CN109394560B

CN109394560B - Amino acid facial cleanser and preparation method thereof

Info

Publication number: CN109394560B
Application number: CN201811529846.9A
Authority: CN
Inventors: 车七石; 刘少辉; 李新霞
Original assignee: Guangzhou Times Health Products Co ltd
Current assignee: Guangzhou Times Health Products Co ltd
Priority date: 2018-12-14
Filing date: 2018-12-14
Publication date: 2022-08-16
Anticipated expiration: 2038-12-14
Also published as: CN109394560A

Abstract

The invention belongs to the field of skin care products, and particularly relates to an amino acid facial cleanser and a preparation method thereof. The amino acid cleansing cream provided by the invention comprises the following components in parts by weight: 22-38 parts of humectant, 20-30 parts of amino acid type surfactant, 6-15 parts of auxiliary surfactant, 4-6 parts of thickener and 6.9-46.3 parts of water. The amino acid facial cleanser provided by the invention has strong cleaning and decontaminating capabilities, is close to the pH value of human skin, has good skin affinity, is safe and mild, and is not irritant; the moisturizing effect is good, and the moisturizing cream has the functions of nourishing, repairing, bacteriostasis and anti-inflammation, and is suitable for long-term use of skin.

Description

Amino acid facial cleanser and preparation method thereof

Technical Field

The invention belongs to the technical field of skin care products, and particularly relates to an amino acid facial cleanser and a preparation method thereof.

Background

The facial cleansing cream is a special facial cleansing product, and consumers increasingly pay more attention to whether the facial cleansing product has better cleansing ability but is mild and safe. Currently, the commercially available cleansing products can be roughly divided into soap-based systems, surfactant systems, amino acid systems and emulsifying systems. The soap-based system has strong dirt and fat removing capability, but after the soap-based system is used, the skin is lack of water and is tight, the skin is excessively cleaned and easily damaged, and in addition, as the normal and healthy skin presents weak acidity, if the normal and healthy skin is used for a long time, the acid-base balance of the skin can be damaged, so that the skin sebum barrier is damaged. Compared with a soap base system, the surfactant system is mild, the decontamination and degreasing capability is moderate, but the surfactant is not easy to clean, has more residues after washing, and has certain irritation when staying on the surface of the skin; the amino acid system facial cleanser has rich foam and weak acid pH value, can deeply clean the skin without damaging the weak acid environment of the skin, and is mild and safe to the skin. The amino acid surfactant is weakly acidic, has a pH value close to that of the skin surface, has good skin-friendly property, moderate cleaning power and less residue after washing, has high mildness compared with products of a soap base system and a surfactant system, and also has the problem of water shortage and tightness of the skin after use. With the development of the times, the natural and safe properties of skin care products, particularly facial cleansing creams, are more and more emphasized.

Chinese patent application CN106236690A discloses an amino acid facial cleanser containing multiple plant components, which comprises glycerin: 17-19 parts; sodium cocoyl glycinate: 10-12 parts; alkyl polyglycoside: 9-11 parts; cocamidopropyl betaine: 8-10 parts; sodium N-lauroyl-L-glutamate: 4-6 parts; cocoyl amphodiacetate disodium: 2-4 parts; cholesterol hydroxystearate: 1.5-2.5 parts; high-molecular cation conditioner: 1.5-2.5 parts; ethylene glycol distearate: 1.4-1.6 parts; glycerol stearate: 0.8-1.2 parts; saccharide isomerate: 0.7-0.9 part; natural plant extracts: 2-4 parts. Although the facial cleanser can deeply clean the skin, the amino acid type facial cleanser only has the functions of cleaning and moisturizing, does not have the functions of repairing and nourishing, has certain irritation to the currently common sensitive and fragile skin, and can cause sensitive desquamation, stabbing pain and other feelings after use.

Chinese patent application CN108125859A discloses a multifunctional amino acid facial cleanser and a preparation method thereof, wherein the facial cleanser comprises the following raw materials: 20-25% of glycerin, 7.5-22.5% of amino acid type surfactant, 5-15% of 1, 3-propylene glycol, 0.1-0.3% of xanthan gum, 0.05-0.1% of EDTA disodium, 1-2% of lauryl glucoside, 0.01-0.02% of acne removing component, 1-6% of grease, 0.01-0.05% of sodium hyaluronate, 0.005-0.01% of sodium polyacrylate, 2-3% of plant anti-allergy agent, 0.1-0.3% of plant preservative, 0.1-0.2% of essence and the balance of water. The cleansing cream is mild, skin-friendly and non-irritant, can thoroughly remove dirt in pores, contains 1-6 parts of grease, does not solve the problem of grease defoaming, has poor foaming capacity and is not easy to wash clean.

In conclusion, the facial cleaning products on the market have the problems of strong irritation, residue after washing, less foam, poor cleaning performance and the like to a greater or lesser extent, and the skin can feel tight due to water shortage, sensitive desquamation and stabbing pain after use, so that the mild and non-irritant facial cleaning product with multiple effects of strong cleaning and moisturizing capability, nourishing and repairing, anti-inflammation and bacteriostasis and the like is provided, and has important significance and wide market prospect in the field of daily cosmetics.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide an amino acid facial cleanser and a preparation method thereof. The amino acid facial cleanser provided by the invention has strong cleaning and decontaminating capabilities, is close to the pH value of human skin, has good skin affinity, is safe and mild, and is not irritant; the moisturizing effect is good, and the moisturizing cream has the functions of nourishing, repairing, bacteriostasis and anti-inflammation, and is suitable for long-term use of skin.

The technical scheme of the invention is as follows:

an amino acid facial cleanser comprises the following components in parts by weight: 22-38 parts of humectant, 20-30 parts of amino acid type surfactant, 6-15 parts of auxiliary surfactant, 4-6 parts of thickener and 6.9-46.3 parts of water; the pH value of the amino acid facial cleanser is 5.5-6.

Further, the amino acid facial cleansing cream comprises the following components in parts by weight: 30 parts of humectant, 25 parts of amino acid type surfactant, 10 parts of auxiliary surfactant, 5.3 parts of thickening agent and 26.8 parts of water.

Further, the amino acid type surfactant is sodium cocoyl sarcosinate; the auxiliary surfactant is sodium methyl cocoyl taurate.

Further, the humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 8-13: 2-9: 1-3.

Further, the humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 10: 5: 1.

Further, the antibacterial and anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 3-6: 1-2.

Further, the antibacterial and anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 4: 1.

Further, the thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 5-10: 17-23: 21-28.

Further, the thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 8: 20: 25.

The preparation method of the amino acid facial cleanser comprises the following steps:

s1, adding the humectant and the bacteriostatic and anti-allergic agent into water, and fully stirring and dissolving to obtain a mixed solution A;

s2, adding the amino acid type surfactant, the auxiliary surfactant and the mixed solution A obtained in the step S1 into an emulsifying cylinder, heating and uniformly stirring until the mixture is dissolved, stopping stirring when the temperature of the emulsifying cylinder reaches 70-90 ℃, preserving the temperature for 20-40min, and removing the foam in the solution to obtain a mixed solution B;

s3, adding the thickening agent into the mixed solution B obtained in the step S2, stirring for 15-25min, then opening a cooling system, cooling to 38-45 ℃ while stirring, stopping cooling, and forming the mixed solution into a fine and uniform paste to obtain the ointment.

Further, the stirring speed in the step S1, the step S2 and the step S3 is 15-45 r/min.

In the invention, the added amino acid type surfactant sodium cocoyl sarcosinate and the auxiliary surfactant sodium methyl cocoyl taurate have good foaming capacity and dirt-removing capacity, are mild, have no stimulation, are weakly acidic, have a pH value close to that of human skin, and are easy to wash.

In the amino acid facial cleansing cream provided by the invention, the humectant consists of 1, 3-propylene glycol, glycerol and chondroitin sulfate. The 1, 3-propylene glycol and the glycerol have strong hygroscopicity and good moisturizing effect. Experiments prove that after chondroitin sulfate is added into 1, 3-propylene glycol and glycerol according to a certain proportion, the moisturizing effect of the facial cleanser is effectively improved, the facial cleanser is smooth and not tight after washing, can keep skin moisture for a long time, can relieve the stimulation of a surfactant to the skin during facial cleansing, nourish and repair the skin, and protect the skin from being damaged by the external environment for a long time.

In the amino acid facial cleanser provided by the invention, the antibacterial and anti-allergic agent consists of chitosan powder and limonene. The chitosan powder has good functions of moisture absorption, moisture preservation, conditioning, bacteriostasis and the like, and is safe and non-irritating. The invention unexpectedly discovers that when the weight ratio of chitosan powder to limonene is 4: 1, the antibacterial and anti-allergic agent has obvious anti-inflammatory effect and can inhibit bacteria and fungi on the surface of skin; and experiments show that the amino acid facial cleanser added with the antibacterial and anti-allergy agent has strong foaming capacity, fine and smooth foam and is easier to wash.

In the amino acid facial cleanser provided by the invention, the thickening agent is composed of methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to a certain proportion, the matching is reasonable, the prepared facial cleanser is easy to form paste, the stability is good, the phenomena of high-temperature instability, particle separation and the like are avoided, and the foaming capacity of the facial cleanser is favorably enhanced.

Compared with the prior art, the amino acid facial cleanser provided by the invention has the following advantages:

(1) the amino acid cleansing cream provided by the invention has strong cleansing and decontamination capabilities, the added natural amino acid surfactant is close to the pH value of human skin, the amino acid cleansing cream has good skin-friendly property, is safe, mild, non-irritant and strong in foaming capability, and is easy to wash while deeply cleansing.

(2) According to the amino acid facial cleanser provided by the invention, the chondroitin sulfate is added into the humectant, so that the moisturizing and moisture-locking performance of the humectant is improved, the skin moisture is kept sufficient for a long time after face cleaning, and the amino acid facial cleanser has a nourishing and repairing function.

(3) According to the amino acid facial cleanser provided by the invention, the chitosan powder and the limonene are added into the antibacterial anti-allergy agent, so that the anti-inflammatory function of the facial cleanser is improved, the formation of fungi and bacteria on the skin can be inhibited, and the amino acid facial cleanser is mild, non-irritant and suitable for long-term use of the skin.

Detailed Description

The present invention is further illustrated by the following description of specific embodiments, which are not intended to limit the invention, and various modifications and improvements can be made by those skilled in the art based on the basic idea of the invention, but the invention is within the protection scope of the invention.

Chitosan powder, CAS No.: 9012-76-4; chondroitin sulfate, CAS No.: 9007-28-7; limonene, CAS number: 5138-86-3; betaine crystals; sodium cocoyl sarcosinate, CAS No.: 61791-59-1; sodium methyl cocoyl taurate, CAS number: 12765-39-8; 16-18 alcohol, CAS No.: 67762-27-0; GC04 was obtained from guangzhou bluegrass biotechnology, ltd, without added preservatives.

Example 1 an amino acid cleansing cream

The amino acid facial cleanser comprises the following components in parts by weight: 22 parts of humectant, 1 part of bacteriostatic and anti-allergic agent, 20 parts of sodium cocoyl sarcosinate, 6 parts of sodium methyl cocoyl taurate, 4 parts of thickener and 46.3 parts of water; the pH value of the amino acid facial cleanser is 5.5.

The humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 8: 2: 1.

The antibacterial anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 3: 2.

The thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 5: 23: 28.

s1, adding the humectant and the bacteriostatic anti-allergic agent into water, and fully stirring and dissolving to obtain a mixed solution A;

s2, adding sodium cocoyl sarcosinate, sodium methyl cocoyl taurate and the mixed solution A obtained in the step S1 into an emulsifying cylinder, heating and uniformly stirring until the mixture is dissolved, stopping stirring when the temperature of the emulsifying cylinder reaches 70 ℃, preserving the temperature for 20min, and removing foam in the solution to obtain a mixed solution B;

s3, adding the thickening agent into the mixed solution B obtained in the step S2, stirring for 15min, then opening a cooling system, cooling to 38 ℃ while stirring, stopping cooling, and forming the mixed solution into a fine and uniform paste to obtain the ointment.

The stirring rate in the step S1, the step S2 and the step S3 was 15 r/min.

Example 2 an amino acid cleansing cream

The amino acid facial cleanser comprises the following components in parts by weight: 30 parts of a humectant, 1.5 parts of an antibacterial anti-allergy agent, 25 parts of sodium cocoyl sarcosinate, 10 parts of sodium methyl cocoyl taurate, 5.3 parts of a thickening agent and 26.8 parts of water; the pH value of the amino acid facial cleanser is 5.7.

The humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 10: 5: 1.

The antibacterial anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 4: 1.

The thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 8: 20: 25.

s2, adding sodium cocoyl sarcosinate, sodium methyl cocoyl taurate and the mixed solution A obtained in the step S1 into an emulsifying cylinder, heating and uniformly stirring until the mixture is dissolved, stopping stirring when the temperature of the emulsifying cylinder reaches 80 ℃, preserving the temperature for 30min, and removing foam in the solution to obtain a mixed solution B;

s3, adding the thickening agent into the mixed solution B obtained in the step S2, stirring for 20min, then opening a cooling system, cooling to 42 ℃ while stirring, stopping cooling, and forming the mixed solution into a fine and uniform paste to obtain the ointment.

The stirring rate in the step S1, the step S2 and the step S3 was 30 r/min.

Example 3 an amino acid cleansing cream

The amino acid facial cleanser comprises the following components in parts by weight: 38 parts of humectant, 2 parts of bacteriostatic and anti-allergic agent, 30 parts of sodium cocoyl sarcosinate, 15 parts of sodium methyl cocoyl taurate, 6 parts of thickener and 6.9 parts of water; the pH value of the amino acid facial cleanser is 6.

The humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 13: 9: 3, and (3).

The antibacterial anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 6: 1.

The thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 10: 17: 21, and (3) preparing.

s2, adding sodium cocoyl sarcosinate, sodium methyl cocoyl taurate and the mixed solution A obtained in the step S1 into an emulsifying cylinder, heating and uniformly stirring until the mixture is dissolved, stopping stirring when the temperature of the emulsifying cylinder reaches 90 ℃, preserving the temperature for 40min, and removing foam in the solution to obtain a mixed solution B;

s3, adding the thickening agent into the mixed solution B obtained in the step S2, stirring for 25min, then opening a cooling system, cooling to 45 ℃ while stirring, stopping cooling, and forming the mixed solution into a fine and uniform paste to obtain the ointment.

The stirring rate in the step S1, the step S2 and the step S3 was 45 r/min.

Example 4 an amino acid cleansing cream

The amino acid facial cleanser comprises the following components in parts by weight: 30 parts of a humectant, 25 parts of sodium cocoyl sarcosinate, 10 parts of sodium methyl cocoyl taurate, 5.3 parts of a thickening agent and 26.8 parts of water; the pH value of the amino acid facial cleanser is 5.7.

s1, adding the humectant into water, and fully stirring and dissolving to obtain a mixed solution A;

The stirring rate in the step S1, the step S2 and the step S3 was 30 r/min.

Comparative example 1 amino acid facial cleanser

The humectant is prepared from 1, 3-propylene glycol and glycerol in a weight ratio of 2: 1.

The preparation method of the amino acid facial cleanser is similar to that of example 2.

The difference from example 2 is that chondroitin sulfate is not added to the moisturizer.

Comparative example 2 amino acid cleansing cream

The humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate in a weight ratio of 1: 1: 1.

The difference from example 2 is that the moisturizer consists of 1, 3-propanediol, glycerol and chondroitin sulfate in a weight ratio of 1: 1: 1.

Comparative example 3 an amino acid cleansing cream

The antibacterial and anti-allergic agent is chitosan powder.

The amino acid facial cleanser was prepared similarly to example 2.

The difference from the example 2 is that the bacteriostatic and anti-allergy agent is not added with limonene.

Comparative example 4 amino acid cleansing cream

The bacteriostatic and anti-allergic agent is limonene.

The difference from the example 2 is that chitosan powder is not added in the bacteriostatic and anti-allergic agent.

Comparative example 5 amino acid facial cleanser

The antibacterial anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 1: 1.

The antibacterial and antiallergic agent is different from the antibacterial and antiallergic agent in example 2, wherein the antibacterial and antiallergic agent is prepared from chitosan powder and limonene according to a weight ratio of 1: 1.

Comparative example 6 amino acid facial cleanser

The amino acid facial cleanser comprises the following components in parts by weight: 30 parts of a humectant, 1.5 parts of an antibacterial anti-allergy agent, 25 parts of cocoyl sarcosine sodium, 5.3 parts of a thickening agent and 36.8 parts of water; the pH value of the amino acid facial cleanser is 5.7.

The difference from example 2 is that the amino acid facial cleanser has no sodium methyl cocoyl taurate added.

Test example I, skin feel evaluation test

1. Test materials: amino acid facial cleansers prepared in examples 1-3 and comparative examples 1-6.

2. The test method comprises the following steps: in order to evaluate the use effect of the amino acid facial cleanser of the present invention, 90 volunteers were selected to perform skin feel evaluation tests using the facial cleansers of examples and comparative examples as test samples. Each facial cleanser is used for 1 week, 1 time in the morning and evening each day, and the subjects are scored according to the feeling in the using process, wherein the score is 5 points, 1 point has the worst effect, and 5 points have the best effect.

3. Test results

The test results are shown in table 1.

Table 1 evaluation using skin feel

As can be seen from the skin feeling evaluation table of each volunteer in the table 1, the amino acid facial cleansing cream prepared in the examples 1-3 has strong cleanliness, is mild, does not stimulate, is easy to wash clean, has no dry and tight feeling after use, and has smooth and moist skin, wherein the best effect is obtained in the example 2, which is the best example of the invention; the cleansing cream of comparative example 1 did not contain chondroitin sulfate, and the moisturizing agent in the cleansing cream of comparative example 2 was prepared from 1, 3-propanediol, glycerin, and chondroitin sulfate in a weight ratio of 1: 1: 1, although the two groups have stronger cleanliness and are easy to wash, the skin is dry, tight and rough after the lotion is used, and the lotion has micro-irritation and does not have moistening effect; the cleansing cream of the comparative examples 3 and 4 does not contain chitosan powder and limonene, and the cleansing cream of the comparative example 5 contains the antibacterial and anti-allergy agent prepared from the chitosan powder and the limonene according to the weight ratio of 1: 1, the three groups of comparative examples have obvious conditions of weak cleaning force, difficult washing, slight irritation after use and the like. The amino acid facial cleanser prepared in comparative example 6 has significantly poor cleansing strength, is not easy to wash, and has poor mildness when used, because the auxiliary surfactant of sodium methyl cocoyl taurate is not added.

Test example two, foaming force test

1. Test materials: examples 1-4, comparative examples 1-6.

2. The test method comprises the following steps: the foaming power of the amino acid facial cleansers prepared in examples 1 to 3 and the amino acid facial cleansers prepared in comparative examples 1 to 6 were measured according to GBT13173.6-2000 "measurement of foaming power of detergent" (Ross-Miles method).

3. Test results

The test results are shown in Table 2.

TABLE 2 foaming force test results

As can be seen from Table 2, the foaming power and the retention within 5min of the amino acid facial cleansers prepared in examples 1-3 were better than those of the amino acid facial cleansers prepared in comparative examples 1-6. The amino acid facial cleanser provided by the invention has better foaming capacity.

Test example three, moisture retention Performance test

1. Test materials: amino acid facial cleansers prepared in examples 1-4 and comparative examples 1-6.

2. Test subjects: healthy skin and a test population without cosmetic allergy history are selected for each group, and the test population is 20-45 years old, wherein 45 male patients and 45 female patients are averagely divided into 9 groups, and 10 patients are selected for each group.

3. The test method comprises the following steps: each group measured the average of the moisture content of the skin of 10 volunteers at various times before and after using the amino acid facial cleansers prepared in examples 1-3 and comparative examples 1-6. The detection instrument for the skin moisture addition amount is as follows: corneometer cm825+ german CK skin test instrument.

4. Test results

The test results are shown in table 3.

TABLE 3 test results of moisture retention

As is apparent from Table 3, the amino acid facial cleansers prepared in examples 1-3 are superior in skin moisturizing performance after use and within 2 hours of use, as compared to the comparative examples, and example 2 is the best example of the present invention, in which the effect is the best. The test results of the amino acid facial cleanser prepared in the comparative examples 1-2 and the test results of the example 2 show that the moisturizing agent provided by the invention is reasonable in component proportion, the synergistic effect of the chondroitin sulfate, the 1, 3-propylene glycol and the glycerin is obvious, the skin moisture can be supplemented in time after the facial cleanser provided by the invention is used, and the moisture addition amount of the skin can still reach 39.65 parts 2 hours after the facial cleanser is used.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. The amino acid facial cleanser is characterized by comprising the following components in parts by weight: 22-38 parts of humectant, 20-30 parts of amino acid type surfactant, 6-15 parts of auxiliary surfactant, 4-6 parts of thickening agent, 1 part or 1.5 parts or 2 parts of bacteriostatic and anti-allergic agent and 6.9-46.3 parts of water; the pH value of the amino acid facial cleanser is 5-6;

the humectant is prepared from 1, 3-propylene glycol, glycerol and chondroitin sulfate according to a weight ratio of 8-13: 2-9: 1-3;

the antibacterial anti-allergic agent is prepared from chitosan powder and limonene according to a weight ratio of 3-6: 1-2.

2. The amino acid facial cleanser of claim 1, which is prepared from the following components in parts by weight: 30 parts of humectant, 25 parts of amino acid type surfactant, 10 parts of auxiliary surfactant, 5.3 parts of thickening agent, 1.5 parts of bacteriostatic and anti-allergic agent and 26.8 parts of water.

3. The amino acid facial cleanser of claim 1 or 2, wherein the amino acid type surfactant is sodium cocoyl sarcosinate; the auxiliary surfactant is sodium methyl cocoyl taurate.

4. The amino acid facial cleanser of claim 1, wherein the moisturizer is prepared from 1, 3-propanediol, glycerol and chondroitin sulfate in a weight ratio of 10: 5: 1.

5. The amino acid facial cleanser of claim 1, wherein the bacteriostatic and anti-allergic agent is prepared from chitosan powder and limonene in a weight ratio of 4: 1.

6. The amino acid facial cleanser of claim 1 or 2, wherein the thickener is a mixture of methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride in a weight ratio of 5-10: 17-23: 21-28; the thickening agent is prepared from methyl glucose triisostearic acid, 16-18 alcohol and sodium chloride according to the weight ratio of 8: 20: 25.

7. The method for preparing an amino acid facial cleanser according to any one of claims 1 to 6, comprising the steps of:

8. The method for preparing amino acid facial cleansing cream according to claim 7, wherein the stirring rate in step S1, step S2 and step S3 is 15 to 45 r/min.