JPS5845228A - Preparation of polyester chip - Google Patents

Abstract

PURPOSE:To obtain the titled chip having low acetaldehyde content and excellent moldability, etc., and suitable for the blow molding, by subjecting polyethylene terephthalate chips to the multi-stage heat-pretreatment under specific conditions, and carrying out the continuous solid-phase polymerization. CONSTITUTION:Polyethylene terephthalate chips are fed to the heating vessel 7 furnished with a stirring means through the inlet pipe 1 while introducing hot air having a temperature of T1 deg.C and satisfying the formulaI(Tg and Tm are the glass transition point and the melting point of the polyethylene terephthalate, respectively), the formula T0<T1 and the formula II through the bottom 2 of the vessel 7 and discharging the hot air of T0 deg.C from the top 2' of the vessel. After leaving the pellets in the vessel 7 for >=30min, the chips are fed to the heating vessel 11 from its top, and an inert gas of T2 deg.C and satisfying the formula III is introduced into the vessel 11 from its bottom 3 to effect the heat treatment of the chips for >=30min. The heat-treated chips are discharged through the bottom valve 12, and finally transferred continuously to a moving- bed solid-phase polymerization apparatus 13 under the flow of an inert gas at T3 deg.C and satisfying the formula IV to allow the solid-phase polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing polyester chips, and more particularly to a method for manufacturing polyethylene terephthalate chips suitable for blow molding applications. More specifically, the present invention relates to an efficient method for producing polyester chips that reduces acetaldehyde content in a polymer and improves moldability, practical strength, and transparency of blow-molded products. Polyester, especially polyethylene terephthalate, has excellent physical and chemical properties, making it suitable for fibers, films,
Widely used in plastic molding fields.

Conventionally, polyvinyl chloride has been mainly used as the resin for plastic blow-molded products, but in recent years, due to sanitary issues with this polymer, its use in the field of blow-molded food containers has come to be restricted. . On the other hand, as mentioned above, polyethylene terephthalate has not sufficiently penetrated into the blow molding field, especially the food container field, although it has various excellent custom orders.

The main reasons for this are that the viscosity of the polymer is low when melted, that products that crystallize quickly tend to whiten, and that acetaldehyde remains in the products.

Regarding the first two of these problems, various improvements have been made from the viewpoint of molding technology, and it has come to function as a substitute for polyvinyl chloride. This has the disadvantage that the taste and odor of the filling are likely to change. As a method to reduce the acetaldehyde in this polyethylene terephthalate and increase the degree of polymerization so as to obtain a sufficient melt viscosity for blow molding, specifically, the method is to reduce the amount of acetaldehyde in polyethylene terephthalate and increase the degree of polymerization to obtain a sufficient melt viscosity for blow molding. A so-called solid phase polymerization method is known in which the treatment is carried out for hours to several tens of hours.

Among these, the in-phase polymerization method, which is carried out under a high-temperature inert gas flow, has the advantage of being excellent in economy and productivity because chips can be processed continuously.

However, solid-phase polymerization carried out under a high-temperature inert gas flow sufficiently reduces all the acetaldehyde in polyethylene terephthalate, and under conditions where the degree of polymerization is sufficiently increased, blocking and fusion between chips may occur. The disadvantage is that it is difficult to process stable steps. The present inventors made polyethylene terephthalate suitable for use in blow molding to reduce acetaldehyde in the polymer, and as a result of intensive study on an efficient method for manufacturing chips to improve moldability and customization of blow molded products, the present invention was developed. It has been reached.

That is, the present invention blows hot air at a temperature of 18°C into the heating tank from the lower part of the heating tank having a stirring device WL, and discharges the hot air at a temperature T0°C from the upper part of the heating tank from the inside of the heating tank.
The polyethylene terephthalate chips are continuously fed into the heating tank from the upper part of the heating tank, and after remaining in the cough heating tank for at least 30 minutes, are discharged from the bottom of the chipper core heating tank, and then the chips are placed in a stirring device. [1- Inert gas 5-sq.ft. is continuously supplied into the second heating tank from the upper part of the second heating tank and has a temperature of T2°C from the lower part of the second heating tank. After heat treating the chips for at least a few minutes by blowing into the tank, the chips are discharged from the bottom of the second heating tank, and then the chips are transferred under an inert air flow at a temperature of T1°C. The present invention provides a method for producing polyester chips, characterized in that polyester chips are continuously supplied into a bed-type solid-phase polymerization apparatus and subjected to in-phase polymerization.

[However, LATg ≦ T0 ≦ Tm -120 T0 The glass transition temperature (C) of the polyethylene terephthalate chip shown in 'L
A7'm indicates the melting point (°C) t- of the polyethylene terephthalate chips before being subjected to the method of the present invention. ] 6- What is polyethylene terephthalate used in the present invention?
The least amount of ethylene terephthalate units is 4185 mol-1
It is preferably 90 molar or more, and bisdiol ester and/or It is obtained by polycondensation at high temperature and high vacuum in the presence of a low polymer total polymerization catalyst, such as one or more of conventionally known antimony compounds, germanium compounds, and titanium compounds. Small amounts of dicarboxylic acid residues or diol residues other than the groups may be present.

Dicarboxylic acid residues other than terephthalic acid residues include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid, adipic acid, 5-
There are residues such as sodium sulfoisophthalate.

However, small amounts of other glycols may be used in combination.

Examples include probylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, cyclohexane dimetatool, diethylene glycol, and the like.

The so-called polyethylene terephthalate or prepolymer thus obtained is continuously supplied from the upper part of the first stage heating tank using the stirrer tV, and is discharged from the lower part while being stirred in the filled state. The heating tank has a structure in which hot air at T□° C. is blown into the lower part and exhaust gas at 9° C. is discharged from the upper part of the tank. The cooling tank is used to crystallize the prepolymer without fusing the 5 chips, and the hot air blowing temperature is (7'ya -80
If it exceeds E', the L polyester chips will be significantly deformed and the commercial value will be inferior, and if it is less than (TI+15)c, the chips will block or fuse together in the tank, and sufficient crystallization will not occur. .

The hot air used here can be air or an inert gas such as nitrogen. In order to sufficiently crystallize the polyethylene tere-7-thalerate prebolimer in the first stage heating tank, the heat treatment can be carried out with a residence time of at least 30 minutes, preferably one hour or more. In addition, the hot air blown from the bottom of the tank is discharged from the top of the tank after heat exchange with the prepolymer chips, but the temperature of the discharged hot air is (7'm-
120) If the temperature exceeds Cl, blocking or fusion of the chips may occur on the grain surface of the prepolymer chip, and if the hot air temperature is less than 1° C., blocking or fusion of the chips may occur inside the chip layer, which is undesirable.

Next, the prepolymer chips that have been heat-treated in the first-stage heating tank are continuously discharged from the bottom of the first-stage heating tank, and have the same mechanism as the first-stage heating tank (it has a stirring device and starts from the top). The chips are continuously discharged from the lower part in a filled state, and the hot air is introduced from the lower part and discharged to the upper part).The heated air is continuously introduced from the upper part to the second stage heating tank. The purpose of this tank is to raise the chip temperature to near the homophase polymerization temperature while stirring while preventing fusion between chips.The hot air blown from the bottom of the tank is inert to prevent chip deterioration. Gas is preferred. The temperature of the hot air blown in is higher than the hot air temperature T0 in the first stage heating tank, and is preferably Fir, preferably at a temperature of 15°C or more and below (Tm-25)°C. 6ru. If the temperature of the chips in the second-stage heating tank was raised without stirring, and the temperature exceeded the above range, the temperature inside the tank would cause fusion between the chips in the same-phase polymerization tower that was subsequently introduced. I don't like starvation.

The temperature-raised crystallized chips thus obtained are fed to a moving bed type solid phase polymerization apparatus under an inert gas flow at a temperature of 12°C or higher and (Tm-20)'C or lower, and the temperature is increased for at least 2 hours. A continuous 10-solid phase polymerization is carried out.

Polyethylene terephthalate prepolymer chips are subjected to multi-stage preheat treatment as described above, followed by solid phase polymerization to increase the degree of polymerization and deacetaldehyde.
! % By performing multi-stage pre-heat treatment under specific conditions as in the present invention, there are no problems such as chip deformation, blocking or fusion between chips, which improves chip productivity and improves supply to the molding machine. (2) Since the chip is not subjected to extreme deformation, there is less generation of whiskers and powdery substances in the polymer, and the transparency of the molded product is improved.

The prepolymer obtained by melt polymerization, that is, the polyethylene terephthalate used in the method of the present invention, has an intrinsic viscosity of 0.
A value of 50 or more and 0.72 or less is used, and a value of 0.53 or more and 0.68 or less is particularly preferred. These prepolymers usually contain ~300p of acetaldehyde, but by performing the multistage preheat treatment and in-phase polymerization treatment of the present invention, the intrinsic viscosity of the prepolymers can be reduced to at least 0.
．． The acetaldehyde content in 05 rising whip is 3p
It can be reduced to less than ptn, and exhibits properties suitable for blow molding applications where taste change is a problem.

In the present invention, the glass transition temperature TQ and melting point Ttrs of the polyethylene tere-7-talate tape were measured using a differential calorimeter DEC-IB model manufactured by PerkinElmer Co., Ltd., and the melted polymer 1079'j was quenched at 16°C/m. It is expressed as the peak temperature of the change in heat amount obtained by heating at a heating rate of . The acetaldehyde content in polyethylene terephthalate can be determined by finely pulverizing polyethylene terephthalate in liquid nitrogen, heating the powder to 165°C using a 4CM gas chromatograph manufactured by Shimadzu Corporation, and comparing the production peak with the standard to determine the amount of acetaldehyde released. It is measured by finding .

Blow molding using the chip thus obtained can be performed according to conventionally well-known melt molding techniques such as injection molding and extrusion molding. Moreover, the intrinsic viscosity is a value measured at 25° C. using an O-chlorophenol solvent.

The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A direct ester low polymer of terephthal and 1.2 moles of ethylene glycol was subjected to a polycondensation reaction at 285°C under reduced pressure using antimony trioxide as a polycondensation catalyst in a conventional manner to obtain an intrinsic viscosity of 0.54. , Contains 146p acetaldehyde
pm, T g 78.5 List T 260.5℃ Total average length 3.2 points, major axis 3.41101 x minor axis 2.2-
A cylindrical prepolymer chip was obtained.

The chip is heated through a stirring device 11N in which heated air at 170° C. is blown into the chip from the bottom and rotates at 1 rprn.
The raw material is continuously supplied from the upper part to the first stage heating tank, where it is treated for 2 hours, and then continuously discharged from the lower part of the tank. At this time, the exhaust gas temperature is 1
The temperature was 10°C. The discharged chips are not heated air having the same mechanism as the first stage (200C heated nitrogen is used in the second stage heating tank, which has a residence time of 2 hours) and is continuously flown from the upper part of the machine. The chips treated in the second stage heating tank are then continuously fed to the top of the tower so that they have a residence time of 10 hours. Further, heated nitrogen at 210° C. is introduced from the lower part of the tower at an air volume of 1.5 filtrate/chip, and is discharged from the upper part of the tower.

The chips thus obtained had an intrinsic viscosity of 0.75, acetaldehyde content of LOppm, and very little deformation of the chips, and no blocking or fusion spread between the chips was observed. Using this chip, a cylindrical bottomed mold with an internal volume of 27 cc and a weight of 262 cc was obtained using an injection molding machine (cylinder temperature: 275°C), and then biaxially stretched in an atmosphere of 105°C. 14- An extruded container was obtained. The acetaldehyde content in the obtained bottle polymer was as small as 1.4 pprn and had excellent transparency.

Example 2 A polycondensation reaction following the esterification reaction of dimethyl terephthalate and ethylene glycol was carried out in the presence of 0.013-g germanium dioxide at normal mK, and the intrinsic viscosity was 0.
5? , Contains acetaldehyde 1'12 ppm, Ta7
8.0C, '2'm258.5℃, average length 3.011
A cylindrical prepolymer tip having a major axis of 3.2 mm and a minor axis of 2.0 mm is obtained.

Next, the chips were continuously supplied and discharged to maintain a residence time of 3 hours under the same method as in Example 1, except that the first stage heated air blowing temperature was 165° C. and the exhaust temperature was 11,000° C. As for the second stage heating tank, heating nitrogen at 205° C. was used, and the mixture was kept there for 2.5 hours and then continuously discharged. The discharged chips were continuously fed to a moving bed type solid phase polymerization column having a residence time of 6 hours at 215° C. according to the method of Example 1, and then discharged.

The chip thus obtained had an intrinsic viscosity of 0.79 and an acetaldehyde content of 1.0 pptyhf, and no problems such as chip deformation, blocking, or fusion were observed.

Experimental Example The prepolymer obtained in Example 1 was used to prepare the device f of Example 1.
Table 1 shows experimental examples obtained using t'.

If the heating tank is not stirred as in Experiments 2 and 3, the chips will fuse together, making it impossible to feed the chips into subsequent steps. The air inlet temperature of the first stage heating tank is (7'm
-80) In the case of Experiment 44 exceeding Ck, the obtained solid phase polymerized chips are significantly deformed, resulting in a disadvantage that products with inferior commercial prices are obtained. Furthermore, when the air inlet temperature falls below (7'g+15)C as in Experiment M5, the chips form blocks within m, making it impossible to feed them into subsequent steps.

In addition, when the temperature of the second cypress exceeds the range of the present invention, as in Experimental Houses 6 and 7, the fusion of the cypresses occurs in the second stage heating tank in the case of A6, and in the solid state in the case of House 7. This makes stable TEP discharge impossible. On the other hand, in Experiment &8, the solid phase polymerization temperature exceeds the range of the present invention, and in Experiment 9, the first stage heating tank is not used at all. was waking up.

171 One embodiment of the present invention will be described with reference to the drawings.

The figure is a schematic diagram of an apparatus used for solid phase polymerization of the present invention.

Hot air at a temperature T□°C is blown into the heating tank 7 from the lower part 2 of the heating tank 7 containing a stirring device equipped with a driving device 5 and a stirring blade 6, and while discharging hot air at a temperature 9°C from the upper part 2', After continuously supplying polyethylene terephthalate chips from the upper introduction pipe 1 and leaving them in the heating tank 7 for at least 30 minutes,
The chips are continuously discharged through a discharge nozzle (8 loops),
Next, the upper part of the second heating tank 11, which has a stirring device equipped with the full chip drive unit f9 and stirring blades 10, is continuously supplied into the second heating tank 11, and the lower part 3 is heated to a temperature of T°C. After heat treating the chips for at least 30 minutes by blowing inert gas, the chips are continuously discharged through the bottom discharge valve 12 of the second heating bath 11, and then the chips are heated to a total temperature of 13°C. A moving bed type solid phase polymerization unit [13] under an inert gas flow is a device in which the polymer is continuously fed into the same phase polymerization unit [18].

In addition, 4 is a heated inert gas blowing pipe, 4' is an inert gas outlet, 15 is a solid phase polymerization chip continuous discharge valve, and 16 is a solid phase polymerization chip storage tank.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an example of an apparatus used for solid phase polymerization of the present invention. 19-

Claims (1)

[Claims] Hot air at a temperature of 11°C is blown into the heating tank from the lower part of the heating tank equipped with a stirring device, and the temperature at the upper part of the heating tank is To°C.
While discharging hot air from inside the heating tank, polyethylene terephthalate chips are continuously fed into the heating tank from the upper part of the heating tank, and after staying in the heating tank for at least 30 minutes, the chips are It is discharged from the lower part of the nuclear heating tank, and then continuously supplied into the second heating tank from the upper part of the second heating tank equipped with the TEG stirring device 1, and then from the bottom of the second heating tank. The chip is heat-treated for at least 30 minutes by blowing an inert gas at a temperature of 12°C into the second heating tank, the chip is temporarily discharged from the bottom of the second heating tank, and then the chip is heated to a temperature of T1. 1. A method for producing polyester chips, which comprises continuously supplying polyester chips to a moving bed type in-phase polymerization apparatus under an inert air flow at .degree. C. for in-phase polymerization. However, TQ≦10≦−120 To<T. T(1+ 15≦T, 57m-80 T, <T2≦--25 T2≦13≦--20 and 7% TylriGlass transition temperature (℃) of polyethylene terephthalate chips before being subjected to the method of the present invention
The t-indication LATm indicates the melting point (C) of the polyethylene terephthalate chip before being subjected to the method of the present invention.