A method for synthesizing 1,6-hexanediol polyoxypropylene ether

Abstract

The application relates to a synthesis method of a synthesis method of 1,6-hexanediol polyoxypropylene ether, and belongs to the technical field of organic compound synthesis. The synthesis method of 1,6-hexanediol polyoxypropylene ether comprises the following method: 1,6-hexanediol polyoxypropylene ether is used as raw material, a triphenylaluminum and alkali hydroxide compound catalyst are added, and then propylene oxide is used as a reaction monomer to synthesize 1,6-hexanediol polyoxypropylene ether. The triphenylaluminum has a certain alkalinity, so that the propylene oxide ring opening reaction and 1,6-hexanediol are carried out; meanwhile, due to the space steric hindrance and the relatively weak alkalinity of the triphenylaluminum, the isomerization of the propylene oxide is inhibited, and the production of propylene alcohol byproducts is reduced.

Description

Technical Field

[0001] The invention relates to a method for synthesizing 1,6-hexanediol polyoxypropylene ether, and belongs to the technical field of organic compound synthesis. Background Art

[0002] A synthesis method for 1,6-hexanediol polyoxypropylene ether is an important UV-curable intermediate primarily used in the synthesis of acrylate or methacrylate reactive diluents. It is used in a variety of fields, including chemical coatings, 3D printing, machinery production, automotive manufacturing, electronics, and aerospace.

[0003] 1,6-Hexanediol polyoxypropylene ether is a type of polyether polyol, produced by polymerization of 1,6-hexanediol as an initiator with propylene oxide in the presence of a catalyst. Traditionally, 1,6-hexanediol polyoxypropylene ethers are typically prepared using KOH as a catalyst (e.g., patent CN101225161A). However, the products obtained by this method suffer from defects such as a wide molecular weight distribution and the tendency of propylene oxide to isomerize to propylene alcohol under alkaline conditions, resulting in reduced molecular weight and functionality.

[0004] Amine catalysts such as alkylamines are also used (e.g., patent US3268593). These amine catalysts include trimethylamine and triethylamine. These catalysts have relatively low reactivity, resulting in products with poor appearance and dark color.

[0005] Literature also reports the use of double metal cyanide (DMC) catalysts (e.g., patent CN107200837A). Polyether polyols produced with this type of catalyst have advantages such as a narrow molecular weight distribution and low unsaturation. However, when preparing low-molecular-weight polyether polyols, they suffer from a long induction period and a high risk of catalyst deactivation. This complicates the production process, makes product quality difficult to control, and increases costs.

[0006] Existing methods have problems such as poor distribution of synthetic products, many by-products, poor color or unstable synthetic process, which reduce the added value of products and market competitiveness. Summary of the Invention

[0007] In view of the shortcomings of the existing production methods, the present invention provides a method for synthesizing 1,6-hexanediol polyoxypropylene ether by using triphenylaluminum and alkali metal hydroxide as a composite catalyst.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for synthesizing 1,6-hexanediol polyoxypropylene ether comprises the following steps: using 1,6-hexanediol polyoxypropylene ether as a raw material, adding triphenylaluminum and an alkali metal hydroxide composite catalyst, and then using propylene oxide as a reaction monomer to synthesize the 1,6-hexanediol polyoxypropylene ether.

[0010] The alkali metal hydroxide is selected from one or more of lithium hydroxide, potassium hydroxide and sodium hydroxide.

[0011] The alkali metal hydroxide is selected from potassium hydroxide.

[0012] The compounding ratio of the triphenylaluminum and the alkali metal hydroxide is 100:1~100.

[0013] The compounding ratio of the triphenylaluminum and the alkali metal hydroxide is preferably 10:1.

[0014] The amount of the triphenylaluminum and alkali metal hydroxide composite catalyst is 0.1 to 10‰ of the sum of the mass of 1,6-hexanediol and propylene oxide.

[0015] The amount of the triphenylaluminum and alkali metal hydroxide composite catalyst is 3‰ of the sum of the mass of 1,6-hexanediol and propylene oxide.

[0016] During the synthesis process, the reaction temperature is 90-150° C., and the reaction pressure is -0.05-0.50 MPa.

[0017] During the synthesis process, the reaction temperature is 110±2° C. and the reaction pressure is -0.02~0.3 MPa.

[0018] The 1,6-hexanediol reacts with propylene oxide, and the molar number of propylene oxide can be 1:100.

[0019] The 1,6-hexanediol polyoxypropylene ether prepared by the above method has a propenol by-product content of ≤10ppm.

[0020] Reaction formula of the present invention is:

[0021]

[0022] Triphenylaluminum has a certain alkalinity, which allows propylene oxide to ring-open and react with 1,6-hexanediol. At the same time, due to its steric hindrance and relatively weak alkalinity, triphenylaluminum inhibits the isomerization of propylene oxide and reduces the production of propylene alcohol byproducts. The alkali metal hydroxide can enhance or supplement the alkalinity of triphenylaluminum, creating a synergistic effect when synthesizing higher molecular weight 1,6-hexanediol polyoxypropylene ethers.

[0023] Compared with the existing technology, this patent has the following outstanding advantages and positive effects:

[0024] 1. The prepared 1,6-hexanediol polyoxypropylene ether has a propylene alcohol by-product content of less than 10ppm.

[0025] 2. Color (Pt-Co) ≤ 20, the color is lighter. DETAILED DESCRIPTION

[0026] Analytical methods:

[0027] The number average molecular weight (Mn) of the product was determined by gel permeation chromatography (GPC) using an Agilent 1200 liquid chromatograph G1328B.

[0028] The hydroxyl value is determined according to the phthalic anhydride method specified in GB / T 7383-2007.

[0029] The content of propylene glycol by-products was determined using RID-10a high performance liquid chromatography from Shimadzu Corporation of Japan.

[0030] Preparation of the reactor before implementation: Use distilled water to clean a 2.5L high-pressure glass reactor three times, dry the reactor, and cool it to room temperature for use.

[0031] Under the premise of fixed reaction time, the following examples and comparative examples were carried out. Example 1

[0032] A product with a number average molecular weight of 234 of 1,6-hexanediol polyoxypropylene ether was designed and synthesized.

[0033] A reactor was charged with 504.3 g of 1,6-hexanediol and 3 g of a catalyst mixture of triphenylaluminum and potassium hydroxide (in a 10:1 ratio). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥ -0.098 MPa until the materials were completely melted. 496 g of propylene oxide was then continuously introduced. The reaction temperature was maintained at 100 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction was completed, the temperature was lowered to 100°C for vacuum degassing, and the product was discharged to obtain the finished product. Liquid chromatography analysis of the product revealed a 3 ppm content of propylene alcohol byproducts, a color (Pt-Co) of 7, a number-average molecular weight of 210, and a hydroxyl value of 535.2 mgKOH / g as determined by chemical analysis.

[0034] In Examples 2-6, 504.3 g of 1,6-hexanediol and 496 g of propylene oxide were added to a reactor. A series of experiments were conducted using different ratios and amounts of the triphenylaluminum and potassium hydroxide catalyst, as well as reaction temperatures. Specific indicators are shown in Table 1.

[0035] Table 1 Statistical table of Examples 1-6

[0036] Catalyst ratio Catalyst amount Reaction temperature °C Propenyl alcohol by-product ppm Colour Pt-Co Number average molecular weight Mn Hydroxyl value mg KOH / g Example 1 10:1 3.0 100±2 3 7 210 535.2 Example 2 10:1 3.0 110±2 3 8 234 479.8 Example 3 10:1 3.0 130±2 6 9 235 480.1 Example 4 10:1 3.0 150±2 10 11 234 478.6 Example 5 10:1 1.0 110±2 3 7 226 496.6 Example 6 10:1 4.5 110±2 5 11 235 479.3

[0037] Note: Catalyst ratio* is triphenylaluminum and potassium hydroxide.

[0038] From the comparison of Examples 1-4 in Table 1, it can be seen that when the catalyst amount and catalyst ratio are unchanged, the reaction is best at a reaction temperature of 110±2°C (Example 2). If the reaction temperature is lower than 110°C (Example 1, 100±2°C), the product molecular weight cannot reach the theoretical value of 234, which is due to incomplete reaction, and the molecular weight does not reach the set value. If the reaction temperature is higher than 110°C, the product molecular weight can reach the theoretical value of 234, but it is possible that due to the high temperature, the product has a high content of propylene alcohol by-products and a dark color.

[0039] From the comparison of Examples 2, 5 and 6 in Table 1, it can be seen that when the catalyst ratio and reaction temperature are unchanged, if the catalyst amount is less than 3‰, the product molecular weight is small due to insufficient catalyst amount, leading to incomplete reaction (Example 5); if the catalyst amount is more than 3‰, the product molecular weight is large due to excessive catalyst amount, and the product has a high content of propylene alcohol by-products and a dark color (Example 6).

[0040] It can be seen that for the design of 1,6-hexanediol polyoxypropylene ether products with a number average molecular weight of 234, different conditions can produce products with certain differences in indicators. Next, I will do an example of a product with a larger number average molecular weight.

[0041] Example 7

[0042] Design and synthesis of 1,6-hexanediol polyoxypropylene ether products with a number average molecular weight of 234.

[0043] Into the reaction kettle, 1,6-hexanediol 504.3 g, triphenylaluminum and potassium hydroxide complex catalyst (ratio 30:1) 3 g, vacuum, nitrogen replacement of air in the reaction kettle, replacement of nitrogen 3 times, under the condition of vacuum ≥-0.098 MPa, heating to complete melting of the material, continuously feeding propylene oxide 496 g, controlling the reaction temperature at 110±2°C, the pressure in the reaction kettle is about 0.30 MPa, after adding, keeping the temperature and continuing to react until the system pressure in the reaction kettle no longer decreases. After the reaction is completed, the temperature is lowered to 100°C and vacuum degassing is carried out, and the finished product is obtained after discharging. The product is analyzed by liquid chromatography: the content of propylene alcohol by-products is 3 ppm; the product color (Pt-Co) is 7, the number average molecular weight is 226, and the hydroxyl value is 496.3 mgKOH / g by chemical method.

[0044] Comparing Example 2 and Example 7, it can be seen that the higher the content of triphenylaluminum in the composite catalyst of triphenylaluminum and potassium hydroxide, the weaker the catalyst activity is, resulting in a smaller product molecular weight.

[0045] Example 8

[0046] A product with a number average molecular weight of 234 of 1,6-hexanediol polyoxypropylene ether was designed and synthesized.

[0047] A reactor was charged with 504.3 g of 1,6-hexanediol and 3 g of a catalyst mixture of triphenylaluminum and potassium hydroxide (in a 5:1 ratio). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥ -0.098 MPa until the materials were completely melted. 496 g of propylene oxide was continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction, the temperature was lowered to 100°C for vacuum degassing, and the product was discharged to obtain the finished product. Liquid chromatography analysis of the product revealed an propylene alcohol byproduct content of 6 ppm, a Pt-Co color of 8, a number-average molecular weight of 234, and a hydroxyl value of 479.1 mgKOH / g as determined by chemical analysis.

[0048] Comparing Example 2 and Example 8, it can be seen that the lower the triphenylaluminum content in the triphenylaluminum and potassium hydroxide composite catalyst, the more the catalyst activity increases, resulting in the product molecular weight being able to reach, but the propylene alcohol by-product content of the product increases due to enhanced alkalinity.

[0049] Example 9

[0050] A product with a number average molecular weight of 234 of 1,6-hexanediol polyoxypropylene ether was designed and synthesized.

[0051] A reactor was charged with 504.3 g of 1,6-hexanediol and 3 g of a catalyst mixture of triphenylaluminum and sodium hydroxide (in a 10:1 ratio). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥-0.098 MPa until the materials were completely melted. 496 g of propylene oxide was then continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction, the temperature was lowered to 100°C for vacuum degassing, and the product was discharged to obtain the finished product. Liquid chromatography analysis of the product revealed a 3 ppm content of propylene alcohol byproducts, a Pt-Co color of 8, a number-average molecular weight of 230, and a hydroxyl value of 535.2 mgKOH / g as determined by chemical analysis.

[0052] Comparing Example 2 and Example 7, it can be seen that when the ratio of triphenylaluminum and alkali metal hydroxide composite catalyst is consistent, the product molecular weight is small because the catalyst activity of sodium hydroxide is lower than that of potassium hydroxide.

[0053] According to Examples 2, 7, 8 and 9, as well as our experimental data, the preferred ratio of triphenylaluminum and potassium hydroxide composite catalyst is 10:1, and the preferred alkali metal hydroxide is potassium hydroxide.

[0054] Example 10:

[0055] A product with a number average molecular weight of about 1000 (i.e., the molar number of propylene oxide is about 15.3) was designed and synthesized for 1,6-hexanediol polyoxypropylene ether.

[0056] A reactor was charged with 117.4 g of 1,6-hexanediol and 3 g of a catalyst mixture of triphenylaluminum and potassium hydroxide (in a 10:1 ratio). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥-0.098 MPa until the materials were completely melted. 883 g of propylene oxide was continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction was completed, the temperature was lowered to 100°C for vacuum degassing, and the product was discharged to obtain the finished product. Liquid chromatography analysis of the product revealed a 3 ppm content of propylene alcohol byproducts, a Pt-Co color of 8, a number-average molecular weight of 1003, and a hydroxyl value of 111.9 mgKOH / g as determined by chemical analysis.

[0057] Example 11:

[0058] A product with a number average molecular weight of about 2000 (i.e., the molar number of propylene oxide is about 32.5) was designed and synthesized for 1,6-hexanediol polyoxypropylene ether.

[0059] A reactor was charged with 58.9 g of 1,6-hexanediol and 3 g of a catalyst mixture of triphenylaluminum and potassium hydroxide (in a 10:1 ratio). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥-0.098 MPa until the materials were completely melted. 941 g of propylene oxide was then continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction was completed, the temperature was lowered to 100°C for vacuum degassing, and the product was discharged to obtain the finished product. Liquid chromatography analysis of the product revealed a 3 ppm content of propylene alcohol byproducts, a Pt-Co color of 11, a number-average molecular weight of 2001, and a hydroxyl value of 56.2 mgKOH / g as determined by chemical analysis.

[0060] Comparative Example 1

[0061] A reactor was charged with 117.4 g of 1,6-hexanediol and 3 g of potassium hydroxide (3‰). After evacuation, the air in the reactor was replaced with nitrogen. After three nitrogen replacements, the reactor was heated under a vacuum of ≥-0.096 MPa until the materials were completely melted. 883 g of propylene oxide was then continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction was completed, the temperature was lowered to 100°C for vacuum degassing. The product was then discharged to obtain the finished product. Liquid chromatography analysis of the product revealed an propylene alcohol byproduct content of 63 ppm, a color (Pt-Co) of 15, a number-average molecular weight of 1001, and a hydroxyl value of 112.3 mgKOH / g as determined by chemical analysis.

[0062] Comparing Comparative Example 1 with Example 10, the content of propylene alcohol by-products is relatively high and the product color is relatively dark, which shows that the catalyst used in this patent has certain advantages.

[0063] Comparative Example 2

[0064] A reactor was charged with 117.4 g of 1,6-hexanediol and 1.0 g of DMC (60 ppm, the optimal dosage for this catalyst). After evacuation, the air in the reactor was replaced with nitrogen three times. Under a vacuum of ≥ -0.096 MPa, the temperature was raised until the materials were completely melted. 883 g of propylene oxide was continuously introduced. The reaction temperature was maintained at 110 ± 2°C, and the pressure in the reactor was approximately 0.30 MPa. After addition, the temperature was maintained and the reaction continued until the pressure in the reactor ceased to decrease. After the reaction was completed, the temperature was lowered to 100°C for vacuum degassing. The product was then discharged to obtain the finished product. Liquid chromatography analysis of the product revealed a 10 ppm content of propylene alcohol byproducts, a Pt-Co color of 12, a number-average molecular weight of 890, and a hydroxyl value of 125.6 mgKOH / g as determined by chemical analysis.

[0065] Comparing Comparative Example 2 with Example 10, the product synthesis required multiple DMC activations. This is likely due to the DMC synthesis process requiring a relatively high molecular weight initiator, while 1,6-hexanediol has a relatively low molecular weight. The product of Comparative Example 2 and Example 10 has a similar color, but appears slightly pink. This is a characteristic of DMC catalyst products, resulting from the Co element in the DMC catalyst. This demonstrates that the catalyst employed in this patent possesses certain advantages.

[0066] Comparative Example 3

[0067] Add 117.4g of 1,6-hexanediol and 3.0g of triethylamine to a reactor. After evacuating the reactor, replace the air in the reactor with nitrogen. After three nitrogen replacements, heat the reactor until the materials are completely melted under a vacuum of ≥-0.096 MPa. Continuously add 883g of propylene oxide. The reaction temperature is controlled at 110±2°C and the pressure in the reactor is approximately 0.30 MPa. After addition, maintain the temperature and continue the reaction until the pressure in the reactor no longer decreases. After the reaction is completed, cool the reactor to 100°C for vacuum degassing. Discharge the materials to obtain the finished product. Liquid chromatography analysis of the product revealed a propylene alcohol byproduct content of 10ppm, a color (Pt-Co) of 23, a number-average molecular weight of 950, and a hydroxyl value of 118.5mgKOH / g as determined by chemical analysis.

[0068] Comparing Comparative Example 3 with Example 10, the product produced using triethylamine catalyst has a lower molecular weight, which may be due to the weak activity of the triethylamine catalyst. Furthermore, the product produced using triethylamine catalyst has a darker color. Furthermore, since the product is produced using an amine catalyst, it has a certain peculiar amine flavor, which affects the product's application areas. This shows that the catalyst used in this patent has certain excellent characteristics.

[0069] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for synthesizing 1,6-hexanediol polyoxypropylene ether, characterized in that: The method comprises the following steps: using 1,6-hexanediol as a raw material, adding triphenylaluminum and an alkali metal hydroxide composite catalyst, and then using propylene oxide as a reaction monomer to synthesize 1,6-hexanediol polyoxypropylene ether; the alkali metal hydroxide is selected from one or more of lithium hydroxide, potassium hydroxide and sodium hydroxide; the composite ratio of the triphenylaluminum and the alkali metal hydroxide is 100:1-100; the amount of the triphenylaluminum and alkali metal hydroxide composite catalyst is 0.1-10‰ of the sum of the mass of the 1,6-hexanediol and the propylene oxide; and during the synthesis process, the reaction temperature is 90-150°C and the reaction pressure is -0.05-0.50MPa.

2. A method for synthesizing 1,6-hexanediol polyoxypropylene ether according to claim 1, characterized in that: The alkali metal hydroxide is selected from potassium hydroxide.

3. A method for synthesizing 1,6-hexanediol polyoxypropylene ether according to claim 1, characterized in that: The compounding ratio of the triphenylaluminum and the alkali metal hydroxide is 10:

1.

4. A method for synthesizing 1,6-hexanediol polyoxypropylene ether according to claim 1, characterized in that: The amount of the triphenylaluminum and alkali metal hydroxide composite catalyst is 3‰ of the sum of the mass of 1,6-hexanediol and propylene oxide.

5. A method for synthesizing 1,6-hexanediol polyoxypropylene ether according to claim 1, characterized in that: During the synthesis process, the reaction temperature was 110±2°C and the reaction pressure was -0.02~0.3MPa.

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