JPH0535664B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a polyester melt extrusion molding method,
More specifically, the present invention relates to a molding method that does not have minute thickness unevenness. [Conventional technology] S45C, a polyester melt made mainly of iron,
A method of melt molding using a molding die using materials such as SKD11 and SUS420 is known. [Problems to be Solved by the Invention] However, when such a material is melt-molded, it is not so noticeable immediately after molding, but as it is molded, it becomes 0.5 μm or less in height and 0.1 to 0.1 μm in width along the width direction of the mouthpiece. It had the disadvantage that sawtooth-like minute thickness unevenness with a pitch of 5 mm occurred throughout the width direction. Although this is hardly a problem depending on the application, it becomes a major problem when used as a base film for high-density recording media such as high-end videos. The object of the present invention is to improve these problems and provide a method for melt molding polyester that does not have the above drawbacks. [Means for Solving the Problems] The present invention provides 5 to 500 ppm of at least one selected from polysiloxanes, fluorine-modified polymers, metal salts of higher fatty acids, and alkyl sulfate salts.
When melt-molding the polyester containing
At least the surface has a degree of corrosion when immersed in an ethylene glycol solution of an antimony compound.
The present invention relates to a method for melt-molding polyester, which is characterized in that the melt-molding is performed using a molding die with a concentration of 20 ppm or less. The polyester compound referred to in the present invention is a polymer compound having an ester bond in its molecular chain obtained by polycondensation of a dicarboxylic acid and a diol. Typical polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, phthalates, polyethylene α,β-bis(2-chlorophenoxy)ethane 4,4′ dicarboxylate, and their comonomers such as isophthalic acid, adipic acid, phthalic acid, sebacic acid, naphthalene dicarboxylic acid,
It also includes copolymers of diethylene glycol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol, propylene glycol, dihydrocycyclohexane, dihydroxynaphthalene, and derivatives thereof. Of course, the polyester may contain additives known as polymers, such as stabilizers, viscosity modifiers, antioxidants, fillers, slip agents, antistatic agents, antiblocking agents, and ultraviolet absorbers. Next, polysiloxane is a polymer having a siloxane bond, and representative examples thereof include polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, etc. In the case of the present invention, especially Polymethylphenylsiloxane is preferred. The viscosity is preferably 10 to 5000 centistokes. Examples of metal salts of higher fatty acids include metal salts of Groups 1 to 3 of the periodic table of higher fatty acids having 10 to 35 carbon atoms, and representative examples include calcium stearate, magnesium stearate, and palmitic acid. Calcium, zirconyl octylate,
sodium laurate, etc., and in the case of the present invention,
Particularly preferred is calcium stearate. Typical alkyl sulfate salts include sodium cetyl sulfate, sodium lauryl sulfate, triethanolamine lauryl sulfate, sodium lauryl sulfate, and oleyl sulfate. Fluorine-modified polymers are copolymerized with styrene, vinyl acetate, methyl methacrylate, methyl acrylate, acrylic acid, etc., and have groups containing 0.1 to 10 mol% of fluorine in the side chains or terminals of the polymer, so-called surface active polymers. A dosage form is preferred. Typical fluorine-modified polymers include poly(perfluoroalkyl acrylate), poly(perfluoroalkyl methacrylate), poly(2,2,2-trifluoroethyl methacrylate), poly(2,2,3,3 , 3-pentafluoropropyl methacrylate). Of course, polysiloxanes, fluorine-modified polymers, metal salts of higher fatty acids, alkyl sulfate salts, etc. may be used alone or in combination of two or more, and the total content is 5.
-500ppm, preferably in the range of 10-400ppm. This is because if the content is too large, crater-like surface defects will occur on the film surface, or partial flow will occur during melt extrusion of the polymer, resulting in uneven thickness. On the other hand, if the content is too small, the minute thickness unevenness, which is the object of the present invention, will not be eliminated. Further, in the case of adding polysiloxane, the effect of the present invention becomes more pronounced when the surface concentration of silicon atoms in the polyester has a specific distribution. That is, the mass ratio r of silicon atoms Si to carbon atoms C
The ratio R=r _S /r _C of the ratio r _S at the surface layer and the ratio r _C at a depth of 100 Å from the surface is preferably in the range of 0.8 to 10, more preferably 1.2 to 5.0. That is, it is preferable that Si atoms exist at a relatively high concentration in the outermost layer of the film. When the molding die of the present invention is immersed in an ethylene glycol solution of an antimony compound, the degree of corrosion, that is, the elution of iron ions must be 20 ppm or less, preferably 10 ppm or less. Corrosion degree
If it exceeds 20 ppm, even if the special polyester mentioned above is used, as iron ions are leached from the surface of the molding die, antimony metal reduced from the antimony compound will segregate on the die surface, resulting in , not only do large concave streaks of 0.5 μm or more occur, but also as the melt molding ages,
Microscopic thickness unevenness of 0.5 μm or less occurs over the entire width direction, and thickness unevenness with a large drop occurs, making it impossible to obtain a film with high thickness accuracy. In addition, the degree of corrosion
Even if a molding die of 20 ppm or less is used, unless the polyester used contains the optimum amount of the above-mentioned specific additives, a polyester sheet without minute thickness unevenness, which is the object of the present invention, cannot be obtained. . Suitable cap materials for the present invention include those selected from chrome plating, nickel plating, ceramic composite nickel plating, sputtering of ceramics such as titanium nitride, silicon carbide, and silicon dioxide, ion implantation, and combinations thereof. However, of course, it is not only possible to use a material with a coated surface layer, but also a material that is mainly made of iron and contains a large amount of chromium and nickel, and which has an elution amount of 20 ppm or less. In particular, in the case of plating or spatter method caps, two or three steps should be taken to prevent defects such as cracks, cracks, uneven plating, and uneven spatter on the coating surface.
It is best to perform multi-stage plating or sputtering. Further, the sharpness of the tip of the polymer discharge lip of the molding die is preferably 100 μmR or less, more preferably 30 μmR or less, and the sharpness distribution range in the width direction of the molding die is preferably 10 μmR or less, more preferably 5 μmR or less. It is. In addition, the hardness of the cap is preferably in the range of 28 to 45 degrees, more preferably 31 to 40 degrees, in terms of HRC hardness, taking into account polishability, workability, handleability, and the like. In addition, the surface roughness of the surface where the polymer flows
In the present invention, Rmax is preferably as smooth as 0.8 to 0.1 μm. The shape of the molding die is not particularly limited, but it can be applied to any shape such as a circular die, a T die, or an L die. 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 etc. to be contained in 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. Furthermore, it may be added at the time of charging into the extruder, 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, master pellets containing a high concentration of polyorganosiloxane or the like may be diluted with virgin pellets that do not contain a high concentration of polyorganosiloxane or the like. Furthermore, known additives to polyester, such as lubricants, antioxidants,
Pigments, dyes, nucleating agents, antiblocking agents, heat stabilizers, fillers, plasticizers, antistatic agents, ultraviolet absorbers, anticoloring agents, and the like may be contained. Next, the polyester is sufficiently dried, the discharge pressure P during melt extrusion is increased to 110 to 250 kg/cm ² , and the residence time of the polymer is increased to 20 to 60 minutes to substantially cause hydrolysis and thermal decomposition. It is preferable to carry out melt extrusion in a manner that prevents the reaction from proceeding, and then the molten polymer is discharged from a chrome-plated nozzle with a degree of corrosion of 20 ppm or less and falls onto, for example, an electrically insulated cast drum charged with static electricity. The sheets are brought into close contact with each other and cooled and solidified in a charged state to obtain a cast sheet. The sheet is longitudinally stretched 3 to 6 times in one or multiple stages at 85 to 130°C and heat treated at 100 to 240°C. If necessary, heat treatment may be performed after further stretching in the longitudinal direction and/or width direction. The thickness of the polyester film thus obtained is usually 0.5 to 125 μm, but in the present invention, it is particularly preferably 0.6 to 50 μm, and more preferably 0.6 to 50 μm.
It is highly effective for thin films of about 0.8 to 15 μm. [Effects of the Invention] According to the method according to the present invention, a polyester film having few minute thickness irregularities, large thickness irregularities in the width direction, and few surface defects such as concave streaks can be efficiently obtained. The polyester film thus obtained can be used as a base film for magnetic recording and optical recording, where surface defects are a particular problem, and as a recording film for capacitors, where minute unevenness in surface thickness is a problem.
Alternatively, it can be a film with particularly excellent properties as a base film for vapor deposition. [Measurement method] (1) Corrosion degree An ethylene glycol solution of an antimony compound is prepared by diluting antimony trioxide into ethylene glycol.
% by weight and completely dissolved in a glass container at 110°C. The conditions for immersing the test piece were as follows: A test piece with a specific surface area of 150 cm ² was completely immersed in a glass container containing an ethylene glycol solution of the above antimony compound at 25°C, a reflux condenser was attached, and the temperature was heated to 170°C. After 4 hours of treatment, the test piece is immediately removed to room temperature. Of course, in the case of a coated sample, the entire surface must be coated because it will be immersed in a liquid. On the other hand, if only the inside of the cap is coated, with the cap still assembled, line the cap slit with silicone resin that hardens at room temperature to prevent the liquid from flowing out, and then stand the cap with the slit at the bottom. Attach a reflux condenser to the place where the upper polymer enters, inject the ethylene glycol solution of the above antimony compound, make sure that the entire mouth surface is immersed in the liquid, and heat it to 170°C with a mouth heater.
Leave it for a while. Immediately thereafter, remove the silicone resin patch from the bottom surface and transfer the processing solution to another glass container.
The eluted iron ion sample is corrected to fit 150 m ² /. The amount of iron ions in the obtained treatment solution was determined as follows. (i) Operation Precisely weigh approximately 1 g of the sample into a beaker (100 ml), add 5 ml of sulfuric acid, and heat on a heater (approximately 300°C) to carbonize the sample. Gradually add nitric acid and heat to decompose. When the sample becomes colorless or transparent, heat and concentrate until just before drying. After cooling, add 10ml of hydrochloric acid and heat (approximately 200℃) to dissolve. After cooling to room temperature, transfer to a 25 ml volumetric flask with ion-exchanged distilled water and dilute to the marked line. A blank test was conducted in the same manner as above, and the resulting solution was sprayed into argon plasma, and inductively coupled radio frequency plasma generation spectroscopy was performed.
Iron (measurement wavelength is 259.94nm) is measured using Plasma Atomic Emission Spectrometry. Determine the amount of iron from the calibration curve created in advance. Calculate the iron content in the sample using the following formula. Iron (μg/g) = (S-Sb) x V/W S: Iron concentration (μg/ml) corresponding to the luminescence intensity of the sample solution prepared from the calibration curve Sb: Iron concentration (μg/ml) of the blank test solution determined from the calibration curve Iron concentration corresponding to luminescence intensity (μg/ml) V: Measurement liquid material (ml) W: Collection test amount (g) (ii) Calibration curve creation procedure Add iron standard stock solution (1.0mgFe/ml) to hydrochloric acid (1+4)
Prepare an iron standard solution in the range of 0 to 20 (μgFe/ml) by diluting it with The iron standard solution is measured in the same way as the sample, and the relationship between iron concentration and luminescence intensity is created. (iii) Apparatus A sequential ICP emission spectrometer SPS1100 manufactured by Seiko Electronics Industries was used. (2) The hardness of the cap is expressed as Rockwell hardness (HRC), which is based on the C scale according to JIS Z2245. (3) Surface roughness Rmax is determined from the cross-sectional curve according to JIS BO602-1976. (4) Thickness unevenness was measured using a K313A electronic micro thickness gauge manufactured by Anritsu Electric Co., Ltd. at a tensile speed of 30cm/
Measure a sample length of 5 m in minutes and calculate using the following formula. Thickness unevenness (%) = [(HL)/A] x 100 where H is the maximum thickness, L is the minimum thickness, and A is the average thickness. [Example] The present invention will be explained based on an example. Example 1 Polyethylene terephthalate was used as the polyester (intrinsic viscosity [η] in o-chlorophenol = 0.63 dl/g, antimony trioxide was used as the polymerization catalyst, and 50 ppm of 1000 centistoke methylphenyl polysiloxane was used as the additive. (containing 0.25% by weight of titanium oxide with an average particle size of 300 mμ) was supplied to an extruder in a conventional manner, and guided to a molding die with a width of 1500 mm while being metered with a gear pump. The material of the cap was SKD11, and its surface was plated with chrome in two stages to a thickness of 50 μm, and the corrosion degree of the plated material was 5. In addition, the surface roughness Rt of the plated surface is 0.2 μm, and the HRC hardness
40 degrees, the average curvature R of the lip at the tip of the cap is 20μm,
The distribution range is 5μm, which is uniform in the width direction. In this way, the molten polymer is introduced into the forming T-die die, and while an electrostatic charge is applied to the molten material, it is brought into close contact with the casting drum, cooled, and the thickness
A cast sheet of 150 μm was obtained. The cast sheet was stretched 4.5 times in the longitudinal direction at 98°C using a roll-type stretching machine, then 4 times stretched in the width direction at 95°C in a tenter, and then heat-treated at 185°C to form a biaxial sheet with a thickness of 7 μm. A stretched polyester film was obtained. When the thickness unevenness of the polyester film thus obtained was measured, it was found to be 5.
%, with a period of 0.1 to 1 mm, and a height of 0.5 μm
It was a uniform film with no convex minute unevenness in thickness (Table 1). Comparative Examples 1 to 3 Using the molding die used in Example 1, SKD11 itself before chrome plating, and one without the addition of methylphenylpolysiloxane added to polyethylene terephthalate, were used in Example 1.
A biaxially stretched polyester film was obtained in exactly the same manner as above. As shown in Table 1, minute thickness unevenness is eliminated by perfecting the conditions for both the raw material and the material of the die used to mold it, and when either one is missing, minute thickness unevenness becomes apparent. Examples 2 to 3, Comparative Example 4 A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1, except that only the amount of methylphenylpolysiloxane added in Example 1 was changed. As shown in Table 2, if the amount of polysiloxane added is small, minute thickness unevenness will not be resolved, and if the amount added is too large, a drift of the polymer will occur in the width direction, worsening the thickness unevenness, so the optimal It is necessary to add the amount of Example 4, Comparative Examples 5 to 6 Biaxially oriented polyester films were obtained in exactly the same manner as in Example 1, except that the material of the molding die used in Example 1 was changed and the die had a different degree of corrosion. (Table 3). Example 5 Instead of the polysiloxane used in Example 1,
A biaxially oriented polyester film was obtained in exactly the same manner as in Example 1 except that 200 ppm of calcium stearate was added, but as in Example 1, no minute thickness unevenness was observed. Comparative Example 7 Biaxially stretched polyester with a thickness of 7 μm was produced in the same manner as in Example 1, except that instead of the 2-stage chromium-plated base used in Example 1, a 1-stage chromium-plated base of 50 μm was used. A film was formed. Note that the corrosion degree of the one-stage chrome-plated cap used in this comparative example was 34. The film thus obtained was similarly evaluated for minute thickness unevenness and streak-like surface defects. According to this, it can be seen that even with a single-stage chrome-plated cap, a film without minute thickness unevenness or surface defects cannot be obtained unless the degree of corrosion is 20 ppm or less (Table 4).

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Claims (1)

[Claims] 1. When melt-molding a polyester containing 5 to 500 ppm of at least one selected from polysiloxane, fluorine-modified polymer, metal salts of higher fatty acids, and alkyl sulfate salts, at least the surface is formed in an ethylene glycol solution of an antimony compound. 1. A method for melt-molding polyester, which comprises melt-molding using a molding die that exhibits a degree of corrosion of 20 ppm or less when immersed in water.