JP2018118512A - Polyester multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film that is an environmentally friendly film using biomass-derived raw materials, where the multilayer film has excellent mechanical physical properties while having high gas barrier properties, and is suitable for soft packaging.SOLUTION: A multilayer film satisfies the following (1) and (2): (1) at least one layer is a polyester resin A layer composed of a polyester resin A having a 2,5-furandicarboxylic acid unit and a 1,4-butanediol unit as main constitutional units; and (2) at least another layer is a polyester resin B layer composed of a polyester resin B having a terephthalic acid unit and a 1,4-butanediol unit as main constitutional units.SELECTED DRAWING: None

Description

  The present invention relates to a multilayer film having a polyester resin composition having a furan structure. Specifically, the polyester resin A layer mainly composed of 2,5-furandicarboxylic acid units and 1,4-butanediol units, and the polyester resin mainly composed of terephthalic acid units and 1,4-butanediol units. It is a multilayer film containing B layer, Comprising: It is related with the multilayer film which has a specific film physical property.

  In recent years, plant-derived polymers using biomass-derived raw materials have been developed and put into practical use as environmentally friendly or environmentally sustainable materials, and the needs are expected to increase in the future.

  As such a polymer, for example, poly (butylene-2,5-furandicarboxylate) (hereinafter referred to as “PBF”) composed of 2,5-furandicarboxylic acid units and 1,4-butanediol units, which are raw materials derived from biomass. In other words, Patent Documents 1 and 2 describe examples of films using the polymer.

JP 2012-229395 A Japanese Patent No. 05233390

Many uses are assumed as a film using such a polymer. Therefore, the present inventor tried to use the polymer for a soft packaging material. However, as a result of investigation by the present inventor, the performance of the PBF described in Patent Documents 1 and 2 is insufficient for using the soft packaging material alone. It turned out to be sufficient. More specifically, “soft packaging material” means a material for soft packaging, and soft packaging means a flexible packaging, and the shape of the packaging is formed by putting contents such as food. It is thought that gas barrier properties and mechanical properties are required because of such packaging, but when PBF described in Patent Documents 1 and 2 is used alone as a soft packaging material film, gas barrier performance is obtained, but mechanical properties are obtained. It was found that the physical properties are insufficient and there is a concern that pinholes are likely to occur.
In view of the above problems, the present invention is an environmentally friendly film using biomass-derived raw materials, and has a multilayer film suitable for flexible packaging applications, having high gas barrier properties and excellent mechanical properties. The purpose is to provide.

    As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by adjusting the layer structure of the film, and have completed the present invention.

That is, this invention makes the following a summary.
[1] A multilayer film characterized by satisfying the following (1) and (2).
(1) At least one layer is a polyester resin A layer comprising a polyester resin A mainly composed of 2,5-furandicarboxylic acid units and 1,4-butanediol units. (2) At least one other layer , A polyester resin B layer comprising a polyester resin B having terephthalic acid units and 1,4-butanediol units as main structural units.
[2] The multilayer film according to [1], wherein the thickness ratio of the polyester resin A layer is 10 to 90% with respect to the thickness of the entire multilayer film.
[3] The multilayer film according to [1] or [2], wherein the thickness of the entire multilayer film is 5 to 1000 μm.
[4] The multilayer film according to any one of [1] to [3], further satisfying the following (3).
(3) The polyester resin A layer and the polyester resin B layer are directly laminated.
[5] The multilayer film according to any one of [1] to [3], wherein the multilayer film has a nominal tensile fracture strain of 100% or more.
[6] The multilayer film according to any one of [1] to [5], which is a multilayer film for soft packaging materials.

It is possible to provide a multilayer film suitable for flexible packaging applications having excellent mechanical properties while having high gas barrier properties.
Furthermore, since the adhesiveness between the polyester resin A layer and the polyester resin B layer is excellent, an adhesive layer is not required between the polyester resin A layer and the polyester resin B layer, so that a smaller layer configuration can be realized.

  Below, the typical aspect for implementing this invention is demonstrated concretely, However, This invention is not limited to the following aspects, unless the summary is exceeded.

  The multilayer film of the present invention includes a polyester resin A layer and a polyester resin B layer.

[Polyester resin A layer]
The polyester resin A layer of the present invention comprises a polyester resin A mainly composed of 2,5-furandicarboxylic acid units and 1,4-butanediol units. Specific examples include poly (butylene-2,5-furandicarboxylate) (hereinafter sometimes referred to as “PBF”).
The polyester resin A layer has functions of gas barrier properties and stretchability (when stretched).

  Here, the “unit” means a structural unit derived from the monomer component used in the production of the polyester resin A and contained in the polyester resin A, and includes “2,5-furandicarboxylic acid unit, 1 “, 4-butanediol unit as the main structural unit” means that the total of 2,5-furandicarboxylic acid unit and 1,4-butanediol unit is 50 mol% or more in the total structural unit of polyester resin A. Means that. Among these, from the viewpoint of heat resistance, it is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 95 mol% or more.

<2,5-furandicarboxylic acid unit>
The dicarboxylic acid unit constituting the polyester resin A of the present invention includes a 2,5-furandicarboxylic acid unit. When used in the production of the polyester resin A, 2,5-furandicarboxylic acid and derivatives thereof can be used. Examples of 2,5-furandicarboxylic acid derivatives include alkyl esters having 1 to 4 carbon atoms in the alkyl group. Among them, methyl esters, ethyl esters, n-propyl esters, isopropyl esters, butyl esters, and the like are preferable, and more preferable. Is a methyl ester.
The proportion of the 2,5-furandicarboxylic acid unit in the dicarboxylic acid unit constituting the polyester resin A of the present invention is not particularly limited, but is preferably 50 mol% or more, more preferably 60 mol% or more, Preferably it is 70 mol% or more, Most preferably, it is 80 mol% or more. Moreover, there is no upper limit in particular and 100 mol% may be sufficient. By being in these ranges, the crystallinity of the polyester resin A is maintained, and heat resistance tends to be obtained.

<Other dicarboxylic acid units>
In the polyester resin A of the present invention, dicarboxylic acid units other than 2,5-furandicarboxylic acid units may be copolymerized. Preferably, the other dicarboxylic acid units in all the dicarboxylic acid units constituting the polyester resin A are 10 mol% or less, and more preferably 5 mol% or less. Moreover, Preferably it is 0.1 mol% or more. By being in these ranges, the melting point can be slightly lowered without impairing the crystallinity. Thereby, the polymerization temperature and the processing temperature can be set to a low value, and it tends to be possible to suppress the decomposition reaction and the molecular weight decrease during melting.
Examples of the copolymerizable dicarboxylic acid unit include aromatic dicarboxylic acid compounds, aliphatic (including alicyclic) dicarboxylic acids, and derivatives obtained by esterifying these.

<1,4-butanediol unit>
The diol unit constituting the polyester resin A of the present invention includes a 1,4-butanediol unit. When used for the production of the polyester resin A, 1,4-butanediol is mainly used.

<Other diol units>
In the polyester resin A of the present invention, a small amount of diol units other than 1,4-butanediol may be copolymerized. The proportion of diol units other than 1,4-butanediol in all diol units constituting the polyester resin A is 10 mol% or less, more preferably 5 mol% or less. Moreover, Preferably it is 0.1 mol% or more.

<Other ingredients>
The polyester resin A of the present invention may contain a small amount of a copolymer component as described below in addition to the above. In that case, it is 10 mol% or less in all the structural units of the polyester resin A, Preferably it is 5 mol% or less. By being below the upper limit, the crystallinity of the polyester resin A is maintained and heat resistance tends to be obtained. Examples of the small amount of the copolymer component include aromatic dihydroxy compounds, bisphenols, hydroxycarboxylic acids, diamines, and derivatives thereof.

In the polyester resin A of the present invention, a unit containing a trifunctional or higher functional group may be introduced as another copolymer component other than the above-described copolymer components.
As a compound constituting a structural unit having a functional group having 3 or more functional groups, a polyhydric alcohol having 3 or more functions; a polyvalent carboxylic acid having 3 or more functions or an anhydride, an acid chloride, or an ester thereof; Examples thereof include at least one trifunctional or higher polyfunctional compound selected from the group consisting of hydroxycarboxylic acid or anhydride, acid chloride, or ester thereof; trifunctional or higher amines.

  Specific examples of the trifunctional or higher polyhydric alcohol and the trifunctional or higher polycarboxylic acid include glycerin, trimethylolpropane, pentaerythritol; malic acid, tartaric acid, and citric acid.

<Chain extender, end-capping agent>
In the production of the polyester resin A of the present invention, a chain extender such as diisocyanate, diphenyl carbonate, dioxazoline, or silicate ester may be used. In particular, when carbonate compounds such as diphenyl carbonate are used, polyester carbonates may be obtained by adding these carbonate compounds to 20 mol% or less, preferably 10 mol% or less, with respect to all components of polyester resin A. preferable.

  In the present invention, the polyester terminal group of the polyester resin A may be sealed with carbodiimide, an epoxy compound, a monofunctional alcohol or carboxylic acid.

<Physical properties of polyester resin A>
The polyester resin A of the present invention preferably has a reduced viscosity (ηred = ηsp / c; ηsp is a specific viscosity and c is a polymer concentration) of 0.8 dl / g or more. By setting it as this numerical range, the softness | flexibility requested | required of a soft packaging material becomes easy to be obtained. Here, the reduced viscosity is determined from the solution viscosity measured at 30 ° C. with a polyester resin concentration of 0.5 g / dl in phenol / tetrachloroethane (1: 1 weight ratio).

  The polyester resin A of the present invention preferably has a terminal acid value of 100 μeq / g or less. By making it into this numerical range, it becomes easy to prevent a decrease in thermal stability.

Here, the terminal acid value is measured by neutralization titration. Specifically, after pulverizing the sample, the sample was dried at 140 ° C. for 15 minutes in a hot air dryer, cooled to room temperature in a desiccator, 0.1 g was accurately weighed and collected in a test tube, and benzyl alcohol was collected. Add 3 ml and dissolve in 195 ° C. for 3 minutes while blowing dry nitrogen gas, then slowly add 5 ml of chloroform and cool to room temperature. Add 1 to 2 drops of phenol red indicator to this solution, and titrate with a 0.1N sodium hydroxide benzyl alcohol solution with stirring while blowing dry nitrogen gas, and finish when the color changes from yellow to red. Moreover, the same operation is implemented as a blank, without dissolving a sample, and a terminal acid value is computed by the following formula | equation (2).
Terminal acid value (μeq / g) = (ab) × 0.1 × f / w (2)
(Where a is the amount of 0.1N sodium hydroxide in benzyl alcohol solution required for titration of the sample (μl), b is 0.1N sodium hydroxide benzyl alcohol required for titration with a blank) The amount of solution (μl), w is the amount of polyester resin sample (g), and f is the titer of 0.1N sodium hydroxide in benzyl alcohol.)

The titer (f) of a benzyl alcohol solution of 0.1N sodium hydroxide is determined by the following method. That is, 5 ml of methanol was collected in a test tube, and 1-2 drops of phenol red ethanol solution was added as an indicator. Titrate with 0.4 ml of 1N sodium hydroxide in benzyl alcohol to the color change point, then add 0.2 ml of 0.1N aqueous hydrochloric acid solution with known titer as a standard solution, and add 0.1N hydroxide again. Titrate to the discoloration point with sodium benzyl alcohol solution (the above operation is performed under dry nitrogen gas blowing). The titer (f) is calculated by the following equation (3).
Titer (f) = Titer of 0.1N aqueous hydrochloric acid × Amount of collected 0.1N aqueous hydrochloric acid (μl) / Titration of 0.1N sodium hydroxide in benzyl alcohol (μl) (3)

[How to obtain polyester resin A]
As a method for obtaining the polyester resin A of the present invention, a known method relating to the production of a general polyester resin can be employed. For example, the description in Japanese Patent No. 5233390 can be referred to.

[Polyester resin B layer]
The polyester resin B layer of the present invention comprises a polyester resin B having terephthalic acid units and 1,4-butanediol units as main structural units. Specific examples include PBT resins or copolymer polyester resins having terephthalic acid, 1,4-butanediol, and polytetramethylene ether glycol as structural units.
The polyester resin B layer has functions of flexibility and aroma retention.

  The meaning of the term “unit” is the same as that defined in the polyester resin A, and “the terephthalic acid unit and the 1,4-butanediol unit are the main constituent units” means terephthalic acid. It means that the total of the unit and 1,4-butanediol unit is contained in 50 mol% or more in all the structural units of the polyester resin B. Among these, from the viewpoint of crystallinity, it is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 95 mol% or more. A preferable ratio of these units to all units constituting the polyester resin B is the same as the range described in the polyester resin A.

  The dicarboxylic acid unit constituting the polyester resin B of the present invention includes a terephthalic acid unit. When used in the production of the polyester resin B, terephthalic acid and derivatives thereof are mainly used, and examples of the terephthalic acid derivative include alkyl esters having 1 to 4 carbon atoms in an alkyl group, among which methyl esters, Ethyl ester, n-propyl ester, isopropyl ester, butyl ester and the like are preferable, and methyl ester is more preferable.

  The ratio of the terephthalic acid units to the total dicarboxylic acid units constituting the polyester resin B of the present invention is not particularly limited, but is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol%. It is above, Especially preferably, it is 80 mol% or more. Moreover, there is no upper limit in particular and 100 mol% may be sufficient. By being in these ranges, the crystallinity of the polyester resin B is improved, and heat resistance and good moldability tend to be obtained. The dicarboxylic acid unit other than terephthalic acid constituting the polyester resin B is not particularly limited, and examples thereof include other dicarboxylic acid units other than the 2,5-furandicarboxylic acid unit described for the polyester resin A. The ratio of the other dicarboxylic acid units to the total dicarboxylic acid units constituting the polyester resin B is not particularly limited, and a preferred range is as described in the polyester resin A.

  Further, the diol unit constituting the polyester resin B of the present invention includes a 1,4-butanediol unit, and may further include a polytetramethylene ether glycol unit. When used for the production of the polyester resin B, 1,4-butanediol, or polytetramethylene ether glycol and derivatives thereof are mainly used, and these derivatives have an alkyl group having 1 to 4 carbon atoms. Examples include alkyl esters, among which methyl ester, ethyl ester, n-propyl ester, isopropyl ester, butyl ester and the like are preferable, and methyl ester is more preferable. The ratio of 1,4-butanediol units to all diol units constituting the polyester resin B is preferably 50 mol% or more, more preferably 60 mol% or more, for heat resistance. It is especially preferable that it is 70 or more.

  Further, when the polyester resin B includes a polytetramethylene ether glycol unit as a structural unit, the ratio of the polytetramethylene ether glycol to the total diol constituting the polyester resin B is 1 mol% or more for imparting flexibility. Preferably, it is 3 mol% or more, more preferably 5 mol% or more, and in order to maintain heat resistance, it is preferably 50 mol% or less, and 40 mol% % Or less is more preferable, and 30 mol% or less is particularly preferable.

  The polyester resin B may contain other diol units in addition to 1,4-butanediol and polytetramethylene ether glycol units. The other diol unit is not particularly limited, and other diol units mentioned in the above-described polyester resin A can be used.

  Further, the polyester resin B of the present invention may contain a small amount of a copolymer component other than the above, like the polyester resin A of the present invention. Moreover, you may introduce | transduce the unit containing a trifunctional or more functional group as other copolymerization components other than the above-mentioned copolymerization component.

  Furthermore, in the production of the polyester resin B of the present invention, a chain extender or a terminal blocking agent may be used in the same manner as described in the production of the polyester resin A of the present invention.

<Physical properties of polyester resin B>
The polyester resin B of the present invention preferably has an intrinsic viscosity in the range of 0.6 to 2.0 (dl / g). When it is at least the above lower limit value, flexibility as a soft packaging material is easily obtained, and when it is at least the above upper limit value, the film forming property at the time of extrusion tends to be good. Here, the intrinsic viscosity is measured at a temperature of 30 ° C. using a mixed solvent of 1,1,2,2-tetrachloroethane / phenol = 1/1 (weight ratio).

  The polyester resin B of the present invention preferably has a terminal acid value of 60 μeq / g or less. By being in this numerical range, it becomes easy to prevent the thermal stability from being lowered.

Here, the terminal acid value is measured by neutralization titration in the same manner as described for the polyester resin A. Specifically, after pulverizing the sample, the sample was dried at 140 ° C. for 15 minutes in a hot air dryer, cooled to room temperature in a desiccator, 0.1 g was accurately weighed and collected in a test tube, and benzyl alcohol was collected. Add 3 ml and dissolve in 195 ° C. for 3 minutes while blowing dry nitrogen gas, then slowly add 5 ml of chloroform and cool to room temperature. Add 1 to 2 drops of phenol red indicator to this solution, and titrate with a 0.1N sodium hydroxide benzyl alcohol solution with stirring while blowing dry nitrogen gas, and finish when the color changes from yellow to red. Moreover, the same operation is implemented as a blank, without dissolving a sample, and a terminal acid value is computed by the following formula | equation (2).
Terminal acid value (μeq / g) = (ab) × 0.1 × f / w (2)
(Where a is the amount of 0.1N sodium hydroxide in benzyl alcohol solution required for titration of the sample (μl), b is 0.1N sodium hydroxide benzyl alcohol required for titration with a blank) The amount of solution (μl), w is the amount of polyester resin sample (g), and f is the titer of 0.1N sodium hydroxide in benzyl alcohol.)

The titer (f) of a benzyl alcohol solution of 0.1N sodium hydroxide is determined by the following method. That is, 5 ml of methanol was collected in a test tube, and 1-2 drops of phenol red ethanol solution was added as an indicator. Titrate with 0.4 ml of 1N sodium hydroxide in benzyl alcohol to the color change point, then add 0.2 ml of 0.1N aqueous hydrochloric acid solution with known titer as a standard solution, and add 0.1N hydroxide again. Titrate to the discoloration point with sodium benzyl alcohol solution (the above operation is performed under dry nitrogen gas blowing). The titer (f) is calculated by the following equation (3).
Titer (f) = Titer of 0.1N aqueous hydrochloric acid × Amount of collected 0.1N aqueous hydrochloric acid (μl) / Titration of 0.1N sodium hydroxide in benzyl alcohol (μl) (3)

[How to obtain polyester resin B]
As a method for obtaining the polyester resin B of the present invention, a known method relating to the production of a general polyester resin can be employed. For example, the description of JP-A-2004-137455 can be referred to.
Alternatively, as another acquisition method, a commercially available PBT resin can be used. For example, NOVADURAN 5020 (homopolybutylene terephthalate resin, intrinsic viscosity 1.20 dl / g) manufactured by Mitsubishi Engineering Plastics Co., Ltd. or Juranex 500FP (homopolybutylene terephthalate resin, intrinsic viscosity 0.875 dl / g) manufactured by Wintech Polymer Co. g) and the like.
Examples of commercially available polybutylene terephthalate copolymers include NOVADURAN 5505S (inherent viscosity 1.15 dl / g) manufactured by Mitsubishi Engineering Plastics.

<Polyester resin composition>
In the polyester resin A and the polyester resin B of the present invention, various additives such as a heat stabilizer, an antioxidant, a hydrolysis inhibitor, a crystal nucleating agent, and a crystallization retarder are provided as long as the characteristics are not impaired. In addition, flame retardants, antistatic agents, release agents, lubricants, ultraviolet absorbers, colorants such as dyes and pigments, and the like may be added. Moreover, you may mix | blend another thermoplastic resin.

<Multilayer film>
The multilayer film of the present invention includes a polyester resin A layer and a polyester resin B layer, and the film may or may not be stretched.
In the case of a stretched film, the stretched film can be obtained by uniaxially or biaxially stretching according to a known method. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. As described above, the polyester resin A layer has a function of gas barrier property and stretchability (when stretched), and the polyester resin B layer has a function of flexibility and aroma retaining property. Without requiring a layer, it is possible to obtain a multilayer film having an extremely excellent balance between gas barrier properties and tensile properties.

<Physical properties of multilayer film>
In addition, the multilayer film of the present invention greatly reduces the gas barrier property as compared with a film made of a polyester resin having 2,5-furandicarboxylic acid units and 1,4-butanediol units as main constituent units. And high tensile properties. In general, even if a resin layer and a multilayer film having high tensile properties are formed, if the compatibility between the resins is poor and the adhesion is insufficient, the physical properties are sufficient such as peeling during the tensile property test. Cannot be obtained. The reason why the multilayer film of the present invention has high tensile properties without significantly reducing gas barrier properties is that the polyester resin B layer having high tensile properties has good compatibility with the polyester resin A layer, This is considered to be because a stable multilayer film could be formed while showing good adhesion.

  The oxygen permeability of the multilayer film of the present invention is preferably 350 cc / m 2 · 24 h · atm or less, more preferably 300 cc / m 2 · 24 h · atm or less, and 250 cc / m 2 · 24 h when converted to a thickness of 20 μm. It is more preferably atm or less, particularly preferably 150 cc / m 2 · 24 h · atm or less. When the oxygen permeability of the multilayer film is less than or equal to the above upper limit value, appropriate gas barrier properties can be expected, and since the gas barrier properties and fragrance retention properties are excellent, it can be used appropriately for flexible packaging applications.

  The multilayer film of the present invention preferably has a “tensile fracture nominal strain” of 100% or more. In the case of a stretched film, it means a value measured after stretching, and in the case of an unstretched film, it means a value measured with a non-stretched film. Especially, it is more preferably 110% or more, particularly preferably 120% or more. If it is above the above value, the packaging is flexible and the pinhole is difficult to open, and it is difficult to break, so it can be used appropriately as a flexible packaging application.

Tensile fracture nominal strain can be controlled by appropriately adjusting the thickness ratio of the polyester resin A layer and the polyester resin B layer and the molecular weight of each polyester resin. As the polyester resin B layer is thicker and / or the molecular weight of each polyester resin is larger, the tensile fracture nominal strain tends to increase.
Here, the tensile fracture nominal strain is measured by performing a tensile test according to JIS K-7127.

  Further, the “tensile strength” of the multilayer film of the present invention is preferably 57 MPa or more, and more preferably 60 MPa or more. When the tensile strength of the multilayer film is not less than the above lower limit value, the strength as a packaging material is increased, and it is easy to use it as a flexible packaging application. In addition, the measuring method of the tensile strength of a multilayer film can be measured with the below-mentioned method.

  Moreover, although the whole thickness of the multilayer film of the present invention is arbitrary, it is preferably in the range of 5 to 1000 μm because it is a multilayer film excellent in balance between flexibility and mechanical strength, and in particular, 20 to It is preferable that it is 500 micrometers.

  As thickness of the polyester resin A layer which is gas barrier resin, it is preferable that it is 2.5-500 micrometers, and it is especially preferable that it is 10-250 micrometers.

  Moreover, as thickness of the polyester resin B layer, it is preferable that it is 2.5-500 micrometers, and it is especially preferable that it is 10-250 micrometers.

  Moreover, it is preferable that the thickness ratio of the polyester resin A layer to the thickness of the whole multilayer film is 10 to 90%. More preferably, the lower limit is 20%, more preferably 30%. It becomes easy to obtain favorable gas barrier property by setting it as the said lower limit or more. A more preferred upper limit is 70%, and even more preferably 60%. If it is below the said upper limit, it will become easy to acquire favorable softness | flexibility and it can prevent that a pinhole generate | occur | produces.

  The total thickness of the film is measured with a commercially available micrometer. On the other hand, each thickness of the polyester resin A layer and the polyester resin B layer can be obtained by observation with a transmission electron microscope (TEM) for a sample obtained by cutting a film cross section using a microtome. The thickness control of the polyester resin A layer and the polyester resin B layer is not particularly limited, but can be performed by controlling the discharge amount of each cylinder during film formation.

  Moreover, in the multilayer film of this invention, when laminating | stacking a polyester resin A layer (gas barrier layer) and a polyester resin B layer, it becomes possible to laminate | stack directly without interposing an adhesive layer between them.

<Method for producing multilayer film>
As a method for producing the multilayer film of the present invention, any method can be used as long as the multilayer film can be produced. For example,
(I) a coextrusion cast molding method in which each resin or resin composition is coextruded to obtain a multilayer film;
(Ii) a coextrusion laminate molding method in which an adhesive resin and / or polyester resin B is melt-extruded and laminated on a film constituting a layer made of polyester resin A,
(Iii) A film made of polyester resin B and a polyester using a tandem laminate molding method in which an adhesive resin and polyester resin B are sequentially melt-extruded and laminated to a film constituting a layer made of polyester resin A, and an anchor coating agent. For example, a method of dry laminating a film constituting a layer made of the resin A can be used.

  Among the above molding methods, the coextrusion cast molding method is particularly preferable because of excellent interlayer adhesion, fewer steps, and high productivity. Moreover, what added the uniaxial or biaxial stretching by the arbitrary ratios as needed may be sufficient as a film.

<Use of multilayer film>
The multilayer film of the present invention is useful for flexible packaging materials because it has excellent gas barrier properties and good mechanical properties. And since the multilayer film of the present invention is considered to be excellent in heat sealability, fragrance retention, and heat resistance against retort treatment, for example, kimchi, takuan and the like as foods that require fragrance retention and gas barrier properties. Pickles; considered suitable for packaging bags for long-term preservation of foods such as curry, stew, and dumplings, and packaging bags used for retort cooking.

  Furthermore, it is suitable for treatment bags for medical waste such as industrial waste and filth with strong odor besides food. In addition, when setting it as a packaging bag, it can obtain easily by arrange | positioning the polyester resin B layer in the outer layer of a multilayer film, and binding the polyester resin B layer surface with a heat seal.

Further, as a more preferable embodiment of the present invention, since the adhesiveness between the polyester resin A layer and the polyester resin B layer is excellent, an adhesive layer is unnecessary between the polyester resin A layer and the polyester resin B layer, and therefore, fewer layers. A configuration can be realized.
Specifically, it can be produced not by a special multilayer film molding machine having 5 or more layers but by a more general multilayer film molding machine. For example, a conventional five-layer structure of LLDPE / adhesive layer / EVOH / adhesive layer / PBT can be made into a four-layer structure of LLDPE / adhesive layer / polyester resin A layer / polyester resin B layer according to the present invention. Here, LLDPE provides heat sealing properties, EVOH and PBF provide gas barrier properties, and PBT provides strength.
(Note: LLDPE = a kind of polyethylene. Copolymer of ethylene and α-olefin. EVOH = copolymer of ethylene and vinyl alcohol)

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

<Raw material>
[resin]
Resin 1: Prepared as follows.
In a reaction vessel equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, and a pressure reducing port, as raw materials, 56.07 parts by weight of dimethyl 2,5-furandicarboxylate, 42.51 parts by weight of 1,4-butanediol , And 1.42 parts by weight of a 1,4-butanediol solution in which tetraisopropyl orthotitanate was dissolved in advance by 2% by weight.
Nitrogen gas was introduced into the container while stirring the contents of the container, and the inside of the system was changed to a nitrogen atmosphere by vacuum replacement. Next, the reaction vessel was immersed in an oil bath at 160 ° C. and reacted for 3 hours while stirring the system. Next, the temperature was raised to 240 ° C. over 2 hours, and then the pressure was gradually reduced to 180 Pa or less over 1 hour 30 minutes 30 minutes after the start of temperature raising. Furthermore, polymerization was continued for 1 hour while maintaining the heated and reduced pressure state at this temperature, and then the polymerization was terminated to obtain a polyester resin (furandicarboxylic acid / 1,4-butanediol polyester). The polyester resin obtained had a reduced viscosity of 1.3 dl / g and a terminal acid value of 86 μeq / g.

Resin 2: Copolyester resin of terephthalic acid, 1,4-butanediol and polytetramethylene glycol (PTMG); NOVADURAN 5505S (inherent viscosity 1.15 dl / g) manufactured by Mitsubishi Engineering Plastics Co., Ltd. Using.
Resin 3: Polyamide MXD6; a commercially available resin, Reny S6001, manufactured by Mitsubishi Gas Chemical Company, Inc. was used.

[Evaluation method]
Various evaluations were performed by the following methods.
(1) Oxygen permeability measurement The oxygen permeability measurement was performed as follows based on JIS K7162-2.
Apparatus: OX-TRAN 2/21 (manufactured by MOCON)
Temperature: 23 ° C
Humidity: 50% RH
Transmission area: 50 cm ²
The smaller the oxygen permeability, the better the gas barrier property. Since the oxygen permeability is inversely proportional to the film thickness, Table 1 showing the results shows a numerical value converted to a conventionally used 20 μm thickness.

(2) Measurement of tensile properties (tensile strength and nominal strain at break)
Tensile properties were measured as follows based on JIS K7127.
Apparatus: Precision universal testing machine Autograph AGS-H100N (manufactured by Shimadzu Corporation)
Tensile speed: 100 mm / min
Sample: A sample was punched into a dumbbell shape.

(3) Adhesive evaluation After putting a commercially available cloth gum tape on the surface and the back surface of a multilayer film, it peeled off and evaluated adhesiveness. The cloth gum tape used is a packaging cloth tape (0.2 mm thickness, 50 mm × 25 m roll) manufactured by Teraoka Seisakusho.

[Example 1]
Using dry resin 1 and resin 2, T-die type film forming machine (manufactured by Tokyu Seimitsu Kogyo Co., Ltd.) with take-out rolls, with extruder diameters of φ20mm and φ30mm and one T-die installed at the tip of both extruders Film formation was performed to obtain an unstretched multilayer film in which resin 1 and resin 2 were directly laminated.
Next, various conditions are shown. The resin was dried with a hot air dryer at 100 ° C. for 8 hours. Resin 1 is put into a hopper on the φ20 mm side, and resin 2 is put on a hopper on the φ30 mm side, and the resin temperature is 245 ° C. The film take-up speed was adjusted to 6.3 m / min, the roll temperature was adjusted to 20 ° C., and the total film thickness was adjusted to 90 μm. Moreover, the rotation speed of each extruder was adjusted so that the layer thickness ratio of the resin 1 and the resin 2 might be set to 1: 1.

  The obtained film was cut out to obtain a sample for measuring oxygen permeability. The obtained film was punched out to obtain a sample for measuring tensile physical properties. Each sample was used for oxygen permeability measurement, tensile property measurement, and adhesion evaluation. Various evaluation results are shown in Table 1.

[Example 2]
An unstretched film was obtained in the same manner as in Example 1 except that the number of revolutions of each extruder was adjusted so that the layer thickness ratio of the resin 1 and the resin 2 was 1: 2. Subsequent sample acquisition and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
An unstretched monolayer film of resin 1 monolayer was obtained in the same manner as in Example 1 except that the dried resin 1 was put into the hoppers of two extruders. The film thickness was 100 μm. Subsequent sample acquisition and various evaluations other than adhesion were performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
An unstretched monolayer film of resin 2 monolayer was obtained in the same manner as in Example 1 except that the dried resin 2 was charged into the hoppers of two extruders. The film thickness was 80 μm. Subsequent sample acquisition and various evaluations other than adhesion were performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
An unstretched monolayer film of resin 3 single layer was obtained in the same manner as in Example 1 except that the dried resin 3 was put into the hoppers of two extruders. The film thickness was 100 μm. Subsequent sample acquisition and various evaluations other than adhesion were performed in the same manner as in Example 1. The results are shown in Table 1.

  By contrast with an Example and a comparative example, the multilayer film of this invention which concerns on Example 1 and 2 with respect to the film comprised only from the polyester resin 1 of the comparative example 1 is although oxygen permeability has fallen. , Each of which is 150 or less, and it can be seen that it has sufficient gas barrier properties for soft packaging materials. Surprisingly, the multilayer film of the present invention according to Examples 1 and 2 can improve the tensile properties without depending on the tensile properties of the polyester resin 1 by using the layer made of the polyester resin 2 together. I understand that. Therefore, it turns out that the multilayer film of this invention is a film with few pinholes and tears, and is suitable as a film for soft packaging materials in addition to said gas barrier property. Further, since the adhesiveness between the polyester resin A layer and the polyester resin B layer is excellent, an adhesive layer is not required between the polyester resin A layer and the polyester resin B layer, so that a smaller layer configuration can be realized.

  The multilayer film of the present invention is suitable for soft packaging applications. Specific applications of flexible packaging include packaging applications such as vegetables, fruits, fish, meat, prepared dishes, retort foods, sweets, seasonings, detergents, and shampoos.

Claims (6)

The multilayer film characterized by satisfying the following (1) and (2).
(1) At least one layer is a polyester resin A layer comprising a polyester resin A mainly composed of 2,5-furandicarboxylic acid units and 1,4-butanediol units. (2) At least one other layer , A polyester resin B layer comprising a polyester resin B having terephthalic acid units and 1,4-butanediol units as main structural units.   The multilayer film of Claim 1 whose thickness ratio of the polyester resin A layer is 10 to 90% with respect to the thickness of the whole multilayer film.   The multilayer film of Claim 1 or 2 whose thickness of the whole multilayer film is 5-1000 micrometers. The multilayer film according to any one of claims 1 to 3, further satisfying the following (3).
(3) The polyester resin A layer and the polyester resin B layer are directly laminated.   The multilayer film according to any one of claims 1 to 3, wherein the multilayer film has a tensile fracture nominal strain of 100% or more.   The multilayer film according to any one of claims 1 to 5, which is a multilayer film for a soft packaging material.