JPS62119265A - Polyester film for packaging - Google Patents

Abstract

PURPOSE:A polyester film for packaging, obtained by blending polyethylene naphthalate with a condensation based liquid crystal polymer, having improved elongation, weather resistance and gas barrier properties and suitable for packaging foods, medicines, etc. CONSTITUTION:A polyester film obtained by blending (A) 99.9-90wt% polyethylene naphthalate having >=0.40, preferably 0.40-0.90 intrinsic viscosity and >=1.379 density with (B) 0.1-10wt% condensation based liquid crystal polymer, forming a film and biaxially drawing the film. A liquid crystal polymer consisting of terephthalic acid/p-hydroxybenzoic acid (30/70-70/30 ratio) as a carboxylic acid component and ethylene glycol as a diol component may be cited as the component (B).

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a co-axially oriented polyester film for packaging that has excellent weather resistance and gas barrier properties.

More specifically, it has properties that are even better than the excellent mechanical properties, heat resistance, dimensional stability at high temperatures, and gas barrier properties that co-axis oriented heat-set polyethylene terephthalate films generally have, and it also has excellent film resistance. The present invention relates to a highly transparent co-axis oriented polyester film for packaging.

(b) Conventional technology and its problems Taking advantage of the excellent mechanical properties, heat resistance, high conductivity, dimensional stability, and gas barrier properties that conventional polyethylene terephthalate film generally has, it is possible to heat-seal polyethylene, etc. to it. It is made of laminated polymeric materials that can be heat-sealed to make and seal bags, and is used for food packaging and other purposes. Furthermore, polyethylene terephthalate film is also used for retort packaging, taking advantage of its heat resistance.

However, in such food packaging or other packaging, if air is present inside, there are problems such as the package being oxidized by ultraviolet rays during storage and deteriorating in quality.

This is particularly important when packaging food products containing fats and oils.

Therefore, it is necessary to completely remove air or cut off ultraviolet rays, and it is also necessary to prevent air from entering from outside.

Vacuum packaging is a method for removing air, but it has the drawbacks of high equipment costs and high processing costs. There is also a method of coating the film surface with an ultraviolet absorber to cut ultraviolet rays, but this method also has the drawbacks of complicating the manufacturing process and degrading the properties of the film. Furthermore, in the method of blending an ultraviolet absorber, blending in a large amount leads to deterioration of mechanical properties, deterioration of transparency, and there is a risk that the ultraviolet absorber will leach into the food, which is not preferable.

Therefore, there is a desire for a film that maintains the original properties of the j-'IJ ethylene terephthalate film, has excellent weather resistance, and has excellent gas barrier properties.

(c) Means for solving the problem As a result of intensive studies to meet the above requirements, it was found that a film satisfying the above requirements could be obtained by using polyethylene naphthalate as the main component and blending it with a condensed liquid crystal polymer. We have now arrived at the present invention.

In other words, the gist of the present invention is that 77.9% by weight or less? θ,
Co-axis oriented polyester for packaging with excellent weather resistance and gas barrier properties superior to polymers made by blending shining polyethylene naphthalate with 0.1% by weight or more and 70.0% by weight of non-droplet condensed liquid crystal polymer. exists in

Polyethylene naphthalate as used in the present invention refers to a polymer whose constituent units are substantially composed of ethylene, 6-7 thale units, but a small amount, for example, io
Also included are ethyleneco, 6-naphthalate polymers modified with a submolar or submolar third component.

Polyethylene naphthalate is generally naphthalene, 6
-Dicarboxylic acids or functional derivatives thereof, such as naphthalene, prepared by condensing methyl 6-dicarboxylate and ethylene glycol in the presence of a catalyst under appropriate reaction conditions. In this case, examples of the third component include adipic acid, sepacic acid, phthalic acid, inphthalic acid,
Dicarboxylic acids such as terephthalic acid, naphthalene, and 7-dicarboxylic acid, or lower alkyl esters thereof, oxycarboxylic acids such as p-oxybenzoic acid, or lower alkyl esters thereof, or propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol , dihydric alcohols such as hexamethylene glycol and diethylene glycol, and polyalkylene glycols such as polyethylene glycol and polynato-2-methylene glycol. Further, during polymerization, polymerization regulators, crystallization regulators, plasticizers, matting agents, stabilizers, etc. may be added. In addition, if the degree of polymerization of the polyethylene naphthalate used in the present invention is too low, the mechanical properties will deteriorate, so the intrinsic viscosity thereof is preferably O, 1I or more.

~0.90 is preferred. Also, is the density 4J7? It is desirable that it is above.

The condensed liquid crystal polymer as used in the present invention is any type of polymer as long as it is polymerized with ester bonds or amide bonds, has liquid crystal properties when melted by heat, and melts in co-roc-ssoc, but the most typical example is Examples of such polymers include liquid crystal polymers consisting of terephthalic acid/p-hydroxybenzoic acid-30770-70/30 as a carboxylic acid component and ethylene glycol as a diol component.

The film of the present invention may be only a blend of polyethylene naphthalate and condensed liquid crystal polymer, or may contain fine inert compounds to impart slipperiness depending on the purpose. One such method is to precipitate fine particles by reacting a phosphorus compound or the like with a metal compound dissolved in the reaction system during the production of polyethylene naphthalate, for example, a metal compound dissolved in the system after the transesterification reaction. There is a method called the precipitated particle method. However, since this method has a limit on the amount of precipitated particles, another method, the so-called added particle method, is preferably used.

In other words, the additive particle method is a method in which inert fine particles are blended into polyester at any step from the polyester manufacturing process to the extrusion process before film formation.

For example, kaolin, Merck, magnesium carbonate, calcium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate.

One or more metal compounds selected from calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, lithium fluoride, etc., and terephthalates such as Ca, Ba, Zn, Mn, etc., or carbon black, etc. However, it is not limited to these.

The shape of this inert compound may be spherical, blocky or flat, and there are no particular limitations on its hardness, specific gravity, color, etc. The average particle size of the inert compound is usually 0.05 mm in spherical diameter. /-/θμ preferably θ, J~
Selected from a range of 3μ. The blending amount for the film is 0.0/'-/weight, preferably 0.0 to 0.
, g weight %, more preferably from 0.03 to O,S weight %.

The mixing ratio when mixing the condensed liquid crystal polymer with polyethylene and 6-naphthalide is o and i in terms of weight ratio.
% or more and less than 10%. More preferably (7,5
Tozachi is good.

If the mixing ratio is less than 0% or i%, the effect of mixing the condensed liquid crystal polymer, that is, the excellent heat resistance and gas permeation resistance, cannot be obtained, and if the mixing ratio is 10% or more, transparency is lost, which is preferable. do not have.

The condensed liquid crystal polymer blend polyethylene co, 6-
The naphthalate thick film is sequentially biaxially or simultaneously biaxially stretched by a conventional method, and there are no particular limitations on the manufacturing conditions.

Note that when a single polyethylene terephthalate film is irradiated with a sunshine weatherometer, deterioration is accelerated because it absorbs relatively short wavelengths (high energy), whereas in the film of the present invention, most of the polyethylene terephthalate film is irradiated with polyethylene terephthalate. - Since it is a naphthalate, absorption occurs only in its very surface layer, so deterioration is prevented.

B) Effects of the Invention The gas barrier properties of the polyethylene naphthalate film of the present invention containing a condensed liquid crystal polymer are significantly improved. Furthermore, polyethylene naphthalate has superior heat resistance compared to polyethylene terephthalate, making it a film that can withstand heat sterilization and electron beam sterilization.

That is, according to the present invention, it is possible to produce a biaxially oriented polyester film for packaging that has superior strength and elongation and weather resistance, can block ultraviolet rays, and has excellent gas barrier properties compared to polyethylene terephthalate.

It is extremely preferable to use it not only for food packaging purposes but also for other purposes. For example, it can be used for packaging glass bottles such as soft drinks to prevent glass from scattering due to glass bottles bursting, and for special purposes such as packaging food products that can withstand long-term storage or harsh transportation conditions, precision machinery, optical machinery, etc. It can be used for applications that dislike ultraviolet rays, especially for packaging pharmaceuticals that undergo heat sterilization or electron beam sterilization.

(E) Examples Hereinafter, the present invention will be explained in more detail by examples, but the present invention is not limited by the following examples unless it exceeds the gist thereof. In addition, various physical properties in the following examples were measured by the following methods.

(1) Tensile test Tensile test was measured at room temperature using Tensilon (UTM-i) manufactured by Toyo Baldwin. A load-elongation chart was prepared using the above testing machine, and its value was determined by calculation.

Breaking elongation: The elongation relative to the original length at break (represented by @) Breaking strength: The force required to break the film at room temperature, the force applied to the single cracking area of the original film ( It is expressed as k#/parrot2).

(2) Oxygen permeation rate Automatic oxygen permeability measuring device “ox-Tran” manufactured by Mocon Co., Ltd.
/ 0θ type" in the dry state of -〇C (θ%R, H
, ). The sample is measured after being seasoned for a few hours in a desiccator containing silica gel dried with a thick film. Unit is cc/m'-24'h
It is r.atrn.

(3) Weather resistance test (test using Sunshine Weatherometer) Weather resistance was tested by irradiating the film surface for a predetermined period of time using a Sunshine Weatherometer (Standard Sunshine Weatherometer manufactured by Toyo Rika Kogyo Co., Ltd.). .

Example 1 A polyethylene naphthalate polymer having an intrinsic viscosity of O, t, S is produced. On the other hand, the ratio of terephthalic acid and p-hydroxybenzoic acid as the carboxylic acid component is l:l, the diol component is ethylene glycol, and the intrinsic viscosity is o,
A condensed liquid crystal polymer was prepared. The condensed liquid crystal polymer was blended in an amount of 5 parts to 95 parts of polyethylene naphthalene, and dried and extruded according to a conventional method to obtain an unstretched film. The unstretched film is lengthwise J, j times, width a
After stretching the film to a length of 0 times, it was heat-set using a cottrc to obtain a l-μ film.

Comparative Example/A l-μ non-film was prepared by stretching and forming a film using polyethylene naphthalate alone in the same manner as in Example 1.

Comparative Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was stretched into a film according to a conventional method and heat-set at 210°C to obtain a film of 1 μm.

These results are shown in Table 1.

From Table 1, it can be seen that the film made of polyethylene naphthalate has superior weather resistance compared to polyethylene terephthalate. Furthermore, a film made by blending polyethylene naphthalate with a condensed liquid crystal polymer has both weather resistance and extremely low oxygen permeability, and is found to be an exceptionally excellent film for packaging, particularly for medical packaging.

Table l Applicant: Diafoil Co., Ltd. Agent Patent attorney Long diameter - 1 other person

Claims (1)

[Claims] (1) 99.9% by weight or less and more than 90.0% by weight of polyethylene naphthalate and 0.1% by weight or more of 10.0% by weight
A biaxially oriented polyester film for packaging that is made of a polymer blended with less than % by weight of a condensed liquid crystal polymer and has excellent weather resistance and gas barrier properties.