JPH08143710A - Biodegradable resin composition - Google Patents

Abstract

PURPOSE: To obtain a resin composition having improved water resistance as well as biodegradability by incorporating an esterified starch having a degree of substitution (DS) of a specified or higher value, an esterified cellulose having a DS of a specified or higher value, and an ester-type plasticizer as the essential components.

CONSTITUTION: Each of the esterified starch (a) and the esterified cellulose (b) should have a DS of 0.4 or higher. In particular, the esterified starch is desirably a starch acetate and/or a starch propenoate of a Ds of 1.0-2.8, and the esterified cellulose is desirably cellulose acetate and/or cellulose propionate and/or cellulose butyrate of a DS of 1.0-2.8. The ester-type plasticizer (c) is desirably a phthalic ester or a polyhydric alcohol ester. It is suitable to use high-amylose starch having an amylose content of at least 50% is used as the starting material for the esterified starch. The amounts of the three components (a), (b) and (c) are such that a/b=10/90 to 95/5 by weight, and 5-100 pts.wt. (c) is present per 100 pts.wt. total of components (a) and (b).

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biodegradable thermoplastic resin composition having water resistance.

[0002]

2. Description of the Related Art Since most of discarded plastic remains without being decomposed in a natural environment, social concerns have recently been increasing regarding a treatment problem after use of plastic products. Therefore, there is a demand for a biodegradable plastic that is rapidly decomposed in soil or water after the purpose of use is achieved. Against this background, starch, which is a reproducible natural resource, is low cost and easily biodegradable, has been attracting attention, and a biodegradable plastic (biodegradable resin composition) based on starch has been proposed. There is. (JP-A-5
(See No. 32824, etc.)

[0003]

However, these starch-based biodegradable resin compositions have excellent biodegradability (starch has a milder biodegradable condition and a faster decomposition rate than cellulose). Although it has, the water resistance is not sufficient,
This has been one of the reasons that the applicable products (uses) are limited.

Further, by esterifying starch,
Being able to improve water resistance is "STARCH: Chemistry and Te
chnology, Vol 12, p389 ~ 391 (1967) ", but still it cannot be said to have sufficient water resistance for practical use.

In view of the above, the present invention provides a biodegradable resin composition capable of remarkably improving the water resistance of a resin molded product while maintaining good starch biodegradability. With the goal.

[0006]

Means for Solving the Problems As a result of intensive efforts for development, the present inventors have made intensive efforts to overcome the above-mentioned problem of the starch-based biodegradable resin composition that the water resistance is insufficient. It was found that by blending esterified starch with esterified cellulose, a synergistic effect is exhibited and the water resistance is improved as compared with the value obtained from the arithmetic average value of the physical property values of both, and the present invention is completed. Came to.

The biodegradable resin composition of the present invention is characterized by containing three components of esterified starch, esterified cellulose and ester type plasticizer as essential components.

[0008]

Detailed Description of Means Each means of the present invention will be described in detail below.

(1) Starch as a raw material of esterified starch includes corn, potato, potato, wheat,
Raw starch such as sago, cassava, tapioca, rice, bean, and kudzu, bracken, lotus starch, and further, these are physically modified starches such as alpha (α) -modified, enzyme-modified starch such as enzymatic decomposition, acid treatment, Chemically modified starch treated with hypochlorous acid or etherified can be used.

In particular, high amylose starch having an amylose content of 50% or more has excellent strength when it is formed into a final resin molded product and film (hereinafter, simply referred to as "resin molded product"), and is therefore preferably used. It is possible.

As the esterified acid of esterified starch,
The following various organic acids / inorganic acids can be preferably used.

Saturated fatty acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid and stearic acid, and acrylic acid, crotonic acid, isocrotonic acid,
Unsaturated fatty acids such as oleic acid, erucic acid and sorbic acid.

Aliphatic saturated / unsaturated dicarboxylic acids such as malonic acid, succinic acid, alkenylsuccinic acid, maleic acid and fumaric acid.

Inorganic acids such as phosphoric acid, urea phosphoric acid, etc.

Of these, lower saturated fatty acids such as acetic acid and propionic acid can be preferably used because they have excellent strength in the final resin molded product.

The esterified starch has a degree of substitution (DS) of 0.4.
Or more (total substitution DS3), preferably DS1.0 to 2.8
Use one. If the DS is less than 0.4, it is difficult to impart water resistance to the resin molded product, and the miscibility (Compatibility) when blended with another resin is poor.

The esterified starch can be produced, for example, by heating and dissolving the starch in dimethyl sulfoxide and reacting it with anhydrous acid in the presence of an alkali catalyst to obtain the desired esterified starch.

(2) As the esterified acid of esterified cellulose, those used in the above esterified starch can be used. Of these, lower saturated fatty acids such as acetic acid, propionic acid, butyric acid, and mixed acids thereof have excellent strength when formed into a final resin molded product, as in the case of esterified starch, and are therefore preferably used. It is possible.

As the esterified cellulose, one having a DS of 0.4 or more, preferably a DS of 1.0 to 2.8 is used.
If the DS is less than 0.4, it is difficult to impart water resistance to the resin molded product. (3) As the ester-type plasticizer, it is possible to use one or more selected from the following examples.
In particular, a phthalic acid ester or a polyhydric alcohol ester is preferable because it has excellent miscibility with both esterified starch and esterified cellulose.

This ester-type plasticizer plasticizes the resin composition at a relatively low temperature during the molding process, makes it difficult for the resin composition to be thermally deteriorated, and imparts good molding processability. This is because. The ester type is used as the plasticizer in order to ensure compatibility with both esterified starch and esterified cellulose.

Dimethyl phthalate, diethyl phthalate,
Phthalates such as dibutyl phthalate, dioctyl phthalate, ethylphthalylethyl glycolate, butyl oleate, glycerin monooleate, butyl adipate, aliphatic basic acid esters such as di-n-hexyl adipate, triacetin , Fatty acid mono-di-triglycerides such as diacetylglycerin, tripropionylglycerin, glycerin monostearate, polyhydric alcohol esters such as sucrose octaacetate and diethylene glycol dibenzoate, oxyacid esters such as methyl acetylricinoleate and triethyl acetylcitrate, Phosphoric acid esters such as tributyl phosphate and triphenyl phosphate Epoxidized soybean oil, epoxidized castor oil, epoxy ester such as alkyl epoxy stearate (4) The above three components The composition ratio of the esterified starch (a) to the esterified cellulose (b) and the ester type plasticizer (c) is usually (a) / (b) = 10/90 to 95/5 (weight ratio),
And (c) 5 to 100 relative to 100 parts by weight of (a) + (b)
Parts by weight. Preferably, (a) / (b) = 40 / 60-
80/20 (weight ratio), and (c) 30 to 60 parts by weight with respect to 100 parts by weight of (a) + (b).

If the amount of esterified cellulose is too small, it is difficult to secure water resistance to the resin molded product, and if the amount of esterified cellulose is too large, it is difficult to impart the excellent biodegradability of starch to the resin molded product.

If the amount of the plasticizer is too small, the resin composition must be heated to a relatively high temperature during the molding process, which may cause thermal deterioration of the resin composition.
If too much, it becomes difficult to secure the strength of the resin molded product.

The above-mentioned three components (esterified starch, esterified cellulose and plasticizer) are blended by mixing esterified cellulose and ester type plasticizer in advance to prepare a masterbatch, and then kneading with esterified starch. Preferably.

As the kneading method, known kneaders such as an open roller, a kneader and an extruder can be used. If necessary, the composition of the present invention may further contain a filler, a heat stabilizer, an antioxidant, a coloring agent, an antistatic agent, an ultraviolet absorber, and the like.

Further, the resin composition of the present invention can be used as a molding material for injection molding, extrusion molding, blow molding, vacuum molding, calender molding, foam molding, powder molding, etc., like general-purpose thermoplastic resins. You can

As applicable products, packaging materials (film, sheet, bottle, box, can carrier), agricultural materials (agricultural film, binding tape), consumer products (diaper back sheets, shopping bags, garbage) It can be applied to various things such as bags) and kitchen materials (cups, trays, plates, knives, forks, spoons).

[0028]

The biodegradable resin composition of the present invention has a DS
As a result of the constitution containing three components of esterified starch of 0.4 or more, esterified cellulose of DS 0.4 or more, and ester type plasticizer as essential components, as shown in Examples described later, the water resistance is dramatically improved. Can be improved,
Furthermore, the excellent biodegradability of starch can be retained. On the other hand, the biodegradable resin composition of the present invention can be applied to products that come into contact with water even though it is a biodegradable resin.

[0029]

EXAMPLES AND COMPARATIVE EXAMPLES Test examples conducted to confirm the effects of the present invention will be described below.

(1) Esterified starch was prepared as follows.

Starch acetate: High amylose corn starch (amylose content 70%, water 1
%) 75 g and dimethylsulfoxide 500 ml were added, and the mixture was heated with stirring at 80 ° C. to dissolve the starch. Then, 85 g of sodium hydrogen carbonate and 4.1 g of dimethylaminopyridine previously dissolved in 60 mL of dimethyl sulfoxide.
Was added. Thereto, 104 g of acetic anhydride was added through a dropping funnel over 1 hour. While dropping, keep the liquid temperature at 45 ℃,
Further, after maintaining for 15 minutes as it is, the reaction solution was mixed with water 2.
It was put into 5 L while stirring. The solid matter was filtered, again put into 2.5 L of water, and washed. The same operation was performed 5 times in total, and finally the solid was dried with hot air at 60 ° C. for 24 hours to obtain DS2.1 starch acetate. The yield was 95%.

Starch propionate In the above method for producing starch acetate, 101 g of propionic anhydride was used in place of acetic anhydride to obtain a starch propionate of DS1.6. The yield was 95%.

(2) As the esterified cellulose, "acetate tenex 0660" cellulose acetate (DS2.5) manufactured by Teijin Limited was used.

(3) As the plasticizer, triacetin (TA) or diethyl phthalate (DEP) (both manufactured by Katayama Kagaku Co., Ltd.) was used.

(4) Preparation of Blend and Specimen First, esterified cellulose and a plasticizer were blended according to the formulation shown in Table 1 using a kneading machine “Laboplast Mill C type” (manufactured by Toyo Seiki Co., Ltd.). Kneading was performed for 15 minutes under the condition of 175 ° C. × 50 rpm. The kneaded product was formed into a sheet by a hot press at 170 ° C., and then cut into strips. The flaky pellets and esterified starch were blended in a predetermined composition again using the Labo Plastomill under the conditions of 165 ° C. × 50 rpm for 15 minutes, and a sheet having a thickness of 1 mm was formed by hot pressing at 150 ° C. This sheet was cut into 5 × 5 cm □ to obtain a test piece.

(5) Measurement of water absorption rate and soluble component rate The absorption rate was measured according to JIS K7209.

The test piece was immersed in distilled water for 24 hours in a constant temperature and constant temperature room at 23 ° C. and 50% RH, and the weight before and after water absorption was calculated according to the following formula.

Water absorption rate (%) = (M2-M3) × 100 / M1 M1 mass after drying before water absorption M2 mass after absorbing water M3 mass after re-drying after absorbing water The soluble component ratio was calculated by the following formula. .

Soluble component ratio (%) = (M1−M3) × 100 / M1 (6) Measurement results: The test results are shown in Table 1, and in order to facilitate understanding, three components are shown in FIGS. The graphs are divided into groups A and B having the same combination but different compositions.

From these test results, the arithmetic mean value (indicated by a dotted line) obtained from the water absorption rate and the soluble component rate of each of the esterified starch and the esterified cellulose alone.
Compared with the above, it can be seen that the blends of both have a significantly lower water absorption rate and a soluble component rate, and synergistically improved water resistance.

[0041]

[Table 1]

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the water absorption rate and the mixing ratio of esterified starch and esterified cellulose in the test example of group A.

FIG. 2 is a graph showing the relationship between the mixture ratio of esterified starch and esterified cellulose and the soluble component ratio.

FIG. 3 is a graph showing the relationship between the water absorption rate and the mixing ratio of esterified starch and esterified cellulose in the test example of group B.

FIG. 4 is a graph showing the relationship between the mixture ratio of esterified starch and esterified cellulose and the soluble component ratio.

Front Page Continuation (72) Inventor Raman Narayan United States 48909 Lansing Collins Road, Michigan 3900 Michigan Biotechnology Institute

Claims (4)

[Claims] 1. An esterified starch (a) having a degree of substitution (DS) of 0.4 or more and an esterified cellulose (b) having a DS of 0.4 or more.
And a biodegradable resin composition comprising three components of an ester type plasticizer (c) as essential components. 2. The composition according to claim 1, wherein the composition of the three components is (a) / (b) = 10/90 to 95/5 (weight ratio),
A biodegradable resin composition, characterized in that 5 to 100 parts by weight of (c) is mixed with 100 parts by weight of (a) + (b). 3. The cellulose acetate according to claim 1, wherein the esterified starch is a starch acetate and / or a propionic acid starch having a DS of 1.0 to 2.8, and the esterified cellulose is a DS1.0 to 2.8. And / or cellulose propionate and / or cellulose butyrate, and the ester-type plasticizer is a phthalic acid ester or a polyhydric alcohol ester. 4. The biodegradable resin composition according to claim 1, wherein the esterified starch is prepared from high amylose starch having an amylose content of 50% or more.