KR100785230B1 - Biaxially oriented polyester film with transparency - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film having excellent transparency, wherein the at least one side of the biaxially oriented polyester-based film has an average particle diameter of 0.03 to 5.0 µm and contains 0.001 to 0.6% by weight of sulfonate as a hydrophilic group. Is applied alone or in combination with colloidal inorganic particles to form a coating layer by coating a water-soluble or water-dispersible resin, so that the hydrophilic sulfonate is 0.001 to 5.0% by weight based on the solids content of the coating solution, and the colloidal inorganic By using amorphous silica, titanium dioxide, and aluminum trioxide as the particles, the biaxially oriented polyester film of the present invention is uniformly dispersed in the coating liquid by sulfonation of organic crosslinked fine particles, and as a result, uniformly applied to the surface of the film. Excellent transparency, good activity and smoothness, friction coefficient, winding property, It provides an excellent film with remarkably improved surface defects.

Description

Biaxially oriented polyester film with transparency {Biaxially oriented polyester film with transparency}

TECHNICAL FIELD The present invention relates to a coated polyester film, and more particularly, to a biaxially oriented polyester film having excellent transparency, both activeness and smoothness.

Generally polyesters, in particular polyethylene terephthalate (polyethylene-

terephthalate (hereinafter abbreviated as "PET") has very good chemical and physical properties, and in particular, it has excellent mechanical strength, heat resistance, chemical resistance, electrical insulation, etc. for magnetic recording media, capacitors, electrical insulation, and packaging materials. It is widely used throughout the industry.

However, when the film is manufactured from PET itself, the friction coefficient is high, so that the activity is lowered, and blocking occurs during the stretching process and the winding by the roll, and thus does not exhibit good winding characteristics.

In order to solve this problem, inorganic fine particles such as calcium carbonate, silica and kaolin are used as a lubricating agent to add them to the PET resin to form irregularities during stretching, but in this case, Increasing the amount of particles had the drawback of impairing transparency due to the light scattering effect of the particles and voids during the stretching process.

In order to solve the problems caused by the generation of voids (void generation) is known as a catalyst wine used in the manufacture of PET (internal particle method), but it is difficult to control the size of the particles, due to the residue of the catalyst particles are crystal nucleating agent Working to raise the limits for the production of uniform quality, transparent films.

In addition, a method of improving the activity by performing machine direction stretching (MD) and then coating (in-line coating: ILC) during the film manufacturing process using an acrylic water-dispersible polymer as an emulsion polymer has been used. Then, the emulsion particles are filmed at the surface portion of the PET film at high temperatures during vertical stretching by stretching (MD) by subsequent tentering, so that most of the shape of the particles is lost, and thus sufficient transfer activity cannot be expected.

In order to improve this, a method of imparting this activity by adding fine particles or crosslinked organic particles of spherical silica, which are inorganic particles or organic particles, to a coating liquid containing an emulsion polymer, a water dispersion, or a water-soluble binder is disclosed in Japanese Patent Laid-Open No. 2001-096696, USP. 6060156 is disclosed. However, in the case of the inorganic particles, the binding force with the binder is poor, and when the particles having a large particle diameter are added, particle dropout occurs. In the case of the organic particles, the dispersibility of water, which is a coating solvent, is poor, thereby improving the activity. It was so limited that it could not improve its closure.                         

In addition, in order to improve this activity, USP 4605591 and USP 5520993 use silicone resins or waxes, but in this case, the problem of lowering the adhesive strength in the printing process is accompanied.

An object of the present invention is to coat with a water-soluble or water-dispersible resin containing the organic fine particles of the sulfonic acid salt having a sulfone group in the surface layer through sulfonation pretreatment in order to solve the problems of the conventional polyester film as described above By forming a coating layer to obtain a biaxially oriented polyester film having excellent activity and smoothness and transparency, the present invention is to provide a film having excellent activity and smoothness and transparency through the sulfonation pretreatment of organic particles.

The present invention has an average particle diameter of 0.03 to 5.0 µm on at least one side of a biaxially oriented polyester base film, and an average particle diameter of crosslinked organic polymer particles having 0.001 to 0.6% by weight of hydrophilic sulfonate represented by the following formula (1): A biaxially oriented polyester film coated with a coating liquid containing colloidal inorganic particles having a thickness of 0.01 to 0.5 µm.

Formula (1)

-SO ₃ ^- M ⁺ (M is a metal ion)

-SO ₃ ^- NH ₄ ⁺

-SO ₃ ^- NR ₄ ⁺ (R is an alkyl or aryl group)

In the present invention, the crosslinked organic fine particles have an average particle size of 0.03 to 5.0 µm, more preferably 0.03 to 3.0 µm. When the particle diameter of the organic fine particles is less than 0.03 μm, uniform quality and transparency are impaired, and when the particle size of the organic fine particles exceeds 5.0 μm, blocking phenomenon occurs during stretching or winding.

Examples of the organic fine particles in the present invention are in the form of crosslinked particles such as crosslinked divinylbenzene polystyrene, crosslinked poly (styrene-co-methacrylic resin), crosslinked benzoguanamine-formaldehyde, and benzoguanamine-melamine-formaldehyde resin. Organic particles having a benzene group capable of sulfonation are sufficient, and those in the form of spherical particles are preferable.

The sulfonation reaction is generally made by using a method of making crosslinked particles through a high concentration of sulfuric acid, a method of fumed sulfuric acid, and sulfur trioxide (SO ₃ ).

After the sulfonation reaction, the mixture is washed well with distilled water and neutralized with tetravalent ammonium hydroxide such as aqueous ammonia, aqueous sodium hydroxide solution, or tetraethylammonium hydroxide.

This process is necessary when the organic particles are put directly into the water, the organic particles are not uniformly dispersed in the water without any treatment due to the lack of affinity with the water and float on the water or settle down, the separation phenomenon occurs when stirring or stirring Even if it is not visible, separation occurs immediately when the stirring is stopped, so that the filter is clogged during coating or coagulation, etc., so that the film cannot be produced smoothly.

The addition amount of the organic particles should be added in an appropriate amount within the range that the organic fine particles do not impair the transparency of the film, it is generally preferable to adjust in the range of 0.001 to 5.0% by weight relative to the resin to be coated. When the organic fine particles added to the coating liquid fall outside of the above ranges for the coating resin, the transparency of the film is significantly lowered.

Coating of the coating liquid in the present invention is preferably performed between longitudinal stretching and transverse stretching in a series of biaxially stretched polyester film manufacturing steps. The polyester film is generally extruded into a sheet through a T-DIE in a molten state after drying the polyester resin, and solidified by contact with a cooling roll by pinning. 2 to 5 times longitudinal stretching by a roll above the glass transition temperature of is obtained, and it is obtained through extending | stretching and heat setting in the lateral stretching apparatus called a "tenter." Such a method is generally called a sequential biaxial stretching method, and recently, a biaxially stretched polyester film can also be obtained by a simultaneous biaxial stretching method, in which case the coating is performed before stretching.

The coating method is not particularly limited, but may be a meyer bar method, a gravure method, or the like, and a corona discharge treatment may be applied to the surface of the film to apply the polar group to the surface before coating. It is preferable to                     

Although the thickness in particular of the biaxially-oriented polyester film which is a base material in this invention is not restrict | limited, 9-350 micrometers is suitable. It is particularly advantageous in the production of transparent films of 50 μmu or more.

The resin used as a binder constituting the coating solution is acrylic resin or copolyester resin, polyurethane resin, epoxy resin, etc. which can be emulsified in water dispersion or water. In the case of acrylic emulsion resin, the glass transition temperature is 5 to 60 It is good to use what is C.

In general, acrylic resins have a functional group capable of self-curing or a functional group capable of bonding with a melamine-based, epoxy-based or aziridine-based crosslinking agent, and are generally coated with a suitable combination with a crosslinking agent. . These crosslinking agents affect the wear resistance or adhesion / adhesion properties of the coating layer.

Since wetting and leveling properties of the coating solution greatly affect the appearance quality of the coating, cationic, anionic or nonionic surfactants can be used.

As the colloidal inorganic particles used in the present invention, amorphous silica (SiO ₂ ), titanium dioxide (TiO ₂ ), aluminum trioxide (Al ₂ O ₃ ), etc. having a particle diameter of 0.01 to 0.5 μm may be used. In addition, the polyester for base films used for this invention uses the polyester of the number average molecular weights 10,000-10,000. If the molecular weight is too low, the breakage occurs at the time of stretching, and if the molecular weight is too large, the melt viscosity is very large, which is unfavorable to extruder or filter.

The polyester of the present invention is obtained by condensation polymerization of a dicarboxylic acid component and a glycol component. Specifically, dicarboxylic acid and ester derivatives thereof may be mentioned among the polyester constituents of the present invention, and a representative example thereof is terephthal.

Acid (terephthalic acid), dimethyl terephthalic acid, naphthalene dicarboxylic acid (naphthalene-dica-rboxylic acid), and other copolymerization components such as aliphatic dicarboxylic acid,

Isophthalic acid, sulfoisophthalic acid, and cyclohexane dicarboxylic acid can be used. As the glycol component, ethylene glycol, propylene glycol, bisphenol-A, butanediol, neopentyl glycol, hexanediol, 2-methylpropanediol and the like can be used, and in some cases, trimellitic acid, trimellitic anhydride, pyro Mellitic acid, trimetholpropane, pentaerythritol and the like can be used.

In the polyester, a matting agent such as titanium dioxide, a phosphorus compound which is a heat stabilizer, an antioxidant, an ultraviolet absorber, or a pigment, a dye, a fluorescent brightener, a flame retardant, or the like may be used. Particularly in the case of a film, an inorganic or organic filler should be included in a polyester in order to impart a diactivation, and the transparency of the film is greatly influenced by the type, size of the filler, and the degree of formation of voids during stretching. Will receive.

     In general, in the case of using a transparent film, no particles are used at all, or a small amount of silica particles, alumina, calcium phosphate, and glass beads (500 ppm or less) may be used. In order to give efficiently, co-extrusion method using particles only on the surface layer is possible, and when used in combination with the single-sided or single-side coating method of the present invention, a more transparent and good process passability can be obtained. Although it does not specifically limit about the thickness of the application layer apply | coated to a base film, It is preferable to carry out in 0.003-0.5 micrometer.

     In particular, in the case of the base film incorporating porous spherical silica having a large specific surface area, a film excellent in transparency and easy activity can be obtained.

The polyester of the present invention uses 65% or more of polyethylene terephthalate or polyethylene naphthalate.

     EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example and a comparative example.

The measurement evaluation method applied in the present invention is as follows.

※ Measurement evaluation method

The physical properties of the present invention were measured by the following method.

(1) Dynamic friction coefficient (uk):

 According to ASTM D1894-78 using a friction coefficient measuring instrument of "Heydon Corporation" of Japan

      Measured under a load of 200 grams.

(2) the average size of the particles:

The size of the average particle diameter of the particles _{(D 50, D 10, D} 90) was a laser light scattering "COULTER company" diffraction system particle size distribution measuring instrument "LS230", wherein D _10, D _50, D ₉₀ is from a low particle size By integrating the volume distribution, the particle size corresponds to 10%, 50%, and 90%, respectively.

(3) Winding:

 In case of slitting, the loss ratio (%) for the production due to the missing section of the film roll and wrinkles is calculated and displayed as follows.

   ◎: loss rate less than 3%

   ○: loss rate less than 3% -5%

   △: loss rate less than 5% -10%

   ×: loss rate 10% or more

(4) Haze:

  Cut the polyester film into 6cm × 6cm size, and place one sample on the haze meter (“AUTOMATIC DIGITAL HAZEMETER” manufactured by Nippon Densoku Co., Ltd., Japan) in the vertical direction, and light having a wavelength of 400 to 700 nm in the transverse direction with respect to the sample. It penetrates.

At this time, the haze value is calculated by the following equation and displayed on the haze meter.

(5) Abnormal defects on the film surface:

  After preparing the polyester film, a sample of A4 size was taken and visually checked to evaluate the degree of abnormal crystal by the following criteria.

  (Circle): When there is no fault in the abnormal eye.

  (Triangle | delta): When there are less than three abnormal faults which are visible to the naked eye.                     

X: When there are three or more defects which are visible to the naked eye.

※ Sulfonation reaction of organic particles:

It is obtained by passing organic powder particles in an amount of about 170 cm ³ / min with a gas mixture of SO ₃ and N ₂ in the gaseous phase from oleum. The temperature of the reaction tube at this time is 0 degreeC-5 degreeC, and reaction time is adjusted to 20-40 minutes. S0 ₃ exposure over a long period of time so when there favorite castle distributed on the particles of water, not good, because changing up the sulfur particles.

After the reaction was completed, unreacted gas was removed using distilled water, and neutralized using 1.0% tetraethyl ammonium hydroxide aqueous solution.

※ Preparation of Coating Solution:

After the prepared particles were added to the pure water passed through the ion exchange resin as shown in Table 1, the mixture was stirred well and the acrylic emulsion resin (from Rohm End Haas Co., Ltd. Methoxymethylmelamine ", a one-component type containing a crosslinking agent) is added and stirred again to prepare a coating solution.

At this time, the pH of the coating liquid is adjusted using ammonia water so as not to be less than 8.0.

However, the crosslinked organic particles of Comparative Example were not subjected to sulfonation treatment, and the crosslinked organic particles of Example were treated by the sulfonation treatment method described above, and then a coating solution was prepared.                     

※ Manufacturing and coating method of polyester base film:

Polyethylene terephthalate pellets having an intrinsic viscosity of 0.625 dl / g containing 60 ppm of porous amorphous spherical silica particles having an average particle diameter of 3.7 µm were sufficiently dried at 160 degrees for 7 hours using a vacuum dryer, melted and cooled through an extrusion die. The drum was applied by electrostatic application to form an amorphous unstretched sheet. It is heated again and stretched 3.5 times in the direction of film advancement at 100 ° C, followed by corona treatment and coating using Maeverbar coating method, and then in a direction perpendicular to the direction of movement of the film in the section at 110-120 ° C tenter. After stretching 3.5 times, heat treatment was performed at 240 ° C. for 4 seconds to obtain a film having a thickness of 25 μm. The coating thickness was measured at about 15 to 30 nm using an ellipsometry method, and the particle content of the coating layer was calculated based on the mixing ratio of the crude liquid.

Table 1 Example 1-4, Comparative Example 1-2

division Type of coating particles (manufacturer / product name / particle size-um) Particle Content of Coating Layer Dynamic friction coefficient Film haze Winding Surface defects weight% uk % Example 1 Crosslinked Polystyrene Particles (Mitsui Chemical / PP240D / 0.5um) 0.008 0.39 0.95 ◎ ○ Example 2 Crosslinked Polystyrene Particles (Mitsui Chemical / PP102P / 0.6um) 0.01 0.37 1.0 ◎ ○ Example 3 Benzoguanamine-Melamine-Formaldehyde Resin (Japan Catalyst / MS / 1.0um) Colloidal Spherical Silica (Japan Catalyst / KE-10W / 0.1um) 0.003                                              0.01 0.34 1.1 ◎ ○ Example 4 Crosslinked Polystyrene Particles (Mitsui Chemical / PP102P / 0.6um) Colloidal Spherical Silica (Japan Catalyst / KE-10W / 0.1um) 0.005                                              0.01 0.31 1.3 ◎ ○ Comparative Example 1 Crosslinked Polystyrene Particles (Mitsui Chemical / PP102P / 0.6um) Colloidal Spherical Silica (Japan Catalyst / KE-10W / 0.1um) 0.005                                              0.01 0.61 0.95 ○ △ Comparative Example 2 Benzoguanamine-Melamine-Formaldehyde Resin (Japan Catalyst / MS / 1.0um) 0.005 0.59 0.9 △ △

As can be seen in Table 1, the particles are uniformly dispersed in the coating liquid by sulfonation of the organic crosslinked fine particles, and as a result, the film is uniformly applied to the surface of the film to provide a film having excellent coefficient of friction, coilability, and surface defects. I can get it.

Claims (3)

Organic cross-linked particles having an average particle diameter of 0.03 to 5.0 μm on at least one side of the biaxially oriented polyester base film were obtained by the following formula (1) using high sulfuric acid or fumed sulfuric acid, and sulfur trioxide (SO ₃ ). After sulfonation to contain 0.001 to 0.6 wt% of the hydrophilic group represented by hydrophilic group, washed with distilled water to remove unreacted substances, and tetravalent ammonium hydroxide such as aqueous ammonia or aqueous sodium hydroxide or tetraethyl ammonium hydroxide. A biaxially oriented polyester film characterized in that a coating layer is formed by applying a water-soluble or water-dispersible resin in which organic crosslinked particles neutralized using a lockside are mixed alone or in combination with colloidal inorganic particles. Formula (1) -SO ₃ ^- M ⁺ (M is a metal ion) -SO ₃ ^- NH ₄ ⁺ -SO ₃ ^- NR ₄ ⁺ (R is an alkyl or aryl group) The method according to claim 1, The amount of the organic crosslinked particles added is in the range of 0.001 to 5.0% by weight based on the resin to be coated biaxially oriented polyester film.     The method according to claim 1, The colloidal inorganic particles are biaxially oriented polyester film, characterized in that composed of any one of amorphous silica (SiO ₂ ), titanium dioxide (TiO ₂ ), aluminum trioxide (Al ₂ O ₃ ) having a particle diameter of 0.01-0.5 ㎛.