Disclosure of Invention
The invention aims to provide a method for preparing 2- (2 '-hydroxy 5' -methoxyphenyl) benzotriazole, which has high absorption rate and high barrier rate and is difficult to leach out.
The technical scheme of the invention is as follows:
a method of making 2- (2 '-hydroxy 5' -methoxyphenyl) benzotriazole comprising the steps of:
a. reacting o-nitroaniline with alkali metal nitrite under the conditions of inorganic strong acid and low temperature to synthesize diazonium salt;
b. under the alkaline condition, p-methoxyphenol is dissolved in an aliphatic solvent and coupled with diazonium salt under the low-temperature condition to obtain an azo compound;
c. the azo compound is used for producing a semi-reduction product under the action of a reducing agent under the alkaline condition;
d. the semi-reduction product is put in organic solvent and under the action of metal reducing agent, so that the product is obtained.
The strong inorganic acid used is hydrochloric acid or sulfuric acid.
The reaction temperature in the a.b step is controlled below 5 ℃.
The alkali metal nitrite used includes sodium nitrite or potassium nitrite.
The alkaline conditions described are the addition of an amount of NaOH, KOH or Ca (OH) to the solvent2And (4) forming.
Aliphatic solvents mentioned include cyclohexane, octane, petroleum ether.
Reducing agents described include inorganic salts: na (Na)2S、NaHS、NH4HS、(NH4)2S and their mixture, the aldehydes include formaldehyde, acetaldehyde, paraformaldehyde, paraldehyde, reducing sugar, and hydrazine.
Metallic reducing agents are described as Zn, Sn, Al, Fe and mixtures thereof.
The organic solvents mentioned are xylene, toluene, benzene.
The molar ratio of the o-nitroaniline to the p-methoxyphenol is 1: 1; the mass ratio of the alkali metal nitrite to the o-nitroaniline is 5-6: 10.
the invention has the beneficial effects that:
1. therefore, the invention discloses a 2- (2 '-hydroxy 5' -methoxyphenyl) benzotriazole ultraviolet absorbent, which can effectively absorb ultraviolet light of 260-400nm and has higher barrier rate (barrier rate 90.1%) compared with other ultraviolet absorbents. The light stabilizer is widely applied to plastics, synthetic rubber, dyes, fibers and the like, and is a high-efficiency light stabilizer.
2. The ultraviolet absorbent has high ultraviolet absorptivity and high blocking rate, is not easy to leach, and has good effect.
Detailed Description
A process for the manufacture of 2- (2 '-hydroxy 5' -methoxyphenyl) benzotriazole, comprising the steps of:
a. reacting o-nitroaniline with alkali metal nitrite under the conditions of inorganic strong acid and low temperature to synthesize diazonium salt;
b. under the alkaline condition, p-methoxyphenol is dissolved in an aliphatic solvent and coupled with diazonium salt under the low-temperature condition to obtain an azo compound;
c. the azo compound is used for producing a semi-reduction product under the action of a reducing agent under the alkaline condition;
d. the semi-reduction product is put in organic solvent and under the action of metal reducing agent, so that the product is obtained.
The strong inorganic acid used is hydrochloric acid or sulfuric acid. The reaction temperature in the a.b step was controlled to 5 ℃ or lower. The alkali metal nitrite used includes sodium nitrite or potassium nitrite. The alkaline conditions described are the addition of an amount of NaOH, KOH or Ca (OH) to the solvent2And (4) forming. Aliphatic solvents mentioned include cyclohexane, octane, petroleum ether. Reducing agents described include inorganic salts: na (Na)2S、NaHS、NH4HS、(NH4)2S and their mixture, the aldehydes include formaldehyde, acetaldehyde, paraformaldehyde, paraldehyde, reducing sugar, and hydrazine. Metallic reducing agents are described as Zn, Sn, Al, Fe and mixtures thereof. The organic solvents mentioned are xylene, toluene, benzene.
Examples
1. a, preparing diazonium salt: adding 10g of o-nitroaniline, 30g of deionized water and 28ml of hydrochloric acid (33%) into a 100ml three-necked bottle provided with a stirrer and a thermometer, stirring, heating to 45 ℃, keeping the temperature for 1 hour, cooling to 0 ℃, adding 5.5g of sodium nitrite, keeping the temperature and stirring for 3 hours to obtain diazonium salt for later use.
b preparation of azo Compound: 100ml of cyclohexane and 10g of p-methoxyphenol were added to a 500ml three-necked flask equipped with a stirrer and a thermometer, and after dissolution by stirring at room temperature, NaOH6g was added, stirring was continued for 1 hour, the temperature was lowered to 0 ℃ and the diazonium salt to be used was added to the three-necked flask within 0.5 hour. 21g of a red azo compound was obtained.
c, half reduction reaction: into a 1000ml three-necked flask equipped with a stirrer and a thermometer were charged the above azo compound, Ca (OH)28g,NH4HS16g, and deionized water 280 ml. Stirring, heating to 50 deg.C, reacting for 1 hr to obtain yellow semi-reduced product 19 g.
d, reduction reaction: 20g of half-reduced product, 280ml of benzene and 10g of Fe powder are respectively added into a 500ml three-necked bottle provided with a stirrer and a thermometer, stirred and heated to 60 ℃, and reacted for 1 hour to obtain 15g of white product with the content of 99.3 percent.
2. a, preparing diazonium salt: adding 10g of o-nitroaniline, 30g of deionized water and 6ml of sulfuric acid (93%) into a 100ml three-necked bottle provided with a stirrer and a thermometer, stirring, heating to 45 ℃, keeping the temperature for 1 hour, cooling to 0 ℃, adding 5g of potassium nitrite, keeping the temperature and stirring for 3 hours to obtain diazonium salt for later use.
b preparation of azo Compound: in a 500ml three-necked flask equipped with a stirrer and a thermometer, 100ml of cyclohexane and 10g of p-methoxyphenol were charged, and after dissolving the mixture by stirring at room temperature, Ca (OH) was added26g, stirring is continued for 1 hour, the temperature is reduced to 0 ℃, and the diazonium salt for standby is added into a three-necked bottle within 0.5 hour. 22.4g of a red azo compound was obtained.
c, half reduction reaction: into a 1000ml three-necked flask equipped with a stirrer and a thermometer were charged the above azo compound, Ca (OH)28g, 10g of paraformaldehyde and 270ml of deionized water. Stirring, heating to 50 deg.C, reacting for 1 hr to obtain yellow semi-reduced product 20.8 g.
d, reduction reaction: 21g of semi-reduction product, 300ml of benzene, 8g of Sn powder and 1.5g of hydrazine are respectively added into a 500ml three-necked bottle provided with a stirrer and a thermometer, and the mixture is stirred and heated to 60 ℃ to react for 1 hour to obtain 17g of white product with the content of 98.9 percent.
3. a, preparing diazonium salt: adding 10g of o-nitroaniline, 30g of deionized water and 6ml of hydrochloric acid (93%) into a 100ml three-necked bottle provided with a stirrer and a thermometer, stirring, heating to 45 ℃, keeping the temperature for 1 hour, cooling to 0 ℃, adding 6g of sodium nitrite, keeping the temperature and stirring for 3 hours to obtain diazonium salt for later use.
b preparation of azo Compound: 50ml of cyclohexane, 30ml of petroleum ether and 10g of p-methoxyphenol are added into a 500ml three-necked flask equipped with a stirrer and a thermometer, after stirring and dissolving at room temperature, 6g of KOH is added, stirring is continued for 1 hour, the temperature is reduced to 0 ℃, and the diazonium salt for standby is added into the three-necked flask within 0.5 hour. 23.4g of a red azo compound was obtained.
c, half reduction reaction: into a 1000ml three-necked flask equipped with a stirrer and a thermometer, the above azo compound, Ca (OH)28g of hydrazine, 18g of hydrazine,280ml of deionized water. Stirring, heating to 50 deg.C, reacting for 1 hr to obtain 21.6g of yellow semi-reduced product.
d, reduction reaction: 20g of half-reduced product, 300ml of benzene, 5.5g of Sn powder and 1.5g of Zn powder are respectively added into a 500ml three-necked bottle provided with a stirrer and a thermometer, and the mixture is stirred and heated to 60 ℃ to react for 1 hour to obtain 16.5g of white product with the content of 99.2 percent.
The absorption principle of benzotriazole ultraviolet absorber
The benzotriazole ultraviolet absorbent can selectively absorb ultraviolet with the wavelength of 290-400nm, and a hydrogen atom on an ortho-hydroxyl and a nitrogen atom on benzotriazole generate a resonance effect. Researches show that the benzotriazole ultraviolet absorbers exist in a phenolic structure, and the light resistance of the benzotriazole ultraviolet absorbers is because the benzotriazole ultraviolet absorbers can perform reversible tautomeric conversion through hydrogen bond chelating rings in molecules, and after ultraviolet light is absorbed, protons can be rapidly transferred to nitrogen atoms to form tautomers, so that excitation energy is effectively converted, and redundant energy is rapidly converted into heat energy to be released, so that the absorbed energy is consumed, and the ultraviolet absorbers return to the ground state. Thus, the ultraviolet energy is converted into heat to be discharged, and the damage of the ultraviolet to the plastic products is avoided.
The synthesis process of the invention is divided into three steps: firstly, synthesizing diazonium salt; secondly, synthesizing an azo compound; and thirdly, reducing the azo compound. Other benzotriazole reductions require two steps (semi-reduction, reduction), thus reducing the synthesis steps.
The absorption intensity peak is 200nm-52nm, the absorption intensity is above 75%, the ultraviolet absorbent synthesized by the patent has wide absorption range and large absorption intensity. The absorption range is 200nm-520nm, and the absorption intensity is more than 75%.
The product synthesis route is as follows: