KR20080094357A - Method for adjusting molecular weight distribution of the polytetramethylene ether glycol - Google Patents

Abstract

A method for preparing polytetramethylene ether glycol is provided to simply produce the polytetramethylene ether glycol having a molecular weight distribution in the special range required by controlling a progress step of polymerization with pulsed water. A method for preparing polytetramethylene ether glycol from tetrahydrofuran using a heteropolyacid catalyst layer includes the steps of: (i) charging tetrahydrofuran, heteropolyacid, and water into a continuous reactor to produce a reaction mixture; (ii) supplying tetrahydrofuran and water while stirring the reaction mixture; and (iii) sampling the polytetramethylene ether glycol produced during the reaction step to measure number average molecular weight and molecular weight distributions of the polytetramethylene ether glycol. The supply of water in the step (ii) is achieved in a pulse form.

Description

Method for Adjusting Molecular Weight Distribution of the Polytetramethylene ether glycol}

1 shows an apparatus for the production process of polytetramethylene ether glycol according to the present invention.

The present invention relates to a method for preparing polytetramethylene ether glycol (PTMG) to have a specific range (1.5 to 2.0) molecular weight distribution for a predetermined number average molecular weight, and in particular, a process of polymerizing polytetramethylene ether glycol. The present invention relates to a method for producing polytetramethylene ether glycol in which a molecular weight distribution of polytetramethylene ether glycol produced by adding a predetermined amount of water to the reaction terminator in a pulsed manner.

Polytetramethylene ether glycol is used as a raw polymer for the preparation of polyurethanes used as materials for spandex fibers, plastics or films. Polyurethanes may be prepared in various forms, such as hard and soft, depending on the application, and should be made to have an optimal molecular weight or molecular weight distribution depending on the application. Therefore, it is necessary to prepare so that the molecular weight of polytetramethylene ether glycol has an appropriate value in consideration of the use of polyurethane. A method for producing polytetramethylene ether glycol while controlling the distribution of molecular weights to 1300 to 1600 is disclosed in US Pat. No. 5,053,553. The invention disclosed in No. 5,053,553 introduces the Z factor, which means the ratio of the weight average molecular weight to the number average molecular weight, and adjusts the Z factor to be, for example, 1.80 or less to have a narrow molecular weight. A method is disclosed. However, according to the present invention, since the PTMG starting material must be mixed with non-polar solvents such as methanol, water and cyclohexane, there is a disadvantage that a process for removing methanol and non-polar solvents must be further performed later. In order to remedy this disadvantage of the prior art, the invention disclosed in WO1999 / 61507 has been proposed. WO1999 / 61507 proposes a method for controlling the residence time distribution and agitation force of the starting monomers to produce polytetramethylene ether glycol (PTMG) having a narrow molecular weight distribution. And WO1999 / 61507 disclose a method of adjusting the amount of catalyst coordination water or reaction temperature supplied to control the residence time distribution, or changing the agitation force for the unit reaction liquid volume. However, when the amount of catalyst coordination number or the reaction temperature is increased to increase the starting target molecular weight distribution to, for example, 0.2 level, it is difficult to predict the actual stirring power required. This raises the problem that the installation cost can be increased because the excess sizing of the equipment is required.

The present invention is to solve this problem of the prior art proposes a method of controlling the input method of water as a reaction terminator and accordingly the molecular weight distribution of polytetramethylene ether glycol.

An object of the present invention is to provide a method for controlling the molecular weight distribution of polytetramethylene ether glycol produced by adding water added as a reaction terminator in the polymerization process of polytetramethylene ether glycol in a pulse form.

According to a preferred embodiment of the present invention, a method for preparing polytetramethylene ether glycol from THF using a heteropolyacid (HPA) catalyst layer comprises the steps of adding a THF and heteropolyacid catalyst with water to a continuous reactor to produce a reaction mixture; Supplying THF and an amount of water while stirring the reaction mixture;

Sampling the polytetramethylene ether glycol produced in the reaction process to measure the number average molecular weight and molecular weight distribution, wherein the supply of a certain amount of water is made in the form of a pulse.

According to another suitable embodiment of the present invention, the sampling of polytetramethylene ether glycol is at least once.

According to another suitable embodiment of the invention, the temperature of the reactor is from 50 to 70 ° C.

According to another suitable embodiment of the present invention, the production of the reaction mixture and the amount of water is dependent on a constant temperature, which has been pre-tested in advance, the amount of HPA catalyst to THF, and the type of pulsed water to the total amount of water supplied. It is determined by the number average molecular weight and the weight average molecular weight distribution test curve.

Hereinafter, the present invention will be described in detail by using examples, but the examples presented are for a clear understanding of the present invention and are not intended to limit the scope of the present invention.

1 shows a polymerization apparatus of polytetramethylene ether glycol according to the present invention.

Referring to FIG. 1, a continuous polymerization apparatus 1 for the production of poly tetramethylene ether glycol comprises a reactor 11, a phase separation vessel 12, a water supply 13 with a flow regulator 131, and a distillation column. (14).

Catalysts that can be used in the preparation of PTMG according to the present invention include heteropoly acids (HPA). Generally, 20 to 40 molecules of water are coordinated per unit molecule of HPA, but this type of HPA cannot effectively induce the polymerization of tetrahydrofuran (THF). Therefore, in order to properly induce the polymerization of tetrahydrofuran, the number of water molecules coordinated to a heteropoly-anion needs to be controlled. In order to control the number of water molecules coordinated to a heteropoly acid, the heteropoly acid is heated to a temperature of, for example, 100 to 300 ° C., as is generally used as a method of changing the activity of the catalyst. The heating temperature and the heating time can be adjusted according to the number of water molecules to be coordinated, but can be adjusted such that, for example, the coordination number of water molecules to heteropoly acid is 3 to 18.

Tetrahydrofuran is first introduced into the reactor 11. Tetrahydrofuran can be prepared, for example, from 1,4-butanediol. However, tetrahydrofuran used in the preparation of PTMG according to the invention can be prepared according to methods known in the art. The prepared tetrahydrofuran is added to the reactor 11 with water. The heteropoly acid with the coordination number of water is then added to the reactor 11 again. The amount of water present on the catalyst in the reactor 11 can be adjusted such that the coordination number of the water is 3 to 18. As the polymerization reaction proceeds, the amount of water may be reduced. Therefore, water may be added so that the polymerization reaction can proceed in a state having a constant number of coordination water. If the amount of water is present such that the coordination number of water to heteropoly-anion is 20 or more, or the molar ratio of water to heteropoly acid is, for example, 0.1 or less, the efficiency of the polymerization reaction can be significantly reduced. The amount of water added may be determined depending on the progress of the polymerization reaction. According to the method for producing PTMG of the present invention, water is introduced into the reactor 11 periodically, intermittently in a predetermined amount for a certain time. For example, a total of 300 ml of water may be introduced into the reactor 11 three times at two hour intervals for six hours. Preferably, 300 ml may be added with water at 0.83 ml / min in continuous form for 6 hours.

As such, the intermittent or discontinuous introduction of water into the reactor 11 at regular intervals over a predetermined time is referred to as pulsed water input. When heteropoly acid is added to reactor 11, the reaction mixture of THF, water and heteropoly acid is stirred for 2-6 hours at 40-80 ° C. The reaction mixture is then transferred to phase separation vessel 12 and held for 30 minutes to 2 hours at room temperature. And PTMG is sampled in the phase separation container 12, and a number average molecular weight and molecular weight distribution are measured. Depending on whether the measured molecular weight distribution has the required value, the time interval, total dose, or amount that should be added in each time period for the pulsed water addition as described above can be assayed.

Split water input for molecular weight distribution can be adjusted based on the following equation.

Y = 1.4186e ^(0.0256X)

Where Y is the molecular weight distribution (PD = Poly dispersity)

X = number of water splits (12 hours)

(Prerequisite: The total amount of water to be added per hour in the case of no divided injection and the divided injection is the same, and the non-divided injection-the molecular weight distribution of continuous injection is 1.45. Same as mol of)

The role of water in the production process according to the present invention is not only a reaction terminator but also an important factor for controlling the activation of the reaction. As a reaction terminator, water molecules bind to the production of PTMG after the ring opening of THF, and when excess water is present, the catalyst is coordinated to lower the activity of the catalyst. By controlling such catalytic reaction activity, the width of the resulting molecular weight becomes much wider. According to this principle, it is possible to obtain a desired molecular weight distribution by adjusting the number of inputs without changing the total amount of water added. If the total amount of water added is constant and the number of water inputs is only increased (increasing to an infinite number, it becomes a continuous type), the activity of the reaction does not change and water acts only as a reaction terminator. However, if the total amount of water input is maintained and the number of water inputs is reduced, some of them act as reaction terminators, and some of them act on the coordination number of the catalyst, which decreases the activity of the reaction. As a result, the total amount of water introduced is constant so that the activity of the catalyst produced after the reaction is maintained as before, so that the reaction mechanism is not affected at all.

In the phase separation vessel 12, the HPA layer and the THF monomer layer are separated into the upper and lower layers while reacting uniformly. The liquid recovered from the phase separation vessel 12 is then fed to the distillation column 14 to obtain polytetramethylene ether glycol (PTMG).

As described above, according to the present invention, the molecular weight distribution of the polytetramethylene ether glycol (PTMG) prepared by adding a certain amount of water in the form of a pulse as a reaction terminator to the reactor 12 can be controlled. That is, the injected water is added in a pulse to enable a change in the catalytic activity. The total amount of water to be added in the form of pulses, the time period or the amount to be added during each time period is determined by sampling PTMG in the middle of the reaction to determine the number average molecular weight and using GPC (Gel Permeation Chromatography) to determine the number average molecular weight (Mn). It can be adjusted by determining the ratio of the weight average molecular weight (Mw) to.

Hereinafter, an embodiment of a manufacturing method of PTMG according to the present invention.

Example

Example 1

60 kg of tetrahydrofuran monomer was charged to the reactor and 60 kg of phosphorus tungstic acid was added to the reactor with a small amount of water equal to the molar number of catalyst and the resulting PTMG. The temperature of the reactor was maintained at 60 ° C. and THF monomer was continuously fed at a rate of 6 kg / hour. At the same time, a total of 72 ml / 12 hr of water through a water supply was added six times (12 ml of two hours at a time), while continuously stirring the mixture in the reactor to separate the catalyst layer. It was. And again while circulating water from the phase separation vessel to the reactor PTMG of the upper layer was accumulated through the formation of overflow (Overflow). After 24 hours of polymerization, the accumulated PTMG was sampled to determine the number average molecular weight and molecular weight distribution. The number average molecular weight was 1790 and the molecular weight distribution was 1.51. The same amount of THF and water were fed continuously to maintain molecular weight distribution.

Example 2

60 kg of tetrahydrofuran monomer was charged to the reactor and 60 kg of phosphotungstic acid was added to the reactor with a small amount of water in the same amount as the number of moles of catalyst and PTMG produced. The temperature of the reactor was maintained at 60 ° C. and THF monomer was continuously fed at a rate of 6 kg / hour. At the same time, a total of 72 ml / 12 hr of water was passed through the water feeder three times (24 ml every 4 hours for one input) while continuously stirring the mixture in the reactor to separate the catalyst layer by separating the catalyst bed. . Again water was circulated from the phase separation vessel to the reactor and PTMG at the top was accumulated through the formation of overflow. About 24 hours after the start of polymerization, the accumulated PTMG was sampled to determine the number average molecular weight and molecular weight distribution. The measured number average molecular weight was 1808 and the molecular weight distribution was 1.56. The overall results are shown in Table 1.

Example 3

60 kg of phosphotungstic acid is charged with a small amount of water, such as 60 kg of tetrahydrofuran monomer and, for example, the number of moles of PTMG produced, and the feed rate of THF monomer is 6 kg / hour, and the reactor The reaction was carried out under the condition of a temperature of 60 ℃. In the course of the reaction, PTMG was sampled and subjected to a total of 72 ml / 12 hr of water twice in a pulsed form (36 ml for 6 hours at a time) so that the number average molecular weight was 1795 and the molecular weight distribution was about 1.65. While stirring the mixture, the mixture was continuously flowed into a phase separation vessel and the catalyst layer was separated. Again water was circulated from the phase separation vessel into the reactor and the upper layer PTMG accumulated through the formation of overflow. About 24 hours after the start of polymerization, the accumulated PTMG was sampled to determine the number average molecular weight and molecular weight distribution.

Comparative example

Comparative Example 1

The reaction was carried out in the same manner as in Example 1 while controlling the supply amount of water to 6 ml / hour continuously. The reaction proceeded for 24 hours to obtain PTMG. The number average molecular weight and molecular weight distribution of the obtained PTMG were 1788 and 1.45. The results are shown in Table 1.

Table 1: Examples 1-3 and Comparative Example 1

division Total reaction time (hr) THF Feed (kg / hr) Reaction catalyst amount (kg) Water input total amount Ml / 12hr Water input times / 12hr Water input amount Ml / 回 Molecular Weight Distribution Example 1 24 6 60 72 6 16 1790 1.51 Example 2 24 6 60 72 3 24 1808 1.56 Example 3 24 6 60 72 2 36 1795 1.66 Comparative Example 1 24 6 60 72 - - 1788 1.45

Referring to Table 1, it can be seen that the number average molecular weight and molecular weight distribution of the produced PTMG can be changed by adding water acting as a reaction terminator in the form of a pulse according to the amount of THF supplied. Since the water introduced into the reactor preferentially serves as a reaction terminator, the total amount of water introduced may be determined according to H and OH attached to the PTMG terminal. If more water is supplied than can act as a reaction terminator, the excess will participate in the catalyst coordination water and affect the reaction activity. Another factor influencing the number average molecular weight and weight average molecular weight distribution may be the temperature in the reactor. According to the present invention, the number average molecular weight and the weight average molecular weight distribution were measured by sampling PTMG in the middle of the polymerization reaction, and the number average of the finally obtained PTMG was changed by changing the input method of water in the form of pulse. The molecular weight and weight average molecular weight distribution can be controlled. Sampling may be carried out several times to best suit the required number average molecular weight and weight average molecular weight distribution. Alternatively, the number average molecular weight and weight average molecular weight distribution test curves according to the water input method can be prepared in advance in a test form at a constant temperature, HPA for THF and the total amount of water supplied. If constant number average and weight average molecular weight distributions are required, the initial curve of the reaction can be determined by the test curve. In addition, sampling may be performed again during the polymerization process according to the initial conditions, and the test curve may be verified. At the same time, the pulsed water input method may be adjusted to obtain PTMG having the required number average molecular weight and weight average molecular weight distribution.

Polytetramethylene ether glycol is a polymer that can be used as a raw material, oil additive or softener of polyurethane and needs to be prepared to have a specific range of molecular weight distribution depending on the application. According to the present invention, polytetramethylene ether glycol having a specific range of molecular weight distribution can be prepared simply by controlling the progress of the polymerization reaction by adding water in a pulse form.

Claims (4)

In the process for producing polytetramethylene ether glycol from tetrahydrofuran (THF) using a heteropoly acid (HPA) catalyst layer, A first step of adding a tetrahydrofuran, a heteropoly acid, and water to a continuous reactor to generate a reaction mixture; A second step of supplying tetrahydrofuran and water while stirring the reaction mixture; A third step of measuring the number average molecular weight and molecular weight distribution by sampling the polytetramethylene ether glycol produced in the reaction process, The method of producing polytetramethylene ether glycol, characterized in that the supply of water in the second step is made in the form of a pulse. The method of claim 1, wherein the temperature of the reactor is 50 to 70 ℃. The number average molecular weight and the average according to the water input method according to claim 1, wherein the production of the reaction mixture and a certain amount of water are carried out in a preliminary experimentally prepared constant temperature, phosphotungstic acid for THF, and pulse form for the total amount of water supplied. Method for producing polyethylene glycol, characterized in that determined by the molecular weight distribution test curve. The method for preparing polytetramethylene ether glycol according to claim 1, wherein the input of pulsed water is controlled by the following equation: Y = 1.4186e ^(0.0256X) Where Y is the molecular weight distribution (PD = Poly dispersity) X = number of water splits (12 hours)

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