JPH11106591A - Saponified ethylene-vinyl acetate copolymer solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a saponified ethylene-vinyl acetate copolymer (EVOH) soln. excellent in solubility and low-temp. stability by dissolving EVOH having a specific water content in a solvent. SOLUTION: This soln. is prepd. by dissolving a water-contg. EVOH, prepd. by causing EVOH having an ethylene content of 60 mol.% or lower and a degree of saponification of 90 mol.% or higher to absorb water to a water content of 10 wt.% or higher, in a solvent contg. at least 20 wt.% 4C or lower alcohol, pref. in a mixed solvent comprising 75-20 wt.% water and 25-80 wt.% alcohol. Based on 100 pts.wt. EVOH, 0.1-20 pts.wt. boric acid compd. [e.g. boric acid or sodium borate (such as sodium metaborate, sodium diborate, sodium tetraborate, or sodium pentaborate)] is added to the soln. in order to further improve its stability. The soln. with a concn. of 1-50 wt.% is applied to a susbtrate having a thickness of 10-1,000 μm to form thereon a coating film having a thickness of 0.5-500 μm, thus imparting gas barrier properties to the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH).
More specifically, the present invention relates to an EVOH solution having excellent solubility and low-temperature stability.

[0002]

2. Description of the Related Art Conventionally, a film obtained from EVOH has excellent transparency and oxygen barrier properties, and is used as a packaging material for foods, medical products, industrial chemicals and the like, or a composite material laminated with a plastic film, paper, or metal foil. Useful as 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. The solution coating method of applying a solution in which EVOH is dissolved in a solvent or an aqueous dispersion in which EVOH is dispersed in water to a base material has attracted attention because of the ability to form a coating and the operation of coating with a relatively simple device. ing. However,
When EVOH is used as a solution, the stability of the solution is always a problem, and the viscosity of the solution may increase or the EVOH may gel due to storage conditions, such as for a long time or at a high temperature. Is where stability is desired. In order to improve the stability, Japanese Patent Application Laid-Open No.
No. 7144 proposes a resin composition of an EVOH solution containing boric acid.

[0003]

However, such a resin composition has a drawback that it takes a long time to manufacture due to the low solubility of EVOH itself, and a new improvement is desired.

[0004]

Accordingly, the present inventor has proposed an E
As a result of intensive studies on the VOH solution, an EVOH solution obtained by dissolving EVOH having a water content of 10% by weight or more in a solvent solves the above-mentioned problems, and is also excellent in storage stability at low temperatures (around 0 ° C.). This led to the completion of the present invention.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The EVOH used in the present invention is not particularly limited, but has an ethylene content of 60 mol% or less (further, 25 to 5%).
5 mol%) and a saponification degree of 90 mol% or more (more preferably 99 mol% or more).
If it exceeds 0 mol% or if the saponification degree is less than 90 mol%, the gas barrier property is undesirably reduced.

The EVOH used in the present invention may contain a small amount of a modifying component such as unsaturated carboxylic acids, anhydrides, salts, esters, α-olefins, vinyl ethers, nitriles, and amides. Components may be included. In the present invention, as long as the EVOH has an ethylene content and a saponification degree within the above ranges, it may be used alone or two or more EVOHs having different compositions may be used in combination.

In the present invention, EVOH as described above is hydrated, and the water content is 10% by weight or more (more preferably 20 to 60%).
(% By weight, particularly 25 to 50% by weight). The use of EVOH which does not contain water as in the conventional case requires a long time until dissolution.
The object of the present invention cannot be achieved due to insufficient storage stability.

In obtaining such a water-containing EVOH,
A normal EVOH (pellet) and water are mixed and stirred to absorb water into the pellet, and then the water content is adjusted.
The method of adjusting the water content by blowing steam into OH (pellet) or adjusting the water content by adding water with a small amount of alcohol such as methanol or isopropyl alcohol during the production of EVOH can be mentioned. It is not limited.

The water-containing EVOH thus obtained is dissolved in a solvent to form an EVOH solution. As the solvent, usually, an alcohol or a mixed solvent of alcohol and water is used. Lower alcohols of 4 or less are preferred, and methyl alcohol, ethyl alcohol, propyl alcohol (n-propyl alcohol, iso-propyl alcohol), butyl alcohol (n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol) ), Etc., and preferably is
o-Propyl alcohol and n-propyl alcohol are used. When a mixed solvent with water is used, the mixing ratio (weight ratio) of water / alcohol is 75/25 to 20/8.
0 (more preferably 60/40 to 30/70).

The mixing of the above-mentioned hydrated EVOH and the solvent can be carried out by a known method. For example, the hydrated EVOH is mixed with the above (mixed) solvent, and the mixture is heated at 50 to 100 ° C. to form a turbine type ribbon. The mixing and stirring may be performed using a stirrer equipped with a stirring blade such as a mold under the conditions of a rotation speed of 10 to 1000 rpm.

Thus, the EVOH solution of the present invention can be obtained. It is also preferable to add a boron compound to the EVOH solution of the present invention for the purpose of further improving the stability. Or a metal salt thereof, for example, calcium borate, cobalt borate, zinc borate (zinc tetraborate, zinc metaborate, etc.),
Aluminum potassium potassium borate, ammonium borate (ammonium metaborate, ammonium tetraborate, ammonium pentaborate, ammonium octaborate, etc.), cadmium borate (cadmium orthoborate, cadmium tetraborate, etc.), potassium borate ( Potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium octaborate, etc.), silver borate (silver metaborate,
Copper tetraborate (copper borate, copper metaborate, copper tetraborate, etc.), sodium borate (sodium metaborate, sodium diborate, sodium tetraborate),
Sodium pentaborate, sodium hexaborate, sodium octaborate, etc., lead borate (lead metaborate, lead hexaborate, etc.), nickel borate (nickel orthoborate, nickel diborate, nickel tetraborate, Nickel octaborate, etc., barium borate (barium orthoborate, barium metaborate, barium diborate, barium tetraborate, etc.), bismuth borate, magnesium borate (magnesium orthoborate, magnesium diborate, metaborate) Magnesium, trimagnesium tetraborate, pentamagnesium tetraborate, etc.), manganese borate (manganese borate, manganese metaborate, manganese tetraborate, etc.), lithium borate (lithium metaborate, lithium tetraborate,
Lithium pentaborate, etc.), borax, carnite,
Boroic acid minerals such as inyoite, garnet, thianite, and ziberite are exemplified, and boric acid, sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium pentaborate, and the like) are preferred. Sodium hexaborate, sodium octaborate, etc.)
The compounding amount is 0.1% with respect to 100 parts by weight of EVOH.
The amount is preferably from 20 to 20 parts by weight (more preferably from 0.2 to 10 parts by weight). If the amount is less than 0.1 part by weight, there is no effect of the compounding. .

The thus-obtained EVOH solution of the present invention is applied to various substrates. The EVOH concentration in the EVOH solution is not particularly limited. Considering stability and the like, 1 to 50% by weight,
Preferably 5 to 40% by weight, more preferably 10 to 30%
% By weight is desirable.

The substrate on which the EVOH is applied in the present invention is not particularly limited, and may be a linear low-density polyethylene,
Low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-acrylate copolymer, polypropylene, propylene
α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, homo- or copolymer of olefin such as polybutene, polypentene, or homo- or copolymer of these olefins with unsaturated carboxylic acid or ester thereof Broadly defined polyolefin resins such as graft-modified resins, polystyrene resins, polyesters, polyamides, copolymerized polyamides, polyvinyl chloride, polyvinylidene chloride, acrylic resins, vinyl ester resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene Stretched or unstretched films, sheets, hollow containers or paper, cellophane, cellulose, cellulose acetate, natural rubber, synthetic rubber, metal foil, woven fabric, nonwoven fabric, metal cotton strip, woody material of various plastics such as chlorinated polypropylene, EVOH, etc. surface And the like, and the thickness of such a substrate is suitably about 10 to 1000 μm.

For such coating, 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, when the drying temperature is 30 to 1
50 ° C., preferably at a temperature of about 70 to 120 ° C. for 3 seconds to
Heating may be performed for about 5 minutes. In such drying, the volatile components in the coating film, that is, water and alcohol are removed, but usually, the drying may be performed 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 500 μm, preferably about 1 to 100 μm. If it is less than 0.5 μm, it is difficult to exhibit sufficient gas barrier properties.
Above μ, it is difficult to control the film 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. E above
When applying the VOH solution, it is useful to apply an anchor coat in order to improve the adhesion to various substrates, and an anchor coat agent such as polyurethane, polyester, or polyethyleneimine may be used in combination.

A laminate in which various substrates are coated with an EVOH solution is used for packaging or containers of foods, beverages, medicines, medicines, electric parts, mechanical parts, etc., for heating pipes, and for building interiors such as wallpaper. It is useful for materials and the like, and can also be used as furniture, automobile interior materials, etc. by coating on PVC leather or the like. As a highly practical packaging material and a layer structure of a container, typically, a substrate (polyester, polyethylene, etc.) having a thickness of 10 to 1000 μ / a thickness of 0.5 to
500 μm of EVOH (volatile content: 0.5 to 5% by weight) or 0.5 μm thick 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 arbitrary such as a film, a sheet, a hollow bottle, and a tube.

[0017]

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 having an ethylene content of 30 mol% and a saponification degree of 99.8 mol% was charged into warm water to obtain a water-containing EVO having a water content of 30%.
H was obtained. 80 ° C. was previously added to 100 parts of the obtained hydrous EVOH.
196 parts of iso-propyl alcohol and water 5
4 parts of a mixed solution (250 parts) was added and mixed and stirred with a homomixer to obtain an EVOH solution of the present invention (with an EVOH content of 20).
%). The following evaluation was performed using the obtained EVOH solution.

(Solubility) During the mixing and stirring (in an atmosphere of 20 ° C.), the EVOH was visually observed until it was completely and completely dissolved, and the required time was examined and evaluated as follows. ○ −−− Complete dissolution within 40 minutes △ −−− Complete dissolution within 40 to 60 minutes × −−− Completely not dissolved even after over 60 minutes (low temperature stability) 50 g of the obtained EVOH solution has a diameter of 40
mm, 60mm high glass bottle
Visually observe the property change over time when left at 0 ° C.,
The evaluation was as follows. ○ −−− Fluid even after 30 minutes △ −−− Fluid within 15 to less than 30 minutes × −−− Loss of fluidity within less than 15 minutes

Example 2 The same procedure as in Example 1 was carried out except that the water content of the water-containing EVOH was changed to 20%, and 0.2 part of boric acid was further added.
A mixed solution (300 parts) of 224 parts of propyl alcohol and 76 parts of water was added to obtain an EVOH solution (20% EVOH content), which was similarly evaluated.

Example 3 In Example 2, iso-propyl alcohol 131 was used.
An EVOH solution (30% EVOH content) was obtained in the same manner except that a mixed solution (167 parts) of 1 part and 36 parts of water was added, and was similarly evaluated.

Example 4 An EV was prepared in the same manner as in Example 2 except that EVOH having an ethylene content of 45 mol% and a saponification degree of 99.7 mol% was used.
An OH solution was obtained and evaluated similarly.

Example 5 An EVOH solution (20% EVOH content) was obtained in the same manner as in Example 3 except that the amount of boric acid was changed to 1 part.
Evaluation was performed similarly.

Example 6 In Example 3, iso-propyl alcohol 506 was used.
An EVOH solution (10% EVOH content) was obtained in the same manner except that a mixed solution (700 parts) of 1 part and 194 parts of water was added, and the evaluation was performed in the same manner.

Comparative Example 1 An EVOH solution (EVOH content: 20%) was obtained in the same manner as in Example 1 except that EVOH having a water content of less than 1% was used, and evaluation was performed in the same manner. Table 1 shows the evaluation results of the examples and the comparative examples.

[0025]

[Table 1]

[0026]

The EVOH solution according to the present invention is a water-containing EVOH solution.
It is excellent in solubility and low-temperature stability and is useful for coating applications. The laminate coated with the EVOH solution can be used for packaging or containers of foods, beverages, drugs, pharmaceuticals, electric parts, machine parts, etc. It is also useful as an interior material for buildings, such as for heating pipes, wallpaper, and the like, and can also be used as furniture, automobile interior materials, etc. by coating on PVC leather or the like.

Claims (4)

[Claims] 1. A saponified ethylene-vinyl acetate copolymer solution obtained by dissolving a saponified ethylene-vinyl acetate copolymer having a water content of 10% by weight or more in a solvent. 2. The saponified ethylene-vinyl acetate copolymer solution according to claim 1, wherein the solvent contains 20% by weight or more of a lower alcohol having 4 or less carbon atoms. 3. The saponified ethylene-vinyl acetate copolymer solution according to claim 1, further comprising a boron compound. 4. The content of the boron compound is 0.1 to 100 parts by weight of the saponified ethylene-vinyl acetate copolymer.
4. The saponified ethylene-vinyl acetate copolymer solution according to claim 3, wherein the amount is 20 parts by weight.