JPH0543677A - Cooling of polyester made by solid-phase polymerization - Google Patents

Abstract

PURPOSE:To cool polyester chips made by solid-phase polymerization and giving a nonwhitening molding excellent in transparency. CONSTITUTION:A process for cooling polyester chips which are made by solid- phase polymerization and are still hot, which process comprises bringing the chips into direct contact with a liquid cooling medium (e.g. water, an aqueous acid or alkali solution, an aqueous metal salt solution, an alcohol, a ketone or an ester).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling a solid-state polymerized polyester, and more specifically, it efficiently cools with a liquid refrigerant, thereby avoiding an unnecessary increase in chip density and increasing the high [η]. The present invention relates to a method for cooling a solid-state polymerized polyester, which is capable of removing a high-density powdery chip, resulting in a molded article having no transparency and having excellent transparency.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate, have hitherto been used in physical properties such as tensile strength, Young's modulus, elastic recovery rate, impact resistance, dimensional stability, etc. and chemical resistance, weather resistance, water resistance, etc. It is well known that it has excellent chemical properties and has great industrial value, and is widely used in fibers, films, industrial resins, bottles and the like.

In addition, particularly high [η], low acetaldehyde,
In applications where low oligomers and the like are required, a polymer that has been once polymerized and further solid-phase polymerized is often used. Since this solid-state polymerization is a polymerization reaction in a solid state such as a chip under a nitrogen stream or under vacuum at a high temperature of 180 ° C. to melting point for a long time, a cooling step after completion of the reaction is indispensable. It was common to air-cool under an inert gas stream such as.

However, this method is not preferable because it requires a relatively long time for cooling, and the cooling is gradually cooled, so that the density of the chips is crystallized and increased even during this cooling. Moreover, the conventional air-cooling method has a drawback in that the powdery chips with high [η] and high density generated in the polymerization cannot be sufficiently removed.

High-density chips and high- [η] / high-density powdery chips cannot be completely melted when formed into a film or the like, and remain as white foreign matters, or partially melted when formed into a molded product. As a result, various problems such as flow unevenness and molding distortion are caused, and crystallization unevenness occurs when the bottle is molded and the mouth is crystallized. There is a method of removing powdery chips with a vibrating screen or the like, but the effect is not sufficient.

Therefore, it has been strongly desired to develop a method for efficiently removing powder chips and an efficient cooling method for solid-state polymerized chips that does not unnecessarily increase the density of chips.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve such problems, to efficiently cool the liquid refrigerant, and to avoid an unnecessary increase in the chip density. It is an object of the present invention to provide a method for cooling a continuous solid-phase polymerized polyester, which can be removed, and as a result, a molded article having no transparency and excellent in transparency can be obtained.

[0008]

The present invention is a method for cooling a solid-phase polymerized polyester, which comprises directly contacting a polyester chip or the like in a high temperature state immediately after solid-phase polymerization with a liquid solvent.

The polyester of the present invention is polycondensed in at least one solid phase polymerization step, and the solid phase polymerization method can be manufactured by a conventionally accumulated method. Since the solid phase polymerization is carried out at a high temperature (180 ° C to melting point) for a long time, a cooling process after the reaction is indispensable.
According to the invention, this cooling method is carried out by directly contacting the chip with a liquid coolant. The refrigerant may be, for example, water, an acidic aqueous solution such as hydrochloric acid, an alkaline aqueous solution such as NH ₃ water, an aqueous solution of other metal salts, alcohols, ketones such as acetone, esters, etc. as long as they are liquid at room temperature. Temperature is 100 ℃
The temperature is preferably 50 ° C. or lower, more preferably 30 ° C. or lower.

The cooling method may be either batch type or continuous type as long as it can contact with a liquid, and in the case of batch method, a method of cooling by putting a refrigerant and a solid-state polymerized chip in a cooling device can be exemplified. .. Further, in the case of the continuous system, a method of continuously supplying a coolant in a countercurrent or a parallel flow to cool the chip can be exemplified. The chips cooled by these methods need to be dried, but a commonly used polyester chip drying treatment method can be used.

[0011]

Industrial Applicability The present invention relates to a cooling method for efficiently cooling with a liquid refrigerant, whereby an unnecessary increase in chip density can be avoided and powder chips of high [η] / high density can be removed. As a result, a molded product with no whitening and excellent transparency is obtained, which is extremely effective as a method for cooling solid-state polymerized polyester.

The present invention will be supplemented by the following examples.

[0013]

Example 1 Polyethylene terephthalate (intrinsic viscosity 0.75) continuously solid-phase polymerized under vacuum at 220 ° C. for 10 hours.
20 kg of dl / g) was placed in a cooling device having a volume of 100 liters containing 50 kg of water at room temperature and cooled for 15 minutes. 100 ° C
When the chip density was measured after drying under vacuum for 5 hours, it was 1.402 g / cm ³ , and the powdery chip amount was 1.
It was 6 g.

[0014]

Examples 2 to 6 The same treatments as in Example 1 were carried out except that the refrigerant and the time were changed. The refrigerants are shown in Table 1.

[0015]

[Comparative Example] The same method as in Example was used, except that cooling was carried out in a nitrogen stream at room temperature at a flow rate of 500 liters / minute and the drying step was omitted. The density of the chip is 1.408 g / cm ³ ,
The amount of powdery chips was 4.8 g.

The results of Examples 1 to 6 and Comparative Example are shown in Table 1.

[0017]

[Table 1]

Claims (1)

[Claims] 1. A method for cooling a solid-state polymerized polyester, which comprises directly contacting a liquid refrigerant with a solid-state polymerized polyester in a high temperature state to cool the polyester.