JPS60124662A - Method for forming coating film of saponified ethylene/ vinyl acetate copolymer - Google Patents

Abstract

PURPOSE:To obtain a coating film having remarkably improved transparency and gas barrier properties, by dissolving a saponified ethylene/vinyl acetate copolymer in a mixture consisting of water, a specified alcohol and acetic acid as a solvent and applying the soln. to a substrate to form a coating film of said saponified copolymer. CONSTITUTION:A saponified ethylene/vinyl acetate copolymer having an ethylene content of 25-55mol% and a degree of saponification of vinyl acetate component of 90mol% or below is dissolved in a mixture consisting of 10-60wt% water, 5-70wt% at least one member selected from among propyl alcohol, butyl alcohol and benzyl alcohol as a solvent. A substrate is coated with the resulting soln. and drived to form a coating film of said saponified copolymer. The soln. contains said saponified copolymer at a concn. of pref. 0.5-15wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION A film obtained from a saponified ethylene-vinyl acetate copolymer with an ethylene content of 1lzs to 55 mol% and a vinyl acetate component having a degree of desiccation of 90 mol% or more has excellent transparency, oxygen barrier properties, etc. It is useful as a packaging material for foods, medical products, industrial chemicals, etc., or as a composite material laminated with plastic film, paper, metal foil, etc.

When forming a film of the saponified product, any method can be used, but it is possible to form a film with a relatively thin film thickness, and it can be easily applied to substrates with complex shapes such as hollow containers. A solution coating method in which a solution prepared by dissolving the saponified product in a solvent is applied to a substrate is attracting attention because it can form a film on the substrate and can be applied using relatively simple equipment.

In this method, many types of saponified sludge have been proposed so far; for example, Japanese Patent Publication No. 46-2
Water-containing propyl alcohol and water-containing butyl alcohol described in Japanese Patent Publication No. 3911 and Japanese Patent Publication No. 47-48489 are considered to be promising in that they produce transparent films.

However, the present inventors have investigated and found that when forming a coating film using such a hydroalcoholic system, a coating film with good transparency cannot be obtained unless the coating solution is maintained at a high temperature of 50°C and the coating operation is performed. It has been found that there are drawbacks such as poor storage stability and storage stability of the coating liquid, and the need to re-dissolve at high temperature when used. Maintaining such a high temperature not only requires extra thermal energy, but also causes changes in the concentration of the coating solution due to evaporation of the solvent, making it difficult to manage the process, such as having to perform the coating process using a II+ system. This is a problem that needs to be solved. Furthermore, it is difficult to form a microscopically homogeneous coating film in terms of coating film properties such as transparency and gas barrier properties, so it is difficult to say that it is necessarily sufficient to meet the recent strict quality requirements. Therefore, it is necessary to further improve the physical properties of the coating film.

However, the inventors of the present invention have solved this problem (as a result of extensive research, they have developed a saponified ethylene-vinyl acetate copolymer with an ethylene content of 25 to 55 mol% and a degree of saponification of the vinyl acetate component of 90 mol% or more). (A) as a solvent when coating a solution on a base material and drying to form a coating film of the saponified product.
The purpose is achieved when using a mixture consisting of: water 10-60% by weight (B) 5-70% by weight of at least one of 7'lopyl alcohol, butyl alcohol or benzyl alcohol (C) acetic acid 2-85% by weight The present invention was completed based on the discovery that the present invention can be completed.

In the present invention, when such a specific mixed solvent is used, a stable coating film with improved transparency and gas barrier properties is always obtained even when the coating operation is performed at room temperature, so no special management is required during the coating operation. Its industrial usefulness is extremely great in that it eliminates the drawbacks of the conventional method.

The saponified ethylene-vinyl acetate copolymer used in the present invention has an ethylene content of 25 to 55 mol%, preferably 28 to 4 mol%.
8 mol%, the degree of saponification of the vinyl acetate component must be 90 mol% or more, preferably 95 mol% or more.If the ethylene content is less than 25 mol%, the gas barrier properties at high humidity will decrease; % or more, the physical properties of the coating film, such as sufficient gas barrier properties and printability, deteriorate. Furthermore, if the degree of saponification is less than 90 mol%, gas barrier properties and moisture resistance will decrease.

The saponified copolymer further contains small amounts of propylene, isobutyne, a-olefins such as a-octene, a-dodecene, and a-octadecene, unsaturated carboxylic acids or salts thereof, partial alkyl esters, complete alkyl esters, nitrile, It may contain a fumonomer such as anhydride, unsaturated sulfonic acid or a salt thereof.

In the present invention, the solvent for the saponified product is (A) 10 to 6011% water, (B) at least one of propyl alcohol, butyl alcohol, or benzyl alcohol.
-70% by weight, (C) acetic acid, 2-85% by weight, which eliminates the above-mentioned drawbacks of conventionally used water/propyl alcohol or water/butyl alcohol solvents by blending a specific amount of acetic acid. This is solved by

In the mixed solvent, the content of (A) water should be 10-60% by weight, preferably 30-50ml%.

If it is less than 1% by weight, it is difficult to obtain a homogeneous solution (but if it is more than 60% by weight, the problem arises that the solubility of the saponified product is significantly reduced. In addition, propylfurcol, butyl alcohol, benzylfurfur of CB> is The content should be ~70% by weight, preferably 40-60% by weight,
5? ! ! If it is less than 1%, there is a problem that the solubility decreases unless a considerably large amount of acetic acid is used, and if it is more than 70% by weight, it is difficult to obtain a homogeneous solution, which is impractical, and (C)
The content of acetic acid should be 2 to 85% by weight, preferably 5 to 40% by weight, and particularly preferably 10 to 30% by weight. If it is less than 2% by weight, the effect of the present invention will be poor and the effect of its addition will be reduced. It is difficult to recognize that the use of acetic acid of 85% by weight or more is undesirable in terms of corrosion of the equipment.As the propyl alcohol of component (B), n-propyl alcohol, 1s
O-propyl alcohol can also be used as butyl alcohol! Examples include n-phthyl alcohol, 1so-butyl alcohol, 5eC-butyl alcohol, tert-butyl alcohol, and 1so-propyl alcohol is preferably used. Even if acetic acid is added to alcohols other than (B), a coating film with good transparency cannot be obtained.

Further, in (C), the effect of the present application can be similarly obtained even if the acetic acid is any alkyl ester such as methyl ester, ethyl ester, propyl ester.

The concentration of the saponified ethylene-vinyl acetate copolymer solution is not particularly limited and can be coated within any range, but it is usually 0.
．． Approximately 5 to 15% by weight is preferable. One of the features of the present invention is that even when using a coating liquid with a low concentration, the coating film does not become cloudy, which is different from the conventional coating method using hydroalcohol as a solvent. In the case of liquid application, a solution with a relatively i1% concentration is used, resulting in a coating of 1! Considering that the adjustment of thickness is unavoidable, the present invention has great advantages in this respect as well.

The effect of the present invention is particularly noticeable at low concentrations, i.e. 3.
This is a case where a coating liquid of about 10% by weight is used. Moreover, since the above coating liquid has excellent stability, there is no need to worry about saponified precipitates being deposited even without special operations such as heating, and the solution has excellent storage stability at low temperatures. 11
%, coating film formation can be carried out at any temperature around room temperature.

In the present invention, the substrate to which the saponified ethylene-vinyl acetate copolymer is applied is not particularly limited, and includes films, sheets, hollow containers, etc. of various plastics such as polyethylene, polypropylene, polyester, polystyrene, and polyvinyl chloride. Examples include paper, cellophane, cellulose acetate, natural rubber, synthetic rubber, and metal.

The film thickness of such a base material is suitably about 10 to 1000 μm. In the present invention, a laminate obtained by coating a saponified ethylene-vinyl acetate copolymer on such a base material can be put to practical use as a packaging material as it is. However, if necessary, the coating film of the saponified ethylene-vinyl acetate copolymer can be peeled off from the base material and used as a single layer film, sheet, etc.

Application methods include roller coating, spray coating, dip coating, and any other known method.

Depending on the type of substrate, surface oxidation treatment, flame treatment, -anchor coating treatment, primer treatment, etc. can be carried out as appropriate in order to improve the adhesive force with the saponified ethylene-vinyl acetate copolymer layer.

As the anchor treatment agent, polyurethane compounds and polyester incyanate compounds can be suitably used. The practical thickness of the anchor coat layer is about 0.05 to 3 μm.

After applying a solution of saponified ethylene-vinyl acetate copolymer to a substrate, drying is performed. Drying temperature is 30-15
It is sufficient to heat the coating at a temperature of 0°C, preferably 50 to 120°C, for about 3 seconds to 5 minutes.During such drying, the volatile components in the coating film, that is, water, alcohol, and acetic acid, are removed. Although it has a fairly high boiling point, the coexisting alcohols seem to promote the evaporation of acetic acid and water, so the drying temperature above is sufficient. The paint film can be dried until most of the volatile matter is removed, but
0.5 to 10% by weight of volatile matter remains in the paint film to prevent tap-king from occurring in the paint film and to maintain the transparency and glabellar adhesive strength of the paint film over a long period of time. is advantageous. Among the volatile components, water is 0.3 to 9
Weight%, alcohol 0-0.53m%, acetic acid 0-0.
It is desirable to set the composition of the coating liquid and drying conditions so that the ratio is 1.5% by weight.

In this way, a transparent coating film of the saponified ethylene-vinyl acetate copolymer is formed, and the film thickness is 0.5~
A value of about lOμ is practical. If the i thickness is less than 0.5μ, it is difficult to exhibit sufficient gas barrier properties, while if the i thickness is more than 10μ, an inner cone will occur in the control. If necessary, it is of course possible to further form a moisture-proof layer on the coating film by coating with a vinylidene chloride resin, coating with a vinyl chloride-vinyl acetate copolymer, or the like. The resulting coating film is useful as a single-layer film or sheet of a saponified ethylene-vinyl acetate copolymer, or as a composite material laminated with polyester, polyolefin, etc., as a packaging material or container for foods, beverages, drugs, pharmaceuticals, etc. The typical layer structure for highly practical packaging materials and containers is base material (polyester, polyethylene, etc.) with a film thickness of 10 to 1000μ/It thickness 0.0
Anchor coat layer with a thickness of 5 to 3μ/saponified ethylene-vinyl acetate copolymer with a film thickness of 0.5 to 1Oμ (volatile content 0.
5 to 5% by weight) or ethylene-fi [
A further film thickness of 0.5 to 3 on the saponified acid vinyl copolymer layer
Vinylidene chloride resin layer or vinyl chloride
A vinyl acetate copolymer layer is provided.

Its shape may be arbitrary, such as a film, a sheet, a hollow bottle, or a tube.

Hereinafter, the method of the present invention will be explained in more detail with reference to examples. Unless otherwise specified, all references to 0% and parts are based on weight.

Example 1 Water 40%, 1so-propyl alcohol 50%, vinegar 11
94 parts of mixed solvent containing 10% and saponified ethylene-vinyl acetate copolymer (ethylene content 36 mol%, degree of saponification 9)
9.5 mol %) was added thereto and stirred at 40 to 50°C for about 1 hour to prepare a transparent solution. On the other hand, on a polyethylene terephthalate violet film with a film thickness of 50 μm, 100 parts of a polyurethane adhesive base agent, 6.5 parts of a hardening agent, and 900 parts of ethyl acetate were added.
Membrane N3μ using a polyurethane compound solution consisting of
Anchor coat treatment was applied.

The film treated in this way was immersed in the coating solution at a temperature of 25°C, and immediately dried at 80°C for 3 minutes to reduce the moisture content to 1.
．． A coating film of saponified ethylene-vinyl acetate copolymer (film thickness: 6 μm) containing 1%, 1so-propyl alcohol content of 0.1%, and acetic acid content of 10.1% was formed.

When the transparency of the laminate was measured according to STH01003-52, the haze value was 13%, indicating extremely good transparency.

(The haze value of the base material is 14%) Also, when the oxygen barrier property was measured according to ^STN 01434-58, the oxygen permeability was acc(NTP)/s'
・It was 24br and 11m, and showed good gas-blocking properties.

Furthermore, when the interlayer adhesion strength was measured, all interlayer adhesion strengths were 3QQg/25m+++ or more, which was extremely good.

In addition, the above laminate was heated to 65% R1+ in an atmosphere of 20°C.
Even after being left for 0 days, no cracking or other deterioration in transparency was observed, and the appearance and interlayer adhesion remained almost unchanged.

Control Example 1 The same experiment as in Example 1 was performed except that the use of acetic acid was omitted, and the haze value was 80% and the oxygen permeability was 43cc (NTP) 7m2・24br 7at+
Both decreased to s. Coating: [When the liquid temperature of A8 was raised to eo''c, the haze value was 53% and the oxygen permeability was 38cc(NTP)/+*2·24hr-ate.

Control Examples 2 and 3 Ethylenediamine was used instead of acetic acid (Control Example 2),
An experiment was conducted according to the same procedure except that ethyl alcohol was used instead of 1so-propyl alcohol (Control Example 3). The haze value is 78% for control example 2 and 31 for control example 3.
%, and the oxygen permeability of Control Example 2 was 38cc (NTI'
)/, m' -241+r-at+w, Control example 3 is 40
cc(NTI')/s" ・241+r-at+sl It wasn't too big.

Examples 2-6. Control Examples 4 to 9 Coating films were formed according to Example 1 under the conditions shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

However, in Example 6, a vinylidene chloride resin layer with a thickness of 2 μm was added on the saponified ethylene-vinyl acetate copolymer layer,
and a vinyl chloride-vinyl acetate copolymer layer.

In addition, the oxygen permeability of each base material (cc (NTP)/+' ・2
4hr-aLm) is as follows.

0PP (biaxially oriented polypropylene) film (60μ)
; Bo.

LDPE (low density polyethylene) film (35μ)
;2100PET (polyethylene terephthalate) bottle (300μ);5,5PP (polypropylene) bottle (
50 ON) ; 205 Procedures Amendment Written December 19, 1980 1, Indication of the case 1982 Patent Application No. 233266 2, Name of the invention Method for forming a coating film of saponified ethylene-vinyl acetate copolymer; ( , Relationship to the case of the person making the amendment Patent Applicant Address 9-6 Nozaki-cho, Kita-ku, Osaka City, ・1. 1fa of the detailed description of the invention in the specification subject to the amendment 5. Contents of the amendment (1) Specification [and vinyl chloride-vinyl acetate 51. respectively] on page 12, lines 4-5 of
"I am corrected."

(2) "2" in the film thickness (μ) column of saponified ethylene-vinyl acetate copolymer in Example 6 in Table 1 (Examples) on page 13 of the specification is corrected to "4".

that's all

Claims (1)

[Scope of Claims] 1. A solution of a saponified ethylene-vinyl acetate copolymer having an ethylene content of 25 to 55 mol% and a degree of saponification of vinyl acetate component of 90 mol% or more is applied to a base material and dried. In forming the compound coating, the solvent is (A) 10 to 60% by weight of water (B) 5 to 70% by weight of at least one of propyl alcohol, butyl alcohol, or benzyl alcohol (C) 2 to 85% by weight of acetic acid 2. A patent claim characterized in that a base material anchor-coated with a polyurethane compound is used. The method according to item 1. 3. Base material with a film thickness of 10 to 1000μ/film thickness of 0.05 to 3μ
The film thickness is 0.5 to 10
The method according to claim 1, characterized in that a coating film of saponified ethylene-vinyl acetate copolymer of μ is formed. 4. The method according to claim W1, item 3, characterized in that the volatile content in the coating film of the saponified ethylene-vinyl acetate copolymer is 0.5 to 10% by weight. 5. FF811, which is characterized in that a solution with a resin concentration of 0.5 to 15% by weight is used as a solution of saponified ethylene-vinyl acetate copolymer! 111, Items 1 to 4 of the present invention. 6. A special FF claim characterized in that after applying a solution of saponified ethylene-vinyl acetate copolymer to a base material, drying is performed at 30 to 150°C for 3 seconds to 5 minutes.
l+The method described in items 1 to 4.