KR20020027113A - The polyester film possessing stable contractibility - Google Patents

Abstract

PURPOSE: Provided is a polyester film which is excellent in heat resistance, hot water resistance, chemical resistance, solvent resistance, weather resistance, optical character and mechanical property, and which has high uniformity, low contractile and improved printability. CONSTITUTION: The polyester film is produced by polycondensing an acidic component comprising aromatic dicarboxylic acid such as dimethyl terephthalate, terephthalic acid, dimethyl isophthalate, isophthalic acid as main components with diol component comprising alkylene glycol as main components. The repeating unit of the diol component consists of 50-86 mol% of ethylene glycol unit, 6-20 mol% of 2,2-dimethyl(1,3-propane)diol unit and 8-30 mol% of trimethylene glycol unit.

Description

The polyester film possessing stable contractibility

The present invention relates to a heat-shrinkable polyester film used for shrink labels or full shrink wrap of containers, more specifically, excellent in heat resistance, hot water resistance, chemical resistance, solvent resistance, weather resistance, optical properties and mechanical properties, It relates to a polyester film having high uniformity of film, low natural shrinkage at room temperature, and excellent printing characteristics.

Various resins such as polyvinyl chloride, polystyrene, polyethylene, polypropylene, and polyester are used as resins used as heat-shrinkable plastic films used for shrink labels or shrink wrapping of various containers. The heat shrink film is used for various purposes such as labeling of plastic containers, labels of glass bottles, coating of packaging containers, labels of batteries or electrolytic capacitors, as well as packing or tightly packing stationery or several containers.

However, in the case of polyvinyl chloride and polystyrene shrink film, which are widely used as a conventional shrink film material, heat resistance, chemical resistance, weather resistance, and mechanical properties are not sufficient. Especially, in the case of polyvinyl chloride shrink film, chlorine It contains a component, which emits a large amount of harmful substances such as hydrochloric acid and dioxin when incineration is disposed of, so it has a poor environmental friendliness, and polystyrene film has poor printability and cannot use general plastic film inks. In addition to the use of special inks, it is difficult to store because of the high rate of natural shrinkage and lack of heat resistance, causing problems in the process of cleaning and sterilizing the container.

In recent years, the use of PET bottles has rapidly increased, and the polyester heat shrink film has been in the spotlight globally in line with the trend of the integration of containers and labels for recycling. In addition to phosphorus heat resistance, chemical resistance and weather resistance, many environmental organizations recommend the use as a pollution-free material with little environmental pollution caused by carcinogens such as dioxins during incineration.

However, the general polyester has some problems such as not enough heat shrinkage to produce a good heat shrink film, and research is being conducted to obtain a good polyester heat shrink film, and as a result, many proposals have been made.

For example, Japanese Patent Laid-Open No. 63-139725 is copolymerized with an acid component of terephthalic acid and isophthalic acid, a diol component of ethylene glycol and 1,4-cyclohexanedimethanol in order to provide sufficient heat shrinkage rate, improve hot water resistance and solvent resistance. A stretched method is proposed, and Japanese Patent Laid-Open No. 63-156833 proposes a method of stretching by copolymerizing with a diol component of terephthalic acid, ethylene glycol and neopentyl glycol, and in Korea Patent Publication No. 92-7711 In order to improve performance and heat resistance and printability, a method of copolymerizing with diol components of terephthalic acid, ethylene glycol, propanediol derivatives and bisphenylsulfone derivatives has been proposed.

In addition, Korean Patent Publication No. 95-8560 proposes a method of stretching by copolymerizing an acid component such as terephthalic acid and a diol component of ethylene glycol, diethylene glycol and neopentyl glycol in order to improve shrinkage characteristics and shrink uniformity. Korean Patent Publication No. 96-590 proposed a method of stretching by copolymerizing a diol component of ethylene glycol and neopentyl glycol with an acid component of terephthalic acid and isophthalic acid in order to improve shrinkage characteristics and hot water resistance.

In addition, Japanese Patent Laid-Open No. 7-53737 discloses acid components of terephthalic acid and isophthalic acid, ethylene glycol, diethylene glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol to improve shrinkage uniformity, solvent adhesion, and tear resistance. And a method of copolymerizing and stretching a diol component of a propanediol derivative has been proposed, and in Japanese Patent Laid-Open No. H7-216107, copolymerization with components of terephthalic acid, butanediol and neopentyl glycol in order to improve shrinkage uniformity and heat resistance. The method of extending | stretching is proposed, and Unexamined-Japanese-Patent No. 7-216109 has proposed the method which blended and expanded the polyethylene terephthalate, the butylene terephthalate, and the polyethylene terephthalate copolymerized with the neopentyl glycol component.

However, the biggest problem that cannot be solved by the above method is that the printed shape of the container label is distorted by the torsional phenomenon of the printed text after shrinkage and the swelling phenomenon caused by the secondary shrinkage in the quadrangular container, and the upper part of the label The bottom and bottom are not straight, such as unsightly appearance, causing the problem of lowering the value of the final product.

The polyester film of the present invention is excellent in basic physical properties such as heat resistance, hot water resistance, chemical resistance, solvent resistance, weather resistance, optical properties and mechanical properties, high thickness uniformity of the film, low natural shrinkage at room temperature, nitrocellulose The printing characteristics by the system ink are excellent, and in particular, the shrinkage in the vertical direction in the main contraction direction is minimized, so that the reconstruction in the vertical direction due to the soot phenomenon of the square bottle, that is, the residual shrinkage stress in the main contraction direction during the secondary contraction, It is possible to minimize, and to minimize the torsional phenomenon caused by non-uniform shrinkage during shrinkage, to provide a polyester film with a uniform form of the post-shrinkage, printed text is smooth, clean and the overall appearance is beautiful.

The present invention for solving the above problems is polycondensation of an acid component containing an aromatic dicarboxylic acid such as dimethyl terephthalate, terephthalate acid, dimethyl isophthalate, isophthalate acid and a diol component containing alkylene glycol as a main component. In the polyester according to the present invention, the repeating unit of the diol component is 50 to 86 mol% of ethylene glycol units, 6 to 20 mol% of 2,2-dimethyl (-1,3-propane) diol units and 8 to 30 trimethylene glycol units It can be achieved by providing a polyester film composed of mol%.

For the production of the polyester film of the present invention, a copolyester resin having a certain amount of units of different diol components may be used alone, or a predetermined amount of homo or copolyester resins having one or more components are mixed with each other. You can also use it.

In general, the heat shrinkage properties of a polyester film are caused by its amorphousness, where the 2,2-dimethyl (-1,3-propane) diol component maintains an amorphous state of the polyester to impart a sufficient heat shrinkage overall. Contribute to

If the content of 2,2-dimethyl (-1,3-propane) diol is 6 mol% or less, sufficient heat shrinkage cannot be obtained, and if it is 20 mol% or more, it inhibits the excellent mechanical properties of the polyester and unnecessary manufacturing cost. Will cause an increase.

In addition, the trimethylene glycol component serves to block the stretching stress of the film without dispersing it in the longitudinal axis and the horizontal axis, thereby enabling the production of a film having a good thickness, and by this role, in the vertical direction of the main shrinkage direction of the shrink film By reducing the contraction rate of or rather inducing expansion, it serves to restrain the undesirable recontraction in the vertical direction due to excessive contraction stress in the main contraction direction during the second contraction.

In addition, by blocking the stretching stress in the longitudinal axis and the horizontal axis, respectively, it is possible to suppress the torsional phenomenon after shrinkage as much as possible, thereby enhancing the product value by making the appearance of the final product by the shrink film beautiful.

When the trimethylene glycol component is 8 mol% or less, the shrinkage in the vertical direction of the main contraction direction is increased, and when it is 30 mol% or more, the amorphous state of the polyester is destroyed to reduce the shrinkage rate in the main contraction direction.

Known additives, such as polycondensation catalysts, dispersants, antistatic agents, antistatic agents, sunscreens, antiblocking agents and other inorganic lubricants, are added within the range of not impairing the effects of the present invention in the production of the polyester film of the present invention. You may.

The polyester film of the present invention as described above has a refractive index of 1.605 or more in the main shrinkage direction of the film, and a birefringence of 0.030 or more, providing sufficient stretch orientation in the main shrinkage direction to have sufficient strength and shrinkage rate, By minimizing the orientation in the vertical and vertical direction, the effect of minimizing the shrinkage in the vertical direction.

Further, the natural shrinkage at 40 ° C. is 2% or less in the main shrinkage direction of the film, the shrinkage in the main shrinkage direction of the film is at least 40% in hot water at 80 ° C., and the shrinkage in the vertical direction is 1% to 1%. In the range of 5%, the shrinkage stability at room temperature, the swelling rate of the secondary shrinkage by the beverage injection and sterilization process in the tetrahedron becomes 2% or less, and the twist rate after shrinkage becomes 5% or less. When used in a packaging container, such as excellent heat resistance, chemical resistance, solvent resistance, weather resistance, optical properties and mechanical properties, high film uniformity and excellent printing properties to provide a heat shrinkable packaging.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not necessarily limited to the examples.

Example 1

20 mole parts of 2,2-dimethyl (-1,3-propane) diol and 150 mole parts of ethylene glycol are added to an autoclave equipped with a distillate with respect to 100 mole parts of dimethyl terephthalate as a diol. The reaction was carried out while removing 0.05% by weight of terephthalate at 150 by adding 150 at 130 and heating the temperature to 220 for 130 minutes. After the completion of the transesterification reaction, 0.05 wt% of silica having an average particle diameter of 2.5 μm was added to dimethyl terephthalate, and 0.045 wt% of trimethylphosphate was added to dimethyl terephthalate as a stabilizer. 0.03% by weight of monitrioxide was added to the second reactor equipped with a vacuum facility after 5 minutes, and then polymerized at 280 for about 150 minutes to obtain a dimethylpropanediol 20% copolymerized polyester polymer having an ultimate viscosity of 0.65. In addition, except that 2,2-dimethyl (-1,3-propane) diol and 140 mol parts of trimethylene glycol instead of ethylene glycol as a diol component was prepared in the same manner as in the preparation of dimethyl propanediol copolymer polyester A polypropylene terephthalate polymer having an intrinsic viscosity of 0.90 was obtained. 80 parts by weight of the dimethylpropanediol copolymer polyester and 20 parts by weight of the polypropylene terephthalate polymer were mixed and dried in a vacuum dryer so that the internal moisture content was 0.05 w% or less. (Mixed constituents of diol: 64 mol% of ethylene glycol, 16 mol% of 2,2-dimethyl (-1,3-propane) diol, 20 mol of trimethylene glycol) melt-extruded the dried mixed polyester resin to 280 It adhered to the cooling roll cooled at 30, and obtained the amorphous sheet. The amorphous sheet thus obtained was successively stretched 3.6 times in a tenter to obtain a stretched film having a thickness of 50 µm.

Thermal contraction rate (longitudinal / transverse direction), natural shrinkage rate, refractive index (longitudinal / transverse direction) and birefringence, haze, NC ink adhesion, thickness deviation, torsion rate and secondary of polyester film produced by the above method As a result of measuring the slid rate by shrinkage, it showed a fairly good result as shown in Table 1 below.

<Example 2-4>

A stretched film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the mixing ratio of the two kinds of polymers was changed so that the mixed constituents of the diol were as shown in Table 1. The properties of the polyester film showed good overall results as shown in Table 1.

Example 5

15 mole parts of 2,2-dimethyl (-1,3-propane) diol and 155 mole parts of ethylene glycol are added to an autoclave equipped with a distillate with respect to 100 mole parts of dimethyl terephthalate as a diol. The reaction was carried out while removing 0.05% by weight of terephthalate at 150 by adding 150 at 130 and heating the temperature to 220 for 130 minutes. After the completion of the transesterification reaction, 0.05 wt% of silica having an average particle diameter of 2.5 μm was added to dimethyl terephthalate, and 0.045 wt% of trimethylphosphate was added to dimethyl terephthalate as a stabilizer. 0.03% by weight of monitrioxide was added to the second reactor equipped with a vacuum facility after 5 minutes, and then polymerized at 280 for about 150 minutes to obtain 15% copolyester polyester polymer having an ultimate viscosity of 0.65. In addition, a polypropylene terephthalate polymer having an intrinsic viscosity of 0.90 was obtained by the same production method as in Example 1. 90 parts by weight of the dimethylpropanediol copolymer polyester and 10 parts by weight of the polypropylene terephthalate polymer were mixed and dried in a vacuum dryer so that the internal moisture content was 0.05 w% or less. (Mixed components of diol: 76.5 mol% of ethylene glycol, 13.5 mol% of 2,2-dimethyl (-1,3-propane) diol, 10 mol% of trimethylene glycol) Melt extrusion of the dried mixed polyester resin to 280 And contact with a cooling roll cooled to 30 to obtain an amorphous sheet. The amorphous sheet thus obtained was successively stretched 3.6 times in a tenter to obtain a stretched film having a thickness of 50 µm. The properties of the polyester film showed good overall results as shown in Table 1.

<Example 6-8>

A stretched film having a thickness of 50 μm was obtained in the same manner as in Example 5 except that the mixing ratio of the two types of polymers of Example 5 was changed so that the mixed constituents of the diol were as shown in Table 1. The properties of the polyester film showed good overall results as shown in Table 1.

<Comparative Example 1-3>

A stretched film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the mixing ratio of the two types of polymers of Example 1 was changed so that the mixed constituents of the diol were as shown in Table 1. The properties of the polyester film showed poor overall results as shown in Table 1.

<Comparative Example 4-6>

A stretched film having a thickness of 50 μm was obtained in the same manner as in Example 5 except that the mixing ratio of the two types of polymers of Example 5 was changed so that the mixed constituents of the diol were as shown in Table 1. The properties of the polyester film showed poor overall results as shown in Table 1.

Comparative Example 7

180 mol parts of ethylene glycol as a diol component was added to an autoglove equipped with a distillate with respect to 100 mol parts of dimethyl terephthalate, and 0.05 wt% of manganese acetate was added at 150 to 150 for 130 minutes while heating a manganese acetate as a transesterification catalyst. The reaction proceeded while removing the by-product methanol. After the completion of the transesterification reaction, 0.05 wt% of silica having an average particle diameter of 2.5 μm was added to dimethyl terephthalate, and 0.045 wt% of trimethylphosphate was added to the dimethyl terephthalate as a stabilizer. 0.03% by weight of monitrioxide was added, and after 5 minutes, it was transferred to a second reactor equipped with a vacuum facility, and then polymerized at 280 for about 150 minutes to obtain a polyethylene terephthalate polymer having an ultimate viscosity of 0.64. In addition, a polypropylene terephthalate polymer having an intrinsic viscosity of 0.90 was obtained by the same production method as in Example 1. 80 parts by weight of the polyethylene terephthalate polymer and 20 parts by weight of the polypropylene terephthalate polymer were mixed, and dried in a vacuum dryer so that the internal moisture content was 0.05 w% or less. (Mixed Structural Components of Diol: 80 mol% of ethylene glycol, 20 mol of trimethylene glycol) The dried mixed polyester resin was melt-extruded to 280 and brought into close contact with a cooling roll cooled to 30 to obtain an amorphous sheet. The amorphous sheet thus obtained was successively stretched 3.6 times in a tenter to obtain a stretched film having a thickness of 50 µm. The properties of the polyester film showed poor overall results as shown in Table 1.

Performance evaluation of the film produced by the above Examples and Comparative Examples was carried out by the following method and the results are shown in Table 1.

Shrinkage

The prepared film was cut into a width of 15 mm and a length of 200 mm, heat treated for 10 seconds in hot water maintained at 80 ° C., and then the length of the film was measured before and after heat treatment and calculated according to Equation 1 below.

Shrinkage (%) = [(L-ℓ) / L] × 100

Here, L means the length of the film before the heat treatment, l means the length of the film after the heat treatment.

Natural Shrinkage

The prepared film was cut into a width of 15 mm and a length of 200 mm, and then left in an oven maintained at 40 ° C. for 7 days, and then the length before and after standing was measured and calculated by the above (heat shrinkage) calculation formula.

Refractive index and birefringence

Abbe refractometer was measured at 25 ℃ using a Na-D light source, the refractive index of the main shrinkage direction (TD) and the vertical direction (MD) was measured, birefringence was calculated by the following equation (2).

Birefringence (Δn) = n (TD) -n (MD)

Here, n (TD) means the refractive index in the main contraction direction, n (MD) means the refractive index in the vertical direction.

-Nitrocellulose ink adhesion on film surface-

The adhesion of nitrocellulose ink to the film surface was tested by ASTM D3359-83 diameter.

-The haze of the film-

The haze of the film was tested by applying the United States federal standard ASTM D1003 (diameter 25 mm, scattering angle 2.5 degrees).

-Thickness variation of film-

The thickness variation of the film was measured using a film thickness measuring apparatus, and 50 points were measured at 5 cm intervals in the longitudinal direction and the transverse direction, respectively, and calculated by Equation 3 below.

Thickness deviation of film (%) = (T _max -T _min ) / (T _ave ) × 100

Here, T _max means the maximum thickness of the film, T _min means the minimum thickness of the film, T _ave means the average thickness of the film.

Bowing rate (%)

Shrink film prepared on the outer surface of each PET bottle of about 8cm width of one side is cut into a 10cm width circular shape with a length of 110% with respect to the circumference of PET bottle, and then shrunk at 80 ° C for 10 seconds. Labeling conditions), and the mixture was left at room temperature for 24 hours, and then subjected to secondary shrinkage at 90 ° C. for 5 minutes (beverage and sterilization conditions), and the degree of bowing of the upper and lower parts was measured and calculated by Equation 4 below. .

Sliding Rate (%) = (ℓ / L) × 100

Here, L means the square PET bottle width (80mm), l means the length sagging down.

Twist Rate (%)

After the prepared film was chopped to 150 mm in width (main shrinkage direction) and 100 mm in length, and then heat treated in a glycerin solution maintained at 100 for 15 seconds, the degree of twisting before and after the heat treatment was measured. Calculated by

Torsion Rate (%) = (ℓ / L) × 100

Here, L is the length of the film in the vertical direction in the main contraction direction after heat treatment, and L is the degree of twist (length) in the main contraction direction after heat treatment.

-Comprehensive Evaluation-

After applying the front-printed film to the actual container in the same manner as the sliding rate measuring method, the appearance after the second shrinkage, etc. were evaluated in total, and shown in Table 1.

◎: Good

△: normal

×: defective

Composition of film Characteristics of the film Comprehensive Evaluation Diol repeating unit Heat Shrinkage (80 ℃) Natural shrinkage Refractive Index n (TD) Birefringence Δn Haze NC Ink Adhesive Thickness deviation Torsion rate 100 ℃ Sliding rate 90 ℃ EG TMG DMPG TD MD mole% mole% mole% % % % - - % Rating % % % 50-86 3-30ink 6-20MD 40 ↑ 1-(-5) ↓ 2 ↓ 1.06 ↑ 0.03 ↑ 5 ↓ 5B 5 5 ↓ 2 ↓ Example 1 64 20 16 66 -2 0 1.620 0.060 3.0 5B 2 0 0 ◎ Example 2 72 10 18 71 0 0.2 1.622 0.061 2.5 5B 3 2 0.2 ◎ Example 3 68 15 17 68 -One 0.1 1.621 0.059 2.5 5B 3 One 0.1 ◎ Example 4 60 25 15 61 -2 0.1 1.619 0.058 3.5 5B One 0 0 ◎ Example 5 76.5 10 13.5 62 -One 0.1 1.621 0.060 3.0 5B 2 3 0.2 ◎ Example 6 72.2 15 12.8 60 -2 0.1 1.620 0.060 3.5 5B 2 2 0.2 ◎ Example 7 68 20 12 57 -2` 0 1.620 0.059 3.5 5B 2 2 0.2 ◎ Example 8 63.8 25 11.2 56 -3 0 1.619 0.059 4.0 5B One One 0.1 ◎ Comparative Example 1 80 0 20 64 7 2 1.595 0.025 3.5 3B 15 21 9 × Comparative Example 2 76 5 19 59 6 3 1.610 0.042 3.0 4B 13 11 7 × Comparative Example 3 52 35 13 32 3 4 1.617 0.028 6.5 5B 6 8 3 × Comparative Example 4 85 0 15 62 7 1.5 1.598 0.027 3.5 3B 15 20 8 × Comparative Example 5 80.8 5 14.2 43 5 4 1.611 0.043 3.0 4B 12 14 7 × Comparative Example 6 55.3 35 9.7 27 3 4 1.614 0.044 7.0 5B 5 7 3 × Comparative Example 7 80 20 0 20 16 0 1.625 0.027 7.5 5B 5 11 3 ×

In Table 1, EG is ethylene glycol, TMG is trimethylene glycol, DMPG is 2,2-dimethyl (-1,3-propane) diol, NC ink is nitrocellulose-based ink, TD is main shrinkage direction, and MD is Means the vertical direction of the main contraction direction.

As confirmed from the above table, in Examples 1 to 8, which is the case of the polyester film formed within the scope of the present invention, the thickness deviation, the torsion rate, the sliding rate, and the like are compared with those of Comparative Examples 1 to 7. Although it is shown very well and it is favorable as 5B also in ink adhesiveness, it turns out that it falls below 4B in the comparative example except the comparative example 3, the comparative example 6, and the comparative example 7.

In addition, in the case of Comparative Example 1, Comparative Example 2, Comparative Example 4, and Comparative Example 5 having a low content of trimethylene glycol, the MD shrinkage rate and the natural shrinkage rate were excessively represented, and the ink adhesion force and the thickness deviation were poorly shown, And increased slid rate was confirmed that the desired effect can not be achieved.

In the case of Comparative Example 3 and Comparative Example 6, the content of trimethylene glycol is excessive, and in this case, the amorphous state of the polyester is destroyed, so that the shrinkage in the TD direction is decreased, the thickness variation is poor, the torsion rate and the bow As the phase rate was increased, it was confirmed that the problem occurred from the excessive content of trimethylene glycol.

In Comparative Example 7, experiments were performed in which no trimethylene glycol was added. The crystallinity of the polyester was increased and the shrinkage in the TD direction was decreased, resulting in poor thickness deviation, increase in torsion rate, and increase in slid rate. It was confirmed that the same result as in the case of Comparative Example 6 added excessively was obtained.

As can be seen from the results of Examples 1 to 8 and Comparative Examples 1 to 7, ethylene glycol, trimethylene glycol, 2,2-dimethyl (-1,3) as diol components constituting the polyester By adding propane) diol as a component in the composition range of the present invention, a polyester film having stable heat shrinkability that can be easily used in various packaging materials, such as a label of a plastic container, a label of a glass bottle, and a coating of a packaging container. It is a useful invention that can be provided.

Claims (1)

In polyester by polycondensation of the acid component which has aromatic dicarboxylic acid, such as dimethyl terephthalate, terephthalate acid, dimethyl isophthalate, isophthalate acid, and the diol component which has alkylene glycol as a main component in polycondensation, Poly repeat, characterized in that the repeating unit is composed of 50 to 86 mol% of ethylene glycol units, 6 to 20 mol% of 2,2-dimethyl (-1,3-propane) diol units and 8 to 30 mol% of trimethylene glycol units Ester film.