Process for the preparation of 2-hydroxypropyltrimethylammonium formate

Abstract

The application relates to the chemical production field and provides a preparation method of 2-hydroxypropyltrimethylammonium formate salt, which comprises the following steps: putting trimethylamine, sodium borohydride and a solvent into a reaction kettle, adding formic acid dropwise into the reaction kettle, controlling the reaction temperature at 0-25 DEG C, obtaining an intermediate after the reaction is completed; adding propylene oxide dropwise into the intermediate, preferably controlling the reaction temperature at 15-30 DEG C, preferably controlling the reaction time at 1-2 hours, and obtaining finished product 2-hydroxypropyltrimethylammonium formate salt. The 2-hydroxypropyltrimethylammonium salt is prepared by using a neutralization method, a small amount of sodium borohydride is added in the reaction process, the formation of formic acid ester compounds is effectively inhibited, the by-products are reduced, the reaction between formaldehyde and amine is inhibited, metal ions existing in the production process are complexed, the obtained product has good color, and the amine value content is high. A proper solvent is introduced into the reaction system, the influence of excess trimethylamine on the by-product alcohol of the 2-hydroxypropyltrimethylammonium salt is controlled, the product purity is improved, and the single consumption of the original material is reduced.

Description

Technical Field

[0001] This invention relates to the field of chemical production, specifically to a method for preparing 2-hydroxypropyltrimethylformate ammonium salt. Background Technology

[0002] Polyurethane is an important class of engineering plastics, widely used in construction, automotive, aerospace, and other fields. The production of polyurethane relies heavily on catalysts. Among them, 2-hydroxypropyltrimethylformate ammonium salt (TMR-2) is a commonly used polyurethane catalyst, playing a crucial role in polyurethane production. TMR-2 catalysts efficiently promote the polyurethane formation reaction, accelerating polymer chain growth, thereby improving production efficiency and product quality. Furthermore, TMR-2 catalysts help control the rate and selectivity of the polyurethane reaction, ensuring a stable and controllable reaction process, reducing the generation of undesirable products, and improving product consistency and predictability. In terms of physical and mechanical properties, including strength, hardness, and abrasion resistance, TMR-2 catalysts result in better performance of the final product. Moreover, the catalyst produces fewer volatile organic compounds during use, exhibiting lower toxicity and environmental pollution risks, thus meeting environmental protection requirements.

[0003] Patent CN111690110A discloses a technical solution that involves reacting a polyol initiator with an epoxide, then adding an excess of a dicarboxylic acid relative to the alkaline catalyst to neutralize it. The carboxylate formed by the reaction of the dicarboxylic acid and the alkaline catalyst is retained in the polyether polyol, resulting in a polyether polyol containing a carboxylate catalyst. This patent presents demanding reaction conditions, fails to address the issue of product color grade, and does not consider the presence of quaternary ammonium salts with polyether structures in the product.

[0004] Patent CN109456171A discloses a method for preparing 2-hydroxypropyltrimethylisooctanoate ammonium salt. The method involves reacting isooctanoic acid and trimethylamine in the presence of a solvent, then removing the trimethylamine from the reaction solution to obtain a first reaction solution. The reaction temperature is 5-25℃, preferably 10-20℃. The second step involves reacting the first reaction solution with propylene oxide in the presence of an alkaline anion exchange resin, filtering and removing unreacted propylene oxide to obtain 2-hydroxypropyltrimethylisooctanoate ammonium salt. This patent does not discuss the fact that isooctanoic acid reacts with trimethylamine to generate a byproduct, trimethylisooctanoamide, and that residual isooctanoic acid can react with the subsequent catalytic alkaline anion exchange resin, reducing the catalyst's lifespan. Excess trimethylamine is also not recycled. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, the present invention provides a method for preparing 2-hydroxypropyltrimethylammonium formate, which has mild reaction conditions, low production cost, can be used for industrial production, and produces a product with high yield, good color, high amine value, and low acid value.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The method for preparing 2-hydroxypropyltrimethylammonium salt is characterized by comprising the following steps: Step 1: Add trimethylamine, sodium borohydride and solvent to the reaction vessel, and add formic acid dropwise to the reaction vessel. Control the reaction temperature at 0-25℃. After the reaction is completed, the intermediate is obtained. Step 2: Add propylene oxide dropwise to the intermediate. The preferred reaction temperature is 15-30℃ and the preferred reaction time is 1-2h to obtain the finished product, 2-hydroxypropyltrimethylammonium formate.

[0007] The chemical reaction that occurs in this invention is as follows:

[0008]

[0009] In this invention, the reaction temperature of formic acid and trimethylamine is controlled within the range of 0-25°C, preferably 0-5°C, to reduce the amount of trimethylamine vaporization and decrease the pressure in the reactor.

[0010] In this invention, the molar ratio of trimethylamine to formic acid is 1:1-1.5:1, preferably 1.2:1.

[0011] In the preparation process of this invention, an excess of trimethylamine can ensure that the formic acid in the system reacts fully, thereby reducing the formic acid ions in the product and ensuring the content of the amine value of the product.

[0012] In this invention, the preferred mass ratio of sodium borohydride is 0.01wt%-0.03wt%, more preferably 0.02wt%. Research has shown that trimethylamine, the raw material, is industrially prepared primarily through the catalytic reaction of methanol and ammonia or the methylation reaction of methylamine. This process inevitably carries alcohols and aldehydes. Adding a small amount of sodium borohydride during the reaction effectively inhibits the formation of formate esters, reduces byproducts, and also inhibits the reaction between aldehydes and amines, thus reducing color.

[0013] In this invention, the ring-opening reaction between the intermediate and propylene oxide is carried out at a low temperature, which reduces the color number of the product; at the same time, the low temperature also reduces the amount of by-products.

[0014] The solvent used in this invention is 25wt%-35wt%, preferably 30wt%-35wt%, of the total mass of the starting materials. The solvent is one or more of water, alcohols, and ethers. An appropriate solvent (alcohol, water, ether) is introduced into the reaction system. Excess trimethylamine is used to control the influence of the byproduct alcohol on 2-hydroxypropyltrimethylammonium salt. Simultaneously, trimethylamine is absorbed and recovered through solvents such as alcohols, water, and ethers, reducing the consumption of the original materials.

[0015] In this invention, the molar ratio of trimethylamine to propylene oxide is 1:1 to 1:1.05.

[0016] By adopting the above technical solution, this application has the following technical effects: 2-Hydroxypropyltrimethylammonium salt was prepared by neutralization. A small amount of sodium borohydride was added during the reaction to effectively inhibit the formation of formate compounds, reduce byproducts, and suppress the reaction between formaldehyde and amines. At the same time, it complexed the metal ions present in the production process, resulting in a product with good color and high amine content.

[0017] Introduce appropriate solvents (alcohols, water, ethers) into the reaction system, use excess trimethylamine to control the influence of by-product alcohols on 2-hydroxypropyltrimethylammonium salt, and then absorb and recover trimethylamine through solvents such as alcohols, water, and ethers to reduce the original material consumption. Detailed Implementation

[0018] Example 1:

[0019] 71g of trimethylamine was dissolved in a certain amount of solvent (water, alcohol, ether, etc.), and 0.023g of sodium borohydride was added to the reaction vessel. At 0-25℃, 46g of formic acid was gradually added dropwise at a rate of 1-10ml / min. After the addition was completed, the reaction was allowed to proceed at room temperature for 1-2 hours to obtain an intermediate. The reaction temperature was controlled at 0-20℃, and 58g of propylene oxide was gradually added dropwise to react with the intermediate at a rate of 1-10ml / min for 2-6 hours to obtain the crude product. The product was desolventized, and its color was 5 Hazen, acid value was 0 mg KOH / g, total amine value was 160 mg KOH / g, and gas phase detection showed a purity of 99.4%. The product was filtered, and the sodium borohydride solid was recovered.

[0020] Comparative Example 1: 71g of trimethylamine was added to a reaction vessel, and 46g of formic acid was gradually added dropwise at a rate of 1-10ml / min at 0-25℃. After the addition was completed, the reaction was allowed to proceed at room temperature for 1-2 hours to obtain an intermediate. Then, 58g of propylene oxide was gradually added dropwise to react with the intermediate at a rate of 1-10ml / min for 2-6 hours, while maintaining the reaction temperature at 0-20℃, to obtain the product. The product had a color of 35 Hazen, an acid value of 1 mg KOH / g, a total amine value of 149 mg KOH / g, and a purity of 96.1% as determined by gas chromatography.

[0021] Comparative Example 2: 71g of trimethylamine was dissolved in a certain amount of solvent (water, alcohol, ether, etc.) and added to a reactor. At 0-25℃, 46g of formic acid was gradually added dropwise at a rate of 1-10ml / min. After the addition was complete, the reaction was allowed to proceed at room temperature for 1-2 hours to obtain an intermediate. The reaction temperature was then controlled at 0-20℃, and 58g of propylene oxide was gradually added dropwise to react with the intermediate at a rate of 1-10ml / min for 2-6 hours to obtain the crude product. The product was then desolventized, and its color was 20 Hazen, acid value was 0 mg KOH / g, total amine value was 151 mg KOH / g, and gas phase content was 98.2%.

[0022]

[0023] Compared to Comparative Example 1, Example 1 effectively suppressed the generation of by-product alcohols by adding a solvent and recovered excess trimethylamine, resulting in a product purity of over 99%. Compared to Comparative Examples 1-2, Example 1 effectively suppressed the formation of formate ester compounds by adding sodium borohydride, reduced by-products, and inhibited the reaction between formaldehyde and amines. Simultaneously, it complexed metal ions present during the production process, significantly improving the color of the resulting product.

Claims

A method for preparing 1,2-hydroxypropyltrimethylammonium formate, characterized in that, Includes the following steps: Step 1: Add trimethylamine, sodium borohydride and solvent to the reaction vessel, and add formic acid dropwise to the reaction vessel. Control the reaction temperature at 0-25℃. After the reaction is completed, the intermediate is obtained. Step 2: Add propylene oxide dropwise to the intermediate. The preferred reaction temperature is 15-30℃ and the preferred reaction time is 1-2h to obtain the finished product, 2-hydroxypropyltrimethylammonium formate.

2. The method for preparing 2-hydroxypropyltrimethylformate ammonium salt according to claim 1, characterized in that, The preferred molar ratio of trimethylamine to formic acid is 1.1:1 to 1.5:

1.

3. The method for preparing 2-hydroxypropyltrimethylformate ammonium salt according to claim 1, characterized in that, The preferred mass ratio of sodium borohydride is 0.01wt%-0.03wt%.

4. The method for preparing 2-hydroxypropyltrimethylformate ammonium salt according to claim 1, characterized in that, The solvent is water, alcohol, or ether, preferably in a mass ratio of 25wt%-35wt%.

5. The method for preparing 2-hydroxypropyltrimethylformate ammonium salt according to claim 1, characterized in that, The molar ratio of trimethylamine to propylene oxide is 1:1 to 1:1.05.

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