JPH10722A - Strongly adhesive transparent laminate for boiling retort - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate with high transparency and superior gas barrier properties and make it possible to sterilize the laminate using a boiling retort. SOLUTION: A transparent primer layer 2, a thin film layer 3 of an inorganic oxide with a thickness of 5-300nm, and an aqueous polymer are formed on at least, one of the faces of a base material 1, and further, a coating agent comprising an aqueous solution containing at least, either of (a) at least, one type of metal alkoxide and its hydrolyte or (b) tin chloride, or a mixed solution of water and alcohol as a chief agent is laminated on the face of the base material by applying and thermally drying the coating agent. In addition, a polyolefin thermoplastic resin layer is laminated on the top of the described layers through an adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate for packaging used in the field of packaging of foods, non-foodstuffs, pharmaceuticals and the like, and more particularly to the field of packaging requiring sterilization such as boiling and retort.

[0002]

2. Description of the Related Art In recent years, packaging materials used for packaging foods, non-foods, and the like are required to prevent deterioration of contents and maintain their functions and properties. It is necessary to prevent the influence of gas that alters the contents, and it is required to have a gas barrier property that blocks these gases. Therefore, conventionally, a packaging material using a metal foil made of a metal such as aluminum, which is less affected by temperature, humidity, and the like, as a gas barrier layer has been generally used.

[0003] However, a packaging material using a metal foil made of a metal such as aluminum has excellent gas barrier properties, but the contents cannot be checked through the packaging material. However, there is a problem in that the metal detector has to be disposed of, and a metal detector cannot be used.

Accordingly, as a packaging material which overcomes these drawbacks, for example, US Pat.
A film formed by depositing an inorganic oxide such as silicon oxide, aluminum oxide, and tin oxide on a polymer film by a forming means such as a vacuum evaporation method or a sputtering method as described in -28017 and the like. Is being developed. These films are known to have transparency and gas barrier properties against oxygen, water vapor and the like, and are considered suitable as packaging materials having both transparency and gas barrier properties that cannot be obtained with metal foils and the like. .

[0005]

However, even a film suitable for the above-mentioned packaging material is rarely used alone as a vapor deposition film as a packaging container or a packaging material. A package is completed through various processes such as printing or laminating characters and pictures on the surface or laminating the film with a film or the like, and shape processing into a package such as a container. In particular, packaging materials that are subjected to boil sterilization or retort sterilization are sterilized through various processes, so that careful attention must be paid to the design of the packaging materials.

[0006] Therefore, after the sealant film is bonded and bag-formed using the above-mentioned vapor-deposited film, the contents are filled and subjected to boil sterilization or retort sterilization. Had the problem that it decreased.

[0007] That is, the conditions for use as a packaging material for boil and retort include transparency enough to allow the contents to be directly seen through, high gas barrier properties to block gases that affect the contents, and boiling. -There is a demand for a material that does not deteriorate gas barrier properties even after retort sterilization and has boil and retort resistance that does not generate delamination, etc. At present, a packaging material that satisfies all of these has not been found.

Accordingly, an object of the present invention is to provide a highly practical laminate having excellent transparency and high gas barrier properties and capable of sterilizing boil and retort.

[0009]

Means for Solving the Problems The present invention has been made to achieve the above-mentioned object, and the invention described in claim 1 is to provide a base made of a transparent plastic material on at least one side of a transparent primer layer having a thickness of 5 mm. An aqueous solution or a water / alcohol mixed solution containing a thin film layer composed of an inorganic oxide having a thickness of about 300 nm, an aqueous polymer, and at least one of (a) one or more metal alkoxides and hydrolysates thereof, and (b) tin chloride. For a boil retort, characterized in that a gas barrier coating layer formed by applying a coating agent comprising as a main component and drying by heating is sequentially laminated, and a polyolefin-based thermoplastic resin layer is further laminated as a seal layer via an adhesive. It is a strong adhesion transparent laminate.

According to a second aspect of the present invention, based on the first aspect, an intermediate layer made of a transparent plastic material is provided between the gas barrier coating layer and the polyolefin-based thermoplastic resin layer via an adhesive. Are laminated, and the intermediate layer is
A strongly adhered transparent laminate for boiling and retorting, characterized in that the laminate is one of a biaxially stretched nylon film, a biaxially stretched polyethylene terephthalate film, and a biaxially stretched polypropylene film.

According to a third aspect of the present invention, based on the first and second aspects, the transparent primer layer is a polyester resin or a mixture of the resin and a mixed resin, and the mixed resin is (a) an isocyanate. A strongly adhesive transparent laminate for boil and retort, characterized by being a mixture of at least one selected from a group consisting of a series resin, (b) an epoxy resin, and (c) a melamine resin.

According to a fourth aspect of the present invention, based on the third aspect, the mixed resin is an isocyanate-based resin, and the mixing ratio of the polyester resin and the isocyanate-based resin is equivalent ratio (OH group of the polyester): (NCO group of isocyanate) in a ratio of 1: 0.5 to 1:20, which is a strong adhesion transparent laminate for boiling and retorting.

According to a fifth aspect of the present invention, based on the first to fourth aspects, the transparent primer layer has a thickness of 0.1%.
A strongly adhered transparent laminate for boiling and retorting, wherein the thickness is in the range of 1.0 to 1.0 μm.

According to a sixth aspect of the present invention, based on the first to fifth aspects, the inorganic oxide is aluminum oxide,
A strongly adhered transparent laminate for boiling and retorting, characterized by being silicon oxide or a mixture thereof.

According to a seventh aspect of the present invention, based on the first to sixth aspects, the water-soluble polymer is a polyvinyl alcohol, wherein the water-soluble polymer is a polyvinyl alcohol.

According to an eighth aspect of the present invention, the metal alkoxide is tetraethoxysilane or triisopropoxyaluminum, or a mixture thereof, based on the first to seventh aspects. It is a strong adhesion transparent laminate.

The laminate of the present invention comprises a transparent plastic substrate, a polyester resin alone, or a transparent primer layer composed of the resin and a mixed resin and having excellent adhesion, provided with an inorganic oxide layer as a gas barrier layer, and a water-based layer. Polymer and
A gas barrier obtained by applying a coating agent mainly comprising an aqueous solution or a water / alcohol mixed solution containing at least one of (a) one or more metal alkoxides and hydrolysates thereof, and (b) tin chloride, and drying by heating. Since the coating layer is sequentially laminated, and the polyolefin-based thermoplastic resin layer is further laminated as a seal layer via an adhesive, it is excellent in transparency and gas barrier properties, and also for sealing after boiling and retort sterilization. It is a highly practical laminate that does not generate delamination or the like and does not deteriorate gas barrier properties.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a strongly adhered transparent laminate for boil and retort of the present invention.

First, the strongly adhered transparent laminate for boil and retort of the present invention shown in FIG. 1 will be described. In FIG. 1, a substrate 1 is a film made of a transparent plastic material, and a transparent primer layer 2, a thin film layer 3 made of an inorganic oxide, a gas barrier coating layer 4, an intermediate layer 5 made of a transparent plastic material, a polyolefin heat The plastic resin layers 6 are sequentially laminated.

The substrate 1 is a transparent plastic material, and a transparent film is preferable in order to make use of the transparency of the vapor-deposited thin film layer. For example, polyethylene terephthalate (PET), polyester films such as polyethylene naphthalate, polyolefin films such as polyethylene and polypropylene, polystyrene films, polyamide films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, polyimide films, and the like are used. Either stretched or unstretched may be used, and those having mechanical strength and dimensional stability are preferred. These are processed into a film and used. Particularly, polyethylene terephthalate arbitrarily stretched in the biaxial direction is preferably used. In addition, various known additives and stabilizers, for example, an antistatic agent, an ultraviolet ray inhibitor, a plasticizer, a lubricant, and the like may be used on the surface of the substrate 1 in order to improve the adhesion to the thin film. Further, a corona treatment, a low-temperature plasma treatment, an ion bombardment treatment or a chemical treatment, a solvent treatment or the like may be applied as a pretreatment.

Although the thickness of the base material 1 is not particularly limited, it is suitable as a packaging material, other layers may be laminated, the transparent primer layer 2, the inorganic oxide thin film layer 3, the gas barrier In consideration of workability when forming the coating layer 4, it is practically preferably in the range of 3 to 200 μm, and preferably 6 to 30 μm depending on the use.

Also, in consideration of mass productivity, it is desirable to use a long film so that each layer can be formed continuously.

The transparent primer layer 2 of the present invention is provided on a substrate 1 made of a transparent plastic material, improves the adhesion between the substrate 1 and the thin film layer 3 made of an inorganic oxide, and sterilizes it with boiling or retort. The purpose is to prevent later occurrence of delamination.

To achieve the above object, the primer resin may be used alone or as a mixture of a polyester resin and one or more kinds of mixed resins selected from isocyanate resins, epoxy resins and melamine resins. Must be a mixture.

The above polyester resins are terephthalic acid, isophthalic acid, phthalic acid, methylphthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, succinic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid , Hexahydrophthalic acid and acid raw materials such as reactive derivatives thereof, ethylene glycol, propylene glycol, 1,3-butanediol,
1,4-butanediol, 1,6-hexanediol,
Diethylene glycol, dipropylene glycol, 1,
4-cyclohexanedimethanol, neopentyl glycol, isopentyl glycol, bishydroxyethyl terephthalate, hydrogenated bisphenol A, alkylene oxide adduct of hydrogenated bisphenol A, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, 2,2 , 4-trimethylpentane-
Those manufactured by a known method from an alcohol raw material such as 1,3-diol can be used, but are not particularly limited thereto.

The mixed resin added to the polyester resin is added in order to further enhance the adhesion, and mainly functions as a crosslinking agent or a curing agent. In order to achieve this, as a mixed resin, isocyanate resins such as tolylene diisocyanate (TDI), xylene diisocyanate (XDI), and hexadiisocyanate (MDI), bisphenol A diglycine ether type epoxy and hydrogenated bisphenol type epoxy Epoxy resins, melamine resins, and mixtures of one or more of these. Among them, isocyanate resin (particularly, TDI) is preferred because it has the best adhesion.

The mixing ratio of the polyester resin and the mixed resin may be such that isocyanate group, epoxy group, amino group, etc. are contained in an equivalent amount or more with respect to the OH group or COOH group of the polyester resin. For example, when an isocyanate-based resin alone is used as the mixed resin, the mixing ratio of the polyester resin and the isocyanate-based resin is equivalent ratio of (OH group of polyester) :( NCO group of isocyanate) and is 1:
A range of 0.5 to 1:20 is desirable. If it is less than the equivalent, poor curing and insufficient cross-linking will result in a problem in adhesion. However, if it is added too much, the added resin does not react and adversely affects the remaining film, which is not preferable. A known method can be used for the mixing method, and is not particularly limited.

The organic solvent for dissolving the primer resin is not particularly limited as long as the resin can be dissolved.
Esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatic hydrocarbons such as toluene and xylene may be used alone or in any combination. Preferably, a mixture of toluene and methyl ethyl ketone is preferable from the viewpoint of coating film processing and odor.

Various additives such as 3
Curing accelerators such as quaternary amines, imidazole derivatives, carboxylic acid metal salt compounds, quaternary ammonium salts, and quaternary borophonium salts; antioxidants such as phenol-based, sulfur-based, and phosphite-based agents, leveling agents, and flow regulators , A catalyst, a crosslinking reaction accelerator, a filler and the like can be added.

The thickness of the transparent primer layer 2 is not particularly limited as long as a uniform coating film can be formed, but is generally preferably in the range of 0.01 μm to 1.0 μm. When the thickness is less than 0.01 μm, it is difficult to obtain a uniform coating film, and the adhesion may be reduced. The thickness is 1.0
If the thickness exceeds μm, the film cannot be kept flexible because of the thickness, and cracks may occur in the film due to external factors. Particularly preferred is a range of 0.1 to 1.0 μm.

The method for forming the transparent primer layer 2 is as follows.
For example, a known printing method such as an offset printing method, a gravure printing method, or a silk screen printing method, or a known coating method such as a roll coat, a knife edge coat, or a gravure coat can be used. The drying conditions may be those generally used.

The thin film layer 3 made of an inorganic oxide is made of a deposited film of an inorganic oxide such as aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof.
Any material may be used as long as it has transparency and gas barrier properties such as oxygen and water vapor. Among them, aluminum oxide and silicon oxide are particularly preferable. However, the thin film layer 3 of the present invention
Is not limited to the inorganic oxides described above, and any material that meets the above conditions can be used.

The optimum conditions for the thickness of the thin film layer 3 vary depending on the type and constitution of the inorganic compound used.
The range is desirably in the range of ~ 300 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. On the other hand, if the thickness exceeds 300 nm, flexibility cannot be maintained in the thin film, and the thin film may be cracked by external factors such as bending and pulling after the film is formed. Preferably, it is in the range of 10 to 150 nm.

There are various methods for forming the thin film layer 3 made of an inorganic oxide on the transparent primer layer 2, which can be formed by a usual vacuum deposition method. A plating method, a plasma vapor deposition method (CVD), or the like can also be used. However, in consideration of productivity, the vacuum deposition method is currently the most excellent. As a heating means of the vacuum evaporation apparatus by the vacuum evaporation method, an electron beam heating method, a resistance heating method, and an induction heating method are preferable. In order to improve the adhesion between the thin film and the base material and improve the denseness of the thin film, a plasma assist method or an ion heating method is used. It is also possible to use a beam assist method. Also,
At the time of vapor deposition, reactive vapor deposition such as blowing in oxygen gas may be used in order to increase the transparency of the deposited film.

The gas barrier coating layer 4 is provided on the inorganic oxide thin film layer 3 and is provided to provide a gas barrier property as high as aluminum foil.
It comprises a coating agent mainly comprising an aqueous solution or a water / alcohol mixed solution containing at least one of (a) one or more metal alkoxides and hydrolysates or (b) tin chloride. A water-soluble polymer and tin chloride are mixed with water (water or water /
A solution obtained by coating a solution obtained by dissolving with a solvent or a solution obtained by directly treating a metal alkoxide directly or by preliminarily hydrolyzing the solution onto the inorganic oxide thin film layer 3 and drying by heating. It is.
Each component contained in the coating agent will be described in more detail.

The water-soluble polymer used for the coating agent in the present invention includes polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like. In particular, when polyvinyl alcohol (hereinafter, referred to as PVA) is used as a coating agent for the laminate of the present invention, the gas barrier properties are most excellent. The PVA referred to here is generally obtained by saponifying polyvinyl acetate, and a few percent of acetic acid groups remain from so-called partially saponified PVA in which several tens of percent of acetic acid groups remain.
There is no particular limitation, including up to complete PVA that only remains.

Tin chloride is stannous chloride (SnCl ₂ ),
Stannic chloride (SnCl ₄ ) or a mixture thereof may be used, and either anhydrous or hydrated can be used.

Further, the metal alkoxide is tetraethoxy.
Silane [Si (OC_Two H_Five )_Four ], Triisopropoxy
Aluminum [Al (O-2'-C_Three H₇ )_Three ]
General formula, M (OR)_n(M: Si, Ti, Al, Zr, etc.
Metal, R: CH_Three , C_Two H _Five Such as an alkyl group)
Things. Among them, tetraethoxysilane, triiso
After propoxyaluminum is hydrolyzed, it is dissolved in aqueous solvent.
Is relatively stable in this case.

Each of the above-mentioned components can be added to the coating agent alone or in combination of several components. Further, as long as the gas barrier properties of the coating agent are not impaired, isocyanate compounds, silane coupling agents, dispersants, and stabilizers Known additives such as a viscosity modifier and a coloring agent can be added.

For example, an isocyanate compound added to a coating agent has two or more isocyanate groups (NCO groups) in its molecule. For example, tolylene diisocyanate (hereinafter, TDI), triphenylmethane triisocyanate (hereinafter, TTI) ), Tetramethylxylene diisocyanate (hereinafter, TMXDI), and polymers and derivatives thereof.

As a method for applying the coating agent, conventionally known means such as a commonly used dipping method, roll coating method, screen printing method, spray method and the like can be used. The thickness of the coating varies depending on the type of coating agent and processing conditions, but the thickness after drying is 0.01μ.
It is sufficient that the thickness is at least m, but if the thickness is at least 50 μm, cracks are likely to occur in the film.

Further, another layer can be laminated on the gas barrier coating layer 4. For example, it is a printing layer or the like. The printing layer is formed for practical use as a packaging bag or the like, and various pigments are added to conventionally used ink binder resins such as urethane, acrylic, nitrocellulose, rubber, and vinyl chloride. , A layer composed of an ink to which an additive such as an extender, a plasticizer, a desiccant, a stabilizer and the like are added, and on which characters, pictures, and the like are formed. As a forming method, for example, a well-known printing method such as an offset printing method, a gravure printing method, or a silk screen printing method, or a well-known coating method such as a roll coat, a knife edge coat, or a gravure coat can be used. The thickness may be 0.1 to 2.0 μm.

The intermediate layer 5 made of a transparent plastic material and provided between the gas barrier coating layer 4 and the polyolefin-based thermoplastic resin layer 6 is provided for the purpose of increasing the breaking strength during sterilization of boiling and retort. It may not be provided depending on the application. In order to achieve the above object, it is possible to use as an intermediate layer, from the viewpoint of mechanical strength and thermal stability, a biaxially stretched nylon film, a biaxially stretched polyethylene terephthalate film, a biaxially stretched polypropylene film Needs to be The thickness is determined according to the material and required quality, etc.
Generally, it is in the range of 10 to 30 μm. As a forming method, lamination can be performed by a known method such as a dry laminating method in which two adhesives such as a two-component curable urethane resin are used.

The polyethylene-based thermoplastic resin layer 6 is used for an adhesive portion when forming a bag-shaped package or the like.
Resins such as vinyl acetate copolymers, ethylene-methacrylic acid copolymers, ethylene-methacrylic acid ester copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers and their metal crosslinked products are used. Can be The thickness is determined according to the purpose, but is generally 15
２００200 μm. As a forming method, it is general to use a dry lamination method in which a film-like material made of the above resin is bonded using an adhesive such as a two-component curable urethane resin.

[0045]

EXAMPLES The strongly adhered transparent laminate for boil and retort of the present invention will be further described with reference to specific examples.

<Example 1> As the substrate 1, a thickness of 12 μm
A resin having the following composition was formed as a transparent primer layer 2 on one surface of a biaxially stretched polyethylene terephthalate (PET) film by a gravure coating method. Resin: polyester / isocyanate compounding ratio: OH group (polyester) / NCO group (isocyanate) = 1/8 (equivalent ratio) Thickness: 0.1 μm Solvent: toluene / methyl ethyl ketone = 5/5 Then on transparent primer layer 2 The silicon oxide was deposited to a thickness of about 40 nm by a vacuum deposition apparatus using a resistance heating method (not shown) to form an inorganic oxide thin film layer 3. Further, a coating agent having the following composition was applied thereon with a bar coater and dried at 120 ° C. for 1 minute with a drier to form a gas barrier coating layer 4 having a thickness of 0.3 μm. The composition of the coating agent is a mixture of liquid and liquid at a mixing ratio (wt%) of 60/40. (Note: 89.6 g of hydrochloric acid (0.1N) was added to 10.4 g of tetraethoxysilane, and the mixture was stirred for 30 minutes and hydrolyzed to a solid content of 3 wt% (in terms of SiO ₂ ). Isopropyl alcohol solution (weight ratio of water: isopropyl alcohol: 90:10)) Next, as an intermediate layer 5, a biaxially stretched nylon film having a thickness of 15 µm is laminated by a dry lamination method via a two-component curable urethane-based adhesive. Further, as the polyolefin-based thermoplastic resin layer 6, a polypropylene film having a thickness of 60 μm was laminated by a dry lamination method via a two-component curable urethane-based adhesive to obtain a strongly adhered transparent laminate for boiling and retorting of the present invention.

<Example 2> In Example 1, metal aluminum was evaporated by an electron beam heating type vacuum evaporation apparatus (not shown) as the inorganic oxide thin film layer 3, and oxygen gas was introduced therein. A strongly adhered transparent laminate for boiling retort of the present invention was obtained in the same manner except that an aluminum oxide thin film layer was formed.

Example 3 A strongly adhered transparent laminate for boil and retort of the present invention was obtained in the same manner as in Example 1, except that the following resin was used as the transparent primer layer 2. Resin: polyester / isocyanate compounding ratio: OH group (polyester) / NCO group (isocyanate) = 1/4 (equivalent ratio) Thickness: 0.5 μm Solvent: toluene / methyl ethyl ketone = 5/5

<Example 4> In Example 1, the intermediate layer 5 was used.
Except that no was provided, a strongly adherent transparent laminate for boil and retort of the present invention was similarly obtained.

Comparative Example 1 A transparent laminate was obtained in the same manner as in Example 1, except that the transparent primer layer 2 and the gas barrier coating layer 4 were not provided.

Comparative Example 2 A transparent laminate was obtained in the same manner as in Example 1, except that the transparent primer layer 2 was not provided.

<Test 1> Examples and Comparative Examples
A four-way pouch was prepared for boil sterilization, filled with 150 g of water as a content, and subjected to boil sterilization at 90 ° C. for 30 minutes. As an evaluation, the oxygen permeability before and after the boiling (cc
/ M ² / day) and the occurrence of delamination after boiling was visually observed. Table 1 shows the results.

<Test 2> Examples and Comparative Examples
A four-way pouch was prepared for retort sterilization, filled with 150 g of water as a content, and subjected to retort sterilization at 125 ° C. for 30 minutes. As an evaluation, the oxygen permeability (cc / m ² / day) before and after the retort and the presence or absence of delamination after the retort were visually observed. Table 1 shows the results.

[0054]

[Table 1]

The comparative example is different from the embodiment in that
Transparency that allows the contents to be directly seen through, conditions that are used as packaging materials for retorts, high gas barrier properties that block gases that affect the contents, gas barrier properties even after boiling and retorting Without deterioration
Although not all of the boil and retort resistance, which does not cause delamination, are satisfied, the examples can be said to satisfy all of them.

[0056]

As described above, according to the present invention, a versatile packaging material having excellent transparency and a high gas barrier property comparable to that of aluminum foil can be obtained. It can be widely used in the packaging field.

[0057]

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a strongly adhered transparent laminate for boil and retort of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent plastic base material 2 Transparent primer layer 3 Inorganic oxide thin film layer 4 Gas barrier coating layer 5 Intermediate layer 6 Polyolefin-based thermoplastic resin layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B65D 65/40 B65D 65/40 D 81/24 81/24 N

Claims (8)

[Claims] 1. A transparent primer layer on at least one side of a substrate made of a transparent plastic material, a thin film layer made of an inorganic oxide having a thickness of 5 to 300 nm, an aqueous polymer, and (a) one or more metal alkoxides and Hydrolyzate or
(B) A coating agent mainly composed of an aqueous solution containing at least one of tin chloride and a water / alcohol mixed solution is applied, and a heat-dried gas barrier coating layer is sequentially laminated, and further as a seal layer via an adhesive. Characterized by laminating a polyolefin-based thermoplastic resin layer
Strongly adhered transparent laminate for retort. 2. The method according to claim 1, wherein an intermediate layer made of a transparent plastic material is further laminated between the gas barrier coating layer and the polyolefin-based thermoplastic resin layer via an adhesive, and the intermediate layer is formed of a biaxially stretched nylon. The strongly adhered transparent laminate for boil and retort according to claim 1, wherein the laminate is one of a film, a biaxially oriented polyethylene terephthalate film, and a biaxially oriented polypropylene film. 3. The transparent primer layer is a polyester resin or a mixture of the resin and a mixed resin, wherein the mixed resin comprises (a) an isocyanate resin, (b) an epoxy resin, and (c) a melamine resin. The strongly adherent transparent laminate for a boil / retort according to claim 1 or 2, wherein the mixture is at least one mixture selected from the group consisting of: 4. The mixed resin is an isocyanate resin, and the mixing ratio of the polyester resin and the isocyanate resin is equivalent to (OH group of polyester) :( NCO group of isocyanate) in the range of 1: 0.5-1. The strongly adhered transparent laminate for boil and retort according to claim 3, wherein the ratio is 20. 5. The transparent primer layer having a thickness of 0.1 to 0.1.
The strongly adhered transparent laminate for a boil / retort according to any one of claims 1 to 4, wherein the thickness is in a range of 1.0 µm. 6. The strong adhesive transparent laminate for a boil retort according to claim 1, wherein the inorganic oxide is aluminum oxide, silicon oxide or a mixture thereof. 7. The strongly adhered transparent laminate for boil and retort according to claim 1, wherein the water-soluble polymer is polyvinyl alcohol. 8. The method according to claim 1, wherein the metal alkoxide is tetraethoxysilane, triisopropoxyaluminum, or a mixture thereof.
The strongly adhered transparent laminate for boiling and retorting described in the above.