JP3029280B2 - Manufacturing method for biodegradable molded products - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a molded article having biodegradability by a melt molding method, especially under a substantially plasticizer-free and substantially anhydrous condition. And a method for producing the same by melt molding.

2. Description of the Related Art Plastics molded products such as plastics films and bundling tapes as agricultural materials and plastics films discarded by other than regular processing routes maintain their shape for many years, causing serious waste pollution. Has occurred.
Therefore, it is desired that a molded article which may be discarded outdoors or in a river is quickly decomposed by microorganisms in soil or water after the purpose of use is achieved.

Against this background, the development of biodegradable molded articles has recently been active.

It is known that blending a starch-based polymer is effective for imparting biodegradability to a molded product.

For example, Japanese Patent Application Laid-Open No. 2-14228 discloses a blended polymeric material which results in a melt containing degraded starch containing water and at least one synthetic thermoplastic polymer which is substantially insoluble in water. In this case, a water-soluble polysaccharide, a cellulosic polymer, a water-soluble synthetic polymer, and the like can be further added as an additive.

U.S. Pat. No. 3,949,145 discloses that 1 to 4 parts by weight of polyvinyl alcohol having a degree of saponification of 85 to 100 mol%, starch 8
A film comprising 1 to 5 parts by weight of glycerin, 0.1 to 0.2 part by weight of a polyol-toluene diisocyanate prepolymer containing free isocyanate groups and 1 part by weight of a polyvinylidene chloride-acrylonitrile copolymer or a plasticizer-containing poly A degradable agricultural multi-film coated with a water-resistant coating composition comprising a mixture of 1 part by weight of vinyl chloride is disclosed.

The present applicant has also filed a patent application for a polyvinyl alcohol-starch film comprising a polyvinyl alcohol and a starch having a degree of saponification of 93 mol% or more and stretched in at least one axis direction (Japanese Patent Application No. 63
-307225).

Problems to be Solved by the Invention The method of blending a starch-based polymer with a general-purpose thermoplastic resin such as polyolefin to form a film or the like has already been practiced, but the molded product exhibits biodegradability. Since only the starch-based polymer inside is used, even if the film shape or the like can be lost, the thermoplastic resin portion such as polyolefin remains for a long time without being decomposed.

However, if a starch-based polymer is blended with polyvinyl alcohol, which is a water-soluble resin, and molded into a film, etc.,
A molded article having the required strength can be obtained, and it is expected that not only a starch-based polymer but also a water-soluble resin portion such as polyvinyl alcohol is biodegraded.

However, since polyvinyl alcohol is inherently close to its melting temperature and thermal decomposition temperature, it is difficult to melt-mold under anhydrous conditions. It is necessary to mix water or a plasticizer (such as glycerin) and mold in a melt-dissolved state. There are similar restrictions when molding a composition of polyvinyl alcohol and a starch-based polymer.

However, the method of casting and casting a film of polyvinyl alcohol (or a composition of this and a starch-based polymer) as an aqueous solution requires the preparation of an aqueous solution, a slow film-forming speed, and drying after film formation. There are disadvantages such as taking a long time. A method in which a considerable amount of water is blended and molded in a melt-dissolved state also has a disadvantage that drying after molding takes a long time. In addition, the moldings obtained in this way lack flexibility under low-humidity conditions, which severely limits their applications. When using a plasticizer together to ensure flexibility,
A new problem of bleeding caused by the blended plasticizer occurs.

On the other hand, the method of blending polyvinyl alcohol (or a composition of this and a starch-based polymer) with a considerable amount of a plasticizer and molding in a melt-dissolved state is not satisfactory in terms of the film-forming speed. There is a quality problem that bleeding and adhesion between molded products occur due to the agent.

The present invention has been made in view of such a situation, and has as its object to provide a method for producing a biodegradable molded article that has solved the above-described problems.

Means for Solving the Problems The method for producing a biodegradable molded article of the present invention comprises a method of substantially plasticizing a composition comprising an oxyalkylene group-containing vinyl alcohol polymer (X) and a natural polymer (Y). It is characterized in that it is melt-molded under the condition of being substantially free of an agent and being substantially anhydrous.

 Hereinafter, the present invention will be described in detail.

<Polymer (X)> As the oxyalkylene group-containing vinyl alcohol polymer (X), a saponified product of a copolymer of an oxyalkylene group-containing ethylenically unsaturated monomer and a vinyl ester is used. Here, examples of the oxyalkylene group-containing ethylenically unsaturated monomer include polyoxyalkylene (meth) acrylate and polyoxyalkylene (meth)
Acrylamide, polyoxyalkylene (1- (meth)
Acrylamide-1,1-dimethylpropyl) ester,
Examples thereof include polyoxyalkylene (meth) allyl ether and polyoxyalkylene vinyl ether. Oxyalkylene is oxyethylene, oxypropylene, or the like. The number of moles of the added oxyalkylene unit is 1
From 300 to 300 mol, in particular from 5 to 50 mol, are suitable.

The oxyallequine group-containing vinyl alcohol polymer (X) can also be obtained by reacting an alkylene oxide with polyvinyl alcohol, or polymerizing vinyl acetate with polyalkylene glycol and then saponifying it.

However, among the above, particularly preferred as the oxyalkylene group-containing vinyl alcohol polymer (X) is the oxyalkylene allyl ether type vinyl alcohol polymer described below, which will be described in detail below.

The following formula Wherein each of the vinyl alcohol unit (A), the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) contains a mol%, b mol%, and c mol%, and R ¹ in (B) is an alkyl group; R ² and R ³ in (C) are H or an alkyl group, R ⁴ in (C) is H,
An alkyl group, a phenyl group or a substituted phenyl group, wherein n is 1 to 300, and the following relationship is satisfied: 0.1 ≦ c ≦ 20 (i) 50 ≦ 100a / (a + b) ≦ 100 (ii), and With a melt index of 5g / 10min or more at a temperature of 210 ° C and a load of 2160g.

In the above formula (i), the proportion of the oxyalkylene allyl ether unit (C) in the copolymer (X) is 0.1 to 20.
Mol%. The ratio of this unit (C) is 0.1
If the amount is less than 20 mol%, the modifying effect is insufficient, and if it exceeds 20 mol%, the intrinsic properties of the vinyl alcohol polymer are impaired. A particularly preferred range is from 0.1 to 5 mol%.

The above formula (ii) means that the saponification degree of the vinyl ester component before saponification is 50 to 100 mol%.
If the saponification degree is less than 50 mol%, the properties of the vinyl alcohol group such as hydrophilicity, fragrance retention, oil resistance, antistatic properties, oxygen barrier properties, and heat retention properties cannot be sufficiently obtained. A particularly preferred range is 80 to 100 mol%.

If necessary, monomer units other than (A), (B) and (C) may contain about 30 mol% or less. Examples of such units include α-olefins (ethylene, propylene). , Long-chain α-olefins, etc.), ethylenically unsaturated carboxylic acid-based monomers (acrylates, methacrylates) acrylonitrile, methacrylonitrile, vinyl chloride, vinyl ether, etc.).

For the above copolymerization resistance, it is useful to use vinyl acetate as the unit (B). Moreover, in this case, if the ratio of the oxyalkylene unit CHR ² —CHR ³ —O in the unit (C) to the whole resin is ³ to 40% by weight, the effect becomes more remarkable. That is, focusing on the oxyalkylene unit, the molar ratio of (C) in the copolymer is 0.1%.
Not only 1 to 20 mol% (preferably 0.1 to 5 mol%), but also the weight ratio of the oxyalkylene unit in (C) is 3 to 40% by weight (preferably 5 to 40% by weight) of the whole resin.
Is desired. This means that the degree of localization-delocalization of the oxyalkylene unit in the vinyl alcohol-based polymer and Indicates that the length of the oxyalkylene unit is restricted. Further, the number of n is 3 to 50, and the degree of saponification is 80 to 100 mol%, which is a higher range for practical use.

Further, it is desired that the oxyalkylene group-containing vinyl alcohol copolymer used in the present invention has a melt index of 5 g / 10 min or more at a temperature of 210 ° C. and a load of 2160 g. When this value is less than 5 g / min, it is difficult to perform smooth melt molding even if other conditions are satisfied. Here, the melt index is measured using a melt indexer manufactured by Toyo Seiki Seisakusho with a nozzle of 1 mmφ × 10 mm.

As described above, in the present invention, the oxyalkylene group-containing vinyl alcohol polymer (X) satisfying the above conditions is
By using the compound, melt molding under a condition substantially free of a plasticizer and under a substantially anhydrous condition can be performed industrially.

The oxyalkylene group-containing vinyl alcohol polymer (X) is obtained by polymerizing a monomer constituting the vinyl ester unit (B) and the oxyalkylene allyl ether unit (C) together with another copolymerizable monomer as necessary. It is then produced by saponification. Most or all of the vinyl ester units (B) are converted to vinyl alcohol units by saponification.

As a polymerization method, a solution polymerization method is usually employed, and a suspension polymerization method, an emulsion polymerization method, or the like may be employed depending on the case.

As the saponification reaction, an alkali saponification method, an acid saponification method, or the like is employed.

<Natural polymer (Y)> As the natural polymer (Y), a starch polymer, a cellulose polymer, other polysaccharide polymers, a protein polymer, and the like are used.

Among them, as the starch-based polymer, corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch, rice starch, bean starch,
Raw starch such as kud's starch, bracken starch, lotus starch, and sis starch; physically modified starch (α-starch, fractionated amylose, wet heat-treated starch, etc.), enzyme-modified starch (hydrolyzed dextrin, enzyme-decomposed dextrin, amylose, etc.), chemical degradation Starch (acid-treated starch, hypochlorite oxidized starch, dialdehyde starch, etc.), chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.) and the like. Among the chemically modified starch derivatives, the esterified starch includes acetate esterified starch, succinic esterified starch, nitrated esterified starch, phosphorylated esterified starch, urea phosphorylated esterified starch, xanthated esterified starch, and acetoacetic acid. As etherified starch such as esterified starch, allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, and the like, as cationized starch, starch and 2- Crosslinked starch such as a reactant of diethylaminoethyl chloride, a reactant of starch and 2,3-epoxypropyltrimethylammonium chloride, and the like, formaldehyde crosslinked starch, epichloroform Hydrin crosslinked starch, phosphoric acid crosslinked starch, acrolein-crosslinked starch and the like.

Examples of the cellulosic polymer include methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose, carboxymethylcellulose, and acetylcellulose.

Other polysaccharide-based polymers include elegans mannan, salep mannan, wood mannan, seaweed mannan,
Mannans such as yeast mannan, inulin, fructans such as levan, glycogen, caronine, laminaran,
Xylan, chitin, chitosan, pectic acid, hyaluronic acid, agarose, alginic acid, heparin, chondroitin sulfate, carrageenan, arabic gum, tragacanth gum, karaya gum, guar gum, locust bean gum,
Meskit gum, gatch gum, seaweed, agar, and the like.

Examples of the protein-based polymer include gelatin, collagen such as glue, casein, zein, gluten, blood albumin, and soybean protein.

<Blending Ratio, Melt Molding Method> The mixing ratio of the oxyalkylene group-containing vinyl alcohol polymer (X) and the natural polymer (Y) is 9 by weight.
It is set in the range of 0:10 to 10:90, especially 80:20 to 30:70 by weight. When the proportion of the natural polymer (Y) is too large, the moldability is impaired, and the strength of the molded article is deteriorated. On the other hand, when the proportion is too small, the biodegradability is impaired.

In the present invention, the melt molding is carried out under a condition substantially free of a plasticizer and substantially anhydrous (having a water content of about several percent by weight or less, particularly 1 percent by weight or less, and even 0.5 percent by weight or less). Do. Even in such a case, smooth melting can be performed is one of the features of the present invention.

That is, in the present invention, flexibility can be obtained without blending a plasticizer such as a polyhydric alcohol during melt molding.
Melt molding can be performed without using water. The use of plasticizers has the disadvantage of deteriorating the properties of the molding.
In addition, the addition of water at the time of melt molding is also a minus because a drying step is required.

During melt molding, fillers, colorants, stabilizers,
Additives such as water-resistant agents, fertilizers, agricultural chemicals, enzymes, fungicides, deodorants, functional agents such as fragrances, and other water-soluble or water-insoluble resins can also be blended.

As the melt molding method, an arbitrary melt molding method such as an extrusion molding method and an injection molding method is employed.

Extrusion molding includes blow molding, inflation molding,
Coextrusion molding, extrusion coating and the like are also included. At the time of extrusion molding, set the die temperature to about 150 to 300 ° C and set the screw compression section temperature to 5
It is desirable to set the temperature to a temperature higher by 30 ° C.

Injection molding, cylinder temperature 150 ~ 250 ℃, mold temperature 30
It is desirable to carry out under conditions of 100100 ° C. and injection pressure of 500-2000 kg / cm ² . It should be said that the water-soluble or hydrophilic polymer composition of the present invention can be injection-molded under non-plastic and anhydrous conditions.

By such a melt molding, a molded article having an arbitrary shape including a film, a sheet, a tape, a tube, a fiber, a bottle, and a tray can be obtained.

The obtained molded product can be further subjected to a secondary treatment or processing such as a water resistance treatment, a stretching treatment, a splitting treatment, and a bag making process.

Function and Effect of the Invention In the present invention, since the composition comprising the oxyalkylene group-containing vinyl alcohol polymer (X) and the natural polymer (Y) is melt-molded, it has sufficient strength at the time of use. Despite its properties, it is quickly degraded by microorganisms in the soil or water after the intended use is achieved.

In addition, the melt molding can be carried out under substantially no plasticizer-containing and substantially anhydrous conditions, which is extremely advantageous from the viewpoint of industrial productivity. The elimination of the use of a plasticizer means that bleeding of the plasticizer from the molded article and adhesion of the molded articles do not occur, which is preferable in terms of the quality of the molded article.

In particular, it is preferable to use the oxyalkylene allyl ether type vinyl alcohol polymer described above as the oxyalkylene group-containing vinyl alcohol polymer (X). That is, the oxyalkylene group of the oxyalkylene allyl ether unit (C) is not eliminated during the saponification reaction to obtain this polymer, and the vinyl alcohol unit (A) And the oxyalkylene allyl ether units (C) are distributed at an appropriate ratio, and the weight ratio of the oxyalkylene units in the unit (C) is set to a specific range. This is because the degree of localization and the length of the oxyalkylene unit are balanced so as to be suitable for melt molding. Therefore, a composition in which a natural polymer (Y) such as a starch-based polymer is blended with this polymer can be produced by industrial molding even if it is melt-molded under a condition substantially free of a plasticizer and substantially anhydrous. Thus, a smooth molding that can be adopted for the above can be achieved.

In addition, the molded product obtained by the method of the present invention has water solubility or water dispersibility and flexibility, and has a fragrance retention property, an oil resistance property, a chemical resistance property, an antistatic property and an oxygen content based on the vinyl alcohol unit (A). It also has properties such as barrier properties and heat retention.

EXAMPLES Next, the present invention will be further described with reference to examples.

<Polymer (X)><Polymer (X) Production Example 1> Polyoxyethylene monoallyl ether having an average number of added moles of oxyethylene of 25 and vinyl acetate in methanol in the presence of azobisisobutyronitrile Copolymerized into
Then, after the remaining monomer was driven off, a methanol solution of sodium hydroxide was added to perform saponification. The polymer was filtered from the slurry generated by the saponification reaction, washed and dried to obtain an oxyalkylene group-containing vinyl alcohol-based polymer (X-1), which was the target product.

Vinyl alcohol unit (A) of this polymer (X-1)
Was 93 mol%, the proportion b of the vinyl acetate units (B) was 6 mol%, and the proportion c of the oxyethylene allyl ether units (C) was 1 mol%.

 This shows that a + b + c = 100 mol% c = 1 mol% 100a / (a + b) = 94.

Further, it is understood that the weight ratio of the oxyethylene unit to the total weight of (A), (B) and (C) is 19% by weight.

The melt index of this polymer (X-1) at a temperature of 210 ° C. and a load of 2160 g was 25 g / 10 min.

The viscosity of the 4% by weight aqueous solution of the polymer (X-1) was 4.0 cps / 20 ° C.

<Polymer (X) Production Examples 2 to 6> Polymers (X-2) and (X-3) having characteristic values as shown in Table 1 according to the production method of polymer (X-1). ,
(X-4), (X-5), (X-6) and (x-7) were produced.

<Natural polymer (Y)> The following natural polymer was used.

(Y-1): corn starch (Y-2): oxidized starch (Y-3): tapioca starch (Y-4): cellulose (Y-5): chitosan <Production of biodegradable molded product> Examples 1 to 8 The powder of the oxyalkylene group-containing vinyl alcohol polymer (X) was dried to a water content of 0.1% by weight or less.

After mixing the above polymer (X) and the above natural polymer (Y) at the ratio shown in Table 2 with a Henschel mixer, the mixture was supplied to a twin screw extruder and extruded linearly at a temperature of 200 ° C. Pelletized.

Then, the pellets were supplied to a single screw extruder and extruded from a T-die under the conditions of a cylinder temperature of 200 ° C. and a die temperature of 180 ° C. to obtain a film having a thickness of 10 μm.

Comparative Example 1 In place of the oxyethylene group-containing vinyl alcohol-based polymer (X), a saponification degree of 99 mol%, and a melt index
The molding was carried out according to the above-mentioned example except that polyvinyl alcohol (Z-1) was used at 8 g / 10 min.

Comparative Example 2 In place of the oxyethylene group-containing vinyl alcohol polymer (X), the saponification degree was 88 mol%, and the melt index was
The molding was carried out in accordance with the above example, except that polyvinyl alcohol (Z-2) for 10 g / 10 minutes was used.

Comparative Example 3 Low density polyethylene having a melt index of 6 g / 10 min (F-161 manufactured by Mitsubishi Kasei Co., Ltd.) instead of the oxyethylene group-containing vinyl alcohol polymer (X) (Z-
Except for using 3), molding was performed in accordance with the above-described example.

<Conditions and Results> Table 2 shows the conditions and results. The measurement or judgment of various properties was performed as follows.

<Water-soluble> A test piece (10 mm x 50 mm x
1 mm) was immersed and the dissolution performance after 10 minutes was observed. In addition, the presence or absence of water turbidity after the test was observed.

○: Dissolution residue is less than 30% by weight △: Dissolution residue is 30% by weight or more and less than 70% by weight ×: Dissolution residue is 70% by weight or more <Biodegradability (disintegration test)> Using a sunshine weather meter manufactured by Kiki Co., Ltd., 110 cycles were carried out at 50 ° C. with water spray for 12 minutes and light irradiation for 48 minutes.

The post-test strength was determined by adjusting the humidity at 20 ° C. and 65% RH, and then measuring the breaking strength by an autograph. The tensile speed is
It was set to 40 mm / min and the sample length was 20 mm.

 The appearance of the film was determined according to the following criteria.

A: Collapse is confirmed visually.

B: The shape of the film is maintained, but easily collapses.

C: The shape of the film is maintained. Does not collapse.

<Presence or absence of decomposition of natural polymer (Y) during molding> Judgment was made according to the following criteria.

：: No decomposition ×: Decomposition <Strength, elastic modulus (1% elastic modulus)> After the sample was conditioned at 20 ° C and 65% RH, the breaking strength was measured by an autograph. The tensile speed was set at 40 mm / min, the sample length was 20 mm, and the sample width was 5 mm.

<Bleeding> Press the moldings at <20 ° C, 65% RH, 16 hours> and <40 ° C, 80%
% RH, 8 hours> alternately 30 times each time, and observe the condition of the molded product surface. Observe bleeding is not observed, ○ is slightly observed, Δ is clearly observed. X was determined.

From the above results, it can be seen that in the examples, the melt molding can be performed smoothly, and the molded product has excellent biodegradability, mechanical properties, and water solubility.

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Claims (4)

(57) [Claims] 1. A composition comprising an oxyalkylene group-containing vinyl alcohol polymer (X) and a natural polymer (Y) is melt-molded under a condition substantially free of a plasticizer and substantially anhydrous. A method for producing a biodegradable molded article. 2. The method according to claim 1, wherein the content of the oxyalkylene unit in the polymer (X) is 3 to 40% by weight. 3. The method according to claim 1, wherein the natural polymer (Y) is a starch-based polymer. 4. The process according to claim 1, wherein the mixing ratio of the polymer (X) and the natural polymer (Y) is 90:10 to 10:90 by weight.