JP2013155223A - Polylactic acid-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film improved in elasticity and tear propagation resistance.SOLUTION: A polylactic acid-based film consisting of a composition containing a resin (A) and a resin (B) is characterized in that the resin (A) is a polylactic acid-based resin, and the resin (B) is an aliphatic polyester-based resin other than the polylactic acid-based resin and/or an aliphatic-aromatic polyester-based resin, and it has ≤40 μm thickness and satisfies both of the following formula 1: 0.8≤Oa≤1.6 and formula 2: 0.8≤Ob≤2. Wherein, Oa is an orientation parameter of the resin (A) in the film obtained by Raman spectrophotometry, and Ob is the orientation parameter of the resin (B) in the film obtained by the Raman spectrophotometry.

Description

  The present invention relates to a film containing a polylactic acid resin, an aliphatic polyester resin other than a polylactic acid resin and / or an aliphatic aromatic polyester resin, in order to improve the flexibility and tear propagation resistance. It is related with the polylactic acid-type film characterized by making the orientation parameter of resin (A) and resin (B) in the film calculated | required by the method into a specific value.

  In recent years, due to increasing environmental awareness, there are concerns about soil pollution problems caused by the disposal of plastic products and global warming problems caused by increased carbon dioxide caused by incineration of the products. As a countermeasure against the former, biodegradable resin that is completely decomposed into carbon dioxide molecules and water molecules under the environment in the soil, and as a countermeasure against the latter, synthesized from biological raw materials such as plants and incinerated Research and development on biomass resins that do not impose a new carbon dioxide load in the atmosphere are being actively conducted.

  Attention to polylactic acid-based resins is increasing as it is compatible with both of them and is relatively advantageous in terms of cost. However, since the polylactic acid resin is rigid and brittle, its flexibility and tear propagation resistance when formed into a film are relatively small, and as a result, it is difficult to use as a substitute for a polyolefin-based soft film such as polyethylene. . Therefore, various attempts have been made to improve these properties of the polylactic acid-based resin and put it into practical use as a flexible film.

  For example, Patent Document 1 discloses a film made of a composition containing a polylactic acid-based resin and a plasticizer and defining elongation, thickness, and heat shrinkage rate. Patent Document 2 discloses a film made of a polylactic acid resin, an aliphatic aromatic polyester resin, a plasticizer, and an inorganic filler. Patent Document 3 discloses a film made of a composition containing a polylactic acid-based resin and a biodegradable aromatic polyester and defining the elongation, thickness, and heat seal start temperature.

JP 2009-138085 A JP 2002-327107 A JP 2004-224870 A

  In the above-mentioned patent document, although there is a description relating to improvement in flexibility and / or impact resistance of a polylactic acid-based resin film, no technology relating to improvement in tear propagation resistance is disclosed at all. In particular, previous reports have not been sufficient for the technical idea related to the control of orientation parameters, which leads to an improvement in tear propagation resistance of polylactic acid-based films.

  The present invention solves such a conventional problem, whereby a film containing a polylactic acid-based resin, an aliphatic polyester-based resin excluding the polylactic acid-based resin and / or an aliphatic aromatic polyester-based resin, It is intended to improve tear propagation resistance.

  In order to solve the above problems, the present invention proposes the following configurations. That is, a polylactic acid film comprising a composition containing resin (A) and resin (B), wherein resin (A) is a polylactic acid resin and resin (B) is an aliphatic polyester type other than polylactic acid resin A polylactic acid film, which is a resin and / or an aliphatic aromatic polyester-based resin, has a thickness of 40 μm or less, and satisfies both the following formulas 1 and 2.

0.8 ≦ Oa ≦ 1.6 Formula 1
0.8 ≦ Ob ≦ 2 Equation 2
Here, Oa means the orientation parameter of the resin (A) in the film obtained by Raman spectroscopy, and Ob means the orientation parameter of the resin (B) in the film obtained by Raman spectroscopy.

  It is preferable that the polylactic acid-type film of this invention consists of a composition containing a plasticizer (C).

  Furthermore, the plasticizer (C) in the polylactic acid film of the present invention is more preferably a block copolymer having a polyether segment and a polylactic acid segment.

  Moreover, the polylactic acid-type film of this invention takes the resin discharged from the cyclic | annular nozzle | cap | die, the process 1 which makes resin cylindrical, the process 2 which cools resin made cylindrical, the process 3 which winds up cooled resin In this order, the lip gap of the annular die in the step 1 is preferably 1 mm or less.

  According to the present invention, the flexibility and tear propagation resistance of a film containing a polylactic acid resin, an aliphatic polyester resin other than a polylactic acid resin, and / or an aliphatic aromatic polyester resin can be improved. It becomes possible. The polylactic acid-based film of the present invention is required to have high flexibility and tear propagation resistance, and is used in agricultural and forestry applications such as agricultural multi-films and pine worm fumigation sheets, garbage bags, compost bags, vegetables and fruits It can be preferably used for various packaging applications such as bags for food products, bags for various industrial products and the like.

  The polylactic acid-based film of the present invention is a polylactic acid-based film comprising a composition containing a resin (A) and a resin (B), wherein the resin (A) is a polylactic acid-based resin and the resin (B) is a polylactic acid-based film. In order to improve the flexibility and tear propagation resistance of a polylactic acid film which is an aliphatic polyester-based resin and / or an aliphatic aromatic polyester-based resin other than the resin, the resin (A ) And the orientation parameter of the resin (B) are set to specific values.

Hereinafter, the polylactic acid film of the present invention will be described.

(Resin (A))
It is important that the polylactic acid film of the present invention comprises a composition containing a polylactic acid resin as the resin (A). The polylactic acid-based resin is a polymer mainly composed of an L-lactic acid unit and / or a D-lactic acid unit. Here, the main component means that the ratio of lactic acid units is the maximum in 100 mol% of all monomer units in the polymer, and preferably 70% of lactic acid units in 100 mol% of all monomer units. ˜100 mol%.

  The poly L-lactic acid of the present invention refers to those having a content ratio of L-lactic acid units of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polymer which is a polylactic acid resin. On the other hand, the poly D-lactic acid of the present invention refers to those having a D-lactic acid unit content of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polymer which is a polylactic acid resin.

  In poly L-lactic acid, the crystallinity of the resin itself varies depending on the content ratio of the D-lactic acid unit. That is, if the content ratio of the D-lactic acid unit in the poly-L-lactic acid increases, the crystallinity of the poly-L-lactic acid becomes lower and becomes closer to an amorphous state, and conversely, the content ratio of the D-lactic acid unit in the poly-L-lactic acid. As the amount decreases, the crystallinity of poly-L-lactic acid increases. Similarly, in poly D-lactic acid, the crystallinity of the resin itself changes depending on the content ratio of the L-lactic acid unit. That is, if the content ratio of the L-lactic acid unit in the poly-D-lactic acid increases, the crystallinity of the poly-D-lactic acid becomes low and approaches an amorphous state. Conversely, the content ratio of the L-lactic acid unit in the poly-D-lactic acid. As the amount decreases, the crystallinity of poly-D-lactic acid increases.

  The content ratio of the L-lactic acid unit in the poly L-lactic acid used in the present invention or the content ratio of the D-lactic acid unit in the poly D-lactic acid used in the present invention is from the viewpoint of maintaining the mechanical strength of the film. 80-100 mol% is preferable in 100 mol% of all lactic acid units, More preferably, it is 85-100 mol%.

  The crystalline polylactic acid resin of the present invention is measured with a differential scanning calorimeter (DSC) at a temperature rising rate of 20 ° C./min after leaving the polylactic acid resin to stand for 1 hour under heating at 100 ° C. In this case, it means a polylactic acid resin in which the heat of crystal melting derived from polylactic acid is observed.

  On the other hand, the amorphous polylactic acid-based resin referred to in the present invention refers to a polylactic acid-based resin that does not exhibit a clear melting point when measured in the same manner.

  As will be described later, the polylactic acid resin is preferably a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin.

  The polylactic acid resin used in the present invention may randomly copolymerize other monomer units other than lactic acid. Other monomers include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentane. Glycol compounds such as erythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid , Isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, -Dicarboxylic acids such as sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, caprolactone, valerolactone, Examples include lactones such as propiolactone, undecalactone, and 1,5-oxepan-2-one. The copolymerization amount of the other monomer units as described above is preferably 0 to 30 mol% with respect to 100 mol% of the whole monomer units in the polymer of the polylactic acid resin, and is 0 to 10 mol%. More preferably. In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

  Moreover, about the polylactic acid-type resin used by this invention, when the main component is poly L-lactic acid, conversely, when the main component is poly D-lactic acid, poly L-lactic acid, respectively, It is also preferable to mix a small amount. The reason is that the stereocomplex crystal formed thereby plays a role as a crystal nucleating agent for polylactic acid-based resins, and maintains transparency of the film compared to the case where a normal crystal nucleating agent is added. Because it can. At this time, the mass average molecular weight of the polylactic acid mixed in a small amount is preferably smaller than the mass average molecular weight of the main component polylactic acid from the viewpoint of efficient formation of stereocomplex crystals. The mass average molecular weight of the polylactic acid to be mixed in a small amount is preferably 0.5 to 50%, more preferably 1 to 40%, more preferably 2 to 30% of the mass average molecular weight of the main component polylactic acid. More preferably it is.

  Furthermore, the polylactic acid resin used in the present invention is preferably a polylactic acid block copolymer composed of a segment composed of an L-lactic acid unit and a segment composed of a D-lactic acid unit from the viewpoint of improving heat resistance. . In this case, since the polylactic acid block copolymer forms a stereocomplex crystal in the molecule, the melting point is higher than that of a normal crystal. For efficient stereocomplex crystal formation, the segment length should satisfy Y <X / 2 with respect to the mass average molecular weight X of the polylactic acid block copolymer and the maximum mass average molecular weight Y of one segment. preferable.

  The mass average molecular weight of the polylactic acid resin used in the present invention is preferably 50,000 to 500,000, more preferably 80,000 to 400,000, in order to satisfy practical mechanical properties. More preferably, it is ˜300,000. In addition, the mass average molecular weight in this invention means the molecular weight which measured with the chloroform solvent by the gel permeation chromatography (GPC), and was calculated by the polymethylmethacrylate conversion method.

  As a method for producing the polylactic acid-based resin, a known polymerization method can be used, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

The amount of the polylactic acid-based film of the present invention is not limited as long as it contains a polylactic acid-based resin in the composition constituting the film, but the polylactic acid-based resin is contained in 100% by mass of the entire composition constituting the film. It is preferable to contain 30-95 mass%. By setting the content of the polylactic acid resin in the composition to 30% by mass or more, the tear propagation resistance and the degree of biomass (content ratio of plant-derived raw materials) of the film are increased. On the other hand, when the content of the polylactic acid resin is 95% by mass or less, the film has excellent flexibility. In addition, it is more preferable that content of polylactic acid-type resin is 40-85 mass% in 100 mass% of the whole composition which comprises a film.

(Resin (B))
The composition constituting the polylactic acid film of the present invention is an aliphatic polyester resin and / or an aliphatic aromatic polyester resin excluding the polylactic acid resin as the resin (B) in order to improve flexibility and tear propagation resistance. It is necessary to contain a resin. In addition, it is preferable that these resins (B) also have biodegradability in order to develop biodegradability of the film. In addition, these resins (B) also serve to adjust the biodegradation rate of the film and to adjust the melt viscosity of the entire composition constituting the film, and in particular to form stable bubbles in the inflation film forming method. .

  Examples of the aliphatic polyester resin other than the polylactic acid resin used as the resin (B) include polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyhexanoate). ), Poly (3-hydroxybutyrate / 3-hydroxyvalerate), polycaprolactone, or an aliphatic diol such as ethylene glycol or 1,4-butanediol, and an aliphatic dicarboxylic acid such as succinic acid or adipic acid. Aliphatic polyesters are preferably used.

  As the aliphatic aromatic polyester resin used as the resin (B), for example, poly (butylene succinate / terephthalate), poly (butylene adipate / terephthalate) and the like are preferably used.

  The resin (B) of the present invention may be a blend and / or copolymer of those listed above.

  Among them, the resin (B) is at least selected from the group consisting of polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate because it has a large improvement effect on flexibility and tear propagation resistance. One is more preferable, and polybutylene adipate terephthalate is most preferable.

The amount of the polylactic acid-based film of the present invention is not limited as long as the resin (B) is included in the composition constituting the film, but the resin (B) is contained in 100% by mass of the entire composition constituting the film. It is preferable that it is 5-80 mass%. If it is 5% by mass or more, it is easy to obtain an effect of improving flexibility, tear resistance, and impact resistance. If it is 80% by mass or less, it is appropriate in a field that requires biodegradability, particularly for agricultural and forestry applications. Biodegradability can be imparted, and the degree of biomass can be increased at a low cost. In addition, it is further more preferable that content of resin (B) is 15-50 mass% in 100 mass% of the whole composition which comprises a film.

(Plasticizer (C))
The polylactic acid film of the present invention is preferably composed of a composition containing a plasticizer (C) in order to mainly impart flexibility.

  Although it does not specifically limit as a plasticizer (C) used for this invention, For example, phthalic acid ester type | system | groups, such as diethyl phthalate, dioctyl phthalate, and dicyclohexyl phthalate, Di-1-butyl adipate, Di-n adipate -Aliphatic dibasic acid esters such as octyl, di-n-butyl sebacate, di-2-ethylhexyl azelate, phosphate esters such as diphenyl-2-ethylhexyl phosphate, diphenyloctyl phosphate, acetylcitric acid Hydroxypolyesters such as tributyl, tri-2-ethylhexyl acetylcitrate, tributyl acetylcitrate, fatty acid esters such as methyl acetylricinoleate and amyl stearate, glycerin triacetate, triethylene glycol dicaprylate, etc. Multivalent Cole ester, Epoxidized soybean oil, Epoxy linseed oil Fatty acid butyl ester, Epoxy plasticizer such as octyl epoxy stearate, Polyester plasticizer such as polypropylene glycol sebacate, Polyalkylene ether, Ether ester, Acrylate The system etc. are mentioned. Moreover, it is also possible to use a mixture of two or more of these.

It is contained in the composition constituting the film in order to suppress bleed out of the plasticizer (C), maintain transparency of the film, improve plasticization efficiency, and lower the orientation parameter of the resin, particularly lower the orientation parameter of the resin (A). Solubility parameter of all plasticizers (C): SP is preferably (16-23) ^1/2 MJ / m ³ , more preferably (17-21) ^1/2 MJ / m ³ preferable. The method for calculating the solubility parameter is described in P.A. Small, J.M. Appl. Chem. 3, 71 (1953).

  Moreover, it is preferable that the plasticizer (C) of this invention is a biodegradable plasticizer from a viewpoint of maintaining the biodegradability of the whole film.

  Furthermore, considering the suitability for food packaging applications and the possibility of residual undegraded products remaining in compost and farmland for temporary or agricultural applications, the plasticizer of the present invention is ) Or polyolefin hygiene council or the like. Examples of the plasticizer (C) include triacetin, epoxidized soybean oil, epoxidized linseed oil, epoxidized linseed oil fatty acid butyl ester, adipic acid aliphatic polyester, acetyl citrate tributyl, acetyl ricinoleic acid ester, glycerin fatty acid ester Sucrose fatty acid ester, sorbitan fatty acid ester, adipic acid dialkyl ester, bis (alkyldiglycol) adipate or polyethylene glycol.

  Furthermore, from the viewpoint of the bleed-out resistance of the plasticizer (C) and the blocking resistance of the film, the plasticizer used in the present invention is, for example, polyethylene glycol having a number average molecular weight of 1,000 or more, such as normal temperature (20 ° C. ± 15 ° C) in a solid state, that is, the melting point is preferably higher than 35 ° C. Note that the upper limit of the melting point of the plasticizer is 150 ° C., in order to match the melt processing temperature with the polylactic acid resin, the aliphatic polyester resin and / or the aliphatic aromatic polyester resin other than the polylactic acid resin. .

  From the same viewpoint, the plasticizer (C) used in the present invention is more preferably a block copolymer having a polylactic acid segment and a polyether segment. Here, it is the polyether segment that actually acts as a plasticizing component. These block copolymers (hereinafter referred to as “block copolymer plasticizer”) will be described below.

  The mass ratio of the polylactic acid segment contained in the block copolymer plasticizer is preferably 50% by mass or less of the entire block copolymer plasticizer, since a desired flexibility can be imparted with a smaller amount of addition, preferably 5 mass. % Or more is preferable from the viewpoint of suppressing bleed-out. The number average molecular weight of the polylactic acid segment in one molecule of the block copolymer plasticizer is preferably 1,200 to 10,000. When the polylactic acid segment of the block copolymer plasticizer is 1,200 or more, sufficient affinity is produced between the block copolymer plasticizer and the polylactic acid resin, and a part of the segment Is incorporated into crystals formed from polylactic acid-based resins and forms so-called eutectics, thereby causing the plasticizer to be anchored to the polylactic acid-based resin, resulting in suppression of bleed-out of the block copolymer plasticizer. Demonstrate great effect. The number average molecular weight of the polylactic acid segment of the block copolymer plasticizer is more preferably 1,500 to 6,000, and further preferably 2,000 to 5,000. In addition, the polylactic acid segment which the block copolymer plasticizer has is that L-lactic acid is 95 to 100% by mass or D-lactic acid is 95 to 100% by mass. Therefore, it is preferable.

  Moreover, although a block copolymer plasticizer has a polyether segment, it is more preferable to have the segment which consists of polyalkylene ether as a polyether segment from a viewpoint which can provide a desired softness | flexibility by addition of a small quantity. Specifically, examples of the polyether segment include polyalkylene ether segments made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymers, etc., and in particular, polyalkylene ether segments made of polyethylene glycol. Is preferable because it has a high affinity with the polylactic acid resin as the resin (A) and is excellent in reforming efficiency, and as a result, desired flexibility can be imparted with a small amount of plasticizer.

  In addition, when the block copolymer plasticizer has a segment composed of a polyalkylene ether, the polyalkylene ether segment tends to be easily oxidized or thermally decomposed when heated at the time of molding, etc. It is preferable to use a hindered amine-based antioxidant or a phosphorus-based heat stabilizer in combination.

  The number average molecular weight of the polyether segment in one molecule of the block copolymer plasticizer is preferably 7,000 to 20,000. By setting the above range, the composition constituting the polylactic acid-based resin film has sufficient flexibility, and the melt viscosity of the entire composition constituting the film is set to an appropriate level, such as an inflation film forming method. The film forming processability can be stabilized.

  In the block copolymer plasticizer, there is no particular limitation on the order configuration of each of the polyether segment and the polylactic acid segment, but at least one block of the polylactic acid segment is more effectively suppressed from the viewpoint of suppressing bleed out. It is preferably at the end of the block copolymer plasticizer molecule.

  Next, the block copolymer plasticizer in the case where polyethylene glycol (hereinafter referred to as PEG) having hydroxyl ends at both ends is employed as the polyether segment will be specifically described.

The number average molecular weight of PEG having hydroxyl ends at both ends (hereinafter, the number average molecular weight of _PEG is M _PEG ) is usually calculated from the hydroxyl value determined by a neutralization method or the like in the case of a commercially available product. In a system in which lactide w _L parts by mass are added to w _E parts by mass of PEG having hydroxyl groups at both ends, lactide is subjected to ring-opening addition polymerization at both hydroxyl groups of PEG and sufficiently reacted, so that PLA is substantially obtained. A block copolymer of the -PEG-PLA type can be obtained (where "PLA" indicates polylactic acid). This reaction is performed in the presence of a catalyst such as tin octylate as necessary. The number average molecular weight of one polylactic acid segment contained in this block copolymer plasticizer can be substantially determined by (1/2) × (w _L / w _E ) × M _PEG . The mass percentage of the total block copolymer plasticizer of the polylactic acid segment component can be substantially determined by _{100 × w L / (w L} + w E)%. Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire block copolymer plasticizer can be substantially calculated by 100 × w _E / (w _L + w _E )%.

Although content of the plasticizer (C) in the composition which comprises the polylactic acid-type resin film of this invention is not specifically limited, A plasticizer (C) is 5-30 mass% in 100 mass% of the whole composition. It is preferable. By setting it to 5% by mass or more, the flexibility of the film becomes high, and by setting it to 30% by mass or less, the stiffness when made into a film is strong and the handling property, strength, durability, and bleed-out resistance of the plasticizer are improved. Get higher. In addition, content of a plasticizer is 7-25 mass% more preferably in 100 mass% of the whole composition.

(Other resins)
The composition constituting the polylactic acid-based film of the present invention can contain a thermoplastic resin other than those described above for the purpose of improving various physical properties. The content is preferably 0.1 to 50% by mass, more preferably 0.3 to 40% by mass, and still more preferably 0.5 to 30% by mass in 100% by mass of the entire composition constituting the film.

  Examples of such thermoplastic resins include polyacetal, polyethylene, polypropylene, polyamide, poly (meth) acrylate, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyimide, polyether imide, ethylene / glycidyl methacrylate. Examples include copolymers, polyester elastomers, polyamide elastomers, ethylene / propylene terpolymers, ethylene / butene-1 copolymers, thermoplastic starch, and polymers containing starch.

Examples of improving physical properties by containing a thermoplastic resin other than the resin (A) or resin (B) include improving the high-temperature rigidity of a polylactic acid-based film by containing poly (meth) acrylate, thermoplastic starch, or The biodegradability promotion of the polylactic acid-type film by containing the polymer containing starch is mentioned. As the polymer containing starch, for example, Novamont's biodegradable resin “Matterby” can be used. Regarding the biodegradation promotion, among the applications in which the polylactic acid film of the present invention is used, it is particularly important in agricultural and forestry applications such as agricultural multi-films and pine worm fumigation sheets.

(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
The polylactic acid resin which is the resin (A) contained in the composition constituting the polylactic acid film of the present invention is preferably a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. This is because, by using a mixture, the advantages of both crystalline and amorphous polylactic acid resins can be achieved.

  That is, the inclusion of the crystalline polylactic acid-based resin is suitable for improving the impact resistance, heat resistance, and blocking resistance of the film. In addition, when a block copolymer plasticizer is used as the plasticizer (C), the crystalline polylactic acid-based resin forms a eutectic with the polylactic acid segment of the block copolymer plasticizer, thereby preventing bleeding out. Great effect on sex.

  On the other hand, the inclusion of an amorphous polylactic acid resin is suitable for improving the flexibility and bleed-out resistance of the film. This has an effect of providing an amorphous part in which a component such as a plasticizer can be dispersed. Further, there is an advantage that the orientation parameter of the polylactic acid resin can be lowered.

  The crystalline polylactic acid-based resin used in the polylactic acid-based film of the present invention is obtained from the viewpoint of improving tear propagation resistance and impact resistance, or the content ratio of the L-lactic acid unit in the poly L-lactic acid or the poly D-lactic acid. The content ratio of D-lactic acid units is preferably 96 to 100 mol%, more preferably 98 to 100 mol%, still more preferably 99 to 100 mol%, and particularly preferably 99.5 out of 100 mol% of all lactic acid units. ˜100 mol%.

When the resin (A) (total of crystalline polylactic acid resin and amorphous polylactic acid resin) in the composition constituting the polylactic acid film of the present invention is 100% by mass, the crystalline polylactic acid resin Is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 40%.

(Organic lubricant)
It is preferable that the composition which comprises the polylactic acid-type film of this invention contains 0.1-5 mass% of organic lubricants in 100 mass% of the whole composition. In this case, blocking after winding can be favorably suppressed. In addition, problems such as a decrease in melt viscosity and deterioration of workability due to excessive addition of an organic lubricant, or poor appearance such as bleed out and haze up when formed into a film are less likely to occur.

Examples of organic lubricants include liquid paraffins, natural paraffins, synthetic paraffins, aliphatic hydrocarbons such as polyethylene, stearic acid, lauric acid, hydroxystearic acid, fatty castors such as hard castor oil, stearic acid amide, oleic acid amide, Fatty acid amides such as erucic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis lauric acid amide, fatty acid metal salts such as aluminum stearate, lead stearate, calcium stearate, magnesium stearate , Fatty acid (partial) esters of polyhydric alcohols such as glycerin fatty acid esters and rubitan fatty acid esters, long chain fatty acid esters such as long chain ester waxes such as butyl stearate and montan wax And the like. Among these, fatty acid amide organic lubricants that are easy to obtain an effect in a small amount due to moderate compatibility with polylactic acid are preferred. Among them, organic lubricants having a relatively high melting point such as ethylene bis stearic acid amide, ethylene bis oleic acid amide, and ethylene bis lauric acid amide are preferable from the viewpoint of expressing better blocking resistance.

(particle)
Particles may be added to the composition constituting the polylactic acid film of the present invention for the purpose of improving the slipperiness and blocking resistance of the processed product.

  Examples of inorganic particles include silicon oxide such as silica, various carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate, various sulfates such as calcium sulfate and barium sulfate, wollastonite, potassium titanate, aluminum boride, and zepiolite. Various composite oxides such as, various phosphates such as lithium phosphate, calcium phosphate and magnesium phosphate, various oxides such as aluminum oxide, titanium oxide, zirconium oxide and zinc oxide, water such as aluminum hydroxide and magnesium hydroxide Fine particles made of various salts such as oxide and lithium fluoride can be used.

  These inorganic particles are surface-treated with fatty acids, resin acids, titanate coupling agents, silane coupling agents, phosphate esters, etc. for the purpose of increasing compatibility with the resin and preventing aggregation in the resin. May be applied.

  As the organic particles, fine particles made of calcium oxalate, terephthalate such as calcium, barium, zinc, manganese, magnesium, or the like are used. Examples of the crosslinked polymer particles include fine particles made of a vinyl monomer such as divinylbenzene, styrene, acrylic acid or methacrylic acid, or a copolymer. In addition, organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also preferably used.

The average particle diameter of both inorganic particles and organic particles is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.1 to 4 μm, and most preferably 0.5 to 3 μm.

(High molecular weight agent)
Examples of the high molecular weight agent used in the present invention include polyvalent carboxylic acids, metal complexes, epoxy compounds, isocyanates, or mixtures thereof. As polyvalent carboxylic acids, (anhydrous) phthalic acid, (anhydrous) maleic acid, trimethyladipic acid, trimesic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) 3, 3 ', 4, 4'-benzophenone tetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid and the like and mixtures thereof. Metal complexes include lithium formate, sodium methoxide, potassium propionate, magnesium ethoxide, calcium propionate, manganese acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, cobalt acetylacetonate, iron acetylacetonate, aluminum Acetylacetonate, aluminum isopropoxide, tetrabutoxytitanium and the like can be mentioned, and divalent or higher metal complexes are particularly preferable. Examples of the epoxy compound include bisphenol A type diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, terephthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, ο-phthalic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl-3,4 epoxy epoxycyclocarboxylate, bis (3,4 epoxycyclohexyl) adipate, tetradecane-1,14-dicarboxylic acid glycidyl ester, and the like can be used. Isocyanates modified with hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, diisocyanate Polyethers modified with diisocyanates, compounds modified with polyfunctional alcohols with bifunctional isocyanates, polyethers modified with polyisocyanates, polyesters modified with polyisocyanates, and mixtures thereof.

Among these high molecular weight agents, polycarboxylic acids and metal complexes are preferable from the viewpoint of safety and coloring, and aliphatic compounds are preferable from the viewpoint of biodegradability. The addition amount of the high molecular weight agent varies depending on the type, but generally, it is preferably 0.001% by mass to 5% by mass, more preferably 0.01% with respect to 100% by mass of the composition in the film. It is preferable to add mass% to 2 mass%. If it exceeds 5% by mass, the polylactic acid resin or the aliphatic polyester resin and / or the aliphatic aromatic polyester resin excluding the polylactic acid resin may cause gelation, coloring, viscosity reduction, etc. Will increase. Moreover, if it is less than 0.001 mass part, the effect of high molecular weight will become inadequate.

(Additive)
In the composition which comprises the polylactic acid-type film of this invention, you may contain additives other than having mentioned above in the range which does not impair the effect of this invention. For example, known antioxidants, crystal nucleating agents, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, antioxidants, ion-exchange agents, and tackifying Agents, antifoaming agents, color pigments, dyes and the like.

  Examples of the antioxidant include hindered phenols and hindered amines.

  Color pigments include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, and quinocridone. Organic pigments such as thioindigo can be used.

Crystal nucleating agents include melamine compounds, phenylphosphonic acid metal salts, benzenecarboxamide derivatives, aliphatic / aromatic carboxylic acid hydrazides, sorbitol compounds, amino acid, polypeptides, organic nucleating agents such as metal phthalocyanines, and talc. Silicate minerals such as clay, mica and kaolinite, and inorganic crystal nucleating agents such as carbon black can be preferably used.

(Orientation parameter)
In the polylactic acid-based film of the present invention, Oa, which is an orientation parameter of the resin (A), is 0.8 or more and 1.6 in both the length direction and the width direction in order to express desired flexibility and tear propagation resistance. Hereinafter, Ob, which is the orientation parameter of the resin (B), needs to be 0.8 or more and 2 or less. In addition, Oa and Ob can be calculated | required by measuring the polarization | polarized-light Raman spectrum of a film cross section by a Raman spectroscopy as follows. The orientation parameter 1.0 is non-orientation. When the orientation parameter is less than 1, the orientation progresses in the cross-sectional direction of the film. When the orientation parameter exceeds 1, the orientation progresses in the direction perpendicular to the cross-section of the film.

  As for the orientation parameter, “length direction” means that a sample whose cross section is parallel to the length direction of the film is used, and “width direction” means a sample whose cross section is parallel to the width direction of the film. This is the case when used.

  When Oa exceeds 1.6 and / or Ob exceeds 2, molecular chain orientation may become remarkable, and flexibility and tear propagation resistance may be reduced. Further, when Oa and / or Ob is less than 0.8, it means that the alignment proceeds in the thickness direction, and is not suitable as the polylactic acid film of the present invention that requires flexibility and tear propagation resistance. Oa is more preferably 0.8 or more and 1.4 or less, and further preferably 0.8 or more and 1.2 or less. Further, Ob is more preferably 0.8 or more and 1.8 or less, and further preferably 0.8 or more and 1.6 or less.

Regarding the orientation parameters of the polylactic acid film of the present invention, Oa is 0.8 or more and 1.6 or less, and Ob is 0.8 or more and 2 or less, for example, the lip gap of the die, the die temperature, and the blow ratio. It becomes possible by setting it as the following preferable ranges.

(Thickness)
The polylactic acid film of the present invention needs to have a film thickness of 40 μm or less in order to exhibit desired flexibility. A more preferable film thickness is 5 to 40 μm. By setting the film thickness to 5 μm or more, the firmness of the film becomes strong, the handleability is excellent, and the roll winding shape and unwinding property are good. Flexibility is improved by making the film thickness 40 μm or less, and it is easy to handle when used for agricultural and forestry applications such as agricultural multi-film and pine worm fumigation sheets, garbage bags, compost bags, or various packaging applications. In addition, the bubble is not destabilized by its own weight particularly in the inflation film forming method. As for film thickness, 7-30 micrometers is more preferable, and 10-20 micrometers is further more preferable.

(Tear propagation resistance)
The polylactic acid film of the present invention preferably has a tear propagation resistance of 30 N / mm or more in both the length direction and the width direction. When the tear propagation resistance is 30 N / mm or more, cut surfaces and holes when used for agricultural and forestry applications such as agricultural multi-films and pine fever fumigation sheets, garbage bags, compost bags, or various packaging applications It will be difficult for the tears to progress. Further, the tear propagation resistance in the length direction and the width direction is more preferably 40 N / mm or more, and further preferably 50 N / mm or more. The upper limit of the tear propagation resistance value does not exist in particular, but since the main component is polylactic acid resin and aliphatic polyester resin and / or aliphatic aromatic polyester resin other than polylactic acid resin, The tear propagation resistance value is estimated to be about 500 N / mm.

In order to set the tear propagation resistance in the length direction and the width direction to 30 N / mm or more, the blending amounts of the resin (A), the resin (B), and the plasticizer (C) are each within the preferred ranges described above. And / or the orientation parameters Oa and Ob are set to the preferred ranges described above, respectively.

(Elongation at break)
In the polylactic acid film of the present invention, the elongation at break in the length direction and the width direction (direction perpendicular to the length direction) is preferably 150% or more and 700% or less. When the elongation at break is 150% or more, the tear resistance and impact resistance are high, and the agricultural and forestry applications such as agricultural multi-film and pine worm fumigation sheets, garbage bags, compost bags, and various packaging applications It is difficult to break and improves practicality. Further, when the elongation at break is 700% or less, tarmi and wrinkles during roll-to-roll running and winding are less likely to occur, and the roll winding shape and unwinding property are improved. The elongation at break in the length direction and the width direction is more preferably from 200% to 600%, and further preferably from 250% to 500%.

As methods for setting the elongation at break in the length direction and the width direction to 150% or more and 700% or less, the blending amounts of the resin (A), the resin (B), and the plasticizer (C) are described above. The method of making it a preferable range and / or setting the orientation parameters Oa and Ob to the preferable ranges described above can be mentioned.

(Elastic modulus)
The polylactic acid film of the present invention preferably has a tensile modulus in the length direction and the width direction of 100 MPa to 1,000 MPa in order to impart sufficient flexibility. The tensile elastic modulus is more preferably 100 or more and 700 MPa or less, and further preferably 100 or more and 500 MPa or less.

As a method for adjusting the tensile elastic modulus in the length direction and the width direction to 100 to 1,000 MPa, the preferred ranges described above for the blending amounts of the resin (A), the resin (B), and the plasticizer (C), respectively. And / or setting the orientation parameters Oa and Ob within the aforementioned preferred ranges.

(Production method)
Next, although the method for producing the polylactic acid film of the present invention will be specifically described, the method is not limited thereto.

  The polylactic acid resin in the present invention can be obtained, for example, by the following method. As a raw material, a lactic acid component of L-lactic acid or D-lactic acid is mainly used, and a hydroxycarboxylic acid other than the lactic acid component described above can be used in combination. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide, glycolide, etc. can be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.

  The polylactic acid resin can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

  In obtaining the composition constituting the polylactic acid film of the present invention, that is, the composition containing the resin (A), the resin (B), the plasticizer (C), or other components such as a crystal nucleating agent, It is possible to produce a composition by uniformly mixing a solution in which each component is dissolved in a solvent, and then removing the solvent. However, practical steps such as dissolving the raw material in the solvent and removing the solvent are unnecessary. It is preferable to employ a melt-kneading method, which is a method for producing a composition by melt-kneading each component. The melt kneading method is not particularly limited, and a commonly used known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity, it is preferable to use a single screw or twin screw extruder.

  The temperature at the time of melt kneading is preferably in the range of 150 ° C. to 240 ° C., and more preferably in the range of 180 ° C. to 210 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

  The polylactic acid film of the present invention can be obtained by an existing film production method such as a known inflation method using, for example, the composition obtained by the above-described method.

In producing the polylactic acid film of the present invention, for example, when the composition obtained by the above-described method is once pelletized, melt-kneaded again, and extruded and formed into a film, the pellet is heated at 60 to 100 ° C. It is preferable to use a composition containing a polylactic acid-based resin or the like having a moisture content of 1,200 ppm or less, preferably 500 ppm or less, more preferably 200 ppm or less by drying for more than an hour. Furthermore, it is preferable to reduce the lactide content in the composition containing the polylactic acid resin or the like by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. By reducing the water content of the composition containing the polylactic acid resin and the like to 1,200 ppm or less and the lactide content, hydrolysis during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. It is also preferable because the melt viscosity at the time of preparing a composition containing a resin or the like can be set to an appropriate level and the film forming process can be stabilized. From the same point of view, when pelletizing or melt-extrusion / film formation, a twin-screw extruder with a vent hole is used and melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances. It is preferable.

When the polylactic acid-based film of the present invention is produced by an inflation method, the resin discharged from the annular die is taken into a cylindrical step 1, the cylindrical resin is cooled in step 2, and the cooled resin is cooled. It is preferable to set it as the manufacturing method which has the process 3 which winds up in this order.

  In step 1, the resin prepared by the method as described above is melt-extruded by a single-screw or twin-screw extruder, guided to the annular die, and supplied with dry air from the inside of the die, thereby discharging the resin from the annular die. Is formed into a balloon shape (bubble), and it is preferably formed into a cylindrical shape by taking it out. In addition, from the viewpoint of thickness accuracy and uniformity, the annular die is preferably a spiral type, and from the same viewpoint, the annular die is preferably a rotary type.

  The extrusion temperature of the composition constituting the polylactic acid film of the present invention is usually in the range of 150 to 240 ° C., but the orientation parameter Oa is 0.8 or more and 1.6 or less and Ob is 0.8 or more and 2 or less. Therefore, the temperature of the annular die is preferably in the range of 155 to 190 ° C, more preferably in the range of 160 to 185 ° C.

  In step 2, it is preferable to uniformly cool and solidify the cylindrical resin by an air ring.

  In step 3, it is preferable that the cooled resin is taken up at a predetermined take-up speed while being folded flat with a nip roll, and then wound up after opening both ends or one end as necessary. Moreover, in order to suppress the heat shrink of a film, it is also preferable to heat-process in a heating roll or oven before winding up and after winding up a film.

  In order to make the thickness of the film 40 μm or less, the discharge amount from the annular die, the take-up speed of the nip roll, and the bubble blow ratio may be adjusted to an appropriate degree.

  The blow ratio of the bubble depends on the relationship between the discharge amount and the take-up speed of the nip roll, but the film may be anisotropic if it is too low or too high. It tends to be unstable and is usually in the range of 2.0 to 4.0.

  Furthermore, after forming into a film, various surface treatments may be applied for the purpose of improving printability, laminate suitability, coating suitability, and the like. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and any method can be used, but continuous treatment is possible, and equipment for existing film forming equipment is used. Corona discharge treatment can be exemplified as the most preferable because of its easy installation and simple processing.

  Since the polylactic acid-based film of the present invention is excellent in bleed resistance and blocking resistance, it can be smoothly unwound without problems when the film is unwound from the film roll after being wound.

(Lip gap of the base)
In order to achieve an improvement in the flexibility and tear strength of the film by controlling the orientation parameter close to 1, Oa being 0.8 or more and 1.6 or less, and Ob being 0.8 or more and 2 or less, In step 1 in the case of forming a film by the inflation method, the lip gap of the annular die is preferably 1 mm or less. As the lip gap is smaller, the orientation parameter tends to approach 1. However, if the lip gap is too small, it becomes difficult to assemble and clean the die, and there is a problem that the thickness unevenness of the film becomes large. The gap is preferably 0.3 mm or more and 1.0 mm or less, more preferably 0.3 mm or more and 0.7 mm or less, and further preferably 0.5 mm or more and 0.7 mm or less.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.
(1) Elongation at break (%)
Stress-strain measurement was performed using TENSILON UCT-100 manufactured by Orientec Co., Ltd. Specifically, a sample is cut into a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and measurement is performed according to the method defined in JIS K 7127 (1999) at an initial tensile chuck distance of 50 mm and a tensile speed of 200 mm / min. went. Moreover, the measurement was performed 5 times and the average value was calculated. This was calculated for each of the length direction and width direction of the film.
(2) Elastic modulus (MPa)
The stress-strain measurement is performed by the method described in (1), and the stress difference between the two points on the straight line is divided by the strain difference between the two points using the first straight line portion of the stress-strain curve. The elastic modulus was calculated. The measurement was performed 5 times, and the average value was calculated. This was calculated for each of the length direction and width direction of the film.
(3) Tear propagation resistance (N / mm)
Using a tear propagation resistance meter (Elmendorf) manufactured by Toyo Seiki Seisakusho Co., Ltd., the measurement was performed according to the method defined in JIS K 7128-2 (1998). The sample size was 63 mm in the tear direction × 76 mm in the direction perpendicular to the tear, and 20 mm incision was made in the tear direction, and the indicated value when the remaining 43 mm was torn was read. The measurement was performed 5 times, and the average value was calculated. This was calculated for each of the length direction and width direction of the film.
(4) Orientation parameter The following apparatus and conditions were measured by Raman spectroscopy.
・ Device: T-64000 (manufactured by Jobin Yvon)
・ Conditions: Measurement mode; Microscopic Raman objective lens; × 100
Beam diameter: 1 μm
Light source: Argon ion laser / 514.5 nm
Laser power: 100mW
Diffraction grating; Single 600gr / mm
Slit; 100 μm
Detector: CCD / Jobin Yvon 1024 × 256
The film used for measurement was sampled, embedded in an epoxy resin, and then cut with a microtome to prepare a cross-sectional sample of the film. In addition, as for the cross-sectional sample of the film, two types each having a cross section parallel to the length direction of the film and a cross section parallel to the width direction were prepared, and the center of each sample was used as a measurement point.

  Laser light (incident light) used for measurement was polarized using a polarizer. And after passing the polarizer arrange | positioned in the polarization direction parallel to the polarization direction of incident light, it detected with the detector and calculated | required the Raman band intensity | strength.

  For each sample, the spectrum is acquired by setting the polarization direction of the laser beam (incident light) and the length direction or width direction of the sample in parallel, and further, the polarization direction of the laser beam (incident light) and the sample The spectrum was acquired by installing in such a way that the length direction or width direction was vertical.

The orientation parameter of the resin (A) was calculated by the following formula. The measurement was performed 5 times, and the average value was calculated. This was calculated for each of the sample whose cross section was parallel to the length direction of the film and the sample whose cross section was parallel to the width direction of the film.

Oa = I1765 perpendicular / I1765 parallel I1765 parallel: Raman band intensity of 1765 cm ⁻¹ in the Raman spectrum measured in the polarization direction parallel to the length direction or the width direction.

I1765 perpendicular: Raman band intensity of 1765 cm ⁻¹ in a Raman spectrum measured in the polarization direction perpendicular to the length or width direction.

When the resin (B) is polybutylene adipate terephthalate, the orientation parameter was calculated by the following formula. The measurement was performed 5 times, and the average value was calculated. This was calculated for each of the sample whose cross section was parallel to the length direction of the film and the sample whose cross section was parallel to the width direction of the film.

Ob = I1612 parallel / I1612 perpendicular I1612 parallel: Raman band intensity of 1612 cm ⁻¹ in a Raman spectrum measured in a polarization direction parallel to the length direction or the width direction.

I1612 perpendicular: Raman band intensity of 1612 cm ⁻¹ in a Raman spectrum measured in the polarization direction perpendicular to the length direction or the width direction.

When the resin (B) is polyhydroxybutyrate / valerate, the orientation parameter was calculated by the following equation. The measurement was performed 5 times, and the average value was calculated. This was calculated for each of the sample whose cross section was parallel to the length direction of the film and the sample whose cross section was parallel to the width direction of the film.

Ob = I1725 vertical / I1725 parallel I1725 parallel: Raman band intensity of 1725 cm ⁻¹ in a Raman spectrum measured in the polarization direction parallel to the length direction or the width direction.

I1725 perpendicular: 1725 cm ⁻¹ Raman band intensity in a Raman spectrum measured in the polarization direction perpendicular to the length direction or the width direction.

The Raman band selected when obtaining the Raman band intensity used for calculating the orientation parameters of the resin (A) and the resin (B) may be a band of a Raman spectrum unique to the resin (A) and the resin (B). It is important to use a band whose overlap with other bands is small and whose intensity changes greatly by changing the polarization direction of light incident on the sample. For example, a C = O stretch band of 1765 cm ⁻¹ for the polylactic acid resin of the resin (A), a C═C stretch band of 1612 cm ⁻¹ when using a polybutylene adipate terephthalate resin as the resin (B), When a polyhydroxybutyrate / valerate resin is used as the resin (B), a 1725 cm ⁻¹ C═O stretch band can be used.

When the vibration direction of the selected band is orthogonal to the molecular chain, when calculating the orientation parameter, a laser beam with a polarization direction perpendicular to the length direction is used for a sample whose cross section is parallel to the length direction of the film. Divide the value of the Raman band intensity measured by irradiating with the value of the Raman band intensity measured by irradiating the laser beam in the polarization direction parallel to the length direction, or the section is parallel to the width direction of the film. For a large sample, the value of the Raman band intensity measured by irradiating the laser beam with the polarization direction perpendicular to the width direction is divided by the value of the Raman band intensity measured by irradiating the laser beam with the polarization direction parallel to the width direction. To determine the orientation parameter.

On the contrary, when the vibration direction of the selected band is parallel to the molecular chain, when calculating the orientation parameter, the sample whose cross section is parallel to the length direction of the film has a polarization direction parallel to the length direction. Divide the value of the Raman band intensity measured by irradiating the laser beam with the value of the Raman band intensity measured by irradiating the laser beam in the polarization direction perpendicular to the length direction, or the cross section is in the width direction of the film. The value of the Raman band intensity measured by irradiating the laser beam with the polarization direction parallel to the width direction, and the value of the Raman band intensity measured by irradiating the laser beam with the polarization direction perpendicular to the width direction. The orientation parameter is obtained by dividing by.

[Resin (A)]
(A1)
Poly L-lactic acid, “4032D” manufactured by Natureworks, mass average molecular weight 200,000, D-form content 1.4%, melting point 166 ° C.
(A2)
Poly L-lactic acid, “4060D” manufactured by Natureworks, mass average molecular weight 200,000, D-form content 12.0%, no melting point.

  The mass average molecular weight was measured using Waters 2690 manufactured by Nippon Waters Co., Ltd., using polymethyl methacrylate as a standard, a column temperature of 40 ° C., and a chloroform solvent.

[Resin (B)]
(B1)
Polybutylene adipate terephthalate, “Ecoflex C1200” manufactured by BASF.
(B2)

[Plasticizer (C)]
(C1)
62 parts by mass of polyethylene glycol having a number average molecular weight of 8,000, 38 parts by mass of L-lactide and 0.05 parts by mass of tin octylate are mixed and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 3 hours in a nitrogen atmosphere. Thus, a plasticizer PLA-PEG having a polylactic acid segment having a number average molecular weight of 2,500 at both ends of polyethylene glycol having a number average molecular weight of 8,000 was obtained.
(C2)
Polyethylene glycol, “PEG-6000S” manufactured by Sanyo Chemical Industries.

[Organic lubricant]
(S-10)
"Alflow S-10" made of stearamide, NOF.

[particle]
(CaCO ₃ )
“Cartex R” made of calcium carbonate, Maruo calcium, average particle size 2.8 μm.

[Production of polylactic acid film]
Example 1
13 parts by mass of polylactic acid resin (A1), 34 parts by mass of polylactic acid resin (A2), 19 parts by mass of plasticizer (C1), 1 part by mass of organic lubricant (S-10), ₃ parts by mass of particles (CaCO ₃ ) The mixture was subjected to a twin-screw extruder with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm and equipped with a vacuum vent, melt-kneaded while degassing the vacuum vent, homogenized, and pelletized to obtain Composition 1.

The pellets of the composition 1 were vacuum-dried at a temperature of 60 ° C. for 12 hours using a rotary drum type vacuum dryer. 70 parts by weight of the dried composition 1 and an aliphatic polyester resin excluding a polylactic acid resin And / or aliphatic aromatic polyester-based resin (B1) at a ratio of 30 parts by mass to finally obtain the composition shown in Table 1, and uniaxial extrusion with a screw diameter of 65 mm at an extruder cylinder temperature of 190 ° C. Supplied to the machine, extruded upward in a bubble shape with a blow ratio of 3.4 from a spiral annular die with a diameter of 250 mm, a lip gap of 0.5 mm, and a temperature of 165 ° C., air cooled with a cooling ring, and folded with a nip roll above the die While taking up at 22 m / min, both ends are cut with an edge cutter and cut into two pieces, and each film is wound with a winder at a tension of 5.5 kgf. The wound. A film having a final thickness of 18 μm was obtained by adjusting the discharge amount. Table 1 shows the physical properties of the obtained film.

  In Examples 2 to 6 and Comparative Examples 1 to 6, films were obtained in the same manner as in Example 1 except that the film composition and film forming conditions were changed as shown in Table 1. Table 1 shows the physical properties of the obtained film.

  Note that “MD” in the table refers to the length direction, and “TD” refers to the width direction.

  The polylactic acid film of the present invention is a film containing a polylactic acid resin, an aliphatic polyester resin other than the polylactic acid resin, and / or an aliphatic aromatic polyester resin. The polylactic acid-based film of the present invention is required to have high flexibility and tear propagation resistance, and is used in agricultural and forestry applications such as agricultural multi-films and pine worm fumigation sheets, garbage bags, compost bags, vegetables and fruits It can be preferably used for various packaging applications such as bags for food products, bags for various industrial products and the like.

Claims (5)

A polylactic acid film comprising a composition containing a resin (A) and a resin (B),
The resin (A) is a polylactic acid resin, the resin (B) is an aliphatic polyester resin and / or an aliphatic aromatic polyester resin other than the polylactic acid resin,
The thickness is 40 μm or less,
The polylactic acid-type film characterized by satisfy | filling both the following formula | equation 1 and Formula 2.
0.8 ≦ Oa ≦ 1.6 Formula 1
0.8 ≦ Ob ≦ 2 Equation 2
Here, Oa means the orientation parameter of the resin (A) in the film obtained by Raman spectroscopy, and Ob means the orientation parameter of the resin (B) in the film obtained by Raman spectroscopy.   The polylactic acid film according to claim 1, comprising a composition containing a plasticizer (C).   The polylactic acid film according to claim 2, wherein the plasticizer (C) is a block copolymer having a polyether segment and a polylactic acid segment.   The polylactic acid according to any one of claims 1 to 3, wherein the resin (B) is at least one resin selected from the group consisting of polybutylene adipate terephthalate, polybutylene succinate and polybutylene succinate adipate. Film. A method for producing a polylactic acid-based film, which has a step 1 for taking a resin discharged from an annular die and making the resin into a cylindrical shape, a step 2 for cooling the tubular resin, and a step 3 for winding the cooled resin in this order. In
The method for producing a polylactic acid-based film according to any one of claims 1 to 4, wherein a lip gap of the annular cap in the step 1 is 1 mm or less.