JP5069434B2 - Polyester composition and method for producing the same - Google Patents

Description

  The present invention relates to a polyester composition and a method for producing the same, and more particularly to a polyester composition in which silica particles are uniformly dispersed and a method for producing the same.

  Polyesters typified by polyethylene terephthalate or polyethylene naphthalate have excellent physical and chemical properties, and are widely used for film applications such as magnetic tapes, electrical insulating materials, capacitors, photographic films or packaging materials.

  When such a polyester is used for a film or the like, inert particles are added for the purpose of imparting excellent winding properties to the obtained film. Among such inert particles, true spherical silica particles obtained by the alkoxide method or the water glass method have a very true spherical shape and a sharp particle size distribution, so that protrusions are uniformly formed on the film surface. It is easy to use suitably.

  By the way, the demand for films in recent years is becoming higher and higher, for example, higher surface flatness than before has been required. For this reason, there is an increasing need for using spherical particles having a smaller average particle diameter, specifically, silica particles having an average particle diameter of 0.5 μm or less.

  However, as described above, although it is a true spherical silica particle having excellent characteristics, as the particle diameter becomes smaller, the silica particles tend to aggregate with each other, and defects such as fish eyes frequently occur during film forming. There was a problem of coming. Therefore, it has been desired that the spherical silica particles having a smaller average particle diameter be uniformly dispersed in the polyester composition while suppressing aggregation.

  As a technique for suppressing aggregation of such inert particles such as silica particles, for example, hydrolyzable organometallic compounds are hydrolyzed in glycol using inert particles as ethylene glycol slurry, and further condensed fine particles are added. The method is Patent Document 1 (Japanese Patent Laid-Open No. 7-21668), and a method of kneading silica fine particles surface-treated with a silicon-containing organic substance having a hydrophilic functional group with a thermoplastic resin in a vent type twin-screw kneading extruder is patented. Patent Document 3 (Japanese Patent Laid-Open No. 2003-155351), which is proposed in Document 2 (Japanese Patent Laid-Open No. 11-216722), and a polyester resin powder passing through a JIS standard sieve of 16 mesh or more is added simultaneously with inorganic particles and kneaded. Etc.) have been proposed. However, even the methods proposed in these publications are insufficient for extremely small spherical silica particles having an average particle size of 0.5 μm or less, and a process for treating the inert particles separately is necessary. Therefore, there is also a problem that the production efficiency is inferior to the process of simply adding inert particles. Also, a method of performing high-temperature pressurization at a temperature of 150 to 260 ° C. and a pressure of 0.05 to 0.3 MPa between the addition of inert particles and the start of the polycondensation reaction is also disclosed in Patent Document 4 No. 2003-238671), but even with this method, the effect of suppressing aggregation is not sufficient for extremely small spherical silica particles having an average particle size of 0.5 μm or less, and further improvement is desired. It was rare.

Japanese Patent Laid-Open No. 7-21068 Japanese Patent Laid-Open No. 11-216722 JP 2003-155351 A JP 2003-238671 A

  An object of the present invention is to solve the problems of the prior art and to produce a polyester composition in which true spherical silica particles having a small average particle diameter are dispersed very uniformly with little aggregation, and a polyester composition capable of efficiently producing the same. It is to provide a method.

  As a result of intensive studies to solve the above problems, the present inventors have found that the dispersibility of silica particles is improved by adding silica particles and a specific phosphonate compound under specific conditions, and have reached the present invention. It is.

（式中、Ｒ^１およびＲ^２は、それぞれ炭素数２以上のアルキレン基であり、ｍおよびｎは整数で、ｍ＋ｎは３〜１０の範囲である。）
で示すホスホネート化合物が添加され、該ホスホネート化合物の含有量が、ポリエステル組成物の重量を基準として、リン元素量で１５〜７０ｐｐｍの範囲にあるポリエステル組成物によって達成される。 Thus, according to the present invention, the object of the present invention is to
Spherical silica particles have an average particle size of 0.5 μm or less, and the proportion of aggregated particles in which two or more primary particles aggregate is formed into a film based on the number of all silica particles (the aggregation rate is measured). When the polyester composition has ethylene-2,6-naphthalate units as the main repeating unit, the film is dried at 180 ° C. for 4 hours, then melted at 290 ° C., and rotated. The molten resin composition is extruded onto a casting drum to obtain an unstretched sheet material having a thickness of 350 μm, and this unstretched sheet is stretched at 150 ° C. in the biaxial stretching apparatus at the same magnification in the longitudinal direction and the width direction. When a film sample having a thickness of 25 μm is formed by simultaneous biaxial stretching and the polyester composition has ethylene terephthalate units as main repeating units, the composition is 1 After drying at 0 ° C. for 4 hours, the molten resin composition is made into a molten state at 280 ° C., and the molten resin composition is extruded onto a rotating casting drum to obtain an unstretched sheet having a thickness of 400 μm. In a biaxial stretching apparatus, the film is biaxially stretched at the same magnification in the longitudinal direction and the width direction at 110 ° C. at the same magnification to make a film having a thickness of 25 μm) at most 25%, based on the weight of the composition 0.01 to 3.0% by weight, and
The polyester resin has the following formula (I) as a main heat stabilizer.

(In the formula, R ¹ and R ² are each an alkylene group having 2 or more carbon atoms, m and n are integers, and m + n is in the range of 3 to 10.)
A phosphonate compound represented by the formula (1) is added, and the content of the phosphonate compound is achieved by a polyester composition having a phosphorus element content in the range of 15 to 70 ppm based on the weight of the polyester composition.

Furthermore, according to the present invention, another object of the present invention is:
When producing a polyester via an esterification reaction or a transesterification reaction and a polycondensation reaction using a terephthalic acid component or a 2,6-naphthalenedicarboxylic acid component and an ethylene glycol component,
(A) In the reaction system of the esterification reaction or transesterification reaction, spherical silica particles having an average particle diameter of 0.5 μm or less can be obtained before the temperature rises to 150 ° C. or higher and 215 ° C. It is added in the range of 0.01 to 3.0% by weight with respect to the polyester composition, and (B) from the addition of the silica particles to the start of the polycondensation reaction, the above formula (I) The phosphonate compound represented by the above formula is achieved by a method for producing a polyester composition in which the content of the phosphonate compound is added so that the amount of phosphorus element is in the range of 15 to 70 ppm based on the weight of the polyester composition.

  Furthermore, according to the present invention, as a preferred embodiment of the polyester composition of the present invention or a method for producing the same, the content of the phosphonate compound is in the range of 10 to 100 ppm in terms of phosphorus element based on the weight of the polyester composition. The silica particles are particles obtained by hydrolysis and polymerization using tetraalkoxysilane as a raw material, and the silica particles are particles added during the transesterification or esterification reaction of polyester. And at least one of those used for forming a film is also provided.

  According to the present invention, by using the phosphonate compound represented by the above formula (I) as a heat stabilizer, true spherical silica particles having an extremely small average particle diameter can be uniformly dispersed in the polyester composition, and the surface flatness is extremely high. Can be suitably used as a raw material for films and the like that are required.

  The polyester in the present invention is a polyester composed of a terephthalic acid component or a 2,6-naphthalenedicarboxylic acid component and an ethylene glycol component, and is not particularly limited as long as it has film-forming properties on a film or the like. Among such polyesters, polyesters in which 85 mol% or more of all repeating units are composed of ethylene terephthalate units or ethylene-2,6-naphthalate units are preferable from the viewpoint of mechanical properties. Of course, a copolymer obtained by copolymerizing the other third component within a range not impairing the effects of the present invention, for example, 15 mol% or less, preferably 10 mol% or less, with respect to all repeating units of the aromatic polyester. It may be. As the third component (copolymerization component), terephthalic acid (in the case of ethylene-2,6-naphthalate unit), 2,6-naphthalenedicarboxylic acid (in the case of ethylene terephthalate unit), 2,7-naphthalenedicarboxylic acid, isophthalate Aromatic dicarboxylic acids such as acids and phthalic acids, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, trimethylene glycol, diethylene glycol, tetra Examples include glycols such as methylene glycol and cyclohexanedimethanol, and these may be used alone or in combination of two or more. In addition, the polyester composition of the present invention contains other resins different from the ethylene terephthalate unit or ethylene-2,6-naphthalate unit in a range that does not impair the object of the present invention, for example, based on the weight of the polyester composition. It may be blended in the range of not more than wt%, preferably not more than 10 wt%.

The polyester composition of the present invention needs to contain true spherical silica particles having an average particle size of 0.5 μm or less. The true spherical shape in the present invention is, for example, by taking a photograph of each particle at a magnification according to the size of the silica particles used by a scanning electron microscope, using an image analysis processor Luzex 500 (manufactured by Japan Regulator Co., Ltd.), A particle whose volume spherical coefficient (f) is 0.4 to π / 6, which is obtained by calculating the maximum projection surface diameter (D) (μm) and the volume (V) (μm ³ ) of the particle and dividing V by D ³ Means.

  In addition, since the silica particles in the present invention are preferably particles having a spherical shape that easily forms protrusions having a relatively uniform protrusion height when formed into a film, the average value (Dl) of the major axis of the inert particles is determined. The value (Dl / DS) divided by the average value (DS) of the minor axis of the inert particles is preferably in the range of 1.0 to 1.2.

  As a method for producing such silica particles, a method obtained by hydrolysis / polycondensation of tetraalkoxysilane (alkoxide method) or a method of hydrolysis / polymerization hydrolysis / polycondensation using sodium silicate as a raw material. The silica particles produced by these methods are in the form of a slurry and have a high surface potential and stability against aggregation suppression. In particular, when silica particles are obtained by an alkoxide method, the dispersibility is extremely excellent.

  The effect of improving dispersibility in the present invention is easily manifested by silica particles having a smaller average particle diameter, and the average particle diameter of the silica particles needs to be 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0. .2 μm or less is preferable. The lower limit of the average particle diameter of the inert particles is not particularly limited, but is preferably 0.01 μm or more from the viewpoint of handleability.

  In the polyester composition of the present invention, spherical silica particles can be uniformly dispersed to a level that cannot be achieved with conventional phosphorus compounds by using a specific phosphorus compound. In order to express, the agglomeration rate of the spherical silica particles in the polymer described later needs to be 25% or less, more preferably 15% or less, and particularly preferably 10% or less. In addition, the aggregation rate of the spherical silica particles in the polymer in the present invention means the aggregation rate in a state where the film is once formed on a film under the conditions described later.

  In the present invention, the amount of silica particles contained in the polyester composition needs to be 0.01 to 3.0% by weight based on the weight of the obtained polyester resin composition. When the content of the silica particles is less than the lower limit, the effect of improving the winding property of the film during film formation is not sufficiently exhibited. On the other hand, when the content of the silica particles is more than the upper limit, aggregation of the silica particles is likely to occur. Become. The content of the silica particles is preferably 0.05 to 2.0% by weight and 0.1 to 1.2% by weight.

  Further, the inert particles used in the present invention are preferably those containing few coarse particles contained in the inert particles themselves, and an integrated volume of a particle diameter (D70) of an integrated volume of 70% integrated on a volume basis from the small particle diameter side. The value (D70 / D30) divided by the particle size (D30) of 30% is preferably in the range of 1.1 to 2.0, more preferably 1.2 to 1.5.

The polyester composition of the present invention needs to contain the phosphonate compound represented by the general formula (I) as a main heat stabilizer. R ¹ and R ² of the phosphonate compound represented by the general formula (1) are alkylene groups having 2 or more carbon atoms, and may be linear or branched. Specific examples of the alkylene group include alkylene groups having 2 to 18 carbon atoms, preferably 2 to 8 carbon atoms. Specifically, ethylene groups, propylene groups, butylene groups, isopropylene groups, t-butylene groups, sec- A butylene group can be exemplified. The cycloalkylene group is a cycloalkylene group having 3 to 18 carbon atoms, preferably 3 to 8 carbon atoms. Specific examples include a cyclobutylene group, a cyclopentylene group, and a cyclohexylene group. Can do. In the formula, R ¹ and R ² may be the same group or different groups.

  In the general formula (1), m and n are integers which may be the same or different from each other, and the range of m + n is 3 to 10. If it is less than 3, the acidity becomes strong and the effect of improving the dispersibility of the silica particles is poor. On the other hand, if it exceeds the upper limit, the thermal stability of the phosphonate compound itself becomes poor. A preferable range of m + n is 4 to 8, and a particularly preferable range is 4 to 7.

  The reason for improving the dispersibility of the silica particles obtained by using such a phosphonate compound as a heat stabilizer is not clear, but is considered as follows. First, in general, in order to uniformly disperse inert particles such as silica particles, it is advantageous to add to the polyester at an earlier stage, and at the stage of esterification reaction or transesterification reaction in the polyester production process. Is preferred. On the other hand, a phosphorus compound is usually added as a heat stabilizer in order to improve the thermal stability of the resulting polyester after completion of the esterification reaction or transesterification reaction. According to the study by the present inventors, when this phosphorus compound is added, aggregation of silica particles occurs, which is suppressed by the phosphonate compound represented by the above formula (I) mentioned in the present invention. It is thought that there is not.

  As specific examples of the phosphonate compound represented by the general formula (1), for example, compounds shown in the following Table 1 are preferably exemplified.

  In the present invention, the amount of the phosphonate compound of the general formula (I) to be contained in the polyester composition is not particularly limited, but is 10 to 100 ppm and 15 to 70 ppm in terms of the amount of phosphorus element based on the weight of the polyester composition. The range is preferable from the viewpoint of the effect of the present invention.

Next, another method for producing a polyester composition according to the present invention will be described.
The method for producing the polyester composition of the present invention is a melt polymerization method in which a low polymer obtained therefrom is subjected to a polycondensation reaction via a transesterification method or a direct esterification method. In addition, transesterification reaction catalyst, esterification reaction catalyst, etherification inhibitor, polycondensation catalyst used for polycondensation, antioxidant, light stabilizer, ultraviolet absorber, end-capping agent, etc. impair the effect of the present invention. As long as it is not present, those known per se can be preferably used. For example, compounds such as manganese, cobalt, zinc, titanium and calcium are used as transesterification catalysts, compounds such as manganese, cobalt, zinc, titanium and calcium are used as esterification catalysts, and amine compounds are used as anti-etherification agents. Etc. can be suitably exemplified. Examples of the polycondensation catalyst include compounds such as germanium, antimony, tin, titanium, and aluminum.

  One of the features of the production method of the present invention is an esterification reaction or a transesterification reaction in the range until the temperature of the reaction system rises to 215 ° C. It is to add so that it may become 01-3.0 weight%. By adding silica particles to the esterification reaction or transesterification reaction at a stage before the temperature of the reaction system reaches 215 ° C., the affinity between silica and polyester is improved, leading to an aggregation-inhibiting effect. After completion of the esterification reaction or transesterification reaction, the effect of improving the affinity between silica and polyester is not sufficiently exhibited. The lower limit of the temperature added to the reaction system is not particularly limited, but is preferably 150 ° C. or higher from the viewpoint of the effect of the present invention. On the other hand, when the temperature of the reaction system exceeds 215 ° C., aggregation of silica particles occurs when added. In addition, as a method for adding silica particles, it is preferable to add the silica particles in the state of an ethylene glycol solution because aggregation of silica particles is more easily suppressed. The concentration of the phosphonate compound in the ethylene glycol solution is not particularly limited, but is preferably as low as possible from the viewpoint of suppressing aggregation. However, when the concentration is excessively low, ethylene glycol is excessively added, and there is a problem that the amount of diethylene glycol in the polyester composition is increased, and it is added in the range of 1 to 30 wt%, and further 3 to 25 wt%. Is preferred. In addition, you may perform addition at once and may divide | segment into 2 times or more.

  Furthermore, another feature of the present invention is that the phosphonate compound represented by the formula (I) is added as a main thermal stabilizer between the addition of the silica particles and the start of the polycondensation reaction. is there. Conventional phosphoric acid and the like conventionally used as a heat stabilizer can improve the thermal stability of the polymer, but agglomeration of silica particles occurs. The addition amount of the phosphonate compound represented by the formula (I) is preferably adjusted so as to be the amount of the above-mentioned composition, for example, 8 to 80 mmol% based on the number of moles of all acid components, and further 10 to 10 It is preferable to add in the range of 60 mmol%.

  By the way, as the addition method of this phosphonate compound, since it is easy to suppress aggregation of a silica particle, adding in the state of an ethylene glycol solution is preferable. Although the concentration of the phosphonate compound in the ethylene glycol solution is not particularly specified, the concentration is preferably as low as possible from the viewpoint of suppressing aggregation. However, when the concentration is excessively low, ethylene glycol is excessively added, and there is a problem that the amount of diethylene glycol in the polyester composition is increased, and in the range of 0.5 to 30 wt%, further 1 to 20 wt%. It is preferable to add. In addition, you may perform addition at once and may divide | segment into 2 times or more.

  In this way, after adding the silica particles and the phosphonate compound, the polycondensation reaction is performed until the desired intrinsic viscosity is obtained, and if necessary, solid-state polymerization is performed to produce the polyester composition of the present invention. can do. In addition, the intrinsic viscosity of the obtained polyester composition is preferably 0.40 dl / g or more, more preferably in the range of 0.45 to 1.0 dl / g, from the viewpoint of strength and abrasion resistance when used as a film. It is preferable that

  As described above, if the production method of the present invention described above is used, the dispersibility of the silica particles in the polyester composition can be improved, and a uniformly dispersed polyester can be produced without any special treatment for the silica particles. can do.

  The present invention will be specifically described below with reference to examples. In addition, the characteristic of the polyester composition in this invention was measured and evaluated by the following method.

(1) Intrinsic viscosity (IV)
A polymer sample was dissolved in orthochlorophenol at a temperature of 35 ° C. and measured.

(2) Average particle diameter of silica particles, cumulative particle number (volume conversion) 70% and 30% particle diameter Accumulated particles from the cumulative particle size distribution measured using a laser scattering particle size distribution analyzer (SALD2000 manufactured by Shimadzu Corporation) The particle diameter of a number (volume conversion) 50% was taken as the average particle diameter. Similarly, the particle diameter (D70) of 70% and the particle diameter (D30) of 30% were also measured.

(3) Particle size ratio of silica particles For 100 particles of silica particles, the major axis and minor axis were measured with a scanning electron microscope (Hitachi S-3100 type), the average value of each was obtained, and the average major axis was averaged. The value divided by the minor axis was taken as the particle size ratio.

(4) Phosphorus content in polymer The polymer sample was heated and melted to prepare a circular disk, which was measured using a Rigaku fluorescent X-ray apparatus 3270 type and quantified.

(5) Aggregated particle ratio of silica particles in polymer A film sample is subjected to ion etching treatment on the film surface under the following conditions using a sputtering apparatus (1B-2 type ion coater apparatus) manufactured by Eiko Engineering Co., Ltd. The condition is that a sample is placed in a cylinder jar, the degree of vacuum is increased to a vacuum state of about 6.65 Pa (5 × 10 −2 Torr), and ion etching is performed at a voltage of 0.45 kV and a current of 5 mA for about 15 minutes. Furthermore, gold sputtering was performed on the film surface with the same apparatus. Then, using a scanning electron microscope (S-2150 manufactured by Hitachi), the total number of primary particles and the number of aggregated particles in the range of 2 × 10 ⁻³ mm ^{2 at} a measurement magnification of 5,000 to 20,000 times were counted, and the following Obtained from the equation. Here, the aggregate of two or more silica particles is an aggregated particle. When two primary particles are formed, the number of aggregated particles is two, and when the three primary particles are formed, the number of aggregated particles is Counted as three.
Aggregated particle ratio (%) = number of aggregated particles ÷ total number of primary particles × 100

  When the film sample is a polyester composition having ethylene-2,6-naphthalate units as the main repeating unit, the composition is dried at 180 ° C. for 4 hours, then melted at 290 ° C., and rotated. The molten resin composition is extruded onto a casting drum to obtain an unstretched sheet material having a thickness of 350 μm, and this unstretched sheet is stretched at 150 ° C. in the biaxial stretching apparatus at the same magnification in the longitudinal direction and the width direction. And a biaxially stretched film sample having a thickness of 25 μm. On the other hand, in the case of a polyester composition having ethylene terephthalate units as the main repeating unit, the composition is dried at 160 ° C. for 4 hours, then melted at 280 ° C., and the molten casting resin on the rotating casting drum. The composition was extruded to obtain an unstretched sheet material having a thickness of 400 μm, and this unstretched sheet was simultaneously biaxially stretched at the same magnification in the longitudinal direction and the width direction at 110 ° C. with a biaxial stretching apparatus to obtain a thickness. A film sample having a thickness of 25 μm was prepared.

[Example 1]
100 mol of dimethyl terephthalate (DMT), 200 mol of ethylene glycol (EG) and 0.03 mol of manganese acetate tetrahydrate were charged into a transesterification reactor, and the temperature was raised to 190 ° C. Subsequently, it added so that it might become 0.5 wt% on the basis of the weight of the polyester which can obtain the spherical silica particle with an average particle diameter of 0.1 micrometer obtained by the alkoxide method as a 10% ethylene glycol slurry. Thereafter, methanol was removed while raising the temperature to 240 ° C. to complete the transesterification reaction.

Subsequently, 0.02 mol of 10 wt% ethylene glycol solution of 0.02 mol of diantimony trioxide and dioxyethylene trioxyethylene hydroxymethylphosphonate (manufactured by CBW, trade name: Wofaplexx33, m + n = 5) is 0.04 mol in phosphorus amount. Added.
The obtained reaction product is transferred to a polymerization reaction tank, the pressure in the polycondensation reaction tank is slowly reduced while the temperature is raised, and finally polycondensation is performed under a polycondensation temperature of 290 ° C. and a vacuum of 50 Pa. It was. The polyester composition was taken out when the target stirring power was reached.
The properties of the obtained polyester composition are shown in Table 1.

[Example 2, Comparative Examples 1-2]
The same operation as in Example 1 was repeated except that the type of phosphorus compound (phosphonate compound), the amount of silica particles, and the addition temperature were changed as shown in Table 1. The properties of the obtained polyester composition are shown in Table 1.

[Example 3]
100 mol of dimethyl 2,6-naphthalenedicarboxylate (NDCM), 200 mol of ethylene glycol (EG) and 0.03 mol of manganese acetate tetrahydrate were charged into a transesterification reactor, and the temperature was raised to 190 ° C. Subsequently, it added so that it might become 0.3 wt% on the basis of the weight of the polyester which can obtain the spherical silica particle with an average particle diameter of 0.3 micrometer obtained by the alkoxide method as a 10% ethylene glycol slurry. Thereafter, methanol was removed while raising the temperature to 250 ° C. to complete the transesterification reaction.

Subsequently, 0.02 mol of 10 wt% ethylene glycol solution of 0.02 mol of diantimony trioxide and dioxyethylene trioxyethylene hydroxymethylphosphonate (manufactured by CBW, trade name: Wofaplexx33, m + n = 5) is 0.04 mol in phosphorus amount. Added.
The obtained reaction product is transferred to a polymerization reaction tank, the pressure in the polycondensation reaction tank is slowly reduced while raising the temperature, and finally polycondensation is performed under a polycondensation temperature of 300 ° C. and a vacuum of 50 Pa. It was. The polyester composition was taken out when the target stirring power was reached.
The properties of the obtained polyester composition are shown in Table 1.

[Examples 4-5, Comparative Examples 3-4]
The same operation as in Example 4 was repeated except that the amount of the phosphorus compound (phosphonate compound) and the type, amount and addition temperature of the silica particles were changed as shown in Table 1. The properties of the obtained polyester composition are shown in Table 1.

[Example 6]
100 mol of 2,6-naphthalenedimethyl ester (NDCM) and 200 mol of ethylene glycol (EG) were charged into a transesterification reactor and heated to 170 ° C. Next, 0.01 mol of titanium trimellitic acid was added and 1.0 wt% based on the weight of the polyester from which true silica particles having an average particle size of 0.05 μm obtained as an 10% ethylene glycol slurry by the alkoxide method were obtained. % Was added. Thereafter, the entire transesterification reaction tank was pressurized to 0.10 MPa, and the transesterification reaction was carried out at 230 ° C. After the internal temperature of the transesterification reaction tank reached 250 ° C., the pressure was released and a 10 wt% ethylene glycol solution of dioxyethylene trioxyethylene hydroxymethylphosphonate (manufactured by CBW, trade name: Wofaplexx33, m + n = 5) was 0 in phosphorus amount. .015 mole was added. The obtained reaction product is transferred to a polymerization reaction tank, the pressure in the polycondensation reaction tank is slowly reduced while raising the temperature, and finally polycondensation is performed under a polycondensation temperature of 300 ° C. and a vacuum of 50 Pa. It was. The polyester composition was taken out when the target stirring power was reached.
The properties of the obtained polyester composition are shown in Table 1.

Here, A in the column of the type of phosphonate compound in Table 2, A is dioxyethylene trioxyethylene hydroxymethyl phosphonate , B is oxyethylene tetraoxyethylene hydroxymethyl phosphonate , C is normal phosphoric acid, D is diethoxyphospho It means ethyl acetate.

  According to the present invention, it is possible to uniformly disperse silica particles having a small average particle diameter that easily cause aggregation in the polyester composition, and when used in a film, it is possible to obtain a film having extremely excellent surface flatness. For example, it can be suitably used for a base film of a magnetic recording medium.

Claims (5)

A polyester composition containing a spherical silica particle and a heat stabilizer in a polyester having ethylene terephthalate units or ethylene-2,6-naphthalate units as main repeating units,
True spherical silica particles have an average particle size of 0.5 μm or less, and the proportion of aggregated particles in which two or more primary particles are aggregated is at most 25% when formed into a film based on the number of all silica particles. 0.01 to 3.0% by weight based on the weight of the product, and
The polyester is added with a phosphonate compound represented by the following formula (I) as a main heat stabilizer, and the content of the phosphonate compound is in the range of 15 to 70 ppm in terms of phosphorus element based on the weight of the polyester composition. A polyester composition characterized by being.

(In the formula, R ¹ and R ² are each an alkylene group having 2 or more carbon atoms, m and n are integers, m + n is in the range of 3 to 10, and the film for measuring the aggregation rate is polyester. When the composition has ethylene-2,6-naphthalate units as the main repeating unit, the composition is dried at 180 ° C. for 4 hours, then melted at 290 ° C., and is melted on the rotating casting drum. The resin composition was extruded to obtain an unstretched sheet having a thickness of 350 μm, and this unstretched sheet was simultaneously biaxially stretched at the same magnification in the longitudinal direction and the width direction at 150 ° C. by a biaxial stretching apparatus, When the polyester composition has an ethylene terephthalate unit as a main repeating unit, the composition is dried at 160 ° C. for 4 hours, The molten resin composition was extruded on a rotating casting drum to obtain an unstretched sheet having a thickness of 400 μm, and this unstretched sheet was elongated at 110 ° C. with a biaxial stretching apparatus. respectively and widthwise simultaneously biaxially stretched at the same magnification, Ru der which thickness was 25μm film.)   The polyester composition according to claim 1, wherein the silica particles are particles obtained by hydrolysis and polycondensation using tetraalkoxysilane as a raw material.   The polyester composition according to claim 1, wherein the silica particles are particles added during a transesterification reaction or an esterification reaction of the polyester.   The polyester composition according to claim 1, which is used for forming a film. When producing a polyester via an esterification reaction or a transesterification reaction and a polycondensation reaction using a terephthalic acid component or a 2,6-naphthalenedicarboxylic acid component and an ethylene glycol component,
(A) In the reaction system of the esterification reaction or transesterification reaction, spherical silica particles having an average particle diameter of 0.5 μm or less can be obtained before the temperature rises to 150 ° C. or higher and 215 ° C. Addition in the range of 0.01 to 3.0% by weight to the polyester composition, and (B) from the addition of the silica particles to the start of the polycondensation reaction, the following formula (I) A method for producing a polyester composition comprising adding the phosphonate compound represented by the formula (1) such that the content of the phosphonate compound is in the range of 15 to 70 ppm in terms of phosphorus element, based on the weight of the polyester composition. .

(In the formula, R ¹ and R ² are each an alkylene group having 2 or more carbon atoms, m and n are integers, and m + n is in the range of 3 to 10.)