KR930007508B1 - Polyester film - Google Patents

Abstract

This is a biaxially oriented polyester film which improves the crystal structure, surface tension and surface resistance of film by adding a new composition of sulfonic acid derivatives. The film has 0.4-1.0 dl/g of critical viscosity; 20-80 angstroms of crystal size; 30-65 dyne/cm of surface tension; and below 1016Ω of surface resistance. The polyester film comprises (a) 70 wt.% polyethylene terephthalate; (b) 0.5-20.0 wt.% of formula (I); and (c) 0.1-10.0 wt.% of formula (II). In formulas, R1 is C1-10 alkyl and M is alkali earth metal such as Li, Na, K. The compounds of (I) are selected from sodium 3,5-dicarbomethoxybenzenesulfonate, sodium 3,5-dicarboethoxybenzenesulfonate, lithium 3,5-dicarbomethoxybenzenesulfonate, and potassium, 3,5-dicarbo pentoxybenzene sulfonate; and (II) from potassium oltylbenzenesulfonate, potassium nonyl benzenesulfonate, sodium nonylsulfonate, and lithium tridecylbenzenesulfonate, etc.

Description

Polyester film

The present invention relates to a biaxially oriented polyester film of a novel physical property, and more particularly, by adding a sulfonic acid derivative of a new composition to improve the crystal structure, surface tension and surface resistance of the film, thereby preventing antistatic properties, transparency, and various mechanical properties. The present invention relates to a polyester film having excellent properties and adhesion to inks and coating solutions.

Among the polyesters, polyethylene terephthalate (PET) is chemically stable, has high physical and mechanical strength, and has excellent heat resistance, durability, chemical resistance, and electrical insulation, and thus is used for medical, industrial, magnetic tape, and capacitors. It is widely used for packaging, photographic film, labeling as well as various molded products.

However, these polyesters have the drawback of generating and accumulating static electricity due to high electrical insulation and causing various static electricity problems.

For example, the generation and accumulation of static electricity in polyester film may be caused by deterioration of workability due to film-to-roll adhesion, film-to-film friction, static shock, sparking, etc. in film forming, printing, and packaging processes. Uneven printing, poor adhesion of the ink, uneven coating, dust and foreign matters on the film surface can cause deterioration of product quality.

In order to solve these drawbacks, an antistatic agent is applied to the surface of the polyester film or mixed into the film to improve the charging property. However, the antistatic agent applied to the surface is economically disadvantageous because a separate coating process is required for film production. The antistatic effect of the film also has the drawback that its efficacy is inferior due to surface friction, cleaning, and the passage of time.

On the other hand, the internally mixed type film exhibits an antistatic effect by the transfer of the antistatic agent inside the polymer to the film surface.However, in the case of a film formed due to the high secondary transition temperature of the polyester resin, the antistatic agent forms a film surface at room temperature. It is difficult to release, and the antistatic effect is generally bad. In particular, in the case of biaxially stretched polyester film, since the antistatic agent on the surface of the film is widely dispersed during stretching, the antistatic effect is very poor.

Therefore, as a conventional internal incorporation technique for improving the antistatic property of a film, films that have been biaxially stretched by containing polyalkylene glycol in polyester or simultaneously containing polyalkylene glycol and an alkylsulfonic acid metal salt are proposed.

However, when the amount of the additive is small, the antistatic property is very poor, and it is difficult to apply. Increasing the amount of the additive improves the antistatic property, but the physical properties of the film, in particular, the thermal and mechanical properties are greatly reduced. There is a drawback that the film becomes very opaque.

Therefore, in the present invention, in order to solve the drawback in the conventional polyester film as described above, in the polyester film having an intrinsic viscosity of 0.4 to 1.0 dl / g of 70 wt% or more of PET, sulfonic acid having a new composition as an antistatic agent It is an object of the present invention to provide a new polyester film having excellent various physical properties by improving the crystal structure, surface tension and surface resistance of the film by using an appropriate amount of a derivative.

Hereinafter, the present invention will be described in detail.

The present invention is a biaxially oriented polyester film having an extreme viscosity of 0.4 ~ 1.0dl / g of 70% or more of the film constituents of PET, 0.5 ~ 20.0% by weight of the compound represented by the following structural formula (I) and the following structural formula (II) A polyester film containing 0.1 to 10.0% by weight of the compound represented by) at the same time, having a crystal size of 20 to 80 angstroms, a surface tension of 30 to 65 dyne / cm, and a surface resistance of 10 ¹⁶ ohms or less. It is characterized by.

In said formula, R <_1> is a C1-C10 alkyl group, M is alkaline-earth metals, such as Li, Na, K, and R <_2> is a C8-C25 alkyl group.

Referring to the present invention in more detail as follows.

The polyester of the present invention is PET obtained by polycondensation of dimethyl terephthalate and ethylene glycol at 70 wt% or more, and the intrinsic viscosity measured at a concentration of 0.3 grams per 25 milliliters of autochlorophenol and a temperature of 35 ° C. is 0.4 to 1.0. dl / g, but preferably 0.5 to 0.8 dl / g. Below 0.4 dl / g, breakage occurs frequently during film formation and production, so productivity is very low, and above 1.0 dl / g, film production is difficult.

R ₁ in the compound of formula (I) used in the present invention has 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. If the carbon number is 10 or more, the solubility and the reactivity with ethylene glycol worsen, causing discoloration of the polyester and the transparency of the film is lowered.

The addition amount of the structural formula (I) is 0.5 to 20.0% by weight, but preferably 0.5 to 10.0%. At 0.5 wt% or less, the transparency of the film is poor, and a fine swelling (fish swelling) phenomenon is generated on the surface of the film, so that the physical properties of the film are greatly reduced, and ink and coating liquid adhesion is not improved. In addition, at 20.0 wt% or more, the polycondensation reaction rate is very slow, so that the productivity is greatly reduced and the residence time in the reactor is long, which is not preferable because the thermal decomposition of the polyester may occur.

Specific examples of such a compound of formula (I) include sodium 3,5-dicarbo-methoxybenzenesulfonate, sodium 3,5-dicarbo-ethoxybenzenesulfonate, sodium 3,5-dicarbo-pentoxybenzene Sulfonates, lithium 3,5-dicarbo-methoxybenzenesulfonates, potassium 3,5-dicarbo-pentoxybenzenesulfonates, and the like, but are not limited thereto.

In addition, as the compound of the formula (II) used in the present invention, potassium olylbenzenesulfonate nonylbenzenesulfonate, potassium undecylbenzenesulfonate, lithium eicosylbenzenesulfonate, sodium nosyl sulfonate, sodium decylsulfonate, sodium heptadecyl sulfonate, Examples of metal salts of alkyl sulfonates having 8 to 25 carbon atoms include sodium nonadecyl sulfonate, sodium tridecylbenzene sulfonate, sodium tetradecylbenzene sulfonate, lithium hexadecylbenzene sulfonate, lithium stearyl sulfonate, lithium decyl sulfonate and lithium dodecyl sulfonate. It is not necessarily limited thereto. Since the sulfonic acid derivatives of the structural formula (II) have excellent heat resistance and excellent compatibility with the compound of the structural formula (I), the film prepared by adding to the polyester together with the compound has excellent antistatic properties and transparency. In addition, the surface tension of the film is increased to exhibit excellent ink and coating liquid adhesion.

In particular, in the compound of the formula (II) used in the present invention R ₂ represents an alkyl group having 8 to 25 carbon atoms, when the carbon number is 7 or less, the compatibility with the polyester and the thermal stability of the sulfonic acid derivative is poor, When the film is produced using a sulfonic acid derivative having an alkyl group having 7 or less carbon atoms, breakage occurs frequently during film formation, resulting in low productivity, and very low antistatic property of the film.

In addition, when the carbon number is 26 or more, the fluidity of the sulfonic acid derivative is poor in the polyester, so that it is difficult to disperse. Therefore, an alkyl group having 8 to 25 carbon atoms is usually used, or a mixture thereof is used.

The addition amount of the sulfonic acid derivative of the structural formula (II) is 0.1 to 10.0% by weight, preferably 0.3 to 5.0% by weight. In the present invention, a sufficient effect can be obtained by using a relatively small amount of antistatic agent, but the antistatic property is very poor at 0.1 wt% or less, and the antistatic property is excellent at 10.0 wt% or more, but the mechanical properties and transparency of the film are greatly reduced. .

According to the present invention, when only the sulfonic acid derivative of the above formula (II) is used alone, poor dispersion in polyester results in poor transparency of the film, and swelling is generated on the surface of the film by the undispersed product, thereby physically releasing the film. Since the property becomes very bad, it is preferable to mix and use the compound of formula (I).

The addition time of the additives represented by the structural formulas (I) and (II) to the PET in the present invention is not necessarily limited, but may be any time before the completion of the polycondensation reaction. In particular, when added during the polycondensation reaction, it is preferable after the transesterification reaction or half an hour before the polycondensation reaction. In addition, in the case of the sulfonic acid derivative of the formula (II), a high concentration of polyester mast chips may be made and blended to a predetermined concentration in a conventional polyester to melt extrusion.

On the other hand, the film of the present invention shows excellent antistatic properties and transparency when the crystal size is 20 to 80 angstroms, if the crystal size is 20 angstroms or less, the antistatic property of the film is very poor, 80 Above Angstrom, not only the film is vulnerable, but also frequent breakage occurs during film formation, which reduces production. In addition, the surface tension of the film exhibits excellent transparency and ink and coating liquid adhesion in the case of 30 to 65 dyne / cm, and more preferably 35 to 60 dyne / cm. If at 30 dyne / cm or less, transparency and ink and coating liquid adhesion are not improved at all, and at 65 dyne / cm or more, the heat resistance of the film is lowered.

Although the manufacturing method of the polyester film of this invention is not specifically limited, The unstretched sheet of 0.4-1.0 dl / g of intrinsic viscosity melt-extruded the polyester containing the said additive by T-Die, inflation method, etc. After making, it is biaxially stretched to produce a biaxially oriented polyester film of the present invention.

The stretching method is the same as that of ordinary polyester stretching, and there is no change even if the above additive is used. The stretch temperature is 60 ~ 150 ℃ in the film production, the draw ratio is 2.5 ~ 6.0 times in the longitudinal direction and 2.5 ~ 6.0 times in the transverse direction. After stretching, open and set at 160 ~ 240 ℃ for 20 seconds to obtain a biaxially oriented film having a crystal size of 20 to 80 angstroms, a surface tension of 30 to 65 dyne / cm, and a surface resistance of 10 ¹⁶ ohms or less.

The film of the present invention thus obtained can be designed with a suitable thickness according to the use, usually made of a film with a thickness of 3.0 to 300 microns, corona discharge treatment, coating and lamination of other resins, pneumatic on the film surface as needed All kinds of surface treatment are available.

As described above, the biaxially oriented polyester film according to the present invention is excellent in antistatic property, transparency, and adhesion of ink and coating solution, and thus has excellent practical performance, so that packaging, graphic or magnetic fields such as transparency and antistatic properties are required. It is possible to apply to all fields, to improve ink adhesion without corona discharge treatment, and to solve the problem of deterioration of surface properties over time, which has been a problem in the past.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to Examples.

Various performance evaluation of the film manufactured in the Example and the comparative example of this invention was performed by the following method.

1) Mechanical Properties

Using Instron's UTM Model-4206, a 50 mm long, 20 mm wide and 100 micron thick film was stretched at 200 mm / cm at room temperature and 65% relative humidity to create load-elongation charts. Calculated and evaluated.

Elongation at Break: The elongation at break in% of the original length.

Breaking Strength: The force required to break a film at room temperature is expressed as the force applied per unit area of the film (kg / mm2).

Films with low breaking elongation and high breaking strength have excellent mechanical properties.

2) transparency

Transparency was measured by Hadometer of Gardner Neotek of the United States, and the ratio of scattered light / (transmitted light + scattered light) was expressed in haze value in% value using a C-light source. The lower the haze value, the better the transparency.

3) Ink and coating liquid adhesive

The surface tension was measured by checking the degree of coagulation of the Toreji Co., Ltd. standard solution of Hwagwang New Pharma on the film surface, and the unit was dyne / cm. The higher the surface tension, the better the adhesion between the ink and the coating liquid.

4) Antistatic

The surface resistivity was measured at 20 ° C. and 65% RH using an insulation resistance tester manufactured by Hurett, USA. The applied voltage is 500V and the resistance unit is ohms. Lower surface resistivity means better antistatic effect.

5) Crystal size

Crystal size was measured using the wide ankle (WAXS) mode of Rikaku's X-Ray analyzer, and the unit is Angstrom.

Example 1

After completion of the transesterification reaction during the polymerization of PET in a conventional manner, 4.0 wt% of sodium 3,5-dicarbo-propoxybenzenesulfonate was added to make a polymer having an intrinsic viscosity of 0.70.

Subsequently, 1.5 wt% of sodium decylbenzenesulfonate was added during melt extrusion to make an unstretched sheet by a conventional method, and stretched 3.5 times in a longitudinal direction at 90 ° C. and 4.0 times in a lateral direction at 110 ° C. to heat-set at 230 ° C. for 20 seconds. Micron biaxially oriented films were made and evaluated for performance. Performance evaluation results of the produced film are shown in Table 1 below.

[Example 2 above]

In the same manner as in Example 1, the amount of sodium 3,5-dicarbopropoxybenzenesulfonate added was changed from 4.0 wt% to 3.0 wt%, and sodium decylbenzenesulfonate was changed from 1.5 wt% to 1.2 wt%. . Performance evaluation results of the produced film are shown in Table 1 below.

Example 3

In the same manner as in Example 2, the amount of sodium 3,5-dicarbopropoxybenzenesulfonate added was changed from 3.0 wt% to 2.0 wt%, and sodium decylbenzenesulfonate was changed from 1.2 wt% to 1.0 wt%. . Performance evaluation results of the produced film are shown in Table 1 below.

EXAMPLES 4-6

In the same manner as in Examples 1, 2 and 3, the sodium decylbenzenesulfonate was changed to the same amount of lithium decylsulfonate, and all other conditions were performed in the same manner. Performance evaluation results of the prepared film are shown in Table 1 below, respectively.

EXAMPLES 7-9

In the same manner as in Examples 1, 2 and 3, respectively, sodium 3,5-dicarbo-propoxybenzenesulfonate was replaced with sodium 3,5-dicarbo-methoxybenzenesulfonate, and decylbenzenesulfonate sodium wasdecylated. It changed to potassium sulfonate and performed all other conditions similarly. Performance evaluation results of the prepared film are shown in Table 1 below, respectively.

Example 10

The same procedure as in Example 7 was carried out, except that sodium 3,5-dicarbo-methoxybenzenesulfonate was added in an amount of 1.0% by weight, and potassium decylsulfonate was added in an amount of 0.5% by weight. It was. Performance evaluation results of the produced film are shown in Table 1 below.

As a result of the performance test of the film according to the above embodiment, in all cases of Examples 1 to 10, the film of the present invention was found to have excellent antistatic property, transparency, mechanical properties, ink and coating liquid adhesion.

Comparative Example 1

For comparison, melt extruding only PET with an ultimate viscosity of 0.7 to make an unstretched sheet in the usual way, stretch it at 90 ° C for 3.5 times in longitudinal direction and at 110 ° C for 4.0 times and heat-set at 230 ° C for 20 seconds to achieve 100 micron thickness. The biaxially oriented film was made and performance evaluated. The performance evaluation results of the prepared film are shown in Table 1.

Comparative Example 2

The same procedure as in Example 2 was carried out, but the film was prepared without adding sodium decylbenzenesulfonate to evaluate performance. As a result, the transparency, mechanical properties, ink and coating liquid adhesion of the film were greatly improved, but the antistatic property was not improved at all. The evaluation results are shown in Table 1 below.

Comparative Example 3

In the same manner as in Example 2, but was added 0.05% by weight of sodium decylbenzenesulfonate. As a result, the antistatic property of the film was not improved at all as in Comparative Example 2. The evaluation results are shown in Table 1 below.

Comparative Example 4

The same procedure as in Comparative Example 3 was carried out, but 15.0 wt% of sodium decylbenzenesulfonate was added. As a result, the antistatic property of the film was excellent, but other mechanical properties, transparency, ink and coating liquid adhesion were greatly reduced. The evaluation results are shown in Table 1 below.

Comparative Example 5

The same procedure as in Comparative Example 4 was carried out, except that sodium 3,5-dicarbo-propoxybenzenesulfonate was added and 2.0 wt% sodium decylbenzenesulfonate was added. As a result, as in Comparative Example 4, the antistatic property of the film was excellent, but other mechanical properties, transparency, ink and coating liquid adhesion were greatly reduced. The evaluation results are shown in Table 1 below.

Comparative Example 6

In the same manner as in Example 9, 0.05% by weight of potassium decylsulfonate was added. As a result, the film was excellent in transparency, mechanical properties, ink and coating liquid adhesion, but the antistatic property was not improved at all. The evaluation results are shown in Table 1 below.

Comparative Example 7

The same method as in Comparative Example 6 was carried out, but 12.0 wt% of potassium decylsulfonate was added. As a result, the antistatic property of the film is excellent, but other mechanical properties, transparency, ink and coating liquid adhesion is greatly reduced. The evaluation results are shown in Table 1 below.

Comparative Example 8

In the same manner as in Comparative Example 7, but not adding sodium 3,5-dicarbo-methoxybenzenesulfonate, only 2.0% by weight of potassium decylsulfonic acid was added. As a result, the film was excellent in antistatic properties as in Comparative Example 7, but other mechanical properties, transparency, ink and coating liquid adhesion was greatly reduced. The evaluation results are shown in Table 1 below.

TABLE 1

Claims (1)

In the biaxially oriented polyester film having an intrinsic viscosity of 0.4 to 1.0 dl / g of 70% or more of the film constituents of PET, 0.5 to 20.0% by weight of the compound represented by the following structural formula (I) and the following structural formula (II) A polyester film containing 0.1 to 10.0% by weight of the compound at the same time, the crystal size of the film is 20 to 80 angstroms, the surface tension is 30 to 65 dyne / cm, the surface resistance is 10 ¹⁶ ohms or less . In said formula, R <_1> is a C1-C10 alkyl group, M is alkaline-earth metals, such as Li, Na, K, and R <_2> is a C8-C25 alkyl group.