JPH0661828B2 - Method for manufacturing laminated blow container - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a laminated blow container in which a gas barrier resin layer is provided on a base material layer made of polyethylene terephthalate.

(Prior Art) Conventionally, in order to improve the gas barrier of a container made of polyethylene terephthalate excellent in transparency and strength, a preform is coated with a saponified solution of an ethylene-vinyl acetate polymer and then biaxially stretch blow molded. Method (JP-A-60-
2361), a method of applying a solution of a saponified ethylene-vinyl acetate copolymer in a special solvent in a solvent (JP-A-60-124661), and the like have been proposed.

(Problems to be Solved by the Invention) In the former of the above-mentioned conventional techniques, a solution of 50
There is a problem that a transparent product is difficult to obtain unless the temperature is as high as ℃ and the stability of the solution is poor. In the latter case, there is a problem that a strange odor remains due to formic acid in the solvent.

(Means for Solving Problems) The present invention is intended to solve the above problems and provide a method for producing a laminated blow container having excellent gas barrier properties, the gist of which is an ethylene content of 25 to 55 mol. %, A saponification product of an ethylene-vinyl acetate copolymer having a saponification degree of 90 mol% or more of a vinyl acetate component in a mixed solvent composed of the following components (A), (B) and (C) in an amount of 0.5 to 15% by weight. % Solution dissolved in polyethylene terephthalate preform to form a coating layer, and the surface of the coating layer is not coated, and biaxially stretch blow molded to saponify ethylene-vinyl acetate copolymer. A method for producing a laminated blow container, characterized in that the average thickness of the coated portion of the layer is 3 μm or less: (A) 10 to 60% by weight of water, (B) propyl alcohol, butyl alcohol or benzyl alcohol At least one selected 5-70
% By weight, (C) at least one selected from formic acid or acetic acid 2
It is 85% by weight.

The saponified ethylene-vinyl acetate copolymer used in the present invention must have an ethylene content of 25 to 55 mol% and a saponification degree of the vinyl acetate component of 90 mol% or more. When the ethylene content is 25 mol% or less, the gas barrier property under high humidity is lowered, while when it is 55 mol% or more, the gas barrier property is lowered and printability is deteriorated. The saponification degree is 90 mol%
Below, the gas barrier property is lowered. Here, the saponified product of the ethylene-vinyl acetate copolymer may contain a small amount of a comonomer such as α olefin such as propylene.

The solvent in the present invention is (A) water 10 to 60% by weight, (B) propyl alcohol, butyl alcohol or at least one selected from benzyl alcohol 5 to 70% by weight,
(C) A mixed solvent of 2-85 wt% formic acid or acetic acid is used. If the amount of water (A) is less than 10% by weight, it is difficult to obtain a uniform solution, and if it is more than 60% by weight, the solubility of the saponified product decreases. If the alcohol (B) is less than 5% by weight, the solubility is lowered, and if it is 70% by weight or more, it is difficult to obtain uniform dissolution. When the content of (C) formic acid or acetic acid is less than 2% by weight, the transparency of the coating film and the stability of the solution are deteriorated, and when it is 85% by weight or more, a nasty odor is likely to remain and workability is poor.

In the present invention, the concentration of the saponified ethylene-vinyl acetate copolymer solution is in the range of 0.5 to 15% by weight, which is practical from the viewpoint of coating and drying operations.

The greatest feature of the present invention is to coat and dry the above solution on a polyethylene terephthalate preform to form a coating layer. The surface of the coating layer is not coated, but is biaxially stretch blown to form an ethylene-vinyl acetate copolymer. By setting the thickness of the saponified product coating portion to 3 μm or less, the residual offensive odor is completely eliminated. This is because heating to the stretching temperature subsequent to coating and drying and making the coating portion extremely thin, and the surface of the coating layer being uncoated, the solvent component of the solution is completely evaporated by the biaxial stretching step. Seems to be.

Here, the drying can be performed at 50 to 80 ° C. for 3 seconds to 10 minutes, and the heating to the stretching temperature can be performed to such an extent that the preform becomes 80 to 120 ° C. The biaxial stretching blow may be performed by a conventionally known method.

Further, since the coating layer of the obtained container can be made extremely thin by stretching after coating, the average thickness is preferably 0.2 μm or more in order to secure the gas barrier property.

Hereinafter, description will be made with reference to examples.

(Example) A polyethylene terephthalate preform obtained by injection molding of polyethylene terephthalate having an intrinsic viscosity of 0.75 dl / g, having a length of 120 mm, an outer diameter of 28 mm and a thickness of 4.3.
A mm bottomed preform was prepared.

On the other hand, as a coating solution, a saponified ethylene vinyl acetate copolymer having an ethylene content of 29 mol% and a saponification degree of 99 mol% was added to a mixed solvent of 45% by weight of water, 45% by weight of isopropyl alcohol and 10% by weight of formic acid at a concentration of 10%. What was melt | dissolved so that it might be set to weight% was prepared.

A polyester anchor coating agent was applied to the polyethylene terephthalate preform and dried at room temperature (20
C.) was immersed once in the coating solution and dried with hot air at 70.degree. C. for 5 minutes.

Furthermore, after heating this coating preform to 90 to 95 ° C.,
Biaxially stretched and blown to obtain a laminated blow container having a capacity of 1.5. The ethylene-vinyl acetate copolymer layer of the obtained container had an average thickness of 0.5 μm and had no offensive odor. Table 1 shows the results of measuring the oxygen transmission rate (cc / bottle, 24 hr) of this container. The measuring method is as follows.

Testing machine OX-Trdn 100 type (Modern Control Co., Ltd.) Conditions 23 ° C., 0% RH gas Air (numerical value is converted to 100% oxygen) (Comparative example 1.2) What is the same polyethylene terephthalate preform as the example Blow container (Comparative Example 1) obtained by biaxially stretch-blowing in the same manner as in Example without coating, and polyethylene terephthalate preform treated with the same anchor coat as in Example were added to the same coating solution as in Example 1 Two times of the laminated blow container (Comparative Example 2) obtained by repeating the operation of dipping once and drying with hot air at 70 ° C. for 5 minutes three times, and biaxially stretch blow molding the coated preform in the same manner as in the Example. Table 1 shows the results of measuring the oxygen transmission rate of the above container in the same manner as in the example.

The container of Comparative Example 2 had a strong offensive odor.

As is clear from Table 1, the laminated blow container of the example had an oxygen permeability of 0.22 (cc / bottle, 24 hours) and 1.12 (cc / bottle, 24 hours) of Comparative Example 1 having no coating layer. ), The barrier property is about 5 times higher than that of), and the offensive odor was sensed in Comparative Example 2 in which the coating layer was as thick as 4.5 μm.
There was no strange odor.

(Effects of the Invention) As described above, the method for manufacturing a laminated blow container according to the present invention is
An ethylene-vinyl acetate copolymer solution dissolved in a special solvent is applied to a preform and dried to form a coating layer, and the surface of the coating layer is not covered, and further biaxially stretch blown to form a coating layer of 3 μm. Since it is thinly finished as follows, not only does it have an extremely excellent gas barrier property even if it is thin due to the stretching effect of the ethylene-vinyl acetate copolymer, and (1) no offensive odor due to the solvent component remains.

(2) Since the coating layer is thin, there is no adverse effect on stretch formability, and coating unevenness disappears during stretching.

And the like.

Claims (1)

[Claims] 1. A saponified ethylene-vinyl acetate copolymer having an ethylene content of 25 to 55 mol% and a saponification degree of a vinyl acetate component of 90 mol% or more is prepared from the following (A), (B) and (C): A solution prepared by dissolving 0.5 to 15% by weight of a mixed solvent containing the components is applied to polyethylene terephthalate preform and dried to form a coating layer, and the surface of the coating layer is not coated and biaxially stretched blown. A method for producing a laminated blow container, characterized in that the saponified ethylene-vinyl acetate copolymer layer has an average thickness of 3 μm or less on the coated part: (A) 10 to 60% by weight of water; ) At least one selected from propyl alcohol, butyl alcohol or benzyl alcohol is 5 to 70% by weight. (C) At least one 2-8 selected from formic acid or acetic acid
5% by weight.