JP3009272B2 - Easily disintegrable composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily disintegrable composition having excellent spreadability during film melt molding.

[0002]

2. Description of the Related Art In general, synthetic polymers are widely used in various fields because they have high material properties, are excellent in processability, and are inexpensive. However, the molded product is bulky,
Due to its own durability, it does not collapse naturally even when it is dumped or landfilled, and its heat generation is high when incinerated. Therefore, studies have been made to reduce the bulk of the plastic waste by partially decomposing it by light or microorganisms, and to effectively use the waste treatment facility or landfill.

[0003] Above all, research on biodegradable thermoplastic resin compositions by blending relatively inexpensive and completely biodegradable starch with a thermoplastic resin as an easily disintegrating agent has been actively conducted. (Japanese Patent Application Laid-Open Nos. 2-142228 and 3-31333).

[0004]

However, these compositions are not easy to disintegrate and have a problem in spreadability in molding, so that a thin film cannot be obtained.

An object of the present invention, therefore, is to provide a composition which is excellent in easy disintegration and excellent in spreadability during film formation.

[0006]

The above object is achieved by providing a composition comprising an ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 3 to 24 mol% and a polysaccharide.

In the present invention, when EVOH having an ethylene content of 3 to 24 mol% is used, a composition comprising the EVOH and various polysaccharides has a mechanical strength that can withstand use, and an excellent spreadability when forming a film. When it is buried in soil as waste after use, it has the property of easily disintegrating that its shape and mechanical strength are quickly lost.

[0008] The ease of disintegration of EVOH by living organisms is partially described in the Nikkei New Materials, March 26, 1990, and a resin composition comprising EVOH and starch which is a natural product is disclosed in Japanese Unexamined Patent Publication No. Hei. 14228 and JP-A-3-31333. However, the ethylene content of EVOH conventionally used in the art is 25 mol% or more, and these publications or publications disclose EVOH having a low ethylene content as specified in the present invention. There is no specific example of using.
Among the above publications, JP-A-3-31333 discloses an ethylene content of 10 to 90% by weight (14.9% in terms of mol%).
(93.4 mol%), but there is no description that EVOH having an ethylene content of less than 25 mol% is excellent in easy disintegration. Further, as a result of the additional tests by the present inventors, the ethylene content 2
It was found that EVOH of 5 mol% or more had significantly lower disintegration than the EVOH described in the present invention. This is clear from a comparative example described later.

In the present invention, it is important that the ethylene content of EVOH is 3 to 24 mol%, preferably 3 to 20 mol%, more preferably 3 to 14 mol%, and most preferably 5 to 12 mol%. %. If the ethylene content is more than 24 mol%, the spreadability at the time of forming the film, which is the object of the present invention, cannot be obtained, and the disintegration property is not sufficient. On the other hand, if the amount is less than 3 mol%, a sufficient strength that can withstand practical use cannot be obtained when molded into a film, and the disintegration property is also insufficient.

The degree of saponification of the vinyl ester component of EVOH is preferably at least 50%. From the viewpoint of thermal stability, it is preferably at least 80%, more preferably at least 90%. If the degree of saponification is less than 50%, the thermal stability is reduced and a large amount of gel is generated at the time of molding. From the viewpoint of solubility in hot water, the degree of saponification is 50
９５95%, more preferably 60-95%. EVOH is a saponified copolymer of ethylene and vinyl ester. Here, vinyl acetate is a typical example of vinyl ester. Other fatty acid vinyl esters (eg, vinyl pivalate) can also be used. . In addition, EVOH, olefins having 3 or more carbon atoms such as propylene, (meth) acrylic acid, vinylsilane-based compounds (vinyltrimethoxysilane, vinyltriethoxysilane, etc.), vinylpyrrolidone-based compounds can be used as long as the object of the present invention is not impaired. It is free to copolymerize the third component such as. In addition, EVOH having an alkyl group having 4 to 50 carbon atoms at the terminal and / or side chain, EVOH having a partially oxidized hydroxyl group, EVOH having a fatty acid polyester grafted thereon, and an ionic group (a carboxylic acid group Or EVOH having a salt thereof, a sulfonic acid group or a salt thereof, an ammonium group, etc.). In addition, the intrinsic viscosity of EVOH [solvent water / phenol
15/85 (weight ratio), 30 ° C.] is 0.05 to 0.2 l / g, preferably 0.07 to 0.15 l / g.

It is particularly preferable that the EVOH used in the present invention is soluble in hot water because it has an effect of promoting the easy disintegration of the EVOH. Here, the term "soluble in hot water" means a property of substantially completely dissolving when immersed in hot water of 95 ° C for 1 minute. EVOH is preferably thermoplastic because it can be melt-molded.

The amount of each component of the EVOH and the polysaccharide of the present invention is 1 to 99 parts by weight of the EVOH and 99 to 1 part by weight of the polysaccharide. If the EVOH content is 1 part by weight or less or the polysaccharide content exceeds 99 parts by weight, a sufficient easily disintegrable resin due to microorganisms cannot be obtained after dumping as waste. Preferred amounts are 10 to 90 parts by weight of EVOH and 90 to 10 parts by weight of polysaccharide.

The polysaccharide used in the present invention includes starch, cellulose, chitin, chitosan, hemicellulose, pectin, pullulan, agar, alginic acid, carrageenan, dextran and the like. It is preferred in terms of. Examples of the starch include raw starches such as corn and potato, and chemically or chemically modified starches (textulin, oxidized starch, esterified starch, etherified starch, cationized starch, etc.).

As is clear from the examples described below, the composition of the present invention is superior in the spreadability of the film to the conventional composition in which EVOH having a high ethylene content is added to starch.

The composition of the present invention may be freely added with other additives, for example, a plasticizer such as water or glycerin, in order to further enhance the moldability and flexibility of the resin. Examples of the plasticizer include polyethylene glycol, ethylene glycol, diglycerin, glycerin, 1,3
-And 1.4-butanediol, 1,2-propylene glycol, sorbitol, ε-caprolactam, urea, toluenesulfonamide, laurylamide, acetamide, formamide, dimethylsulfoxide, dioctylphthalate, dibutylphthalate, water and the like. One type or a mixture of two or more types may be used. Preferably, glycerin, water, urea and the like are used.

The composition of the present invention may further contain a filler (talc, clay, mica, cellulose fiber, PVA fiber, etc.), a heat stabilizer, an ultraviolet absorber, an antioxidant, a vegetable oil, as long as the effects of the invention are not impaired. It is also free to blend a coloring agent or the like.

As a means for compounding the components for obtaining the composition of the present invention, a ribbon blender, a high-speed mixer co-kneader, a mixing roll, an extruder, an intensive mixer and the like are used.

The composition of the present invention can be used to obtain any molded product (eg, film, sheet, various containers, various injection molded products) by using a well-known extruder, injection molding machine, press machine and the like. Alternatively, the obtained film may be stretched into a split yarn, which may be formed into a woven or knitted fabric.

Examples of the molded product are not particularly limited, but the molded product is discarded after being used for a certain period of time, for example, a cup, a bottle, a tray as a food container, a sheet, a pile, and a mulch as an agricultural material ( Multi-film), planters, containers or carrier materials for agricultural chemicals, fertilizers, soil conditioners, etc., binding straps as daily necessities, toys for children, trash cans, cushioning materials for industrial use, packing,
Examples include various containers and colostomy bags.

When the molded article is discarded after use, the disintegration starts immediately after being dumped in a garbage collection area similar to general garbage. However, in order to enhance the effect of microorganisms in the soil, A landfill method is preferred.

In the present invention, the composition can be used as a multilayer having at least one composition layer. The other layer in the case of forming a multilayer body is preferably a biodegradable resin layer or a photodegradable resin layer. Here, as the biodegradable resin layer, proteins (gelatin, collagen), polypeptides, polyesters (polyadipate,
Thermoplastic resin containing polylactone, aliphatic polyester, aliphatic polyesteramide), polyether, polyurethane, polystyrene, and polysaccharide (starch, cellulose, chitin, chitosan, etc.) ｛Polyolefin (polyethylene, etc.), polystyrene, vinyl alcohol Resin (EVOH with an ethylene content of 25 to 65 mol%)
Etc.), and a film or sheet obtained by blending a polysaccharide with a thermoplastic resin such as an ethylene-acrylic acid copolymer. Further, as the photodegradable resin layer, a copolymer of ethylene and carbon monoxide,
Copolymers of methyl vinyl ketone with ethylene, styrene, vinyl chloride, methyl acrylate, etc., and various thermoplastic resins blended with photodegradable master batch (polyethylene grafted with methyl vinyl ketone and a small amount of methyl styrene) The resulting film or sheet is representative. In addition, examples of other layers include cellulose-based paper, nonwoven fabric, and net.

The other layer can be provided on one side or both sides of the composition layer of the present invention, and the composition layer of the present invention can be provided on both sides of the other layer. When producing these multilayer bodies, an adhesive, preferably a biodegradable adhesive, can be used if necessary.

Examples of the adhesive include a polyurethane resin, a starch resin, and an unsaturated carboxylic acid or an anhydride thereof (maleic anhydride or the like) containing the resin or the olefin polymer or copolymer [polyethylene ｛low-density polyethylene]. (LDPE), linear low density polyethylene (LL
DPE), ultra-low density polyethylene (SLDPE), ethylene-vinyl acetate copolymer, ethylene- (meth) acrylate (methyl ester or ethylene ester) copolymer].
These adhesives are used as interlayer adhesives or compounded in a composition layer or other layers.

The multilayer body may be obtained by extrusion lamination, dry lamination, coextrusion lamination, coextrusion sheet molding, coextrusion pipe molding, coinjection molding, or the like.
Solution coating method and the like can be mentioned. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0025]

【Example】

Example 1 The easy disintegration of the EVOH alone of the present invention was examined. EVOH having an ethylene content of 7 mol% and a degree of saponification of 99.7% was converted to water /
Using a mixed solution of propanol as a solvent, 10% by weight of E
A VOH solution was obtained. The solvent was evaporated by applying the solution on a rotating drum adjusted to a temperature of 75 ° C.
A uniform film of μ was obtained.

The film was cut into a size of 15 × 100 mm, immersed in hot water adjusted to 95 ° C. for 1 minute, and examined for hot water solubility. The results are shown first. The hot water solubility was evaluated in three stages as described below. ○ ・ ・ ・ Completely dissolved △ ・ ・ ・ Swelled and separated × ・ ・ ・ Invariant

The film was cut out in an amount of 0.2 g and immersed in 100 ml (ml) of a liquid medium containing 0.3% of polyvinyl alcohol (PVA) previously sterilized. This medium is inoculated with 1 milliliter (ml) of a PVA-degrading bacterium solution previously grown by shaking for 3 days in a liquid medium containing 0.3% of PVA, and the pH is adjusted to 7 to 7.5 on the way for 2 weeks. After shaking, the change in weight of the film was determined by the following equation and is shown in Table 1. The shaking conditions were 120 rpm (30
° C).

[0028] The weight is a value measured after allowing the film to stand at 20 ° C. and 50% RH for 48 hours.

The composition of the liquid culture medium containing 0.3% of PVA (PH = 7.5) is as follows. PVA (polymerization degree 1700, saponification degree _{99.9%) 0.3% NH 4 NO} 3 0.1% KH 2 PO 4 0.02% K 2 HPO 4 0.1% MgSO 4 · 7H 2 O 0.02 % NaCl 0.01% NaCl ₂ .2H ₂ O 0.01% FeSO ₄ .7H ₂ O 0.001% Peptone 0.005% ext. 0.005% pyrroloquinoline quinone 1 μg / ml

Examples 2 to 3 and Comparative Examples 1 to 4 The procedure was carried out under the same conditions as in Example 1 except as shown in Table 1. Table 1 shows the results.

Example 4 EVOH having an ethylene content of 10 mol% and a saponification degree of 90%
30 parts by weight, 70 parts by weight of corn starch, 20 parts by weight of glycerin as a plasticizer and 20 parts by weight of water are blended and melt-kneaded using a single screw extruder having a full flight type screw having a screw diameter of 40 mm and L / D = 26. Then, the extruder was formed into a strand at a temperature of 180 ° C. from a pellet die attached to the tip of the extruder, and then formed into pellets using a pelletizer.

The pellets are 550 mm wide in the above extruder,
The film was extruded from a film forming apparatus equipped with a coat hanger die having a lip opening of 0.3 mm, and formed into a film by a take-off apparatus having a cast drum having a diameter of 800 mm. At this time, the film thickness of the film obtained by sequentially increasing the rotation speed of the cast drum of the take-off device becomes thin, and the film is eventually broken by further increasing the speed, so that a thinner film cannot be obtained any more. The thickness of the film at this breaking point was measured and is shown in Table 2 as spreadability.

Further, a 100 μm uniform film formed by the above film forming apparatus was sampled 15 mm in width and 150 mm in length.
And chucking distance is 50m with a tensile tester.
m, and the tensile strength and elongation at break were measured at a tensile speed of 500 mm / min. Table 2 shows the results.

The film was buried in the soil (5 to 10 cm below the surface layer), and the state of the film after three months was evaluated according to the following four grades. The results are shown in Table 2. A: severely damaged B: considerably damaged C: slightly damaged D: unchanged

Examples 5 to 6 and Comparative Examples 5 to 6 The same conditions as in Example 4 were carried out except as shown in Table 2. Table 2 shows the results.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

The composition of the present invention has excellent disintegration properties and excellent spreadability during film formation. Further, when the molded product obtained from the composition of the present invention is buried in soil as waste after use, it is rapidly disintegrated by microorganisms and loses its shape and strength.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-31333 (JP, A) JP-A-2-14228 (JP, A) JP-A-54-16576 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08L 1/00-5/06 C08L 29/00-29/14 C08L 23/00-23/36

Claims (3)

(57) [Claims] An easily disintegrable composition comprising an ethylene-vinyl alcohol copolymer having an ethylene content of 3 to 24 mol% and a polysaccharide. 2. The easily disintegratable composition according to claim 1, wherein the ethylene-vinyl alcohol copolymer is soluble in hot water. 3. An ethylene-vinyl alcohol copolymer,
3. The easily disintegrable composition according to claim 1 , which is thermoplastic .