JP3105451B2 - Biodegradable resin composition and molded article thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a biodegradable mixture of a polyvinyl alcohol resin having a limited molecular weight and a polyhydric alcohol, where necessary, wherein cellulose particles are added as a component for promoting biodegradability. In addition, the present invention relates to a composition which is decomposed in a natural environment such as soil or seawater, and which comprises borax added as a component for improving water resistance in some cases. The present invention also relates to a molded article formed from the composition.

[0002]

2. Description of the Related Art In general, molded articles made of synthetic polymers have been used in a very wide range of fields because of their excellent mechanical properties and economical efficiency. However, in recent years,
Due to the durability and weather resistance, which are the most useful characteristics of the synthetic polymer molded article, it is a serious problem that the environment is deteriorated by disposing of the used resin molded article, and the improvement has been studied. To address this issue, to date,
Polyesters produced by microorganisms and aliphatic polyesters produced by synthetic methods have already been put into practical use, but these are still economically expensive and have the disadvantage that biodegradation requires a long time.

On the other hand, it has been reported in many reports that among synthetic polymers, polyvinyl alcohol resins widely used for packaging films and the like are decomposed by specific microorganisms such as Pseudomonas putida. However, molded products such as films and bottles made of polyvinyl alcohol-based resin usually have a rough surface or bacterial adhesion even after one year in the environment such as soil or seawater. Although there is a change in appearance due to this, the molded article itself does not collapse or decompose. Even with such a water-soluble polyvinyl alcohol-based resin, it takes a very long time to disintegrate or decompose, and various compositions for promoting the biodegradability of the polyvinyl alcohol-based resin have been conventionally used. Many more have been proposed. For example, in JP-A-2-51639, a polyvinyl alcohol-starch film containing polyvinyl alcohol and starch and stretched in at least one direction is disclosed in JP-A-3-79645. The composition of resin and modified starch is disclosed in
In the Patent Publication No. 200108, a composition of a polyvinyl alcohol-based resin and gluten is disclosed, but the moldability of the composition is not good, and the water resistance of a molded article produced thereby,
The heat resistance was poor, and the biodegradation time was unnecessarily long, and none was satisfactory.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and retains excellent moldability of a polyvinyl alcohol-based resin and has good mechanical strength. Another object of the present invention is to provide a biodegradable resin composition.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive research and studies to achieve the above object, and as a result, have found that polyvinyl alcohol resins having a limited molecular weight and polyhydric alcohols have become necessary. Accordingly, it has been found that molded articles obtained from compositions comprising cellulose particles and / or borax, or both, promote disintegration in environments such as ordinary soil and seawater and can significantly reduce the decomposition time. .

That is, in the present invention, a polyhydric alcohol having a plasticizing effect is added to a relatively low molecular weight polyvinyl alcohol resin having a specific range of molecular weight, and cellulose particles having a controlled particle size are added as required. Thereby, the biodegradability is improved. Further, by appropriately adding borax having an effect of improving water resistance, the moldability and water resistance of the polyvinyl alcohol-based resin and the mechanical properties of the molded product are hardly impaired, and excellent production is achieved. Degradability is achieved. That is, the present invention has a number average molecular weight
More than 10,000 and less than 30,000, 15% of more than 100,000 fractions
It is characterized by using a polyvinyl alcohol-based resin having the following specific molecular weight range, a polyhydric alcohol exhibiting a plasticizing effect on the polyvinyl alcohol-based resin 10 to 100 parts by weight, and, if necessary, particles Diameter 50
It is a biodegradable resin composition mixed and dispersed in 10 to 300 parts by weight of cellulose particles having a particle size of 1 μm or less and / or 2 to 10 parts by weight of borax 100 parts by weight of a polyvinyl alcohol resin.

The polyvinyl alcohol resin used in the present invention comprises a vinyl alcohol polymer having a number average molecular weight of 10,000 or more and 30,000 or less and a fraction of 100,000 or more of 15% or less, mainly comprising a vinyl alcohol unit. It is preferably used, the number average molecular weight is 20,000 or less, 100,
10% or less of 000 or more fractions and 15 vinyl alcohol units
mol% or more, and more preferably a saponification degree of 75 mol% or more. A composition using a polyvinyl alcohol resin having a number average molecular weight of 30,000 or more and a fraction of 100,000 or more of 15% or more and a molded article formed from the composition is significantly reduced in biodegradability. Can not. Conversely, a polyvinyl alcohol resin having a number average molecular weight of 10,000 or less is extremely difficult to mold, and even if a molded article is obtained, it cannot be used because the mechanical strength of the molded article is extremely reduced.

The polyhydric alcohol used in the present invention has the effect of improving not only the plasticity or processability of the obtained polyvinyl alcohol-based resin composition, but also the flexibility of the molded product, as well as the biodegradability. I have.
Preferred polyhydric alcohols for this purpose include glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, propylene glycol, pentaerythritol, glycerol monoacetate, glycerol diacetate, sorbitol, polyethylene glycol, polyzolopyrene glycol, poly
(Ethylene-propylene) glycol. Also, the amount of the polyhydric alcohol to be added is less than 10 parts by weight, the moldability is significantly deteriorated, the mechanical properties of the molded article are extremely lost, and if it is more than 100 parts by weight, the moldability is good. However, the water resistance and mechanical properties of the obtained molded product are significantly reduced, so that it cannot be used practically.

The cellulose particles in the present invention have a particle diameter of
When cellulose particles larger than 50 μm are used, not only the moldability is impaired, but also the mechanical properties of the molded product are significantly reduced, so that the cellulose particles must have a particle size of 50 μm or less, but are preferably 30 μm or less. More preferably, cellulose particles having a particle diameter of 10 μm or less are preferred. The particle diameter here is, needless to say, a diameter if the cellulose particles are spherical, but in the case of a columnar shape or a similar shape, that is, when there are a short diameter and a long diameter, the particle diameter means a long diameter. I do. Further, the addition amount of the cellulose particles is less than 10 parts by weight, the disintegration of the molded product obtained from the resin composition is extremely slow, it takes a long time to decompose,
If the amount is more than 300 parts by weight, the moldability deteriorates remarkably, and the mechanical properties of the molded product are extremely lost. As the cellulose particles satisfying the above conditions, for example, selected wood pulp is fractionated into short fibers, dried, and powdered cellulose mechanically pulverized to the limit by a dry ball mill, or a cellulose raw material such as wood pulp or cotton linter. The amorphous portion is hydrolyzed with a mineral acid to disintegrate, microcrystalline cellulose that has been washed and dried, and then pulverized, or a suspension of the microcrystalline cellulose that has been treated with a high-pressure homogenizer, and a cellulose that has been subjected to delignification treatment. The material is subjected to depolymerization such as acid hydrolysis, alkali oxidative decomposition, enzymatic decomposition, steam explosion decomposition, and steam steaming, and the cellulose-based material is subjected to forced stirring in a container, and wet-pulverized fine powder. Cellulose is mentioned.

The borax used in the present invention has an effect of improving the water resistance of the obtained resin composition. It has been known for a long time that borax thickens and gels by chemically bonding with polyvinyl alcohol, and utilizes this effect. The amount of borax added is less than 3 parts by weight, which has no effect of improving water resistance.
If the amount is more than 10 parts by weight, the moldability is remarkably deteriorated due to gelation. Therefore, the amount must be in the range of 2 to 10 parts by weight.

The resin composition of the present invention comprises the polyvinyl alcohol-based resin, a polyhydric alcohol, and, if necessary, cellulose powder and / or borax. A filler, a lubricant, a modifier, a foaming agent, a bulking agent, a flow accelerator, a release agent, a dispersion stabilizer, an anti-blocking agent, a coloring agent and the like are prepared and added according to the purpose of use. The resin composition of the present invention can be formed into a film by an aqueous solution casting method in which the aqueous solution is cast on a hot drum by a slit or a casting hopper and dried, or a known extrusion molding machine or injection molding machine can be used. Also, molded products such as films, sheets, various injection molded products, various containers, etc. can be obtained by a hot press molding machine, a blow molding machine, an inflation molding machine, a T-die casting molding machine and the like.

[0012]

The present invention will be described in more detail with reference to the following Examples, which do not limit the scope of the present invention. Further, the measurement of mechanical properties, the measurement of swelling degree and the biodegradability test of Examples, Reference Examples and Comparative Examples were evaluated by the following methods. As a measurement of the mechanical properties of this film, the film was cut into strips having a sample width of 15 mm and a length of 200 mm, and using a tensile tester, a chuck interval of 100 mm and a tensile speed of 100 mm.
The strength and elongation at break were measured at mm / min. The measurement of the degree of swelling as an indicator of the water resistance of the film was performed as follows. A sample is cut into 50 mm × 50 mm, immersed in distilled water for 48 hours, and the weight of the swollen film is measured. Thereafter, the swollen film is completely dried, and the weight of the film is measured. The weight of the dried film was subtracted from the weight of the swelled film, and the value was divided by the weight of the dried film to obtain the degree of swelling. Therefore, the smaller the value of the degree of swelling, the higher the water resistance. Furthermore, regarding the biodegradability test of molded products, cut a sample into 50 mm x 50 mm, hold it with a 20-mesh wire net, and bury it in the soil (depth about 15 cm) of Toyohashi City, Aichi Prefecture, or The molded product was immersed in the seawater of Toyohashi Port (depth about 50 cm), and the state of decomposition of the molded product after one year was observed. The area of decomposition and disappearance was expressed as a percentage of the original sample.

[0013]

Example 1 After 5 parts by weight of borax (manufactured by Wako Pure Chemical Industries) was dissolved in warm water at 90 ° C., the number average molecular weight was 15,000 and 100,000.
The above fraction was dissolved in 5% and 100 parts by weight of a polyvinyl alcohol resin having a saponification degree of 98.6 mol%. After dissolution, 20 parts by weight of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a polyhydric alcohol, and the mixture was sufficiently stirred and mixed. The aqueous solution was cast from a slit on a drum maintained at 90 ° C., and blown with hot air at 90 ° C. to dry the solvent to obtain a uniform film having a thickness of 50 μm. Table 1 shows the results of the mechanical properties, swelling degree measurement and biodegradability test of the film.

[0014]

Example 2 200 parts by weight of cellulose particles having an average particle size of 6.0 μm (Asahi Kasei crystalline cellulose, Avicel PH-M06) were sufficiently dispersed in warm water at 90 ° C., and then borax (manufactured by Wako Pure Chemical Industries). Add 7 parts by weight and dissolve. Number average molecular weight is 25,000.
With more than 100,000 fractions at 12% and a degree of saponification of 99.6m
ol% of polyvinyl alcohol was dissolved in 100 parts by weight. After dissolution, 50 parts by weight of diglycerin (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a polyhydric alcohol, and the mixture was sufficiently stirred and mixed. The aqueous solution was cast from a slit on a drum held at 90 ° C.
The solvent was dried by blowing hot air at ° C to obtain a uniform film having a thickness of 50 µm. Table 1 shows the results of the mechanical properties, swelling degree measurement and biodegradability test of the film.

[0015]

Example 3 5% of a fraction having a number average molecular weight of 15,000 and 100,000 or more, 100% by weight of extruded flake polyvinyl alcohol resin having a saponification degree of 78mol%, 2 parts by weight of borax and an average molecular weight as polyhydric alcohol Blend 50 parts by weight of 400 polyethylene glycol (manufactured by Sanyo Chemical)
Melt and knead with a single screw extruder having a single flight type screw with a screw diameter of 50 mm and L / D = 26, make a strand from the pellet die at the tip of the extruder, and use a pelletizer to make a diameter.
It was cut into pellets of 2.0 mm and 5.0 mm in length. Using a blow molding machine, the above pellets have a side thickness of 1.0m
m, a bottle with a bottom thickness of 2.0 mm and an internal volume of 500 ml was molded. Table 1 shows the results of the biodegradability test of the bottle.

[0016]

Example 4 Cellulose particles having an average particle diameter of 6.0 μm were added to 100 parts by weight of an extrusion grade flake polyvinyl alcohol resin having a number average molecular weight of 25,000, a fraction of 100,000 or more and a saponification degree of 78 mol%, and 50 parts by weight of crystalline cellulose manufactured by Asahi Kasei, Avicel PH-M06), 2 parts by weight of borax, and 50 parts by weight of polyethylene glycol having an average molecular weight of 400 (manufactured by Sanyo Chemical) as a polyhydric alcohol are blended with a screw diameter of 50 mm, L / D = 26 single-flight extruder with single-flight screw, melt-kneaded, make strand from pellet die at extruder tip, diameter 2.0m with pelletizer
m, and cut into a length of 5.0 mm to form a pellet. The above pellets were formed into a bottle having a side thickness of 1.0 mm, a bottom thickness of 2.0 mm, and an inner volume of 500 ml using a blow molding machine.
Table 1 shows the results of the biodegradability test of the bottle.

[0017]

Reference Example 1 100 parts by weight of a polyvinyl alcohol resin having a number average molecular weight of 15,000, a fraction of 100,000 or more and 5% and a saponification degree of 98.6 mol% were sufficiently decomposed and dissolved in warm water at 90 ° C. After dissolution, 20 parts by weight of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a polyhydric alcohol, and the mixture was sufficiently stirred and mixed. The aqueous solution was cast from a slit on a drum held at 90 ° C, and blown with hot air at 90 ° C to dry the solvent.
A uniform film of 50 μm was obtained. Table 1 shows the results of the mechanical properties, swelling degree measurement and biodegradability test of the film.

[0018]

[Reference Example 2] Shimadzu laser diffraction particle size distribution analyzer (SA
LD-1100) 50 parts by weight of cellulose particles (Asahi Kasei Microcrystalline Cellulose, CEOLUS CREAM FP-03) having an average particle diameter of 3.5 μm were sufficiently dispersed in warm water at 90 ° C. Polyvinyl alcohol resin of 18,000, 9% of the fractions with 100,000 or more, and saponification degree of 98.5mol%
100 parts by weight were dissolved. After dissolution, 30 parts by weight of glycerin (manufactured by Wako Pure Chemical Industries) was added as a polyhydric alcohol, and the mixture was sufficiently stirred and mixed. The aqueous solution was cast from a slit on a drum maintained at 90 ° C., and blown with hot air at 90 ° C. to dry the solvent to obtain a uniform film having a thickness of 50 μm. Table 1 shows the results of the mechanical properties, swelling degree measurement and biodegradability test of the film.

[0019]

[Reference Example 3] Polyethylene glycol having an average molecular weight of 400 as a polyhydric alcohol is added to 100 parts by weight of an extruded flake polyvinyl alcohol resin having a number average molecular weight of 15,000, a fraction of 100,000 or more, 5%, and a saponification degree of 78 mol%. (Sanyo Chemical Co., Ltd.) is blended with 50 parts by weight, melt-kneaded with a single screw extruder having a single flight type screw with a screw diameter of 50 mm and L / D = 26, made into a strand from the pellet die at the tip of the extruder, and diametered with a pelletizer. 2.0mm, length
It was cut into 5.0 mm and pelletized. The pellets were extruded from a film forming apparatus equipped with a 600 mm wide T-die on the extruder to obtain a sheet having a thickness of 0.2 mm. Table 1 shows the mechanical properties of the sheet and the results of the biodegradability test.

[0020]

REFERENCE EXAMPLE 4 Cellulose particles having an average particle diameter of 6.0 μm were added to 100 parts by weight of an extrusion-grade flake polyvinyl alcohol resin having a number average molecular weight of 18,000, a fraction of 100,000 or more and a saponification degree of 78 mol% ( Asahi Kasei Microcrystalline Cellulose, Avicel PH-M06) Blend 50 parts by weight and 50 parts by weight of polyethylene glycol (manufactured by Sanyo Chemical) having an average molecular weight of 400 as a polyhydric alcohol, screw diameter 50 mm, L /
The mixture was melt-kneaded with a single-screw extruder having a single flight screw of D = 26, made into a strand from a pellet die at the tip of the extruder, and cut into a pellet with a diameter of 2.0 mm and a length of 5.0 mm using a pelletizer. The above pellets were formed into a bottle having a side thickness of 1.0 mm, a bottom thickness of 2.0 mm, and an inner volume of 500 ml using a blow molding machine. Table 1 shows the results of the biodegradability test of the bottle.

[0021]

Comparative Example 1 100 parts by weight of a polyvinyl alcohol resin having a number average molecular weight of 37,000 and a fraction of 100,000 or more and a saponification degree of 99.6 mol% was dissolved in hot water at 90 ° C., and glycerin (Plasticizer) was used. (Wako Pure Chemical Industries, Ltd.) was added in an amount of 30 parts by weight, followed by sufficient stirring. The aqueous solution was cast on a drum maintained at 90 ° C. from a slit and dried to obtain a uniform film having a thickness of 50 μm. Table 1 shows the mechanical properties of the film and the results of a biodegradability test.

[0022]

Comparative Example 2 100% by weight of a polyvinyl alcohol resin having a number average molecular weight of 8,000, a fraction of 100,000 or more and a saponification degree of 99.6 mol% was dissolved in warm water at 90 ° C., and glycerin (P (Wako Pure Chemical Industries, Ltd.) in an amount of 10 parts by weight and thoroughly stirred. The aqueous solution was cast from a slit on a drum maintained at 90 ° C. and dried to obtain a 50 μm thick film. Table 1 shows the mechanical properties and biodegradability test results of the film.

[0023]

Comparative Example 3 When observed with a scanning electron microscope, 75 μm
Cellulose powder containing a large amount of cellulose particles having a particle size of m or more (Sanyo Kokusaku Valve, valve block W-1) 2
After sufficiently dispersing 00 parts by weight in warm water at 90 ° C., add 100 parts by weight of a polyvinyl alcohol resin having a number average molecular weight of 37,000 and a fraction of 100,000 or more at 20% and a saponification degree of 99.6 mol%. did. After dissolution, 50 parts by weight of diglycerin (manufactured by Tokyo Chemical Industry) was added as a polyhydric alcohol, and the mixture was sufficiently stirred. The aqueous solution was cast on a drum maintained at 90 ° C. through a slit and dried to obtain a film having a thickness of 50 μm.
Table 1 shows the mechanical properties and biodegradability test results of the film.

[0024]

Comparative Example 4 After dissolving 15 parts by weight of borax (manufactured by Wako Pure Chemical Industries) in warm water at 90 ° C., 5% of a fraction having a number average molecular weight of 15,000 and having a molecular weight of 100,000 or more was 5% and a polyvinyl alcohol having a saponification degree of 98.6 mol%. I tried to disperse and dissolve 100 parts by weight of alcohol resin.
It was gelled and a molded article such as a film could not be obtained.

[0025]

[Table 1] Mechanical properties Biodegradability Molding method ────────Swelling degree────────── Breaking strength Breaking elongation Seawater in soil (kgf / mm ² ) (%) (%) (%) ────── ──────────────────────────── Actual 1 Casting method 4.3 230 0.5 90 90 Application 2 Casting method 3.5 200 0.4 90 80 Example 3 Blow method ── ── ── 75 70 4 Blow method 75 70 ────────────────────────────────── Reference 1 Casting method 3.8 250 1.0 90 80 Consideration 2 Casting method 4.0 200 0.8 95 85 Example 3 Casting method 4.3 600 ── 80 70 4 Blowing method ── ── ── 80 75 ────────比 Ratio 1 Casting method 5.0 280 ── 50 Comparison 2 Casting method 1.5 85 85 90 85 Example 3 Casting method 1.0 30 ── 90 85 4 Unable to form ──────────────────────────────────

[0026]

Industrial Applicability The biodegradable resin composition of the present invention exhibits good moldability and the molded article has good mechanical properties, but the molded article obtained from this resin composition is used in soil or seawater. When placed in an environment such as inside, it has a remarkable effect that it is broken down by microorganisms and loses its shape, strength and the like remarkably.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C08K 3:38 5: 053) (56) References JP-A-61-228057 (JP, A) JP-A-61-200147 (JP) JP-A-2-75650 (JP, A) JP-A-54-131654 (JP, A) JP-A-5-125266 (JP, A) JP-A-61-204254 (JP, A) 4-132748 (JP, A) JP-A-54-97229 (JP, A) JP-A-5-86209 (JP, A) JP-A-50-113556 (JP, A) JP-A-51-77643 (JP, A) A) JP-A-58-75111 (JP, A) JP-B-44-15554 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 29/04 C08J 5/00-5 / 24 C08L 1/02-1/06 C08K 3 / 38,5 / 053

Claims (4)

(57) [Claims] (A) a number average molecular weight of 10,000 or more and 30,000
A biodegradable resin comprising 100 parts by weight of a polyvinyl alcohol resin having 15% or less of a fraction of 100,000 or more, (B) 10 to 100 parts by weight of a polyhydric alcohol, and (D) 2 to 10 parts by weight of borax Composition. (A) a number average molecular weight of 10,000 or more and 30,000
In the following, 100 parts by weight of a polyvinyl alcohol-based resin in which the fraction of 100,000 or more is 15% or less, (B) 10 to 100 parts by weight of a polyhydric alcohol, (C) 10 to 300 parts by weight of cellulose particles having a particle diameter of 50 μm or less And (D) a molded article obtained from a biodegradable resin composition comprising 2 to 10 parts by weight of borax. (A) a number average molecular weight of 10,000 or more and 30,000
A biodegradable resin comprising 100 parts by weight of a polyvinyl alcohol resin having 15% or less of a fraction of 100,000 or more, (B) 10 to 100 parts by weight of a polyhydric alcohol, and (D) 2 to 10 parts by weight of borax A molded article obtained from the composition. (A) a number average molecular weight of 10,000 or more and 30,000
In the following, 100 parts by weight of a polyvinyl alcohol-based resin in which the fraction of 100,000 or more is 15% or less, (B) 10 to 100 parts by weight of a polyhydric alcohol, (C) 10 to 300 parts by weight of cellulose particles having a particle diameter of 50 μm or less And (D) a molded article obtained from a biodegradable resin composition comprising 2 to 10 parts by weight of borax.