CN113429557A

CN113429557A - Continuous preparation method of low-viscosity polyether polyol

Info

Publication number: CN113429557A
Application number: CN202110687202.8A
Authority: CN
Inventors: 刘佳奇; 叶天; 翟永锋; 李付国; 秦承群
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2021-09-24
Anticipated expiration: 2041-06-21
Also published as: CN113429557B

Abstract

The invention discloses a continuous preparation method of polyether polyol with low viscosity and narrow molecular weight distribution, which selects proper stirring power according to the difference of catalyst concentration and material retention time in a reaction system, ensures that the chain transfer rate of the catalyst is greater than the intermolecular mixing rate in the reaction process under the condition of ensuring the conversion rate of reactants, can fully ensure the safety of a device, and can avoid the broadening of the molecular weight distribution caused by overhigh mixing efficiency, and the product achieves the effects of narrow molecular weight distribution and low viscosity.

Description

Continuous preparation method of low-viscosity polyether polyol

Technical Field

The invention belongs to the technical field of polyether polyol, and particularly relates to a continuous preparation method of low-viscosity narrow-molecular-weight-distribution soft-foam polyether polyol.

Background

Polyether polyol is an important chemical raw material, and polyurethane foam produced by using the polyether polyol is widely applied to the fields of furniture and household appliances, automobiles, aerospace, buildings, clothes, packaging and the like. Polyether polyol continuous production process generally adopts Double Metal Cyanide (DMC) catalyst for catalysis, has the advantages of high productivity, small occupied area, low cost and the like, and is adopted by a plurality of companies in the world. However, compared with the batch production process, the polyether product obtained by the continuous process has large viscosity and wide molecular weight distribution, thereby causing certain influence on the application of polyether polyol.

CN 100497438C and CN 103694465B respectively disclose a preparation method of continuous polyether polyol, the process can be used for continuously, efficiently and stably producing the soft-foam polyether polyol, but the problems of wide molecular weight distribution and high viscosity of polyether polyol products are still not solved.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for continuously producing polyether polyol with narrow molecular weight distribution and low viscosity.

In order to achieve the purpose, the invention adopts the following technical scheme.

A method for preparing low-viscosity narrow-molecular-weight-distribution continuous polyether comprises the following steps:

1) adding polyether polyol and Double Metal Cyanide (DMC) catalyst into a reaction kettle in advance, heating, introducing propylene oxide for induction,

2) after the catalyst is successfully induced, continuously introducing an epoxy compound, a DMC catalyst and a small molecule initiator into a reaction kettle for reaction, enabling a reaction product to flow out of the kettle top, enter an aging kettle, and enter a storage tank after aging;

wherein, the concentration (c) of the catalyst in the reaction kettle in the step 2) is controlled to be 15-100 ppm, the average residence time (t) of the mixed material in the reaction kettle is 0.5-10 h, the stirring power (P) is 1.1-2.1 kW, and the three satisfy the relation:

wherein P is in kW, t is in h, and c is in ppm.

In the method, in the step 1), the hydroxyl value of the polyether polyol added in advance is 20-280 mgKOH/g, preferably 40-120 mgKOH/g; in the reaction starting stage, the amount of the added catalyst is large, and the concentration of the DMC catalyst in the pre-added material is 20-5000 ppm, preferably 60-1000 ppm;

the temperature of the reaction kettle is raised to 130-190 ℃, and preferably 145-160 ℃;

the adding amount of the propylene oxide is 1 to 5 percent of the mass of the polyether glycol added in advance.

In the method, in the step 2), when the temperature in the reaction kettle obviously rises and the pressure rapidly drops, the successful induction of the catalyst is shown;

the epoxy compound is ethylene oxide, propylene oxide or a mixture of the two;

the micromolecule initiator is one or more of ethylene glycol, 1, 2-propylene glycol, glycerol and trimethylolpropane;

the proportion of the added epoxy compound and the small molecular initiator is controlled according to the hydroxyl value of the product of 20-168 mgKOH/g;

as can be understood by those skilled in the art, the average residence time (t) of the mixed materials in the reaction kettle is the ratio of the mass of the materials in the reaction kettle to the sum of the mass flow rates of all the materials fed in the reaction kettle during the stable operation of the system; the reaction kettle catalyst concentration (c) is the concentration of catalyst in the mixture of epoxy compound, DMC catalyst and small molecule starter;

the epoxy compound, DMC catalyst and small molecule starter may be fed in a manner conventional in the art;

after the system is stable, the temperature of the reaction kettle and the aging kettle is 130-190 ℃, and the pressure is 0-1 MPa.

The invention has the following advantages:

in the continuous reaction process, the chain transfer speed and the intermolecular mixing speed have a crucial influence on the molecular weight distribution of the product. The chain transfer speed is determined by the molecular weight and the type and concentration of the catalyst, and the mixing speed between molecules is influenced by the back mixing degree of the reaction kettle. If the mixing speed is higher than the chain transfer speed, the molecular weight distribution of the product is widened, and the viscosity is increased; if the mixing speed is too low, the reaction rate of the epoxy compound is lowered, and the safety risk of the apparatus is increased, so that it is important to control the mixing speed between molecules reasonably. The invention can determine the range of stirring power according to the concentration and the residence time of the catalyst, thereby reasonably controlling the back mixing degree of the system, and ensuring that the chain transfer rate of the catalyst is greater than the intermolecular mixing rate under the condition of ensuring the conversion rate of the epoxy compound, thereby obtaining the polyether polyol product with narrow molecular weight distribution and low viscosity.

Detailed Description

The method provided by the present invention is further illustrated by the following examples, but the present invention includes but is not limited to the examples listed, and also includes any other known variations within the scope of the claims of the present invention.

The product performance testing method comprises the following steps:

polyether polyol hydroxyl value test method reference: GB/T12008.3-2009

Polyether polyol viscosity test method reference: GB/T12008.7-2009

The polyether polyol molecular weight distribution test method adopts gel chromatography (GPC).

Example 1

(1) 0.2g of DMC catalyst (Huaian Bade polyurethane science and technology Co., Ltd.) was dispersed in advance into 1kg of polyether polyol (polyether base material, hydroxyl value 56mgKOH/g) to prepare a catalyst slurry, and the catalyst slurry was charged into a catalyst slurry tank.

0.06g of DMC catalyst was dispersed in 2kg of polyether polyol (polyether base material, hydroxyl value 56mgKOH/g) to obtain a dispersion, and the dispersion was put into a 5L reactor, heated to 150 ℃ and introduced with 50g of propylene oxide.

(2) When the pressure of the reaction kettle rapidly decreases and the temperature rapidly rises, the catalyst is successfully activated, then a mixture of glycerol, ethylene oxide and propylene oxide (the content of ethylene oxide in the epoxy compound is 10 wt%) and catalyst slurry are continuously fed according to the required proportion, after the reaction kettle is full of liquid, the polyether glycol overflows from the kettle top to the aging kettle for aging reaction, and after the aging kettle is full of liquid, the polyether glycol overflows from the kettle top of the aging kettle and enters a product storage tank. During the continuous and stable operation, the temperature of the reaction kettle is controlled to be 150 ℃, the pressure of the reaction kettle is controlled to be 0.4MPa, the concentration of the catalyst is controlled to be 30ppm, the residence time is 2 hours, and the stirring power of the reaction kettle is 1.4kW, so that the hydroxyl value of the product is 55.87mgKOH/g, the viscosity is 503cP (25 ℃), and the molecular weight distribution is 1.14.

Examples 2 to 6

The differences between examples 2-6 and example 1 are shown in table 1 below.

TABLE 1

Comparative example 1

Based on example 1, the stirring power was 1.9kW under otherwise identical conditions, and the product viscosity was 556cP @25 ℃ and the product molecular weight distribution was 1.31.

Comparative example 2

Based on example 4, under otherwise identical conditions, a stirring power of 2.3kW was used, and the product viscosity was 420cP @25 ℃ and the product molecular weight distribution was 1.22.

Claims

1. A continuous preparation method of polyether polyol with low viscosity and narrow molecular weight distribution is characterized by comprising the following steps:

1) adding polyether polyol and DMC catalyst into a reaction kettle in advance, heating, raising the temperature, introducing propylene oxide for induction,

2) after the catalyst is successfully induced, continuously introducing an epoxy compound, a DMC catalyst and a small molecule initiator into a reaction kettle for reaction;

wherein P is in kW, t is in h, and c is in ppm.

2. The method as claimed in claim 1, wherein the polyether polyol added in advance to the reaction kettle in the step 1) has a hydroxyl value of 20 to 280 mgKOH/g.

3. The method as set forth in claim 1 or 2, wherein the DMC catalyst previously charged in the reaction kettle in the step 1) has a concentration of 20 to 5000 ppm.

4. The method according to any one of claims 1 to 3, wherein the temperature of the reaction vessel is raised to 130 to 190 ℃ in the step 1).

5. The method according to any one of claims 1 to 4, wherein in step 1), the propylene oxide is added in an amount of 1% to 5% by mass of the previously added polyether polyol.

6. The process according to any one of claims 1 to 5, wherein in step 2), the epoxy compound is ethylene oxide and/or propylene oxide;

the micromolecule initiator is one or more of ethylene glycol, 1, 2-propylene glycol, glycerol and trimethylolpropane.

7. The method according to any one of claims 1 to 6, wherein in step 2), the ratio of the epoxy compound to the small molecule starter is controlled in accordance with the hydroxyl value of the product of 20 to 168 mgKOH/g.

8. The method according to any one of claims 1 to 7, wherein in the step 2), the reaction product flows out from the top of the reaction kettle, enters the aging kettle, and enters the storage tank after aging.

9. The method according to any one of claims 1 to 8, wherein in the step 2), the temperature of the reaction vessel is 130 to 190 ℃ and the pressure is 0 to 1 MPa.

10. The method as claimed in claim 8, wherein in the step 2), the temperature of the aging kettle is 130-190 ℃ and the pressure is 0-1 MPa.