JP2000218743A - Production of laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a laminate which is an inexpensive material to be used in place of PVDC and has good oxygen barrier properties under high humidity conditions. SOLUTION: A laminate is obtained by a method in which a water soluble polyvinyl alcohol resin containing 1-10 mole % of a <=4C α-olefin is applied on a base film, the coating film is formed, and a solution comprising a zirconium compound is applied on the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an oxygen gas barrier laminate suitable for packaging, particularly for a film for food packaging.

[0002]

2. Description of the Related Art Oxygen gas barrier films and packaging materials using the same are already well known. Aluminum (hereafter "Al") foil has the most perfect oxygen gas barrier properties. However, it has low pinhole strength by itself and cannot be used except for special cases. Is done. Although the gas barrier properties of this laminated film are almost perfect, there are drawbacks such as the invisible contents due to opacity.

As other oxygen gas barrier films, polyvinylidene chloride (hereinafter "PVDC") films and PVDC coated films are well known. In particular, PVDC coating films are well known, and when oxygen gas and water vapor barrier properties are required,
It is often used as a base film for lamination.
PVDC has almost no hygroscopicity and has good gas barrier properties even under high humidity, so it is used after being coated on various substrates. For example, biaxially oriented polypropylene (OP
P), biaxially oriented nylon (ON), biaxially oriented polyethylene terephthalate (OPET), cellophane and other films are used. The laminated film makes use of gas barrier properties and is used for various food packaging regardless of whether it is dried or watery. However, after these packaging materials are used, they are discarded from households as general waste. However, since PVDC generates hydrogen chloride gas by combustion, it is strongly desired to transfer to other materials. However, at present, there is no alternative material for PVDC in terms of performance and cost.

Further, polyvinyl alcohol (hereinafter, referred to as "PVA") conventionally known as an oxygen gas barrier film is used.
System films are also well known. PVA film is a film having very good oxygen gas barrier property in a state of low moisture absorption, but it is considered that it absorbs violently and the oxygen gas barrier property rapidly deteriorates when the relative humidity exceeds 70%, and is not practical. Have been. There is also a problem that the adhesion to OPP and OPET used as a base film is low. To improve the hygroscopicity of PVA,
20% by mole or more of ethylene is copolymerized to form an ethylene / vinyl alcohol copolymer (hereinafter referred to as “EVOH”),
A proposal has been made in which both sides of PVA are coated with PVDC to take measures against moisture. However, in the case of EVOH, a large amount of an organic solvent must be used in order to perform solution coating, and furthermore, the barrier property is insufficient. In addition, the one coated with PVDC generates hydrogen chloride gas when incinerated. It is as follows. Further, for the purpose of improving oxygen gas barrier properties under high humidity, there has been proposed a method in which PVA and a zirconium compound are mixed and a mixed solution is applied on a base film. However, in this case, there are fatal problems such as the viscosity stability of the mixed solution being extremely poor and the thickness unevenness of the coating film being large.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a laminate which is an inexpensive material replacing PVDC and has excellent oxygen gas barrier properties under high humidity, based on the above-mentioned situation. is there.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have at least 4 carbon atoms.
After coating a water-soluble polyvinyl alcohol-based polymer (A) containing the following α-olefin in an amount of 1 mol% or more and 10 mol% or less on a base film to form a coating film, the water-soluble polyvinyl alcohol polymer is The present inventors have found that the above problem can be solved by a method for producing a laminate, which is characterized in that a solution comprising a zirconium compound (B) is applied on (A) to obtain a laminate, and the present invention has been completed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present invention relates to a method for forming a coating film by applying a water-soluble polyvinyl alcohol-based polymer (A) containing at least 1 mol% and not more than 10 mol% of an α-olefin having at least 4 carbon atoms on a base film. A method of producing a laminate by applying a solution comprising a zirconium compound (B) on the water-soluble polyvinyl alcohol-based polymer (A) to obtain a laminate, preferably a water-soluble polyvinyl alcohol-based polymer. The degree of saponification of the coalescence is 90 to 99.99 mol%, and the sodium acetate content is 0.01 to 2.0 wt%.
And more preferably contains 5 mol% or less of a silyl group, and the weight ratio (A) / (B) of the water-soluble polyvinyl alcohol-based polymer (A) to the zirconium compound (B) is 9
9.9 / 0.1 to 50/50, wherein the base film on which the water-soluble polyvinyl alcohol-based polymer is applied is a polyolefin film, a polyamide film or a polyester film, and contains 2 wt% or less of silicon. It is a manufacturing method of.

Usually, a heat-sealing layer is laminated on the water-soluble polyvinyl alcohol-based polymer layer of these laminates to form a multilayer to obtain a gas barrier film.

The present invention will be described in more detail. The degree of modification of the α-olefin having 4 or less carbon atoms in the water-soluble polyvinyl alcohol polymer used in the present invention is 1 mol% or more and 10 mol% or less.
Mol% or less, preferably 3 mol% or more, 9 mol%
Or less, more preferably 4 mol% or more and 8 mol% or less. If the degree of modification is less than 1 mol%, good barrier properties cannot be obtained, and if it exceeds 10 mol%, the water solubility decreases and it becomes difficult to carry out aqueous coating.

The degree of saponification of the water-soluble polyvinyl alcohol polymer used in the present invention is preferably 90 to 99.99 mol%, more preferably 97 to 99.95 mol% or more.
More preferably, it is 98.5 to 99.90 mol% or more. It is difficult to industrially obtain a degree of saponification exceeding 99.99 mol%, and if the degree of saponification is less than 90 mol%, sufficient barrier properties cannot be obtained.

The water-soluble polyvinyl alcohol polymer used in the present invention preferably contains a specific amount of sodium acetate, and the content is preferably 0.01 to 2.0% by weight or less, more preferably 0.02% by weight or less. To 1% by weight or less, more preferably 0.03 to 0.5% by weight or less, and most preferably 0.35 to 0.45% by weight or less. If the sodium acetate content is not in the range of 0.01 to 2.0% by weight, sufficient barrier properties cannot be obtained.

The water-soluble polyvinyl alcohol-based polymer used in the present invention preferably contains a specific amount of a silyl group, and the content is preferably 5 mol% or less, more preferably 3 mol% or less, and further preferably 0 mol% or less. .1 mol% ~
1.5 mol%. When the silyl group content exceeds 5 mol%, the aqueous polyvinyl alcohol solution becomes extremely unstable.

The type of α-olefin of the water-soluble polyvinyl alcohol polymer used in the present invention is not particularly limited as long as it has 4 or less carbon atoms, but ethylene and propylene are preferably used.

The degree of polymerization of the water-soluble polyvinyl alcohol polymer used in the present invention is not particularly limited, but those having 2,000 or less are preferably used, more preferably 1,000 or less, further preferably 600 or less, and most preferably 10 or less.
It is 0 or more and 400 or less. If the degree of polymerization exceeds 2,000, the viscosity of the aqueous solution becomes too high and it is difficult to handle.

The method for producing the water-soluble polyvinyl alcohol polymer used in the present invention is not particularly limited as long as it is a conventionally known method.

The water-soluble polyvinyl alcohol-based polymer of the present invention has a carboxyl group, a sulfonic acid group, an amino group or a salt thereof at a side chain or a molecular terminal as long as the object of the present invention is not impaired. Is also good. Usually, the modification amount is 0.05 to 10 mol%.

The water-soluble polyvinyl alcohol-based polymer of the present invention may be used alone, but it can be used as a composition with a commonly known crosslinking agent for the purpose of imparting water resistance. Examples of the crosslinking agent include an epoxy compound, an isocyanate compound, an aldehyde compound, a silica compound, an aluminum compound, and a boron compound.
Silica compounds such as colloidal silica and alkyl silicate are preferably used. The addition amount of these crosslinking agents is not particularly limited as long as the object of the present invention is not impaired, but is usually 5 to 60 parts, preferably 10 to 40 parts based on 100 parts of the polyvinyl alcohol-based polymer. And more preferably 15 to 30 parts. If the amount of the crosslinking agent exceeds 60 parts, the barrier properties may be adversely affected.

Next, the zirconium compound used in the present invention will be described in detail. Examples of the zirconium compound (B) of the present invention include zirconium oxychloride, zirconium sulfate, zirconium nitrate, zirconium acetate, zirconium carbonate, ammonium zirconium carbonate, zirconium stearate, zirconium octylate, and zirconium silicate. Among these zirconium compounds, those having no chlorine are preferred. Specific examples include zirconium sulfate, zirconium nitrate, zirconium acetate, and ammonium zirconium carbonate. These zirconium compounds do not necessarily have to be used alone, and may be used as a mixture of two or more as needed. Zirconium compounds are used as aqueous solutions, aqueous dispersions, and organic solvent solutions.

The weight ratio (A) / (B) of the water-soluble polyvinyl alcohol polymer (A) of the present invention to the zirconium compound (B) is preferably 99.9 / 0.1 to 50/50, more preferably. 99.85 / 0.15-90 / 1
0, more preferably 99.5 / 0.5 to 95 /
5

Next, the method for producing a laminate of the present invention will be described in detail. The laminate of the present invention is obtained by first applying the above-mentioned water-soluble polyvinyl alcohol-based polymer on a base film such as a polyolefin film, a polyester film or a polyamide film, forming a coating film, and then forming the water-soluble polyvinyl alcohol-based polymer. It is necessary to apply the above-mentioned zirconium compound on the body side.

The water-soluble polyvinyl alcohol polymer is applied as an aqueous solution or a mixed solution of water and a lower aliphatic alcohol. The concentration of the aqueous solution or the mixed solution of water and lower aliphatic alcohol is not particularly limited, but is usually 5 wt%.
It is desirable to select from the range of ５０50 wt%. If the concentration is less than 5 wt%, the drying load increases, and the concentration becomes 50 wt%.
If it exceeds, the solution viscosity becomes high, and handling becomes a problem. When using a lower aliphatic alcohol as a solvent,
Its content must be 50 wt% or less in the total solvent, preferably 0.5 wt% to 40 wt%, more preferably 1 wt% to 20 wt%, and most preferably 3 wt%.
% To 10 wt%. When the content of the lower aliphatic alcohol exceeds 50 wt%, the solubility of the water-soluble polyvinyl alcohol-based polymer decreases. The lower aliphatic alcohol is not particularly limited as long as it can be mixed with water, but methanol, ethanol, isopropyl alcohol, n-propyl alcohol and the like are preferably used. When applying the aqueous resin solution composed of the water-soluble polyvinyl alcohol-based polymer, a surfactant, a leveling agent, and the like may be added. Further, addition of a fungicide, a preservative, and the like to the aqueous polyvinyl alcohol polymer solution of the present invention is not limited at all.

The aqueous solution temperature at the time of coating is preferably from 20 ° C. to 80 ° C., and the coating method is gravure roll coating,
A generally known method such as a reverse gravure coating method, a reverse roll coating method, and a Meyer bar coating method is suitably used.

The thickness of the polyvinyl alcohol layer in the laminate of the present invention is not particularly limited, but is usually 0.1 μm to 20 μm.

The base film such as the polyolefin film, polyester film or polyamide film of the present invention preferably contains silicon (Si). Its content is preferably 2 wt% or less,
More preferably 1 wt% or less, more preferably 0.1 wt%.
~ 0.5 wt%. Silicon content is 0.1 ~ 2wt%
Within this range, the adhesion between the polyolefin film, polyester film or polyamide film layer and the resin for film application of the present invention is improved. The silicon to be used is introduced from a silica compound, and generally known silica compounds such as silicon oxide and alkyl silicate are used, but colloidal silica (SiO ₂ ) is preferably used. In general, a method of introducing a silica compound is to previously mix a resin into a resin when forming a polyolefin film, a polyester film or a polyamide film.

The water-soluble polyvinyl alcohol-based polymer or its composition layer and the polyolefin film,
There is no problem in providing a generally known anchor coating agent layer as an adhesive layer between the polyester film or the polyamide film layer.

The water-soluble polyvinyl alcohol-based polymer is coated on a polyolefin film, polyester film or polyamide film, dried and then coated with a zirconium compound solution. This coating method is preferably used in the same manner as in the case of the water-soluble polyvinyl alcohol-based polymer. That is, the liquid temperature during coating is 20
C. to 80.degree. C., and a generally known coating method such as a gravure roll coating method, a reverse gravure coating method, a reverse roll coating method, or a Meyer bar coating method is suitably used.

The laminate of the present invention is obtained by applying a water-soluble polyvinyl alcohol-based polymer on a polyolefin film, polyester film or polyamide film, drying to form a coating film, and then applying a zirconium compound. There is no particular limitation on the presence or absence of stretching, heat treatment temperature, and the like, or the procedure thereof. Generally, a method of applying a water-soluble polyvinyl alcohol-based polymer after stretching or heat-treating a base film, or both, or after applying a water-soluble polyvinyl alcohol-based polymer to a base film, A method of performing heat treatment or both of them is common. The heat treatment temperature, the draw ratio and the like are also suitably performed in the conventionally known ranges.

In the obtained gas barrier laminate film, a heat seal resin layer is usually formed on the side to which zirconium is applied. The formation of the heat seal resin layer is usually performed by an extrusion lamination method or a dry lamination method. HDPE, LDP as heat seal resin
E, polyethylene resin such as LLDPE, PP resin,
What is usually used as a heat seal resin, such as an ethylene-vinyl acetate copolymer, an ethylene / α-olefin random copolymer, and an ionomer resin, can be used as it is.

[0029]

Next, the present invention will be described in detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Examples 1 to 7, Comparative Examples 1 and 2 Various polyvinyl alcohols (PV
A) was slowly added with stirring, uniformly dispersed, and then heated to about 95 ° C to completely dissolve. Next, the mixture was filtered and then cooled to prepare a 20% PVA solution. A urethane-based anchor coating agent is applied to the corona-treated base film shown in Table 1 with a gravure coater to a thickness of 0.2 μm, followed by coating the PVA solution at 50 ° C. and drying at 100 ° C. did. The thickness of the obtained PVA coating layer was from 1.8 μm to 4.2 μm. Next, an aqueous solution of a zirconium compound shown in Table 1 was applied to the obtained PVA coating layer by the same gravure coater.
C. and dried at 100.degree. C. to obtain a laminate. The oxygen transmission amount (OTR) of the obtained laminate was measured. The oxygen permeation amount measurement film was used for 5 days at a temperature of 20 ° C. and a relative humidity of 85%, and the oxygen permeation amount was measured under the same conditions. The obtained results are shown in Table 1 in terms of a thickness of 2 μm. [Unit of OTR: cc · 2 μm / m ²
・ Day ・ atm]

Example 8 After the laminate was obtained, the laminate was fixed to a wooden frame.
A sample was prepared and the amount of oxygen permeation was measured in the same manner as in Example 5 except that the heat treatment was performed for one minute.

Comparative Example 3 A solution of PVA shown in Table 1 was prepared in the same manner as in the Example, and then added to the obtained solution of the zirconium compound shown in Table 1. Lost
Coating was not possible on the base film, and a laminate was not obtained.

[0033]

[Table 1]

[0034]

According to the production method of the present invention, it is possible to provide a laminate excellent in oxygen gas barrier properties under high humidity using an inexpensive material instead of PVDC.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4F006 AA12 AA35 AA38 AB20 AB64 AB69 AB73 BA05 CA07 DA04 4F100 AA27C AB11A AH06B AH08B AK03A AK03B AK21B AK41A AK46A AK51G AL05B AT00A BA03 J07 BA10EBAB02B07 BA12BAB12C

Claims (7)

[Claims] 1. A water-soluble polyvinyl alcohol-based polymer (A) containing at least 1 mol% and at most 10 mol% of an α-olefin having at least 4 carbon atoms is applied on a base film to form a coating film. Thereafter, a solution comprising a zirconium compound (B) is applied onto the water-soluble polyvinyl alcohol-based polymer (A) to obtain a laminate. 2. The method according to claim 1, wherein the water-soluble polyvinyl alcohol polymer (A) has a degree of saponification of 90 to 99.99 mol%. 3. The method for producing a laminate according to claim 1, wherein the water-soluble polyvinyl alcohol-based polymer (A) contains 0.01 to 2.0% by weight of sodium acetate. 4. The method for producing a laminate according to claim 1, wherein the water-soluble polyvinyl alcohol-based polymer (A) contains 5 mol% or less of a silyl group. 5. The weight ratio of the water-soluble polyvinyl alcohol polymer (A) to the zirconium compound (B) (A) /
(B) is 99.9 / 0.1-50 / 50.
5. The method for producing a laminate according to any one of items 4 to 4. 6. The method according to claim 1, wherein the base film is a polyolefin film, a polyamide film or a polyester film. 7. The method according to claim 1, wherein the base film contains 2% by weight or less of silicon.