JP2007268742A - Multilayer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging film which is biodegradable, has sufficient transparency, gloss, and antifogging properties, and is excellent in processability and film recoverability at room temperature. <P>SOLUTION: The multilayer film comprises at least three layers of at least one inner layer composed of a resin composition containing a mixture of an aliphatic polyester resin with a glass transition temperature of 0°C or below and a phenoxy resin as a main component and surface and back layers composed of a thermoplastic resin different from the resin composition. The percentage of the phenoxy resin in the mixture is 20-60 mass%. The percentage of the thickness of the inner layer in the thickness of the total layers is ≥50% and <80%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a packaging film having biodegradability and excellent moldability and film recoverability at room temperature.

  In recent years, due to increasing environmental problems, when plastic products are discarded in the natural environment, it is beginning to be required to decompose and disappear over time and ultimately not have a negative impact on the natural environment. Conventional plastics are stable in the natural environment for a long time and have a low bulk specific gravity. Therefore, they point out problems such as promoting the shortening of the life of landfills, or damaging the natural landscape and the living environment of wild animals and plants. It had been.

Therefore, biodegradable resin materials are attracting attention today. Biodegradable resins are known to gradually disintegrate and decompose by hydrolysis and biodegradation in soil and water, and finally become harmless degradation products due to the action of microorganisms. It is also known that waste can be easily treated by composting (composting).
Biodegradable resins that have begun to be put into practical use include aliphatic polyesters, modified PVA, cellulose ester compounds, starch modified products, and blends thereof.

  Each of these biodegradable plastics has unique characteristics and can be used in accordance with these characteristics. Among them, aliphatic polyesters having a wide range of properties and processability similar to general-purpose resins are beginning to be widely used. Aliphatic polyesters are derived from polyhydroxycarboxylic acids such as polylactic acid, aliphatic polyhydric alcohols and aliphatic polyhydric carboxylic acids, and have been developed so far as biodegradable polymers. . As a highly versatile biodegradable resin, polylactic acid, polycaprolactone, polybutylene succinate and the like are on the market.

  Polylactic acid has recently been produced in large quantities and at low cost by the fermentation method of L-lactic acid as a raw material, has a fast decomposition rate in compost, has resistance to mold, and has good odor resistance to foods. It has been expected to expand its application field by having excellent characteristics such as coloring resistance. However, lactic acid-based resins such as polylactic acid have high rigidity and are not suitable resins for applications that require flexibility such as films and packaging materials.

  Therefore, in order to soften lactic acid-based resins such as polylactic acid, methods such as addition of a plasticizer, copolymerization, and blending of soft polymers have been made. However, these methods cannot provide sufficient flexibility, and have problems such as blocking and bleed out of the plasticizer.

  In contrast, among the same aliphatic polyesters, polybutylene succinate has a high crystallization rate, high crystallinity, and excellent heat resistance. It has the potential to become. Moreover, it can be said that the glass transition temperature is significantly lower than that of polylactic acid and the resin has flexibility.

  However, polybutylene succinate, due to its low glass transition temperature, for example, when used as a film material, can give relaxation characteristics near room temperature as required for a food packaging wrap film. Can not. It can be said that the relaxation characteristics of the film are developed around the glass transition temperature of the resin. Therefore, in order to impart relaxation characteristics at a higher temperature, a technique such as copolymerization or blending with a polymer having a glass transition temperature higher than that of the resin is required.

  Polybutylene succinate is often blended with polylactic acid and other lactic acid resins which are the same biodegradable resin and have a relatively high glass transition temperature. However, these techniques are mainly aimed at softening lactic acid-based resins such as polylactic acid, and the temperature at which relaxation characteristics are expressed cannot be freely designed.

  Patent Document 1 discloses a technique in which polybutylene succinate is blended with a lactic acid resin and the lactic acid resin is made flexible. However, although such methods can improve impact resistance and the like, since these blend polymers are incompatible systems, a peak appears near the glass transition temperature of each polymer, and at room temperature (0 ° C. to 30 ° C.). Relaxation properties cannot be imparted.

  Patent Document 2 discloses a technique in which a polybutylene succinate and a plasticizer are blended with a lactic acid resin to give the lactic acid resin flexibility. However, they give flexibility by using a plasticizer in combination, and are different from the present invention because they have an effect of suppressing bleeding of the plasticizer or blocking of the film.

  Patent Document 3 provides a resin composition having a sufficient flexibility without adding a phenol derivative which is a low-molecular compound to an aliphatic polyester such as a lactic acid-based resin so that the plasticizer does not bleed out. The method is described. However, in this method, a phenol derivative is added as a plasticizer to an aliphatic polyester such as a lactic acid resin to soften the lactic acid resin, and the temperature at which relaxation characteristics are expressed can be freely designed. is not.

  Another problem with polybutylene succinate is that it alone does not have airtightness as a package due to heat sealing, adhesion, etc. Therefore, it is necessary to modify it by adding additives, etc. There is sex. However, when the additive is added by a kneading method, there are disadvantages such as poor bleedability and difficulty in exhibiting the antifogging property, particularly when an antifogging agent is added.

  Therefore, a method of laminating a thermoplastic resin other than the resin in order to impart the above characteristics can be mentioned. Patent Document 4 discloses a technique in which an ethylene-vinyl acetate copolymer is arranged on the surface layer in order to impart characteristics as a package. However, the inner layer is made of a polyolefin resin such as polypropylene and is not a biodegradable structure.

  Patent Document 5 describes a package having a laminated structure of an aliphatic polyester resin such as a lactic acid resin and an ethylene-vinyl acetate copolymer or another polyolefin resin. However, since this has an ethylene-vinyl acetate copolymer or other polyolefin resin in the inner layer, it is inadequate in packaging suitability such as heat sealability and adhesion, and additives are bleeded on the film surface. Cannot play a role to make it happen.

JP 2003-286354 A JP-A-11-116788 JP 2001-81300 A Japanese Patent No. 3606611 JP 2000-26623 A

  The present invention relates to a biodegradable multilayer film, and further provides a packaging film having sufficient transparency, gloss and antifogging properties, and excellent workability and film recoverability at room temperature. Is.

The resin composition of the present invention is as follows.
(1) At least one inner layer composed of a resin composition containing as a main component a mixture of an aliphatic polyester resin having a glass transition temperature of 0 ° C. or less and a phenoxy resin, and a thermoplastic resin different from the resin composition A multilayer film composed of at least three layers having front and back layers composed of a resin, wherein the proportion of the phenoxy resin in the mixture is 20% by mass or more and 60% by mass or less; A multilayer film, wherein the thickness ratio of the inner layer is 50% or more and less than 80%.
(2) The aliphatic polyester resin having a glass transition temperature of 0 ° C. or lower is an aliphatic polyester obtained by copolycondensation of an aliphatic oxycarboxylic acid, an aliphatic or alicyclic diol, and an aliphatic dicarboxylic acid or a derivative thereof. The multilayer film according to (1), which is characterized in that it exists.
(3) The resin forming the front and back layers is at least one selected from ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic ester copolymer. The multilayer film according to any one of (1) and (2).
(4) The storage elastic modulus (E ′) at 20 ° C. measured at a vibration frequency of 10 Hz and strain of 0.1% by the dynamic viscoelasticity measurement method described in JIS K-7198 A method is in the range of 100 MPa to 3 GPa. And the value of the loss tangent (tan-delta) in 20 degreeC exists in the range of 0.1-0.5, The multilayer film in any one of (1)-(3) characterized by the above-mentioned.

  According to the present invention, it is possible to provide a packaging film that is biodegradable, has sufficient transparency, gloss, and antifogging properties, and is excellent in processability and film recoverability at room temperature.

Embodiments of the present invention will be described below, but the scope of the present invention is not limited to the embodiments described below.
In the present invention, a sheet and a film are not distinguished. In general, a “sheet” is a product that is thin by definition in JIS and generally has a thickness that is small and flat for the length and width. In general, a “film” has a thickness that is smaller than the length and width. A thin flat product that is extremely small and has an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

In addition, the expression “main component” in the present invention includes the meaning of allowing other components to be contained within a range that does not hinder the function of the main component, unless otherwise specified. Although the content ratio of the main component is not particularly specified, the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, preferably 70% by mass in the composition. As mentioned above, it occupies 90 mass% or more (100% is included) especially preferably.
In addition, in this specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “X or more and Y or less” unless otherwise specified, and “greater than X and smaller than Y”. The intention of “preferably” is also included.

(Form of film)
As a result of intensive studies, the inventors of the present invention have at least one inner layer composed of a resin composition containing as a main component a mixture in which a specific amount of a phenoxy resin is blended with an aliphatic polyester resin having a glass transition temperature of 0 ° C. or less. And having a front and back layer composed of a thermoplastic resin different from the resin composition, and a multilayer film composed of at least three layers, thereby providing biodegradability, film deformation recovery, and adhesion. The inventors have found that it can be expressed at the same time, and reached the present invention.

(About the inner layer of the film)
For example, when an aliphatic polyester having a Tg of 0 ° C. or lower is to be used as a film material, it cannot impart relaxation characteristics in the vicinity of room temperature as required for a food packaging wrap film. It can be said that the relaxation characteristics of the film are developed around the glass transition temperature of the resin. Therefore, in order to impart relaxation characteristics at a higher temperature, a technique such as copolymerization or blending with a polymer having a glass transition temperature higher than that of the resin is required. The inner layer mainly composed of aliphatic polyester in the present invention is a resin composition obtained by blending an aliphatic polyester having a Tg of 0 ° C. or less and a phenoxy resin.

(About aliphatic polyester)
In the present invention, an aliphatic polyester having a glass transition temperature of 0 ° C. or lower is an aliphatic polyester obtained by copolycondensation of an aliphatic oxycarboxylic acid, an aliphatic or alicyclic diol, an aliphatic dicarboxylic acid or a derivative thereof, An aliphatic polyester obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic diol as main components, an aliphatic polyester obtained by ring-opening polymerization of a cyclic lactone, a synthetic aliphatic polyester, and an aliphatic polyester biosynthesized in a cell. The glass transition temperature (hereinafter also referred to as “Tg”) is 0 ° C. or lower. If Tg is 0 ° C. or less, the effect of improving the impact resistance can be expressed predominantly. In addition, Preferably Tg is -20 degrees C or less.

  In addition, the glass transition temperature (Tg) in this invention says the value calculated | required as follows. That is, a sample cut to about 10 mg by measurement with a differential scanning calorimeter (DSC) was heated from −100 ° C. to 200 ° C. at a heating rate of 10 ° C./min according to JIS K7121, and 1 at 250 ° C. After holding for 1 minute, the temperature was lowered to −100 ° C. at a cooling rate of 10 ° C./min, held at −100 ° C. for 1 minute, and then reheated at a heating rate of 10 ° C./min. )

  Specific examples of the aliphatic oxycarboxylic acid in the copolycondensed aliphatic polyester include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxy-3-methyl. Examples include butyric acid, 2-hydroxyisocaproic acid, and mixtures thereof. Among these, lactic acid or glycolic acid, which has a particularly remarkable increase in polymerization rate during use and is easily available, is preferable. A 30-95% aqueous solution is preferable because it can be easily obtained. These aliphatic oxycarboxylic acids can be used alone or as a mixture of two or more.

  Specific examples of the aliphatic or alicyclic diol in the copolycondensed aliphatic polyester include ethylene-glycol, 1,3-propion glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane. Preferred examples include diol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. In view of the physical properties of the obtained copolymer, 1,4-butanediol is particularly preferable.

  Specific examples of the aliphatic dicarboxylic acid or its derivative in the copolycondensed aliphatic polyester include oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, and their lower alcohols. And esters, succinic anhydride, adipic anhydride, and the like. From the viewpoint of the physical properties of the resulting copolymer, succinic acid, adipic acid, sebacic acid or their anhydrides, and lower alcohol thereof are preferred, and succinic acid, succinic anhydride, or a mixture thereof is particularly preferred. These can be used alone or in combination of two or more.

  Examples of aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones include ring-opening polymers selected from one or more cyclic monomers such as ε-caprolactone, δ-valerolactone, and β-methyl-δ-valerolactone. Can be mentioned. Examples of synthetic aliphatic polyesters include copolymers of succinic anhydride, cyclic acid anhydrides such as ethylene oxide and propylene oxide, and oxiranes.

  What is particularly preferably used as the aliphatic polyester having a glass transition temperature (Tg) of 0 ° C. or lower of the present invention is a copolycondensed aliphatic polyester which is considered to be relatively transparent among the above, and specific examples thereof. Examples include polyethylene-adipate, polypropylene adipate, polybutylene adipate, polyhexene adipate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate lactic acid, polybutylene succinate adipate lactic acid, polyethylene-succinate, etc. . Among them, aliphatic polyesters such as polybutylene succinate lactic acid and polybutylene succinate adipate lactic acid, which are copolycondensated with aliphatic oxycarboxylic acids, aliphatic or alicyclic diols, and aliphatic dicarboxylic acids or derivatives thereof, It is preferable to select. By copolymerizing an oxycarboxylic acid such as lactic acid, an aliphatic polyester having a number average molecular weight of 10,000 or more can be obtained very easily without using a chain extender, and the introduction of an oxycarboxylic acid component As a result, the crystallinity of the resulting polyester is lowered, and flexibility can be imparted.

  Commercially, as an aliphatic polyester obtained by polycondensation of an aliphatic dicarboxylic acid and an aliphatic diol as main components, “Bionore” series manufactured by Showa Polymer Co., Ltd., and aliphatic oxycarboxylic acid, aliphatic or alicyclic “GSPla” series manufactured by Mitsubishi Chemical Corporation is available as an aliphatic polyester obtained by copolycondensation of a diol and an aliphatic dicarboxylic acid or a derivative thereof.

  As a method for polymerizing the aliphatic polyester, a known method such as a direct method or an indirect method can be employed. In the direct method, for example, polycondensation is performed by selecting the dicarboxylic acid compound anhydride or derivative thereof as the aliphatic dicarboxylic acid component, and selecting the diol compound or derivative thereof as the aliphatic diol component and performing polycondensation. A high molecular weight product can be obtained while removing the water generated at the time. The indirect method can be obtained by adding a small amount of chain extender, for example, a diisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate to the oligomer polycondensed by the direct method to obtain a high molecular weight. . The weight average molecular weight of the aliphatic polyester is preferably in the range of 20,000 to 500,000, more preferably in the range of 150,000 to 250,000. When the molecular weight is less than 20,000, practical physical properties such as mechanical strength cannot be obtained sufficiently, and when the molecular weight exceeds 500,000, there is a problem that molding processability is inferior.

(Phenoxy resin)
Phenoxy resins include hydroquinone, resorcin, 4,4'-bisphenol, 4,4'-dihydroxydiphenyl ether, bisphenol A, bisphenol F, and aromatic dihydroxy compounds such as 2,6-dihydroxynaphthalene, or ethylene-glycol di One or more selected from aliphatic dihydroxy compounds such as glycidyl ether propylene glycol diglycidyl ether, neopentyl glycol, neopentyl glycol diglycidyl ether, polyethylene-glycol diglycidyl ether, polypropylene glycol diglycidyl ether Examples thereof include polyhydroxy polyether obtained by condensing a compound with glycerin and epichlorohydrin. Commercially available are E1256, E4250, E4275 manufactured by Japan Epoxy Resin, PKHH, PKHC, PKHJ, PKHB, PKFE, etc. manufactured by InChem.

  The weight average molecular weight of the phenoxy resin is preferably 10,000 to 500,000. The lower limit is preferably 30,000 or more, and particularly preferably 50,000 or more. Moreover, as an upper limit, 400,000 or less is further preferable, and 300,000 or less is especially preferable. Therefore, a condensate with glycerin and epichlorohydrin is preferable among the phenoxy resins. When the phenoxy resin to be mixed is an aliphatic dihydroxy compound alone, its molecular weight is low, so the molecular weight of the resin mixture may be lowered, and moldability may not be ensured.

  It is important that the ratio of the phenoxy resin in the mixture of the aliphatic polyester resin having a glass transition temperature of 0 ° C. or less and the phenoxy resin is 20% by mass or more and 60% by mass or less. As a lower limit, Preferably it is 30 mass% or more. Moreover, as an upper limit, Preferably it is 40 mass% or less. When the amount is less than 20% by mass, the glass transition temperature of the blend cannot be increased to 0 ° C. or more. When the amount is more than 60% by mass, the storage elastic modulus rapidly decreases in the vicinity of Tg, so that mechanical design is difficult. The problem of becoming. Further, when the proportion of the phenoxy resin increases, the flexibility of the aliphatic polyester resin having a glass transition temperature of 0 ° C. or less is impaired by the phenoxy resin having high elasticity at room temperature.

  When the melt flow index (MFR) of the resin composition comprising the present invention is measured at 190 ° C. and 2.16 kg, the lower limit is usually 0.1 / 10 min or more, and the upper limit is usually 100 g / 10 min or less, More preferably, it is 30 g / 10min or less, Most preferably, it is 20 g / 10min or less.

(About front and back layers)
In the present invention, since a single layer of the above composition cannot produce an effect, it is important to have a laminated structure. The front and back layers reinforce the mechanical strength such as tear strength, puncture strength, and impact strength with synergistic effects with the specific inner layer of the present invention while ensuring airtightness as a package by heat sealing and adhesion. Required as a layer. In addition, when film forming is performed by inflation molding or tubular stretching, it can serve as an anti-blocking layer during film winding, as well as ensuring stability during molding. Furthermore, it also serves as a surface layer that bleeds by adding an anti-fogging agent, antistatic agent, lubricant, etc. as an additive, but in addition, an adhesive layer between each layer, and also in terms of mechanical strength The reinforcing layer and the additive-holding layer can also be used for the inner layer.

  The resin constituting the surface layer is at least one copolymer resin selected from ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer. . The ethylene-vinyl acetate copolymer preferably has a vinyl acetate group content of 5 to 25% by mass and an MFR (190 ° C., 2.16 kgf) of 0.3 to 10 g / 10 min, and more preferably 0.5 to A range of 3 is preferable. When the amount of vinyl acetate is less than 5% by weight, the transparency is inferior, and when it exceeds 26% by weight, the extrusion moldability is inferior, the odor of acetic acid becomes strong, and stickiness tends to occur.

  Next, ethylene-aliphatic unsaturated carboxylic acid copolymer and ethylene-aliphatic unsaturated carboxylic acid ester copolymer include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid. And ester (selected from C1-C8 alcohol components such as methyl, ethyl, propyl, butyl, etc.) copolymers. The resin constituting the surface layer is selected from at least one of the above resins, and an ethylene-vinyl acetate copolymer is preferable in terms of optical properties and sealing properties.

  An adhesive layer may be provided between the surface layer and the inner layer. In this case, another resin other than the above may be used alone or as a mixture, and examples of these resins include partially saponified ethylene-vinyl acetate copolymers, ionomer resins, ethylene-α- Olefin copolymer, high-pressure low-density polyethylene, high-density polyethylene, and α-olefin copolymer having a crystallinity of 30% or less by X-ray method different from the above ethylene-α-olefin copolymer Examples include soft resins, polypropylene resins, polybutene resins, styrene-conjugated diene block copolymers, those obtained by hydrogenating at least a part of the block copolymers, and those modified by acid modification. .

  The multilayer film of the present invention is a multilayer film composed of at least three layers having at least one inner layer and front and back layers, for example, a three-layer structure consisting of a surface layer / inner layer / back layer, surface layer / adhesive layer / inner layer / In addition to a four-layer structure consisting of a back layer, a five-layer structure consisting of a surface layer / adhesive layer / inner layer / adhesive layer / back layer, a surface layer / inner layer / adhesive layer / inner layer / back layer, and a surface layer / adhesive layer / inner layer / adhesive layer A multilayer structure such as / inner layer / adhesive layer / back layer can be representatively exemplified. In this case, the resin composition and thickness ratio of each layer may be the same or different.

  In the multilayer film of the present invention, the storage elastic modulus (E ′) at 20 ° C. measured at a vibration frequency of 10 Hz and a strain of 0.1% by the dynamic viscoelasticity measurement method described in JIS K-7198 A method is 100 MPa to It is preferably in the range of 3 GPa, and more preferably in the range of 200 MPa to 1 GPa. When used as a flexible film, the value of elastic modulus near room temperature is an index. Therefore, if the storage elastic modulus (E ′) at 20 ° C. is 100 MPa or more, the films do not adhere to each other or the film and other substances at room temperature due to excessive flexibility, and if it is 3 GPa or less, the film Is not excessively hard and is appropriately stretched, which is advantageous for soft film applications.

  In the same measurement, the value of the loss tangent (tan δ) at 20 ° C. is preferably in the range of 0.1 to 0.5, and more preferably in the range of 0.1 to 0.3. The peak value of loss tangent (tan δ) is a physical property indicating a delay in deformation when a force is applied, and is one of parameters indicating a stress relaxation behavior. If the value of the loss tangent is small, the relaxation behavior of the film is fast, and conversely if the value is large, the stress relaxation is slow. If the value of loss tangent (tan δ) at 20 ° C. is 0.1 or more, the restoring behavior against deformation of the film does not occur instantaneously, and if it is 0.5 or less, the restoring behavior is not too slow.

  Additives such as a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, a colorant, a lubricant, a plasticizer, and an antifogging agent can be formulated within a range not impairing the effects of the present invention. The additive suitably used in the present invention is a mixture of an aliphatic alcohol having 1 to 12 carbon atoms, preferably 1 to 6 carbons, and an aliphatic alcohol having 10 to 22 carbon atoms, preferably 12 to 18 carbon atoms. Specific examples include aliphatic alcohol fatty esters such as monoglycerinolate, diglycerin monooleate, polyglycerin oleate, glyceryl trilysylate, glyceryl acetyl cinnolate, polyglyceryl stearate, polyglycerin laurate, methyl. Examples thereof include acetyl ricinolate, ethyl acetyl ricinolate, butyl acetyl ricinolate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, and polyethylene-glycol sorbitan laurate. Furthermore, at least one compound selected from paraffinic oils can be added. A suitable addition amount of these additives is 0.1 to 12 parts by mass, preferably 2 to 8 parts by mass, more preferably 3 to 6 parts by mass, when the total of various resin components is 100 parts by mass. In the present invention, it is preferably added to at least the surface layer.

  In the film of the present invention, the thickness ratio of the inner layer to the entire layer is preferably 50% or more and less than 80%, and the front and back layers including the adhesive layer and the like are the remaining 20% or more and the thickness ratio of less than 50%. It is preferable to become. When there are two or more inner layers, the total thickness of each inner layer is preferably 50% or more and less than 80% of the total thickness. A more preferable thickness ratio of the inner layer is in a range of 65% or more and 75% or less in all layers. When the thickness ratio of the inner layer is 50% or more, biodegradability and film relaxation properties are good, and mechanical strength such as tear strength, puncture strength, and impact strength can be prevented from being lowered. In addition, if the thickness ratio of the inner layer is less than 80%, the thickness ratio of the front and back layers can be increased, so that the antifogging properties and seal strength of the front and back layers can be ensured, and the multilayer film having excellent practicality can be obtained. Design becomes possible.

  The film forming method using the resin composition in the present invention will be described below. First, a mixture of an aliphatic polyester resin having a glass transition temperature of 0 ° C. or lower, a phenoxy resin, and other additives used as an inner layer can be molded by putting the respective raw materials into the same injection molding machine. it can. A method in which raw materials are directly mixed using an extruder or injection molding machine, or a dry blended raw material is extruded into a strand shape using a twin screw extruder to form pellets, and then a film or sheet is formed There is a way to do it.

  In any method, it is necessary to consider a decrease in the molecular weight of the aliphatic polyester resin having a glass transition temperature of 0 ° C. or lower due to decomposition, but the latter is preferably selected for uniform mixing. In the present invention, for example, an aliphatic polyester resin having a glass transition temperature of 0 ° C. or less, a phenoxy resin, and other additives are sufficiently dried to remove moisture, and then melt mixed using a twin-screw extruder. The pellet is formed by extruding into a strand shape. It is preferable to appropriately select the melt extrusion temperature in consideration of the viscosity of the mixture changing depending on the mixing ratio of the aliphatic polyester resin having a glass transition temperature of 0 ° C. or less, the phenoxy resin, and other additives. In practice, a temperature range of 160-230 ° C. is usually selected.

  After the pellets prepared by the above method are sufficiently dried to remove moisture, the film or sheet is formed by the following method.

  Resins constituting each layer and other layers used as necessary are melted in respective extruders, coextruded with a multilayer die, and rapidly cooled and solidified to obtain a multilayer film original. As the extrusion method, a multilayer T-die method, a multilayer circular method, or the like can be used, but the latter is preferable. The multilayer film original obtained as described above is heated and stretched under an appropriate temperature condition. The stretching temperature is usually 120 ° C. or less, preferably 100 ° C. or less, at the surface temperature at the stretching start point of the film (in the inflation method, the position where expansion starts as a bubble).

  Examples of the stretching method include a roll stretching method, a tenter method, and an inflation method. A method of forming a film by simultaneous biaxial stretching is preferable in view of stretchability and rationality. By adopting the inflation method, biaxial simultaneous stretching is possible, and it is possible to manufacture at a relatively low cost with high productivity, and because the shape is a bag (seamless), take-out bags for supermarkets, frozen foods It is suitable for the production of bags and bags such as bags, compost bags, and the like for preventing water condensed on low temperature food packs such as meat and meat from getting wet. By combining with the coextrusion method, a multilayer film can be produced with high productivity by using a plurality of resin compositions and / or other types of polymers according to the present invention having different properties.

  Films or sheets comprising the resin composition according to the present invention include shopping bags, garbage bags, compost bags, food / confectionery packaging films, food wrap films, cosmetic / cosmetic wrap films, pharmaceutical wrap films, and herbal medicines. Wrap film, wrap film for surgical patches applied to stiff shoulders and sprains, packaging film for sanitary materials (paper diapers, sanitary products), agricultural and horticultural film, wrap film for agricultural products, greenhouse film, fertilizer bag It can be suitably used as a film for packaging magnetic tape cassette products such as video and audio, a film for packaging flexible disks, a film for plate making, an adhesive tape, a tape, a waterproof sheet, a sandbag, and the like. The film or sheet which is one embodiment of the molded article of the present invention can be used particularly suitably for applications that require degradability by taking advantage of its properties. In the coextrusion method, a multilayer film can be produced using a plurality of the polymers having different properties and / or other types of polymers.

  Examples are shown below, but the present invention is not limited by these. In addition, the result shown in an Example evaluated by the following method.

(Measurement and evaluation method)
(1) Dynamic Viscoelasticity Measurement According to the dynamic viscoelasticity measurement method described in JIS K-7198 A method, using a spectro rheometer “VES-F3” manufactured by Iwamoto Seisakusho Co., Ltd., vibration frequency 10 Hz, strain 0.1 %, The MD of the film (flow direction from the extruder of the film) was measured at a temperature of 20 ° C., and the storage elastic modulus (E ′) and loss tangent (tan δ) at a temperature of 20 ° C. were obtained.

(2) Stability during molding The stability during inflation molding was judged from the state of bubbles. The evaluation criteria are as follows.
(O): A stable molding state is maintained without bubbles being blown off.
(×) ... Bubbles fluctuate or break in the middle.

(3) Adhesiveness of film Water (50cc) was put into the container of the earthenware, and the adhesion degree with the container after storing at 0 degreeC for 15 hours was evaluated. The evaluation criteria are as follows.
(◯): The film is in close contact with the container in a state of elasticity.
(Δ): The film and the container are displaced, and some slack is generated.
(×) ... Almost not adhered.

[Comparative Example 1]
Using GSPla AZ91T (succinic acid-lactic acid-1,4-butanediol copolymer, weight average molecular weight 160,000, Tg-32 ° C.) manufactured by Mitsubishi Chemical Corporation as polybutylene succinate lactic acid, extrusion temperature 190 to 200 ° C., A film having a thickness of 10 μm was obtained by coextrusion inflation molding at an annular die temperature of 200 ° C. and a blow-up ratio of 10. The obtained sheet was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Comparative Example 2]
Comparative Example 1 except that GSPla AD92W (succinic acid-adipic acid-lactic acid-1,4-butanediol copolymer, weight average molecular weight 160,000, Tg-45 ° C.) manufactured by Mitsubishi Chemical Corporation was used as polybutylene succinate lactic acid. In the same manner as above, a film having a thickness of 10 μm was produced by coextrusion and inflation molding. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Comparative Example 3]
GSPla AZ91T and E1256 were mixed at a mass ratio of 70:30 by using GSPla AZ91T manufactured by Mitsubishi Chemical Co., Ltd. as polybutylene succinate lactic acid and E1256 manufactured by Japan Epoxy Resin Co., Ltd. (bisphenol A type) as phenoxy resin. A film having a thickness of 10 μm was produced in the same manner as in Example 1. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Comparative Example 4]
Using GSPla AD92W manufactured by Mitsubishi Chemical Corporation as polybutylene succinate lactic acid, GSPla AD92W and E1256 were mixed at a mass ratio of 70:30, and a 10 μm thick film was produced in the same manner as in Comparative Example 1. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Example 1]
As an inner layer, a mixture of GSPla AZ91T and E1256 at a mass ratio of 70:30 was introduced into an extruder, and ethylene-vinyl acetate as an anti-fogging agent was added as an antifogging agent to 2 parts of diglycerin monooleate as front and back layers. A film having a thickness of 10 μm was produced by coextrusion and inflation molding in the same manner as in Comparative Example 1 except that the mixed composition of 0.0 part by mass was put into an extruder. The thickness ratio of each layer was 75% for the inner layer and 25% for the front and back layers. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Example 2]
A film having a thickness of 10 μm was produced in the same manner as in Example 1 except that GSPla AZ91T and E1256 were mixed at a mass ratio of 60:40 as the inner layer. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Example 3]
As an inner layer, a mixture of GSPla AD92W and E1256 at a mass ratio of 70:30 was put into an extruder, and ethylene-vinyl acetate as an anti-fogging agent was added as an antifogging agent to 2 parts by weight as a front and back layer. A film having a thickness of 10 μm was produced by coextrusion and inflation molding in the same manner as in Comparative Example 1 except that the mixed composition of 0.0 part by mass was put into an extruder. The thickness ratio of each layer was 67% for the inner layer and 33% for the front and back layers. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Example 4]
A 10 μm-thick film was produced in the same manner as in Example 3 except that GSPla AD92W and E1256 were mixed at a mass ratio of 60:40 as the inner layer. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

[Comparative Example 5]
A 10 μm thick film was produced in the same manner as in Example 3 except that the thickness ratio of each layer was 80% for the inner layer and 20% for the front and back layers. The obtained film was evaluated for storage elastic modulus (E ′) and loss tangent (tan δ) at 20 ° C., and stability during molding and film adhesion. The results are shown in Table 1.

As is apparent from Table 1, when the films made of the resin compositions shown in Comparative Examples 1 and 2 and Examples 1 to 4 are compared, the tan δ value at 20 ° C. is improved by blending the phenoxy resin. It can be seen that relaxation characteristics could be imparted to Moreover, when the film which consists of Comparative Examples 3 and 4 and Examples 1-4 is compared, when there is no front and back layer, since stability at the time of inflation molding is not maintained, there is a problem in productivity, and adhesion It was also confirmed that it could not be granted. In addition, the film of Comparative Example 5 could not exhibit excellent effects in both stability and adhesion during molding due to the small thickness ratio of the front and back layers.

Claims (4)

  Consists of at least one inner layer composed of a resin composition containing as a main component a mixture of an aliphatic polyester resin having a glass transition temperature of 0 ° C. or less and a phenoxy resin, and a thermoplastic resin different from the resin composition A multilayer film comprising at least three layers, wherein the proportion of the phenoxy resin in the mixture is 20% by mass or more and 60% by mass or less, and further, A multilayer film having a thickness ratio of 50% or more and less than 80%.   The aliphatic polyester resin having a glass transition temperature of 0 ° C. or lower is an aliphatic polyester obtained by copolycondensation of an aliphatic oxycarboxylic acid, an aliphatic or alicyclic diol, and an aliphatic dicarboxylic acid or a derivative thereof. The multilayer film according to claim 1.   The resin forming the front and back layers is at least one selected from ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer. The multilayer film according to claim 1 or 2. The storage elastic modulus (E ′) at 20 ° C. measured at a vibration frequency of 10 Hz and a strain of 0.1% by the dynamic viscoelasticity measurement method described in JIS K-7198 A method is in the range of 100 MPa to 3 GPa, and The multilayer film according to any one of claims 1 to 3, wherein a value of a loss tangent (tan δ) at 20 ° C is in a range of 0.1 to 0.5.