Background and overview[1][2]
Propylene glycol ether compounds mainly include propylene glycol methyl ether (PM), propylene glycol ethyl ether (PE) and propylene glycol butyl ether PB). Ethylene glycol ether and propylene glycol ether are important fine chemical products in coatings, inks, leather, It has a wide range of uses in dyes, cleaning agents and other industries. Since ethylene glycol ether is toxic to the human body, and propylene glycol ether is a non-toxic product, propylene glycol ether is gradually replacing ethylene glycol ether products. The production of propylene glycol ether mostly uses an ether solution of boron trifluoride (BF3) as a catalyst, and uses propylene oxide and alcohol (such as methane, ethanol, butanol) as raw materials to react in a reactor. The solution after the reaction is then introduced into the distillation Fractionation is carried out in the equipment to obtain the product. This process is relatively old and has a long process flow.
Application[1, 3]
In view of the low toxicity of propylene glycol ether compounds and their excellent solvent properties, their research and development applications are becoming increasingly widespread. The main applications are as follows.
1. Detergent:
The detergent must be able to wet and penetrate dust, lifting it away from the surface being cleaned so that it can be wiped or washed away; it must also be able to remove water-insoluble grease. The hydroxyl group of propylene glycol ether, including propylene glycol ether, can act on water-soluble dust, and the ether group can dissolve grease and water-insoluble dust, so it is widely used as a household and industrial detergent. Such as glass cleaner, carpet cleaner, liquid soap, metal cleaner, paint and ink cleaner, stove cleaner, tire cleaner, etc.
2. Solvent:
Propylene glycol ethers, including propylene glycol ether, are excellent industrial solvents and are widely used in coatings, dyes, printing, inks, hydraulic oils, antifreezes, lubricants and other fields.
1) Ink and dye solvent: Propylene glycol ether can dissolve resins used in coatings. It is also an excellent solvent for dyes and inks due to its unique solubility and high penetration, low evaporation rate and low surface tension.
2) Silane coupling agent and solvent for dyes in printing ointments for textiles: Many printing ointments use cellulose derivatives of alkyd resin as the main body, and propylene glycol ether is used in the formula to control the evaporation rate and help penetration And dyeing evenly, increase the solubility of textile dyes and increase the color.
3) Leather dyeing solvent: The formula for leather dyeing is composed of dye or pigment, carrier (casein or nitrocellulose) and a solvent. The leather is first treated with a carrier, which serves as a base for color retention. If the dyeing is based on casein, the dyed leather will have a nitrocellulose coating as the final protective layer. The application of propylene glycol ether will help with color leveling, penetration and control of evaporation rate.
4) Printing and writing inks: Propylene glycol ether is added to printing and writing inks to increase penetration. Propylene glycol ether has a slow evaporation rate, which can make the dye evenly distributed in the printed letters and prevent dried ink from accumulating on the printing mold. on board. Propylene glycol ether can also be used in ballpoint pen refill oil to allow the resins, pigments, dyes, etc. in the refill oil to flow freely without clogging or drying up. If there is research and development of a solvent for bismuth oxide-based ink for glass digital inkjet printing, its composition and mass percentage are: main solvent 65~85%, dispersant 8~22%, surfactant 6~11%, Light stabilizer 0.1~2%, the sum of each component is 100%.
The main solvent is 1-(2-methoxy-1-methylethoxy)isopropanol, 1-ethoxy-2-propanol, 1-methoxy-2-propanol, One or any mixture of cyclohexanone; the dispersant is diethylene glycol butyl ether; the surfactant is 1,2-propylene glycol diacetate; the light stabilizer is HS-508. The solvent of the above-mentioned bismuth oxide-based ink for glass digital inkjet printing has a surface tension of 28~32mN/m, good dispersion of bismuth oxide-based inorganic powder colorants, fast volatilization speed, and good inkjet printing performance. Its preparation The method is simple and efficient, has good controllability, is suitable for industrial large-scale production, has low cost, and has broad application prospects in the field of glass digital inkjet printing.
5) Cosmetics: Propylene glycol methyl ether and dipropylene glycol methyl ether are used in the formulation of cosmetics to prevent one of the components from precipitating from the formula and maintain the transparency of cosmetics at low temperatures. Propylene glycol methyl ether can also be used as a solvent for colorless nail polish or as a nail polish remover.
6) Agricultural chemical solvents: Agricultural pesticides are generally insoluble in water and require the addition of surfactants. Propylene glycol ether has some of the same properties as surfactants. It has a synergistic effect on surfactants and helps Dissolve pesticides and combine with water. Surfactants and pesticides are often solids. Adding propylene glycol methyl ether or dipropylene glycol methyl ether can make them liquid and easy to dilute with water. Mixing propylene glycol ether with pesticides can reduce the volatility of the product and reduce the volatilization loss of pesticides. In addition, propylene glycol ether can also be used as an adhesive tape remover, paint, paint, silicone coating and ink remover.
3. Organic synthesis intermediates and raw materials
Propylene glycol ether is an important raw material for the synthesis of organic intermediates and fine chemical products. Its main applications are as follows:
1) Aldol condensation reaction: Propylene glycol ethers all have hydroxyl groups and are prone to condensation reactions with aldehydes under acidic conditions:
2) Nitrilation reaction: The active hydrogen of the hydroxyl group in propylene glycol ethers can undergo the “Michael Reaction”.
3) Reaction with propylene oxide: Propylene glycol ethers can further react with ethylene oxide or propylene oxide to obtain more complex propylene glycol ethers.
4) Esterification reaction: The esterification of propylene glycol ether can obtain a new series of products that are more useful than propylene glycol ether itself, namely propylene glycol ether lower fatty acid esters, such as acetate and propionate. They are valuable solvents, particularly useful in the coatings industry. Substituting the hydroxyl group of propylene glycol ether with an ester group improves compatibility with cellulose acetate and nitrocellulose. Stearate, phthalate and adipate are representative plasticizers with a wide range of uses. They have low volatility and are related to synthetic rubber fiber ethers, fiber esters and polyolefin resins. High degree of compatibility. Carboxylate derivatives of propylene glycol ethers can be prepared by reacting carboxylic acids with propylene glycol ethers in the presence of strong acids.
Preparation [1]
The synthesis routes of propylene glycol ether include Williamson synthesis method, acetal method, alkoxypropylene oxide method, propylene oxide method, etc. Among them, the first three methods have not been industrialized due to complex processes or high costs. The propylene oxide method is currently the most actively developed and developed, and the only synthesis route that has achieved industrialization.
1. Williamson synthesis
For formula (1-7), the main product structure is single, and the generated Na Cl entrains raw materials and products, resulting in large losses. For (1-8), in addition to the main product (I), a considerable amount of isomeric product (II) is also generated, which is undesirable, and there is also the problem of entrained materials. In addition to the above-mentioned problems of the Williamson synthesis method, there are also many problems in industrialization, such as multiple processing procedures, equipment, operators, long production cycle, and low production efficiency.
Stearic acid 1801
2. Acetal route
The catalyst is Co(CO)8-Rh(CHAc2)3 or (Co2(CO)8-Ph3Ge H. This method requires CO and H2, and the catalyst is also very expensive and requires high temperature and high pressure, making industrial production difficult. Realized.
3. Ethoxypropylene oxide route
The disadvantages of this method are that the raw materials are expensive, the yield is low, it is not suitable for industrial production, and it is difficult to operate.
4. Propylene oxide route
Preparation [1]
The synthesis routes of propylene glycol ether include Williamson synthesis method, acetal method, alkoxypropylene oxide method, propylene oxide method, etc. Among them, the first three methods have not been industrialized due to complex processes or high costs. The propylene oxide method is currently the most actively developed and developed, and the only synthesis route that has achieved industrialization.
1. Williamson synthesis
For formula (1-7), the main product structure is single, and the generated Na Cl entrains raw materials and products, resulting in large losses. For (1-8), in addition to the main product (I), a considerable amount of isomeric product (II) is also generated, which is undesirable, and there is also the problem of entrained materials. In addition to the above-mentioned problems of the Williamson synthesis method, there are also many problems in industrialization, such as multiple processing procedures, equipment, operators, long production cycle, and low production efficiency.
Stearic acid 1801
2. Acetal route
The catalyst is Co(CO)8-Rh(CHAc2)3 or (Co2(CO)8-Ph3Ge H. This method requires CO and H2, and the catalyst is also very expensive and requires high temperature and high pressure, making industrial production difficult. Realized.
3. Ethoxypropylene oxide route
The disadvantages of this method are that the raw materials are expensive, the yield is low, it is not suitable for industrial production, and it is difficult to operate.
4. Propylene oxide route
This method is a method of synthesizing propylene glycol ether using propylene oxide and ethanol as raw materials. It has high atom utilization and low operating risk. It is a widely used synthesis method and the only industrialized method in the world.
Main reference materials
[1] Yu Yanru. Hydrotalcite-like catalytic synthesis of propylene glycol ether [D]. Tianjin University, 2008.
[2] CN92110430.8 A production method of propylene glycol ether
[3] CN201510551801.1 A solvent for bismuth oxide-based ink for glass digital inkjet printing
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This method is a method of synthesizing propylene glycol ether using propylene oxide and ethanol as raw materials. It has high atom utilization and low operating risk. It is a widely used synthesis method and the only industrialized method in the world.
Main reference materials
[1] Yu Yanru. Hydrotalcite-like catalytic synthesis of propylene glycol ether [D]. Tianjin University, 2008.
[2] CN92110430.8 A production method of propylene glycol ether
[3] CN201510551801.1 A solvent for bismuth oxide-based ink for glass digital inkjet printing
