WO2017002852A1

WO2017002852A1 - Crystal polyester pellet, application thereof and production method therefor

Info

Publication number: WO2017002852A1
Application number: PCT/JP2016/069262
Authority: WO
Inventors: 豪坂野; 雅紀田中
Original assignee: 株式会社クラレ
Priority date: 2015-06-30
Filing date: 2016-06-29
Publication date: 2017-01-05
Also published as: TWI704166B; JP6689846B2; JPWO2017002852A1; TW201718700A

Abstract

This crystal polyester pellet comprises a resin composition containing polyester and a complex particle. The polyester contains 25-50% by mole of terephthalic acid units, 25-49.5% by mole of ethylene glycol units, 0.5-2.5% by mole of diethylene glycol units, and 1.5-25% by mole of other co-monomer units having 5 carbons or more. The intrinsic viscosity of the polyester is 0.75-1.5 dL/g. The crystal melting enthalpy of the pellet is 20 J/g or greater. The complex particle is a complex particle of hydrotalcite and titanium dioxide. The complex particle content of the pellet is 10-300 ppm. In this manner, a copolymer PET crystal pellet causing little environmental stress can be produced by a method having excellent productivity.

Description

Crystalline polyester pellets, their use and production method

The present invention relates to a crystalline polyester pellet comprising a resin composition containing a polyester containing terephthalic acid units and ethylene glycol units as main components and composite particles. Moreover, it is related with the use and its manufacturing method.

Polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as PET) are excellent in properties such as transparency, mechanical properties, gas barrier properties, and flavor barrier properties. Furthermore, polyester has less concern about residual monomers and harmful additives when formed into molded articles, and is excellent in hygiene and safety. Therefore, taking advantage of these characteristics, polyester is a hollow container for filling juice, soft drinks, seasonings, oils, cosmetics, detergents, beverage cans, etc. Widely used as a coating film for laminated steel plates. In recent years, it has been widely used as an optical film such as a protective film for a liquid crystal display.

Since the contamination of foreign substances in optical films is severely restricted, the film is often formed by removing foreign substances from the molten resin using a fine filter. Therefore, in the polyester resin used as the raw material for the optical film, if the content of unmelted foreign matter is large, it will cause clogging of the extrusion filter during melt molding. Therefore, a polyester resin pellet having a small size and a small amount of foreign matter is desired.

PET resin is industrially produced by the esterification or transesterification of terephthalic acid or dimethyl terephthalate with ethylene glycol, and then using bis (2-hydroxyethyl) terephthalate as a catalyst at high temperature under vacuum. Obtained by polycondensation. As a method for removing minute foreign matters during polymerization of such polyester, a method of filtering a high temperature oligomer with a heat resistant filter and a method of filtering a PET resin after polycondensation with a heat resistant filter are generally used.

However, when a fine filter such as that used in the production of an optical film is applied to the polymerization process, not only the polyester resin after polycondensation but also the oligomer in the polymerization is allowed to pass through. Since the pressure increase becomes intense, it is not practical to apply a filter with a small mesh size to the actual polymerization process.

One of the main factors of foreign particles contained in the polyester resin is a polymerization catalyst. Currently widely used catalysts have their own problems. When antimony oxide (Sb ₂ O ₃ ) is used, since the transparency of the resulting polyester resin is lowered, it is not suitable for applications requiring high transparency. When using an organic titanium catalyst such as titanium (IV) tetraisoproxide, the resulting polyester resin is colored yellow, and the inherent viscosity is lowered due to thermal decomposition during melt molding, and further the coloration proceeds. ing. In addition, when germanium dioxide (GeO ₂ ) is used, the carboxyl group content of the resulting polyester is increased, and a decrease in intrinsic viscosity when the resin is recovered and melt-formed again cannot be avoided, and the catalyst cost is greatly increased. To rise.

In the case where importance is attached to transparency, adhesiveness or moldability, a copolymerized PET resin containing a comonomer component is used. In the case of optical films that require a high degree of transparency, film laminated metal plates for cans that require adhesiveness and formability, and extrusion blow-molded containers that require transparency and formability, comonomer components can be used depending on the application. A PET resin in which is copolymerized is used (see, for example, Patent Documents 1 and 2). In any of these applications, a polyester resin having a high intrinsic viscosity is used in order to improve the strength of the molded product. Therefore, after polycondensation is performed in the liquid phase to obtain pellets, the pellets are solid-phase polymerized to produce crystalline polyester pellets with high intrinsic viscosity.

Generally, when the amorphous pellets after liquid phase polymerization are raised as they are to a temperature suitable for solid phase polymerization, the pellets are stuck together during solid phase polymerization. Therefore, usually, a preliminary crystallization step is performed in which crystallization is performed by heating at a relatively low temperature before solid phase polymerization. At this time, if it is unmodified PET, it can be sufficiently pre-crystallized in a short time, but in the case of copolymerized PET containing a certain amount of comonomer component or more, the crystallization speed is greatly reduced, and pre-crystallization The process took a long time. This not only reduced productivity, but also increased energy consumption.

Patent Document 3 reports a composite particle catalyst in which the surface of solid base particles is covered with titanium oxide as a polyester polymerization catalyst, and a high molecular weight polyester having excellent color and transparency by using it. Is supposed to be obtained. However, in that example, only liquid phase polymerization of unmodified PET is carried out.

JP-A-9-176296 JP-A-6-263893 JP 2006-188567 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide copolymerized PET crystal pellets having a low environmental load and uses thereof. Moreover, it aims at manufacturing such a pellet by the method excellent in productivity.

The above problem is a crystalline polyester pellet comprising a resin composition containing polyester and composite particles,
The polyester comprises 25 to 50 mol% terephthalic acid units, 25 to 49.5 mol% ethylene glycol units, 0.5 to 2.5 mol% diethylene glycol units, and other comonomer units having 5 or more carbon atoms. Containing 1.5 to 25 mol%,
The polyester has an intrinsic viscosity of 0.75 to 1.5 dL / g,
The crystal melting enthalpy of the pellet is 20 J / g or more,
This is solved by providing pellets characterized in that the composite particles are composite particles of hydrotalcite and titanium dioxide, and the content of the composite particles is 10 to 300 ppm.

At this time, when the pellet was dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 1 to 5 μm contained in 1 g of the pellet was 5.0 × 10. It is preferably ⁻¹⁴ m ³ / g or more. When the pellet was dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 5 to 20 μm contained in 1 g of the pellet was 1.2 × 10 ⁻¹² m. It is also preferable that it is ³ / g or less. It is also preferred that the polyester has a carboxyl group content of 18 μmol / g or less.

A preferred embodiment of the present invention is a film formed by molding the pellet. Another preferred embodiment of the present invention is a laminated metal plate in which a film formed by forming the pellet is laminated on a metal plate. Another preferred embodiment of the present invention is an extrusion blow molded container formed by molding the pellet.

The above problem is that terephthalic acid or its ester-forming derivative, ethylene glycol, and another comonomer having 5 or more carbon atoms are melt-polymerized in the presence of a catalyst composed of composite particles of hydrotalcite and titanium dioxide and then cut. This can also be solved by providing a method for producing the crystalline polyester pellets, characterized in that amorphous polyester pellets are produced, followed by solid-phase polymerization after pre-crystallization of the amorphous polyester pellets. At this time, it is preferable that at least terephthalic acid or an ester-forming derivative thereof and ethylene glycol are heated to advance an esterification reaction to obtain an oligomer, and then the catalyst is added to perform melt polymerization.

The crystalline polyester pellets of the present invention include copolymerized PET, but have a high crystallization speed during preliminary crystallization, excellent productivity, and a low environmental load. Since the pellet contains copolymerized PET having a high degree of polymerization and the content of foreign matter having a large particle size is small, it is excellent in strength, transparency, moldability, adhesiveness, etc., and suitable for various applications. Can be used. Moreover, since the density | concentration of a terminal carboxyl group can be made low, degradation of the resin at the time of collect | recovering the scraps of a molded article and melt-molding again can also be suppressed. Thus, it can be said that it is a crystalline polyester pellet with low environmental load because it is excellent in productivity and can suppress required energy and is also excellent in recyclability. In addition, according to the production method of the present invention, such crystal pellets can be pre-crystallized without imposing a heavy load on the environment and then solid phase polymerized to produce with good productivity.

Particle size distribution in pellets of Example 1 and Comparative Example 3 (20 μm or less) Particle size distribution in the pellets of Example 1 and Comparative Example 3 (enlarged by 5 to 20 μm)

The present invention relates to a crystalline polyester pellet made of a resin composition containing polyester and composite particles. When the composite particles are composite particles of hydrotalcite and titanium dioxide, the crystallization rate can be increased even if the polyester is a copolymer polyester having a lowered crystallinity. Thereby, since precrystallization can be performed in a short time prior to solid phase polymerization, a polyester having a high degree of polymerization can be obtained with high productivity.

The polyester contained in the crystal pellet of the present invention comprises 25 to 50 mol% of terephthalic acid units, 25 to 49.5 mol% of ethylene glycol units, 0.5 to 2.5 mol% of diethylene glycol units, and 5 carbon atoms. It contains 1.5 to 25 mol% of the above other comonomer units.

Since terephthalic acid units occupy more than half of dicarboxylic acid units and ethylene glycol units occupy more than half of diol units, polyethylene terephthalate units are the main constituents. By containing 1.5 to 25 mol% of another comonomer unit having 5 or more carbon atoms, the regularity of the polyethylene terephthalate crystal is lowered, so that the melting point is lowered and the crystallinity is also lowered.

The content of the terephthalic acid unit is 25 to 50 mol%, and if it is less than this, the melting point and the crystallinity are significantly lowered. The content of the terephthalic acid unit is preferably 30 mol% or more, and more preferably 35 mol% or more. The content of ethylene glycol units is 25 to 49.5 mol%, and if it is less than this, the melting point and crystallinity are remarkably lowered. The content of ethylene glycol units is preferably 30 mol% or more, and more preferably 35 mol% or more. The content of the diethylene glycol unit is 0.5 to 2.5 mol%, and usually, a unit by-produced by dimerization of ethylene glycol during the polycondensation reaction is contained in the polyester. The content of diethylene glycol units is preferably 2 mol% or less.

The polyester contained in the crystal pellet of the present invention contains 1.5 to 25 mol% of another comonomer unit having 5 or more carbon atoms. By containing 1.5 mol% or more of such other comonomer units, the crystallinity of polyethylene terephthalate can be reduced, and transparency, moldability, adhesiveness, and the like can be improved. The content of other comonomer units is more preferably 2 mol% or more, and even more preferably 2.5 mol% or more. On the other hand, when other comonomer units are contained in an amount of 25 mol% or more, the crystallinity and the melting point are too low, and the resulting molded product is liable to be stuck at the time of solid phase polymerization, and the heat resistance of the obtained molded product is lowered. The content of other comonomer units is more preferably 20 mol% or less, further preferably 15 mol% or less, and particularly preferably 10 mol% or less.

The polyester contained in the crystal pellet of the present invention contains a comonomer unit other than a terephthalic acid unit, an ethylene glycol unit, and a diethylene glycol unit. The comonomer unit has 5 or more carbon atoms. When the number of carbon atoms is less than 5, the boiling point is lowered and volatilizes during the condensation polymerization reaction, which may make it difficult to recover ethylene glycol. Moreover, crystallinity can be reduced effectively by having 5 or more carbon atoms. The carbon number of the dicarboxylic acid unit or diol unit is more preferably 8 or more. The upper limit of the carbon number is not particularly limited, but is usually 50 or less.

The method for producing the crystal pellet of the present invention is not particularly limited, but a catalyst comprising terephthalic acid or an ester-forming derivative thereof, ethylene glycol, and another comonomer having 5 or more carbon atoms, composed of composite particles of hydrotalcite and titanium dioxide. It is preferable to melt-polymerize in the presence of and then cut to produce amorphous polyester pellets, and then to pre-crystallize the amorphous polyester pellets before solid-phase polymerization.

As other comonomers having 5 or more carbon atoms, bifunctional compounds such as dicarboxylic acid and ester-forming derivatives thereof, diol, hydroxycarboxylic acid and ester-forming derivatives thereof are mainly used. At this time, a polyfunctional compound having three or more carboxyl groups, hydroxyl groups, or ester-forming groups thereof, or a monofunctional compound that is a monocarboxylic acid, a monoalcohol, or an ester-forming derivative thereof may be used in combination.

Dicarboxylic acids and ester-forming derivatives thereof include aliphatic dicarboxylic acids and ester-forming derivatives thereof such as glutaric acid, adipic acid, azelaic acid, sebacic acid and dimer acid (and hydrogenated products thereof); cyclohexanedicarboxylic acid and norbornene Alicyclic dicarboxylic acids such as dicarboxylic acid and tricyclodecane dicarboxylic acid and ester-forming derivatives thereof; isophthalic acid, phthalic acid, biphenyldicarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid, sulfoisophthalic acid Aromatic dicarboxylic acids such as sodium, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and ester-forming derivatives thereof.

Examples of the diol include aliphatic diols such as 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and methylpentanediol; alicyclic diols such as cyclohexanedimethanol, norbornene dimethanol, and tricyclodecane dimethanol. Etc. A diol in which one or more molecules of ethylene oxide are added to two hydroxyl groups of an aromatic diol can also be used. For example, a diol (bisphenol A ethylene oxide adduct) in which 1 to 8 molecules of ethylene oxide are added to two phenolic hydroxyl groups of bisphenol A can be exemplified.

Hydroxycarboxylic acid and its ester-forming derivatives include aliphatic hydroxycarboxylic acids such as 10-hydroxyoctadecanoic acid or ester-forming derivatives thereof; hydroxymethylcyclohexanecarboxylic acid, hydroxymethylnorbornenecarboxylic acid, hydroxymethyltricyclodecanecarboxylic acid Alicyclic hydroxycarboxylic acids such as acids or ester-forming derivatives thereof; hydroxybenzoic acid, hydroxytoluic acid, hydroxynaphthoic acid, 3- (hydroxyphenyl) propionic acid, hydroxyphenylacetic acid, 3-hydroxy-3-phenylpropion Aromatic hydroxycarboxylic acids such as acids and their ester-forming derivatives.

Examples of polyfunctional compounds having three or more carboxyl groups, hydroxyl groups or ester-forming groups thereof include trimellitic acid, pyromellitic acid, trimesic acid, cyclohexane-1,2,4-tricarboxylic acid, trimethylolpropane, pentaerythritol And triol components contained in bisphenol A ethylene oxide adducts, and ester-forming derivatives thereof. These can be added in a small amount to increase the melt tension and can be used to adjust the melt extrusion moldability. The content of the unit derived from the polyfunctional compound is preferably 1 mol% or less, and more preferably 0.5 mol% or less. If the ratio of the polyfunctional compound unit exceeds 1 mol%, gelation tends to occur, which is not preferable.

Examples of monofunctional compounds having only one carboxyl group, hydroxyl group or ester-forming group thereof include benzoic acid, 2,4,6-trimethoxybenzoic acid, 2-naphthoic acid, stearic acid and stearyl alcohol. . These function as sealing monomer units, seal molecular chain end groups in the polyester, and may be blended to prevent excessive crosslinking and gel formation in the polyester. The content of the unit derived from the monofunctional compound is preferably 1 mol% or less, and more preferably 0.5 mol% or less. When the ratio of the monofunctional compound unit exceeds 1 mol%, the polymerization rate in producing the polyester is slowed, and the productivity tends to be lowered.

In producing the crystal pellet of the present invention, first, terephthalic acid or an ester-forming derivative thereof and ethylene glycol are heated to advance an esterification reaction or a transesterification reaction to obtain an oligomer. At this time, another comonomer having 5 or more carbon atoms may be added in advance and an esterification reaction or transesterification reaction may be allowed to proceed simultaneously to obtain an oligomer, or another comonomer having 5 or more carbon atoms may be obtained after obtaining the oligomer. May be added to the melt polymerization reaction. The esterification reaction or transesterification reaction is preferably carried out at a temperature of 180 to 300 ° C. while distilling off the generated water or alcohol under an absolute pressure of about 5 kg / cm ² or less or under normal pressure. The ratio of raw materials in the esterification reaction or transesterification reaction is preferably such that the molar ratio (diol component / dicarboxylic acid component) is in the range of 1.1 to 2.5.

When the esterification reaction is carried out using terephthalic acid, a cocatalyst for improving the speed of the polycondensation reaction may be added, or the reaction can be carried out without a catalyst. Examples of the cocatalyst include zinc compounds, nickel compounds, and cobalt compounds. Examples of the zinc compound include fatty acid zinc salts such as zinc acetate, zinc carbonate, zinc chloride, zinc acetylacetonate salt, zinc phosphate, zinc phosphite and the like, and zinc acetate and zinc carbonate are particularly preferable. Examples of the cobalt compound include fatty acid cobalt salts such as cobalt acetate, cobalt carbonate, cobalt chloride, cobalt acetylacetonate salt, and the like, and cobalt acetate and cobalt carbonate are particularly preferable. Examples of the nickel compound include fatty acid nickel salts such as nickel acetate, nickel carbonate, nickel chloride, nickel acetylacetonate salt, and nickel acetate and nickel carbonate are particularly preferable. The amount of the cocatalyst used is preferably 0.001 to 0.02 parts by mass with respect to 100 parts by mass of the dicarboxylic acid component. When the amount of the cocatalyst is too small, the reaction rate is not sufficiently improved. On the other hand, when the amount of the cocatalyst is too large, the pressure increase speed of the filter used at the time of extrusion molding may be increased. The amount of the cocatalyst is more preferably 0.015 parts by mass or less.

On the other hand, when the transesterification reaction is performed using dimethyl terephthalate, one or more metal compounds such as calcium, manganese, magnesium, zinc, titanium, sodium and lithium are preferably used as the transesterification catalyst. However, in order to prevent unnecessary fine particles from remaining in the pellet, it is preferable to perform the esterification reaction without using a transesterification catalyst. In proceeding the esterification reaction, composite particles of hydrotalcite and titanium dioxide can be added in advance as a polymerization catalyst, but after the esterification reaction is completed, the polymerization catalyst is added and the subsequent melt polymerization reaction It is preferable to use it for increasing the precrystallization rate.

The melt polycondensation reaction following the esterification reaction or transesterification reaction is performed in the presence of a catalyst composed of composite particles of hydrotalcite and titanium dioxide. Here, it is important to use a catalyst composed of composite particles of hydrotalcite and titanium dioxide, and amorphous pellets having a high crystallization rate can be obtained by polymerization using the catalyst. The composite particles may have a structure in which titanium dioxide is introduced between the layers of hydrotalcite, or may have a structure in which the surface of the hydrotalcite particles is covered with titanium dioxide. It preferably comprises 50 to 95% by weight of hydrotalcite and 5 to 50% by weight of titanium dioxide. The particle size is not particularly limited, but is preferably fine particles having an average particle size of 1 μm or less, and more preferably fine particles having an average particle size of 0.4 μm or less. Hydrotalcite is a compound comprising magnesium and aluminum carbonate and hydroxide, typically having a chemical composition that _{_{_{_{Mg 6 Al 2 (CO 3)}}}} (OH) 16 · 4 (H 2 O). The amount of the catalyst used is preferably 0.001 to 0.03 parts by mass with respect to 100 parts by mass of the dicarboxylic acid component. When the amount of the catalyst used is too small, the polymerization reaction rate decreases. The amount of the catalyst used is more preferably 0.002 parts by mass or more, and further preferably 0.003 parts by mass or more. On the other hand, when the amount of the catalyst used is too large, the pressure increase rate of the filter used during extrusion molding increases. The amount of the catalyst used is more preferably 0.02 parts by mass or less, and further preferably 0.015 parts by mass or less.

In the melt polycondensation reaction, if necessary, an additive such as a coloring inhibitor or an antioxidant is added to obtain a polyester having a desired viscosity at a temperature of 200 to 300 ° C. under a reduced pressure of 1 kPa or less. It is preferable to carry out until it is done. The melt polycondensation reaction can be performed using, for example, a tank-type batch polycondensation apparatus or a continuous polycondensation apparatus including a biaxial rotating horizontal reactor. In addition, when using an anti-coloring agent in the melt polycondensation reaction, for example, phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, triphenyl Phosphorus compounds such as phosphate can be used. These phosphorus compounds may be used alone or in combination of two or more. When using an anti-coloring agent comprising the above-described phosphorus compound, it is preferably in the range of 0.001 to 0.5 mass% based on the mass of the dicarboxylic acid component. When adding a promoter such as a zinc compound, a nickel compound, or a cobalt compound, it is preferable to use the phosphorus compound in combination from the viewpoint of preventing coloring. At this time, the phosphorus compound is preferably added at the time of the esterification reaction. By doing so, it is possible to suppress a decrease in the polymerization rate due to the addition of the phosphorus compound and obtain pellets with good color tone.

Depending on the application, antioxidants, UV absorbers, light stabilizers, antistatic agents, antiblocking agents, lubricants (fatty acid amides, etc.), flame retardants, inorganic or organic fillers, crosslinking agents, dyes, Colorants such as pigments and additives such as modifying resins may be blended. Such an additive may be mixed with the raw material slurry, may be added during the esterification reaction, or may be added during the polycondensation.

The intrinsic viscosity of the polyester obtained by melt polycondensation is preferably in the range of 0.4 to 0.85 dL / g from the viewpoint of handleability. When the intrinsic viscosity of the polyester obtained by melt polycondensation is less than 0.4 dL / g, when the polyester is taken out from the reactor, the melt viscosity is too low and it becomes difficult to extrude in the form of a strand or a sheet, Moreover, it becomes difficult to cut into pellets uniformly. Furthermore, when solid-phase polymerization is performed, it takes a long time to increase the molecular weight, resulting in a decrease in productivity. The intrinsic viscosity is more preferably 0.5 dL / g or more, and still more preferably 0.6 dL / g or more. On the other hand, if the intrinsic viscosity of the polyester is higher than 0.85 dL / g, the melt viscosity is too high, so that it is difficult to take out the polyester from the reactor, and coloration due to thermal deterioration tends to occur. The intrinsic viscosity is more preferably 0.8 dL / g or less, and still more preferably 0.75 dL / g or less.

The polyester obtained by melt polymerization as described above is extruded into a strand shape, a sheet shape, and the like, cooled, and then cut with a strand cutter or a sheet cutter to obtain a cylindrical shape, an elliptical column shape, a disk shape, a die shape. Amorphous pellets of the shape such as are manufactured. The above-described cooling after extrusion can be performed by, for example, a water cooling method using a water tank, a method using a cooling drum, an air cooling method, or the like.

The amorphous pellets thus obtained are preferably heated in a temperature range of 100 to 160 ° C. and preliminarily crystallized before being subjected to solid phase polymerization. If it is not pre-crystallized, the pellets will easily stick together during solid phase polymerization. In the case of precrystallization, unmodified PET can be sufficiently crystallized in a short time, but in the case of copolymerized PET containing a certain amount of comonomer components, the crystallization speed is greatly reduced and precrystallization is performed. The problem was that the process took a long time. The present inventors have found that the crystallization rate can be greatly improved by producing amorphous pellets using a catalyst comprising composite particles of hydrotalcite and titanium dioxide. Thereby, the solid phase polymerization time can be shortened, and not only productivity is improved, but also energy consumption can be reduced. As a precrystallization method, crystallization may be performed in a vacuum tumbler, or crystallization may be performed by heating in an air circulation type heating apparatus. The time required for the precrystallization is not particularly limited, but is usually about 30 minutes to 24 hours. Prior to precrystallization, the pellets may be dried at a temperature below 100 ° C.

The amorphous pellets used for the precrystallization may be a blend of two or more kinds of polyesters. For example, amorphous pellets obtained by melt-kneading two or more kinds of polyester pellets obtained by melt polymerization can be subjected to preliminary crystallization. In this case, what is necessary is just to satisfy the ratio of the monomer unit contained, a polymerization degree, etc. as the whole amorphous pellet obtained by blending. In addition, the pellets obtained by pre-crystallizing the amorphous pellets and solid-phase polymerization may satisfy the conditions defined by the present invention as a whole.

The solid-state polymerization of the pre-crystallized pellet is preferably performed under reduced pressure or in an inert gas such as nitrogen gas. Further, it is preferable to carry out solid phase polymerization while moving the pellets by an appropriate method such as a rolling method or a gas fluidized bed method so that no sticking occurs between the pellets of the polyester resin composition. Among these, it is preferable to perform solid-state polymerization under reduced pressure. The pressure when solid-state polymerization is performed under reduced pressure is preferably 10 kPa or less, and more preferably 1 kPa or less.

The solid phase polymerization temperature is preferably 170 to 230 ° C. When the solid-phase polymerization temperature is less than 170 ° C., the solid-phase polymerization time becomes long and the productivity may be lowered. The solid state polymerization temperature is more preferably 180 ° C. or higher. On the other hand, when the solid phase polymerization temperature exceeds 230 ° C., the pellets may be stuck. The solid state polymerization temperature is more preferably 220 ° C. or lower, and further preferably 210 ° C. or lower. The solid phase polymerization time is usually about 5 to 70 hours.

The intrinsic viscosity of the polyester after solid phase polymerization is 0.75 to 1.5 dL / g. When the intrinsic viscosity is less than 0.75 dL / g, the strength, impact resistance and transparency of the obtained molded product are lowered. The intrinsic viscosity is more preferably 0.8 dL / g or more, and even more preferably 0.85 dL / g or more. On the other hand, when the intrinsic viscosity exceeds 1.5 dL / g, the melt viscosity becomes too high, the melt moldability is lowered, and the productivity is also lowered. The intrinsic viscosity is more preferably 1.4 dL / g or less, and even more preferably 1.3 dL / g or less. The intrinsic viscosity of the polyester after the solid phase polymerization is preferably 1.15 times or more, more preferably 1.2 times or more, more preferably 1.25 times or more of the intrinsic viscosity of the polyester before melt kneading. More preferably.

The carboxyl group content of the polyester after the solid phase polymerization is preferably 18 μmol / g or less. In general, it is widely practiced to produce molded products by blending scrap crushed material collected in the factory, such as pinch-off parts generated during extrusion blow molding and ear parts generated during film extrusion, into crystal pellets. It has been broken. Here, it is known that when the content of the carboxyl group at the end of the polyester increases, the degree of polymerization decreases when the molded product is remelted and recycled. Therefore, when using a polyester having a low carboxyl group content, it is possible to suppress a decrease in the degree of polymerization during remelting and facilitate recycling. Thus, it is possible to realize a manufacturing process with little waste and a low environmental load. The carboxyl group content is more preferably 15 μmol / g or less.

The crystal melting enthalpy of the polyester contained in the crystal pellet of the present invention is 20 J / g or more. Since the crystal pellets obtained by solid-phase polymerization contain polyester that has been crystallized at high temperature for a long time, it has a larger crystal melting enthalpy than the polyester contained in the pellet after precrystallization. ing. The polyester contained in the pellets of the present invention has a large crystal melting enthalpy despite the fact that it contains a certain amount or more of another comonomer unit having 5 or more carbon atoms and thus the crystallinity is lowered. The crystal melting enthalpy is preferably 25 J / g or more, and more preferably 30 J / g or more. The crystal melting enthalpy is usually 50 J / g or less.

The melting point of the polyester contained in the crystal pellet of the present invention is preferably 190 to 250 ° C. Decreasing the melting point can improve transparency, moldability, adhesion and the like. The melting point is more preferably 245 ° C. or less, and further preferably 240 ° C. or less. On the other hand, when the melting point is less than 190 ° C., the crystallinity and the melting point become too low, and it becomes easy to stick at the time of solid phase polymerization, and the heat resistance of the obtained molded product is lowered. The melting point is more preferably 200 ° C. or higher, and even more preferably 205 ° C. or higher.

The content of the composite particles of hydrotalcite and titanium dioxide contained in the pellet of the present invention is 10 to 300 ppm. When there is too little content of the said composite particle which is a polymerization catalyst, the crystallization rate of an amorphous pellet will fall. The content of the composite particles is more preferably 20 ppm or more, and further preferably 30 ppm or more. On the other hand, when the content of the composite particles is too large, the pressure increase rate of the filter used during extrusion molding increases. In addition, the transparency may be lowered and the manufacturing cost is also increased. The content of the composite particles is more preferably 200 ppm or less, and even more preferably 140 ppm or less.

The crystal pellet of the present invention may contain a resin component other than polyester as long as the effects of the present invention are not impaired. However, the content is usually 5% by mass or less, preferably 1% by mass, and more preferably substantially not contained. The crystal pellet of the present invention may contain inorganic particles other than the composite particles of hydrotalcite and titanium dioxide as long as the effects of the present invention are not impaired. However, the content is usually 1000 ppm or less, preferably 100 ppm or less, and more preferably substantially free.

When the crystal pellet of the present invention was dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 1 to 5 μm contained in 1 g of the pellet was 5.0 × 10. It is preferably ⁻¹⁴ m ³ / g or more. It has now been clarified that the crystallization rate of amorphous pellets increases as the total volume of particles having a diameter of 1 to 5 μm increases. As shown in FIG. 1 and FIG. 2, it seems that a large number of particles having a diameter of less than 1 μm does not affect the crystallization rate, and particles in a specific particle size range affect the crystallization rate. It seems. By increasing the crystallization speed, the time required for the precrystallization can be shortened, productivity can be improved, and energy consumption can be reduced. The total volume of particles having a diameter of 1 to 5 μm is more preferably 1.0 × 10 ⁻¹³ m ³ / g or more, and further preferably 2.5 × 10 ⁻¹³ m ³ / g or more. The total volume of particles having a diameter of 1 to 5 μm is usually 1 × 10 ⁻¹⁰ m ³ / g or less, and in many cases 1 × 10 ⁻¹¹ m ³ / g or less.

On the other hand, when the crystal pellet of the present invention is dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 5 to 20 μm contained in 1 g of the pellet is 1.2. ^{X10 −12} m ³ / g or less is preferable. Since the total volume of particles having a diameter of 5 to 20 μm is small, the pressure increase rate of the filter during extrusion molding can be reduced, and a highly transparent molded product can be continuously melt-formed over a long period of time. The total volume of particles having a diameter of 5 to 20 μm is more preferably 1.0 × 10 ⁻¹² m ³ / g or less, and further preferably 0.9 × 10 ⁻¹² m ³ / g or less. The total volume of particles having a diameter of 5 to 20 μm is usually 1 × 10 ⁻¹⁴ m ³ / g or more, and in many cases 1 × 10 ⁻¹³ m ³ / g or more.

The use of the crystalline polyester pellets thus obtained is not particularly limited. Since it contains copolymerized PET containing a comonomer component, it is suitably used for applications that require transparency, adhesion, or moldability. Further, since the degree of polymerization is increased by solid phase polymerization, it is suitably used for applications requiring further strength and impact resistance. Optical films that require a high degree of transparency, film-laminated metal plates that require adhesion and formability, and extrusion blow molded containers that require transparency and impact resistance are particularly suitable applications.

The optical film is suitably used as a surface protective film for flat display devices such as liquid crystal displays and organic EL displays, and a polarizing plate support film for liquid crystal displays. Since the crystalline polyester pellets of the present invention have a low pressure increase rate even when a fine filter is used during extrusion molding, by using the pellets, a film having excellent transparency with few coarse particles can be obtained with high productivity. Can be molded.

As the laminated metal plate on which the polyester film is laminated, a film laminated metal plate for can making is suitable. When forming a can, it is drawn and ironed together with a metal plate, so it is preferable to use the pellet of the present invention having good adhesion and formability. Moreover, the polyester of the present invention having a high degree of polymerization is preferable because the film is hardly damaged when the molded can is deformed. Examples of the metal plate on which the polyester film is laminated include a steel plate and an aluminum plate. When laminating a polyester film on a metal plate, a pre-formed film can be laminated on the metal plate by heating and pressing, or a film can be laminated by coating a molten resin on the metal plate. .

As the extrusion blow molded container, it is suitably used as a blow molded bottle for storing cosmetics, beverages, pharmaceuticals, seasonings and the like. The crystalline polyester pellet of the present invention has high transparency and is less likely to be whitened due to crystallization during molding. In addition, the degree of polymerization is high and the impact resistance is also excellent. Furthermore, by using a polyfunctional monomer as a comonomer, it is possible to obtain pellets having good draw-down resistance and good moldability.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

(1) Intrinsic viscosity The intrinsic viscosity of the polyester in the amorphous pellets and the crystal pellets after solid-phase polymerization is 30 ° C. using an equal mass mixture of phenol and 1,1,2,2-tetrachloroethane as a solvent. Measured with Since the mass of the particles contained in the pellet was very small, it was ignored.

(2) Melting point (Tm), melting enthalpy (ΔHm) and glass transition temperature (Tg)
The melting point (Tm) and melting enthalpy (ΔHm) of the crystal pellet after solid-phase polymerization were measured using a differential scanning calorimeter (TA Q2000 model, manufactured by TA Instruments) at a heating rate of 10 ° C./min. The glass transition temperature (Tg) of the polyester was the same apparatus, using the crystal pellets after solid-phase polymerization as a sample, heated to 280 ° C. at a temperature increase rate of 10 ° C./min, and then 30 ° C. at −50 ° C./min. The temperature was calculated from the data when the temperature was increased again at a rate of temperature increase of 10 ° C./min. Further, the melting enthalpy of the pre-crystallized pellet was also measured in the same manner as described above.

(3) Particle size distribution 0.4 g of crystal pellets after solid-phase polymerization was dissolved at 100 ° C. in 500 g of an equal mass mixture of phenol and 1,1,2,2-tetrachloroethane filtered through a 1 micron mesh filter. And returned to room temperature and allowed to stand for 1 day. 50 mL (65 g) of the solution was passed through an in-liquid particle counter (Accurizer 780SIS manufactured by Particle Sizing Systems), and the number of particles contained in the solution was measured. The number of particles contained in the pellet was calculated by subtracting the measured value of the blank solution not containing the pellet from this measured value. The measurement was performed 3 times and the average value was used. The volume of particles having a diameter of 1 to 5 μm was integrated, and the total volume was determined as a value per 1 g of pellets. Further, the volume of particles having a diameter of 5 to 20 μm was integrated, and the total volume was determined as a value per 1 g of pellets.

(4) Carboxyl group content After 0.1 g of crystal pellets after solid-phase polymerization were dissolved in 10 ml of benzyl alcohol by heating, a 0.1N NaOH methanol / benzyl alcohol = 1/9 (mass ratio) solution was used. Then, the acid value was determined by titration, and this was defined as the carboxyl group content (μmol / g) of the polyester. Since the mass of the particles contained in the pellet was very small, it was ignored.

(5) Melt Viscosity Crystal pellets after solid-phase polymerization were vacuum-dried at 120 ° C. for 24 hours, and using a sample with a moisture content of 50 to 100 ppm contained in the pellets, a capillary rheometer “Toyo Seiki Seisakusho Co., Ltd.” The melt viscosity was measured by “Capillograph 1D”. Measurement temperature 260 ° C., a shear rate was measured in the range of 6000Sec ^-1 from 10 sec ^-1, the values at 15 sec ^-1, was obtained as a melt viscosity.

(6) b value The resin color (b value) of the crystal pellets after solid-phase polymerization is determined according to ASTM-D2244 (color scale system 2), a colorimetric color difference meter “ZE-2000” manufactured by Nippon Denshoku Industries Co., Ltd. It measured using.

Example 1
(1) Melt polycondensation A slurry consisting of 85.0 parts by mass of terephthalic acid (TA), 15.0 parts by mass of isophthalic acid (IPA) and 44.8 parts by mass of ethylene glycol (EG) was prepared and subjected to pressure (gauge pressure 0 The oligomer was produced by heating to 250 ° C. at a temperature of 250 MPa for esterification reaction. The obtained oligomer was transferred to a polycondensation tank, and 0.033 parts by mass of SATICA SPC-124-20 (manufactured by Sakai Chemical Industry Co., Ltd.), which is an ethylene glycol dispersion of composite particles of hydrotalcite and titanium dioxide. Of these, 0.007 parts by mass of composite particles as a polymerization catalyst and 0.026 parts by mass of ethylene glycol) and 0.007 parts by mass of phosphorous acid were added. The average particle size of the composite particles in ethylene glycol is 0.3 μm. Polyester having an intrinsic viscosity of 0.69 dL / g was produced by melt polycondensation at 0.1 kPa and 280 ° C. for 90 minutes. The obtained polyester was extruded into a strand form from a nozzle and cooled with water, and then cut into a cylindrical shape (diameter: about 2.5 mm, length: about 2.5 mm) to obtain an amorphous pellet of polyester.

(2) Precrystallization of amorphous pellets The polyester amorphous pellets obtained as described above were put into a rolling vacuum solid-phase polymerization apparatus and precrystallized at 120 ° C for 10 hours under 0.1 kPa. went. The melting enthalpy of the precrystallized pellet thus obtained was measured and found to be 14 J / g.

(3) Solid Phase Polymerization After the preliminary crystallization, the temperature was raised and solid phase polymerization was performed at 185 ° C. under 0.1 kPa for 30 hours to obtain crystal pellets. The intrinsic viscosity of the obtained copolyester was 0.89 dL / g. The ratio of the monomer components constituting the copolymerized polyester was confirmed by ¹ H-NMR spectrum (apparatus: “JNM-GX-500 type” manufactured by JEOL Ltd., solvent: deuterated trifluoroacetic acid). Terephthalic acid unit: isophthalic acid unit: ethylene glycol unit: diethylene glycol unit = 42.5: 7.5: 48.5: 1.5 (molar ratio). The carboxyl group content was 10 μmol / g. The melting point (Tm), glass transition temperature (Tg) and melting enthalpy (ΔHm) were 212 ° C., 76 ° C. and 38 J / g, respectively. The b value was 8. In the particle size distribution measurement, the volume of particles having a diameter of 1 to 5 μm is 7.2 × 10 ⁻¹³ m ³ / g, and the volume of particles having a diameter of 5 to 20 μm is 7.6 × 10 ⁻¹³ m ³ / g. there were. The melt viscosity at 260 ° C. and 15 sec ⁻¹ was 2000 Pa · sec.

(4) Filter pressurization test during extrusion Attach a triple filter (mesh size 50μm / 500μm / 10μm) to a 20φ single-screw extruder and continuously extrude for 1 hour. From the change in resin pressure at the start and end of extrusion The rate of increase in the resin pressure per hour (MPa / h) was measured. The rotation speed of the screw was 130 rpm, and the discharge rate was 8 kg / hr. The cylinder temperature was set at 280-290 ° C., and the resin temperature during extrusion was 270-285 ° C. As a result, the pressure increase rate of the filter was 0.8 MPa / hr.

Example 2
Example 1 except that the amount of the polymerization catalyst was 0.0023 parts by mass, the amount of phosphorous acid was 0.0023 parts by mass, the melt polymerization time was 120 minutes, and the solid-phase polymerization time was 40 hours. In the same manner, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Example 3
Example 1 except that the amount of the polymerization catalyst was 0.010 parts by mass, the amount of phosphorous acid was 0.010 parts by mass, the melt polymerization time was 80 minutes, and the solid phase polymerization time was 17 hours. In the same manner, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Example 4
Example 1 except that the amount of the polymerization catalyst was 0.017 parts by mass, the amount of phosphorous acid was 0.017 parts by mass, the melt polymerization time was 75 minutes, and the solid phase polymerization time was 12 hours. In the same manner, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Comparative Example 1
Melt polymerization was carried out in the same manner as in Example 1 except that the amount of the polymerization catalyst was 0.0006 parts by mass and the amount of phosphorous acid was 0.0006 parts by mass, but the degree of polymerization was sufficiently increased. As a result, pellets could not be obtained and subsequent evaluation was not performed. The results are summarized in Tables 1 and 2.

Comparative Example 2
Example except that 0.041 parts by mass of titanium (IV) tetraisopropoxide was added as a polymerization catalyst, the amount of phosphorous acid was 0.007 parts by mass, and the solid phase polymerization time was 35 hours. In the same manner as in Example 1, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Comparative Example 3
As a polymerization catalyst, it is the same as Example 1 except that 0.012 parts by mass of germanium dioxide (GeO ₂ ) is added, the amount of phosphorous acid is 0.012 parts by mass, and the solid phase polymerization time is 20 hours. Crystal pellets were manufactured and evaluated. The results are summarized in Tables 1 and 2.

Comparative Example 4
Example except that 0.042 parts by mass of antimony trioxide (Sb ₂ O ₃ ) was compounded as a polymerization catalyst, the amount of phosphorous acid was 0.012 parts by mass, and the solid phase polymerization time was 25 hours. In the same manner as in Example 1, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Example 5
A slurry composed of 85.0 parts by mass of terephthalic acid, 15.0 parts by mass of isophthalic acid, and 44.8 parts by mass of ethylene glycol was prepared, and “SATA SPC-124-20” (manufactured by Sakai Chemical Industry Co., Ltd.) 033 parts by mass (of which 0.007 parts by mass of composite particles as a polymerization catalyst and 0.026 parts by mass of ethylene glycol) and 0.007 parts by mass of phosphorous acid were added. This slurry was heated to a temperature of 250 ° C. under pressure (gauge pressure of 0.25 MPa) to carry out an esterification reaction to produce a low polymer. Using this low polymer, crystal pellets were produced and evaluated in the same manner as in Example 1 except that the solid phase polymerization time was set to 70 hours. The results are summarized in Tables 1 and 2.

Comparative Example 5
Example 5 except that 0.041 parts by mass of titanium (IV) tetraisopropoxide was added as a polymerization catalyst, the amount of phosphorous acid was 0.007 parts by mass, and the solid-state polymerization time was 40 hours. In the same manner, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Comparative Example 6
As Example 5, except that 0.012 parts by mass of germanium dioxide (GeO ₂ ), 0.012 parts by mass of phosphorous acid, and 20 hours of solid phase polymerization were used. Crystal pellets were manufactured and evaluated. The results are summarized in Tables 1 and 2.

Comparative Example 7
Example except that 0.042 parts by mass of antimony trioxide (Sb ₂ O ₃ ) was compounded as a polymerization catalyst, the amount of phosphorous acid was 0.012 parts by mass, and the solid phase polymerization time was 25 hours. In the same manner as in Example 5, crystal pellets were produced and evaluated. The results are summarized in Tables 1 and 2.

Example 6
That 0.007 parts by mass of zinc acetate was added before the esterification reaction, that the addition time of 0.007 parts by mass of phosphorous acid was changed before the esterification reaction, that the melt polymerization time was 80 minutes, Crystal pellets were produced and evaluated in the same manner as in Example 1 except that the polymerization time was 25 hours. The results are summarized in Tables 1 and 2.

Example 7
A slurry composed of 73.1 parts by mass of terephthalic acid, 10.7 parts by mass of isophthalic acid, 16.2 parts by mass of hydrogenated dimer acid (HDA) and 39.0 parts by mass of ethylene glycol was prepared, and the solid-state polymerization time was 30 hours. Except that, crystal pellets were produced and evaluated in the same manner as in Example 1. The results are summarized in Tables 1 and 2.

Example 8
(1) Production of crystal pellets A slurry consisting of 100 parts by mass of terephthalic acid, 42.6 parts by mass of ethylene glycol and 9.5 parts by mass of bisphenol A ethylene oxide adduct (BPE) was prepared. Crystal pellets were produced and evaluated in the same manner as in Example 1 except that the phase polymerization time was 40 hours. The filter pressurization test during extrusion was not performed. The results are summarized in Tables 1 and 2.

(2) Production of bottles Using the obtained crystal pellets, using an extrusion blow molding apparatus (“MSE-40E type” manufactured by Tahara Co., Ltd.), cylinder temperature 260-290 ° C., die temperature 240-250 ° C., molding cycle A transparent bottle (27.5 g ± 0.5 g) having a volume of 220 mL was molded at 15 seconds, a screw rotational speed of 20-24 rpm, an extrusion resin pressure of 19-25 MPa, and a mold temperature of 20 ° C. The obtained bottle had good transparency.

(3) Bottle drop test After putting water (water temperature 20-25 ° C) so that the total weight becomes 263 g ± 0.5 g in the bottle immediately after molding, it is passed through a 10 cm diameter cylinder installed vertically, From a height of 100 cm, it was dropped alternately on a horizontal concrete surface and a concrete surface inclined 45 degrees. The number of cycles until the bottle was cracked or cracked (the bottle was dropped twice in total, once on the horizontal surface and once on the 45 ° slope) was measured. Up to 10 cycles were repeated. As a result of a drop test of a total of 10 bottles, no bottles were broken.

Example 9
That 0.007 parts by mass of cobalt acetate was added before the esterification reaction, that the addition time of 0.007 parts by mass of phosphorous acid was changed before the esterification reaction, that the melt polymerization time was 80 minutes, Crystal pellets and extrusion blow molded bottles were produced and evaluated in the same manner as in Example 8 except that the polymerization time was 35 hours. The results are summarized in Tables 1 and 2.

Example 10
A slurry consisting of 100 parts by weight of terephthalic acid, 38.1 parts by weight of ethylene glycol and 13.0 parts by weight of cyclohexanedimethanol (CHDM) is prepared and heated to a temperature of 250 ° C. under pressure (gauge pressure of 0.25 MPa) to form an ester. A low polymer was produced by carrying out a polymerization reaction. The obtained low polymer was transferred to a polycondensation tank, and 0.033 parts by mass of SATICA SPC-124-20 (manufactured by Sakai Chemical Industry Co., Ltd.) (of which, composite particles as a polymerization catalyst were 0.007 parts by mass). Parts, ethylene glycol is 0.026 parts by mass), hindered phenol-based antioxidant (“Irganox 1010” manufactured by BASF) 0.012 parts by mass and phosphite-based antioxidant (“ADEKA STAB PEP-36 manufactured by ADEKA Corporation) ]) 0.029 parts by weight were added. Polyester having an intrinsic viscosity of 0.69 dL / g was produced by melt polycondensation at 280 ° C. for 90 minutes under 0.1 kPa. The obtained polyester was extruded into a strand form from a nozzle and cooled with water, and then cut into a cylindrical shape (diameter: about 2.5 mm, length: about 2.5 mm) to obtain an amorphous pellet of polyester. Using the obtained amorphous pellets, crystal pellets and extrusion blow molded bottles were produced and evaluated in the same manner as in Example 8 except that the solid-state polymerization temperature was set to 205 ° C. As a result of the bottle drop test, no bottle was damaged. The results are summarized in Tables 1 and 2.

Comparative Example 8
Except that a slurry consisting of 98.0 parts by mass of terephthalic acid, 2.0 parts by mass of isophthalic acid and 44.8 parts by mass of ethylene glycol was prepared, the solid phase polymerization temperature was 225 ° C., and the solid phase polymerization time was 20 hours. As in Example 8, crystal pellets and extrusion blow molded bottles were produced and evaluated. Since the mouth of the bottle was whitened during molding and a bottle with good transparency could not be obtained, the bottle drop test was not performed. The results are summarized in Tables 1 and 2.

As shown in Tables 1 and 2, in the examples using the composite particles of hydrotalcite and titanium dioxide as the catalyst, the crystallization speed of the amorphous pellets is increased, the color tone is good, and the carboxyl concentration is low. Crystalline polyester pellets could be obtained with good productivity. Since the crystal pellet has few coarse particles, it has high transparency, and the rate of increase in the filter pressure during extrusion molding is also small. At this time, it was found that the crystallization rate of amorphous pellets was faster in the melt polymerization by adding the catalyst after the esterification reaction than in the case of adding the catalyst before the esterification reaction (Examples 1 and 5). Contrast).

When titanium (IV) tetraisopropoxide was used as a catalyst (Comparative Examples 2 and 5), the color tone of the pellet deteriorated. When germanium dioxide was used as the catalyst (Comparative Examples 3 and 6), the precrystallization rate decreased and the carboxyl group content increased. When antimony trioxide was used as a catalyst (Comparative Examples 4 and 7), the precrystallization rate decreased and the filter pressure increase rate during extrusion molding increased.

FIG. 1 and FIG. 2 show the particle size distribution measurement charts of Example 1 using composite particles of hydrotalcite and titanium dioxide as a catalyst and Comparative Example 3 using germanium dioxide (GeO ₂ ) as a catalyst. Contrast. In Comparative Example 3, the peak of the particle size distribution was 0.60 μm, whereas in Example 1, it was 1.04 μm, and the peak value of Comparative Example 3 was smaller. However, the number of particles having a diameter of 1 to 5 μm was larger in Example 1, and the number of particles having a diameter of 5 to 20 μm was larger in Comparative Example 3. From this, it is presumed that particles having a diameter of 1 to 5 μm have an influence on the crystallization speed.

From the comparison between Example 1 and Example 6 and the comparison between Example 8 and Example 9, the addition of the cocatalyst and phosphorous acid prior to the esterification reaction shortens the polymerization time and improves the color tone. It was found that good pellets were obtained.

Claims

A crystalline polyester pellet comprising a resin composition containing polyester and composite particles;
The polyester comprises 25 to 50 mol% terephthalic acid units, 25 to 49.5 mol% ethylene glycol units, 0.5 to 2.5 mol% diethylene glycol units, and other comonomer units having 5 or more carbon atoms. Containing 1.5 to 25 mol%,
The polyester has an intrinsic viscosity of 0.75 to 1.5 dL / g,
The crystal melting enthalpy of the pellet is 20 J / g or more,
A pellet characterized in that the composite particles are composite particles of hydrotalcite and titanium dioxide, and the content of the composite particles is 10 to 300 ppm.
When the pellet was dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 1 to 5 μm contained in 1 g of the pellet was 5.0 × 10 −14 m. The pellet of Claim 1 which is 3 / g or more.
When the pellet was dissolved in an equal mass mixed solvent of phenol and tetrachloroethane and measured with a particle counter, the total volume of particles having a diameter of 5 to 20 μm contained in 1 g of the pellet was 1.2 × 10 −12 m. The pellet of Claim 1 or 2 which is 3 / g or less.
The pellet according to any one of claims 1 to 3, wherein the polyester has a carboxyl group content of 18 µmol / g or less.
A film formed by molding the pellet according to any one of claims 1 to 4.
A laminated metal plate obtained by laminating a film formed by molding the pellet according to any one of claims 1 to 4 on a metal plate.
An extrusion blow-molded container formed by molding the pellet according to any one of claims 1 to 4.
Amorphous terephthalic acid or its ester-forming derivative, ethylene glycol, and other comonomers having 5 or more carbon atoms are melt-polymerized in the presence of a catalyst composed of composite particles of hydrotalcite and titanium dioxide, and then cut to amorphous. The method for producing crystalline polyester pellets according to any one of claims 1 to 4, wherein the polyester pellets are produced and subsequently the amorphous polyester pellets are pre-crystallized and then subjected to solid phase polymerization.
The pellet production according to claim 8, wherein at least terephthalic acid or an ester-forming derivative thereof and ethylene glycol are heated to advance an esterification reaction to obtain an oligomer, and then the catalyst is added to perform melt polymerization. Method.