Surfactants and Gemini-type surfactants

Abstract

The present invention aims to provide a surfactant having a novel structure that exhibits excellent water solubility at low temperatures, critical micelle concentration, and surface tension reduction ability. [Solution] A surfactant according to one aspect of the present invention is represented by the following formula (1). TIFF2026062378000007.tif29165[In the above formula (1), alkyl group C n H 2n+1 The number of carbon atoms n is between 8 and 20. The chain length m of polyoxyethylene is between 2 and 30. - represents a counterion. If the compound has optically active forms, diastereomers, or geometric isomers, this includes both mixtures of each and their isolated isomers.

Description

[Technical Field]

[0001] This invention relates to surfactants and gemini-type surfactants. [Background technology]

[0002] Surfactants are amphiphilic compounds with a single-chain structure having one hydrophilic group and one hydrophobic group in the molecule, and cationic surfactants and nonionic surfactants are known examples (Patent Documents 1 and 2).

[0003] Cationic surfactants often possess bactericidal, flexible, antistatic, and rust-preventive properties. They also have a high ability to reduce surface tension, making them easily adsorbed to various surfaces. However, a disadvantage of cationic surfactants is their poor compatibility with anionic surfactants. Due to these properties, cationic surfactants are primarily used in fabric softeners, antistatic agents, corrosion inhibitors, hair finishing agents, and disinfectants, and are also used in asphalt emulsifiers and ore flotation agents.

[0004] Examples of the hydrophilic groups in cationic surfactants include amine salts and quaternary ammonium salts. Many amine salts are poorly soluble in water, while quaternary ammonium salts have increased solubility.

[0005] Nonionic surfactants have high solubility at low temperatures and low critical micelle concentrations. They possess excellent emulsifying, cleaning, and penetrating properties, as well as resistance to acids, alkalis, and heat, low foaming, and are highly safe and low-irritant. For these reasons, they are used in cosmetics, food products, and various industrial products.

[0006] Nonionic surfactants are broadly classified into polyoxyethylene type (polyethylene glycol type) and polyhydric alcohol type (polyol type). Polyoxyethylene-type nonionic surfactants have a structure that includes ether bonds, ester bonds, and amide bonds between the polyoxyethylene chain and the alkyl chain. Surfactants have also been developed in which anionic groups such as sulfate ester salts and phosphate ester salts are introduced to the hydroxyl group terminus of polyoxyethylene-based surfactants. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-35121 [Patent Document 2] Special Publication No. 2012-527511 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, surfactants are required to have high water solubility at low temperatures, low critical micelle concentration, and high surface tension reduction ability.

[0009] The present invention has been made based on the circumstances described above, and aims to provide a novel surfactant and a gemini-type surfactant having a novel structure that is excellent in water solubility at low temperatures, critical micelle concentration, and surface tension reduction ability. [Means for solving the problem]

[0010] As a result of extensive research on surfactants, the inventors discovered that by combining a quaternary ammonium group with a polyoxyethylene chain, a surfactant exhibiting excellent surface activity, such as low critical micelle concentration and high surface tension reduction ability, while ensuring water solubility at low temperatures, can be obtained, thus completing the present invention.

[0011] In other words, a surfactant according to one aspect of the present invention is represented by the following formula (1). [Chemical formula] [In the above formula (1), the alkyl group C , [Figure 3] , [Figure 4] H 2n+1 has a carbon number n of 8 or more and 20 or less. The polyoxyethylene chain length m is 2 or more and 30 or less. A - represents a counter ion. When the compound has an optically active form, a diastereomer, or a geometric isomer, it includes both the respective mixtures and the isomers isolated therefrom.]

[0012] The gemini surfactant according to another aspect of the present invention is represented by the following formula (2). [Chemical formula] [In the above formula (2), the alkyl group C n H 2n+1 has a carbon number n of 8 or more and 20 or less. The polyoxyethylene chain length m is 2 or more and 30 or less. A - represents a counter ion. When the compound has an optically active form, a diastereomer, or a geometric isomer, it includes both the respective mixtures and the isomers isolated therefrom.] [Advantages of the Invention] <000009​​​​​​​​​​​​​​​​​​​​

Mode for Carrying Out the Invention

[0015] Hereinafter, a surfactant and a gemini surfactant according to an embodiment of the present invention will be described.

[0016] <Surfactant> The surfactant is represented by the above formula (1) and has a quaternary ammonium group and a polyoxyethylene chain.

[0017] Here, the number of carbon atoms n of the alkyl group is 8 or more and 20 or less. Specifically, it is an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group or an icosyl group. Among these, a dodecyl group (n = 12), a tetradecyl group (n = 14), a hexadecyl group (n = 16) and an octadecyl group (n = 18) are preferable.

[0018] The chain length m of the polyoxyethylene chain is 2 or more and 30 or less, preferably 2 or more and 12 or less, and more preferably a tetraoxyethylene chain (m = 4).

[0019] In the above formula (1), A - The counter ion represented by is not particularly limited. For example, hydroxide ion, fluoride ion, chloride ion, bromide ion, iodide ion and other halide ions, nitrate ion, formate ion, acetate ion, trifluoroacetate ion, p-toluenesulfonate ion, hexafluorophosphate, tetrafluoroborate and the like can be mentioned. Among them, bromide ion (Br - ) generally used as a counter ion of a cationic surfactant is preferable.

[0020] In the above formula (1), A -The counterions represented by may be replaced with halide ions such as fluoride ions, chloride ions, bromide ions, and iodide ions, or with counterions such as nitrate ions, formate ions, acetate ions, trifluoroacetate ions, p-toluenesulfonate ions, hexafluorophosphates, and tetrafluoroborates, and are not particularly limited, but for example, chloride ions can be replaced with formate ions or acetate ions.

[0021] The above counterions may be a combination of two or more types. That is, the above counterions may be the same for each molecule represented by formula (1) above, or they may be different. There are no particular restrictions on the types and ratios of the counterions when they are different, and they can be changed as desired.

[0022] In this surfactant, the alkyl chain (alkyl group) is used as the hydrophobic group, and the polyoxyethylene chain is used as the hydrophilic group. Therefore, by changing the lengths of both the alkyl chain and the polyoxyethylene chain, the hydrophilic-hydrophobic balance (HLB) of this surfactant can be freely changed.

[0023] Furthermore, because this surfactant has high surface activity and excellent safety, it can be used as a component of emulsifier compositions, dispersant compositions, detergent compositions, etc., and can be widely used as an emulsifier, dispersant, detergent, etc., containing these compositions.

[0024] Furthermore, this surfactant, which has a polyoxyethylene chain and a quaternary ammonium group, can be synthesized by a relatively simple method and is extremely useful industrially due to its economic efficiency and productivity.

[0025] To explain the case where n=14 and m=4, the product can be manufactured by the following method, for example. First, tetraethylene glycol and hydrogen bromide are reacted in toluene at a temperature of 120°C to 140°C for a reaction time of 5 to 10 hours to synthesize tetraethylene glycol in which one of the hydroxyl groups is brominated. The surfactant can then be obtained by reacting this with N,N-dimethylalkylamine in acetonitrile at a temperature of 80°C to 100°C for a reaction time of 15 to 30 hours. For purification, it is advisable to repeatedly wash with hexane and ether, for example.

[0026] <Gemini-type surfactant> The gemini-type surfactant is represented by formula (2) above. This gemini-type surfactant has two alkyl chains and two polyoxyethylene chains in its molecule. The structure of the alkyl chains, polyoxyethylene chains, counterions, etc., can be constructed in the same way as the surfactant represented by formula (1) above, so a detailed explanation is omitted.

[0027] By adopting this Gemini-type structure, the Gemini-type surfactant exhibits even better surface activity, such as a low critical micelle concentration and high surface tension reduction ability.

[0028] This gemini-type surfactant can be synthesized, for example, by reacting N,N'-dimethyl-N,N'-didodecylethylenediamine, obtained by reacting N,N'-dimethylalkylamine with 1-bromododecane, with tetraethylene glycol, in which one of the hydroxyl groups has been brominated, at a temperature of 80°C to 100°C and a reaction time of 25 to 50 hours (for n=12, m=4). [Examples]

[0029] The present invention will be described in more detail below with reference to examples.

[0030] [Synthesis of surfactants] The single-chain surfactant in question (n=12, 14, 16, m=4; hereafter C nAmEO4 (sometimes abbreviated as AmEO4) was synthesized by the following procedure. First, 5-10 g of tetraethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) and 5-10 g of hydrogen bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) were reacted at 120°C for 5 hours to synthesize tetraethylene glycol in which one of the hydroxyl groups was brominated. N,N-dimethylalkylamine was then reacted with this at 80°C for 15 hours to produce C n AmEO4 was obtained. Purification was performed by repeated washing with hexane and ether. 12 AmEO4, C 14 AmEO4, C 16 The yields for AmEO4 were 8%, 11%, and 12%, respectively.

[0031] [evaluation] Kraft temperature, electrical conductivity, surface tension, and small-angle X-ray scattering were evaluated.

[0032] <Crafting temperature> Each C n Regarding AmEO4, crafting temperature (T k The Kraft temperature was measured by visually observing the state of an aqueous solution of a surfactant prepared at 1.0 mass% (wt%) while increasing the temperature from a low temperature. The results are shown in Table 1.

[0033] [Table 1]

[0034] The results in Table 1 show that the Krafft temperature is independent of the chain length, and all exhibit high water solubility below 5°C. Conventional quaternary ammonium salt cationic surfactants have a Krafft temperature of 40°C or higher with a chain length of 14. Therefore, it has become clear that the introduction of polyoxyethylene chains can add high water solubility even with long chain lengths.

[0035] <Electrical conductivity> Each C nFor AmEO4, the electrical conductivity was measured, and the critical micelle concentration (CMC) was determined from the results. Specifically, the following procedure was followed.

[0036] First, each C n An aqueous solution of AmEO4 was prepared. Each C was added to a cell containing 50 ml of Millipore water kept at 25°C. n An aqueous solution of AmEO4 was added dropwise, and the electrical conductivity at that time was recorded. n The relationship between AmEO4 concentration and electrical conductivity was plotted on a graph. The critical micelle concentration (CMC) was calculated from the inflection point of the graph.

[0037] Each C n Figure 1 shows the relationship between the concentration of AmEO4 and its electrical conductivity. Table 2 shows the calculated CMC. In Table 2, α represents the degree of dissociation. Table 2 also includes, for reference, alkyltrimethylammonium bromide (C n The CMC values ​​for TAB (where n is the alkyl chain length) are also listed.

[0038] [Table 2]

[0039] From the results in Table 2, C n The CMC of AmEO4 corresponds to C n Although slightly higher than TBA's CMC, it can be said to be almost equivalent. n The reason for the high CMC of AmEO4 is thought to be the increased hydrophilicity due to the addition of a tetraoxyethylene chain to the quaternary ammonium group.

[0040] <Surface tension> Each C n The surface tension of AmEO4 was measured. The surface tension was measured using the Wilhelmy Plate method, in which a platinum plate is brought into contact with the surface of an aqueous surfactant solution. The results are shown in Figure 2.

[0041] According to Figure 2, C nUnlike the behavior of the surface tension of conventional surfactants, AmEO4 exhibits a peculiar behavior in that it shows a minimum at a concentration lower than the CMC determined from the surface tension, and the surface tension increases at a concentration higher than that. This is considered to be due to the influence of the tetraoxyethylene chain introduced between the alkyl chain and the quaternary ammonium group. The "CMC determined from the surface tension" refers to the CMC determined from the intersection of two straight lines that form a kink when the surface tension is plotted against the logarithm of the concentration.

[0042] <Small-angle X-ray scattering> C 12 AmEO4 and C 14 For AmEO4, small-angle X-ray scattering measurements were performed. When the sample is irradiated with X-rays, the X-rays are scattered if there are regions with different electron densities in the sample. Small-angle X-ray scattering is a technique for measuring scattered X-rays with scattering angles of a few degrees or less. Measuring scattered light with a smaller scattering angle corresponds to measuring a larger structure in real space. The results are shown in FIGS. 3 and 4.

[0043] As shown in FIGS. 3 and 4, C with alkyl chain lengths of 12 and 14 n AmEO4 formed aggregates with a core-shell structure that are considered to be micelles of a small size regardless of the concentration. This is the same as the micelles formed by conventional surfactants.

Industrial Applicability

[0044] As described above, the surfactant and gemini surfactant of the present invention are excellent in water solubility at low temperatures, critical micelle concentration, and surface tension reduction ability. In addition, the surfactant and gemini surfactant of the present invention can be synthesized by a relatively simple method, and are excellent in economy and productivity, so they are extremely useful industrially. And the surfactant and gemini surfactant of the present invention have high surface activity and excellent safety, so they can be used as constituent substances of emulsifier compositions, dispersant compositions, detergent compositions, etc., and can be widely used as emulsifiers, dispersants, detergents, etc. containing these compositions.

Claims

1. A surfactant represented by the following formula (1). 【Chemistry 1】 [In the above formula (1), alkyl group C ｎ H ２ｎ＋１ The number of carbon atoms n is between 8 and 20. The polyoxyethylene chain length m is between 2 and 30. A － represents a counterion. If the compound has optically active forms, diastereomers, or geometric isomers, this includes both mixtures of these and their isolated isomers.

2. A gemini-type surfactant represented by the following formula (2). 【Chemistry 2】 [In formula (2) above, alkyl group C ｎ H ２ｎ＋１ The number of carbon atoms n is between 8 and 20. The polyoxyethylene chain length m is between 2 and 30. A － represents a counterion. If the compound has optically active forms, diastereomers, or geometric isomers, this includes both mixtures of these and their isolated isomers.

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