JP2003155403A - Polyester film excellent in hand-cutting property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a polyester film excellent in hand-cutting property. SOLUTION: This polyester film comprises a mixture of a polyester resin (A) and a polyester resin (B), and the acid component of the polyester resin (A) is mainly terephthalic acid, and the diol component of it is mainly ethylene glycol, and the acid component of the polyester resin (B) is mainly terephthalic acid and it contains as the diol component cyclohexane dimethanol, and the mass ratio A/B of polyester resin (A) to polyester (B) is 95/5-30/70.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film which is useful as a packaging material for foods, pharmaceuticals, daily necessities, cosmetics and the like and which has excellent hand tearability.

[0002]

2. Description of the Related Art Biaxially stretched polyester films are excellent in durability, moisture resistance, mechanical strength, heat resistance and oil resistance. They are tubular method, flat simultaneous biaxial stretching method and flat sequential biaxial stretching method. A biaxially stretched polyester film produced by using such as is widely used in the food packaging field and the like. However, polyester film
Due to its high mechanical strength, it cannot be easily torn by hand. Cellophane is known as a film having excellent hand tearability, but cellophane has high hygroscopicity, lacks dimensional stability, and is troublesome to handle.

There is a method of notching the film for tearing by hand, but if the tearing from the notch fails, it is necessary to use a tool such as scissors, and tearing from a place other than the notch. However, the method of providing a notch and opening the bag has a low degree of freedom.

As a method for improving the hand tearability of a polyester film, a method of making fine holes (Japanese Patent Laid-Open No. 7-165).
256), a method of copolymerizing and crosslinking a polyfunctional monomer (JP-A-2-47038), and a method of using a multilayer film having a low melting point layer (JP-A-5-104618). However, there were problems such as high cost, insufficient cuttability, and poor productivity.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a polyester film having excellent hand tearability.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies and found that polyethylene terephthalate (PE
It has been found that these problems can be solved by mixing T) with a specific polyester, and the present invention has been completed. That is, the present invention is a polyester film comprising a mixture of a polyester resin (A) and a polyester resin (B), wherein the acid component of the polyester resin (A) is mainly terephthalic acid and the diol component is mainly ethylene glycol. The acid component of the polyester resin (B) is mainly terephthalic acid, contains cyclohexanedimethanol as a diol component, and the mass ratio A / B of the polyester resin (A) and the polyester resin (B) is 95/5 to 30.
The present invention relates to a polyester film having excellent hand-cutting properties, which is / 70.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the present invention, polyethylene terephthalate (PET) is preferably used as the polyester resin (A), and it can be used by copolymerizing other components at a ratio of usually 5 mol% or less. Copolymerization components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, and anhydrous. Dicarboxylic acids such as maleic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid,
-Hydroxybenzoic acid, ε-caprolactone, oxycarboxylic acids such as lactic acid, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, bisphenol Examples of the glycol include A and ethylene oxide adducts of bisphenol S. Also, trimellitic acid, trimesic acid, pyromellitic acid,
A small amount of a polyfunctional compound such as trimethylolpropane, glycerin and pentaerythritol may be copolymerized, and trimellitic acid is preferably copolymerized and used in an amount of 0.5 to 3.0 mol%.

In the present invention, the polyester resin (B)
It is necessary to contain cyclohexanedimethanol as a diol component, and the content thereof is preferably 5 to 100 mol% of the diol component, more preferably 20 to 100 mol%, and particularly preferably 30 to 100 mol%. Any isomer of cyclohexanedimethanol may be used,
The 1,4-substituted form is preferable, and a mixture of cis form and trans form is more preferable. The diol to be copolymerized is usually ethylene glycol, but 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, bisphenol are used as long as the effects of the present invention are not impaired. A glycol such as an ethylene oxide adduct of A or bisphenol S may be used. Further, a small amount of a polyfunctional compound such as trimethylolpropane, glycerin, and pentaerythritol may be used.

The acid component of the polyester resin (B) is usually terephthalic acid, but within the range that does not impair the effects of the present invention.
Isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid,
Succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, maleic anhydride, maleic acid, fumaric acid,
It is possible to copolymerize dicarboxylic acids such as itaconic acid, citraconic acid, mesaconic acid and cyclohexanedicarboxylic acid, and oxycarboxylic acids such as 4-hydroxybenzoic acid, ε-caprolactone and lactic acid. Further, a small amount of a polyfunctional compound such as trimellitic acid, trimesic acid and pyromellitic acid may be copolymerized.

In the present invention, the polyester resin (A)
And polyester resin (B) have a mass ratio A / B of 95 /
It is necessary to mix 5 to 30/70, preferably 95/5 to 50/50, and more preferably 90/10 to 60/40. The ratio of polyester resin (A) is 9
If it exceeds 5% by mass, hand tearability is not exhibited. Also,
When the ratio of the polyester resin (A) is less than 30% by mass, the effect of hand tearability is saturated and the cost is increased, which is not preferable. Further, the mixture may contain other additives such as other polyesters, polyamides, slip agents, etc. within a range that does not impair the effects of the present invention.

The polyester film of the present invention may be subjected to surface treatment by corona discharge treatment, surface effect treatment, plating treatment, coloring treatment, or various coating treatments.

The polyester film of the present invention preferably has an end tear resistance of 100 N or less. Edge tear resistance is 10
If it exceeds 0 N, it becomes difficult to tear by hand.

Next, an example of the method for producing the film of the present invention will be described. A mixture of the polyester resin (A) and the polyester resin (B) in a chip shape is put into an extruder, heated and melted, and then extruded in a sheet shape from a die orifice of a T die and discharged. However, when the polyester resin (B) is amorphous, it is preferable to melt-knead the polyester resin (A) with a twin-screw extruder and crystallize it in advance.

The softened sheet discharged from the die orifice is closely wound around the cooling drum and cooled. Then, the obtained unstretched sheet is 90 to 14
Biaxial stretching is usually performed at a temperature of 0 ° C. at a stretching ratio of 3.0 to 5.0 times in each of the length and width. If the stretching temperature is less than 90 ° C, a homogeneous stretched film may not be obtained in some cases, and if it exceeds 140 ° C, crystallization of the polyester (A) may be promoted, resulting in poor transparency. Further, if the stretching ratio is less than 3.0 times, the strength is low, and pinholes are likely to occur when the bag is made into a bag, and if it exceeds 5.0 times, stretching becomes difficult.

The biaxially stretched film is subsequently processed into 20
Heat treatment is performed at a temperature of 0 to 250 ° C. Heat treatment temperature is 20
If the temperature is lower than 0 ° C, the shrinkage rate of the film becomes large, which may cause the bag to be deformed, and if the temperature is higher than 250 ° C, the film may melt. The biaxial stretching method may be a tenter simultaneous biaxial stretching method, a sequential biaxial stretching method using a roll and a tenter, or a tubular method.

The thickness of the film of the present invention is 6 μm or more and 5
It is preferably 0 μm or less. When the thickness is less than 6 μm, the strength is lowered, and wrinkles, lumps, and cutting are likely to occur in the film in the steps of printing and bag making. If the thickness is larger than 50 μm, the hand-cutting property is lowered and it is economically disadvantageous.

[0017]

〔material〕

PET: manufactured by Unitika Ltd. Relative viscosity 1.38. PETG: Eastman 6763 manufactured by Eastman Chemical Company. PCTA: Eastman AN00 manufactured by Eastman Chemical Company
1. PCTG: 1,4-cyclohexanedimethanol, ethylene glycol (molar ratio 7: 3) and terephthalic acid were charged in an esterification tank and reacted at 240 ° C for 4 hours to obtain an esterified product. Next, under antimony trioxide catalyst,
Melt polymerization was carried out at 300 ° C. under a reduced pressure of 1.3 hPa to obtain a polyester resin PCTG having a relative viscosity of 1.4. PCT: 1,4-Cyclohexanedimethanol and terephthalic acid were charged in an esterification tank and reacted at 240 ° C for 4 hours to obtain an esterified product. Next, under antimony trioxide catalyst, under reduced pressure of 1.3 hPa, melt polymerization at 300 ℃,
A polyester resin PCT having a relative viscosity of 1.4 was obtained. AP: Ethylene glycol as a glycol component, terephthalic acid as an acid component, trimellitic acid having a copolymerization ratio of 1 mol%, and isophthalic acid having a copolymerization ratio of 5 mol% were charged in an esterification tank and reacted at 240 ° C. for 4 hours. An esterified product was obtained. Next, under antimony trioxide catalyst, 1.3 hP
Melt polymerization at 300 ° C. under reduced pressure of a, relative viscosity 1.3
6, a polyester resin AP having a melting point of 232 ° C. was obtained.

[Measurement of Edge Tear Resistance] The edge tear resistance is measured according to JIS
It was measured according to C 2318 6.3.4 and the average value was shown.

Example 1 PET and PETG were PET / PETG = 90/10
Using a 50 mmφ extruder equipped with a coat hanger type T die, a mixture of chips in a ratio of (mass ratio) is melt extruded at a resin temperature of 270 ° C. for a residence time of 5 minutes,
Applying a voltage of 7 kV to a pinning wire on a cast roll whose temperature was controlled at 20 ° C to bring it into close contact and quenching to a thickness of 210 μm.
An unstretched sheet of m was obtained. The obtained unstretched sheet was stretched 3.8 times at 90 ° C. by a roll longitudinal stretching machine and 1 by a tenter transverse stretching machine.
After stretching 4.6 times at 20 ° C, the transverse relaxation rate is 5%
As a result, a heat treatment was performed at 230 ° C., and the film was gradually cooled to room temperature to obtain a film having a thickness of 12 μm. The resulting film was seen to be hand-cut. The edge tear resistance was measured and the results are shown in Table 1.

Examples 2 to 4 The same procedure as in Example 1 was carried out except that the polyester resin (B) was changed as shown in Table 1 and in Examples 3 and 4 the resin temperature was changed to 300 ° C. Each of the obtained films was found to be hand-cut. The edge tear resistance was measured and the results are shown in Table 1.

Example 5 PET and PETG were obtained by using PET / PETG = 60/40.
The same procedure as in Example 1 was carried out except that the chips mixed in the ratio (mass ratio) were melt-kneaded by a twin-screw extruder and then the chips were used. The resulting film was seen to be hand-cut. The edge tear resistance was measured and the results are shown in Table 1.

Example 6 Example 6 was repeated except that the polyester resin (A) was changed as shown in Table 1. The resulting film was seen to be hand-cut. The edge tear resistance was measured and the results are shown in Table 1.

Comparative Example 1 A film was produced in the same manner as in Example 1 using only PET. The resulting film was not hand-tearable and could not be torn by hand. The edge tear resistance was measured and the results are shown in Table 1.

[0024]

[Table 1]

[0025]

According to the present invention, including foods,
It is possible to provide a film having excellent hand tearability, which is useful as a packaging material for pharmaceuticals, daily necessities, cosmetics and the like.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA45 AA46 AF16 AH04 BA01                       BB08 BC01                 4J002 CF05X CF06W GG02

Claims (3)

[Claims] 1. A polyester film comprising a mixture of a polyester resin (A) and a polyester resin (B), wherein the acid component of the polyester resin (A) is mainly terephthalic acid and the diol component is mainly ethylene glycol. The acid component of the resin (B) is mainly terephthalic acid, cyclohexanedimethanol is contained as a diol component, and the mass ratio A / B of the polyester resin (A) and the polyester resin (B) is 95/5 to
A polyester film with excellent hand-cutting characteristics, which is 30/70. 2. The excellent hand tearability according to claim 1, wherein the acid component of the polyester resin (A) is mainly composed of terephthalic acid and 0.5 to 3.0 mol% of trimellitic acid. Polyester film. 3. The polyester film excellent in hand tearability according to claim 1 or 2, which has an end tear resistance of 100 N or less.