L-menthol composition having improved cool sensation diffusion and penetration performance and use thereof

Abstract

An L-menthol composition having improved cool sensation diffusion and penetration performance and a use thereof. The L menthol composition mainly comprises L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol. On the basis of the total mass of the composition, the sum of the mass contents of L-menthol and D-menthol is greater than 99.50%, and the mass content of L-menthol is greater than 99.00%; and the mass content of L-neoisomenthol is greater than or equal to 0.004%, the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.005-0.050%, the mass content of L-neoisomenthol is greater than the mass content of D-neoisomenthol, and the value of the difference between the mass content of L-neoisomenthol and the mass content of D-neoisomenthol is greater than 0.001%.

Description

L-menthol composition with improved cooling and penetrating properties and its application Technical Field

[0001] The present invention relates to the technical field of L-menthol products, and further relates to an L-menthol composition with improved cooling and penetrating properties and an application thereof. Background Art

[0002] Menthol, also known as menthol, is a terpene organic compound with extensive applications in oral care, tobacco, food, and medicine. There are eight menthol isomers, but only the L-menthol configuration possesses the purest minty aroma and cooling sensation. Due to the similar physical properties of different menthol isomers, complete separation of the isomers is challenging. Consequently, commercially available L-menthol products often contain multiple menthol isomers. Because each isomer has distinct characteristic flavors and cooling sensations, even trace amounts of residual isomers can significantly impact sensory perception, resulting in varying degrees of cooling penetration across commercially available L-menthol products.

[0003] The structural formulas of the eight isomers of menthol are shown below.

[0004] How to improve the permeability of the cooling sensation of L-menthol products is still one of the technical difficulties in this field that urgently needs a breakthrough.

[0005] Summary of the Invention

[0006] The present invention addresses the technical problem of how to improve the cooling and penetrating properties of L-menthol products and provides an L-menthol composition with improved cooling and penetrating properties and its application. The L-menthol composition provided by the present invention has significantly improved cooling and penetrating properties.

[0007] To achieve its purpose, the present invention provides the following technical solutions:

[0008] In one aspect, the present invention provides an L-menthol composition with improved cooling and penetrating properties, wherein the L-menthol composition mainly comprises L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol;

[0009] Based on the total mass of the composition, the sum of the mass contents of the L-menthol and the D-menthol is greater than 99.50%, and the mass content of the L-menthol is greater than 99.00%;

[0010] The mass content of the L neoisomenthol is ≥0.004%, and the sum of the mass contents of the L neoisomenthol and the D neoisomenthol is 0.005%-0.050%. The mass content of the L neoisomenthol is greater than the mass content of the D neoisomenthol, and the difference between the mass content of the L neoisomenthol and the mass content of the D neoisomenthol is greater than 0.001%.

[0011] The present inventors have discovered that, in the above-mentioned composition whose main ingredients are L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol, the composition whose contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol meet the above-mentioned content requirements has significantly improved cooling and penetrating properties, and is a high-quality L-menthol composition product.

[0012] In some embodiments, in the L-menthol composition, the sum of the mass contents of L-menthol and D-menthol is, for example, 99.51%, 99.60%, 99.65%, 99.70%, 99.80%, 99.87%, 99.90% or 99.95%, etc.; the mass content of the L-menthol is, for example, 99.01%, 99.20%, 99.30%, 99.40%, 99.50%, 99.55%, 99.60%, 99.67%, 99.79% or 99.90%, etc. In some embodiments, in the L-menthol composition, the mass content of L-neoisomenthol is, for example, 0.004%, 0.010%, 0.020%, 0.030%, 0.035%, 0.040%, etc.; the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is, for example, 0.005%, 0.006%, 0.010%, 0.020%, 0.025%, 0.030%, 0.035%, 0.045%, or 0.050%, etc.; the difference between the mass content of L-neoisomenthol and the mass content of D-neoisomenthol is, for example, 0.002%, 0.004%, 0.005%, 0.015%, 0.020%, 0.023%, 0.025%, 0.030%, 0.040%, or 0.045%, etc.

[0013] In some preferred embodiments, the mass content of the L-menthol is greater than 99.60%, preferably greater than 99.70%. Compositions meeting this preferred content requirement have further improved cooling and penetrating properties.

[0014] In some preferred embodiments, the difference between the mass content of L neoisomenthol and the mass content of D neoisomenthol is greater than 0.005%, preferably greater than 0.016%. Compositions meeting this preferred content requirement have further improved cooling and penetrating properties.

[0015] In some preferred embodiments, the sum of the mass contents of the L-menthol and the D-menthol is 99.60-99.95%, and the mass content of the L-menthol is 99.30-99.80%, preferably 99.60-99.80%;

[0016] The mass content of the L-neoisomenthol is 0.004-0.040%, the sum of the mass contents of the L-neoisomenthol and the D-neoisomenthol is 0.005-0.050%, and the mass content of the L-neoisomenthol is greater than the mass content of the D-neoisomenthol. The difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol is 0.002-0.025%, preferably 0.010-0.025%. Compositions meeting the preferred content requirements have further improved cooling and penetrating properties.

[0017] Specifically, the L-menthol composition may further contain other components in the balance, such as isopulegol, menthone, isomenthone, neomenthol, and / or isomenthol, etc., with the total weight content of these components being less than 0.5%, such as 0.4%, 0.2%, 0.1%, 0.05%, 0.03%, etc., such as less than 0.4%, such as less than 0.2%, such as less than 0.1%, etc. In some examples, the L-menthol composition contains, by weight, 0.020-0.240% isopulegol, 0.005-0.070% menthone, 0.004-0.025% isomenthone, 0.003-0.007% neomenthol, and 0.003-0.008% isomenthol.

[0018] A second aspect of the present invention provides the use of the L-menthol composition described above, which is used in the preparation of cosmetics or pharmaceutical products. By adding the L-menthol composition provided by the present invention to cosmetics or pharmaceutical products, these products can be given a better cooling sensation.

[0019] A third aspect of the present invention provides use of the L-menthol composition described above in enhancing the cooling sensation of a product, wherein the product includes a cosmetic or pharmaceutical product.

[0020] The "cosmetics" mentioned above can be, for example, toothpaste, skin care products, hair care products, shaving foam, etc., and pharmaceutical products such as fever-reducing patches, mouthwash, cooling oil, etc. There is no particular limitation on the specific product type. The above-mentioned composition provided by the present invention can be applied to products that require a cooling sensation improvement.

[0021] A fourth aspect of the present invention provides a method for improving the cooling and penetrating properties of an L-menthol product, wherein the L-menthol product comprises L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol. The cooling and penetrating properties of the L-menthol product are improved by ensuring that the mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol in the L-menthol product meet the following conditions (I) and (II):

[0022] (I) based on the total mass of the L-menthol product, the sum of the mass contents of L-menthol and D-menthol is greater than 99.50%, and the mass content of L-menthol is greater than 99.00%;

[0023] (II) Based on the total mass of the L-menthol product, the mass content of L-neoisomenthol is ≥0.004%, and the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.005%-0.050%, the mass content of L-neoisomenthol is greater than the mass content of D-neoisomenthol, and the difference between the mass content of L-neoisomenthol and the mass content of D-neoisomenthol is >0.001%.

[0024] The present inventors have discovered that by ensuring that the components of an L-menthol product, whose main ingredients are L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol, meet conditions (I) and (II), the cooling and penetrating properties of the L-menthol product can be significantly improved. There are various ways to ensure that the contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meet conditions (I) and (II). For example, these conditions (I) and (II) can be met simultaneously by blending the corresponding components. Alternatively, an L-menthol product meeting conditions (I) and (II) can be obtained by purifying crude L-menthol. Purification processes such as distillation, rectification, crystallization, and / or extraction of the crude L-menthol are well known in the art. Those skilled in the art can adjust the process conditions and / or operating steps during the purification process to obtain a product meeting the desired conditions. During the purification process, the fraction meeting conditions (I) and (II) can be selected as the L-menthol product of the present invention.

[0025] In some preferred embodiments, in the condition (I), the mass content of the L-menthol is >99.60%, preferably >99.70%.

[0026] In some preferred embodiments, in the condition (II), the difference between the mass content of the L neoisomenthol and the mass content of the D neoisomenthol is greater than 0.005%, preferably greater than 0.016%.

[0027] In some preferred embodiments, in the condition (I), the sum of the mass contents of the L-menthol and the D-menthol is 99.60-99.95%, and the mass content of the L-menthol is 99.30-99.80%, preferably 99.60-99.80%;

[0028] In the condition (II), the mass content of the L-neoisomenthol is 0.004-0.040%, the sum of the mass contents of the L-neoisomenthol and the D-neoisomenthol is 0.005-0.050%, and the mass content of the L-neoisomenthol is greater than the mass content of the D-neoisomenthol. The difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol is 0.002-0.025%, preferably 0.010-0.025%.

[0029] In some examples, the L-menthol product obtained by the above method, in addition to L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meeting conditions (I) and (II), further contains other components, such as isopulegol, menthone, isomenthone, neomenthol, and / or isomenthol. For example, the total weight content of these components is less than 0.5%, such as 0.4%, 0.2%, 0.1%, 0.05%, 0.03%, etc., such as less than 0.4%, such as less than 0.2%, such as less than 0.1%, etc. In some examples, the L-menthol product obtained contains, by weight, 0.020-0.240% isopulegol, 0.005-0.070% menthone, 0.004-0.025% isomenthone, 0.003-0.007% neomenthol, and 0.003-0.008% isomenthol.

[0030] Furthermore, the crystallization is, for example, solution crystallization or melt crystallization, preferably melt crystallization, and more preferably static melt crystallization. Static melt crystallization can be performed in a static melt crystallizer known in the art, for example, a static melt crystallizer having a plurality of heat exchange walls can be used, wherein a refrigerant or heat medium can flow through the heat exchange walls to achieve cooling or heating.

[0031] In some embodiments, the crude L-menthol is purified by static melt crystallization, which specifically comprises the following steps:

[0032] (1) heating the crude L-menthol in a static melt crystallizer to melt it, then cooling it to precipitate crystals, and discharging the uncrystallized residual liquid;

[0033] Preferably, the temperature of the heating and melting is 43-50°C;

[0034] Preferably, the cooling comprises cooling to 40-42°C at a cooling rate of 0.2-1.0°C / h, then maintaining for 1-3 hours; and then cooling to 41.2-41.5°C at a cooling rate of 0.03-0.06°C / h;

[0035] (2) heating the crystals to induce sweating, continuously discharging the generated distillate during the sweating process, and continuously monitoring the mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol in the distillate; when the mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meet the conditions (I) and (II), collecting the distillate portion that meets the conditions (I) and (II) as the L-menthol product;

[0036] Preferably, the heating rate of the sweating process is 0.05-0.08°C / h.

[0037] The static melt crystallization steps and conditions described above are merely examples. Those skilled in the art may also obtain an L-menthol product that meets conditions (I) and (II) by using other crystallization processes or adjusting the crystallization process according to the different crude L-menthol.

[0038] In some embodiments, the L-menthol product satisfying conditions (I) and (II) is obtained by fractionating crude L-menthol. The fractionation comprises the following steps:

[0039] The crude L-menthol is distilled in a distillation tower, and the mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol in the distillate withdrawn from the top of the distillation tower are continuously monitored. The distillate portion whose mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meet the conditions (I) and (II) is collected as the L-menthol product.

[0040] In some embodiments, the operating conditions of the distillation tower include: a bottom temperature of 100-130°C, a top temperature of 40-60°C, a top pressure of 0.5-5 kPa absolute, and a reflux ratio of 5:1-15:1. The above is an example of the operating conditions of a distillation tower, and those skilled in the art may also adjust the specific operating conditions of the distillation tower according to actual conditions.

[0041] In some embodiments, the sum of the mass contents of L-menthol and D-menthol in the crude L-menthol used to prepare the L-menthol product is greater than 95.00%, such as 95.10%, 95.50%, 96.00%, 96.50%, 97.00%, or 98.00%, etc.; wherein the mass content of L-menthol is greater than 90.00% (such as 90.10%, 93.00%, 95.00%, 95.70%, 96.00%, 97.00%, or 98.00%, etc.). The sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.01%-0.60% (for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05% or 0.06%, etc.), wherein the mass content of L-neoisomenthol is greater than 0.005% (for example, 0.006%, 0.010%, 0.100%, 0.200%, 0.300%, 0.330%, 0.350%, 0.400%, 0.500% or 0.550%, etc.).

[0042] Herein, cooling penetration refers to the cooling diffusion and penetration properties of an L-menthol product or composition. The cooling penetration quality of an L-menthol product or composition is evaluated by comparing the cooling sensation of the L-menthol composition with that of an L-menthol reference sample after application to the skin. Specific evaluation methods are described below.

[0043] The technical solution provided by the present invention has the following beneficial effects:

[0044] The present invention provides an L-menthol composition, wherein the main components L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meet specific content requirements, and the composition has significantly improved cooling and penetrating properties. The present invention also provides a method for improving the cooling and penetrating properties of an L-menthol product. By ensuring that the main components L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol meet specific content requirements in the L-menthol product, the composition has significantly improved cooling and penetrating properties compared to L-menthol products that do not meet these requirements. DETAILED DESCRIPTION

[0045] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0047] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0048] The crystallizer used in the following examples and comparative examples is a static melt crystallizer, the heating / cooling medium is an ethylene glycol aqueous solution (the mass ratio of ethylene glycol to water is 1:1), and the temperature control accuracy is ±0.5°C.

[0049] The main raw materials used in the following examples and comparative examples are:

[0050] Crude L-menthol, wherein the sum of the mass contents of L-menthol and D-menthol is 96.50%, the mass content of L-menthol is 95.70%, the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.51%, and the mass content of L-neoisomenthol is 0.33%, is from SigmaAldrich reagent network.

[0051] In the following examples, the phrase "the mass contents of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol in the liquid distillate meet the content requirements" means that the following conditions are met: (I) the sum of the mass contents of L-menthol and D-menthol is greater than 99.50%, and the mass content of L-menthol is greater than 99.00%; (II) the mass content of L-neoisomenthol is ≥ 0.004%, the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is within the range of 0.005%-0.050%, the mass content of L-neoisomenthol is greater than the mass content of D-neoisomenthol, and the difference between the mass content of L-neoisomenthol and the mass content of D-neoisomenthol is greater than 0.001%.

[0052] The composition analysis method of the L-menthol product is described as follows: chromatographic column model: Alpha-DEX-120, column length 30m, column inner diameter 0.25mm, vaporizer temperature: 220℃, detector temperature: 300℃, injection volume: 0.2μL, split ratio: 100:1, column temperature program: initial temperature 85℃, maintain for 55min, then increase the temperature to 130℃ at 20℃ / min and maintain for 15min.

[0053] Example 1

[0054] 2 kg of crude L-menthol was added to a melt crystallizer, and the system temperature was raised to 45°C at a rate of 10°C / h. The temperature was maintained at 45°C for 5 hours to completely melt the crude L-menthol. The temperature was then lowered at a rate of 0.5°C / h to 42.0°C and maintained stable. After 2 hours, the temperature was slowly lowered at a rate of 0.05°C / h and continued to cool to 41.5°C. The bottom valve was then opened to discharge the uncrystallized residual liquid. The temperature was then slowly raised at a rate of 0.05°C / h to sweat the crystals, and the liquid distillate produced during the sweating process was continuously discharged. At the same time, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the liquid distillate met the content requirements, the liquid distillate that met the content requirements was used as the L-menthol product, and samples were taken for cooling sensation evaluation. The composition and cooling sensation evaluation results of the L-menthol product are recorded in Table 1.

[0055] Example 2

[0056] 2 kg of crude L-menthol was added to a melt crystallizer, and the system temperature was raised to 45°C at a rate of 10°C / h. The temperature was maintained at 45°C for 5 hours to completely melt the crude L-menthol. The temperature was then lowered at a rate of 0.5°C / h to 42.0°C and maintained stable. After 3 hours, the temperature was slowly lowered at a rate of 0.05°C / h and continued to cool to 41.5°C. The bottom valve was then opened to discharge the uncrystallized residual liquid. The temperature was then slowly raised at a rate of 0.06°C / h to sweat the crystals, and the liquid distillate produced during the sweating process was continuously discharged. At the same time, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the liquid distillate met the content requirements, the liquid distillate that met the content requirements was used as the L-menthol product, and samples were taken for cooling evaluation. The composition and cooling evaluation results of the L-menthol product are recorded in Table 1.

[0057] Example 3

[0058] 2 kg of crude L-menthol was added to a melt crystallizer, and the system temperature was raised to 45°C at a rate of 10°C / h. The temperature was maintained at 45°C for 5 hours to completely melt the crude L-menthol. The temperature was then lowered at a rate of 0.5°C / h to 42.0°C and maintained stable. After 2 hours, the temperature was slowly lowered at a rate of 0.06°C / h and continued to cool to 41.5°C. The bottom valve was then opened to discharge the uncrystallized residual liquid. The temperature was then slowly raised at a rate of 0.07°C / h to sweat the crystals, and the liquid distillate produced during the sweating process was continuously discharged. At the same time, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the liquid distillate met the content requirements, the liquid distillate that met the content requirements was used as the L-menthol product, and samples were taken for cooling evaluation. The composition and cooling evaluation results of the L-menthol product are recorded in Table 1.

[0059] Comparative Example 0

[0060] 2 kg of crude L-menthol was added to a melt crystallizer. The operating conditions and parameters for the melting process, cooling crystallization process, and sweating process were the same as in Example 3. While the liquid distillate produced during the sweating process was continuously discharged, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol, and D-neoisomenthol in the liquid distillate was the same as that of the L-menthol product collected in Example 3, the sweating process was continued and samples were collected for analysis. The composition results of the liquid distillate collected after 20 minutes are recorded in Table 1. This portion of the liquid distillate was used as the L-menthol product of this comparative example, and the cooling sensation was evaluated. The results are recorded in Table 1.

[0061] Comparative Example 1

[0062] 2 kg of crude L-menthol was added to a melt crystallizer, and the system temperature was raised to 45° C. at a rate of 10° C. / h. The temperature was maintained at 45° C. for 5 hours to completely melt the crude L-menthol. The temperature was then lowered at a rate of 0.5° C. / h to 42.0° C. and maintained stable. After 6 hours, the temperature was slowly lowered at a rate of 0.02° C. / h and continued to cool to 41.5° C. After that, the bottom valve was opened to discharge the uncrystallized residual liquid; the temperature was then slowly raised at a rate of 0.04° C. / h to sweat the crystals, and the liquid distillate produced during the sweating process was continuously discharged. At the same time, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the liquid distillate reached the desired level, the composition of the liquid distillate was recorded and used as the L-menthol product of this comparative example. Samples were taken for cooling evaluation, and the results are recorded in Table 1.

[0063] Comparative Example 2

[0064] 2 kg of crude L-menthol was added to a melt crystallizer, and the system temperature was raised to 45° C. at a rate of 10° C. / h. The temperature was maintained at 45° C. for 5 hours to completely melt the crude L-menthol. The temperature was then lowered at a rate of 0.5° C. / h to 42.0° C. and maintained stable. After 3 hours, the temperature was slowly lowered at a rate of 0.06° C. / h and continued to cool to 41.0° C. After that, the bottom valve was opened to discharge the uncrystallized residual liquid; the temperature was then slowly raised at a rate of 0.05° C. / h to sweat the crystals, and the liquid distillate produced during the sweating process was continuously discharged. At the same time, the liquid distillate was continuously collected for composition analysis. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the liquid distillate reached the desired level, the composition of the liquid distillate was recorded and used as the L-menthol product of this comparative example. Samples were taken for cooling evaluation. The results are recorded in Table 1.

[0065] Comparative Example 3

[0066] 2 kg of crude L-menthol was added to a melt crystallizer. The system temperature was raised to 45°C at a rate of 10°C / h and maintained at 45°C for 5 h to completely melt the crude L-menthol. Afterwards, all the material in the melt crystallizer was discharged as the L-menthol product. Its composition was analyzed, and samples were taken for cooling evaluation. The results are shown in Table 1.

[0067] Example 4

[0068] 1 kg of crude L-menthol was added to the bottom of the distillation tower, and then the distillation operation was started. The distillate was continuously collected from the top of the tower, and the mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol were analyzed. The distillate whose mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol met the content requirements was collected as the L-menthol product, and samples were taken for cooling sensation evaluation. The results are listed in Table 1.

[0069] The operating conditions of the distillation tower are as follows:

[0070] The tower bottom temperature is 101-110℃, the tower top temperature is 45-60℃, the tower top pressure is 1-3KPa (absolute pressure), and the reflux ratio is 10:1.

[0071] The parameters of the distillation equipment are as follows:

[0072] The packing is 3*3 triangular spiral packing, the inner diameter of the distillation tower is 50mm, and the packing height is 1.2m.

[0073] Comparative Example 4

[0074] 1 kg of crude L-menthol was added to the bottom of the distillation tower, and then the distillation operation was started. The distillate was continuously collected from the top of the tower, and the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol was analyzed. After the mass content of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the distillate was the same as that of the L-menthol product collected in Example 4, the top distillate was continued to be sampled and analyzed. After 20 minutes, the composition of the top distillate sampled and analyzed was recorded in Table 1. This part of the distillate was used as the L-menthol product of this comparative example, and a cooling sensation evaluation was performed. The results are recorded in Table 1.

[0075] The operating conditions and equipment parameters of the distillation tower are the same as those in Example 4.

[0076] The composition analysis results of the L-menthol products obtained in various examples and comparative examples are shown in Table 1 below.

[0077] Cooling sensation evaluation method

[0078] When evaluating the quality of the L-menthol products in the Examples and Comparative Examples, the benchmark sample used was the crude L-menthol raw material sample used in the Examples. The specific scoring process is as follows:

[0079] The jury is composed of 5 judges with the qualification of second-level perfumer. The jury is responsible for evaluating and scoring the samples. After the scoring is completed, the average score is taken as the final score of the test sample.

[0080] Evaluation method for coolness and penetrability: The baseline sample and the sample to be tested were diluted with a solvent (bisaldehyde alcohol) to a concentration of 1wt%, respectively, and then applied to the inner side of the elbow joints of the assessors on both sides. Scores were given according to the degree of coolness. The baseline sample was scored as 5.0 points. A higher score represents a higher coolness and penetrability. The scoring levels are as follows: penetrable (9.1-10 points), relatively penetrable (8.1-9.0 points), acceptable (7.1-8.0 points), fair (6.1-7.0 points), passing (5.0-6.0 points), and failing (less than 5.0 points).

[0081] The evaluation results are shown in Table 1 below:

[0082] Table 1

[0083] From the above experimental results, it can be seen that the L-menthol product of the embodiment of the present invention, compared with the product of the comparative example, has the contents of the main ingredients L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol, which simultaneously meet the following requirements: "the sum of the mass contents of L-menthol and D-menthol is greater than 99.50%, and the mass content of L-menthol is greater than 99.00%" and "the mass content of L-neoisomenthol is ≥0.004%, the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.005%-0.050%, the mass content of L-neoisomenthol is greater than the mass content of D-neoisomenthol, and the difference between the mass content of L-neoisomenthol and the mass content of D-neoisomenthol is greater than 0.001%." The L-menthol product provided by the embodiment has significantly improved cooling and permeability compared with the comparative example.

[0084] The products of Examples 2 and 3 can further enhance the cooling property of the L-menthol product compared to Example 1. The product of Example 3 has a more excellent cooling property compared to the product of Example 2.

[0085] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. An L-menthol composition with improved cool-sensation permeability, characterized in that, The L-menthol composition mainly comprises L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol; Based on the total mass of the composition, the sum of the mass contents of the L-menthol and the D-menthol > 99.50%, and the mass content of the L-menthol > 99.00%; The mass content of the L-neoisomenthol ≥ 0.004%, and the sum of the mass contents of the L-neoisomenthol and the D-neoisomenthol is 0.005% - 0.050%. The mass content of the L-neoisomenthol is greater than the mass content of the D-neoisomenthol, and the difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol > 0.001%; 2. The L-menthol composition according to claim 1, wherein The mass content of the L-menthol > 99.60%, preferably > 99.70%; And / or, the difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol > 0.005%, preferably > 0.016%; 3. The L-menthol composition according to claim 1, characterized in that, The sum of the mass contents of the L-menthol and the D-menthol is 99.60 - 99.95%, and the mass content of the L-menthol is 99.30 - 99.80%, preferably 99.60 - 99.80%; The mass content of the L-neoisomenthol is 0.004 - 0.040%, the sum of the mass contents of the L-neoisomenthol and the D-neoisomenthol is 0.005 - 0.050%, and the mass content of the L-neoisomenthol is greater than the mass content of the D-neoisomenthol. The difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol is 0.002 - 0.025%, preferably 0.010 - 0.025%; 4. The L-menthol composition according to any one of claims 1-3, characterized in that, The L-menthol composition further contains the balance of other components. The other components include isopulegol, menthone, isomenthone, neomenthol and / or isomenthol; the total mass content of the other components in the L-menthol composition < 0.5%; 5. Use of the L-menthol composition according to any one of claims 1-4, characterized in that, The composition is used in the preparation of cosmetics or pharmaceutical products.

6. Use of the L-menthol composition according to any one of claims 1 to 4 in enhancing the cooling sensation of a product, characterized in that, The product includes cosmetics or pharmaceutical products.

7. A method for improving the coolness transmittance of L-menthol products, characterized in that, The L-menthol product includes L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol. The cool feeling transmittance of the L-menthol product is improved by making the mass contents of the L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the L-menthol product satisfy the following conditions (I) and (II): (I) Based on the total mass of the L-menthol product, the sum of the mass contents of the L-menthol and the D-menthol > 99.50%, and the mass content of the L-menthol > 99.00%; (II) Based on the total mass of the L-menthol product, the mass content of the L-neoisomenthol ≥ 0.004%, and the sum of the mass contents of the L-neoisomenthol and the D-neoisomenthol is 0.005% - 0.050%. The mass content of the L-neoisomenthol is greater than the mass content of the D-neoisomenthol, and the difference between the mass content of the L-neoisomenthol and the mass content of the D-neoisomenthol > 0.001%.

8. The method according to claim 7, wherein The L-menthol product that meets the above conditions (I) and (II) is obtained by purifying crude L-menthol, and the purification includes distilling, rectifying, crystallizing and / or extracting the crude L-menthol.

9. The method according to claim 8, characterized in that The crystallization is solution crystallization or melt crystallization, preferably melt crystallization, more preferably static melt crystallization; Preferably, the crude L-menthol is purified by static melt crystallization, and the specific steps are as follows: (1) Heat and melt the crude L-menthol in a static melt crystallizer, then cool down to precipitate crystals, and discharge the uncrystallized residual liquid; Preferably, the temperature for heating and melting is 43-50 °C; Preferably, the cooling includes cooling at a cooling rate of 0.2-1.0 °C / h to 40-42 °C, and then holding for 1-3 h; then cooling at a cooling rate of 0.03-0.06 °C / h to 41.2-41.5 °C; (2) Heat and sweat the crystals, continuously discharge the produced distillate during the sweating process, and continuously monitor the mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the distillate. When the mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol meet the above conditions (I) and (II), collect the distillate part that meets the above conditions (I) and (II) as the L-menthol product; Preferably, the heating rate for heating and sweating is 0.05-0.08 °C / h.

10. The method according to claim 8, wherein The rectification includes the following steps: Rectify the crude L-menthol in a rectification column, and continuously monitor the mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol in the distillate taken from the top of the rectification column. Collect the distillate part whose mass contents of L-menthol, D-menthol, L-neoisomenthol and D-neoisomenthol meet the above conditions (I) and (II) as the L-menthol product; The operating conditions of the rectification column preferably include: the bottom temperature is 100-130 °C, the top temperature is 40-60 °C, the top pressure is 0.5-5 KPa absolute pressure, and the reflux ratio is 5:1-15:

1.

11. The method according to any one of claims 8 - 10, characterized in that, The sum of the mass contents of L-menthol and D-menthol in the crude L-menthol > 95.00%, among which the mass content of L-menthol > 90.00%, the sum of the mass contents of L-neoisomenthol and D-neoisomenthol is 0.01%-0.60%, and among which the mass content of L-neoisomenthol > 0.005%.

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