JPS62244616A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a high quality cast film, without any surface defect and small in the variability of minor thickness, by a method wherein the containing concentration of poly organic siloxane, added to polyester, is limited and concentration distribution in the sectional direction of the film is specified. CONSTITUTION:In a polyester film, containing 1-100ppm of poly organic siloxane compound with respect to 100pts.wt. of polyester, the ratio R of the mass ratio (rs) of silicon atom in the surface layer of the polyester film to carbon atom in the same layer to the mass ratio (rc) at 100Angstrom from the surface layer of the film or the ratio R=rs/rc is within the range of 0.8-10. When the containing concentration of the poly organic siloxane compound becomes lower than 1ppm, longitudinal stripe-type defects are developed on a polyester molten body sheet and when it exceeds 100ppm, strong adhesive force can not be obtained. On the other hand, when the value of R is up to 0.8, the variability of thickness due to minor recesses and projections can not be eliminated and when it exceeds 10, crater type defects may be generated on the surface of the film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polyester film, and more specifically, the present invention relates to a polyester film. The invention relates to an excellent polyester film.

[Prior Art] In order to eliminate surface defects of polyester films, the following methods have been used so far.

(1) Eliminate dead space in the extrusion system so that the polymer does not become an abnormal 2FH swamp.

(2) Use a material for the polymer system that prevents the molten polymer from adhering to or corroding the walls of the extrusion system.

(3) Improve the surface finish accuracy of polymer systems, make the flow behavior of the polymer uniform, and prevent the adhesion of minute foreign matter.

(4) Make sure that there is no difference in surface peripheral speed between the film and the roll using the drawn yarn or the film conveyance yarn.

[Problems to be solved by the invention] However, despite these various measures, it is still not possible to resolve minute scratches on the surface of polyester film, fixation lines in the longitudinal direction, and minute irregularities on the surface. is the current situation. In particular, in recent years, it has been desired to have completely defect-free surfaces for raw paper for vapor deposition recording and raw paper for photographic recording, and production in such fields has been nearly impossible using conventional methods.

Means for Solving Problem E] The present invention provides a polyester film containing 1 to iooppm of a polyorganosiloxane compound based on 100 parts by weight of polyester, in which the silicon atoms relative to the carbon atoms in the surface layer of the polyester film are The ratio R-r between the mass ratio rs and the same mass ratio r of 100 people from the film surface layer
The present invention relates to a polyester film characterized in that s/rs is in the range of 0.8 to 10.

The polyester in the present invention is a polymer having ester bonds obtained by condensation polymerization from a dicarboxylic acid and a diol, and the dicarboxylic acid component includes terephthalic acid, phthalic acid, isophthalic acid, adipic acid, sepatic acid, naphthalene dicarboxylic acid. , and its derivatives, and diol components include ethylene glycol,
Diethylene glycol, propylene glycol, butylene glycol, cyclohexane dimetatool, dihydroxycyclohexane, resorcinol, hydroquinone, dihydroxynaphthalene, polyethylene glycol, etc. Polyesters can also be obtained from such oxyacids. The intrinsic viscosity of polyester is 0.
4 or more, preferably in the range of 0.6 to 1.0. Polyesters suitable for the present invention include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and the like. Of course, the polyester may contain optional additives, such as slip agents, heat stabilizers, anti-blocking agents, antioxidants, colorants, antistatic agents, ultraviolet absorbers, thickening (lowering) agents, etc. Good too.

When casting by applying an electrostatic application casting method, the present polyester should contain metal compounds such as Z, Mg, Ml, 00, etc. in an amount of about 20~'+oooppm in terms of atomic superposition relative to the polyester. It is preferable to leave it there. Polyorganosiloxane is a general term for organic polymer compounds having a siloxane bond consisting of a bond between silicon and oxygen, and includes alkyl, allyl, There are polysiloxanes containing aralkyl, phenyl, etc., and other polyorganosiloxanes, their copolymers, blend pairs, etc. In the case of the present invention, dimethyl polysiloxane, methyl phenyl polysiloxane, Particularly preferred are phenylpolysiloxanes. It is preferable to add polyorganosiloxane before the polymerization of polyester, especially before the esterification reaction, but it is not necessarily limited to this.Although the effect will be slightly weaker, it can be added before melt extrusion due to polymerization. Good too.

In the case of the present invention, the viscosity of the polyorganosiloxane is 10 to 5.0.
00 centistokes (CS) is preferred. This is because when it is less than 10C5, not only is the effect of improving surface defects such as streaks on the melt sheet weak, but also the resulting film transparency and adhesion tend to deteriorate;
This is because, if it exceeds the above range, the compatibility and dispersibility with polyethylene terephthalate will deteriorate, and the effect of improving the above-mentioned streaky surface defects will almost disappear.

The content of the polyorganosiloxane compound is 1 to 1100 Dp, preferably 2 to 20 pD relative to the polyester.
Must be within the range of m. If the content is less than lppm, the surface defects of the polyester film, which is the object of the present invention, cannot be completely eliminated. For example, longitudinal streak-like defects appear on the polyester melt sheet, and in severe cases, defects near the streaks may appear. Air/bubbles are trapped between the molten material and the cooling material surface, which not only makes it impossible to obtain a sheet with a uniform thickness and no surface defects, but also causes uneven stretching when the sheet is stretched, especially in the width direction.・Surface defects become noticeable. On the other hand, if it exceeds 1,100 pp, the melt tends to peel off from the surface of the cooling element, and not only will strong adhesion not be obtained, but the resulting film may develop crater-like defects, poor adhesion, deteriorated transparency, and Roughness and surface waviness become apparent.

In this way, simply containing a specific amount of a polyorganosiloxane compound does not make the polyester film surface completely defect-free, and the surface concentration of silicon atoms caused by the polyorganosiloxane compound has a specific distribution. Otherwise, the surface of the present invention cannot be made completely defect-free. The specific Si surface concentration distribution is the ratio r3 of the mass ratio r of silicon atoms S to carbon atoms C in the surface layer and the ratio r when 100 people enter from the surface. Ratio R=
rs/ro is 0.8 to 10, preferably 1°2 to 5.0
It must be within the range of

That is, it is essential that Si atoms exist at a relatively high concentration in the outermost layer of the film.

The concentration distribution of the Si atoms and C atoms in the film is determined by the 31MS method described above.

If the value of R is less than 0.8, not only the surface defect-free which is the objective of the present invention cannot be achieved, but also the thickness unevenness due to minute irregularities cannot be eliminated, and conversely, the value of R exceeds 10. This can cause crater-like defects on the film surface, poor adhesion, deterioration of transparency, surface waviness, and even
This is because fluidity unevenness occurs during melting.

Next, the method for manufacturing the polyester film of the present invention will be explained.

A polyester represented by polyethylene terephthalate, polyethylene naphthalate, etc. is obtained by a polycondensation reaction from a dicarboxylic acid component and a diol component by a conventional transesterification method (DMT method) or a direct polymerization method. In the case of the present invention, it is particularly effective for direct polymerization polyesters. In the case of the DMT method, the timing of addition of the polyorganosiloxane compound to be partitioned into the polyester is preferably before the transesterification reaction, but is not particularly limited to this, and may be added before the polymerization reaction or after the completion of the polymerization reaction. In general, it may be added at the time of charging into the extrusion chamber, but considering the amount added in the present invention, it is preferable to add it before polyester polymerization in order to uniformly contain a small amount added. Of course, it is clear that master pellets containing a high concentration of polyorganosiloxane may be diluted with virgin pellets that do not contain a high concentration of polyorganosiloxane. In addition, known additives to polyester, such as lubricants, antioxidants, pigments, dyes, nucleating agents, antiblocking agents, heat stabilizers, fillers, plasticizers, antistatic agents, ultraviolet absorbers, color inhibitors, etc. may be included.

In the case of the present invention, it is particularly preferred in the present invention that the polyester is subjected to a biaxial stretching process different from the conventional method, as described below, so that silicon atoms are selectively arranged on the surface layer of the polyester film.

That is, the polyester is sufficiently dried, the discharge pressure p during melt extrusion is increased to 110 to 250 kcJ/-, and the residence time of the polymer is increased to 20 to 60 minutes, so that hydrolysis and thermal decomposition reactions do not substantially proceed. Then, the molten polymer is discharged from the die, dropped onto an electrically insulated cast drum charged with static electricity, and cooled and solidified in the charged state to form a cast sheet of 1 q. . The sheet is stretched in the longitudinal direction at 85 to 130°C by 3 to 8 times in one or multiple stages, and then stretched in the width direction at 85 to 130°C.
It is stretched 3 to 6 times at 0 to 200°C and heat treated at 100 to 240°C.

If necessary, heat treatment may be performed again after stretching roughly in the longitudinal direction and/or width direction.

The silicon atoms contained in the polyether film thus obtained are selectively arranged on the surface layer.

In addition, the thickness of the polyester film is 0.5 to 125 μm.
Preferably, those having a diameter of about 3 to 80 μm are effective and often used.

[Applications] The thus obtained polyester film of the present invention can be used as a base film for magnetic recording or optical recording, where surface defects are a particular problem, or as a recording film for a capacitor, where minute unevenness in surface thickness is a problem, or It can be a film with particularly excellent properties as a base film for vapor deposition.

[Effects of the Invention] In this way, the concentration of polyorganosiloxane added to polyester is limited, and the concentration distribution in the cross-sectional direction of the film is specified, so that the surface of the resulting film has no craters, bubble marks, streaks, or Not only can a high-quality cast film with no surface defects such as waviness or scratches and small thickness unevenness be obtained, but also a uniform ultra-thin polyester film can be obtained that can be cast stably at high speed and has no surface defects.

In general, the polyester film of the present invention not only has excellent stretchability, but also has excellent slitting suitability and winding properties.

[Method for Measuring Characteristics, Method for Evaluating Effects] Methods for measuring and evaluating characteristic values of the present invention are as follows.

(1) The mass concentration distribution of carbon (silicon) atoms is determined by secondary ion mass spectrometry.
3p, electrometry, hereinafter SIMS>.

SIMS is a method in which an ion beam with an energy of about 5 to 15 Kev is applied to the surface of a sample, and secondary ions generated from the sample are subjected to mass spectrometry by sputtering. The device is A-DIDA300 manufactured by ATOMIKA, West Germany.
0, 02+ for the -order ion species, V for the -order ion acceleration voltage 12, -order ion current 200nA, raster region 4
00μ2, measurement vacuum level 1Xl 0-8Torrs E
-guno, measured under the conditions of 5KV-3A.

The silicon atom SL and the polyester constituent atoms (C) are measured in the depth direction. As the measurement depth, the depth of the crater in the sputtered portion after SIMS measurement is determined using a surface roughness meter (DEKTAK, manufactured by Sloan), and the value thereof is used. From the concentration distribution of each atom in the thickness direction q), S;
The ratio of St 2 /C is re-plotted in the depth direction of the film to determine the concentration distribution r of St 2 /C with respect to the film thickness.

(2) Surface roughness: Ra (μm) Measured value using a stylus type surface roughness meter, cutoff value C100, 25mm, measurement length 4nyn, however, J l
5-B-0601. ) Surface roughness μm > (C100, 25mm>:
0.10 or more , the static friction coefficient (μS) and the dynamic friction coefficient (μm) were measured.

Generally, the range in which a film is considered to have excellent slipperiness is 1.0 or less in μS and 0.8 or less in μm.

1.6 or more X 1.0 or more to less than 1.6 Δ 0.7 or more to less than 1.0 O Less than 0.7 ◎ (4) Depositing AI equivalent to 200 people on surface defect samples Then, the surface is observed in 20 fields of view using a stereomicroscope with a magnification of 60 times, and judgment is made based on the degree of surface scratches.

Classification ◎ No scratches at all 0 1 or 2 scratches △
〃 3 to 5 fields of view Depending on the time and severity, it is classified as follows.

Classification Thickness variation value (mμ) Coloring unevenness 0 Less than 100 None 0 Slightly visible〃 Δ Less than 500 Yes The surface wetting tension γCA of the film
and the surface wetting tension γ of the film before treatment. JIS
Measurements are made in accordance with K6768-1971, and adhesion is determined based on the following criteria.

Judgment T. A 1γ. −γ. A1◎ 3
8 or more, less than 1○ Same as above 1-3 △ 30 or more, less than 38 3 or more, less than 10X 30
Less than 10 or more [Examples] In order to clarify the effects of the present invention, comparative examples will be given and explained below.

Example 1 Colloidal silica SiO2 with an average particle size of 300 mμ was uniformly dispersed, and ethylene glycol from which coarse particles of 6 μm or more were removed was transesterified with dimethyl terephthalate using lithium acetate as a transesterification catalyst. Siloxane was mixed as a surface defect improving agent, the temperature was raised, and a transesterification reaction was carried out by removing methanol. Next, this reaction product contains phosphoric acid,
Add antimony trioxide together with triethyl phosphate, complete the polymerization according to a conventional method, and obtain an intrinsic viscosity [η]-〇, 6
Polyethylene terephthalate No. 5 was obtained.

After drying the polyethylene terephthalate under vacuum at 180'C for 2 hours, it was supplied to an extruder, melted at 285°C, and extruded from a T-die nozzle under the conditions of discharge pressure 1) = 150 kq/cnf and polymer residence time of 40 minutes. A casting drum that is electrically insulated and has a high voltage applied to it (
Front gas is used as the refrigerant) for close cooling. That is, the molten sheet was cooled to the glass transition temperature of polyethylene terephthalate, which is 70° C. or lower, while it remained charged.

The cast sheet thus obtained was heated to 125°C in the longitudinal direction.
Stretched roughly 1.8 times at 90°C in the same direction,
Next, after stretching 4 times in the width direction at 95°C, 3x stretching at 150°C.
Heat set for seconds, then roughly biaxially stretched 1.4 times in the longitudinal direction and 1.1 times in the width direction in a simultaneous biaxial stretching tenter.
Heat setting was performed at 185° C. for 2 seconds while relaxing 2% in both the longitudinal and width directions. The thickness thus obtained is 9
The film quality of polyethylene terephthalate in μm is shown in Table 1.

Table 1 In this way, by adding a specific polyorganosiloxane and forming a film under specific conditions, a film with no surface defects can be created.
It can be seen that the surface becomes a smooth and easily slippery film.

Comparative Example 1 The casting method used in Example 1 was changed, and an electrostatic charge was applied to the molten sheet discharged from the T-die die from a tungsten wire placed between the die and the casting drum to charge the molten sheet. Later, they were secretly assimilated onto a grounded casting drum (using water as a refrigerant). Roughly 1, the discharge pressure P and residence time were changed to the values shown in Table 2, but the other steps were carried out in exactly the same manner as in Example 1 to produce two-wheel stretched polyethylene terephthalate having the properties shown in Table 2. Got the film.

In this way, it can be seen that even if the composition is the same, the surface characteristics can vary widely depending on the film forming conditions.

[Comparative Example 2] A polyethylene terephthalate film with a thickness of 9 μm was obtained in the same manner as in Example 1 except that the content of methylphenylpolysiloxane in Example 1 was increased from 8 ppm to 300 ppm.

Thus, it can be seen that even if a large amount of polysiloxane is contained, not only the surface defects are not eliminated, but also the adhesiveness is significantly reduced.

Claims (1)

[Claims] In a polyester film containing 1 to 100 ppm of a polyorganosiloxane compound based on 100 parts by weight of polyester, the mass ratio r_s of silicon atoms to carbon atoms in the surface layer of the polyester film is the same as 100 Å from the surface layer of the film. Ratio R with ratio r_c = r_s/
A polyester film characterized in that r_c is in the range of 0.8 to 10.