KR100661231B1 - Process for preparing a heat-shrinkage polyester film having the improved property of gas-barrier - Google Patents

Abstract

The present invention is a method for producing a heat shrink polyester film with improved gas barrier properties.

The present invention is characterized in that the silicon oxide or aluminum oxide is deposited on the surface of a conventional heat-shrinkable polyester film containing inorganic fine particles such as silica, but the thickness of the deposited layer is 20 to 150 nm.

Since the heat-shrinkable polyester film produced by the present invention has low oxygen permeability and water vapor permeability, it has excellent gas barrier properties and does not cause environmental pollution during recycling, so it can be used for labeling PET bottles.

PET bottle, gas barrier, evaporation, silicon oxide, heat shrinkable polyester film

Description

Process for preparing a heat-shrinkage polyester film having the improved property of gas-barrier

The present invention relates to a method for producing a transparent heat-shrinkable polyester film with improved gas barrier properties, and more particularly, as a heat-shrinkable polyester film for labels, transparent deposition by depositing oxides such as silicon oxide (SiOx) and aluminum oxide. The present invention relates to a method of making a film by making a film, gas barrier properties are greatly improved, and at the same time there is no environmental problem when recycled.

Heat shrinkable film has been mainly used in the field of shrink film for labeling PET bottles, polyvinyl chloride, polyethylene film, etc. Recently, polyvinyl chloride is discharged from the incineration disposal of pollution gas such as dioxine or chloride gas Problems with hygiene stability due to additives such as plasticizers, polyethylene, etc., and difficult printing, and when recovering PET bottles for incineration, it is a different ingredient from PET, so it is necessary to separate labels. Heat-shrinkable polyester film is drawing attention.                         

PET bottles are lightweight, do not easily break, are advantageous for sewing, and are easily used by consumers because they can be recycled and used around the world.

However, PET bottles had limitations on their use as permeable materials such as oxygen or carbon dioxide.

If the PET bottle is small, it has a close relationship with the surface area according to the size of the container, and the outflow of gas through the outer wall is of greater importance.

At smaller doses, the carbon dioxide in the carbonated beverage is lost more quickly and oxygen penetrates into the interior more quickly.

Due to the outside air penetration through the outer walls of these PET bottles or the emission of carbon dioxide on the inside, the use of some products such as beer has been restricted.

In order to supplement the problems of the PET bottle, various techniques for increasing the gas barrier performance of the PET bottle itself have been developed, but the application is still limited to some.

Conventional methods for improving the gas barrier properties of PET bottles themselves include a method of applying a high-strength carbon film to the inner wall of a PET bottle to have barrier properties (JP-A-8-53 117), or ethylene vinyl to block oxygen. A method of forming a multilayer using an alcohol (aka EVA) as an intermediate layer (US Pat. No. 5,153,038) has been proposed, and a method of coating polyvinyl chloride (aka PVDC) on a polyamide, although not PET, as a heat shrink film. (US Patent No. 5035955) and the like have been proposed.

However, applying a high-strength carbon film to a PET bottle, forming a multi-layer, etc., cost competitiveness is reduced due to supplementation of equipment and the use of expensive materials, and there is a limit to use due to problems in recycling.

In addition, when PVDC is coated to give gas barrier property to the heat shrink film, similar to PVC, the gas barrier property of PET bottles is improved due to the problem of chlorine emission during incineration disposal, and there is no environmental problem when recycling. It was not enough to satisfy the object of the present invention to make a film.

The present invention provides a method for producing a polyester film having excellent gas barrier properties, that can be used for labeling PET bottles, that is not only excellent in gas barrier properties but also contaminating the environment when recycled. I have a problem.

Hereinafter, the present invention will be described in detail.

The polyester resin composition which is the raw material which forms the polyester film used by this invention consists of polyester comprised by the dicarboxylic acid component and the diol component as a main component.

As the dicarboxylic acid component, in addition to terephthalic acid composed of repeating units of ethylene terephthalate, any one of aromatic dicarboxylic acid, aliphatic dicarboxylic acid and alicyclic dicarboxylic acid may be used.

As aromatic dicarboxylic acid, isophthalic acid and orthophthalic acid. Benzene dicarboxylic acids such as 5-tert-butyl isophthalic acid; Polycarboxylic acids such as 2,6-naphthalin dicarboxylic acid; Dicarboxybiphenyls such as 4,4'-dicarboxyl diphenyl and 2,2,6,6-tetramethylbiphenyl-4,4'-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and its substituents; 1,2-diphenoxyethane-4,4'-dicarboxylic acid and substituents thereof.

Examples of the aliphatic dicarboxylic acids include oxalic acid, maronic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, pimelic acid, sumeric acid, dodecanedicarboxylic acid, brassyric acid, tetradecane dicarboxylic acid, and tafsinic acid. , Nonadecane dicarboxylic acid, docoic acid dicarboxylic acid and substituents thereof, 4,4'-dicarboxy cyclohexane, and substituents thereof.

As said diol component, there exist ethylene glycol which comprises the repeating unit of ethylene terephthalate, In addition, any of aliphatic diol, alicyclic diol, and aromatic diol can be used.

Aliphatic diols include diethylene glycol, propylene glycol, propanediol, butadiol, neopentyl glycol, 1,10-decanediol and the like.

Examples of the alicyclic diols include 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol.

As aromatic dicarboxylic acid, Ethylene oxide addition products of bisphenol type compounds, such as 2, 2-bis (4'- (beta) -hydroxy diethoxyphenyl) propane and bis (4'- (beta) -hydroxy diethoxyphenyl) sulfone; Polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; Oxycarboxylic acid components, such as paraoxybenzoic acid, can be selected arbitrarily and used.

The polyester used in the present invention usually contains a combination of at least one acid component and / or at least one diol component, whereby the properties as a heat shrinkable film can be improved.

The kind of monomer components used in combination and their monomer ratios are appropriately selected based on desired film properties, economical efficiency, and the like.

The polyester resin composition for forming the heat-shrinkable polyester film of this invention is comprised from the 1 type (s) or 2 or more types of polyesters mentioned above as a main component.

Preferably at least one monomer selected from terephthalic acid and ethylene glycol as a monomer component and at least one monomer selected from neopentyl glycol, bisphenol-based compound, 2,6-naphthalenedicarboxylic acid, cyclohexanedimethanol and propanediol, adipic acid And at least one monomer selected from sebacic acid.

In addition, polyethylene terephthalate and at least one monomer selected from neopentyl glycol, bisphenol-based compound, 2,6-naphthalenedicarboxylic acid, cyclohexane dimethanol as a monomer component and selected from propanediol, adipic acid, sebacic acid It is preferable to independently control other resin characteristics as long as it is formed from the polyester resin composition which contains polyester containing 1 or more types of monomers as a main component, ie, the polyester resin composition which consists of three types of monomer composition from another polyester.                     

There is no restriction | limiting in particular as a manufacturing method of this heat-shrinkable polyester, The direct-polymerization method which directly reacts aromatic dicarboxylic acid and glycol which is a conventionally well-known method, and the transesterification reaction which performs transesterification reaction of the dimethyl ester of aromatic dicarboxylic acid and glycol Either method is applicable and the reactor can be either batch or continuous.

In the present invention, a direct polymerization method was used, and the preparation method was prepared by a widely known method.

In addition to the said polyester at the time of manufacture, if necessary, various additives are added in the range which does not inhibit the effect | action of this invention.

First, the polymerization catalyst can be appropriately selected from antimony compounds, germanium compounds and titanium compounds.

The inorganic particles finely dispersed in the polyester are made of silica, which is a relatively large particle.

The average particle diameter of this silica generally has a range of 0.05 to 3.0 micrometers. The content of these particles in the film ranges from 0.01 to 0.5% by weight.

In the present invention, the method of adding these inert particles to the polyester may be added in any of a slurry and a powder state, but is preferably dispersed and dispersed in a slurry phase from the standpoint of preventing scattering of particles and improving uniformity. Preference is given to adding in a slurry of ethylene glycol.

In addition, the inert particles are made of polydispersed slurry that is soluble in ethylene glycol and selected from dispersants such as acryl-based compounds such as sodium polyacrylate, sodium methacrylate and ammonium acrylate, and benzenesulfonate-based compounds. It is preferred to add to the ester preparation.

The polyester film in this invention is obtained by forming in a film form by a well-known method (for example, extrusion method, calender method), etc ..

The shape of the film is not particularly limited, and may be, for example, planar or tubular.

The obtained film is stretched in the range of 2.5 times to 7.0 times, preferably 3.0 times to 6.0 times, in one direction (major stretching direction) determined under predetermined conditions, for example, when shrinking only in the uniaxial direction, and perpendicular to this direction. In the direction of, the film is drawn in a range of 1.0 to 2.0 times, preferably 1.1 to 1.8 times.

The order of this stretching may be any one.

Stretching in the main stretching direction is performed to obtain high heat shrinkage in that direction.

When the elongation in the perpendicular direction exceeds 2 times, the heat shrinkability in the direction perpendicular to the main contraction direction becomes excessively large, and the finish at the time of thermal contraction tends to be waved, that is, a state commonly referred to as secondary shrinkage.

The stretching method is not particularly limited, and can be usually carried out by a known method such as a roll stretching method, a long interval stretching method, a tenter stretching method, a tubla stretching method, or the like.

In the biaxial stretching, stretching in the longitudinal and transverse directions may be simultaneously performed, but sequential biaxial stretching in which one direction is performed first is effective, and the longitudinal and transverse order may be any first.

Preferably, the stretching is carried out in the following process.

For example, the film is first preheated at a temperature above the average glass transition temperature (Tg) of the polymers constituting them, for example, at a temperature below Tg + 80 ° C.

When preheating in the said temperature range at the time of main direction extending | stretching, thermal contraction of the direction orthogonal to this direction can be suppressed.

It is preferable that heat setting is performed at the time of these extending | stretching. For example, after extending | stretching, it is recommended to pass the heating zone of 30 degreeC-150 degreeC for about 1 second-30 second.

In addition to controlling the orientation arbitrarily by this heat setting treatment, the crystallization ratio in the material is also controlled.

Therefore, desired physical properties can be appropriately controlled by the ratio and distribution of crystallization.

Silicon oxide or aluminum oxide is deposited on the surface of the heat-shrink polyester film.

As the deposition method, a known plasma chemical vapor deposition method or a vacuum deposition method is used.

The thickness of the deposited layer is usually about 20 to 150 nm, preferably about 30 to 150 nm.

If the thickness is less than 20 nm, it does not have sufficient gas barrier property.

If the thickness exceeds 150nm, cost competitiveness will decrease due to higher material costs.

Hereinafter, the present invention will be described in detail by way of examples.

Various performance characteristics of the polyester film produced in Examples and Comparative Examples of the present invention are measured as follows.

(1) heat shrinkage rate measurement

The film was cut to have a width of 15 mm in the lengthwise direction. A line was drawn about 100 mm from one side of this film, and the sample was made 200 mm in the longitudinal direction from the line.

This sample was immersed in warm water at a temperature of 70 to 90 ° C., and then taken out after 30 seconds, and the change in distance was measured.

The percentage with respect to the original length (200 mm) of this change was made into thermal contraction rate (%).

It is expressed as the average of five values except the maximum case and the minimum case.

(2) oxygen permeability measurement

The oxygen permeation amount was measured according to the method of ASTM D 3985-95.

The measurement was carried out using Mocon's [OX-TRAN] to measure the average permeability at room temperature and five times, and expressed as the average of three times except the maximum and the minimum.

(3) water vapor permeability measurement

The water vapor transmission rate was measured according to the method of ASTM F 372-99.

The measurement is performed five times using the Morcon's [PERMATRAN] and the average value of three times except the maximum and minimum.                     

Examples 1-4

In Examples 1 and 2, silicon oxide (SiOx) or the like was deposited on a heat-shrinkable polyester film having a copolymer-PET content of 95% by weight, and as shown in Table 1 below, the heat shrinkage was 68%. The oxygen permeation amount was reduced by about 3 times while being more than%.

In Examples 3 and 4, as a result of depositing silicon oxide (SiOx) on a heat-shrinkable polyester film having a copolymer-PET content of 90% by weight, heat shrinkage was slightly reduced than in Examples 1 and 2, but gas barrier properties were somewhat reduced. You can see the increase.

Table 1 shows the results of the performance evaluation of the film measured by the measuring method.

It can be seen that the heat-shrinkable polyester film used in the examples has a good heat shrinkage rate and a very high gas barrier property, which is very suitable for increasing the shelf life of PET bottles.

Comparative Examples 1 to 4

In Comparative Examples 1 to 2, copolymer-PET was used in the same manner as in Examples 1 to 2, but when coated with PVDC, the oxygen permeation amount increased about 3 times compared to the Example.

In Comparative Example 3, the copolymerization-PET was the same as Comparative Examples 1 and 2, but the multilayer was formed of EVOH, indicating that the heat shrinkage rate was very poor.

Comparative Example 4 is a 95% by weight of PET, it can be seen that the heat shrinkage and gas barrier properties are very poor.                     

The results of evaluating the performance are shown in Table 1.

It can be seen that the method of the comparative example is of low quality because the barrier efficiency is much lower than that of the example.

TABLE 1

Test subject Polyester composition Barrier Women Heat shrinkage Oxygen permeability Water vapor transmission rate Component 1 (wt%) Component 2 (wt%) Component 3 (wt%) (%) (cc-mil) / (100 in ² -day-bar) (cc-mil) / (100 in ² -day-bar) Example 1 PET (5) NPG-coPET (85) PDO-coPET (10) SiOx 68 0.020 0.080 Example 2 PET (5) CHDM-coPET (85) PDO-coPET (10) " 70 0.025 0.084 Example 3 PET (10) CHDM-coPET (85) PDO-coPET (5) " 60 0.018 0.077 Example 4 PET (10) NPG-coPET (85) PDO-coPET (5) " 58 0.018 0.075 Comparative Example 1 PET (5) NPG-coPET (85) PDO-coPET (10) PVDC ^* 68 0.07 1.0 Comparative Example 2 PET (5) CHDM-coPET (85) PDO-coPET (10) PVDC 70 0.073 1.4 Comparative Example 3 PET (5) NPG-coPET (85) PDO-coPET (10) EVOH ^** 30 0.07 1.2 Comparative Example 4 PET (95) CHDM-coPET (5) - --- 10 5.0 21.0

* In this case it is not formed as SiOx, but rather as a coating.

** In this case, rather than depositing like SiOx, it is formed as a multi-layer.

The heat-shrinkable polyester film produced by the present invention has improved transparency, very good gas barrier properties, and at the same time does not pollute the environment when recycled.

Therefore, it can be used for labeling PET bottles.

Claims (1)

The surface of the heat-shrinkable polyester film containing inorganic fine particles is deposited by silicon oxide or aluminum oxide, but the thickness of the deposited layer is 20 to 150nm, characterized in that the heat shrinkable polyester film with improved gas barrier properties Manufacturing method.