KR20180046117A - Method of manufacturing biodegradable polyester resin - Google Patents

Abstract

The present invention relates to a method of producing a biodegradable polyester resin, comprising the steps of: (1) mixing an aliphatic dihydroxyl compound, an aliphatic dicarboxylic acid compound and an aromatic dicarboxylic acid compound to prepare slurry; (2) performing an esterification process on the slurry under an absolute pressure ranging from 1.5 bar to 4 bar to obtain an esterified reaction product; and (3) performing a condensation polymerization reaction process on the esterified reaction product. According to the present invention, the method of producing a biodegradable polyester resin minimizes the loss rate of the aliphatic dihydroxyl compound lost into an effluent and is able to inhibit the generation of by-products such as tetrahydrofuran (THF) by comprising the step of performing the esterification process under pressure.

Description

TECHNICAL FIELD The present invention relates to a method for producing biodegradable polyester resin,

The present invention relates to a process for producing a biodegradable polyester resin, and more particularly to a process for esterifying a biodegradable polyester resin under a pressure of 1.5 to 4 bar (absolute pressure), thereby minimizing the loss rate of an aliphatic dihydroxy compound And by-products such as tetrahydrofuran (THF) in the presence of an acid catalyst.

BACKGROUND ART Resin molded articles molded from aromatic polyester resins such as polyethylene terephthalate and polybutylene terephthalate are used in various fields such as beverage bottles, packaging films, textile products and electronic products due to their light specific gravity, excellent strength and transparency. However, these polyester products are becoming serious environmental problems after disposal.

In order to solve the above problems, studies have been made on aliphatic polyester resins having biodegradability. However, the aliphatic polyester resin has a disadvantage in that it has excellent biodegradability but lacks mechanical properties. Accordingly, in order to compensate the mechanical strength of the aliphatic polyester resin, there has been developed a method for producing a biodegradable resin in the form of an aliphatic-aromatic copolymer synthesized by incorporating an aromatic monomer during the production of the resin.

Poly (butylene adipate-co-terephthalate) (PBAT) is a typical biodegradable resin in the form of an aliphatic-aromatic copolymer. A commonly used aromatic monomer in PBAT is dimethyl terephthalate (DMT). The DMT has an advantage that the reaction can be easily conducted at a reaction temperature of 200 ° C or lower. However, there is a problem that the cost burden is large due to the high price.

Accordingly, efforts have been made to produce copolymers using aromatic monomers lower in cost than DMT. As a representative example, a method of using purified terephthalic acid (PTA), an aromatic dicarboxylic acid, in the synthesis reaction of a copolymer has been proposed.

For example, in Patent Document 1 (US 8,614,280 B2), terephthalic acid, adipic acid, 1,4-butanediol and glycerol are physically mixed, and further 1,4-butanediol and tetrabutylorthotitanate (TBOT) Is subjected to an esterification reaction at a temperature of 240 DEG C, a residence time of 1.5 hours and a pressure of 0.85 bar, and then subjected to pre-condensation, polycondensation and chain extension to prepare PBAT.

However, according to the above-mentioned embodiment, 1,4-butanediol (BDO) is a major component of tetrahydrofuran (THF) due to high acid value of terephthalic acid and low solubility in the esterification reaction at a high temperature ) Is caused to occur. Accordingly, in consideration of the loss ratio of 1,4-butanediol by the side reaction, the 1,4-butanediol is used in a molar ratio of 2 times or more with respect to the total amount of terephthalic acid and adipic acid. Part of the 1,4-butanediol charged in such an excess amount is converted into THF as described above, but is also contained in the effluent under the reduced pressure and high temperature conditions to escape from the reactor. The loss ratio of 1,4-butanediol to the effluent is also 10% Respectively. In this case, there is a disadvantage that 1,4-butanediol should be recycled by a special recovery equipment in order to recycle the expensive 1,4-butanediol.

As another conventional method for producing the PBAT, Patent Document 2 (Korean Patent Laid-Open Publication No. 10-2014-0018468) discloses a process for producing PBAT by reacting 1,4-butanediol with adipic acid, tetrabutyl titanate, triphenyl phosphate, glycerin Is subjected to a primary esterification reaction, terephthalic acid is sequentially added and added to the reactor to carry out a secondary esterification reaction, and then a polycondensation reaction is carried out to prepare PBAT. In this case, the primary and secondary It is stated that the acetylation reaction is carried out at atmospheric pressure (1 bar).

Patent Document 2 discloses that the THF conversion of 1,4-butanediol can be reduced by side reactions by increasing the solubility of terephthalic acid by the above method. However, the effect of suppressing the side reaction is still insufficient, and the problem of the 1,4-butanediol loss which is contained in the effluent and escaped from the reactor has not been solved.

That is, in the method of performing the esterification reaction under reduced pressure as in Patent Document 1, or performing the esterification reaction under atmospheric pressure as in Patent Document 2, the generation of THF by side reaction and the loss of 1,4-butanediol It is difficult to solve the problem, and it is necessary to study biodegradable polyester resin polymerization technology which can solve such problems.

US 8614280 B2 US 1020140018468 A

The present invention relates to a process for producing a biodegradable polyester (hereinafter abbreviated as " biodegradable polyester ") capable of minimizing the loss rate of an aliphatic dihydroxy compound to an effluent and suppressing the generation of by-products such as THF by performing an esterification reaction under a pressure of 1.5 to 4 bar To provide a method for producing a resin.

Disclosure of the Invention In order to solve the above problems, the present invention provides a process for producing a slurry, comprising: (1) mixing an aliphatic dihydroxy compound, an aliphatic dicarboxylic acid compound and an aromatic dicarboxylic acid compound to prepare a slurry; (2) esterifying the slurry under a pressure of from 1.5 to 4 bar (absolute pressure); And (3) polycondensation of the esterification reaction product. The present invention also provides a method for producing a biodegradable polyester resin.

The slurry may have a solid content of 40 to 90% by weight. In the step (1), the slurry may contain the aliphatic dihydroxy compound, the aliphatic dicarboxylic acid compound, and the aromatic dicarboxylic acid compound at 25 to 80 ° C For 30 minutes to 3 hours.

Preferably, the aliphatic dihydroxy compound may be 1,4-butanediol, and the aromatic dicarboxylic acid compound may be terephthalic acid (PTA).

The content of the aliphatic dihydroxy compound may be 1.3 to 1.7 moles based on 1 mole of the total amount of the aliphatic and aromatic dicarboxylic acid compounds.

In the step (2), an additive including at least one selected from the group consisting of a catalyst, a heat stabilizer and a branching agent may be further added to the slurry, and the esterification reaction may be performed under a pressurized condition.

The additive may include a catalyst and a heat stabilizer, and the weight ratio of the catalyst to the heat stabilizer (catalyst / thermal stabilizer) may be 1.5 to 5.5.

The thermal stabilizer may include one or more selected from the group consisting of phosphorous acid, organic phosphites, and organic phosphates.

The branching agent may be a trifunctional or multivalent alcohol branching agent having 3 to 6 carbon atoms, and the amount of the branching agent may be 0.095 to 0.23% by weight based on the weight of the condensation polymerization product.

The method for producing a biodegradable polyester resin according to the present invention may further comprise the step of subjecting the condensation polymerization product produced according to the step (3) to a chain extension reaction.

According to the process for producing a biodegradable polyester resin of the present invention, the esterification reaction is carried out under a pressurizing condition in the range of 1.5 to 4 bar (absolute pressure), thereby increasing the solubility of the aromatic dicarboxylic acid compound and accelerating the reaction rate of the reaction and effluent discharge . Thus, in the esterification reaction, the side reaction in which the aliphatic dihydroxy compound is converted into a by-product such as THF can be suppressed, and the loss rate of the aliphatic dihydroxy compound included in the effluent can be minimized. Therefore, according to the present invention, the use amount of the aliphatic dihydroxy compound can be reduced.

For example, when terephthalic acid is used as the aromatic dicarboxylic acid compound and 1,4-butanediol is used as the aliphatic dihydroxy compound, the side reaction is inhibited and the production rate of THF is reduced when the esterification reaction is conducted under the pressurized condition . In addition, since the loss rate of 1,4-butanediol escaped in the effluent is also significantly reduced, there is no need for a separate recycling facility for recovering the expensive 1,4-butanediol.

The present invention relates to (1) a process for producing a slurry by mixing an aliphatic dihydroxy compound, an aliphatic dicarboxylic acid compound and an aromatic dicarboxylic acid compound; (2) esterifying the slurry under a pressure of from 1.5 to 4 bar (absolute pressure); And (3) subjecting the esterification reaction product to polycondensation. The present invention also relates to a method for producing a biodegradable polyester resin.

A method of manufacturing a biodegradable polyester resin according to an embodiment of the present invention will be described step by step.

(1) Slurry preparation step

This step is a step of preparing a slurry by mixing an aliphatic dihydroxy compound, an aliphatic dicarboxylic acid compound and an aromatic dicarboxylic acid compound.

The solid content of the slurry is preferably 40 to 90% by weight. Here, the term " slurry " refers to a suspension of high concentration in which the solid content is chemically or physically dispersed in the liquid, and the content of the solid content in the present invention is such that when the total weight of the slurry is 100 wt% And the weight% of the aromatic dicarboxylic acid compound. When the solid content is less than 40% by weight, it is difficult to continuously transfer the slurry prepared at a low point to the esterification reactor through a mono pump. On the other hand, when the content of the slurry exceeds 90% by weight, It may be difficult to manufacture.

In the present invention, the slurry may be prepared by stirring the aliphatic dihydroxy compound, the aliphatic dicarboxylic acid compound and the aromatic dicarboxylic acid compound at 25 to 80 ° C for 30 minutes to 3 hours, Is not particularly limited. By adjusting the temperature and time for the preparation of the slurry to the above-mentioned range, a slurry having a low fluidity and uniformly mixing the compounds can be prepared.

The aliphatic dihydroxy compound may be at least one selected from the group consisting of ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, Ethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, -Isobutyl-1,3-propanediol, and 2,2,4-trimethyl-1,6-hexanediol, preferably 1,4-butanediol.

The aliphatic dicarboxylic acid compound may be at least one selected from the group consisting of malonic acid, succinic acid, glutaric acid, 2-methylglutaric acid, 3-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, May include one or more selected from the group consisting of acid, dodecanedic acid, brassylic acid, tetradecanedic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid, maleic acid, itaconic acid and maleic acid, Preferably adipic acid.

The aromatic dicarboxylic acid compound may include at least one member selected from the group consisting of terephthalic acid, isophthalic acid, 2,6-naphthoic acid and 1,5-naphthoic acid, and preferably terephthalic acid (terephthalic acid, PTA).

The content of the aliphatic dihydroxy compound may be 1.3 to 1.7 moles based on 1 mole of the total amount of the aliphatic and aromatic dicarboxylic acid compounds. This is achieved by reducing the side reaction by performing the esterification reaction step under pressure in accordance with the present invention, thereby significantly lowering the amount of the aliphatic dihydroxy compound to be used compared to the conventional reduced pressure method.

(2) Esterification reaction step

This step is an esterification reaction of the slurry under a pressure of 1.5 to 4 bar (absolute pressure). At this time, the pressurization may be performed using an inert gas containing nitrogen (N ₂ ), argon (Ar) and a mixed gas thereof, or a mixed gas of the inert gas and CO ₂ . By using such an inert gas pressure method, the solubility of the aromatic dicarboxylic acid compound can be increased, and the reaction rate of the reaction and effluent discharge can be accelerated. Thus, the side reaction can be suppressed and the loss rate of the aliphatic dihydroxy compound to the effluent can be minimized.

When the pressure is less than 1.5 bar during the esterification reaction, a large amount of by-products due to the side reaction occurs during the esterification reaction, and the loss rate of the aliphatic dihydroxy compound to the effluent is high. Particularly, when terephthalic acid is used as the aromatic dicarboxylic acid compound and 1,4-butanediol is used as the aliphatic dihydroxy compound under such a low pressure as described above, the high acid value of terephthalic acid in the esterification reaction at a high temperature (> 200 ° C) Butanediol is converted to THF due to low solubility, and the loss of unreacted 1,4-butanediol escaped from the effluent is increased to separate the 1,4-butanediol loss Recycling facilities are required. On the other hand, when the pressure is higher than 4 bar during the esterification reaction, there arises a problem that the esterification conversion rate is lowered.

In the step (2), an additive including at least one selected from the group consisting of a catalyst, a heat stabilizer and a branching agent may be further added to the slurry, and the esterification reaction may be performed under a pressurized condition.

The additive may comprise a catalyst and a heat stabilizer, wherein the weight ratio of catalyst input to the heat stabilizer (catalyst / thermal stabilizer) may be 1.5 to 5.5. When the ratio is less than 1.5, the biodegradable polyester resin finally produced has excellent chromaticity, but the reaction rate is slow and the productivity may be deteriorated. On the other hand, when the ratio is more than 5.5, the reaction rate is fast, but the aliphatic / aromatic polyester resin There is a possibility that the thermal stability and the chromaticity become poor.

The catalyst serves to accelerate the esterification reaction. Examples of the catalyst include calcium acetate, manganese acetate, magnesium acetate, zinc acetate, monobutyltin oxide, dibutyltin oxide, dibutyltin dichloride, monobutylhydroxy tin oxide, Octyltin, tetrabutyltin, tetraphenyltin, triethyltitanate, acetyltripropyltitanate, tetramethyltitanate, tetrapropyltitanate, tetraisopropyltitanate, tetra n-butyltitanate and tetra (2-ethyl Hexyl) titanate, and the like.

The heat stabilizer is added to improve the thermal stability and chromaticity of the biodegradable polyester resin by suppressing the adverse reactions and side reactions that can be additionally promoted by the catalyst. The thermal stabilizer may include at least one member selected from the group consisting of phosphorous acid, organic phosphites and organic phosphates, preferably phosphorous acid, phosphonous acid, trimethyl phosphite, triethyl phosphite, Triphenyl phosphite, sodium phosphite, sodium hypophosphite, and triphenyl phosphate. These phosphates may be used alone or in combination of two or more thereof.

The branching agent may be an alcohol type branching agent of a short chain, which is used for obtaining a polymer of brenched by linking linear oligomers in the production of the polymer, and preferably a trifunctional or more It may be a polyhydric alcohol branching agent. Specifically, the branching agent may include one or more selected from the group consisting of glycerol, pentaerythritol, and trimethylolpropane. The illustrated branching agents are preferable because they have three or more hydroxyl groups (-OH) and do not have a carboxy (-COOH) group as a functional group because they can help lower the acid value of the finally produced biodegradable polyester resin.

The amount of the branching agent is preferably 0.095 to 0.23% by weight based on the weight of the polycondensation product. If the amount is less than 0.095% by weight, it may be difficult to obtain a biodegradable polyester resin having a desired molecular weight. On the other hand, if the amount is more than 0.23% by weight, local gelation may proceed and the final properties of the biodegradable polyester resin may be affected have.

(3) Concentration polymerization step

This step is a step of polycondensation of the esterification reaction product obtained in the step (2).

The polycondensation reaction is carried out for the purpose of increasing the molecular weight of the esterification reaction product (oligomer), and may be carried out in a temperature range of 220 to 260 ° C under a vacuum of 0.1 to 2 Torr for 40 to 300 minutes. If the polymerization temperature is lower than 220 deg. C, the reactivity of the oligomer is lowered, and the condensation polymerization time may increase. On the other hand, if the temperature exceeds 260 deg. C, pyrolysis of the resulting polymer may occur. When the polymerization pressure is higher than 2 Torr, the removal of the by-product (for example, 1,4-butanediol) for carrying out the condensation polymerization reaction is not advantageous, It is practically difficult to lower it below Torr.

As the condensation polymerization proceeds, unreacted raw materials (unreacted monomers) and low molecular weight oligomers are removed, and oligomers are condensation-polymerized to obtain high molecular weight biodegradable polyester resins.

In the meantime, the method for producing a biodegradable polyester resin according to the present invention may further comprise a chain extension reaction of the condensation polymerization product produced in the step (3). At this time, the polycondensation reaction product may be directly chain-extended in a molten state, or may be chain-elongated after being pelletized and remelted.

Thus, when the chain extension reaction is performed through the steps (1) to (3), each of these processes can be performed in any one of a batch mode, a continuous mode and a semi-continuous mode. In this case, when the semi-continuous method is used, the steps (1) to (3) may be carried out continuously, and the chain extension reaction step may be carried out batchwise.

This chain extension reaction can be carried out without limitation according to a known method, for example, by a method of introducing a chain extender after the condensation polymerization and reacting.

Examples of the chain extender include polyisocyanate compounds such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate Isocyanate, and triphenylmethane triisocyanate may be used.

The content of the chain extender may be 0.01 to 5 parts by weight based on 100 parts by weight of the polycondensation product, and the biodegradable resin having desired physical properties can be obtained by increasing the molecular weight through the chain extension reaction.

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

Example 1

(18.06 mol) of terephthalic acid (PTA), 3.22 kg (22.04 mol) of adipic acid (AA) and 5.42 kg (60.14 mol) of 1,4-butanediol (BDO) were stirred in a slurry tank at 30 DEG C for 1 hour, . At this time, the solid content was 53.4 wt%.

Subsequently, the slurry was transferred to an esterification reactor through a mono pump, to which 3.4 g of tetra n-butyl titanate as a catalyst, 0.87 g of phosphorous acid as a heat stabilizer, and 10.4 g of glycerol as a branching agent were further added. Then, the internal pressure of the reactor was pressurized to 2 bar (absolute pressure) by using nitrogen (N ₂ ) gas, and the esterification reaction was carried out for 260 minutes while maintaining the pressure at 2 bar while raising the temperature to 240 ° C. At this time, the produced water flowed out of the esterification reactor. At this time, the input amount of BDO (60.14 mol) is 1.5 mol when the total amount of TPA and AA (40.1 mol) is converted into 1 mol.

After the completion of the esterification reaction, the esterification reaction product was transferred to a condensation polymerization reactor, and condensation polymerization was carried out for 170 minutes while gradually reducing pressure from 240 ° C. to 1 torr (0.0013 bar). As a result, 8.25 kg of polybutylene adipate-co-terephthalate (PBAT) (I-1) which is a biodegradable polyester resin was prepared.

Example 2

PBAT (I-2) was prepared in the same manner as in Example 1 except that the amount of BDO was adjusted to 4.70 kg (52.13 mol). At this time, the amount of BDO (52.13 mol) was 1.3 mol when the total amount (40.1 mol) of TPA and AA was converted to 1 mol, the solid content was 56.96 wt%, and the weight of PBAT Is 8.21 kg.

Example 3

The slurry prepared in Example 1 was transferred to an esterification reactor through a mono pump, and tetra n-butyl titanate, phosphorous acid and glycerol were added thereto in the same amount as in Example 1. Then, the internal pressure was maintained at 4 bar (absolute pressure) until the temperature of the reactor rose to 220 ° C., the pressure was increased to 2 bar (absolute pressure) while the temperature was raised to 240 ° C., Pressure. At this time, it took about 180 minutes until the temperature of the reactor reached 220 ° C and then 40 minutes until reaching 240 ° C. After reaching 240 ° C, the esterification reaction was conducted for 40 minutes under a pressure of 2 bar (absolute pressure) .

After completion of the esterification reaction, PBAT (I-3) was prepared in the same manner as in Example 1.

Example 4

PBAT (I-4) was prepared in the same manner as in Example 1 except that 1.3 g of triphenylphosphate was used instead of 0.87 g of phosphorous acid as the heat stabilizer.

Example 5

After completion of the condensation polymerization according to Example 1, the strand discharged from the reactor was cooled in water and then pelletized with a pelletizer to prepare a PBAT (I-1) chip .

Subsequently, 1 kg of the PBAT (I-1) chip and 5 g of hexamethylene diisocyanate as a chain extender were mixed in a super mixer, and this was mixed with a twin-screw extruder (product of SM Plate, L / D: 40/1, ) And chain extension reaction was carried out at 180 ° C for 1.5 minutes. Thereafter, the strand discharged from the twin-screw extruder was cooled in water and then pelletized with a pelletizer to prepare a PBAT (II-1) chip.

Examples 6 to 8

Example 6 was prepared in the same manner as in Example 2 except that PBAT (I-2) prepared in Example 2 was used, PBAT (I-3) prepared in Example 7 was used in Example 7, (II-2) chip, a PBAT (II-3) chip and a PBAT (II-4) chip were obtained in the same manner as in Example 5 except that the prepared PBAT (I- respectively.

Example 9

1 kg of molten PBAT (I-1) in which the condensation polymerization reaction was completed according to Example 1 was quantitatively injected through a gear pump into a twin-screw extruder (product of SM Platte, L / D: 40/1, diameter: 65 mm) And 4 g of hexamethylene diisocyanate was supplied to the inlet through a metering pump, and then a chain extension reaction was carried out at 190 DEG C for 1.5 minutes in a twin-screw extruder. Thereafter, the strand discharged from the twin-screw extruder was cooled in water and then pelletized with a pelletizer to prepare a PBAT (II-5) chip.

Examples 10 to 12

Example 10 is PBAT (I-3) prepared in accordance with Example 3, Example 11 is PBAT (I-3) prepared in accordance with Example 3, Example 12 is PBAT (II-6) chip, a PBAT (II-7) chip and a PBAT (II-8) chip in the same manner as in Example 9 except that the prepared PBAT (I- respectively.

Comparative Example 1

To the esterification reactor, 5.42 kg (60.14 mol) of BDO, 3.22 kg (22.04 mol) of AA, 3.4 g of tetra n-butyl titanate as a catalyst, 0.87 g of phosphorous acid as a heat stabilizer and 10.4 g of glycerol as a branching agent were mixed, Followed by primary esterification at 200 < 0 > C. At this time, the primary ester reaction time was 77 minutes, and the pressure inside the esterification reactor was controlled at 1 bar.

Then, the internal temperature of the esterification reactor was raised to 230 ° C., and the secondary esterification reaction was carried out while adding the same amount of PTA four times every 15 minutes. In this case, the total amount of the PTA was 3 kg (18.06 mol), the internal temperature of the reactor was raised to 240 ° C during the third injection of the PTA, and then the secondary esterification The reaction was further advanced. The total secondary esterification reaction time was 90 minutes, and the pressure was maintained at 1 bar at atmospheric pressure as in the case of the primary ester reaction.

After completion of the esterification reaction, the esterification reaction product was transferred to a polycondensation reactor and subjected to polycondensation reaction for 180 minutes at 240 ° C. and gradually reduced to 1 torr (0.0013 bar) to produce PBAT (I-5) .

Comparative Example 2, Comparative Example 4 and Comparative Example 5

PBAT (I-6), PBAT (I-8) and PBAT (I-9) were obtained in the same manner as in Example 1 except that the pressure inside the esterification reactor was adjusted as shown in Table 1 below. .

Comparative Example 3

PBAT (I-7) was prepared in the same manner as in Comparative Example 2, except that the amount of BDO was adjusted to 7.95 kg (88.22 mol). At this time, the charged amount (88.22 mol) of BDO was 2.2 mol when the total amount (40.1 mol) of TPA and AA was converted to 1 mol, and the solid content was 43.90% by weight.

<Evaluation method>

1. Conversion rate (%)

In this evaluation method, the conversion rate represents the conversion rate of the esterification reaction. The conversion rate is determined by the acid value of the oligomer produced after the esterification reaction, Quot; acid value measurement &quot; method, and evaluated by the ratio of the oligomeric acid to the theoretical acid value.

2. THF production rate and BDO loss rate

First, in the esterification reactions according to Examples 1 to 12 and Comparative Examples 1 to 5, the content of THF and BDO contained in water (effluent) flowing out of the esterification reactor was measured by gas chromatography . Then, the ratio of the THF and BDO contents contained in the effluent was calculated on the basis of the BDO input amount, and evaluated by the THF generation rate and the BDO loss rate, respectively.

3. Melt index (MI)

The melt index was measured according to ASTM D1238. Specifically, the amount (g) flowing out through an orifice (radius: 2 mm, length: 8 mm) for 10 minutes under a temperature of 190 캜 and a load of 2.16 kg was measured by a melt index (MI).

However, in the case of Examples 1 to 4 and Comparative Examples 1 to 5, after the end of the condensation polymerization, the strand discharged from the reactor was cooled in water and then pelletized with a pelletizer to obtain PBAT (I-1 to I- and each of the chips was used to measure the melt index. In the case of Examples 5 to 12, the melt index was measured using PBAT (II-1 to II-8) chips prepared according to the respective methods.

4. Chromaticity

PBAT (I-1 to I-9) chips (see Evaluation Method 3) prepared from PBAT (I-1 to I-9) according to Examples 1 to 4 and Comparative Examples 1 to 5, The chromaticities L * and b * of the PBAT (II-1 to II-8) chips prepared according to Examples 5 to 12 were measured using a Konica Minolta colorimeter to CIE-L * a * b * (CIE 1976) Respectively. The "L *" value indicates the brightness, and the larger the value, the brighter. The "b *" value indicates the degree of yellow color, and the higher the value, the higher the degree of yellowness.

5. Acid value measurement

PBAT (I-1 to I-9) chips (see Evaluation Method 3) prepared from PBAT (I-1 to I-9) according to Examples 1 to 4 and Comparative Examples 1 to 5, 0.5 g of the PBAT (II-1 to II-8) chip prepared according to Examples 5 to 12 was dissolved in 30 ml of chloroform at 25 ^° C, and further 20 ml of ethyl alcohol was added thereto to prepare a solution After the preparation, the solution was titrated with 0.1N KOH in an autotitrator to determine the acid value.

Esterification reaction pressure BDO
Molar ratio ^* Conversion Rate THF
Generation rate BDO
Loss rate MI
(g / 10 min) Acid value
(mgKOH / g) Chromaticity
(L * / b *) Example 1 2 bar 1.5 moles 97% 5.7% 0.5% 30 0.80 85 / 11.0 Example 2 2 bar 1.3 moles 95% 6.6% 0.4% 29 0.88 85 / 12.0 Example 3 4 → 2bar 1.5 moles 97% 5.3% 0.3% 31 0.75 84 / 9.9 Example 4 2 bar 1.5 moles 97% 6.0% 0.4% 28 0.91 86 / 10.0 Example 5 2 bar 1.5 moles 97% 5.7% 0.5% 3.8 0.79 87 / 9.5 Example 6 2 bar 1.3 moles 95% 6.6% 0.4% 3.6 0.88 87 / 10.2 Example 7 4 → 2bar 1.5 moles 97% 5.3% 0.3% 3.9 0.74 86 / 8.7 Example 8 2 bar 1.5 moles 97% 6.0% 0.4% 3.4 0.90 88 / 8.8 Example 9 2 bar 1.5 moles 97% 5.7% 0.5% 3.6 0.80 87 / 10.0 Example 10 2 bar 1.3 moles 95% 6.6% 0.4% 3.4 0.86 87 / 11.0 Example 11 4 → 2bar 1.5 moles 97% 5.3% 0.3% 3.5 0.73 86 / 9.2 Example 12 2 bar 1.5 moles 97% 6.0% 0.4% 3.2 0.88 87 / 9.5 Comparative Example 1 1bar
(Atmospheric pressure) 1.5 moles 97% 10.5% 14.3% 32 0.87 81 / 10.0 Comparative Example 2 0.85 bar
(Decompression) 1.5 moles 96% 6.6% 9.9% 28 0.83 84 / 11.0 Comparative Example 3 0.85 bar
(Decompression) 2.2 moles 98% 9.1% 11.7% 30 0.73 84 / 17.0 Comparative Example 4 1.2bar 1.5 moles 97% 8.5% 5.0% 32 0.92 83 / 12.0 Comparative Example 5 5 bar 1.5 moles 85% 4.0% 0.3% 80 1.2 84 / 15.0

The results are shown in Table 1. The results are shown in Table 1. Comparative Example 1 wherein the esterification reaction was carried out under the pressure of 1.5 to 4 bar and the esterification reaction was carried out under reduced pressure, To 4, the THF production rate was found to be equal to or less than that, and the BDO loss rate was remarkably lowered. Comparing Example 1 and Comparative Example 2 in which PBAT was produced under the same conditions except for the esterification reaction pressure, when the esterification reaction was carried out under a pressurized state according to the present invention, not only the BDO loss ratio but also the THF generation rate , Respectively.

In the case of Comparative Example 5 in which the esterification reaction was carried out at a high pressure of 5 bar, although the THF production rate and the BDO loss rate were lowered, the esterification conversion conversion rate was remarkably low, the melt index and the acid value were excessively high, It can be seen that the whiteness is low due to the high value.

In addition, PBAT (II) of Examples 5 to 12 in which the condensation-condensed PBAT (I) was directly subjected to chain extension reaction in a molten state or pelletized and then remelted to react with the chain extender In the case of a chip, the low solubility index can be confirmed by excellent processability, and it shows low acid value, and it can be confirmed that the hydrolysis resistance is excellent, and it is confirmed that the whiteness is excellent when the b * value is low have.

Therefore, in the case of PBAT that has undergone the chain extension reaction process, excellent physical properties can be secured in the development of a low-cost film application by blending with a different biodegradable resin (for example, starch, polylactic acid or polybutylene succinate) have.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Should be construed as being included in the scope of the present invention.

Claims (9)

(1) preparing a slurry by mixing an aliphatic dihydroxy compound, an aliphatic dicarboxylic acid compound, and an aromatic dicarboxylic acid compound;
(2) esterifying the slurry under a pressure of from 1.5 to 4 bar (absolute pressure); And
(3) A method for producing a biodegradable polyester resin, which comprises polycondensing the esterification reaction product. The method according to claim 1,
Wherein the solid content of the slurry is 40 to 90% by weight. The method according to claim 1,
Wherein the aliphatic dihydroxy compound is 1,4-butanediol, and the aromatic dicarboxylic acid compound is terephthalic acid (PTA). The method according to claim 1,
Wherein the content of the aliphatic dihydroxy compound is 1.3 to 1.7 moles relative to 1 mole of the total amount of the aliphatic and aromatic dicarboxylic acid compounds. The method according to claim 1,
Wherein the step (2) further comprises adding an additive containing at least one selected from the group consisting of a catalyst, a heat stabilizer and a branching agent to the slurry, and then carrying out an esterification reaction under a pressurized condition A method for producing a resin. 6. The method of claim 5,
Wherein the additive comprises a catalyst and a heat stabilizer, and the catalyst weight ratio (catalyst / thermal stabilizer) to the heat stabilizer is 1.5 to 5.5. 6. The method of claim 5,
Wherein the thermal stabilizer comprises at least one selected from the group consisting of phosphorous acid, organic phosphites, and organic phosphates. 6. The method of claim 5,
Wherein the branching agent is a trifunctional or more polyfunctional alcohol branching agent having 3 to 6 carbon atoms and the amount of the branching agent is 0.095 to 0.23 wt% based on the weight of the polycondensation reaction product. The method according to claim 1,
Further comprising the step of subjecting the condensation polymerization product produced according to the step (3) to a chain extension reaction.