JP2012031329A - Biodegradable resin composition and molded article obtained by molding the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin composition having favorable mechanical strength and a controlled biodegrading rate, and to provide a molded article of the composition.SOLUTION: The biodegradable resin composition contains an aliphatic polyester resin, starch and a plasticizer, and the composition contains a synthetic organic compound-based biodegradation inhibitor in an amount of 0.001 part by weight or more and 3 pts.wt or less with respect to 100 pts.wt in total of the aliphatic polyester resin, starch and plasticizer. The molded article is obtained by molding the above composition.

Description

  The present invention relates to a biodegradable resin composition having good mechanical strength and a controlled biodegradation rate, and a molded article thereof.

  Conventionally, paper, plastic film, aluminum foil, and the like have been used in a wide range of applications such as liquids and granules for various foods, medicines, miscellaneous goods, solid packaging materials, agricultural materials, and building materials. In particular, plastic films are excellent in strength, water resistance, moldability, transparency, cost, etc., and are used in many applications as bags and containers.

  In recent years, biodegradable resins have attracted attention from the viewpoint of protecting the global environment. The aliphatic polyester resin as the biodegradable resin has good moldability, but, for example, the mechanical properties of the film are insufficient (see, for example, Patent Document 1).

  In addition, as an attempt to improve the mechanical properties and cost of aliphatic polyester resins, a composition of starch and aliphatic polyester is also prepared. However, even if the mechanical properties are improved, the starch itself is fatty. Since the biodegradability rate is faster than that of the group polyester, the mechanical strength may be reduced during use (see, for example, Patent Document 2).

  Moreover, in order to suppress the biodegradation rate of the biodegradable resin itself, an example using an inorganic antibacterial agent that elutes antibacterial metal ions is disclosed (for example, see Patent Document 3). There is no mention of physical properties or biodegradability related to soil contamination and starch combination, and there is still concern about actual use.

  In addition, from the viewpoint of controlling the biodegradation rate of the biodegradable resin, an example of using a plant-derived organic substance as a biodegradable rate promoting substance and using a natural organic antibacterial agent as a biodegradable rate inhibitor Is disclosed (for example, see Patent Document 4). Although it seems to be sufficiently effective from the viewpoint of controlling the biodegradability rate, it is particularly effective for the dispersibility of plant-derived organic substances that are biodegradable rate accelerators and the dispersibility of naturally-derived organic antibacterial agents. Is not taken into account, and since there is a large amount of naturally-occurring organic antibacterial agent, there is a concern that the mechanical properties may be deteriorated.

JP-A-8-239461 Japanese Patent Laid-Open No. 5-39381 JP-A-5-117507 JP 2001-323177 A

  This invention is made | formed in view of the said background art, The subject is providing the biodegradable resin composition which has favorable mechanical strength, and the biodegradation rate was controlled, and its molded object. .

  As a result of intensive studies to solve the above problems, the present inventors have melt-kneaded polyester resin (biodegradable resin), starch, plasticizer and biodegradation inhibitor containing dicarboxylic acid and diol as structural units. Therefore, since the starch is plasticized by the plasticizer, the resulting biodegradable resin composition has good mechanical strength, and a synthetic organic compound-based biodegradation inhibitor should be used. Thus, it was found that the biodegradability rate promoted by starch addition can be appropriately controlled, and the present invention has been completed.

  That is, the first aspect of the present invention is 0.001 part by weight or more 3 with respect to 100 parts by weight of the total amount of aliphatic polyester resin, starch, plasticizer, and aliphatic polyester resin, starch, and plasticizer. The present invention provides a biodegradable resin composition containing no more than parts by weight of a synthetic organic compound-based biodegradation inhibitor.

  In the first invention, the plasticizer is preferably an organic compound containing water or a hydroxyl group and having a molecular weight of 3000 or less.

  In the first aspect of the present invention, the synthetic organic compound biodegradation inhibitor is preferably a benzimidazole compound.

  In 1st this invention, content of an aliphatic polyester-type resin is 20 to 90 weight part with respect to 100 weight part of total amounts of aliphatic polyester-type resin, starch, and a plasticizer, Content of starch Is preferably 9 to 70 parts by weight, and the plasticizer content is preferably 1 to 20 parts by weight.

  2nd this invention provides the molded object formed by shape | molding the resin composition which concerns on 1st this invention.

  The molded body according to the second aspect of the present invention is preferably a film formed by inflation molding.

  According to the present invention, it is possible to provide a biodegradable resin composition having good mechanical strength and a controlled biodegradability rate, and a molded body thereof.

<1. Biodegradable resin composition>
Hereinafter, the present invention will be described. However, the present invention is not limited to the specific embodiments described below, and includes modifications that are arbitrarily modified within the technical scope of the present invention. The biodegradable resin composition of the present invention comprises an aliphatic polyester resin, starch, a plasticizer, and a predetermined amount of a synthetic organic compound biodegradation inhibitor.

In this specification, the term “polymer” refers to a polymer composed of a single type of repeating structural unit (a so-called “homopolymer”) and a polymer composed of a plurality of types of repeating structural units (a so-called “polymer”). It is used as a concept including “copolymer”).
In the following description, a partial structural unit of a polymer derived from a certain monomer is represented by adding the word “unit” to the name of the monomer. For example, the partial structural unit derived from dicarboxylic acid is represented by the name “dicarboxylic acid unit”.
Moreover, the monomer which gives the same partial structural unit is named generically by the name which replaced the "unit" of the name of the partial structural unit with "component." For example, monomers such as aromatic dicarboxylic acids and aromatic dicarboxylic acid diesters form aromatic dicarboxylic acid units, even if the reaction in the process of forming the polymer is different. Therefore, these aromatic dicarboxylic acids and aromatic dicarboxylic acid diesters are collectively referred to as “aromatic dicarboxylic acid component”.

(1.1. Aliphatic polyester resin)
The biodegradable resin composition according to the present invention contains an aliphatic polyester resin as a biodegradable resin. In the present invention, the “system resin” includes the resin as a main component, and the main component means that the component is the most, and may include a component other than the main component. Absent. The aliphatic polyester-based resin is one having an aliphatic polyester as a main component. Specifically, an aliphatic polyester containing 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more can be mentioned. The aliphatic polyester-based resin of the present invention may contain a constituent component other than the aliphatic polyester, for example, may have an aromatic polyester structure portion as a copolymer component in addition to the aliphatic polyester structure, It may be a mixture of an aliphatic polyester resin and an aromatic polyester resin or aromatic / aliphatic polyester resin. Specifically, the aliphatic polyester resin includes not only an aliphatic polyester composed of succinic acid (aliphatic dicarboxylic acid) and 1,4-butanediol (aliphatic diol), but also adipic acid and 1,4-cyclohexanedi It may be an aliphatic polyester having a cyclic structure composed of methanol (cyclic diol) or the like, and may contain an aliphatic polyester component having the cyclic structure as a copolymerization component. It may be a polymer alloy of an aliphatic polyester having a cyclic structure and an aliphatic polyester resin not having a cyclic structure. Alternatively, it may be an aromatic / aliphatic polyester containing terephthalic acid (aromatic dicarboxylic acid) as a copolymerization component, and an aliphatic polyester and an aromatic polyester and / or an aromatic / aliphatic polyester. It may be a polymer alloy.

(1.1.1. Aliphatic polyester resin)
As for the aliphatic polyester resin, a chain aliphatic and / or alicyclic diol unit represented by the following formula (1), and a chain aliphatic and / or alicyclic dicarboxylic acid represented by the following formula (2) It consists of acid units.

—O—R ¹ —O— (1)
[In the formula (1), R ¹ represents a divalent chain aliphatic hydrocarbon group and / or a divalent alicyclic hydrocarbon group. When copolymerized, two or more types of R ¹ may be contained in the resin. ]

^-OC-R 2 -CO- (2)
[In the formula (2), R ² represents a divalent chain aliphatic hydrocarbon group and / or a divalent alicyclic hydrocarbon group. When copolymerized, two or more types of R ¹ may be contained in the resin. ]

  In the formulas (1) and (2), “and” in the “divalent chain aliphatic hydrocarbon group and / or divalent alicyclic hydrocarbon group” means in one molecule of the constituent component. This means that it may contain both a divalent chain aliphatic hydrocarbon group and a divalent alicyclic hydrocarbon group. Hereinafter, “chain aliphatic and / or alicyclic” may be simply abbreviated as “aliphatic”.

  Although the aliphatic diol component which gives the diol unit of Formula (1) is not particularly limited, an aliphatic diol component having 2 to 10 carbon atoms is preferable, and an aliphatic diol component having 4 to 6 carbon atoms is particularly preferable. Specifically, for example, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like can be mentioned, among which 1,4-butanediol is particularly preferable. Two or more types of aliphatic diol components can be used.

  The aliphatic dicarboxylic acid component that gives the dicarboxylic acid unit of the formula (2) is not particularly limited, but an aliphatic dicarboxylic acid component having 2 to 10 carbon atoms is preferable, and an aliphatic dicarboxylic acid component having 4 to 8 carbon atoms is preferable. Particularly preferred. Specific examples of the aliphatic dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like, and succinic acid or adipic acid is particularly preferable. Two or more types of aliphatic dicarboxylic acid components can be used.

  Furthermore, the aliphatic polyester resin in the present invention may contain an aliphatic oxycarboxylic acid unit. Specific examples of the aliphatic oxycarboxylic acid component that gives an aliphatic oxycarboxylic acid unit include, for example, lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy Examples include -3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, and the like, or lower alkyl esters or intramolecular esters thereof. When optical isomers exist in these, any of D-form, L-form and racemic form may be sufficient, and a form may be a solid, a liquid, or aqueous solution. Of these, lactic acid or glycolic acid is particularly preferred. These aliphatic oxycarboxylic acids can be used alone or as a mixture of two or more.

  As for the amount of the aliphatic oxycarboxylic acid component, the lower limit is usually 0 mol% or more, preferably 0.01 mol% or more, and the upper limit is usually 30 mol% or less, among all the components constituting the aliphatic polyester resin. , Preferably it is 20 mol% or less.

  In addition, the aliphatic polyester resin in the present invention includes “a trifunctional or higher aliphatic polyhydric alcohol”, “a trifunctional or higher aliphatic polyvalent carboxylic acid or acid anhydride thereof”, or “a trifunctional or higher aliphatic polyvalent alcohol”. Copolymerization of “oxycarboxylic acid” is preferred because the melt viscosity of the resulting aliphatic polyester resin can be increased.

  Specific examples of the trifunctional aliphatic polyhydric alcohol component include trimethylolpropane and glycerin, and specific examples of the tetrafunctional aliphatic polyhydric alcohol component include pentaerythritol. These may be used alone or in combination of two or more.

  Specific examples of the trifunctional aliphatic polyvalent carboxylic acid component or its acid anhydride include propanetricarboxylic acid or its acid anhydride, and specific examples of the tetrafunctional polyvalent carboxylic acid component or its acid anhydride. Includes cyclopentanetetracarboxylic acid or its acid anhydride. These may be used alone or in combination of two or more.

  In addition, the trifunctional aliphatic oxycarboxylic acid component includes (i) a type having two carboxyl groups and one hydroxyl group in the same molecule, and (ii) one carboxyl group and two hydroxyl groups. Any type can be used. Specifically, malic acid or the like is preferably used. In addition, the tetrafunctional aliphatic oxycarboxylic acid component includes (i) a type in which three carboxyl groups and one hydroxyl group are shared in the same molecule, and (ii) two carboxyl groups and two hydroxyl groups. It is divided into a type that shares a group in the same molecule, and (iii) a type that shares three hydroxyl groups and one carboxyl group in the same molecule, and any type can be used. Specific examples include citric acid and tartaric acid. These may be used alone or in combination of two or more.

  The amount of such a tri- or higher functional compound is generally 0 mol% or more, preferably 0.01 mol% or more, and the upper limit is usually 5 mol in all the components constituting the aliphatic polyester resin. % Or less, preferably 2.5 mol% or less.

  A preferred aliphatic polyester resin in the present invention is a polybutylene succinate resin, a polybutylene succinate adipate resin, or a mixture thereof. That is, as the aliphatic polyester resin, polybutylene succinate, polybutylene succinate adipate, or a mixture thereof is particularly preferably used.

  The aliphatic polyester resin used in the present invention can be produced by a known method. For example, a general method of melt polymerization in which an esterification reaction and / or a transesterification reaction between the aliphatic dicarboxylic acid component and the aliphatic diol component is performed, followed by a polycondensation reaction under reduced pressure, Although it can manufacture also by the well-known solution heating dehydration condensation method using a solvent, the method of manufacturing by melt polymerization performed without a solvent from a viewpoint of economical efficiency or the simplicity of a manufacturing process is preferable.

  When the melt flow rate (MFR) of the aliphatic polyester resin used in the present invention is measured at 190 ° C. and 2.16 kg, the lower limit is usually 0.1 g / 10 min or more, and the upper limit is usually 100 g / 10 min. Hereinafter, it is preferably 50 g / 10 min or less, particularly preferably 30 g / 10 min or less.

(1.1.2. Aromatic / aliphatic polyester resin)
Of the aliphatic polyester resins according to the present invention, the aromatic / aliphatic polyester resin is mainly composed of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol. In this case, the content of the aromatic dicarboxylic acid unit is preferably 5 mol% or more and 60 mol% or less based on the total amount of the aliphatic dicarboxylic acid unit and the aromatic dicarboxylic acid unit (100 mol%). Specifically, for example, an aliphatic diol unit represented by the following formula (3), an aliphatic dicarboxylic acid unit represented by the following formula (4), and an aroma represented by the following formula (5) Group dicarboxylic acid unit as an essential component. However, it may have an oxycarboxylic acid unit.

—O—R ³ —O— (3)
[In the formula (3), R ³ represents a divalent chain aliphatic hydrocarbon group and / or a divalent alicyclic hydrocarbon group, and is not limited to one type when copolymerized. ]

—OC—R ⁴ —CO— (4)
[In the formula (4), R ⁴ represents a direct bond or a divalent chain aliphatic hydrocarbon group and / or a divalent alicyclic hydrocarbon group. It is not limited to species. ]

—OC—R ⁵ —CO— (5)
[In Formula (5), R ⁵ represents a divalent aromatic hydrocarbon group, and is not limited to one type when copolymerized. ]

  The diol component giving the diol unit of the formula (3) is usually one having 2 to 10 carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexane. Examples include dimethanol. Among these, diols having 2 to 4 carbon atoms are preferable, ethylene glycol and 1,4-butanediol are more preferable, and 1,4-butanediol is particularly preferable.

  The dicarboxylic acid component that gives the dicarboxylic acid unit of the formula (4) usually has 2 to 10 carbon atoms, and examples thereof include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Among these, succinic acid or adipic acid is preferable.

  Examples of the aromatic dicarboxylic acid component that gives the aromatic dicarboxylic acid unit of the formula (5) include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like, among which terephthalic acid and isophthalic acid are preferable, and terephthalic acid is particularly preferable. preferable. Moreover, aromatic dicarboxylic acid in which a part of the aromatic ring is substituted with a sulfonate is exemplified. Two or more types of aliphatic dicarboxylic acid components, aliphatic diol components, and aromatic dicarboxylic acid components can be used.

  The aromatic / aliphatic polyester resin in the present invention may contain an aliphatic oxycarboxylic acid unit. Specific examples of the aliphatic oxycarboxylic acid component that gives an aliphatic oxycarboxylic acid unit include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, and 2-hydroxy-3. , 3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, or a mixture thereof. Furthermore, these lower alkyl esters or intramolecular esters may be used. When optical isomers exist in these, any of D-form, L-form and racemic form may be sufficient, and a form may be any of solid, liquid, or aqueous solution. Among these, lactic acid or glycolic acid is preferable. These aliphatic oxycarboxylic acids can be used alone or as a mixture of two or more.

  As for the amount of the aliphatic oxycarboxylic acid component, the lower limit is usually 0 mol% or more, preferably 0.01 mol% or more, and the upper limit is usually 30 mol%, among all the components constituting the aromatic aliphatic polyester resin. Hereinafter, it is preferably 20 mol% or less.

  The aromatic / aliphatic polyester resin can be produced by the same production method as that for the aliphatic polyester resin.

  The melt flow rate (MFR) of the aromatic / aliphatic polyester resin used in the present invention, when measured at 190 ° C. and 2.16 kg, usually has a lower limit of 0.1 g / 10 min or more and an upper limit of usually 100 g / It is 10 minutes or less, preferably 50 g / 10 minutes or less, particularly preferably 30 g / 10 minutes or less.

  The content of the aromatic / aliphatic polyester resin is preferably 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the aliphatic polyester resin. The lower limit of the content is more preferably 5 parts by mass or more, particularly preferably 10 parts by mass or more, and most preferably 20 parts by mass or more. The upper limit of the content is more preferably 70 parts by mass or less, particularly preferably 60 parts by mass or less. If the content of the aromatic / aliphatic polyester resin is too large, the stiffness of the film is insufficient, and it may be necessary to increase the thickness of the film for use as various packaging materials. On the other hand, if the content of the aromatic / aliphatic polyester resin is too small, the tensile elongation rate, tear strength, etc. may be insufficient.

  The aliphatic polyester resin used in the present invention is mainly composed of the above-described aliphatic polyester resin and may further contain an aromatic / aliphatic polyester resin. In the biodegradable resin composition of the present invention, the content of the aliphatic polyester resin is 20 wt. Based on the total amount (100 parts by weight) of the aliphatic polyester resin and the starch and plasticizer described below. Part to 90 parts by weight, preferably 30 parts to 80 parts by weight, and more preferably 35 parts to 70 parts by weight. Here, if it is less than 20 parts by weight, film molding or injection molding may be difficult, and if it exceeds 90 parts by weight, the film tear strength may be remarkably insufficient.

(1.2. Starch)
The starch in the present invention is a carbohydrate (polysaccharide) having a molecular formula (C ₆ H ₁₀ O ₅ ) _n and is a natural polymer obtained by polymerizing a number of α-glucose molecules by glycosidic bonds or a modified product thereof. Here, “denaturation” includes all modifications such as chemical, physical and biological. Chemical modification indicates that some or all of the structural units of starch are modified by chemical reactions such as esterification, etherification, oxidation, reduction, coupling, dehydration, hydrolysis, dehydrogenation, halogenation, etc. In particular, it indicates that the hydroxyl group is etherified or esterified. Physical modification means changing physical properties such as changing the crystallinity. Biological degeneration refers to changing a chemical structure or the like using a living organism.

  Specific examples of the starch in the present invention include corn starch, waxy corn starch, high amylose corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, pea starch, α starch and the like. Corn starch or potato Starch is preferred, and corn starch is particularly preferred.

  The blending amount of the starch is 9 parts by weight or more and 70 parts by weight or less, preferably 20 parts by weight or more, based on the total amount of the aliphatic polyester resin, the starch, and the plasticizer described later (100 parts by weight). 60 parts by weight or less, more preferably 25 parts by weight or more and 50 parts by weight or less. Here, if the amount is less than 9 parts by weight, the effect of improving physical properties such as tear strength of the film may be insufficient. If the amount exceeds 70 parts by weight, water resistance, hydrolysis resistance, flexibility, and the like may be impaired. is there.

(1.3. Plasticizer)
The plasticizer in the present invention has affinity for starch and is not particularly limited as long as it has a hydroxyl group. Specifically, for example, water, monohydric alcohol, polyhydric alcohol, Examples thereof include organic compounds containing a hydroxyl group such as a partial ester or a partial ether of a monohydric alcohol. Among these, sorbitol, pentaerythritol, trimethylolpropane, trimethylolethane, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-heptanediol, 1, 6-hexanediol, 1,8-octanediol, 1,9-nanonediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol , Polypropylene glycol, glycerol, glycerol monoalkyl ester, glycerol dialkyl ester, glycerol monoalkyl ether, glycerol dialkyl ether, diglycerol, diglycerol alkyl Ester etc., more preferably ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, glycerin monoester, sorbitol or pentaerythritol, particularly preferably glycerin, sorbitol, pentaerythritol, propylene glycol or ethylene glycol . One or two or more organic compounds containing water and a hydroxyl group are used.
The molecular weight of the organic compound containing a hydroxyl group is preferably 3000 or less, more preferably 2500 or less, and particularly preferably 2000 or less.

  The compounding amount of the plasticizer is 1 part by weight or more and 20 parts by weight or less, preferably 3 parts by weight, based on the total amount of the above-described aliphatic polyester resin and starch and the plasticizer (100 parts by weight). It is 15 parts by weight or less, more preferably 5 parts by weight or more and 10 parts by weight or less. When the content of the plasticizer exceeds 20 parts by weight, the plasticizer may bleed out from the film surface or the elastic modulus of the resulting film may be reduced. On the other hand, when the content of the plasticizer is less than 1 part by weight, the starch cannot be sufficiently plasticized, the dispersed particle diameter of the starch becomes coarse, and the starch may not be properly dispersed.

(1.4. Biodegradation inhibitor)
The biodegradable resin composition according to the present invention contains a synthetic organic compound-based biodegradation inhibitor. More specifically, synthetic organic compound antibacterial agents and fungicides can be used as biodegradable inhibitors. Inorganic compound-based biodegradation inhibitors are feared of soil contamination by metal ions, and natural products have a low amount of active ingredient in the substance, so the added amount increases, leading to a decrease in the mechanical strength of the composition. Organic compound antibacterial / antifungal agents are preferable in that they can be obtained with a small amount of addition because of their high purity and high effect. Examples of synthetic organic compound biodegradation inhibitors include morpholine fungicides, dicarboximide fungicides, methoxyacrylate fungicides, acid amide fungicides, benzimidazole fungicides, and more. In addition to being able to express the expected effect in a small amount, a benzimidazole-derived structure is included in the molecular structure from the viewpoint of safety during the production of a resin composition or when using various products comprising the resin composition thereafter. A benzimidazole compound is preferable. Furthermore, a compound having a thiazolyl group in its molecular structure is more preferable.

  Examples of imidazole-based synthetic organic compound-based biodegradation inhibitors that are preferably used as biodegradation inhibitors used in the biodegradable resin composition according to the present invention include benzimidazole carbamic acid compounds, sulfur atom-containing benzimidazole compounds, benzoates. Examples thereof include cyclic compound derivatives of imidazole. Examples of the benzimidazole carbamate compound include methyl 1H-2-benzimidazole carbamate, methyl 1-butylcarbamoyl-2-benzimidazole carbamate, methyl 6-benzoyl-1H-2-benzimidazole carbamate, 6- (2- Examples include thiophenecarbonyl) -1H-2-benzimidazole carbamate methyl.

  Examples of the sulfur atom-containing benzimidazole compound include 1H-2-thiocyanomethylthiobenzimidazole and 1-dimethylaminosulfonyl-2-cyano-4-bromo-6-trifluoromethylbenzimidazole.

  As cyclic compound derivatives of benzimidazole, 2- (4-thiazolyl) -1H-benzimidazole, 2- (2-chlorophenyl) -1H-benzimidazole, 2- (1- (3,5-dimethylpyrazolyl)) Examples thereof include -1H-benzimidazole and 2- (2-furyl) -1H-benzimidazole.

  In the biodegradable resin composition according to the present invention, a plurality of the above-described biodegradation inhibitors may be used in combination. Even in the same imidazole system, by using two different types together, a synergistic effect of antibacterial action against microorganisms can be obtained, especially those having a thiazolyl group in the benzimidazole ring and those having a carbamate group in the benzimidazole ring Is preferable because a remarkable synergistic effect is obtained.

  Examples of the thiazolyl group include 2-thiazolyl, 4-thiazolyl, 5-thiazolyl and the like. Further, as the carbamate group, the hydrocarbon group in the carbamate group is preferably an alkyl group such as methyl, ethyl, n-propyl, iso-propyl, etc., and particularly preferably has a methyl group or an ethyl group. Specifically, 2- (4-thiazolyl) -1H-benzimidazole (thiabendazole (TBZ)) and the like can be exemplified as those having a thiazolyl group. Examples of those having a carbamate group include methyl-2-benzimidazole carbamate methyl (carbendazim (BCM)), ethyl-2-benzimidazole carbamate methyl, and the like. In particular, 2- (4-thiazolyl) -1H-benzimidazole and methyl 2-benzimidazole carbamate have relatively high thermal stability and are particularly easy to use as a resin molded product.

  The blending amount of the biodegradation inhibitor is 0.001 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the total amount of the above-described aliphatic polyester resin, starch, and plasticizer, preferably, The amount is from 01 to 2 parts by weight, more preferably from 0.1 to 1 part by weight. By setting the above range, the mechanical strength of the composition can be made sufficient, the appearance of the molded product can be made good, and the biodegradation rate of the composition is further improved. It is possible to control the biodegradation speed at a speed that is faster than necessary without causing problems during use and without causing inconveniences such as the occurrence of environmental problems without progressing biodegradation.

(1.5. Other components)
In the biodegradable resin composition according to the present invention, a compatibilizer, an inorganic filler, a crystal nucleating agent, an antioxidant, an anti-blocking agent, an ultraviolet absorber, a light-resistant agent, an antioxidant, a heat stabilizer, and a colorant , Flame retardants, mold release agents, antistatic agents, antifogging agents, surface wetting improvers, incineration aids, pigments, lubricants, dispersion aids, surfactants, slip agents, hydrolysis inhibitors, end-capping agents, etc. The “other ingredients” may be used. These can be arbitrarily used as long as the effects of the present invention are not impaired.

(1.5.1. Compatibilizer)
The biodegradable resin composition of the present invention may contain a compatibilizing agent. The compatibilizing agent is an additive that improves the compatibility when the incompatible dissimilar resin or the starch and the resin are mixed. By adding a solubilizer, the compatibility can be improved.

  The compatibilizer is preferably added in an amount of 0.01 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the total amount of the above-described aliphatic polyester resin, starch and plasticizer.

  Examples of the compatibilizer include a polymer compatibilizer, a low molecular organic compound, an inorganic compound, an organic-inorganic composite, etc., but the polymer compatibilizer and the low molecular organic compound are molded products. From the viewpoint of physical properties, a polymer type compatibilizer is more preferable from the viewpoint of the molding process. The compatibilizer is preferably one having an acid anhydride group, glycidyl group or ether group structure, and a polymer type compatibilizer having any one of these structures is more preferred. By using a compatibilizing agent having these structures, the effect of improving the compatibility is increased.

  Polymeric compatibilizers include polyester, polyolefin, polyamide, polyether, polycarbonate, acrylic, styrene, urethane, polyacetal, olefin elastomer, unsaturated aliphatic elastomer, hydrogenated Examples thereof include resins such as unsaturated aliphatic elastomers, and two or more kinds of these blocks, grafts, or random copolymers. A polar group may be introduced into the molecule by further adding an unsaturated fatty acid anhydride to these copolymers. Maleic anhydride is preferably used as the unsaturated fatty acid anhydride to be added.

  Among these, polyester-based, polyolefin-based, polyamide-based, polyether-based, acrylic-based, styrene-based, olefin-based elastomers, unsaturated aliphatic elastomers, hydrogenated unsaturated aliphatic elastomers, and co-polymerization of two or more of these More preferred are coalesced and the like, and polyolefin-based, polyamide-based, polyether-based, acrylic-based, styrene-based, hydrogenated unsaturated aliphatic elastomers, and copolymers of two or more of these are more preferable.

(1.5.2. Inorganic filler)
An inorganic filler may be added to the biodegradable resin composition of the present invention. Examples of such inorganic fillers include silica, mica, talc, titanium oxide, calcium carbonate, diatomaceous earth, allophane, bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin, kaolinite, glass, limestone, carbon, wollastonite. , Calcined perlite, "silicates such as calcium silicate and sodium silicate", hydroxides such as aluminum oxide, magnesium carbonate, calcium hydroxide, ferric carbonate, zinc oxide, iron oxide, aluminum phosphate, barium sulfate, etc. Can be mentioned. These may be used alone or in combination of two or more.

  The amount of the inorganic filler contained in the biodegradable resin composition of the present invention is not particularly limited, but the inorganic filler is added to the total amount of 100 parts by weight of the above-described aliphatic polyester resin, starch, and plasticizer. The agent is preferably 1 part by weight or more and 30 parts by weight or less. If the amount of the inorganic filler is too small, the effect of improving the mechanical properties may be reduced. On the other hand, if the amount is too large, the moldability and impact resistance may be deteriorated.

(1.5.3. Various additives)
The biodegradable resin composition in the present invention can further contain various conventionally known additives. Examples of additives include crystal nucleating agents, antioxidants, anti-blocking agents, ultraviolet absorbers, light-resistant agents, plasticizers, heat stabilizers, colorants, flame retardants, mold release agents, antistatic agents, and antifogging agents. , Surface wettability improvers, incineration aids, pigments, lubricants, dispersion aids, various surfactants, slip agents, hydrolysis inhibitors and the like. These may be used alone or in combination of two or more.

  The antifogging agent may be previously kneaded into the resin, or may be applied to the surface of the molded article after molding. Specifically, the antifogging agent used is preferably an ester surfactant of a saturated or unsaturated aliphatic carboxylic acid having 4 to 20 carbon atoms and a polyhydric alcohol. Examples of the slip agent include unsaturated fatty acid amides and unsaturated fatty acid bisamides composed of unsaturated fatty acids having 6 to 30 carbon atoms, most preferably erucic acid amide.

  Examples of the anti-blocking agent include saturated fatty acid amides having 6 to 30 carbon atoms, saturated fatty acid bisamides, methylol amides, ethanol amides, natural silicas, synthetic silicas, synthetic celite, talc and the like.

  Examples of light-proofing agents include bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl-bis. (1,2,2,6,6-pentamethyl-4-piperidyl) malonate is preferred.

  As the ultraviolet absorber, a benzotriazole-based ultraviolet absorber is preferable, and 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (4,6- Diphenyl-1,3,5-triazin-2-yl) -5-hexyloxy-phenol is particularly preferred

  As the antioxidant, a hindered phenol-based antioxidant is preferably used, and Irganox 3790 (1,3,5-tris [(4-tert-butyl-3-hydroxy-2,6-xylyl) methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione), Irganox 1330 (3,3 ', 3 ", 5,5', 5" -hexa-tert-butyl -Α, α ', α "-(mesitylene-2,4,6-triyl) tri-p-cresol) is particularly preferred.

  The addition amount of these additives is usually 0.001 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the total amount of the above-described aliphatic polyester resin, starch, and plasticizer.

  End-capping agents used mainly for the purpose of suppressing hydrolysis due to moisture in the atmosphere include carbodiimide compounds, epoxy compounds, oxazoline compounds, etc., among which have one or more carbodiimide groups in the molecule. Compounds (including polycarbodiimide compounds) and monocarbodiimide compounds such as dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β- Examples include naphthyl carbodiimide. Of these, dicyclohexylcarbodiimide and diisopropylcarbodiimide, which are easily available industrially, are preferred.

<2. Kneading and forming method>
(2.1. Kneading method)
In the present invention, the biodegradable resin composition containing the aliphatic polyester-based resin described above is mixed / kneaded using a conventionally known mixing / kneading technique. As the mixer, a horizontal cylindrical type, V-shaped, double-cone type mixer, a blender such as a ribbon blender or a super mixer, various continuous mixers, or the like can be used. Moreover, as a kneading machine, a batch type kneading machine such as a roll or an internal mixer, a one-stage type, a two-stage type continuous kneading machine, a twin screw extruder, a single screw extruder, or the like can be used.

  The method for preparing the biodegradable resin composition of the present invention is not particularly limited, and examples thereof include a method in which the blended raw materials are melt-mixed in the same extruder, a method in which the raw materials are melted in separate extruders, and the like. . Moreover, it is also possible to obtain the molded body at the same time as preparing each biodegradable resin composition by supplying each raw material directly to the molding machine. Examples include a method in which various additives, inorganic fillers, organic fillers, other biodegradable resins, and the like are added and blended when the components are mixed and heated and melted. At this time, blending oil or the like can also be used for the purpose of uniformly dispersing the various additives.

(2.2. Molding method)
The biodegradable resin composition in the present invention can be used for molding by various molding methods applied to general-purpose plastics. The molding methods include, for example, compression molding (compression molding, laminate molding, stampable molding), injection molding, extrusion molding and coextrusion molding (film molding by inflation method or T-die method, laminate molding, pipe molding, electric wire / cable molding. , Profile molding), hollow molding (various blow molding), calendar molding, foam molding (melt foam molding, solid phase foam molding), solid molding (uniaxial stretching molding, biaxial stretching molding, roll rolling molding, stretch oriented nonwoven fabric Examples thereof include molding, thermoforming (vacuum forming, pressure forming), plastic working), powder forming (rotary forming), various non-woven fabric forming (dry method, adhesion method, entanglement method, spunbond method, etc.). Among these, extrusion molding, injection molding, foam molding, and hollow molding are preferably applied. As a specific shape, application to a film, a container and a fiber is preferable. Since the biodegradable resin composition of the present invention has good melting characteristics and mechanical properties, it is preferably used for products produced from a film formed by inflation molding, and further from a film formed by inflation molding.

<3. Application>
The biodegradable resin composition of the present invention is suitably used in a wide range of applications such as various foods, medicines, miscellaneous liquids and powders, solid packaging materials, agricultural materials, and building materials. Specific applications include injection molded products (for example, fresh food trays, fast food containers, outdoor leisure products, etc.), extruded products (films, such as fishing lines, fishing nets, vegetation nets, water retaining sheets, etc.), hollow molding. Products (bottles, etc.), other agricultural films, coating materials, fertilizer coating materials, laminate films, plates, stretched sheets, monofilaments, non-woven fabrics, flat yarns, staples, crimped fibers, striped tape, Examples include split yarns, composite fibers, blow bottles, foams, shopping bags, garbage bags, compost bags, and the like.

  The biodegradable resin composition of the present invention has good moldability and mechanical strength, and the biodegradability rate is controlled, so it is applied to shopping bags or garbage bags manufactured from a film formed by inflation molding. It is preferred that

  In addition, packaging materials such as packaging films, bags, trays, bottles, cushioning foams, fish boxes, etc., and agricultural materials such as mulching films, tunnel films, house films, sun covers, grass protection sheets, etc. , Cocoon sheets, germination sheets, vegetation mats, nursery beds, flower pots and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.

<Manufacture and molding of composition>
(material)
Polybutylene succinate resin Polybutylene succinate resin GSPla (grade name: AD92WN) manufactured by Mitsubishi Chemical Corporation was used as the polybutylene succinate resin.

-Unprocessed starch Corn starch (Nippon Corn Starch company make; Y-3P) was used as unprocessed starch.

-Plasticizer Glycerin (Wako Pure Chemical; special grade) was used as a plasticizer for starch.

-Polyalkylene terephthalate adipate resin Polybutylene terephthalate adipate resin Ecoflex (grade name: FBX7011) manufactured by BASF was used as the polyalkylene terephthalate adipate resin.

・ Biodegradable inhibitors (antibacterial and antifungal agents)
Thiabendazole (2- (4-thiazolyl) benzimidazole) was used as a synthetic organic compound-based biodegradable inhibitor.

(Kneading)
The kneading was performed using a twin screw extruder TEX30 (22 cylinders: L / D = 77) manufactured by Nippon Steel Works, with a set temperature of 80 to 160 ° C. and a screw rotation speed of 150 to 300 rpm.

(Inflation molding)
Inflation molding was carried out by forming a film having a blow ratio of 3, a fold diameter of 360 mm, a molding temperature of 160 ° C., and a thickness of 20 μm using a model E30SP manufactured by Engineering Plastics Co., Ltd.

(Tear strength)
The Elmendorf tear strength was measured according to JIS K7128.

(Criteria for mold resistance)
As one of the indicators of the biodegradation inhibitory effect, mold resistance was evaluated. The judgment criteria were as follows.
0: No mold growth was observed on the surface of the sample as observed with a 50 × stereomicroscope.
1: The surface of the sample is observed with the naked eye, and no mold growth is observed.
2: Mold growth is observed in less than 25% of the sample surface.
3: Mold growth is observed at 25% or more and less than 50% of the sample surface.
4: Mold growth is observed at 50% or more and less than 100% of the sample surface.
5: Mold growth completely covers the sample surface.

(Soil extension test)
Tensile tests and mold resistance were performed on film samples stretched for 30 days from April to May in a field in Ureshinogawa Kitamachi, Matsusaka City, Mie Prefecture. Regarding the tensile elongation at break before and after stretching, the strength retention was calculated according to the following formula.
Strength retention (%) = Tensile rupture elongation after stretching / Tensile rupture elongation before stretching Here, the greater the strength retention, the more sufficient the strength of the film can be maintained during use. Is preferable.

(Measurement method of tear strength)
In accordance with JIS K7128, the Elmendorf tear strength in the MD direction (flow direction) of the film before the soil extension test was measured.

(Tensile test)
Based on JIS K7113, the tensile yield stress, the tensile breaking stress, and the tensile breaking elongation were measured. The result of measuring the material before the soil extension test is the “initial” value, and the result of measuring the material after the soil extension test is the “after extension” value. Table 1 shows the tensile yield stress difference, tensile rupture stress difference, and tensile rupture elongation difference, respectively. A smaller value indicates that it is possible to maintain a sufficient strength during use of the film.

Example 1
30 parts by weight of corn starch, 20 parts by weight of Ecoflex, 6 parts by weight of glycerin and 0.5 parts by weight of thiabendazole are fed into a screw-type twin screw extruder and kneaded. Feed and knead. The resin composition was extruded onto a strand from a die, cooled in a water bath and cut to obtain white pellets. Thereafter, pellets of the resin composition were dried at 70 ° C. in a nitrogen atmosphere for 8 hours. Thereafter, when this pellet was used for inflation molding, a film having an easy molding and a smooth surface was obtained, and a film having a high tensile stress, elongation, tensile elastic modulus and tear strength was obtained. In addition, Table 1 below shows the strength retention and the mold resistance after the predetermined number of days of stretching.

(Example 2)
As shown in Table 1 below, Example 1 is applied except that the amount ratio of each component is changed. The results are shown in Table 1 below.

(Comparative Examples 1 and 2)
As shown in Table 1 below, Example 1 is applied except that the amount ratio of each component is changed. The results are shown in Table 1 below.

表中「−」はその材料を使用していないことを示す。

In the table, “-” indicates that the material is not used.

  As can be seen from the results in Table 1, the films formed using the biodegradable resin compositions according to Examples 1 and 2 are all different in tensile yield stress difference as compared with the film according to Comparative Example 1. It turns out that it is excellent in the tensile rupture elongation difference, strength retention, and mold resistance (biodegradation inhibitory property). Moreover, in the film shape | molded using the biodegradable resin composition which concerns on the comparative example 2, when performing inflation shaping | molding, the bubble became unstable and the uniform film sample could not be obtained. Although the film molded using the biodegradable resin composition according to Comparative Example 3 had relatively high mold resistance, the tear strength was low. As described above, in the biodegradable resin compositions according to Examples 1 and 2, it is possible to obtain a film having both the mechanical properties and the biodegradation rate control performance, and excellent in mold resistance. According to the resin composition, it is possible to provide a film having comprehensively excellent performance.

  The biodegradable resin composition of the present invention and the molded product thereof are excellent in mechanical properties and have a controlled biodegradability rate, so that various foods, medicines, powders for sundries, packaging materials for solids, It is widely used for agricultural materials and building materials.

Claims (6)

An aliphatic polyester resin;
Starch,
A plasticizer,
0.001 part by weight or more and 3 parts by weight or less of a synthetic organic compound biodegradation inhibitor with respect to 100 parts by weight of the total amount of the aliphatic polyester resin, the starch, and the plasticizer;
A biodegradable resin composition comprising:   The biodegradable resin composition according to claim 1, wherein the plasticizer is an organic compound having a molecular weight of 3000 or less containing water or a hydroxyl group.   The biodegradable resin composition according to claim 1, wherein the synthetic organic compound-based biodegradation inhibitor is a benzimidazole-based compound.   The content of the aliphatic polyester resin is 20 parts by weight or more and 90 parts by weight or less with respect to 100 parts by weight of the total amount of the aliphatic polyester resin, the starch, and the plasticizer, and the starch content is 9 parts. The biodegradable resin composition according to any one of claims 1 to 3, wherein a content of the plasticizer is 1 part by weight or more and 20 parts by weight or less.   The molded object formed by shape | molding the resin composition of any one of Claims 1-4.   The molded body according to claim 5, wherein the molded body is a film formed by inflation molding.