JPS5843422B2 - polyester composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a biaxially oriented polyethylene terephthalate film for magnetic tapes having excellent slipperiness and surface condition.

Saturated linear polyester, represented by polyethylene terephthalate, has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, and chemical resistance, so it is used in film form in various fields such as magnetic tape, electrical parts, photography, and packaging. widely used in

When polyester is used in these forms, it is difficult to pass through the molding processes of melt extrusion, stretching, and heat treatment;
Also, the workability of winding, cutting, surface coating of magnetic layers, etc., and incorporation into electrical parts, and the slippage of film products.
From the value of the final product such as surface properties, we create a polyester composition containing fine particles, which facilitates film flow during film formation, and also gives the film surface an appropriate level of roughness to give it surface slipperiness. This is what is normally done.

Therefore, polyester compositions containing such fine particles include: ■ Polyesters containing insoluble, inert inorganic particles (external particles) such as titanium dioxide ■ Metal compound catalysts used in polyester synthesis, such as alkali metal compounds, alkali Polyesters containing particles formed inside the polymer during polyester production due to earth metal compounds, ie, internal particles, are known.

However, such known fine particle-containing polyester compositions have the following problems. In particular, when molded into a biaxially stretched film for magnetic tape, the static friction coefficient, surface roughness, roughness density, and manufacturing The film properties were not satisfactory.

In other words, in the external particle-containing polyester composition described in (2) above, it is difficult to make the additive particles finer, coarse particles are mixed together due to agglomeration of particles, and in addition to uneven particle diameter, there is a lack of affinity between the particles and the polyester. When molding the polyester composition, tears occur during film formation, and when it is made into a film for magnetic tape, fisheyes (microscopic imperfections in the shape of fish eyes) and dropouts (magnetic memory There are many drawbacks, such as problems such as omissions.

On the other hand, polyester obtained by the internal particle method (2) improves the above-mentioned disadvantage (2) to some extent, but still has the problem of polyester.

For example, Japanese Patent Publication No. 34-5144 describes the use of an alkaline earth metal compound as a transesterification catalyst to produce an alkaline earth metal salt of terephthalic acid which is insoluble in a polymer.

The alkaline earth metal compound used in this case is once dissolved in the polyester reaction system or a raw material for polyester synthesis such as glycol, and is immediately or gradually precipitated into the system depending on the state of the system to which it is added.

Therefore, the diameter of the particles obtained is relatively uniform and small, and the particles have a high affinity for the polyester substrate.

However, in the case of the internal particle generation method using the alkaline earth metal salt of terephthalic acid, when attempting to generate a relatively large amount of particles, coarse particles are generated, perhaps due to the strong cohesive force between the particles, especially in magnetic tape films. In this case, undesirable defects such as fish eyes and dropouts occur.

Furthermore, if the amount of catalytic metal compound added is increased to increase the number of particles, problems such as an increase in the amount of coarse particles mixed together due to agglomeration of particles, coloring of the polyester due to an increase in the rate of side reactions, a decrease in the melting point, and an increase in carboxyl terminal groups, etc. A problem occurs.

In the conventional internal particle method, when the thickness of the magnetic layer is made extremely thin to 5 μm or less in magnetic applications where a high degree of fineness of the surface irregularities of the film is required, the difference between the highest and lowest parts of the surface irregularities is 0. It is difficult to prevent coarse particles of 5μ or more from being mixed.

The present inventors have discovered the drawbacks of conventional polyester compositions containing fine particles for obtaining the above-mentioned biaxially stretched polyethylene terephthalate film for magnetic tapes, particularly the fact that a necessary and sufficient amount of particles could not be obtained with polyester compositions containing internal particles. In order to avoid the mixture of aggregated coarse particles and to improve the problem of non-uniform particle diameter, we conducted an investigation.

That is, magnetic tape films are used for audio, computers, and video.

The magnetic tape is used at high speeds in the magnetic tape manufacturing process, that is, the magnetic layer coating process or slitting process, and in the use of open reels, cassettes, etc., and requires extremely good slipperiness.

Furthermore, it is often used repeatedly, for example, over 1000 times, and the surface characteristics must remain unchanged even after repeated wear.

In addition, it is well known that large protrusions on magnetic tape films cause dropouts and a decrease in the S/N ratio during audio and video recording. Large protrusions that exceed the height should be avoided.

Usually, as an indicator of preferable surface characteristics for a magnetic tape film, a film has a static friction coefficient of 0.3 to 0.6 and a surface roughness of 0.1 to 0.5 μm.

If the coefficient of static friction of the polyester film exceeds 0.6, the high-speed running properties will be poor, especially if the film is 1/2 inch,
When slitting to a narrow width of 1/4 inch, curling occurs.

On the other hand, if the coefficient of static friction is less than 0.3, it is undesirable because it tends to slip when starting or stopping a cassette tape.

Furthermore, the presence of coarse protrusions with a roughness of more than 0.5 microns on the surface is undesirable because it causes dropouts of the magnetic tape film during recording and recording, and reduces the S/N ratio.

On the other hand, if the roughness of the surface is less than 0.1μ, the slip resistance is poor and the static friction coefficient cannot be satisfied.

Here, the present inventor proposed a polyester composition having 0.2 to 3.0% by weight of lithium element-containing internal particles in JP-A-48-61556.

The composition is useful for obtaining polyester films and fibers having excellent slipperiness, opacity, and surface condition, and has good yarn-forming properties and excellent productivity.

Furthermore, when a polyester film made of such a polyester composition is applied to a magnetic tape, the above-mentioned properties are well balanced, but the roughness and roughness density of the surface of the film need to be further improved. It was requested.

In other words, the polyethylene terephthalate film of the present invention has excellent sliding properties, does not cause loose winding especially when running at high speed, and has no fish eyes, so when applied to magnetic tape, it does not cause dropouts or image unevenness during playback. , it is possible to provide a biaxially stretched polyethylene terephthalate film for magnetic tape that does not cause skipping.

The object of the present invention is to add a calcium compound, a phosphorus compound, and a lithium compound to the polyester manufacturing process, and to add some or all of the lithium compound to a polyester so that the intrinsic viscosity does not exceed 0.2 after completion of the transesterification or esterification reaction. 0.03 to 5% by weight of lithium, 0.03 to 15% by weight of calcium and 0.03 to
The internal particles containing 10% by weight of phosphorus are 0.05-3.
The surface roughness of the film containing 0% by weight is 0.
This can be achieved by using a biaxially stretched polyethylene terephthalate film for magnetic tape that has a thickness of 3μ or less.

The various properties of the biaxially stretched polyethylene terephthalate film for magnetic tape of the present invention are even better than those of the above-mentioned preferred film for magnetic tape.

That is, it is a biaxially stretched polyethylene terephthalate film having a static friction coefficient of 0.3 to 0.6, a surface roughness of 0.3 microns or less, and a roughness density (protrusion density) of 35 peaks/frame or more.

The polyethylene terephthalate constituting the biaxially stretched polyethylene terephthalate film for magnetic tape in the present invention may be homopolyester or copolyester.

In the case of copolyester, the components to be copolymerized include, for example, diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, P-
Diol components such as xylylene glycol, 1,4-cyclohexane dimetatool, 5-sodium sulforesorcin, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 5-sodium sulfoisophthalic acid, etc. Examples include dicarboxylic acid components, polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid, and P-oxyethoxybenzoic acid.

In the case of copolymerization, from the viewpoint of molding a biaxially stretched film for magnetic tape, it is preferable that the amount of the copolymerized component is kept at about 20 mol % or less of the ethylene terephthalate component serving as the base material.

Ma1. -1 Of course, the basic polyethylene terephthalate may be mixed with other saturated linear polyesters, unsaturated polyesters, polyamides, polystyrene, polypropylene, polyethylene, etc. to an extent not exceeding 20% by weight.

In addition, within the range that satisfies the requirements of the present invention, the polyethylene terephthalate composition of the present invention may contain additives such as titanium oxide, talc, and kaolinite, and may also contain flame retardants, color inhibitors, antistatic agents, Various modifiers such as heat resistant agents and light resistant agents may be included.

The internal particles containing lithium, calcium, and phosphorus elements as used in the present invention are contained in a polyester composition forming a film or a film formed from the composition, and are specifically defined as follows, for example. refers to organic substances containing lithium, calcium, and phosphorus that are separated by a method that

(Internal particle separation method) Approximately 3002 of a polymer composition or film was collected, 2.7 kg of O-chlorophenol was added to it, the temperature was raised to 100°C while stirring, and after the temperature was raised, it was left as it was for another 1 hour. Dissolve the polymer part.

However, if the polymer part is not sufficiently dissolved under these conditions, such as when it is highly crystallized, the polymer composition can be melted and then rapidly cooled, and then the sample can be used for the melting process under the above-mentioned melting conditions.

Next, in order to remove insoluble matter other than internal particles such as dust contained in the polymer or reinforcing agent added, it is filtered using a liquid G-3 glass filter, and this weight is subtracted from the sample amount.

Hitachi Separation Ultracentrifuge 40p type rotor Rp3
After injecting the above solution 3QCC per cell, rotate the rotor at 4500 rpm, and after confirming that there is no rotation abnormality, evacuate the rotor and rotate the rotor at 3000 rpm.
The rotation speed is increased to 0 rpm, and particles are centrifuged at this rotation speed.

The separation is completed after approximately 40 minutes, and this is confirmed by the fact that the light transmittance at 375 mμ of the liquid after separation becomes a constant value that is higher than that before separation.

After separation, the supernatant is removed by decanting to obtain separated particles.

Since the separated particles may be contaminated with polymer components due to insufficient separation, O-chlorophenol at room temperature is added to the collected particles, and after homogeneous turbidity, centrifugation-like treatment is performed again.

This operation needs to be repeated until a melting peak corresponding to the polymer can no longer be detected by scanning differential calorimetry of the particles after drying the particles, which will be described later.

Finally, the separated particles obtained in this way were heated at 120°C and 16°C.
Vacuum dry for hr and weigh.

In the present invention, the amount of internal particles present in the polyester composition used for the biaxially stretched polyethylene terephthalate film for magnetic tape is 0.0% relative to the polyester composition.
It is necessary to make it 0.05 to 3.0% by weight, and 0.2 to 3.0% by weight.
% by weight is more preferred.

If the amount of internal particles is less than 0.05% by weight, the slipperiness during film molding is insufficient, sufficient film formability is not achieved, and operability in post-processing steps is not improved.

*On the other hand, if it exceeds 3.0% by weight, coarse particles will be mixed in, and sufficient film forming properties will not be achieved, and the resulting film will also have various defects due to the coarse particles mixed in. undesirable.

In addition, the internal particles are 0.03 to 5.0% by weight of lithium element.
, 0.03 to 15.0% by weight of calcium element and 0.03 to 10.0% by weight of phosphorus element (both relative to internal particles)
It is necessary to include the following.

By setting the contents of lithium element and calcium element in the internal particles within the above ranges, the roughness density can be reduced to 3.
It is possible to make the number of particles more than 5, and it is also possible to prevent agglomeration between particles.

In addition, when the phosphorus element in the internal particles is less than 0.03% by weight, the particles aggregate together to form coarse particles.

On the other hand, if the phosphorus element exceeds 10% by weight, the particles will be solubilized in the polyester and the slipperiness will decrease.

The internal particles contained in the polyethylene terephthalate film of the present invention are composed of the following two types of compositions produced by combining the metal element component, the phosphorus element component, and the components constituting polyethylene terephthalate added during the synthesis reaction of polyethylene terephthalate. It is considered to have.

(However, m and n represent integers of 1 to 4.

) The internal particles referred to in the present invention may contain trace amounts of other metal components, such as zinc, manganese, magnesium, cobalt, aluminum, antimony, germanium, titanium, etc., to the extent that they do not impede the effects of the present invention. Good too.

Here, as mentioned above, the roughness of the surface of the film for magnetic tape is set to be 0.1 to 0.5μ, but the polyethylene terephthalate film of the present invention has uniformly fine particles. The roughness of the convexes and convexities can be reduced to 0.1 to 0.3μ by using a magnetic tape, and the resulting magnetic tape has no dropouts during recording and recording, and has good slippage properties. .

The polyethylene terephthalate composition constituting the magnetic tape film of the present invention preferably has a solution haze value of 10 to 70%, particularly preferably 30 to 60%, as determined by the measurement method described below.

When the solution haze value is less than 10%, the number of particles that can substantially contribute to slipping properties is reduced, resulting in insufficient slipping properties.

. On the other hand, if the solution haze exceeds 70%, aggregation of particles occurs.

The calcium compound, phosphorus compound, and lithium compound used in the present invention are added to the polyester manufacturing process, and part or all of the lithium compound is added at a point when the intrinsic viscosity does not exceed 0.2 after the end of the transesterification or esterification reaction. Produced by performing a polycondensation reaction after addition,
Polyester compositions containing internal particles containing lithium, calcium, and phosphorus elements contain a large amount of uniform fine particles with a particle size of 1 μm or less, so simply melt extruding into a film does not have a significant effect, but it is difficult to manufacture. During the biaxial stretching process, fine irregularities are created on the film surface to prevent contact between the films or with equipment, improving slipperiness. Since there are no coarse particles in the product, there are fewer product defects, less than 50μ,
In particular, it is possible to obtain an extremely high quality biaxially stretched thin film for magnetic tapes mainly having a thickness of 12 μm or less.

Particularly, in the case of a biaxially stretched film (so-called reinforced film) in which the stretching is strengthened in the uniaxial direction, all of the above-mentioned improvements of the present invention work advantageously, resulting in an extremely excellent and highly marketable film.

The polyethylene terephthalate composition constituting the biaxially stretched polyethylene terephthalate film for magnetic tape of the present invention can be prepared by adding, for example, soluble lithium compounds, calcium compounds, and phosphorus compounds to the reaction system during the synthesis process of polyethylene terephthalate. obtained by doing.

Specifically, dimethyl terephthalate is transesterified with ethylene glycol to produce bis-β-hydroxyethyl terephthalate from the point at which the transesterification reaction is substantially completed, or terephthalic acid is esterified with ethylene glycol and directly transesterified into bis-β-hydroxyethyl terephthalate. - From the time when the esterification reaction to form β-hydroxyethyl terephthalate is substantially completed, a lithium compound, a calcium compound and a phosphorus compound are reacted separately or together, preferably as a glycol solution, during the polycondensation process in which the intrinsic viscosity does not exceed O12. It is best to add it to the reaction system in a mixed state under conditions that do not cause any reaction.

The lithium compound used in the present invention has an intrinsic viscosity of 0.00% from the time the esterification or transesterification reaction is completed.
It is essential to add a lithium compound or a calcium compound to no more than two times the polycondensation process, but a lithium compound or a calcium compound may be added as a transesterification catalyst at a stage before the transesterification reaction.

The amounts of the lithium compound, calcium compound, and phosphorus compound to be added may be such as to generate a predetermined amount of internal particles as defined in the present invention, but the lithium compound 'l'! 270.0 O5
Preferably, ~0.3% by weight of calcium compounds, ~0.5% by weight of calcium compounds and 0.01-0.5% by weight of phosphorus compounds are added.

In addition, in order to obtain the particle composition specified in the present invention,
It is preferable that the molar ratio of the lithium compound added is 1/10 to 10/1 as a lithium compound/calcium compound molar ratio.

If the amount of the phosphorus compound added is less than 0.01% by weight, the internal particles specified in the present invention cannot be obtained, and if it exceeds 0.5% by weight, the polymerization reaction will be delayed, the amount of diethylene glycol by-product will increase, and the internal particles formed Problems such as easy solubility of the particles in the system occur, which is not preferable.

The lithium compound to be added is preferably a compound soluble in the reaction system, such as lithium chloride, lithium iodide, or lithium acetate.

As the calcium compound, organic acid salt compounds such as calcium acetate and calcium oxalate are particularly preferred as they are soluble in the reaction system.

In addition, the phosphorus compound used in the production of polyester for films having excellent properties as in the present invention is
In particular, it is more preferable to use a phosphoric acid and an ester of a phosphoric acid in combination, from the viewpoints of suppressing the generation of coarse particles and making the resulting particles uniform and fine.

Specific examples of such combinations of phosphorus compounds include phosphoric acid and dimethylphenylphosphonate, phosphoric acid and dimethylbenzylphosphonate, phosphorous acid and trimethyl phosphate, phosphorous acid and triethyl phosphate, phosphorous acid and dimethylphenylphosphonate, and phosphorous acid and dimethylphenylphosphonate. Examples include phosphoric acid and dimethylbenzylphosphonate, methylphosphonic acid and trimethyl triphosphate, phenylphosphonic acid and trimethyl phosphate, and benzylphosphonic acid and triethyl phosphate.

In obtaining the polyethylene terephthalate composition constituting the biaxially stretched polyethylene terephthalate film for magnetic tape of the present invention, there is no problem in using conventionally known transesterification catalysts, esterification catalysts, and polymerization catalysts.

The polyethylene terephthalate composition of the present invention contains a relatively large number of uniform, fine internal particles of a specific composition, and unlike the prior art, 1) formation of coarse particles due to agglomeration of particles, 2) non-uniformity of particle size, ■ Fluctuations in the amount of particles produced and particle diameter due to changes in polymerization conditions; ■ Deterioration in heat resistance and electrical insulation of the polyethylene terephthalate composition caused by the dispersant added to prevent particles from aggregating, etc., do not occur.
A biaxially stretched polyethylene terephthalate film for magnetic tape, which is substantially free of these internal particles and retains both the excellent physical and chemical properties of polyethylene terephthalate, can be obtained.

In order to obtain a biaxially stretched film for magnetic tape from the polyethylene terephthalate composition, it is melt-extruded into a film, cooled and solidified, and then sequentially stretched vertically and horizontally, or simultaneously stretched vertically and horizontally. A known method such as the following can be used.

Alternatively, the orientation can be strengthened by increasing the stretching ratio in either the longitudinal or lateral directions, such as carrying out transverse stretching at a normal stretching ratio and then increasing the longitudinal stretching ratio, or stretching again in the longitudinal direction after carrying out normal longitudinal and lateral stretching. method etc. can also be used.

As already mentioned, the polyethylene terephthalate film for magnetic tape used in the present invention is 0.05 to 3% by weight.
Contains many uniform and fine internal particles, and contains 0.03 to 5% by weight of lithium, 0.03 to 5% by weight based on the particles.
Contains 15% by weight of calcium and 0.03 to 10% by weight of phosphorus, and has a surface roughness of 0.3
μ or less.

Therefore, it is possible to provide a biaxially stretched film for magnetic tape that has excellent slipperiness and surface properties, especially excellent roughness density, and exhibits the following excellent effects.

■ Film forming speed increases due to increased polymer deformation speed during stretching, ■ Uniformity of polymer deformation during stretching improves, and uniformity of physical properties such as thickness unevenness of film products improves, ■ During horizontal stretching The tension of polymer deformation in the film is reduced, which reduces the burden on the mechanical strength of the stretching machine, ■ The frictional force between the cut surface of the film and the cutting blade during narrow cutting is reduced, and the deformation of the cut edge is reduced; The rolled appearance of the product as a roll is uniform and hard, ■ The slipperiness of the film product is improved and it is easy to handle during subsequent reprocessing, ■ The surface roughness of the film product is small. , it is possible to reduce the roll diameter after winding up the same weight.

These effects are effects that can only be obtained insufficiently or not at all with conventional biaxially oriented polyester films, and can only be fully obtained with the polyester composition of the present invention.

To explain in more detail, in magnetic tape applications such as cassette cartridges, which is the object of the present invention, it is necessary to make the film as thin as 50 μm or less, especially 12 μm or less, so that the volume of the tape is as small as possible.
In addition, the tape must have high mechanical strength, be easy to slip, be easy to apply magnetic material, and have few coarse protrusions that can cause dropouts and a decrease in the S/N ratio. be.

So-called reinforced films with reinforced orientation to improve mechanical strength are suitable for the above purpose.

The polyethylene terephthalate containing internal particles containing lithium element, calcium element, and phosphorus element according to the present invention has sufficient slipperiness even when made into a reinforced film.

This is because, since it contains a large number of uniform fine particles, sufficient surface irregularities remain to facilitate smoothness even under stretching and strengthening conditions.

The film not only has excellent handling properties and high-speed running stability due to its good slipperiness, but also has a fine roughness on the film surface and a large number of protrusions, making it difficult to use as an adhesive layer. Coating a magnetic layer is also preferred.

The present invention will be explained in detail with reference to Examples below.

In the examples, parts are parts by weight, and quantitative analysis of lithium, calcium, and phosphorus elements in internal particles and measurement of each characteristic value were performed according to the following method.

(Elemental lithium) Sulfuric acid is added to the internal particle sample obtained by the above-mentioned separation method, the sample is wet-ashed, heated at 600° C. for 1 hour, dissolved in an aqueous hydrochloric acid solution, and quantified by atomic absorption method.

(Calcium element) After heating the internal sample particles at 100°C for 2 hours to incinerate,
Dissolve in hydrochloric acid solution and quantify by atomic absorption method.

(Elemental phosphorus) After the internal particle sample was wet-ashed in the presence of sulfuric acid and perchloric acid, it was colored with ammonium molybdate in an acidic sulfuric acid solution, the absorbance at 845 mμ was measured, and the absorbance was measured using a calibration curve prepared in advance. Quantitate.

(Solution haze) Add 5.41 ml of polyethylene terephthalate composition to 40 cc of a 4/6 mixed solvent of tetrachloroethane/phenol,
After stirring and dissolving at 02°C for 2 hours, the solution was collected into a 20 mm thick cell made of quartz glass, and the haze value was measured using an integrating sphere HTR meter SEP-H-2 model (manufactured by Nippon Seimitsu Kogaku). It is expressed as

(Friction coefficient of film) Measured using a slip tester according to ASTM-D-1894B method.

Note that the static friction coefficient was used as a measure of the slipperiness of the film.

(Roughness of the surface irregularities of the film) The difference between the highest and lowest parts of the surface irregularities obtained by observing the film surface with a microscopic light wave interferometer is expressed in μ.

(Density of unevenness on film surface (roughness density)) The number of peaks in a length of 1 mm is counted using the stylus method and expressed in units of peaks/mm.

Example 1 100 parts of dimethyl terephthalate, 7 parts of ethylene glycol
A transesterification reaction is carried out by a conventional method using 0.035 parts of manganese acetate as a catalyst, and the resulting product contains 0.04 parts of antimony dioxide, 0.15 parts of lithium acetate dissolved in ethylene glycol, and 0.09 parts of calcium acetate.
of phosphoric acid trimethyl ester followed by 0.1 parts of phosphoric acid trimethyl ester
After adding 0 parts and 0.02 parts of phosphorous acid, a polycondensation reaction was carried out, and the intrinsic viscosity was 0.615 and the softening point was 260.8°C.
, a polymer with a solution haze of 41% was obtained.

The polymer was pressed between cover glasses on a hot plate at 290°C, and when this sample was observed in the dark field using a polarizing microscope, many uniform particles with an average particle size of 0.5μ were observed. .

Also, the polymer is about 300'? When the particles in the polymer were separated using the method described in the text, the amount was 0.65% by weight based on the original polymer.

The separated particles were then subjected to scanning differential calorimetry to confirm that there was no contamination of polyethylene terephthalate using the method described in the text, and then carbon and hydrogen were analyzed using the conventional method, and lithium, calcium, and Quantitative analysis of each element of phosphorus was performed and the following results were obtained.

Further, the KBrBr normal external absorption spectrum was determined for this separated particle, and FIG. 1 was obtained.

(This is shown in Figure 2 of the KBrBr normal external absorption spectrum of low molecular weight polyethylene terephthalate with an average degree of polymerization of 4, which was prepared separately.

) Therefore, differential calorimetry has confirmed that there is no contamination of polyethylene terephthalate itself, and elemental analysis has detected C and H, and Figures 1 and 2 suggest the presence of ethylene terephthalate structural units. It is clear that the above-mentioned separated particles have a structure in which lithium, calcium, and phosphorus elements are bound in some form to the constituent unit of ethylene terephthalate.

Furthermore, when calculating the elemental abundance ratio of Li, Ca, and P from the results of elemental analysis, Li:Ca:P=0.243:0.035:0
．． 152, which means (-L i +Ca ): P=0.155: 1 in 0.152.

Therefore, it is considered that most of the elements lithium, calcium, and phosphorus exist in the separated particles in combinations of lithium and phosphorus, and calcium and phosphorus.

From these facts, it is presumed that the internal particles are mainly composed of two types of components having the structures (1) and (2) below, with the abundance ratio shown in (2) below, but this is not yet certain.

(However, m and n represent any integer from 1 to 4.

) ■, ■ Existence molar ratio I/n book 1/4 ・・・・・・
・・・・・・■ Next, using the above polyester composition, the stretching ratio was 3.3 times in the vertical direction, 3.4 times in the horizontal direction, and the heat treatment temperature was 215 times.
℃, heat treatment time 5 seconds, film forming speed 200m/
The film was formed in minutes.

As a result, there was no film tearing at all, and the obtained thickness was 1
The coefficient of static friction of the 2μ biaxially stretched film is 0.53, the roughness of the surface irregularities of the film is 0.18μ, and the density of the surface irregularities of the film is 38 pieces/mm, which provides satisfactory slipperiness for magnetic tape applications. It has a uniform and fine surface unevenness, with no defects of coarse protrusions of 0.5μ or more, and 0.3μ
It was found that there were no larger protrusions.

On the other hand, using the polymer, the stretching ratio was 3.0 times (vertical) and 3.0 times (horizontal).
．． After normal biaxial stretching of 2 times, longitudinal re-stretching of 1.8 times was carried out at 150° C. to obtain a strengthened film with a thickness of 10 μm.

The coefficient of static friction of the film is 0.58, the roughness of the unevenness on the film surface is 0.17μ, and the density of unevenness on the film surface is 35 pieces/mm, which provides satisfactory slipperiness and uniform fine surface unevenness for magnetic tape applications. It was found that there were no coarse protrusions of 0.3μ or more.

Comparative Example 1 After completion of the transesterification reaction, a polycondensation reaction was carried out in exactly the same manner as in Example 1, except that only 0.04 part of antimony trioxide and 0.15 part of lithium acetate were added, and the intrinsic viscosity was 0.
610, a softening point of 261.2° C. and a solution haze of 52%.

The amount of separated particles obtained from the polymer was 1.5% by weight, and the composition analysis results of the particles were C58.9%, H3.7%
, Li 2.8%.

A biaxially stretched film with a thickness of 12μ produced using the above polymer under the conditions of a stretching ratio of 3.3 times vertically and 3.4 times horizontally, a heat treatment temperature of 215°C, and a heat treatment time of 12 seconds had a static friction coefficient of 0.
．． 48. The roughness of the surface irregularities of the film was 0.35μ, indicating that coarse protrusions were present on the film surface.

Comparative Examples 2 to 5 Each polymer was produced in exactly the same manner as in Example 1, except that antimony trioxide and the compounds shown in Table 1 were added after the transesterification reaction was completed.

Table 1 shows the measurement results of the weight of the separated particles obtained from the polymer and the weight percent content of C, H, Li, Ca, and P elements in the separated particles (relative to the separated particles).

Also, the measured values of the softening point and solution haze of the obtained polymer,
Table 2 shows the characteristic values of the film obtained by the film forming method shown in Comparative Example 1.

The internal particles in the polymer obtained in Comparative Example 2 had well-balanced properties of the biaxially stretched film containing lithium and phosphorus, but the present invention was superior in terms of roughness and density.

Furthermore, in the polymer containing calcium-containing internal particles obtained in Comparative Example 3 in which only calcium acetate was added, the static friction coefficient of the film when made into a 12μ thick film was as high as 0.72, and the roughness of the surface irregularities was 0.72. 60μ, which was not preferable because the internal particles were coarsened in both cases.

The separated internal particles in the polymer obtained in Comparative Example 4 contained calcium and phosphorous elements, and the coarse particles observed in Comparative Example 3 were relatively few. The coefficient of static friction of the obtained film was 0.64, and the surface The roughness of the unevenness was 0.2μ, which was more preferable than Comparative Example 3.

However, when the film was formed at a stretching ratio of 3.3 times vertically and 3.4 times horizontally at a heat treatment temperature of 215°C and a heat treatment time of 5 seconds, and the film formation speed was increased, the film broke at a speed of 120 m/min. It was found that this occurred frequently and a good biaxially stretched film could not be obtained.

This is because some side reaction occurs during the polymerization reaction, increasing the amount of diethylene glycol generated, and the softening point of the polymer is 256.
This is because the temperature dropped to 4°C.

Furthermore, it is clear that the polymer obtained in Comparative Example 5 to which lithium acetate and calcium acetate were added but no phosphorus compound was added cannot prevent the generation of coarse particles, and the effects of the present invention cannot be exhibited.

Example 2 Same as Example 1 except that the transesterification reaction catalyst was changed to 0.08 part of calcium acetate, the lithium acetate added after the transesterification reaction was changed to 0.17 parts, and the calcium acetate was changed to 0.09 part. The polymer was produced using a method.

The intrinsic viscosity of the polymer is 0.620, and the softening point is 260.0°C.
, solution haze 41.5%, separated particle amount 0.75% by weight
, the particle composition is C49.8%, H4.0%, Li83%,
Ca was 2.8% and P was 4.3%.

In addition, the estimated compounds ■ and ■ described in Example 1 in the separated particles
It is estimated that the molar ratio of ■/■ is 7/6.

In addition, the film can be formed at a speed of 200 m/min without tearing, the coefficient of static friction of a 12μ thick film is 0155, the roughness of the surface unevenness of the film is 0.20μ, and the density of the surface unevenness is 52 pieces/home. It was found to have good uniformity and fineness.

In addition, the coefficient of static friction of a strengthened film with a thickness of 10μ obtained by the same method as in Example 1 was 0.59, the roughness of the film surface irregularities was 0.18μ, and the density of surface irregularities was 40 pieces/home, indicating good results. It had surface characteristics.

Example 3 The phosphorus compound used was dimethylphenylphosphonate) 0
．． Example 1 except that 15 parts and 0.02 parts of phosphoric acid were used.
A transesterification reaction and a polycondensation reaction were carried out in the same manner as above to obtain a polymer having an intrinsic viscosity of 0.611, a softening point of 261.0° C., and a solution haze of 45.2%.

The amount of separated particles obtained from the polymer was 0.70% by weight,
Its composition is C50.1%, ■4.2%, Li1.8%,
Ca was 13% and P was 4.5%.

Using this polymer, a good biaxially stretched film without tearing was obtained at a film forming rate of 200 ml/min.

The coefficient of static friction of the film was 0.58, the roughness of the surface irregularities of the film was 0.20 μm, and the density of the surface irregularities was 48 pieces/square.

In addition, the static friction coefficient of the 10μ strengthened film obtained under the same conditions as in Example 1 was 0.59, the roughness of the surface unevenness of the film was 0.18, and the density of the surface unevenness was 40 pieces/square. It has excellent slipperiness, and the surface condition is uniform and fine.
It was preferable as a film for magnetic tape.

Comparative Example 6 In Example 2, 0.17 parts of calcium acetate and 0.17 parts of lithium acetate were added together as transesterification reaction catalysts, and when the transesterification reaction was carried out by a conventional method, it became overheated from 175°C and caused bumping. caused.

In the present invention, it is not preferable to add a large amount of a lithium compound or a calcium compound before the transesterification reaction in terms of reaction control.

[Brief explanation of the drawing]

Figure 1 shows the infrared absorption spectrum of internal particles separated from the polyester composition of the present invention, and Figure 2 shows the average degree of polymerization of 4.
This is the infrared absorption spectrum of polyethylene terephthalate.

Claims (1)

[Claims] 1 Calcium compounds, phosphorus compounds, and lithium compounds are added to the polyester manufacturing process, and after adding = part or all of the lithium compounds at a point when the intrinsic viscosity does not exceed 0.2 after the completion of the transesterification or esterification reaction, Internal particles containing 0.03 to 5% by weight of lithium, 0.03 to 15% by weight of calcium, and 0.03 to 10% by weight of phosphorus, as defined in the text, produced by carrying out a condensation reaction are A biaxially oriented polyethylene terephthalate film for use in a magnetic tape, which contains .05 to 3.0% by weight and has a surface roughness of 0.3 μm or less.