CN1589966A - Preparation of bimetal cyanide catalyst using acid treating metal salt - Google Patents

Abstract

A process for preparing high-activity bimetal cyanide as complexing catalyst from zinc chloride features that as said zinc chloride has higher basicity, it is treated by acid to regulate its basicity to optimal value and then is used to prepare said catalyst with higher activity, resulting in high quality of catalyzed product.

Description

Preparation of double metal cyanide catalysts by acid treatment of metal salts

Technical Field

The present invention belongs to a technological method for preparing double metal cyanide complex catalyst by using acid to treat metal salt.

Background

Double Metal Cyanide (DMC) complex catalysts have been widely used in epoxide polymerization. Compared with alkali catalyst, DMC catalyst inhibits the disproportionation of Propylene Oxide (PO), and catalyzes and synthesizes polyether polyol with low unsaturation degree, low content of unit alcohol and narrow molecular mass distribution, thus improving the quality of downstream polyurethane products. The DMC catalyst has extremely high activity, the use amount is about 25ppm, and the DMC catalyst can not be removed from the product polyhydric alcohol, so that the post-treatment procedures of neutralization, filtration and the like of an alkali catalysis process are omitted, the production flow is simplified, and the product cost is reduced.

Since the 60's of the 20 th century, a series of related patents emerged after the U.S. general rubber company first patented DMC. In particular, in the last decade, DMC catalysts have been studied with dramatic progress, e.g., U.S. Pat. No. 5,470,813, 5,482,908, 5,545,601, 5,627,120, 5,714,428, Jan. Pat. No. 4-145,123, Ep 0,761,708A₂，DE19745120A₁CN1,233,529A et al, which discuss and continuously perfect the preparation technology of non-crystallization high activity DMC complex catalyst, the technical point is ①. the zinc hexacyanocobaltate (Zn) is determined₃[Co(CN)₆]₂) The most suitable double metal cyanide salt is zinc chloride, which is preferably prepared by direct reaction of an aqueous solution of zinc chloride with an aqueous solution of hexacyanocobaltate (e.g., potassium, calcium, etc.) to form a precipitate of zinc hexacyanocobaltate ② zinc hexacyanocobaltate must be treated with a low molecular weight organic substance, the most suitable organic substance being t-butanol, which acts as a complexing agent and which is catalytically active only if the t-butanol complexes to the structure of the DMC ③. for better complexing of the t-butanol with the DMC, it is preferably premixed with ZnCl₂Aqueous solution or K₃Co(CN)₆Adding potassium hexacyanocobaltate and tert-butanol solution dropwise into zinc chloride and tert-butanol solution, and simultaneously stirring with emulsifier under high-speed shearing, ④ adding polymer with certain functional group to further improve catalyst activitySuch as polyether polyols or polyester polyols, and the like.

But double metal cyanide complex catalysts also have disadvantages,for example: the polyether polyol catalyzed and synthesized by the polyether polyol contains a small amount of components (2-40 ten thousand Da) with extremely high molecular mass, and although the content is very low, the polyether polyol influences the mass of downstream polyurethane materials, causes the soft foam to be tight, has poor rebound resilience, and can cause the molded polyurethane to collapse in severe cases. The american Arco corporation has done much intensive research work. WO99/56874, WO99/59719 and U.S. Pat. No. 6,063,897, all of which are incorporated herein by reference in their entirety. These patents discuss the disadvantages of DMC catalysts and also point out the presence of free (non-bonded) Zn (OH) in double metal cyanide complex catalysts⁺The grouping is a direct reason that DMC polyether polyol contains more components with extremely high molecular mass and seriously influences the performance of downstream polyurethane products. The method of adding acid into the reaction liquid during the preparation of the catalyst is proposed to eliminate Zn (OH)⁺The quality of DMC polyether polyol is improved by the group, and certaineffect is achieved. However, these solutions are cumbersome, for example: the type of acid, the amount of acid added, the treatment temperature, the treatment time and the like must be strictly controlled, otherwise, negative effects are caused, and even if the acid treatment conditions are well controlled, the activity of the catalyst is reduced by 10 percent, and generally reduced by 20 percent.

U.S. Pat. No. 5,783,513 teaches that the basicity of zinc chloride (zinc oxide as a weight percentage of zinc chloride) has a significant effect on the activity of the DMC catalyst, and that the basicity value is preferably controlled in the range of 0.4 to 0.9 wt.%. Commercial zinc chloride on the us market has a low basicity, typically below 0.2 wt.%, and is not suitable for direct use in preparing DMC catalysts for reasons not discussed in this patent. This U.S. patent proposes the adjustment of ZnCl by adding an alkaline substance (ZnO)₂The alkalinity method. But how to treat ZnCl with higher alkalinity₂It has not been discussed at all, nor does it relate to ZnCl₂The reason for the higher alkalinity and the harm of the higher alkalinity to the quality of the downstream polyurethane product.

Disclosure of Invention

It is an object of the present invention to provide a process for preparing double metal cyanide catalysts by treating metal salts with acids

The technical scheme of the invention is as follows:

a process for preparing a double metal cyanide catalyst by treating a metal salt with an acid, which is characterized in that:

1. cheap high-alkalinity metal salt is used as a raw material;

2. adjusting the alkalinity value of the cheap high-alkalinity metal salt to be optimal by a method ofadding an acidic substance;

the metal salt is zinc chloride, the cheap zinc chloride with high alkalinity refers to industrial zinc chloride, particularly zinc chloride which is agglomerated after being placed for a long time, and the alkalinity value is more than 1.8 wt.%, even more than 2 wt.%.

The acidic substance is preferably hydrochloric acid.

Metal salt ZnCl₂The optimum value of the alkalinity is 0.55-0.80 wt.%, less than 0.55 wt.%, the activity of the prepared catalyst is reduced rapidly, and is higher than 0.80 wt.%, the activity of the catalyst is also reduced, but the reduction speed is relatively slow.

When the basicity of zinc chloride exceeds 0.80 wt.%, during the preparation of the DMC catalyst, a greater amount of white Zn (OH) Cl precipitation, more Zn (OH) occurs⁺The end groups are carried over into the DMC catalyst, the catalyst activity decreases and the content of very high molecular mass components in the DMC polyether polyol increases, affecting the downstream polyurethane product quality.

The process for adjusting high alkalinity zinc chloride by acid comprises the following steps:

1. reacting ZnCl₂Preparing a water solution with the concentration of 63-65 wt.%, and filtering to remove impurities;

2. analysis of ZnCl₂Alkalinity of the filtrate;

3. ZnCl analyzed according to the above₂The alkalinity value of the aqueous solution, the required alkalinity value and the concentration of hydrochloric acid are calculated to adjust ZnCl₂Alkalinity requires the amount of hydrochloric acid added;

4. analysis of ZnCl after acid treatment₂Alkalinity and concentration values of the aqueous solution.

The invention is characterized in that: due to treatment of ZnCl with acid₂Adjustment of the basicity to an optimum value reduces Zn (OH) in the DMC catalyst⁺The content of groups is correspondingly reduced to more DMCThe polyol contains extremely high molecular weight components, so that the rebound rate of downstream polyurethane flexible foam is improved, and the defects of the DMC catalyst are overcome to a certain extent.

Drawings

FIG. 1 is ZnCl₂Relationship between alkalinity and precipitation concentration

FIG. 2 is a reaction curve of PO catalyzed by the catalyst in FIG. 6

FIG. 3 is ZnCl₂Relationship between alkalinity and catalytic activity

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

We have found that the starting material ZnCl₂The water in the air is absorbed during the placing process to generate basic salt:

the basic salt is a white precipitate insoluble in water, the formation of which causes the ZnCl starting material₂The alkalinity is increased. Particularly, after long-term storage, the generation amount of basic salt is large, and the raw material ZnCl is₂Caking, alkalinity will exceed 2 wt.%. In the preparation of DMC according to the method proposed in U.S. Pat. No. 5,482,908 et al, ZnCl with high basicity (>0.80 wt.%) is used₂When the aqueous solution (with a concentration of 62 wt.%) is used to prepare a reaction raw material solution with deionized water and tert-butyl alcohol, a significant white precipitate of Zn (OH) Cl is generated. We examined ZnCl₂Alkalinity as a function of amount of Zn (OH) Cl precipitate produced, by light transmittanceThe amount of precipitate in the reaction raw material liquid was measured. The data are shown in Table-1, and FIG. 1 is plotted according to the data in Table-1.

TABLE 1 ZnCl₂Relationship between basicity and amount of Zn (OH) Cl precipitate formed

	ZnCl2Alkalinity of (wt.％)	Reaction raw material liquid Light transmittance (%)
			1	0.60	84.5
2	0.75	83.3
			3	0.80	81.1
4	0.95	46.7
			5	1.03	14.7
6	1.12	6.70
			7	1.30	1.30
8	1.60	0.30
			9	2.10	0.30

Note: 1. using UV-160 type ultraviolet-visible spectrophotometer (Shimadzu, Japan);

2. the wavelength of the light used was 550 nm;

3. deionized water is used as reference;

4. the thickness of the sample cell is 1 cm.

It is evident that, with ZnCl₂The increase in alkalinity, the increase in the amount of Zn (OH) Cl produced, and the corresponding Zn (OH) carry over into the DMC catalyst produced⁺The more clusters. That is to say, Zn (OH) contained in the double metal cyanide complex catalyst⁺Group is just because of the raw material metal salt ZnCl with slightly high alkalinity₂Caused by, ZnCl₂The higher the basicity value, the more Zn (OH) the DMC catalyst contains⁺The more clusters. By direct acid treatment of the metal salt ZnCl as starting material₂Effective reduction of Zn (OH) in DMC catalysts can be achieved by controlling the basicity value within a suitable range⁺The content of the groups improves the activity of the catalyst, reduces the content of components with extremely high molecular mass in the DMC polyether polyol, and solves the problems of tightening and collapse of products such as downstream polyurethane flexible foam and the like.

Using ZnCl of different basicity₂The catalytic activity of the prepared double metal cyanide catalyst is obviously different. The method and the calculation formula provided by the invention can be used for adjusting the industrial ZnCl with high alkalinity₂To have an optimum basicity, and using it to produce Zn (OH)⁺High activity DMC catalyst with very low group content for further catalytic synthesis of polyether with good performanceA polyhydric alcohol. Practice proves that the metal salt ZnCl is treated by acid₂The method is simple, effective and more practical. This will be further illustrated by way of example.

The invention adopts a method of adding acid substances to ZnCl₂The alkalinity is adjusted to an optimum value, and the acidic substance can be inorganic acid such as hydrochloric acid, acetic acid, sulfuric acid, etc., or organic acid, preferably hydrochloric acid. The specific method is to firstly prepare ZnCl₂Preparing an aqueous solution with the concentration of 63-65 wt.%, filtering the aqueous solution by using a common plate and frame filter, removing impurities, and then measuring the alkalinity of the aqueous solution (see appendix). Raw material ZnCl₂Alkalinity value is given as A₁The alkalinity value to which adjustment is required is represented by A₂Typically, the amount of hydrochloric acid added to adjust the basicity is calculated by equation-1.

$V=\frac{W\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A0314424600141.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\&CenterDot;(A_1-A_2)}{406.9\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A0314424600141.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}$ Equation-1

V: volume of hydrochloric acid (ml) added;

W：ZnCl₂amount of aqueous solution (g);

C₁：ZnCl₂concentration of aqueous solution (wt.%);

C₂: concentration of added hydrochloric acid (wt.%);

A₁、A₂: ZnCl before and after conditioning₂Alkalinity (wt.%) of the aqueous solution.

Example 1

Obtaining industrial product ZnCl₂330.1 g, adding 180.2 g of deionized water, stirring and dissolving to prepare ZnCl₂The aqueous solution was filtered to remove solid impurities and analyzed to have a concentration of 63.40 wt.%. Taking the ZnCl₂The equivalent point (PH 3.7) was determined graphically by potentiometric titration with 0.1N hydrochloric acid in 8.071 g aqueous solution, and the alkalinity value was measured as 1.88 wt.% using a volume of 23.60ml of hydrochloric acid, which was too high and required adjustment.

Set adjusted ZnCl₂The alkalinity value of the aqueous solution was 0.60 wt.%. 450.5 g of the solution was taken, and 9.40ml of hydrochloric acid having a concentration of 9.6N was added as calculated by the formula-1. Hydrochloric acid is added slowly to ZnCl with stirring₂And (3) uniformly stirring the mixture for 3-5 minutes after the water solution is added, and sampling and analyzing the sample to obtain the water solution with the alkalinity of 0.57 wt.%. Due to the addition of hydrochloric acid, ZnCl is diluted₂The aqueous solution, again analyzed for concentration of 61.5 wt.%.

As per U.S. Pat. No. 5,482,908 et alThe method uses ZnCl with the concentration of 61.5 wt.% and the alkalinity of 0.57 wt%₂Preparation of DMC-1 in aqueous solution^#The catalyst is then used to synthesize a pure Propylene Oxide (PO) polyether triol (PPG-3000), DMC-1, having a molecular weight of 3000^#The concentration of the catalyst was 25 ppm. The catalyst activity is expressed as the reaction rate of propylene oxide, POThe reaction data are shown in Table 4, DMC-1^#The time required for catalyst activation and the properties of the synthesized PPG-3000 are shown in Table-5.

Examples 2 to 4

Three ZnCl formulations were prepared according to the method of example 1 at concentrations of 62.3 wt.% alkalinity 0.89 wt.%, 60.9 wt.% alkalinity 1.6 wt.% and 61.3 wt.% alkalinity 1.9 wt.%₂An aqueous solution. Preparation of DMC-2 by the procedure used in example 1^#、3^#、4^#A catalyst. In the process of preparing DMC catalyst, the three ZnCl catalysts with high alkalinity are used₂When the aqueous solution is prepared into a reaction raw material solution with water and tertiary butanol, white precipitates with different degrees are generated. By DMC-2^#、3^#、4^#The PPG-3000 was synthesized using the catalyst in the same manner as in example 1, and the reaction data of PO are shown in Table-4, and the catalyst activation time and the properties of the synthesized PPG-3000 are shown in Table-5.

Comparative examples 1 to 2

ZnCl was formulated as in example 1 at a concentration of 61.5 wt.% alkalinity 0.37 wt.%, and at a concentration of 61.4 wt.% alkalinity 0.18 wt.% both at lower alkalinity₂Aqueous solution, DMC-5 prepared in the same manner^#、6^#A catalyst. By DMC-5^#、6^#The PPG-3000 is synthesized by the catalyst by the method. The PO reaction data are shown in Table-4, and the catalyst activation times and the properties of the synthesized PPG-3000 are shown in Table-5.

PO absorption curves were plotted against the data of Table-4 for 6 DMC catalysis, as shown in FIG. 2. ZnCl was plotted according to the data of Table-5₂The alkalinity is plotted against the rate of PO reaction, as shown in FIG. 3.

Foaming test example:

DMC-1 was used in example 1, example 2 and example 3, respectively^#、DMC-2^#、DMC-3^#Synthetic DMC polypropylene oxide triol(PPG-3000), taking corresponding base-catalyzed polypropylene oxide triol, and carrying out foaming test, wherein the foaming formula is shown in a table-2:

TABLE-2

Name of raw materials	Weight (g)
		PPG-3000	300
Deionized water	9
		A33(amine catalyst)	0.9
T9(tin catalyst)	0.9
		L-580 (surfactant)	1.2
TDI	120

The four soft bubbles were measured for resilience and the data are shown in Table-3:

TABLE-3

Soft bubble numbering	Rebound resilience of foam*(％)
		Soft foam-1 (DMC-1)#)	39.2
Soft foam-2 (DMC-2)#)	35.6
		Soft foam-3 (DMC-3)#)	34.7
Soft bubble-4 (KOH)	40.0

^*Note: all were mean data from 5 or more tests.

As is apparent from the data in Table-3, ZnCl having a higher basicity₂Prepared DMC-2^#、DMC-3^#The soft foam of the catalytic synthesis polyether polyol has poor rebound resilience, and ZnCl is treated by acid₂Adjusting the alkalinity to an optimum value reduces DMC-1^#Zn (OH) in catalyst⁺The content of the group correspondingly reduces the content of components with extremely high molecular mass in the DMC polyol, improves the rebound rate of downstream polyurethane flexible foam, and overcomes the defects of the DMC catalyst to a certain extent.

As is clear from the above examples and data, the starting material ZnCl₂The basicity of (a) is very closely related to the DMC catalyst activity and the properties of the polyether polyol synthesized. ZnCl₂The optimum alkalinity range is 0.55-0.80 wt.%. Using ZnCl with basicity in this range₂It is most advantageous to increase the activity of the prepared DMC complex catalyst, to reduce the time required for catalyst activation, to improve the properties of the synthesized polyether polyol and to increase the resilience of the prepared polyurethane foam, etc. Alkalinity below 0.55 wt.% decreased catalyst activity very rapidly, alkalinity above 0.80 wt.% also decreased catalyst activity, but at a relatively slow rate.

We believe that the use of high basicity ZnCL₂When preparing the DMC reaction raw material liquid, the white Zn (OH) Cl precipitate generated is one of the factors for reducing the activity of the catalyst, and Zn (OH)⁺The group is brought into the DMC catalyst, so that the synthesized polyether polyol contains more extremely high molecular weight components, the polyurethane is foamed and tightened, and the rebound resilience is reduced. By treatment with appropriate amounts of acidIndustrial metal salt ZnCl₂The catalyst has proper alkalinity, not only reduces the raw material cost, but also inhibits the generation of Zn (OH) Cl, thereby preparing the DMC complex catalyst with high activity and overcoming the defects of the DMC complex catalyst to a certain extent.

TABLE-PO absorption data for 46 DMC catalyst catalyzed polymerizations

300	-	-	-	-	623	387
							330	-	-	-	-	698	431
360	-	-	-	-	739	465

① PPG-700 synthesized using a base catalyst was used as the starting polymer;

② propylene oxide from Tianjin chemical plant was used as the starting material.

TABLE-5 ZnCl₂Comparison of alkalinity with the Activity of the prepared catalyst and the Performance of the synthesized PPG-3000

Catalyst and process for preparing same Row number	ZnCl2 Aqueous solution Alkalinity (wt%)	Catalyst and process for preparing same Required for activation Time of day mm	Average of PO Rate of reaction (g/min)	PPG-3000 Performance
							Hydroxyl number (mgKOH/g)	Degree of unsaturation (meq/g)	Viscosity of the oil (mpa.s)
				DMC-1#	0.57	38				8.2	56.4	0.0051	540
DMC-2#	0.89	38	5.7				55.7	0.0062	560
				DMC-3#	1.6	56				4.9	56.6	0.0065	630
DMC-4#	1.9	67	4.2				55.8	0.0072	645
				DMC-5# Comparative example 1	0.37	47				2.1	55.5	0.0090	750
DMC-6# Comparative example 2	0.18	63	1.3				-	-	-

Appendix:

ZnCl₂determination of the alkalinity of aqueous solutions

ZnCl₂The alkalinity of the aqueous solution was determined by potentiometric titration using an 809 automatic titrator (Metrohm) and directly titrated with a standard solution of hydrochloric acid. Alkalinity results arein zno wt.%.

The specific analysis steps are as follows:

weighing 0.5-1 g (standard to 0.0001g) of sample in a beaker (according to the alkalinity), taking 50ml of 0.01 wt.% potassium hydroxide aqueous solution by a pipette, adding the potassium hydroxide aqueous solution into the beaker, titrating the potassium hydroxide aqueous solution by a 0.01mol./L hydrochloric acid standard titration solution on an 809 automatic titrator, and recording the volume V of the consumed hydrochloric acid by taking a potential mutation point of a titration curve as an end point. The basicity was calculated as follows:

$\mathrm{ZnOwt}.\%=\frac{C_{\mathrm{HCl}}(V-V_0)406.9}{\mathrm{<figure-callout\; id="2"\; label="n\; C\; ZnCl"\; filenames="A0314424600141.png"\; state="\{\{state\}\}">n</figure-callout>}{C}_{\mathrm{ZnCl}}{2}_{}}$

in the formula: c_HCl-hydrochloric acid calibration concentration mol./L

V-volume ml of hydrochloric acid consumed by the sample.

V₀-blank consumes volume ml of hydrochloric acid.

m-sample weighing g

C_ZnCl2ZnCl in the sample₂Content%

Blank tests were performed in the same manner.

Claims (6)

1. A process for preparing a double metal cyanide catalyst by treating a metal salt with an acid, which is characterized in that:

①, adopting cheap high-alkalinity metal salt as raw material;

② the alkalinity value of the cheap high alkalinity metal salt is adjusted by adding acidic substance.

2. The process for preparing double metal cyanide catalysts according to claim 1, characterized in that: the metal salt is zinc chloride, the cheap zinc chloride with high alkalinity refers to industrial zinc chloride, particularly zinc chloride which is agglomerated after being placed for a long time, and the alkalinity value is more than 1.8 wt.%, even more than 2 wt.%.

3. The process for preparing double metal cyanide catalysts according to claim 1, characterized in that: the acidic substance is preferably hydrochloric acid.

4. The process for preparing double metal cyanide catalysts according to claim 1, characterized in that: the optimum value of the alkalinity of the metal salt ZnCl2 is 0.55-0.80 wt.%, is lower than 0.55 wt.%, the activity of the prepared catalyst is reduced rapidly, is higher than 0.80 wt.%, the activity of the catalyst is also reduced, but the reduction speed is relatively slow.

5. The process for preparing double metal cyanide catalysts according to claim 4, characterized in that: when the basicity of zinc chloride exceeds 0.80 wt.%, during the preparation of the double metal cyanide catalyst, a greater amount of white Zn (OH) Cl precipitates, and more Zn (OH)⁺The groups are carried into the double metal cyanide catalyst, the activity of thecatalyst is reduced, and the content of the extremely high molecular weight components in the double metal cyanide polyether polyol is increased, thereby influencing the quality of downstream polyurethane products.

6. The process for preparing double metal cyanide catalysts according to claim 1, characterized in that: the process for adjusting high alkalinity zinc chloride by acid comprises the following steps:

① refining ZnCl₂Preparing a water solution with the concentration of 63-65 wt.%, and filtering to remove impurities;

② analysis of ZnCl₂Alkalinity of the filtrate;

③ ZnCl analyzed as described above₂The alkalinity value of the aqueous solution, the required alkalinity value and the concentration of hydrochloric acid are calculated to adjust ZnCl₂Alkalinity requires the amount of hydrochloric acid added;

④ reanalysis of ZnCl after acid treatment₂Alkalinity and concentration values of the aqueous solution.

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