JP2000169611A - Shaped foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a shaped foam having excellent biodegradability, water resistance, moisture resistance and strength, and useful as a cushioning material, etc., for packages by sealing specific starch-based foams in lots in a specific biodegradable film bag. SOLUTION: This shaped foam is obtained by sealing starch-based foams in lots having a density of 0.005-0.6 g/cm3, preferably 0.008-0.20 g/cm3, a water absorption of <=50%, preferably 5-35%, and a thickness of <=100 μm, preferably 0.5-100 μm. The starch-based foams in lots are obtained by adding a biodegradable plastic such as polyvinyl alcohol, a foam-nucleating agent such as talc, water as a foaming agent, etc., to the starch-based foams in lots. A material for the biodegradable film is preferably polycaprolactone, etc. It is preferable that the inside of the biodegradable film bag is vacuumed on the above-described sealing treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to water resistance, moisture resistance,
The present invention relates to a biodegradable foam having improved strength.

[0002]

2. Description of the Related Art In recent years, the problem of plastic waste disposal as an environmental problem has attracted much attention. As one effective means for solving them, the development of biodegradable plastics that can be decomposed by microorganisms in soil or water is being promoted. The biodegradable plastics are broadly classified into those produced by microorganisms, those based on starch or cellulose, and those based on synthetic polymers having a special structure.

[0003] Among them, in particular, natural polymer-based and starch-based polymers are particularly widely used for practical use from the viewpoint of good compatibility with the environment and low cost because they are derived from natural products. Have been developed. These have been continuously studied for their biodegradation performance, practical physical properties, productivity, and the like. In particular, since foams are porous and have a large volume per unit weight, they are attracting attention as buffer materials and the like. .

[0004]

However, since starch-based foams are themselves hydrophilic, they have poor water resistance and moisture resistance in practical use, and shrink due to the plasticizing effect of water under high temperature and high humidity. It had an essential problem of deformation. In addition, compared to other plastic molded products, the cell film as the surface layer must be thin, so its water resistance,
It is inevitable that the moisture resistance will be remarkably deteriorated, and in use, the environmental conditions at the time of use have been significantly restricted. In addition, the contact with water is not limited to the shrinkage deformation of the foam, and there is a serious problem that mold is generated if the contact period is prolonged. In order to solve such a problem, Japanese Patent Application Laid-Open No. 5-230272 discloses that the water absorption rate is 1%.
Density of from 0.03 to 30% formed on at least one side of a coating layer having a thickness of 0.5 to 30 [mu] m, which is made of a substance of 0% or less.
A starch-based foam of 0.45 g / cm ³ is disclosed. The foam has satisfactory water resistance and moisture resistance, but the strength of the foam is low, and when a load is applied, the foam cracks or generates fine powder, which again causes the above-mentioned problems.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such a problem, and as a result, have a density of 0.01 to 0.01.
0.6 g / cm ³ starch-based rose foam having a water absorption of 50%
Hereinafter, the present inventors have found that a molded foam sealed with a biodegradable film bag having a thickness of 100 μm or less has excellent biodegradability, water resistance, moisture resistance, and strength, and has completed the present invention.

Hereinafter, the present invention will be described in detail. First, the starch-based rose foam of the present invention is a foam mainly composed of starch and has a density of 0.005 to 0.6 g / cm ³ , preferably 0.008 to 0.20 g / cm ³ . A thing. If the density is less than 0.005 g / cm ³ , the strength of the foam tends to decrease and practical problems tend to occur. If the density exceeds 0.6 g / cm ³ , the foaming ratio is low and the cushioning material is low. It cannot be used for such purposes.

The foam preferably comprises starch blended with a biodegradable plastic such as polyvinyl alcohol (hereinafter referred to as PVA) or aliphatic polyester, a foam nucleating agent, and a plasticizer.

As the starch, raw starch (corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch, kuzu starch, bracken starch, lotus starch, Physically modified starch (α-starch, fractionated amylose, heat-moisture treated starch, etc.); enzyme-modified starch (hydrolyzed dextrin, enzyme-decomposed dextrin, amylose, etc.); chemically-degraded starch (acid-treated starch, hypoxia). Chloric acid oxidized starch, dialdehyde starch, etc.); chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.) and the like are used. Among the chemically modified starch derivatives, the esterified starches include acetic esterified starch, succinic esterified starch, nitrated esterified starch, phosphorylated esterified starch, urea phosphorylated esterified starch, xanthated esterified starch, and acetoacetated starch. Examples of etherified starch such as acetic esterified starch include allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, and hydroxypropyl etherified starch. Reaction product of diethylaminoethyl chloride, starch and 2,3-
Examples of crosslinked starch such as a reaction product of epoxypropyltrimethylammonium chloride include formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphoric acid crosslinked starch,
Acrolein cross-linked starch and the like.

When PVA is used, the degree of saponification is from 80 to
Preferred are those having 99.9 mol% and a degree of polymerization of about 500 to 3500. Examples of the aliphatic polyester include polycaprolactone, aliphatic polyester, and polylactic acid. Polycaprolactone is preferred. (Preferably talc), and examples of the plasticizer include glycerin and sorbitol. The amount of each of the above components is not particularly limited, but is preferably 5 to 25 parts by weight of PVA and 0 to 10 parts by weight of an aliphatic polyester based on 100 parts by weight of starch. 2-1 to 100 parts by weight of starch
0 parts by weight is preferred. The amount of the plasticizer is preferably 5 to 20 parts by weight based on 100 parts by weight of the biodegradable plastic (PVA and aliphatic polyester). In addition, if necessary, resin components other than the above, for example, saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) and other polyolefins, hydrogenated styrene-butadiene rubber, polyurethane, polyamide, polyhydroxybutyrate,
Etc.), natural polymers other than starch (polysaccharide polymers, cellulose polymers, protein polymers, etc.), heat stabilizers, extenders, fillers, lubricants, coloring agents, flame retardants, water resistance agents, Examples thereof include an autoxidizer, an ultraviolet stabilizer, a crosslinking agent, an antibacterial agent, and an antioxidant. Urea, an alkaline earth, an alkali metal hydroxide, and a mixture thereof can be added as a starch modifier.

A known foaming method can be appropriately selected as a method for producing a starch-based rose foam using the above components. In particular, a foaming method using water as a foaming agent is preferable, and a method in which water is added to starch to perform an extrusion foaming method is generally used, and an extrusion foaming method using water-containing starch and using the water in the water-containing starch as a foaming agent is also used. Used. In any case, the amount of water at the time of foaming is preferably 20 to 50 parts by weight of water with respect to 100 parts by weight of starch. As a specific production method, the above-mentioned components are put into a pellet extruder, extruded at a temperature at which foaming is possible, and extruded from a nozzle die at the tip of the extruder into a rod-shaped foam rod. At this time, at the moment when the foam comes out of the die, it is cut with several cutting blades rotating at an appropriate rotation speed to obtain a starch-based rose foam. By adjusting the number of rotating blades or the number of rotations, starch-based rose foams having different lengths according to the shape used can be obtained.

As a biodegradable film, water absorption (AST)
5. MD570 method, (A) measured according to the 24-hour immersion method) must be 50% or less, and preferably 5 to 35%. When the water absorption exceeds 50%, the effect of improving water resistance and moisture resistance aimed at in the present invention is reduced. Further, the thickness of the biodegradable film needs to be 100 μm or less, and preferably 0.5 to 100 μm. Those having a thickness of more than 100 μm have water and moisture resistance effects, but have a drawback in that the biodegradable film has poor followability to a molding die during molding and is difficult to mold.

As the material of the biodegradable film, any of organic and inorganic substances can be used as long as it satisfies the above-mentioned water absorption rate and is biodegradable. And waxes are preferable, and it is particularly preferable to use a synthetic polymer and a natural polymer in combination. Examples of the synthetic polymer include polycaprolactone, EVOH, polyhydroxyalkanoate and the like, and preferably polycaprolactone and EVOH. Examples of the natural polymer include a cellulosic polymer, a starch-based polymer, a chitin-based polymer, and the like. Preferred is a cellulosic polymer, specifically, ethylcellulose, (mono,
Di, tri) cellulose acetate, cellulose nitrate, propionated cellulose acetate, butylated cellulose acetate, natural rubber, or a mixture containing at least one of them. When a synthetic polymer and a natural polymer are used in combination, for example, when polycaprolactone, starch, and EVOH are used in combination, the compounding amount is polycaprolactone / starch / EVOH.
= 40-60 / 20-55 / 5-30 (weight ratio) is preferred. Further, as a plasticizer, it is preferable to add 5 to 10 parts by weight of glycerin, urea or the like to 100 parts by weight of the polymer component.

The method for obtaining the biodegradable film having the above composition is not particularly limited. Usually, the composition is mixed with a single-screw or twin-screw extruder to obtain a biodegradable film.
Melt kneading is performed at about 230 ° C. to form pellets, and the pellets are formed into a film by an inflation film forming method or formed into a biodegradable film by extrusion.

The biodegradable film thus obtained is formed into a bag using a heat sealer, an impulse sealer, an adhesive or the like, and a starch-based rose foam is placed therein. A mold (preferably a rectangular parallelepiped,
While pressing it into a square or spherical shape with a capacity of about 0.5 to 50 l). Thereafter, all of the bag is sealed with a heat sealer, an impulse sealer, or the like, except for a circular vent hole. After the sealing, the air is expelled from the air holes with a vacuum pump or the like, while the mold is prepared, the removal under reduced pressure is stopped to the extent that the foam in the biodegradable film bag is not broken, the air holes are closed, and the mold is taken out. At this time, the inside of the biodegradable film bag is under reduced pressure. As a closing method, a heat sealer, an impulse sealer, an adhesive, or the like may be used.

The foam of the present invention is excellent in water resistance, moisture resistance, strength, and biodegradability, and thus is useful as a cushioning material for packing.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, "%" and "parts"
Unless otherwise specified, it is based on weight. (Preparation of resin pellets) Pellets 1 [for production of biodegradable film] 24 parts of corn starch, EVOH (ethylene content: 44
Mol%, saponification degree 99.4 mol%) 20 parts, polycaprolactone 50 parts and glycerin 6 parts were put into a twin screw type vented extruder (40 mm diameter),
To obtain pellets 1. Pellets 2 [for biodegradable film production] 46 parts of corn starch, EVOH (ethylene content 44
Pellets 2 were obtained in the same manner as described above, using 8 parts by mol, saponification degree 99.4 mol%), 40 parts of polycaprolactone and 6 parts of glycerin. Pellets 3 [for producing biodegradable film used for control] 40 parts of corn starch, 14 parts of PVA (degree of saponification 99.0 mol%, degree of polymerization 2000), polycaprolactone 4
Pellets 3 were obtained in the same manner as above using 0 parts and 6 parts of glycerin. Pellets 4 [for the production of starch-based rose foam] 68 parts of corn starch, 10 parts of PVA (degree of saponification 90.0 mol%, degree of polymerization 2000), 2 parts of talc, water 20
The part was previously placed in a twin screw type vented extruder (40 mm diameter) and extruded at 90 ° C. or lower to obtain pellets 4.

(Film formation) Inflation film formation was performed using the pellets 1 under the following molding conditions. Molding condition Extruder 50mm diameter extruder Screw L / D = 28, Screw for HDPE (high density polyethylene) Die lip diameter 60mm, center feed spiral die with die gap 1mm Extrusion temperature Cylinder tip 140 ° C Die 145 ° C Resin (T ₁ ) 148 ° C Screw rotation speed 70 rpm Discharge rate 390 kg / hr Air ring air temperature 20 ° C Blow ratio 3.2 Take-off speed 13 m / min Film temperature (T ₂ ) 25 ° C (just before passing through a nip roll)

In order to adjust the film temperature, two aluminum rolls having a diameter of 100 mm and circulating cooling water (20.degree. C.) were provided with a clearance of 5 mm in front of the nip roll, and a cooling water of 40 mm was further circulated. An aluminum guide roll having a diameter was provided so as to be in contact with the surface of the tube film, and passed through the two rolls and the guide roll to be guided to a nip roll. By the above operation, a film 1 having a folding width of 300 mm, a film thickness of 50 μm, and a water absorption of 10% was obtained.
was gotten.

Using the pellet 2 under the following molding conditions:
Inflation film formation was performed. Molding condition Extruder 50mm diameter extruder Screw L / D = 28, screw screw for HDPE (high-density polyethylene) Die lip diameter 60mm, center feed spiral die with die gap 1mm Extrusion temperature Cylinder tip 130 ° C Die 125 ° C Resin (T₁) 145 ° C. Screw rotation speed 40 rpm Discharge rate 390 kg / hr Air ring air temperature 15 ° C. Blow ratio 3.2 Take-off speed 8 m / min
0 mm, a film thickness of 40 μm, and a film 2 having a water absorption of 25% were obtained.
Was done.

Inflation film formation was performed using the pellets 3 under the following molding conditions. Molding conditions Extruder 50mm diameter extruder Screw L / D = 28, screw screw for HDPE (high density polyethylene) Die lip diameter 60mm, center feed spiral die with die gap 1mm Extrusion temperature Cylinder tip 130 ° C Die 125 ° C Resin (T ₁ ) 145 ° C. Screw rotation speed 40 rpm Discharge rate 390 kg / hr Air ring air temperature 15 ° C. Blow ratio 3.2 Take-off speed 8 m / min Film temperature (T ₂ ) 20 ° C. (just before passing through a nip roll) Perform the same, folding width 3
A film 3 having a thickness of 40 mm, a thickness of 40 μm, and a water absorption of 55% was obtained.

(Production of Bulk Foam) Bulk foam was prepared from the pellets 4 as follows. A rose foam 1 having a density of 0.11 g / cm ^{3 under} the above conditions
I got

Example 1 The film 1 formed above was cut into a length of 40 cm.
The lower part was heat-sealed to produce a bag. Put the rose foam 1 prepared above in the bag until the 8th minute, about 2 cm
The upper part was heat-sealed, leaving a vent having a diameter. Next, while bleeding air from the vent hole with a vacuum pump,
The shape of l) was adjusted. When the foam had formed, the pump was stopped and the vent was closed with adhesive tape. Immediately thereafter, the air holes were heat-sealed and taken out of the mold to obtain a mold foam, which was evaluated as follows.

(Biodegradability) The mold foam obtained above is
It was buried in the fertilizer mixed soil, excavated after 3 or 6 months, visually inspected, and evaluated in the following three stages. ◎: The shape was hardly maintained, to the extent that residual fragments could be confirmed.・ ・ ・: The shape remains, but many cracks and holes are observed on the entire surface. ×: Almost no change was observed, and the original shape was maintained.

(Water Resistance) Water was applied to the molded foam obtained above with a shower and evaluated as follows.・ ・ ・: No change △: film bag swelled ・ ・ ・: film bag partially dissolved The foamed mold obtained above was immersed in water and evaluated as follows. ○ ・ ・ ・ No change at all. Δ: The film was broken, and a small amount of water penetrated into the bag. X: The film was completely broken, and the loose foam was broken apart. (Humidity resistance) The mold foam obtained above was heated at 25 ° C and 90 RH.
% For 1 day, and evaluated as follows. ○ ・ ・ ・ No change at all △ ・ ・ ・ Slight deformation × ・ ・ ・ Severe deformation

(Strength) 10 g per 100 g of the obtained molded foam
A load of kg was evaluated as follows. Deformation ○ ・ ・ ・ No change at all. Δ: Slightly deformed. ×: Large deformation. Film tear ○ ・ ・ ・ The film does not tear. Δ: The film was slightly torn. ×: The film was considerably torn, and a part of the rose foam inside jumped out.

Example 2 The film 2 formed above was cut into a length of 40 cm.
The lower part was heat-sealed to produce a bag, and a molded foam was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

Comparative Example 1 Example 1 was repeated except that the water content of the pellet 4 was changed from 10 parts to 40 parts.
A starch-based rose buffer was prepared in the same manner as
g / cm ^3, a loose foam was manufactured, a mold foam was manufactured in the same manner as in Example 1, and evaluation was performed in the same manner as in Example 1.

Comparative Example 2 A starch-based rose buffer was prepared in the same manner as in Example 1 except that the water content of the pellet 4 was changed from 10 parts to 5 parts, and the density was 0.7 g / c.
to produce a rose foam m ^3, was prepared similarly mold foam as in Example 1, it was evaluated in the same manner as in Example 1.

Comparative Example 3 Using the above-mentioned film 3, a molded foam was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

Comparative Example 4 In Example 1, the take-up speed was 4
m / min to produce a biodegradable film having a thickness of 150 μm. A mold foam was prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

Comparative Example 5 The starch-based rose foam obtained above was immersed in a solution of polycaprolactone (manufactured by Daicel Chemical Industries, Ltd., 3% water absorption) in tetrahydrofuran for 1 minute. Thereafter, the rose foam is pulled up, tetrahydrofuran is diffused, and a coating layer of polycaprolactone is formed on the surface of the foam (the thickness of the coating layer is calculated by weight change and surface area to obtain a 10 μm coating layer). A foam was obtained. Table 1 shows the evaluation results of the examples and the comparative examples.

[0031]

[Table 1] Biodegradability Water resistance Moisture resistance Strength 3 months 6 months Example 1 ◎ ○ ○ ○ ○ ○ ○ Example 2 ◎ ○ ○ ○ ○ ○ ○ ○ Comparative Example 1 ○ ○ × × × × ○ Comparative Example 2 ◎ ○ ○ ○ ○ △ × Comparative Example 3 ◎ ◎ × × × △ △ Comparative Example 4 ○ × ○ ○ ○ ○ ○ Comparative Example 5 ◎ ○ △ △ △ × ×

[0032]

The mold foam of the present invention has a density of 0.01 to 0.1.
6 g / cm ³ starch-based rose foam is sealed in a biodegradable film bag having a water absorption of 50% or less and a thickness of 100 μm or less, so it has excellent biodegradability, water resistance, moisture resistance and strength. I have.

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Claims (2)

[Claims] 1. A starch-based rose foam having a density of 0.005 to 0.6 g / cm ³ has a water absorption of 50% or less and a thickness of 10%.
A molded foam, which is sealed in a biodegradable film bag of 0 μm or less. 2. The foam according to claim 1, wherein the inside of the biodegradable film bag is evacuated during sealing.