What is a neutral detergent in chemistry? For example, cellulose needs to be dissolved when it is measured.

Neutral detergent refers to nonionic surfactant.

definition

surfactant that does not generate ions in aqueous solution. The solubility of nonionic surfactant in water is due to the strong hydrophilic functional groups in the molecule.

the nonionic surfactant is second only to the anionic surfactant in quantity, and it is an important variety that is widely used. With the development of petroleum industry, the cost of ethylene oxide used as raw material is decreasing, and its output will continue to increase.

uses

nonionic surfactants do not ionize in water. They are amphiphilic structural molecules with hydroxyl group (OH) or ether bond () as hydrophilic groups, and the hydrophilicity of hydroxyl group and ether bond is weak. Therefore, the molecule must contain multiple such groups-to show certain hydrophilicity, which is very different from anionic and cationic surfactants that can show hydrophilicity with only one hydrophilic group. It is the non-ionic surfactant that does not ionize in water, which determines that it is superior to ionic surfactant in some aspects, such as good solubility in water and organic solvents, high stability in solution, and is not easily affected by strong electrolyte inorganic salts, acids and bases. Because it has good compatibility with other types of surfactants, it can often be mixed and used well. Non-ionic surfactants have the characteristics of good hard water resistance and low foaming, so they are suitable for special detergent. Because it has many properties, such as dispersion, emulsification, foaming, wetting and solubilization, it has been used in many fields.

classification

nonionic surfactants are classified into the following categories according to hydrophilic groups.

1. polyoxyethylene nonionic surfactant

This type of surfactant, also known as polyethylene glycol, is the product of addition reaction between ethylene oxide and compounds containing active hydrogen;

(1) The main products of alkylphenol polyoxyethylene ether (APEO) include octylphenol polyoxyethylene ether () and nonylphenol polyoxyethylene ether. As a detergent, the number of ethylene oxide added in the molecule is n = 9 ~ 12. Because hydrophilic groups are composed of hydroxyl groups and ether bonds, and there is only one hydroxyl group at the end group of the molecule, the hydrophilicity is very small. In order to make the molecule have enough hydrophilicity, it is necessary to increase the number of molecules added with ethylene oxide, that is, the more ether bonds are contained, the better the hydrophilicity is. Therefore, the hydrophilicity can be adjusted by combining different numbers of ethylene oxide molecules. Generally, the ethylene oxide addition products obtained are all mixtures with different molecular numbers (n), usually n is an average value.

HLB value of nonylphenol polyoxyethylene ether addition ethylene oxide, the greater the HLB value, the better the hydrophilicity.

For polyethylene glycol nonionic surfactant, a prominent property is cloud point, which is determined by its structural characteristics. In the anhydrous state, the polyoxyethylene chain in the polyethylene glycol nonionic surfactant is zigzag, and the oxygen atom on the ether bond forms a weak hydrogen bond with the hydrogen atom in the water after being dissolved in water, and the molecular chain is zigzag, and the hydrophilic oxygen atom is located at the outside of the chain, while the ethylidene (-—CH2CH2—-) is located at the inside of the chain, so the chain is like a hydrophilic whole.

The reaction of forming hydrogen bonds is exothermic, and the bonding force of hydrogen bonds is weak. Therefore, when the temperature rises, the hydrophilic property of polyoxyethylene nonionic surfactant aqueous solution is weakened due to the destruction of the bonded hydrogen bonds, so it changes from the original transparent solution to a white turbid emulsion. This change is reversible, and the solution becomes transparent again when the temperature decreases. When the transparent aqueous solution of polyoxyethylene nonionic surfactant is slowly heated, the temperature at which the solution begins to appear white and turbid is called its "cloud point". The cloud point reflects the hydrophilicity of nonionic surfactants, and the greater the hydrophilicity, the higher the cloud point. In order to ensure that nonionic surfactants are in a good state of dissolution, the cloud point should generally be controlled below its cloud point, and the HLB value and usability are related to the number (n) of ethylene oxide molecules added to nonionic surfactants. For example, the reaction adduct of nonylphenol and ethylene oxide with n=9, when its mass fraction is .2% ~ 1%, has a cloud point of 53℃ and an HLB value of 12. This product has good penetrability, detergency and strong emulsifying power, so it is widely used and is the main component of detergent. When the addition number of ethylene oxide reaches 12, the HLB value rises to 14 and the cloud point rises to 7℃. Although the detergency of this product is improved, its permeability is slightly poor. When the added ethylene oxide n >: At 15℃, the cloud point exceeds 1℃, and the permeability and detergency are very poor, so it can only be used as a special purpose emulsion dispersant. Therefore, the addition number of ethylene oxide should be controlled according to the actual needs.

after hydration (combined with water relaxation), nonionic surfactant becomes zigzag polyoxyethylene chain (in the state of aqueous solution)

When inorganic salt or anionic surfactant is added and compounded with nonionic surfactant, its cloud point will be affected. The existence of inorganic salts is not conducive to the formation of hydrogen bonds between polyoxyethylene chains and water in nonionic surfactants, which leads to dehydration, so it will reduce the solubility and cloud point I of nonionic surfactants in water. When anionic surfactants are added to compound them, the cloud point of nonionic surfactants will rise due to synergistic effect, which will expand its application temperature range. These should be paid attention to in practical application.

cloud point determination method: Weigh 1g of sample, dissolve it to make 1% aqueous solution, pour it into a large test tube (diameter 26mm, height 2mm) so that the liquid level in the tube is SOmm, then slowly heat the large test tube in a glycerin bath, carefully observe the change of transparency, and stir it up and down with a stirrer while heating. When the test solution becomes turbid, the thermometer reading in the tube at this time is the cloud point. Then take out the big test tube and cool it down, and write down the temperature when it returns to transparency for comparison. If the cloud point is higher than 1℃, it can be measured in a closed tube, and if the cloud point is very low, it can be measured in butyl diethylene glycol or ethanol solution. For products with extremely low cloud point, the turbidity drop value can be determined, that is, 1g surfactant solution is about 1mL propanol, and distilled water is slowly dropped at (3 soil 1)℃ until turbidity appears.

The commercial products of alkylphenol polyoxyethylene ether used in industry mainly include OP series and TX series products. For example, OP-1 is a kind of diffusion, leveling and emulsifying wetting agent commonly used in textile industry. The molecular structure of TX-1 belongs to octylphenol polyoxyethylene ether. The number after TX varies with the addition number of ethylene oxide and alkyl. Because the addition number of ethylene oxide can be adjusted according to the process conditions when synthesizing these compounds. With the increase of the addition number of ethylene oxide in the molecule, the surfactant gradually changes from lipophilic to hydrophilic, and with the change of HLB value, it can be made into emulsifier, wetting agent, detergent, solubilizing agent and other varieties with different uses. The product obtained by adding 9 ethylene oxide molecules to alkylphenol with 8 ~ 12 carbon atoms in alkyl carbon chain has good washing performance and is a commonly used detergent product.

(2) High-carbon fatty alcohol polyoxyethylene ether (AEO) The alkylphenol polyoxyethylene ether introduced above is a widely used non-ionic surface activity cloud point measuring agent in Figure 7-13. However, due to its poor biodegradability, it has a tendency to reduce its use, and mainly uses carbon fatty alcohol polyoxyethylene ether with good biodegradability.

the water solubility of high-carbon fatty alcohol polyoxyethylene ether is greatly influenced by the number of carbon atoms in the alcohol structure and the number of added ethylene oxide molecules. The commonly used fatty alcohols contain between 12 and 18 carbon atoms. If the number of carbon atoms of saturated ten-membered alcohols is three more than the number of ethylene oxide molecules added, they are generally soluble at room temperature. For example, the products of lauryl alcohol (dodecyl alcohol) adding nine ethylene oxide molecules, and the products of cetyl alcohol (cetyl alcohol) adding 13 ethylene oxide molecules are all very water-soluble at room temperature, but the products of cetyl alcohol adding 11 ethylene oxide molecules are poor in water-solubility.

However, the high-carbon unsaturated alcohol containing 18 carbon atoms, octadecenol-9-enol (oleyl alcohol) is influenced by unsaturated groups, and the product added with 12 ethylene oxides has good water solubility and good cleaning ability, while its 15-2 ethylene oxide adducts have poor detergency and permeability, but it is suitable for use as emulsifier, dispersant and detergent used with alkali.

Because the high-carbon fatty alcohol polyoxyethylene ether has good washing and decontamination ability at the temperature below its cloud point, the detergent made from I can meet the requirements of low temperature, low foam and hard water resistance.

the most important feature of AEO products is their chemical stability, which is stable in hot dilute alkali, acid and oxidant. The commercial names of these products used in industry are peregal O (C18H35o (CH2 H2O) 15h), leveler O (C12H25 (CH2 C2) 22h), penetrant JFC (C7 ~ 9H15 ~ 19O (CH2 C2) 5h) and so on. The products with fatty alcohol alkyl chain containing 12 ~ 14 carbon atoms plus about 1 ethylene oxide have the best detergency and are commonly used detergent ingredients.

(3) Fatty acid polyoxyethylene ester (AE) Fatty acid can be added with ethylene oxide under the action of catalyst to form polyoxyethylene nonionic surfactant whose hydrophilic group and hydrophobic group are connected by ester bond. However, unlike the above two kinds of nonionic surfactants bonded by ether bonds, these compounds will be hydrolyzed into soap when used in strong alkali solution because ether bonds are easy to hydrolyze. Compared with the ethylene oxide adducts of higher alcohols or alkyl phenols, these compounds are generally poor in permeability and detergency, so they are not suitable for detergents, mainly used as emulsifiers, dispersants, dyeing auxiliaries and so on. This kind of compound used in industry, such as softener

(4) polyoxyethylene amine, is the reaction product of the addition of higher fatty amine and ethylene oxide. The higher aliphatic amine used may be primary amine, secondary amine or tertiary amine.

For example, the process of the addition reaction between coconut amine, soybean oil amine, tallow amine, stearylamine and ethylene oxide is as follows:

The polyoxyethylene fatty amine with low addition number is cationic, insoluble in water under neutral and alkaline conditions, and reacts with H+ under acidic conditions with low pH value to form water-soluble amine ions, which enhances the surface activity, and is a good surfactant. This kind of surfactant has the characteristics of acid and alkali resistance and bactericidal power. The polyoxyethylene fatty amine with high addition number has nonionic characteristics and is soluble in water under neutral and alkaline conditions. With the increase of ethylene oxide chain length, the wetting ability also increases, which can be used as nonionic surfactant. Because the incompatibility with anionic surfactants is weakened, they can be mixed with each other.

(5) polyoxyethylene amide is generally the product of the addition of fatty amide and ethylene oxide under alkaline conditions. Because one or two active hydrogens on the amide group can be added with ethylene oxide, several products with different structures can be obtained, such as: < P > a new type of polyoxyethylene nonionic surfactant developed. According to the different structure and addition number of ethylene oxide, it can be used as detergent, L-seeking agent, wetting agent, demulsifier, antistatic agent, lubricant and dispersant, etc., and has a wide range of applications.

In addition, oils and fats such as castor oil containing hydroxyl groups can also be added with ethylene oxide to form polyoxyethylene nonionic surfactants.

(6) Ethylene oxide adduct of polypropylene glycol (polyether nonionic surfactant), which is polypropylene glycol produced by addition polymerization of propylene oxide, is a compound with a relative molecular mass of 1,-2,5. Due to the space barrier of methyl in the molecule, its water solubility is very small, so it is suitable as an oleophilic raw material for surfactants. When polypropylene glycol is added with ethylene oxide or polymerized with ethylene oxide and propylene oxide, a polymer surfactant with polyoxyethylene and polyoxypropylene embedded in it is formed. These products are called polyether nonionic surfactants, and the general formula is RO(C3H6)m(C2H4O)nH.

The lipophilicity (hydrophobicity) and hydrophilicity of this surfactant can be controlled by adjusting the ratio of polyoxyethylene to polyoxypropylene. Various surfactants with different properties were obtained by different proportions and different polymerization methods. Polyether nonionic surfactant has the ability to reduce interfacial tension at very low concentration, and can be used as emulsifier of W/O and O/W emulsions, dispersing calcium soap in hard water and having good solubilization effect, and some can be used as defoamer and foam inhibitor.

Polyether nonionic surfactant is odorless, non-toxic and non-irritating, and has good stability to chemical reagents. It is a new type of nonionic surfactant.

(7) The hydroxyl group on the molecular terminal group of polyoxyethylene ionic surfactant fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether can be esterified with sulfuric acid or phosphoric acid, so it can be made into nonionic-anionic mixed surfactants such as alcohol ether sulfate or alcohol ether phosphate;

alcohol ether sulfate (AES) hAS better water solubility than sulfate anionic surfactant (as) at room temperature, and unlike fatty alcohol polyoxyethylene ether (AE), whose cloud point will precipitate out of water at high temperature, it is an excellent surfactant with good solubility in water, good dispersibility in calcium soap, good foaming ability, hard water resistance and inorganic salt resistance.

The cleaning and decontamination ability of alcohol ether phosphate is obviously improved compared with phosphate anionic surfactant, and it has the characteristics of high cleaning ability, low foaming, alkali resistance, hard water and electrolyte resistance and high temperature resistance. Sulfonation and neutralization of fatty alcohol polyoxyethylene ether can obtain alcohol ether sulfonate nonionic-anionic mixed surfactant,

so2cl2na2so3

r (och2ch2) noh —— >: R(CH2CH2)nC1————> R (och2ch2) nsona

8 ~ 86℃ 155℃, 1MPa

products have good stability to acids, bases and inorganic salts.

A nonionic-cationic mixed surfactant can be obtained by quaternization of ethylene oxide adduct of higher fatty amine. For example, this product has the characteristics of cationic and nonionic surfactants and can be used as antistatic agent, emulsifier, dispersant, etc.

2. Polyol type

Polyol type nonionic surfactant is composed of ethylene glycol, glycerol pentaerythritol, sorbitan and sucrose.