阅读说明：本技术 一种高熔体强度共聚甲醛及其制备方法 (High-melt-strength copolyformaldehyde and preparation method thereof ) 是由 王亚涛 杨大志 李建华 关礼争 刘莉莉 马小丰 于 2019-09-24 设计创作，主要内容包括：一种高熔体强度共聚甲醛及其制备方法,属于共聚甲醛技术领域。包括以下步骤：将三聚甲醛和共聚单体、引发剂以及多元链转移剂或多元链转移剂与扩链剂的配合,通过双螺杆反应器在50～70℃下,进行聚合反应,完成支化、交联共聚,获得聚甲醛粉料；将聚甲醛粉料与高效微量助剂混合,通过热脱挥工艺,在180～230℃熔融塑化,经过冷却造粒获得高熔体强度共聚甲醛产品。利用多元链转移剂或多元链转移剂与扩链剂的配合,巧妙实现聚甲醛分子链的支化与交联,通过高效微量助剂,提高聚甲醛粉料稳定性的同时,减少助剂对熔体强度的损失。(A high melt strength copolyformaldehyde and a preparation method thereof belong to the technical field of copolyformaldehyde. The method comprises the following steps: trioxymethylene, a comonomer, an initiator, a multi-chain transfer agent or a multi-chain transfer agent is matched with a chain extender, and a polymerization reaction is carried out at 50-70 ℃ through a double-screw reactor to complete branching and crosslinking copolymerization so as to obtain polyformaldehyde powder; mixing polyformaldehyde powder with an efficient trace auxiliary agent, performing melt plasticization at 180-230 ℃ through a thermal devolatilization process, and cooling and granulating to obtain a high-melt-strength co-polyoxymethylene product. The branching and crosslinking of a polyformaldehyde molecular chain are ingeniously realized by utilizing the matching of a multi-element chain transfer agent or the multi-element chain transfer agent and a chain extender, and the loss of the auxiliary agent to the melt strength is reduced while the stability of polyformaldehyde powder is improved by virtue of the efficient trace auxiliary agent.)

1. A preparation method of high melt strength copolymerized formaldehyde is characterized by comprising the following steps: trioxymethylene, a comonomer, an initiator, a multi-chain transfer agent or a multi-chain transfer agent is matched with a chain extender, and a polymerization reaction is carried out at 50-70 ℃ through a double-screw reactor to complete branching and crosslinking copolymerization so as to obtain polyformaldehyde powder; mixing polyformaldehyde powder with an efficient trace auxiliary agent, performing melt plasticization at 180-230 ℃ through a thermal devolatilization process, and cooling and granulating to obtain a high-melt-strength co-polyoxymethylene product.

2. The process for producing a high melt-strength polyoxymethylene as claimed in claim 1, wherein the comonomer is selected from the group consisting of 1, 3-dioxolane, 1, 3-heptanedioxide; the mass of the comonomer accounts for 3-5% of that of trioxymethylene; the initiator is boron trifluoride ethyl ether, and accounts for 50-150 ppm of the mass of the trioxymethylene.

3. The method for preparing high melt strength copolyoxymethylene as claimed in claim 1, wherein at least 3H of C1-C3 alkane as the polybasic chain transfer agent is substituted by alkoxy, the alkyl in the alkoxy is alkyl with 1-5 carbon atoms, and the addition amount is 100 ppm-1000 ppm of the mass of trioxymethylene.

4. The process for preparing high melt-strength copolyoxymethylenes according to claim 3, wherein the polybasic chain transfer agent is selected from one or more of tetraethoxymethane, tetrabutoxymethane and triethoxymethane.

5. The preparation method of the high melt strength copolymerized formaldehyde according to claim 1, wherein the chain extender is polyisocyanate, and when the chain extender is used in combination with a polybasic chain transfer agent, the mass ratio of the chain extender to the polybasic chain transfer agent is 0.5-5: 1, the total amount of the chain extender and the polybasic chain transfer agent is not more than 2000ppm of the mass of the trioxymethylene.

6. The process for preparing a high melt strength copolyoxymethylene according to claim 5, wherein the chain extender is selected from the group consisting of diisocyanate and triisocyanate.

7. The method for preparing the high melt strength copolyoxymethylene as claimed in claim 1, wherein the amount of the high efficiency micro-additives in the mass of the polyoxymethylene powder comprises: 100-500 ppm of antioxidant, 500-5000 ppm of plasticizer and 100-500 ppm of calcium stearate.

8. The process for preparing a high melt strength copolyoxymethylene as claimed in claim 7, wherein the antioxidant is 245 antioxidant and the plasticizer is fatty ester plasticizer.

9. The process for producing a high melt-strength polyoxymethylene according to claim 1,

the reaction is carried out by adopting a continuous feeding mode or a sequential feeding mode.

10. A copolyformaldehyde prepared by the method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of copolyoxymethylene, and particularly relates to high melt strength copolyoxymethylene and a preparation method thereof.

Background

Polyformaldehyde is divided into two categories of homopolymerized formaldehyde and copolymerized formaldehyde, most of polyformaldehyde products sold conventionally are linear polymers, and a molecular main chain is formed by carbon-oxygen bonds. The polyformaldehyde is polymerized by trioxymethylene and comonomers, the common comonomers comprise 1, 3-dioxolane, 1, 3-dioxolane and the like, the production of the polyformaldehyde follows a cationic polymerization mechanism, the polyformaldehyde obtained by using the monomers is a linear polymer, meanwhile, the addition amount of a conventional auxiliary agent is large, the loss of the melt strength is large, namely impurities exist in the melt, the melt strength is low under the condition of certain molecular weight and molecular weight distribution, and the preparation requirements of high-performance products such as polyformaldehyde fibers, films and the like are difficult to meet. At present, the main application market of polyformaldehyde products is still injection molding, the application in the aspects of spinning, extrusion molding and blow molding is limited by low melt strength, the polyformaldehyde products cannot be widely used, the quality competition is serious, and the development of the polyformaldehyde industry is not facilitated. In the aspect of the development of high melt strength copolyoxymethylene products, no relevant reports are seen at home and abroad, the difference of the performance of the polymer products is realized mainly by changing the types and the dosage of an initiator and a comonomer, and the molecular weight and the distribution thereof are changed by improving the rheological property of the products, so that the melt index (melt mass/volume flow rate) of a polymer is changed, the linear structure of the copolyoxymethylene molecules is not changed, and the melt strength of the products cannot be effectively improved; in the development of other polymers, such as polyethylene, the melt strength is changed by a copolymerization method, and the melt strength of the polymer can be changed by adding a multi-component comonomer or changing the form of a catalyst, so that the molecular chain of the polymer can be crosslinked and branched. The polyformaldehyde can also realize branching and crosslinking through a multi-functionality comonomer, such as a ternary epoxy monomer, but the method of the multi-element chain transfer agent provided by the invention is more ingenious and novel, and is a method for preparing a high-melt-strength polymer by effectively utilizing the characteristic that a cationic polymerization reaction is easy to generate a chain transfer reaction; the structural characteristics of the copolyoxymethylene determine that the product has poor thermal stability, and an effective stabilizing auxiliary is indispensable, so that the thermal stability of the product can be ensured by using the efficient trace auxiliary, and the influence of the added auxiliary on the melt strength is improved.

Disclosure of Invention

The invention aims to provide high-melt-strength copolyoxymethylene and a preparation method thereof.

A preparation method of high melt strength copolymerized formaldehyde comprises the following steps: trioxymethylene, a comonomer, an initiator, a multi-chain transfer agent or a multi-chain transfer agent is matched with a chain extender, and a polymerization reaction is carried out at 50-70 ℃ through a double-screw reactor to complete branching and crosslinking copolymerization so as to obtain polyformaldehyde powder; mixing polyformaldehyde powder with an efficient trace auxiliary agent, performing melt plasticization at 180-230 ℃ through a thermal devolatilization process, and cooling and granulating to obtain a high-melt-strength co-polyoxymethylene product.

The comonomer is selected from 1, 3-dioxolane, 1, 3-dioxolane and the like; the mass of the comonomer accounts for 3-5% of that of trioxymethylene.

The initiator is boron trifluoride ethyl ether, and accounts for 50-150 ppm of the mass of the trioxymethylene.

Polybasic chain transfer agent: at least 3H on C1-C3 alkane (namely alkane with 1-3 carbon atoms) are substituted by alkoxy, the alkyl in the alkoxy is alkyl with 1-5 carbon atoms, such as one or more selected from tetraethoxymethane, tetrabutoxymethane, triethoxymethane, and the like, and the addition amount is 100 ppm-1000 ppm of the mass of trioxymethylene.

The chain extender is polyisocyanate, preferably diisocyanate or ternary isocyanate, and when the chain extender is matched with the polybasic chain transfer agent for use, the mass ratio of the chain extender to the polybasic chain transfer agent is 0.5-5: 1, the total adding amount of the chain extender and the polybasic chain transfer agent is not more than 2000ppm of the mass of the trioxymethylene.

The dosage of the high-efficiency trace auxiliary agent in the mass of the polyformaldehyde powder material comprises: 100-500 ppm of antioxidant (245), 500-5000 ppm of plasticizer (fatty ester plasticizer such as dioctyl sebacate), and 100-500 ppm of calcium stearate.

The preparation method of the invention adopts a continuous feeding mode or a sequential feeding mode to carry out the reaction.

According to the method, branching and crosslinking can be realized through the multi-element chain transfer agent or/and the chain extender, so that the winding of a molecular chain is improved; the loss of the added auxiliary agent to the melt strength can be avoided by the high-efficiency trace auxiliary agent, and the high-melt-strength co-polyformaldehyde product is obtained. The melt strength can reach 50 cN-200 cN when tested at 190 ℃, and the conventional polyformaldehyde is about 15 cN.

Detailed Description

The present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples.