JPH0664117A - Laminate - Google Patents

Abstract

PURPOSE:To provide a laminate, in which the coating layer of a saponified ethylene-vinyl acetate copolymer having excellent adhesive properties and gas barrier properties is formed as an intermediate layer. CONSTITUTION:In a laminate, the coating layer of a saponified ethylene-vinyl acetate copolymer solution, in which a saponified ethylene-vinyl acetate copolymer having 20-60mol% ethylene content (Et), a not less than 90mol% saponification degree and the melting point (Tm) satisfying the following formula is dissolved into the mixed solvent of water and 1-4C lower alcohol, is formed as an intermediate layer, and surface layers are formed onto both surfaces of this layer. Tm( deg.C) 220-1.46Et+3.31(Sv-99.6).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laminate having an intermediate layer provided with a coating layer of a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) having excellent adhesiveness and gas barrier property. Regarding

[0002]

2. Description of the Related Art A film obtained from an EVOH solution is excellent in transparency and oxygen barrier property, but it lacks water resistance and mechanical properties, so that it is laminated with another polyolefin resin, polyester resin or polyamide resin. Often used. In other words, EV that utilizes the characteristics of each resin
It is used as a so-called three or more layered product having an OH layer as an intermediate layer and surface layers such as a polyolefin resin layer, a polyester resin layer and a polyamide resin layer provided on both surfaces thereof.

The laminate is used as a container, a sheet or a film, and in recent years, its use as an inner bag of a bag-in-box has been expanded. However, EVO
When H is laminated with other resin as described above, particularly with polyolefin resin, EVO is directly applied to the polyolefin resin.
It is quite difficult to bond H. Therefore, flame treatment, anchor coating treatment, primer treatment, etc. have been conventionally performed on the surface of the base material in order to improve adhesion to the base material such as polyolefin resin. Compounds and polyester / isocyanate compounds are preferably used. However, when the above anchor coat treatment is performed, the process becomes long and the treatment agent and treatment device are required, which leads to an increase in cost. To solve this drawback
No. 8745 proposes blending a polyoxazoline compound with an EVOH solution.

[0004]

However, when the present inventor examined the above technique in detail, it was difficult to say that the adhesiveness was sufficient for resins other than polyolefin resins.
Further, it was found that the coating film of the EVOH solution had insufficient transparency and gas barrier property. That is, it is desired to develop a laminate in which an intermediate layer is provided with an EVOH layer formed from an EVOH solution that is excellent in gas barrier properties, adhesion, and transparency, and that can be sufficiently adhered to a substrate without anchor treatment. It is rare.

[0005]

The present inventor has conducted extensive studies to solve such problems, and as a result, as an intermediate layer,
EVOH having an ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more, and a melting point (Tm) satisfying the following formula:
A layered product characterized in that a coating layer of an EVOH solution in which is dissolved in a mixed solvent of water and a lower alcohol having 1 to 4 carbon atoms is provided, and a surface layer is provided on both surfaces of the layer, the above-mentioned object can be achieved. The inventors have found the fact that the present invention has been completed.

Tm <220-1.46Et + 3.31
(Sv-99.6) However, Tm: melting point (° C) by differential scanning calorimeter Et: ethylene content (mol%) Sv: degree of saponification (mol%)

The present invention will be specifically described below.
The intermediate layer of the present invention is formed by interposing a coating layer of a specific EVOH solution between the surface layers. EVOH used in the solution has an ethylene content of 20 to 60 mol%,
It is preferable that the saponification degree of the vinyl acetate component is 25 to 55 mol% and 90 mol% or more, preferably 95 mol% or more. When the ethylene content is less than 20 mol%, the gas barrier property at high humidity is deteriorated, while when it exceeds 60 mol%, the coating property such as sufficient gas barrier property and printability is deteriorated.
If the saponification degree is less than 90 mol%, the gas barrier property and the moisture resistance will be reduced.

Moreover, the EVOH has a melting point (T) determined from a peak temperature measured by a differential scanning calorimeter (DSC).
m) is ethylene content (Et mol%) and saponification degree (S
EVOH in a range satisfying the following formula defined by
Is the most important feature. Tm <220-1.46Et + 3.31 (Sv-99.
6) When the Tm value is larger than the above range, the adhesive strength to the substrate is lowered, and the object of the present invention cannot be achieved. When a layer having a poor gas barrier property such as a polyolefin resin is used as the surface layer of the laminate, it is necessary for the intermediate layer to have a gas barrier property. For that purpose, the Tm value is 120
−1.46Et + 3.31 (Sv-99.6) <Tm <
It is preferably in the range of 220-1.46 Et + 3.31 (Sv-99.6).

EVOH as defined in the present invention is generally not commercially available. That is, the melting point of conventional EVOH is higher than the melting point of the present invention regardless of the ethylene content or saponification degree, and the EVOH having such a high melting point cannot attain the object of the present invention. Further, the EVOH is an even smaller amount of α-olefin such as propylene, isobutene, α-octene, α-dodecene and α-octadecene, unsaturated carboxylic acid or a salt thereof.
It may be possible to include a comonomer such as a partial alkyl ester, a complete alkyl ester, a nitrile, an amide, an anhydride, an unsaturated sulfonic acid or a salt thereof as a copolymerization component.

The solvent for the EVOH solution for forming the intermediate layer of the present invention is 10 to 90% by weight of water and at least one lower alcohol having 1 to 4 carbon atoms, particularly propyl alcohol or butyl alcohol, methyl alcohol and ethyl alcohol. Is used in an amount of 90 to 10% by weight. The amount of the water is 10 to 90% by weight, preferably 30 to 90% by weight as described above.
The amount is 70% by weight, and if it is 10% by weight or less or 90% by weight or more, it is difficult to obtain a uniform solution and the coating film becomes opaque. Examples of propyl alcohol as an alcohol component include n-propyl alcohol and iso-propyl alcohol, and examples of butyl alcohol include n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. -Propyl alcohol is preferably used.

Any method can be used to obtain EVOH satisfying the above Tm value, and the degree of polymerization may be controlled during EVOH polymerization or saponification, or the saponification degree distribution may be considered. However, practically, it is advantageous to treat EVOH obtained by an ordinary industrial production method with a peroxide or the like. Hereinafter, such a method will be described in detail.

The ethylene content is 20 to 60 mol%, the saponification degree is 90 mol% or more, and the melting point (Tm) is 220-
Those having a melting point higher than the value calculated from 1.46Et + 3.31 (Sv-99.6) (for example, when the ethylene content is 38 mol% and the saponification degree is 99.6 mol%, The value of the formula is 164.5 ° C, and a higher temperature (for example, one having a melting point of 173 ° C) is dissolved in the above mixed solvent of water and lower alcohol. The EVOH concentration is 1 to 5
0 wt% is suitable. Hydrogen peroxide (usually 3
0% by weight aqueous solution) to EVOH at 1 to 100% by weight
And added under agitation at 40-90 ° C., 5-50
Time to process. The order of adding water, alcohol, EVOH, and hydrogen peroxide at this time is not limited to the above order. Of course, it is also possible to charge the above-mentioned compounds all at once. At the end of the treatment, one point is that the viscosity of the solution at the time of start is about 10% or less of the initial viscosity.

The EVOH solution thus obtained can be used as it is as an EVOH solution for forming an intermediate layer, but it is preferable to add an enzyme such as catalase to decompose and remove residual hydrogen peroxide. The method for removing the residual hydrogen peroxide is not limited to the above method, and a known removal method can be adopted as long as the effect of the present invention is not impaired. When the EVOH solution thus obtained is applied to a substrate, the concentration of the EVOH solution is not particularly limited, but 1 to 50% by weight in consideration of coatability to various substrates and leaving stability.
The degree is desirable.

In the present invention, the substrate to which EVOH is applied, that is, the surface layer is not particularly limited, but at least one of them has an ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more, and a melting point ( TM) is the formula TM ≧ 2
20-1.46ET + 3.31 (SV-99.6) [however, TM: melting point (° C) by differential scanning calorimeter, ET:
It is preferable that the EVOH satisfy the ethylene content (mol%) and SV: saponification degree (mol%)].
VOH can form an EVOH layer having excellent gas barrier properties. In addition to the above EVOH, polyolefin resin, polyester resin, polyamide resin, etc. may be used as the surface layer. Specific examples of the polyolefin resin include polyethylene and polypropylene. Further, the polyethylene includes low, medium and high density polyethylene, and linear low density polyethylene (LLDPE).
And the like, among them, copolymer L with α-olefin
LDPE is preferable for applications requiring flex fatigue resistance such as inner bags of bag-in-boxes. Examples of the polyester resin include stretched polyester (O-PET) and amorphous polyester (A-PET), and among them, O-PET
Is preferred. As a polyamide resin, nylon-
6, Nylon 6-66, Nylon 6-12, Aromatic Nylon, Nylon-6, Nylon 6-6
6 is preferred. The above-mentioned resin is used in any form such as a stretched or unstretched film, a sheet, a hollow container, etc., and the thickness of such a substrate is suitably about 10 to 1000 µ.

According to the present invention, the EVOH coating film and the base material can be firmly adhered to each other at the time of coating (formation of the intermediate layer) without subjecting the base material to anchor treatment as in the prior art.
As a coating method at this time, a roller coating method such as a Mayer bar, a gravure and a reverse roll method, a spray coating method, a dip coating method or any other known method can be applied. Then, after the EVOH solution is applied to the base material, it is dried by a known method. For example, the drying temperature is 30 to 150 ° C., preferably 70.
It may be heated at a temperature of about 120 ° C for about 3 seconds to 5 minutes. Although the volatile components in the coating film, that is, water and alcohol, are removed by such drying, it is usually performed until the volatile components become 2% by weight or less.

Thus, a transparent EVOH coating film (intermediate layer)
However, it is formed on the substrate, but the film thickness is 0.
About 5 to 15 μ is practical. If it is less than 0.5, it is difficult to exhibit sufficient gas barrier properties and adhesiveness with the surface layer.
If the film thickness is more than μ, it will be difficult to control.

The laminate of the present invention is useful as a packaging material or container for foods, beverages, medicines, medicines and the like. As a layer structure of packaging materials and containers having high practicality, a surface layer (polyester, polyethylene, etc.) having a film thickness of 10 to 1000 μ / EVOH intermediate layer having a film thickness of 0.1 to 15 μ (volatile content of 0. 5-5% by weight) / EV with a film thickness of 0.1-15μ
OH (ethylene content 20-60 mol%, saponification degree 90
At a mol% or higher, melting point TM ≧ 220-1.46ET + 3.
31 (SV-99.6)) layer. The shape may be arbitrary such as a film shape, a sheet shape, a hollow bottle, and a tube. Further, the outermost layer / surface layer / intermediate layer / intermediate layer / of the above-mentioned polyolefin resin, polyester resin or polyamide resin is further laminated on the outer layer of the laminate (surface layer / intermediate layer / surface layer) of the present invention. Surface layer /
A five-layer laminate such as an outermost layer may be used, and further, an intermediate layer of the present invention may be provided between the outermost layer and the surface layer to form the outermost layer / intermediate layer / surface layer / intermediate layer / surface layer / intermediate layer. It is also possible to adopt a seven-layer structure of layers / outermost layer. If necessary, one of the outermost layers may be omitted.

[0018]

Since the laminate of the present invention uses a specific EVOH coating layer as the intermediate layer, it has excellent adhesion to the substrate to be laminated, and further has gas barrier property, transparency and coatability. Is excellent.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, "parts" and "%" mean weight basis unless otherwise specified. Example 1 To 30.5 parts of water and 42.5 parts of iso-propyl alcohol, EVOH (ethylene content 29 mol%, saponification degree 9
9.6 mol%, melting point 188 ° C.) 15 parts, and 60 to 7
A clear solution was prepared by stirring at 0 ° C. for about 2 hours. Next, 12 parts of hydrogen peroxide (30% aqueous solution) was added to the solution, reacted at 80 ° C. for about 20 hours under stirring, and then catalase was further added to 3000 ppm to remove residual hydrogen peroxide. Removal gave a 15% EVOH solution. The ethylene content of EVOH in the solution was 29 mol%, the saponification degree was 99.6 mol, and the melting point (Tm) was 158 ° C. as measured by DSC. This Tm value is the T specified in the present application.
m <178 ° C. was satisfied.

Next, a stretched polyester film (thickness 2
5 μ) surface is coated with the EVOH solution of the present invention by an applicator coating method and dried at 100 ° C. for 3 minutes,
An intermediate layer having an EVOH film thickness of 3 μm was obtained. An EVOH solution having an ethylene content of 29 mol%, a saponification degree of 99.6 mol% and a melting point of 188 ° C. (EVOH 30%)
Water-alcohol solution) to form a surface layer,
A three-layer laminate was prepared. The oxygen permeability of the laminate is 3.
Delamination adhesion (surface layer / (intermediate layer) / surface layer) at 3 cc / m ² · day · atm (20 ° C., 65% RH) is 1
It was 85 g / 15 mm (the surface layers were pulled to each other to measure the adhesive strength. 300 mm / min pulling speed). The transparency was 3.8% in haze value.

Examples 2 to 5 The EVOH solution of the present invention was prepared in the same manner as in Example 1 according to the composition shown in Table 1, and then the laminate shown in Table 2 was prepared in the same manner as in Example 1. Incidentally, in Examples 3 to 5,
After forming the intermediate layer, the surface layer was extruded to form a laminate. The same evaluation as in Example 1 was performed on the produced laminate.

Comparative Example 1 85 parts of a mixed solvent containing 50% water and 50% iso-propyl alcohol and commercially available EVOH (ethylene content 29 mol%, saponification degree 99.6 mol%, melting point 188 ° C .; Example 1)
Similarly, the Tm value was calculated to be Tm <178 ° C., and the melting point is out of the specified range of the present application.
Stir at ~ 70 ° C for about 2 hours to prepare a clear solution.
An intermediate layer was formed using this solution to prepare a laminate in the same manner as in Example 1, and the oxygen permeability, the delamination adhesion and the transparency of the laminate were examined.

Comparative Examples 2 to 3 EVOH was prepared in the same manner as in Comparative Example 1 except that the blending composition shown in Table 1 was used.
A solution was prepared, a laminate was prepared, and the same evaluation was performed. Comparative Example 4 Using the EVOH solution of Comparative Example 1, the same L as in Example 3 was used.
A laminated body of LDPE / intermediate layer / LLDPE was prepared and evaluated in the same manner. Table 2 shows the configurations of the laminates of Examples and Comparative Examples and the evaluation results thereof.

[0024]

[Table 1] EVOH (for forming intermediate layer) water-alcohol solvent Et Sv melting point amount calculated Tm value mixing ratio amount (mol%) (mol%) (° C) (part) (° C) (water / alcohol) (part) Example 1 29 99.6 158 15 Tm <178 50/50 85 Example 2 29 99.4 125 30 Tm <177 23/77 70 Example 3 29 99.6 100 30 Tm <178 20/80 70 Example 4 38 99.6 150 15 Tm <165 42/58 85 Example 5 38 96.0 145 15 Tm <153 42/58 85 Comparative Example 1 29 99.6 188 15 Tm <178 50/50 85 Comparative Example 2 38 99.6 173 15 Tm <165 50/50 85 Comparative Example 3 29 99.6 188 15 Tm <178 50/50 84 Comparative Example 4 29 99.6 188 15 Tm <178 50/50 85 Note) Et and Sv represent ethylene content and saponification degree, respectively. The calculated Tm value refers to the Tm value calculated by the formula of claim 1 of the present invention. The mixing ratio indicates a mixing weight ratio of water / isopropyl alcohol. However, in Example 4, ethyl alcohol was used as the alcohol. In Comparative Example 3,
One part of polyoxazoline compound was added.

[0025]

[Table 2]Stacked layer structure Evaluation results (Surface layer / intermediate layer / surface layer) *¹ Transparency *² Adhesion *³ Transparency*^Four  *² (G) (%) Example 1 PES / Interlayer / EVOH (1) 3.8 185 3.8 Example 2 LLDPE / Interlayer / EVOH (2) 3.8 270 3.5 Example 3 LLDPE / Interlayer / LLDPE 12.0 385 5.2 Example 4 O-PP / Interlayer / C-PP 10.3 250 4.9Example 5 O-PP / Interlayer / LDPE 14.4 275 4.8 Comparative Example 1 PES / Interlayer / EVOH (1) 3.0 0 4.1 Comparative Example 2 PES / Interlayer / EVOH (1) 4.1 2 5.2 Comparative Example 3 PES / Interlayer / EVOH (1) 3.5 50 4.8Comparative Example 4 LLDPE / interlayer / LLDPE 4.3 0 6.3 note)*¹The abbreviations of the surface layers are as follows. PES; stretched polyester (25 μm thick) EVOH (1); ethylene content 29 mol%, saponification degree 9
9.6 mol%, melting point 188 ° C. (3 μm thick) EVOH (2); ethylene content 38 mol%, saponification degree 9
6.0 mol% Melting point 161 ° C. (5 μ thick) LLDPE; linear low density polyethylene (20 μ thick) O-PP; stretched polypropylene (20 μ thick) C-PP; unstretched 〃 (40 μ thick) LDPE; low density polyethylene (40μ thickness) *²The permeability means the oxygen permeability, and the unit is cc / m.
²・ Day ・ atm. *³The adhesive force indicates the delamination adhesive force, which is 15 mm wide.
Represents the adhesive strength. *^FourRepresents the haze value. In Comparative Example 1, the anchor coat treatment (polyester
The adhesive force for delamination when using a stell coating is 65g
It was / 15 mm.

[0026]

INDUSTRIAL APPLICABILITY The laminate of the present invention has a specific EV for the intermediate layer.
Since the OH coating layer is used, it has excellent adhesiveness to the base material to be laminated, and further has excellent gas barrier properties, transparency and coating properties.

Claims (3)

[Claims] 1. The intermediate layer has an ethylene content of 20 to
At 60 mol%, the saponification degree is 90 mol% or more, and the melting point (T
m) the saponified ethylene-vinyl acetate copolymer satisfying the following formula is dissolved in a mixed solvent of water and a lower alcohol having 1 to 4 carbon atoms to form a coating layer of a saponified ethylene-vinyl acetate copolymer solution. And a surface layer provided on both surfaces of the layer. Tm <220-1.46Et + 3.31 (Sv-99.
6) However, Tm: melting point (° C) by differential scanning calorimeter Et: ethylene content (mol%) Sv: degree of saponification (mol%) 2. A saponified ethylene-vinyl acetate copolymer, wherein at least one of the surface layers has an ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more, and a melting point (TM) satisfying the following formula. The laminated body according to claim 1, wherein TM ≧ 220-1.46ET + 3.31 (SV-99.
6) However, TM: melting point (° C.) by differential scanning calorimeter ET: ethylene content (mol%) SV: degree of saponification (mol%) 3. The laminate according to claim 1, wherein at least one of the surface layers is made of any one of polyolefin resin, polyester resin and polyamide resin.