Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L101/00—Compositions of unspecified macromolecular compounds
  • C08L101/16—Compositions of unspecified macromolecular compounds the macromolecular compounds being biodegradable
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones

Definitions

• the present invention relates to a stretched film containing a poly(3-hydroxyalkanoate) resin.
• Poly(3-hydroxyalkanoate) resins such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), are attracting attention as plastic materials with compost and marine degradability.
• a method of stretching a film is known as a technique for producing a thin, high-strength film.
• a method of stretching a film is known as a technique for producing a thin, high-strength film.
• a stretched film from a general-purpose resin such as polypropylene
• the molten resin is cooled and solidified using a cast roll to form a raw roll, which is then preheated to a temperature at which it can be stretched and then stretched, allowing the stretched film to be produced continuously and with good productivity.
• poly(3-hydroxyalkanoate) resins are known to be difficult to stretch. For this reason, various technologies are being investigated for efficiently producing stretched films containing poly(3-hydroxyalkanoate) resins.
• Patent Document 1 describes a method for efficiently producing biaxially stretched films by melting a film raw material containing a poly(3-hydroxybutyrate) resin in an extruder, forming it into a film, and then continuously stretching the film in both the MD and TD directions to a stretch ratio of 1.1 times or more.
• Patent Document 2 describes a method of producing a stretched film by melting a film raw material containing a poly(3-hydroxybutyrate-based) resin, extruding it onto a casting roll, peeling the film from the casting roll under conditions where the film temperature is 0 to 50°C, and then stretching the film in the MD direction under conditions where the film temperature is 10 to 65°C.
• This method controls the crystallinity of the poly(3-hydroxybutyrate-based) resin to a relatively low level by controlling the film temperature to a relatively low temperature, thereby achieving stretching at a high ratio.
• Patent Document 1 makes it possible to produce biaxially stretched films containing poly(3-hydroxybutyrate)-based resin, but the stretching ratio achieved in the examples was limited to approximately 1.5 to 1.6 times.
• Patent Documents 1 and 2 describe stretching a film containing a poly(3-hydroxyalkanoate) resin by controlling the manufacturing conditions of the stretched film, but there has been no sufficient study into improving stretchability by varying the composition of the film raw material containing the poly(3-hydroxyalkanoate) resin.
• the present invention aims to provide a stretched film containing poly(3-hydroxyalkanoate)-based resin with improved stretchability.
• the present invention relates to a stretched film comprising a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), in which the poly(3-hydroxyalkanoate) resin (A) comprises a copolymer (A-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 10 mol % or more and less than 24 mol % and has a weight-average molecular weight of 700,000 or more, and the content of the copolymer (A-1) is more than 20 wt % and 75 wt % or less of the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).
• the present invention also relates to a laminate comprising the above-mentioned stretched film and a layer containing a poly(3-hydroxyalkanoate) resin (C) laminated on at least one surface of the stretched film.
• the stretchability can be improved by adjusting the composition of the film raw material, and therefore, it is not necessary to adopt the specific temperature conditions as described in Patent Document 2, and the film can be stretched under temperature conditions that are easier to control and stabilize than the above temperature conditions. Therefore, it is possible to continuously and stably produce a poly(3-hydroxyalkanoate)-based resin-containing stretched film. As a result, the quality of the stretched film can be stabilized, and in particular, a long stretched film can be stably produced. In addition, a high stretch ratio can be achieved. According to a preferred embodiment of the present invention, a uniaxially stretched film stretched in the MD direction, or a biaxially stretched film stretched in both the MD and TD directions can be produced, and a high stretch ratio can be achieved in each direction.
• the present embodiment relates to a stretched film containing a poly(3-hydroxyalkanoate)-based resin (A) and a polylactic acid-based resin (B).
• A poly(3-hydroxyalkanoate)-based resin
• B polylactic acid-based resin
• the "stretched film” may be simply referred to as "film”.
• the poly(3-hydroxyalkanoate) resin (A) may be a single poly(3-hydroxyalkanoate) resin or a mixture of two or more poly(3-hydroxyalkanoate) resins. However, in order to easily achieve both strength and stretchability of the film, a mixture of at least two poly(3-hydroxyalkanoate) resins having different types of constituent monomers and/or different content ratios of the constituent monomers is preferred.
• the poly(3-hydroxyalkanoate) resin (A) is preferably a polymer having a 3-hydroxyalkanoate unit, specifically a polymer containing a unit represented by the following general formula (1). [-CHR-CH 2 -CO-O-] (1)
• R represents an alkyl group represented by C p H 2p+1 , and p represents an integer of 1 to 15.
• R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl.
• p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 8.
• poly(3-hydroxyalkanoate) resin (A) a poly(3-hydroxyalkanoate) resin produced from a microorganism is particularly preferred.
• a poly(3-hydroxyalkanoate) resin produced from a microorganism all of the 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.
• Poly(3-hydroxyalkanoate) resin (A) preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol% or more of all constituent units, more preferably 60 mol% or more, and even more preferably 70 mol% or more.
• Poly(3-hydroxyalkanoate) resin (A) may contain only one or more types of 3-hydroxyalkanoate units as the constituent units of the polymer, or may contain other units (e.g., 4-hydroxyalkanoate units, etc.) in addition to one or more types of 3-hydroxyalkanoate units.
• the poly(3-hydroxyalkanoate) resin (A) is preferably a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units (hereinafter, both polymers are collectively referred to as "poly(3-hydroxybutyrate) resin").
• 3HB 3-hydroxybutyrate
• both polymers are collectively referred to as "poly(3-hydroxybutyrate) resin”
• all of the 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units.
• the poly(3-hydroxyalkanoate) resin (A) preferably contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.
• poly(3-hydroxybutyrate) resins include poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH).
• P3HB4HB poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred.
• composition ratio of the repeating units By changing the composition ratio of the repeating units, it is possible to change the melting point, degree of crystallinity, and physical properties such as Young's modulus and heat resistance, and it is possible to impart physical properties between polypropylene and polyethylene.
• poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred from the viewpoint that it is easy to produce industrially and is a physically useful plastic.
• poly(3-hydroxybutyrate)-based resins that have the property of being easily thermally decomposed when heated to 180°C or higher
• poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred from the viewpoint that it can lower the melting point and enable molding processing at low temperatures.
• poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) products include Kaneka Biodegradable Polymer Green Planet (registered trademark) from Kaneka Corporation.
• the average content ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A) can be determined by a method known to those skilled in the art, for example, the method described in paragraph [0047] of WO 2013/147139.
• the average content ratio means the molar ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A), and when the poly(3-hydroxyalkanoate) resin (A) is a mixture of two or more poly(3-hydroxyalkanoate) resins, it means the molar ratio of each monomer unit contained in the entire mixture.
• the poly(3-hydroxyalkanoate) resin (A) may be a mixture of at least two poly(3-hydroxyalkanoate) resins differing in the type of constituent monomer and/or the content ratio of the constituent monomer.
• at least one highly crystalline poly(3-hydroxyalkanoate) resin and at least one lowly crystalline poly(3-hydroxyalkanoate) resin can be used in combination.
• the content of 3-hydroxybutyrate units in the highly crystalline poly(3-hydroxyalkanoate) resin is preferably higher than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A).
• the content of 3-hydroxybutyrate units in the low-crystalline poly(3-hydroxyalkanoate) resin is preferably lower than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A).
• the poly(3-hydroxyalkanoate)-based resin (A) contains a copolymer (A-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol% and the weight average molecular weight is 700,000 or more.
• the copolymer (A-1) having a medium degree of crystallinity and a high molecular weight in combination with the polylactic acid-based resin (B), the stretchability of the poly(3-hydroxyalkanoate)-based resin-containing film can be improved.
• the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol%, but is preferably 10 to 20 mol%, more preferably 10 to 17 mol%, and even more preferably 10 to 14 mol%.
• copolymer (A-1) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) being particularly preferred.
• the weight average molecular weight of the copolymer (A-1) is 700,000 or more, preferably 750,000 or more. There is no particular upper limit, but from the viewpoint of productivity, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less.
• the weight average molecular weight of the poly(3-hydroxyalkanoate) resin or copolymer can be measured in terms of polystyrene using gel permeation chromatography (Shimadzu Corporation HPLC GPC system) using a chloroform solution.
• a column suitable for measuring the weight average molecular weight should be used as the column for the gel permeation chromatography. The same applies to the following description.
• the content of copolymer (A-1) is more than 20% by weight and not more than 75% by weight of the total weight of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B) from the viewpoint of the balance between the stretchability of the film and productivity and strength.
• the lower limit is preferably 25% by weight or more, and more preferably 30% by weight or more.
• the upper limit is preferably 60% by weight or less, more preferably 50% by weight or less, and even more preferably 45% by weight or less.
• the poly(3-hydroxyalkanoate) resin (A) preferably further contains, in addition to the copolymer (A-1), a copolymer (A-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 1 mol % or more and less than 10 mol %.
• the content of other hydroxyalkanoate units is preferably 3 to 9 mol%, more preferably 4 to 8 mol%, and even more preferably 5 to 7 mol%.
• copolymer (A-2) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) being particularly preferred.
• the weight average molecular weight of copolymer (A-2) is not particularly limited, but is preferably smaller than the weight average molecular weight of copolymer (A-1). Specifically, it is preferably less than 700,000, and more preferably 650,000 or less. There is no particular lower limit, but it is preferably 200,000 or more, more preferably 300,000 or more, even more preferably 400,000 or more, and particularly preferably 500,000 or more.
• the weight ratio (A-1/A-2) of the copolymer (A-1) to the copolymer (A-2) is preferably 10/90 to 80/20, more preferably 20/80 to 70/30, even more preferably 30/70 to 60/40, even more preferably 30/70 to 50/50, and particularly preferably 35/65 to 45/55, from the viewpoints of the stretchability, productivity, and physical properties of the film.
• the method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis.
• a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, etc., or a blend may be obtained by dissolving two or more resins in a solvent, mixing, and drying.
• the weight average molecular weight of the entire poly(3-hydroxyalkanoate) resin (A) is not particularly limited, but from the viewpoint of achieving both strength and extensibility of the film, it is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 400,000 to 1,000,000.
• the method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a production method by chemical synthesis or a production method using microorganisms. Among these, production methods using microorganisms are preferred. Known methods can be applied to the production method using microorganisms.
• known bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB.
• genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used according to the poly(3-hydroxyalkanoate) resin to be produced, and the culture conditions, including the type of substrate, may be optimized.
• an unmodified poly(3-hydroxyalkanoate) resin can be used as the poly(3-hydroxyalkanoate) resin (A).
• a resin obtained by modifying an unmodified poly(3-hydroxyalkanoate) resin with a raw material that reacts with the resin such as a peroxide (hereinafter referred to as a "modifying raw material"), may also be used.
• the modified resin obtained by reacting the resin with the modifying raw material in advance may be molded into a film, or the modified raw material may be mixed with the resin and reacted during film molding.
• the entire resin may be reacted with the modifying raw material, or a portion of the resin may be reacted with the modifying raw material to obtain a modified resin, and the remaining unmodified resin may then be added to the modified resin.
• the raw material for modification is not particularly limited as long as it is a compound that can react with poly(3-hydroxyalkanoate) resins, but organic peroxides are preferably used because of their ease of handling and the ease of controlling the reaction with poly(3-hydroxyalkanoate) resins. Any known compound may be used as the organic compound.
• the content of poly(3-hydroxyalkanoate)-based resin (A) is preferably 50% by weight or more and 90% by weight or less of the total weight of poly(3-hydroxyalkanoate)-based resin (A) and polylactic acid-based resin (B) from the viewpoint of achieving both stretchability and biodegradability (particularly biodegradability in compost and marine degradability) of the film.
• the lower limit is more preferably 60% by weight or more, even more preferably 70% by weight or more, even more preferably 75% by weight or more, and particularly preferably 80% by weight or more.
• the upper limit is more preferably 85% by weight or less, and even more preferably 80% by weight or less.
• the polylactic acid resin (B) is a polyester containing lactic acid as a constituent monomer. Since polylactic acid resins usually have a glass transition temperature of around 60° C. and are difficult to crystallize when quenched from a molten state, becoming amorphous, the incorporation of the polylactic acid resin (B) makes it easier to soften the film. Therefore, by using the polylactic acid resin (B) in combination with the copolymer (A-1), the stretchability of the poly(3-hydroxyalkanoate) resin-containing film can be improved. This makes it possible to obtain a high-quality stretched film without breakage during stretching and without uneven stretching. In addition, the film can be continuously and stably stretched even under temperature conditions other than the specific temperature described in Patent Document 2. Furthermore, a high stretching ratio can also be achieved.
• the polylactic acid resin (B) is preferably a homopolymer of lactic acid, but may contain trace amounts of other monomers in addition to lactic acid.
• the lactic acid constituting the polylactic acid resin (B) may be either the L-form or the D-form, or may contain both. In the latter case, the ratio of the L-form to the D-form is not particularly limited.
• the polylactic acid resin (B) may be any one of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin, or may be a blend of these.
• Examples of the other monomers that may be contained in the polylactic acid-based resin (B) include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, and polyfunctional polysaccharides.
• the content of the other monomer is preferably about 0 to 3 mol %, and more preferably 0 to 2 mol %, based on the total monomers contained in the polylactic acid resin (B).
• the polylactic acid resin (B) may be either a crystalline polylactic acid resin or an amorphous polylactic acid resin, but it is preferable to use a crystalline polylactic acid resin from the viewpoint of heat resistance, such as shrinkage during heating in subsequent processes such as printing and deposition.
• a crystalline polylactic acid resin from the viewpoint of heat resistance, such as shrinkage during heating in subsequent processes such as printing and deposition.
• the crystalline polylactic acid resins polylactic acid resins having a melting point peak with a peak temperature of less than 170°C in differential scanning calorimetry are particularly preferable.
• the peak temperature of the melting point peak of the polylactic acid resin (B) (hereinafter also referred to as “melting point peak temperature”) is preferably 165°C or less, more preferably 160°C or less, from the viewpoint of increasing the extensibility and strength of the film.
• the lower limit of the peak temperature is preferably 120°C or more, more preferably 130°C or more, and even more preferably 140°C or more, from the viewpoint of increasing the extensibility of the film.
• the melting point peak temperature refers to the peak top temperature Tm of the crystal melting peak in a DSC curve obtained by differential scanning calorimetry (DSC measurement).
• the DSC curve was obtained by precisely weighing out about 5 mg of the resin to be measured and heating it from 0°C to 200°C at a heating rate of 10°C/min using a differential scanning calorimeter.
• polylactic acid resin (B) that exhibits the above-mentioned melting point peak temperature
• commercially available products can be used, but a specific example is a polylactic acid resin with an L-isomer purity of lactic acid units of 88% or more and 98% or less.
• the melting peak temperature of the polylactic acid resin (B) is close to the melting peak temperature of the poly(3-hydroxyalkanoate) resin (A).
• the absolute value of the difference between the melting peak temperature of the polylactic acid resin (B) and the melting peak temperature of the poly(3-hydroxyalkanoate) resin (A) is preferably 40°C or less, more preferably 30°C or less, and even more preferably 20°C or less.
• the melting peak temperature of poly(3-hydroxyalkanoate) resin (A) is measured in the same manner as the melting peak temperature of polylactic acid resin (B). If multiple melting peaks appear in the DSC curve measured for poly(3-hydroxyalkanoate) resin (A), the peak temperature of the melting peak on the high temperature side is taken as the melting peak temperature of poly(3-hydroxyalkanoate) resin (A).
• the molecular weight of the polylactic acid resin (B) is not particularly limited and may be set as appropriate, but the number average molecular weight is preferably 1,000 to 700,000, and more preferably 10,000 to 300,000.
• the lactic acid raw material for producing the polylactic acid resin (B) is not particularly limited, and may be L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, meso-lactide, or a mixture thereof, etc. Lactic acid obtained by microbial fermentation from renewable raw materials derived from plants such as starch can be suitably used.
• the method for producing the polylactic acid resin (B) is not particularly limited, and any known method such as a dehydration condensation polymerization method or a ring-opening polymerization method can be used.
• the content of the polylactic acid resin (B) is preferably 10% by weight or more and 50% by weight or less of the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) from the viewpoint of achieving both stretchability and biodegradability (particularly biodegradability in compost and marine degradability) of the film.
• the lower limit is more preferably 15% by weight or more, and even more preferably 20% by weight or more.
• the upper limit is more preferably 40% by weight or less, even more preferably 30% by weight or less, even more preferably 25% by weight or less, and particularly preferably 20% by weight or less.
• the stretched film according to this embodiment is a resin film mainly composed of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B).
• the total proportion of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B) in the total amount of the stretched film may be 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may be 95% by weight or more, or 98% by weight or more.
• the stretched film according to the present embodiment may contain other resins in addition to the poly(3-hydroxyalkanoate)-based resin (A) and the polylactic acid-based resin (B) within a range that does not impair the effects of the invention.
• other resins include aliphatic polyester-based resins such as polybutylene succinate adipate, polybutylene succinate, and polycaprolactone, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.
• the content of the other resin is not particularly limited, but is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). It may be 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less. There is no particular lower limit for the content of the other resin, and it may be 0 parts by weight or more.
• the stretched film according to the present embodiment may contain additives that can be used together with the poly(3-hydroxyalkanoate)-based resin (A) and the polylactic acid-based resin (B) within a range that does not impair the effects of the invention.
• additives include colorants such as pigments and dyes, odor absorbents such as activated carbon and zeolite, fragrances such as vanillin and dextrin, fillers, plasticizers, antioxidants, weather resistance improvers, ultraviolet absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding property improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately set by a person skilled in the art depending on the purpose of use. The crystal nucleating agent, lubricant, filler, and plasticizer will be described in more detail below.
• the stretched film according to the present embodiment may contain a crystal nucleating agent.
• the crystal nucleating agent include polyhydric alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride.
• pentaerythritol is preferred because of its particularly excellent effect of promoting the crystallization of the poly(3-hydroxyalkanoate) resin (A).
• the crystal nucleating agent may be used alone or in combination with two or more other agents, and the ratio of use may be appropriately adjusted depending on the purpose.
• a crystal nucleating agent When a crystal nucleating agent is used, its amount is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) combined.
• the stretched film according to this embodiment can achieve good productivity even without substantially blending in a crystal nucleating agent such as pentaerythritol.
• substantially not blending in a crystal nucleating agent means that the blended amount of the crystal nucleating agent is less than 0.1 parts by weight per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). It may be less than 0.01 parts by weight.
• pentaerythritol is not substantially blended in, the problem of contamination of the cast roll surface due to bleed-out of pentaerythritol can be avoided.
• the stretched film according to the present embodiment may contain a lubricant.
• the lubricant include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauramide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid.
• behenamide or erucamide is preferred because of its particularly excellent lubricant effect on the poly(3-hydroxyalkanoate) resin (A).
• One type of lubricant may be used, or two or more types may be used, and the ratio of use may be appropriately adjusted depending on the purpose.
• the amount used is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).
• the stretched film according to this embodiment preferably contains a lubricant, but does not have to contain one.
• the stretched film according to the present embodiment may contain a filler.
• a filler By including a filler, a stretched film with higher strength can be obtained.
• the filler may be either an inorganic filler or an organic filler, or both may be used in combination.
• the inorganic filler is not particularly limited, and examples thereof include silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Only one type of inorganic filler may be used, or two or more types may be used in combination.
• the filler When the filler is used, its content is not particularly limited, but is preferably 1 to 100 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) combined, more preferably 3 to 80 parts by weight, even more preferably 5 to 70 parts by weight, and even more preferably 10 to 60 parts by weight.
• the stretched film according to this embodiment may be substantially free of filler.
• Substantially no filler is blended means that the amount of filler blended is less than 1 part by weight per 100 parts by weight of the resin (A) and the resin (B) combined. It may be less than 0.1 part by weight.
• the stretched film according to the present embodiment may contain a plasticizer.
• the plasticizer include glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, adipate ester compounds, polyether ester compounds, benzoic acid ester compounds, phthalic acid ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds.
• glycerin ester compounds, citrate ester compounds, sebacic acid ester compounds, and dibasic acid ester compounds are preferred because of their particularly excellent plasticizing effect on the poly(3-hydroxyalkanoate) resin (A).
• the glycerin ester compounds include glycerin diacetomonolaurate.
• citrate compounds include acetyl tributyl citrate.
• sebacic acid ester compounds include dibutyl sebacate.
• dibasic acid ester compounds include benzyl methyl diethylene glycol adipate.
• the plasticizer may be used alone or in combination of two or more kinds, and the ratio of use can be appropriately adjusted depending on the purpose.
• the amount used is not particularly limited, but is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) combined.
• the stretched film according to this embodiment may be substantially free of plasticizer.
• Substantially no plasticizer is blended means that the amount of plasticizer blended is less than 1 part by weight per 100 parts by weight of the resin (A) and the resin (B) combined. It may be less than 0.1 part by weight.
• the stretched film according to the present embodiment is a stretched film that has been subjected to a stretching treatment in the MD direction and/or the TD direction after film formation.
• the thickness of the stretched film according to this embodiment is preferably 10 to 200 ⁇ m, more preferably 15 to 150 ⁇ m, and even more preferably 20 to 100 ⁇ m, from the viewpoints of the uniform thickness, appearance, strength, light weight, etc. of the film.
• the stretched film according to this embodiment is preferably a long stretched film that is industrially produced, and is particularly preferably a strip-shaped stretched film wound into a roll.
• the length of such a stretched film is not particularly limited, but may be, for example, 50 m or more, or 100 m or more.
• such a long stretched film can be continuously and stably produced.
• the stretched film according to the embodiment can exhibit an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more at least in the MD direction. It may also be a biaxially stretched film exhibiting an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more in both the MD and TD directions.
• the elastic modulus is preferably 2000 MPa or more, more preferably 2500 MPa or more.
• the breaking strength is preferably 60 MPa or more, more preferably 70 MPa or more.
• the elastic modulus and the breaking strength are values measured by the method described in detail in the Examples section.
• the melting method is not particularly limited, but it is preferable to extrude the molten film raw material from a T-die, i.e., to carry out an extrusion molding method.
• an extrusion molding method By using the extrusion molding method, a film with a uniform thickness can be easily produced.
• extrusion molding a single screw extruder, twin screw extruder, etc. can be used as appropriate.
• the conditions for melting the film raw material may be any conditions under which the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) melt, and the temperature of the molten film raw material may be, for example, about 140 to 210°C.
• the molten film material is then extruded onto a casting roll to form a film.
• the molten film material comes into contact with the casting roll and moves along the surface of the casting roll, causing it to cool and solidify.
• This step may be a step of extruding a molten material onto one or more casting rolls, or a step of opposing a touch roll to a casting roll and sandwiching the molten material extruded onto the casting roll between the touch rolls.
• an air knife or an air chamber may be used.
• the casting roll may be placed in a water tank or an air chamber may be used.
• the lower limit of the set temperature of the casting roll is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, in order to suppress the adhesion of the poly(3-hydroxyalkanoate) resin (A) and improve its releasability from the casting roll.
• the temperature is preferably higher than the glass transition temperature (Tg) of the poly(3-hydroxyalkanoate) resin (A) + 10°C.
• the upper limit of the temperature setting of the cast roll is not particularly limited, but from the viewpoint of promoting the solidification of the poly(3-hydroxyalkanoate) resin (A), it is preferably 80°C or less, and more preferably 60°C or less.
• the film cooled on the casting roll is transported while the casting roll is rotating, and the film is peeled off from the casting roll. This produces an unstretched film.
• the MD direction is also called the machine direction, flow direction, or longitudinal direction.
• the TD direction which will be described later, is the direction perpendicular to the MD direction, and is also called the perpendicular direction or width direction.
• the stretching process in the MD direction can be carried out continuously from the peeling off of the cast roll within one production line.
• This process is not particularly limited, but can be carried out, for example, by using a roll longitudinal stretching machine to create a difference in the rotation speed between multiple rolls that transport the film.
• the stretching process in the MD direction is preferably carried out while heating the film.
• the heating method includes a method in which an air current adjusted to a predetermined temperature is applied to the film, a method in which the film temperature is controlled by setting a roll to a predetermined temperature, a method in which the film is heated using auxiliary heating means such as an IR heater to control the film temperature to a predetermined temperature, and a method in which the film is passed through an oven whose temperature is adjusted to a predetermined temperature. These methods may be used alone or in combination.
• Patent Document 2 a relatively low film temperature of 20°C or 30°C is used in the examples in order to achieve film stretching by suppressing crystallization of the resin during the MD stretching process.
• the stretchability of the film is improved by the composition of the film raw materials, so there is no need to control the film temperature as described above, and stretching in the MD can be achieved even at temperatures higher than the above temperatures.
• the temperature during stretching in the MD direction is preferably 35°C or higher, more preferably 45°C or higher, and even more preferably 55°C or higher.
• Polylactic acid-based resins usually have a glass transition temperature of around 60°C, and are difficult to crystallize when rapidly cooled from a molten state, becoming amorphous. Therefore, even if the temperature is below the melting point of the poly(3-hydroxyalkanoate)-based resin, the stretched film according to this embodiment is likely to soften in the above temperature range, allowing for good stretching.
• the above temperature is easy to control and stabilize. Therefore, the film can be stretched continuously and stably, making it possible to stably produce long stretched films.
• the upper limit of the temperature during stretching in the MD direction is not particularly limited, but from the viewpoint of avoiding breakage of the film during stretching, it is preferably 110°C or less, more preferably 100°C or less, and even more preferably 90°C or less.
• the stretching ratio in the MD direction is not particularly limited, but is preferably 2 times or more. More preferably, it is 2.5 times or more, and even more preferably, it is 3 times or more.
• the composition of the film raw material according to this embodiment makes it possible to achieve such a high stretching ratio. There is no particular upper limit to the stretching ratio, and it may be determined appropriately, but it may be, for example, 8 times or less.
• a biaxially stretched film with high strength in both the MD and TD directions can be obtained.
• the stretching process in the TD direction can be carried out continuously from the stretching process in the MD direction in one production line. This process is not particularly limited, but can be carried out, for example, by clamping both widthwise ends of the film using a transverse stretching machine such as a clip-type tenter and pulling it in the TD direction.
• the stretching process in the TD direction is also preferably carried out while heating the film.
• heating method There are no particular limitations on the heating method, and examples include those described above for the stretching process in the MD direction.
• the temperature conditions in the TD stretching process do not need to be controlled to the specific temperature disclosed in Patent Document 2.
• the temperature during TD stretching may be the same as the temperature during MD stretching described above, and is preferably 35 to 110°C, more preferably 45 to 100°C, and more preferably 55 to 90°C.
• the stretching ratio in the TD direction is not particularly limited, but is preferably 2 times or more. More preferably, it is 3 times or more, and even more preferably, it is 4 times or more. Such a high stretching ratio can be achieved according to the composition of the film raw material according to this embodiment. There is no particular upper limit to the stretching ratio, and it may be determined appropriately, but it may be, for example, 8 times or less.
• the stretched film is heated to a temperature at which high-melting point crystals grow. This increases the crystallinity of the stretched film, increases its strength, and stabilizes the physical properties of the stretched film.
• the heating temperature during heat setting is preferably 80 to 150°C, more preferably 90 to 135°C, and most preferably 100 to 130°C. If the heating temperature is 80°C or higher, the crystallization degree of the stretched film increases, and the crystals formed may have a high melting point. If the heating temperature is 150°C or lower, breakage due to melting of the film can be avoided.
• This heating can be carried out, for example, by stretching in the TD direction using a transverse stretching machine such as a clip-type tenter, and then heating while maintaining the stretched state. At this time, since heat shrinkage occurs in the opposite direction to the stretching direction, it is preferable to relax it so as not to break it. Relaxation is an operation in which tension is released in the opposite direction to the stretching direction, and it is preferable to appropriately adjust the amount of relaxation between 5 and 30%.
• a step of cooling the film may be carried out as appropriate. After this, it is preferable to carry out a step of winding the stretched film on a winding roll.
• the method for producing a stretched film according to this embodiment is preferably carried out while continuously transporting the film from melt extrusion to the final step. This makes it possible to produce a stretched film with good productivity through an industrially simple process.
• the production method according to this embodiment can be carried out while continuously winding up the produced stretched film on a winding roll.
• the transport speed is not particularly limited, but from the viewpoint of productivity of the stretched film, it is preferable that the transport speed be 5 m/min or more before the start of stretching. Also, from the viewpoint of production stability, it is preferable that the transport speed be 50 m/min or less before the start of stretching.
• the stretched film according to the present embodiment may be a resin film composed of an independent single layer, but may also be a laminate in which another layer is laminated on one or both sides of the stretched film. Such a laminate also constitutes one aspect of the present invention.
• the other layer include a resin layer, an inorganic layer, a metal layer, a metal oxide layer, a printed layer, etc. These other layers may be laminate layers, coating layers, or vapor deposition layers.
• the resin layer which is one of the other layers in the laminate, is not particularly limited, but from the viewpoint of enhancing the biodegradability of the entire laminate, it is preferably a layer containing a poly(3-hydroxyalkanoate)-based resin (C).
• a poly(3-hydroxyalkanoate)-based resin (C) those mentioned above for the poly(3-hydroxyalkanoate)-based resin (A) can be used as appropriate, but are not particularly limited.
• the components other than the poly(3-hydroxyalkanoate)-based resin (C) and components known as additives to the resin layer can be used as appropriate.
• This resin layer may function as a heat seal layer.
• the stretched film according to this embodiment can be suitably used as a packaging film, a heat-sealable film, a twist film, and the like.
• [Item 1] Contains a poly(3-hydroxyalkanoate)-based resin (A) and a polylactic acid-based resin (B),
• the poly(3-hydroxyalkanoate) resin (A) contains a copolymer (A-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of the other hydroxyalkanoate units being 10 mol % or more and less than 24 mol % and having a weight average molecular weight of 700,000 or more;
• a stretched film, comprising a copolymer (A-1) content of more than 20% by weight and not more than 75% by weight of the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).
• [Item 7] 7 A laminate comprising the stretched film according to any one of items 1 to 6, and a layer containing a poly(3-hydroxyalkanoate)-based resin (C) laminated on at least one surface of the stretched film.
• Polylactic acid resin (B) B-1 PLA (LX175 grade, manufactured by Total Corbion PLA)
• Crystal nucleating agent C-1 Pentaerythritol (manufactured by Mitsubishi Chemical Corporation, NeuRizer P)
• T-die film formability (Roll Contamination) Each resin composition was melted at 165°C in a single-screw extruder with a screw diameter of 20 mm, and drawn from a die with a lip width of 250 ⁇ m at a casting roll (CR) temperature of 40 to 60°C at the molding speed shown in Table 1 to obtain a T-die film. At that time, the roll contamination was evaluated according to the following evaluation criteria.
• a film was produced from each resin composition using a T-die and continuously stretched 3 times in the MD direction (the flow direction of the T-die film production) using a roll stretching machine at a temperature range of 60°C to 70°C, and the stretchable region (stretch ratio) was evaluated according to the following evaluation criteria.
• the film stretched in the MD direction was fixed at both ends in the MD direction and stretched 5 times in the TD direction (perpendicular to the MD direction) at a temperature range of 70°C to 80°C, and the stretchable region (stretching ratio) was evaluated according to the following evaluation criteria.
• ⁇ Evaluation criteria> The film was not broken during stretching, and a stretched film was obtained, and no stretching unevenness (uneven stretching portions such as uneven film thickness) was visually observed in the obtained stretched film.
• x The film broke during stretching, or stretching unevenness (uneven stretching portions such as uneven film thickness) was visually observed in the obtained stretched film.
• ⁇ Film tear strength> The stretched film was stored for one week in an atmosphere of 23° C. and 50% humidity, and then the tear strength was measured using the Elmendorf tear method based on JIS K-1281. The measurement was carried out five times, and the average value was recorded as the tear strength in Table 1.
• Example 1 (Method for producing resin composition) 50 parts by weight of poly(3-hydroxyalkanoate) resin PHBH-1, 50 parts by weight of PHBH-2, and 0.5 parts by weight of D-1 as a lubricant were dry-blended. The resulting resin material was charged into a hopper of a ⁇ 26 mm co-rotating twin-screw extruder with cylinder and die temperatures set to 150° C., melt-kneaded, and extruded from the die in the form of strands, which were solidified by passing through a water tank filled with hot water at 45° C., and cut with a pelletizer to obtain resin pellets P-1.
• the resin pellets P-1 and B-1 were put into a single-screw extruder so that the weight ratio was 80:20, and extruded into a film shape with a T-die.
• the formed film was cooled with a cooling roll set at 50 ° C., then taken up with a take-up roll, and continuously stretched 3 times in the MD direction at 60 to 70 ° C. with a roll longitudinal stretching machine, and then continuously stretched in the TD direction at a stretching temperature of 70 to 80 ° C. with a clip-type tenter transverse stretching machine so that the stretch ratio was 5 times, and then heated to 130 ° C. while relaxing the stretching by 15% to heat set.
• the biaxially stretched film was cooled to 50 ° C., and the width direction end was slit to obtain a biaxially stretched film having a width of 1200 mm and a thickness of 20 ⁇ m.
• the above process was carried out continuously.
• the roll contamination was evaluated after 1 hour of continuous operation from the start of T-die film production.
• the film was observed after MD stretching and after TD stretching to evaluate the stretchability of the film.
• the elastic modulus, breaking strength, breaking elongation, and tear strength of the obtained stretched film were also evaluated, and the evaluation results are shown in Table 1.
• Example 2 Resin pellets P-2 were produced in the same manner as in Example 1, except that the composition was changed to that shown in Table 1.
• a film was produced in the same manner as in Example 1, and the roll contamination property, the stretchability of the film, the elastic modulus of the stretched film, the breaking strength, the breaking elongation, and the tear strength were evaluated. The evaluation results are shown in Table 1.
• the maximum molding speed at which film molding could be performed without the resin material sticking to the casting roll was 8 m/min, whereas in Example 2, the maximum molding speed was 15 m/min.
• Comparative Examples 1 to 5 Resin pellets P-3 to P-7 were produced in the same manner as in Example 1, except that the formulation was changed to that shown in Table 1. An attempt was made to produce a film in the same manner as in Example 1, but the stretched film was uneven and broke during stretching, and a stretched film could not be obtained. In Comparative Example 4, the molten film did not solidify on the casting roll, and even when the molding speed was less than 1 m/min, the film stuck to the casting roll and could not be peeled off, and a film could not be obtained.
• Comparative Examples 1 and 2 which contained a poly(3-hydroxyalkanoate)-based resin (A) and a polylactic acid-based resin (B) but did not contain the copolymer (A-1)
• Comparative Example 3 which contained neither the copolymer (A-1) nor the polylactic acid-based resin (B)
• Comparative Example 5 which used a copolymer having the same 3HH ratio but a weight-average molecular weight of less than 700,000 instead of the copolymer (A-1)
• Comparative Example 4 which contained the copolymer (A-1) but did not contain the polylactic acid resin (B), the film material was prone to sticking to the casting roll, and a film could not be produced. Furthermore, in Comparative Examples 2 and 3 in which pentaerythritol was blended, roll contamination was observed.

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