JP3438256B2 - Gas barrier material with boil resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas barrier material used in the field of packaging foods, pharmaceuticals and the like.

[0002]

2. Description of the Related Art As a transparent gas barrier packaging material, polyvinyl alcohol (hereinafter abbreviated as PVA), ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH), polyvinylidene chloride resin (hereinafter abbreviated as PVDC) and the like have a gas barrier property. It is known that an excellent resin is laminated or coated, and it is used as a packaging material for long-term preservation of the quality of contents such as foods.

However, PVA and EVOH-based barrier materials have a large temperature and humidity dependency, and the oxygen barrier properties are lowered at high temperatures or high humidity. When boiling treatment or retort treatment is performed, the barrier properties are significantly reduced. There are drawbacks such as.

Further, in the PVDC system, humidity dependency is small.
Oxygen barrier property is 1 cm³/ M ²・ Day ・ atm
It is difficult to realize the following high gas barrier materials,
Also, since the membrane contains a large amount of chlorine,
There are many difficulties in waste disposal such as recycling.

On the other hand, barrier materials provided with a film of an inorganic compound such as SiO _x by a vacuum process such as a vacuum vapor deposition method, a sputtering method, or a plasma chemical vapor deposition (CVD) method have been developed.

These barrier materials have a high barrier performance that cannot be realized by a resin-based barrier material, no toxic gas is generated even when incinerated, and the thickness of the inorganic coating is very high at several hundred angstroms. It is extremely thin and can be recycled as a resin substrate.

However, these inorganic barrier materials require careful handling because the inorganic coating as the barrier layer lacks flexibility and has poor adhesion to the substrate. Further, these vacuum processes have drawbacks such as expensive equipment, poor productivity, and high cost.

As a technique for solving such a problem, there has been proposed a gas barrier material having a base material provided with a coating of a metal alkoxide (JP-A-62-295931).

This gas barrier material has a certain degree of flexibility, and since the metal alkoxide is harmless, it is environmentally friendly, and since the film is thin, it can be disposed of or recycled and the cost is low. .

However, although the gas barrier material provided with this metal alkoxide coating has an improvement in oxygen barrier property as compared with the case of the base material alone, it is not satisfactory in terms of absolute gas barrier property. .

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, has flexibility to withstand messy handling, and is environmentally friendly for disposal or recycling, and is cost effective. Of course, it is also an object of the present invention to provide a gas barrier material which is excellent in gas barrier property, is hardly affected by humidity, and has water resistance and boil resistance as well.

[0012]

[Means for Solving the Problems] The invention according to claim 1 is
At least one surface of the base material made of plastic, a metal alkoxide or a hydrolyzate of a metal alkoxide,
A gas barrier material comprising a ternary composite of a water-soluble polymer and an isocyanate compound having at least two or more isocyanate groups in the molecule, wherein the metal alkoxide or the metal alkoxide in the coating is When the metal alkoxide hydrolyzate was converted into a metal oxide, the weight ratio of the metal oxide and the water-soluble polymer was 20:
A gas barrier material having boil resistance, which is 80 to 95: 5 and the proportion of the isocyanate compound is 0.1 to 20% of the whole.

The invention according to claim 2 is based on the invention according to claim 1, characterized in that the metal in the metal alkoxide or the hydrolyzate of the metal alkoxide is Si, Al or a mixture of both. A gas barrier material having boil resistance .

The invention according to claim 3 is based on the invention according to claim 1 or claim 2, and is characterized in that the water-soluble polymer is polyvinyl alcohol and has boil resistance.
It is a gas barrier material that does.

[0015]

The plastic substrate used in the present invention includes polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate,
Polybutylene terephthalate, polyethylene naphthalate, etc.), polyamide (nylon-6, nylon-66)
Etc.), polyvinyl chloride, polyimide and the like, or copolymers of these polymers and the like, which are used as usual packaging materials.

Further, these polymers may contain known additives such as antistatic agents, ultraviolet absorbers, plasticizers, lubricants, colorants and the like.

Next, the composite coating formed on the substrate will be described in detail. The metal alkoxide used in the present invention is tetraethyl orthosilicate (Si
(OC ₂ H ₅ ) ₄ ), tripropyl aluminum (Al
(OC ₃ H ₇ ) ₃ ). General formula M (OR) _n (M is S
Metals such as i, Ti, Al and Zr, R is CH3, C2 H
Alkyl groups such as 5). Among them, M is Si, Al, or a mixture of both is excellent in various characteristics.

The water-soluble polymer is polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate and the like. Among them, polyvinyl alcohol (PV
The barrier property is most excellent when A) is used. PVA as used herein is generally obtained by saponifying vinyl acetate alcohol, and is a general term from so-called partially saponified PVA in which acetic acid groups remain about several tens of percent to fully saponified PVA in which only a few percent or less remain. However, it is not particularly limited.

The isocyanate compound has two or more isocyanate groups (NCO groups) in its molecule, and is typically tolylene diisocyanate (hereinafter abbreviated as TDI) or triphenylmethane triisocyanate (hereinafter Monomers such as TTI), isophorone diisocyanate (hereinafter abbreviated as IPDI), tetramethylxylene diisocyanate (hereinafter abbreviated as TMXDI), and polymers and derivatives thereof.

The film is formed by coating such a metal alkoxide directly or in advance with a hydrolysis reaction with a water-soluble polymer and an isocyanate compound to prepare a composite solution, and coating it on a substrate.

The ratio of the composite is such that when the metal alkoxide or its hydrolyzate is converted into a metal oxide, the weight ratio of the metal oxide and the water-soluble polymer is 20:80 to 95: 5.
Is excellent in both barrier property and flexibility. Further, the proportion of the isocyanate compound is 0.1 to 2 of the whole.
0% is preferable, and if it is 0.1% or less, the water resistance effect is small, and if it is 20% or more, the barrier property is remarkably lowered.

The coating method is a commonly used dipping method, roll coating method, screen printing method,
Any method such as a spray method may be used.

The thickness of the coating varies depending on the type of composite used, but may be in the range of about 0.01 to 1000 μm. However, if the thickness is 50 μm or more, cracks are likely to occur in the film, so it is more preferable that the thickness is in the range of 0.01 to 50 μm.

On the gas barrier material provided with such a composite coating, a heat-sealable thermoplastic resin layer may be laminated if necessary, a printing layer may be provided, or a plurality of resins may be laminated via an adhesive layer. You can also use it.

[0026]

In the gas barrier material according to the present invention, a ternary composite coating film of a metal alkoxide or its hydrolyzate, a water-soluble polymer such as polyvinyl alcohol, and an isocyanate compound is provided on at least one surface of a base material made of plastic. As a result, it has a high level gas barrier property and is not easily affected by humidity.

[0027]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the materials described in the examples.

<Example 1> Tetraethyl orthosilicate (Si (OC ₂ H ₅ ) ₄ hereafter abbreviated as TEOS) 8.7
g of 0.01 N hydrochloric acid (91.3 g) and stirred for 30 minutes, a hydrolysis solution (SiO ₂ concentration 3%) and a 3% aqueous solution of polyvinyl alcohol (polymerization degree 2400, saponification degree 98.5%) were added in a weight ratio of 60. After mixing to give a composite solution of / 40, TDI, IPDI, TMXDI, TDI
And 5 kinds of isocyanate compounds of trimer of TMXDI were diluted with isopropyl alcohol and added to the above composite solution so that the solid content was 5% by weight to prepare a ternary composite solution. These solutions were coated on one side of a polyethylene terephthalate (hereinafter abbreviated as PET) film (50 μm, corona treated) as a base material with a bar coater and then dried with a dryer at 120 ° C. for 10 minutes to form a film having a thickness of 0.3 μm. Then, a test body was obtained.

These test specimens were boiled at 100 ° C. for 10 minutes, and the gas barrier properties before and after the treatment were measured by an oxygen permeability measuring device (MOCON OXTR manufactured by Modern Control Co.).
(AN10 / 50A) was measured under the conditions of 25 ° C.-100% RH atmosphere. The results are shown in (Table 1).

[0030]

[Table 1]

In all cases, the addition of an isocyanate compound was observed to reduce the absolute barrier property, but it was possible to suppress the reduction in the gas barrier property after boiling.

Example 2 A hydrolyzed solution of 2% SiO ₂ TEOS and tripropylaluminum (Al (OC ₃ H ₇ ) ₃ hereafter abbreviated as TPA) prepared in the same manner as in Example 1 were heated at 80 ° C. After dissolving in hot water, hydrochloric acid was added and deflocculated to prepare a mixed solution of a hydrolysis solution having a solid content of 2% and an aqueous solution of 2% PVA in a weight ratio of 1/1/1.
A predetermined amount of I was added to the total solid content in the range of 0 to 30% by weight to prepare a composite solution. PE as in Example 1
Coat T to form a film with a thickness of 0.2 μm,
The oxygen permeability before and after the boil was measured. The results are shown in (Table 2).

[0033]

[Table 2]

[0034]

[Table 3]

<Embodiment 3> In the same manner as in Embodiment 1, TE
The solid content of OS and PVA is 3%, and the mixing ratio is 60/4 by weight.
0 and 97/3 two kinds of composite solutions were prepared and I
Using a solution in which PDI was added so as to be 2% with respect to the solid content, PET (film thickness 50 μm) was used as in Example 1.
A sample having a thickness of about 0.3 μm was formed on m). After the deformation due to bending (curvature radius: 1 mm, elongation of PET surface was about 5%), oxygen permeability before and after bending was measured to evaluate flexibility. As a comparative example, SiO (purity 3
N, manufactured by Osaka Titanium Co., Ltd.) was used as a vapor deposition source to form a coating having a thickness of 0.2 μm by a vacuum vapor deposition method using an electron beam heating method, and the same evaluation was performed. The results are also shown in (Table 3). .

[0036]

[Table 3]

The coating having a composition ratio of Si alkoxide and PVA of 60/40 has a good barrier property, and the barrier property is not deteriorated even when a bending deformation is applied. When the ratio is 97/3, the original barrier property is poor, but
A remarkable decrease was observed after bending deformation. Further, although the vapor-deposited coating has excellent barrier properties, the barrier properties after deformation were largely reduced and the flexibility was remarkably inferior.

[0038]

As described above, the gas barrier material according to the present invention comprises a metal alkoxide or its hydrolyzate, a water-soluble resin such as polyvinyl alcohol, and an isocyanate compound on at least one surface of a plastic substrate. It has a high-level gas barrier property as well as excellent water resistance and flexibility because it has an original composite coating, so it will not impair the barrier property even in a high humidity atmosphere, boil treatment or messy handling. Without
It enables long-term storage of food and other contents. Also, even if it is incinerated, it can be disposed of without generating toxic gas and harmful substances, the manufacturing method is simple, and no special equipment is required, so it is highly productive and can be manufactured at low cost. is there.

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Claims (3)

(57) [Claims] 1. A ternary of a metal alkoxide or a hydrolyzate of a metal alkoxide, a water-soluble polymer, and an isocyanate compound having at least two or more isocyanate groups in a molecule, on at least one surface of a plastic substrate. A gas barrier material having a coating composed of a system composite, wherein the metal alkoxide in the coating or a hydrolyzate of the metal alkoxide is converted to a metal oxide, and a water-soluble polymer. Is 20:80 to 95: 5, and the proportion of the isocyanate compound is 0.1 to 20% of the whole gas barrier material having boil resistance . 2. The anti-boiling boiler according to claim 1, wherein the metal in the metal alkoxide or the hydrolyzate of the metal alkoxide is Si, Al or a mixture of both.
A gas barrier material that has good properties . 3. The method according to claim 1 or 2, wherein the water-soluble polymer is polyvinyl alcohol.
Gas barrier material with boil resistance .