JPS5921337B2 - Processing method for polyvinyl alcohol film, sheet or container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polyvinyl alcohol film, sheet or container with a non-blocking coating treatment on its surface in order to impart water resistance and moisture resistance and maintain oxygen barrier properties even in high humidity conditions. It is related to the method of application.

Polyvinyl alcohol film has excellent gas impermeability at low humidity, and is highly expected to be applied to various packaging fields that require gas barrier properties.
In addition to poor moisture permeation resistance, oxygen barrier properties are significantly reduced under high humidity conditions, which severely limits its use.

Therefore, recently, a solution of vinyl chloride-vinylidene chloride copolymer or vinyl chloride-vinyl acetate copolymer is applied to the surface of polyvinyl alcohol film and dried to form a film that has water resistance, moisture permeability, and oxygen barrier properties. Various attempts have been made to provide this, but since polyvinyl alcohol is a typical polar resin, it has poor adhesion to the coated film, resulting in damage or chipping of the coated film, resulting in reduced functionality. In order to improve this adhesion, it has also been proposed to use vinyl chloride-vinylidene chloride copolymers and vinyl chloride-vinyl acetate copolymers exemplified above that are copolymerized and modified with a third component (often maleic anhydride). However, since the polymerization process becomes complicated, it is unavoidable that this is disadvantageous industrially, and even if such a modified copolymer is used, there are problems with the variety of polyvinyl alcohol, the thermal history or stretching conditions of the polyvinyl alcohol film. In the past, there was a problem that the adhesion was not necessarily sufficient. Furthermore, prior to coating a polyvinyl alcohol film with a vinyl chloride-vinyl acetate copolymer, it has been attempted to anchor-coat an organic titanate solution to improve adhesion, but the cost is high due to the use of an anchor coating agent. In terms of process, there are two steps: the application process of the anchor coating agent and the drying process.
Since it requires a number of steps, the production speed is slow, and it is undesirable in terms of equipment cost and area occupied by the equipment, which is extremely disadvantageous from an industrial perspective. However, as a result of various studies, the present inventors found that the coating on the surface of a polyvinyl alcohol film, sheet, or container is made of (a) vinyl chloride copolymer or vinylidene chloride copolymer, (b) polyester, and (c) styrene resin. When using a specific proportion of mixed resin, the adhesion of the coating becomes extremely strong, so there is no need to perform industrially disadvantageous operations such as anchor coating, and water resistance.
It was discovered that fully satisfactory results could be obtained in terms of moisture permeability, oxygen barrier properties, and blocking prevention properties, leading to the completion of the present invention.

That is, the present invention provides a mixed resin of Lαa) and (b) in a weight ratio of 10 to 95:90 to 5 on one or both sides of a polyvinyl alcohol film, sheet, or container, and 0.2 to the mixed resin. It is characterized by providing a coating layer of a composition consisting of ~10% by weight of (c). Polyvinyl alcohol film as a base material in the present invention,
The sheet or container refers to fully or partially saponified products of polyvinyl acetate or copolymers of vinyl acetate with ethylene, propylene, long-chain α-olefin, unsaturated acids or esters thereof, or these saponified products. Refers to products formed from polyvinyl alcohol derivatives such as partially acetalized products and partially urethanized products by casting methods, extrusion molding methods, blow molding methods, etc., and also includes products obtained by reprocessing such molded products by vacuum forming methods, etc.

These polyvinyl alcohol films, sheets, or containers do not need to be stretched, but in the case of films in particular, those that are uniaxially or biaxially stretched have increased water resistance and oxygen barrier properties under high humidity. As a result, the properties of the paste film itself are improved, and when the paste film is coated, it provides more favorable results than when a non-stretched film is used.

Vinyl chloride copolymers and vinylidene chloride copolymers include, for example, vinyl chloride monovinyl acetate copolymers (especially those with a vinyl chloride content of 55 to 95% by weight), vinyl chloride monovinylidene chloride copolymers (especially those with a vinylidene chloride content of 5% by weight), ~95% by weight) acrylonitrile monovinylidene chloride copolymer (especially with a vinylidene chloride content of 65-95% by weight) Vinyl chloride monovinyl acetate-maleic anhydride copolymer (especially with a vinyl chloride content of 55-95% by weight, anhydrous) Examples include those containing 0.5 to 5% by weight of maleic acid.

Polyester refers to a condensate of acid components such as unsaturated dibasic acids and saturated dibasic acids with glycols, and as necessary, it can be combined with crosslinkable monomers, polybasic acids, allyl alcohol, polyhydric alcohols, and isocyanates. Including those modified by adding etc.

An example of a commercially available product is Byron 200 manufactured by Toyobo Co., Ltd.
, Byron 300. The mixing ratio of vinyl chloride copolymer or vinylidene chloride copolymer and polyester is selected from the range of 10 to 95:90 to 5 by weight, and when the ratio of polyester is less than this range, the effect of improving the adhesion of the film is If the amount is insufficient, and if it is more than this range, the oxygen barrier properties will be insufficient and blocking will occur more easily.

As the styrene resin, a homopolymer or copolymer of styrene such as polystyrene, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, maleic acid-styrene copolymer, etc. is used.

In the case of copolymers, the copolymerization ratio of styrene is approximately 80 mol%
It is desirable that the amount is above 80% by mole, but in some cases it may be less than 80% by mole. The blending ratio of styrene resin should be 0.2 to 10% by weight of the total amount of vinyl chloride copolymer or vinylidene chloride copolymer and polyester, and if the amount is less than 0.2% by weight, the film When the film is rolled up into a roll or the sheets are stacked, blocking may occur between the films or between the sheets, which may impede handling or cause the film surface to become mottled and cloudy.

On the other hand, if the amount of styrene resin exceeds 10% by weight, the adhesion and mechanical strength of the coating layer tend to be poor.
Styrene resin has a remarkable effect on preventing blocking, and other resins do not give good results.

This is because the styrene resin has moderate incompatibility with the mixed resin of vinyl chloride copolymer or vinylidene chloride copolymer and polyester, so it moves slightly to the surface layer during coating formation. It is thought that this will lead to an excellent effect on preventing protrusion. The addition of styrene resin also has the effect of having almost no adverse effect on the adhesion of the coating or the heat sealability of the coated film. In addition to the above-mentioned components, compounds having an isocyanate group, such as tolylene diisocyanate or its hydride or its adduct with trimethylolpropane, triphenylmethane triisocyanate, methylene bis-di-phenyl isocyanate or its hydride, hexamethylene diisocyanate, Xylene diisocyanate, 4.4'
Monodicyclohexylmethane diisocyanate or a polymer thereof may be blended in an amount of about 1 to 20% by weight based on the polyester, thereby making it possible to further improve the adhesion of the film.

Solution coating is suitable as a method for coating a polyvinyl alcohol film, sheet or container with such a mixed resin.

That is, the three are dissolved in an organic solvent that can dissolve the vinyl chloride copolymer or vinylidene chloride copolymer and the polyester and styrene resin, and the solution thus prepared is applied to the surface of the polyvinyl alcohol molded product. It is coated by any method such as spraying, dipping, etc., and then dried at room temperature or under heat. In this case, organic solvents include hydrocarbons such as benzene, toluene, and xylene, halogenated hydrocarbons such as methylene chloride, propylene dichloride, and trichlene, ketones such as methylethyl ketone and cyclohexanone, and esters such as ethyl acetate. Ethers such as tetrahydrofuran, dioxane, and cellosolve acetate, and nitrous compounds such as 2-nitropropane are used. Mixed solvents, e.g. toluene/
Methyl ethyl ketone, toluene/ethanol, toluene/acetone, etc. are also used. Moreover, any solvent or mixed solvent that can dissolve the resin composition can be used without being limited to those exemplified above. In addition to such solution coating, a method of coating an aqueous emulsion of the mixed resin is also effective, and in some cases, a method of melt coating the mixed resin, or a method of coextruding the mixed resin at the time of solution extrusion of polypynyl alcohol is also effective. It is also possible to do this.

The coated polyvinyl alcohol film, sheet, or container obtained by the above-mentioned addition method has extremely good adhesion of the coating layer, and has good water resistance, moisture permeation resistance, and oxygen barrier properties. It also has excellent heat-sealability, so it is suitable for packaging foods and beverages, luxury items, seasonings, pharmaceuticals, and various other items.

Next, the method of the present invention will be further explained with reference to Examples.

Examples 1 to 3 A polyvinyl alcohol cylindrical film was simultaneously biaxially stretched three times in the length and width by an inflation method, and then cut to obtain a film having a thickness of 18 μm.

Next, a solution having the following composition was applied to one side of the film using a roll coater so that the solid content was about 57/I,
It was then dried in a hot air dryer at a temperature of 130°C. A similar coating was applied to the other side of the film. Example 1 Example 2 Example 3 The adhesive strength and heat seal strength of the thus obtained double-sided coated film were measured, the presence or absence of blocking was observed, and the moisture permeability and oxygen permeability were measured after impact was applied by dropping. did.

The results are shown in the table. Control Examples 1 to 3 20% toluene solution of vinyl chloride monovinyl acetate copolymer (used in Example 1) (Comparative Example 1), vinyl chloride monovinylidene chloride copolymer (used in Example 2) 2
0% toluene monoethyl acetate 1:1 mixed solvent solution (Control example 2), 20% ethyl methyl ketone solution of acrylonitrile-vinylidene chloride copolymer (used in Example 3) (Control example 3), containing vinyl chloride Polyvinyl alcohol [■■ As shown in the table, the adhesion was poor, and as a result, the desired moisture resistance and oxygen barrier properties could not be achieved.

Comparative Examples 5 to 7 Solutions having the following compositions were used to coat polyvinyl alcohol biaxially stretched films in the same manner as in Example 1, but satisfactory results were not always obtained in terms of prevention of blocking.

The results are shown in the table below. Control example 5 Control example Control example Example 4 Ethylene content 29 mol%, degree of saponification of vinyl acetate moiety 9
A film obtained by extrusion molding a 9.2 mol % saponified ethylene monovinyl acetate copolymer was simultaneously biaxially stretched to twice the length and width using a tenter at a temperature of 170°C to a thickness of 2.
A film of 0μ was obtained.

The mixed resin solution used in Example 1 was applied to both sides of this film and dried. The properties of the thus obtained coated film were as follows. Example 5 A film obtained by extrusion molding a saponified α-dodecene monovinyl acetate copolymer containing 7 mol % of d-dodecene and a degree of saponification of the vinyl acetate portion of 98 mol % was biaxially stretched to a thickness of 25 μm. The coating treatment was carried out in the same manner as in Example 4 except that the film was used.

Claims (1)

[Claims] 1. A weight ratio of vinyl chloride copolymer or vinylidene chloride copolymer to polyester of 10 to 95:90 on one or both sides of the polyvinyl alcohol film, sheet or container.
~5 ratio of mixed resin and 0.2 to 1 for the mixed resin
A polyvinyl alcohol film, characterized in that it is provided with a coating layer of a composition consisting of 0% by weight of a styrene resin;
Method of processing sheets or containers.