JP2002088246A - Resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lignin/polyvinyl alcohol-based resin composition biodegradable in itself and moreover capable of accelerating a biodegradation rate making use of the characteristics of lignin. SOLUTION: The resin composition is obtained by mixing lignin with a polyinyl alcohol in a specific ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin composition useful as a biodegradable plastic.

[0002]

BACKGROUND OF THE INVENTION Lignin, together with cellulose and hemicellulose, is a major component of plants and is a reproducible and biodegradable organic resource. At present, lignin mainly used industrially is lignin sulfonic acid obtained from sulphite cooking effluent, kraft lignin obtained from kraft cooking effluent, and modified products thereof, and cement dispersants, dye dispersants. , Fertilizer granules, pesticide granules,
It is used in a very wide variety of fields such as soil conditioners.

[0003] On the other hand, due to increasing interest in environmental issues in recent years, environmentally friendly biodegradable plastics have been receiving attention. Biodegradable plastics are plastics that can be used in the same way as ordinary plastics during use, and after use, become low molecular compounds due to the involvement of microorganisms or moisture in nature and eventually decompose to water and carbon dioxide. In use, the same quality as that of conventional plastics is required during use, but it is required that biodegradation be promptly made after use.

[0004] Lignin is a biodegradable organic resource, but at present it has hardly been used as a raw material for biodegradable plastics. As an existing technology using lignin as a raw material of a biodegradable plastic, for example, a resin composition comprising a thermoplastic resin such as polyethylene, lignin, animal and vegetable oils, and a metal compound (JP-A-7-179654) has been proposed. I have. However, there is a problem that it contains a substance such as polyethylene that is hardly decomposed by microorganisms.

On the other hand, polyvinyl alcohol, which is a thermoplastic water-soluble resin, has high crystallinity and forms a film excellent in tensile strength, tear strength, elongation, abrasion resistance and the like. In addition, it has excellent adhesiveness to natural products and inorganic materials, and is used in a wide range of materials such as synthetic fibers and film materials, fiber processing agents, adhesives, and inorganic binders. Furthermore, since it is biodegradable even though it is a synthetic resin, it has been attracting attention as an environmentally friendly biodegradable plastic due to the growing interest in environmental issues in recent years.

However, polyvinyl alcohol has a problem that the biodegradation rate is extremely slow as compared with other so-called biodegradable plastics such as resins and natural polymers. Further, although polyvinyl alcohol is a water-soluble resin, it dissolves easily in warm water, but swells in cold water but takes a considerable amount of time to completely dissolve. This also contributes to being less susceptible to biodegradation.

[0007] In addition, since blocking tends to occur under high temperature and high humidity, there are various problems in the manufacturing process when processing into films and sheets. For example, when processing into a film by a melt extrusion molding method, the molten material causes blocking with the inner wall of the die, resulting in poor die separation and impairing the smoothness and transparency of the film. Also, in the subsequent stretching step, since the peeling from the surface of the stretching roll is not smooth, a part of the molten material remains on the roll surface, causing the film surface to be roughened in a certain pattern, and as a result, the film becomes transparent. The properties and smoothness are impaired. These problems become more significant as the discharge speed and the stretching speed of the molten material are higher and the operation time is longer, so that productivity and operability are significantly reduced.

As an existing technique for improving the blocking and surface roughness of polyvinyl alcohol, a technique of blending 0.05 to 15 parts by weight of a silicone oil emulsion with 100 parts by weight of polyvinyl alcohol (Japanese Patent Laid-Open No. 5-194812).
However, the present situation is that not only the silicone emulsion does not have biodegradability but also the film blocking and operability have not been improved to a sufficient level. In addition, there is almost no study on a technique for accelerating or adjusting the biodegradation rate.

[0009]

In view of the above situation, an object of the present invention is to provide a biodegradable plastic, in which the composition itself is biodegradable, and furthermore, utilizing the characteristics of lignin, accelerates the biodegradation rate. An object of the present invention is to provide a lignin / polyvinyl alcohol-based resin composition that can be used.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a resin composition containing lignin (A) and polyvinyl alcohol (B) in the ratio of general formula 1 is: The inventors have found that the above-mentioned problems can be solved, and have accomplished the present invention. General formula 1 A: 70 to 10 parts by weight B: 30 to 90 parts by weight A + B = 100 parts by weight

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The lignin (A) used in the present invention is not particularly limited.
In addition to lignin sulfonic acid obtained from sulphite cooking effluent, kraft lignin obtained from kraft cooking effluent, and their modified products, MWL (milling lignin), explosion lignin, wood Lignin and the like extracted with an organic solvent can also be used.

The polyvinyl alcohol (B) used in the present invention is not particularly limited, and various degrees of polymerization and saponification are used. Considering the degree of saponification is 85-98
It is preferably mol%, and it has excellent solubility and tends to be easily biodegraded. More preferably, it is around 90%.
Further, the degree of polymerization is preferably about 500 to 3000.

In the present invention, the ratio of lignin (A) to polyvinyl alcohol (B) must be mixed within the range of the following general formula 1. General formula 1 A: 70 to 10 parts by weight B: 30 to 90 parts by weight A + B = 100 parts by weight

A molded product having a lignin (A) ratio of more than 70 parts by weight is very brittle and cannot maintain strength and elasticity sufficient for practical use. Or molding itself is difficult. On the other hand, when the ratio of lignin (A) is less than 10 parts by weight, the solubility of the resin becomes insufficient and the promotion of the biodegradation rate becomes insufficient. Further, the effect of improving blocking is insufficient. A more preferable compounding ratio is in the range of the general formula 2. General formula 2 A: 40 to 10 parts by weight B: 60 to 90 parts by weight A + B = 100 parts by weight

The composition of the present invention can adjust the biodegradation rate according to the use. For example, when used as an agricultural film, lignin can be eluted from the film by rainwater to make the film extremely thin, thereby promoting biodegradation. If a large amount of lignin having a high organic sulfur content in lignin and strong hydrophilicity is used, elution of lignin and biodegradation of the resin composition can be further promoted. The eluted lignin diffuses into the soil and biodegrades, but it can also be expected to be effective as a soil conditioner.

If the effect of promoting biodegradation is too large, the function as a plastic such as a film may be impaired.
For applications requiring a certain degree of water resistance, the content of organic sulfur in lignin is preferably 4% by weight or less. The organic sulfur content indicates the degree of hydrophilicity of lignin,
The higher the value, the higher the hydrophilicity.

The lignin particles are preferably fine particles sieved with a sieve having an opening of 40 μm or less. By using the fine particles, a more uniform and highly smooth molded product can be produced. In particular, the effect is great in an anhydrous melt extrusion method.

In the present invention, other water-soluble resins may be used in combination as long as the effects of the present invention are not impaired. In a natural system, starch such as corn starch, wheat, rice, potato, sweet potato, dextran, Natural high-molecular polysaccharides such as chitin and chitosan; plant gums such as gum arabic and gum arabic; plant gums such as yam, konjac, and trolley mallow; seaweeds such as alginic acid, funori, and agar; And animal proteins such as gelatin, glue, casein and the like. Further, in the semi-synthetic system, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, cellulose derivatives such as hydroxyethyl cellulose, oxidized starch,
Various modified starches such as phosphate esterified starch, etherified starch, cold water soluble starch and enzyme modified starch are exemplified.

In the present invention, a thermoplastic biodegradable resin may be used as long as the effects of the present invention are not impaired. As the thermoplastic biodegradable resin, biopolyesters such as polyhydroxybutyric acid and polyhydroxy valeric acid, polycaprolactone, polybutylene succinate, polybutylene adipate, polyethylene succinate, polybutylene succinate, polyglycolic acid,
Examples thereof include aliphatic polyesters such as polylactic acid.
Among these, polylactic acid, polycaprolactone, and polybutylene succinate, which are industrially produced in large quantities, are advantageous.

In the present invention, a plasticizer, a foaming agent, a dye, a pigment, a fertilizer, an agricultural chemical, etc., which are generally used, may be added as necessary. The plasticizer may be ethylene glycol, propylene glycol, or the like. Glycerin, polyethylene glycol and the like can be mentioned, and they are appropriately added without departing from the effects of the present invention. In consideration of biodegradability, polyethylene glycol has an average molecular weight of 400 to 200.
About 00 is preferable.

The amounts of these additives can be appropriately determined according to the purpose, but if the biodegradable composition of the present invention is contained in 50% by weight or more, the effect is exhibited.

The resin composition of the present invention is produced by mixing the above-mentioned lignin and polyvinyl alcohol at a fixed ratio, and the biodegradable resin composition thus produced is stretched and formed into a film by a molding apparatus. It is processed or molded.

Examples of the method for molding the resin composition include a casting method (solution casting method) and an extrusion method (melt extrusion method) using a T-die or an inflation die. In the solution casting method, the resin is dissolved in water, defoamed, filtered, and temperature controlled to prepare a membrane-forming stock solution.
A film is formed by casting from the slit to a Yankee drum or Yankee belt surface having a mirror surface. As a process after film formation, adjustment of solubility by drying and heat treatment, adjustment of application of moisture content by humidity control, improvement of surface properties such as slip property and blocking resistance by embossing and the like are performed.

The melt extrusion method is roughly divided into a water-containing method and an anhydrous method. In the water-containing method, a resin containing a suitable amount of water is added, and if necessary, a compound is added thereto.
After defoaming, it is extruded on a roll, and the extruded melt is gradually dried on several cooling rolls and wound up after a heat treatment, a humidity control and a trimming process. In the case of the water-containing method, it is preferable to adjust the frictional heat of the screw, the cylinder temperature, and the die temperature so that the melting temperature is 100 ° C. or less. The water content is 30
It is preferable to adjust in the range of ６０60%. On the other hand, in the anhydrous method, an additive such as a plasticizer is added to a resin that has been dried until it is almost anhydrous, mixed, put into an extruder, extruded, and taken up through a cooling step, a humidity control step, and a trimming step. In the case of the anhydrous method, the dissolution temperature must be set to a value equal to or higher than the softening point of polyvinyl alcohol.However, if the kneading temperature is excessively high, thermal decomposition of polyvinyl alcohol and lignin and reduction in molecular weight are promoted. And compounding ratio,
It is appropriately changed according to the kneading condition and the like.

Other production methods include a calender method of rolling with a calender roll, a biaxial stretching method, a hot pressing method, and the like, which can be appropriately used depending on the application and purpose.

The molded resin composition is cooled to produce a product as it is, or surface oxidation such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation, sand blast treatment or solvent treatment Surface unevenness, bonding by solvent, adhesive or heat, lamination processing such as extrusion method, hot melt method, dry method, wet method, gravure roll, Meyer bar, doctor blade, reverse roll coater,
Secondary processing such as coating processing using an air knife coater, vacuum deposition processing, antistatic processing, mold forming in which a film is brought into close contact with a forming die to form a desired mold, and vacuum forming processing are performed as necessary.

The processed products include, for example, agriculture, forestry and fishery materials such as multi-sheets, seedling mats, coated seeds, seed bands, seedling pots for transplantation, sandbags, curing sheets, packaging materials for pesticides, fishing lines, fishing nets, and thermal insulation. Materials and water retention sheets, civil engineering and construction materials such as formwork, fresh food trays and instant food containers, lunch boxes, food applications such as moisture absorbing sheets, hygiene products such as disposable diapers and sanitary products, office supplies, daily necessities, stationery and miscellaneous goods Or medical supplies such as sutures, fracture fixatives, medical films, and medical non-woven fabrics. In the textile industry, it is used as a dyeing aid, nadori paste, finishing agent, and the like. In the cosmetics industry and toiletry industry, it is used as an emulsifier, an emulsifier, a thickener, a gelling agent, a humectant, a film forming agent, and the like. In the civil engineering industry, it is used for admixtures such as concrete and mortar, soil conditioners, curing agents, water treatment agents, lubricants, lubricants, water retention agents, cement bags, etc.
For example, when used as a cement bag, it is not necessary to open the bag because it dissolves instantly when water is applied, so that scattering of cement can be prevented. In addition, there is an advantage that the contained lignin works as a dispersant.

[0028]

In the present invention, by blending polyvinyl alcohol and lignin in a certain ratio, problems in the production process such as biodegradability and blocking of polyvinyl alcohol are solved, but biodegradability is promoted. This is considered to be because the addition of lignin reduced the crystallinity of polyvinyl alcohol, and the hydrophilic effect of lignin significantly improved the solubility of the resin composition, which made it more susceptible to biodegradation.

It is presumed that the blocking was improved because the area where the polyvinyl alcohol and the inner wall of the die and the roll surface were in direct contact with each other was reduced by blending lignin, and there was no problem such as surface roughness. It is considered that a molded article having improved surface properties is obtained.

[0030]

EXAMPLES The present invention will be described below more specifically with reference to examples, but the present invention is not limited to the scope. In the examples, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified.

Evaluation Items and Evaluation Method (1) Solubility The molded body was immersed in a thermostat having a stirrer and set at a water temperature of 25 ° C., and it was confirmed whether or not the molded body was dissolved on a daily basis. The time required for dissolution was measured. The measurement period was limited to a maximum of 30 days. (2) State of occurrence of blocking Three hours after the start of the operation, the state of blocking occurring on the stretching roll was visually evaluated. ：: Not generated at all, ○: Almost not generated, Δ: Generated, ×: Remarkably generated (3) Surface roughness A molded body was sampled three hours after the start of operation, and the state of the surface roughness of the molded body was visually evaluated. did. ◎: Not generated at all, ：: Almost not generated, Δ: Generated, ×: Markedly generated (4) Moldability The ease of molding was visually judged. A: Easily moldable, A: Moldable, C: Difficult to mold, C: Extremely difficult to mold (5) Uniformity The uniformity of the molded body was visually evaluated. ◎: Very uniform, ：: Uniform, Δ: Non-uniform, ×: Extremely non-uniform (6) Organic sulfur content in lignin Inductively coupled plasma emission spectrometer (manufactured by Seiko Instruments Inc.) , SPS1700VRI), and the total sulfur content in lignin was determined from a previously prepared calibration curve. Next, the inorganic sulfur content in the lignin was determined using ion chromatography, and the organic sulfur content was determined from the difference between the total sulfur content and the inorganic sulfur content to calculate the sulfur content.

Example 1 30 parts of ligninsulfonic acid (trade name: Vanirex HW, manufactured by Nippon Paper Industries Co., Ltd.) having an organic sulfur content of 2.4% after passing through a 400-mesh sieve having a mesh size of 37 μm, polyvinyl alcohol Water was added to 70 parts (trade name: Poval, manufactured by Kuraray Co., Ltd.), mixed and kneaded with an intensive mixer, and a pellet-shaped molded body having a solid content of 45% was produced by a compression molding machine. This molded body was put into a general-purpose twin-screw extruder having a width of 50 mm, L / D = 30, and a compression ratio of 3 to perform melt kneading and defoaming.
The sheet was discharged from a T-die having a lip width of 0.3 mm, stretched, dried and conditioned to obtain a sheet-like molded body having a water content of about 6% and a thickness of 60 μm. At this time, the temperature of the cylinder of the extruder and the temperature of the T-die are set to 8 so that the melting temperature is about 90 ° C.
0 ° C., 95 ° C. each for C2, C3, C4, C5 and C6,
D1, D2 and D3 were each set at 90 ° C.

Example 2 Lignin sulfonic acid having an organic sulfur content of 2.4% based on 85 parts of polyvinyl alcohol (trade name: Vanilex HW, Nippon Paper Industries Co., Ltd.)
Was prepared according to Example 1 except that 15 parts of the same were mixed.

Example 3 Lignin sulfonic acid having an organic sulfur content of 2.4% with respect to 40 parts of polyvinyl alcohol (trade name: Vanilex HW, Nippon Paper Industries Co., Ltd.)
Sample was prepared in accordance with Example 1 except that 60 parts of was manufactured.

Example 4 Example 1 was repeated except that 70 parts of polyvinyl alcohol was mixed with 30 parts of kraft lignin (trade name: lignin alkali, manufactured by Aldrich Reagent) having an organic sulfur content of 1.3%. A sample for evaluation was prepared according to the above.

Example 5 Lignin sulfonic acid (trade name: Sun Extract P252, Nippon Paper Industries Co., Ltd.) having an organic sulfur content of 4.4% based on 70 parts of polyvinyl alcohol
Samples for evaluation were prepared in accordance with Example 1 except that 30 were mixed.

Example 6 Lignin sulfonic acid (trade name Pearlrex NP, Nippon Paper Industries Co., Ltd.) having an organic sulfur content of 5.8% based on 70 parts of polyvinyl alcohol
Samples for evaluation were prepared in accordance with Example 1 except that 30 were mixed.

Example 7 Lignin sulfonic acid having an organic sulfur content of 2.4% based on 60 parts of polyvinyl alcohol (trade name: Vanilex HW, Nippon Paper Industries Co., Ltd.)
30 parts), carboxymethylcellulose (CMC,
Product name Sunrose F10LC, manufactured by Nippon Paper Industries Co., Ltd.
A sample for evaluation was prepared according to Example 1 except that 0 part was blended.

Example 8 An average plasticizer content of 30 parts of ligninsulfonic acid (trade name: Vanilex HW, manufactured by Nippon Paper Industries Co., Ltd.) having an organic sulfur content of 2.4% and 70 parts of polyvinyl alcohol was used. Polyethylene glycol having a molecular weight of 20,000 is added and mixed, and the water content is about 4% and the thickness is 6
An evaluation sample was prepared in accordance with Example 1 except that a sheet-shaped molded product of 0 μm was manufactured. At this time, the temperature of the cylinder and T-die of the extruder was 140 ° C. for C1, C2, C
3, C4, C5 and C6 at 170 ° C. each, D1, D2,
D3 was set at 170 ° C each.

Example 9 A sample for evaluation was prepared in accordance with Example 8 except that lignin was not sieved.

[Comparative Example 1] Polyvinyl alcohol was added to 10
A sample for evaluation was prepared according to Example 1 except that 0 part was blended.

Comparative Example 2 Lignin sulfonic acid having an organic sulfur content of 2.4% with respect to 95 parts of polyvinyl alcohol (trade name: Vanirex HW, Nippon Paper Industries Co., Ltd.)
) Was prepared according to Example 1 except that 5 parts were prepared.

Comparative Example 3 Lignin sulfonic acid having an organic sulfur content of 2.4% with respect to 25 parts of polyvinyl alcohol (trade name: Vanirex HW, Nippon Paper Industries Co., Ltd.)
Was prepared according to Example 1 except that 75 parts of the same were mixed.

Comparative Example 4 Example 1 was repeated except that 100 parts of ligninsulfonic acid (trade name: Vanilex HW, manufactured by Nippon Paper Industries) having an organic sulfur content of 2.4% was blended.
A sample for evaluation was prepared according to the above.

Table 1 shows the above results.

[0046]

[Table 1]

[0047]

As is clear from Table 1, Examples 1 to 9
The molded body obtained in 1) starts dissolving instantly when immersed in a constant temperature bath, the period required for complete dissolution is short, and the solubility is excellent. In addition, die separation, good separation with the stretching roll, no occurrence of blocking was observed, no surface roughness was observed on the surface of the molded body, high smoothness was obtained, and a molded body with uniform and good surface properties was obtained. .

On the other hand, Comparative Examples 1 and 2 hardly dissolved even after 30 days. In addition, the occurrence of blocking and surface roughness was remarkable. In Comparative Example 3, molding was difficult, and a uniform molded product could not be obtained. In Comparative Example 4, a molded product could not be obtained, and other items could not be evaluated. Therefore, the effect of the resin composition obtained in the present invention is clear.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshito Nishimori 2-8-1 Iidacho, Iwakuni-shi, Yamaguchi Japan Nippon Paper Industries Co., Ltd. Chemical Development Laboratory F-term (reference) 4J002 AH00W BE02X

Claims (3)

[Claims] 1. A resin composition comprising lignin (A) and polyvinyl alcohol (B) at a ratio represented by the general formula 1. General formula 1 A: 70 to 10 parts by weight B: 30 to 90 parts by weight A + B = 100 parts by weight 2. The resin composition according to claim 1, wherein the lignin (A) has an organic sulfur content of 4% by weight or less. 3. The resin composition according to claim 1, wherein lignin powder is passed through a sieve having an opening of 40 μm or less.