Resin film

Abstract

This resin film contains a poly(3-hydroxyalkanoate)-based resin component. The tensile elastic modulus of the resin film is 500-2000 MPa. The swelling degree of the resin film measured after being immersed in methyl ethyl ketone for 2 hours is 1-5. The poly(3-hydroxyalkanoate)-based resin component is preferably a mixture of at least two types of poly(3-hydroxyalkanoate)-based resins that are different from each other in terms of the types of constituent monomers and / or the content ratio of the constituent monomers.

Description

Technical Field

[0001] The present invention relates to a resin film containing a poly(3-hydroxyalkanoate) - based resin component.

Background Art

[0002] Petroleum-derived plastics are discarded in large quantities every year, and the shortage of landfill sites and environmental pollution caused by these large amounts of waste have been taken up as serious problems. In recent years, microplastics have become a major problem in the marine environment.

[0003] Poly(3-hydroxyalkanoate) - based resins have excellent seawater degradability and are materials that can solve the environmental problems caused by discarded plastics. For example, poly(3-hydroxybutyrate - co - 3-hydroxyhexanoate), which is a type of poly(3-hydroxyalkanoate) - based resin, can flexibly control mechanical properties by changing the composition ratio of 3-hydroxyhexanoate.

[0004] However, when the composition ratio of 3-hydroxyhexanoate is increased, although the mechanical properties improve due to a decrease in crystallinity, the productivity tends to decrease. In order to achieve the mechanical properties required for molded articles such as films, it was necessary to increase the composition ratio of 3-hydroxyhexanoate until industrial production became extremely difficult. Therefore, it has been difficult to obtain a molded article that satisfies both good productivity and mechanical properties using poly(3-hydroxyalkanoate) - based resins.

[0005] In Patent Document 1, a polyester resin composition containing two types of polyhydroxyalkanoates is described in order to improve solidification properties in melt molding processing and improve processing speed, and films and sheets are described as examples of the molded articles.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 International Publication No. 2015 / 146194 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the polyester resin composition described in Patent Document 1, even if a film can be produced with good productivity, the tear strength of the obtained film is not sufficiently high, and it has been difficult to achieve both high tear strength and productivity of the film.

[0008] In view of the above situation, an object of the present invention is to provide a resin film containing a poly(3-hydroxyalkanoate) - based resin component, which has high tear strength and can be produced with good productivity. MEANS FOR SOLVING THE PROBLEMS

[0009] As a result of intensive studies to solve the above problems, the inventors have found that a resin film containing a poly(3-hydroxybutyrate) - based resin component and configured to satisfy specific numerical ranges of tensile modulus and degree of swelling respectively has high tear strength and can be produced with good productivity, and thus have completed the present invention.

[0010] That is, the present invention relates to a resin film containing a poly(3-hydroxyalkanoate) - based resin component, wherein the tensile modulus of the resin film is 500 MPa or more and 2000 MPa or less, and the degree of swelling measured by immersing the resin film in methyl ethyl ketone for 2 hours is 1 or more and 5 or less. Preferably, the poly(3-hydroxyalkanoate) - based resin component is a mixture of at least two poly(3-hydroxyalkanoate) - based resins having different types of constituent monomers and / or different content ratios of constituent monomers. Preferably, the poly(3-hydroxyalkanoate) resin component contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. More preferably, the poly(3-hydroxyalkanoate) resin component contains a copolymer (A) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content ratio of the other hydroxyalkanoate units is 1 to 6 mol%, and a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content ratio of the other hydroxyalkanoate units is 24 mol% or more. Preferably, in the poly(3-hydroxyalkanoate) resin component, the proportion of the copolymer (A) is 35% by weight or more, and the proportion of the copolymer (B) is 65% by weight or less. Preferably, the average content ratio of the other hydroxyalkanoate units in all the monomer units constituting the poly(3-hydroxyalkanoate) resin component is 8 to 18 mol%. Preferably, the other hydroxyalkanoate unit is a 3-hydroxyhexanoate unit. Preferably, the tear strength of the resin film is 2 N / mm or more and 200 N / mm or less. Preferably, the thickness of the resin film is 10 μm or more and 1 mm or less.

Advantages of the Invention

[0011] According to the present invention, there is provided a resin film containing a poly(3-hydroxyalkanoate) resin component, which has high tear strength and can be produced with good productivity.

Embodiments for Carrying Out the Invention

[0012] Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0013] One embodiment of the present invention relates to a resin film containing a poly(3-hydroxyalkanoate) - based resin component.

[0014] (Poly(3-hydroxyalkanoate)-based resin component) The poly(3-hydroxyalkanoate) resin component may be a single poly(3-hydroxyalkanoate)-based resin or a mixture of two or more poly(3-hydroxyalkanoate)-based resins. However, since it is easy to control the tensile modulus and the degree of swelling described later, it is preferably a mixture of at least two poly(3-hydroxyalkanoate)-based resins having different types of constituent monomers and / or different contents of constituent monomers.

[0015] The poly(3-hydroxyalkanoate)-based resin is preferably a polymer having 3-hydroxyalkanoate units, specifically, a polymer containing units represented by the following general formula (1). [-CHR-CH2-CO-O-] (1)

[0016] In the general formula (1), R represents an alkyl group represented by C p H 2p+1 and p represents an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, methylpropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, and hexyl group. As p, 1 to 10 is preferable, and 1 to 8 is more preferable.

[0017] As the poly(3-hydroxyalkanoate)-based resin, a poly(3-hydroxyalkanoate)-based resin produced particularly from microorganisms is preferable. In the poly(3-hydroxyalkanoate)-based resin produced from microorganisms, all 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0018] The poly(3-hydroxyalkanoate) - based resin preferably contains 3-hydroxyalkanoate units (particularly, the units represented by the general formula (1)) in an amount of 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of all the constituent units. The poly(3-hydroxyalkanoate) - based resin may contain only one or more 3-hydroxyalkanoate units as the constituent units of the polymer, or may contain, in addition to one or more 3-hydroxyalkanoate units, other units (for example, 4-hydroxyalkanoate units, etc.).

[0019] The poly(3-hydroxyalkanoate) - based resin is preferably a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units. In particular, the 3-hydroxybutyrate units are preferably all (R)-3-hydroxybutyrate units. Also, the poly(3-hydroxyalkanoate) - based resin is preferably a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0020] Specific examples of the poly(3-hydroxyalkanoate) resin include, for example, 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), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and the like. In particular, from the viewpoints of film productivity and mechanical properties, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are preferred.

[0021] When the poly(3-hydroxyalkanoate) resin component contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, the average content ratios of 3-hydroxybutyrate units and other hydroxyalkanoate units in all the monomer units constituting the poly(3-hydroxyalkanoate) resin component are preferably 3-hydroxybutyrate units / other hydroxyalkanoates = 93 / 7 to 80 / 20 (mol% / mol%) from the viewpoint of achieving both the tear strength and productivity of the film, more preferably 92 / 8 to 82 / 18 (mol% / mol%), and even more preferably 90 / 10 to 84 / 16 (mol% / mol%).

[0022] The average content ratio of each monomer unit in all the monomer units constituting the poly(3-hydroxyalkanoate) resin component 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 the monomer units constituting the poly(3-hydroxyalkanoate) resin component. When the poly(3-hydroxyalkanoate) resin component is a mixture of two or more poly(3-hydroxyalkanoates), it means the molar ratio of each monomer unit contained in the whole mixture.

[0023] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin component is not particularly limited. However, from the viewpoint of achieving both the tear strength and productivity of the film, it is preferably from 200,000 to 2,000,000, more preferably from 250,000 to 1,500,000, and still more preferably from 300,000 to 1,000,000.

[0024] When the poly(3-hydroxyalkanoate) resin component is a mixture of two or more poly(3-hydroxyalkanoates), the weight average molecular weight of each poly(3-hydroxyalkanoate) resin is not particularly limited. However, for example, when blending a highly crystalline poly(3-hydroxyalkanoate) resin and a low-crystalline poly(3-hydroxyalkanoate) resin as described later, the weight average molecular weight of the highly crystalline poly(3-hydroxyalkanoate) resin is preferably from 200,000 to 1,000,000, more preferably from 220,000 to 800,000, and still more preferably from 250,000 to 600,000 from the viewpoint of achieving both the tear strength and productivity of the film. On the other hand, the weight average molecular weight of the low-crystalline poly(3-hydroxyalkanoate) resin is preferably from 200,000 to 2,500,000, more preferably from 250,000 to 2,300,000, and still more preferably from 300,000 to 2,000,000 from the viewpoint of achieving both the tear strength and productivity of the film.

[0025] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin or the poly(3-hydroxyalkanoate) resin component can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) with a chloroform solution. As the column for the gel permeation chromatography, a column suitable for measuring the weight average molecular weight may be used.

[0026] The method for producing the poly(3-hydroxyalkanoate) resin is not particularly limited and may be a production method by chemical synthesis or a production method by microorganisms. Among them, the production method by microorganisms is preferred. For the production method by microorganisms, known methods can be applied. For example, as copolymer-producing bacteria of 3-hydroxybutyrate and other hydroxyalkanoates, Aeromonas caviae which is a P3HB3HV and P3HB3HH-producing bacterium, Alcaligenes eutrophus which is a P3HB4HB-producing bacterium, etc. are known. In particular, regarding P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) into which the genes of the P3HA synthase group are introduced is more preferable, and microbial cells in which P3HB3HH is accumulated in the cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, depending on the poly(3-hydroxyalkanoate) resin to be produced, genetically modified microorganisms into which various genes related to the synthesis of poly(3-hydroxyalkanoate) resins are introduced may be used, or the culture conditions including the type of substrate may be optimized.

[0027] (Other resins) The resin film according to an embodiment of the present invention may contain other resins other than poly(3-hydroxyalkanoate) resins as long as the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate. Only one kind of other resin may be included, or two or more kinds may be included.

[0028] The content of the other resin is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 10 parts by weight or less with respect to a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin component. The lower limit of the content of the other resin is not particularly limited and may be 0 parts by weight.

[0029] (Silica) The resin film according to an embodiment of the present invention may further contain silica for the purpose of obtaining an improvement effect on mechanical properties such as tear strength.

[0030] The type of the silica is not particularly limited, but from the viewpoint of versatility, synthetic amorphous silica produced by a dry method or a wet method is preferable. Also, either a hydrophobically treated or non-hydrophobically treated one can be used, and one kind can be used alone, or two or more kinds can be used in combination.

[0031] As the silica, silica having a water adsorption amount of 0.5% by weight or more and 7% by weight or less is preferable. The water adsorption amount can be measured as the volatile content at 160 °C using, for example, an electromagnetic balance MX-50 manufactured by Ken Seiko Kogyo Co., Ltd. as the water adsorption amount. When the water adsorption amount is greater than 7% by weight, it becomes difficult to disperse due to the cohesive force of the water adsorbed on the silica surface or between particles, and fisheyes may occur during film formation, resulting in poor appearance. Conversely, when it is less than 0.5% by weight, the remaining water between the particles forms a crosslinked liquid film, generating a large binding force due to surface tension, and separation and dispersion tend to be extremely difficult.

[0032] The average primary particle diameter of the silica is not particularly limited as long as it can improve the tear strength of the film, hardly cause appearance defects such as fisheyes, and does not significantly impair transparency. However, in terms of easily obtaining the effect of improving mechanical properties such as tear strength and excellent transparency, it is preferably 0.001 to 0.1 μm, and particularly preferably 0.005 to 0.05 μm. The average primary particle diameter is determined by arithmetically averaging the diameters of any 50 or more primary particles observed using a transmission electron microscope (TEM).

[0033] The compounding amount (total compounding amount) of the silica is preferably 1 to 12 parts by weight with respect to a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin component. When it is less than 1 part by weight, the sufficient improvement effect of the silica compounding on mechanical properties such as tear strength may not be exhibited when compounded with the poly(3-hydroxyalkanoate) resin component. When it is more than 12 parts by weight, it may be difficult to disperse the silica well. The compounding amount of the silica is more preferably 2 parts by weight or more, and even more preferably 4 parts by weight or more. Also, it is more preferably 11 parts by weight or less, and even more preferably 10 parts by weight or less.

[0034] However, the resin film according to an embodiment of the present invention can have high tear strength even if it does not substantially contain silica. When the resin film does not substantially contain silica, the blending amount (total blending amount) of the silica may be less than 0.1 part by weight, or may be less than 0.01 part by weight, based on 100 parts by weight in total of the poly(3-hydroxyalkanoate) - based resin components.

[0035] For the purpose of improving the dispersibility of the silica, it is preferable to use the silica and a dispersion aid in combination.

[0036] Examples of the dispersion aid include glycerin ester - based compounds, adipic acid ester - based compounds, polyether ester - based compounds, phthalic acid ester - based compounds, isosorbide ester - based compounds, polycaprolactone - based compounds, etc. Among these, modified glycerin - based compounds such as glycerin diacetomonolaurate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate; adipic acid ester - based compounds such as diethylhexyl adipate, dioctyl adipate, and diisononyl adipate; and polyether ester - based compounds such as polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate are preferable because of their excellent affinity for the resin component and difficulty in bleeding. Further, those containing a large amount of biomass - derived components are particularly preferable because they can increase the biomass degree of the entire composition. Examples of such dispersion aids include the "Likemal" (registered trademark) PL series of Riken Vitamin Co., Ltd. and the Polysorb series of ROQUETTE. The dispersion aid can be used alone or in combination of two or more kinds.

[0037] The blending amount (total blending amount) of the dispersion aid is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. If it is less than 0.1 part by weight, the function of the silica as a dispersion aid may not be fully exerted, or when it is compounded with the poly(3-hydroxyalkanoate) resin component, a sufficient improvement effect due to the blending of the silica may not be exhibited in terms of mechanical properties such as tear strength. On the other hand, if it exceeds 20 parts by weight, it may cause bleed-out. The blending amount of the dispersion aid is more preferably 0.3 part by weight or more, and even more preferably 0.5 part by weight or more. Also, it is more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.

[0038] (Additive) The resin film according to an embodiment of the present invention may contain an additive as long as the effects of the present invention are not inhibited. As the additive, for example, a crystallization nucleating agent, a lubricant, a plasticizer, an antistatic agent, a flame retardant, a conductive agent, a heat insulating agent, a crosslinking agent, an antioxidant, an ultraviolet absorber, a colorant, an inorganic filler, an organic filler, a hydrolysis inhibitor, etc. can be used according to the purpose. In particular, an additive having biodegradability is preferable.

[0039] Examples of the crystallization nucleating agent include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, etc. Among them, pentaerythritol is preferable in that the effect of promoting the crystallization of the poly(3-hydroxyalkanoate) resin component is particularly excellent. The usage amount of the crystallization nucleating agent 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 with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. Also, one kind of the crystallization nucleating agent may be used, or two or more kinds may be used, and the usage ratio can be appropriately adjusted according to the purpose.

[0040] Examples of the lubricant include behenic acid amide, oleic acid amide, erucic acid amide, stearic acid amide, palmitic acid amide, N-stearyl behenic acid amide, N-stearyl erucic acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, ethylene bis lauric acid amide, ethylene bis capric acid amide, p-phenylene bis stearic acid amide, polycondensate of ethylenediamine, stearic acid and sebacic acid, etc. Among them, behenic acid amide and erucic acid amide are preferred in that they have particularly excellent lubricant effects on the poly(3-hydroxyalkanoate)-based resin component. The amount of the lubricant 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 still more preferably 0.1 to 1.5 parts by weight with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate)-based resin component. Further, one type of lubricant may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted according to the purpose.

[0041] Examples of the plasticizer include glycerin ester-based compounds, citric acid ester-based compounds, sebacic acid ester-based compounds, adipic acid ester-based compounds, polyether ester-based compounds, benzoic acid ester-based compounds, phthalic acid ester-based compounds, isosorbide ester-based compounds, polycaprolactone-based compounds, dibasic acid ester-based compounds, etc. Among them, glycerin ester-based compounds, citric acid ester-based compounds, sebacic acid ester-based compounds, and dibasic acid ester-based compounds are preferred in that they have particularly excellent plasticizing effects on the poly(3-hydroxyalkanoate)-based resin component. Examples of the glycerin ester-based compounds include glycerin diacetomonolaurate, etc. Examples of the citric acid ester-based compounds include tributyl acetylcitrate, etc. Examples of the sebacic acid ester-based compounds include dibutyl sebacate, etc. Examples of the dibasic acid ester-based compounds include benzyl methyl diethylene glycol adipate, etc. The amount of the plasticizer 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, based on 100 parts by weight in total of the poly(3-hydroxyalkanoate)-based resin component. Also, one type of plasticizer may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted according to the purpose.

[0042] (Tensile modulus of the resin film) The resin film according to one embodiment of the present invention satisfies a tensile modulus of 500 MPa or more and 2000 MPa or less. When the tensile modulus exceeds 2000 MPa, it becomes difficult for the resin film to have a sufficient level of tear strength. Also, when the tensile modulus is less than 500 MPa, the shape is less likely to be restored after applying force to deform the resin film, and the usability of the resin film tends to deteriorate.

[0043] The tensile modulus is preferably 1800 MPa or less, more preferably 1700 MPa or less, even more preferably 1600 MPa or less, and particularly preferably 1500 MPa or less. Also, the tensile modulus is preferably 600 MPa or more, more preferably 700 MPa or more, and even more preferably 800 MPa or more.

[0044] The tensile modulus is calculated based on an S-S curve obtained by performing a tensile test on the resin film under the condition of a tensile speed of 100 mm / min in accordance with JIS K 7127 using a tensile tester (manufactured by Shimadzu Corporation: EZ-LX 1 kN).

[0045] The tensile modulus can be controlled, for example, by adjusting the average content ratio of other hydroxyalkanoate units in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin component.

[0046] (Swelling degree of the resin film) The resin film satisfies the condition that the degree of swelling measured by immersing it in methyl ethyl ketone for 2 hours is 1 or more and 5 or less. The degree of swelling is calculated by the following formula by weighing the resin film after swelling it by immersing it in methyl ethyl ketone at room temperature (23°C) for 2 hours. Degree of swelling = (weight of the resin film after swelling / weight of the resin film before swelling) The closer the value of the degree of swelling is to 1, the less likely the resin film is to absorb methyl ethyl ketone, and the larger the value, the more likely the resin film is to absorb methyl ethyl ketone.

[0047] The degree of swelling is an index indicating the density of tie molecules contained in the poly(3-hydroxyalkanoate) - based resin component. Tie molecules are molecules that crosslink fine resin crystal particles in the resin component, and by forming a network with them, the tear strength of the film composed of the poly(3-hydroxyalkanoate) - based resin component can be significantly increased. When the density of tie molecules is high, the resin film becomes less likely to absorb methyl ethyl ketone, so the value of the degree of swelling remains at a relatively low value.

[0048] If the degree of swelling exceeds 5 and the density of tie molecules is low, the tear strength of the poly(3-hydroxyalkanoate) - based resin film will not be sufficiently high. The degree of swelling is preferably 4 or less, more preferably 3.5 or less, even more preferably 3 or less, and particularly preferably 2.5 or less.

[0049] However, when evaluating the influence of the degree of swelling on the tear strength, it is desirable to compare resin components with an equivalent level of resin crystal content contained in the poly(3-hydroxyalkanoate) - based resin component. Specifically, since the resin crystal content contained in the poly(3-hydroxyalkanoate) - based resin component depends on the content ratio of the comonomer, it is desirable to compare resin components with an equivalent content ratio of the comonomer to each other.

[0050] The swelling degree can be controlled, for example, by forming the poly(3-hydroxyalkanoate) resin component with at least two types of poly(3-hydroxyalkanoate) resins having different types of constituent monomers and / or different content ratios of constituent monomers, and forming each of the two types of poly(3-hydroxyalkanoate) resins from a copolymer of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit. In particular, when the poly(3-hydroxyalkanoate) resin component includes a copolymer (A) of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content ratio of the other hydroxyalkanoate unit is 1 to 6 mol%, and a copolymer (B) of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content ratio of the other hydroxyalkanoate unit is 24 mol% or more, it is easy to control the swelling degree to 5 or less and further control the tensile modulus to 500 MPa or more and 2000 MPa or less. Details of each copolymer will be described later.

[0051] (Tear strength of resin film) The resin film can exhibit high tear strength and is difficult to tear and break. The tear strength exhibited by the resin film is preferably 2 N / mm or more, more preferably 4 N / mm or more, still more preferably 6 N / mm or more, and particularly preferably 8 N / mm or more as the Elmendorf tear strength.

[0052] The upper limit value of the tear strength is not particularly limited, but in consideration of slit processability, it is preferably 200 N / mm or less, more preferably 100 N / mm or less, still more preferably 80 N / mm or less, and particularly preferably 60 N / mm or less.

[0053] The Elmendorf tear strength is a value obtained by dividing the value measured by a light-load tear degree tester (manufactured by Kumagai Riki Kogyo Co., Ltd.: NO. 2037 special specification machine) having a function and structure compliant with the standard Elmendorf tear tester specified in JIS P-8116 by the film thickness (mm).

[0054] (Thickness of the resin film) The thickness of the resin film is not particularly limited, but is preferably 10 μm or more and 1 mm or less, more preferably 15 μm or more and 500 μm or less, and even more preferably 20 μm or more and 300 μm or less. The resin film in the present application may include those having a thickness generally called a sheet.

[0055] (Method for producing the resin film) As a method for producing the resin film according to an embodiment of the present invention, for example, when the poly(3-hydroxyalkanoate) - based resin component contains a copolymer, a method of adjusting the content ratio of each monomer constituting the copolymer, a method of mixing at least two poly(3-hydroxyalkanoate) - based resins having different types of constituent monomers and / or different content ratios of constituent monomers, etc. can be mentioned. In particular, a method of mixing at least two poly(3-hydroxyalkanoate) - based resins having different types of constituent monomers and / or different content ratios of constituent monomers is preferable.

[0056] When mixing at least two poly(3-hydroxyalkanoate) - based resins, it is preferable to combine and mix at least one highly crystalline poly(3-hydroxyalkanoate) - based resin and at least one low - crystalline poly(3-hydroxyalkanoate) - based resin. Generally, a highly crystalline poly(3-hydroxyalkanoate) - based resin has excellent productivity but poor mechanical strength, and a low - crystalline poly(3-hydroxyalkanoate) - based resin has poor productivity but excellent mechanical properties. It is presumed that the highly crystalline poly(3-hydroxyalkanoate) - based resin forms fine resin crystal particles, and the low - crystalline poly(3-hydroxyalkanoate) - based resin forms tie molecules that crosslink these resin crystal particles. By using these resins in combination, the tear strength of the resin film can be remarkably improved.

[0057] When the highly crystalline poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units, the content ratio of the 3-hydroxybutyrate units contained in the highly crystalline poly(3-hydroxyalkanoate) resin is preferably higher than the average content ratio of the 3-hydroxybutyrate units in all the monomer units constituting the poly(3-hydroxyalkanoate) resin component. When the highly crystalline poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units and other hydroxyalkanoate units, the content ratio of the other hydroxyalkanoate units in the highly crystalline resin is preferably 1 to 10 mol%, more preferably 1 to 8 mol%, and still more preferably 1 to 6 mol%.

[0058] As the highly crystalline poly(3-hydroxyalkanoate) resin component, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferable, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferable.

[0059] When the low crystalline poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units, the content ratio of the 3-hydroxybutyrate units contained in the low crystalline poly(3-hydroxyalkanoate) resin is preferably lower than the average content ratio of the 3-hydroxybutyrate units in all the monomer units constituting the poly(3-hydroxyalkanoate) resin component. When the low crystalline poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units and other hydroxyalkanoate units, the content ratio of the other hydroxyalkanoate units in the low crystalline resin is preferably 24 to 99 mol%, more preferably 24 to 50 mol%, still more preferably 24 to 35 mol%, and particularly preferably 24 to 30 mol%.

[0060] As the low-crystalline poly(3-hydroxyalkanoate) resin, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferable, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferable.

[0061] When a high-crystalline poly(3-hydroxyalkanoate) resin and a low-crystalline poly(3-hydroxyalkanoate) resin are used in combination, the usage ratio of each resin to the total amount of both resins is not particularly limited, but it is preferably 35% by weight or more and 90% by weight or less for the former and 10% by weight or more and 65% by weight or less for the latter, and more preferably 45% by weight or more and 80% by weight or less for the former and 20% by weight or more and 55% by weight or less for the latter.

[0062] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and it may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Also, two or more resins may be melt-kneaded using an extruder, kneader, Banbury mixer, roll, etc. to obtain a blend, or two or more resins may be dissolved in a solvent, mixed, and dried to obtain a blend.

[0063] The resin film according to an embodiment of the present invention can be manufactured by various molding methods such as T-die extrusion molding, inflation molding, and calendar molding. Specific conditions may be set as appropriate. For example, in the inflation method, the pellets are dried with a dehumidifying dryer or the like until the moisture content becomes 500 ppm or less before inflation molding, and the cylinder set temperature is preferably 100°C to 160°C, and the adapter and die set temperatures are preferably 130°C to 160°C.

[0064] Since the resin film according to an embodiment of the present invention has excellent biodegradability, it can be suitably used in agriculture, fishery, forestry, horticulture, medicine, hygiene products, food industry, clothing, non-clothing, packaging, automobiles, building materials, and other fields. For example, it is used in applications such as garbage bags, shopping bags, packaging bags for vegetables and fruits, pillow packaging, agricultural mulch films, fumigation sheets for forestry, binding tapes including flat yarns, root wrapping films for plants, back sheets for diapers, packaging sheets, shopping bags, drainage bags, and other compost bags.

Examples

[0065] Hereinafter, the present invention will be specifically described by way of examples, but the technical scope of the present invention is not limited by these examples.

[0066] The substances used in the examples and comparative examples are shown below. [Poly(3-hydroxyalkanoate)-based resin] P3HB3HH-1: P3HB3HH (average content ratio 3HB / 3HH = 97.2 / 2.8 (mol% / mol%), weight average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 2 of International Publication No. 2019 / 142845. P3HB3HH-2: P3HB3HH (average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 9 of International Publication No. 2019 / 142845. P3HB3HH-3: X131A (Kaneka biodegradable polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 600,000 g / mol) P3HB3HH-4: P3HB3HH (average content ratio 3HB / 3HH = 83 / 17 (mol% / mol%), weight average molecular weight is 700,000 g / mol) Manufactured according to the method described in Example 7 of International Publication No. 2019 / 142845. When using a mixture of two or more poly(3-hydroxyalkanoate)-based resins as the poly(3-hydroxyalkanoate)-based resin component, the average HH ratio shown in Table 1 is the average value calculated from the 3HH ratio in each poly(3-hydroxyalkanoate)-based resin and the weight ratio of each poly(3-hydroxyalkanoate)-based resin.

[0067] [Additive] Additive-1: Pentaerythritol (manufactured by Mitsubishi Chemical Corporation: Neutralizer P) Additive-2: Behenic acid amide (manufactured by Nippon Seika Chemical Co., Ltd.: BNT-22H) Additive-3: Erucic acid amide (manufactured by Nippon Seika Chemical Co., Ltd.: Neutron-S) Regarding the evaluation methods carried out in the examples and comparative examples, they will be described below.

[0068] [Evaluation of Swelling Degree] · Film Preparation A polyimide film was placed on a 2 mm thick SUS plate (30 cm × 35 cm), and 2.0 g of resin composition pellets were placed on the polyimide film. Further, a 200 μm thick shim plate was placed as a spacer so as to surround the resin composition pellets. Then, the same plate as the SUS plate was covered so as to sandwich the resin composition pellets, and it was placed on the heated press plate of a press machine (manufactured by Kando Metal Industry Co., Ltd.: Compression Molding Machine NSF-50) heated to 170 °C and preheated for 5 minutes. After preheating, it was gradually pressurized to 5 MPa over a period of 2 minutes, and then the pressure was maintained for 2 minutes. After the pressing was completed, it was cooled to room temperature on a cooling plate cooled to approximately 20 °C to obtain a film with a thickness of about 200 μm. This film was cured for 1 week in an environment of room temperature 23 °C and humidity 50% to obtain a film sample for measuring the swelling degree.

[0069] · Measurement of Swelling Degree The above film sample was cut to a weight of approximately 0.5 g to obtain a sample before swelling, and its exact weight was measured using an electronic balance. Then, it was immersed in methyl ethyl ketone (MEK) at room temperature (23°C) for 2 hours. After immersion, the sample was taken out, and the MEK adhering to the surface was quickly wiped off with a Kimwipe, and the weight of the sample after swelling was measured. The degree of swelling was calculated according to the following formula and used as the degree of swelling of the sample. Degree of swelling = (Weight of the sample after swelling / Weight of the sample before swelling)

[0070] [Tensile test: Evaluation of tensile modulus] · Film preparation A polyimide film was placed on a 2-mm-thick SUS plate (30 cm × 35 cm), and 2.0 g of resin composition pellets were placed on the polyimide film. Further, a 100-μm-thick shim plate was placed as a spacer so as to surround the resin composition pellets. Then, the same plate as the SUS plate was covered so as to sandwich the resin composition pellets, and it was placed on the heated press plate of a press machine (manufactured by Kando Metal Industry Co., Ltd.: Compression molding machine NSF-50) heated to 170°C and preheated for 5 minutes. After preheating, it was gradually pressurized to 5 MPa over a period of 2 minutes and then the pressure was maintained for 2 minutes. After the pressing was completed, it was cooled to room temperature on a cooling plate cooled to approximately 20°C to obtain a film with a thickness of about 100 μm. This film was cured in an environment of room temperature 23°C and humidity 50% for 1 week to obtain a film sample for measuring the tensile modulus.

[0071] · Measurement of tensile modulus Regarding the above film sample, a tensile test was carried out using a tensile tester (manufactured by Shimadzu Corporation: EZ-LX 1kN) in accordance with JIS K 7127 under the condition of a tensile speed of 100 mm / min. Based on the S-S curve obtained from the tensile test, the tensile modulus was calculated.

[0072] [Evaluation of tear strength] · Film preparation A polyimide film was placed on a 2-mm-thick SUS plate (30 cm × 35 cm), and 2.0 g of resin composition pellets were placed on the polyimide film. Further, a 50-μm-thick shim plate was placed as a spacer so as to surround the resin composition pellets. Then, the same plate as the SUS plate was placed on top to sandwich the resin composition pellets, and it was placed on the heated press plate of a press machine (manufactured by Shindo Metal Industry Co., Ltd.: compression molding machine NSF-50) heated to 170°C and preheated for 5 minutes. After preheating, it was gradually pressurized to 5 MPa over a period of 2 minutes and then the pressure was maintained for 2 minutes. After the pressing was completed, it was cooled to room temperature on a cooling plate cooled to approximately 20°C to obtain a film with a thickness of about 50 μm. This film was cured for 1 week in an environment at room temperature of 23°C and humidity of 50% to obtain a film sample for measuring the tear strength.

[0073] ·Measurement of Tear Strength The value measured by a light-load tear strength tester (manufactured by Kumagai Riki Kogyo Co., Ltd.: NO. 2037 special specification machine) having a function and structure compliant with the standard Elmendorf tear tester specified in JIS P-8116 was divided by the thickness (mm) of the film sample to obtain the Elmendorf tear strength of the film sample.

[0074] [Evaluation of Productivity] Using a small kneader (manufactured by DSM: DSM Xplore 5 model 2005), about 4.5 g of film raw material was kneaded for 5 minutes under the conditions of a barrel temperature of 170°C and a screw rotation speed of 100 rpm. Then, the molten strand-like resin composition was discharged from the die and immediately put into a water bath heated to 60°C, and the time for crystal solidification was measured. If it solidified within 100 seconds, the productivity was evaluated as good.

[0075] (Example 1) 1.76 g of P3HB3HH-1 and 2.74 g of P3HB3HH-2 were blended to obtain the resin composition described in Table 1. To this blend, 0.045 g of Additive-1, 0.0225 g of Additive-2, and 0.0225 g of Additive-3 were added, and the mixture was charged into a small kneader (manufactured by DSM: DSM Xplore 5 Model 2005). Kneading was carried out for 5 minutes under the conditions of a barrel temperature of 170 °C and a screw rotation speed of 100 rpm. Immediately after the completion of kneading, a molten strand-like resin composition was discharged from the die and introduced into a water bath heated to 60 °C to evaluate productivity. As a result, the productivity was good. Thereafter, the strands crystallized and solidified in the water bath were cut with nippers to obtain resin composition pellets.

[0076] From the resin composition pellets, a film was produced using a press machine, and after curing for one week, the swelling degree, tensile elastic modulus, and tear strength were measured. As a result of the measurement, the swelling degree was 2.73, the tensile elastic modulus was 508 MPa, and the tear strength was 69.7 N / mm. The results were summarized in Table 1.

[0077] (Examples 2 to 9, Comparative Examples 1 to 2) Resin composition pellets were produced in the same manner as in Example 1 except that the resin formulation was changed as shown in Table 1, and the same evaluation as in Example 1 was carried out. The results were summarized in Table 1.

[0078]

Table 1

[0079] From Table 1, the following can be understood. Each film of Examples 1 to 9 had a tensile elastic modulus in the range of 500 MPa or more and 2000 MPa or less and a swelling degree in the range of 1 or more and 5 or less. The time required for crystal solidification of each resin composition was short, and the productivity was good. Furthermore, the obtained films had high tear strength.

[0080] On the other hand, the film of Comparative Example 1 had a swelling degree in the range of 1 or more and 5 or less, but had an excessively high tensile elastic modulus. Although the productivity was good, the tear strength was low. In addition, the film of Comparative Example 2 had a tensile elastic modulus in the range of 500 MPa or more and 2000 MPa or less, but the degree of swelling was as large as 5.12, resulting in poor productivity. Further, when comparing Comparative Example 2 with Example 1 or 2 where the average HH ratio is at the same level, it can be seen that by setting the degree of swelling to 5 or less as in Example 1 or 2, the tear strength is significantly improved by 10 times or more.

Claims

1. A resin film containing a poly(3-hydroxyalkanoate) - based resin component, wherein the tensile modulus of the resin film is 500 MPa or more and 2000 MPa or less, the degree of swelling measured by immersing the resin film in methyl ethyl ketone for 2 hours is 1 or more and 5 or less, the poly(3-hydroxyalkanoate) - based resin component is a copolymer (A) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, wherein the content ratio of the other hydroxyalkanoate units is 1 to 6 mol%, and a copolymer (B) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, wherein the content ratio of the other hydroxyalkanoate units is 24 mol% or more.

2. The resin film according to claim 1, wherein in the poly(3-hydroxyalkanoate) - based resin component, the proportion of the copolymer (A) is 35% by weight or more and the proportion of the copolymer (B) is 65% by weight or less.

3. The resin film according to claim 1 or 2, wherein the average content ratio of the other hydroxyalkanoate units in all the monomer units constituting the poly(3-hydroxyalkanoate) - based resin component is 8 to 18 mol%.

4. The resin film according to any one of claims 1 to 3, wherein the other hydroxyalkanoate unit is a 3-hydroxyhexanoate unit.

5. The resin film according to any one of claims 1 to 4, wherein the tear strength of the resin film is 2 N / mm or more and 200 N / mm or less.

6. The resin film according to any one of claims 1 to 5, wherein the thickness of the resin film is 10 μm or more and 1 mm or less.

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