Resin composition, its uses, and manufacturing method

Abstract

The present invention provides a resin composition that can form molded articles that meet practical requirements in terms of flexibility and strength, and that also exhibits excellent dimensional stability after molding. [Solution] In a resin composition containing a biodegradable resin (A) and a plasticizer (B), the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution is adjusted to 330,000 or more, and the polydispersity Mz / Mw, which indicates the ratio of Mz to the weight-average molecular weight Mw in the said region, is adjusted to 1.7 to 2.5. This resin composition may further contain a chain extender (C) such as a carbodiimide compound. The resin composition may be prepared by heating and melt-kneading the biodegradable resin (A), the plasticizer (B), and the chain extender (C). The resin composition may be blown to form a film with an average thickness of 10 to 200 μm.

Description

[Technical Field]

[0001] This disclosure relates to a film-molded resin composition, as well as its applications and manufacturing methods. [Background technology]

[0002] Biodegradable resins used in the manufacture of biodegradable films include polyhydroxybutyrate (PHB), polylactic acid (PLA), polycaprolactone (PCL), polyethylene succinate (PES), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), aliphatic polyester resins such as aromatically modified aliphatic polyester resin polybutylene adipate terephthalate (PBAT), and polyvinyl alcohol (PVA). However, because the constituent units of biodegradable resins are limited in order to exhibit biodegradability, it is difficult to balance various properties. In particular, it is difficult to achieve both flexibility and strength, which are in a trade-off relationship, making it difficult to use them in film applications that require such properties. In particular, for garbage bags, shopping bags, and packaging bags, biodegradability is important because they are easily discarded, but it is especially difficult to form biodegradable resins into bag-shaped films.

[0003] Regarding the molding of biodegradable resin films, Japanese Patent Publication No. 2015-193750 (Patent Document 1) discloses a resin composition containing a rigid biodegradable resin, a flexible biodegradable resin, a plasticizer, and at least one selected from the group consisting of fatty acid amide compounds, aliphatic monoepoxy compounds, and aliphatic monocarboxylic acid compounds.

[0004] Japanese Patent Publication No. 2009-185227 (Patent Document 2) discloses a film made of a chip-shaped resin composition that mainly consists of a polylactic acid resin, further containing a plasticizer and an organic lubricant, and having a melt flow rate of 0.1 to 15 g / 10 min.

[0005] Japanese Patent Publication No. 2013-155224 (Patent Document 3) discloses a biodegradable film containing a lactic acid-based resin and a biodegradable resin other than a lactic acid-based resin, having a structure in which a dispersed phase made of the biodegradable resin is dispersed in a long elliptical or layered manner within a continuous phase made of the lactic acid-based resin.

[0006] Japanese Patent Publication No. 2010-126619 (Patent Document 4) discloses a film molded using a chip-shaped resin composition comprising a polylactic acid resin, an aliphatic polyester and / or an aliphatic aromatic polyester, a plasticizer, and an organic lubricant, wherein the melt mass flow rate is 0.1 to 15 g / 10 min and the heat of fusion of crystals is 5 to 40 J / g.

[0007] Japanese Patent Publication No. 2009-138085 (Patent Document 5) discloses a polylactic acid resin film comprising a polylactic acid resin and a plasticizer, having an elongation of 200-700%, a thickness error ΔTr relative to the average thickness Ta in the width direction of ±10%, and a heat shrinkage rate Sm (in the winding length direction) and St (in the width direction) of 0-5% and -1-2%, respectively, when treated at 65°C for 30 minutes. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2015-193750 [Patent Document 2] Japanese Patent Publication No. 2009-185227 [Patent Document 3] Japanese Patent Publication No. 2013-155224 [Patent Document 4] Japanese Patent Publication No. 2010-126619 [Patent Document 5] Japanese Patent Publication No. 2009-138085 [Overview of the project] [Problems that the invention aims to solve]

[0009] Furthermore, when a resin composition is molded, for example, in film molding, when a bag-shaped film is manufactured by inflation molding, the film is prone to shrinkage, and therefore dimensional stability is also required. In particular, dimensional stability tends to decrease over time after molding. In contrast, Patent Documents 1 to 4 do not describe dimensional stability. Moreover, including Patent Document 5, which mentions the heat shrinkage rate, none of the patent documents disclose a resin composition that can produce molded articles such as films that satisfy flexibility, strength, and dimensional stability.

[0010] Therefore, the object of this disclosure is to provide a resin composition, its applications, and a method for manufacturing the same, which can form molded articles having practical levels of flexibility and strength, and which also exhibits excellent dimensional stability after molding. [Means for solving the problem]

[0011] As a result of diligent research to achieve the above objectives, the present inventors have found that in a resin composition containing a biodegradable resin (A) and a plasticizer (B), by adjusting the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution to 330,000 or more, and by adjusting the polydispersity Mz / Mw, which represents the ratio of Mz to the weight-average molecular weight Mw in the said region, to 1.7 to 2.5, it is possible to form a molded article with practical levels of flexibility and strength, and also improve dimensional stability after molding, thus completing the present invention (or present disclosure).

[0012] In other words, this disclosure includes the following aspects:

[0013] Embodiment [1]: A resin composition comprising a biodegradable resin (A) and a plasticizer (B), wherein the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution is 330,000 or more, and the polydispersity Mz / Mw, which indicates the ratio of Mz to the weight-average molecular weight Mw in the said region, is 1.7 to 2.5.

[0014] Embodiment [2]: The resin composition according to Embodiment [1], wherein the area of ​​the region with a molecular weight of 2,000 or more in the molecular weight distribution is 75 to 85% of the area of ​​the total region.

[0015] Embodiment [3]: The resin composition according to Embodiment [1] or [2], which exhibits crystallization behavior during a cooling process of 10°C / min from a molten state and has a crystallization enthalpy of 10 to 100 J / g.

[0016] Embodiment [4]: ​​The resin composition according to any one of Embodiments [1] to [3], wherein the biodegradable resin (A) comprises a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1).

[0017] Embodiment [5]: The resin composition according to Embodiment [4], wherein the polyester resin (A2) comprises a polyester resin containing an aliphatic skeleton.

[0018] Embodiment [6]: The resin composition according to any one of Embodiments [1] to [5], wherein the plasticizer (B) comprises an ester-based plasticizer.

[0019] Embodiment [7]: The resin composition (or molten compound) according to any of Embodiments [1] to [6], further comprising a chain extender (C).

[0020] Embodiment [8]: The resin composition according to Embodiment [7], wherein the chain extender (C) comprises a carbodiimide compound.

[0021] Embodiment [9]: The resin composition according to Embodiment [7] or [8], wherein the biodegradable resin (A) comprises a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1), and is obtained by heating and melt-kneading the biodegradable resin (A), the plasticizer (B), and the chain extender (C).

[0022] Embodiment

[10] : The resin composition according to any one of Embodiments [7] to [9], wherein the biodegradable resin (A) comprises a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1), the mass ratio of the polylactic acid resin (A1) to the polyester resin (A2) is 80 / 20 to 10 / 90, and the proportions of the plasticizer (B) and the chain extender (C) are 1 to 15 parts by mass and 0.1 to 1 part by mass, respectively, per 100 parts by mass of the biodegradable resin (A).

[0023] Embodiment

[11] : A method for producing a resin composition according to any one of Embodiments [7] to

[10] , comprising heating and melt-kneading the biodegradable resin (A), the plasticizer (B), and the chain extender (C).

[0024] Embodiment

[12] : A molded article formed from the resin composition described in any of Embodiments [1] to

[10] .

[0025] Embodiment

[13] : The molded article according to Embodiment

[12] , wherein the film has an average thickness of 10 to 200 μm.

[0026] Embodiment

[14] : The molded article according to Embodiment

[12] or

[13] , which is an inflation film.

[0027] Embodiment

[15] : A molded body according to any of Embodiments

[12] to

[14] , which is a bag-shaped or tubular film, agricultural material, construction / industrial material, or packaging material.

[0028] Embodiment

[16] : A method for producing a molded article by heating and melting a resin composition according to any of Embodiments [1] to

[10] .

[0029] Embodiment

[17] : The manufacturing method according to Embodiment

[16] , wherein the resin composition is blown to form a film.

[0030] Embodiment

[18] : A method for improving the dimensional stability of a molded article formed from a resin composition comprising a biodegradable resin (A) and a plasticizer (B) by adjusting the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution to 330,000 or more, and adjusting the polydispersity Mz / Mw, which is the ratio of Mz to the weight-average molecular weight Mw in the said region, to 1.7 to 2.5, thereby achieving both flexibility and strength in the resin composition.

[0031] Furthermore, this disclosure may achieve the following secondary objectives (solve the following problems).

[0032] Another object of this disclosure is to provide a resin composition, its uses, and a method for producing the same, which, even when containing a rigid polylactic acid-based resin as a biodegradable resin, can be obtained by inflation molding to produce a film with practical levels of flexibility and strength, as well as excellent dimensional stability.

[0033] In this specification and in the claims, the number of carbon atoms in substituents, etc., is defined as C1, C6, C 10 It is sometimes indicated in these ways. For example, "C1 alkyl group" means an alkyl group with 1 carbon atom, and "C 6-10 The term "aryl group" refers to an aryl group with 6 to 10 carbon atoms.

[0034] In this specification and in the claims, when a numerical range is indicated using "X~Y", it may include the end numbers X and Y.

[0035] In this specification and in the claims, the term "carboxylic acid component," such as lactic acid component, is used to include not only carboxylic acids but also their reactive derivatives. [Effects of the Invention]

[0036] According to this disclosure, it is possible to provide a resin composition that can form molded articles having practical levels of flexibility and strength, and that exhibits excellent dimensional stability after molding. [Modes for carrying out the invention]

[0037] [Resin composition] The resin composition (biodegradable resin composition) of this disclosure comprises a biodegradable resin (A) and a plasticizer (B), and by having a specific molecular weight distribution, the resin composition can form a molded article (particularly a film) that satisfies practical levels of flexibility and strength, and also improves dimensional stability after molding. In particular, even when a rigid polylactic acid-based resin is used as the biodegradable resin and a bag-shaped film is manufactured by inflation molding, practical levels of flexibility (high elongation and / or low modulus of elasticity) and strength (breaking strength and / or dirt impact strength), which are in a trade-off relationship, can be satisfied, and dimensional stability after molding can also be improved.

[0038] The resin composition of this disclosure is characterized by containing a biodegradable resin with a higher molecular weight than general-purpose biodegradable resins, and the average molecular weight Mz, which emphasizes the contribution of high molecular weight components, is important. The resin composition of this disclosure has an average molecular weight Mz of 330,000 or more in the region of molecular weight of 2,000 or more (hereinafter referred to as the "polymer region") in the molecular weight distribution, for example, 330,000 to 1,000,000, preferably 335,000 to 500,000, more preferably 340,000 to 400,000, more preferably 345,000 to 380,000, and most preferably 350,000 to 370,000. When Mz is above the lower limit, dimensional stability tends to improve, and when it is below the upper limit, moldability tends to improve.

[0039] The resin composition of this disclosure has a polydispersity Mz / Mw ratio, which indicates the ratio of the z-average molecular weight Mz in the polymer region to the weight-average molecular weight Mw in the polymer region, of 1.7 to 2.5, preferably 1.75 to 2.4, more preferably 1.8 to 2.3, more preferably 1.9 to 2.2, and most preferably 2 to 2.1. Mz / Mw is an indicator of the contribution of high molecular weight components to the physical properties of the polymer. When Mz / Mw is above the lower limit, ultra-high molecular weight components tend to be more readily present among the high molecular weight components, and dimensional stability tends to improve. When it is below the upper limit, moldability tends to improve.

[0040] In this disclosure, the details of the mechanism by which the Mz and Mz / Mw in the polymer region of the resin composition are within the aforementioned range, thereby achieving both flexibility and strength in the molded article and improving dimensional stability, are unknown. However, it can be inferred that having the aforementioned molecular weight distribution (Mz in the polymer region and the polydispersity Mz / Mw) means that the biodegradable resin (A) contains high molecular weight components in a predetermined distribution ratio, thereby maintaining the strength of the molded article, such as a film, without impairing flexibility, and also maintaining the shape of the molded article after molding.

[0041] In this specification and in the claims, the molecular weight distribution, Mz, and Mw of the resin composition refer to the differential molecular weight distribution, Mz, and Mw obtained by subjecting the resin composition itself (particularly the molten compound) to gel permeation chromatography (GPC) and determining it by the polystyrene equivalent method. More specifically, they refer to the molecular weight distribution, Mz, and Mw obtained by the method described in the examples below.

[0042] The resin composition disclosed herein has a polymer region area of, for example, 75-85%, preferably 76-84%, more preferably 77-83%, more preferably 78-82%, and most preferably 79-81.5% of the total region area. When the polymer region area is above the lower limit, dimensional stability tends to improve, and when it is below the upper limit, flexibility tends to improve.

[0043] In this specification and in the claims, the area of ​​the polymer region refers to the area in the molecular weight range of 2,000 to 10,000,000 in the molecular weight distribution, and the total area refers to the sum of the area of ​​the polymer region and the area of ​​the region with a molecular weight of 2,000 or less in the molecular weight distribution (hereinafter referred to as the "low molecular weight region"). Furthermore, the area of ​​the low molecular weight region refers to the area in the molecular weight range of 100 to 2,000. The reason why the lower limit of molecular weight in the low molecular weight region is set at 100 is that molecular weights of 100 or less can be ignored. Therefore, the area of ​​the total area does not include the area of ​​the region with a molecular weight of 100 or less.

[0044] The resin composition of this disclosure preferably does not have a peak in the molecular weight range of 2,000 to 6,000 in its molecular weight distribution. When there is no peak in this range, the strength and dimensional stability of the molded article tend to improve.

[0045] The resin composition of this disclosure is preferably crystalline, and is particularly preferably crystalline when cooled from a molten state at a rate of 10°C / min, in order to improve the dimensional stability of the molded article.

[0046] The crystallization temperature (crystallization peak top temperature) of the resin composition disclosed herein may be 40°C or higher, for example, 40 to 120°C, preferably 50 to 100°C, more preferably 60 to 90°C, and most preferably 80 to 85°C. When the crystallization temperature is above the lower limit, the dimensional stability of the molded article tends to improve, and when it is below the upper limit, the moldability tends to improve.

[0047] The crystallization enthalpy of the resin composition disclosed herein is, for example, 5 to 150 J / g, preferably 8 to 120 J / g, particularly preferably 10 to 100 J / g, even more preferably 12 to 50 J / g, more preferably 13 to 30 J / g, and most preferably 15 to 20 J / g. When the crystallization enthalpy is above the lower limit, the dimensional stability of the molded article tends to improve, and when it is below the upper limit, the flexibility of the molded article tends to improve.

[0048] In this specification and in the claims, the crystallization behavior, crystallization peak top temperature, and crystallization enthalpy of the resin composition and the biodegradable resin (A) described later can be measured using a differential scanning calorimeter, and in particular, they can be measured by the method described in the examples described later.

[0049] (A) Biodegradable resin The resin composition (biodegradable resin composition) of this disclosure comprises a biodegradable resin (A). The biodegradable resin (A) is not particularly limited, as long as the resin composition after melt-kneading has a predetermined molecular weight distribution.

[0050] The biodegradable resin (A) can be selected from conventional biodegradable resins, but it is preferable that it contains a polylactic acid resin (A1), and it is particularly preferable that it contains a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1). In the resin composition of this disclosure, even if a polylactic acid resin (A1) that is rigid and has low flexibility and moldability is included, it is possible to mold a molded article that has practical flexibility and strength and excellent dimensional stability.

[0051] (A1) Polylactic acid resin The polylactic acid resin (A1) can be any resin (polymer) that contains a lactic acid component as a polymerization component. The lactic acid component may be lactic acid (2-hydroxypropanoic acid or 2-hydroxypropionic acid), or a reactive derivative of lactic acid.

[0052] Lactic acid may be in the form of optical isomers (D-form, L-form) or a racemic mixture (DL-form), but it is preferable to include the L-form (L-lactic acid) from the viewpoint of the mechanical properties of the resin composition.

[0053] When lactic acid contains the L-isomer, the proportion of the L-isomer in the lactic acid is preferably 10 mol% or more, more preferably 50 mol% or more, more preferably 70 mol% or more, and most preferably 90 mol% or more.

[0054] When lactic acid contains both L-form and D-form (D-lactic acid), the molar ratio of L-form to D-form may be L-form / D-form = 99.9 / 0.1~10 / 90, for example, 99.5 / 0.5~50 / 50, preferably 99 / 1~70 / 30, more preferably 98.5 / 1.5~80 / 20, more preferably 98 / 2~90 / 10, and most preferably 97 / 3~95 / 5.

[0055] Reactive derivatives of lactic acid include lactide (lactic acid dimer), acid anhydride, methyl ester, etc. 1-3 Examples include alkyl esters and acid halides such as acid chlorides.

[0056] These lactic acid components can be used individually or in combination of two or more. Of these lactic acid components, those containing L-lactic acid [(S)-2-hydroxypropanoic acid] or its reactive derivatives are preferred, and a combination of L-lactic acid and D-lactic acid [(R)-2-hydroxypropanoic acid] is particularly preferred.

[0057] The polylactic acid resin (A1) is preferably a polymer in which lactic acid is the main polymerization component, and may be a homopolymer of lactic acid (e.g., poly-D-lactic acid, poly-L-lactic acid, poly-D,L-lactic acid, etc.), or a copolymer of lactic acid and copolymer components.

[0058] Examples of copolymerizable components with lactic acid components include diols, dicarboxylic acid components, and hydroxycarboxylic acid components.

[0059] The diol is not particularly limited and may be an aliphatic diol, alicyclic diol, or aromatic diol, but an aliphatic diol is preferred from the viewpoint of the biodegradability of the resin composition. Examples of aliphatic diols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, octamethylene glycol, etc. 2-10 Examples include aliphatic diols. These diols can be used individually or in combination of two or more.

[0060] Of these diols, C 2-8 Aliphatic diols are preferred, such as ethylene glycol, 1,4-butanediol, and neopentyl glycol. 2-6 Aliphatic diols are particularly preferred.

[0061] The dicarboxylic acid component is not particularly limited and includes aliphatic dicarboxylic acid components, alicyclic dicarboxylic acid components, aromatic dicarboxylic acid components, etc.

[0062] Examples of aliphatic dicarboxylic acids include C such as oxalic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid 2-12 and aliphatic dicarboxylic acids, etc.

[0063] Examples of alicyclic dicarboxylic acids include C such as cyclohexanedicarboxylic acid 5-10 cycloalkane-dicarboxylic acids; dicyclic or tricyclic alkane dicarboxylic acids such as decahydrophthalic acid, norbornanedicarboxylic acid, and adamantanecarboxylic acid, etc.

[0064] Examples of aromatic dicarboxylic acids include C such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, anthracenedicarboxylic acid, and phenanthrenedicarboxylic acid 6-14 and arene-dicarboxylic acids, etc.

[0065] Examples of reactive derivatives of these dicarboxylic acids include C such as acid anhydrides, alkyl esters 1-3 alkyl esters, and acid halides such as acid chlorides. These dicarboxylic acid components can be used alone or in combination of two or more.

[0066] Among these dicarboxylic acid components, aliphatic dicarboxylic acid components are preferred from the viewpoint of easy improvement of biodegradability, etc., and C 2-8 aliphatic dicarboxylic acid components are more preferred, and C such as oxalic acid, succinic acid, adipic acid, etc. 2-6 aliphatic dicarboxylic acid components are even more preferred.

[0067] The hydroxycarboxylic acid component may be any of a hydroxyaliphatic carboxylic acid component, a hydroxyalicyclic carboxylic acid component, or a hydroxyaromatic carboxylic acid component, but a hydroxyaliphatic carboxylic acid component is preferred from the viewpoint of biodegradability, etc.

[0068] The hydroxyaliphatic carboxylic acid component may be a hydroxyaliphatic carboxylic acid itself, or a reactive derivative of a hydroxyaliphatic carboxylic acid.

[0069] Examples of hydroxyaliphatic carboxylic acids include glycolic acid, 3-hydroxypropanoic acid (3HP), 2-hydroxybutyric acid (2-hydroxybutanoic acid or 2HB), 3-hydroxybutyric acid (3HB), 4-hydroxybutyric acid (4HB), 3-hydroxy-3-methylbutyric acid, 2-hydroxyvaleric acid (2-hydroxypentanoic acid), 3-hydroxyvaleric acid (3HV), 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxy-2-methylvaleric acid, 3-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 7-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 8-hydroxyoctanoic acid, 3-hydroxynanoneic acid, 9-hydroxynanoneic acid, 3-hydroxydecanoic acid, 10-hydroxydecanoic acid, etc. 1-6 Hydroxy C which may have an alkyl group 2-15 Examples include alkanic acids.

[0070] Reactive derivatives of hydroxyaliphatic carboxylic acids include acid anhydrides, methyl esters, etc. 1-3 Examples include alkyl esters, acid halides such as acid chlorides, and lactones corresponding to hydroxyaliphatic carboxylic acids.

[0071] Examples of lactones include diC14, glycoside, β-propiolactone, β-dimethylpropiolactone, γ-butyrolactone, γ-dimethylbutyrolactone, δ-valerolactone, ε-caprolactone, etc. 1-6 C may have an alkyl group 3-15 Lactones are an example. These lactones can be used alone or in combination of two or more. Of these lactones, C 3-10 Lactones are preferred, such as glycosides, propiolactones, and caprolactones. 3-8 Lactones are particularly preferred.

[0072] These hydroxycarboxylic acid components can be used individually or in combination of two or more.

[0073] Of these hydroxycarboxylic acid components, hydroxyC 2-10 Alkanic acid components are preferred, and hydroxy C 2-8 Alkanic acid components are even more preferred, such as glycolic acid and 3-hydroxypropanoic acid. 2-6 Alkanic acid components are more preferable.

[0074] These copolymer components can be used individually or in combination of two or more. Among these copolymer components, C such as ethylene glycol... 2-4 Alkanediols, adipic acid, etc. 2-6 Alkanedicarboxylic acid components, glycolic acid, and other hydroxy C 2-4 Alkanic acid components, such as glycosides and caprolactone. 4-6 Lactones are preferred.

[0075] In the polylactic acid resin (A1), the proportion of the lactic acid monomer may be the largest proportion among all constituent monomers, for example, 50 mol% or more of all constituent monomers (e.g., about 50 to 99.5 mol%), preferably 70 mol% or more (e.g., about 70 to 99 mol%), more preferably 80 mol% or more (e.g., about 80 to 98 mol%), more preferably 90 mol% or more, and most preferably 95 mol% or more. The polylactic acid resin (A1) may also be a resin consisting only of the lactic acid component. When the proportion of the lactic acid component is above the lower limit, the biodegradability of the resin composition tends to be improved.

[0076] Furthermore, the polylactic acid resin (A1) may be a single type of polylactic acid resin, or it may be an alloy resin formed by combining two or more different types (or polymerization compositions) of polylactic acid resins.

[0077] The z-average molecular weight Mz of the polylactic acid resin (A1) (Mz of the raw material that has not been melt-kneaded to prepare the resin composition) is, for example, 200,000 to 500,000, preferably 250,000 to 350,000, and more preferably 300,000 to 330,000.

[0078] The polydispersity Mz / Mw of the polylactic acid resin (A1) (Mz / Mw of raw materials not melt-kneaded to prepare the resin composition) is, for example, 1.6 to 2, preferably 1.65 to 1.8, and more preferably 1.7 to 1.75.

[0079] In this specification and in the claims, the Mz and Mw of the polylactic acid resin (A1) can be measured using gel permeation chromatography (GPC) by the polystyrene equivalent method.

[0080] The polylactic acid resin (A1) may be crystalline or amorphous.

[0081] The proportion of polylactic acid resin (A1) may be 10% by mass or more of the biodegradable resin (A), preferably 30-90% by mass, more preferably 40-80% by mass, more preferably 50-70% by mass, and most preferably 55-65% by mass.

[0082] The proportion of polylactic acid resin (A1) may be 38 to 78% by mass in the resin composition, preferably 40 to 70% by mass, more preferably 42 to 65% by mass, more preferably 45 to 60% by mass, and most preferably 50 to 55% by mass.

[0083] (A2) Polyester resin The polyester resin (A2) may be any polyester resin different from the polylactic acid resin (A1), but a polyester resin containing an aliphatic backbone is preferred due to its excellent biodegradability and flexibility.

[0084] A polyester resin containing an aliphatic skeleton only needs to contain constituent monomers (aliphatic monomers) having an aliphatic skeleton as polymerization components.

[0085] In polyester resins containing an aliphatic skeleton, the proportion of aliphatic monomers may be 30 mol% or more of the total constituent monomers, preferably 50 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more, and most preferably 100 mol%. When the proportion of aliphatic monomers is above the lower limit, it tends to suppress the decrease in biodegradability and flexibility of the molded article.

[0086] Polyester resins containing an aliphatic skeleton may be polymers containing diol and dicarboxylic acid components as the main polymerization components (polymers containing diol and dicarboxylic acid components in a proportion of 50 mol% or more of the total constituent monomers, hereinafter referred to as "polymers mainly composed of diol and dicarboxylic acid components") or polymers containing hydroxycarboxylic acid components (polymers containing hydroxycarboxylic acid components in a proportion of 50 mol% or more of the total constituent monomers, hereinafter referred to as "polymers mainly composed of hydroxycarboxylic acid components").

[0087] In polymers mainly composed of diols and dicarboxylic acid components, examples of diols include those exemplified as copolymerizable components with lactic acid components in the polylactic acid resin (A1). The diols can be used alone or in combination of two or more. Among the diols, C such as ethylene glycol and 1,4-butanediol can be used. 2-8 Aliphatic diols are preferred, C 2-6 Aliphatic diols are more preferred, C 2-4 Aliphatic diols are preferred.

[0088] Examples of dicarboxylic acid components include those exemplified as copolymerizable components with lactic acid components in the polylactic acid resin (A1). The dicarboxylic acid components can be used alone or in combination of two or more. Among the dicarboxylic acid components, C is an example of oxalic acid, succinic acid, adipic acid, sebacic acid, etc. 2-10 Aliphatic dicarboxylic acid components are preferred, C 3-8 Aliphatic dicarboxylic acid component is even more preferred, C 3-6 Aliphatic dicarboxylic acid components are more preferred, C 3-5 Aliphatic dicarboxylic acid components are most preferred.

[0089] A polymer mainly composed of diol and dicarboxylic acid components may further contain a hydroxycarboxylic acid component. Examples of hydroxycarboxylic acid components include those exemplified as copolymerizable components with lactic acid components in the polylactic acid resin (A1).

[0090] In polymers mainly composed of diol and dicarboxylic acid components, the total proportion of diol and dicarboxylic acid components should be 50 mol% or more of the total constituent monomers, preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably 100 mol%.

[0091] In a polymer mainly composed of a hydroxycarboxylic acid component, examples of the hydroxycarboxylic acid component include the hydroxycarboxylic acid component exemplified as a copolymerizable component with the lactic acid component in the polylactic acid resin (A1). The hydroxycarboxylic acid component can be used alone or in combination of two or more types. Among the hydroxycarboxylic acid components, hydroxy C such as 2HB, 3HB, 4HB, 3HV, and caprolactone can be used. 4-10 Aliphatic carboxylic acid components (alkanoic acid components) are preferred, and hydroxy C 4-8 Aliphatic carboxylic acid components are more preferred, and hydroxy C 4-6 Aliphatic carboxylic acid components are more preferable.

[0092] A polymer mainly composed of a hydroxycarboxylic acid component may further contain a diol and / or a dicarboxylic acid component. Examples of diols include those exemplified in the polylactic acid resin (A1) as copolymerizable components that can copolymerize with the lactic acid component. Examples of dicarboxylic acid components include those exemplified in the polylactic acid resin (A1) as copolymerizable components that can copolymerize with the lactic acid component.

[0093] In polymers mainly composed of hydroxycarboxylic acid components, the proportion of the hydroxycarboxylic acid component should be 50 mol% or more of the total constituent monomers, preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably 100 mol%.

[0094] These polyester resins (A2) can be used individually or in combination of two or more. Of these polyester resins (A2), C 2-8 Aliphatic diols and C 2-10 Polymers mainly composed of aliphatic dicarboxylic acid components, hydroxy C 4-10 A polymer mainly composed of an alkanic acid component is preferred, C 2-8 Aliphatic diols and C 3-8 Polymers mainly composed of aliphatic dicarboxylic acid components, hydroxy C 4-8 Polymers mainly composed of alkanic acid components are more preferred, such as PES, PBS, polybutylene adipate, PBSA, etc. 2-6 Aliphatic diols and C 3-6 Polymers consisting of aliphatic dicarboxylic acid components, such as PHB and PCL, and hydroxy C 4-6 Polymers consisting of aliphatic carboxylic acid components are more preferred, such as PES, PBS, etc. 2-5 Aliphatic diols and C 3-5 Polymers consisting of aliphatic dicarboxylic acid components are most preferred.

[0095] The z-average molecular weight Mz of the polyester resin (A2) (Mz of the raw material that has not been melt-kneaded to prepare the resin composition) is, for example, 200,000 to 500,000, preferably 250,000 to 350,000, and more preferably 280,000 to 330,000.

[0096] The polydispersity Mz / Mw of the polyester resin (A2) (Mz / Mw of raw materials that have not been melt-kneaded to prepare the resin composition) is, for example, 1.7 to 2.5, preferably 1.8 to 2.3, and more preferably 1.9 to 2.1.

[0097] In this specification and in the claims, the Mz and Mw of the polyester resin (A2) can be measured using gel permeation chromatography (GPC) by the polystyrene equivalent method.

[0098] The polyester resin (A2) may be crystalline or amorphous, but it is preferable that it be crystalline.

[0099] The crystallization temperature of the polyester resin (A2) (the crystallization temperature of the raw material that has not been melt-kneaded to prepare the resin composition) is, for example, -30°C to 120°C, preferably 0 to 100°C, more preferably 30 to 90°C, more preferably 50 to 80°C, and most preferably 60 to 70°C.

[0100] The crystallization enthalpy of the polyester resin (A2) is, for example, 5 to 150 J / g, preferably 8 to 120 J / g, more preferably 10 to 100 J / g, more preferably 30 to 80 J / g, and most preferably 50 to 70 J / g.

[0101] The mass ratio of polylactic acid resin (A1) to polyester resin (A2) may be 80 / 20 to 10 / 90, for example, 77 / 23 to 20 / 80, preferably 75 / 25 to 30 / 70, more preferably 70 / 30 to 40 / 60, more preferably 65 / 35 to 50 / 50, and most preferably 63 / 37 to 55 / 45. When the proportion of polyester resin (A2) is above the lower limit, the dimensional stability of the molded article tends to improve, and when it is below the upper limit, the strength of the molded article tends to improve.

[0102] The proportion of polyester resin (A2) may be 20 to 50% by mass in the resin composition, preferably 23 to 45% by mass, more preferably 25 to 40% by mass, more preferably 28 to 38% by mass, and most preferably 30 to 35% by mass.

[0103] The total proportion of polylactic acid resin (A1) and polyester resin (A2) may be 50% by mass or more of the biodegradable resin (A), preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass. When the total proportion is above the lower limit, it tends to be possible to achieve both flexibility and strength in the molded article, and to improve dimensional stability.

[0104] The biodegradable resin (A) may be 50% by mass or more in the resin composition, for example, 50-98% by mass, preferably 60-95% by mass, more preferably 70-93% by mass, more preferably 80-90% by mass or more, and most preferably 85-88% by mass. When the proportion of the biodegradable resin is above the lower limit, the biodegradability tends to improve.

[0105] (B) Plasticizer The resin compositions of this disclosure further include a plasticizer (B) to improve flexibility. The plasticizer (B) can be selected from conventional plasticizers depending on the type of biodegradable resin (A), and if the biodegradable resin (A) includes a polylactic acid resin (A1) and a polyester resin (A2), it may be a conventional plasticizer used as a plasticizer for polyester resins.

[0106] Conventional plasticizers include ester-based plasticizers such as aliphatic dicarboxylic acid esters, aromatic dicarboxylic acid esters, oxycarboxylic acid esters, and polyhydric alcohol fatty acid esters; phosphate ester-based plasticizers such as aliphatic phosphate esters, aromatic phosphate esters, and condensed phosphate esters; epoxy-based plasticizers such as alkyl epoxy stearates; amide-based plasticizers such as sulfonamides; and oligomeric plasticizers such as ester oligomers and amide oligomers. These plasticizers can be used individually or in combination of two or more.

[0107] Of these plasticizers, ester-based plasticizers and oligomeric plasticizers such as ester oligomers are preferred, and ester-based plasticizers are particularly preferred, from the viewpoint of compatibility with biodegradable resin (A).

[0108] Preferred ester-based plasticizers include polycarboxylic acid esters and polyhydric alcohol esters.

[0109] The polycarboxylic acid ester may also be a dicarboxylic acid ester, or a polycarboxylic acid ester having three or more carboxyl groups.

[0110] Examples of dicarboxylic acid esters include aliphatic dicarboxylic acid esters and aromatic dicarboxylic acid esters.

[0111] Examples of aliphatic dicarboxylic acid esters include aliphatic dialkyl dicarboxylic acids, diesters of aliphatic dicarboxylic acids with glycol ethers, and diesters of aliphatic dicarboxylic acids with aralkyl alcohols and (poly)alkylene glycol monoalkyl ethers.

[0112] Examples of aliphatic dialkyl dicarboxylates include dibutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, isononyl adipate, diisodecyl adipate, dibutyl sebacate, dioctyl sebacate, diethyl azelaate, dibutyl azelaate, and di-2-ethylhexyl azelaate.2-10 Aliphatic dicarboxylic acid diC 1-18 Alkyl (especially C 4-10 Alkanedicarboxylic acid diC 4-14 Examples include alkyl esters.

[0113] Diesters of aliphatic dicarboxylic acids and glycol ethers include diesters of aliphatic dicarboxylic acids and (poly)alkylene glycol monoalkyl ethers, such as bis(methyldiethylene glycol) adipate [or di(methoxyethoxyethyl) adipate], bis(butyldiethylene glycol) adipate, bis(methyldiethylene glycol) succinate, methyldiethylene glycol ethyl diethylene glycol adipate (or methoxyethoxyethyl / ethoxyethoxyethyl adipate), methyldiethylene glycol butyldiethylene glycol adipate, etc. 2-10 Aliphatic dicarboxylic acids and di or tetraC 2-4 Alkylene glycol mono C 1-4 Examples include diesters with alkyl ethers.

[0114] Examples of diesters of aliphatic dicarboxylic acids with aralkyl alcohols and (poly)alkylene glycol monoalkyl ethers include benzyl methyl diethylene glycol adipate (or methoxyethoxyethyl benzyl adipate), benzyl ethyl diethylene glycol adipate, benzyl butyl diethylene glycol adipate, benzyl methyl diglycol succinate, benzyl butyl diglycol succinate, and other C21 compounds. 2-10 Aliphatic dicarboxylic acids and C 6-10 Aryl C 1-4 Alkyl alcohols and C 2-4 Alkylene glycol mono C 1-4 Examples include diesters with alkyl ethers.

[0115] Examples of aromatic dicarboxylic acid esters include dialkyl aromatic dicarboxylic acids, alkyl aralkyl aromatic dicarboxylic acid esters, and diesters of aromatic dicarboxylic acids and glycol ethers.

[0116] Examples of dialkyl aromatic dicarboxylates include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, and diisodecyl phthalate. 8-14 Allene dicarboxylate diC 1-12 Alkyl esters (especially benzenedicarboxylic acid C) 4-8 Examples include alkyl esters.

[0117] Examples of aromatic alkyl dicarboxylates include C14, such as butyl benzyl phthalate. 8-14 Allenedicarboxylic acid C 1-12 Alkyl C 6-10 Aryl C 1-4 Examples include alkyl esters.

[0118] Diesters of aromatic dicarboxylic acids and glycol ethers include diesters of aromatic dicarboxylic acids and (poly)alkylene glycol monoalkyl ethers, such as bis(methyldiethylene glycol) phthalate (or di(methoxyethyl) phthalate). 8-14 Allene dicarboxylic acid (especially C 8-12 (alenedicarboxylic acid) and di or tetraC 2-4 Alkylene glycol mono C 1-4 Examples include diesters with alkyl ethers.

[0119] Polycarboxylic acid esters having three or more carboxyl groups may also be esters of aliphatic or aromatic carboxylic acids having approximately 3 to 8 (particularly 3 to 6) carboxyl groups. Examples of such polycarboxylic acid esters include citrate esters such as tributyl citrate, tributyl acetyl citrate, and tri-2-ethylhexyl acetyl citrate; trimellitic acid esters such as trimethyl trimellitic acid, triethyl trimellitic acid, trioctyl trimellitic acid, and tri-2-ethylhexyl trimellitic acid; and pyromellitic acid esters such as tetraoctyl pyromellitic acid.

[0120] The polyhydric alcohol ester may be an ester of a polyhydric alcohol having three or more hydroxyl groups and a fatty acid. Examples of the polyhydric alcohol include alcohols having about 3 to 6 hydroxyl groups, such as sucrose, glycerin, diglycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol. An example of the polyhydric alcohol fatty acid ester is glycerin diacetate mono-C. 8-10 (Poly)C such as alkyl esters, triacetin, diglycerin tetraacetate 3-10 Alkane polyol mono or hexa C 2-10 Examples include alcanoates.

[0121] These ester-based plasticizers can be used individually or in combination of two or more. Of these ester-based plasticizers, aliphatic dicarboxylic acid esters are preferred from the viewpoint of biodegradability, etc. Furthermore, among aliphatic dicarboxylic acid esters, C such as adipic acid esters are preferred. 4-8 Alkanedicarboxylic acid esters are preferred, as they easily provide both flexibility and hydrolysis resistance for the biodegradable resin (A), C 4-8 Alkanedicarboxylic acids and C 6-10 Aryl C 1-4 Alkyl alcohols and mono- or tri-C alcohols 2-4 Alkylene glycol mono C 1-4 Diesterification with alkyl ether is even more preferred, C 5-7Alkanedicarboxylic acids and phenyl C 1-3 Alkyl alcohols and mono or diC 2-3 Alkylene glycol mono C 1-3 Diesterification with alkyl ether is even more preferred, C 5-7 Alkanedicarboxylic acids and phenyl C 1-2 Alkyl alcohols and diethylene glycol monoC 1-2 Diesterification with alkyl ether is most preferred.

[0122] The z-average molecular weight Mz of the plasticizer (B) may be less than 2,000 (particularly 1,500 or less), for example, 100 to 1,500, preferably 200 to 1,000, more preferably 300 to 800, and more preferably 400 to 500.

[0123] The polydispersity Mz / Mw of the plasticizer (B) is, for example, 1.0 to 2.5, preferably 1.0 to 2.0, more preferably 1.0 to 1.5, and even more preferably 1.0 to 1.1.

[0124] In this specification and in the claims, the Mz and Mw of the plasticizer (B) can be measured by the polystyrene equivalent method using gel permeation chromatography (GPC).

[0125] The proportion of plasticizer (B) may be 20 parts by mass or less (for example, 0.1 to 20 parts by mass) per 100 parts by mass of biodegradable resin (A), for example, 1 to 15 parts by mass, preferably 3 to 14.5 parts by mass, more preferably 5 to 14 parts by mass, more preferably 6 to 13 parts by mass, and most preferably 8 to 12 parts by mass. When the proportion of plasticizer (B) is above the lower limit, the flexibility of the molded article tends to improve, and when it is below the upper limit, the biodegradability, strength, and dimensional stability of the molded article tend to improve.

[0126] The proportion of plasticizer (B) may be 2 to 12% by mass in the resin composition, preferably 3 to 11.5% by mass, more preferably 5 to 11% by mass, more preferably 6 to 10.5% by mass, and most preferably 8 to 10% by mass.

[0127] (C) Chain extender The resin composition of this disclosure preferably further contains a chain extender (C) because it is easier to adjust the molecular weight distribution to the aforementioned range. Specifically, when the biodegradable resin (A) and the chain extender (C) are heated and melt-kneaded, a portion of the biodegradable resin (A) is chain-extended (or cross-linked) by the chain extender (C) to increase its molecular weight, thereby adjusting the Mz and Mz / Mw in the polymer region to the aforementioned range. When the biodegradable resin (A) contains a polylactic acid resin (A1) and a polyester resin (A2), it can be presumed that when the two are melt-kneaded in the presence of the chain extender (C), polymers are formed in the biodegradable resin (A) where polylactic acid resins (A1) are polymerized with each other via the chain extender (C), polymers where polylactic acid resins (A1) and polyester resins (A2) are polymerized with each other via the chain extender (C), and polymers where polyester resins (A2) are polymerized with each other via the chain extender (C).

[0128] The chain extender (or crosslinking agent) (C) only needs to have a reactive group (functional group) with respect to the biodegradable resin (A). The reactive group can be appropriately selected depending on the type of biodegradable resin (A), and examples include isocyanate groups, carbodiimide groups, carboxyl groups, acid anhydride groups, carbonate ester groups, halogen atoms, epoxy groups, amino groups, oxazoline rings, etc.

[0129] The chain extender (C) preferably has two or more reactive groups, more preferably three or more reactive groups, and even more preferably five or more (e.g., 5 to 20) reactive groups, as this makes it easier to adjust the molecular weight distribution of the resin composition.

[0130] Examples of chain extenders (C) include diisocyanate components, dicarboxylic acid components (such as dicarboxylic acid halides like dicarboxylic acid chlorides), dianhydrides of tetrabasic acids, carbonate bond forming components [for example, phosgenes such as phosgene and phosgene polymers (such as diphosgene and triphosgene); diesters of carbonates such as diphenyl carbonate], diamine compounds, carbodiimide compounds, epoxy compounds, and oxazoline ring-containing compounds.

[0131] These chain extenders (C) can be used alone or in combination of two or more. Among these, carbodiimide compounds are preferred from the viewpoint of easy adjustment of the molecular weight distribution of the resin composition.

[0132] The carbodiimide compound may be any compound having a carbodiimide skeleton or carbodiimide group (-N=C=N-) in the molecule, and it may have at least one carbodiimide group, and may have two or more carbodiimide groups. In the carbodiimide compound, the carbodiimide group is not particularly limited, but usually may be bonded to a hydrocarbon group (or hydrocarbon skeleton).

[0133] Typical carbodiimide compounds can be roughly classified into monocarboxydiimide compounds (compounds having one carbodiimide group) and polycarbodiimide compounds (compounds having two or more carbodiimide groups).

[0134] Examples of the monocarboxydiimide compound include compounds represented by the following formula (1).

[0135] A 1 -N=C=N-A 2 (1)

[0136] (In the formula, A 1 and A 2 each represent a hydrocarbon group which may have a substituent.)

[0137] In the formula (1) above, examples of the hydrocarbon group represented by A 1 and A 2 include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups and the like.

[0138] Examples of aliphatic hydrocarbon groups include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, hexyl group, 2-ethylhexyl group, octyl group, decyl group, dodecyl group, etc. Among these, C 1-30 alkyl group is preferred, C 1-12 alkyl group is more preferred, and C 1-8 alkyl group is even more preferred.

[0139] Examples of alicyclic hydrocarbon groups include cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cyclododecyl group, etc. Among these, C 5-10 cycloalkyl group is preferred.

[0140] Examples of aromatic hydrocarbon groups include aryl groups such as phenyl group, tolyl group, naphthyl group, etc. Among these, C 6-20 aryl group is preferred.

[0141] The alicyclic hydrocarbon group and the aromatic hydrocarbon group may have substituents. Examples of substituents include alkyl groups such as methyl group and ethyl group; alkoxy groups such as methoxy group and ethoxy group; alkylthio groups such as methylthio group and ethylthio group; acyl groups such as acetyl group and propionyl group; alkoxycarbonyl groups such as methoxycarbonyl group; halogen atoms such as chlorine atom and bromine atom; nitro group; cyano group; dialkylamino groups such as dimethylamino group, etc. These substituents can be used alone or in combination of two or more. Among these, C 1-4 alkyl groups such as methyl group, and C 1-4 alkoxy groups such as methoxy group are preferred, and C 1-3 alkyl group is more preferred.

[0142] A 1 and A 2 The hydrocarbon groups represented by may be the same as each other or different from each other, but it is preferred that they are the same.

[0143] Specifically, aliphatic monocarbodiimide compounds include diC such as 1,3-dimethylcarbodiimide and 1,3-diisopropylcarbodiimide. 1-20 Alkylcarbodiimides and other alicyclic monocarbodiimides, such as 1,3-dicyclohexylcarbodiimide, are examples of diC 5-10 Cycloalkylcarbodiimides, etc.; as aromatic polycarbodiimides, diC such as N,N'-diphenylcarbodiimide and N,N'-ditolylcarbodiimide. 6-20 Examples include arylcarbodiimides.

[0144] Polycarbodiimide compounds are not particularly limited as long as they have two or more carbodiimide groups, but examples include compounds having a skeleton (structural unit, repeating unit) represented by the following formula (2) (oligomer or polymer-type carbodiimide compounds).

[0145] -(N=C=NA 3 ) n - (2)

[0146] (In the formula, A 3 (where n is a divalent hydrocarbon group which may have substituents, and n is an integer of 2 or more)

[0147] In formula (2) above, the divalent hydrocarbon group A 3 Examples include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups.

[0148] Examples of divalent aliphatic hydrocarbon groups include linear or branched alkylene groups such as methylene, ethylene, propylene, trimethylene, butylene, tetramethylene, hexamethylene, isohexylene, octamethylene, decamethylene, and dodecamethylene; and C13 groups such as vinylene, allylene, metalylene, 1-propenylene, isopropenylene, butenylene, pentenylene, and hexenylene. 2-20 Alkenylene group; such as ethynylene group, propynylene group, etc. 2-20 Examples include the alkynylene group. Of these, C 1-30An alkylene group is preferred, C 2-12 Alkylene group is more preferred, C 3-8 Alkylene groups are more preferred.

[0149] Examples of divalent alicyclic hydrocarbon groups include cycloalkylene groups such as cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, and cyclododecane-diyl; alkylenecycloalkylene groups such as methylene-cyclohexylene; dicycloalkylalkanediyl groups such as dicyclohexylmethane-4,4'-diyl; and C113 groups such as cyclohexenylene. 3-12 Cycloalkenylene group; such as bicycloheptanylene group, bicycloheptenylene group, etc. 4-15 Examples include cross-linked cyclic hydrocarbon groups. Of these, C 5-10 Cycloalkylene group, C 1-10 Alkylene-C 5-10 Cycloalkylene group, diC 5-10 Cycloalkyl-C 1-6 Alkane-diyl group is preferred, diC 5-8 Cycloalkyl-C 1-4 Alkane-diyl groups are even more preferred.

[0150] Examples of divalent aromatic hydrocarbon groups include phenylene groups such as 1,4-phenylene groups, arylene groups such as torylene groups and naphthylene groups; diarylalkanediyl groups such as diphenylmethane-4,4'-diyl groups; and dialkylarenediyl groups such as α,α'-xylylene groups. Among the above aromatic hydrocarbon groups, C 6-20 Arylene group, diC 6-10 Aryl-C 1-6 Alkanediyl group, diC 1-6 Alkyl-C 6-10 An arene-diyl group is preferred.

[0151] The divalent alicyclic hydrocarbon group and the divalent aromatic hydrocarbon group may have substituents. Examples of substituents include the hydrocarbon group A. 1 and A 2Examples of substituents are those exemplified in the section. The substituents can be used individually or in combination of two or more. Among the substituents, C such as a methyl group. 1-4 C such as alkyl groups and methoxy groups 1-4 An alkoxy group is preferred, C 1-3 Alkyl alkyl groups are even more preferred.

[0152] Divalent hydrocarbon group A 3 In the repeating unit, the groups may be the same or different, but it is preferable that they be the same.

[0153] The number of repeating units n represented by formula (2) above can be 2 or more, for example, 2 to 100, preferably 3 to 50, more preferably 4 to 30, more preferably 5 to 20, and most preferably 7 to 15. In this disclosure, adjusting the number of repeating units n within this range makes it easier to adjust the molecular weight distribution of the resin composition.

[0154] Specifically, as aliphatic polycarbodiimide compounds, poly(C) such as polyhexamethylenecarbodiimide 2-20 Alicyclic polycarbodiimides such as alkylenecarbodiimides, and poly(C)(cyclohexylenecarbodiimides) 5-10 Poly(C) such as cycloalkylenecarbodiimide; poly(methylene-cyclohexylenecarbodiimide) 1-10 Alkylene-C 5-10 Poly(4,4'-dicyclohexylmethanecarbodiimide), such as poly(4,4'-dicyclohexylmethanecarbodiimide) 5-10 Cycloalkyl-C 1-10 Aromatic polycarbodiimides include poly(C) such as alkanecarbodiimide, polyphenylenecarbodiimide, polytylenecarbodiimide, poly(diisopropylphenylenecarbodiimide), and poly(methyldiisopropylphenylenecarbodiimide). 6-20 Arylenecarbodiimide; poly(4,4'-diphenylmethanecarbodiimide) and other poly(diC 6-10 Aryl-C 1-10Examples include alkanecarbodiimides.

[0155] The terminal groups of polycarbodiimide compounds are not particularly limited and may be groups derived from the raw materials, such as isocyanate groups or hydrocarbon groups, or they may be groups in which part or all of the terminal isocyanate isocyanate isocyanate isocyanate (e.g., amines, alcohols, monoisocyanates, etc.). Since polycarbodiimide compounds are usually obtained by reacting (polymerizing) isocyanate compounds (e.g., diisocyanate compounds), the terminal groups may form isocyanate groups.

[0156] The weight-average molecular weight Mw of the polycarbodiimide compound may be 200 or more, for example, 200 to 50,000, preferably 300 to 30,000, more preferably 500 to 10,000, more preferably 1,000 to 5,000, and most preferably 1,500 to 3,000. When Mw is above the lower limit, it tends to be easier to adjust the molecular weight distribution of the resin composition, and when it is below the upper limit, it tends to suppress the decrease in the biodegradability of the resin composition.

[0157] In this specification and in the claims, the Mw of a polycarbodiimide compound can be measured by the polystyrene-based method using gel permeation chromatography (GPC).

[0158] The carbodiimide compound may be in the form of a urea compound in the resin composition after melt kneading.

[0159] These carbodiimide compounds can be used individually or in combination of two or more. Of these carbodiimide compounds, aliphatic monocarbodiimide compounds, alicyclic monocarbodiimide compounds, aliphatic polycarbodiimide compounds, and alicyclic polycarbodiimide compounds are preferred, and polycarbodiimide compounds (such as polycarbodiimide compounds in formula (2) above where n is 7 to 15) are preferred because they allow for easy adjustment of the molecular weight distribution of the resin composition, and alicyclic polycarbodiimide compounds are even more preferred. 5-8 Cycloalkyl-C 1-5 Alkanecarbodiimide is more preferred.

[0160] The proportion of the chain extender (C) may be 0.1 parts by mass or more (for example, 0.1 to 10 parts by mass) per 100 parts by mass of the biodegradable resin (A), for example, 0.1 to 5 parts by mass, preferably 0.1 to 1 part by mass, more preferably 0.2 to 0.95 parts by mass, more preferably 0.3 to 0.9 parts by mass, and most preferably 0.5 to 0.85 parts by mass. When the proportion of the chain extender (C) is above the lower limit, it tends to be easier to adjust the molecular weight distribution of the resin composition, and when it is below the upper limit, it tends to be possible to achieve both biodegradability and strength of the resin composition, and dimensional stability tends to be improved.

[0161] The proportion of the chain extender (C) may be 0.1 to 5% by mass in the resin composition, preferably 0.1 to 1% by mass, more preferably 0.2 to 0.9% by mass, more preferably 0.3 to 0.85% by mass, and most preferably 0.4 to 0.8% by mass.

[0162] (D) Slip agent (or scratch preventative) The resin composition of this disclosure may further contain a slip agent (D) because it is easier to improve the handling properties of the film when it is formed into a film.

[0163] Slip agents (D) include waxes such as plant waxes, animal waxes, paraffin waxes, polyethylene waxes, ethylene copolymer waxes, and polypropylene waxes; C 8-35 Higher fatty acids such as fatty acids; C 8-35Higher fatty acid metal salts such as alkali metal salts of fatty acids; C 8-35 Alkyl esters of higher fatty acids, such as fatty acid alkyl esters; C 8-35 Examples include fatty acid amides and higher fatty acid amides such as alkylenebis-fatty acid amides; silicone compounds such as silicone oils, silicone resins, and polyorganosiloxanes having polyoxyalkylene units; and fluorine compounds such as fluorine oils and fluorine resins. These slip agents can be used alone or in combination of two or more. Of these, when the biodegradable resin (A) includes a polylactic acid resin (A1) and a polyester resin (A2), higher fatty acid amides are preferred because they easily improve the handling properties of the film.

[0164] Examples of higher fatty acid amides include capric acid amide, capric acid amide, pelargonic acid amide, lauric acid amide, palmitic acid amide, margaric acid amide, stearic acid amide, arachidin acid amide, and behenic acid amide. 12-30 Saturated fatty acid amides; such as myristoleamide, palmitoleamide, petroseamide, oleamide, vacceamide, linoleamide, linolenic acidamide, eleostearateamide, gadelineamide, arachidonic acidamide, erucamide, etc. 12-30 Acid amides of unsaturated fatty acids; such as ethylenebisstearylamide and hexamethylenediamine-distearate amide. 12-30 C, such as saturated fatty acid bisamide and ethylenebisoleamide. 12-30 Examples include unsaturated fatty acid bisamides. These higher fatty acid amides can be used alone or in combination of two or more. Among these, erucic acid amide and others are C 16-28 Acid amides of unsaturated fatty acids are particularly preferred.

[0165] The proportion of the slip agent (D) is, for example, 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 1 to 7 parts by mass, more preferably 1.5 to 5 parts by mass, and most preferably 2 to 3 parts by mass, per 100 parts by mass of the biodegradable resin (A).

[0166] (E) Antiblocking agent The resin composition of this disclosure may further contain an antiblocking agent (E) as it is easier to improve the handling properties of the film when it is formed into a film.

[0167] Examples of antiblocking agents (E) include inorganic particles such as silica, alumina, talc, titanium dioxide, and calcium carbonate; organic particles such as high heat-resistant thermoplastic resin particles like engineering plastics, crosslinked resin particles such as crosslinked acrylic resin particles and crosslinked melamine resin particles, and thermosetting resin particles. These antiblocking agents can be used alone or in combination of two or more. Of these, inorganic particles such as silica are preferred due to their excellent transparency.

[0168] The shape of the antiblocking agent (E) is not particularly limited and may be amorphous, but a spherical shape such as a perfect sphere is preferred.

[0169] The average secondary particle size of the antiblocking agent (E) is, for example, 0.1 to 50 μm, preferably 0.5 to 30 μm, more preferably 1 to 20 μm, and more preferably 5 to 15 μm.

[0170] In this specification and in the claims, the average secondary particle diameter of the antiblocking agent (E) can be measured on a volume basis by laser diffraction scattering.

[0171] The proportion of the antiblocking agent (E) is, for example, 0.1 to 10 parts by mass, preferably 0.2 to 7 parts by mass, more preferably 0.3 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, and most preferably 1 to 2 parts by mass, per 100 parts by mass of the biodegradable resin (A).

[0172] (F) Other ingredients The resin compositions of this disclosure may further contain conventional additives as other components (F). Examples of conventional additives include hydrolysis inhibitors, shrinkage inhibitors, stabilizers (anti-aging agents, antioxidants, ozone degradation inhibitors, UV absorbers, light stabilizers, heat stabilizers, etc.), acid scavengers, conductive agents, antistatic agents, flame retardants (phosphorus-based flame retardants, halogen-based flame retardants, inorganic flame retardants, etc.), flame retardant enhancers, impact resistance enhancers, flowability enhancers, leveling agents, defoamers, reinforcing agents (fibrous reinforcing agents such as glass fibers, carbon fibers, synthetic fibers; granular fillers such as carbon black, etc.), colorants, mold release agents, hue enhancers, dispersants, compatibilizers, antibacterial agents, antifungal agents, preservatives, stress reducers, and crystal nucleating agents. These additives can be used individually or in combination of two or more.

[0173] The total proportion of the other components (F) may be, for example, 100 parts by mass or less (e.g., 0.1 to 100 parts by mass) per 100 parts by mass of the biodegradable resin (A), preferably 50 parts by mass or less (e.g., 1 to 50 parts by mass), more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0174] [Mechanical properties of resin compositions] The resin composition of this disclosure has excellent dimensional stability, and in films obtained by inflation molding, the shrinkage rate after 1 day from film formation is preferably 3% or less in both the MD direction (longitudinal direction) and the TD direction (width direction), more preferably 2.5% or less, even more preferably 2% or less, particularly preferably less than 1%, and most preferably 0.9% or less.

[0175] In this specification and in the claims, the shrinkage rate of the film can be measured by the method described in the examples below.

[0176] The resin composition of this disclosure has excellent strength, and the breaking strength may be 25 MPa or more in either the MD direction or the TD direction, for example, 25 to 100 MPa, preferably 28 to 80 MPa, more preferably 30 to 60 MPa, and more preferably 35 to 50 MPa.

[0177] In this specification and in the claims, the tensile strength of the resin composition can be measured in accordance with JIS Z 1702, and in detail, it can be measured by the method described in the examples below.

[0178] The dirt impact strength of the resin composition disclosed herein may be 1 kg / mm ​​or more (particularly 10 kg / mm ​​or more), for example, 1 to 100 kg / mm, preferably 5 to 80 kg / mm, more preferably 10 to 50 kg / mm, more preferably 13 to 40 kg / mm, and most preferably 15 to 30 kg / mm.

[0179] In this specification and in the claims, the dirt impact strength of the resin composition can be measured in accordance with JIS Z 1702, and in detail, it can be measured by the method described in the examples below.

[0180] The resin composition of this disclosure has excellent flexibility, and the elongation at break in the MD direction may be 200% or more, for example 200 to 1000%, preferably 220 to 800%, more preferably 230 to 500%, and more preferably 240 to 300%. The elongation at break in the TD direction may be 230% or more, for example 230 to 1000%, preferably 250 to 800%, more preferably 270 to 500%, and more preferably 280 to 350%.

[0181] In this specification and in the claims, the elongation at break of the resin composition can be measured in accordance with JIS Z 1702, and more specifically, it can be measured by the method described in the examples below.

[0182] The resin composition of this disclosure may have an elastic modulus in the MD direction of 500 MPa or less, for example, 100 to 500 MPa, preferably 150 to 450 MPa, more preferably 200 to 400 MPa, and more preferably 280 to 350 MPa. The elastic modulus in the TD direction may be 600 MPa or less, for example, 150 to 600 MPa, preferably 200 to 500 MPa, more preferably 300 to 450 MPa, and more preferably 350 to 400 MPa.

[0183] In this specification and in the claims, the elastic modulus of the resin composition can be measured in accordance with JIS Z 1702, and in detail, it can be measured by the method described in the examples below.

[0184] [Method for producing resin compositions] The method for producing the resin composition of this disclosure is not particularly limited as long as the molecular weight distribution of the resin composition can be adjusted to a predetermined range. However, a method of heating and melt-kneading a biodegradable resin (A), a plasticizer (B), and a chain extender (C) is preferred because it is easier to adjust the molecular weight distribution of the resin composition. As described above, when the biodegradable resin (A) and the plasticizer (B) are melt-kneaded in the presence of the chain extender (C), a portion of the biodegradable resin (A) polymerizes via the chain extender (C), producing a biodegradable resin with a higher molecular weight, which makes it easier to adjust the molecular weight distribution. In particular, when the biodegradable resin (A) includes a polylactic acid resin (A1) and a polyester resin (A2), polymers are formed when polylactic acid resins (A1) polymerize with each other via a chain extender (C), polymers are formed when polylactic acid resins (A1) and polyester resins (A2) polymerize with each other via a chain extender (C), and polymers are formed when polyester resins (A2) polymerize with each other via a chain extender (C), thereby allowing the Mz and Mz / Mw in the polymer region to be adjusted to the aforementioned range.

[0185] Conventional methods for melt-mixing include mixing rollers, kneaders, Banbury mixers, and extruders (such as single-screw or twin-screw extruders). Of these methods, kneaders and twin-screw extruders capable of applying high shear force are preferred.

[0186] Mixing can be carried out in air or under an inert gas atmosphere (such as nitrogen or argon), and in an open system, but it is usually carried out in a closed mixing system.

[0187] The heating temperature can be appropriately selected depending on the type of biodegradable resin (A), for example, 100 to 300°C, preferably 130 to 250°C, more preferably 150 to 220°C, even more preferably 160 to 200°C, and most preferably 170 to 190°C. When the heating temperature is above the lower limit, it tends to be easier to adjust the molecular weight distribution of the resin composition, and when it is below the upper limit, it tends to be easier to improve the mechanical properties of the resin composition.

[0188] [Molded body] The molded articles of this disclosure are formed from the resin composition. The shape of the molded articles of this disclosure is not particularly limited and can be selected according to the application, and examples include one-dimensional structures such as linear or thread-like structures; two-dimensional structures such as film-like, sheet-like, or plate-like structures; and three-dimensional structures such as block-like, rod-like, tubular, or hollow structures. In particular, the resin composition of this disclosure can ensure practical flexibility and strength and easily improves dimensional stability even after film molding, so the shape of the molded articles of this disclosure is preferably a two-dimensional structure such as a film-like or sheet-like structure, and particularly preferably a film-like structure.

[0189] The average thickness of the film-like molded body (film) is, for example, 10 to 200 μm, preferably 15 to 150 μm, more preferably 20 to 100 μm, and more preferably 25 to 50 μm.

[0190] The molded articles of this disclosure can be manufactured by molding the resin composition using conventional molding methods. Conventional molding methods include compression molding, injection molding, injection compression molding, extrusion molding, transfer molding, blow molding, pressure molding, and casting molding.

[0191] When the molded article of the present disclosure is a two-dimensional structure in the form of a film or sheet, the molded article of the present disclosure can be manufactured by forming (or molding) the resin composition using conventional film-forming methods, such as inflation molding, T-die molding, casting (solvent casting), or calendering. In particular, the resin composition of the present disclosure is preferred because it is easy to improve dimensional stability after molding even when applying the highly productive inflation molding method. That is, the film may be an inflation film. Since inflation molding directly yields a bag-shaped film, the inflation film can be suitably used as a bag-shaped or tubular film (for example, a garbage bag, a packaging bag, a shopping bag, etc.).

[0192] In inflation molding, molding conditions can be appropriately selected, and the melting temperature (molding temperature) of the resin composition is, for example, 120 to 230°C, preferably 130 to 220°C, more preferably 140 to 200°C, and particularly 150 to 180°C. In addition, in inflation molding, the blow ratio is, for example, 1 to 10, preferably 1.5 to 7, and more preferably 2 to 5. [Examples]

[0193] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. The raw materials, equipment, and evaluation methods used in the examples are as follows.

[0194] [Raw materials] (A) Biodegradable resin (A1-1) PLA (Polylactic Acid): Total Corbion "LX175", Mw 189,000, Mz 328,000, Mz / Mw 1.73, L-isomer content 96 mol%, no crystallization peak. (A2-1) PBS (Polybutylene Succinate): "BioPBS FZ91PM" manufactured by Mitsubishi Chemical Corporation, Mw 151,000, Mz 290,000, Mz / Mw 1.91, crystallization temperature 63.5℃, crystallization enthalpy 58.0 J / g (A2-2) PBSA (Polybutylene succinate adipate): "BioPBS FD92PM" manufactured by Mitsubishi Chemical Corporation, Mw 156,000, Mz 325,000, Mz / Mw 2.08, crystallization temperature 1.1℃, crystallization enthalpy 22.3 J / g (A2-3)PBAT: Manufactured by Kahosha, Mw110,000, Mz196,000, Mz / Mw1.78, crystallization temperature 36.7℃, crystallization enthalpy 36.67J / g (B) Plasticizer (B-1) Adipic acid ester: "DAIFATTY-101" manufactured by Daihachi Chemical Industry Co., Ltd., Mw450, Mz473, Mz / Mw1.05 (C) Chain extender (C-1) Carbodiimide: "Carbodilite LA-1" manufactured by Nisshinbo Chemical Co., Ltd. (D) Other additives (D-1) Erucic acid amide: "Alflow P-10" manufactured by NOF Corporation (D-2) Silica: "AY-603" manufactured by Tosoh Silica Co., Ltd.

[0195] [GPC] The resin composition was dissolved in chloroform, and gel permeation chromatography (HLC-8220GPC manufactured by Tosoh Corporation, column (Showa Denko K.K., "Shodex GPC KF-405L HQ×3")) and an RI detector were used to measure the weight-average molecular weight Mw and z-average molecular weight Mz of the polymer region using the polystyrene equivalent method (standard polystyrene Mn: 3,209,000, 1,800,000, 321,000, 93,800, 34,800, 9,630, 3,500, 370, 266) under the conditions of sample concentration 0.2 w / v%, injection volume 40 μL, flow rate 0.3 mL / min, and column temperature 40°C. The weight-average molecular weight Mw and z-average molecular weight Mz of the polymer region were then measured, and the polydispersity Mz / Mw and the area ratio of the polymer region to the total region were calculated. Furthermore, since both a region (peak) of high molecular weight components on the short-term elution side and a region (peak) of low molecular weight components on the long-term elution side were detected, the former was designated as the first region derived from biodegradable resin.

[0196] [DSC] Using a differential scanning calorimeter (TA Instruments, Inc. "DSC25"), the crystallization temperature (crystallization peak top temperature) and crystallization enthalpy of a resin composition were measured when the temperature was lowered from 200°C to -50°C at a rate of 10°C / min under a nitrogen atmosphere. Specifically, the crystallization temperature and crystallization enthalpy of the resin composition were calculated by taking the peak top temperature of the exothermic peak as the crystallization peak top temperature and the area of ​​the exothermic peak as the crystallization enthalpy in the obtained measurement chart.

[0197] [Breaking strength, elongation at breaking, modulus of elasticity] In accordance with JIS Z 1702, the breaking strength and elongation at break of inflation film punched into the shape of a No. 1 dumbbell in both the MD and TD directions were measured at a tensile speed of 500 mm / min, a parallel section length of 40 mm, and a grip distance of 80 mm. In addition, the elastic modulus of inflation film cut into 20 mm wide strips was measured in both the MD and TD directions at a tensile speed of 10 mm / min and a grip distance of 100 mm.

[0198] [Dirt impact strength] The dirt impact strength of the inflation film was measured in accordance with JIS Z 1702.

[0199] [Shrinkage rate] The length of the raw material obtained by inflation molding was measured at one point in both the TD direction (width direction) and MD direction (longitudinal direction) immediately after film formation and one day after film formation under conditions of 25°C and 60% RH. The shrinkage rate in the TD direction and the shrinkage rate in the MD direction were then evaluated based on the following formulas.

[0200] Shrinkage rate = (Length immediately after film formation - Length after 1 day) / Length immediately after film formation

[0201] [Examples 1-5 and Comparative Examples 1-5] The components in the mass proportions shown in Tables 1 and 2 were melt-kneaded using a twin-screw extruder (IKG "PTMT73") with a screw diameter of 73 mm at a temperature of 180°C, a screw rotation speed of 150 rpm, and a discharge rate of 150 kg / hour to prepare a pelletized resin composition. The biodegradable resin raw material was pre-dried at a temperature of 70°C to 90°C for 120 hours. During melt-kneading, the plasticizer was introduced through a side feed using a liquid transfer pump, and the components other than the plasticizer were introduced through a top feed. The obtained pelletized resin composition was used to measure GPC and DSC.

[0202] Furthermore, an inflation film was prepared using the obtained resin composition by a general method. First, the resin composition was melt-kneaded in a single-screw extruder with a screw diameter of 50 mm and a temperature of 160 °C, and extruded through a circular die with a diameter of 85 mm. The blow ratio was set to 3 by adjusting the internal pressure. The film thickness was set to 30 μm by adjusting the extrusion amount. The film was cooled to room temperature and wound up, and its breaking strength, elongation at breaking, modulus of elasticity, dirt impact strength, and shrinkage rate were measured.

[0203] The mixing ratios and evaluation results are shown in Tables 1 and 2.

[0204] [Table 1]

[0205] [Table 2]

[0206] As is clear from Tables 1 and 2, in Examples 1 to 5, where the Mz of the first region was 330,000 or higher and the polydispersity Mz / Mw was 1.7 to 2.5, film bases with low base shrinkage were obtained, with shrinkage rates of 2.2% or less in the TD and MD directions. In particular, Examples 1 and 2 had high crystallization temperatures and rapidly crystallized during slow cooling, resulting in a high crystallization enthalpy of 15.9 J / g or higher, which may explain the excellent dimensional stability with a shrinkage rate of 0.8% or less, and the resulting films were wrinkle-free.

[0207] On the other hand, Comparative Examples 1 and 3-4 shrank significantly in the MD direction, while Comparative Examples 2 and 5 shrank significantly in both the TD and MD directions. It is thought that the presence of ultra-high molecular weight material is likely to have an influence on whether or not shrinkage occurs. Comparative Examples 1-5, which showed significant shrinkage of the original material, had low Mz / Mw ratios, and among them, Comparative Example 2, which also shrank significantly in the TD direction, had the lowest Mz / Mw ratio at 1.42.

[0208] Furthermore, the area ratio of the first region derived from biodegradable resin was 80% or more in the examples, but less than 75% in the comparative examples.

[0209] A higher area ratio in the first region indicates a greater amount of high molecular weight components. In addition, a higher Mz / Mw ratio indicates a greater amount of ultra-high molecular weight components within the high molecular weight components. Therefore, it is considered that the abundance of high molecular weight components and the presence of ultra-high molecular weight components in the resin composition are effective in maintaining the shape of the original roll.

[0210] Regarding Examples 1-5 and Comparative Examples 1-5, the mechanical properties of the films were evaluated. As a result, Examples 1-5 and Comparative Examples 1-3 and 5 all had physical properties that met practical standards in terms of breaking strength, elongation, and impact strength, but Comparative Example 4 had low dirt impact strength. [Industrial applicability]

[0211] Because the resin composition of this disclosure has high biodegradability, it can be used in molded articles in various fields [for example, packaging materials (films or sheets, cushioning materials, etc.), daily necessities (daily goods, etc.), agricultural materials, containers (containers for food, daily necessities, electrical and electronic equipment and parts, etc.), building materials (wall materials, casings, etc.), civil engineering materials, automobile parts, electrical and electronic components, machine parts or equipment (housings, etc.), optical components, etc.].

[0212] The resin composition disclosed herein can achieve both flexibility and strength even when formed into a film, and can also improve dimensional stability. Therefore, it can be suitably used for various films or sheets (for example, various bags such as garbage bags and shopping bags; agricultural materials such as mulch films; construction and industrial materials such as protective sheets; packaging materials such as food wrap, etc.). Because it is suitable for inflation molding, it can be particularly suitably used as bag-shaped or tubular films or sheets such as garbage bags, packaging bags, and shopping bags.

Claims

1. A resin composition comprising a biodegradable resin (A) and a plasticizer (B), wherein the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution is 330,000 or more, and the polydispersity Mz / Mw, which indicates the ratio of Mz to the weight-average molecular weight Mw in the said region, is 1.7 to 2.

5.

2. The resin composition according to claim 1, wherein the area of ​​the region with a molecular weight of 2,000 or more in the molecular weight distribution is 75 to 85% of the total area.

3. The resin composition according to claim 1 or 2, wherein it exhibits crystallization behavior during a cooling process of 10°C / min from a molten state, and has a crystallization enthalpy of 10 to 100 J / g.

4. The resin composition according to claim 1 or 2, wherein the biodegradable resin (A) comprises a polylactic acid-based resin (A1) and a polyester-based resin (A2) other than the polylactic acid-based resin (A1).

5. The resin composition according to claim 4, wherein the polyester resin (A2) comprises a polyester resin containing an aliphatic skeleton.

6. The resin composition according to claim 1 or 2, wherein the plasticizer (B) comprises an ester-based plasticizer.

7. The resin composition according to claim 1 or 2, further comprising a chain extender (C).

8. The resin composition according to claim 7, wherein the chain extender (C) comprises a carbodiimide compound.

9. The resin composition according to claim 7, wherein the biodegradable resin (A) comprises a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1), and is obtained by heating and melt-kneading the biodegradable resin (A), the plasticizer (B), and the chain extender (C).

10. The resin composition according to claim 7, wherein the biodegradable resin (A) comprises a polylactic acid resin (A1) and a polyester resin (A2) other than the polylactic acid resin (A1), the mass ratio of the polylactic acid resin (A1) to the polyester resin (A2) is 80 / 20 to 10 / 90, and the proportions of the plasticizer (B) and the chain extender (C) are 1 to 15 parts by mass and 0.1 to 1 part by mass, respectively, per 100 parts by mass of the biodegradable resin (A).

11. A method for producing a resin composition according to claim 7, comprising heating and melt-kneading the biodegradable resin (A), the plasticizer (B), and the chain extender (C).

12. A molded article formed from the resin composition according to claim 1 or 2.

13. The molded article according to claim 12, wherein the film has an average thickness of 10 to 200 μm.

14. The molded article according to claim 12, which is an inflation film.

15. The molded article according to claim 12, which is a bag-shaped or tubular film, agricultural material, construction / industrial material, or packaging material.

16. A method for producing a molded article by heating and melting the resin composition according to claim 1 or 2.

17. The manufacturing method according to claim 16, wherein the resin composition is subjected to inflation molding to form a film.

18. A method for improving the dimensional stability of a molded article formed from a resin composition comprising a biodegradable resin (A) and a plasticizer (B), by adjusting the z-average molecular weight Mz in the region of molecular weight 2,000 or more in the molecular weight distribution to 330,000 or more, and adjusting the polydispersity Mz / Mw, which represents the ratio of Mz to the weight-average molecular weight Mw in the said region, to 1.7 to 2.5, thereby achieving both flexibility and strength in the resin composition.

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