High-melt-strength copolyoxymethylene and preparation method thereof

Abstract

The invention discloses a high-melt-strength copolyoxymethylene and a preparation method thereof, and belongs to the technical field of copolyoxymethylene. The preparation method comprises the following steps: carrying out a polymerization reaction on trioxymethylene, a comonomer, an initiator, a multi-element chain transfer agent or a mixture of the multi-element chain transfer agent and a chainextender in a double-screw reactor at 50-70 DEG C to complete branching and crosslinking copolymerization so as to obtain a polyformaldehyde powder; and mixing the polyformaldehyde powder with a high-efficiency trace additive, melting and plasticizing the obtained mixture at 180-230 DEG C through a thermal devolatilization process, and cooling and granulating the mixture to obtain the high-melt-strength copolyformaldehyde product. Branching and crosslinking of polyformaldehyde molecular chains are ingeniously achieved through the multi-element chain transfer agent or the mixture of the multi-element chain transfer agent and the chain extender, and the high-efficiency trace additive is used to improve the stability of the polyformaldehyde powder and reduce the loss of the melt strength caused by assistants.

Description

technical field [0001] The invention belongs to the technical field of polyoxymethylene copolymer, and in particular relates to a polyoxymethylene copolymer with high melt strength and a preparation method thereof. Background technique [0002] Polyoxymethylene is divided into two categories: homopolyoxymethylene and copolymerized polyoxymethylene. Most of the conventionally sold polyoxymethylene products are linear polymers, and the main chain of the molecule is composed of carbon-oxygen bonds. Among them, polyoxymethylene is polymerized by trioxane and comonomers. Commonly used comonomers include 1,3-dioxane, 1,3-dioxane, etc. The production of polyoxymethylene follows the mechanism of cationic polymerization. The polyoxymethylene copolymer obtained from the above monomers is a linear polymer. At the same time, the addition of conventional additives is large, and the melt strength is greatly lost, which is equivalent to the presence of impurities in the melt. Under a certa...

AI Technical Summary

Problems solved by technology

Among them, polyoxymethylene is polymerized by trioxane and comonomers. Commonly used comonomers include 1,3-dioxane, 1,3-dioxane, etc. The production of polyoxymethylene follows the mechanism of cationic polymerization. The polyoxymethylene copolymer obtained from the above monomers is a linear polymer. At the same time, the addition of conventional additives is large, and the melt strength is greatly lost, which is equivalent to the presence of impurities in the melt. Under a certain molecular weight and molecular weight distribution, the melt The body strength is low, and it is difficult to meet the preparation requirements of high-performance products such as polyoxymethylene fibers and films.

At present, the main application market of polyoxymethylene products is still injection molded parts. The application of spinning, extrusion molding and blow molding is limited by the low melt strength, so they cannot be widely used, resulting in serious homogeneous competition, which is not conducive to the polyoxymethylene industry. development of

In terms of the development of high melt strength polyoxymethylene copolymers, there are no relevant reports at home and abroad. The development work that has been carried out is mainly to realize the differentiation of the performance of polymerization products by changing the types and amounts of initiators and comonomers, which involves product rheology. The improvement of chemical properties is mostly to change the molecular weight and its distribution, thereby changing the polymer melt index (melt mass / volume flow rate), and the linear structure of the copolymerized polyoxymethylene molecule does not change, which cannot effectively improve the melt strength of the product; in other In terms of polymer development, such as polyethylene, it is reported that the melt strength can be changed by copolymerization. By adding multi-component comonomers or changing the catalyst form, the cross-linking and branching of polymer molecular chains can be achieved, thereby changing the polymer’s Melt strength, this technology adopts the mechanism of coordination polymerization, which is essentially different from the technology of multi-chain transfer agent and high-efficiency micro-auxiliary proposed by the present invention