co., Ltd .; hereinafter, referred to as "foam D") mainly composed of starch and polyvinyl alcohol disclosed in Japanese Patent No.
The bottom placed in a room with a temperature of 85 ° C and humidity of 85% is 50x50cm
In each of the two tubes 50 cm high and 50 c
m, a plate was placed on top of it, and a load of 7 kg was applied, and the state of compression was observed.
The foam 6 was compressed to 46 cm after 4 hours, 45 cm after 36 hours, and 35 cm after 120 hours. However, the foam 6 was compressed to 48 cm after 24 hours, 49 cm after 36 hours, and 48 cm after 120 hours. It has been found that the biodegradable resin foam according to the invention has excellent compression resistance.

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Claims (6)

[Claims] 1. Acetyl cellulose 20-4
A biodegradable resin foam comprising 0 parts by weight and 60 to 80 parts by weight of starch. 2. Acetyl cellulose 20-4
0 parts by weight, starch 60-80 parts by weight, and shell powder 1-
Biodegradable resin foam comprising 5 parts by weight 3. Mainly acetylcellulose 5-20
1 part by weight, 5-20 parts by weight of polyvinyl alcohol, 60-80 parts by weight of starch, and 1-5 parts by weight of shell powder 4. Addition of 6 to 15 parts by weight of water to 20 to 40 parts by weight of acetylcellulose and sufficient swelling, followed by starch 6
2. The method for producing a biodegradable resin foam according to claim 1, wherein the foam to which 0 to 80 parts by weight or the like has been added is extruded from an extruder and foamed. 5. A mixture of 20 to 40 parts by weight of acetyl cellulose and 1 to 5 parts by weight of shell powder is added with 6 to 15 parts by weight of water to sufficiently swell, and then 60 to 80 parts by weight of starch is added. 3. The method for producing a biodegradable resin foam according to claim 2, wherein the foam is extruded from an extruder and foamed. 6. After adding 2 to 7 parts by weight of water to 5 to 20 parts by weight of acetylcellulose and sufficiently swelling, or adding a mixture of 5 to 20 parts by weight of acetylcellulose and 1 to 5 parts by weight of shell powder. After adding 2 to 7 parts by weight of water and sufficiently swelling, 5 to 20 parts by weight of polyvinyl alcohol are mixed,
4. The method for producing a biodegradable resin foam according to claim 3, further comprising extruding a mixture obtained by mixing 60 to 80 parts by weight of starch from an extruder.