KR840002023B1 - Process for preparing poly(ethylene terephthalate - Google Patents

Abstract

Polyethylene terephthalater was prepared from ethylene glycol and terephthalic acid by esterification under atmospheric press., and polymerization under low press. and elevated temp. condition. Glycol was recovered from the vapor generated in the polymerization step using a spray condensation with ethylene glycol containing water, and was continuously recycled to the esterification reactor. The mole ratio of glycol to TPA in the esterification process was 1.5-4.0, and the esterification temp. was 280-315≰C. Temp. conditions in the preliminary and final polymerization steps were 25-300≰C and 270- 305≰C, respectively.

Description

Continuous production process of poly (ethylene terephthalate)

A schematic production process flow diagram illustrating an apparatus for use in the method of the present invention.

The present invention relates to a continuous direct esterification and polymerization process for preparing fiber forming polyesters from ethylene glycol and terephthalic acid, and in particular to the continuous recovery and reuse of ethylene glycol evaporated in the polymerization reaction.

내지 285

C, 약 5 내지 60mmHg의 절대압력하에서 행해지고, 형성된 예비중합체가 최종 중합기로 이동하여 또 다른 중합이 초기 중합시와 유사한 온도와 약 0.5 내지 10mmHg의 저압에서 수행되어 섬유 또는 필라멘트로 압출하기 위한 폴리에스테르를 제조하는 방법을 예시하고 잇다. 이 히진스의 특허는 중합으로부터 회수된 에틸렌 글리콜이 해로운 영향없이 직접 에스테르화 반응에 직접 사용될 수 있음을 교시하고 있다.Continuous methods for the direct esterification of terephthalic acid and ethylene glycol are described in US Pat. No. 3,590,072 to Keybourne III, US Pat. No. 3,676,485 to Lewis et al, Balint et al. al., US Pat. No. 3,697,579, Chapman et al., and US Pat. No. 3,927,982. Terephthal esters are continuously converted to high molecular weight polyesters by condensation polymerization under low absolute pressure conditions. Higins, U.S. Pat.

To 285

C, polyester under pressure of about 5 to 60 mmHg, and the prepolymer formed is transferred to the final polymerizer so that another polymerization is carried out at a similar temperature as the initial polymerization and at a low pressure of about 0.5 to 10 mmHg to extrude into fibers or filaments It illustrates a method for producing. This Higins patent teaches that ethylene glycol recovered from polymerization can be used directly in the direct esterification reaction without deleterious effects.

In the continuous process of this type, steam consisting mainly of ethylene glycol but containing about 2 to 35% by weight of water vapor is formed upon polymerization. It is important to recover ethylene glycol for reuse.

The vapor from the polymerization vessel can be condensed and recycled for use in feeding directly to the esterification reaction without removing water. However, since the capacity and efficiency of the vacuum pump member for maintaining the low pressure used for polymerization depend on the load of uncondensed steam, a highly efficient method is required to condense this steam.

The present invention provides a direct esterification of terephthalic acid with excess ethylene glycol, preferably at atmospheric pressure, to produce an esterification product of low polymerization degree, to polymerize at elevated temperature under reduced pressure to produce a prepolymer, and further to lower temperature under elevated pressure. Polymerizing to produce a melt-spinable polymer, wherein poly (ethylene terephthalate) is prepared by a continuous process in which the vapor produced in the course of the polymerization is treated to recover glycol and recycle the glycol to esterification. The method of claim 1, wherein the vapor is sprayed with ethylene glycol in a spray condenser under low pressure of the polymerization, and also low water content by adding low water moisture content ethylene glycol to the ethylene glycol liquid feed to spray in the spray condenser. And spray From the supply body to be sprayed from both axial and by being taken out by the glycol is recycled to the esterification provides a continuous method of producing poly (ethylene terephthalate), characterized by maintaining the low pressure.

It is preferred that the vapor from each polymerizer is sprayed in a spray condenser operated at the low pressure of each polymerizer, adding fresh ethylene glycol to the process by addition to the feed for the spray condenser receiving the vapor from the final polymer. Preferably, the ethylene glycol liquid is recovered from this feed and added to the feed for the spray condenser that receives the vapor from the prepolymer, and the ethylene glycol liquid is recovered from the latter vapor to recycle to esterification.

It is also preferred to add this slurry of additives in fresh ethylene glycol to the esterification product to which fresh ethylene glycol is fed to the polymerization.

C 내지 315

C와 대략 대기압하에서 반응생성물에서 가열해서 테레프탈산을 에스테르화하고 2 내지 10의 평균 중합도를 갖는 에스테르반응 생성물을 형성하며, 에스테르 생성물을 연속중합기에서 250

C 내지 300

C, 낮은 절대압력에서 가열하여 예비중합체를 형성하며, 이 예비중합체를 최종 중합기에서 270

내지 305

C, 실제로 낮은 절대압력에서 가열하여 필라멘트로 방사하기 위한 중합체를 형성하는, 이러한 형태인 것이 바람직하다.The continuous direct esterification and polymerization process provided a feed of ethylene glycol and terephthalic acid in a molar ratio of 1.5-4.0 (preferably 1.8-3.0) glycol to terephthalic acid of 1.0.

C to 315

Heating at C and the reaction product at about atmospheric pressure to esterify terephthalic acid to form an esterification product having an average degree of polymerization of 2 to 10, the ester product being 250 in a continuous polymerizer.

C to 300

C, heated at low absolute pressure to form a prepolymer, which was

To 305

C, it is preferred in this form to form a polymer for actually spinning at filament by heating at low absolute pressure.

Improvement of the present invention

(A) In a continuous polymerizer, steam of ethylene glycol and water is led from this polymerizer to the spray condenser under this pressure and water of not more than 10% by weight (preferably between 2 and 7% by weight) is allowed to condense almost all of the vapors. These vapors are sprayed together with the containing ethylene glycol solution and used to atomize these vapors and contain up to 10% by weight (preferably between 2 and 7% by weight) of water for reaction with terephthalic acid to form esterification products. Ethylene glycol liquid containing up to 3% by weight of water is mixed with the bicondensate to form an ethylene glycol liquid,

(B) directing the vapor of ethylene glycol and water in the final polymerizer from this final polymerizer to the spray condenser at this pressure, and spraying the water with an ethylene glycol solution containing no more than 3% by weight of water to condense almost all of these vapors; And an ethylene glycol solution containing up to 1% by weight of water to form an ethylene glycol solution containing up to 3% by weight of water for use in spraying these vapors and for mixing with the condensate formed in the condenser system. The condensate is mixed and added to this polymer, which contains up to 1% by weight of water, at about 0.4 to 1.15 moles of glycol per mole of ethylene terephthalate,

(C) Continuous transfer of ethylene glycol liquid from the final condenser system (b) to the system (a) and from the system (a) to an esterification reaction at a rate determined by the rate at which ethylene glycol is used in the esterification reaction. It is preferable to include the.

Ethylene glycol liquids containing up to 1% by weight of water used in the final condenser system (b) are usually pure glycols, ie, glycols which have not been used previously and have less than 0.1% water.

Conventional additives may be mixed with the polymer. They are preferably added to the feed to the continuous polymerizer as a suspension or solution of an additive in ethylene glycol containing up to 1% by weight of water. About 0.25 glycols per mole of ethylene terephthalate in the polymer in which the ethylene glycol demineralizer TiO ₂ slurry containing 1 wt% or less of water is mixed with the ester product prior to feeding the ester product into the continuous polymerizer, and the glycol addition rate to the ester product is formed. It is preferable that it is from 0.60 mol. The total percentage of addition of ethylene glycol to the ester product and also to the final condenser can be adjusted to about 1 mole of glycol per mole of ethylene terephthalate in the polymer formed. The TiO ₂ slurry mixed with the ester product may comprise one or more other additives, such as dyeing control agents, color inhibitors, dyeing materials or crosslinking additives.

The present invention is preferably operated to recycle the esterification reaction from the polymerizer condenser system at a rate of about 0.75 to 1.50 moles of glycol per mole of ethylene terephthalate in the polymer in which the ethylene glycol is formed.

As shown in the figure, terephthalic acid is fed by a screw feeder 12 from bin 10 to mixing tank 14. Ethylene glycol is supplied from the glycol tank 16 to the mixing tank 14 at a ratio of 1.5 to 4.0 (preferably 1.8 to 3.0) moles of glycol per 1.0 mole of terephthalic acid. These reactants are mixed to form a slurry by mixer 18, which is driven by motor 20.

내지 315

C, 대략 대기압하에서 반응 생성물에서 가열되어 테레프탈산을 에스테르화하고 2 내지 10의 평균 중합도를 갖는 에스테르반응 생성물을 형성한다. 반응 증기가 글리콜 회수 시스템(glycol recovery system) 26에 도입되며 이 글리콜 회수 시스템은 글리콜로부터 반응의 유기부산물과 물을 제거하는데 적당한 어떤 장치일 수 있다. 회수된 글리콜은 글리콜 탱크 16에 재순환된다.Slurry pump 22 feeds the slurry directly to esterification reactor 24, which may be of the type described in US Pat. No. 3,927,982 to Chapman dd et al. The reactants are about 280

To 315

C, heated in the reaction product at about atmospheric pressure to esterify terephthalic acid and form an esterification product having an average degree of polymerization of 2 to 10. The reaction vapor is introduced into a glycol recovery system 26 which may be any device suitable for removing the organic byproducts and water of the reaction from the glycol. The recovered glycol is recycled to glycol tank 16.

The liquid ester reaction product is withdrawn from the reactor continuously and pumped to a continuous polymerizer 30 through a transfer line 28 to a stuffer pump 32. Additives of the type indicated below may be mixed with the ester reaction product passing through the conveying pipe. For this purpose, a slurry or solution of one or more additives in ethylene glycol is introduced into the conveying pipe at a rate determined by passage of the ester reaction product through a meter pump 34.

Mixer 36 and bulge 38 having a total time of 1 to 10 minutes are used to thoroughly mix the additives.

It is preferred to use an amount of ethylene glycol which provides a glycol addition rate of about 0.25 to 0.60 moles of glycol per mole of ethylene terephthalate in the polymer produced. Additives that may be introduced include the following.

(1) deglossants such as TiO ₂

(2) polymerization catalysts such as antimony glycolate, antimony oxide, titanium compounds

(3) color inhibitors, such as phosphoric acid and trikenyl phosphite

(4) dyeing regulators such as 1,3-dihydroxyethyl-5- (sodium silo) -isophthalate, dihydroxyethyl adipate, dihydroxyethyl glutarate, adipic acid, glutaric acid

(5) Dyeing materials such as pigments, dyes, fluorescent brighteners, cobalt coloring concentrates

(6) Crosslinking Additives such as Trimethylolpropane Viscosity forming compounds, such as tetracus (2-hydroxyethyl) silicate, can be added to the prepolymers that are produced continuously.

내지 305

C의 온도를 유지하도록 가열된다. 약 12 내지 29의 상대점도(HRV)를 갖는 중합체가 섬유용 필라멘트로 방사하기 위해 나사식 펌프(screw pump) 48을 통해 배출된다. 이 방법은 산업용 필라멘트로 방사하기 위한 보다 높은 상대점도를 형성하도록 조작될 수 있다.The continuous polymerizer 30 may be an upflow prepolymerizer of the type described in US Patent No. 2,727,882 to Vodonik. The feed passes upwards into the polymerization tower through back-pressure valve 40 and heater 42. The prepolymer having a relative viscosity (HRV) of about 5 to 8 is recovered near the screen of the polymerization tower and passed through transfer line 44 to finish polymerizer 46. The finished polymerizer may be of the type described in Kilpatrick, US Pat. No. 3,248,180. The finished polymerizer is 270

To 305

Heated to maintain a temperature of C. Polymers having a relative viscosity (HRV) of about 12 to 29 are discharged through a screw pump 48 to spin into filaments for fibers. This method can be manipulated to form higher relative viscosities for spinning into industrial filaments.

C이하, 바람직하게는 50

C이하의 온도이어야 한다. 이 냉각된 혼합물은 분무헤드(spray head) 61에 의해 응축기내 증기에 분무된다. 진공 파이프(vaccum line) 62는 진공펌핑부재(도시안됨)까지 달하여 있어 5 내지 60mmHg (0.67 내지 800 kpa)의 절대 압력으로 응축기와 연속 종합기를 유지시킨다. 2 내지 7중량%의 물을 함유하는 글리콜 분무는 증기를 응축하는데 매우 효과적이며 진공펌핑부재에 대한 부하를 최소로 한다. 또한 이 분무는 방해를 야기하는 표면상의 고체 퇴직을 방지한다.The steam from the continuous polymerizer 30 is led to the condenser 52 from the government of the tower by means of a vapor line 50. The vapor contains ethylene glycol, about 2 to 35% by weight of water, about 1 to 4% by weight of organic matter which forms a solid at low temperatures, and a small amount of other organic impurities. The condensate from this steam flows into a hot well 54 where it is mixed with ethylene glycol containing less than 3% by weight of water to produce less than 10% by weight (preferably between 2 and 7% by weight) of water. It forms a containing mixture which is used as a spray in the condenser. Pump 57 feeds this mixture to the government of the condenser via pipe 58 and cooler 60. In order to operate under a small pressure, the cooled spray mixture is 60

C or less, preferably 50

It should be below C. This cooled mixture is sprayed onto the vapor in the condenser by spray head 61. The vacuum line 62 extends up to the vacuum pumping member (not shown) to maintain the condenser and continuous synthesizer at an absolute pressure of 5 to 60 mmHg (0.67 to 800 kpa). Glycol sprays containing 2 to 7% by weight of water are very effective at condensing the vapor and minimize the load on the vacuum pumping member. This spray also prevents solid retirement on the surface causing interference.

C이하, 바람직하게는 50

C이하의 온도이어야만 한다. 냉각된 혼합물은 분무헤드 78이 의해 응축기내 증기에 분무된다. 진공파이프 80은 진공펌핑부재(도시안됨)까지 달하여 있고 연속중합기내 압력보다 낮은 0.5 내지 10mmHg (0.07-1.3 kpa)의 절대압력으로 응축기와 완성 중합기를 유지시킨다.Vapor from the finished polymerizer 46 is sent from the finished polymerizer to the condenser 66 through the steam pipe 64. The condensate from this steam flows into the heat tank 68 where it is mixed with ethylene glycol from glycolpipe 70 containing up to 1% by weight of water to form a mixture containing up to 3% by weight of water and used as a spray in the condenser. do. Low water content is required because the pressure in the finished polymerizer and its condenser 66 is lower than the pressure in the continuous polymerizer and its condenser 52. The pump 72 feeds the mixture to the government of condenser 66 through pipe 74 and cooler 76. To operate at the desired pressure, the cooled mixture is 60

C or less, preferably 50

It must be below C. The cooled mixture is sprayed onto the vapor in the condenser by sprayhead 78. Vacuum pipe 80 extends to the vacuum pumping member (not shown) and maintains the condenser and finished polymerizer at an absolute pressure of 0.5 to 10 mmHg (0.07-1.3 kpa) below the pressure in the continuous polymerizer.

Ethylene glycol liquid containing less than 3% by weight of water flows from the finished heat tank 68 through heat 82 to heat tank 54. Ethylene glycol liquid containing not more than 10% by weight (preferably 2 to 7% by weight) of water is transferred from the heat tank 54 to the glycol tank 16 via pipe 58, recycle pump 84 and pipe 86.

The transfer rate is determined by the rate at which ethylene glycol from glycol tank 16 is used in the esterification reaction. The rate of movement is controlled by valve 88, which may be a conventional automatic valve operated by a level sensing device 90. The addition rate of glycol to finisher hotwell 68 is similarly determined by the level of liquid in heat tank 54.

Ethylene glycol liquids containing up to 1% by weight of water used in the finished condenser system should be added at a rate of about 0.4 to 1.15 moles of glycol per mole of ethylene terephthalate in the polymer formed. The process is preferably operated to recycle to the esterification reaction from the polymerizer condenser system at a rate of about 0.75 to 1.50 moles of glycol per mole of ethylene glycol in the polymer in which the ethylene glycol is formed.

Example 1

Using a device of the type as shown in the figure, 545 kg (1,200 lbs.) Of terephthalic acid per hour were reacted with ethylene glycol to form an oligomer having a relative viscosity (HRV) of 2.8, which reached up to the continuous polymerizer. Pumped through the transfer pipe.

Pure glycol and the additive were injected into this oligomer as follows.

(1) 17.3 kg (38.2 lbs) glycol per hour containing 1% by weight of Sb ₂ O ₃ polymerization catalyst,

(2) 7.45 kg (16.4 lbs) glycol containing 20% TiO ₂ deglossant,

(3) 24,6 kg (54.3 lbs) glycol to react with free carboxyl terminus,

This oligomer, glycol and additive were passed through the mixer under a pressure of 35 psig (341 kpag) and the mixture was kept under pressure in the star for about 5 minutes. The mixture was passed through a pressure reducing valve, another 25.4 kg (56 lbs) per pure glycol hour was added and the mixture was introduced into the upflow continuous polymerizer. A prepolymer was formed having a relative viscosity (HRV) of 5.6 and free carboxyl containing 98 equivalents per million grams. This prepolymer was transferred through a transfer pipe to the finished polymerizer, where a polymer having a relative viscosity of 21.3 and about 28 equivalents of free carboxyl per million grams was formed. The polymer was melt spun into filaments at an average rate of 630 kg (1388 lbs) per hour, leaving the ring polymerizer.

Filament yarns containing 0.9% by weight of diethyl glycol were prepared.

Vapor from a continuous polymerizer containing 87.2 wt% ethylene glycol and 12.8 wt% water was transferred into the spray condenser at 276 ° C. at 68.5 kg (151 lbs.) Per 24 mHg (3.2 kpa) pressure. This vapor was sprayed with 6% water recycled from the heat tank and 0.757 m 3 (200 gallons) of 94% ethylene glycol per minute. This spray was maintained at about 45.5 ° C. by passing through a cooler between the heat tank and the spray condenser. This spray and condensed vapor were transferred from the condenser to the heat tank where they were mixed with 146 kg (322 pounds) per hour of ethylene glycol per hour containing 0.95% water from the heat tank of the finished condenser. Ethylene glycol containing 6% water was recycled from the heat tank of the condenser condenser at a rate of 214.5 kg (473 pounds) per hour for use in reaction with terephthalic acid to form oligomers.

The vapor from the finished polymer, containing 91.1% ethylene glycol and 8.9% water, was transferred into the finished spray condenser at 9.0 kg (19.9 lbs) per hour at 291 ° C. and 1.3 mm Hg (0.17 kpa) pressure. This vapor was sprayed with ethylene glycol containing 0.95% water from a heat tank of 0.757 m 3 (200 gallons) of bicondenser per hour. This mass was maintained at about 31 ° C. by passing a cooler between the heat tank and the spray condenser. This spray and the condensed vapor were transferred from the condenser to the finisher heat tank where they were mixed with 137 kg (303 pounds) of pure ethylene glycol per hour containing about 0.1% water. Ethylene glycol 0.95% water flowed from the finisher heat tank to the heat tank of the continuous condenser condenser at a rate of 146 kg (322 pounds) per hour. The feed rate of pure ethylene glycol is controlled by a control valve which maintains a constant level in the heat tank of the condenser condenser in response to the level signal.

C에서 측정되었고 동일한 단위로 표시되었다.Relative viscosity (HRV) is the ratio of the viscosity of a solution of 0.8 gm of polyester dissolved in sulfuric acid-containing hexafluoroisopropane hexafluoroisopropane containing 80 ppm sulfuric acid to its own viscosity at 10 ml room temperature, both 25 on the capillary viscometer

Measured at C and indicated in the same units.

Claims (1)

Terephthalic acid is esterified directly with excess ethylene glycol under atmospheric pressure in an ester reactor to produce a low polymerization ester reaction product, and polymerized at elevated temperature under reduced pressure in a continuous polymerizer to produce a prepolymer, followed by lower pressure in the final polymerizer. In the method of final synthesis at elevated temperature to form a melt-spinable polymer, (A) In a continuous polymerizer, mixed steam consisting of ethylene glycol and water is led to a spray condenser under the same pressure, and the mixed distillation steam is almost completely condensed. Spray di-mixed steam together with an ethylene glycol solution containing not more than 10% by weight of water, and use the spray condensate obtained again for spraying, and not more than 10% by weight of water so as to be suitable for recovery and use in the ester reaction. To make ethylene glycol containing 3% by weight Ethylene glycol solution containing water is mixed with this spray condensate, (b) in the final polymerizer to lead the mixed steam consisting of ethylene glycol and water to the spray condenser under the same pressure and to condense the mixed steam almost completely. Spray this mixed vapor together with an ethylene glycol liquid containing 3% by weight or less of water, and use the spray condensate obtained here for spraying again and mix with the spray condensate formed in the spray condenser system described above. In order to make an ethylene glycol liquid containing not more than 3% by weight of water, an ethylene glycol solution containing not more than 1% by weight of water is mixed with the spray condensate, and the glycol containing not more than 1% by weight of water is To the polymer produced is added about 0.4 to 1.15 moles of glycol per mole of ethylene terephthalate, and (c) from the final spray condenser system (b) to the system (a). In addition, from the system (a) to the esterification reaction, the ethylene glycol liquid is continuously transferred at a rate determined by the ratio of ethylene glycol used in the esterification reaction to recover the glycol from the vapor generated during the polymerization process, A process for producing poly (ethylene terephthalate) by a continuous method of recycling the ester to esterification.

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