JPH05305667A - Polyester shrink film - Google Patents

Abstract

PURPOSE:To enhance low temp. heat shrinkage characteristics, solvent adhesiveness or tear resistance by forming a film from copolyester containing terephthalic acid, isophthalic acid, ethylene glycol and a propane diol derivative represented by a specific formula to stretch the same. CONSTITUTION:A shrink film used in a shrink label or food packing is formed by stretching a film formed from specific copolyester. Specific copolyester contains 95-70mol% of terephthalic acid and 5-30mol% of isophthalic acid as dicarboxylic acid components and contains 90-50mol% of ethylene glycol and 5-20mol% of diethylene glycol and/or tetramethylene glycol as diol components and further contains 5-30mol% of a propane diol derivative represented by formula (wherein R1 is a 1-6C straight chain or branched chain saturated hydrocarbon group and R2 is a 2-6C straight chain or branched chain staturated hydrocarbon group).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester-based shrink film used for shrink labels, packaging, etc., which is excellent in appearance when heat-shrinked at low temperature and solvent adhesion and tear resistance of the film. ..

[0002]

2. Description of the Related Art Conventionally, stretched films made of polyvinyl chloride or polystyrene have been mainly used as shrink labels used for glass bottles and polyethylene terephthalate (hereinafter referred to as PET) bottles and shrink films for food packaging. Came. But in recent years
Polyester shrink film with excellent safety and hygiene, chemical resistance, and heat shrinkage has been demanded, and terephthalic acid and ethylene glycol, neopentyl glycol, isophthalic acid, 1,4-cyclohexanedimethanol, etc. A stretched film made of a polyester obtained by copolymerizing the above has been proposed (for example, JP-A-57-42).
726, JP-A-63-156833).

Recently, a stretched film made of polyester obtained by copolymerizing terephthalic acid and ethylene glycol with a propanediol derivative having a side chain has been proposed (for example, JP-A-1-136722 and JP-A-2-36722).
235920, JP-A-3-290441,
JP-A-3-292333).

[0004]

However, these films have insufficient heat shrinkage performance at a low temperature of 50 to 80 ° C., or when they are used for shrink labels,
Insufficient solvent adhesiveness, poor appearance such as wavy edges of the label due to shrinkage in the non-shrinking direction, and generally uniaxial stretching to shrink in only one direction, but as a result, the film tends to tear in the stretching direction. That is, there is a problem that the strength and elongation in the direction perpendicular to the stretching is reduced, and it is difficult to use it for a plastic bottle such as a PET bottle. Therefore, an object of the present invention is to provide a polyester-based shrink film excellent in low-temperature heat shrinkability, solvent adhesion, tear resistance and the like.

[0005]

Means for Solving the Problems As a result of earnest studies to achieve these objects, the present inventors have formed a film of a copolyester obtained from a dicarboxylic acid component and a diol component having a specific composition by film-forming. This has led to the finding that a polyester-based shrink film having excellent low-temperature heat-shrinkability, improved solvent adhesion, non-shrinkage-direction shrinkage, and film tearability can be obtained, and arrived at the present invention.

That is, in the present invention, 95 to 70 mol% of terephthalic acid and 5 parts of isophthalic acid are used as dicarboxylic acid components.
~ 30 mol%, 90 to 50 mol% ethylene glycol as a diol component, diethylene glycol and /
Or 5 to 20 mol% of tetramethylene glycol, the general formula

[Chemical 2] (Wherein R ₁ represents a linear or branched saturated hydrocarbon group having 1 to 6 carbon atoms, and R ₂ represents a linear or branched saturated hydrocarbon group having 2 to 6 carbon atoms). Polyester shrink film, which is obtained by forming and stretching a component copolyester containing 5 to 30 mol% of a propanediol derivative, and dimer acid or 12-hydroxystearic acid as a steam copolymer component. It is a polyester-based shrink film obtained by forming a film of a copolyester having added thereto and stretching.

The present invention will be described in detail below. Of the present invention,
The composition ratio of each component constituting the polyester shrink film is such that terephthalic acid is 95 as the dicarboxylic acid component.
-70 mol%, preferably 92-85 mol%, isophthalic acid 5-30 mol%, preferably 8-15 mol%, and ethylene glycol 90-5 as the diol component.
0 mol%, preferably 85 to 65 mol%, 5 to 2 diethylene glycol and / or tetramethylene glycol
0 mol%, preferably 7 to 15 mol%, and the propanediol derivative is 5 to 30 mol%, preferably 8 to 20 mol%.

When isophthalic acid is less than 5 mol%, the heat shrinkage rate is low, and when it exceeds 30 mol%, tear resistance and stretchability in the case of uniaxial stretching are deteriorated, and heat shrinkage reaches saturation in a short time so that shrinkage unevenness occurs. Cause Diethylene glycol and /
Alternatively, if tetramethylene glycol is less than 5 mol%, the low-temperature heat shrinkability is poor, and if it exceeds 20 mol%, tear resistance is deteriorated and shrinkage unevenness occurs. The propanediol derivative is 5
When it is less than 30 mol%, improvement in solvent adhesion and tear resistance is insufficient, and when it exceeds 30 mol%, the solvent-bonded portion remarkably whitens, which is not preferable. When neopentyl glycol is used instead of the propanediol derivative, solvent adhesion is improved, but tear resistance by uniaxial stretching is not sufficiently improved. Further, dimer acid and 12-hydroxystearic acid have the effect of slowing the heat shrinkage rate and optimizing it, and further improve the appearance quality after heat shrinkage. Dimer acid is a dicarboxylic acid obtained by dimerizing an unsaturated fatty acid, and examples of the unsaturated fatty acid include oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, and linoleic acid. The dimer acid may be the same unsaturated fatty acid or different unsaturated fatty acids, may be hydrogenated after dimerization, or may partially contain a cyclo ring or an aromatic ring.

The shrink film formed by forming a film of a copolyester having the above composition and stretching is different from the conventional shrink film when heat-shrinking, unlike low-temperature heat-shrinking properties, solvent adhesiveness, and resistance to uniaxial stretching. Excellent tearability,
It becomes suitable as a shrink film.

Copolymer components other than those described above can be added to the copolyester of the present invention within a range that does not significantly change the properties thereof. For example, dicarboxylic acids include 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-sulfone. Examples of the acid salt include isophthalic acid and dimer acid. Examples of the diol component include propylene glycol, neopentyl glycol, hexamethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, and a diethoxy compound of bisphenol A or bisphenol S.

Further, oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid, benzoic acid,
A range in which the product can substantially retain a linear polymer even in the case of a monofunctional compound such as benzoylbenzoic acid and methoxypolyalkylene glycol, a polyfunctional compound such as glycerin, pentaerythritol, trimethylolethane, and trimethylolpropane. Can be used inside.

Further, other polyesters, other polymers or various additives may be added within the scope of the present invention. For example, known inorganic external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride as an inorganic lubricant and an organic lubricant for improving the slipperiness of a film. , An insoluble high melting point organic compound to be blended during the melt film formation of a polyester resin, and a cross-linked polymer, and further formed inside a polymer such as a metal compound catalyst used in polyester production, such as an alkali metal compound or an alkaline earth metal compound. There are internal particles. Further, as an additive, a stabilizer, a colorant, an antioxidant, an antifoaming agent and the like can be contained as required. The fine particles contained in the film are 0.005 to 0.5% by weight.

The intrinsic viscosity as a measure of the molecular weight of the copolyester of the present invention is 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more. Intrinsic viscosity is 0.
If it is less than 5, the mechanical strength of the film decreases.

Next, the film manufacturing method of the present invention will be specifically described. An unstretched sheet is produced by a known method such as a melt extrusion method or a calender method using the copolymerized polyester of the present invention, and then 2.0 to 5.0 in one direction or two directions.
The stretched film having a thickness of about 20 to 100 μm is finally produced by stretching the stretched film twice, more preferably 2.5 to 4.5 times.

The stretching means is not particularly limited, and roll stretching, tenter stretching, tubular stretching and the like can be applied, and the shape of the film may be flat, tubular or the like. The type of stretching depends on the application.
Any of uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching may be used. The stretching temperature is appropriately selected depending on the stretching stress and the stretched film, but is usually 10 to 30 ° C above the glass transition temperature.
It is preferable to stretch at a relatively low temperature in order to obtain a high temperature and low temperature heat shrinkage property.

When a shrink label is made from a film stretched in a flat shape, it is stuck in a tube shape using a solvent. The solvent may be used alone or as a mixture of a plurality of solvents in consideration of the adhesive strength, the appearance of the adhesive portion, the volatility of the solvent, and the like. Preferred solvents include methylene chloride, chloroform, trichloroethane, tetrachloroethane, benzene, toluene, xylene, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate and the like.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The measurement and evaluation methods are shown below.

(1) Intrinsic viscosity [η] Using a mixed solvent of phenol / tetrachloroethane = 50/50, measurement was carried out at a sample concentration of 1 g / dl and 30 ° C.

(2) Solvent Adhesion An unstretched sheet having a thickness of about 200 μm is uniaxially stretched 4 times at Tg + 20 ° C. to form a film, which is then laminated with tetrahydrofuran so that the stretching direction is in the circumferential direction. Make a label for. Then, the degree of adhesion was evaluated as follows, and the appearance of the adhered portion was evaluated. ○ Good, △ Adhesive but practically problematic, × Bad.

(3) Low-temperature heat shrinkability The label prepared by the solvent adhesiveness evaluation is 1.5 l PET.
The bottle was covered, placed in a hot air drier at 80 ° C. for 30 seconds for heat shrinkage, taken out, and then the appearance and tightness of the label were evaluated as follows. ◎ Very good, ○ good, × bad.

(4) Tear resistance The uniaxially stretched film was subjected to a tensile test in the direction perpendicular to the stretching in the same manner as in the above solvent adhesion and low temperature heat shrinkage evaluation, and evaluated in the following manner. ○ Good, × Bad.

Examples 1 to 6 and Comparative Examples 1 to 6 First, a dicarboxylic acid dimethyl ester and a diol component were subjected to transesterification reaction, and then polycondensation reaction was performed under reduced pressure to obtain a copolyester shown in Table 1. .. Then T
A sheet was prepared by a die extruder and further stretched to prepare a polyester shrink film. Table 2 shows the results of the above-described evaluations of the film thus obtained.

[0023]

[Table 1]

[0024]

[Table 2]

As shown in Table 2, in the examples, it was possible to obtain a polyester type shrink film having excellent low temperature heat shrinkability, solvent adhesiveness of the film, and tear resistance when uniaxially stretched. On the other hand, in the comparative example, a well-balanced polyester shrink film could not be obtained.

Examples 7, 8 85 mol% of terephthalic acid and 10 mol% of isophthalic acid
And a polyester-based shrink film was obtained in the same manner as in Example 2 except that the dimer acid having 36 carbon atoms was changed to 5 mol% (Example 7). In addition, after the completion of the transesterification reaction of Example 3, 5 mol% of 12-hydroxystearic acid (against dicarboxylic acid component) was added, the esterification reaction was performed, and then polycondensation was performed under reduced pressure. A polyester shrink film was obtained in the same manner as in (Example 8). Table 2 shows the results of the above-described evaluations of the film thus obtained.

[0027]

The polyester-based shrink film of the present invention has good solvent adhesiveness to the film, tear resistance when uniaxially stretched, excellent workability when used as a shrink label, and low temperature heat shrinkability. It is suitable for shrink labels and shrink packaging because it gives a high-quality appearance when it is shrunk.

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Claims (5)

[Claims] 1. A dicarboxylic acid component containing terephthalic acid in an amount of 95 to 70 mol% and an isophthalic acid in an amount of 5 to 30 mol%, and a diol component containing ethylene glycol in an amount of 90 to 5 mol%.
0 mol%, 5 to 20 mol% of diethylene glycol and / or tetramethylene glycol, represented by the general formula: (Wherein R ₁ represents a linear or branched saturated hydrocarbon group having 1 to 6 carbon atoms, and R ₂ represents a linear or branched saturated hydrocarbon group having 2 to 6 carbon atoms). A polyester-based shrink film obtained by forming a copolyester containing 5 to 30 mol% of a propanediol derivative, and stretching the film. 2. R ₁ and R of the propanediol derivative
The shrink film according to claim 1, wherein ₂ is an ethyl group or an n-butyl group. 3. The shrink film according to claim 1, which is obtained by uniaxially stretching the copolyester 2 to 5 times. 4. A polyester shrink film obtained by forming a film of a copolyester obtained by replacing a part of terephthalic acid with dimer acid among the copolymerization components according to claim 1 and stretching the film. 5. A polyester-based shrink film obtained by forming and stretching a copolymerized polyester containing 12-hydroxystearic acid in addition to the copolymerization component according to claim 1.