KR20060030587A - Method of solid-state polymerization of polyethyleneterephthalate - Google Patents

Abstract

The present invention relates to a solid phase polymerization method and apparatus of polyethylene terephthalate, and more particularly, to crystallize polyethylene terephthalate pellets, and then injected into a solid phase polymerization reactor, and a small amount of inert gas is injected into the solid phase polymerization reactor during the reaction. It relates to a solid phase polymerization method of polyethylene terephthalate. The present invention also relates to a batch type vacuum solid phase reaction apparatus for polyethylene terephthalate solid phase polymerization having a supply line through which an inert gas is supplied into the reactor, and having an orifice on one side of the supply line for adjusting the pressure in the reactor.

According to the present invention, a small amount of inert gas is administered during the solid phase polymerization reaction and controlled by an orifice to increase the solid phase polymerization rate and effectively prevent color discoloration of the finished product.

Solid State Polymerization, Polyethylene Terephthalate, Batch Vacuum Solid State Reactor, Discoloration, Orifice, Inert Gas, Solid State Polymerization Rate

Description

Solid phase polymerization method of polyethylene terephthalate {METHOD OF SOLID-STATE POLYMERIZATION OF POLYETHYLENETEREPHTHALATE}             

1 is a view schematically illustrating a solid state polymerization apparatus according to the prior art,

2A is a diagram schematically illustrating a solid state polymerization apparatus according to the present invention;

FIG. 2B is an enlarged cross-sectional view of region A of FIG. 2A,

Figure 3 is a graph showing the color value of the PET resin prepared in Examples and Comparative Examples of the present invention.

<Description of the main symbols in the drawing>

100, 200: solid state polymerization apparatus 120, 220: inert gas supply means

122, 222, 226: inert gas supply line 124, 224: valve

140, 240: solid state polymerization reactors 142, 242: heating means

160, 260: vacuum means 162, 262: vacuum line

228: orifice

The present invention relates to a solid phase polymerization method for producing a polyethylene terephthalate product having excellent color and a solid phase polymerization apparatus used therein.

Polyethylene terephthalate (hereinafter referred to as “PET”) is widely used in fibers, beverage containers, films, and tire cords. Among them, the amount of PET used for bottles, such as beverage containers, is increasing very rapidly.

In the production of bottles using PET, a stretch blow molding method is employed, and high molecular weight PET is generally used. In order to manufacture such high molecular weight PET, a solid phase polymerization method is widely used.

1 is a schematic diagram of a conventional solid state polymerization reaction apparatus of a batch vacuum system.

Referring to FIG. 1, the solid-state polymerization reaction apparatus 100 according to the related art is disposed in a batch-type solid state polymerization reactor 140 and one side of the solid state polymerization reactor 140, and the solid phase A nitrogen supply line 122 connected to a nitrogen supply means 120 for injecting nitrogen gas into the polymerization reactor 140, and a valve 124 for adjusting a flow rate of nitrogen gas at one side of the nitrogen supply line 122. ) Is located, located under one side of the solid-phase polymerization reactor 140, is composed of a vacuum means 160 provided for maintaining the pressure in the solid-state polymerization reactor 140.

The solid state polymerization apparatus 100 further includes a heating means 142 formed in the form of a steam jacket or an electric heater surrounding the solid state polymerization reactor 140, and the vacuum means 160 has a form of a vacuum pump. The solid phase polymerization reactor 140 and the vacuum line 162 is connected.

In order to polymerize PET using the solid state polymerization apparatus 100 of FIG. 1, first, a low-polymerization PET preform (near viscosity of 0.6 dl / g) produced by melt polymerization is introduced into a crystallization plant (not shown). To crystallize at a temperature of 120 to 190 ℃ above the glass transition temperature. The crystallization can also be carried out in a solid state polymerization apparatus.

The crystallized PET resin also has a portion of an amorphous (morphous phase), which causes a problem that fusion between pellets easily occurs, so that the pellet is stirred or crystallization equipment or solid state polymerization reactor to prevent the fusion phenomenon The pellets collide with each other while rotating 140.

Subsequently, when the low degree of polymerization PET resin has a degree of crystallinity of a predetermined level or more, the pressure in the reactor is maintained in a vacuum state by using the vacuum means 160 located below the solid phase polymerization reactor 140.

Subsequently, the heating means 142 in the solid phase polymerization reactor 140 adjusts the temperature to 190 to 240 ° C. to start the solid phase polymerization reaction of the low polymerization PET resin.

When the reaction was terminated after a certain time of reaction, the valve 124 of the nitrogen supply line 122 connected to the nitrogen supply means 120 was opened to fill the inside of the solid-phase polymerization reactor 140 which was a vacuum with nitrogen and the temperature was room temperature. Cooled to

At this time, since the state of the finally obtained polymer is a solid, this process is generally referred to as solid-state polymerization. In the solid phase polymerization method, the reactants are obtained in the solid state, and the progress of the polymerization reaction is ethylene glycol, water, or acetic acid, which is a volatile by-product produced by the chemical reaction and the end-term chemical reaction of the PET polymer. Aldehyde (acetaldehyde) and the like proceeds by the diffusion process is diffused from the inside of the pellet to the outside.

However, the polymerization method using the solid-state polymerization apparatus 100 of the batch method as described above has some disadvantages.

In the case of the solid phase polymerization apparatus, a vacuum is applied to lower the oxygen concentration and promotes the diffusion of reaction byproducts. Since the pressure in the system is lower than that of the outside, a small amount of oxygen is likely to flow into the system because the pressure in the system is lower than the outside. exist. In particular, the use of practical solid phase polymerization equipment inevitably leads to the occurrence of minute cracks. Oxygen, once introduced into the reactor, causes an oxidation reaction on the surface of the PET pellets as described above, which causes the color of the PET product to be discolored, thereby degrading the quality of the product.

Accordingly, an object of the present invention for solving the above problems is to minimize the content of oxygen in the reactor and yellowing phenomenon does not occur in the solid phase polymerization method of PET for producing a PET product having excellent color and the solid phase polymerization apparatus used therein to provide.

The present invention to achieve the above object

Crystallizing the polyethylene terephthalate pellets; And                     

And injecting the crystallized pellet into a solid phase polymerization reactor, followed by solid phase polymerization at 180 to 240 ° C.

Provided is a solid phase polymerization method of polyethylene terephthalate in which a small amount of inert gas is injected into the solid phase polymerization reactor during the solid phase polymerization reaction.

In this case, the polyethylene terephthalate pellets have an IV of 0.40 to 0.70 dl / g, preferably 0.50 to 0.65 dl / g, and the IV of the polymer polymerized with the polyethylene terephthalate pellets is 0.7 to 1.2 dl / g.

In addition, the present invention includes a batch-type solid-state polymerization reactor equipped with a heating means, and a vacuum device for maintaining the pressure in the solid-state polymerization reactor, located on one side of the solid-state polymerization reactor,

A gas supply means for injecting an inert gas into the solid phase polymerization reactor, and the gas supply means comprises two or more gas supply lines divided into branches from the solid phase polymerization reactor,

A purge valve that controls the flow of inert gas in at least one line side of the gas supply line to prevent the flow of inert gas during the solid state polymerization reaction and to inject a high velocity of inert gas before the reaction or at the end of the reaction to destroy the vacuum. Is located,

Polyethylene terephthalate for solid phase polymerization having an orifice for adjusting the pressure in the reactor in one side of at least one other line of the gas supply line to maintain the vacuum and injection of a small amount of inert gas during the solid phase polymerization reaction Provided is a solid phase reaction device.

In this case, the heating means is in the form of a steam jacket or an electric heater surrounding the solid state polymerization reactor.

Hereinafter, the present invention will be described in more detail.

The polyethylene terephthalate product excellent in color can be manufactured using the solid-state polymerization apparatus of this invention.

First, in order to solidify the polymerization of PET, PET pellets prepared from melt polymerization are crystallized. The PET pellet is prepared by melt polymerization of terephthalic acid and ethylene glycol as a main raw material, and has an intrinsic viscosity (Intrinsic Viscosity, hereinafter referred to as 'IV') of 0.40 to 0.70 dl / g, preferably 0.50 to 0.65 dl / g. use.

The crystallization is carried out in a separate crystallization apparatus or in the solid phase polymerization reactor to carry out subsequent solid phase polymerizations continuously. At this time, the crystallization process is carried out for 0.5 to 4 hours at a temperature of 120 to 190 ℃, to rotate the crystallization apparatus or solid state polymerization reactor to prevent fusion between the PET pellets.

The crystallized PET resin is injected into a solid phase polymerization reactor to perform a solid phase polymerization reaction. At this time, the solid phase polymerization reaction is carried out at a temperature of 180 to 240 ℃ and 0.1 to 100 torr or less, preferably 10 torr or less, more preferably 1 torr or less. In particular, the partial pressure of oxygen in the reactor system is ideally 0 torr is most preferable in order to suppress the yellowing phenomenon of the final PET product, but in the actual process 50 torr or less, preferably 5 torr or less, more preferably 0.5 Control to below torr.

The control of the oxygen partial pressure in the solid phase polymerization reactor can be preferably made by the solid phase polymerization apparatus according to the present invention, by installing an orifice inside one of the supply lines for supplying an inert gas into the solid phase polymerization reactor. Specifically, the partial pressure of oxygen may be controlled to a proper level or less by substituting a small amount of an inert gas into the solid state polymerization reactor before the solid state polymerization reaction to replace oxygen in the reactor. As the inert gas, nitrogen gas, halogen elements such as helium and argon are used, and preferably a high purity of 99.9% or more that contains little oxygen in the gas.

At this time, the amount of inert gas introduced into the system is controlled by adjusting the diameter of the installed orifice, and the precise flow rate can be measured by installing a flowmeter outside the orifice from the system. In addition, the partial pressure of oxygen in the system is calculated from the measured flow rate of the inert gas, the capacity of the vacuum pump, the reactor volume, the pressure of the reactor when inert gas is injected, and the pressure of the reactor when no inert gas is injected.

After completion of the reaction, a sufficient amount of inert gas is injected into the solid state polymerization reactor, and the reaction pressure is increased to destroy the vacuum state. The solid state polymerized PET resin according to the present invention has a high molecular weight IV of 0.7 to 1.2 dl / g, and does not have a yellowing phenomenon on the surface and has excellent color characteristics.

FIG. 2A schematically illustrates a solid state polymerization apparatus according to an embodiment of the present invention, and FIG. 2B is an enlarged view of region A of FIG. 2A.                     

According to FIG. 2A, the solid-state polymerization apparatus according to the present invention is a batch-type solid state polymerization reactor 240 equipped with a heating means, and is located below one side of the solid state polymerization reactor 240, and the solid phase A vacuum device 260 for maintaining pressure in the polymerization reactor 240,

Gas supply means 220 for injecting inert gas into the solid state polymerization reactor 240 and gas supply lines 222 and 226 connected thereto, and the gas supply line is branched from the solid state polymerization reactor 240 ( branched), comprising two or more gas supply lines 222, 226,

Purging to prevent the flow of inert gas during the solid state polymerization reaction in one side of at least one line 222 of the gas supply lines 222 and 226 and to inject a high speed inert gas before the reaction or at the end of the reaction to destroy the vacuum Valve 224 is located,

An orifice 228 is provided in one side of at least one other line 226 of the gas supply line to adjust the pressure in the reactor to maintain the vacuum and injection of trace amounts of inert gas during the solid phase polymerization.

The solid phase polymerization reactor 240 employed in the present invention is a closed-type batch system, wherein the shape of the solid phase polymerization reactor 240 is not limited in the present invention and is represented by a cylindrical shape that is commonly used for convenience.

The solid phase polymerization reactor 240 is provided with a heating means 242 for maintaining the temperature in the reactor, the heating means is in the form of a steam jacket or electric heater surrounding the solid phase polymerization reactor 240.

The vacuum means 260 is to remove ethylene glycol, water and acetaldehyde, etc., which are volatile by-products generated during the polymerization, out of the reactor 240. One side of the solid phase polymerization reactor 240 and the vacuum line 262 Vacuum pumps are commonly used. Thus, the vacuum means 260 maintains the pressure in the solid phase polymerization reactor 240 at a constant of 100 torr or less, preferably 10 torr or less, more preferably 0.1 torr or less during the solid phase polymerization reaction.

The solid state polymerization apparatus 200 of the present invention follows a form of an open system in which an inert gas is introduced and circulated from the outside during the reaction despite being a closed system.

Specifically, in order to inject an inert gas into the solid state polymerization reactor 240 during the solid state polymerization reaction, divided into a branched form (branched) from the solid state polymerization reactor 240, as shown in area A of FIG. 222, 226).

A purging valve 224 for controlling the flow of inert gas is located in one side of at least one line 222 of the gas supply lines 222 and 226 and the pressure in the reactor in one side of the at least one other line 226. It has an orifice 228 for adjusting it.

When the PET resin and other additives crystallized in the previous step are injected into the solid-phase polymerization reactor 240, the purging valve 224 is closed and the temperature of the reactor rises to the reaction temperature, and the vacuum pump is operated to reduce the pressure of the reactor. Maintain a vacuum. At the same time, the concentration of oxygen remaining in the system is reduced due to the inert gas continuously and finely injected through the orifice.

At this time, the flow rate and the rate of inert gas may vary depending on the size of the batch, the capacity of the vacuum pump and the diameter of the orifice, and can be appropriately adjusted by those skilled in the art.

Orifice 228 is a mechanism for throttling the flow of fluid (quickly reducing the flow cross-sectional area) and is used to control or reduce the flow rate of fluid flow in a tube.

As an enlarged view of region A of FIG. 2B, a plate-shaped orifice 228 having a hole having a predetermined size is located inside the gas supply line 226. That is, the flow rate can be measured using the pressure difference generated between the upstream (inlet side) and the downstream (outlet side) of the orifice 228, and the flow and amount of the injected fluid can be controlled, so that Injection of trace amounts of inert gas and vacuum can be maintained.

At this time, the diameter of the hole of the orifice 228 may affect the maintenance of the pressure difference and the color of the product, and may vary depending on the size of the batch and the content of the PET resin to be treated, preferably 50 It is about 100 micrometers, but it is not limited to this range.

를 기준으로 규격화된 표준 오리피스(228)가 정해져 있다. 특히, 공업규격으로 치수와 유량계수가 정해져 있으므로, 실제로 유체를 흐르게 하지 않아도 유량과 압력차 사이의 관계를 알 수 있다. 원판에 구멍만 뚫은 간단한 구조로 되어 있고 값이 저렴하면서도 신뢰성이 있다. The orifice 228 can be purchased commercially available, and the diameter and diameter of the tube for the shape or dimensions

The standardized orifice 228 is determined based on the standard. In particular, since the dimensions and flow rate coefficients are determined by the industrial standard, the relationship between the flow rate and the pressure difference can be known without actually flowing the fluid. It has a simple structure with only holes in the disc, and is inexpensive and reliable.

In the present invention, a small amount of inert gas is injected into the solid state polymerization reactor 240 through the gas supply lines 222 and 226 during the solid state polymerization, so that the partial pressure of oxygen in the polymerization process is below an appropriate level, preferably 50 torr or less, and more. Preferably 5 torr or less, most preferably 0.5 torr or less. As such, by minimizing the partial pressure of oxygen in the reactor 240 during the solid state polymerization, it is possible to minimize the yellowing phenomenon that occurred during the conventional PET solid state polymerization to increase the quality of the final product.

In addition, even if an inert gas is injected into the reactor 240 during the solid phase polymerization, the pressure in the reactor may be kept constant by the gas supply line 226 provided with the orifice 228 installed separately. As such, by maintaining a constant pressure in the solid phase polymerization reactor 240, it is possible to promote mass transfer in the reactor 240 to more effectively remove reaction by-products generated during solid phase polymerization.

As such, the present invention further includes a separate gas supply line 226 provided with an orifice 228 during the solid state polymerization of PET to inject an inert gas during the solid state polymerization to minimize the concentration of oxygen in the reactor 240, The effect of increasing the solid phase polymerization rate and preventing discoloration such as yellowing of the product is obtained.

The solid polymerized PET is variously applicable to fibers, beverage containers, films and tire cords.

Representatively, the bottle container using PET is injection-molded the solid-phase polymerized PET at 250 to 290 ° C to prepare a preform (interform) as an intermediate product.                     

Subsequently, the preform is heated to a glass transition temperature (Tg) of 90 to 110 ° C. or higher, and then the heated preform is injected into a molding mold.

Subsequently, the preform injected into the molding mold is blown with a compressed gas of a predetermined pressure, molded into a container, and then cooled and extracted.

The manufactured bottle container has no color discoloration and exhibits very surface condition.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are only examples of the present invention, and the present invention is not limited to these examples.

<Example>

Melt polymerization was performed to prepare PET pellets having a degree of polymerization of IV 0.60 dl / g and an average size of 2 × 2 × 1.5 mm. The PET pellet was injected into a crystallization apparatus to perform a crystallization process at 180 ° C. for 30 minutes.

Next, the crystallized PET was added to the solid phase polymerization equipment according to the present invention of FIG. 2, and then the solid phase polymerization reaction was performed at 210 ° C. for 7 hours. At this time, nitrogen was used as the inert gas, and the purging valve provided in the gas supply line was locked throughout the reaction time to maintain the pressure in the solid-phase polymerization reactor 240 to maintain 1.0 torr. In addition, the orifice provided in another gas supply line used what is 50 micrometers in diameter.

Comparative Example                     

Melt polymerization was performed to prepare PET pellets having a degree of polymerization of IV 0.60 dl / g and an average size of 2 × 2 × 1.5 mm. The PET pellet was injected into a crystallization apparatus to perform a crystallization process at 180 ° C. for 30 minutes.

Next, the crystallized PET was added to the solid state polymerization equipment according to the prior art of Figure 1, and then subjected to a solid state polymerization reaction at 210 ° C for 7 hours. At this time, nitrogen was used as the inert gas, and the purging valve provided in the gas supply line was locked throughout the reaction time so that the pressure in the solid-phase polymerization reactor 240 was maintained at 0.5 torr.

Experimental Example

Intrinsic viscosity (IV) and color purity of the PET pellets prepared in Examples and Comparative Examples were measured.

A: Measurement of intrinsic viscosity (IV)

o Pellets dissolved in -Chlorophenol (OCP) were dissolved to determine the number of drops ( t 1) in the Ubbelodhe viscometer, and the number of drops ( t 0) of pure solvent (OCP) alone. At this time, the relative viscosity (ηr, Relative Viscosity) can be obtained by the relative ratio of the falling seconds of the solvent only and the falling seconds of the polymer solution, the intrinsic viscosity ([η], Intrinsic Viscosity, IV) was obtained by the following formula (1).

(In Formula 1, c is the concentration of the PET solution expressed in g / 100ml (g / dl).)                     

B: measurement of color values (L, a, b)

The color of PET pellets was measured using a Minolta spectrophotometer (Minolta Spectrophotomer, Japan, model number: CR410).

10 g of PET pellets were injected into a test cup prepared in advance, and the color of the pellets was analyzed by detecting light reflected from the pellets with a camera, and the standard color was defined by the American Society for Testing & Materials (ASTM) E308 and D2244. See.

Table 1 and FIG. 3 show IV and color value data of PET before and after solid state polymerization.

Intrinsic Viscosity (IV) Color value Before solid state polymerization After solid state polymerization Example 0.60 dl / g 0.74 dl / g L 89, a 0.1, b -2.0 Comparative example 0.60 dl / g 0.72 dl / g L 88, a 0.1, b -0.5

According to Table 1, it can be seen that the PET of the embodiment according to the present invention increases the intrinsic viscosity compared to that of the comparative example, which means that the production of higher molecular weight PET is possible.

In addition, also in transparency, the numerical value of L of the Example was 89, and it showed similarly to 88 of the comparative example.

However, referring to FIG. 3, in the measurement results of the numerical value a indicating the red color and the numerical value b indicating the yellow color, it was found that the yellowing phenomenon occurred when the PET of the comparative example showed yellow color.

 As described above, according to the present invention, by installing a separate inert gas supply line with an orifice in the solid phase polymerization reactor and introducing a small amount of nitrogen into the system throughout the solid phase polymerization reaction time, the solid phase polymerization rate is increased and the high phase polymerization product is The effect of preventing color discoloration can be obtained.

Claims (8)

Crystallizing the polyethylene terephthalate pellets; And Injecting the crystallized pellet into a solid phase polymerization reactor and then performing solid phase polymerization at 180 to 240 ° C., Solid phase polymerization method of polyethylene terephthalate injecting a small amount of inert gas into the solid phase polymerization reactor during the solid phase polymerization reaction. The method of claim 1, wherein the polyethylene terephthalate pellets have an intrinsic viscosity (Intrinsic Viscosity, IV) of 0.4 to 0.7 dl / g, characterized in that the solid phase polymerization method. The solid state polymerization method according to claim 1, wherein the solid state polymerized polyethylene terephthalate has an intrinsic viscosity of 0.7 to 1.2 dl / g. The solid state polymerization method according to claim 1, wherein the inert gas is one gas selected from the group consisting of nitrogen, helium and argon gas. The solid phase polymerization method according to claim 1, wherein the solid phase polymerization is performed at 0.1 to 100 torr. A batch-type solid phase polymerization reactor equipped with a heating means, and a vacuum device positioned at one side of the solid phase polymerization reactor to maintain pressure in the solid phase polymerization reactor, A gas supply means for injecting an inert gas into the solid phase polymerization reactor, and the gas supply means comprises two or more gas supply lines divided into branches from the solid phase polymerization reactor, A purge valve that controls the flow of inert gas in at least one line side of the gas supply line to prevent the flow of inert gas during the solid state polymerization reaction and to inject a high velocity of inert gas before the reaction or at the end of the reaction to destroy the vacuum. Is located, Polyethylene terephthalate for solid phase polymerization having an orifice for adjusting the pressure in the reactor in one side of at least one other line of the gas supply line to maintain the vacuum and injection of a small amount of inert gas during the solid phase polymerization reaction Solid state reaction device. 7. The solid phase reactor according to claim 6, wherein said heating means is selected from the form of a steam jacket or an electric heater surrounding said solid phase polymerization reactor. 7. The solid state polymerization apparatus according to claim 6, wherein the orifice has a diameter of 50 to 100 mu m.

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