JPH0710585B2 - Biodegradable film or sheet with heat sealability - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film or sheet having heat sealability, which is a useful property in applications such as packaging materials, and excellent in degradability by microorganisms.

[0002]

2. Description of the Related Art Polyolefin,
Films, sheets or foamed molded products made of thermoplastic resins such as polyvinyl chloride and polystyrene are used for various purposes such as packaging materials, agricultural materials and industrial materials by taking advantage of their characteristics. However, since films and sheets made of these thermoplastic resins are chemically stable,
Once abandoned in the natural world, it remains indefinitely without being decomposed, and the problem of their disposal has become a kind of social problem in recent years.

In view of such circumstances, various degradable plastics have been developed in recent years. For example, a starch material such as corn starch is added to polyolefin to impart microbial degradability, polyhydroxybutyrate and its derivatives produced by microorganisms, or photodegradation in which a carbonyl group is introduced into the polymer molecular chain. Plastics have been reported.

The present inventors have found that a novel biodegradable composite material can be obtained by previously compositing a natural material, cellulose fiber, and chitosan (Japanese Patent Laid-Open No. 2-6689). No. 2-12748
No. 6). The composite material made of this natural material has advantages over other degradable plastics in that it has a high microbial decomposition rate and that the decomposition products are harmless to the environment. However, due to the characteristics of the raw material, it does not have heat-sealing properties like general-purpose plastics, and when joining films or making bags, complicated steps such as gluing are required.

On the other hand, thermoplastic synthetic resins such as aliphatic polyesters such as poly-ε-caprolactone, polyethylene glycol, polyvinyl alcohol, polyester polyurethanes, polyamino acids, etc. have heat sealability and are decomposed by microorganisms. It is known (Polymer Processing 36 volume 1, No. 18 to 26 P: Sakai, Polymer Collection 45 volume 4, No. 4, Aikawa et al.). However, the rate of microbial decomposition of these thermoplastic synthetic resins is relatively slow, and when molded to a thickness that can maintain sufficient strength for applications such as packaging materials, it takes a long time for complete decomposition. Under such circumstances, there is a demand for a material having a fast microbial decomposition rate and further having a heat-sealing property which is useful as a packaging material.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention provides a novel biodegradable film or sheet having a high microbial decomposition rate and a good heat-sealing property.

[0007]

The present invention provides at least a base film or sheet comprising cellulose fibers and chitosan, or a base film or sheet comprising cellulose fibers, chitosan and a thermoplastic synthetic resin having biodegradability. The present invention relates to a film or sheet having good biodegradability and heat sealability, which is characterized in that a film of a thermoplastic synthetic resin having biodegradability is formed on one surface.

That is, the heat-sealable biodegradable film or sheet of the present invention is a biodegradable base film or sheet comprising cellulose fiber and chitosan, or cellulose fiber, chitosan and microbial degradability. At least one surface of a base film or sheet made of a thermoplastic resin is formed with a film of a thermoplastic synthetic resin having microbial degradability, so that the microbial decomposition rate is fast and the heat sealing property is also excellent. .
Further, when a cellulose fiber, a base film or a sheet in which a thermoplastic synthetic resin having microbial degradability is further added to chitosan is used, the action of the blended microbial degradable thermoplastic resin causes a base film or sheet. The adhesion between the coating and the coating is enhanced, and the heat seal strength is excellent.

Cellulose fibers used in the present invention include cellulose obtained from plants such as wood, straw, cotton, hemp, bamboo and bagasse, hemicellulose, lignocellulose, pectocellulose and bacterial cellulose produced by fungi. Particularly, finely beaten fibers are preferably used.

The chitosan used in the present invention is deacetylated of chitin, which is a nitrogen-containing polymeric substance obtained from the shells of crustaceans such as crab and shrimp and mycelium. The acetylation degree is not particularly limited. Since chitosan is insoluble in water as it is, it is used by dissolving it in water by forming a chitosan salt with an inorganic acid such as hydrochloric acid or an organic acid such as formic acid, acetic acid and lactic acid.

Examples of the thermoplastic synthetic resin having biodegradability used in the present invention include aliphatic polyesters such as poly-ε-caprolactone, polylactic acid and polymalic acid, polyvinyl alcohol, polyester polyurethane, polyethylene oxide, polyamino acid, Examples thereof include polyhydroxybutyrate and its derivatives produced by microorganisms. From the viewpoint of performance and economy, poly-ε-caprolactone, polyester-based polyurethane, and polyethylene oxide are preferably used. These synthetic resins may be used alone or as a mixture of plural synthetic resins. Here, the polyester-based polyurethane means a polyurethane obtained by reacting a polyester polyol and a diisocyanate compound, but it is possible to use a part of polyether polyol in combination.

The blending ratio of the raw materials to be used is 2 to 100 parts by weight of chitosan to 100 parts by weight of cellulose fiber, and when a thermoplastic synthetic resin having biodegradability is added, the thermoplastic synthetic resin is 10 to 400 parts by weight. Part, especially
5 to 80 parts by weight of chitosan and 20 to 300 parts by weight of a thermoplastic synthetic resin having biodegradability are preferable. If the amount of chitosan is less than 2 parts by weight or more than 100 parts by weight, the wet strength becomes weak, which is not preferable. In addition, the thermoplastic synthetic resin having biodegradability is extremely important in increasing the affinity with the film when forming the film of the thermoplastic resin layer that imparts heat sealability, and the blending ratio is Is 10
If the amount is less than parts by weight, the adhesion between the base film and the film is poor and high heat seal strength cannot be obtained. On the other hand, the compounding ratio is 4
If the amount exceeds 100 parts by weight, the biodegradability of the obtained film or sheet will be delayed, which is not preferable. The substrate film or sheet made of a cellulose fiber used in the present invention, chitosan, or a thermoplastic synthetic resin having further biodegradability contains known additives such as a plasticizer, a filler, and a colorant. It doesn't matter.

The base film or sheet made of cellulose fiber and chitosan used in the present invention, or the base film or sheet made of cellulose fiber, chitosan and a thermoplastic synthetic resin having biodegradability is a cellulose fiber and chitosan salt. It is obtained by mixing an aqueous solution, or a cellulose fiber, an aqueous chitosan salt solution, and a solution or dispersion of a thermoplastic synthetic resin having biodegradability, casting and drying by a known method. The solution or dispersion of the microbial degradable thermoplastic synthetic resin is a solution or dispersion of the thermoplastic synthetic resin in water or a solvent that dissolves in water.

A base film or sheet composed of the thus obtained cellulose fiber and chitosan, or
A substrate having a heat-sealing property of the present invention is formed by forming a film of a thermoplastic synthetic resin having biodegradability on at least one surface of a base film or sheet made of a cellulose fiber, chitosan and a thermoplastic synthetic resin having biodegradability. A degradable film or sheet is obtained. As a method for forming a film, a thermoplastic synthetic resin having microbial degradability is melted by heat to form a base film or sheet made of cellulose fiber and chitosan, or cellulose fiber, chitosan and microbial degradable thermoplastic synthetic resin. A method for forming a film on a base film or sheet made of a resin, a method of dissolving a thermoplastic synthetic resin having microbial decomposability in a solvent and coating the base film or sheet, or the thermoplastic synthesis. A method of immersing the substrate film or sheet in a resin solution,
Alternatively, a method in which these synthetic resins are formed into a film in advance by an extrusion molding method or a solution casting method is attached to a base film or sheet with an adhesive, or a method of heat fusion without an adhesive is used. The film can be formed by a method suitable for the characteristics of the synthetic resin used.

The coating is a base film or sheet composed of cellulose fibers and chitosan, or cellulose fibers,
It may be formed on only one side or both sides of a base film or sheet made of chitosan and a thermoplastic synthetic resin having biodegradability. The thickness of the film is 1-2
0 μ is preferable. When the film thickness is less than 1 μ, there is no problem in the rate of microbial degradability, but sufficient heat seal strength cannot be obtained, and when it exceeds 20 μ, good heat seal strength is obtained, but microbial degradability is slow. It is not preferable.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. Here, the seal strength was evaluated by heat-sealing each film with an impulse sealing machine, cutting out the film into a width of 10 mm, and measuring the maximum strength until the film was pulled and ruptured at a speed of 300 mm / min. The biodegradability was evaluated by burying each film in soil under an environment of a temperature of 23 ° C. and a humidity of 95 to 100% and observing the condition of the film after 3 months.

Example 1 1 part by weight of chitosan, 98 parts by weight of water and 1 part by weight of acetic acid were mixed and stirred to obtain an aqueous solution of chitosan acetate. 28 parts by weight of the aqueous chitosan acetate solution thus obtained, 140 parts by weight of an aqueous dispersion of fine cellulose (concentration of component: 1% by weight), and 1.05 parts by weight of glycerin as a plasticizer were mixed to obtain a suspension of chitosan / cellulose. A liquid was obtained. This chitosan-cellulose suspension was cast on a glass plate and dried at 70 ° C. to obtain a film made of cellulose fibers and chitosan having a thickness of 70 μm. Using a bar coater, a 20 wt% ethyl acetate solution of poly-ε-caprolactone was applied onto the film composed of this cellulose fiber and chitosan, and 50
After drying at 5 ° C. for 5 minutes, a film composed of cellulose fibers and chitosan having a film thickness of 3μ, 9μ, and 15μ formed with poly-ε-caprolactone was obtained. The sealing strength of the obtained film was 33 g / 10 mm, 9 μ when the film of poly-ε-caprolactone was 3 μ.
145 g / 10 mm, 15 μ is 303 g
Was / 10 mm. In the biodegradability test, all the films disappeared completely.

Example 2 A 10 wt% tetrahydrofuran solution of polyester polyurethane was coated on a film made of cellulose fiber having a thickness of 70 μm and chitosan obtained in the same manner as in Example 1 by using a bar coater, and the solution was heated at 50 ° C. for 5 minutes. Dry it,
A 9 μm-thick film made of cellulose fibers on which a polyester-based polyurethane film was formed and chitosan was obtained. The sealing strength of the obtained film is 130 g / 10 m.
m, and the film almost completely disappeared in the biodegradability test.

Example 3 A 10 wt% aqueous solution of polyethylene oxide was applied onto a film made of cellulose fibers having a thickness of 70 μm and chitosan obtained in the same manner as in Example 1 using a bar coater and dried at 50 ° C. for 5 minutes. This was performed to obtain a film of cellulose fiber and a chitosan having a polyethylene oxide film formed thereon and having a thickness of 9 μm. The obtained film had a sealing strength of 80 g / 10 mm, and the film completely disappeared in the biodegradability test.

Example 4 An aqueous dispersion of fine cellulose fibers (concentration 1% by weight) and an aqueous solution of chitosan acetate (concentration 1% by weight) were mixed so as to be 20 parts by weight of chitosan per 100 parts by weight of fine cellulose fibers. Then, it was cast on a glass plate and dried at 70 ° C. to obtain a film having a thickness of 80 μm. Poly-ε on this film
A 20 wt% ethyl acetate solution of caprolactone was applied using a bar coater and dried at 50 ° C. to obtain a film having a poly-ε-caprolactone film having a thickness of 3 μ. The sealing strength of the obtained film is 39 g / 10 m.
m, which completely disappeared in the biodegradability test.

Example 5 An aqueous dispersion of fine cellulose fibers (concentration 1% by weight), an aqueous solution of chitosan acetate (concentration 1% by weight) and an aqueous dispersion of polyester ether type polyurethane (Daiichi Kogyo Seiyaku Superflex 300, concentration) 30% by weight), 20 parts by weight of chitosan to 100 parts by weight of fine cellulose fiber,
The polyester ether type polyurethane was mixed so as to be 100 parts by weight, cast on a glass plate and dried at 70 ° C. to obtain a film having a thickness of 80 μ. A film having a film of poly-ε-caprolactone with a thickness of 3 μm formed on this film was obtained in the same manner as in Example 4. The sealing strength of the obtained film was 1135 g / 10 mm, and the film disappeared completely in the microbial decomposition test.

Example 6 A 10% by weight solution of polyester polyurethane in tetrahydrofuran was applied onto a film of cellulose fiber having a thickness of 80 μm and chitosan obtained in the same manner as in Example 4 using a bar coater and dried at 50 ° C. Thus, a film having a 9 μm-thick polyester-based polyurethane film was formed. The resulting film has a sealing strength of 158 g / 1
It was 0 mm and almost disappeared in the biodegradability test.

Example 7 An aqueous dispersion of fine cellulose fibers (concentration 1% by weight), an aqueous solution of chitosan acetate (concentration 1% by weight), and an aqueous dispersion of polyester ether type polyurethane (Daiichi Kogyo Seiyaku Co., Ltd.)
Superflex 300, concentration 30% by weight) 20 parts by weight of chitosan per 100 parts by weight of fine cellulose fiber,
Polyester ether polyurethane 50 parts, and 15
Mix so that 0 parts by weight and cast on a glass plate,
It was dried at 0 ° C. to obtain two films having a thickness of 80 μ and different polyester ether type polyurethane contents. In the same manner as in Example 6, a film in which a polyester-based polyurethane film having a thickness of 9 μm was formed on each film was obtained. The sealing strength of the obtained film is 907 g when 50 parts of polyester ether type polyurethane is used.
/ 10 mm, with 1313 g when 150 parts are used
Was / 10 mm. Also, in the microbial degradability test, almost all the films disappeared.

Example 8 An aqueous dispersion of fine cellulose fibers (concentration 1% by weight), an aqueous solution of chitosan acetate (concentration 1% by weight), a 10% by weight aqueous solution of polyethylene oxide, and glycerin as a plasticizer were added to fine cellulose. 20 parts by weight of chitosan and 100 parts by weight of polyethylene oxide per 100 parts by weight of fiber
By weight, glycerin was mixed in an amount of 75 parts by weight, cast on a glass plate, and dried at 70 ° C. to obtain a film having a thickness of 80 μ. A 10 wt% aqueous solution of polyethylene oxide was applied onto this film using a bar coater,
It was dried at 50 ° C. to obtain a film having a 15 μm-thick polyethylene oxide film. The sealing strength of the obtained film was 1220 g / 10 mm, and the film was almost disappeared in the microbial decomposition test.

Comparative Example 1 An aqueous dispersion of fine cellulose fibers (concentration 1% by weight) and an aqueous solution of chitosan acetate (concentration 1% by weight) were mixed so as to be 20 parts by weight of chitosan per 100 parts by weight of fine cellulose fibers. And cast on a glass plate and dried at 70 ° C. to obtain a film having a thickness of 80 μ. Further, 75 parts by weight of glycerin as a plasticizer was further mixed with the above raw material mixture to obtain a 70 μm film in the same manner. Each of the obtained films completely disappeared in the biodegradability test, but did not have any sealing property.

Comparative Example 2 A 20% by weight ethyl acetate solution of poly-ε-caprolactone was cast on a glass plate and dried at 50 ° C. to obtain a poly-ε-caprolactone film having a thickness of 80 μm. The sealing strength of the obtained film was 1286 g / 10 mm, but in the microbial degradability test, the film was only slightly degrading.

Comparative Example 3 A 10 wt% tetrahydrofuran solution of polyester polyurethane was cast on a glass plate and dried at 50 ° C. to obtain a polyester polyurethane film having a thickness of 80 μm. The resulting film has a sealing strength of 1211 g / 10
However, the film was hardly decomposed in the biodegradability test.

[0028]

The heat-sealable biodegradable film or sheet of the present invention is a base film or sheet made of a natural material cellulose fiber and chitosan, or a natural material cellulose fiber, chitosan and microbial degradability. On a base film or sheet made of a thermoplastic synthetic resin having a, since a thin film of a thermoplastic synthetic resin having microbial degradability is formed, it has excellent microbial degradability of natural materials, and It has an excellent effect of imparting a heat-sealing property which is useful in applications such as packaging materials. When a base material film or sheet containing a thermoplastic synthetic resin having microbial decomposability is used, the adhesiveness between the base material film or sheet and the film is increased by the action of the thermoplastic synthetic resin. It also has the effect of being enhanced and obtaining high heat sealing strength.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Issei Yoshihara 2-3-3 Hananomiyacho, Takamatsu City, Kagawa Prefecture, Shikoku Institute of Industrial Technology (72) Inventor Takamasa Kubo, Hana, Takamatsu City, Kagawa Prefecture 2-3-3 Miyanomachi, Shikoku Institute of Industrial Technology, Institute of Industrial Technology (72) Inventor Satoshi Maruyama 1515, Nakatsu-cho, Marugame, Kagawa Okura Industrial Co., Ltd. (72) Kunio Kanaoka, Marugame, Kagawa 1515 Nakatsucho, Nakatsu, Okura Industrial Co., Ltd. (72) Inventor Akihiko Ueda 1515 Nakatsucho, Marugame, Kagawa Pref. Industrial Co., Ltd. Research Institute Company (72) Inventor Kazuo Kondo 1515 Nakatsu-cho, Marugame City, Kagawa Prefecture Okura Industrial Co., Ltd. Corporate Researcher Tomoko Anabuki (56) Reference References JP 62-209144 (JP, A) JP 50-86543 (JP, A) JP 2-6689 (JP, A) JP 2-127486 (JP, A)

Claims (3)

[Claims] 1. A biodegradable material having a heat-sealing property, characterized in that a film of a thermoplastic synthetic resin having biodegradability is formed on at least one surface of a base film or sheet made of cellulose fibers and chitosan. Film or sheet. 2. A coating film of the above-mentioned microbial-decomposable thermoplastic synthetic resin is formed on at least one surface of a base film or sheet made of cellulose fiber, chitosan and microbial-decomposable thermoplastic synthetic resin. A biodegradable film or sheet having a heat seal characteristic. 3. The heat-sealable biodegradation according to claim 1 or 2, wherein the microbial degradable thermoplastic synthetic resin is selected from poly-ε-caprolactone, polyester polyurethane and polyethylene oxide. Film or sheet.