JP3270338B2 - Polyester production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyester by a continuous melt polymerization method, and more particularly to a method for producing a polyester which is continuously produced by introducing an inert gas into a reactant transport pipe without using a solid-state polymerization method. It relates to a polymerization method.

[0002]

2. Description of the Related Art Polyesters represented by polyethylene terephthalate and polybutylene terephthalate have been widely used in various applications because of their excellent physical and chemical properties. In particular, fibers, films, and other molded products are excellent in mechanical properties such as strength and elastic modulus, heat resistance, and the like, and are therefore used as industrial fibers such as clothing and tire cords and engineering plastics.

In general, polyesters used for such various uses are produced by a direct polymerization method or a transesterification method. Here, the former direct polymerization method is a method in which a polyester precursor is formed by a direct esterification reaction between an acid component and a diol component, and then the polyester precursor is polycondensed under reduced pressure. On the other hand, the latter transesterification method is a method of producing a polyester precursor by subjecting a lower alkyl ester of an acid component and a diol to a transesterification reaction, and then subjecting the polyester precursor to polycondensation under reduced pressure.

Conventionally, the polymerization of polyester has been often carried out by a batch polymerization system. However, in order to make use of economies of scale and to produce polyester at a low cost, switching to a continuous polymerization system has been promoted. Some of the advantages are extremely large, such as a decrease in yield, an improvement in quality, a uniform degree of polymerization, and an operability factory.

However, since the polyester produced by the above-described method must be reacted at a high temperature for a long time in the polycondensation reaction, the obtained polyester may be colored or the molecular weight distribution range may be reduced. growing.
In addition, a decomposition reaction occurs and the amount of carboxyl end groups increases, so that there is a problem in hydrolysis resistance. Therefore, it is desired to produce at a high polymerization rate while shortening the residence time in the polymerization reaction tank as much as possible.

Based on such a viewpoint, many methods for shortening the time required for a polymerization reaction in a polymerization reaction tank have been proposed and put into practical use.

As one of such methods, there is a method in which a polyester having a low polymerization degree is obtained in a short time by melt polymerization, and then the polymerization degree is further increased by solid phase polymerization. However, this method consumes a large amount of energy and requires solid-state polymerization equipment, which increases equipment costs and is not preferable in terms of cost.

For these reasons, a method using a thin-film polymerization reactor has been proposed separately from the above-mentioned method. In this method, in order to rapidly separate and remove the by-product glycol In the polycondensation reaction, the reaction was a thin layer, it has been made to perform vigorous stirring. Thus, a method is employed in which the reaction area is increased by increasing the evaporation area of the reactant and facilitating the evaporation.

[0009] Conventionally, the thin film polymerization reaction tank has a reaction method in which a stirring blade is provided to agitate the reactant to increase an evaporation area, and the reactant is allowed to flow naturally using a wet wall. A method of increasing the evaporation area, a method of forming the reaction product into a thin filament, and increasing an evaporation area of by-products are used.

First, regarding the reaction method described above, many reaction vessels having stirring blades devised so that the stirring efficiency is higher and the free surface area of the reactant can be increased by each manufacturer have been proposed and are commercially available. . However, these reaction vessels require a large amount of stirring power and are not preferable in terms of energy consumption. In addition, a dead space is easily generated, and a reactant that stays in the dead space for a long time has a problem that the quality is degraded by a thermal decomposition reaction.

In addition, the above-mentioned reaction methods require a relatively large facility corresponding to the necessity of enlarging the evaporation area, and there are also many restrictions on the reaction throughput.

Therefore, as a technique using a method other than the thin film polymerization reaction tank, a continuous melt polymerization method in which an inert gas is directly introduced into the polymerization reaction tank is proposed in, for example, Japanese Patent Publication No. 51-44039. In this method, a by-product vapor such as alkylene glycol is introduced into the inert gas bubbles in the reaction liquid while stirring the reaction liquid by blowing the inert gas into the reaction liquid in a specific reaction tank as a small gas bubble. Is to spread. However, in this method, since the reaction liquid is stirred by the inert gas, it is difficult to uniformly inject the inert gas into the reaction liquid when the melt viscosity increases. Therefore,
It is necessary to disperse the flowing raw material liquid by centrifugal force and collide with the inner wall of the tank, which causes problems such as energy consumption and formation of a dead space.

In Japanese Patent Publication No. 4-58806,
In a heated inert gas atmosphere, screw- (β-
A method of continuously extruding (hydroxyalkyl) terephthalate and / or an initial condensate which is a low polymer thereof has been proposed. However, if the pore size of the die is large, a sufficient reaction rate cannot be obtained, which is not practical. hard.

Further, Japanese Patent Application Laid-Open No. 7-278278 discloses that a part of the internal solution is continuously extracted from the reactor, and
A circulation pump and a circulation pipe are attached to the reactor to circulate the internal liquid, and a gas inert to the reaction is continuously injected into the circulation pipe to obtain a mass transfer coefficient and a gas-liquid contact area. There has been proposed a method of increasing the number. However, in this method, it is necessary to circulate the inert gas and the internal solution of the reactor together, and the circulation amount of the circulated internal solution per hour is preferably 3 times or more the amount of the internal solution. Because of the conditions, the melt viscosity of the reactants will increase, a large amount of power is required to circulate,
There are problems such as the fact that it is a batch type reactor and that scale-up is limited.

[0015]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a continuous melt polymerization method capable of greatly accelerating a polycondensation reaction rate, and furthermore, having a high resistance to polymer hydrolysis. An object of the present invention is to provide a method for producing a high-quality polyester having a small number of carboxyl terminals, which deteriorates decomposability.

[0016]

Means for Solving the Problems Here, as the invention according to claim 1, there is provided a dicarboxylic acid having an aromatic dicarboxylic acid as a main component or an ester-forming derivative thereof, an alicyclic dicarboxylic acid, or an aliphatic dicarboxylic acid and a diol component. From the above, in a method for producing a polyester by a continuous melt polymerization method, a polyester monomer and / or a low polymer thereof obtained by a transesterification reaction or an esterification reaction, and / or a high polymer obtained by a subsequent polymerization reaction There is provided a method for producing a polyester, which comprises introducing an inert gas into a transport pipe for transporting the coalesced product to a polymerization reactor.

Next, according to a second aspect of the present invention, when introducing the inert gas, the reactant and the inert gas are forcibly mixed in the transport pipe for the reactant.
A process for the preparation of the described polyester is provided.

According to a third aspect of the present invention, there is provided a method for producing a polyester according to the first or second aspect, wherein an inert gas is dispersed in a diol component in advance and introduced into the transport pipe.

According to a fourth aspect of the present invention, there is provided the method for producing a polyester according to any one of the first to third aspects, wherein an inert gas is introduced into the gas phase of the polymerization reactor.

Finally, as a fifth aspect of the present invention, there is provided a method for producing a polyester according to any one of the first to fourth aspects, wherein the polyester is produced in one polymerization reactor.

In the present invention, the polyester and the reactant are polyethylene terephthalate,
Monomers such as polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate and polybutylene isophthalate, low polymers and high polymers can be mentioned. Further, as a dicarboxylic acid having an aromatic dicarboxylic acid component as a main component or an ester-forming derivative thereof, for example, terephthalic acid, isophthalic acid, phthalic acid,
Examples thereof include 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and / or lower alkyl esters thereof (the alkyl group usually has 1 to 4 carbon atoms). it can. Furthermore, examples of the alicyclic dicarboxylic acid component include cyclohexanedicarboxylic acid and the like, and examples of the aliphatic dicarboxylic acid include adipic acid, sebacic acid, suberic acid, and the like. -Naphthalenedicarboxylic acid, isophthalic acid, dimethyl terephthalate. In addition, these aromatic dicarboxylic acid component, alicyclic dicarboxylic acid component, and aliphatic dicarboxylic acid component may be used alone or in combination of two or more.

The diol component includes ethylene glycol, neopentyl glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,
Examples thereof include 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, and propylene glycol. Of these, ethylene glycol, 1,4-butanediol, and diethylene glycol are preferable. These glycol components may be used alone or in combination of two or more.

The polyester may be copolymerized with trifunctional or higher polyfunctional compounds such as trimellitic acid, pyromellitic acid, and glycerol, and monofunctional compounds such as benzoic acid and phenyl isocyanate.

In the present invention, the production of the polyester is carried out in the presence or absence of a catalyst. When the reaction is carried out using a catalyst, any of the commonly used catalysts may be used. For example, manganese compounds, titanium compounds, tin compounds, zinc compounds, magnesium compounds ,
An antimony compound or the like is used. Also, if necessary,
One or more kinds of other commonly used thermoplastic resins, additives, inorganic fillers, organic fillers, etc., directly at the outlet side of the polycondensation reaction tank of the present invention, molding machine, extruder, mixing It can also be kneaded in a vessel or the like. Also, after making it pellet,
Of course, they can be re-melted and kneaded. Examples of other thermoplastic resins include polyester resins, polyamide resins, polystyrene resins, polycarbonates, polyacetals, and the like. Also, as an additive,
Known antioxidants, antistatic agents, brominated polycarbonates, flame retardants such as brominated epoxy compounds, antimony trioxide, flame retardant auxiliary agents such as antimony pentoxide, plasticizers, lubricants,
Examples thereof include a release agent, a colorant, and a crystal nucleating agent. Examples of inorganic fillers include metals such as glass fiber, talc, mica, glass flakes, carbon fiber, silica, alumina fiber, milled glass fiber, clay, carbon black, kaolin, titanium oxide, iron oxide, antimony oxide, and alumina. Examples thereof include compounds, alkali metal compounds such as potassium and sodium. Examples of the organic filler include aromatic polyester fibers and liquid crystalline polyester fibers.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 illustrates a schematic flow chart of a polyester production process for carrying out the present invention.

In the figure, reference numeral 1 denotes a first (previous stage) polymerization reaction tank, and reference numeral 2 denotes a second (rear stage) polymerization reaction tank. Reference numerals 3 and 4 denote condensers (condensers) provided in the respective polymerization reaction tanks, and reference numerals 5 and 6 denote extraction devices for taking out gas condensed in the condensers, respectively. Is preferably used. Furthermore,
Numerals 7 and 8 denote mixers for mixing the reactant and the inert gas, respectively. Reference numerals 9 and 10 denote gear pumps for transferring each reactant obtained in each polymerization reaction tank to the next step.

Here, reference numerals 11 and 12 denote inert gas heating devices, respectively, reference numerals 13 and 14 denote respective inert gas delivery pumps, reference numerals 15 and 16 denote respective reaction liquid transport pipes, and reference numeral 17. And 18 indicate the respective supply pipes of the inert gas. The mixers 7 and 8 are provided on transport pipes 15 and 16, respectively.

In the polymerization step of the polyester constituted as described above, a dicarboxylic acid having an aromatic dicarboxylic acid as a main component or an ester-forming derivative thereof, an alicyclic dicarboxylic acid, or an aliphatic dicarboxylic acid and a diol component are used. A polyester monomer produced by a transesterification reaction vessel or an esterification reaction vessel (not shown) and / or a low polymer thereof, and / or a high polymer obtained by subsequent polymerization reaction is used as a polymerization raw material. Then, the polymerization raw material is supplied from the first polymerization reaction tank 1 through a transport pipe 15 for reactants. In addition, an inert gas made of, for example, nitrogen is sent from the supply pipe 17 to the transport pipe 15 via the delivery pump 13, and at this time, the inert gas is heated to an appropriate temperature by the heating device 11. Warmed up. At this time, since the transport pipe 15 is provided with the mixer 7 as described above, the inert gas supplied via the pump 13 is supplied to the transport pipe 15 by the mixer 7.
It is forcibly mixed with the reaction solution flowing through it. Here, the “transport pipe” of the reactant in the present invention refers to “pipe for transporting a polyester monomer, a low polymer, and a high polymer to a polymerization reaction tank”.

It should be noted that it is not essential that the mixer 7 be provided. However, the mixer 7 is preferably installed in the transport pipe 15 in order to improve the dispersibility of the inert gas in the reactant. Here, as the mixer 7, as long as the above object can be achieved,
There is no particular limitation, and static mixers (static mixers) of Noritake, Sulzer, Toray, etc.,
It is preferable to provide one or more dynamic mixers such as a drive mixer provided with a screw or a stirring blade .

With the above-described structure, a gas-liquid mixture comprising a polyester monomer containing an inert gas and / or a low polymer thereof and / or a high polymer obtained by a subsequent polymerization reaction is obtained. A multi-phase flow is formed in the transport pipe 15, and the gas-liquid multi-phase flow is supplied to the first polymerization reactor 1, and the polycondensation reaction proceeds rapidly in the first polymerization reactor 1 due to the effect of the inert gas. Let me do. The reaction product thus obtained by the polycondensation reaction is sent from the first polymerization reaction tank 1 to the second polymerization reaction tank 2 via the gear pump 9.

At this time, in the same manner as in the first polymerization reaction tank 1, the reactant obtained in the first polymerization reaction tank 1
The inert gas supplied via the pump 14 is mixed by the mixer 8 provided in the transport pipe 16 for the reactant before the second polymerization reaction tank 2. Next, the second polymerization reaction tank 2
After a rapid polycondensation reaction occurs in the above, the polyester is taken out using a gear pump 10. In the method for producing a polyester by continuous polycondensation of the present invention, the pressure during the reaction is not particularly limited, and the present invention can be applied to a polymerization reaction under vacuum, normal pressure or a pressure higher than normal pressure. I will add that.

Here, the greatest advantage of introducing an inert gas into the reactant transport pipe is that unlike the conventional method of directly introducing the polymerization reaction into the polymerization reaction tank, the polymerization reaction tank itself must be specially worked. Low-energy, low-cost equipment and easy introduction. Furthermore, by introducing an inert gas into the transport pipe for the reactants, the reactants can be uniformly mixed with the reactants without difficulty, whereby the effect of increasing the polymerization rate by increasing the mass transfer coefficient and the evaporation area can be obtained. And the like.

The rate and flow rate of introducing the inert gas into the reactant transport pipe may be a desired amount within a range where stable and continuous operation can be performed. At this time, it is preferable that the inert gas to be introduced be heated with a heater or the like and introduced so as not to lower the temperature of the reactant. Further, it is also preferable to introduce the reactant into the transport pipe after previously mixing with the diol component and the like. in this case,
By supplying an inert gas together with the diol component, an increase in the substantial reaction molar ratio and a high dispersion of the inert gas can be expected, and the effect of accelerating the polycondensation reaction is increased. Further, the inert gas to be introduced does not adversely affect the reaction, and is preferably a gas at the reaction temperature in the polymerization reaction tank. Examples of the inert gas include N ₂ , Ar, and He. In view of low cost, nitrogen is particularly desirable. Then, it is preferable that such an inert gas be introduced into the gas phase of the reactor while being introduced into the reaction product transport pipe.

The polyester finally obtained as described above can be continuously supplied to a spinning process and spun to form a fiber, or supplied to a film forming process to form a thin film. it can. Further, it can be once pelletized in a granulation step or the like and sent to a fiberization step, a thinning step, a resin molding step, or the like.

In the above-mentioned polyester production process, the inert gas containing reaction by-products and the like is removed from the polymerization reaction tank by a known method using a condenser, a filter, a combustion device, an absorption device, etc. of each polymerization reaction tank. It can be separated from reaction by-products and the like. Then, the separated inert gas can be circulated and used by providing a circulation pump or the like and refluxing the gas to the transport pipes 15 and / or 16. The advantage of such recycle use is that it can be operated with almost no reaction by-products being discharged out of the system. This not only reduces the operating cost, but also allows the operation to be discharged directly out of the system. Since there is no need to do so, there are significant benefits in terms of preventing environmental destruction and preventing pollution.

Here, it should be added just in case that the degree of polymerization of the polyester in the production process of the polyester of the present invention increases, and the melt viscosity of the reactant increases accordingly. Therefore, the moving speed in the liquid phase in which the inert gas moves in the reactant liquid decreases. In this case, it is preferable to spread the reactant in a thin film form by using a thin film polymerization reaction tank and shorten the moving distance of the reactant, whereby a higher polycondensation reaction rate is obtained.

The number of polymerization reactors is not particularly limited, but polyester can be obtained very efficiently by using the method of the present invention. This makes it possible to produce high-quality polyester with good quality and good quality. At this time, for the purpose of improving the dispersion of the inert gas in the polymerization reaction tank, it is preferable to provide a stirring blade, a dispersion plate, a baffle plate and the like in the polymerization reaction tank as necessary.

[0038]

EXAMPLES The method of the present invention will be described in detail below with reference to examples of polyethylene terephthalate, a typical polyester.

The term "intrinsic viscosity [η]" used in the following examples and the like is a value calculated from the melt viscosity measured in orthochlorophenol at 25 ° C., and the terminal carboxyl group concentration ([COOH]) Is based on the method of A. Conix (Makromol. Che).
m, 26, 226 (1958)}, the number of equivalents per 10 ⁶ g of polymer (eq / T). In the following examples and the like, "part" indicates a ratio expressed by weight.

Example 1 Using the process shown in FIG. 1, 86 parts of terephthalic acid (TA) and 55 parts of ethylene glycol (EG) were esterified in a continuous esterification reactor at 278 ° C. under normal pressure. A reaction product obtained by adding 0.04 parts by weight of antimony trioxide to the polyethylene terephthalate low polymer (average degree of polymerization: about 8) obtained by the above method was transported to a transportation pipe
5 and was continuously fed to the first polymerization reaction tank 1 at a feed rate of 104 kg / h. At this time, an inert gas (nitrogen) heated to 275 ° C. by the heating device 11 is supplied from the supply pipe 17 via the pump 13 at a supply speed of 4 Nm ³ / h, and the reactant and the static mixer 7 are supplied. Mixed. Then, in the first polymerization reaction tank 1, the average reaction temperature 275
The polymerization reaction was performed at a temperature of 20 ° C. and a degree of vacuum of 20 mmHg. At this time, the prepolymer obtained in the first polymerization reaction tank 1 had an intrinsic viscosity [η] of 0.42 and [COOH] = 20 eq / T.

Next, the prepolymer was added to the gear pump 9
The liquid is fed to the horizontal second polymerization reaction tank 2 having a single-screw wing blade through the transport pipe 16. At that time, the first
In the same manner as in the case of the polymerization reaction tank 1, an inert gas (nitrogen) supplied at a supply rate of 1 Nm ³ / h heated to 281 ° C. by the heating device 12 from the supply pipe 18 via the pump 14 is mixed with the prepolymer. After mixing in the static mixer 8, the mixture is supplied to the second polymerization reaction tank 2, and the average reaction temperature is 282 ° C. and the degree of vacuum is 2
The polymerization reaction was performed at mmHg. Then, the obtained reaction product was continuously withdrawn through the gear pump 10 and formed into chips. The polyethylene terephthalate thus obtained had [η] = 0.72, [COOH] = 16e
q / T, and the hue was also very good.

Example 2 In Example 1, nitrogen heated to 289 ° C. by the heating device 12 was supplied at ⁵ Nm ³ / h.
The polymerization conditions were the same as in Example 1 except that the polymerization reaction was carried out at an average reaction temperature of 290 ° C. and a degree of vacuum of 3 mmHg. [Η] = 0.86, [COOH] = 1 of the obtained polyethylene terephthalate
It was 8 eq / T, and the hue was extremely good.

Example 3 The conditions were the same as in Example 1 except that nitrogen was introduced without providing the static mixers 7 and 8. At this time, [η] of the polyethylene terephthalate obtained from the second polymerization reaction tank was 0.65,
[COOH] = 17 eq / T, and the hue was extremely good.

[Embodiment 4] In Embodiment 1, the pump 1
3 nitrogen supplied from the feed rate 0.8 Nm ³ / h, conditions other than the nitrogen supplied from the pump 14 then the polymerization reaction was conducted as feed rate 0.3 Nm ³ / h was the same as in Example 1. At this time, the polyethylene terephthalate obtained from the second polymerization reactor was [η] = 0.63, [COO
H] = 19 eq / T, and the hue was extremely good.

Example 5 In Example 1, when supplying nitrogen to the reactant transport pipe 15, the supply rate was set to 400 Nm ³ / h, the average reaction temperature in the first polymerization reactor 1 was 282 ° C., and the atmospheric pressure was , And the reaction product was continuously extracted without being supplied to the mixer 8 via the gear pump 9 to form a chip. The polyethylene terephthalate obtained from the first polymerization reactor 1 has [η] = 0.57, [CO
OH] = 10 eq / T, the hue was extremely good, and polyethylene terephthalate having sufficient commercial value was obtained in one polymerization tank.

[0046] Except for Comparative Example 1 that was not performed at all the introduction of the inert gas, under the same conditions as in Example 1 using the same process as in Example 1 (FIG. 1), the polymerization reaction was conducted. At this time, the prepolymer obtained from the first polymerization reaction tank had [η] = 0.20,
[COOH] = 95 eq / T. The finally obtained polyethylene terephthalate has [η] = 0.
50, [COOH] = 39 eq / T. Not only does [η] not rise much, but [COO]
H] increased and the hue was not good.

[0047]

According to the present invention, the polymerization rate is greatly increased as compared with the conventional continuous melt polymerization method, and a good quality polyester having few carboxyl terminals can be produced. It is extremely useful as a molding material.

[Brief description of the drawings]

FIG. 1 is a schematic process diagram of a continuous polymerization production process of a polyester for carrying out the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st polymerization reaction tank 2 2nd polymerization reaction tank 3, 4 Condenser 5, 6 Extraction device 15, 16 Transport piping 17, 18 Inert gas supply piping

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (5)

(57) [Claims] 1. A method for producing a polyester from a dicarboxylic acid having an aromatic dicarboxylic acid as a main component or an ester-forming derivative thereof, an alicyclic dicarboxylic acid, or an aliphatic dicarboxylic acid and a diol component by a continuous melt polymerization method. In the transport piping for transporting the polyester monomer and / or its low polymer obtained by the transesterification reaction or the esterification reaction and / or the high polymer obtained by the subsequent polymerization reaction to the polymerization reaction tank A method for producing a polyester, comprising introducing an inert gas. 2. The method for producing a polyester according to claim 1, wherein upon introducing the inert gas, the reactant and the inert gas are forcibly mixed in the reactant transport pipe. 3. The method according to claim 1, wherein an inert gas is dispersed in the diol component in advance and introduced into the transport pipe.
A method for producing the polyester described above. 4. The method for producing a polyester according to claim 1, wherein an inert gas is introduced into a gas phase portion of the polymerization reaction tank. 5. The method for producing a polyester according to claim 1, wherein the polyester is produced in one polymerization reactor.