JP3054267B2 - Polyester 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 used for shrink labels and packaging, which is excellent in appearance when heat-shrinked at a low temperature and in solvent adhesion and tear resistance of the film. .

[0002]

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

Recently, a stretched film comprising a 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-2-13672).
JP-A-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., and when used for shrink labels,
Insufficient solvent adhesion, poor appearance such as the edge of the label waving due to shrinkage in the non-shrinkage direction, and generally uniaxial stretching to shrink in only one direction, but as a result, the film tends to tear in the stretching direction In other words, there is a problem that the strength and elongation in the direction perpendicular to the stretching are reduced, and it is difficult to use the material for plastic bottles such as PET bottles. Accordingly, an object of the present invention is to provide a polyester shrink film excellent in low-temperature heat shrinkage characteristics, solvent adhesion, tear resistance and the like.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve these objects, and as a result, have formed a film-formed stretch of a copolymerized polyester obtained from a dicarboxylic acid component and a diol component having a specific composition. As a result, the present inventors have found that a polyester shrink film having excellent low-temperature heat shrinkage properties, improved solvent adhesion, shrinkage in a non-shrinkage direction, and improved tearability of the film can be obtained, and the present invention has been achieved.

[0006] That is, the present invention provides a method for preparing a total dicarboxylic acid component of 100
Relative mol%, 95 to 70 mol% of terephthalic acid as the dicarboxylic acid component, and isophthalic acid 5-30 mol%
Containing 90 to 50 mol% of ethylene glycol as a diol component and 5 to 20 mol% of diethylene glycol and / or tetramethylene glycol with respect to 100 mol% of the total diol component;

Embedded image (Wherein R1 is a linear or branched saturated hydrocarbon group having 1 to 6 carbon atoms, and R2 is a linear or branched saturated hydrocarbon group having 2 to 6 carbon atoms). A polyester-based shrink film obtained by forming and stretching a component copolymerized polyester containing a diol derivative in an amount of 5 to 30 mol%, and further adding dimer acid or 12-hydroxystearic acid to the copolymerized component. It is a polyester-based shrink film obtained by forming and stretching a copolymerized polyester film.

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

If the isophthalic acid content is less than 5 mol%, the heat shrinkage is low, and if it exceeds 30 mol%, the tear resistance and stretchability when uniaxially stretched are reduced, and the heat shrinkage reaches saturation in a short period of time. Is generated. Diethylene glycol and / or
If the content of tetramethylene glycol is less than 5% by mole, the low-temperature heat shrinkage is inferior. If the content exceeds 20% by mole, tear resistance decreases and shrinkage unevenness occurs. The propanediol derivative is 5
If it is less than mol%, the solvent adhesion and tear resistance are not sufficiently improved, and if it exceeds 30 mol%, the solvent-adhered portion is significantly whitened, which is not preferable. When neopentyl glycol is used instead of the propanediol derivative, the solvent adhesion is improved, but the improvement in tear resistance by uniaxial stretching is insufficient. Also, dimer acid and 12-hydroxystearic acid have the effect of slowing down the heat shrinkage and making it suitable, and further improve the quality of the appearance after heat shrinkage. Dimer acid is a dicarboxylic acid obtained by dimerizing an unsaturated fatty acid. Examples of the unsaturated fatty acid include oleic acid, elaidic acid, setreic acid, erucic acid, brassic acid, and linoleic acid. As the dimer acid, the same unsaturated fatty acid or a different unsaturated fatty acid may be used. The dimer acid may be hydrogenated after dimerization, or may partially contain a cyclo ring or an aromatic ring.

A shrink film formed by forming a copolymerized polyester of the above composition and stretching is different from a conventional shrink film when subjected to heat shrinkage, and has a low-temperature heat shrinkage characteristic, a solvent adhesive property, and a resistance when uniaxially stretched. Excellent tearability,
It becomes suitable as a shrink film.

[0010] The copolymerized polyester of the present invention may contain other copolymerizable components as long as its properties are not significantly changed. For example, as dicarboxylic acids, adipic acid, oxalic acid, malonic acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, 5-t-butylisophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, cyclohexanedicarboxylic acid, 5-sulfone Isophthalic acid, dimer acid and the like. 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,
Monofunctional compounds such as benzoylbenzoic acid and methoxypolyalkylene glycol, and polyfunctional compounds such as glycerin, pentaerythritol, trimethylolethane, and trimethylolpropane also have a range in which the product can substantially hold a linear polymer. Can be used within.

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. An insoluble high-melting organic compound and a cross-linked polymer to be blended during the melt-forming of a polyester resin, and 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. Further, as additives, a stabilizer, a coloring agent, an antioxidant, an antifoaming agent, and the like can be contained as necessary. The fine particles contained in the film are 0.005 to 0.5% by weight.

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

Next, the film production method of the present invention will be specifically described. Using the copolymerized polyester of the present invention, an unstretched sheet is produced by a known method such as a melt extrusion method or a calendering method, and then in one direction or two directions in a range of 2.0 to 5.0.
The film is stretched 2 times, more preferably 2.5 to 4.5 times, and finally a stretched film having a thickness of about 20 to 100 μm is produced.

The stretching means is not particularly limited, and methods such as roll stretching, tenter stretching and tubular stretching can be applied, and the film may have any shape such as a flat shape or a tube shape. 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 in view of the stretching stress and the stretched film.
It is preferable to stretch at a relatively low temperature in order to obtain a high temperature and a low temperature heat shrinkage property.

When a shrink label is made from a flat stretched film, the shrink label is attached to a tube using a solvent. The solvent is used alone or in combination of a plurality of solvents in consideration of the adhesive strength, the appearance of the bonded 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]

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

(1) Intrinsic viscosity [η] The viscosity was measured at a sample concentration of 1 g / dl and 30 ° C. using a mixed solvent of phenol / tetrachloroethane = 50/50.

(2) Solvent Adhesiveness An unstretched sheet having a thickness of about 200 μm is uniaxially stretched four times at Tg + 20 ° C. to form a film, which is then laminated with tetrahydrofuran such that the stretching direction is a circumferential direction. Make a label. The degree of adhesion was evaluated as follows, and the appearance of the bonded portion was also evaluated. ○ Good, △ Adhesive but practical problem, × Poor.

(3) Low-temperature heat shrinkability The label prepared in the above evaluation of the solvent adhesion was 1.5 l PET.
The label was placed on a bottle, placed in a hot air dryer at 80 ° C. for 30 seconds, heat-shrinked, taken out, and the appearance and tightness of the label were evaluated as follows. ◎ extremely good, ○ good, × bad.

(4) Tear Resistance A uniaxially stretched film was subjected to a tensile test in a direction perpendicular to the stretching in the same manner as in the evaluation of the solvent adhesiveness and the low-temperature heat shrinkability, and evaluated as follows. ○ good, × bad.

Examples 1 to 6 and Comparative Examples 1 to 6 First, a transesterification reaction was carried out between dimethyl dicarboxylate and a diol component, followed by a polycondensation reaction under reduced pressure to obtain a copolymerized polyester shown in Table 1. . Then T
A sheet was made with a die extruder and further stretched to make a polyester shrink film. Table 2 shows the results of the above-described evaluation performed on the film thus obtained.

[0023]

[Table 1]

[0024]

[Table 2]

As shown in Table 2, in Examples, a polyester shrink film excellent in low-temperature heat shrinkage, solvent adhesiveness of the film, and tear resistance when uniaxially stretched could be obtained. On the other hand, in the comparative example, a balanced polyester shrink film was not obtained.

Examples 7, 8 85 mol% of terephthalic acid, 10 mol% of isophthalic acid
A polyester shrink film was obtained in the same manner as in Example 2 except that dimer acid having 36 carbon atoms was changed to 5 mol% (Example 7). After the transesterification reaction of Example 3 was completed, 5 mol% of 12-hydroxystearic acid (based on the dicarboxylic acid component) was added, an 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 evaluation performed on the film thus obtained.

[0027]

The polyester shrink film of the present invention has good solvent adhesiveness of the film, good tear resistance when uniaxially stretched, excellent workability in making shrink labels, etc., and also has low-temperature heat shrinkability. It is suitable for shrink labels and shrink wrapping since a high quality appearance can be obtained when shrinked.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // B29K 67:00 105: 02 B29L 7:00 C08L 67:02 (56) References JP-A-4-173231 (JP, A JP-A-5-208447 (JP, A) JP-A-2-28244 (JP, A) JP-A-3-143619 (JP, A) JP-A-3-86522 (JP, A) JP-A-1- 160632 (JP, A) JP-A-4-4229 (JP, A) JP-A-3-142224 (JP, A) JP-A-63-114629 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 C08G 63/16-63/21 C08G 63/60 B29C 61 / 02,61 / 06

Claims (5)

(57) [Claims] (1) relative to 100 mol% of all dicarboxylic acid components
And terephthalic acid as a dicarboxylic acid component in an amount of 95 to 70.
Mol%, wherein the isophthalic acid 5 to 30 mol%, the total Jio
90 to 50 mol% of ethylene glycol as a diol component, 5 to 20 mol% of diethylene glycol and / or tetramethylene glycol , based on 100 mol% of the diol component. (Wherein R1 is a linear or branched saturated hydrocarbon group having 1 to 6 carbon atoms, and R2 is a linear or branched saturated hydrocarbon group having 2 to 6 carbon atoms). A polyester shrink film obtained by forming a film of a copolymerized polyester containing a diol derivative in an amount of 5 to 30 mol% and stretching the film. 2. R ₁ and R of said 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, wherein the copolyester is uniaxially stretched 2 to 5 times. 4. A polyester shrink film obtained by forming a film of a copolymerized polyester obtained by replacing a part of terephthalic acid with dimer acid among the copolymerized components according to claim 1, and stretching the film. 5. A polyester shrink film obtained by forming a film of a copolymerized polyester containing 12-hydroxystearic acid in addition to the copolymerized component of claim 1, and stretching the film.