Preparation method for antimony-free polyester for bottles

Abstract

The invention discloses a preparation method for antimony-free polyethylene glycol terephthalate (PET) for bottles. An esterification, fusion polycondensation and liquid-phase viscosity-increasing one-step method is used for preparing the PET resin for bottles, and the PET resin has the characteristic viscosity of 0.70-1.00 dL / g. A polycondensation catalyst is a titanium-serial catalyst. The PET resin for bottles is high in safety to human body, solid-phase polycondensation and other processes are saved, equipment investment is reduced, the process flow is shortened, and production energy consumption is reduced.

Description

technical field [0001] The invention belongs to the technical field of polyester production for bottles, and in particular relates to a preparation method of heavy metal antimony-free polyethylene terephthalate (PET) material. Background technique [0002] Polyester, especially polyethylene terephthalate (PET), is widely used in the field of food packaging because of its excellent physical and mechanical properties, low price, and recyclable recycling. At present, the preparation of PET resin for bottles generally adopts a two-step method, that is, through esterification and melt polycondensation (generally including pre-condensation and final polycondensation) to obtain a PET resin with an intrinsic viscosity of 0.60~0.65dL / g, and then through solidification. Phase polycondensation (temperature 180-230°C) produces PET resin for bottles with an intrinsic viscosity of 0.70-0.90 dL / g. Another function of solid-state polycondensation is to reduce the acetaldehyde content in PET...

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Problems solved by technology

[0003] On the other hand, antimony (Sb)-based catalysts are usually used in the polycondensation process of PET, and a small amount of antimony element will be precipitated in the process of making containers to store food and beverages, which poses a threat to human health

Titanium-based catalysts are the most promising environmentally friendly catalysts to replace antimony-based catalysts. A lot of research work has been done at home and abroad, but the application effect and promotion are still not ideal. The main reason is that titanium-based catalysts have higher catalytic activity and catalytic selectivity. Poor, side reactions are obvious, and the melt color is yellowish. The current research and development work is mainly focused on the improvement of the titanium-based catalyst itself, and there is no report on solving the yellowish color of the titanium-based catalyst polyester from the transformation of the polycondensation reactor.

[0004] Due to the one-step melt polycondensation method to prepare PET high-viscosity melt, it is easy to produce problems such as yellowish hue and high acetaldehyde content, and titanium-based catalysts will aggravate the yellowish hue and high acetaldehyde content of PET high-viscosity melt due to high catalytic activity and poor selectivity. Therefore, it is generally believed that the one-step melt polycondensation method cannot use titanium-based catalysts to prepare PET high-viscosity melts.

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