JPH03273049A - Polyester composition and its preparation - Google Patents

Abstract

PURPOSE:To prepare a polyester compsn. which contains a colloidal silica with an improved dispersibility and has improved high-speed film-forming properties by adding a slurry comprising an alkali metal-contg. colloidal silica and a glycol to a transesterification product, removing the glycol from the reaction system, and conducting the polycondensation of the transesterification product. CONSTITUTION:In producing a polyester from an arom. dicarboxylate (e.g. dimethyl terephthalate) and a glycol (e.g. ethylene glycol), after the substantial completion of transesterification, a slurry comprising 1 pt.wt. colloidal silica contg. 0.5-1.0wt.% alkali metal (e.g. Na) and having a mean particle diameter of 50-1000mum and 5-20 pts.wt. glycol is added to the transesterification product. During or after the addition of the slurry, the glycol is removed from the reaction system while keeping the system at an atmospheric pressure; after the molar ratio of the glycol to the acid component reaches 1.5-3.0, the polycondensation is conducted at a reduced pressure, giving a polyester compsn. A film prepd. from the compsn. has a surface with a uniform unevenness and an improved slipperiness and is suitable for a magnetic medium.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a dispersion of colloidal silica useful for magnetic media films having uniform surface irregularities and improved slipperiness, particularly for magnetic media laminated composite films. The present invention relates to a polyester composition with improved properties and high-speed film forming properties, and a method for producing the same.

[Prior Art] Attempts have been proposed to improve the dispersibility of colloidal silica and to make film surface protrusions uniform (for example, Japanese Patent Laid-Open No.
9-171623, etc.).

Furthermore, in order to prevent a decrease in polymerizability and coloration of colloidal silica-containing polyester, an attempt has been made to add colloidal silica containing an alkali metal (JP-A-56-171623).

On the other hand, a method has been proposed to improve film forming productivity by lowering the specific resistance of polyester during melting (
For example, Japanese Patent Application Laid-Open No. 51-70269, etc.).

However, even with the above-described method, when used, for example, in a film, the flatness is insufficient or the slipperiness is unsatisfactory. Furthermore, film forming productivity is unfavorable.

[Problems to be Solved by the Invention] An object of the present invention is to provide a polyester composition with improved dispersibility even when polyester contains colloidal silica at a high concentration, and a method for producing the same.

Another object of the present invention is to provide a polyester composition that, when used as a film, can produce a biaxially stretched film with uniform film surface protrusions and improved running properties with good productivity, and a method for producing the same. be.

[Means to solve the problem] The object of the present invention is achieved by the following configuration.

(1) A polyester whose main repeating unit is an aromatic dicarboxylate, the polyester containing 0.05 to 1.0% by weight of an alkali metal with an average particle diameter of 50
A polyester composition containing 2.0 to 20% by weight of colloidal silica having a particle size of ~1000 mμ, and having a specific resistance when melted of less than 1.0×10 8 Ω·am.

(2) When producing polyester from aromatic dicarboxylic acid ester and glycol, after the transesterification reaction is substantially completed, 0.0% alkali metal is added to the reaction product.
Average particle diameter 50-1000 mμ containing 05-1.0% by weight
A slurry consisting of colloidal silica and 5 to 20 parts of glycol to 1 part of the colloidal silica is added, and during or after the addition of the slurry, the reaction system is maintained at atmospheric pressure and the glycol is removed from the reaction system. A method for producing a polyester composition, which comprises performing a polycondensation reaction under reduced pressure after the glycol and acid components reach a molar ratio of 1.5 to 3.0.

The polyester of the present invention may be a homopolymer such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, or ethylene terephthalate. A copolyester having ethylene-2,6-naphthalate as the main repeating unit may be used.

In the copolyester, the amount of other dicarboxylic acid components and glycol components, which are copolymerization components, is preferably 20 mol % or less.

Copolymerization components of this copolyester include aromatic dicarboxylic acids such as isophthalic acid and adipic acid, aliphatic dicarboxylic acids, oxycarboxylic acids such as oxybenzoic acid, ethylene glycol, propylene glycol, trimethylene glycol, pentyl glycol,
Examples include diol components such as 1,4-cyclohexane dimetatool.

The colloidal silica of the present invention means substantially spherical synthetic silica, and can be synthesized, for example, by a hydrolysis method using sodium silicate as a starting material or an alkoxysilicate as a starting material.

The melt specific resistance of the polyester composition of the present invention is 1.0X
It is necessary that it is less than 108 Ω·am. 1.0X
If it is less than 108 Ω·m, the adhesion with the casting drum is improved when forming a film from the polyester composition,
High-speed film formation becomes possible.

Particularly preferred is 0.8×10 8 Ω·cm.

The specific resistance of the polyester in the present invention when melted is measured as follows.

A pair of electrodes 6 are inserted into the polyester 5 to be measured using the melt resistivity measuring device shown in FIG. It is melted and stored, and a 3KV voltage is applied from the DC high voltage generator 1.

From the indicated values of the ammeter 2 and voltmeter 3 at this time, the electrode area, and the distance between the electrodes, the specific resistance is determined according to the following formula.

P: Melting specific resistance (Ω cm) V: Applied voltage (V) S: Area of electrode (cJ) I: Measuring current (A) D = Distance between electrodes (cm) The polyester composition of the present invention has an average particle size of Diameter 50~10
00 mμ, preferably 100 to 500 mμ, more preferably 150 to 500 mμ colloidal silica.

When the average particle diameter is less than 50 mμ, when used as a film, the height of surface protrusions is insufficient, and slipperiness is unfavorable. Furthermore, when colloidal silica is added at a high concentration as in the present invention, particles tend to aggregate together, causing dropout.

On the other hand, when the average particle diameter exceeds 1000 mμ, although the slipperiness improves, the average particle diameter is relatively several microns (for example, 2
A small amount of coarse particles (~lOμ) are present in the colloidal silica. These coarse particles clog filters used in the polyester manufacturing process and film formation. Furthermore, coarse particles cause dropout, which is undesirable.

The average particle diameter in the present invention means the equivalent spherical diameter of particles at a point of 50% by volume of all particles measured with a conventional centrifugal sedimentation type particle size distribution analyzer (for example, Horiba CAPA700).

The polyester composition of the present invention contains 2 colloidal silica.
．． It contains 0 to 20% by weight, preferably 5 to 15% by weight.

When the content of colloidal silica is less than 2.0% by weight,
The slipperiness when used as a laminated composite film is unfavorable.

Moreover, if it exceeds 20% by weight, when used as a film, the surface averageness will be impaired and the electromagnetic conversion characteristics will be deteriorated, which is not preferable.

Examples of the alkali metal contained in the colloidal silica of the present invention include lithium, sodium, potassium, etc. Among them, sodium is most preferred because it has a large effect of improving dispersibility in the polymer. Although the existence state of the alkali metal is not clear, it is thought that it is either inside the colloidal silica or bonded to its surface.

The content of alkali metal contained in the colloidal silica of the present invention is 0.05 to 1.0% by weight, more preferably 0.05 to 0.2% by weight.

If the alkali metal content is less than 0.05% by weight,
Colloidal silica aggregates and causes recording defects, ie, dropouts, when used as a film for magnetic media.

On the other hand, if the alkali metal content exceeds 1.0% by weight, the dispersibility of colloidal silica will not be further improved, and particles derived from the alkali metal will precipitate during the polyester production stage, which is preferable. do not have.

Furthermore, even if an alkali metal is added to the polycondensation reaction system for the purpose of improving dispersibility of colloidal silica containing an amount of alkali metal that is less than the range of the present invention, the effect of improving dispersibility will be insufficient. .

In addition, in the present invention, the amount of alkali metal contained in colloidal silica can be determined by separating the colloidal silica slurry by filtration, centrifugation, etc., or by dissolving the colloidal silica-containing polymer in a solvent such as orthochlorophenol, and then centrifuging the colloidal silica-containing polymer. Alternatively, after incinerating the polymer, the separated colloidal silica is dissolved in a solvent such as hydrofluoric acid, and the amount of alkali metal contained is determined by atomic absorption method.

The polyester composition of the present invention can also contain other inert particles in order to further improve slipperiness and prevent scratches on the film.

Examples of insoluble particles include TiO2, Al2O3,5
i02, ZnO, Mg0SCaCO3, CaSO4, B
a5Oa, tetrafluoroethylene, crosslinked polystyrene,
Examples include silicone, and two or more types can be used in combination.

Although there is no particular restriction on the content of these inert particles, it is preferably 1150 to 11500 of the colloidal force content.

Furthermore, in order to impart electrostatic properties to the film, for example, polyethylene glycol or an organic sulfonic acid metal salt can be contained.

The method for producing the polyester composition of the present invention will be explained.

The polyester in the present invention is produced from an aromatic dicarboxylic acid ester and a glycol. Examples include dimethyl phenoxy)ethane-4,4'-dicarphonate.

Glycol is the aforementioned glycol component, and ethylene glycol can be used most preferably.

Aromatic dicarboxylic acid ester and glycol are first transesterified. At this time, the transesterification reaction is usually carried out at 130 to 250°C in the presence of an alkali metal compound, an alkaline earth metal compound, or a manganese compound. After the transesterification reaction is completed, a phosphorus compound is added. The reaction product thus obtained is further subjected to a polycondensation reaction in the presence of a polycondensation reaction catalyst such as an antimony compound, a titanium compound, or a germanium compound to obtain a polyester.

In the present invention, the conditions when adding colloidal silica, the timing of addition, and the conditions within the reaction system when adding colloidal silica are such that after the transesterification reaction is substantially completed, 0.05% of the alkali metal is added to the reaction product. A slurry consisting of ~1.0% by weight of colloidal silica with an average particle diameter of 50 to 1000 mμ and 5 to 20 parts of ethylene glycol to 1 part of the colloidal silica is added, and during or after the addition of the slurry, a reaction is performed. The system is maintained at atmospheric pressure, ethylene glycol is removed from the reaction system, and after the molar ratio of ethylene glycol and acid component reaches a point of 1.5 to 3.0, the polycondensation reaction is carried out under reduced pressure. In two cases, the amount of ethylene glycol is 1 in colloidal silica.
If the amount is less than 5 parts, colloidal silica tends to aggregate.

On the other hand, if the amount of ethylene glycol exceeds 20 parts, not only will the dispersibility of colloidal silica not be further improved, but the addition of excess ethylene glycol will likely lower the softening point, and it will also be economical. It is also undesirable.

In addition, if the molar ratio at the start of pressure reduction is less than 1.5, colloidal silica will aggregate in the polycondensation reaction system, and the molar ratio will be less than 3.
．． If it exceeds 0, the liquid level of the reactant in the transesterification reactor will increase, and the colloidal silica attached to the reactor coil and reactor wall will tend to aggregate, which is not preferable.

As the transesterification catalyst, known alkali metal compounds, alkaline earth metals, and manganese compounds can be used, preferably magnesium, manganese, and alkali metal compounds. Specifically, manganese acetate, magnesium acetate, lithium acetate, potassium acetate, sodium acetate, magnesium propionate, manganese propionate, potassium propionate, magnesium chloride, lithium chloride, manganese bromide, magnesium hydroxide, manganese hydroxide, Mention may be made of lithium hydroxide, magnesium glycolate, lithium methylate, butyl potassium, and the like. Note that two or more of these may be used in combination.

Furthermore, as the phosphorus compound, at least one selected from phosphoric acid, phosphorous acid, and esters thereof can be used. Specific examples include phosphoric acid, monomethyl phosphate, dimethyl phosphate, trimethyl phosphate, tributyl phosphate, phosphorous acid, trimethyl phosphite, and tributyl phosphite.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

The parts in the examples are parts by weight, and the measurement methods for each characteristic are as follows.

(intrinsic viscosity) Measurement was performed at 25°C using 0-chlorophenol as a solvent.

(softening point) It was measured with a penetrometer and expressed as an SP ("C) value.

(Melting specific resistance) Using the melting specific resistance measuring device shown in FIG. 1, the specific resistance of the polyester was measured when the polymer was melted and stored at 280° C. in an N2 gas atmosphere and a 3 KV voltage was applied.

(Dispersion state of particles) The monodispersion state of colloidal silica was observed using a process electron microscope at a magnification of 10,000 times, and evaluated according to the following criteria.

Note that the monodisperse state here refers to how many of the total particles are dispersed in the form of primary particles, expressed as a percentage.
Level 1.2 was considered a passing grade.

Rank Monodisperse number state (%) 1st grade 95 or higher 2nd grade 81-94 3rd grade 51-80 4th grade Less than 51 (polymer filtration test) Dry polymer was melted at 290°C, opening 5μ, filtration area 19. The polymer was extruded by feeding it to a 6 cd sintered filter at a rate of 5 g/min using an extruder.

The pressure difference in the extruder at the time of starting supply and when 2 kg of polymer passed through was defined as ΔP, and evaluation was made according to the following criteria, and A%B was considered to be a pass.

Rank Filterability evaluation ΔP (kg/cJ) A
10 or less 8 11-20 C21-50 D 51 or more Example 1 90 parts of dimethyl terephthalate, 55 parts of ethylene glycol
part, magnesium acetate 0.04 part, antimony dioxide 0
．． 3. From 150°C to 230°C using 03 parts as a catalyst.
The temperature was gradually raised over a period of 5 hours, and methanol was distilled off to complete the ester conversion reaction.

After adding 0.02 parts of trimethyl phosphate to the reaction mixture, sodium was added to colloidal silica at 0.02 parts.
．． A slurry consisting of 10 parts of colloidal silica containing 2% by weight and having an average particle diameter of 300 mμ and 100 parts of ethylene glycol was continuously fed over a period of 30 minutes. During this time, the temperature of the reaction system was maintained between 220 and 230°C, and ethylene glycol was continuously distilled out. Furthermore, the reaction system was held at 23° C. for 10 minutes. The molar ratio of glycol to acid component was 1.85.

Next, the mixture was transferred to a polycondensation reactor, and a polycondensation reaction was carried out for 3.0 hours by a conventional method to obtain a polymer. The intrinsic viscosity of the polymer is 0.628, and the sp is 261. At 5°C, the fractional state of the particles was grade 1, the filterability evaluation was grade A, and the polyester had good colloidal silica dispersibility. Further, the specific resistance of the polyester when melted was 0.5×10 8 Ω.

Examples 2 to 4, Comparative Examples 1.2 A polyester was obtained in exactly the same manner as in Example 1, except that the amount of sodium metal contained in the colloidal silica was changed.

When the sodium content was less than the range of the present invention, the filterability of the dispersible polymer particles was poor (Comparative Example 1).

On the other hand, when the sodium content exceeded the range of the present invention, the filterability was poor (Comparative Example 2).

Example 5.6, Comparative Example 3.4 Polyester was obtained in exactly the same manner as in Example 1 except that the average particle diameter of colloidal silica was changed.

When the average particle diameter of colloidal silica was less than the range of the present invention, particle aggregation occurred and the filterability test was also poor (Comparative Example 3).

On the other hand, when the average particle diameter of colloidal silica exceeded the range of the present invention, the dispersion state of the particles was good, but the filterability was poor (Comparative Example 4).

Example 7.8, Comparative Example 5.6 Polyester was obtained in exactly the same manner as in Example 6, except that the amount of colloidal silica added was changed and the content of colloidal silica in the polyester was changed.

When the content was less than the range of the present invention, the dispersibility and transient properties were good, but the slipperiness was poor when formed into a film (Comparative Example 5).

On the other hand, when the content exceeds the range of the present invention, both the dispersibility and transient properties of the particles are unfavorable (Comparative Example 6).

Examples 9 to 13 In Example 1, the amount of ethylene glycol used in the colloidal silica slurry was changed to give the slurry concentrations shown in Table 1.

Furthermore, when removing ethylene glycol from the reaction system under atmospheric pressure during and after addition of the slurry, the molar ratio of glycol/acid component at the start of pressure reduction was changed by changing the removal amount.

Table 1 shows the conditions and polymer properties. In all cases, favorable results were obtained in terms of particle dispersibility and transient properties.

Example 14 To 90 parts of dimethyl 2.6-naphthalene dicarboxylate and 50 parts of ethylene glycol, 0.06 part of magnesium acetate and 0.01 part of antimony trioxide were added as a catalyst, and 17
The temperature was gradually raised from 0℃ to 240℃ over 3.5 hours.
Methanol was distilled off to complete the transesterification reaction. After adding 0.03 parts of trimethyl phosphate to the reaction product, sodium was added to the colloidal silica.
A slurry consisting of 10 parts of colloidal silica containing 0.15% by weight and having an average particle diameter of 450 mμ and 100 parts of ethylene glycol was continuously fed over a period of 20 minutes. During this time, the temperature of the reaction system was maintained between 220 and 230°C.
Ethylene glycol was removed continuously. Furthermore, the reaction system was held at 230°C for 10 minutes. The molar ratio of glycol to acid component after retention was 1.83.

Next, the mixture was subjected to polycondensation, followed by polycondensation for 2.5 hours using a conventional method to obtain a polymer. The ultimate temperature of the polymer is 0.
610, the softening point was 270.3, the specific melting resistance was 0.6, the particle dispersibility was first class, and the transient property was class A.

Comparative Example 7 The transesterification reaction was completed in the same manner as in Example 1, except that 0.03 part of zinc acetate was used as the transesterification catalyst instead of magnesium acetate. After adding 0.04 parts of trimethyl phosphate to the reaction mixture, a slurry consisting of 10 parts of colloidal silica with an average particle diameter of 300 mμ containing 0.2 parts by weight of sodium and 100 parts of ethylene glycol was prepared in the same manner as in Example 1. After addition, a polycondensation reaction was performed to obtain a polyester. The specific melt resistance of the polyester is 3゜5X108
It was Ω・Bi.

When forming the polyester into a film, a DC voltage of 10 KV was applied from an electrode installed on the top surface of the molten sheet, and the molten sheet was cooled by a caster tram, but the adhesion between the sheet and the caster tram was unfavorable, and the film A crater-shaped defect occurred.

[Effects of the Invention] The polyester composition of the present invention has excellent dispersibility even when it contains colloidal silica at a high concentration, so it is useful as a polyester for compounding.

Furthermore, since the polyester composition of the present invention has uniform particle dispersibility, it is extremely effective in forming surface protrusions in a composite film formed by extremely thinly laminating a polyester substantially free of particles.

Furthermore, since the polyester composition of the present invention has a low melting specific resistance, it has excellent high-speed film forming properties.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for measuring the specific resistance of polyester when it is melted. 1. DC high voltage generator 2, ammeter 3, voltmeter 4, heating element 5, polyester for measurement 6, electrode 7, container

Claims (3)

[Claims] (1) Add 0.05 to 1 alkali metal to a polyester whose main repeating unit is an aromatic dicarboxylate.
．． The polyester contains 2.0 to 20% by weight of colloidal silica with an average particle diameter of 50 to 1000 mμ, and the specific resistance when melted is 1.0 x 10^8 Ω・c.
A polyester composition characterized in that the polyester composition is less than m. (2) The polyester composition according to claim (1), wherein the alkali metal is Na. (3) When producing polyester from aromatic dicarboxylic acid ester and glycol, after the transesterification reaction is substantially completed, 0.0% alkali metal is added to the reaction product.
Average particle diameter 50-1000 mμ containing 05-1.0% by weight
A slurry consisting of colloidal silica and 5 to 20 parts of glycol to 1 part of the colloidal silica is added, and during or after the addition of the slurry, the reaction system is maintained at atmospheric pressure and the glycol is removed from the reaction system. A method for producing a polyester composition, which comprises performing a polycondensation reaction under reduced pressure after the glycol and acid components reach a molar ratio of 1.5 to 3.0.