JP3250749B2 - Saponified ethylene-vinyl acetate copolymer solution and use thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of applying a coating film of a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) on a surface of various plastics and the like to prevent oxygen. The present invention relates to an EVOH solution useful for imparting high properties and a coating laminate thereof.

[0002]

2. Description of the Related Art A film obtained from EVOH is excellent in transparency, oxygen barrier property, etc., and is useful as a packaging material for foods, medical products, industrial chemicals and the like, or as a composite material laminated with plastic film, paper and metal foil. is there. In the case of forming an EVOH film, any method can be used. However, a relatively thin film can be formed, and the film can be easily formed on a complex base material such as a hollow container. A solution coating method of applying a solution obtained by dissolving EVOH in a solvent to a base material has attracted attention because it can form a film and a coating operation can be performed with a relatively simple apparatus.

In such a method, flame treatment, anchor coat treatment, primer treatment and the like are conventionally performed on the surface of the substrate in order to increase the adhesion to the substrate. Polyurethane compounds and polyester / isocyanate compounds are suitably used. However, when the above-mentioned anchor coat treatment is performed, the process becomes longer, or the treatment agent or treatment device is required, which leads to an increase in cost. In order to solve this drawback, Japanese Patent Application Laid-Open No. Hei 4-8745 proposes blending a polyoxazoline compound with EVOH.

[0004]

However, the present inventor studied the above technique in detail and found that the stability of the EVOH solution and the transparency of the coating film after molding were insufficient. In other words, there is a demand for an EVOH solution which is excellent in gas barrier properties, adhesiveness, transparency of a coating film, storage stability, coating property, and can be sufficiently adhered to a substrate without performing anchor treatment. is there.

[0005]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above problems. As a result, (a) the ethylene content is 20 to 60 mol%, the saponification degree is 90 mol% or more, and Melting point (Tm) saponified ethylene-vinyl acetate copolymer satisfying the following formula: (b) saponified ethylene-vinyl acetate copolymer other than the above (a); (c) water and 1 carbon atom The present inventors have found that the above object can be achieved by using a saponified solution of an ethylene-vinyl acetate copolymer characterized by comprising a mixed solvent of lower alcohols of (1) to (4), and completed the present invention.

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

Hereinafter, the method of the present invention will be specifically described. (A) EVOH used in the present invention has an ethylene content of 20 to 60 mol%, preferably 25 to 55 mol%,
The degree of saponification of the vinyl acetate component must be at least 90 mol%, preferably at least 95 mol%. If the ethylene content is less than 20 mol%, the gas barrier property at high humidity decreases, while if it exceeds 60 mol%, the film properties such as sufficient gas barrier property and printability deteriorate. On the other hand, when the saponification degree is less than 90 mol%, the gas barrier properties and the moisture resistance are reduced.

Further, as (a), EVOH has a melting point (Tm) determined from a peak temperature measured by a differential scanning calorimeter (DSC), an ethylene content (Et mol%) and a saponification degree (Sv The most characteristic feature is that EVOH is used in a range satisfying the following expression defined by the following formula: Tm <220-1.46Et + 3.31 (Sv-99.
6) When the Tm value is larger than the above range, the stability of the solution is deteriorated, the solution is solidified at room temperature, and further, the adhesive strength to the base material is reduced, so that the object of the present invention cannot be achieved. In order to maintain the gas barrier property at a high level, the Tm value should be 120-1.46.
Et + 3.31 (Sv-99.6) <Tm <220-
It is preferable to set it in the range of 1.46 Et + 3.31 (Sv-99.6).

(A) EVOH as defined in the present invention
Is generally not commercially available. That is, in the conventional EVOH, the melting point is higher than the melting point of the present invention, regardless of the ethylene content and the degree of saponification. Can not reach. In addition, as (b), E other than (a)
There is no particular limitation as long as it is VOH, but the melting point (TM) is represented by the formula TM ≧ 220-1.46ET + 3.31.
(SV-99.6) [where, TM: melting point (° C.) by differential scanning calorimeter, ET: ethylene content (mol%), S
V: Degree of saponification (mol%). It is preferable to use a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or more. EVOH of (a) and (b) above
In each case, a smaller amount of propylene, isobutene, α-octene, α-dodecene, α-octadecene, or another α-olefin, unsaturated carboxylic acid or a salt thereof, a partial alkyl ester, a complete alkyl ester, a nitrile,
Comonomers such as amides / anhydrides, unsaturated sulfonic acids or salts thereof may be contained as a copolymer component.

As a solvent for dissolving the EVOH of (a) and (b) of the present invention, a lower alcohol containing 10 to 90% by weight of water and having 1 to 4 carbon atoms, particularly propyl alcohol or butyl alcohol, methyl alcohol A mixture in which at least one of ethyl alcohol is 90 to 10% by weight is used. As described above, the amount of water is 10 to 90% by weight, preferably 30 to 70% by weight. If the amount is 10% by weight or less or 90% by weight or more, a uniform solution is difficult to obtain and the coating film becomes opaque. A point occurs. Examples of the alcohol component propyl alcohol 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. Iso-propyl alcohol is preferably used.

As a method for obtaining (a) EVOH that satisfies the above-mentioned Tm value, there is an arbitrary method, such as controlling the degree of polymerization at the time of polymerization or saponification of EVOH, or considering the saponification degree distribution. Practically, it is advantageous to treat EVOH obtained by a usual industrial production method with a peroxide or the like. Hereinafter, such a method will be described in detail.

An ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more and a melting point (Tm) of 220-
Those having a melting point higher than the value calculated from 1.46 Et + 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., which is higher,
Is dissolved in the above-mentioned mixed solvent of water and lower alcohol. The concentration of the EVOH is 1 to
50% by weight is suitable. Hydrogen peroxide (usually a 30% by weight aqueous solution) is added to the solution in an amount of 1 to 100% by weight with respect to EVOH, and the mixture is stirred at 40 to 90 ° C and 5 to 5%.
Treat for 0 hours. At this time, water, alcohol, EVOH,
The order of adding hydrogen peroxide is not limited to the above order. Of course, it is also possible to charge the above-mentioned composition at once. At the end of the treatment, one point is that the point at which the viscosity of the solution at the time of starting becomes about 10% or less of the initial viscosity.

[0013] The EVOH solution thus obtained comprises (a)
This is a water-alcohol solution that can be used as a component, and a water-alcohol solution containing component (b) EVOH can be added to the EVOH solution as it is, and used as the EVOH solution of the present invention. This method is preferable. At this time, it is preferable to add an enzyme such as catalase to decompose and remove the residual hydrogen peroxide. The method for removing the residual hydrogen peroxide is not limited to the above method, and any known removal method may be employed as long as the effects of the present invention are not impaired. Also,
(A) and (b) are not limited to a solution, but may be a solid. In this case, (c) mix (a) and (b) with a water-alcohol solution, respectively. By doing so, the EVOH solution of the present invention can be obtained. The mixing method at this time can be performed by a known method. In the present invention, the mixing weight ratio of (a) and (b) is (a) /
(B) = 90/10 to 5/95, preferably 70/3
0 to 10/90. If the amount of (a) is too large, the gas barrier properties decrease, while if the amount is too small, the adhesion decreases and it is unsuitable. Further, an arbitrary solution can be prepared by replacing the solvent of the obtained EVOH solution with another solvent different from that used when preparing the solutions (a) and (b).
When applying the EVOH solution thus obtained to a substrate,
The concentration of the EVOH solution is not particularly limited, but is preferably about 1 to 50% by weight in consideration of coatability to various base materials, storage stability, and the like.

In the present invention, the substrate on which EVOH is applied is not particularly limited, and may be polyethylene, polypropylene, polyester, polystyrene, polyvinyl chloride, or the like.
Stretched or unstretched films, sheets, hollow containers or papers of various plastics such as nylon, cellophane,
Examples include cellulose acetate, natural rubber, synthetic rubber, and metal. The thickness of such a substrate is suitably about 10 to 1000 μm.

According to the present invention, the EVOH coating film and the substrate can be firmly adhered to each other without applying an anchor treatment to the substrate as in the prior art at the time of such coating. As a coating method at this time, a roller coating method such as a Meyer bar, gravure and reverse roll method, a spray coating method, a dip coating method and any other known methods can be applied. Then, after applying the EVOH solution to the substrate, drying is performed by a known method. For example,
Drying temperature is 30 to 150 ° C, preferably 70 to 120 ° C
It may be heated at a temperature of about 3 seconds to 5 minutes. In such drying, the volatile components, that is, water and alcohol, in the coating film are removed, but usually, the drying is carried out until the volatile component becomes 2% by weight or less.

Thus, a transparent coating film of EVOH is formed, and its thickness is practically about 0.5 to 15 μm. If it is less than 0.5, it is difficult to exhibit sufficient gas barrier properties, while if it is more than 15 μm, it will be difficult to control the thickness. If necessary, a moisture-proof layer can be formed on the coating by a vinylidene chloride resin coat or a vinyl chloride-vinyl acetate copolymer coat.

A laminate in which various substrates are coated with an EVOH solution is useful as a packaging material or container for foods, beverages, medicines, medicines and the like. As a highly practical packaging material and a layer structure of a container, typically, the film thickness is 10 to 1000 μm.
Base material (polyester, polyethylene, etc.) / Film thickness 0.5
EVOH (volatile content: 0.5 to 5% by weight) or a thickness of 0.5 to 5 μm on the EVOH layer having the above structure.
It is provided with a vinylidene chloride resin layer of about 3 μm or a vinyl chloride-vinyl acetate copolymer layer. The shape may be any shape such as a film shape, a sheet shape, a hollow bottle, and a tube.

[0018]

In the present invention, two types of EVs having different melting points are used.
Due to the combined use of OH, the EVOH water-alcohol solution has excellent storage stability, and can be coated on various substrates, and has barrier properties, adhesion, transparency and coatability of a coating film. Is excellent.

[0019]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” mean on a weight basis unless otherwise specified. Example 1 EVOH (ethylene content: 29 mol%, degree of saponification : 99.7 mol%, melting point : 188 ° C . : Nihon Gosei) in 36 parts of a mixed solvent containing 50% of water and 50% of iso-propyl alcohol
"Soarnol D2908" manufactured by Chemical Industry Co. )
The mixture was stirred at 0 to 70 ° C. for about 2 hours to prepare a clear solution. Next, 6 parts of hydrogen peroxide (30% aqueous solution) was added to the solution, and the mixture was reacted at 80 ° C. for about 20 hours with stirring. Then, catalase ( “ASK SUPER” manufactured by Mitsubishi Gas Chemical Company) was further added.
Was added so as to be 3000 ppm, and residual hydrogen peroxide was removed to obtain a 16% EVOH solution (A-1). The ethylene content of (a) EVOH in the EVOH solution is 2
9 mol%, degree of saponification is 99.7 mol, melting point Tm is DS
It was 158 ° C as measured by C. This Tm value satisfied the Tm <178 ° C. specified in the present application. Separately, EVOH (ethylene content 29%) was added to 42 parts of a mixed solvent containing 50% of water and 50% of iso-propyl alcohol.
Mol%, saponification degree 99.7 mol%, melting point 188 ° C : Japan
8 parts of “Soarnol D2908” manufactured by Synthetic Chemical Industry Co., Ltd. ) was added, and the mixture was stirred at 60 to 70 ° C. for about 2 hours to obtain a transparent solution (B).
Was prepared. The solution (A-1) and the solution (B) were mixed and stirred to obtain an EVOH solution of the present invention. The EVOH solution was allowed to stand in a constant temperature chamber at 20 ° C., and the number of days until the EVOH started to gel (standing stability) was good.

Next, a stretched polyester film (thickness 2
5 μ) on the surface of the present invention by an applicator coating method.
Apply a VOH solution, dry at 100 ° C for 3 minutes,
A laminate having a VOH film thickness of 3 μ was obtained. The oxygen permeability of the laminate was 3.3 cc / m ² · day · atm (20 ° C.,
65% RH) and the delamination adhesion is 185 g / 15 m
m (a cellophane tape was adhered to the EVOH surface, and the cellophane tape and the polyester film were pulled and the adhesive strength was measured, and the drawing speed was 300 mm / min). Also,
A 3 μm-thick EVOH single-layer film was prepared from the EVOH solution, and the transparency of the film was measured. The haze value was 3.8%.

Examples 2 to 5 According to the composition shown in Table 1, an EVOH solution of the present invention was obtained in the same manner as in Example 1. The same evaluation as in Example 1 was performed for the EVOH solution. In addition, it used in Examples 2-5.
EVOH is as follows. Example 2 (a): "Soarnol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
DC3203 "was treated with hydrogen peroxide according to Example 1.
Things of Example 2 (b): The Nippon Synthetic Chemical Industry Co., Ltd. "SoarnoL
D2908 " Example 3 (a):" Soarnol "manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
D2908 "was treated with hydrogen peroxide according to Example 1.
Of Example 3 (b): The Nippon Synthetic Chemical Industry Co., Ltd. "SoarnoL
"DC3203" Example 4 (a): "Soarnol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
E3808 "was treated with hydrogen peroxide according to Example 1.
Of Example 4 (b): The Nippon Synthetic Chemical Industry Co., Ltd. "SoarnoL
"DC3203" Example 5 (a): "Soarnol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
E3808 "was treated with hydrogen peroxide according to Example 1.
Of Example 5 (b): The Nippon Synthetic Chemical Industry Co., Ltd. "SoarnoL
E3808 "

Comparative Example 1 42 parts of a mixed solvent containing 50% of water and 50% of iso-propyl alcohol and a commercially available EVOH (ethylene content: 29 mol%, saponification degree: 99.7 mol%, melting point : 188 ° C . : Nippon Gohsei)
"Soarnol D2908" manufactured by Chemical Industry Co . ; Tm value calculated in the same manner as in Example 1 is Tm <178 ° C., and the melting point is outside the range specified in the present application.
The mixture was stirred at 0 ° C for about 2 hours to prepare a clear solution (A-2). The liquid (A-2) and the liquid (B) obtained in Example 1
The liquid was mixed and stirred to obtain an EVOH solution. With respect to the solution, the storage stability, the oxygen permeability of the laminate, the delamination adhesive strength, and the transparency were examined in the same manner as in Example 1.

Comparative Examples 2 to 3 EVOH was prepared according to the composition shown in Table 1 according to Comparative Example 1.
A solution was prepared and evaluated similarly. Comparative Example 2 (a): "Soarnol" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
E3808 " (b) of Comparative Example 2:" Soarnol "manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
D2908 " (a) of Comparative Example 3:" Soarnol "manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
D2908 "was treated with hydrogen peroxide according to Example 1.
Of Table 2 shows the Tm values and evaluation results of Examples and Comparative Examples.

[0024]

(A) EVOH (b) EVOH (c) Mixed solvent Et Sv Melting point amount ET SV Melting point amount Mixing ratio Amount (mol%) (mol%) (° C) (parts) (mol%) (mol%) (° C.) (parts) (parts) Example 1 29 99.7 158 8 29 99.7 188 8 5/5 84 Example 2 32 99.7 125 15 29 99.5 188 5 4/6 80 Example 3 29 99.6 100 15 32 99.6 181 15 2/8 70 Example 4 38 99.4 150 10 32 99.8 180 5 4/6 85 Example 5 38 96.0 145 20 38 99.4 173 5 3/7 75 Comparative Example 1 29 99.7 188 16 5/5 84 Comparative Example 2 38 99.6 168 4 29 99.6 188 16 5/5 80 Comparative Example 3 29 99.6 100 30 5/5 70 Note) Et, ET, SV and SV indicate the ethylene content and the degree of saponification, respectively. The mixing ratio in the mixed solvent of (c) indicates the mixing weight ratio of water / isopropyl alcohol.
However, in Example 4, ethyl alcohol was used as the alcohol. In Comparative Example 2, EVOH having a normal melting point was used as the component (a).

[0025]

TABLE 2 Stability of claim 1 of the present invention *¹Transparency *^TwoAdhesive strength *^ThreeTransparency*^Four Tm Tm calculated from the formula         (℃) (℃) (Days) * ² (g) (%) Example 1 158 Tm <178> 60 3.3 3.3 185 3.8 Example 2 125 Tm <173> 60 3.7 245 3.7 Example 3 100 Tm <178 30 3.4 380 3.4 Example 4 150 Tm <164> 60 3.5 225 3.5Example 5 145 Tm <152> 60 3.7 290 3.7 Comparative Example 1 <3 3.4 0 3.4 Comparative Example 2 (168 Tm <165) <3 3.5 2 4.1Comparative Example 3 100 Tm <178> 60 15.4 400 3.3  note)*¹Stability refers to standing stability. *^TwoThe permeability indicates oxygen permeability, and the unit is cc /
m²* Day * atm. *^Three; Adhesive force means delamination adhesive force, 15 mm width
Represents the adhesive strength. *^FourA haze value. In Comparative Example 1, the anchor coat treatment (Polyester
Delamination adhesion when using a stell-based coating agent) is 65 g
/ 15 mm.

[0026]

According to the present invention, since two types of EVOH having different melting points are used in combination, a water-alcohol solution of the EVOH has excellent storage stability and can be coated on various substrates. Excellent effects on the barrier properties, adhesion, transparency and coating properties of the film can be obtained.

Claims (5)

(57) [Claims] 1. A saponified ethylene-vinyl acetate copolymer 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: b) saponified ethylene-vinyl acetate copolymer other than the above (a), (c) a mixed solvent of water and a lower alcohol having 1 to 4 carbon atoms,
A saponified ethylene-vinyl acetate copolymer solution, comprising: Tm <220-1.46Et + 3.31 (Sv-99.
6) Tm: melting point (° C.) by differential scanning calorimeter Et: ethylene content (mol%) Sv: saponification degree (mol%) 2. A method according to claim 1, wherein the melting point (Tm) is represented by the formula Tm.
≧ 220-1.46Et + 3.31 (Sv-99.6)
Is obtained by treating a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol% and a saponification degree of 90 mol% or more with hydrogen peroxide in a mixed solvent of water and alcohol. The ethylene-vinyl acetate copolymer saponified product according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer is used.
Saponified vinyl acetate copolymer solution. (B) a melting point (TM) of the formula TM
≧ 220-1.46ET + 3.31 (SV-99.6)
[However, TM: melting point (° C.) by differential scanning calorimeter, E
T: ethylene content (mol%); SV: saponification degree (mol%). Is satisfied, and the ethylene content is 20 to 60.
The saponified ethylene-vinyl acetate copolymer solution according to claim 1 or 2, wherein a saponified ethylene-vinyl acetate copolymer having a saponification degree of 90 mol% or more in mol% is used. 4. The mixing weight ratio of (a) and (b) is (a)
/ (B) = 1/9 to 9 claims 1, characterized in that a / 1 to 3 ethylene according to any one - vinyl acetate copolymer saponified solution. 5. A laminate comprising a substrate coated with the saponified solution of the ethylene-vinyl acetate copolymer according to any one of claims 1 to 4.