JP2000070848A - Formation of coating film consisting of ethylene-vinyl alcohol copolymer resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a raw material of a laminate film of ethylene-vinyl alcohol copolymer resin which has higher strength by enhancing adhesion of an ethylene- vinyl alcohol copolymer resin with a synthetic resin base material. SOLUTION: An adhesive in which a polyurethane-based adhesive is a main component and an epoxy-based adhesive is a curing component, is applied to the surface of a base material consisting of a film made of a synthetic resin such as polyethylene, polypropylene or polyethylene terephthalate. Then, an alcohol solution of an ethylene-vinyl alcohol copolymer resin is applied to the surface of the adhesive layer of a semicuring state. The coating film consisting of the ethylene-vinyl alcohol copolymer resin is formed by drying and curing both the coating film of the ethylene-vinyl alcohol copolymer resin and the adhesive layer and unifying them with the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an ethylene vinyl alcohol copolymer resin coating film on a surface of a substrate made of a plastic film or the like.

[0002]

2. Description of the Related Art Ethylene vinyl alcohol copolymer resin (hereinafter abbreviated as EVOH), which is a kind of polyvinyl alcohol, is a resin having particularly excellent gas barrier properties among various plastics. It is widely used as a packaging material for food such as a wrap film, a stretch film, a food distribution or storage container, because it can suppress the quality deterioration of the product and maintain the fragrance of the packaged product for a long time.

In recent years, so-called gas-filled packaging, in which a container such as a bag for packing food is filled with nitrogen gas or carbon dioxide gas, has often been adopted. Due to its excellent gas barrier properties, a container having extremely good retention of the filled gas can be obtained.

[0004] Incidentally, EVOH is a random copolymer of ethylene and vinyl alcohol, and has the formula (CH ₂ -C
H ₂₎ is a crystalline polymer having a molecular structure represented by _{m (CH 2 -CH (OH)} ) n.

[0005] In order to form a composite (lamination) of such an EVOH with another substrate, the EVOH is heated and dissolved in a mixed solvent of water and a lower alcohol, and this is rolled on the surface of a substrate made of polyethylene or polyester film. It is applied by coating or the like and dried to form a coating film, or is laminated and integrated by lamination (extrusion method, wet method, dry method, hot melt method, coextrusion method, etc.).

However, the EVOH layer thus laminated or coated has a disadvantage that it is relatively easily peeled off from a base material such as a synthetic resin. Therefore, an anchor coat agent is previously applied to the surface of the synthetic resin base material. In some cases, it is also possible to adopt a method of keeping the information.

[0007] For example, Japanese Patent Publication Nos. 41171/1993 and 21947/1993 disclose an anchor coat layer comprising a polyurethane-based compound or a polyester / isocyanate-based compound having a thickness of about 0.05 to 3 μm. It is described that the adhesive strength between the material and EVOH is improved.

[0008]

However, an anchor coating agent is previously applied to the surface of a synthetic resin base material, and EV
Even for composite products with OH coating film, EVO
The peel strength of the H film is only about 50-60 g, and EVOH
The peel strength of the coating film was insufficient.

An object of the present invention is to solve the above-mentioned problems, improve the adhesion between EVOH and a synthetic resin substrate, and produce a material such as an EVOH laminate film having a large peel strength.

[0010]

In order to solve the above-mentioned problems, in the invention according to claim 1 or 2 of the present invention, a polyurethane adhesive is used as a main component and an epoxy adhesive is used as a curing component on the surface of a substrate. Then, an alcohol solution of ethylene vinyl alcohol copolymer resin is applied to the surface of the adhesive layer in a semi-cured state, and this is heated and dried to form an ethylene vinyl alcohol copolymer resin coating film on the substrate. Thus, a method of forming an ethylene vinyl alcohol copolymer resin coating film by bonding and integrating was adopted. As the substrate, a film made of a synthetic resin such as polyethylene, polypropylene, or polyethylene terephthalate can be employed.

Further, in the invention according to claim 3 of the present application, in order to solve the above-mentioned problems, in the invention according to claim 1 or 2, the adhesive or the alcohol of the ethylene-vinyl alcohol copolymer resin before coating is used. This is a method for forming an ethylene vinyl alcohol copolymer resin coating film in which an aqueous dispersion of a block type isocyanate insoluble in water is added to the solution or both.

Alternatively, in the invention according to claim 4 of the present application, in the invention according to claim 1 or 2, one of the laminated portions comprising the base material, the adhesive layer, and the ethylene vinyl alcohol copolymer resin coating film is used. The method for forming a coating film of an ethylene-vinyl alcohol copolymer resin in which an aqueous dispersion or solution of a water-insoluble block type isocyanate is applied to the above surface.

According to the invention described in each claim of the present application, the polyurethane adhesive having the above structure has a high reactivity and polarity of the NCO group and a chemical secondary bond between the NCO group and the surface of the adherend. And adheres to the substrate and EVOH with good adhesion.

The compounded epoxy adhesive is
By acting as a curing component, the adhesive strength which is insufficient with the polyurethane-based adhesive alone is increased, and the peel strength of the coating film is improved.

Further, since an alcohol solution of ethylene vinyl alcohol copolymer resin is applied on the adhesive layer in a semi-cured state, the NCO group acts on both the synthetic resin base material and the EVOH to improve the adhesion between them. Tightens to increase adhesion.

Further, a water-insoluble block type isocyanate is added to the adhesive or the alcohol solution of the ethylene-vinyl alcohol copolymer resin or both, or the base material, the adhesive layer and the ethylene-vinyl alcohol copolymer resin coating film are added. If an aqueous dispersion or an organic solvent solution of a water-insoluble block type isocyanate is applied to at least one surface of the laminated portion, more NCO groups act on both the synthetic resin substrate and the EVOH. The peel strength between the substrate and the EVOH is further improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The type of substrate used in the present invention is not particularly limited. For example, films, sheets, plates made of polyethylene, polypropylene, polyester, polystyrene, polyvinyl chloride, polyamide, etc. as synthetic resins. A well-known shaped body such as a container, a pipe and the like can be employed. The substrate made of a synthetic resin film may be stretched or unstretched. In addition, synthetic rubber, natural rubber and other elastomers, cellulose such as paper or cellophane, wood, metal, ceramics and the like can also be used as the base material.

The polyurethane-based adhesive used in the present invention comprises an isocyanate component and a polyol component as basic raw materials, and if necessary, a catalyst, a stabilizer, a pigment, a filler, and the like. The type and the ratio of the isocyanate component and the polyol component can be appropriately changed according to the desired adhesive strength.

The isocyanate includes aliphatic isocyanates such as hexamethylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aromatic isocyanates such as tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). . Further, as the polyol, ethylene glycol, low molecular weight polyol such as diethylene glycol, polyethylene glycol, polyether polyol such as polypropylene glycol,
And polyester polyols such as polycaprolactone.

Among the polyurethane adhesives composed of the above-mentioned materials, it is necessary to use a solvent-based or solvent-free one-pack type polyurethane adhesive for use in the present invention. Preferred for use.

The solvent-type polyurethane adhesive is prepared by diluting a thermoplastic polyurethane obtained by polymerizing a polyol and an isocyanate such as TDI or MDI with an organic solvent such as alcohol, ethyl acetate or methyl ethyl ketone. Yes, use alone (one-pack) or add a small amount of polyisocyanate (two-pack)
It can be used as such. Examples of commercially available solvent-based polyurethane adhesives include AD-393 manufactured by Toyo Morton Co., Ltd.

The solventless polyurethane adhesive is prepared by reacting a diisocyanate and a polyol to form a prepolymer having a terminal NCO group, and the moisture (steam) of the atmosphere during the bonding process.
Is to be cured. Examples of commercially available solvent-free polyurethane adhesives include Takenate A-753, an NCO-terminated prepolymer manufactured by Takeda Pharmaceutical Company.

Incidentally, the epoxy adhesive has two molecules in the molecule.
It is a compound obtained by combining a curing agent with an epoxy resin composed of an oligomer such as diglycidyl ether bisphenol A having at least two oxirane rings (epoxy groups) and polyoxypropylene glycol diglycidyl ether.

The epoxy adhesive used in the present invention is preferably a one-part type adhesive which uses a latent curing agent such as dicyanamide, aromatic amine, imidazole or the like as a curing agent and is heated at the time of use. Examples of commercially available one-part epoxy adhesives include CAT manufactured by Toyo Morton Co., Ltd.
-EPI and the like.

The mixing ratio of each component of the mixed adhesive containing the polyurethane adhesive and the epoxy adhesive in the present invention will vary slightly depending on the composition of each adhesive. Is modified polyurethane resin 50% by weight, isopropyl alcohol 20 ~
30% by weight, 20 to 30% by weight of ethyl acetate, 5% by weight or less of methyl ethyl ketone, which is a commercially available product, wherein the epoxy adhesive is 84% by weight of an epoxy resin and 16% by weight of ethyl acetate; System adhesive:
The most favorable result is obtained by mixing the epoxy adhesives in a ratio of 15: 1 (weight ratio).

When the mixing ratio of the two types of adhesives is represented by the mixing ratio excluding the solvent component, the ratio of the polyurethane resin component to the epoxy resin component is 9: 1 (weight ratio). The mixing ratio of the components ranges from 3: 1 to 10: 1. The reason that such a blending ratio is preferable is that if the epoxy resin component is in a small amount less than the predetermined blending amount, an uncured state may occur, which is not preferable. Is unfavorable because it adversely affects the gas barrier performance of EVOH.

When the above-mentioned adhesive is mixed with two kinds of adhesives, a viscosity may be reduced by adding a diluent to improve applicability. As the diluent, alcohols such as isopropyl alcohol, denatured ethanol and methanol, or a mixture of alcohols and water (up to 20% by weight of water) can be used. As an application method of the adhesive, a spray coating method, a dip coating method, and other well-known application methods can be adopted in addition to a roller coating method using a gravure or a reverse roll.

The amount of the adhesive applied to the surface of the base material is, for example, 1.5 to 3.0 g / m2 in dry weight in the case of the above-mentioned compounding ratio.
^2. Drying temperature is 50 ~ 90 ℃, lamination condition is Nip
When the printing pressure is 10 to 20 kg / cm at 50 to 70 ° C. and the aging is 40 ° C. for 2 days or more, a preferable laminated film can be obtained.

EVOH to be applied to the surface of the adhesive layer in a semi-cured state by a roll coating method is preferably applied with a composition of about 85% by weight of alcohol and about 15% by weight of EVOH. It may be a solvent. As a preferable mixed solvent for dissolving EVOH, a solvent of isopropyl alcohol, water and normal butanol of 1: 2: 1 (weight ratio) can be exemplified.

EVOH is obtained by copolymerizing ethylene and vinyl acetate to produce an ethylene-vinyl acetate copolymer (EVAC), and saponifying the EVAC with caustic soda to obtain an ethylene-vinyl alcohol copolymer. EVAL (registered trademark) manufactured by Kuraray Co., Ltd. can be used as a commercially available EVOH.

When the composite material is a film, the thickness of the coating film of the EVOH resin in the present invention is approximately 0.5 to 1
It can be formed to about 5 μm, but usually 3 μm.
It is appropriate to form a film having a thickness of about m, and about 6 μm for a film used for drawing. If the thickness is less than 0.5 μm, sufficient gas barrier properties cannot be exhibited, and if the thickness exceeds 15 μm, it becomes difficult to control the thickness of the coating film. When an EVOH layer having a thickness of 8 μm or more is formed, a method of laminating a film is employed. In view of such a tendency, the preferable thickness of the EVOH in the present invention is 3 to 6 μm.

Specific steps for forming an EVOH coating film on the surface of a synthetic resin film substrate will be described below with reference to the accompanying drawings.

In order to form an EVOH coating film industrially by the dry lamination process shown in FIG. 1, a guide in which a synthetic resin film base material (web of the first layer) 1 wound in a roll is disposed at a key position. It is unwound while being guided by a roller 2, and an adhesive 3 having a polyurethane-based adhesive as a main component and an epoxy-based adhesive as a hardening component is applied by a gravure coater 4 on its surface, and this is applied to the vicinity of the entrance and the exit by 50%.
A temperature gradient of 80 to 100 ° C. is passed through a drying device 5 having a temperature gradient of 80 to 100 ° C., and the surface of the adhesive layer in a semi-cured state is further separated by a gravure coater 6 separately provided in the process. The adhesive layer 3 'and the EVOH coating film 7' are dried and hardened by applying an alcohol solution 7 of an ethylene vinyl alcohol copolymer resin and passing the same through a drying device 8 which is temperature-controlled by providing a temperature gradient similar to that described above. It is integrated with the film substrate 1 and wound up (see FIG. 2). In the illustrated final step,
The composite film that has passed through the drying device 8 is
To improve the density and strength of the EVOH coating film.

The EVO formed as described above
H On top of the coating, another synthetic resin coating or film 9
Is heated with a heat roll (80 to 100 ° C.) 10 and a pressure roll 1
After passing through a space between the cooling rolls 12 under a pressurized state of 10 kg / cm ² or less, the laminate may be passed through a space between a pair of cooling rolls 12.

[0035]

EXAMPLES and COMPARATIVE EXAMPLES Example 1 Using a dry lamination apparatus shown in FIG. 1, a polyethylene terephthalate resin film substrate 1 wound into a roll is stretched while being guided by a guide roller 2, and is spread on the surface thereof. 15 parts by weight of a polyurethane adhesive (AD-393, manufactured by Toyo Morton) and an epoxy adhesive (CAT-, manufactured by Toyo Morton)
EPI) An adhesive 3 mixed with 1 part by weight is applied by a gravure coater 4 so as to have a dry weight of 1.5 to 3.0 g / m ^2, and this is applied to the vicinity of the inlet and outlet at 50 to 80 g / m ^2.
C., the central zone is passed through a drying device 5 with a temperature gradient of 80 to 100.degree. C., and then a gravure coater 6 arranged in the process applies alcohol of EVOH to the surface of the semi-cured adhesive layer. Solution 7 was applied.
In this case, as the alcohol-based mixed solvent, isopropyl alcohol, water and normal butanol in a ratio of 1: 2:
1 (weight ratio) was used.

Next, the EVOH coating film and the adhesive layer are dried and hardened by passing through a drying device 8 which is provided with a temperature gradient similar to that described above and is integrated with the film substrate 1, and this is wound up to form an adhesive. A composite film having an EVOH coating 7 'formed through the layer 3' was produced (see FIG. 2).

Example 2 Adhesive and EVO before Application
H alcohol solution was mixed with 1 block of water-insoluble block isocyanate (A3070, manufactured by Takeda Pharmaceutical Company Limited).
A composite film having an EVOH coating film was produced in exactly the same manner as in Example 1 except that it was added at a concentration of ２2% by weight.

Example 3 The same procedure as in Example 1 was carried out except that an aqueous dispersion of a water-insoluble block type isocyanate (A3070, manufactured by Takeda Pharmaceutical Co., Ltd.) was applied to the surfaces of the base material and the adhesive layer, respectively. Similarly, a composite film having an EVOH coating film was produced.

Comparative Example 1 EVO was carried out in the same manner as in Example 1, except that a polyurethane-based adhesive (AD-393, manufactured by Toyo Morton Co., Ltd.) was used alone.
A composite film having an H coating was produced.

The peel strength between the EVOH coating film and the substrate of the composite films of Examples 1 to 3 and Comparative Example 1 obtained as described above was examined according to JIS 6301. Examples 1 to 3 were 300 to 500, whereas the 15 mm width was 50 to 60 g.
g, confirming that there is a significant effect of improving the peel strength.

[0041]

As described above, the invention described in each claim of the present application applies a mixed adhesive containing a polyurethane-based adhesive and an epoxy-based adhesive to the adhesive layer in a semi-cured state. A method of forming an ethylene vinyl alcohol copolymer resin coating film that is applied repeatedly and dried and cured by applying an ethylene vinyl alcohol copolymer resin solution, so that it is firmly integrated and the peel strength is improved, and the NCO group is a synthetic resin base material. Acts on both the EVOH and the EVOH to improve the adhesion between the EVOH and the synthetic resin base material, and provides a higher peel strength of the EVOH.
There is an advantage that a material such as a laminate film can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a dry lamination process.

FIG. 2 is a cross-sectional view of a composite film having an EVOH coating film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film base material 2 Guide roller 3 Adhesive 3 'Adhesive layer 4, 6 Gravure coater 5, 8 Drying device 7 EVOH alcohol solution 7' EVOH coating film 9 Film 10 Heat roll 11 Pressure roll 12 Cooling roll

Continuation of the front page F term (reference) 4D075 AA02 AB03 AC54 AC55 BB27X BB93X CA42 DA06 DB48 DC36 EA07 EA27 EB19 EB38 4J038 CE031 DG302 JA17 KA06 PA07 PC08

Claims (4)

[Claims] 1. A mixture adhesive comprising a polyurethane adhesive and an epoxy adhesive as a component is applied to the surface of a base material, and then the alcohol of ethylene vinyl alcohol copolymer resin is applied to the surface of the adhesive layer in a semi-cured state. A method for forming an ethylene-vinyl alcohol copolymer resin coating film, comprising applying a solution, heating and drying the solution, and bonding and integrating the ethylene-vinyl alcohol copolymer resin coating film onto a substrate. 2. The method according to claim 1, wherein the substrate is a substrate made of a synthetic resin film. 3. The method of forming an ethylene vinyl alcohol copolymer resin coating film according to claim 1 or 2, wherein the adhesive or the alcohol solution of the ethylene vinyl alcohol copolymer resin or an alcohol solution before coating is insoluble in water. A method for forming an ethylene-vinyl alcohol copolymer resin coating film, characterized by adding an isocyanate. 4. The method for forming an ethylene vinyl alcohol copolymer resin coating film according to claim 1 or 2, wherein at least one of a laminated portion composed of a substrate, an adhesive layer, and an ethylene vinyl alcohol copolymer resin coating film. A method for forming a coating film of an ethylene-vinyl alcohol copolymer resin, comprising applying a water-insoluble aqueous dispersion or solution of a block-type isocyanate to the surface.