JP2011006483A - Method for producing amphoteric propionate surfactant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a salt-free amphoteric propionate surfactant.SOLUTION: The method for producing the improved salt-free amphoteric propionate surfactant includes reacting an imidazoline compound with a mixture of acrylic acid and sodium acrylate in an aqueous medium at high temperatures, wherein acrylic acid and sodium acrylate are blended as the mixture in a molar ratio ranging from 1:6 to 1:3 of each of them.

Description

  The present invention relates broadly to surfactants and cleaning compositions useful for cosmetics and personal care applications such as soaps, shampoos, facial cleansing and cosmetic products. In particular, the present invention relates to the manufacture of these compositions and improved methods that are user and environmentally friendly.

  Surfactants are useful in cleaning compositions because they reduce the intermolecular attractive force of one compound or material from another compound or material. That is, they reduce the surface tension that exists between dust, oil or grease and other inert materials such as skin, hair or porcelain, textiles, hard surfaces and the like. In doing so, the dust or grease moves away from the surface of the second material that is thereby cleaned.

  There are three basic types of surfactants and many different species of each. The detergent lowers the surface tension of the water and exerts an emulsifying action especially at the oil-water interface, thus acting to remove dirt. An emulsifier is basically a type of detergent that holds more than one liquid in suspension. The wetting agent reduces the surface tension of the water so that it can more easily penetrate or diffuse across the surface of another material.

  In addition, surfactants can be classified by their charge. Anionic surfactants are negatively charged, cations are positively charged, nonionics have no charge, but amphoteric surfactants can be positively or negatively charged depending on their environment It has the ability to act as either an acid or a base depending on the pH. In addition, there are many different species in each group, and each can act in different ways. Amphoteric surfactants derived from imidazolines are usually characterized by relatively mildness and are ideal for use in personal care compositions such as baby shampoo formulations. Moreover, they tend to be stable and effective over a wide pH range, which is a useful property for many alkali or acidic detergents used in specific cleaning applications.

  McBride U.S. Pat. No. 3,187,003 discloses a process for producing zwitterions of 1- (2-amino-ethylimidazoline) which are useful as oil stabilizers, grease additives, fiber antistatic agents, and the like. . An imidazoline having an aminoethyl substituent is reacted with an α-β-unsaturated acid having 12 to 22 carbon atoms.

  US Pat. No. 2,820,043 to Rafney et al. Is a process for the preparation of imidazoline propionic acid derivatives that are virtually amphoteric surfactants and are useful as wetting, penetrating, emulsifying, dispersing and cleaning agents. Is disclosed. They have been useful over a wide range of pH and are made by reacting 2-hydrocarbon substituted imidazolines with lower alkyl acrylates in the presence of heat, thus forming lower alkyl esters of 2-substituted imidazoline propionic acids. Then it is hydrolyzed.

  Katz U.S. Pat. No. 3,555,041 discloses one amphoteric imidazoline surfactant having effective surfactant properties over a wide range of pH values. These surfactants are made by reacting long-chain imidazoline compounds containing amino, alkyl, or hydroxyalkyl substituents with acrylonitrile, methyl acrylate or beta-propiolactone. Preferably methyl acrylate is used.

  Finally, Arndt British Patent 1,078,101 teaches a class of amphoteric imidazolines known as 2-R-imidazoline-1-ethylene-2-oxy-propionic acids, which are aminoethylethanolamine and fatty acids. To produce an imidazoline intermediate, which is then reacted with acrylic acid to give the final product. The compounds are claimed to be useful as emulsifiers, detergents, wetting and surfactants over a wide range of pH.

  Amphoteric surfactants based on imidazolines can be divided into two groups: those that are salt-contained and those that are salt-free. Salt-containing amphoteric surfactants having the general structure shown immediately below are usually produced from the condensation reaction of imidazoline and sodium monochloroacetate, but sodium chloride is produced as a by-product.

  Salt-free amphoteric substances such as the monoamphoteric propionate shown in the formula below have several advantages over salt-containing counterparts in industrial applications. A salt-free amphoteric material can be prepared by michael addition reaction with methyl acrylate or acrylic acid between imidazolines under anhydrous conditions, followed by alkaline hydrolysis. Unfortunately, the reaction gives a complex mixture as suggested by NMR, capillary electrophoresis and HPLC. Therefore, it is highly desirable to produce a mono-amphoteric propionic acid as shown below in a high yield and a salt-free amphoteric substance from imidazoline and acrylic acid.

  The use of the reactant compound acrylic acid as opposed to methyl acrylate provides numerous advantages. For example, acrylic acid has a higher flash point and is therefore relatively safe and easy to use together. In addition, the compound has much less unpleasant odor.

  Even more valuable in the process of the present invention is that the production of a salt-free amphoteric surfactant such as monoamphoteric propionate does not generate methanol as a by-product. Methanol is listed on the list as a dangerous chemical by the US Environmental Protection Agency. Most amphoteric propionate surfactants made with methyl acrylate contain about 2.0 to more than 5.0% methanol as a by-product. Storage of methyl acrylate requires expensive tanks and ventilation and absorption equipment for its vapor removal.

  Another major problem associated with producing salt-free amphoteric propionate using previously known methods is the relatively low yield of the resulting monoamphoteric propionate. Reaction of the imidazoline coco-condensate with methyl acrylate yields a salt-free mono-amphoteric propionate in a yield of only 20% to 25%. In addition, this is a very impure product containing as many as seven different compounds produced in the reaction mixture.

  An improved method for producing salt-free amphoteric surfactants in high yield involves the condensation reaction of imidazoline with a mixture of acrylic acid and sodium acrylate in a molar ratio of about 1: 3 each. The reaction is carried out in an aqueous medium at an elevated temperature of about 85 ° C to 100 ° C.

It is well known that imidazoline readily undergoes a Michael addition reaction with methyl acrylate or acrylic acid under anhydrous conditions. NMR analysis of carbon-13 suggests that after hydrolysis with sodium hydroxide, the reaction product contains more components than the single compound, ie, the desired amphoteric propionate of the above formula. One possible explanation for why the Michael reaction gives a complex mixture is outlined in Scheme 1. In the first stage, the Michael reaction takes place with sp ² nitrogen, giving intermediate 2a, which is stabilized by the formation of 2b by a resonance mechanism.

  Hydrolysis of the adducts (2a) and (2b) with sodium hydroxide gives two monoamphoteric propionates (3) and (4) by cleavage of either one of the two CN bonds. In the presence of excess alkylating reagent, (3) and (4) can be further converted to dipropionates (5) and (6), respectively. In the case of methyl acrylate, it was found that in addition to the nitrogen atom of the imidazoline ring, the hydroxyl group also undergoes a Michael addition reaction. This is evidenced by the appearance of the carbon-13 signal in the 67 ppm region.

Alkylation can also occur at the sp ³ nitrogen atom. However, as shown in Scheme 2, the resulting intermediate (7) is less stable than intermediate (2) which is stabilized by a resonance structure. Thus, the desired amphoteric propionate is only a minor component in the mixture.

  The product obtained by carrying out the reaction in an aqueous medium is expected to be rich in (8). Because imidazoline is known to undergo hydrolysis with water to give amidoamine (a) with a small amount of (10), and then (10) reacts with an alkylating agent at the amine nitrogen to react with (8) and (8), respectively. (11) is produced (see Scheme 3). The conversion of imidazoline to its product is low and the resulting product contains a significant amount of unreacted amidoamine (a).

  The present invention is a process for producing a salt-free amphoteric surfactant having a high content of mono-amphoteric propionate from readily available acrylic acid and coco-imidazoline. Clearly, the Michael reaction must be utilized to produce amphoteric propionate from acrylic acid and coco-imidazoline. However, the direct treatment of imidazolines with acrylic acid is a typical acid-based reaction and can compete with the Michael addition reaction. One way to overcome this problem is by using sodium acrylate.

  Michael addition with amidoamine (a) gives intermediate (12) first as shown in Scheme 4 and then undergoes rearrangement to give (8) in a relatively high yield.

  The present invention then involves the preparation of a salt-free amphoteric propionate that yields a high yield of monoamphoteric propionate with little impurities and other undesirable by-products. The process typically involves reacting imidazoline with a mixture of acrylic acid and sodium acrylate in an aqueous medium at elevated temperatures. The use of acrylic acid instead of methyl acrylate makes it possible to carry out the reaction without producing methanol or other dangerous by-products. In the past, methanol was produced in amounts of 2.0 wt% to 5.0 wt% of the total amount of the mixture of target organisms.

  By completely removing methanol as a by-product, amphoteric surfactants without salt can be produced and can be incorporated into personal care products and especially cosmetic compositions, which are excellent cleans with little irritation Gives a chemical effect. In addition, these surfactants can be incorporated into hypoallergenic compositions that are in increasing demand worldwide.

  The Michael addition reaction occurs in aqueous media at elevated temperatures. The imidazoline and acrylic acid / sodium acrylate mixture are combined in a molar ratio of 1: 1, ie, an equal amount of imidazoline and acid / acrylate mixture. The mixture itself consists of acrylic acid and sodium acrylate in a molar mass ratio of about 1: 6 to about 1: 3. Preferably, the two compounds are mixed in 75 parts of sodium acrylate in an amount of 25 parts acrylic acid. The compounds are mixed together in water before the imidazoline addition. The imidazoline derivatives useful in the practice of this invention are made from 2- (2-aminoethylamino) ethanol and fatty acids. Examples of fatty acids can include coconut oil fatty acids, capryl, caprin, myristic, palmitic acid and stearic acid.

When lauric imidazoline (structure 1; R = C ₁₁ H ₂₃ ) was treated with sodium acrylate prepared from acrylic acid and sodium hydroxide in an aqueous medium at about 70 ° C., the desired Michael addition reaction was 5 hours. It didn't happen later. Carbon-13 NMR showed that the imidazoline was hydrolyzed to amidoamine in 1 hour under the reaction conditions used. The reaction mixture was then heated to 90 ° C. and the temperature was maintained for 20 hours. The carbon 13 NMR spectrum of the reaction product showed that the desired Michael addition reaction occurred and that the amphoteric propionate surfactant (structure 8) was produced in 37% yield based on imidazoline. The structural assignment to 8 was based on a comparison of its ¹³ C-NMR spectrum with that of the well-known amphoteric acetate spectrum as shown in the previous formula.

  The following examples are intended to disclose the invention in more detail for carrying out the method of the invention. However, it will be appreciated that they are for illustrative purposes only and minor changes may be made as would not be expected here. To the extent that such changes do not substantially affect the final reaction product or result, it should be understood that they are considered to fall within the spirit and scope of the invention as defined in the claims. .

Example I
In a four-necked round bottom flask equipped with a stirrer, thermometer and dropping funnel, 268 g (1.0 mol) of coco-imidazoline, 400 g of water, and a mixture of acrylic acid and sodium acrylate (72 g (1.0 mol) of acrylic acid) , Prepared in a separate container by adding with stirring and cooling to 24 g of 50% NaOH (0.3 mol) in 200 g of water). The reaction mixture was heated to 90 ° C. and continued for 20 hours.

  The analyzed product was 38.0% solids. Analysis by carbon 13 NMR showed that the reaction produced mono-amphoteric propionic acid (8) in 40% yield based on the amount of coco-imidazoline and 20% unreacted amidoamine (9). .

Example II
This example illustrates that the monoamphoteric propionate (8) can be improved by changing the ratio of acrylic acid to sodium acrylate.

  The method of Example I was repeated using a mixture of acrylic acid and sodium acrylate prepared from 72 g (1.0 mol) acrylic acid and 60 g 50% sodium hydroxide (0.75 mol) in 200 g water. The yield of monoamphoteric propionate (8) was improved to 52% based on the amount of coco-imidazoline.

Example III
This example illustrates that using sodium acrylate alone as described above does not increase the yield of monoamphoteric propionate (8).

  The procedure of Example I was repeated using sodium acrylate prepared from 72 g (1.0 mol) acrylic acid and 80 g 50% sodium hydroxide (1.0 mol) in 200 g water. The yield of amphoteric propionate (8) was 37% based on the amount of coco-imidazoline.

Example IV
This example shows a process in which imidazoline is first converted to amidoamine with sodium hydroxide and then alkylated with a mixture of acrylic acid and sodium acrylate. Furthermore, it shows that the yield of amphoteric propionate (8) is further increased by using an excess of acrylic acid and sodium acrylate.

  To a 4-neck round bottom flask equipped with a stirrer, thermometer and dropping funnel was added 268 g (1.0 mol) 50% NaOH (0.05 mol) 4 g coco-imidazoline and 200 g water. The resulting mixture was heated at 85 ° C. with stirring for 1 hour. In a separate container, a mixture of acrylic acid and sodium acrylate was prepared by adding 90 g (1.25 mol) acrylic acid to 71 g 50% NaOH (0.89 mol) in 200 g water with stirring and cooling. It was done. 200 g of water was added to the reaction flask, followed by a mixture of acrylic acid and sodium acrylate. Heating was continued for another 16 hours and the reaction temperature was maintained at 85 ° C.

  The analyzed product was 38.4% solids. Analysis of carbon 13 by NMR showed that based on the amount of imidazoline, 80% yield of monoamphoteric propionate (8) was less than 10% unreacted amidoamine (9) and about 10% unidentified component (probably ( 5) and dipropionate as in (6)). Rhone-Poulenc, Inc. Compared to a commercial product such as Miranol C2M SF from No. 1, a high content of monoamphoteric propionate (8) in the product was confirmed by capillary electrophoresis. Under these conditions, the reaction conversion for amidoamine was shown to be 90%. About 25% of the acrylate mixture remains unconsumed at the end of the reaction, as determined by NMR as well as liquid chromatography. Although it is possible to obtain a higher reaction conversion with a large excess of acrylate mixture, it is certainly not desirable to have a large excess of unreacted acrylate in the final product. The final product may contain up to 10% dipropionate, such as structures (5) and (6).

  Unconsumed acrylate can be easily removed by treatment with a stoichiometric amount of sodium bisulfite at 85 ° C. for 1 hour, if desired. The possible modification of acrylic acid by the reverse Michael addition reaction does not occur at a noticeable rate after 3 months. This is supported by the fact that the final product was found to contain less than 100 ppm acrylic acid after treatment with sodium bisulfite and still contain less than 100 ppm acrylic acid after 3 months at room temperature. Preferably, the reaction is carried out in the presence of air, otherwise the final product can be cloudy, which is attributed to the polymerization of acrylic acid or sodium acrylate.

Example V
The functional surfactant properties of the amphoteric material of the present invention, free of salt, are found in the commercially available amphoteric Miranol C2M SF® (Rhone-Poulenc Inc., Monmouth Jct, NJ) (coco-amphoteric The properties of sodium propionate) were compared. The surfactant properties of amphoteric acetate without salt were compared both before and after the amphoteric acetate was treated with sodium bisulfite. The results are summarized in Table 1.

  As shown in Table 1, both amphoteric propionates with or without sodium bisulfite treated with or without sodium bisulfite have reduced surface tension and form micelles compared to Miranol C2M SF. Even more efficient. The novel amphoteric surfactant further exhibits better bubble formation and wetting properties than Miranol C2M SF.

Example VI
This example shows an alternative to that shown in Example I. Imidazoline was added to sodium acrylate, so that separate containers for the preparation of acrylic acid / acrylic acid mixtures can be avoided.

  To a four-necked round bottom flask containing 75 g of 50% NaOH (0.94 mol) and 300 g of water was added 63.9 g (0.89 mol) acrylic acid, followed by 268 g coco-imidazoline. The resulting mixture was heated with stirring at 65 ° C. for 1 hour, and then 26.1 g (0.36 mol) of acrylic acid was added. The reaction temperature was raised to 90 ° C. and maintained at this temperature for 20 hours.

Claims (7)

  Reacting an imidazoline compound with a mixture of acrylic acid and sodium acrylate in an aqueous medium at elevated temperature, wherein the acrylic acid and sodium acrylate are each formulated in the mixture in a molar ratio range of 1: 6 to 1: 3 Process for producing an improved amphoteric propionate surfactant composition free of inorganic salts.   The method according to claim 1, wherein the imidazoline compound is selected from the group consisting of lauric imidazoline, capryluimidazoline, caprin imidazoline, myristic imidazoline, palmitic imidazoline, stear imidazoline, derivatives thereof and mixtures thereof.   The process of claim 2 wherein said imidazoline compound is reacted with said acrylic acid / sodium acrylate mixture in a 1: 1 to 1: 1.25 molar ratio.   The process according to claim 3, wherein the reaction is carried out at a temperature of 80C to 100C.   The process according to claim 4, wherein the reaction is carried out at a temperature of 85C to 95C.   The method of claim 1, further comprising subsequently adding sodium bisulfite in an amount sufficient to remove excess acrylic acid.   The process of claim 6, wherein the reaction is carried out without producing methanol.