JPH0931274A - Ionomer composition, its thin film and molding article having formed coating film comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both an ionomer composition capable of forming a coating film excellent in transparency, adhesivity, water resistance, etc., from an aqueous dispersion and to prepare the aqueous dispersion SOLUTION: This ionomer composition comprises (A) 80-99.9 pts.wt. of an ionomer of an ethylene/unsaturated carboxylic acid copolymer and (B) 0.1-20 pts.wt. of chitosan. The ionomer composition obtained is soluble or dispersible into water. Consequently, a thin film of the ionomer composition or a molding article obtained by forming the thin film of the ionomer composition on a substrate can be produced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel ionomer composition. More specifically, it relates to a composition comprising an ionomer and chitosan, which exhibits good water resistance when a film is formed from an aqueous dispersion.

[0002]

2. Description of the Related Art A polymer obtained by partially neutralizing an ethylene / unsaturated carboxylic acid copolymer with a metal or ammonium is called an ionomer. Among them, it is known that an ionomer neutralized with an alkali metal or ammonium can be dispersed in water without using a dispersant such as a surfactant, and has been industrialized.

The ionomer is dispersed in water by adding the ionomer itself or an ethylene / unsaturated carboxylic acid copolymer and an ion source for neutralization to water to obtain 100 to 200 ° C.
It is achieved by stirring under high temperature and pressure. An aqueous dispersion of an ionomer is coated on a base material such as aluminum foil or paper, and used for the purpose of waterproofing, heat sealing, bending resistance, imparting surface gloss and the like. Further, the ionomer containing highly hydrophilic alkali metal such as Na, K, Rb and Cs ions in a high concentration exhibits excellent dispersibility and becomes a transparent aqueous dispersion, which is applied to the surface of a substrate to obtain an ionomer. It is known that a film having a strong heat-sealing property, which is a feature of the above, is formed.

However, the ionomer coating thus obtained cannot be said to have sufficiently excellent water resistance,
Under severe conditions of use, it may swell or peel off due to moisture.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present inventors
A method for improving the water resistance of the above coating while maintaining the excellent properties of the ionomer was investigated. as a result,
We have found that the objective can be achieved by compounding a small amount of chitosan with an ionomer to form a composite. Therefore, an object of the present invention is to provide a novel ionomer composition. Another object of the present invention is to provide an ionomer aqueous dispersion which forms a thin film or a film of a molded article having excellent transparency, adhesion and water resistance.

[0006]

Means for Solving the Problems That is, the present invention provides an ionomer (A) of an ethylene / unsaturated carboxylic acid copolymer.
80-99.9 parts by weight and chitosan (B) 0.1-20
And an ionomer composition comprising 100 parts by weight (total of both parts is 100 parts by weight). The present invention also provides ionomers (A) 80-9 of ethylene / unsaturated carboxylic acid copolymers.
The present invention relates to an ionomer composition in which 9.9 parts by weight and 0.1 to 20 parts by weight of chitosan (B) (total of 100 parts by weight) are dissolved or dispersed in water.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The ionomer (A) used in the present invention is a polymer obtained by partially neutralizing an ethylene / unsaturated carboxylic acid copolymer with a metal or ammonium. As the unsaturated carboxylic acid that constitutes a certain ethylene / unsaturated carboxylic acid copolymer,
Examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic acid and fumaric acid monoalkyl esters, and maleic anhydride, with acrylic acid or methacrylic acid being particularly preferred.

Such a copolymer does not need to be a copolymer of ethylene and an unsaturated carboxylic acid alone, but may be an unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, isobutyl acrylate, acrylic acid n. It may be copolymerized with butyl, 2-ethylhexyl acrylate, methyl methacrylate, or vinyl ester such as vinyl acetate.

The ionomer used in the present invention is preferably one which can be dispersed in water. Usually, the ionomer of an ethylene / unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 10 to 30% by weight, particularly 18 to 25% by weight. Is preferred. The higher the unsaturated carboxylic acid content in the copolymer, the easier the water dispersion. However, if the content is too high, the water resistance in the case of forming a coating film decreases.

As the copolymer, those having various molecular weights can be used. However, if the molecular weight becomes too small, the mechanical strength decreases, so that the melt flow rate at 190 ° C. under a load of 2160 g is 0.1 to 3000 g / 10 min. Things are good. However, when used as an aqueous dispersion, it is desirable that the molecular weight is not too large in order to obtain a stable aqueous dispersion, for example, the melt flow rate is 10 to 10
The most preferable one is 00 g / 10 minutes, especially about 30 to 500 g / 10 minutes.

Various ion sources can be used as the ion source of the ionomer of the present invention. Examples thereof include alkali metals such as lithium, sodium, potassium, rubidium and cesium, alkaline earth metals such as calcium and magnesium, transition metals such as zinc and copper, ammonia and amines. Especially when used as an aqueous dispersion, an alkali metal is preferable. The degree of neutralization in the ionomer is arbitrary, but when used as an aqueous dispersion, it is preferably 50 mol% or more, particularly 60 mol% or more.

Chitosan (B) used in the present invention is widely distributed in crustaceans, insects and fungi in nature,
Chitin, which is a polysaccharide similar to cellulose, is partially or completely deacetylated by alkali treatment.

Chitosan is industrially produced from crab shells and the like as a raw material, and its specific production method is known. For example, crab shells are crushed and treated with 3-5% hydrochloric acid, washed with water, further treated with 3-5% sodium hydroxide solution, and sufficiently washed with water to leave chitin as a solid content. It is obtained by treating this chitin in a 40 to 50% sodium hydroxide solution at 100 ° C. for several hours.

The chitosan used in the present invention is preferably dispersed uniformly in an ionomer aqueous dispersion as described below, and therefore, an aqueous chitosan is preferable.
However, if the amino group content of chitosan is low, or if the molecular weight is high, the presence of an acid is necessary in order to dissolve in water, and when the amount of acid is high, gelation and solid content in the ionomer aqueous dispersion are compounded. Precipitation occurs, which is not preferable. Therefore, in the present invention, it is preferable to use chitosan which can be dissolved in water without the presence of an acid, has a high amino group content, or has a low molecular weight.

Specifically, the chitosan used in the present invention contains 40% or more of amino groups deacetylated from chitin per glucose unit, that is, the degree of deacetylation is 40% or more, preferably 70% or more. It is preferable that some or all of their amino groups are converted into ammonium salts by an acid such as acetic acid or citric acid. In addition, since the solubility in water or acid is increased, the molecular weight of chitosan is such that the viscosity of a 1% aqueous solution is 50 c at 20 ° C.
A low molecular weight product having p or less is preferable. In particular, from the viewpoint of solubility in water, those having 20 cp or less are preferable. As the low molecular weight chitosan, chitosan which has been subjected to a low molecular weight treatment with an enzyme may be used.

The acid used for dissolving chitosan in water is not particularly limited, but citric acid, acetic acid, glycolic acid,
Lactic acid or the like is usually used.

The preferred mixing ratio of the ionomer (A) and chitosan (B) in the present invention varies depending on the type of chitosan used and the required level of physical properties of the composition,
(A) / (B) (weight ratio) is 99.9 / 0.1-80 /
The range is 20, preferably 99.8 / 0.2 to 90/10, more preferably 99.7 / 0.3 to 95/5.
Chitosan is usually added to the ionomer aqueous dispersion in the form of an aqueous solution, but since the acid is added to the chitosan aqueous solution in many cases, if the amount added is too large,
It should not be used in excess, as the alkaline ionomer aqueous dispersion may gel and precipitate.
On the other hand, if the blending amount is too small, the water resistance improving effect is not sufficiently exhibited.

By mixing the ionomer and chitosan, it is assumed that they are bound to each other by forming an ammonium salt or forming an amide bond between the carboxyl group of the ionomer and the amino group of chitosan. This means that, for example, in the infrared absorption spectrum, the absorption peak appearing in the vicinity of 1700 cm ⁻¹ based on the unneutralized carboxyl group dimer in the ionomer is
This is supported by the weak spectrum of the ionomer composition of the present invention. The unique physical properties of the ionomer composition of the present invention are believed to be based on the novel product resulting from such binding.

The ionomer and chitosan can be blended in such a manner that the ionomer is in the form of an aqueous dispersion and the chitosan is in the form of an aqueous solution as described above, whereby a uniform blend can be obtained. In this case, it can be produced not only by mixing the ionomer aqueous dispersion prepared in advance with the chitosan aqueous solution, but also by dispersing the ionomer in the chitosan aqueous solution.

The method for producing an aqueous dispersion of an ionomer is already well known. For example, the ionomer and water are stirred in an autoclave at a temperature above the melting point of the ionomer, for example above 80 ° C., preferably above 95 ° C. Method, a method of simultaneously performing neutralization and production of an aqueous dispersion by stirring an ethylene / unsaturated carboxylic acid copolymer which is a base polymer of an ionomer and an alkali metal compound at high temperature under pressure, etc. There is.

In the case of an aqueous dispersion containing an ionomer and chitosan, considering the viscosity and the drying efficiency after coating, the amount of the ionomer is 1 to 60% by weight, and particularly 5 to 5.
It is preferable to adjust the concentration to 40% by weight.

Various additives can be added to the ionomer composition of the present invention. Examples of such additives include antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, plasticizers, colorants, cross-linking agents, and inorganic fillers.

The aqueous dispersion obtained according to the present invention can be used as a coating material for various substrates. Examples of the base material that can be used for such a purpose include high, medium,
Low density polyethylene, ethylene / α-olefin copolymer, ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer or its ionomer, ethylene / (meth) acrylic acid ester copolymer, polystyrene, ABS Styrene resin such as resin, polyethylene terephthalate, polyester such as polybutylene terephthalate, nylon 6, nylon 66, nylon 6
10, polyamide such as nylon 12, ethylene / vinyl alcohol copolymer, polycarbonate, polyacetal polysulfone, polyvinyl chloride, thermoplastic olefin elastomer, styrene block copolymer, thermoplastic polyester elastomer, thermoplastic polyamide elastomer, phenol resin, aluminum Evaporated film,
Examples thereof include silica vapor deposition film, paper, metal and the like. These base materials may be graft-modified with a substance such as maleic anhydride, or may be blended with the same additives as described above. Further, surface treatment such as corona treatment or flame treatment may be applied. Molded articles of various shapes such as films, sheets, containers and tubes can also be used as the substrate.

To apply the aqueous dispersion onto the substrate, a method generally used for plastic coating, for example, a method using a roll coater, a bar coater, a sprayer, an air knife coater, a brush or the like, or a substrate is used. It can be performed by a method such as immersing in an aqueous dispersion.
After application, heat drying to evaporate the water content,
A uniform film can be obtained. The drying temperature is arbitrary, but is generally in the range of about 50 to 200 ° C. The coating amount varies depending on the permeability and smoothness of the base material,
The thickness is generally 0.05 to 200 μm, especially 0.1 to 50 μm.

It is also possible to produce a thin film from the aqueous dispersion obtained according to the present invention. The thin film can be produced by forming a thin film on a substrate made of a material that is easily peeled off in the same manner as the above coating, and peeling the thin film from the substrate. This ionomer composition thin film is used for applications such as a selective permeation film.

[0026]

The ionomer composition obtained by the present invention exhibits various excellent properties which are considered to be derived from the chemical bond between the ionomer and chitosan. In particular, the water resistance is improved while maintaining the excellent properties inherent in ionomers. It also exhibits improved adhesion to certain substrates. Furthermore, the gas barrier properties, particularly the oxygen / carbon dioxide permeability ratio, are greater than those of ionomers.

By making use of such improved properties, it is possible to form a film which is tough, has excellent heat sealability and is excellent in water resistance on the surface of the substrate by applying it to the applications conventionally used in ionomers. As a thin film utilizing the function of chitosan, application to antibacterial membranes, permselective membranes, ion exchange membranes, medical wound healing membranes, etc. is expected.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples. The methods for measuring the types and physical properties of the components constituting the aqueous dispersion used in the examples are as follows.

1. Ionomer and its base polymer (1) Ethylene / methacrylic acid copolymer (EMAA) composition Ethylene: 80 wt% Methacrylic acid: 20 wt% MFR 67 dg / min Melting point 85 ° C

(2) Potassium ionomer 90 mol% neutralized potassium salt of EMAA of the above (1) MFR 0.05 dg / min melting point 85 ° C.

(3) Ionomer Aqueous Dispersion 25 wt% potassium ionomer of the above (2), water 75
wt% aqueous dispersion

2. Chitosan aqueous solution Koyo Chitosan (manufactured by Koyo Chemical Co., Ltd.) 10
% Aqueous solution, viscosity (1% aqueous solution, 20 ° C.) 15 CP or less,
Deacetylation degree of 85% or more

3. Method for measuring physical properties of raw material resin and coating film obtained (1) MFR (melt flow rate): JISK-67
60 temperature 190 ℃, load 2160g

(2) Water resistance: The coating film coated and dried on the substrate was immersed in water at 23 ° C. for 3 minutes and the state of the film was observed. ○: No change ×: Swelling, peeling

[Example 1] 0.5 g of an aqueous chitosan solution ("Koyo chitosan" 10% chitosan solution) was added to 4 g of an aqueous dispersion of potassium ionomer (solid content: 25 wt%) at room temperature (20 ° C) (100% by weight of potassium ionomer). (5 parts by weight per part), and stirred well to homogenize. The mixed solution did not cause solid precipitation and gelation. A part of the obtained transparent low-viscosity aqueous dispersion was poured into polypropylene having a thickness of 50 μm, and was uniformly spread and coated using a No. 12 wire coating bar. The coating spread evenly without repelling on the film surface and without bubbles. The coating film surface was dried by heating with a dryer at 80 ° C. for 60 seconds, and then dried by heating on a hot plate at 100 ° C. for 60 seconds.

The resulting coating was transparent with a thickness of about 2 μm and no bleeding was observed on the surface. When the water resistance and gas permeability were measured, the results shown in Table 1 were obtained.

[Comparative Example 1] A polypropylene (thickness: 50 µm) was coated on the aqueous dispersion of the ionomer used in Example 1 without adding chitosan, followed by heating and drying to give a thickness of about 2 µm. A transparent and glossy coating of Water resistance, gas permeability and adhesion were measured. The results are shown in Table 1.

[0038]

[Table 1]

Claims (6)

[Claims] 1. An ethylene / unsaturated carboxylic acid copolymer consisting of 80 to 99.9 parts by weight of ionomer (A) and 0.1 to 20 parts by weight of chitosan (B) (total of 100 parts by weight of both). Ionomer composition. 2. An ethylene / unsaturated carboxylic acid copolymer ionomer (A) in an amount of 80 to 99.9 parts by weight and chitosan (B) in an amount of 0.1 to 20 parts by weight (both are 100 parts by weight) in water. An ionomer composition which is dissolved or dispersed. 3. The ionomer (A) is an alkali metal ionomer having a neutralization degree of an ethylene / unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 10 to 30% by weight and a molar ratio of 50 mol% or more. Or the ionomer composition according to 2 above. 4. Chitosan (B) is a 1% aqueous solution at 20 ° C.
The viscosity in is less than 50 cp.
The ionomer composition described in 1. 5. A thin film comprising the ionomer composition according to claim 1, 3 or 4. 6. A molded product comprising a thin film according to claim 5 formed on a base material.