JPH069765A - Heat shrinkable polyester film - Google Patents

Abstract

PURPOSE:To obtain a heat-shrinkable polyester film which exhibits a relatively high shrinkage factor, causes no uneven shrinkage, and is excellent in bondability with solvent and practical usability. CONSTITUTION:The polyester film is produced from a polyester produced from a dicarboxylic acid component which mainly comprises terephthalic acid and isophthalic acid or their ester-forming derivs. and contains isophthalic acid or its ester-forming deriv. in an amt. of 7-30mol% and a diol component which mainly comprises ethylene glycol and a bisphenol compd. or ethylene oxide adducts of their ester-forming derivs. and contains the bisphenol compd. or an ethylene oxide adduct of its ester-forming deriv. in an amt. of 0.1-50mol%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film used for various packaging materials, and more specifically, it has a high shrinkage ratio and excellent heat shrinkage characteristics such as uneven shrinkage. The present invention relates to a polyester film having the same.

[0002]

2. Description of the Related Art Heat-shrinkable plastic films are used for marking and protecting containers, fishing rods, condensers, rod-shaped fluorescent lamps, etc.
It is used for bundling and improving the added value of products, and is also used for the integrated packaging of books and notebooks and the close packaging. At present, it is expected to develop various applications in many other fields by utilizing the shrinkability and shrinkage stress of the heat-shrinkable film.

Conventionally, resins such as polyvinyl chloride, polystyrene, and polyolefin have been used as the material for the heat-shrinkable plastic film. However, such resins have problems in heat resistance, weather resistance, chemical resistance and the like. For example, although polyvinyl chloride film can be used as a heat-shrinkable film having various shrinkage characteristics, fish eyes are likely to occur frequently, and the product printed with this film has a poor aesthetic appearance and a reduced commercial value. It was easy to become what I did. In addition, excessive quality control is required to obtain a heat-shrinkable film without fish eyes, which causes a problem that the film manufacturing cost is significantly increased. Furthermore, polyvinyl chloride causes pollution problems when incinerated at the time of disposal, and additives such as plasticizers in polyvinyl chloride resin bleed out over time, causing dirt due to adhesion of dust, etc. Also, it was not preferable.

On the other hand, a heat-shrinkable film obtained from polystyrene has a good finish after shrinkage, but has a low solvent resistance, so that a special ink must be used for printing, and even at room temperature. It had to be stored in a cool place due to spontaneous shrinkage. In addition, there is a big problem in the disposal because it needs to be incinerated at a high temperature and a large amount of black smoke and a strange odor are generated during the incineration. As a material capable of solving these problems, polyester film is highly expected, and its usage amount has been remarkably increasing.

[0005]

However, the conventional heat-shrinkable polyester film has not been sufficiently satisfactory in its heat-shrinkable property. In particular, when covering and shrinking a container such as a bottle, shrinkage unevenness is likely to occur at the time of shrinking, characters and patterns printed on the film are distorted, or the shrinkage amount is not sufficient and the adhesion of the film to the container is not sufficient. There was a problem such as doing.

A polyester film prepared by copolymerizing an ethylene oxide adduct of a bisphenol compound or its derivative is proposed for the purpose of solving the problems of uneven shrinkage and insufficient shrinkage of a heat-shrinkable polyester film. Has been done. However, with such a copolyester film, a heat-shrinkable film having a sufficient shrinkage amount and less shrinkage unevenness can be obtained, but there is a drawback that the solvent adhesiveness is not sufficient. In particular, when used as a heat-shrinkable label for a container such as a bottle, since the end of the heat-shrinkable film is generally solvent-bonded with a solvent such as tetrahydrofuran to be used in a tube shape, it is sufficiently adhered at the end. If this is not done, the label will peel off.

[0007]

The present inventors have arrived at the present invention as a result of earnestly examining the solvent adhesiveness of a polyester film in view of such circumstances.
That is, the heat-shrinkable polyester film of the present invention,
Isophthalic acid or an ester-forming derivative thereof, which comprises a dicarboxylic acid component containing terephthalic acid and isophthalic acid or an ester-forming derivative thereof as a main component and a diol component containing ethylene glycol and a bisphenol compound or an ethylene oxide adduct of a derivative thereof as a main component Is contained in the total dicarboxylic acid component in an amount of 7 to 30 mol%, and the ethylene oxide adduct of the bisphenol compound or its derivative is included in the total diol component in an amount of 0.1 to 50 mol%.

The polyester resin used in the heat-shrinkable polyester film of the present invention contains terephthalic acid and isophthalic acid or their ester-forming derivatives as main components as dicarboxylic acid components, and ethylene glycol and bisphenol compounds or their derivatives as diol components. The main component is an ethylene oxide adduct.

In the present invention, terephthalic acid and isophthalic acid or their ester-forming derivatives, which are the main components of the dicarboxylic acid component constituting the polyester resin, are
It is preferably contained in the dicarboxylic acid component in an amount of 80 mol% or more, more preferably 85 mol% or more. This is because if the content of the aromatic dicarboxylic acid or its ester-forming derivative is less than 80 mol%, the mechanical strength of the formed polyester film may be reduced. Examples of ester-forming derivatives of terephthalic acid or isophthalic acid include derivatives of these dialkyl esters and diaryl esters.

In the present invention, isophthalic acid or its ester-forming derivative is contained in the total dicarboxylic acid component in an amount of 7 to 30 mol%, preferably 10%.
To 30 mol%, more preferably 12 to 2
It is in the range of 8 mol%. This is for imparting sufficient solvent adhesiveness to the film when the ends of the heat-shrinkable polyester film are joined in a tube shape by using an organic solvent, and the content is less than 7 mol%. This is because there is no sufficient effect of improving the solvent adhesiveness, and when it exceeds 30 mol%, the shrinkage characteristics such as uneven shrinkage and high shrinkage ratio are deteriorated.

Further, in the present invention, for the purpose of enhancing the effects of the present invention and increasing the amount of heat shrinkage, dicarboxylic acids or ester derivatives thereof other than the above are contained in less than 20 mol%, preferably 15%, of all dicarboxylic acid components. You may contain in the range less than mol%. This is because when the content of these dicarboxylic acids exceeds 20 mol%, the mechanical properties of the film deteriorate. Examples of the dicarboxylic acid usable in the present invention include naphthalene-1,4-dicarboxylic acid,
Examples thereof include naphthalene-2,6-dicarboxylic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid.

The diol component constituting the polyester resin in the present invention is mainly composed of ethylene glycol and an ethylene oxide adduct of a bisphenol compound or its derivative, and the ethylene oxide adduct of a bisphenol compound or its derivative is contained in all the diol components. It is necessary to be contained in the range of 0.1 to 50 mol%, preferably 0.5 to 30 mol%, and more preferably 1 to 20 mol%. this is,
This is because if the content of the ethylene oxide adduct of the bisphenol compound or its derivative is less than 0.1 mol%, there is no effect of reducing shrinkage unevenness, and conversely, if it exceeds 50 mol%, the low temperature shrinkability decreases.

The ethylene oxide adduct of the bisphenol compound or its derivative used in the present invention has the structures represented by the following general formulas (1) and (2).

[0014]

[Chemical 1]

(Where X is CH ₂ , C (CH ₃ ) ₂ ,
O, SO ₂ , and n and m satisfy 2 ≦ n + m ≦ 6. )

[0016]

[Chemical 2]

(In the formula, X is CH ₂ , C (CH ₃ ) ₂ , C
_{(CF 3) 2, O,} S, and SO _2, R represents an alkyl group or a halogen group C ₁ ~C _5, n and m are 2 ≦ n
+ M ≦ 6 is satisfied, and a and b are integers of 1 to 4. ) Are included, and among them, an ethylene oxide adduct of bisphenol A having a structure of the following general formula (3) is preferable.

[0018]

[Chemical 3]

(In the formula, n and m satisfy 2 ≦ n + m ≦ 6.) In the present invention, polyoxytetramethylene is used as a diol component together with ethylene glycol and a bisphenol compound or an ethylene oxide adduct of a derivative thereof. It may contain glycol and / or polyethylene glycol. By containing polyoxytetramethylene glycol and / or polyethylene glycol, excellent effects can be obtained by reducing the shrinkage unevenness of the heat shrinkable film. The polyoxytetramethylene glycol or polyethylene glycol is preferably contained in the resin in an amount of 0.1 to 20% by weight, more preferably 0.3 to 15% by weight. This is because when the content of the polyoxytetramethylene glycol or polyethylene glycol component is less than 0.1% by weight, the effect of reducing shrinkage unevenness is small, and when it exceeds 20% by weight, the melting point and glass transition temperature of the resin become low. This is because the film forming property is inferior. The molecular weight of polyoxytetramethylene glycol used is 30.
The molecular weight of polyethylene glycol is preferably in the range of 0 to 4000, and the molecular weight of polyethylene glycol is preferably in the range of 300 to 20,000. This is because those having a molecular weight lower than this do not exhibit the effect of reducing uneven shrinkage, and conversely, those having a molecular weight higher than this have poor compatibility with the resin and are not preferred.

Further, in the present invention, propylene glycol, triethylene glycol, butylene glycol, diethylene glycol, neopentyl glycol, cyclohexane dimethanol and the like can be used as the diol component within a range not impairing the effects of the present invention. In the present invention, the total amount of copolymerization components other than terephthalic acid and ethylene glycol is preferably 40 mol% or less, more preferably 35 mol% or less. this is,
This is because when the content of the copolymerization component exceeds 40 mol%, it becomes difficult to handle the polyester resin and the workability is deteriorated.

The polyester resin used in the heat-shrinkable polyester film of the present invention contains at least one trivalent or higher polyvalent carboxylic acid or polyhydric alcohol in the total amount with respect to the acid component or the alcohol component. 0.01 ~
You may use it in the range of 3 mol%. This is because the shrinkage unevenness of the film can be further reduced by containing a trivalent or higher polyvalent carboxylic acid or polyhydric alcohol, and if the content is less than 0.01 mol%, the shrinkage unevenness is reduced. This is because the reduction effect is small and if it exceeds 3 mol%, gelation occurs during polymerization of the polyester resin.
Examples of these polyvalent carboxylic acids and polyhydric alcohols include trimellitic acid, pyromellitic acid, their anhydrides, trimethylolpropane, glycerin, pentaerythritol, and the like. Mellitic acid, trimethylolpropane and pentaerythritol are particularly preferred.

The polyester resin in the present invention can be produced by a known direct polymerization method, transesterification method or the like, and the degree of polymerization thereof is not particularly limited. It is preferably 0.5 to 1.2 (measured in a mixed solution of phenol / tetrachloroethane and the like at 25 ° C.).

The obtained polyester resin is formed into a film original film by a known film forming method such as a casting roller method or a calendar method. Then, the raw film is placed at 3 ° C from the glass transition temperature of the polyester resin.
1.5 to 5.0 times in the vertical or horizontal direction, preferably 1.5 to
The film is stretched 4.8 times to give a high shrinkage factor to the film.
Further, if necessary, 1.0 in the direction perpendicular to the stretching direction.
It is stretched to a stretch ratio of 1.8 to 1.8 times, preferably 1.0 to 1.5 times.
This is effective in increasing the tensile strength of the film and preventing shrinkage in the stretching direction more than necessary. The stretching of the film is performed by a method such as simultaneous biaxial stretching, sequential biaxial stretching, uniaxial stretching, etc. Either of the longitudinal stretching and the transverse stretching may be performed first.

Although the stretched heat-shrinkable polyester film can be used as it is as a product,
From the viewpoint of dimensional stability, the heat treatment may be performed at a temperature of 50 to 150 ° C. for several seconds to several tens of seconds. By carrying out such heat treatment, preferable properties such as adjustment of the shrinkage ratio in the shrinking direction of the polyester film of the present invention, reduction of shrinkage over time during storage of the unshrinked film, reduction of shrinkage unevenness, etc. can be exhibited.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but it is 1 to 600 μm.
Those in the range of are practically used. 6 to 380 μm for packaging applications, especially packaging of foods, beverages, pharmaceuticals, etc.
Those in the range of are used. When used for labels such as PET bottles and glass bottles, those having a range of 20 to 70 μm are used.

In order to impart more specific performance to the present invention, various conventionally known processing treatments may be applied, and suitable additives may be added. Examples of processing treatments include irradiation with ultraviolet rays, α rays, β rays, γ rays or electron beams, corona treatment, plasma irradiation treatment, flame treatment, vinylidene chloride, polyvinyl alcohol, polyamide, polyolefin, etc. Examples thereof include resin coating, laminate, and metal vapor deposition. Examples of additives include polyamide, polyolefin, polymethylmethacrylate, resins such as polycarbonate, silica, talc, kaolin, inorganic particles such as calcium carbonate, titanium oxide, pigments such as carbon black, ultraviolet absorbers, release agents, and the like. Flame retardants and the like can be mentioned.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. The shrinkage ratio in the examples is 150 m in the stretching direction.
m, a polyester film cut into a size of 20 mm in a direction perpendicular to the m, and marked lines at intervals of 100 mm 6
The film was heated in 0 ° C. and 90 ° C. warm water for 60 seconds without load, and the length before shrinkage (L) and the length after shrinkage (L ′) were measured in the stretching direction of the film. I asked. Shrinkage (%) = {(L−L ′) / L} × 100 Shrinkage unevenness is 150 mm in the stretching direction and 2 in the direction perpendicular to the stretching direction.
A polyester film cut into a size of 0 mm
After shrinking by heating in a warm air of 100 ° C. for 30 seconds with no load, appearance of shrinkage unevenness on the film was evaluated by the following criteria in terms of appearance. ○: Almost no uneven shrinkage was observed ×: Significantly uneven shrinkage Also, solvent adhesiveness was obtained by stacking both side edges of the polyester film, joining them with tetrahydrofuran as an organic solvent, and leaving them for 24 hours. After that, the joint portion was pulled by hand and the adhesive strength was evaluated according to the following criteria. ⊚: Sufficient adhesive strength was obtained ◯: Adhesive strength was a little weak but practically no problem X: Insufficient adhesive strength or unadhered bisphenol As the ethylene oxide adduct of the compound or its derivative,
Bisphenol A ethylene oxide adduct of the general formula (3) or bisphenol S of the general formula (1)
An ethylene oxide adduct having n + m = 2 was used.

Example 1 87 mol parts of terephthalic acid, 13 mol parts of isophthalic acid, 150 mol parts of ethylene glycol, 3 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane, polyoxytetramethylene glycol (molecular weight 1000) 7% by weight (based on the polymer) was placed in a reaction vessel, and 450 ppm of antimony trioxide as a polycondensation catalyst was added to all acid components, and the polyester was polymerized by a direct polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 75 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Example 2 87 mol parts of terephthalic acid, 13 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, 5 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane, polyoxytetramethylene glycol (molecular weight 1000) 7% by weight (based on the polymer) was placed in a reaction vessel, trimethyl phosphate as a stabilizer was added at 100 ppm to all acid components, and antimony trioxide as a polycondensation catalyst was added at 450 ppm to all acid components,
Polymerization was carried out by the direct polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Example 3 90 mol parts of terephthalic acid, 10 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, 3 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane, polyoxytetramethylene glycol (molecular weight 1000) 7% by weight (based on the polymer) was placed in a reaction vessel, trimethyl phosphate as a stabilizer was added at 100 ppm to all acid components, and antimony trioxide as a polycondensation catalyst was added at 450 ppm to all acid components,
Polymerization was carried out by the direct polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Example 4 90 mol parts of terephthalic acid, 10 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, and 10 mol parts of bisphenol S ethylene oxide adduct were placed in a reaction vessel.
Trimethyl phosphate was added as a stabilizer in an amount of 100 ppm with respect to all acid components, and antimony trioxide was added as a polycondensation catalyst in an amount of 450 ppm with respect to all acid components. Polymerization was performed by a direct polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film is stretched at 60 ° C. in the stretching direction (TD
Direction) was uniaxially stretched 3.8 times to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Example 5 75 mol parts of terephthalic acid, 25 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, 5 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane, polyoxytetramethylene glycol (molecular weight 1000) 7% by weight (based on the polymer) was placed in a reaction vessel, trimethyl phosphate as a stabilizer was added at 100 ppm to all acid components, and antimony trioxide as a polycondensation catalyst was added at 450 ppm to all acid components,
Polymerization was carried out by the direct polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Comparative Example 1 90 mol parts of terephthalic acid, 10 mol parts of isophthalic acid, and 150 mol parts of ethylene glycol were placed in a reaction vessel, and antimony trioxide as a polymerization catalyst was added to 450 parts of all acid components.
ppm was added and polymerized by the direct polymerization method to obtain a polyester resin. The obtained polyester resin was treated in the same manner as in Example 1 to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the evaluation results of the solvent seizing property and shrinkage unevenness.

Comparative Example 2 93 mol parts of terephthalic acid, 7 mol parts of isophthalic acid, and 140 mol parts of ethylene glycol were placed in a reaction vessel, and trimethyl phosphate as a stabilizer was added to 1 mol of all acid components.
00 ppm and 450 ppm of antimony trioxide as a polycondensation catalyst were added to all the acid components, and the polyester was polymerized by the direct polymerization method. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Comparative Example 3 95 mol parts of terephthalic acid, 5 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, 2 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane and polyoxytetramethylene glycol (molecular weight 1000) 4% by weight (against the polymer) was placed in a reaction vessel, trimethyl phosphate as a stabilizer was added at 100 ppm with respect to all acid components, and antimony trioxide as a polycondensation catalyst was added at 450 ppm with respect to all acid components. Polymerization was carried out by a polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a thickness of 4
A 0 μm heat-shrinkable polyester film was obtained. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

Comparative Example 4 95 mol parts of terephthalic acid, 5 mol parts of isophthalic acid, 140 mol parts of ethylene glycol, 5 mol parts of bisphenol A ethylene oxide adduct, 0.15 mol parts of trimethylolpropane and polyoxytetramethylene glycol (molecular weight 1000) 7% by weight (against the polymer) was placed in a reaction vessel, trimethyl phosphate as a stabilizer was added at 100 ppm to all acid components, and antimony trioxide as a polycondensation catalyst was added at 450 ppm to all acid components. Polymerization was carried out by a polymerization method to obtain a polyester resin. The obtained polyester resin was melt extruded at 270 ° C. to prepare a raw film. This raw film was uniaxially stretched 3.8 times in the stretching direction (TD direction) at 60 ° C. to obtain a thickness of 4
A 0 μm heat-shrinkable polyester film was obtained. Table 1 shows the results of measuring the shrinkage ratio of the obtained film, and the results of evaluating the solvent adhesiveness and uneven shrinkage.

[0037]

[Table 1]

The components shown in the table are as follows.

TPA: terephthalic acid IPA: isophthalic acid EG: ethylene glycol BPAE: bisphenol A ethylene oxide adduct BPSE: bisphenol S ethylene oxide adduct PTMG: polyoxytetramethylene glycol TMP: trimethylolpropane

[0040]

EFFECT OF THE INVENTION The heat-shrinkable polyester film of the present invention has a relatively high heat-shrinkage rate, is free from uneven shrinkage, is excellent in solvent adhesion, and is highly practical as various packaging materials. Is.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29K 105: 02 C08L 67:00

Claims (2)

[Claims] 1. A dicarboxylic acid component containing terephthalic acid and isophthalic acid or their ester-forming derivatives as main components, and a diol component containing ethylene glycol and bisphenol compounds or ethylene oxide adducts of their derivatives as main components. Acid or its ester-forming derivative in the total dicarboxylic acid component
.About.30 mol%, an ethylene oxide adduct of a bisphenol compound or its derivative in an amount of 0.
A heat-shrinkable polyester film containing 1 to 50 mol%. 2. A heat-shrinkable polyester film, wherein the ethylene oxide adduct of the bisphenol compound or its derivative is an ethylene oxide adduct of bisphenol A.