Preparation method of N-lauroyl isopropyl sarcosinate

Abstract

The invention relates to the technical field of fine chemical engineering, and discloses a preparation method of N-lauroyl isopropyl sarcosinate. The preparation method comprises the following steps: S1, mixing sarcosine, isopropanol, a solid acid catalyst and a molecular sieve, carrying out esterification reaction, carrying out solid-liquid separation, and collecting a liquid phase to obtain a primary reaction solution; and S2, mixing a condensing agent with the primary reaction liquid, dropwise adding lauroyl chloride at a low temperature, heating to react, and distilling to obtain the N-lauroyl isopropyl sarcosinate. According to the preparation method provided by the invention, the solid acid catalyst is adopted to replace traditional liquid acid (such as sulfuric acid), the problems of equipment corrosion and waste acid treatment are solved, molecular sieve dehydration is adopted, esterification reaction balance is promoted, the conversion rate is increased to 95-98%, toxic residues of a dehydrating agent are not caused, side reactions are avoided through a two-step method of first esterification and then amidation, and the preparation method is suitable for industrial production. And the purity of the product is up to 97-98%.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and in particular to a method for preparing N-lauroyl sarcosine isopropyl ester. Background Art

[0002] The current demand for sunscreen is growing rapidly, and consumers' demand for diversified and personalized products has increased significantly, especially sunscreen products for different skin types and scenarios. At the same time, product quality and stability have also become the focus of consumer attention.

[0003] Isopropyl N-lauroylsarcosinate is a colorless or pale yellow liquid with good stability, not easily decomposed at room temperature, and a long shelf life. It is a highly efficient solubilizing agent commonly used in the cosmetics field. It is suitable for products such as sunscreen sprays and sunscreens, and can significantly improve the solubility and stability of sunscreen products.

[0004] The traditional preparation method of N-lauroylsarcosine isopropyl ester involves first condensing sarcosine or a sarcosinate with lauroyl chloride or lauric acid to produce N-lauroylsarcosine, which is then esterified with isopropyl alcohol under acid catalysis. Dehydration during the esterification reaction involves removing water using a water separator, adding a dehydrating agent such as benzene, toluene, or cyclohexane to form an azeotropic reaction with water, and then condensing the mixture and removing water by stratification in the water separator. However, when using highly water-soluble alcohols (such as ethanol, propanol, and butanol) as raw materials, they often participate in the azeotropic reaction, making stratification difficult and resulting in poor water separation. Furthermore, dehydrating agents typically have relatively high boiling points and are toxic, easily leaving residues, making them unsuitable for preparing green and safe products. EP0928608A2 discloses an N-long alkyl acyl amino acid ester and a method for synthesizing the same. Using N-lauroyl sarcosine and excess isopropyl alcohol as raw materials, the product is refluxed for 8 hours under concentrated sulfuric acid catalysis and subjected to multiple post-processing steps to obtain N-lauroyl sarcosine isopropyl ester in a yield of 73%. This method uses concentrated sulfuric acid as a catalyst, but the strong corrosiveness and oxidizing properties of concentrated sulfuric acid can cause problems, such as corrosion of production equipment and side reactions that can lead to product coloration. Post-processing requires multiple steps, such as neutralization and washing, and generates a large amount of waste liquid, placing significant pressure on environmental protection. Furthermore, the esterification reaction is reversible, and this method fails to remove water from the reaction system to promote equilibrium in the positive direction, thereby increasing the esterification rate, resulting in a low yield. CN 119409584 A discloses a method for synthesizing N-lauroyl sarcosine isopropyl ester. The method uses an activated carbon-solid acid composite catalyst to replace a conventional concentrated sulfuric acid catalyst, and designs an external circulating dehydration system. Utilizing the characteristic that water and isopropyl alcohol form a low-boiling-point azeotrope, a circulating dehydration device is designed outside a stirred reactor. A dehydrating material is used to perform multiple depth dehydrations on the azeotrope vapor and azeotrope condensate. Water generated by the esterification reaction is effectively transferred outside the reaction system, while the isopropyl alcohol can be circulated into the stirred reactor, thereby greatly improving the esterification reaction efficiency and achieving the purpose of improving the esterification conversion efficiency. However, when preparing N-lauroyl sarcosine isopropyl ester using this method, the yield is less than 95%, and the product has a chromaticity of greater than or equal to 20, resulting in insufficient stability.

[0005] Therefore, there is an urgent need to develop a method for preparing N-lauroyl sarcosine isopropyl ester that is efficient, environmentally friendly, has high product purity and good stability to meet market demand. Summary of the Invention

[0006] The present invention aims to solve at least one of the above-mentioned technical problems in the prior art. To this end, one of the objects of the present invention is to provide a method for preparing N-lauroyl sarcosine isopropyl ester.

[0007] A second object of the present invention is to provide a sunscreen.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a method for preparing N-lauroyl sarcosine isopropyl ester, comprising the following steps:

[0010] S1, mixing sarcosine, isopropanol, a solid acid catalyst and a molecular sieve, performing an esterification reaction, and collecting the liquid phase by solid-liquid separation to obtain a primary reaction liquid;

[0011] S2. Mixing the condensing agent with the primary reaction solution, adding lauroyl chloride dropwise at low temperature, heating the mixture for reaction, and then distilling the mixture to obtain the N-lauroyl sarcosine isopropyl ester.

[0012] In some embodiments of the present invention, the mass ratio of sarcosine, isopropanol, solid acid catalyst, molecular sieve, condensation agent and lauroyl chloride is 1:(0.7-10):(0.05-0.5):(1-5):(1-10):(1-2.5).

[0013] In some preferred embodiments of the present invention, the mass ratio of the sarcosine, isopropyl alcohol, solid acid catalyst, molecular sieve, condensation agent and lauroyl chloride is 1:(2-5):(0.1-0.4):(2-4):(3-6):(1.5-2).

[0014] In some embodiments of the present invention, the purity of the sarcosine, isopropyl alcohol and lauroyl chloride is greater than or equal to 98%.

[0015] Specifically, the higher the purity of sarcosine, isopropyl alcohol, and lauroyl chloride, the more conducive it is to improving the reaction yield and the quality of N-lauroylsarcosine isopropyl ester.

[0016] In some embodiments of the present invention, the solid acid catalyst is selected from SO4 2- / Fe2O3、SO4 2- / TiO2、SO4 2- / ZrO2, AlCl3-TiCl3, BF5 / graphite, SbF5 / Al2O3, WO3 / ZrO2, heteropoly acid, zeolite super acid.

[0017] In some embodiments of the present invention, the molecular sieve is at least one selected from 3A molecular sieve, 4A molecular sieve, and 5A molecular sieve.

[0018] In some embodiments of the present invention, the esterification reaction is carried out at a temperature of 100-180° C. and for a time of 4-30 h.

[0019] In some preferred embodiments of the present invention, the esterification reaction is carried out at a temperature of 120-160° C. and for a time of 10-24 hours.

[0020] In some embodiments of the present invention, the condensing agent is selected from at least one of dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), 4-N,N-dimethylpyridine (DMAP), O-(7-azabenzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate (HAPyU), O-(benzotriazol-1-yl)-N,N,N',N'-dipyrrolyl uronium hexafluorophosphate (HBPyU), and N,N-diisopropylethylamine (DIPEA).

[0021] In some embodiments of the present invention, the lauroyl chloride is added at a temperature of -20°C to 20°C.

[0022] In some preferred embodiments of the present invention, the lauroyl chloride is added dropwise at a temperature of -10°C to 10°C.

[0023] In some embodiments of the present invention, the temperature of the temperature-raising reaction is 40-150° C. and the time is 6-48 hours.

[0024] In some preferred embodiments of the present invention, the temperature of the temperature-raising reaction is 60-100° C. and the time is 12-24 hours.

[0025] In some embodiments of the present invention, the distillation temperature is 200-300° C. and the pressure is -0.05 MPa to -0.1 MPa.

[0026] In some preferred embodiments of the present invention, the distillation temperature is 220-280° C. and the pressure is -0.08 MPa to -0.1 MPa.

[0027] The basic principles of the present invention are described as follows:

[0028] The present invention adopts a two-step process of first esterification and then amidation to prepare N-lauroyl sarcosine isopropyl ester:

[0029] First, sarcosine and isopropyl alcohol undergo an esterification reaction under the action of a solid acid catalyst and a molecular sieve to produce sarcosine isopropyl ester and water. During this process, the solid acid catalyst provides an acidic environment, promoting the esterification reaction between the carboxylic acid (sarcosine) and the alcohol (isopropyl alcohol), thereby increasing the reaction rate and selectivity. The molecular sieve absorbs the water produced by the esterification reaction, pushing the reaction equilibrium toward the esterification direction and increasing the conversion rate. The ratio of the raw material sarcosine to isopropyl alcohol is controlled to be 1:(0.7-10), ensuring an excess of alcohol and promoting complete reaction. The primary reaction liquid can be obtained through solid-liquid separation, and the solid acid catalyst and molecular sieve can be recovered to reduce waste.

[0030] Then, lauroyl chloride is added dropwise to the primary reaction solution at low temperature, and an amidation reaction is carried out under the action of a condensing agent to obtain a crude N-lauroyl sarcosine isopropyl ester product. The condensing agent can activate the carboxyl group of the sarcosine isopropyl ester, making it easier for the carboxyl group to react with the acyl chloride group of the lauroyl chloride to form an amide bond, thereby avoiding the direct use of a strong acid or a strong base and reducing by-products. The low-temperature addition of the lauroyl chloride can control the exothermic reaction and prevent local overheating from causing hydrolysis of the lauroyl chloride or decomposition of the product. The temperature-raising reaction can promote the formation of the amide bond, while simultaneously distilling away the generated HCl to avoid corrosion of equipment. Finally, the crude N-lauroyl sarcosine isopropyl ester product is subjected to reduced-pressure distillation to remove low-boiling-point impurities, such as unreacted isopropyl alcohol and condensing agent by-products, and to separate the high-boiling-point product, N-lauroyl sarcosine isopropyl ester, under reduced-pressure distillation to avoid high-temperature decomposition.

[0031] The second aspect of the present invention provides a sunscreen comprising N-lauroyl sarcosine isopropyl ester obtained by the preparation method described in the first aspect of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The preparation method of N-lauroylsarcosine isopropyl ester provided by the present invention uses a solid acid catalyst instead of a traditional liquid acid (such as sulfuric acid), solving the problems of equipment corrosion and waste acid disposal. The use of molecular sieves for dehydration can promote the equilibrium of the esterification reaction, increasing the conversion rate to 95-98%, without causing toxic residues of the dehydrating agent. The two-step process of esterification followed by amidation avoids side reactions, and the product purity is as high as 97-98%.

[0034] 2) The preparation method of N-lauroyl sarcosine isopropyl ester provided by the present invention has no wastewater discharge throughout the entire process, the catalyst can be recycled, solid waste is reduced, and environmental benefits are high. Moreover, the conditions are mild, the yield is high, and it is suitable for large-scale production;

[0035] 3) The N-lauroyl sarcosine isopropyl ester prepared by the preparation method of the present invention has high solubility for insoluble UVA / UVB filters such as diethylamino hydroxybenzoyl hexyl benzoate, and has the characteristics of low acid value, low moisture content, colorless and transparent. It is suitable for products such as sunscreen sprays and creams, which is beneficial to improving the stability of the formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 1;

[0037] Figure 2 This is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 2;

[0038] Figure 3This is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 3;

[0039] Figure 4 This is a photograph of N-lauroyl sarcosine isopropyl ester prepared in Example 1. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below by way of specific examples. Unless otherwise specified, the raw materials, reagents, or devices used in the examples are all commercially available or can be obtained by conventional methods. Unless otherwise specified, all experiments or testing methods are conventional methods in the art.

[0041] Example 1

[0042] In this embodiment, N-lauroyl sarcosine isopropyl ester is prepared by the following steps:

[0043] S11, 89g sarcosine, 63g isopropanol, 44.5g SO4 2- / Fe2O3 solid acid catalyst and 90g 3A molecular sieve were added to a 2000mL flask, stirred, heated to 180℃ and reacted for 6h. After the reaction was completed, cooled to room temperature, filtered to recover the solid acid catalyst and molecular sieve (DCC), and a primary reaction solution was obtained;

[0044] S21. Add the primary reaction liquid to a 2000 mL reaction flask, then add 445 g of dicyclohexylcarbodiimide to the reaction flask, cool to -20°C, start stirring, and dropwise add 110 g of lauroyl chloride under stirring. After the addition is complete, heat to 150°C and react for 6 hours. Then, distill under reduced pressure at -0.1 MPa, collect the fraction distilled at 200°C, and obtain N-lauroyl sarcosine isopropyl ester.

[0045] The actual yield of N-lauroyl sarcosine isopropyl ester was 297 g, the theoretical yield was 313 g, and the yield was 95%.

[0046] Example 2

[0047] In this embodiment, N-lauroyl sarcosine isopropyl ester is prepared by the following steps:

[0048] S11, 89g of sarcosine, 445g of isopropanol, 26.7g of AlCl3-TiCl3 solid acid catalyst and 267g of 4A molecular sieve were added to a 2000mL flask, stirred, heated to 150°C and reacted for 12h. After the reaction was completed, the mixture was cooled to room temperature, and the solid acid catalyst and molecular sieve were filtered to recover to obtain a primary reaction solution;

[0049] S21. Add the primary reaction solution to a 2000 mL reaction flask, then add 890 g of O-(7-azabenzotriazole-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate (HAPyU) to the reaction flask, cool to 0°C, start stirring, and add 175 g of lauroyl chloride dropwise under stirring. After the addition is complete, heat to 100°C and react for 24 hours. Then, distill under reduced pressure at -0.1 MPa, collect the fraction distilled at 250°C, and obtain N-lauroyl sarcosine isopropyl ester.

[0050] The actual yield of N-lauroyl sarcosine isopropyl ester was 240 g, the theoretical yield was 250 g, and the yield was 96%.

[0051] Example 3

[0052] In this embodiment, N-lauroyl sarcosine isopropyl ester is prepared by the following steps:

[0053] S11, 89g of sarcosine, 890g of isopropanol, 4.5g of AlCl3-TiCl3 solid acid catalyst and 445g of 5A molecular sieve were added to a 2000mL flask, stirred, heated to 100°C and reacted for 24h. After the reaction was completed, the mixture was cooled to room temperature, and the solid acid catalyst and molecular sieve were filtered to obtain a primary reaction solution;

[0054] S21. Add the primary reaction liquid to a 2000 mL reaction flask, then add 89 g of N,N-diisopropylethylamine (DIPEA) to the reaction flask, cool to 20°C, start stirring, and dropwise add 219 g of lauroyl chloride under stirring. After the addition is complete, heat to 60°C and react for 48 hours. Then, distill under reduced pressure at -0.05 MPa, collect the fraction distilled at 300°C, and obtain N-lauroyl sarcosine isopropyl ester.

[0055] The actual yield of N-lauroyl sarcosine isopropyl ester was 154 g, the theoretical yield was 157 g, and the yield was 98%.

[0056] Characterization and performance testing

[0057] 1. Fourier transform infrared spectrometer (Nicolet IS5) was used to characterize the N-lauroyl sarcosine isopropyl ester prepared in Example 1-3 by infrared spectroscopy:

[0058] Figure 1 is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 1, Figure 2 is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 2, Figure 3 is the infrared spectrum of N-lauroyl sarcosine isopropyl ester prepared in Example 3, Figure 1-Figure 3It can be seen that the infrared spectra of N-lauroyl sarcosine isopropyl ester in Examples 1-3 are all at 1640-1690 cm -1 The characteristic peak of amide I band appeared near the 1730-1750 cm -1 The ester group characteristic peak appeared near 2850-2960cm -1 The characteristic peaks of CH from the fatty chain of lauroyl (C12 long chain) and isopropyl appear near 3200-3600 cm -1 There is no free -OH peak nearby, indicating that there is no water or unreacted alcohol remaining. The infrared spectrum characterization results show that the present invention successfully prepares N-lauroyl sarcosine isopropyl ester.

[0059] Figure 4 is a photograph of N-lauroyl sarcosine isopropyl ester prepared in Example 1, Figure 4 It can be seen that the N-lauroyl sarcosine isopropyl ester prepared in Example 1 is a colorless liquid and can meet the application requirements in the cosmetics field.

[0060] 2. The purity, acid value, color, iodine value and moisture content of N-lauroyl sarcosine isopropyl ester prepared in Examples 1-3 were tested. The test methods and reference standards are as follows:

[0061] 1) Purity: detected by high performance liquid chromatography (Agilent 1220 Infinity II);

[0062] 2) Acid value: Determine according to GB / T 5009.229-2016 "National Food Safety Standard - Determination of Acid Value in Foods";

[0063] 3) Chroma: Measured in accordance with GB / T 3143-1982 “Determination of color of liquid chemical products”;

[0064] 4) Iodine value: Determine according to GB / T 5532-2022 “Determination of iodine value of animal and vegetable fats and oils”;

[0065] 5) Moisture content: Determined using a Karl Fischer titrator in accordance with GB T6283-2008 “Determination of moisture content in chemical products – Karl Fischer method”.

[0066] Table 1 Performance test results of N-lauroyl sarcosine isopropyl ester in Examples 1-3

[0067]

[0068] Table 1 shows the performance test results of N-lauroyl sarcosine isopropyl ester in Examples 1-3. As can be seen from Table 1, the purities of the N-lauroyl sarcosine isopropyl esters prepared in Examples 1-3 are 98%, 97%, and 98%, respectively, which meet the high purity requirements of cosmetic raw materials; the acid values ​​are all less than 0.1 mgKOH / g, which is low, indicating that there is no free fatty acid residue and the product is highly stable; the chromaticity is all less than 10 Hazen, and the product is nearly colorless, meeting the standards for cosmetic raw materials; the moisture content is less than 0.1%, which is low in moisture, ensuring that the product will not hydrolyze or deteriorate during storage. The above results show that the purity, acid value, chromaticity, etc. of the N-lauroyl sarcosine isopropyl ester prepared by the preparation method provided by the present invention meet the standards for high-end cosmetic raw materials.

[0069] 3. The solubility performance of N-lauroyl sarcosine isopropyl ester prepared in Examples 1-3 was tested for diethylamino hydroxybenzoyl hexyl benzoate, ethylhexyl triazone and butyl methoxydibenzoylmethane, and dicaprylyl carbonate (CC), caprylic capric triglyceride (GTCC) and C12-15 alcohol benzoate were used as comparisons. The amount of each oil used in the test was the same.

[0070] Table 2 Solubility test results of N-lauroyl sarcosine isopropyl ester in Examples 1-3

[0071]

[0072]

[0073] Table 2 shows the solubility test results of N-lauroyl sarcosine isopropyl in Examples 1-3. As shown in Table 2, the N-lauroyl sarcosine isopropyl prepared in Examples 1-3 can completely dissolve the three difficult-to-use UVA / UVB filters, diethylamino hydroxybenzoyl hexyl benzoate, ethylhexyl triazone, and butyl methoxydibenzoylmethane, at 50°C. Its solubility is significantly better than that of dicaprylyl carbonate, caprylic capric triglyceride, and C12-15 alcohol benzoate. This shows that the N-lauroyl sarcosine isopropyl prepared by the preparation method provided by the present invention is suitable for the preparation of sunscreen products, can completely dissolve the filters, prevent precipitation of the formula, and improve stability.

Claims

1. A method for preparing N-lauroyl sarcosine isopropyl ester, characterized in that: The following steps are involved: S1, mixing sarcosine, isopropyl alcohol, a solid acid catalyst and a molecular sieve, performing an esterification reaction, and collecting the liquid phase by solid-liquid separation to obtain a primary reaction liquid; S2. Mixing the condensing agent with the primary reaction solution, adding lauroyl chloride dropwise at low temperature, heating the mixture for reaction, and then distilling the mixture to obtain the N-lauroyl sarcosine isopropyl ester.

2. The preparation method according to claim 1, characterized in that The mass ratio of the sarcosine, isopropyl alcohol, solid acid catalyst, molecular sieve, condensation agent and lauroyl chloride is 1:(0.7-10):(0.05-0.5):(1-5):(1-10):(1-2.5).

3. The preparation method according to claim 1, characterized in that The solid acid catalyst is selected from SO4 2- / Fe2O3、SO4 2- / TiO2、SO4 2- / ZrO2, AlCl3-TiCl3, BF5 / graphite, SbF5 / Al2O3, WO3 / ZrO2, heteropoly acid, zeolite super acid.

4. The preparation method according to claim 1, characterized in that The molecular sieve is at least one of 3A molecular sieve, 4A molecular sieve and 5A molecular sieve.

5. The preparation method according to claim 1, characterized in that The temperature of the esterification reaction is 100-180° C., and the time is 4-30 hours.

6. The preparation method according to claim 1, characterized in that The condensing agent is selected from at least one of dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 4-N,N-lutidine, O-(7-azabenzotriazole-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate, O-(benzotriazole-1-yl)-N,N,N',N'-dipyrrolyl uronium hexafluorophosphate, and N,N-diisopropylethylamine.

7. The preparation method according to claim 1, characterized in that The dropping temperature of the lauroyl chloride is -20°C to 20°C.

8. The preparation method according to claim 1, characterized in that The temperature of the temperature-raising reaction is 40-150° C. and the time is 6-48 hours.

9. The preparation method according to claim 1, characterized in that The distillation temperature is 200-300° C.; the pressure is -0.05 MPa to -0.1 MPa.

10. A sunscreen, characterized in that: The invention comprises N-lauroyl sarcosine isopropyl ester obtained by the preparation method according to any one of claims 1 to 9.

Images