The general properties of amphoteric surfactants, such as rheology, water solubility, calcium soap dispersibility and hard water resistance, are introduced. The relationship between the rheology of amphoteric surfactant and the concentration of surfactant is discussed, and the method to adjust the rheology of mixed system is given. Based on the mixed micelle theory, the author puts forward a new viewpoint that amphoteric surfactants are superior to other types of surfactants as calcium soap dispersants. At the same time, the ecological characteristics of amphoteric surfactants, such as biodegradability and fish toxicity, are also introduced in detail.
Key words: amphoteric surfactant; Rheological properties; Dispersion of calcium soap; Ecological nature
China Library ClassificationNo.: TQ423.3 Document ID: A DocumentNo.:1001-1803 (2000) 06-0047-04.
1 rheology
The viscosity of surfactant solution increases with the increase of surfactant concentration, but sometimes when the concentration increases further, the viscosity of solution will decrease. The relationship between surfactant concentration and surfactant cluster shape has been described in the second lecture. At low concentration, the surfactant solution has spherical micelles, and its rheology is basically similar to Newtonian fluid, so its viscosity is very low. With the increase of surfactant concentration, when spherical micelles transition to modified spherical micelles, especially rod micelles, the viscosity increases sharply. It is expected that this is because the overlapping of non-spherical micelles reduces the free fluidity of the system. At this time, the solution shows the rheological characteristics of non-Newtonian fluid, or has thixotropy or reverse rheology. When the concentration of the system is further increased, the micelle will be deformed into hexagonal rod micelle, which is generally called entering the mesophase (M phase). At this time, due to the orderly arrangement of micelles, it is not easy to slip between micelles, so the viscosity of the system is further increased and the rheology is very strong. When the solution concentration is very high, it will enter the layered phase (G phase) and transition to the layered micelle. Because the sliding surface of each layer of micelle in layered micelle moves relatively freely, the viscosity is lower than that of M phase. Of course, the rheological properties of solutions with different concentrations and different micelle shapes are different with different surfactants.
Because amphoteric surfactants have positive and negative charge centers, their critical micelle concentration is lower than that of the corresponding anionic or cationic surfactants. When the concentration reaches a certain level (generally about 30%), it is easy to form a viscous liquid with poor rheology. By adding the third component to it to change its micelle structure, it is possible to improve the rheological properties of amphoteric surfactants and make it possible to obtain a higher concentration of amphoteric surfactant solution. For example, an amphoteric concentrated solution with good rheology contains 5% ~ 40% water, 36% ~ 70% amphoteric surfactant and 5% ~ 45% water-soluble non-surfactant organic solvent, which can be used for personal care products. Due to the addition of non-surfactant organic solvent, amphoteric surfactant enters G phase or L 1 phase, so it has good pumpability and free fluidity.
When 40.2% cocoamidopropyl betaine is mixed with 60/40 propylene glycol/water, the system can be in G phase. Adding sulfobetaine amphoteric surfactant, amphoteric glycinate and trimethylglycine to betaine amphoteric surfactant with concentration ≥40% can also improve rheological properties and obtain liquid with good fluidity and storage stability. ChevalierY Y studied the relationship between molecular structure of amphoteric surfactants and micelle structure and rheology. It is reported that the layered phase of a new type of double long-chain amphoteric surfactant in aqueous solution can instantly form vesicle dispersion by simple dilution.
2. Water solubility
Hydroponics is a substance that can prevent the formation of liquid crystal phase and inhibit the formation of micelle phase. Hydroponics is often used to maintain the fluid state of surfactant solution at low temperature, improve the cloud point of polyoxyethylene nonionic surfactants, and reduce the critical solution temperature of ionic surfactants, that is, KP temperature. The hydrotropic property of coconut oil imino dipropionate sodium is attributed to the existence of two ionic groups in the molecule, which makes the molecule hydrophilic. The surfactant hydrotrope destroys the liquid crystal phase by forming mixed micelles with the main surfactant, and its strong hydrophilic head improves the hydrophilic repulsion between the mixed molecules of the surfactant, so that the liquid crystal is transformed into spherical micelles. Amphoteric surfactant is a hydrotrope of soap, so it can improve water solubility. Due to the synergistic effect of soap and amphoteric surfactant on KP temperature, the KP temperature of the mixed system can reach a low value that can not be achieved when the two components exist alone. The mixed system of hexadecanoic acid soap and hexadecyl hydroxysulfopropyl betaine (CHSB) shown in Figure 1 has a positive KP temperature synergistic effect, and the lowest KP temperature of this system is 30℃, which is much lower than that of sodium hexadecanoate soap (58℃) and CHSB (89℃). Even when the molar fraction of CHSB is 10%, the KP temperature of the mixed system is much lower.
[ 1]
Figure 1 km cooperation
3 calcium soap dispersity
Some anionic and amphoteric surfactants can prevent soap from forming soap scale suspension in hard water. Substances with this function are called calcium soap dispersants. The dispersion value of calcium soap of some amphoteric surfactants is the lowest value that can be achieved at present, and the dispersion value of calcium soap is less than 2%, which is even difficult to measure. Alkyl betaine has certain calcium soap dispersibility in hard water, but sulfobetaine has better calcium soap dispersibility, for example, amidopropyl sulfobetaine has a calcium soap dispersibility as low as 2%. Parris [2 ~ 5] reported the calcium soap dispersion values of many sulfobetaines, aminosulfobetaines and sulfated betaines, and pointed out that sulfated betaines and aminosulfobetaines have better calcium soap dispersion than sulfobetaines. Diaminobetaine has a strong ability to reduce surface tension, and its calcium soap has good dispersibility. Hydroxysulfobetaine with polyoxyethylene group in amide nitrogen was synthesized in Fang Yun.
：
[6]
As can be seen from Table 2, the calcium soap dispersibility of betaine phosphate is stronger than that of sulfobetaine.
Soap has two main disadvantages: low solubility at low temperature and poor hard water resistance. As mentioned above, ionic or amphoteric surfactants as hydrotropes can reduce their KP temperature and improve their low-temperature water solubility. In addition, some kinds of anionic and amphoteric surfactants can also prevent soap from forming soap scale suspension in hard water.
The earliest dispersion mechanism of calcium soap is that calcium soap dispersant is only a simple dispersion effect on calcium soap, but this mechanism is difficult to explain the experimental fact that calcium soap dispersant has different dispersion effects at different adding times. Later, it was suggested that the dispersion mechanism of calcium soap was that calcium soap dispersant was inserted into soap micelle to form mixed micelle. Typical soap micelles are formed in soft water. Once calcium and magnesium ions are added, the soap micelle will reverse, resulting in precipitation or suspension of calcium soap.
When p= 1 or 2, the dispersibility of calcium soap is 2%, and that of its counterpart without polyoxyethylene is 3%.
Zhu Shuiping [7] reported hydroxyl sulfobetaine with polyoxyethylene chain in hydrophobic group. However, if the calcium soap dispersant exists and forms mixed micelles with soaps, the carboxyl groups of soaps are separated from each other by the calcium soap dispersant, which is not enough to form insoluble calcium-magnesium soaps and make the micelles reverse.
Considering the mixed micelle mechanism of calcium soap dispersion and the possible synergistic or compound effect of mixed micelle, it can explain why amphoteric surfactant is better than anionic or nonionic surfactant as calcium soap dispersant. From the third lecture (see Daily Chemicals, No.5, 2000), the intermolecular interactions of the mixed system are listed in Table 2.
Its calcium soap dispersion is 3%. The number of carbon atoms in the hydrophobic chain is 18, but
The dispersity of calcium soap of analogues without -O- bond is 5%. [8] Zhu Zhi reported by Qin Dynasty
The dispersion of betaine calcium soap is shown in table 1. He reports from Yuan Jun [9]
The calcium soap dispersion of betaine phosphate is shown in Table 2.
. As can be seen from the value of parameter b, b
No 6, June 5438+February 2000
Fang Yun et al.: Amphoteric surfactants (IV) General properties of amphoteric surfactants.
Obviously, the mixed system of anionic and amphoteric surfactants is the strongest. The reason is that cationic groups in amphoteric surfactants can interact strongly with anionic groups in anionic surfactants. Similar to anionic-cationic surfactants, anionic groups carried in amphoteric surfactants can maintain the water solubility of the composite system after interaction. The third lecture also proves that the mixed system of anionic and amphoteric surfactants will reduce the synergistic effect of cmc or have obvious compound effect. It is because of this strong intermolecular interaction that the cmc value of the mixed micelle of soap and sulfobetaine amphoteric surfactant decreases. The decrease of critical micelle concentration means that the monomer of soap in solution decreases, that is, the probability of interaction between soap and calcium and magnesium ions decreases, so the calcium soap of amphoteric surfactant has higher dispersibility.
Table 3 lists the successful application examples of coconut oil-based sulfopropyl betaine (CoSB) amphoteric surfactant as calcium soap dispersant. When CoSB was added to the soap with the trademark "Ivory", the precipitation of calcium soap in 100mgCaCO3/L hard water was observed when the soap concentration was 0.075%. The experimental results show that a very small amount of CoSB amphoteric surfactant can effectively inhibit the precipitation of calcium soap and improve the foaming performance of soap in hard water. Similar application examples have been reported in many literatures.
Table 3 results of "ivory" soap in hard water after adding CoSB
"Ivory" soap (weight percentage)
0.0750.0750.0750.075
CoSB (weight percentage)
proportion
The result is precipitation without bubbles.
0.00 1500.003750.00750
50÷ 120÷ 1 10÷ 1
No precipitation, no precipitation in middle bubble, no precipitation in big bubble, big bubble.
Carboxybetaine lost soluble organic carbon roughly quantitatively and formed a large amount of CO2, so it was inferred that it had been completely biodegraded. Sturm test and Fisher closed bottle test show that carboxybetaine is superior to linear alkylbenzene sulfonate (LAS) which has been recognized as biodegradable. Betaine and amidopropyl betaine belong to biodegradable surfactants. The organic matter contained in this kind of products, the BOD28/DOC value reaches at least 60% in the sealed bottle experiment, and the method is improved.
In the screening test of coconut oil amide by OECD, at least 70% DOC can be removed.
In the OECD30 1D test, the BOD28 value of propyl betaine reached 93%. Fernley[ 10] used Fischer, Sturm and OECD test procedures to study the biodegradability of alkyl betaine and sulfobetaine. In the OECD test, the primary biodegradation of hydroxysulfobetaine was very rapid and thorough, with the degradation degree reaching 96% and the verification test reaching 94.8%. However, sulfobetaine can not be directly degraded in Fischer and Sturm experiments. In Sturm experiment, the CO2 produced by alkyl betaine is 81%(c14 ~15 betaine) and 9 1%(C 12 betaine) of the theoretical amount, while dodecyl sulfobetaine and hexadecyl sulfobetaine are 49% and 56% respectively. This may be due to the formation of fairly stable intermediates. In the same experiment, betaine lost 93% ~ 99% of the initial value of DOC, indicating that betaine is completely biodegradable and will not form refractory intermediates. The ratio of oxygen absorbed by betaine to theoretical oxygen is also higher than that of sulfobetaine and hydroxysulfobetaine in Fischer closed bottle experiment, which confirms the above results.
The results of BOD5/COD method prove that amphoteric imidazoline is a good biodegradable variety. The above conclusion is also confirmed by testing 20mg/L alkyl amphoteric carboxyl glycinate solution by RiverDie method, and judging its biodegradability according to the decrease of its surface activity. According to the report of Re-wo company, the biodegradability of amphoteric imidazoline is 77% as determined by DIN384 12, which belongs to biodegradable substances. Henkel's report also believes that amphoteric imidazoline biodegrades rapidly. The test method includes: according to OECD classification, BOD28/COD is at least above 60% in the closed bottle test or at least above 70% in the improved OECD screening test.
All organic components that meet the above requirements are considered to be easy to remove DOC. In terms of biodegradation.
All surfactants, including amphoteric surfactants, have similar aquatic toxicity, and the typical LC50 value (fish and Daphnia toxicity) is1mg/L ~15 mg/L. The report of acute fish poisoning is LC50, and the range is 1mg/L ~ 10mg/L (goldfish: DIN384 12T 15 method, or zebrafish: ISO7346 method). The acute toxicity LC50 of alkyl betaine (goldfish: DIN384 12T 15 or grouper: ISO7346) to fish is 10- 100 mg/L. The LC50 of amidopropyl betaine is1L by the same method. The LC50(96h, OECD203) of cocoamidobetaine is 2.0 mg/L. ..
The acute and chronic bacterial toxicity of amidopropyl betaine was studied. The acute toxicity EC50 (pseudomonas putida, oxygen consumption test) value was greater than.
4 Hard water resistance
The structural characteristics of zwitterionic surfactant determine that it has strong electrolyte resistance, so it also has hard water resistance. The hard water resistance of surfactants is mainly reflected in two aspects, namely, the dispersibility of calcium soap and its own tolerance to calcium and magnesium hard ions. Many betaine amphoteric surfactants show excellent stability to calcium and magnesium ions. Lin-Field's research group investigated the calcium ion stability of betaine amphoteric surfactants, and found that the calcium ion stability of most sulfobetaine amphoteric surfactants is above 1800mgCaCO3/L, which is one of the best surfactants with hard water resistance. However, the calcium ion stability value of the corresponding secondary amine compounds is much lower. Fang Yun [8] reported that after introducing polyoxyethylene group into the amide nitrogen of acyl hydroxyl sulfobetaine, its calcium ion stability can still reach more than 1800mgCaCO3/L, which proved that this kind of substance itself is insensitive to water hardness. It is reported that the calcium ion stability of C8 ~ 16 series N-(3- alkoxy -2- hydroxypropyl) betaine is also greater than 1800mgCaCO3/L, and it has good calcium soap dispersion performance.
5 Ecology
It can be inferred from the chemical structure of amphoteric surfactants that they are good biodegradable varieties. In SturmCO2 test and DOC test.
100mg/L, which is the same as the EC50(72h, OECDEC50) of the algae growth inhibition test (Ps.putida) with chronic toxicity. 20 1) is 3.3 mg/l.
Sodium tripropyltetramine pentacarboxymethyl (TN4A5) is a good amphoteric surfactant, and its ecological safety was studied. The results are shown in Tables 4 and 5. In Table 5, the samples were exposed to the biodegradation products of the coupling test (OECD303A) (see Table 4). At the beginning of the biodegradation test, the initial concentration of TN4A5 was 7 1mg/L, and the total biodegradation rate reached about 80%. The toxicity test of TN4A5 to fish showed that the EC50(48h, Daphnia) was 65438 04mg/L, and the LC50 (48h, Salmon) was 2.4mg/L. ..
Table 4 Biodegradability of TN4A5
test method
1. Closed bottle test (OECD30 1D, 5 days) 2. Improved SCAS test (OECD302A)3. Coupling unit testing (OECD303A).
mock test
& gt90.0
Primary biodegradation value determined by HPLC
Intrinsic biodegradation
80.0
Expressed as document value
Experimental characteristics of easy biodegradation
Test result (%)72.5
Evaluation of simple biodegradation
As can be seen from the data listed in Table 6, the total organic carbon (TOC) of washing powder containing about 12% surfactant is 1 16g/kg, while that of liquid detergent with a solid content of about 46% reaches 336g/kg, so high TOC value becomes a big disadvantage of liquid detergent. The recommended dosage of TN4A5 in liquid detergent is 10% ~ 15%, and the TOC value of this amphoteric surfactant-based liquid detergent is only about 107g/kg, which is of great significance for popularizing liquid detergent.
Table 6 TOC data
Washing powder liquid detergent
Total organic carbon (g/kg)
1 16
336
Amphoteric surfactant-based liquid detergent
107
References:
Fang Yun. The relationship between KP and cmc and PMAX [J]. Daily chemical industry,1991(1): 20-24.
[2] Paris. , Wei, Lin, Wang, et al. Journal of Petrochemical Technology, 2003, 1 1(2):209.
[3] Paris. Wang Xiaohua, Wang Xiaohua, et al. Journal of Petrochemical Engineering, 2003,11(2):100. [4] Paris. , Wei, Lin, Wang, et al. Journal of Petrochemical Technology, 2003, 1 1(2): 100.
Pierce parrish. Et al., Linfield W.M., Formula-Function of Soap-based Detergent [XII) [J]. J of American Chemical Society. 1977,54: 294.[6] Fang Yun. Master's degree thesis of Wuxi Institute of Light Industry: Synthesis of new sulfobetaine.
, Xia,, et al. Synthesis of novel alkoxy sulfobetaine amphoteric surfactant [J]. Daily chemical industry, 1995( 1):4-8.
Qin Sam. Master thesis of Wuxi Institute of Light Industry: Study on synthesis and properties of a new sulfur-containing amphoteric surfactant [D] .54438.098588588895
[9] He Yuan Jun. Master's degree thesis of East China University of Science and Technology: Study on a New Phosphate Betaine Amphoteric Surfactant [D] .45438.099948988895
Feinleg W. zwitterionic surfactants: structure and properties [J]. American Journal of Oil Chemistry c. 1978, 55:98.
Table 5 Fish Toxicity Test Method of TN4A5 Biodegradation Products
1. Oral toxicity (OECD202)2. Oral toxicity (OECD203)
Theme Daphniamagna
zebra fish
50% effective concentration (48h) (mg/L)
35.5 >7 1
Excellent biodegradability and low fish toxicity make TN4A5 have a good application prospect, and it can become a green chemical component in detergents and personal care products. If combined with its low TOC value, the above conclusion becomes more meaningful. In recent years, the ecological effects of washing powder and liquid detergent have been widely discussed, from
Amphoteric surfactant ⅳ
General properties of amphoteric surfactants
Fang Yun Xia Yong May
(School of Chemistry and Materials Engineering, Wuxi Institute of Light Industry, Wuxi 2 14036, China)
Abstract: The general properties of amphoteric surfactants, such as rheology, hydrophilicity, dispersion of lime milk and water resistance, are introduced. The relationship between rheological properties and concentration of surfactant is discussed, and the method of adjusting rheological properties of mixed system is put forward. Thenewpinionto explains why AmphotericSurfactantinShebestlMe Soapdispersingagentwas given from the view point of Mixed Micelle Theory.
Key words: amphoteric surfactant; Dispersion ability of rhologicalproperty lime; Environmental aspects