JP2011052149A - Polylactic acid resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition from which a pouched film having practically-satisfactory flexibility and strength can be formed and which can be solubilized satisfactorily in an anaerobic atmosphere. <P>SOLUTION: The polylactic acid resin composition includes: polylactic acid; a plasticizer for the polylactic acid (for example, an ester-based plasticizer such as aliphatic dicarboxylate) and/or a soft resin (for example, polyalkylene alkanoate such as polyalkylene succinate and poly(alkylene alkanoate/allylate)); and a polymer having a thickening function. It does not matter if the polymer having the thickening function is typically a polymer having a reactive group (particularly, an epoxy group) to be reacted with a hydroxy group and/or a carboxy group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polylactic acid resin composition that can be formed into a film (in particular, formed into a bag shape by inflation molding), a film formed from the resin composition, and a method for producing the same.

  Conventionally, biodegradable resins used for the production of biodegradable films include microbial polyhydroxybutyrate (PHB), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate adipate (PBSA). ), Polybutylene succinate (PBS), aliphatic polyester resins such as polybutylene adipate terephthalate (PBAT), which is an aromatic modified aliphatic polyester resin, and polyvinyl alcohol (PVA). Among these, PHB, PLA, PVA, and the like are hard resins, and among these, PLA is excellent in characteristics such as heat resistance and has high utility value in terms of cost. However, such a hard resin alone cannot combine practical flexibility and strength, and it is particularly difficult to form a film into a bag shape such as a garbage bag or a packaging bag.

On the other hand, since PBS, PBSA, PBAT, etc. are soft resins, inflation molding and T-die film molding are easy. However, although PBS, PBSA, PBAT, and the like are biodegradable plastics, they are manufactured from petrochemical raw materials, so that combustion leads to an increase in CO ₂ emissions. On the other hand, PLA or the like is a plant-derived resin, and even if it is burned, it does not increase the emission of CO ₂ , so there is a strong demand for practical use from the viewpoint of carbon neutral. Currently, the “Biomass Plastic” certification is received from the Japan Bioplastics Association (JBPA) for plastics containing more than 25% plant-derived resin such as PLA. Therefore, a technique for combining a soft resin and a hard resin has been developed, such as blending a soft resin partially with a hard resin.

  For example, JP-A-8-245866 (Patent Document 1) discloses a copolymer containing lactic acid as a main component (such as a copolymer obtained by block copolymerization of an aliphatic polyester such as polyethylene adipate with respect to polylactic acid). And a plasticizer of an aliphatic polyester (polyethylene adipate or the like) mainly composed of an aliphatic dicarboxylic acid and a chain molecular diol, wherein the weight ratio of the plasticizer is less than 50% A polylactic acid composition characterized by the above is disclosed. JP-A-9-111107 (Patent Document 2) describes at least a polylactic acid polymer and a biodegradable aliphatic polyester having a glass transition point Tg of 0 ° C. or lower (for example, 1,4-butanediol). And a biodegradable plastic film or sheet comprising a condensate of succinic acid and adipic acid). However, when these technologies are applied to a garbage bag or the like, in order to give flexibility to withstand use, in reality, a soft system is used in a large proportion (for example, 60% or more of the resin component) with respect to PLA. It is necessary to mix the resin, and the characteristics of PLA are impaired in the resin composition. In addition, if the added amount of PBSA, PBAT or the like is large, the transparency of the film is lost and the contents of the garbage bag cannot be seen from the outside.

  Biodegradable resin films, on the other hand, are expected to be decomposed in soil and aerobic atmosphere into fertilizer by putting them in compost as garbage bags, but the amount of garbage generated In large cities where there are many, there are few land and fields to disassemble into the center. Therefore, instead of using fertilizer, it is desired to convert garbage into biogas. As a technology for converting into biogas, biodegradable resin film is solubilized in an anaerobic atmosphere. Technology for methane fermentation is being developed.

  However, none of the resin compositions and films disclosed in Patent Document 1 and Patent Document 2 and commercially available garbage bags are solubilized easily. Therefore, it is difficult to practically use such a resin composition or film for solubilization. In the case of a garbage bag, it is necessary to separate the garbage bag from the garbage bag and put it in a solubilization tank. was there.

  And the subject about such solubilization is the same also in PLA, and although it is known that PLA is not easily solubilized in methane fermentation, in recent years, it is easy to solubilize polylactic acid. Technology is being developed. For example, JP 2005-232336 A (Patent Document 3) discloses a solubilization method including a step of mixing polylactic acid and waste water after methane fermentation in JP 2009-154125 A (Patent Document 4). Discloses a method for solubilizing polylactic acid, which includes a step of heating an organic substance containing polylactic acid in an anaerobic atmosphere in the presence of methane fermentation sludge under a temperature condition of 65.5 ° C. or higher. Patent Document 4 is a technology developed by the present inventors. Polylactic acid has a solubilization tank temperature of 65.5 ° C. or higher, and PLA is very anaerobic atmosphere in an alkaline environment such as ammonia. It is disclosed that it becomes easy to hydrolyze.

  Under such circumstances, development of a bag-like film formed of PLA is desired, but as described above, PLA has many problems in forming into a bag-like shape. For example, PLA alone has a high melt flow rate and a low melt viscosity, making it difficult to apply typical inflation molding as a molding method for producing a bag-like film. Although it can be formed into a thin sheet by the T-die type film forming method, in order to make it into a bag shape, it is necessary to fusion-bond three sides of the two films, which takes time and cost. It is also very difficult to increase the sealing strength. Furthermore, PLA is a material with high rigidity and low elongation, so even if it is molded into a bag shape, if there are projections such as fish bones, it is expected to tear, leak water, or peel off from the seal part. Is done. As described above, the practical application of the PLA film by inflation molding has many problems including such a problem of strength.

As a technique for improving the inflation moldability of PLA, Japanese Patent Application Laid-Open No. 2008-260895 (Patent Document 5) includes 100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzylalkyldiglycol adipate, and water. A film containing a polylactic acid resin composition containing 1 to 5 parts by weight of a decomposition inhibitor (carbodiimide or the like) and having a melt viscosity of 1 × 10 ³ to 10 × 10 ³ Pa · s at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ Is disclosed. In this document, by setting the addition amount of the hydrolysis inhibitor within the above range, a decrease in viscosity due to a decrease in molecular weight can be prevented, inflation molding can be performed smoothly, and an increase in viscosity due to an excessive crosslinking reaction can be achieved. It is described that inflation molding can be performed smoothly. However, a hydrolysis inhibitor such as carbodiimide is difficult to produce a transparent film because it has a low effect of extending the chain of the polylactic acid resin, or is not sufficiently effective in increasing the viscosity and is easily colored.

JP-A-8-245866 (Claims) JP-A-9-111107 (Claims, Examples) JP 2005-232336 A (Claims) JP 2009-154125 A (Claims) JP 2008-260895 A (claims, paragraph number [0019])

  Accordingly, an object of the present invention is to provide a polylactic acid resin composition that can achieve both flexibility and strength at a practical level and can be film-formed (particularly film-formed by inflation molding), a film formed from this resin composition, and It is to provide a manufacturing method.

  Another object of the present invention is to form a polylactic acid resin composition that can form a bag-like film that can satisfy a practical level in flexibility and strength, and that can be sufficiently solubilized in an anaerobic atmosphere, and is formed from this resin composition. It is in providing a film and its manufacturing method.

  Still another object of the present invention is to provide a resin composition that can be solubilized and capable of forming a film having antibacterial properties, a film formed from the resin composition, and a method for producing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that polylactic acid is a plasticizer of polylactic acid (for example, an ester plasticizer such as aliphatic dicarboxylic acid ester) and / or a soft resin, By using a resin composition combined with a polymer having a thickening action (or a polymer that imparts viscosity), it is possible to form a polylactic acid film having sufficient flexibility and strength that can withstand practical use in garbage bags, Despite having these characteristics, it is possible to form a film that can be easily solubilized in an anaerobic atmosphere in methane fermentation technology. The present invention was completed.

  That is, the polylactic acid resin composition (first resin composition) of the first aspect of the present invention is composed of polylactic acid, a plasticizer for plasticizing polylactic acid, and a polymer having a thickening action. Has been. The polylactic acid resin composition (second resin composition) of the second aspect of the present invention is composed of polylactic acid, a soft resin, and a polymer having a thickening action.

  In the resin composition of the first aspect, the plasticizer may be an ester plasticizer (particularly an aliphatic dicarboxylic acid ester). In the resin composition, the plasticizer ratio may be about 5 to 25 parts by mass with respect to 100 parts by weight of polylactic acid.

  In the second resin composition, the soft resin may be an aliphatic polyester resin [eg, polyalkylene alkanoate (eg, polyalkylene succinate) poly (alkylene alkanoate / arylate), etc.]. In the second resin composition, the ratio of polylactic acid to soft resin may be about the former / the latter = 99/1 to 50/50.

  In the first and second resin compositions, the polymer having a thickening action is typically a polymer having a reactive group (particularly, an epoxy group) with respect to a hydroxyl group and / or a carboxyl group. Good. In the polymer having such a reactive group, the ratio of the reactive group may be, for example, about 0.1 to 5 mol per kg of the polymer. Further, the proportion of the polymer having a thickening action may be about 1 to 15 parts by mass with respect to 100 parts by mass of polylactic acid.

  The first and second resin compositions of the present invention may further contain an anti-blocking agent, and the ratio of such an anti-blocking agent is, for example, 0.1 with respect to 100 parts by mass of polylactic acid. About 10 mass parts may be sufficient.

The melt viscosity of the first and second resin compositions of the present invention is 190 ° C. At a shear rate of 600 s ⁻¹ , for example, it is about 70 to 500 Pa · s, and is excellent in film moldability, particularly inflation moldability. Therefore, the resin composition of the present invention may be a resin composition for film molding (particularly for inflation molding).

  The present invention includes a film (particularly, an inflation film) formed from the resin composition. Such a film has moderate flexibility and strength. For example, the tensile strength may be about 10 to 50 MPa, and the elongation at break may be about 100 to 600%.

  As described above, since the resin composition of the present invention is suitable as a resin composition for inflation molding, the present invention further includes a method for producing a bag-like film by inflation molding of the resin composition. included.

  Although the resin composition of the present invention is composed of polylactic acid, it can achieve both flexibility and strength at a practical level, and can be formed by film molding, particularly by inflation molding. In addition, the resin composition of the present invention can form a bag-like film that can satisfy a practical level of flexibility and strength as described above, and can be sufficiently solubilized in an anaerobic atmosphere. As described above, the resin composition of the present invention can be efficiently formed into a bag-like film such as a garbage bag by inflation molding or the like, and can be easily decomposed by a methane fermentation technique and is extremely useful. Moreover, the resin composition of the present invention can be solubilized as described above, and can surprisingly form a film having antibacterial properties. Therefore, when using as a garbage bag etc., generation | occurrence | production of a microbe is prevented or suppressed, and when discarding, it can use for solubilization with garbage etc., without separating.

<Polylactic acid resin composition>
The polylactic acid resin composition is a resin composition according to any of the following aspects (I) or (II).

(I) a polylactic acid resin composition composed of polylactic acid, a plasticizer (plasticizer for plasticizing polylactic acid), and a polymer having a thickening action. (II) polylactic acid, a soft resin, A polylactic acid resin composition comprising a polymer having a thickening action.

[Polylactic acid]
Polylactic acid (polylactic acid-based resin) is a polymer having a lactic acid component as a polymerization component. Examples of the lactic acid component include lactic acid (D-lactic acid, L-lactic acid, DL-lactic acid), reactive derivatives of lactic acid [for example, C _1-3 alkyl esters such as lactide (lactic acid dimer), methyl ester, etc.] Etc. are included. Lactic acid components may be used alone or in combination of two or more.

  The polylactic acid may be a polymer having a lactic acid component as a main component, and may be a homopolymer of the lactic acid component (for example, poly D-lactic acid, poly L-lactic acid, poly D, L-lactic acid, etc.) It may be a copolymer of a lactic acid component and a copolymer component. Examples of the copolymerizable component copolymerizable with the lactic acid component include a diol component (for example, an aliphatic diol component described later such as ethylene glycol), a dicarboxylic acid component (for example, an aliphatic dicarboxylic acid component described later), and a hydroxycarboxylic acid. Alternatively, lactones (for example, components described later such as glycolic acid and glycolide) can be used. These copolymer components may be used alone or in combination of two or more. In such a copolymer, the proportion of the lactic acid component is, for example, 70 mol% or more (for example, about 75 to 99.5 mol%), preferably 80 mol% or more (for example, 85 to 99 mol) of the total constituent monomers. %), More preferably 90 mol% or more (for example, about 92 to 98 mol%).

  In addition, you may comprise polylactic acid combining 2 or more types of polylactic acid of a different kind (or polymerization composition).

  The weight average molecular weight of polylactic acid can be selected from the range of, for example, 100 to 1,000,000, typically 1000 to 800,000 (for example, 5000 to 700,000), preferably 10,000 to 600000, and more preferably 20000 to 500000 (for example, 30000). ˜400000) or about 10000 to 5000000 (for example, 30000 to 400000, preferably 50000 to 200000).

  The acid value of polylactic acid is, for example, 0 to 100 mgKOH / g (for example, 0.1 to 80 mgKOH / g), preferably 0.2 to 80 mgKOH / g, more preferably 0.3 to 60 mgKOH / g, particularly It may be about 0.5 to 30 mg / KOH / g. In addition, when an acid value is too large, it will become easy to hydrolyze. The hydroxyl value of polylactic acid can also be selected from the same range as above.

  The melt flow rate of polylactic acid is, for example, 1 to 30 g / 10 minutes, preferably 2 to 20 g / 10 minutes, more preferably 3 to 15 g / 10 minutes under the conditions of 190 ° C. and a load of 2.16 kg. In particular, it may be about 4 to 10 g / 10 minutes.

[Plasticizer]
The plasticizer may be any component that can plasticize polylactic acid. For example, an ester plasticizer, a phosphate ester plasticizer, an epoxy plasticizer (alkyl epoxy stearate, etc.), an amide plasticizer (for example, N -Sulfonamides such as butylbenzenesulfonamide) and oligomer type plasticizers (for example, ester oligomers such as caprolactone oligomers). Typical plasticizers are ester plasticizers (carboxylic ester plasticizers) and phosphoric ester plasticizers, and ester plasticizers can be particularly preferably used. The plasticizers may be used alone or in combination of two or more.

(Ester plasticizer)
Examples of the ester plasticizer include polycarboxylic acid esters {for example, dicarboxylic acid esters (aliphatic dicarboxylic acid esters, aromatic dicarboxylic acid esters, etc.), polycarboxylic acid esters having three or more carboxyl groups [for example, citric acid Esters (eg, tributyl acetylcitrate, tri-2-ethylhexyl acetylcitrate), trimellitic esters (eg, trimethyl trimellitic acid, triethyl trimellitic acid, trioctyl trimellitic acid, tri-2-ethylhexyl trimellitic acid, etc.) ), Esters of aliphatic or aromatic carboxylic acids having about 3 to 8 (preferably 3 to 6) carboxy groups such as pyromellitic acid esters (for example, tetraoctyl pyromellitic acid)}, polyhydric alcohols (Glycerin, di Glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, with alcohol) esters 3-6 about the hydroxyl group, such as sorbitol (eg, glycerin diacetate mono C _8-10 alkyl esters, triacetin, diglycerin (Poly) C _3-10 alkane polyol mono to hexa C _2-10 alkanoate) such as tetraacetate). Glycerin diacetate mono C _8-10 alkyl ester can also be obtained from Riken Vitamin Co., Ltd. under the trade name “Riquemar”.

In dicarboxylic acid esters (esters of dicarboxylic acid and alcohol), the corresponding dicarboxylic acids include aliphatic dicarboxylic acids (for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelain). C _2-10 aliphatic dicarboxylic acid such as acid or sebacic acid, preferably C _2-8 alkane dicarboxylic acid, more preferably C _3-6 alkane dicarboxylic acid), non-aliphatic dicarboxylic acid [for example, aromatic dicarboxylic acid ( Examples thereof include _C8-16 aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, preferably _C8-14 arene dicarboxylic acid). In terms of biodegradability, aliphatic dicarboxylic acids are preferred.

In the dicarboxylic acid ester, the corresponding alcohol includes, for example, an aliphatic alcohol [eg, alkanol (eg, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, hexanol, heptanol, octanol). C _1-12 alkanols such as C _1-10 alkanols, etc.]], aromatic alcohols [eg, aralkyl alcohols (eg, C _6-10 aryl-C _1-4 alkyl alcohols such as benzyl alcohol, phenethyl alcohol, etc.) etc.], glycol [e.g., alkylene glycol (e.g., C _2-4 alkylene glycols such as ethylene glycol), polyalkylene glycols (e.g., di- to tetra C such as diethylene glycol _-4 alkylene glycols; and poly C _2-4 alkylene glycol such as polypropylene glycol), etc.], glycol ethers {or glycol monoethers, such as alkylene glycol monoalkyl ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, C _2-4 alkylene glycol mono C _1-6 alkyl ether such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, preferably C _2-3 alkylene glycol mono C _1-4 alkyl ether), polyalkylene glycol monoalkyl ether (for example, , Diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether Di- or hexa-C _2-4 alkylene glycol mono C _1-8 alkyl ether, preferably di-tetra C _2-3 alkylene glycol mono C _1-4 alkyl ether), such glycol ethers, Aryl or aralkyl ethers corresponding to the above [eg, alkylene glycol monoaryl ethers (eg, C _2-4 alkylene glycol mono C _6-10 aryl ethers such as ethylene glycol monophenyl ether), polyalkylene glycol monoaryl ethers (eg, dialkyl ethers) or di- to tetra-C _2-3 alkylene glycol mono C _6-10 aryl ether such as triethylene glycol monophenyl ether), an alkylene glycol mono aralkyl ether (E.g., C _2-4 alkylene glycol mono C _6-10 aryl C _1-4 alkyl ethers such as ethylene glycol monobenzyl ether), polyalkylene glycol mono aralkyl ethers (e.g., di-and di or triethylene glycol monobenzyl ether Thru | or tetra _C2-3 alkylene glycol mono _C6-10 aryl _C1-4 alkyl ether) etc. are mentioned.

Of these alcohols, alkanols (eg C _1-6 alkanols such as methanol, ethanol, butanol, preferably C _1-4 alkanols), aralkyl alcohols (eg C _6-10 aryl C such as benzyl alcohol, phenethyl alcohol, etc.) _1-4 alkyl alcohols, preferably C _6-8 aryl C _1-2 alkyl alcohols), alkylene glycol monoalkyl ethers (eg C _2-3 alkylene glycol mono C _1-4 alkyl ethers such as ethylene glycol monomethyl ether), Di to tetraalkylene glycol monoalkyl ethers (eg di to tetra C _2-3 alkylene glycol mono C _1-4 alkyl ethers such as di- or triethylene glycol monomethyl ether) Is preferred.

  Alcohols may be used alone or in combination of two or more. That is, the dicarboxylic acid ester may be a diester with the same alcohol as the dicarboxylic acid, or may be a diester with two different alcohols different from the dicarboxylic acid. In esters with two different alcohols, preferred combinations of alcohols include, for example, combinations of aliphatic alcohols (eg, alkanols) or aromatic alcohols (eg, aralkyl alcohols) and glycol ethers. Such esters of dicarboxylic acids and different alcohols (diesters) are often advantageous in terms of biodegradability.

  Examples of the dicarboxylic acid ester include an aliphatic dicarboxylic acid ester (an ester of an aliphatic dicarboxylic acid and an alcohol) and an aromatic dicarboxylic acid ester (an ester of an aromatic dicarboxylic acid and an alcohol).

Representative aliphatic dicarboxylic acid esters include, for example, dialkyl aliphatic dicarboxylates (eg, dibutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, diisodecyl adipate, dibutyl sebacate, dioctyl sebacate, azelain C _2-10 alkanedicarboxylic acid diC _1-12 alkyl, preferably C _4-10 alkanedicarboxylic acid diC _4-8 alkyl ester) such as diethyl acid, dibutyl azelate, azelaic acid-di-2-ethylhexyl), fat Diesters of aliphatic dicarboxylic acids and glycol ethers {eg diesters of aliphatic dicarboxylic acids and (poly) alkylene glycol monoalkyl ethers [eg bis (methyldiethylene glycol) adipate (or adipic acid di (methoxy) Ciethoxyethyl) ester, ie diester of adipic acid and diethylene glycol monomethyl ether), bis (butyldiethylene glycol) adipate, bis (methyldiethylene glycol) succinate, methyldiethylene glycol ethyldiethylene glycol adipate (or adipic acid methoxyethoxyethyl ethoxyethoxyethyl ester) That is, diesters of adipic acid and diethylene glycol monomethyl ether and diethylene glycol monoethyl ether), C _2-10 alkane dicarboxylic acids such as methyl diethylene glycol butyl diethylene glycol adipate, and di to tetra C _2-4 alkylene glycol mono C _1-4 alkyl ethers. Diester], aliphatic dicarboxylic acid and a Diesters of alkyl alcohols and (poly) alkylene glycol monoalkyl ethers [eg benzylmethyldiethylene glycol adipate (or adipic acid methoxyethoxyethyl benzyl ester, ie diesters of adipic acid with benzyl alcohol and diethylene glycol monomethyl ether), benzylethyl C _2-10 alkane dicarboxylic acids such as diethylene glycol adipate, benzyl butyl diethylene glycol adipate, benzyl methyl diglycol succinate, benzyl butyl diglycol succinate and C _6-10 aryl C _1-4 alkyl alcohol and C _2-4 alkylene glycol mono _{Diester with} C _1-4 alkyl ether] and the like.

Representative aromatic dicarboxylic acid esters include dialkyl aromatic dicarboxylates (eg, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, phthalate). C _8-14 arene dicarboxylic acid di C _1-12 alkyl ester such as diisodecyl acid, preferably C _8-10 arene dicarboxylic acid di C _1-10 alkyl ester, more preferably benzene dicarboxylic acid C _4-8 alkyl ester, etc.) An aromatic dicarboxylic acid alkyl aralkyl ester (for example, C _8-14 arene dicarboxylic acid C _1-12 alkyl C _6-10 aryl C _1-4 alkyl ester such as butylbenzyl phthalate), aromatic dicarboxylic acid and the like Glycol ether Diesters of {e.g. diesters of aromatic dicarboxylic acids and (poly) alkylene glycol monoalkyl ethers [e.g. bis (methyldiethylene glycol) phthalate (or phthalic acid di (methoxyethyl) ester, i.e. phthalic acid and diethylene glycol monomethyl ether] _Diesters of C _8-14 arene dicarboxylic acid (preferably C _8-10 arene dicarboxylic acid) and di to tetra C _2-4 alkylene glycol mono C _1-4 alkyl ether].

(Phosphate ester plasticizer)
Examples of phosphate ester plasticizers include aliphatic phosphate esters [eg, trialkyl phosphate esters (tri-C _1-12 alkyl esters such as triethyl phosphate and tributyl phosphate), trialkoxyalkyl phosphates. Esters (eg, tri-C _1-6 alkoxy C _1-12 alkyl esters such as tributoxyethyl phosphate)], aromatic phosphates [alkyl diaryl phosphates (eg, phosphorous such as octyl diphenyl phosphate) Acid C _1-12 alkyl-diC _6-10 aryl ester), phosphate triaryl ester (eg, triphenyl phosphate, tricresyl phosphate, tri (isopropylphenyl) phosphate, trixylenyl phosphate, cresyl diphenyl phosphate phosphoric acid tri _{C 6-10} aryl such as Ester, etc.), etc.], condensed phosphoric acid esters {e.g., dihydroxy arene - bis (diaryl phosphate) [e.g., resorcinol bis (diphenyl phosphate), resorcinol bis (dicresyl phosphate), dihydroxy C such as resorcinol bis (dixylyl phosphate) _6-10 arene-bis (di-C _6-10 aryl phosphate, etc.)] and the like}.

Preferred plasticizers are the ester plasticizer, particularly, aliphatic dicarboxylic acid esters {e.g., alkane dicarboxylic acid dialkyl ester _{(e.g., C 4-8} alkane dicarboxylic acid di _{C 1-10} alkyl ester, preferably a _{C 4- 8} alkanedicarboxylic acid di-C _4-8 alkyl ester), diesters of alkane dicarboxylic acid and (poly) alkylene glycol monoalkyl ethers [for example, C _4-8 alkane dicarboxylic acids such as bis (methyldiethylene glycol) adipate and di to tetra _{Diesters of} C _2-4 alkylene glycol mono C _1-4 alkyl ethers], diesters of alkane dicarboxylic acids with aralkyl alcohols and (poly) alkylene glycol monoalkyl ethers [eg benzylmethyldiethylene Diesters of C _4-8 alkane dicarboxylic acids such as glycol adipate with C _6-8 aryl C _1-2 alkyl alcohols and C _2-4 alkylene glycol mono C _1-4 alkyl ethers] (especially, C _4-8 alkanecarboxylic acid ester such as adipic acid ester)} and the like.

  Since such aliphatic dicarboxylic acid esters are often biodegradable, they can be suitably used.

  The plasticizer is preferably biodegradable. In addition, even if it remains as a residue in the methane fermentation process, a highly safe plasticizer that complies with food additive standards is preferable for use in compost and the like.

  In addition, the plasticizer may be contained in the resin composition of the aspect of said (II).

[Soft resin]
Examples of the soft resin include aliphatic polyester resins and esterified starch. A typical soft resin is an aliphatic polyester resin.

  Examples of the aliphatic polyester resin (aliphatic polyester resin that is not polylactic acid) include a polyester obtained by polycondensation of an aliphatic dicarboxylic acid component and an aliphatic diol component, and polycondensation of an aliphatic oxycarboxylic acid component. Polyoxycarboxylic acid, polylactone obtained by ring-opening polymerization of lactone, polyester polymerized by combining these components (for example, obtained by polycondensation of aliphatic dicarboxylic acid component, aliphatic diol component and aliphatic oxycarboxylic acid component) Polyesters obtained by polycondensation of aliphatic oxycarboxylic acid components and lactones, and the like. These aliphatic polyester resins can be used alone or in combination of two or more.

Examples of the aliphatic dicarboxylic acid component (usually a saturated aliphatic dicarboxylic acid component) include aliphatic dicarboxylic acids (for example, C such as oxalic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid). _2-10 aliphatic dicarboxylic acids, preferably C _2-8 aliphatic dicarboxylic acids), reactive derivatives of aliphatic dicarboxylic acids (for example, C _1-3 alkyl esters such as acid anhydrides and methyl esters, acid chlorides, etc. Acid halide, etc.). These dicarboxylic acid components can be used alone or in combination of two or more. Of these dicarboxylic acid components, C _2-6 alkane dicarboxylic acid components such as oxalic acid, succinic acid, and adipic acid are preferred.

Examples of the aliphatic diol component (usually saturated aliphatic diol component) include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, and octane. Examples thereof include C _2-10 aliphatic diols such as methylene glycol, preferably C _2-8 aliphatic diols. These diol components can be used alone or in combination of two or more. Of these diol components, C _2-6 alkanediols such as ethylene glycol, 1,4-butanediol, and neopentyl glycol are preferred.

In the polyoxycarboxylic acid, the aliphatic oxycarboxylic acid component (usually a saturated aliphatic oxycarboxylic acid component) is, for example, an aliphatic oxycarboxylic acid (for example, glycolic acid, lactic acid, malic acid, oxypropionic acid, oxy C _2-10 aliphatic oxycarboxylic acids such as butyric acid, preferably C _2-8 aliphatic oxycarboxylic acids), reactive derivatives of aliphatic oxycarboxylic acids (for example, C _1-3 such as acid anhydrides and methyl esters) It may be an acid halide such as an alkyl ester or an acid chloride). These aliphatic oxycarboxylic acids can be used alone or in combination of two or more. Of these oxycarboxylic acids, hydroxy C _2-6 alkanoic acid components such as glycolic acid, lactic acid, malic acid, and oxybutyric acid are preferred. In the aliphatic polyester resin, lactic acid (component) constitutes the aliphatic polyester resin in a form used in combination with components other than the lactic acid component. In such an aliphatic polyester resin, the ratio of the lactic acid component is less than 30 mol% (for example, about 0.1 to 25 mol%), preferably 20 mol% or less (for example, 0.5 to 18) of the total constituent monomers. About 15 mol% or more (for example, about 1 to 10 mol%).

In the lactone, examples of the lactone include C _3-12 lactone such as propiolactone, butyrolactone, valerolactone, and caprolactone. These lactones can be used alone or in combination of two or more. Among these lactones, C _3-10 lactones such as propiolactone and caprolactone (eg, ε-caprolactone), preferably C _4-8 lactones are preferable.

Further, the aliphatic polyester resin may be a resin containing a component other than the above components (aliphatic dicarboxylic acid component, aliphatic oxycarboxylic acid component, lactone) as a polymerization component. Examples of such components include non-aliphatic dicarboxylic acid components {for example, aromatic dicarboxylic acid components [for example, aromatic dicarboxylic acids (for example, C ₈₋ such as terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, etc. ₁₆ aromatic dicarboxylic acids, preferably C _8-14 aromatic dicarboxylic acids), reactive derivatives of aromatic dicarboxylic acids (eg, acid anhydrides, C _1-3 alkyl esters such as methyl esters, acid halides such as acid chlorides) Etc.], etc.], non-aliphatic diol components (for example, aromatic diol components, etc.). These components (aromatic dicarboxylic acid component etc.) can be used individually or in combination of 2 or more types. Of these components, C _8-12 arene dicarboxylic acid components such as terephthalic acid are preferred. In the aliphatic polyester resin, the proportion of such a component (non-aliphatic component) is, for example, 60 mol% or less (for example, 1 to 55 mol%) with respect to the entire monomer constituting the aliphatic polyester resin. , Preferably it may be 50 mol% or less (for example, 2 to 40 mol%). In particular, in an aliphatic polyester resin (aromatic modified aliphatic polyester resin) having an aromatic dicarboxylic acid component as a polymerization component, the ratio of the aromatic dicarboxylic acid component is the total amount of the aliphatic dicarboxylic acid component and the aromatic dicarboxylic acid component. On the other hand, for example, 50 mol% or less (for example, 1 to 45 mol%), preferably 40 mol% or less (for example, 2 to 35 mol%), more preferably 30 mol% or less (for example, 3 to 25 mol%). ).

  The aliphatic polyester resin may have a carbonate bond (carbonate group) in a part of the resin skeleton.

  Soft resins (such as aliphatic polyester resins) may usually be biodegradable. The soft resin may be any of synthetic, microbial, and natural products. Further, the soft resin may be a resin regenerated by recycling (recycled resin).

Typical aliphatic polyester resins include, for example, esters of alkanediols and alkanedicarboxylic acids {eg, polyalkylene alkanoates [eg, polyalkylene succinates (eg, polyethylene succinate, polybutylene succinate, polyneopentyne). Poly C _2-8 alkylene succinates such as lensuccinate), polyalkylene adipates (eg, poly C _2-8 alkylene adipates such as polyethylene adipate, polybutylene adipate), alkanediols and multiple C _2-10 alkanedicarboxylic acids esters of (e.g., polybutylene succinate adipate) polyalkylene _{C 2-10,} such as alkanoates, preferably poly _{C 2-6} alkylene _{C 2-8} alkanoate, more preferably Po C _2-4 alkylene _{C 2-6} alkanoates, poly (alkylene alkanoates / arylate) [e.g., polybutylene adipate / terephthalate, polyalkylene _{C 2-10} alkanoate _{/ C 8-12} arylate such as polytetramethylene adipate / terephthalate , Preferably poly C _2-6 alkylene C _2-8 alkanoate / C _8-10 arylate, more preferably poly C _2-4 alkylene C _2-6 alkanoate / terephthalate], poly (alkylene alkanoate / carbonate) [eg, Polybutylene succinate / polycarbonate such as poly C _2-6 alkylene C _2-8 alkanoate / carbonate], polyalkylene alkanoate / polyaliphatic oxycarboxylic acid (eg, polybutylene succinate) DOO / polylactic _{C 2-6} alkylene _{C 2-8} such alkanoate / polyhydroxy _{C 2-6} alkanoic acid), polyalkylene alkanoates / polylactone (e.g., poly polybutylene succinate / polycaprolactone _{C 2- 6} alkylene C _2-8 alkanoate / poly C _3-10 lactone etc.)}, polyaliphatic oxycarboxylic acids (eg polyglycolic acid, polyhydroxybutyrate, polyhydroxybutyrate / polyhydroxyhexanoate etc.) Polyhydroxy C _2-6 alkanoic acid other than lactic acid), polylactone (for example, poly C _3-10 lactone such as polycaprolactone, preferably poly C _4-8 lactone), and the like.

  Note that the glass transition temperature of the soft resin may usually be a temperature not higher than room temperature (for example, 25 ° C.).

[Polymer having thickening action]
In the present invention, as a component for thickening the polylactic acid resin composition, a general thickener [or thixotropy imparting agent, for example, an inorganic thickener (for example, bentonite, calcium carbonate, etc.), an organic thickener It is characterized in that a polymer component is used instead of an agent (for example, a carboxylate metal salt such as wax, calcium stearate, aluminum oleate, etc.) and combined with the plasticizer or a soft resin described later.

  By combining such a polymer component with the plasticizer or the soft resin described later, the polylactic acid resin composition is moderately thickened, and has excellent film formability (particularly inflation moldability) and sufficient strength and flexibility. A film having both properties can be obtained. Such a resin composition (or a film obtained from the resin composition) surprisingly includes the polymer component, the plasticizer, or the soft resin described later, but surprisingly, methane fermentation technology. In order to maintain the solubilization characteristics, the film has three characteristics: film formability, film strength, and solubilization characteristics.

  The polymer having a thickening action may be a polymer having a function of thickening polylactic acid (or a resin system containing polylactic acid), but is usually a polymer having a reactive group for a hydroxyl group and / or a carboxyl group. There may be. The polymer having such a reactive group can efficiently increase the viscosity of the resin system because it reacts as a hydroxyl group or a carboxyl group which is a terminal group of polylactic acid to form a bond.

  In the polymer having a reactive group, examples of the reactive group include an acid group (such as a carboxyl group carboxylic anhydride group), an isocyanate group, a hydroxyl group, a mercapto group, an epoxy group, an amino group, and an oxazoline ring group. . The polymer having a reactive group may have these reactive groups alone or in combination of two or more.

  Among these reactive groups, the polymer having a reactive group has at least one group selected from a carboxyl group, an isocyanate group, an epoxy group, and an oxazoline ring group in terms of reactivity. In particular, it preferably has at least an epoxy group.

  Examples of such a polymer having a reactive group include a polymer obtained by polymerizing a polymerization component containing at least a monomer having a reactive group, a polymer obtained by graft polymerization of a monomer having a reactive group, and a functional group of the polymer (for example, a hydroxyl group). A polymer obtained by reacting a monomer (or compound) having a binding group to the functional group and the reactive group with a carboxyl group, an amino group, etc., particularly a terminal group of the polymer) Also good. The polymer having a reactive group may be in the form of a blend of polymers having a reactive group, a blend with a polymer having no reactive group, or the like.

As the monomer (or compound) having a typical reactive group, for example, an acid group-containing monomer {for example, C ₃ such as unsaturated monocarboxylic acid (for example, (meth) acrylic acid, crotonic acid, 3-butenoic acid) _-6 alkene carboxylic acids; unsaturated aromatic monocarboxylic acids such as vinyl benzoic acid), unsaturated polycarboxylic acids or anhydrides thereof (for example, C _4-8 alkene dicarboxylic acids such as itaconic acid, maleic acid, maleic anhydride, etc. Or an anhydride thereof), an isocyanate group-containing monomer (such as vinyl isocyanate), a hydroxyl group-containing monomer {for example, a (meth) acrylic monomer having a hydroxy group or a mercapto group [for example, a (poly) alkylene glycol mono (meth) ) Acrylates (eg 2-hydroxyethyl (meth) acrylate, 2 Hydroxypropyl (meth) acrylate, C _2-6 alkylene glycol mono (meth) such as butanediol mono (meth) acrylate acrylate diethylene glycol mono (meth) polyoxy C _2-4 alkylene glycol mono (meth) acrylates such as acrylate), etc. ], Alkenols (for example, C _3-6 alkenols such as allyl alcohol, 2-buten-1-ol, 3-buten-2-ol, etc.), monomers corresponding to these, in which the hydroxyl group is substituted with a mercapto group, etc.], Epoxy group-containing monomers [for example, (meth) acrylic monomers having an epoxy group (for example, glycidyl (meth) acrylate), alkenyl glycidyl ether (for example, vinyl glycidyl ether, allyl glycidyl ether, etc.) C _2-6 alkenyl-glycidyl ether), epoxy alkene (eg, epoxy C _4-10 alkene such as 3,4-epoxy-1-butene), etc.], amino group-containing monomer [eg, alkenyl amine (eg, allyl amine, etc.) C _3-6 alkenylamine), aminostyrene (4-aminostyrene and the like)], oxazoline ring-containing compound [eg, bisoxazoline (eg, 2,2′-bis (2-oxazoline), etc.), bisoxazoly Nyl alkanes (eg, bisoxazolinyl C _1-8 alkanes such as 1,4-bis (2-oxazolin-2-yl) ethane, 1,8-bis (2-oxazolin-2-yl) butane), bis Oxazolinylcycloalkane (eg, 1,4-bis (2-oxazolin-2-yl) cyclohexa Bis oxazolinyl sulfonyl _{C 5-10} cycloalkane such as), bis oxazolinyl arenes (e.g., 1,2-bis (2-oxazolin-2-yl) bis oxazolinyl sulfonyl _{C 6-10} arene such as benzene), etc. And the like, etc.]. These monomers (or compounds) may be used alone or in combination of two or more as a polymerization component of a polymer having a reactive group.

  Examples of the polymer having a typical reactive group include a polymer having an acid group, a polymer having an epoxy group, and a polymer having an oxazoline ring.

Examples of the polymer having an acid group include acid-modified (meth) acrylic resins [for example, C ₂ such as olefin / maleic anhydride / (meth) acrylate copolymer (for example, ethylene maleic anhydride ethyl acrylate copolymer). _-4 olefin-maleic anhydride-C _1-10 alkyl (meth) acrylate copolymer), acid-modified olefin resin [for example, acid-modified polyethylene (carboxylated polyethylene graft copolymer, acid-modified polyethylene wax, ethylene maleic anhydride Copolymer), acid-modified polypropylene (carboxylated polypropylene graft copolymer, etc.), C _2-4 alkene homo- or copolymer acid-modified products), etc.], acid-modified styrene resins (eg, styrene / anhydrous maleic anhydride) Acid copolymer, etc.) That. The ethylene / maleic anhydride / ethyl acrylate copolymer is, for example, trade name “Bondaine” from Sumitomo Chemical Co., Ltd., and the acid-modified polyethylene wax is, for example, trade name “APEW” from Mitsui Chemicals, Inc. Etc.

  The polymer having an acid group includes a polymer containing an oxazoline ring-containing monomer (or compound) such as a bisoxazoline / styrene / maleic anhydride copolymer, a bisoxazoline / maleic anhydride-modified polyethylene, and a bisoxazoline / maleic anhydride. Acid-modified polypropylene is also included.

Examples of the polymer having an epoxy group include polymers having glycidyl (meth) acrylate as a polymerization component [for example, ethylene / glycidyl (meth) acrylate copolymer, ethylene / glycidyl (meth) acrylate / (meth) acrylate copolymer). (For example, ethylene / glycidyl (meth) acrylate / C _1-10 alkyl (meth) acrylate copolymer such as ethylene / glycidyl methacrylate / methyl methacrylate copolymer), ethylene and glycidyl (meth) acrylate and other copolymerization Copolymers with monomers (for example, ethylene / glycidyl methacrylate / vinyl alcohol copolymer, ethylene / glycidyl methacrylate / acrylonitrile / styrene copolymer, ethylene / glycidyl methacrylate / styrene copolymer) A polymer comprising at least a polymerization component of an olefin monomer (such as C _2-10 alkene such as ethylene) and glycidyl (meth) acrylate; a styrene-based monomer such as a styrene / glycidyl (meth) acrylate copolymer A polymer having at least a polymerization component of a monomer (such as styrene) and glycidyl (meth) acrylate]. In addition, polymers having such epoxy groups are “Bond First E” and “Bond First 2C” from Sumitomo Chemical, and “Lex Pearl RA”, “Lex Pearl ET” and “Lex Pearl RC” from Nippon Polyolefin Co., Ltd. Available from Nippon Oil and Fat Co., Ltd. as “Modiper”, from Toa Gosei Co., Ltd. as “acrylic polymer ARUFON”, and the like.

  In the polymer having a reactive group, the ratio of the reactive group (for example, epoxy group, acid group) (or the ratio of the monomer having the reactive group to the whole monomer) depends on the type of the reactive group. It may be 0.1 to 5 mol, preferably 0.2 to 4 mol, more preferably about 0.3 to 3 mol, and usually 0.5 to 4 mol (for example, 0.7 to 3 mol) per 1 kg of polymer. 0.5 mol, preferably 1 to 3 mol, more preferably 1.2 to 2.5 mol).

  Moreover, when the polymer which has a reactive group is a polymer which used the monomer which has a reactive group as a polymerization component, the ratio of the monomer which has a reactive group (for example, epoxy group) with respect to the whole monomer is, for example, 1- It is about 50 mol% (for example, 2 to 45 mol%), preferably 3 to 40 mol% (for example, 4 to 35 mol%), more preferably about 5 to 30 mol% (for example, 8 to 25 mol%). It may be about 5 to 40 mol% (for example, 7 to 35 mol%, preferably 10 to 30 mol%, more preferably 12 to 25 mol%).

  The weight average molecular weight of the polymer having a thickening action is, for example, 800 to 200000 (for example, 1000 to 100000), preferably 1200 to 80000 (for example, 1500 to 50000), and more preferably 1800 to 30000 (for example, 2000 to 20000). Or about 1000 to 25000 (for example, 1500 to 20000, preferably 2000 to 15000).

[Ratio of each component]
In the embodiment of the resin composition (I), the proportion of the plasticizer can be selected from a range of 1 to 40 parts by mass (for example, 3 to 30 parts by mass) with respect to 100 parts by mass of polylactic acid. Part by mass, preferably 4 to 22 parts by mass (eg 5 to 20 parts by mass), more preferably 7 to 18 parts by mass (eg 8 to 16 parts by mass), especially about 10 to 15 parts by mass. Usually, about 5-25 mass parts (for example, 8-22 mass parts) may be sufficient. Moreover, when resin composition (II) contains a plasticizer, the ratio of the plasticizer with respect to 100 mass parts of polylactic acids can be selected from the range similar to the above. Furthermore, the ratio of a plasticizer can be selected from the range of 0.8-35 mass parts (for example, 1-30 mass parts) with respect to 100 mass parts of total amounts of polylactic acid and a soft resin, for example, 2.5- 25 parts by mass, preferably 3 to 22 parts by mass (for example, 4 to 20 parts by mass), more preferably 5 to 18 parts by mass (for example, 6 to 16 parts by mass), and particularly about 8 to 15 parts by mass. It may be about 5 to 25 parts by mass (for example, 8 to 20 parts by mass). If the proportion of the plasticizer is too large or too small, film properties such as breaking strength and impact strength may be deteriorated. Moreover, when the ratio of a plasticizer is too large, film moldability may fall.

  In the embodiment of the resin composition (II), the ratio between the polylactic acid and the soft resin is the former / the latter (parts by mass) = 99.5 / 0.5 to 40/60 (for example, 99/1 to 50/50). Can be selected from a range of degrees, for example 98/2 to 50/50 (eg 97/3 to 55/45), preferably 95/5 to 60/40 (eg 93/7 to 62/38), Preferably 90/10 to 65/35 (for example, 85/15 to 68/32), particularly about 83/17 to 70/30, and usually 90/10 to 60/40 (for example, 85/15). ~ 65/35). In particular, when the resin composition (II) contains a plasticizer, the ratio of the polylactic acid to the soft resin is the former / the latter (parts by mass) = 99.5 / 0.5 to 50/50 (for example, 99.5). /0.5 to 55/45), preferably 99/1 to 60/40 (eg, 98.5 / 1.5 to 62/38), more preferably 98/2 to 65/35 (eg, 97. 5 / 2.5 to 70/30), particularly about 97/3 to 75/25, and usually about 99/1 to 60/40 (for example, 98/2 to 65/35). Good. In addition, when the ratio of a soft resin becomes large too much, it may become impossible to fully solubilize a resin composition.

  The ratio of the polymer having a thickening action can be selected from a range of 0.1 to 30 parts by mass (for example, 0.3 to 20 parts by mass) with respect to 100 parts by mass of polylactic acid, for example, 0.5 to 15 The mass may be about 0.7 to 12 parts by mass (for example, 1 to 10 parts by mass), more preferably about 1.5 to 8 parts by mass (for example, 2 to 8 parts by mass). -10 mass parts (for example, 2-9 mass parts, Preferably 3-8 mass parts) may be sufficient. If the proportion of the polymer having a thickening action is too small, a sufficient thickening effect cannot be obtained, and if the proportion of the polymer having a thickening action is too large, the melt viscosity becomes too large and the inflation moldability is increased. In some cases, the resin composition may not be sufficiently solubilized.

  Furthermore, the ratio of the plasticizer to the polymer having a thickening action is the former / the latter (mass ratio) = 95/5 to 20/80 (for example, 90/10 to 30/70), preferably 85/15 to It may be 40/60, more preferably 83/17 to 50/50, particularly 80/20 to 60/40 (for example, 75/25 to 65/35). In particular, when the resin composition (II) includes a plasticizer, the ratio of the plasticizer to the polymer having a thickening action is the former / the latter (mass ratio) = 95/5 to 20/80 (for example, 90 / 10/25/75), preferably 85/15 to 30/70, more preferably about 83/17 to 35/65 (for example, particularly 80/20 to 40/60). When used in the above range, excellent inflation moldability and solubilization characteristics can be efficiently achieved while suppressing bleed-out of the plasticizer.

  Furthermore, the ratio of the soft resin and the polymer having a thickening action is the former / the latter (mass ratio) = 95/5 to 20/80, preferably 90/10 to 30/70, more preferably 88/12 to It may be about 40/60, especially 85/15 to 50/50 (for example, 83/17 to 60/40). In particular, when the resin composition (II) contains a plasticizer, the ratio between the soft resin and the polymer having a thickening action is the former / the latter (mass ratio) = 95/5 to 20/80 (for example, 90 / 10-22 / 78), preferably 88 / 12-25 / 75, more preferably about 85 / 15-30 / 70 (for example, 80 / 20-35 / 65). When used in the above range, both excellent inflation moldability and solubilization characteristics can be efficiently achieved.

  Moreover, in the aspect of resin composition (II), the ratio of the polymer which has a thickening effect | action can be selected from the range of 0.1-20 mass parts with respect to 100 weight part of total amounts of polylactic acid and a soft resin, for example, 0.3 to 18 parts by mass, preferably 0.5 to 15 parts by mass (for example, 0.7 to 12 parts by mass), more preferably about 1 to 10 parts by mass (for example, 2 to 7 parts by mass). Usually, about 1-15 mass parts (for example, 1-12 mass parts) may be sufficient.

  Note that the resin composition of the present invention only needs to contain at least (I) polylactic acid or (II) polylactic acid and a soft resin as a resin component, and other resins (heat Plastic resin) may be included, but it is preferable that substantially no such other resin is contained. Usually, even when included in the resin component, the ratio of such other resin is 20% by mass or less (for example, 0.1 to 15% by mass) of the entire resin component, preferably 10% by mass or less (for example, 0.3 to 8% by mass), and more preferably 5% by mass or less (for example, 0 .5-3 mass%) in many cases.

[Additive]
The resin composition of the present invention further includes other additives such as anti-blocking agent, slip agent (or anti-scratch agent), stabilizer (anti-aging agent, antioxidant, ozone degradation inhibitor, ultraviolet absorber, Light stabilizers, heat stabilizers, etc.), flame retardants, compatibilizers (in the case of the resin composition (II), etc.), softeners, lubricants, antistatic agents, crystal nucleating agents, colorants, antiseptics, fungicides An agent or the like may be included. The additives may be used alone or in combination of two or more.

  Of these additives, an anti-blocking agent and the like can be preferably used. In addition, a slip agent or a colorant may be suitably used depending on the application (for example, a garbage bag). The colorant is preferably a biodegradable colorant (biodegradable ink). When the colorant is in the form of a solution, the solution is a neutral solution in terms of suppressing hydrolysis of polylactic acid. Is preferred.

Examples of the anti-blocking agent include inorganic particles (for example, particles of silica, calcium carbonate, titania, mica, talc, zeolite, etc.), organic particles (polymethyl methacrylate particles, etc.) and the like. The silica preferably contains 95% or more of SiO _2, and more preferably SiO ₂ is anhydrous silica. In addition, you may use an antiblocking agent with the form (for example, the form which mixes an antiblocking agent and a polylactic acid resin composition at the time of inflation molding) which was made to contain in biodegradable resin etc. in high concentration as a masterbatch.

  The average particle diameter of the anti-blocking agent can be appropriately selected according to the kind of the particles, and may be, for example, about 1 nm to 20 μm, preferably about 2 nm to 10 μm. In particular, from the viewpoint of transparency of the obtained film, inorganic particles (for example, silica particles) having an average particle diameter of about 3 to 100 nm (for example, preferably 5 to 80 nm, more preferably 7 to 50 nm) are preferably used. May be. Moreover, the ratio of an antiblocking agent is 0.01-10 mass parts with respect to 100 mass parts of polylactic acid, Preferably it is 0.03-8 mass parts, More preferably, it is about 0.05-2 mass parts. There may be.

  In particular, when a slip agent and an anti-blocking agent are used in combination, the amount used is 0.1 parts by weight of the total amount of the slip agent and the anti-blocking agent with respect to 100 parts by mass of the total amount of polylactic acid, plasticizer or soft resin, and thickener. It may be about 2 to 7 parts by mass. If the total amount of the slip agent and the antiblocking agent is too small, the antifogging sustaining effect is not expressed, and if it is too much, the molding may become unstable or the appearance of the film may be inferior.

Examples of the slip agent include fatty acid ester, hydrocarbon resin, paraffin, higher fatty acid, oxy fatty acid, fatty acid amide (for example, C _2-34 saturated or unsaturated acid amide such as erucic acid amide, preferably C _4-30 saturated. or non飽酸amides, preferably C _8-24 saturated or unsaturated飽酸amide), alkylene bis fatty acid amides, aliphatic ketones, fatty acid lower alcohol esters, fatty acid polyhydric alcohol esters, fatty acid polyglycol esters, fatty alcohols, polyhydric Examples include alcohol, polyglycol, polyglycerol, metal soap, and modified silicone. Of these, fatty acid esters, polyethylene wax (hydrocarbon resin), modified silicone (particularly methylstyryl-modified silicone, alkyl-modified silicone, etc.) are preferred. Slip agents may be used alone or in combination of two or more. The viscosity of the slip agent at 25 ° C. may be, for example, about 100 to 10,000 cps. Moreover, the usage-amount of a slip agent is 0.001-5 mass parts with respect to 100 weight part of polylactic acid, for example, Preferably it is 0.002-1 mass part, More preferably, it is 0.003-0.5. A mass part (for example, 0.004-0.3 mass part) may be about a mass part. In addition, you may use a slip agent in the form (for example, the form which mixes a slip agent and a polylactic acid resin composition at the time of inflation molding) made into a biodegradable resin etc. in high concentration as a masterbatch.

  Examples of the compatibilizer include elastomeric compatibilizers (for example, styrene elastomers such as styrene ethylene butadiene copolymer, styrene ethylene butadiene styrene copolymer, hydrogenated styrene isopropylene styrene copolymer, etc.), copolymer Systemic compatibilizer (eg, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene resin, acrylonitrile-butadiene rubber, EVA / PVC / graft copolymer, vinyl acetate-ethylene copolymer) Polymer resin, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropylene-block copolymer, etc.), ionomer resin (for example, ethylene- (meth) acrylic acid copolymer) Coalescence Ionomers of (meth) acrylic copolymers such as ionomers, styrene-methacrylic acid copolymers, telechelic polybutadiene acrylic acid ionomers, styrene-butadiene acrylic acid ionomers; ethylene-vinylsulfonic acid copolymer ionomers, Sulfonate ionomers such as sulfonated polystyrene ionomer, sulfonated styrene-2-acrylamido-2-methylpropanesulfate ionomer, sulfonated ethylene-propylene-diene copolymer ionomer; fluorine ionomer; hydrogenated polypentamer ionomer, Alkenamer ionomers such as polypentamer ionomers; Pyridinium salt ionomers such as poly (vinylpyridium salt) ionomers; Ammonium salt ionomers such as ionomers, phosphonium salt ionomers such as poly (vinylbenzylphosphonium salt) ionomers, polyurethane ionomers, ionomers such as aliphatic ionones and aromatic ionenes, and the like. These may be used alone or in combination of two or more.

  The proportion of the compatibilizer is, for example, about 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, and more preferably about 1 to 10 parts by weight with respect to 100 parts by weight of polylactic acid. Also good.

The resin composition of the present invention can be usually obtained by melt-mixing polylactic acid and each component. The melt viscosity of the resin composition of the present invention is, for example, about 70 to 500 Pa · s, preferably about 80 to 400 Pa · s, more preferably about 100 to 350 Pa · s at a temperature of 190 ° C. and a shear rate of 600 s ⁻¹ . It may be 90 Pa.s or more (for example, about 100 to 300 Pa.s).

The melt viscosity range is a range at a temperature of 190 ° C. and a shear rate of 600 s ⁻¹ , but a molding (or processing) temperature range of the resin composition [for example, a molding temperature range described later (for example, 170 to 210 ° C. Degree)] and a predetermined shear rate range (for example, about 100 to 1000 s ⁻¹ , preferably about 300 to 800 s ⁻¹ ), the melt viscosity range is preferably satisfied.

Further, it is preferable that the change in melt viscosity is small at the molding temperature. For example, the melt viscosity at 170 ° C. and a shear rate of 600 s ⁻¹ of the resin composition is A (Pa · s), 190 ° C. and a shear rate of 600 s. ^When the melt viscosity in ^-1 is B (Pa · s), the absolute value of AB is, for example, 0 to 700 Pa · s, preferably 0 to 500 Pa · s, and more preferably about 0 to 300 Pa · s. There may be.

  Furthermore, the melt flow rate of the resin composition of the present invention is, for example, 1 to 35 g / 10 minutes, preferably 3 to 30 g / 10 minutes, more preferably 4 to 25 g under the conditions of 190 ° C. and a load of 2.16 kg. / 10 minutes, especially about 5-20 g / 10 minutes (for example, 6-18 g / 10 minutes).

  In the present invention, since polylactic acid and a specific component are combined as described above, a resin composition having an appropriate melt viscosity and melt fluidity can be efficiently obtained in the above film forming. Therefore, the resin composition of the present invention can be easily compounded (resin composition) and can be easily formed into a film by inflation molding or the like.

<Film>
The resin composition of the present invention can be used as a resin composition for molding various molded articles, and in particular, has excellent film moldability despite being composed of polylactic acid as described above. Yes. For example, a film can be easily formed even when subjected to inflation molding. In addition, the film obtained by molding is a film having both moderate strength and flexibility despite having polylactic acid as a main component, and is excellent in film characteristics. Therefore, the resin composition of the present invention is suitable as a film-forming resin composition (particularly, an inflation-molding resin composition).

  Such a film of the present invention is formed of the resin composition. Such a film can be obtained by molding the resin composition by a known film molding method. T-die molding, inflation molding, etc. can be suitably applied as the film molding method. In particular, since the resin composition can be film-molded even by applying highly productive inflation molding, it is more efficient by inflation molding. You may shape | mold well. That is, the film may be an inflation film. In the inflation molding, since a bag-like film is directly obtained, the inflation film can be suitably used as a bag-like film (for example, a garbage bag or a packaging bag).

  In the inflation molding, molding conditions can be appropriately selected. For example, the melting temperature (molding temperature) of the resin composition is 120 to 230 ° C., preferably 140 to 220 ° C., more preferably 150 to 210 ° C., particularly 170 to 200. It may be about ° C. In the blow molding, the blow ratio may be, for example, 1 to 10, preferably 1.5 to 7, and more preferably about 2 to 5.

  In addition, although the thickness of a film can be suitably selected according to a use, it is 10-5000 micrometers, Preferably it is 20-1000 micrometers, More preferably, about 30-800 micrometers may be sufficient.

  The film of the present invention is excellent in flexibility and strength. For example, the tensile strength may be about 10 to 50 MPa, preferably about 15 to 45 MPa, and more preferably about 20 to 40 MPa. Further, the elongation at break of the film may be, for example, about 100 to 600%, preferably 120 to 500%, and more preferably about 150 to 400%. The tensile strength and elongation at break can be measured under the conditions described later.

  Such a film of the present invention is easily solubilized. The film may be subjected to solubilization (or solubilization treatment or solubilization step) together with components that can be solubilized (or methane fermentation) depending on the mode of the film. For example, the garbage bag-like film may be subjected to solubilization together with a state including (or wrapped in) raw garbage and the like. Moreover, the film to be subjected to solubilization (and the inclusion components such as garbage) may be crushed to an appropriate size and subjected to solubilization.

  Such a film can be solubilized, for example, by mixing a film (or an inclusion component such as dust) with an appropriate solvent component (or dispersion component). The solvent component is usually a component containing at least water, and such a component containing water may be a basic aqueous solution or an acidic aqueous solution (for example, a carboxylic acid aqueous solution such as formic acid or acetic acid). Good. In particular, the solvent component is a basic aqueous solution [for example, an aqueous solution containing a hydroxide (for example, an alkali hydroxide or alkaline earth metal salt such as sodium hydroxide or calcium hydroxide), an ammonia component (for example, ammonia, ammonium carbonate). An aqueous solution containing an ammonium salt such as When such a basic aqueous solution is used, the film can be solubilized more efficiently. Moreover, you may utilize wastewater and sludge (for example, basic wastewater or sludge) as a solvent component. Wastewater and sludge often contain microorganisms that are advantageous for solubilization and can be suitably used. The pH of the basic aqueous solution may be, for example, 7.1 to 13, preferably 8 to 12, and more preferably about 9 to 11.

  Solubilization may be performed under stirring. Typically, the film (and its inclusion component) and a mixture containing a solvent component are often solubilized by mixing at a predetermined temperature for a predetermined time.

  Solubilization temperature is not specifically limited, For example, 0-120 degreeC, Preferably it is 20-100 degreeC, More preferably, about 30-90 degreeC may be sufficient. In particular, the solubilization temperature may be a relatively high temperature [eg, about 60 ° C. or higher (eg, 65 to 100 ° C.), preferably about 70 ° C. or higher (eg, about 75 to 90 ° C.)]. Such a process at a high temperature is advantageous for solubilization in a short time. The solubilization in a basic aqueous solution often proceeds efficiently even at a general solubilization temperature.

  The solubilization (process or treatment) may be performed in an aerobic atmosphere or an anaerobic atmosphere, but the film of the present invention can be efficiently solubilized even in an anaerobic atmosphere. Examples of the anaerobic atmosphere include a biogas generation atmosphere and an inert gas atmosphere such as nitrogen. The anaerobic atmosphere may be a sealed atmosphere in which oxygen (air) is not sufficiently supplied.

  The solubilization time can be appropriately selected according to the type of solvent component, the solubilization temperature, and the like, and is, for example, 30 minutes to 10 days, preferably 3 hours to 3 days, more preferably about 5 to 24 hours. Also good. In particular, when solubilized at a high temperature, a relatively short time [for example, 12 hours or less (for example, 30 minutes to 10 hours), preferably 10 hours or less (for example, 1 to 9 hours), more preferably 8 hours or less ( For example, about 1.5 to 6 hours).

  Then, the solubilized film (and its inclusion component, etc.) is subjected to a methane fermentation process and subjected to methane fermentation. In addition, the mixture after solubilization may use only a liquid component for a methane fermentation process, and may use for a methane fermentation as it is. As a standard of solubilization to be subjected to methane fermentation, for example, it may be a standard that it is decomposed to such an extent that the shape cannot be maintained. In addition, methane fermentation can be performed using a well-known methane fermentation microbe and a methane luminescence tank.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  In the examples and comparative examples, the following materials were used.

[(A) Polylactic acid resin]
Polylactic acid (Okami Pharmaceutical Co., Ltd. Kaisho Biological Materials (China) “REVODE”)
[(B) Soft biodegradable resin (soft resin)]
(B1) Polybutylene succinate ("GS Plastic AD92W" manufactured by Mitsubishi Chemical Corporation)
(B2) Polybutylene succinate adipate (“Bionore # 300” manufactured by Showa Polymer Co., Ltd.)
[(C) Plasticizer]
Adipic acid ester ("Daifitty-101" manufactured by Daihachi Chemical Industry Co., Ltd.)
[(D) Thickener]
(D1) Acrylic polymer having an epoxy group (“ARUFON UG4040” manufactured by Toagosei Co., Ltd., weight average molecular weight 11000, epoxy equivalent 2.1 meq / g)
(D2) Polymer having epoxy ("Bond First CG5004" manufactured by Sumitomo Chemical Co., Ltd.), ethylene / glycidyl methacrylate copolymer (19% glycidyl methacrylate, epoxy equivalent 1.34 meq / g, weight average molecular weight about 5000)
[(E) Anti-blocking (AB) agent]
(E1) Zeolite-based antiblocking agent (manufactured by Tokyo Ink Co., Ltd. Bioblock antiblocking agent “TEPBP-AB1”, polybutylene adipate terephthalate (PBAT, trade name “Ecoflex”), dispersed in 40 parts by mass and talc 60 parts by mass Agent (wax component) added 5 parts by mass)
(E2) Silica-based anti-blocking agent [linear low density polyethylene (“Ultimex 2022L” manufactured by Prime Polymer Co., Ltd.) and silica (“ML367” manufactured by Tokai Chemical Industry Co., Ltd.) at a ratio of 10% by weight Kneaded product]
In Examples 3 to 5, an antiblocking agent was mixed at the time of inflation molding.

[(F) Slip (S) agent]
(F) Erucamide (Slip agent “3010MB” manufactured by Showa Polymer Co., Ltd.) (mixture of 5% by mass of erucamide, 90% by weight of Bionor manufactured by Showa Polymer Co., Ltd., 5% by mass of silica) (melt flow rate 6. 9)
[(G) Colorant]
Green colorant (manufactured by Tokyo Ink Co., Ltd. FB632 green, LLDPE base added with green pigment and dispersant (wax component)).

Using the above materials, a resin composition was prepared and a film was prepared, and various measurements and evaluations were performed as follows.
(Bending test)
After mixing each component with polylactic acid at the ratio shown in Table 1, a kneading temperature of 190 ° C. (Comparative Examples 4 to 6) or 180 ° C. using a small twin screw extruder (manufactured by Technovel, KZW15-30MG) In Comparative Examples 4 to 6, the strands obtained by melt-kneading, then extruding into water with a diameter of about 3 mm and cooling and solidifying were subjected to a bending test, and evaluated according to the following criteria. In addition, those that are easily cracked or severely whitened are poor in resin, and are not suitable for inflation molding or T-die film molding.
A: No change even when bent.
○: Slightly cracked or whitened when bent.
Δ: Some cracks and whitening are observed when bent.
X: Cracks and a wide range of whitening are observed when bent.

(Compound properties)
After mixing each component with polylactic acid at the ratio shown in Table 1, it was melt kneaded at a kneading temperature of 180 ° C. using a twin screw extruder, then extruded into water with a diameter of about 3 mm, solidified, and then 3 mm long To obtain a compound resin. The compound resin was dried in dehumidified dry air (dew point: −35 ° C.), and the water content was adjusted to 100 ppm by weight or less. Compounding property (ease of compounding) was evaluated according to the following criteria.
A: High melt viscosity and easy to compound.
○: Melt viscosity is high to some extent and can be compounded.
(Triangle | delta): Melt viscosity is a little low and it is hard to compound.
X: Melt viscosity is low and cannot be compounded.

(Melt flow rate)
The cylinder of a melt indexer (manufactured by Toyo Seiki Co., Ltd.) was filled with the dry compound resin used in the evaluation of the compounding property for representative examples and comparative examples, and the predetermined temperature shown in Table 1 (190 ° C) , 150 ° C. and 190 ° C.) for 5 minutes, place a plunger weighing 2.16 kg on top of the cylinder, and measure the mass of the resin flowing out from the bottom of the cylinder at n = 3 for 10-30 seconds And converted into the mass of resin flowing out from the bottom of the cylinder in 10 minutes.

(Melt viscosity)
For representative examples and comparative examples, the melt viscosity η of the dried compound resin was measured using a capillary flow tester [Toyo Seiki Co., Ltd., IMC-1544 (capillary size: L = 10 mm, D = 1 mm)]. The measurement was performed under conditions of a temperature of 190 ° C. and a shear rate of 600 s ⁻¹ . In addition, it has been empirically found that it is advantageous to have a melt viscosity of 90 Pa · s or more at 190 ° C. for film formation.

(Inflation formability)
Using the dried compound resin, an inflation film was produced as usual. First, the compound resin was melt-kneaded with a single screw extruder having a temperature gradient suitable for melting each compound resin, and extruded from a circular die having a diameter of 85 mm. The blow ratio (BUR) was changed by adjusting the internal pressure (blow ratio = 1-5). The film thickness was adjusted to 25 to 80 μm by adjusting the extrusion amount. The inflation moldability was evaluated according to the following criteria.
(Double-circle): It has moderate melt viscosity and is excellent in inflation moldability. Also, no blocking has occurred.
○: Inflation molding can be performed without hindrance. In addition, there is no blocking, and there is no problem even if it exists.
Δ: Inflation moldability is poor. Or a little blocking is happening.
X: Inflation molding is not possible. Or quite a lot of blocking is happening.

(Film strength)
A dumbbell-shaped test piece having a parallel portion of 10 mm, a gauge interval of 40 mm, and a length of 100 mm was cut out from the film obtained by inflation molding, and the test piece was pulled at a tensile speed of 500 mm / min to obtain a tensile strength (MPa). The elongation at break (%) was measured and evaluated according to the following criteria.
◎: Tensile strength 25 or more, Breaking elongation 200 or more ○: Tensile strength 20 or more and less than 25, Breaking elongation 150 or more and less than 200 Δ: Tensile strength 15 or more and less than 20, Breaking elongation 100 or more and less than 150 Less than 15 and less than 100 elongation at break.

(Heat seal strength)
Two strips of 15 mm × 100 mm strips were cut out from the film obtained by inflation molding, the two strips of strips were overlapped, and a part from one end to 10 mm (size of 15 mm × 10 mm) was obtained. Fused with a desktop vacuum sealer. Thereafter, the other ends that were not fused were pulled using a tensile tester under the condition of a tensile speed of 100 mm / min, and the fracture load (N) of the fused part was measured and evaluated according to the following criteria.
A: Breaking load of 10 or more ○: Breaking load of 8 or more and less than 10 Δ: Breaking load of 5 or more and less than 8 ×: Breaking load of less than 5.

(Solubilization experiment)
Film pieces of the film obtained by inflation molding (for those that could not be blow-molded, the obtained compound resin was made into a thin film with an iron) were compounded into 20 ml of a 1% by weight ammonium carbonate aqueous solution. An amount of 0.2 g of resin (solid-liquid ratio = 10 kg compound resin / m ³ ) was added, and the upper gas was replaced with nitrogen to make an anaerobic state, and then heated to 80 ° C. in a sealed vial. After 24 hours, 1 ml of the liquid in the vial is taken in a mixed state, mixed with 19 ml of high-temperature methane fermentation sludge that is continuously operated at 55 ° C. using garbage as a substrate, and the upper gas is replaced with nitrogen to make an anaerobic state. After that, it was heated to 55 ° C. in a sealed vial. The methanation rate after being allowed to stand for 6 days was calculated by the following formula.
Methanation rate = COD equivalent of generated biogas / COD equivalent of 0.01 g of compound resin The COD equivalent of biogas was calculated from the methane concentration in the biogas based on the methane combustion formula. The COD equivalent of the compound resin was measured using a CODcr measuring reagent manufactured by HACH.

And the value of the methanation rate was evaluated according to the following criteria.
◎: 90% or more at an elapsed time of 144 hours (6 days) ○: Elapsed time of 144 hours (6 days) 70% or more and less than 90% Δ: Elapsed time 144 hours (6 days) 50% or more and less than 70% ×: Elapsed time Less than 50% for 144 hours (6 days).

  Table 1 shows the composition of the resin composition, and Table 2 shows the results of various measurements and evaluations. In Table 1, the composition (unit of composition) is “part by mass” unless otherwise specified. In addition, matters that should be noted in the evaluation are described in addition to evaluations such as ○.

  Further, as the film of the representative example, the inflation film of Example 3, the film of Comparative Example 1 (polylactic acid), and the film of Comparative Example 8 (polylactic acid / polybutylene succinate (weight ratio) = 60/40) And the antibacterial activity value of the film corresponding to Comparative Example 15 [Polyethylene (LLDPE)] (manufactured by Ecobiz Co., Ltd.) according to the test method of “JIS Z 2801: 2000 antibacterial processed product-antibacterial test method / bacterial effect” The measurement was performed as follows.

That is, a test piece obtained by cutting the film into 5 cm × 5 cm, placed in a sterile Petri dish, concentration 10 ⁵ cells / mL of the test bacterial liquid [ST medium (standard agar medium "Daigo" 23.5g and distilled water 1000 mL (pH 7 .2) medium) was diluted 1000 times with 1/500 NB (NB medium of 3.0 g of meat extract, 10.0 g of peptone, 5.0 g of sodium chloride and 1000 mL of distilled water (pH 7.2)). Prepared] was added dropwise. On top of that, another film (a stomacher bag cut to 4 cm × 4 cm) was covered, and lightly pressed so that the test bacterial solution spread over the entire film, and the petri dish was covered. And in order to prevent evaporation, it put into the bag and left to stand at 35 degreeC for 24 hours in a thermostat. In addition, the test number was performed 3 samples with respect to each film, and the average value of these was taken.

Then, the test piece immediately after inoculation with the test bacterial solution, the film and the bacterial solution are placed in a 50 mL tube, and the SCDLP medium (20 g of peptone, 5.0 g of potassium chloride, 2.5 g of potassium dihydrogen phosphate, 2.5 g of glucose, lecithin) 1 g, 7 g of nonionic surfactant (trade name “TRITONX100”, manufactured by Wako Pure Chemical Industries, Ltd.), 10 mL of distilled water 1000 mL (pH 7.2) and 10 mL of vortex (1 minute, volume 7) are added. It was finally washed out. This test solution is diluted with a physiological saline (0.85%) stock solution, 10 ⁻¹ , 10 ⁻² , 10 ⁻³ , and 1 mL of each diluted solution and 10 mL of the ST medium (50 ° C.) are added to the petri dish and mixed. Incubation was performed. After culturing at 35 ° C. for 48 hours, colonies were counted, and the antibacterial activity value was calculated from the results using the following formula.
Antibacterial activity value = {log (B / A) -log (C / A)} = log (B / C)
A: Average number of viable bacteria immediately after inoculation of unprocessed test piece (pieces)
B: Average number of viable bacteria after 24 hours of unprocessed test piece
C: Average value (number) of the number of viable bacteria after 24 hours of each test piece.

  In addition, as an unprocessed test piece, a polyethylene (LLDPE) film (manufactured by Ecobiz Co., Ltd.) was used.

  The results are shown in Table 3.

  As is clear from the results in Table 3, it was surprisingly found that the inflation films obtained in the examples had an antibacterial action. Therefore, it can be expected to prevent garbage from being spoiled and prevent infection of germs from the garbage bag. On the other hand, the polylactic acid film of Comparative Example 1 was found to have poor antibacterial properties. Further, the film obtained in Comparative Example 8 is a film having the same composition as “Ecoporin Green” manufactured by Yoshitada Chemical Industry Co., Ltd., which is known as a biodegradable film. I found out. However, this film is difficult to solubilize as described above.

  The reason for the antibacterial action is not clear, but when water adheres to the surface of the film (garbage bag), the polylactic acid on the surface partially hydrolyzes to produce lactic acid, which lowers the pH. This seems to be part of the reason.

  The resin composition of the present invention has an appropriate melt viscosity despite being formed of polylactic acid, and is excellent in film moldability (particularly inflation moldability). The resin composition (or film) of the present invention has sufficient strength and flexibility. In addition, the heat sealability is excellent as compared with the case of polylactic acid alone, and a sufficient sealing strength can be maintained at the fused portion even when molded or fused in a bag shape by inflation molding or the like. Furthermore, the film of the present invention also has an antibacterial action. In particular, the film of the present invention can be solubilized in an anaerobic atmosphere in methane fermentation. Therefore, the resin composition of the present invention is suitable as a resin composition for film molding (particularly for inflation molding). And since the film of this invention can be solubilized not only with the outstanding biodegradability and film characteristic but easily (or in a short time), it can be used suitably as a bag-like film, especially a garbage bag. The garbage bag formed of such a film of the present invention can be converted into biogas by methane fermentation technology together with garbage without sorting. Usually, in a garbage bag containing raw garbage, the weight of the garbage bag is about 10% by mass. Therefore, the amount of energy recovered can be increased by about 10% by methane fermentation of the garbage bag together. In addition, the resin composition and film of the present invention can be solubilized, but each component (plasticizer, polymer having a thickening action, after solubilization, as long as the shape cannot be retained by solubilization) Soft resin or the like) may remain as a residue.

Claims (19)

  A polylactic acid resin composition comprising polylactic acid, a plasticizer for plasticizing polylactic acid, and a polymer having a thickening action.   A polylactic acid resin composition comprising polylactic acid, a soft resin, and a polymer having a thickening action.   The polylactic acid resin composition according to claim 2, further comprising a plasticizer for plasticizing the polylactic acid.   The resin composition according to claim 1 or 3, wherein the plasticizer is an ester plasticizer.   The resin composition according to claim 1, 3 or 4, wherein the plasticizer is an aliphatic dicarboxylic acid ester.   The resin composition according to claim 1, 3, 4, or 5, wherein the proportion of the plasticizer is 5 to 25 parts by mass with respect to 100 parts by weight of polylactic acid.   The resin composition according to claim 2, wherein the soft resin is an aliphatic polyester resin.   The resin composition according to claim 2, 3 or 7, wherein the ratio of polylactic acid to soft resin is the former / the latter = 98/2 to 50/50.   The resin composition according to any one of claims 1 to 8, wherein the polymer having a thickening action is a polymer having a reactive group with respect to a hydroxyl group and / or a carboxyl group.   The resin composition according to claim 9, wherein the reactive group is an epoxy group.   The resin composition according to claim 9 or 10, wherein in the polymer having a reactive group, the ratio of the reactive group is 0.1 to 5 mol per kg of the polymer.   The resin composition according to any one of claims 1 to 11, wherein the proportion of the polymer having a thickening action is 1 to 15 parts by mass with respect to 100 parts by mass of polylactic acid.   Furthermore, the resin composition in any one of Claims 1-12 containing 0.1-10 mass parts of antiblocking agents with respect to 100 mass parts of polylactic acid. The resin composition according to claim 1, wherein the melt viscosity is 70 to 500 Pa · s at a temperature of 190 ° C. and a shear rate of 600 s ⁻¹ .   It is a resin composition for inflation molding, The resin composition in any one of Claims 1-14.   The film formed with the resin composition in any one of Claims 1-15.   The film according to claim 16, which is an inflation film.   The film according to claim 16 or 17, which has a tensile strength of 10 to 50 MPa and an elongation at break of 100 to 600%.   A method for producing a bag-like film by inflation-molding the resin composition according to claim 1.