JP2013049758A - Polyester resin with good flowability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing polyester resin having high flowability without impairing the polycondensation reactivity and the quality and with little possibility of the thickening (gelling) even if a compound having three or more functional groups is added.SOLUTION: In a method for producing a polyester through an esterification step of performing an esterification reaction and/or a transesterification reaction of a dicarboxylic acid component composed mainly of a terephthalic acid or an ester-forming derivative thereof with a diol composed mainly of 1,4-butanediol and a polycondensation step of subjecting an oligomer produced in the esterification step to polycondensation reaction, the method for producing a polyester resin includes adding a compound having three or more functional groups to the reaction system and using a titanium compound and a compound of a Group II metal of the periodic table as reaction catalysts.

Description

  The present invention relates to a method for producing polybutylene terephthalate having high fluidity during melt molding, among polyesters.

  Polybutylene terephthalate (hereinafter sometimes referred to as PBT) has excellent mechanical properties, heat resistance, moldability and recyclability, and has high mechanical strength and chemical resistance. It is widely used for films, fibers and the like, and in particular, it is widely used as a material for industrial molded products such as connectors, relays and switches for automobiles and electrical / electronic devices.

  PBT usually forms an oligomer which is a polyester precursor by direct esterification reaction between terephthalic acid and 1,4-butanediol (hereinafter sometimes referred to as 1,4-BG), and then the oligomer is subjected to atmospheric pressure or A method of producing by polycondensation reaction under reduced pressure, or an ester exchange reaction between an ester-forming derivative of terephthalic acid and 1,4-BG to form an oligomer which is a polyester precursor, and then the oligomer is subjected to atmospheric pressure or It is produced by a method of producing by polycondensation reaction under reduced pressure. At this time, it is well known that a titanium compound is used as a reaction catalyst.

On the other hand, in recent years, there has been an increasing demand for miniaturization and weight reduction of industrial molded products, and it is desired to improve the fluidity during melt molding at the same time as further improving mechanical strength. It has been desired to produce PBT efficiently.
Conventionally, a method for efficiently producing a polyester resin having high fluidity by adding a compound having three or more functional groups in the course of producing the polyester resin has been proposed (see Patent Document 1). However, with the disclosed technique, good flowability PBT can be obtained, but the polycondensation reaction rate tends to be slow due to the influence of the addition of a polyfunctional branching agent. In order to compensate for this, since polymerization is performed at a high temperature and using a large amount of catalyst, there is a problem that the quality (color tone, AV) of the polyester resin is deteriorated and there is a concern about thickening (gelation).

JP 2011-84737 A

  In view of the above problems, the problem of the present invention is that even if a compound having three or more functional groups is added, the polycondensation reactivity, the quality is not impaired, and there is little concern about thickening (gelation), high fluidity It is providing the method of manufacturing efficiently the polyester resin which has this.

  As a result of intensive studies on the above problems, the present inventors have added a compound having three or more functional groups to the reaction system in a method for producing a polyester resin, and used a titanium compound as a reaction catalyst and the second periodic table. The present inventors have found a production method using a group metal compound and arrived at the present invention. In addition, the periodic table group 2 metal in this invention is a group 2 element of the long period type periodic table (Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005).

That is, the gist of the present invention resides in the following [1] to [4].
[1] An esterification step in which an esterification reaction and / or a transesterification reaction between a dicarboxylic acid component having terephthalic acid or an ester-forming derivative thereof as a main component and a diol having 1,4 butanediol as a main component, and In a method for producing a polyester through a polycondensation step in which a polycondensation reaction is performed on an oligomer obtained by an esterification step, a compound having three or more functional groups is added to the reaction system, and a titanium compound and a periodic table are used as a reaction catalyst. A method for producing a polyester resin, comprising using a group 2 metal compound.
[2] The method for producing a polyester resin according to [1], wherein the amount of the Group 2 metal compound added to the reaction system is 5 to 100 ppm by weight as a metal atom with respect to the obtained polyester resin. .
[3] The method for producing a polyester resin according to [1] or [2], wherein 0.2 to 2.0 parts by weight of a compound having three or more functional groups is added to 100 parts by weight of the obtained polyester resin. . [4] The method for producing a polyester resin according to [1] to [3], wherein the polycondensation reaction temperature is 235 ° C. or higher and 245 ° C. or lower.

  According to the present invention, even when a compound having three or more functional groups is added, a polycondensation reactivity and a polyester resin having a high fluidity can be efficiently produced without impairing the viscosity without impairing the quality. Can be manufactured.

Hereinafter, the present invention will be described in detail. However, the description of each constituent element described below is a representative example of the embodiment of the present invention, and the present invention is not limited thereto.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. Moreover, the lower limit value or the upper limit value in this specification means a range including the numerical value of the lower limit value or the upper limit value.

<Production raw materials>
The polyester resin of the present invention is obtained by subjecting a dicarboxylic acid component mainly composed of terephthalic acid or an ester-forming derivative thereof and a diol mainly composed of 1,4 butanediol to an esterification reaction and / or a transesterification reaction. It can be obtained by polycondensation reaction.
The dicarboxylic acid component mainly comprising terephthalic acid or an ester-forming derivative thereof used in the present invention means that terephthalic acid or an ester-forming derivative thereof in the dicarboxylic acid is usually 80 mol% or more. Preferably it is 90 mol% or more, More preferably, it is 95 mol% or more. Examples of other dicarboxylic acids include isophthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid, succinic acid, oxalic acid, cyclohexanedicarboxylic acid, and ester-forming derivatives thereof. These may be used alone or in combination of two or more.

  The diol mainly composed of 1,4 butanediol used in the present invention means that 1,4 butanediol in the diol is usually 80 mol% or more. Preferably it is 90 mol% or more, More preferably, it is 95 mol% or more. Other diols include alkylene glycols such as ethylene glycol, propylene glycol, neopentyl glycol, hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol, poly (oxy) ethylene glycol, polytetramethylene glycol, and polymethylene glycol. These may be used alone or in combination of two or more, and can be arbitrarily selected according to the purpose. In addition, polyalkylene glycol is poor in thermal stability and is liable to cause a decomposition reaction.

The ester-forming derivative used in the present invention is an ester-forming derivative that can form an ester as a diol in the resin production process, and is a lower alkyl ester of terephthalic acid or other dicarboxylic acid, specifically methyl ester, ethyl ester, propyl. Examples include esters and butyl esters. One or two or more of these may be mixed, and can be arbitrarily selected depending on the purpose.

Examples of the functional group of a compound having three or more functional groups include at least one functional group selected from a hydroxyl group and a carboxyl group.
Specifically, examples of the polyhydric alcohol that is a compound having three or more hydroxyl groups include aliphatic hydrocarbons such as glycerin, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, sucrose, and pentaerythritol monostearate. A polyhydric alcohol is mentioned, As carbon number of the polyhydric alcohol which is a compound which has a 3 or more hydroxyl group, 3-30 are preferable. The number of hydroxyl groups is preferably 3-12, particularly preferably 3-8, and most preferably 3-6. These polyhydric alcohols, which are compounds having three or more hydroxyl groups, can be used alone or as a mixture of two or more. Among these, pentaerythritol and dipentaerythritol are preferably used in that they exhibit high fluidity without significantly impairing the polycondensation reactivity.

Specific examples of the polyvalent carboxylic acid that is a compound having three or more carboxyl groups include propanetricarboxylic acid, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, cyclopentatetracarboxylic anhydride, and the like. These can be used alone or as a mixture of two or more.
Specific examples of the oxycarboxylic acid having three or more functional groups and the functional group is a compound composed of a hydroxyl group and a carboxyl group include malic acid, hydroxyglutaric acid, hydroxymethylglutaric acid, tartaric acid, and citric acid. , Hydroxyisophthalic acid, hydroxyterephthalic acid and the like, and can be used alone or as a mixture of two or more.

The amount of the compound having 3 or more functional groups is preferably 2.0 parts by weight or less, more preferably 1.5 parts by weight or less, and particularly preferably 1. parts by weight with respect to 100 parts by weight of the obtained polyester resin. 0 parts by weight or less. On the other hand, it is preferably 0.2 parts by weight or more, more preferably 0.35 parts by weight or more, and particularly preferably 0.5 parts by weight or more. If the upper limit is exceeded, thickening and gel tend to occur during production. Moreover, when it is less than the lower limit, it tends to be difficult to obtain a polyester resin having high fluidity.

<Manufacturing method>
As a known production method of PBT, there are a so-called direct polymerization method using terephthalic acid and 1,4-BG as main raw materials, and a transesterification method using terephthalic acid dialkyl ester and 1,4-BG as main raw materials.
In the present invention, a conventionally known method is used except that a compound having three or more functional groups is added to the reaction system, and a titanium compound and a Group 2 metal compound are used as a reaction catalyst. Obtained by an esterification step of performing an esterification reaction and / or a transesterification reaction of a dicarboxylic acid component having an ester-forming derivative as a main component and a diol having 1,4 butanediol as a main component, and an esterification step It can be performed by a method of obtaining a polyester through a polycondensation step in which an oligomer is polycondensed.

In the present invention, an oligomer is a polyester resin having a number average molecular weight of 500 to 10,000.
In the present invention, the reaction system is an esterification step or a polycondensation step. The esterification step includes an esterification reaction tank and an apparatus connected to the esterification reaction tank by piping, and the polycondensation process includes a polycondensation reaction tank and an apparatus connected to the polycondensation reaction tank by piping.

The esterification step is optional as long as the esterification reaction and / or transesterification reaction can proceed, and the temperature is 120 ° C. or higher, preferably 150 ° C. or higher, and usually 245 ° C. or lower, preferably 230 ° C. It is as follows. The reaction time is 2 to 8 hours, preferably 2 to 6 hours, and more preferably 2 to 4 hours.
The esterification step produces an oligomer in which a diol having 1,4 butanediol as a main component, a terephthalic acid or a dicarboxylic acid component having an ester-forming derivative as a main component is reacted. And in the polycondensation process mentioned later, this oligomer polycondensation reaction is performed.

  In the polycondensation process, the oligomer obtained in the esterification process is subjected to a polycondensation reaction. The polycondensation reaction usually proceeds as a melt polycondensation reaction. The conditions in the polycondensation step are arbitrary as long as the polycondensation reaction can proceed. The reaction temperature (internal temperature) during the polycondensation reaction is preferably 245 ° C. or lower, more preferably 240 ° C. or lower, on the other hand, preferably 230 ° C. or higher, more preferably 235 ° C. or higher. If the reaction temperature exceeds the upper limit, the concentration of the terminal vinyl group is significantly increased, the viscosity is likely to increase during production, and the color tone tends to deteriorate. If the reaction temperature is less than the lower limit, the polycondensation reactivity tends to deteriorate.

  Further, the pressure in the polycondensation step is preferably reduced pressure. Specifically, it is 10 Torr or less, preferably 3 Torr. Furthermore, the polycondensation reaction time is preferably 2 to 8 hours. By the polycondensation step, a diol having 1,4 butanediol as a main component, a compound having three or more functional groups, a dicarboxylic acid component having a main component of terephthalic acid or an ester-forming derivative as a main component is obtained. be able to.

In the present invention, the compound having three or more functional groups is added at the start of the esterification reaction and / or transesterification reaction, during the esterification reaction and / or transesterification reaction, after the esterification reaction and / or transesterification reaction. Alternatively, it may be added during the polycondensation reaction, but it is preferably added at the start of the esterification reaction or transesterification reaction.
The titanium compound used as a reaction catalyst is added at the beginning of the esterification reaction and / or transesterification reaction, during the esterification reaction and / or transesterification reaction, after the esterification reaction and / or transesterification reaction, or polycondensation reaction. Although there may be times, etc., it is preferable to add them separately at the beginning of the esterification reaction or transesterification reaction and before the polycondensation reaction.

The period of addition of the Group 2 metal compound is also determined at the beginning of the esterification and / or transesterification, during the esterification and / or transesterification, after the esterification and / or transesterification, or polycondensation. Although it may be at the time of reaction, it is preferable in terms of polycondensation and color tone to be added at the end of transesterification and before the start of polymerization.
Titanium compounds used in the present invention are inorganic titanium compounds such as titanium oxide and titanium tetrachloride, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, Tetraalkyl titanates such as tetracyclohexyl titanate and tetrabenzyl titanate are preferable, and tetra-n-butyl titanate is particularly preferable. In addition, a titanium compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The addition amount of the titanium compound is preferably 20 mass ppm or more, more preferably 30 mass ppm or more, on the other hand, preferably 100 mass ppm or less, more preferably 70 mass ppm or less as a titanium atom with respect to the obtained polyester resin. . If the upper limit is exceeded, not only the color tone and thermal stability tend to deteriorate, but also the solution haze and foreign matter tend to increase due to the deactivation of the titanium catalyst. Moreover, polycondensation reactivity will deteriorate that it is less than a lower limit.

The content of titanium atoms in the polyester resin is measured by ICP (Inductively Coupled Plasma) -MS (Mass Spectrometer) method after recovering the metal in the polymer by wet ashing.
Examples of the metal atom of the Group 2 metal compound used in the present invention include beryllium, magnesium, calcium, strontium, and barium. Of these, magnesium and calcium compounds are preferred from the viewpoint of handling and availability, and catalytic effect. Examples of the magnesium compound include magnesium acetate and hydrates thereof, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, and the like. Examples of the calcium compound include calcium acetate and its hydrate, calcium hydroxide, calcium carbonate and the like. Of these, magnesium acetate is particularly preferred. In addition, the compound of a periodic table group 2 metal may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The amount of the group 2 metal compound in the periodic table is preferably 5 ppm by weight or more, more preferably 20 ppm by weight or more, more preferably 100 ppm by weight or less, more preferably 70 ppm by weight as a metal atom with respect to the polyester resin obtained. Weight ppm or less. If it is less than the lower limit, the improvement in the polycondensation reaction rate tends to be small, the terminal carboxyl group concentration also increases, and the hydrolysis resistance and color tone tend to deteriorate. If the upper limit is exceeded, the polycondensation reaction rate decreases, and hydrolysis resistance and color tone tend to deteriorate.

In addition, content of the metal atom of the compound of the periodic table group 2 metal in a polyester resin can be measured similarly to the measuring method of content of a titanium atom.
In the present invention, a heat stabilizer can be added to the reaction system. Although there is no restriction | limiting in particular in the heat stabilizer to be used, A hindered phenol type heat stabilizer is preferable. Examples of the hindered phenol heat stabilizer include pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4, Examples include 6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) benzene. Among these, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is more preferable in terms of thermal stability during melt residence. In addition, a hindered phenol-based heat stabilizer may be used alone, or 2
You may use a seed | species or more together by arbitrary combinations and ratios.

The intrinsic viscosity of the polyester resin of the present invention, particularly PBT, is not particularly limited, but is preferably 0.70 dL / g or more, more preferably from the viewpoints of mechanical properties, pelletization stability, moldability, and fluidity. 0.80 dL / g or more. When the intrinsic viscosity of PBT is less than the lower limit, the fluidity is improved, but good mechanical properties tend to be hardly obtained.
The terminal carboxyl group concentration of the PBT of the present invention is not particularly limited, but the lower limit is preferably 1 equivalent / ton, more preferably 2 equivalent / ton, and particularly preferably 3 equivalent / ton. Most preferably, it is 5 equivalents / ton, and the upper limit is preferably 50 equivalents / ton, more preferably 40 equivalents / ton, particularly preferably 30 equivalents / ton, and 25 equivalents / ton. Most preferably. When the terminal carboxyl group concentration of PBT is less than the upper limit, the hydrolysis resistance of PBT tends to be good, and when it exceeds the lower limit, polycondensation reactivity tends to be good.

  The terminal vinyl group concentration of the PBT of the present invention is not particularly limited, but is preferably 15 equivalents / ton or less, more preferably 10 equivalents / ton or less, and particularly preferably 5 equivalents / ton from the viewpoint of color tone or polycondensation reactivity. Tons or less. The terminal vinyl group concentration of PBT is determined by measuring each magnetic resonance spectrum (NMR) after dissolving PBT in a solvent.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example at all unless the summary is exceeded. In addition, the measurement method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.
<Intrinsic viscosity (IV) dL / g>
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1), the number of seconds falling of only the polymer solution having a concentration of 1.0 g / dL and the solvent at 30 ° C. was measured, and the following formula (1) Asked.

IV = ((1 + 4K _H η _sp ) ^0.5 −1) / (2K _H C) (1)
(Where η _SP = η / η ₀ −1, η is the polymer solution falling seconds, η ₀ is the solvent dropping seconds, C is the polymer solution concentration (g / dL), and K _H is the Huggins constant. there .K _H adopted the 0.33.)
<Terminal carboxyl group concentration (AV) equivalent / ton>
After pulverizing the sample, it was dried at 140 ° C. for 15 minutes in a hot air dryer, and 0.1 g was accurately weighed from the sample cooled to room temperature in a desiccator, taken into a test tube, 3 ml of benzyl alcohol was added, The solution was dissolved at 195 ° C. for 3 minutes while blowing dry nitrogen gas, and then 5 ml of chloroform was gradually added and cooled to room temperature. One to two drops of phenol red indicator were added to this solution, and titrated with a 0.1N sodium hydroxide benzyl alcohol solution with stirring while blowing dry nitrogen gas, and the procedure was terminated when the color changed from yellow to red. Moreover, the same operation was implemented as a blank, without melt | dissolving a polyester resin sample, and the terminal carboxyl group density | concentration (acid value) was computed by the following formula | equation (2).

Terminal carboxyl concentration (equivalent / ton) = (ab) × 0.1 × f / w (2)
(Where a is the amount of 0.1N sodium hydroxide in benzyl alcohol solution required for titration (μl), b is the amount of 0.1N sodium hydroxide in benzyl alcohol solution required for titration with a blank. The amount (μl), w is the amount of the polyester resin sample (g), and f is the titer of 0.1N sodium hydroxide in benzyl alcohol.)
In addition, the titer (f) of the benzyl alcohol solution of 0.1N sodium hydroxide was calculated | required with the following method. Collect 5 ml of methanol in a test tube, add 1-2 drops as an indicator of an ethanol solution of phenol red, Titrate with 0.4 ml of 1N sodium hydroxide in benzyl alcohol to the color change point, then add 0.2 ml of 0.1N aqueous hydrochloric acid solution with known titer as a standard solution, and add 0.1N hydroxide again. The solution was titrated with a sodium benzyl alcohol solution to the discoloration point (the above operation was performed under dry nitrogen gas blowing). The titer (f) was calculated by the following formula (3).

Titer (f) = Titer of 0.1N aqueous hydrochloric acid × Amount of collected 0.1N aqueous hydrochloric acid (μl) / Titration of 0.1N sodium hydroxide in benzyl alcohol (μl) (3)
<Pellet color tone (b value)>
Reference Example 1 of JIS Z8730 using pelletized polyester filled in a cylindrical powder measurement cell having an inner diameter of 30 mm and a depth of 12 mm and using a colorimetric color difference meter Z300A (manufactured by Nippon Denshoku Industries Co., Ltd.) The b value by the color coordinate of Hunter's color difference formula in the Lab display system described in the above was obtained as a simple average value of four values measured by rotating the measurement cell by 90 degrees by the reflection method.

<Terminal vinyl group concentration equivalent / ton>
About 20 mg of the sample was dissolved in 0.75 ml of a deuterated chloroform / heavy hexafluoroisopropanol (7/3) mixed solvent, 25 μl of deuterated pyridine was added, and the sample was transferred to an NMR sample tube having an outer diameter of 5 mm. 1H NMR spectra were measured at room temperature using a Bruker AVANCE400 spectrometer. As a standard for chemical shift, the signal of TMS (trimethylsilane) was set to 0.00 ppm. The terminal vinyl group concentration (equivalent / ton) was calculated from the signal intensity corresponding to the terminal vinyl group.

<Melt viscosity Pa · sec>
Measurement of melt viscosity, using a Toyo Seiki Capillograph (Capillograph 1B), the melt viscosity was measured under the conditions of a temperature of 245 ° C., a shear rate of 10 to 10,000, a capillary length of 10 mm, and a capillary diameter of 1 mm.
(Reference Example 1)
In a reaction vessel equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, a distillation pipe, and a vacuum outlet, 132 parts by weight of dimethyl terephthalate (manufactured by Teijin), 74 parts by weight of 1,4-butanediol and a catalyst First, 0.59 parts by weight of a 1,4-butanediol solution in which 6% by weight of tetra-n-butyl titanate was dissolved in advance (33 ppm by weight as titanium atoms with respect to the obtained PBT) was added, and the system was replaced with nitrogen by vacuum-replacement. It was under atmosphere.

The system was heated to 150 ° C. with stirring, and reacted for 3 hours while distilling off the methanol produced by the transesterification reaction while raising the temperature to 210 ° C. to obtain an oligomer.
Subsequently, 1.08 parts by weight of a 1,4-butanediol solution in which 6% by weight of tetra-n-butyl titanate was dissolved in advance as a catalyst (61 ppm by weight as titanium atoms with respect to the obtained PBT) was charged, and magnesium acetate 4 0.64 parts by weight of a 1,4-butanediol solution in which 10% by weight of a hydrate had been dissolved in advance (48 ppm by weight as Mg atoms relative to the obtained PBT) was charged.

  Next, the temperature was raised to 240 ° C. over 1 hour, and the pressure was reduced to 0.4 kPa over 1.5 hours, and a polycondensation reaction was performed at the same degree of pressure reduction. When the predetermined stopping power was reached, the reaction system was returned to normal pressure to complete the polycondensation reaction. The obtained PBT was extracted as a strand from the bottom of the reaction vessel, submerged in water at 10 ° C., and then the strand was cut with a cutter to obtain a pellet-like PBT. The intrinsic viscosity (IV) of the obtained PBT was 0.90 dL / g. In the following examples and comparative examples, the polycondensation reaction was terminated when the same stopping power as in this reference example was reached.

[Example 1]
In a reaction vessel equipped with a stirrer, a nitrogen inlet, a heating device, a thermometer, a distillation pipe, and a vacuum outlet, 132 parts by weight of dimethyl terephthalate (manufactured by Teijin), 74 parts by weight of 1,4-butanediol and a catalyst First, 0.59 parts by weight of a 1,4-butanediol solution in which 6% by weight of tetrabutyl titanate was dissolved in advance (33 ppm by weight as a titanium atom with respect to the obtained PBT) was added, and pentaerythritol was added as a compound having four functional groups. 0.75 parts by weight of the PBT obtained was charged, and the system was put under a nitrogen atmosphere by nitrogen-vacuum substitution.

The system was heated to 150 ° C. with stirring, and reacted for 3 hours while distilling off the methanol produced by the transesterification reaction while raising the temperature to 210 ° C. to obtain an oligomer.
Subsequently, 1.08 parts by weight of a 1,4-butanediol solution in which 6% by weight of tetra-n-butyl titanate was dissolved in advance as a catalyst (61 ppm by weight as titanium atoms with respect to the obtained PBT) was charged, and magnesium acetate 4 0.64 parts by weight of a 1,4-butanediol solution in which 10% by weight of a hydrate had been dissolved in advance (48 ppm by weight as Mg atoms relative to the obtained PBT) was charged.

  Next, the temperature was raised to 240 ° C. over 1 hour, and the pressure was reduced to 0.4 kPa over 1.5 hours, and a polycondensation reaction was performed at the same degree of pressure reduction. When the same power as in Reference Example 1 was reached, the reaction system was returned to normal pressure to complete the polycondensation reaction. The obtained PBT was extracted as a strand from the bottom of the reaction vessel, submerged in water at 10 ° C., and then the strand was cut with a cutter to obtain a pellet-like PBT.

  The obtained PBT had an intrinsic viscosity (IV) of 0.86 dL / g and a terminal carboxyl group concentration (AV) of 24 equivalents / ton. The polycondensation time was defined as the time from the start of pressure reduction to the end of the polycondensation reaction, and the polycondensation reaction rate was defined as the intrinsic viscosity / polycondensation reaction time. The polycondensation reaction rate was 0.22 dL / g / h. The melt viscosity was 100 Pa · sec under the condition of a shear rate of 1000 (/ sec). The results are shown in Table 1.

[Example 2]
PBT was obtained in the same manner as in Example 1 except that the compound having 4 functional groups in Example 1 was changed to dipentaerythritol, which is a compound having 6 functional groups. Various analysis results are shown in Table 1.
[Example 3]
The same as Example 1 except that the amount of 1,4-butanediol added with magnesium acetate tetrahydrate dissolved in Example 1 was 0.13 parts by weight (10 ppm by weight as Mg atoms relative to the resulting PBT). To obtain PBT. Various analysis results are shown in Table 1.

[Example 4]
The same as Example 1 except that the amount of 1,4-butanediol in which magnesium acetate tetrahydrate was dissolved in Example 1 was 1.6 parts by weight (120 ppm by weight as Mg atoms relative to the obtained PBT). To obtain PBT. Various analysis results are shown in Table 1.
[Example 5]
PBT was obtained in the same manner as in Example 1 except that the amount of pentaerythritol added was 0.3 parts by weight in Example 1. Various analysis results are shown in Table 1.

[Example 6]
PBT was obtained in the same manner as in Example 1 except that the amount of pentaerythritol added was 3.0 parts by weight in Example 1. Various analysis results are shown in Table 1.
[Example 7]
PBT was obtained in the same manner as in Example 1 except that the polycondensation temperature was 250 ° C. in Example 1. Various analysis results are shown in Table 1.

[Example 8]
In Example 1, 0.41 part by weight of a 1,4-butanediol solution in which 10% by weight of calcium acetate tetrahydrate was dissolved instead of magnesium acetate tetrahydrate (48 ppm by weight as Ca atom with respect to PBT obtained) ) Was used in the same manner as in Example 1 to obtain PBT. Various analysis results are shown in Table 1.

[Comparative Example 1]
PBT was obtained in the same manner as in Example 1 except that 1,4-butanediol in which magnesium acetate tetrahydrate was dissolved was not added. The obtained PBT had a slow polycondensation rate and a high AV. Various analysis results are shown in Table 1.
[Comparative Example 2]
PBT was obtained in the same manner as in Example 1 except that 1,4-butanediol in which magnesium acetate tetrahydrate was dissolved was not added and the polycondensation reaction temperature was 250 ° C. The obtained PBT had a poor color tone and a low hydrolysis resistance, and the viscosity was easily increased during continuous production. Various analysis results are shown in Table 1.

[Comparative Example 3]
PBT was obtained in the same manner as in Example 1 except that 1,4-butanediol in which magnesium acetate tetrahydrate was dissolved was not added and a compound having three or more functional groups was not added. It was. The melt viscosity of the obtained PBT was 17 under the condition of a shear rate of 1000 (/ sec).
It was 0 Pa · sec, and high fluidity was not obtained. Various analysis results are shown in Table 1.

According to the present invention, good mechanical properties can be maintained and fluidity during melt molding can be improved. In particular, it is effective for injection molded products having a complicated structure such as electrical / electronic parts and precision equipment parts.

Claims (4)

  Esterification step for performing esterification reaction and / or transesterification reaction of dicarboxylic acid component having terephthalic acid or its ester-forming derivative as a main component and diol having 1,4 butanediol as a main component, and esterification step In the method for producing a polyester through a polycondensation step in which a polycondensation reaction is performed on the oligomer obtained by the above step, a compound having three or more functional groups is added to the reaction system, and a titanium compound and a Group 2 metal of the periodic table are used as a reaction catalyst. The manufacturing method of the polyester resin characterized by using the compound of these.   The manufacturing method of the polyester resin of Claim 1 whose addition amount to the reaction system of the compound of the said periodic table 2 group metal is 5-100 weight ppm as a metal atom with respect to the polyester resin obtained.   The manufacturing method of the polyester resin of Claim 1 or 2 which adds 0.2-2.0 weight part of compounds which have a 3 or more functional group with respect to 100 weight part of polyester resins obtained.   The said polycondensation reaction temperature is 235 degreeC or more and 245 degrees C or less, The manufacturing method of the polyester resin of any one of Claims 1-3 characterized by the above-mentioned.