KR101826812B1 - Preparation method of low crystalline polyester resin that has improved thermal characteristic - Google Patents

Abstract

Disclosed is a preparation method of a polyester resin, which lowers the crystallinity of a resin itself and prevents the whitening phenomenon to improve the transparency of the resin, and which facilitates the solid-state polymerization by sufficiently lowering the crystallinity within a range in which thermal properties are maintained at a certain level. The present invention provides the preparation method of a polyester resin, which performs an esterification reaction and a polycondensation reaction by using a dicarboxylic acid component containing terephthalic acid and a diol component containing ethylene which performs the solid-state polymerization with a product obtained by the polycondensation reaction by further comprising 1 to 5 mol% of isophthalic acid relative to the total dicarboxylic acid component, as the dicarboxylic acid component, and 1 to 5 mol% of 1,4-cyclohexanedimethanol relative to the total diol component, as the diol component.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low crystalline polyester resin having improved thermal properties,

The present invention relates to a method for producing a polyester resin, and more particularly to a method for producing a low crystalline polyester resin with improved thermal properties.

Polyethylene terephthalate (PET) is a polymer produced through polycondensation reaction through esterification reaction of terephthalic acid (TPA) or dimethyl terephthalate (DMT) and ethylene glycol (EG) as main materials. It has excellent physical properties, processability and economical efficiency. It is environmentally friendly and is used in a wide range of fields such as food and beverage containers, packaging materials, textiles for clothing, film, and so on.

In the case of molding with a crystalline resin, the PET is insufficiently cooled or formed into a thick thickness, the quenching efficiency per unit area is lowered due to a rapid crystallization rate, and the whitening phenomenon occurs due to crystallization. In order to prevent such white turbidity, the modified polyester is produced so that the crystallization speed of the resin itself is lowered so that crystallization does not occur under general molding conditions.

In order to satisfy this requirement, DMT or TPA, which is one of the monomers used in PET polymerization, is substituted with Diacid or Diacidester, or EG is substituted with 1,4-cyclohexane dimethanol (CHDM) PET modified by copolymerizing other comonomer with PET has been developed.

However, since the modified PET has thermal properties and is difficult to crystallize due to heat, it can not perform the solid phase polymerization. Therefore, it is difficult to obtain high intrinsic viscosity and the melt polymerization becomes long due to the aimed intrinsic viscosity only by melt polymerization. In addition, since the low-molecular reaction by-products generated during the melt polymerization can not be removed to the outside of the resin through the solid phase polymerization, frequent contamination occurs during molding, resulting in marked reduction in molding productivity and difficulty in sufficient drying due to heat for removing moisture.

In order to improve the transparency of the PET resin, it is desirable to lower the crystallinity of the resin itself. However, since a completely amorphous material may cause the above problems, development of a low crystalline PET resin And the demand for such PET resin molded articles is increasing.

Korean Patent No. 0342734 discloses a method for preliminarily crystallizing a copolyester chip having a low crystallinity and an intrinsic viscosity of 0.5 to 0.7 such that the degree of surface crystallinity is 3 to 10% in hot water before solid phase polymerization. However, Water tank and drying equipment are required. When water is not sufficiently removed, hydrolysis may occur during solid phase polymerization.

Korean Patent Laid-Open No. 1998-0009308 discloses a method for producing polyethylene terephthalate of high polymerization degree which can economically produce polyethylene terephthalate having a high degree of polymerization. However, solid phase polymerization can be carried out without using a crystallization step using silica particles, Is lowered.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in an effort to solve the above problems, and it is an object of the present invention to provide a resin composition which is capable of preventing white turbidity by lowering the crystallinity of the resin itself to improve transparency of the resin, And to provide a method for producing a polyester resin which is easy to use.

In order to solve the above-mentioned problems, the present invention provides a process for producing a dicarboxylic acid, which comprises performing an esterification reaction and a polycondensation reaction using a dicarboxylic acid component containing terephthalic acid and a diol component containing ethylene glycol, In an amount of 1 to 5 mol% based on the total dicarboxylic acid component and 1 to 5 mol% of 1,4-cyclohexanedimethanol as the diol component based on the total diol component to obtain a product obtained by the polycondensation reaction To thereby produce a polyester resin.

And the polyester resin has a cold crystallization temperature (Tcc) of 160 ° C or less and a melting temperature (Tm) of 235 ° C or more.

The solid-state polymerization is carried out at a temperature of 195 to 230 ° C and a pressure of 0.2 to 2 torr or under a nitrogen atmosphere after crystallization in an air atmosphere at a reaction temperature of 170 to 185 ° C.

According to the present invention, the optimum content of isophthalic acid as a dicarboxylic acid component and 1,4-cyclohexanedimethanol as a diol component is lowered to lower the crystallinity of the resin itself to prevent the whitening phenomenon to improve the transparency of the resin, It is possible to provide a method for producing a low crystalline polyester resin having a property of sufficiently lowering the degree of crystallinity to facilitate solid phase polymerization within a range in which thermal properties are maintained at a certain level despite copolymerization of the comonomer.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It is to be understood that various equivalents and modifications may be substituted for those at the time of the present application.

The present inventors have found that a slurry mixture containing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing ethylene glycol, 1,4-cyclohexanedimethanol and other diol compounds in a certain ratio is subjected to esterification and polycondensation The present inventors have confirmed through experiments that a low-crystalline polyester resin can be secured to facilitate solid-state polymerization even when the degree of crystallinity is sufficiently lowered within a range where thermal properties are maintained at a certain level.

Accordingly, the present invention relates to a process for producing a dicarboxylic acid, which comprises subjecting a dicarboxylic acid component containing terephthalic acid and a diol component containing ethylene glycol to an esterification reaction and a polycondensation reaction, 1 to 5 mol% based on the amount of the unsaturated carboxylic acid component and 1 to 5 mol% of 1,4-cyclohexanedimethanol as the diol component with respect to the total amount of the diol component, and performing solid phase polymerization with the product obtained by the polycondensation reaction Thereby producing a polyester resin.

The production of the polyester resin according to the present invention can be carried out, for example, by mixing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing ethylene glycol and 1,4-cyclohexane dimethanol in the above- ; Esterifying the reactant; A step of subjecting the esterification reaction product to a polycondensation reaction; a step of preparing a molten chip by discharging a reactant formed by the polycondensation reaction; and crystallizing the molten chip to perform solid phase polymerization.

The polyester resin produced according to the present invention has a melt temperature (Tm) of 235 DEG C or higher, a cold crystallization temperature (Tcc) of 160 DEG C or lower, a Tcc crystallization energy of 5 J / g or lower, It is possible to facilitate the solid-state polymerization even though the degree of crystallinity is sufficiently lowered within the range of maintaining the constant level. At this time, the polyester resin to be produced preferably has a melting temperature (Tm) of 240 ° C or more and a cold crystallization temperature (Tcc) of 155 ° C or less.

In the present invention, the dicarboxylic acid component is preferably a dicarboxylic acid such as terephthalic acid, an alkyl ester thereof (lower alkyl ester having 1 to 4 carbon atoms such as monomethyl, monoethyl, dimethyl, diethyl or dibutyl ester) and / Of an acid anhydride and may react with the diol component to form a dicarboxylic acid moiety such as a terephthaloyl moiety.

As the dicarboxylic acid component used in the synthesis of the polyester includes terephthalic acid, the heat resistance, the chemical resistance, or the weather resistance (for example, the decrease in molecular weight due to UV or the prevention of sulfur change) of the produced polyester resin Can be improved.

The dicarboxylic acid component may further comprise an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, or a mixture thereof as the other dicarboxylic acid component. Herein, 'other dicarboxylic acid component' means a component other than terephthalic acid among the dicarboxylic acid components.

The aromatic dicarboxylic acid component may be an aromatic dicarboxylic acid having 8 to 20 carbon atoms, preferably 8 to 14 carbon atoms, or a mixture thereof. Examples of the aromatic dicarboxylic acid include naphthalenedicarboxylic acid such as isophthalic acid and 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 4,4'-stilbenedicarboxylic acid, 2, 5-furandicarboxylic acid, 2,5-thiopendicarboxylic acid, and the like, but the specific examples of the aromatic dicarboxylic acid are not limited thereto.

The aliphatic dicarboxylic acid component may be an aliphatic dicarboxylic acid component having 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms, or a mixture thereof. Examples of the aliphatic dicarboxylic acid include cyclohexanedicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid, phthalic acid, sebacic acid, succinic acid, isodecylsuccinic acid, Linear or branched alicyclic dicarboxylic acid components such as maleic acid, fumaric acid, adipic acid, glutaric acid and azelaic acid. However, the specific examples of the aliphatic dicarboxylic acid are not limited thereto.

The dicarboxylic acid component comprises 50 to 99 mol%, preferably 70 to 99 mol% terephthalic acid; And 0 to 50 mol%, preferably 0 to 30 mol%, of an aromatic dicarboxylic acid or aliphatic dicarboxylic acid.

In the present invention, the diol component includes cyclohexane dimethanol, especially 1,4-cyclohexane dimethanol (CHDM). Generally, when 1,4-cyclohexane dimethanol is used as a monomer for copolymerization, the concentration of 1,4-cyclohexane dimethanol should be about 30 mol%, but it may be added at a level of 10 mol% or less according to the present invention Do.

As a result of comparing the melt temperatures of PET resins having similar liquid-phase intrinsic viscosity and low crystallinity prepared to have the same 1,4-cyclohexane dimethanol content according to the method of the present invention and the method of the prior art, It was confirmed that the PET resin thus produced had a melting temperature that was 5 ° C or more higher than that of the polyester resin according to the prior art.

In the present invention, the diol component may further include other diol components in addition to the cyclohexanedimethanol. The 'other diol component' means a diol component other than the cyclohexane dimethanol, and may be, for example, an aliphatic diol, an aromatic diol, or a mixture thereof.

The aromatic diol may include an aromatic diol compound having 8 to 40 carbon atoms, preferably 8 to 33 carbon atoms. Examples of such aromatic diol compounds include polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) Propane, polyoxypropylene- (2.2) -Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (2.3) Bis (4-hydroxyphenyl) propane, polyoxypropylene- (6) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- Propylene, (3,3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (3.0) Ethylene oxide and / or propylene oxide-added bisphenol A derivatives such as 2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene- (6) -2,2-bis (4-hydroxyphenyl) (Polyoxyethylene- (n) -2,2-bis (4-hydroxyphenyl) (N) -2,2-bis (4-hydroxyphenyl) propane or polyoxypropylene- (n) -polyoxyethylene- (n) Phenyl) propane. However, the specific examples of the aromatic diol compound are not limited thereto. Here, n represents the number of polyoxyethylene or polyoxypropylene units.

The aliphatic diol may include an aliphatic diol compound having 2 to 20 carbon atoms, preferably 2 to 12 carbon atoms. Examples of such aliphatic diol compounds include ethylene glycol, diethylene glycol, triethylene glycol, propanediol (such as 1,2-propanediol and 1,3-propanediol), 1,4-butanediol, pentanediol, 1,6-hexanediol), neopentyl glycol (2,2-dimethyl-1,3-propanediol), 1,2-cyclohexanediol, 1,4-cyclohexanediol, Branched or cyclic aliphatic diol components such as methanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexanedimethanol and tetramethyl cyclobutane diol. Specific examples of the aliphatic diol compound are limited thereto It is not.

As described above, a slurry mixture containing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing cyclohexanedimethanol and other diol compounds in a certain ratio is subjected to an esterification reaction and a polycondensation reaction It is crystallized and solid-state polymerization is carried out to produce a polyester resin.

The molar ratio of the dicarboxylic acid component to the diol component in the esterification reaction may be from 1: 1.05 to 1: 3.0, and preferably from 1: 1.05 to 1: 1.5.

The esterification reaction may be carried out at a pressure of from 0 to 10.0 kg / cm 2 and at a temperature of from 150 to 330 ° C. At this time, the esterification reaction conditions can be appropriately controlled according to the specific properties of the polyester to be produced, the mole ratio of the dicarboxylic acid component to the glycol, or the process conditions. A preferable example of the esterification reaction conditions is a pressure of 0 to 5.0 kg / cm 2, more preferably 0.1 to 3.0 kg / cm 2, and a temperature condition of 200 to 330 ° C, and more preferably 230 to 280 ° C.

The esterification reaction may be carried out using an esterification catalyst containing at least one compound selected from the group consisting of a zinc compound, a magnesium compound, an antimony compound and a titanium compound.

For example, in the method for producing a polyester resin according to the present invention, an esterification reaction catalyst of 1 to 500 ppm based on the central metal atom may be used as the final resin. Specific examples of the zinc-based compound include zinc acetate, zinc acetate dihydrate, zinc chloride, zinc sulfate, zinc sulfide, zinc carbonate, zinc citrate, zinc gluconate, and mixtures thereof.

The polycondensation reaction may further include adding at least one catalyst compound selected from the group consisting of a titanium compound, a germanium compound, an antimony compound, an aluminum compound, and a tin compound. Accordingly, the polyester resin produced according to the present invention may contain a polycondensation catalyst in an amount of 1 to 500 ppm based on the central metal atom in the whole resin.

Examples of the titanium compound include tetraethyl titanate, acetyl tripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, polybutyl titanate, 2-ethylhexyl titanate, octyleneglycol titanate, lactate titanate , Triethanolamine titanate, acetylacetonate titanate, ethylacetoacetic ester titanate, isostearyl titanate, titanium dioxide, titanium dioxide / silicon dioxide copolymer, and titanium dioxide / zirconium dioxide copolymer

Examples of the germanium compound include germanium dioxide (GeO ₂ ), germanium tetrachloride (GeCl ₄ ), germanium ethyleneglycoxide, germanium acetate, and copolymers thereof , Mixtures thereof, and the like. Preferably, germanium dioxide can be used, and both germanium dioxide can be crystalline or amorphous, and glycol solubility can also be used.

Meanwhile, a phosphorus stabilizer may be used in the synthesis of the polyester resin according to the present invention. Specifically, the polyester stabilizer may further include a step of adding a phosphorus stabilizer to the esterification reaction or the polycondensation reaction.

Specific examples of the phosphorus stabilizer include phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate, or a mixture of two or more thereof.

Further, in the process of synthesizing the polyester resin according to the present invention, a cobalt compound may be used in order to improve the color during the production of the polyester resin, and the cobalt compound may be used in an amount of 10 to 40 ppm ), Preferably 25 to 35 ppm. When the content of the cobalt compound is less than 10 ppm, the color b value can be increased (a kind of coloring catalyst), and when it exceeds 40 ppm, the production cost can be disadvantageous, and the color L and the color b can be darkened .

Although not limited to these cobalt compounds, it is preferred to use cobalt acetate.

In the present invention, the solid state polymerization may be performed at a temperature of 195 to 230 ° C, a pressure of 0.2 to 2 torr or a nitrogen atmosphere after crystallization in an air atmosphere at a reaction temperature of 170 to 185 ° C, for example.

The polyester resin produced through the above process can be prepared so as to facilitate solid phase polymerization even when the crystallization degree is sufficiently lowered within a range where the thermal property is maintained at a certain level by increasing the melting temperature by 5 ° C or more than the conventional low crystalline polyester resin have.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

Manufacturing example

A batch type polymerization reactor was used as the melt polymerization reactor used in the production of the polyester resin. The reactor contained one esterification reactor, one polycondensation reactor, and a reactor equipped with a cutting system. The esterification reaction was carried out for 3 to 4 hours, The polycondensation reaction was carried out for 2 to 3 hours and the temperature was raised to 285 DEG C while the pressure was reduced so that the final degree of vacuum was 1.0 torr or less to prepare a polyester resin. In the solid state polymerization reactor, a batch type reactor in which solid phase polymerization was carried out at a reaction temperature of 225 ° C. and a pressure of 0.4 torr or less for 10 hours was used.

Example  One

A diol compound consisting of 95 mol% of ethylene glycol and 5 mol% of 1,4-cyclohexanedimethanol was mixed in a molar ratio of 1.2 to the dicarboxylic acid compound consisting of 98.5 mol% of terephthalic acid and 1.5 mol% of isophthalic acid as main raw materials The slurry was prepared, and 640 ppm of catalyst antimony triacetate dissolved in ethylene glycol in an amount of 5 wt% based on the total weight of the polyester resin finally produced was added to the slurry. Then, the mixture was introduced into an esterification reactor, , The reaction was carried out while slowly raising the temperature to 255 캜 while stirring at 120 rpm.

When water outflowed from the esterification reaction was discharged out of the system, 200 ppm of triethyl phosphate (TEP) and 160 ppm of cobalt acetate as a coloring agent were added as a stabilizer. After stirring for 10 minutes, the contents were transferred to a polycondensation reactor.

Thereafter, the internal temperature was raised from 250 ° C to 280 ° C, and the pressure was gradually reduced from atmospheric pressure to 0.1 torr over 1 hour, and subjected to polycondensation reaction under high vacuum until the desired intrinsic viscosity was reached.

The molten chips thus cut are transferred to a solid phase polymerization reactor through a crystallizer having an air atmosphere at a temperature of 170 to 185 ° C to carry out a solid phase polymerization reaction at a temperature of 195 to 230 ° C and a pressure of 0.2 to 2 torr or under a nitrogen atmosphere, To prepare an ester resin.

Example  2

A polyester resin was prepared in the same manner as in Example 1, except that terephthalic acid was used in an amount of 97 mol% and isophthalic acid was used in an amount of 3 mol%.

Example  3

The procedure of Example 1 was repeated except that terephthalic acid was used in an amount of 95 mol%, isophthalic acid was used in an amount of 5 mol%, ethylene glycol was used in an amount of 97 mol%, and 1,4-cyclohexane dimethanol was used in an amount of 3 mol% Resin.

Example  4

The procedure of Example 1 was repeated except that terephthalic acid was used in an amount of 97 mol%, isophthalic acid was used in an amount of 3 mol%, ethylene glycol was used in an amount of 97 mol%, and 1,4-cyclohexane dimethanol was used in an amount of 3 mol% Resin.

Example  5

The procedure of Example 1 was repeated except that terephthalic acid was used in an amount of 99 mol%, isophthalic acid was used in an amount of 1 mol%, ethylene glycol was used in an amount of 99 mol%, and 1,4-cyclohexane dimethanol was used in an amount of 1 mol% Resin.

Comparative Example  One

The procedure of Example 1 was repeated except that 2,000 ppm of diethylene glycol was used in addition to 100 mol% of ethylene glycol as the diol component, and terephthalic acid was adjusted to 97 mol% and isophthalic acid to 3 mol% To prepare an ester resin.

Comparative Example  2

A polyester resin was prepared in the same manner as in Example 1, except that 100 mol% of ethylene glycol was used as the diol component and 95 mol% of terephthalic acid and 5 mol% of isophthalic acid was used in Example 1.

Comparative Example  3

A polyester resin was prepared in the same manner as in Example 1, except that 100 mol% of ethylene glycol was used as the diol component and 93 mol% of terephthalic acid and 7 mol% of isophthalic acid was used in Example 1.

Comparative Example  4

The procedure of Example 1 was repeated except that 100 mol% of terephthalic acid was used as the dicarboxylic acid component and that 93 mol% of ethylene glycol and 7 mol% of 1,4-cyclohexanedimethanol were used. To prepare an ester resin.

Comparative Example  5

The procedure of Example 1 was repeated except for using terephthalic acid as a dicarboxylic acid component in an amount of 100 mol% and controlling the amount of ethylene glycol to 95 mol% and 1,4-cyclohexanedimethanol to 5 mol% To prepare an ester resin.

The compositions used in the above Examples and Comparative Examples are summarized in Table 1 below.

Experimental Example

The thermal properties of the polyester resins prepared according to the Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 2 below.

[Measurement method of thermal property]

The thermal properties of the pellet sample (5 mg) were measured using a differential scanning calorimeter (DSC). (3) quenching at a rate of 80 DEG C / min to 30 DEG C; (4) heating at 30 DEG C for 3 minutes; (6) confirming the melting temperature (Tm) in the endothermic curve to be confirmed, (7) dissolving at 300 DEG C for 3 minutes, (8) heating at 300 DEG C for 3 minutes, (9) The crystallization temperature and the crystallization energy in the exothermic curve to be confirmed were confirmed while cooling at 30 DEG C / min at a rate of 10 DEG C / min.

Referring to Table 2, in the case where isophthalic acid is used alone as a comonomer in the polymerization composition of the copolyester, crystallization temperature and crystallization energy are lowered as the copolymerization ratio is higher, and the crystallinity is lowered sufficiently. However, (Comparative Examples 1 to 3). However, when 1,4-cyclohexanedimethanol was used alone as a comonomer, the crystallization temperature also tended to increase (Comparative Examples 4 and 5).

However, when the comonomer was used in combination with isophthalic acid and 1,4-cyclohexanedimethanol, the thermal properties showed different patterns. In other words, the crystallization energy of Tcc was greatly decreased, but the content of isophthalic acid and 1,4-cyclohexanedimethanol was decreased in the case of melting temperature, (Examples 4 and 5) When the melt temperature is controlled to be in the range of 1: 0.8 to 1: 1.2 molar ratio (Examples 4 and 5), the melting temperature is increased by 5 ° C or more over the conventional low crystalline polyester resin It was confirmed that a low crystalline polyester resin having a sufficiently low crystallinity was produced.

The preferred embodiments of the present invention have been described in detail above. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (3)

The esterification reaction and the polycondensation reaction are carried out by using a dicarboxylic acid component containing terephthalic acid and a diol component containing ethylene glycol, wherein the dicarboxylic acid component is obtained by reacting isophthalic acid with respect to the total dicarboxylic acid component 1 to 5 mol% of 1,4-cyclohexanedimethanol as the diol component, and 1 to 5 mol% of 1,4-cyclohexanedimethanol as the diol component based on the total diol component, to obtain a polyester resin A process for producing
Wherein the polyester resin has a cold crystallization temperature (Tcc) of 160 DEG C or less and a melting temperature (Tm) of 235 DEG C or more.
delete The method according to claim 1,
Wherein the solid state polymerization is carried out at a temperature of 195 to 230 DEG C, a pressure of 0.2 to 2 torr or a nitrogen atmosphere after crystallization in an air atmosphere at a reaction temperature of 170 to 185 DEG C.