JP2013028732A - Sealant film, laminate using the sealant film, packaging container using the laminate, and method for producing the sealant film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-adsorbent sealant film which is molded from a molten mixed resin of an ethylene-vinyl alcohol copolymer and a maleic anhydride-modified polyolefin, a laminate using the sealant film, a packaging container using the laminate, and a method for producing the sealant film.SOLUTION: The sealant film includes 82-90 wt.% of an ethylene-vinyl alcohol copolymer and 10-18 wt.% of a maleic anhydride-modified polyolefin resin, wherein an aspect ratio of a maleic anhydride-modified polyolefin particle dispersed forming island structure in the ethylene-vinyl alcohol copolymer forming sea structure is in the range of 2.0-9.5.

Description

  The present invention relates to a sealant film formed from a melt-mixed resin of an ethylene-vinyl alcohol copolymer and a maleic anhydride-modified polyolefin, a laminate using the sealant film, a packaging container using the laminate, and the above sealant film. It relates to a manufacturing method. More specifically, the present invention relates to a sealant film with little fragrance adsorption.

  A film formed from an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) is excellent in transparency, gas barrier properties, oil resistance, organic solvent resistance, and aroma non-adsorption.

  However, since EVOH film has poor flexibility, impact resistance, and heat sealability, it is generally used as a laminated film in which polyolefin polymer films with flexibility, impact resistance, and heat sealability are laminated. Yes.

  Moreover, in order to improve the softness | flexibility and impact resistance of EVOH film, mix | blending an acid-modified polyolefin polymer with EVOH is proposed (refer patent documents 1-4).

  In addition, in order to improve the physical property of a polyolefin-type polymer film, the mixed resin and film which mix | blended EVOH with the acid modification polyolefin-type polymer are disclosed (patent document 5).

JP-A-55-155042 JP-A-3-68642 JP-A-6-322148 JP-A-7-33925 JP-A-6-136206

  As described above, the EVOH film is used as a laminated film in combination with a flexible and impact resistant film such as a polyolefin polymer film. However, since the EVOH film does not have heat sealability, when this laminated film is used, a packaging container having the EVOH film as the innermost layer cannot be put into practical use.

  Patent Documents 1 to 3 disclose a mixed resin composition in which an acid-modified polyolefin polymer is blended with EVOH or a film formed from a mixed resin composition.

  Patent Document 4 discloses fusion mixing of EVOH and a polyolefin polymer having a functional group introduced only at the end of the polymer in order to prevent resin gelation.

  If the films described in Patent Documents 1 to 4 have heat sealing properties and have excellent EVOH properties, a packaging container having the EVOH properties as the innermost layer is manufactured by heat sealing. It becomes possible. A packaging container having a film having EVOH characteristics and heat sealability as the innermost layer is useful as a packaging container for contents having an aroma component. However, Patent Documents 1 to 4 do not describe anything about the heat sealability of the film and the non-adsorption property of the fragrance. Patent Document 5 also does not describe the heat sealability of the film and the non-adsorption property of the fragrance.

  Patent Documents 1 to 3 describe that resin gelation is likely to occur when EVOH and an acid-modified polyolefin polymer are melt-mixed.

  The inventors of the present invention have investigated the heat sealability and non-adsorbing property of the fragrance of a film obtained by melt-mixing an acid-modified polyolefin polymer with EVOH as a base resin. It has been found that by increasing the blending ratio of the coalesced film, the heat sealability of the film can be improved, but the gelation of the resin is likely to occur and the non-adsorption property of the aroma is also deteriorated.

  The present inventors further studied the heat sealability of a film containing an acid-modified polyolefin polymer using EVOH as a base resin. As a result, the aspect ratio of the acid-modified polyolefin polymer distributed in islands, that is, The inventors have found that by controlling the ratio of the major axis to the minor axis of the island-like particles, the heat sealability of the film is improved, and a film that does not adversely affect the non-adsorbing property of the fragrance can be obtained, thereby completing the present invention. It came to.

  The aspect ratio is basically (1) increasing the MFR (melt flow rate) of the acid-modified polyolefin polymer, (2) increasing the specific energy during melt mixing, and (3) increasing the melt mixing time. Or (4) The higher the winding speed after extrusion into a film shape, the larger the tendency.

  An object of this invention is to provide the sealant film provided with the non-adsorption property of a fragrance.

  The sealant film of the present invention comprises an ethylene-vinyl alcohol copolymer comprising 82 to 90% by weight of an ethylene-vinyl alcohol copolymer and 10 to 18% by weight of a maleic anhydride-modified polyolefin resin and forming a sea structure. The aspect ratio of the maleic anhydride-modified polyolefin particles distributed by forming an island structure is in the range of 2.0 to 9.5.

  The sealant film of the present invention is obtained by melt-mixing 82 to 90% by weight of ethylene-vinyl alcohol copolymer and 10 to 18% by weight of maleic anhydride-modified polyolefin resin with a specific energy of 2.2 MJ / Kg or more. It can be manufactured by forming a film.

  Since the sealant film of the present invention has a non-adsorbing property of a fragrance, an article containing a fragrance component (for example, a pharmaceutical or food containing a volatile component such as menthol, limonene, methyl salicylate, camphor, tocopherol, or the like, or It is very convenient as a packaging container or a tube container for wasabi, mustard, mustard and other foods containing aroma components.

  That is, since the sealant film of the present invention has good heat sealability, it can be used for the innermost layer that enables molding of packaging containers and tube containers, and effectively utilizes the non-adsorbing property of fragrance. be able to. Further, for example, an oxygen barrier film, an intermediate layer or a surface layer can be laminated on one side of the sealant film of the present invention to form a sealant laminate for packaging. When this sealant laminate is used as a packaging container, packaging containers according to various packaging forms can be provided by heat sealing with the sealant film as the innermost layer. The intermediate layer is generally required to have toughness and elasticity of the laminated film, and the surface layer is generally required to have smoothness, light-shielding properties, printability, etc. The layer material may be selected.

  Hereinafter, embodiments of the present invention will be described in detail.

[Embodiment 1]
The present embodiment comprises a resin composition comprising 82 to 90% by weight of EVOH and 10 to 18% by weight of a maleic anhydride-modified polyolefin resin, and is used in an ethylene-vinyl alcohol copolymer forming a sea structure. It is a sealant film in which the aspect ratio of the maleic anhydride-modified polyolefin that forms and distributes the structure is in the range of 2.0 to 9.5.

  EVOH is a saponified ethylene-vinyl ester copolymer, and the content of ethylene units is not particularly limited, but is selected in the range of 10 to 70 mol%, preferably 15 to 60 mol%, and more preferably 20 to 60 mol%. Mole% is preferred, optimally 25-55 mol%. The degree of saponification of the vinyl ester unit of EVOH is selected from the range of 90 to 100 mol%, preferably 95 to 100 mol%, more preferably 99 to 100 mol%. When the degree of saponification is low, crystallization is lowered, gas barrier properties are lowered, and thermal stability at the time of melting may be deteriorated. Therefore, a higher saponification degree is preferable. Here, vinyl acetate is a typical example of the vinyl ester, but also vinyl esters such as vinyl propionate, vinyl pivalate, vinyl valelate, vinyl caprate, vinyl benzoate, and the like. These vinyl esters may be used alone or in combination. EVOH may be used by mixing EVOH having at least one of ethylene content, saponification degree, and polymerization degree. EVOH may contain other copolymerization components as long as the object of the present invention is not impaired.

  The maleic anhydride-modified polyolefin is obtained by grafting maleic anhydride onto an olefin polymer or copolymer. As the olefin polymer or copolymer, polyethylene {low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), high density polyethylene (HDPE)}, ethylene-vinyl acetate copolymer Polymers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid ester (methyl ester or ethyl ester) copolymers, and polypropylene are preferably used.

  The sealant film of this embodiment is formed from 82 to 90% by weight of EVOH and 10 to 18% by weight of maleic anhydride-modified polyolefin resin.

  In general, a film obtained by melt-mixing incompatible resin components and forming a film has a resin component with a high mixing ratio, that is, a base resin is dispersed in a sea state, and a resin component with a low compounding ratio is dispersed in an island shape. It is known to have a structure.

  The film of this embodiment has a structure in which EVOH is in a sea state and an acid-modified polyolefin polymer is dispersed in islands, and the aspect ratio of the acid-modified polyolefin polymer dispersed and distributed in islands is 2 It is in the range of .0 to 9.5. Preferably, it is the range of 2.2 or more and 9.3 or less.

  That is, an acid-modified polyolefin polymer comprising a resin composition containing 82 to 90% by weight of an ethylene-vinyl alcohol copolymer and 10 to 18% by weight of a maleic anhydride-modified polyolefin resin. When the aspect ratio satisfies the condition of 2.0 to 9.5, a film having heat sealability can be obtained. If the aspect ratio is outside this range, the heat sealability of the film is lowered, which is not preferable.

  “Heat sealability” means that the films have an adhesive strength of 1.5 N / 15 mm or more when bonded to each other under the conditions of 130 ° C., 0.2 MPa, and 0.7 seconds. . If it is less than this intensity | strength, the said film cannot fully adhere | attach. The “sealant film” in the present invention means a film having this heat sealability.

  The film of the present embodiment has a non-adsorbing property of fragrance in addition to heat sealability. In the present invention, the non-adsorbing property of fragrance means a property that does not adsorb volatile components such as menthol, limonene, methyl salicylate, camphor, tocopherol, wasabi, mustard, and other fragrant components of food such as mustard. The property which can maintain an internal fragrance component. In the present specification, the non-adsorbing property of a fragrance means that the weight value (mg) of menthol adsorbed by a film exposed for 1 week in menthol vapor is below the measurement limit.

  Since the innermost layer of the packaging container for contents containing an aroma component is in contact with the aroma component, it is important to use a film that does not adsorb the aroma component for the innermost layer. Moreover, when manufacturing a packaging container by bonding innermost layers, it is desirable not to use an adhesive. This is to prevent the adhesive from adsorbing the aromatic component. The sealant film of the present invention having a non-adsorbing property and heat sealing property is a very useful film as a film for the innermost layer.

[Embodiment 2]
The present embodiment is a method for producing the film of the first embodiment.
That is, 82 to 90% by weight of ethylene-vinyl alcohol copolymer and 10 to 18% by weight of maleic anhydride-modified polyolefin resin are melt-mixed at a specific energy of 2.2 MJ / Kg or more, and then formed into a film. This is a featured manufacturing method. Here, the range of specific energy at the time of melt mixing is preferably 2.7 MJ / Kg or more and 12.1 MJ / Kg or less.

  When 82 to 90% by weight of ethylene-vinyl alcohol copolymer and 10 to 18% by weight of maleic anhydride-modified polyolefin resin are melt-mixed at a specific energy of less than 2.2 MJ / Kg, the respective resins are uniformly melted. Not. If the specific energy exceeds 12.5 MJ / Kg, the shear strength is too high, and depending on the type of resin used, it may be decomposed, which is not preferable.

  The melt mixing of EVOH and maleic anhydride-modified polyolefin may be performed by a twin screw or more screw extruder.

  As the screw of the extruder, a screw consisting of a flight screw, a pineapple, and a kneading disk can be used alone or in combination.

  The specific energy refers to the energy given from the melt mixing equipment to the resin per unit weight (1 kg) during melt mixing. The larger the value, the higher the kneading effect. For example, in the case of an extruder, it is approximately represented by the power consumption of a screw driving motor required to extrude 1 kg of resin. Details of the calculation formula will be described later.

  In addition to EVOH and acid-modified polyolefins, additives such as heat stabilizers, weathering stabilizers, lubricants, antistatic agents, nucleating agents, fillers, pigments, dyes, flame retardants, antiblocking agents, etc., that are usually used are included. May be.

  A polymer alloy obtained by melt mixing is formed into a film by a molding machine such as a T-die or inflation. The thickness of the film can be about 10 μm to 100 μm, but 40 μm or more is preferable from the viewpoint of heat seal strength.

[Embodiment 3]
The present embodiment is a sealant laminate in which a layer made of another material, for example, an oxygen barrier film, an intermediate layer, or a surface layer is laminated on one side of the sealant film of the first embodiment. As an oxygen barrier film, an aluminum foil or an aluminum vapor deposition film can be mentioned, for example. This laminate can be used as a packaging material.

[Embodiment 4]
This embodiment is a packaging bag classified from a side seal type, a three-side seal type, and a four-side seal type, or a packaging bag with a spout, an opening zipper, and the like, and a tube type packaging container.

  The packaging bag of the present embodiment may be formed by using the sealant laminated body of the third embodiment, using the sealant film as the innermost layer, forming a packaging bag by heat sealing using a bag making machine, or using a tube forming machine as a tube container.

  As described in the first embodiment, since the sealant film does not adsorb the scent, the scent component adsorption of the contents as the package is held in the container.

  Table 1 shows the production conditions and evaluation results of the sealant films (Examples 1 to 12) and comparative films (Comparative Examples 1 to 9) of the present invention.

  EVOH and maleic anhydride-modified polyolefin are blended in the proportions shown in Table 1, and the specific energy shown in Table 1 is obtained using a L / D = 30 twin screw extruder (lab blast mill, Toyo Seiki Seisakusho Co., Ltd.). And melt mixed in a twin screw extruder.

  EVOH uses Eval F104B and Eval E105B (both made by Kuraray Co., Ltd.), and in Examples 1-9 and 12 and Comparative Examples 1-8, each was used in a mixture of 4: 6. Examples 10 and 11 and Comparative Example 9 used Eval E105B alone.

  Maleic anhydride-modified polyethylene was used as the maleic anhydride-modified polyolefin. The LDPE system in the table is Adtex DL2400 (MFR is 3.0 g / 10 min), the HDPE system is DH4200 (MFR is 0.6 g / 10 min), or the LLDPE system is DU6400 (MFR is 1.7 g / 10 min) ( Each used Nippon Polyethylene Co., Ltd.).

  The melt mixing was carried out using a twin screw extruder (Laboplast Mill, Toyo Seiki Seisakusho Co., Ltd.) equipped with a flight screw, a pineapple, and a kneading disk. L represents the effective length of the screw, and D represents the diameter of the screw.

  The specific energy can be calculated from the following equation.

Here, the torque, the screw rotation speed, and the resin extrusion amount mean the following.
Torque: Force required to rotate the screw of the extruder Screw rotation speed: Screw rotation speed per unit time Resin extrusion amount: Amount of resin extruded from the extruder per unit time

  A polymer alloy obtained by melt mixing was formed into a film with a T-die to produce a sealant film having a thickness of 40 μm. The sealant film had a structure in which EVOH was formed in a sea state and an acid-modified polyolefin polymer having a low blending ratio was dispersed in an island shape.

  About the film obtained by the Example and the comparative example, the aspect-ratio, the heat seal intensity | strength, and the menthol adsorption amount were measured with the following method. The results are shown in Table 1 above.

[aspect ratio]
An atomic force microscope image was analyzed, and an average value of the ratio of the major axis to the minor axis of the maleic anhydride-modified polyolefin particles forming and distributing islands was defined as the aspect ratio. Image analysis was performed by MOUNTECH, an image analysis type particle size distribution measuring software Mac-View ver. Measurement was performed using 4.0. The aspect ratio and area are automatically measured. Calculated as the average value of 100 or more particles in the image. However, particles smaller than 0.2 square micrometers were excluded as noise.

[Heat seal strength]
As a reinforcing film, a biaxially stretched PET film (thickness 25 μm) was dry laminated on the film of each example and each comparative example, and the film surfaces of each example and each comparative example were combined at 130 ° C., 0.2 MPa, Heat sealing was performed under the condition of 0.7 sec. The adhesive strength of 15 mm width of the heat seal part was measured by a T-type peel test based on JIS Z 0238. Those that peeled off with a slight strength during the preparation of a peel test sample were considered to be unmeasurable (ND).

[Menthol adsorption]
The film of each example and each comparative example (100 mm × 100 mm) was exposed to menthol vapor generated at 40 ° C. for one week. Menthol adsorbed on the film was extracted with methyl ethyl ketone, and the amount of adsorption was quantified by gas chromatography. A trace amount (less than 0.05 mg) that could not be quantified was regarded as undetectable (ND).

  From Comparative Examples 1 to 6 and 9, the heat seal strength of the film in which the blending ratio of the maleic anhydride-modified polyolefin is less than 10% by weight or more than 18% by weight is 1.5 N / 15 mm or less, which is said to be a practical level. I understand.

  However, as in Comparative Examples 7 and 8, even when the blending ratio of the maleic anhydride-modified polyolefin is 15% by weight, the heat seal strength may be 0.67 N / 15 mm or less and lower than 1.5 N / 15 mm. there were. It can be seen that the films of Comparative Examples 7 and 8 have a lower aspect ratio of maleic anhydride-modified polyolefin than Examples 1-12.

  From the above, the heat sealability of the sealant film formed from a polymer alloy obtained by melt-mixing EVOH and maleic anhydride-modified polyolefin is as follows: blending ratio of EVOH and maleic anhydride-modified polyolefin and maleic anhydride-modified polyolefin It was found that the aspect ratio of both had an effect.

That is, it can be seen that a sealant film formed from a polymer alloy obtained by melt-mixing EVOH and maleic anhydride-modified polyolefin must satisfy the following conditions.
(1) A resin composition comprising 82 to 90% by weight of an ethylene-vinyl alcohol copolymer and 10 to 18% by weight of a maleic anhydride-modified polyolefin resin.
(2) The aspect ratio of the maleic anhydride-modified polyolefin particles distributed by forming islands in the ethylene-vinyl alcohol copolymer forming the sea structure is in the range of 2.0 to 9.5.

  The aspect ratio of the maleic anhydride-modified polyolefin particles is a ratio given when EVOH and maleic anhydride-modified polyolefin are melt-mixed when the blending amount of the ethylene-vinyl alcohol copolymer and the maleic anhydride-modified polyolefin is within the above range. It can be controlled by energy. Further, the aspect ratio can be controlled by the MFR (melt flow rate) of the maleic anhydride-modified polyolefin resin, the melt mixing time, the winding speed after film extrusion, and the like.

  From Table 1, the resin was melt mixed with a specific energy of 2.2 MJ / Kg or more, preferably 2.7 MJ / Kg or more and 12.1 MJ / Kg or less, and the aspect ratio of the maleic anhydride-modified polyolefin particles of the obtained film It can be seen that heat sealability at a practical level can be obtained by setting the value in a range of 2.0 to 9.5.

  The non-adsorbing property of the aroma tends to be worse when the blending ratio of the acid-modified polyolefin polymer is increased, but in the films of Examples 1 to 12, no menthol absorption was detected (ND). .). That is, the amount of menthol absorbed is comparable to the EVOH single film.

Claims (4)

  An island structure is formed in an ethylene-vinyl alcohol copolymer comprising 82-90% by weight ethylene-vinyl alcohol copolymer and 10-18% by weight maleic anhydride-modified polyolefin resin and forming a sea structure. A sealant film in which the aspect ratio of the distributed maleic anhydride-modified polyolefin particles is in the range of 2.0 to 9.5.   A sealant film laminate in which a layer made of another material is laminated on one side of the sealant film.   A packaging container comprising the sealant film laminate according to claim 2, wherein the sealant film is an innermost layer.   The film is formed after melt-mixing 82-90 wt% ethylene-vinyl alcohol copolymer and 10-18 wt% maleic anhydride-modified polyolefin resin at a specific energy of 2.2 MJ / Kg or more. The manufacturing method of the sealant film of description.