JP2961135B2 - Biodegradable plastic composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biodegradable resin and
The present invention relates to a biodegradable plastic composition comprising a gelatinized starch containing a viscosity stabilizer and a method for producing the same.

[0002]

2. Description of the Related Art Biodegradable plastics have attracted attention as plastics that have less impact on the environment, and various production methods have been proposed. In particular, it is desirable to increase the blending ratio of natural products such as starch as much as possible in all aspects including reducing the burden on the environment, saving petroleum resources, and further reducing manufacturing costs. And manufacturing methods have been proposed. However, if starch is simply added as a bulking agent to a synthetic biodegradable resin, the flowability is poor in the processing step, and if the molding is forcibly performed, burning (coloring brown) is likely to occur, and the resulting mixture is obtained. Inconveniences such as the remarkable decrease in the physical properties of the rubber are caused. Attempts have been made to improve the moldability of the mixture system by imparting thermoplasticity to the starch by pregelatinizing the starch in advance, but also in this case, there is a problem that the physical properties of the mixture do not increase. This tendency is remarkable especially when the ratio of starch to the synthetic biodegradable resin increases, and especially when the amount of the gelatinized starch exceeds the amount of the synthetic biodegradable resin, the phase is reversed and the gelatinized starch becomes a matrix phase. And the strength of the resulting composition tends to decrease.

It is important to control the viscosity of the gelatinized starch so as to prevent this phase inversion and to keep the synthetic biodegradable resin in the matrix phase even in a high gelatinized starch concentration region. Agents are being studied. As a result, the synthetic biodegradable resin was able to be retained as a matrix phase even in a region where the gelatinized starch concentration was high to some extent, but in fact the composition was not yet sufficiently physical. Currently (Reference: JP-A-6-4927)
6, JP-A-8-188671). For example, it stabilized gelatinized starch and polycaprolactone in a weight ratio of 1: 1, but the breaking strength of the resulting composition is blended system is much 800 N / cm ² from 700 N / cm ^2, the tensile elongation (elongation at break) is It reaches only about tens of percent. Rigidity and tensile strength can also be improved by the addition of fillers, but tensile elongation and impact strength are rather reduced by the addition of fillers. Unless a plastic having impact resistance is developed, it can be said that there is no point in developing a biodegradable plastic. Thus, in developing a composite biodegradable plastic composed of stabilized gelatinized starch and a synthetic biodegradable resin, it is important to maintain a high level of tensile elongation while maintaining the rigidity and strength of the plastic. Very important (good elongation compositions generally exhibit good impact strength).

[0004]

SUMMARY OF THE INVENTION The present invention relates to a gelatinized starch containing a biodegradable resin and a viscosity stabilizer (hereinafter referred to as viscosity stabilized gelatinization).
It is an object of the present invention to provide a biodegradable plastic composition comprising starch (which is also referred to as starch) having an improved tensile elongation and a method for producing the same.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, (A) a biodegradable resin, (B) a gelatinized starch containing a viscosity stabilizer, and (C) a tensile elongation improver, the tensile elongation improver (C) comprises: A biodegradable plastic composition is provided which is at least one aliphatic ester selected from sorbitan fatty acid esters, polyethylene glycol difatty acid esters and propylene glycol monofatty acid esters. Further, according to the present invention, in the method for producing the composition, (A) a biodegradable resin, and (B) a low viscosity resin.
Gelatinized starch containing a stabilizing agent and (C) sorbitan fatty acid ester
, Polyethylene glycol difatty acid ester and professional
Selected from pyrene glycol mono fatty acid esters
There is provided a method for producing a biodegradable plastic composition, which comprises melt-kneading a tensile elongation improver comprising at least one aliphatic ester .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As the biodegradable resin (A) used in the present invention, various known resins can be used.
These include, for example, polycaprolactone (P
CL), caprolactone / butyrolactone copolymer, aliphatic polyesters such as condensates (polyesters) of diols (such as 1,4-butanediol and ethylene glycol) and dicarboxylic acids (such as succinic acid and adipic acid), and fats Group polycarbonate and the like. Its melting point is 45
To 150 ° C, preferably 55 to 130 ° C. Also,
Its number average molecular weight is 30,000 or more, preferably 30,000 to
500,000.

In the present invention, a stabilized gelatinized starch (B) is used. In general, starch is easily gelatinized by heating, but immediately after gelatinization, aging phenomenon (starch recrystallization) occurs, causing a sharp increase in viscosity and stable when blended with a synthetic polymer. Difficult to make a perfect composition. This tendency is particularly strong in high-viscosity gelatinized starch having a small amount of water (about 30% by weight or less), and prevention of aging in a high-viscosity region is an important issue. However, this countermeasure has already been studied in various ways, and it has been known that the addition of urea, glycerin esters, polyethylene glycol monoesters, or low molecular weight aliphatic polyesters is effective for this purpose. Specific examples of these viscosity stabilizers are as follows. (Glycerin ester) mono-, di- or tri-fatty acid monoglycerides such as diacetylglycerin monostearate and triacetin; polyglycerides such as diglycerin monooleate, decaglycerin pentastearate and hexaglycerin hexastearate (glycerin polymerization degree 2 to 10) )etc. (Polyethylene glycol monoester) Polyethylene glycol monofatty acid ester such as polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol monolaurate (number average molecular weight 500 to 200)
0). (Low molecular weight aliphatic polyester) ethylene glycol,
Diol and adipic acid such as butylene glycol, polycondensation products of dicarboxylic acids such as succinic acid; polycaprolactone, lactic acid, there is hydroxyalkanoate like made of a low polymers such as hydroxybutyrate, especially the terminal carboxylic acid of the C ₂ ~
Those esterified with an alcohol of C ₈ are preferred. The number average molecular weight of these low molecular weight aliphatic esters is 50
0 to 2000.

[0008] The preferred viscosity-stabilized gelatinized starch used in the present invention is (i) 65-85% by weight of starch, preferably 70-85% by weight.
80% by weight, (ii) 13 to 30% by weight of water, preferably 13 to 25% by weight, and (iii) at least one selected from urea, glycerin ester, polyethylene glycol monoester and low molecular weight aliphatic polyester. Of a viscosity stabilizer of 2 to 20% by weight, preferably 5 to 15% by weight. The ratio of the viscosity-stabilized gelatinized starch (B) used in the present invention is 100 biodegradable resin (A).
50 to 300 parts by weight, preferably 100 to 300 parts by weight per part by weight
The ratio is 200 parts by weight. If it exceeds the above range, it becomes difficult to hold the matrix phase of the composition in the biodegradable plastic phase, which is not preferable.

The tensile elongation improver (C) used in the present invention
Consists of at least one fatty acid ester selected from (i) sorbitan fatty acid esters, (ii) polyethylene glycol difatty acid esters and (iii) propylene glycol monofatty acid esters. The sorbitan fatty acid ester includes a monoester, a diester and a triester thereof, and the use of a monoester is particularly preferable. In this ester, the fatty acid component thereof has 8 to 22 carbon atoms, preferably 12 to 12 carbon atoms.
A fatty acid having 18 alkyl groups or alkenyl groups is used. Such fatty acids include lauric acid, stearic acid, oleic acid, palmitic acid and the like. As the polyethylene glycol difatty acid ester, those represented by the following general formula (1) are used.

Embedded image In the above formula, R ¹ has 2 to 22 carbon atoms, preferably 8 to 18 carbon atoms.
Represents an alkyl group or an alkenyl group. n shows the average degree of polymerization, and shows the number of 10-300, preferably 20-200. As the propylene glycol monofatty acid ester, those represented by the following general formula (2) are used.

Embedded image In the above formula, R is a group having 8 to 22 carbon atoms, preferably 12 to 18 carbon atoms.
Represents an alkyl group or an alkenyl group. Preferred fatty acid esters used in the present invention include propylene glycol monolauryl ester, monostearyl ester, monooleate ester, monopalmitate ester and the like. The tensile elongation improver (C) used in the present invention.
Is used per 100 parts by weight of the biodegradable resin (A).
The proportion is 2 to 20 parts by weight, preferably 3 to 15 parts by weight. If the ratio of the tensile elongation improver (C) is less than the above range, the effect of improving the elongation of the composition will be insufficient, while if it exceeds the above range, the mechanical strength of the composition will be insufficient. .

The composition of the present invention may contain conventional auxiliary components such as fillers, colorants, flame retardants and the like.

The composition of the present invention can be produced by a melt-kneading method. That is, the biodegradable resin (A), the viscosity-stabilized gelatinized starch (B), the tensile elongation improver (C) and the auxiliary component are combined with the components (A), (B) and (C).
Are mixed while heating so as to maintain a molten state, and the obtained molten mixture is formed into a pellet and cooled. The pellet-like composition thus obtained is used as a material for thermoforming such as injection molding, extrusion molding, and press molding.

[0012]

Next, the present invention will be described in more detail with reference to examples.

EXAMPLE 1 18 g of water, 6 g of urea and 16 g of diacetylglycerin monostearate (Poem G002, manufactured by Riken Vitamin Co.) were added to 160 g of corn starch manufactured by Nippon Cornstarch Inc. containing 12.5 wt% of water and mixed well. 90
The mixture was introduced into a 15 mm twin-screw extruder set at a temperature of ° C., and kneaded and extruded to obtain about 150 g of gelatinized starch pellets. 100 g of the pellet and 100 g of polycaprolactone (TONE Polymer P767 manufactured by Union Carbide)
Was mixed with 10 g of sorbitan laurate (Poem L-20 manufactured by Riken Vitamin Co., Ltd.), kneaded and extruded again at 90 ° C. with a 15 mm twin screw extruder, and repelletized. An appropriate amount of this was placed in a spacer having a thickness of 0.5 mm between two iron plates and heated and pressed together with the iron plate to obtain a press-formed plate having a thickness of approximately 0.5 mm. A No. 2 dumbbell-type test piece was cut out from the press-formed plate, and the strength and elongation were measured using a tensile tester (Autograph AGS500D, manufactured by Shimadzu Corporation) in accordance with JIS 7113. As a result, the breaking strength was 944 N / cm ² and the breaking elongation was 258%.

Example 2 Example 1 was repeated except that 10 g of sorbitan laurate was replaced by 12 g of polyethylene glycol dilaurate (Ionet DL-200 manufactured by Sanyo Chemical Co., Ltd., polyethylene glycol part polymerization degree: about 200). The experiment was performed in the same manner as in The breaking strength of the obtained test piece was 84.
4N / cm ² and elongation at break were 246%.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that sorbitan laurate was not used at all. Although the breaking strength of the obtained test piece was 811 N / cm ² , its breaking elongation was as small as 46%.

Example 3 18 g of water, 6 g of urea and 16 g of polyethylene adipate (PN-150, manufactured by Asahi Denka Kogyo KK, molecular weight: about 1100) may be added to 160 g of corn starch manufactured by Nippon Corn Starch containing 12.5 wt% of water. Mix and mix 9
The mixture was introduced into a 15 mm twin-screw extruder set at 0 ° C. and kneaded and extruded to obtain about 150 g of gelatinized starch pellets. 120 g of the pellet and 100 g of polycaprolactone (TONE Polymer P767 manufactured by Union Carbide) are mixed with 10 g of polyethylene glycol dilaurate (Ionet DL-200 manufactured by Sanyo Chemical Co., Ltd .;
The mixture was kneaded and extruded at 90 ° C. with a 5 mm twin screw extruder, and re-pelletized. This is molded with a hot press and has a thickness of about 1mm
Sheet was obtained. A No. 2 dumbbell-type test piece was cut out from the press-formed sheet, and the strength and elongation were measured. Its breaking strength was 770 N / cm ² and breaking elongation was 192%.

Example 4 An experiment was conducted in the same manner as in Example 3 except that 10 g of propylene glycol monooleate (PO-100 manufactured by Riken Vitamin) was used instead of 10 g of polyethylene glycol dilaurate. The obtained test piece had a breaking strength of 850 N / cm ² and a breaking elongation of 141%.

Comparative Example 2 An experiment was conducted in the same manner as in Example 3 except that polyethylene glycol dilaurate was not used at all. Although the breaking strength of the obtained test piece was 720 N / cm ² , its breaking elongation was as small as 35%.

Example 5 Gelatinized starch pellets 10 prepared in the same manner as in Example 3
0 g and 100 g of polybutylene succinate adipate copolymer (Bionole 3010, manufactured by Showa Polymer Co., Ltd.)
10 g of polyethylene glycol dilaurate (Ionnet DL-200, manufactured by Sanyo Chemical Co., Ltd.) was added to the mixture, and the mixture was kneaded and extruded at 90 ° C. using a 15 mm twin-screw extruder to re-pelletize. This is press-formed to form a sheet with a thickness of about 1 mm, from which a test piece is cut out.
When the physical properties were measured, the breaking strength was 920 N / c.
m ² and elongation at break were 215%.

Comparative Example 3 An experiment was conducted in the same manner as in Example 5 except that no polyethylene glycol dilaurate was used. Although the breaking strength of the obtained test piece was 885 N / cm ² , its breaking elongation was as small as 38%.

The experimental conditions and results in Examples 1 to 5 and Comparative Examples 1 to 3 are summarized in Table 1.

[0022]

[Table 1]

[0023]

Industrial Applicability The composition of the present invention has biodegradability and shows high degradability to enzymes such as amylase and rivase.
The composition of the present invention shows a high elongation at break due to the inclusion of a special tensile elongation rate improver, unlike the conventional composition comprising a biodegradable resin and a stabilized gelatinized starch. Accordingly, the composition of the present invention is particularly suitable as a molding material for thin molded articles such as films and containers.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirokazu Kameyama 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Oriental Maritime Building 8th Floor Project Research Institute for Global Environmental Innovation (CO2) ) Inventor Yutaka Tokiwa 1-3-3 Higashi, Tsukuba City, Ibaraki Pref. Examiner Susumu Sugihara, Institute of Biotechnology, Industrial Technology Research Institute (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 1/00-101 / 14 C08K 5/00-5/59

Claims (4)

(57) [Claims] (A) a biodegradable resin, and (B) viscosity stabilization.
Agent-containing gelatinized starch and (C) a tensile elongation improver,
The biodegradable plastic composition, wherein the tensile elongation improver (C) is at least one aliphatic ester selected from sorbitan fatty acid esters, polyethylene glycol difatty acid esters and propylene glycol monofatty acid esters. Stuff. 2. The gelatinized starch containing a viscosity stabilizer comprises : (i) 65 to 85% by weight of starch; (ii) 13 to 30% by weight of water;
(Iii) at least one type of viscosity stabilizer 2 to 20 selected from urea, glycerin esters, polyethylene glycol monoesters and low molecular weight aliphatic polyesters
2. The composition of claim 1 which comprises a mixture with a weight percent. 3. A biodegradable resin (A) 100 parts by weight of per proportion of the viscosity stabilizer containing gelatinized starch (B) 50 to
The composition according to any one of claims 1 to 3, wherein the composition is 300 parts by weight, and the proportion of the tensile elongation improver (C) is 2 to 20 parts by weight. 4. The method for producing the composition according to claim 1, wherein (A) a biodegradable resin, and (B) a low viscosity resin.
Gelatinized starch containing a stabilizing agent and (C) sorbitan fatty acid ester
, Polyethylene glycol difatty acid ester and professional
Selected from pyrene glycol mono fatty acid esters
A method for producing a biodegradable plastic composition, comprising melt-kneading a tensile elongation rate improver comprising at least one aliphatic ester .