JP3329067B2 - High shrink film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester shrink film having a low shrinkage stress, a high heat shrinkage, excellent mechanical strength and heat resistance and used for shrink labels and food packaging.

[0002]

2. Description of the Related Art Conventionally, as a shrink label used for a glass bottle or a polyethylene terephthalate (hereinafter referred to as PET) bottle or a shrink film for food packaging, a stretched film made of polyvinyl chloride or polystyrene is mainly used. Have been.

[0003]

However, in recent years, there has been a demand for a polyester-based shrink film excellent in safety and health, chemical resistance, and transparency. For example, neopentyl glycol or isophthalic acid is copolymerized with PET. There has been proposed a stretched film made of a polyester.

However, these films have a problem that the shrinkage stress is high and the container is deformed, and the heat shrinkage is insufficient when the container is shrunk without deformation.

Accordingly, it is an object of the present invention to provide a polyester shrink film excellent in low heat shrinkage stress, high heat shrinkage, mechanical strength and heat resistance.

[0006]

The high-shrink film of the present invention comprises, as a dicarboxylic acid component, 0.5 to 5 mol% of a long-chain dicarboxylic acid having an alkylene group having 8 or more carbon atoms, and terephthalic acid. And / or 95 to 99.5 isophthalic acid.
% Of diethylene glycol as a diol component.
Different polyesters on at least one side of a film made of a polyester containing 95 to 100 mol% of ethylene glycol and / or tetramethylene glycol.
It is characterized by being laminated with tellurium .

The composition ratio of each component constituting the copolymerized polyester of the present invention is such that 0.5 to 5 mol%, preferably 1 to 3 mol% of long chain dicarboxylic acid having an alkylene group having 8 or more carbon atoms as dicarboxylic acid. %, Terephthalic acid and / or isophthalic acid is 95 to 99.5 mol%, preferably 9%
The diol component is 0 to 5 mol%, preferably 1 to 4 mol%, and the ethylene glycol and / or tetramethylene glycol is 95 to 100 mol%, preferably 96 to 99 mol%.
Mol%.

[0008] The copolymerized polyester of the composition has hygiene properties,
A polyester A different from the copolymerized polyester having the above composition may be laminated on at least one surface in terms of stretchability, printability, adhesiveness, and the like. Examples of the polyester A include polyethylene terephthalate, but are not particularly limited.

The long-chain aliphatic dicarboxylic acids include dodecandionic acid, eicoic acid, dimer acid and derivatives thereof. Particularly, in the present invention, among these, branched aliphatic dicarboxylic acids having a branched structure are preferred. There is
It is preferable from the viewpoint of improving shrinkability, and among them, dimer acid is preferable from the viewpoint of improving heat resistance and transparency.

The dimer acid of the present invention is a dicarboxylic acid composed of an unsaturated aliphatic dimer, and the unsaturated aliphatic preferably has 18 or more carbon atoms. For example, it can be made by dimerizing oleic acid, elaidic acid, setreic acid, erucic acid, brassic acid, linoleic acid, etc.
Different unsaturated aliphatics may be dimerized. Also,
These dimer acids may partially contain an aromatic ring or a cyclo ring.

If the amount of dimer acid is less than 0.5 mol, low shrinkage stress and high heat shrinkage cannot be obtained, and if the amount of dimer acid exceeds 5 mol%, shrinkage at room temperature occurs and handling becomes difficult. .

Furthermore, diethylene glycol is 5 mol%
If the ratio exceeds the above range, the IV of the film after the melt-casting becomes lower, and the heat resistance becomes a problem.

The amount of copolymerized isophthalic acid is not particularly limited, but is preferably 5 to 35 mol%, more preferably 10 to 35 mol%, in view of shrinkage, shrinkage stress, heat resistance and the like.
~ 27 mol%.

The following copolymer components can be added to the copolymerized polyester of the present invention as long as the properties are not significantly changed.

As the dicarboxylic acid component, adipic acid,
Oxalic acid, malonic acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, 5-t-butylisophthalic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid,
Cyclohexanedicarboxylic acid, 5-sulfonate isophthalic acid, and the like.

The diol component is not particularly limited as long as the polyester can be obtained by a usual production method. Propylene glycol, neopentyl glycol, hexamethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol , 2-alkyl-1,3-propanediol, a diethoxy compound of bisphenol A or bisphenol S, and the like.

Furthermore, monofunctional compounds such as oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid, benzoic acid and methoxypolyalkylene glycol; glycerin, pentaerythritol, trimethylolethane and trimethylolpropane. Polyfunctional compounds such as these can be used as long as the product can substantially retain the linear polymer.

Further, other polyesters, other polymers or various additives may be added within a range not changing the gist of the present invention. For example, known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, and lithium fluoride as inorganic and organic lubricants for improving the lubricity of the film. In the case of melt-casting a polyester resin, an insoluble high-melting organic compound to be blended and a crosslinked polymer, further formed inside a polymer such as an alkali metal compound or an alkaline earth metal compound, such as a metal compound catalyst used in the production of polyester. There are internal particles.

If necessary, a stabilizer, a coloring agent, an antioxidant, an antifoaming agent and the like may be contained. The content of these additives contained in the film is usually 0.005 to
0.7% by weight.

The intrinsic viscosity, which is a measure of the molecular weight of the copolymerized polyester of the present invention, is preferably at least 0.5, more preferably at least 0.6. Strength tends to decrease.

The polyester A is laminated on at least one surface of the copolymerized polyester of the composition, and the thickness ratio thereof is as follows.
The ratio of the total thickness of the layer made of the polyester A to the total thickness of the layer made of the copolyester having the composition is 1 or less:
2, preferably 1 or less: 10. If the thickness of the polyester A layer is too large, the properties of the composition are hardly exhibited, which is not preferable. Further, other polyesters, other polymers or various additives may be added to the polyester A as long as the gist of the present invention is not changed. For example, as an inorganic lubricant and an organic lubricant for improving the lubricity of the film, kaolin, clay, calcium carbonate, silicon oxide,
Known inert external particles such as calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, and lithium fluoride, insoluble high-melting organic compounds to be blended when melt-forming a polyester resin, and a crosslinked polymer, and further an alkali metal compound or There are internal particles formed inside a polymer such as a metal compound catalyst used in the production of polyester, such as an alkaline earth metal compound.

Further, the film of the present invention may be provided with various coatings.

Although the thickness of the film of the present invention is not particularly limited, it is effectively used at 1 to 100 μm, preferably 5 to 50 μm.

In the polyester film of the present invention, the heat shrinkage in at least one direction at 100 ° C. for 5 minutes is 10% or more, preferably 25% or more. This makes the film optimal for use in shrink packaging and the like. In this case, the vertical and horizontal shrinkage ratios may be adjusted according to the purpose. For example, a longitudinal uniaxial shrinkage film having a high shrinkage ratio in the vertical direction and a low shrinkage ratio in the horizontal direction and close to 0%, Examples include, but are not limited to, shrink films that exhibit a balanced shrink rate.

Next, the method for producing the film of the present invention will be specifically described. The copolymerized polyester of the composition of the present invention is used alone or in combination with polyester A in the form of a sheet using a feed block or manifold composite die, and is cooled and cast. Next, it is preferably 2.0 to 6.0 times, more preferably 2.5 times in one or two directions.
Stretched up to 5.0 times to obtain a film.

The stretching means is not particularly limited, and a method such as roll stretching or tenter stretching is applied, and the shape may be any shape such as a flat shape or a tube shape. The stretching method may be any one of uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, and sequential or simultaneous biaxial stretching and then longitudinal and / or transverse stretching again. The stretching temperature may be appropriately selected from the stretching stress and the stretched film, but is preferably equal to or higher than the glass transition temperature (hereinafter, referred to as Tg), and more preferably, from the viewpoint of obtaining stretching stability and high shrinkage. Tg + 5 ° C to Tg + 7
Temperatures in the range of 0 ° C.

In particular, when dimer acid is used as the dicarboxylic acid component and successive biaxial stretching is performed, the stretching temperature in both the longitudinal and transverse directions is preferably Tg + 5 ° C. to Tg + 50 ° C. If the stretching temperature exceeds Tg + 50 ° C., the film will whiten during heat shrinkage, and transparency will be impaired.

If necessary, a heat treatment at a temperature of preferably 170 ° C. or less, more preferably 150 ° C. or less, may be performed.

[0029]

[Measurement and evaluation methods of physical properties] The measurement and evaluation methods are shown below.

(1) Thermal Shrinkage Ratio and Appearance The distance between the marked lines of the film sample was set at 200 mm, the film was cut into 10 mm, and heated with hot air at 100 ° C. for 5 minutes to measure the length between the marked lines. The amount of shrinkage was expressed as a percentage relative to the original size.

For the films listed in Table 1,
The average of the shrinkage in the MD and TD directions is 30% or more,
% Or more and less than 30%, and Δ less than 20%. Further, those having appearance defects such as whitening after shrinkage were evaluated as x, and those having good appearance were evaluated as ○.

On the other hand, for the films listed in Table 3,
○: 30% or more shrinkage in MD direction, 20% or more 30%
Less than Δ was rated as less than 20%. Further, those having appearance defects such as whitening after shrinkage were evaluated as x, and those having good appearance were evaluated as ○.

(2) Heat Shrinkage Stress When the film is sampled in a strip shape having a width of 10 mm and heated from a normal temperature to a temperature near the melting point of the film at a heating rate of 10 ° C./min. Was measured to determine the shrinkage stress with respect to temperature. If the maximum shrinkage stress is less than 0.8 kg / mm ² ○, 0.8 or more and less than 1.0 kg / mm ² △.
0 kg / mm ² or more was evaluated as x.

(3) Folding property on aluminum container The framing property on the aluminum container was determined by Toyo Echo No. After shrinking the film in a 53 aluminum container with a dryer and packing it, the appearance was evaluated by classifying as follows.

A: The film is sufficiently shrunk to wrap the aluminum container, and the aluminum retains its original shape. B: The film is sufficiently shrunk to wrap the aluminum container, but is slightly deformed. C: The film shrinks enough to wrap the aluminum container, but some parts are clearly deformed. D: The film does not shrink enough to pack the aluminum container well.

(4) Intrinsic Viscosity The measurement sample was phenol / tetrachloroethane = 50
The mixture was heated and dissolved at about 110 ° C. for 1 hour, and then the intrinsic viscosity (η) was measured at 30 ° C. The difference between the intrinsic viscosities before and after the film formation was 0.15 or more, and x was less than 0.15.

[0037]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

A copolymerized polyester having the composition shown in Table 1 was obtained by a known method. Next, polyethylene terephthalate (PET) was separately melt-extruded as the obtained copolyester and polyester A, and laminated into three layers so that PET / copolyester / PET (laminated thickness 1: 30: 1), An unstretched sheet having a thickness of about 300 μm was obtained. Further, the film was successively biaxially stretched 3.5 times × 3.5 times at an arbitrary temperature and heat-treated at 80 ° C. to prepare a polyester shrink film having a thickness of about 24 μm.

Table 2 shows the results of the above-mentioned evaluation performed on the obtained shrink film.

The copolymer polyester having the composition shown in Table 3
And a three-layer laminated unstretched sheet was obtained in the same manner as described above . The unstretched sheet is longitudinally stretched 1.5 times at any temperature.
(Example 4, Comparative Example 4) or 3.0 at an arbitrary temperature
The polyester-based shrink film was sequentially stretched by a factor of 3.5 times, heat-treated at 120 ° C., and further stretched by a factor of 1.5 at an arbitrary temperature (Example 5, Comparative Example 5) . Table 4 shows the results of the above-described evaluation performed on the obtained shrink film.

[0041]

[Table 1]

[Table 2]

[Table 3]

[Table 4] As described above, a shrink film excellent in shrinkage and heat resistance was obtained in the example, but not in the comparative example.

[0042]

The polyester shrink film of the present invention has a high heat shrinkage, low shrinkage stress, and excellent heat resistance, and is suitable for shrink packaging such as shrink labels and foods.

────────────────────────────────────────────────── (5) References JP-A-5-170944 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 63/00-63/91 C08J 5 / 18

Claims (2)

(57) [Claims] A long chain dicarboxylic acid having an alkylene group having 8 or more carbon atoms as a dicarboxylic acid component in an amount of from 0.5 to 5%.
Mole%, 95% terephthalic acid and / or isophthalic acid
At least one surface of a polyester film containing from 0 to 99.5% and from 0 to 5 mol% of diethylene glycol as a diol component, and from 95 to 100 mol% of ethylene glycol and / or tetramethylene glycol.
A high shrink film characterized by laminating polyester . 2. A high-shrinkable film of claim 1, long-chain dicarboxylic acid having an alkylene group or the carbon atoms 8 characterized in that it is a dimer acid.