JPH0596617A - Polyvinyl alcohol stretch formed object - Google Patents

Abstract

PURPOSE:To improve gas barrier properties under highly humid condition by a method wherein the melt-formed matter of polyvinyl alcohol containing the predetermined amount of metal salt is stretch-formed. CONSTITUTION:Melt-forming is performed out of polyvinyl alcohol containing chloride of alkali metal. such as lithium or the like or containing 0.01.-0.3mmol of metal salt per 1g of the polyvinyl alcohol. A stretch-formed article is produced by stretching the resultant melt-formed matter. Further, laminated formed matter, one layer of which is made of the stretch-formed article, is produced by co-extrusion laminating or the like. In this case, any metal salt, which elevates the decomposition starting temperature of the polyvinyl alcohol higher than its flow starting temperature, can be used. Concretely, bromide, iodide or the like of alkali metal such as sodium, potassium or the like can also be used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention comprises a stretched PVA molded product obtained by stretching a melt molded product comprising a composition of polyvinyl alcohol (hereinafter abbreviated as PVA) and a specific amount of a metal salt, or the molded product. It relates to a laminate molding containing at least one layer.

[0002]

2. Description of the Related Art PVA is a resin having excellent properties such as transparency, gas barrier property, oil resistance and strength, and is widely used industrially. But PVA
Since the crystal melting point is higher than the thermal decomposition initiation temperature, it was difficult to apply to PVA a simple melt molding method that could be easily adopted with polyethylene, polyvinyl chloride, polypropylene or the like. In order to solve this problem, the present inventors have previously mentioned in Japanese Patent Application No. 2-338796 that addition of a specific amount of a metal salt to PVA is difficult even in the case of PVA having a high degree of saponification, which has been considered to be particularly difficult to melt-process. , Enables the melt molding of PVA without reducing its high gas barrier properties.

However, the PVA melt-molded product containing the metal salt thus obtained is also susceptible to humidity as in the PVA molded product containing no metal salt, and the gas permeability tends to remarkably increase by absorbing moisture. there were.

On the other hand, as a method of imparting moisture resistance to a PVA film, a method of forming a protective film on the film surface by applying a solution of a polymer substance having a surface protective property and evaporating the solvent (Japanese Patent Publication No. 48-1238). No. gazette) has been proposed,
It does not improve the moisture resistance of PVA itself, and requires complicated steps such as an organic solvent solution coating step and a solvent evaporation step.

[0005]

The object of the present invention is to improve the moisture resistance of the above-mentioned PVA melt-molded article containing a metal salt in a specific ratio, that is, to improve the gas barrier property under high humidity, and to perform heat melting. An object is to provide a PVA molded product that is easy to mold and has excellent moisture resistance.

As a result of intensive studies by the present inventors, the PVA melt-molded product has excellent stretchability, and the stretching treatment markedly improves the gas barrier property of PVA under high humidity. The inventors have found that and reached the present invention.

[0007]

[Means for Solving the Problems] The above-mentioned object is 1 g of PVA.
This is achieved by a PVA molded product of the present invention obtained by drawing a melt molded product of PVA containing 0.01 to 3.0 mmol of metal salt per unit, and a laminated molded product having at least one layer of the molded product.

The PVA used in the present invention generally has a polymerization degree of 200 or more and a saponification degree of 80% or more, preferably 90% or more, more preferably 95% or more. If the degree of saponification is less than 80%, sufficient gas barrier properties cannot be obtained, and if the degree of polymerization is less than 200, the viscosity is low, and it is not suitable for use in ordinary molding equipment.

The metal salt may be any metal salt as long as it makes the decomposition start temperature (Td) of PVA higher than the flow start temperature (Tf), but lithium is an example.
Alkali metals such as sodium and potassium, alkaline earth metals such as calcium, magnesium and strontium, and chlorides, bromides and iodides of 2 to 4 heavy metals such as cobalt, tin, manganese, nickel, iron and titanium. Inorganic acid salts such as halides, carbonates, sulfates and nitrates, and organic acid salts such as acetates, lactates and stearates are preferable. Among these metal salts, the lithium salt and the divalent metal salt give PVA particularly excellent stretchability,
Particularly preferably used. Further, these metal salts may be used alone or in a mixture.

The amount of the metal salt varies depending on the kind of the metal salt, but 0.01 to 3.0 mmol, preferably 1 to 1 g of PVA, preferably
0.1-2.0 mmol is used. If it is less than 0.01 millimole, the effect of raising Td is lowered, and if it exceeds 3.0 millimole, Td is rather lowered and the condition of Td> Tf becomes difficult to obtain, and coloring due to thermal decomposition becomes remarkable. 0.1 ~
In the range of 2.0 millimole, the gas barrier property of PVA can be further improved, so that it is particularly preferable for applications utilizing high gas barrier property.

Polyethylene, maleic acid-grafted polyethylene, polypropylene, polyamide, polyester, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer may be added to the composition of PVA and a metal salt within a range that does not impair the objects and effects of the present invention. Polymers, modified polyolefins such as ethylene-ethyl acrylate copolymer, thermoplastic resins represented by ionomers, elastomers and plasticizers, stabilizers, lubricants, antioxidants, inorganic fillers, inorganic and organic additives such as pigments. It can be added.

Such a PVA-metal salt composition is molded into an arbitrary molded article such as a film, a sheet, a tube or a container by melt molding such as hot press molding, injection, extrusion molding (T-die, blow). .

The PVA melt-molded product thus obtained is stretched by tenter stretching, inflation stretching or the like. The stretching ratio is preferably high, and at least the area stretching ratio is preferably 2 or more. When the area magnification is 2 times or less, the barrier property under high humidity is not so improved. Stretching is generally 80 to 150 ° C., time is within 5 minutes, preferably 2 seconds to
It takes 1 minute. It is considered that the reason why the gas barrier property is improved by the stretching is that the oriented crystallization of the molecular chain of PVA is improved.

The stretched PVA molded product of the present invention is preferably used as a single-layer or multi-layer molded product in a sheet, a film, or a container such as a cup or a bottle.

The multilayer molded article may be formed by laminating a sheet, film or container of the stretched molded article of the present invention with a sheet or film made of another resin, or PV.
A-metal salt composition and other resins using multiple extruders,
After co-extrusion lamination from a multi-layer die to form a multi-layer film, a container or the like, these molded products may be stretched.

The layer structure of the multilayer molded product of the present invention is arbitrary, but at least one layer may be a layer of the PVA stretched molded product of the present invention, and the thickness thereof is 1 to 100 μm, preferably 3 to 50 μm.
Is preferred.

A coextrudable thermoplastic resin is preferable as the other layer constituting the multilayer, and polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene are preferable. -Ethyl acrylate copolymer, olefin resin such as ionomer, polyester such as polyethylene terephthalate and polybutylene terephthalate, polyamide,
Examples thereof include polycarbonate. These resins are provided with a layer of adhesive that can be coextruded between the layers, if necessary.
It is co-extruded with the PVA-metal salt composition and laminated.
When the obtained multilayer melt-molded product is stretched, the coextruded multilayer molded product of the present invention is obtained.

The layer structure of the coextruded multilayer molded article is PV
It is preferable that the layer of the A-metal salt composition is a core layer and the above-mentioned thermoplastic resin layers are arranged on both outer layers, and in particular, when the thermoplastic resin is an olefin resin, the penetration of moisture into both outer layers. Therefore, in combination with the improvement of the moisture resistance of the PVA layer by stretching, a high gas barrier performance can be maintained even under high humidity, and a particularly preferable layer constitution is achieved.

Further, the single-layer or multi-layer stretch-molded article of the present invention is heat-set after stretching if necessary. Heat setting is preferably carried out at 80 to 200 ° C. within 1 minute.

In the single-layer or multi-layer stretched sheet or film of the present invention, the opposing edge portions thereof are bonded together by an adhesive such as an epoxy or isocyanate adhesive or a joining means such as heat sealing or high frequency sealing. It can be a pouch-shaped container.

[0021]

EXAMPLES Examples 1 to 7 Aqueous metal salt solutions were added to PVA (Kuraray Co., Ltd. Poval (registered trademark) PVA105, degree of polymerization 500, degree of saponification 98.5%) so that the amount of metal salt was as shown in Table 1. The resulting mixture was mixed at a weight ratio of 1: 1, impregnated at room temperature overnight, and dried at 120 ° C. for 3 hours to obtain a metal salt-added PVA. This metal salt-added PVA is a desktop press (Shinto Metal Industry Co., Ltd., AY
SR5 type) and press molding at a temperature of 220 to 230 ° C, and then a biaxial stretching machine (manufactured by Toyo Seiki Co., Ltd.) at a stretching temperature of 80 to 15
Stretching was carried out at 0 ° C., and stretchability was evaluated. In Table 1, those having an area stretching ratio of 4 times or more are indicated by ◯.

[0022]

[Table 1]

Examples 8 to 13 and Comparative Examples 1 to 3 were prepared by adding metal salt aqueous solutions to PVA (Poval (registered trademark) PVA105 manufactured by Kuraray Co., Ltd., polymerization degree 500, saponification degree 98.5%), and the metal salt content was shown in Table 2. Were mixed in a weight ratio of 1: 1 so as to obtain the amount shown in (1), impregnated at room temperature overnight, and dried at 120 ° C. for 3 hours to obtain a metal salt-added PVA. These metal salt-containing PVA were melt extruded by a 30φ single screw extruder (L / D = 22) with a T-die set to a thickness of 30μ.
An unstretched film of m 2 was obtained (Comparative Examples 1 to 3). The die temperature was 220-240 ° C. Subsequently, the obtained unstretched film was stretched with a biaxial stretching machine (manufactured by Toyo Seiki Co., Ltd.) to a stretching ratio shown in Table 2. Table 2 shows the oxygen permeability of the unstretched film and the stretched film (the stretched film has a converted value of 30 μm). The oxygen permeability of the stretched film was much smaller than that of the unstretched film.

The oxygen permeability of the film is ASTM D3985.
-81, using a MOCON (registered trademark) OXTRAN (registered trademark) -100 type manufactured by Modern Control Co., Ltd.
It was measured under the condition of 80 ° C RH.

[0025]

[Table 2]

Example 14, Comparative Example 4 PVA to which 0.5 mmol / g of calcium chloride was added was obtained in the same manner as in Example 1. 1st layer ethylene-vinyl acetate copolymer (NUC3190 manufactured by Nippon Unica Co., Ltd.), 5th layer ionomer resin (HIMIRAN manufactured by Mitsui DuPont Co., Ltd.), 2nd layer, 4th layer adhesive resin (Mitsui Petrochemical Co., Ltd.) Industrial Co., Ltd. Admer SF750) and the above-mentioned calcium chloride-added PVA of the third layer are passed through respective extruders from a circular die at a temperature of 225 ° C. so that the PVA-metal salt composition has a core layer having the above-mentioned layer constitution. Was coextruded, rapidly cooled, and then biaxially stretched in the lengthwise and transverse directions by 3 times by an inflation method.
The stretching conditions were a temperature of 95 ° C. and a time of about 5 seconds. The thickness of each layer of the obtained stretched film (Example 14) was 12 μm in the first layer,
Second and fourth layers 2 μm, third layer 10 μm, fifth layer 28 μm
And the thickness of all layers was 54 μm.

Further, the same resin as in Example 14 was used to obtain the same layer structure from a T-die having a width of 350 mm and a die temperature of 225 ° C.
Was coextruded. This unstretched film and stretched film
Oxygen permeability at 30 ℃ and 80% RH is 140cc / m ²
-Day-atm and 40cc / m ² -day-atm, it can be seen that the oxygen permeability of the stretched film is significantly improved as compared with the unstretched film.

[0028]

INDUSTRIAL APPLICABILITY In the present invention, PV having an excellent gas barrier property under high humidity, which has been conventionally considered difficult, is obtained by adding a specific amount of a metal salt to PVA, melt-forming and stretching.
A stretched product can be obtained.

In particular, the stretching treatment under heating has the effect of heat treatment and the stretching effect, and can exhibit a high gas barrier property even under high humidity.

Since the molded product of the present invention is a melt-molded product,
It is easier to industrially manufacture than the casting method.

Since the stretched sheet or film and the container of the present invention have excellent gas barrier properties, the commercial value is lowered by the permeation of foods which are easily deteriorated by oxygen gas, such as meat, ham, sausage or carbon dioxide gas. Suitable for packaging materials such as carbonated drinks.

Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08K 5/00 7167-4J C08L 29/04 LGM 6904-4J LGN 6904-4J // B29K 29:00 4F B29L 7 : 00 4F

Claims (3)

[Claims] 1. 0.01 to 3. per 1 g of polyvinyl alcohol.
A polyvinyl alcohol stretch-molded product obtained by stretching a melt-molded product of polyvinyl alcohol containing 0 mmol of a metal salt. 2. A laminated molded product having at least one layer comprising the polyvinyl alcohol stretched molded product according to claim 1. 3. A coextrusion laminated molded product having at least one layer comprising the polyvinyl alcohol stretched molded product according to claim 1.