JP2007290144A - Gas barrier laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent gas barrier laminated film having flexibility, excellent in oxygen barrier properties, steam barrier properties and also excellent in water resistance, heat resistance and hot water resistance. <P>SOLUTION: This gas barrier laminate obtained by providing a film comprises a composite, which is composed of at least one metal alkoxide or its hydrolysate (A) and a water soluble resin (ethylene/vinyl alcohol copolymer) (B), on a plastic base material comprising a polymeric resin composition and shows high gas barrier properties, has flexibility, water resistance, heat resistance and hot water resistance and is not deteriorated in its barrier properties by boiling treatment and retorting treatment under a high temperature and pressure condition. Further, the laminate shows excellent gas barrier properties by adding an inorganic layer like mineral to the water soluble resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In recent years, packaging materials used for the packaging of foods, non-foods, pharmaceuticals, etc. have been modified to maintain the taste and freshness by suppressing the alteration of the contents, especially the oxidation and alteration of proteins and oils and fats in foods. In the case of pharmaceutical products that require handling in the state, it is necessary to prevent the influence of oxygen, water vapor, and other gases that alter the contents of the packaging material in order to suppress the alteration of the active ingredient and maintain its efficacy. There is a need for a packaging material having a gas barrier property that blocks these gases.

Conventionally, those having ordinary gas barrier levels are relatively excellent in gas barrier properties among polymers, such as polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), polyacrylonitrile. Resin films such as (PAN) or polymer gas barrier films such as plastic films laminated or coated with these resins have been mainly used. However, these films are highly dependent on temperature and humidity, and can be used at high or high temperatures. Deterioration of the gas barrier property is observed under humidity, and depending on the packaging application, the gas barrier property may be significantly lowered when a boil treatment or a retort treatment under high temperature and high pressure is performed. In addition, a gas barrier laminate using a PVDC polymer resin composition has a low humidity dependency but a high gas barrier material (high gas barrier material) having an oxygen barrier property of 1 cm ³ / m ² · day · atm or less. ) Has a problem that it is difficult to achieve, and it cannot be used particularly for those requiring high moisture resistance and high gas barrier properties.

  In addition, PVDC, PAN, and the like have a risk of generation of harmful substances during disposal / incineration, and there are problems in waste disposal such as incineration and recycling. Therefore, for materials that have high moisture resistance and require high gas barrier properties, a packaging material using a metal foil made of a metal such as aluminum as a gas barrier layer has to be used. However, metal foil and metal vapor-deposited film are excellent in gas barrier properties, but problems such as identification of contents by seeing through packaging materials and the inability to use a metal detector for inspection, and non-combustible materials when discarded after use There are problems such as having to be treated as.

  Therefore, a barrier in which a metal or a metal compound such as aluminum (Al) is provided on a plastic film made of a polymer resin composition by a vacuum process such as a vacuum deposition method, a sputtering method, or a plasma vapor deposition method (CVD method). The material was developed. Examples of the metal to be deposited include aluminum oxide (AlOx), silicon oxide (SiOx) such as silicon monoxide (SiO), magnesium oxide (MgO), and the like. These have gas barrier properties superior to those of a gas barrier material made of a polymer resin composition, are less likely to deteriorate under high humidity, and packaging films using this packaging material are starting to become popular.

  However, the thin film of inorganic compound used for the gas barrier layer lacks flexibility, is weak against stagnation and bending, and has poor adhesion to the base material. When the packaging material is post-processed, there is a problem that the thin film is cracked and the gas barrier property is remarkably lowered. Moreover, the hot water resistance of a transparent vapor deposition film is low, and a barrier property cannot be maintained by boil processing or retort processing.

  Therefore, development of a gas barrier laminate in which the gas barrier property is prevented from lowering as a protective film on the deposited layer has been developed, but the effect is merely a role as a protective layer of the deposited thin film.

Currently, the development of flexible composite coatings is actively underway, but it is transparent enough to allow direct identification of the contents, metal detectors can be used, and environmental adaptability can be improved. Excellent packaging material that shuts off oxygen, water vapor, etc. that have an effect on the contents, and has a high gas barrier property, particularly an oxygen gas barrier property of 1 cm ³ / m ² · day · atm or less. No high gas barrier packaging material has been found so far that does not cause peeling or deterioration of gas barrier properties, and does not have humidity deterioration or temperature dependency. In particular, there is no gas barrier laminate without barrier deterioration even in boil treatment or retort treatment under high temperature and high pressure.

The patent literature is as follows.
JP 2000-169652 A

  The present invention is made to solve the above-mentioned problems, and provides a transparent gas barrier laminate having flexibility, excellent oxygen barrier properties and water vapor barrier properties, and having water resistance, heat resistance, and hot water resistance. The purpose is to do. In particular, it is to provide a transparent gas barrier laminate capable of suppressing barrier deterioration due to boil treatment and retort treatment.

  Means for solving the problem in the invention of claim 1 is that a metal or metal oxide having a film thickness of 5 to 100 nm is formed on at least one surface on a plastic substrate made of a tearable polymer resin composition. It is a strong adhesion gas-barrier laminated film characterized by providing a vapor deposition layer.

  The means for solving the problem in the invention of claim 2 is a strongly-adhesive gas barrier laminate film characterized in that the tearability is linear tearability.

  The means for solving the problem in the invention of claim 3 is that the plastic substrate surface is a reactive ion etching (RIE) mode plasma processing surface. It is a conductive laminated film.

  According to a fourth aspect of the present invention, the reactive ion etching (RIE) mode plasma processing surface is a gas of argon, nitrogen, oxygen, or hydrogen, or a mixed gas thereof. The strongly-adhesive gas barrier laminate film according to any one of claims 1 to 3, which is a plasma-treated surface in a reactive ion etching (RIE) mode.

  The means for solving the problem in the invention of claim 5 is that the material of the plastic substrate is composed of polybutylene terephthalate containing polytetramethylene glycol and polyethylene terephthalate (PET), and has linear tearability in one direction. It is the uniaxial or biaxially stretched polyester film which has, It is a strong adhesion gas-barrier laminated film in any one of Claim 1 to 4 characterized by the above-mentioned.

  The means for solving the problem in the invention of claim 6 is that the plastic substrate contains polybutylene terephthalate (modified PBT) containing 5 to 20 wt% of polytetramethylene glycol having a molecular weight of 600 to 4,000, and polyethylene terephthalate. And a biaxially stretched polyester film in a ratio of PET / modified PET = 70/30 to 95/5 (weight ratio). .

Means for solving the problem in the invention of claim 7 is that one or more metal alkoxides or hydrolysates thereof and a hydroxyl group are formed on the vapor-deposited layer of the strong adhesion gas barrier laminate film of any of claims 1 to 6. It is a strong adhesion gas barrier laminated film characterized by providing a film made of a composite with a water-based polymer having.

  Means for solving the problem in the invention of claim 8 is the method for producing a strongly-adhesive gas barrier laminate film according to any one of claims 1 to 7, wherein the step of treating the plastic substrate by RIE, and the vapor deposition layer are provided. The step of providing is a method for producing a strongly-adhesive gas barrier laminate film having linear tearability, characterized in that the step of providing is performed in a vapor deposition machine inline.

  According to the above invention, a composite film with a water-soluble resin such as ethylene-vinyl alcohol is provided on one or more metal alkoxides or hydrolysates thereof on a plastic substrate made of a polymer resin composition. And high gas barrier properties.

  By providing the composite coating on an inorganic vapor deposition layer having a thickness of 5 to 100 nm, it is possible to provide a transparent gas barrier laminate that does not deteriorate in performance even during heat treatment such as boil treatment and retort treatment.

  As described above, the gas barrier agent according to the present invention is provided with a composite film of at least one metal alkoxide or a hydrolyzate thereof and an ethylene-vinyl alcohol copolymer (EVOH) on at least one surface of a plastic film substrate. Thus, it was confirmed that it has a high level of gas barrier properties and is excellent in water resistance and hot water resistance. By applying on the vapor deposition film, it is possible to suppress the introduction of cracks to the vapor deposition layer by the boil treatment and the retort treatment. Moreover, the further improvement of barrier property and water resistance was obtained by adding an inorganic layered compound to EVOH. Moreover, since it is excellent also in flexibility, the contents, such as food, can be preserved for a long period of time without compromising barrier properties even in messy handling.

  The above-mentioned plastic substrate is preferably a transparent film substrate if possible in order to make use of the transparency of the deposited thin film layer. Examples of substrates include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin films such as polyethylene and polypropylene, polystyrene films, polyamide films, polycarbonate films, polyacrylonitrile films, polyimide films, and the like. Can be mentioned. Furthermore, polyvinyl chloride, cellulose, triacetyl cellulose, polyvinyl alcohol, polyurethane and the like can be mentioned. Materials having at least one or more of the above materials as components, having copolymer components, or having chemically modified compounds as components are also included. The substrate may be either stretched or unstretched, and preferably has mechanical strength and dimensional stability. Among these, a polyethylene terephthalate film or a polyamide film arbitrarily stretched in the biaxial direction is preferably used. Various known additives and stabilizers such as an antistatic agent, an ultraviolet ray preventing agent, a plasticizer, and an activator may be used on the surface of the substrate opposite to the surface on which the vapor deposition layer is provided.

  The thickness of the substrate is not particularly limited, and a film obtained by laminating films having different properties in addition to a single film can be used in consideration of suitability as a packaging material. In view of workability in the case of forming a vapor-deposited thin film layer and a gas barrier composite coating layer made of an inorganic oxide, a range of 3 to 200 m is practically preferable, and a range of 6 to 30 m is particularly preferable.

In general, the thickness of the vapor-deposited thin film layer deposited on the substrate is desirably in the range of 5 to 30 nm, and the value is appropriately selected. However, if the film thickness is less than 5 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier material may not be sufficiently achieved. When the film thickness exceeds 30 nm, the thin film cannot be kept flexible, and there is a problem that the thin film may be cracked due to external factors such as bending and pulling after the film formation. More preferably, it exists in the range of 10-15 nm.

  There are various methods for forming the aluminum oxide layer on the plastic substrate, and the aluminum oxide layer can be formed by a normal vacuum deposition method. Further, other thin film forming methods such as sputtering, ion plating, and plasma vapor deposition (CVD) can also be used. However, considering productivity, the vacuum deposition method is the best at present. As a heating means of the vacuum evaporation method, it is preferable to use any one of an electron beam heating method, a resistance heating method, and an induction heating method, but in consideration of the wide selection of the evaporation material, the electron beam heating method is used. More preferably, it is used. Moreover, in order to improve the adhesiveness of a vapor deposition thin film layer and a base material, and the denseness of a vapor deposition thin film layer, it is also possible to vapor-deposit using a plasma assist method or an ion beam assist method.

  In order to improve the adhesion between the substrate and the deposited thin film layer, a pretreatment by reactive ion etching (RIE) using plasma may be performed.

  Next, the composite coating layer will be described. The composite coating layer is a coating layer having gas barrier properties, and is formed using a coating agent mainly composed of an aqueous solution or water / alcohol mixed solution containing a water-soluble resin and one or more metal alkoxides or hydrolysates thereof. . It is also possible to add an inorganic layered compound in the water-soluble resin. Furthermore, it is also possible to add to the solution a metal alkoxide that has been subjected to a treatment such as hydrolysis or hydrolysis in advance, or polyvinyl alcohol.

  The water-soluble resin used in the present invention is an ethylene-vinyl alcohol copolymer (EVOH). EVOH has a feature of excellent barrier properties and transparency under high humidity. And the ethylene content is 20-50 mol%. When it is less than 20 mol%, water resistance and moisture resistance are lowered, and gas barrier properties under high humidity are impaired. On the other hand, if it is more than 60 mol%, water resistance and moisture resistance are improved, but the original gas barrier properties are deteriorated. Therefore, the ethylene content is preferably 25 to 35 mol%.

  A water / alcohol mixed solution is used as the EVOH solvent. Examples of the alcohol component include n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and the like, and iso-propyl alcohol is preferable. If the amount of water in the total amount is large, gelation is promoted.

  The inorganic layered compound is preferably an inorganic layered compound that swells in a solvent, and its crystal structure forms a three-layer structure in which a tetrahedral layer of silica sandwiches an octahedral layer with aluminum, magnesium, or the like as a central metal from both sides. . Mainly, smectite group, vermiculite group, mica group and the like can be mentioned. Specifically, kaolinite, dickite, nacrite, halloysite, antigolite, chrysotile, pyrophyllite, montmorillonite, beidellite, hectorite, saponite, stevensite, tetrasilic mica, sodium teniolite, muscovite, margarite , Talc, vermiculite, phlogopite, xanthophyllite, chlorite and the like may be natural or synthetic. Also, scaly silica can be used. These may be used alone or in combination of two or more. Among these, use of montmorillonite is preferable from the viewpoint of gas barrier performance and printability when used in a coating agent composition.

  The mass ratio of EVOH and inorganic layered compound used in the present invention is in the range of (30/70) to (50/50). When the mass ratio of the inorganic layered compound is less than 50% by mass, a problem occurs in oxygen barrier properties under high humidity, and when it exceeds 70% by mass, the physical properties (coating film strength) as a coating film are insufficient.

The metal alkoxide used in the present invention is generally a compound represented by M (OR) _n (M: metal such as Si, Ti, Al, Zr, R: alkyl group such as CH ₃ or C ₂ H ₅ ). It is. Specific examples include tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ], triisopropoxyaluminum [Al (OC ₃ H ₇ ) ₄ ] and the like, among which tetraethoxysilane and triisopropoxyaluminum are hydrolyzed. Thereafter, it is preferable because it is relatively stable in an aqueous solvent.

  A known additive such as a silane coupling agent or a dispersant, a stabilizer, a viscosity modifier, a colorant, an ultraviolet absorber, and an antistatic agent is added to the solution as long as the gas barrier property is not impaired. It is also possible to add.

  As a coating method for the coating agent, conventionally known methods such as a dipping method, a roll coating method, a screen printing method, a spray method, and a gravure printing method that are usually used can be used.

  When the gas barrier composite of the present invention is applied by the above application method, the thickness of the dry film varies depending on the intended level, but is usually 0.1 to 10 m. If it is 0.1 m or less, the target gas barrier property cannot be obtained, and if it is 50 m or more, cracks are likely to occur in the film, and sufficient transparency may not be obtained.

  Examples of the present invention will be specifically described below. The present invention is not limited to these examples.

  A vapor-deposited film was produced by depositing aluminum oxide with a thickness of 15 nm on one side of a 12-m thick biaxially stretched polyester terephthalate (PET) film by vacuum deposition using an electron beam heating method.

<Example 1> Tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] (hereinafter abbreviated as TEOS) was added with 0.1N hydrochloric acid and stirred to prepare a hydrolyzed solution (hereinafter referred to as hydrolyzed TEOS). h-TEOS) and added to EVOH solution (ethylene content 29 mol%). Various ratios were applied, and after coating with a bar coater on the above deposited film, it was dried with a dryer at 120 ° C. for 1 minute to form a film having a thickness of 1 m to obtain a test specimen. Moreover, after putting a grid line on the surface of the test body with a magic, a boil test was performed to confirm the water resistance of the coating.

  These gas barrier properties were measured under conditions of 30 ° C. and 70% RH atmosphere using an oxygen permeability immediate device (MOCON OXTRAN 2/21 manufactured by Modern Control). The results are shown in Table 1.

  It can be confirmed that by combining the metal alkoxide and EVOH, not only gas barrier properties but also water resistance is remarkably improved.

<Example 2>
An inorganic layered compound was added to the EVOH solution, and h-TEOS was prepared so that the solid content ratio was 40/60 wt% (a mixed solution of EVOH and inorganic layered compound is abbreviated as modified EVOH).
. A mixed liquid of h-TEOS and PVA prepared in advance was mixed at the following ratio, and compared in the same manner as in Example 1.

  In any ratio, the composite coating of PVA, modified EVOH, and hydrolyzed TEOS exhibits high oxygen barrier properties. Since PVA has a hydroxyl group, it easily swells and dissolves in water. Therefore, by increasing the content of the modified EVOH, a composite coating that does not dissolve even in the boil treatment is made possible.

Claims (7)

  It consists of a composite of one or more metal alkoxides or hydrolysates thereof (A) and an aqueous polymer (ethylene-vinyl alcohol copolymer) (B) on a plastic substrate made of a polymer resin composition. Gas barrier laminate   A gas barrier laminate comprising a composite (C) obtained by adding an inorganic layered compound to the composite according to claim 1.   A gas barrier laminate comprising a composite (D) obtained by adding a water-soluble resin having a hydroxyl group (polyvinyl alcohol-based resin) to the composite according to claim 2.   The gas barrier laminate according to claim 1, wherein the ethylene-vinyl alcohol copolymer has an ethylene content of 25 to 35 mol%.   The material of the plastic substrate has at least one of polyethylene, polypropylene, polyamides, polyesters, polycarbonate, polyacrylonitrile, polystyrene, polyvinyl chloride, cellulose, triacetyl cellulose, polyvinyl alcohol, polyurethanes as a component, The gas barrier laminate according to claim 1, wherein the gas barrier laminate has a copolymer component or a chemical modification thereof as a component.   A gas barrier laminate comprising a metal or metal oxide vapor-deposited layer having a film thickness of 5 to 100 nm on at least one surface of a plastic substrate made of the polymer resin composition.   A gas barrier laminate comprising the gas barrier coating according to any one of claims 1, 2, and 3 on a plastic substrate, and having a thickness of 0.01 to 100 µm.