KR20210067082A - Polyester with improved transparency and thermal properties and manufacturing method the same - Google Patents

Abstract

The present invention relates to a polyester prepared by using isophthalic acid as a dicarboxylic acid ingredient and having improved transparency and showing a minimized decrease in glass transition temperature, and a method for preparing the same. The present invention provides a polyester represented by chemical formula 1, which includes a dicarboxylic acid ingredient derived from terephthalic acid and isophthalic acid and a diol ingredient derived from bis(2-hydroxyethyl) terephthalate, and is amorphous with no melting point. In the chemical formula 1, each of n and m is a real number representing a mole fraction, 0 < n < 1, and m is 1 - n.

Description

Polyester with improved transparency and thermal properties and manufacturing method the same

The present invention relates to a polyester and a method for producing the same, and more particularly, to a polyester having improved transparency and thermal properties and a method for producing the same.

Polyester has excellent physical and chemical properties and is widely used in fibers, films, containers, and tire cords. Among polyesters, polyethylene terephthalate (PET) is a well-known resin. In particular, it is transparent depending on processing conditions, has excellent strength and rigidity, and is environmentally friendly, so it is most often used as a container such as a bottle, and is widely applied to stretched films and sheets.

Since PET is a semi-crystalline resin, it may exist in an amorphous or semi-crystalline form depending on its processing and heat history. When processed into an amorphous form, it has a transparent characteristic, but when processed into a semi-crystalline form, if the crystal grain size is less than 500 nm, it may appear partially transparent or translucent, and as the size of the crystal grain increases, it may appear opaque.

In general, PET uses the DMT method for polymerization using dimethyl terephthalate (DMT) and ethylene glycol (EG) as monomers, and TPA for polymerization using terephthalic acid (TPA) and EG as monomers. There is a law. In commercial manufacturing facilities, TPA is often referred to as purified terephthalic acid (PTA), but here PTA will be referred to as the same term as TPA. These methods form bis(2-hydroxyehtyl) terephthalate (BHET) and its oligomers as reaction intermediates, and their polycondensation reaction produces resins. Currently, most PET commercial products are manufactured. The facility is using the TPA method.

On the other hand, isophthalic acid (IPA) is the most easily applied comonomer to improve the processability and transparency of PET. Currently, most beverages or bottled water bottles, except for juice and sports drinks, are IPA-copolymerized PET. When IPA is applied as a comonomer of PET, the polymer chain regularity in PET is limited. Due to this, it exhibits a relatively slow crystal formation rate compared to Homo-PET during processing, which has good transparency and lowers the melting point, so that the processing temperature can also be lowered. When IPA is copolymerized over a certain amount, PET becomes an amorphous resin, not semi-crystalline, and in the case of an amorphous resin, extrusion and injection can always be transparently performed without being affected by processing conditions. However, there is a disadvantage in that the glass transition temperature (Tg) decreases when IPA is used to show the characteristics of the amorphous resin.

Another monomer that can improve the transparency of PET is diethylene glycol (DEG), but in the case of DEG, the decrease in the glass transition temperature (Tg) is greater than when IPA is used, and the ether chain of DEG during processing. Thermal oxidative decomposition by (ether chain) is easy, so that the amount of acetaldehyde (AA) generated can be increased. Even if DEG is not used as a comonomer, DEG is inevitably produced through the reaction between EGs due to the high polymerization temperature of EG used as a monomer in the PET polymerization process.

A decrease in the glass transition temperature (Tg) causes a problem of lowering the heat resistance of a final product such as a bottle, and an increase in the amount of AA causes a problem of causing off-flavor in PET, which is mainly used as a beverage container.

In particular, when PET is used as a bottle of food and beverage, there is a case in which beverages are stored in a hot storage room in winter. At this time, the temperature of the hot storage room is usually maintained at a temperature of 50 to 65 ° C. Therefore, a bottle capable of sufficiently withstanding this temperature is required. In addition, when PET products processed into food and beverages and other molded products are shipped and moved in a shipping container, if the temperature is 35℃, the inside temperature of the container without thermal insulation rises to 60℃, and if it passes near the equator, it will be higher. Since there is a possibility of increasing the temperature, the resin used must have appropriate glass transition temperature characteristics.

On the other hand, there is an attempt to utilize BHET, a reaction intermediate, as a raw material in the manufacture of PET. For example, Japanese Patent Registration No. 4260719 discloses a technique for polymerizing polyester having a high shrinkage rate by using BHET and IPA as raw materials. However, the BHET mentioned in this patent appears to be an oligomer as an intermediate in PET polymerization, and the problem due to a decrease in the glass transition temperature is not recognized.

In addition, Japanese Patent Registration No. 3684348 discloses a method for manufacturing PET having excellent properties using BHET, but does not mention the glass transition temperature lowering problem caused by the use of BHET.

An object of the present invention is to provide a polyester and a method for producing the same, which minimizes a decrease in glass transition temperature (Tg) while improving transparency in preparing a polyester including isophthalic acid as a dicarboxylic acid component.

In order to solve the above problems, the present invention includes a dicarboxylic acid component derived from terephthalic acid and isophthalic acid, and a diol component derived from bis(2-hydroxyethyl) terephthalate, and has the following formula The polyester represented by 1 is provided.

[Formula 1]

In Formula 1, n and m are real numbers representing mole fractions, 0 < n < 1, and m is 1-n.

In addition, there is provided a method for preparing polyester by polymerizing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing bis(2-hydroxyethyl) terephthalate.

In addition, in the total content of the terephthalic acid, the isophthalic acid and the bis(2-hydroxyethyl) terephthalate, the isophthalic acid is 10 to 60 mol%, and the bis(2-hydroxyethyl) terephthalate is 1 to 60 mol% It provides a polyester manufacturing method, characterized in that used in the content.

Polyethylene terephthalate composed of terephthalic acid and ethylene glycol is a semi-crystalline resin, and may lose transparency due to crystal growth depending on molding conditions. The present invention uses isophthalic acid as a raw material in the existing polyethylene terephthalate composition in producing semi-crystalline or amorphous polyester, and in this case, diethylene glycol is produced by polymerization using bis (2-hydroxyethyl) terephthalate as a raw material. It is possible to provide a polyester capable of minimizing a decrease in the glass transition temperature (Tg) while improving transparency by reducing the probability and a method for manufacturing the same.

Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Accordingly, the configuration of the embodiment described in this specification is only the most preferred embodiment of the present invention, and the technical concept of the present invention It should be understood that not all ideas are represented, and there may be various equivalents and modifications that can be substituted for them at the time of filing the present application.

The present inventors have a problem in that when an attempt is made to improve processability and transparency by using isophthalic acid as a conventional dicarboxylic acid component in PET manufacturing, there is a problem in that the glass transition temperature decreases, so there is a limit to the application for beverages or bottled water. , as a result of repeated research, facing the situation that no technology to solve this problem is presented, bis(2-hydroxyethyl) terephthalate as a raw material along with isophthalic acid in the existing polyethylene terephthalate composition was added in a specific content range. It was confirmed that the decrease in the glass transition temperature can be minimized while improving the transparency by using polymerization, and the present invention was completed.

Accordingly, the present invention relates to an amorphous compound having a dicarboxylic acid component derived from terephthalic acid and isophthalic acid and a diol component derived from bis(2-hydroxyethyl) terephthalate, and having no melting temperature, represented by the following formula (1) Polyester is disclosed.

[Formula 1]

In Formula 1, n and m are real numbers representing mole fractions, 0 < n < 1, and m is 1-n.

The polyester according to the present invention is prepared by polymerizing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing bis(2-hydroxyethyl) terephthalate.

The preparation of the polyester according to the present invention includes, for example, mixing a dicarboxylic acid component containing terephthalic acid and isophthalic acid with a diol component containing bis(2-hydroxyethyl) terephthalate in a predetermined ratio to form a slurry reactant. ; esterifying the reactant; and carrying out a polycondensation reaction of the esterification reaction product. When ethylene glycol is used together with the bis(2-hydroxyethyl) terephthalate as a diol component, the polyester represented by the following formula (1) is prepared can be

[Formula 1]

In Formula 1, n and m are real numbers representing mole fractions, 0 < n < 1, and m is 1-n.

The polyester prepared according to the present invention has a glass transition temperature exceeding 70° C. and a melting temperature that does not appear in the DSC (Differential Scanning Calorimetry) analysis according to the method to be described later, as an amorphous, with improved transparency and a minimized glass transition temperature It exhibits characteristics with

In the present invention, the isophthalic acid is 60 mol% or less, preferably in the total content of the terephthalic acid, the isophthalic acid and the bis(2-hydroxyethyl) terephthalate, based on the repeating unit consisting of isophthalic acid in the polyester chain. It may be contained in a range of 10 to 60 mol% (0.1 ≤ n ≤ 0.6 in Formula 1).

The isophthalic acid is a monomer for imparting amorphous properties to PET, and is polymerized with ethylene glycol or bis(2-hydroxyethyl) terephthalate to exist in the form of Chemical Formula 1 in the main chain of the polymer. As the content of isophthalic acid increases, the glass transition temperature (Tg) and melting temperature (Tm) of the final polyester gradually decrease, and when the isophthalic acid content is 10 mol% or more, preferably 20 mol% or more, the melting temperature (Tm) may have amorphous characteristics that do not exist. When the content of isophthalic acid is 60 mol% or more, the portion of the diol that is insufficient compared to the dicarboxylic acid component of isophthalic acid during polymerization is filled by adding diols such as ethylene glycol to bis(2-hydroxyethyl) terephthalate. Should be. In this case, it may be difficult to realize the object of the present invention to suppress the generation of diethylene glycol during polymerization and to maintain the glass transition temperature of the polymerized product. In the case of diethylene glycol, the degree of reduction in the glass transition temperature is greater than when isophthalic acid is used, and the thermal oxidative decomposition by the ether chain of diethylene glycol during processing is easy, so the amount of acetaldehyde can be increased.

As such, a decrease in the glass transition temperature of the polyester causes a problem of lowering the heat resistance of a final product such as a bottle, and an increase in the amount of acetaldehyde generated causes an off-flavor in the polyester mainly used as a beverage container.

In the present invention, the dicarboxylic acid component other than the terephthalic acid and the isophthalic acid may include aromatic dicarboxylic acid and aliphatic dicarboxylic acid, and the aromatic dicarboxylic acid includes naphthalene dicarboxylic acid and diphenyl dicarboxylic acid. A single substance or a mixture thereof of aromatic dicarboxylic acids having 8 to 20 carbon atoms, preferably 8 to 14 carbon atoms, such as carboxylic acid, may be exemplified, but specific examples are not limited thereto, and the aliphatic dicarboxylic acid Examples include cyclohexanedicarboxylic acid, phthalic acid, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, fumaric acid, adipic acid, glutaric acid, azelaic acid, etc. aliphatic dicarboxylic acids having 4 to 20 carbon atoms, preferably 4 to 12 carbon atoms A single compound or a mixture thereof may be exemplified, but the specific example is not limited thereto. In addition, the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid may be mixed and used.

In the present invention, the glass transition temperature reduction of the final polyester is minimized by including bis(2-hydroxyethyl) terephthalate as a diol component.

The content of such bis(2-hydroxyethyl) terephthalate is based on a diol derived from bis(2-hydroxyethyl) terephthalate in the polyester chain, the terephthalic acid, the isophthalic acid and the bis(2-hydroxyethyl) It may be contained in the range of 60 mol% or less, preferably 10 to 60 mol%, and more preferably 35 to 60 mol% in the total terephthalate content. When the bis(2-hydroxyethyl) terephthalate content does not reach a certain level, the glass transition temperature is reduced, and when the content is excessive, it must be removed as ethylene glycol in the process, which is free ethylene glycol ) by suppressing the production of diethylene glycol by minimizing the content of the present invention does not meet the purpose of the present invention of improving transparency and minimizing the decrease in the glass transition temperature, and, in addition, the vapor of ethylene glycol, which is increased compared to the existing process, is removed under reduced pressure. is required, but it may overload the decompression equipment when removing the decompression.

In the present invention, the diol component other than the bis(2-hydroxyethyl) terephthalate may include an aromatic diol and an aliphatic diol, and the aromatic diol is polyoxyethylene-(a)-2,2-bis(4). -Hydroxyphenyl) propane, polyoxypropylene-(b)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene-(c)-polyoxyethylene-(d)-2,2-bis A single substance of aromatic diol having 8 to 40 carbon atoms, preferably 8 to 33 carbon atoms, such as (4-hydroxyphenyl) propane, or a mixture thereof may be exemplified, but specific examples are not limited thereto. Here, a, b, c, and d mean the number of polyoxyethylene or polyoxypropylene units. In addition, as the aliphatic diol, ethylene glycol, diethylene glycol, triethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, etc. having 2 to 20 carbon atoms, preferably A single compound of an aliphatic diol having 2 to 12 carbon atoms or a mixture thereof may be exemplified, but specific examples are not limited thereto.

Polyester production according to the present invention may be performed in the presence of a metal catalyst consisting of a titanium compound, an antimony compound, a germanium compound, an aluminum compound, a tin compound, or a mixture thereof in the esterification reaction and the polycondensation reaction, The catalyst may be added in an amount of 1 to 500 ppm based on the central metal atom compared to the polyester.

On the other hand, in the manufacturing process of the polyester according to the present invention, a phosphorus-based stabilizer may be used as a heat stabilizer, and thus, the step of adding a phosphorus-based stabilizer to the esterification reaction or the polycondensation reaction may be further included. Specific examples of the phosphorus-based stabilizer include phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphono acetate, or a mixture of two or more thereof.

In addition, in the manufacturing process of the polyester according to the present invention, a cobalt compound or a toner which is commonly used for the role of a colorant for color improvement when manufacturing the polyester may be used.

In the esterification reaction, the molar ratio of the dicarboxylic acid component and the diol component may be 1:1.05 to 1:3.0, preferably 1:1.05 to 1:1.5. In order to match the molar ratio, ethylene glycol may be additionally added, and ethylene glycol may be used as a solvent to dissolve a catalyst, a stabilizer, a colorant, and the like.

In the present invention, the esterification reaction may be performed at a pressure of 0 to 10 kg/cm 2 and a temperature of 150 to 330° C. In this case, it goes without saying that the esterification reaction conditions may be appropriately adjusted according to specific characteristics of the polyester, the molar ratio of the dicarboxylic acid component and the diol component, or process conditions. However, as a preferred example of the esterification reaction conditions, a pressure of 0 to 5.0 kg/cm 2 , more preferably 0.1 to 3.0 kg/cm 2 , and a temperature of 200 to 330° C., more preferably a temperature of 230 to 300° C. conditions can be carried out. At this time, it is preferable that water generated during the esterification reaction can be removed immediately.

Meanwhile, in the present invention, a slurry tank for preparing a slurry mixture containing the dicarboxylic acid component and the diol component in a certain ratio and a reactor in which the esterification reaction is performed are replaced with nitrogen in consideration of color improvement of the finally manufactured polyester It can be used under the specified conditions.

The polycondensation reaction in the present invention may be carried out at a temperature of 250 to 330 °C, preferably at a temperature of 270 to 310 °C, a pressure of 0.1 to 5 torr, preferably 1 to at a pressure of 0.5 to 2 torr. The reaction can be allowed to proceed under stirring for about 20 hours. In this case, it is preferable to immediately remove diols and by-products such as ethylene glycol generated by the polycondensation reaction.

In the present invention, the polyester in a molten state prepared through the esterification reaction and the polycondensation reaction may have an intrinsic viscosity (IV) of 0.45 to 0.90 dl/g, preferably 0.55 to 0.85 dl/g. The polyester prepolymer prepared with an intrinsic viscosity value within the above range may be manufactured as a liquid chip through a cutting machine, and the shape of the chip may be various, such as a cylinder, a sphere, and the like, and is not limited to a specific shape.

The polyester produced through the esterification reaction and the polycondensation reaction may increase intrinsic viscosity through solid-state polymerization, and the solid-state polymerization may be performed under a pressure condition of 0.2 to 2 torr or a nitrogen atmosphere at a reaction temperature of 190 to 240 ° C. can Polyester prepared through the solid-state polymerization may have an intrinsic viscosity of 0.60 to 1.10 dl/g, preferably 0.70 to 1.00 dl/g. However, in the present invention, when isophthalic acid is contained in a high content, it may exhibit an amorphous characteristic and proceed only to melt polymerization and not further proceed to solid-state polymerization.

Hereinafter, the present invention will be described in more detail through specific Preparation Examples, Examples and Comparative Examples.

manufacturing example

A batch-type polymerizer was used as a melt polymerizer used for producing the polyester resin, and the polymerizer includes a reactor equipped with one slurry tank, one esterification reactor, one polycondensation reactor, and a cutting system as a reactor. In this embodiment, a single batch type polymerization method is applied and a slurry tank is not used, but a semi batch type polymerization method may be applied using a slurry tank depending on the purpose of use. When the semi-batch type polymerization method is applied, a method of adding the monomer of the reactant to the slurry tank and then applying a temperature higher than the melting point of BHET to form a slurry can be adopted. It can also be fed into the reactor. The esterification reaction was carried out under conditions of a reactant temperature of 260° C. at a pressure of normal pressure to 2 bar, and the reaction was carried out for 2 to 7 hours while flowing out water, a by-product generated during the reaction, out of the system through a column and a condenser. After the esterification reaction was completed and the heat stabilizer was added before the polycondensation reaction was started, the mixture was stirred at atmospheric pressure for 10 minutes. Thereafter, the polycondensation reaction was carried out for 1.5 to 3 hours, and the temperature was raised to 280° C. while reducing the pressure so that the final degree of vacuum was 1.0 torr or less to prepare a polyester resin. In general, in the case of polyester used for bottles, it is common to obtain an intrinsic viscosity (IV) value of 0.55 dl/g or higher through melt polymerization and then 0.72 dl/g or higher through solid-state polymerization. In the case of polyester containing a high content of phthalic acid, since it exhibited amorphous characteristics and did not further proceed with solid-state polymerization, only melt polymerization was performed in this example.

Examples and Comparative Examples

The raw material was put into the esterification reactor with the composition shown in Table 1 below. Based on the total weight of the final polyester, 630 ppm (256 ppm of antimony element content) of antimony acetate, an antimony catalyst, was dissolved in ethylene glycol and then put into an esterification reactor, and triethylphosphonoacetate 145 ppm ( 20 ppm based on the elemental phosphorus content) was added before the esterification reaction was completed and the polycondensation reaction was started. After the polycondensation reaction, it was discharged and cut into chips to prepare a final polyester.

test example

DSC (Differential Scanning Calorimetry) analysis was performed and intrinsic viscosity and isophthalic acid content were measured for the polyesters prepared according to the Examples and Comparative Examples as follows, and the results are shown in Table 1 below.

[DSC analysis method]

For the prepared polyester chip sample (5 mg), the temperature was raised from 30°C to 300°C at a rate of 10°C/min, dissolved at 300°C for 3 minutes, cooled to 30°C at a rate of 80°C/min, and then cooled at 30°C for 3 minutes After maintaining, the glass transition temperature was checked while the temperature was raised to 300° C. at a rate of 10° C./min, and the melting temperature in the endothermic curve expressed at a temperature above the glass transition temperature was confirmed.

[Method for measuring intrinsic viscosity]

The intrinsic viscosity was measured according to ASTM D4603, and the intrinsic viscosity was measured for a chip sample (250 mg) using an automatic viscometer. Specifically, the sample was completely dissolved by heating in a dissolution bath at 120° C. for 20 minutes using 50 ml of phenol, and then cooled to room temperature. After the cooled solution was filtered through a mesh filter, about 15 ml of the solution was put into an automatic viscometer to measure intrinsic viscosity. Intrinsic viscosity is a factor that can represent the molecular weight of polyester, and in a linear polymer, the higher the intrinsic viscosity, the higher the polymerization degree.

[Method for measuring isophthalic acid content]

Content of the isophthalic acid structure manufactured polyester chain is ^{1 H-NMR (1H-Nuclear} Magnetic Resonance) was measured by dissolving the polyester in Deuterated Chloroform / Trifluoroacetic acid mixture solution of 0.5 wt% concentration in the Agilent DD2 500MHz Spectrometer was measured using

Referring to Table 1, as a result of thermal characteristic analysis using DSC analysis equipment, first, when isophthalic acid is used at a content level of 30 to 50 mol% (see Examples 1 and 2 and Comparative Example 1), crystals are formed and then melted No temperature was detected, indicating that the final produced polyester was amorphous. Here, when comparing Example 2 and Comparative Example 1 using the same content of isophthalic acid, the glass transition temperature (Tg) shows a difference of 5°C, which is bis(2-hydroxyethyl) terephthalate according to the present invention. It can be seen that the degree of decrease in the glass transition temperature is minimized by including the content level.

In addition, when all terephthalic acid as a dicarboxylic acid component is replaced with isophthalic acid (Example 1), the degree of decrease in the glass transition temperature and when the isophthalic acid content does not reach a certain level (Examples 3, 4 and Comparative Examples) 2) From the detection of the melting temperature, it can be confirmed that there is a specific content ratio of isophthalic acid that minimizes the decrease in the glass transition temperature while improving the transparency.

In addition, when comparing the degree of reduction of the glass transition temperature according to the change in the content of bis(2-hydroxyethyl) terephthalate when using isophthalic acid in the same content (Examples 2, 5 to 7), when the content is not too little or too much It is confirmed that the reduction in the glass transition temperature can be minimized.

On the other hand, it can be seen that when the content of isophthalic acid is excessive (Comparative Example 3), the sensitivity of the glass transition temperature (Tg) is further increased.

The preferred embodiment of the present invention has been described in detail above. The description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains will understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

Claims (3)

Polyester represented by the following formula (1), which contains a dicarboxylic acid component derived from terephthalic acid and isophthalic acid, and a diol component derived from bis(2-hydroxyethyl) terephthalate, and is an amorphous type having no melting temperature:
[Formula 1]

In Formula 1, n and m are real numbers representing mole fractions, 0 < n < 1, and m is 1-n. A method for producing polyester by polymerizing a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing bis(2-hydroxyethyl) terephthalate. 3. The method of claim 2,
Among the total contents of the terephthalic acid, the isophthalic acid and the bis(2-hydroxyethyl) terephthalate, the isophthalic acid is 10 to 60 mol%, and the bis(2-hydroxyethyl) terephthalate is 1 to 60 mol%. Polyester production method, characterized in that used.