JP4414415B2 - Biodegradable resin composition and biodegradable film - Google Patents

Description

  The present invention relates to a biodegradable resin composition and a biodegradable film. More specifically, it is suitable for a biodegradable resin composition having improved moldability and a controlled biodegradation rate and hydrolysis rate, a compost bag molded from the composition, an agricultural film, and a packaging material. The present invention relates to a biodegradable film having improved mechanical properties such as tear strength.

Biodegradable resins are known to decompose relatively easily without producing harmful substances in water or soil. For this reason, it is attracting worldwide attention from the viewpoint of environmental conservation such as the problem of waste disposal. Among these, the aliphatic polyester resin may have physical properties close to that of polyethylene, and the film obtained by molding the resin may be used for films such as agricultural materials, civil engineering materials, vegetation materials, and packaging materials. It is expected (see, for example, Patent Documents 1 and 2).
However, all of the conventional biodegradable films have a problem in practical use because the tear strength, particularly the tear strength in the machine (stretching) direction of the film is not sufficient.
On the other hand, building a recycling-oriented society by switching from depleted resources to renewable resources has attracted attention, not only biodegradability but also materials derived from natural products, not materials synthesized from petroleum. There is growing interest. At present, starch is a material that is put into practical use as a natural product.
Starch to which moldability and physical properties as a film are imparted are esterified vinyl ester graft polymerized starch (Patent Document 3) and starch ester (Patent Document 4), and polyester graft polymerized starch and polyester alloy (Patent Document 5). Has been proposed. Further, it is considered that if the starch is highly modified, the moldability and physical properties as a film can be further improved, but this is not practical in terms of cost.
It has also been proposed to combine starch gelatinized material with a thermoplastic resin (see, for example, Patent Documents 6 and 7). Furthermore, various proposals have been made for systems to which modified starch is added (for example, see Patent Documents 8, 9, 10 and 11).
However, all of these compositions have insufficient fluidity when heated and melted. For this reason, it was possible to obtain a molded product having a simple shape, such as a sheet, by extrusion molding to some extent. It is difficult to obtain a molded product having a shape, and it is difficult to form a thin film, and even if it can be formed, the film properties are not practical. Moreover, the gelatinization process and the blending process of starch are needed separately, and there was a problem that the manufacturing cost becomes high.
As a method for solving these problems, a composition of oxidized gelatinized starch and biodegradable resin has been proposed (Patent Document 12). This is a method in which gelatinization and oxidation are performed simultaneously, but in practice, it is necessary to control starch degradation by an oxidizing agent in the presence of water and a plasticizer for gelatinization and to sufficiently blend with a resin. However, there is a problem that the manufacturing cost becomes high. In other words, if gelatinization, oxidation, and compounding are performed simultaneously, the molecular weight of the biodegradable resin also decreases, and it is difficult to achieve film moldability and physical properties. As illustrated, it is oxidized during molding. If the gelatinized starch pellets and the biodegradable resin pellets are molded by dry blending, it may not be a problem in injection molding, but in thin film molding, it is kneaded by a melt extruder in commonly used inflation film molding. However, there is a problem that a problem arises in moldability and physical properties. In addition, the oxidizing agent used is a peroxide, and since the compatibility of gelatinized starch and biodegradable resin is insufficient, the moldability when processing the resin composition into a film is not sufficiently improved. .
From a practical viewpoint, it is a very important problem to control the biodegradability and hydrolyzability as well as improve the moldability. Regarding aliphatic polyesters, it has already been disclosed that these characteristics can be controlled by adding a carbodiimide-based hydrolysis inhibitor (Patent Document 13). The mechanism is a mechanism that blocks the carboxyl group at the terminal of the polyester or at the cleaved portion of the molecule. In view of this mechanism, in a biodegradable resin composition containing starch, the physical properties of starch are dominant and no effect can be expected. In fact, there are no such prior documents and patents.

Japanese Patent Laid-Open No. 5-271377 Japanese Patent Laid-Open No. 6-170941 JP-A-8-239402 Japanese Patent No. 2939586 JP-A-9-31308 JP-A-1-217002 Japanese Patent Laid-Open No. 2-14228 Japanese Patent Laid-Open No. 3-56543 JP-A-3-70752 Japanese Patent Laid-Open No. 3-74445 Japanese Patent Laid-Open No. 3-74446 Japanese Patent No. 3078478 JP 2003-313436 A

In view of the above-mentioned problems of the prior art, an object of the present invention is to improve the moldability, adjust the biodegradation rate and hydrolysis rate, and have excellent economic efficiency, and tearing The object is to provide a biodegradable film having improved mechanical properties such as strength.

As a result of intensive studies to solve the above problems, the present inventors have been conventionally used for aliphatic polyesters as described above in compositions containing a specific proportion of starch and biodegradable resin. It has been found that the above problem can be solved by adding a carbodiimide compound, and the present invention has been completed.
That is, the present invention includes the following:
(1) Oxidized starch gelatinized product 20 to 20 having a structure in which a part of glucose units in the starch is cleaved between C-2 and C-3 and a carboxyl group is formed in C-2 and C-3 Composition (A) containing 50% by mass and 50-80% by mass of biodegradable resin other than the gelatinized product of oxidized starch [the total of both is 100% by mass, hereinafter, composition (A) is a component (A A biodegradable resin composition containing 100 parts by mass and 0.01-10 parts by mass of the carbodiimide compound (B),
(2) The biodegradable resin composition according to the above 1, further comprising an esterification catalyst (C) [hereinafter sometimes referred to as component (C)],
(3) The biodegradable resin composition according to (2), wherein the blending amount of (C) is 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the composition (A).
(4) The above (B) and / or (C), a master batch containing a part of (A), and a part of (A) above, (2) or (3) above Biodegradable resin composition,
(5) The biodegradable resin composition according to any one of (1) to (4), wherein the biodegradable resin is a condensation polymer of a polyol and an aliphatic polycarboxylic acid and / or a derivative thereof,
(6) The biodegradable resin composition according to (5), wherein the polyol is ethylene glycol and / or 1,4-butanediol, and the aliphatic polycarboxylic acid is succinic acid and / or adipic acid,
(7) The biodegradable resin composition according to (6), wherein the biodegradable resin further contains polylactic acid,
(8) The biodegradable resin composition according to any one of (1) to (4), wherein the biodegradable resin is polycaprolactone,
(9) The biodegradable resin is a condensation polymer of an aromatic polycarboxylic acid and an aliphatic polyol and / or a condensation polymer of an aliphatic polycarboxylic acid and an aromatic polycarboxylic acid and an aliphatic polyol ( The biodegradable resin composition according to any one of 1) to (4),
(10) The biodegradable resin composition according to (9), wherein the aliphatic polycarboxylic acid is adipic acid, the aromatic polycarboxylic acid is terephthalic acid, and the aliphatic polyol is butanediol,
(11) The biodegradable resin composition according to any one of (1) to (10), wherein the starch is a gelatinized product of oxidized starch produced using sodium hypochlorite,
(12) The biodegradable resin composition according to any one of (1) to (11), wherein gelatinization of the starch is performed using an extruder with a vent simultaneously with mixing of the biodegradable resin,
(13) The biodegradable resin composition according to any one of (1) to (12), further including a high-boiling polar solvent selected from ethylene glycol, propylene glycol, glycerin, sorbitol, polyethylene glycol, and polypropylene glycol,
(14) The biodegradable resin composition according to any one of (1) to (13), further including a plasticizer,
(15) The biodegradable resin composition according to the above (14) is at least one plasticizer is selected from polyglycerol acetic ester le Contact and adipic acid diester,
(16) The biodegradable resin composition according to any one of (1) to (15) above, wherein the degree of carboxyl group substitution of the oxidized starch by a neutralization titration method is 0.001 to 0.100,
(17) Composition containing 20 to 50% by mass of oxidized starch and 50 to 80% by mass of other biodegradable resin (A) [total of both is 100% by mass] and 100 parts by mass of carbodiimide compound (B A biodegradable resin composition obtained by melt-kneading 0.01 to 10 parts by mass with a twin screw extruder at a temperature of 80 to 140 ° C. and a residence time of 60 to 120 seconds;
And ( 18 ) A biodegradable film obtained by molding the biodegradable resin composition according to any one of (1) to ( 17 ) above is provided.

  According to the present invention, there are provided a biodegradable resin composition having improved moldability, controlled biodegradation rate and hydrolysis rate, and biodegradable film having improved mechanical properties molded therefrom. The The biodegradable film of the present invention has high mechanical properties, particularly tear strength in the machine (stretching) direction, is suitable for compost bags, agricultural films, packaging materials, and the like, is excellent in economy, and has flexibility.

The present invention will be specifically described below.
There is no restriction | limiting in particular as starch which is one component in the composition (A) in the biodegradable resin composition of this invention, Any starch can be used. For example, potato starch, corn starch, sweet potato starch, tapioca starch, sago palm starch, rice starch, wheat starch and other unmodified starches, and various esterified starches, etherified starches, modified starches such as oxidized starches, etc. it can. Among these, oxidized starch is preferable, and gelatinized product of oxidized starch produced using sodium hypochlorite is particularly preferable.
By using oxidized starch as gelatinized material, the moldability when the biodegradable resin composition of the present invention is formed into a film and the physical properties of the resulting biodegradable film can be improved. In order to obtain a gelatinized product of the oxidized starch, first, the following structure, that is, C-2 and C-3 in some glucose units in the starch are cleaved, and C-2 and C-3 are obtained. It is preferable that the starch be modified to an oxidized starch having a structure in which a carboxyl group is formed.

In order to convert the glucose unit in the starch into the structure as described above, for example, it is usually performed by oxidizing the starch with sodium hypochlorite. When starch is oxidized with an oxidizing agent such as a peroxide, open polymerization occurs due to the cleavage of C—C bonds and glycosidic bonds, and the cleavage between C-2 and C-3 is not sufficiently performed. The amount formed is insufficient.
Oxidation of starch with sodium hypochlorite is about 40 to 50% by mass of starch concentration, preferably about 45% by mass of aqueous suspension is adjusted to pH 8 to 11 and chlorine concentration of about 8 to 12% by mass, Preferably, about 10 mass% sodium hypochlorite aqueous solution is added and it reacts at about 40-50 degreeC for about 1 to 2 hours. The reaction is preferably carried out with stirring in a corrosion-resistant reaction vessel under normal pressure. After completion of the reaction, the desired product can be obtained by separating using a centrifugal dehydrator or the like, thoroughly washing with water and drying.

The amount of the carboxyl group is represented by the degree of carboxyl group substitution, and the ordinary one has a degree of carboxyl group substitution (neutralization titration) of 0.001 to 0.100, preferably 0.01 to 0.00. 035.
Commercially available starch can be used as the oxidized starch.
The method of oxidizing starch with sodium hypochlorite is, for example, Eiji Fuwa, “Dictionary of Starch Science”, Asakura Shoten Co., Ltd., March 20, 2003, p408 and Jiro Jikuni, “Starch Science Handbook” "Asakura Shoten Co., Ltd., July 20, 1977, p501".

  The biodegradable resin which is the other component in the composition (A) in the biodegradable resin composition of the present invention is not particularly limited. Any resin composed of a condensation polymer of an aliphatic polycarboxylic acid and an aliphatic polyol or an anhydride thereof, or a polymer of a hydroxycarboxylic acid may be used, and it is preferably thermoplastic in view of moldability. Resins belonging to any of chemically synthesized resins, microbial resins, natural product utilizing resins, and the like may be used. For example, polybutylene succinate, polybutylene succinate-adipate, polyethylene succinate, polycaprolactone, which is a self-condensation polymer of oxycaproic acid, polylactic acid, polyhydroxybutyrate / valerate copolymer, and the like can be mentioned. . These may be used alone or in combination of two or more.

Among these, in view of film moldability, physical properties, and availability, chemically synthesized aliphatic polyesters are preferable. Furthermore, as the aliphatic polyester, a melting point of 50 to 180 ° C. and a mass average molecular weight of 50,000 or more are preferable from the viewpoint of obtaining a good molded product, and they are usually polyols and aliphatic polycarboxylic acids. Is obtained by dehydration cocondensation.
Examples of the polyol include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, decamethylene glycol, neopentyl glycol and the like. Examples of the aliphatic polycarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and anhydrides thereof.
Moreover, what added a small amount of the trifunctional or tetrafunctional polyol, oxycarboxylic acid, or polycarboxylic acid as another component may be used.
As the aliphatic polyester, there are commercially available products, for example, “Bionore” series manufactured by Showa Polymer Co., Ltd. is well known and can be preferably used. Furthermore, a commercially available product of polycaprolactone [PCLH series such as PCLH-7 manufactured by Daicel Chemical Industries, Ltd.] can also be preferably used.
Moreover, in order to adjust the softening temperature of the biodegradable film finally obtained and the softness | flexibility of a film, polylactic acid can also be used together.

Furthermore, as a biodegradable resin, an aliphatic aromatic polyester, that is, a condensation polymer of an aromatic polycarboxylic acid and an aliphatic polyol, an aliphatic polycarboxylic acid, or a condensation polymer of an aromatic polycarboxylic acid and an aliphatic polyol. A combination or a mixture of these condensation polymers can also be used.
Specific examples include polybutylene succinate terephthalate, polybutylene adipate terephthalate, polybutylene succinate adipate terephthalate, polyethylene succinate terephthalate, and polyethylene adipate terephthalate. These may be used alone or in combination of two or more.
Among these, polybutylene adipate terephthalate is preferable in view of film moldability and film properties. Further, the aliphatic aromatic polyester preferably has a melting point of 50 to 180 ° C. and a mass average molecular weight of 50,000 or more from the viewpoint of obtaining a good molded product, and these are usually aliphatic polycarboxylic acids and aromatics. It is obtained by dehydration cocondensation of an aliphatic polycarboxylic acid and an aliphatic polyol, or by dehydration cocondensation of an aliphatic polycarboxylic acid, an aliphatic polyol and an aromatic polyol.
Examples of the aliphatic polyol include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, decamethylene glycol, neopentyl glycol and the like. Examples of the aromatic polyol include hydroquinone, resorcin, catechol, bisphenol A, and the like. Examples of the aromatic polycarboxylic acid include terephthalic acid, isophthalic acid, and anhydrides thereof. Examples of the aliphatic polycarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and anhydrides thereof.
In addition, as other components, a trifunctional or tetrafunctional polyol such as trimethylolpropane or pentaerythritol, an oxycarboxylic acid such as dimethylolpropionic acid, or a polycarboxylic acid such as butanetetracarboxylic acid or trimellitic acid is used. A small amount may be added.
As the aliphatic aromatic polyester, there are commercially available products, for example, “Ecoflex” manufactured by BASF is well known.

The composition (A) in the biodegradable resin composition of the present invention contains 20 to 50% by mass starch and 80 to 50% by mass biodegradable resin, preferably 30 to 50% by mass starch and 70 to 70% biodegradable resin. Including 50% by mass [the total of both is 100% by mass].
Economic efficiency is ensured by including 20% by mass or more of starch, and biodegradability obtained by molding a biodegradable resin composition mixed with component (B) described later by including 50% by mass or less of starch. It prevents the physical properties of the film from deteriorating.
Oxidized starch gelatinized one of the preferred modified starches among starches [For gelatinization reaction, the gelatinized gelatinized starch and biodegradable resin are mixed to prepare a representative composition (A). In the case where a biodegradable resin is blended, the blending ratio is the same as described above.
That is, from the viewpoint of moldability when a biodegradable resin composition mixed with the component (B) described later is formed into a film and physical properties of the resulting biodegradable film, 20-50% by mass of oxidized starch, It is preferable to contain 80-50 mass% of degradable resin, 30-50 mass% of oxidized starch, and 70-50 mass% of biodegradable resin.
By making the gelatinized product of oxidized starch 20% by mass or more, it is possible to improve the moldability when producing a biodegradable film from the biodegradable resin composition and to improve the tear strength of the resulting film. By setting it as the mass% or less, it prevents that a film physical property falls.

The component (B) carbodiimide compound in the biodegradable resin composition of the present invention preferably has an isocyanate group at both ends. These are known methods, for example, using an organophosphorus compound or an organometallic compound as a catalyst, and removing various polyisocyanate compounds described later at a temperature of about 70 ° C. or higher in the presence or absence of an inert solvent. It can be synthesized by a carbonic acid condensation reaction.
Examples of monocarbodiimide compounds that are examples of the carbodiimide compounds include dimethylcarbodiimide, diisopropylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, dicyclohexylcarbodiimide. Etc.
Among these, diisopropylcarbodiimide or dicyclohexylcarbodiimide is preferably used from the viewpoint that it is produced on an industrial scale and is easily available.
Polycarbodiimide, which is an example of the carbodiimide compound, can be prepared by various methods, for example, Japanese Patent Publication No. 47-33279, USP 2,941,956, Journal of 0rganic Chemistry 28, 2069-2075 (1963), Chemical Review l981, Vol.81, No. .4, can be produced by the method described in p619-621.

Examples of the organic diisocyanate that is a raw material for producing polycarbodiimide include aliphatic diisocyanate, alicyclic diisocyanate, aromatic diisocyanate, and mixtures thereof.
Aliphatic diisocyanates include tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, decamethylene diisocyanate, lysine diisocyanate, and alicyclic diisocyanates include isophorone diisocyanate, hydrogenated xylylene diisocyanate, and xylylene diisocyanate. Isocyanate, hydrogenated diphenylmethane diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, etc., as aromatic diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate Examples thereof include a mixture of 2,6-tolylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate and the like.

  Moreover, polycarbodiimide can also be used, adjusting to a desired polymerization degree using the compound which reacts with the terminal isocyanate group of polycarbodiimide like a monoisocyanate compound.

  Thus, as the monoisocyanate compound used for sealing the terminal isocyanate group of polycarbodiimide and adjusting the degree of polymerization, for example, ethyl isocyanate, n-propyl isocyanate, n-butyl isocyanate, tert-butyl isocyanate , Iso-butyl isocyanate, cyclohexyl isocyanate, n-octadecyl isocyanate, phenyl isocyanate, tolyl isocyanate, dimethylphenyl isocyanate, naphthyl isocyanate, and the like.

Moreover, as a sealing agent for sealing the terminal isocyanate group of polycarbodiimide and adjusting the polymerization degree, in addition to the monoisocyanate compound, an aliphatic or alicyclic group having an active hydrogen group that reacts with an isocyanate group Or aromatic compounds.
Specifically, alkanols such as methanol, ethanol and isopropanol; amino alcohols such as N-methylethanolamine; alkylene glycols such as ethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether and polypropylene glycol monomethyl ether Monoalkyl ethers of the following: compounds having a hydroxyl group such as cycloaliphatic alcohols such as cyclohexanol and cyclohexenemethanol, aromatic alcohols such as phenol; compounds having a primary amino group such as ethylamine, butylamine, and cyclohexylamine; Compounds having secondary amino groups such as diethylamine and dicyclohexylamine; succinic acid, benzoic acid and hexahydrobenzoic acid Compounds having a carboxyl group such as; include compounds having an epoxy group such as mono-glycidyl ester of glycidyl methacrylate and bisphenol A and the like; for ethyl mercaptan, allyl mercaptan, compounds having a mercapto group such as thiophenol.

The decarboxylation condensation reaction of organic diisocyanate is usually performed in the presence of a carbodiimidization catalyst. As the carbodiimidization catalyst, an organophosphorus compound or an organometallic compound represented by the general formula M- (OR) _n [M is Na, K, Ca, Ba, V, W, Hf, Zr, Pb, Mn, Ti, Ni, etc. are shown. R represents an alkyl group or aryl group having 1 to 20 carbon atoms, and n represents a valence of M].

  Examples of organophosphorus compounds include phospholene oxides, specifically, 1-methyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1,3-dimethyl-2- Phosphorene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-2-phospholene-1-oxide, 1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, or their 3-phospholene isomers or two Examples include phospholene oxides such as heavy bond isomers, and among these, they are industrially produced and available. Easy Do 3-methyl-1-phenyl-2-phospholene-1-oxide is particularly preferably used.

  Examples of the organometallic compound include titanium (Ti), hafnium (Hf), and zirconium (Zr) alkoxides, specifically, tetramethoxy titanium, tetraethoxy titanium, tetraisopropoxy titanium, and tetra-n-propoxy titanium. , Tetrabutoxytitanium, tetrakis (2-ethylhexoxy) titanium, tetrakis (2-ethoxyethoxy) titanium, tetracyclohexyloxytitanium, tetraphenoxytitanium, tetrapropoxyzirconium, tetrabutoxyzirconium, tetra-n-propoxyhafnium, and tetra-n -Butoxyhafnium is used.

  The blending ratio of the component (A) and the component (B) in the biodegradable resin composition of the present invention is such that the component (B) is 0.01 to 10 parts by mass with respect to 100 parts by mass of the component (A). Preferably it is 0.05-5 mass parts. By adjusting the blending ratio of the component (B) to 0.01 parts by mass or more, an effect of adjusting the biodegradation rate and the hydrolysis rate is obtained, and by setting it to 10 parts by mass or less, economy is exhibited.

Moreover, in the biodegradable resin composition of this invention, an esterification catalyst can also be mix | blended as arbitrary components (C). Specifically, for example, an organic or inorganic compound of at least one metal selected from the group consisting of titanium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium and strontium Is mentioned.
As a compounding quantity of a component (C), it is 0.001-0.1 mass part with respect to a total of 100 mass parts of a component (A) and (B). By making the compounding amount of component (C) 0.001 part by mass or more, the effect of adding a carbodiimide compound is prevented from being lowered, and by making it 0.1 parts by mass or less, the decomposition reaction is promoted too much. To prevent. A desirable amount of component (C) is 0.005 to 0.2 parts by mass, although it varies depending on the type of metal.
Examples of metal organic or inorganic compounds include metal alkoxides, organic acid salts, chelates, and oxides. Particularly, titanium organic compounds such as alkyl titanate, titanium oxyacetylacetonate, and titanium oxalate. Compounds are useful. So-called biodegradable resins are subject to microbial decay in the soil, but metal organic or inorganic compounds are believed to remain in the soil, so a safe type is preferred. From this point of view, desirable metals include titanium, germanium, zinc, magnesium, calcium and the like.

As a method for producing the biodegradable resin composition of the present invention, it is preferable to use an extruder that is used when melt-mixing ordinary thermoplastic resins.
Hereinafter, a case where a typical component (A) is prepared by performing gelatinization and melt-mixing with a biodegradable resin using oxidized starch which is a preferred modified starch among starches will be described as an example.
Specifically, it is equipped with a vent for dehydration with a twin screw system in order to simultaneously gelatinize, dehydrate, and melt-mix the gelatinized oxidized starch and biodegradable resin. is important. Furthermore, in order to ensure a sufficient production amount, sufficient L / D is an important factor, and usually L / D is 32 or more. As a more efficient method of dehydration and mixing, in the first step, the backflow due to the pressure increase in the extruder is prevented with an open vent at the completion of gelatinization of the oxidized starch by heating and mixing, and further in the second step, oxidized starch is used. The dehydration is performed with a vacuum vent while further mixing the gelatinized product and the biodegradable resin.

In order to complete these two steps with a single extruder, it is important that the L / D is 32 at the minimum, and it is possible to increase the discharge amount with an apparatus having a larger L / D. The manufacturing cost can be reduced. In the first step, the set temperature is set to about 60 to 150 ° C., preferably 80 to 140 ° C. according to the softening temperature (or melting point) of the biodegradable resin. Since many biodegradable resins soften (melt) in this temperature range, gelatinized oxidized starch and biodegradable resin are mixed in a molten state simultaneously with gelatinization of the oxidized starch. The residence time in the first step is usually 30 to 180 seconds, preferably 60 to 120 seconds. By setting the residence time to 30 seconds or longer, gelatinization of the oxidized starch proceeds sufficiently, and by setting it to 180 seconds or shorter, decomposition can be suppressed and productivity can be ensured.
In the second step, the set temperature is about 130 to 180 ° C, preferably 150 to 170 ° C. Thereby, the gelatinized product of oxidized starch and the biodegradable resin are completely melt-mixed. The residence time in the second step is usually 30 to 120 seconds, preferably 60 to 90 seconds. By setting the residence time to 30 seconds or more, the gelatinized oxidized starch and the sexolytic resin can be sufficiently mixed, and by setting it to 120 seconds or less, decomposition can be suppressed and productivity can be secured. it can.

In order to gelatinize the oxidized starch in the first step, it may be possible only with the moisture retained by the oxidized starch itself, depending on the temperature, residence time, elasticity, etc., but it is necessary to complete the gelatinization. Water and / or polar high-boiling solvents can be added. Examples of the high boiling polar solvent include ethylene glycol, propylene glycol, glycerin, sorbitol, polyethylene glycol, and polypropylene glycol.
Among these, glycerin is preferably used from the viewpoints of compatibility with starch and biodegradable resin, a balance between pasting ability and cost. The amount of water and / or polar high-boiling solvent added is 0 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of the composition (A) containing starch and biodegradable resin. .
By controlling the amount to 10 parts by mass or less, the high-boiling solvent having polarity is prevented from bleeding.
The same conditions apply when component (A) is prepared by performing gelatinization and melt-mixing with a biodegradable resin using various unmodified starches as described above in place of oxidized starch in the description of gelatinization and the like. Is applicable.
One component (A) in the biodegradable resin composition of the present invention is obtained by the procedure as described above.
There is no restriction | limiting in particular about the compounding method of the component (B) and the component (C) which is an arbitrary component. It is also possible to feed and mix into an extruder for producing the biodegradable resin composition, and to add a high concentration of the carbodiimide compound (B) and / or the esterification catalyst (C) to the component (A) produced in advance. It is also possible to prepare an added master batch and blend it with the component (A) during film formation. In particular, in the case of adding in a master batch method, the amount added can be changed depending on the purpose, so that it is efficient for the production of a small variety of products.
The blending ratio of the component (A) to the carbodiimide compound (B) and / or the esterification catalyst (C) in the master batch is usually 500/1 to 1/1, preferably 50/1 to 5 / in terms of the former / the latter mass ratio. 1 or so.

Next, a biodegradable film formed by molding the biodegradable resin composition of the present invention will be described.
As a method for producing the biodegradable film of the present invention, for example, the gelatinized product of oxidized starch and the biodegradable resin are melt-mixed using an extruder as described above, and further components (B ) And / or (C) masterbatch to obtain a biodegradable resin composition, which is manufactured continuously by connecting an extruder outlet to a known water-cooled or air-cooled inflation molding, T-die type film molding machine. Alternatively, it may be once pelletized or flaked and then molded using a known water-cooled or air-cooled inflation molding or T-die type film extruder.
When the biodegradable resin composition of the present invention is formed into a film, it may further contain a plasticizer. The effect of adding a plasticizer is exhibited when the biodegradable resin further contains polylactic acid. As the plasticizer to be used, a glycerin derivative is preferable, and polyglycerin acetate or a derivative thereof or adipic acid diester is particularly preferable. The addition amount is usually about 1 to 10% by mass, preferably 2 to 8% by mass, based on the total amount of the biodegradable resin composition. When the content is 1% by mass or more, film properties, particularly tensile elongation, and film impact strength are improved, and when the content is 10% by mass or less, the plasticizer is bleed to prevent appearance defects.

In addition, the biodegradable film of the present invention may contain additives that are usually used in the technical field as desired, for example, antioxidants, heat stabilizers, UV inhibitors, antistatic agents, flame retardants, and crystallization accelerators. Etc. may be added within a range not impairing the characteristics of the present invention.
Specifically, hindered phenolic antioxidants such as pt-butylhydroxytoluene and pt-butylhydroxyanisole as antioxidants; triphenyl phosphite, trisnonylphenyl phosphite as thermal stabilizers Etc .; Examples of ultraviolet absorbers include pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2 ^, -carboxybenzophenone, 2,4,5-trihydroxybutyrophenone, etc. N, N-bis (hydroxyethyl) alkylamines, alkylamines, alkylarylsulfonates, alkylsulfonates, etc. as inhibitors; hexabromocyclododecane, tris- (2,3-dichloropropyl) phosphate, pentabromo as flame retardants Feni Allyl ether; the crystallization promoter talc, Holon nitrite, polyethylene terephthalate, poly - trans cyclohexanedimethanol terephthalate and the like.

As described above, when the film is produced using the biodegradable resin composition once pelletized or flaked, instead of continuously producing the film following the preparation of the biodegradable resin composition The preset temperature of the inflation molding and T-die type film extrusion molding machine is the same preset temperature as in the second step, that is, about 130 to 180 ° C, preferably 145 to 170 ° C.
The biodegradable film of the present invention may be obtained by further uniaxially or biaxially stretching the film.
Since the biodegradable resin composition of the present invention has improved moldability when it is formed into a biodegradable film, the productivity is improved, and the obtained biodegradable film has mechanical properties. In particular, since the impact strength of the film is improved, it is suitably used for compost bags having biodegradability, agricultural films, packaging materials, and the like. Furthermore, since it is possible to adjust the biodegradability rate and the hydrolysis rate, it is possible to quickly respond to demands according to the use environment at low cost.

  The present invention will be described in more detail with reference to examples and comparative examples below, but the present invention is not limited to the following examples.

[Examples 1 to 9 and Comparative Examples 1 to 3]
Table 1 shows the types of starch and biodegradable resin, the respective blending amounts and blending amounts of carbodiimide compounds, etc. [the blending amount of each substance in the table represents parts by mass].
The raw materials and additives in each example are mixed using a super mixer, melt-kneaded using a 80 mm screw twin screw extruder (L / D is 32) equipped with a vent for dehydration, and biodegraded. Pellets of the conductive resin composition were obtained. The set temperature is 80 to 140 ° C for the first step, 150 to 180 ° C for the second step, the residence time is 60 to 90 seconds for the first step, and 60 to 90 seconds for the second step.
Each pellet of the obtained biodegradable resin composition was dried at 70 ° C. for 3 hours with a dehumidifying air circulation dryer, and then 30 μm thick and 300 mm folded width (blow-up) using an inflation molding machine manufactured by Yoshii Tekkosha Ratio = equivalent to 3). The molding temperature is 165 ° C.

The measuring method of each characteristic is shown below.
<Physical properties of film>
A four-step evaluation was made based on the results measured by the following method.
A: Tensile breaking strength, 20 MPa or more, Tensile breaking elongation 200% or more, Young's modulus 250-500 MPa, Impact strength 2000 N · cm / mm or more ○: If any of the above items is not achieved Δ: Any of the above When two items are not achieved x: When any of the above three items are not achieved Each measurement method is as follows.
-Tensile strength at break: Measured according to JIS Z-1702.
-Tensile elongation at break: measured according to JIS Z-1702.
-Young's modulus: measured according to ASTM D-822.
Impact strength: measured according to JIS P-8134.
The above-mentioned mechanical properties were measured for each film only when the film formability was evaluated as ◯ or Δ and a film was obtained. Mechanical properties other than impact strength were measured in both the vertical direction (film take-up direction, MD) and the horizontal direction (TD).
<Biodegradation rate (biodegradability)>
Showa Polymer Co., Ltd. Tatsuno Factory The ground cut in the 10cm square at a depth of about 10cm, embedded in nylon mesh for 1 month, measured the amount of mass loss, from the reduction rate, Considering performance required for practical use such as agricultural mulch (If the biodegradation speed is significantly faster than the period of use, problems such as tearing and scattering will occur, and if it is extremely slow, it will remain undecomposed even if it is swallowed. And evaluated in the following four stages.
A: 30 to less than 60% B: 10 to less than 30% B: 60 to less than 80% X: 80% or more or less than 10% <Hydrolysis rate (hydrolysis resistance)>
The film sample was placed in a constant temperature and humidity chamber at 60 ° C. and 95% RH, and a tensile test was conducted after one week, and the retention rate relative to the initial physical properties (physical properties immediately after molding) was determined for the MD tensile fracture elongation. Based on this, the following three stages of evaluation were performed. In Comparative Example 3, since the film could not be formed at all, the hydrolysis resistance was not measured.
○: Retention rate after 1 week is 80% or more Δ: Retention rate after 1 week is 50% or more and less than 80% ×: Retention rate after 1 week is less than 50% <Film formability>
A three-level evaluation was performed as follows.
○: When the bubble is stable and a film with a predetermined size is obtained. Δ: When the bubble is unstable and the film with a predetermined size cannot be adjusted. ×: When the bubble does not stand up or puncture occurs and cannot be formed.

<Materials used>
(1) Biodegradable resin A: dehydration condensation type aliphatic polyester manufactured by Showa Polymer Co., Ltd. [Bionole 3001G (melting point: 95 ° C., MFR; 1.2 g / 10 min)]
(2) Biodegradable resin B: polycaprolactone manufactured by Daicel Chemical Industries, Ltd. [Placcel H-7 (melting point: 60 ° C., MFR; 3.5 g / 10 min)]

The MFRs of the above (1) and (2) were measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N according to JIS K7210.

(3) Starch A: Oxidized starch manufactured by Oji Cornstarch Co., Ltd. [Ace A; carboxyl group substitution degree 0.01, viscosity 300 ± 50 BU (Brabender viscosity, concentration 20% by mass, measured after 1 hour at 50 ° C.) , Moisture 12 mass% (atmospheric pressure heating method 105 ° C, 4 hours)
(4) Starch B: Corn starch manufactured by Oji Corn Starch Co., Ltd. [Raw starch; Carboxyl group substitution degree 0, Viscosity 1100 ± 50 BU (Brabender viscosity, concentration 8 mass%, measured after 1 hour at 50 ° C.), moisture 12 mass % (Normal pressure heating method 105 ° C, 4 hours)
(5) Starch C: Oxidized starch manufactured by Oji Cornstarch Co., Ltd. [Ace C; degree of carboxyl group substitution 0.03, viscosity 200 ± 50 BU (Brabender viscosity, concentration 30% by mass, measured after 1 hour at 50 ° C.) , Moisture 12 mass% (atmospheric pressure heating method 105 ° C, 4 hours)
(6) Water: Deionized water
(7) Polar solvent with high boiling point: Glycerin
(8) Plasticizer A: Polyglycerin acetate [Riquemar PL-710] manufactured by Riken Vitamin Co., Ltd.
(9) Plasticizer B: Adipic acid diester [Adekasizer RS-107] manufactured by Asahi Denka Co., Ltd.
(10) Carbodiimide: Carbodiimide manufactured by Nisshinbo Co., Ltd. [Carbodilite LA-1]
(11) Esterification catalyst: Hydrotalcite [DHT-4A] manufactured by Kyowa Chemical Co., Ltd.
The measurement results are also shown in Table 1.

  From the results shown in Table 1, the biodegradable resin composition of the present invention is superior in film moldability as compared with the comparative example, and the obtained biodegradable film has an appropriate biodegradation rate and water resistance. It can be seen that it has a decomposition rate and is excellent in film physical properties.

  The biodegradable resin composition and biodegradable film of the present invention have an appropriate biodegradation rate and hydrolysis rate, and the biodegradable film has a strong tear strength, particularly a tear strength in the machine (stretching) direction, It is suitably used as a compost bag, agricultural film, packaging material and the like.

Claims (18)

The gelatinized product of oxidized starch having a structure in which C-2 and C-3 in some glucose units in the starch are cleaved and carboxyl groups are formed in C-2 and C-3 And a composition (A) containing 50 to 80% by mass of a biodegradable resin other than the gelatinized product of oxidized starch [the total of both is 100% by mass] and 100 parts by mass of the carbodiimide compound (B) 0.01 to 10 A biodegradable resin composition containing parts by mass.   The biodegradable resin composition according to claim 1, further comprising an esterification catalyst (C).   The biodegradable resin composition according to claim 2, wherein the blending amount of (C) is 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the composition (A).   The biodegradable resin composition according to any one of claims 2 and 3, wherein a master batch containing a part of (B) and / or (C) and (A) and a part of (A) are blended. object.   The biodegradable resin composition according to any one of claims 1 to 4, wherein the biodegradable resin is a condensation polymer of a polyol and an aliphatic polycarboxylic acid and / or a derivative thereof.   The biodegradable resin composition according to claim 5, wherein the polyol is ethylene glycol and / or 1,4-butanediol, and the aliphatic polycarboxylic acid is succinic acid and / or adipic acid.   The biodegradable resin composition according to claim 6, wherein the biodegradable resin further contains polylactic acid.   The biodegradable resin composition according to any one of claims 1 to 4, wherein the biodegradable resin is polycaprolactone.   The biodegradable resin is a condensation polymer of an aromatic polycarboxylic acid and an aliphatic polyol and / or a condensation polymer of an aliphatic polycarboxylic acid or an aromatic polycarboxylic acid and an aliphatic polyol. The biodegradable resin composition according to any one of the above.   The biodegradable resin composition according to claim 9, wherein the aliphatic polycarboxylic acid is adipic acid, the aromatic polycarboxylic acid is terephthalic acid, and the aliphatic polyol is butanediol.   The biodegradable resin composition according to any one of claims 1 to 10, wherein the starch is a gelatinized product of oxidized starch produced using sodium hypochlorite.   The biodegradable resin composition according to any one of claims 1 to 11, wherein the starch is gelatinized using an extruder with a vent simultaneously with mixing of the biodegradable resin.   The biodegradable resin composition according to any one of claims 1 to 12, further comprising a polar solvent having a high boiling point selected from ethylene glycol, propylene glycol, glycerin, sorbitol, polyethylene glycol, and polypropylene glycol.   Furthermore, the biodegradable resin composition in any one of Claims 1-13 containing a plasticizer. The biodegradable resin composition according to claim 14, the plasticizer is at least one selected from polyglycerol acetic ester le Contact and adipic acid diester. The biodegradable resin composition according to any one of claims 1 to 15, wherein the degree of carboxyl group substitution of the oxidized starch by a neutralization titration method is 0.001 to 0.100. Composition (A) containing 20-50% by mass of oxidized starch and 50-80% by mass of other biodegradable resins [total of both is 100% by mass] and 100 parts by mass of carbodiimide compound (B) A biodegradable resin composition obtained by melt-kneading 01 to 10 parts by mass with a twin screw extruder at a temperature of 80 to 140 ° C. and a residence time of 60 to 120 seconds. Biodegradable film obtained by molding the biodegradable resin composition according to any one of claims 1 to 17.