1. The technical requirements for raw materials phenol and formaldehyde are the same as those for resin liquid manufacturing. Hydrochloric acid: concentrated hydrochloric acid for industrial use, mass fraction: 25% ~ 40%, density: 1.12 ~ 1.20g/cm 3. 2. The ratio of raw materials and calculation the molar ratio of phenol to formaldehyde is 1:0.1. Technical requirements of raw materials
The requirements of phenol and formaldehyde are the same as that of resin liquid manufacturing.
Hydrochloric acid: concentrated hydrochloric acid for industrial use, mass fraction: 25% ~ 40%, density: 1.12 ~ 1.20g/cm3.
2. Raw material ratio and calculation
The molar ratio of phenol to formaldehyde is 1:0.8 ~ 0.9. If it is converted into mass ratio, it is 100:25.5-28.7. The amount of HCl depends on the pH value of the solution (usually the pH value of the solution is required to be kept between 1.6 and 2.3). Generally, the amount of pure HCl is about 0.1% ~ 0.3% of phenol. The calculation method of raw material consumption is the same as that of resin liquid, and the equipment used is the same.
3. Key points of synthesis process
(1) Add the measured phenol and formaldehyde into the reactor, stir for 5 min, and add about 30% hydrochloric acid solution. The pH value of the reactant was 1.6 ~ 2.3;
(2) Heat and stir, and stop heating when the material temperature reaches 60-70 ℃;
(3) The exothermic reaction of polycondensation makes the temperature rise to 95 ~ 98 ℃, and starts to boil and stops stirring;
(4) After boiling and stabilizing, add hydrochloric acid and stir again to make the unreacted phenol in the upper layer react with acid continuously;
(5) Sample to determine the degree of polycondensation: the density is required to be in the range of 1.15-1.18g/cm3. If the requirements are not met, the boiling reaction time can be prolonged;
(6) Dry and dehydrate.
If there is a vacuum device, steam can be applied to the jacket to make the temperature of reactant rise to 90-180 ℃, start the vacuum pump and adjust it slowly to make the vacuum degree reach 46.7kpa-54.7kpa. Take samples to measure the softening point. After meeting the requirements, discharge the material for cooling. Get the resin block.
If there is no vacuum device, open drying method shall be adopted. The resin shall be unloaded first, and the upper water shall be removed after standing. Then, electric heating method shall be used to heat the resin directly and slowly to 180 ~ 240 ℃ for 4 hours, and the sample shall be taken to measure the softening point, and the resin block shall be naturally cooled after meeting the requirements.
（7） Generally, the resin powder is crushed into small pieces with a diameter of about 30mm, and then crushed by air separation to obtain the required resin powder.
Resin powder is thermoplastic phenolic resin: hardener (Urotropine) must be added to change into thermosetting resin. Therefore, when the resin block is processed and broken, the required Urotropine is added into the resin to be crushed together, and the resin powder obtained is the thermosetting resin that can be hardened by heating.
4. Factors affecting the quality of thermoplastic phenolic resin powder
(1) Catalyst impact
In the production of thermoplastic phenolic resin, acid catalyst must be used, that is, polycondensation under the condition of pH & lt; 7. The concentration of hydrogen ion has a great influence on the reaction speed, which is in a linear relationship. The catalyst not only catalyzes the reaction, but also affects some properties of the resin.
In addition to hydrochloric acid, acid catalysts include sulfuric acid, phosphoric acid, oxalic acid, formic acid, etc.
Acid catalyst for hydrochloric acid. It is also a commonly used catalyst for thermoplastic resin. The phenol formaldehyde resin made of hydrochloric acid as catalyst is code 2123. In order to avoid large heat emission during the reaction, it should be added into the reactant twice or three times. The advantage of using hydrochloric acid as catalyst is that HCI can be evaporated out in the process of drying and dehydration, but when the amount is too much, the corrosion effect on the equipment is serious.
Sulfuric acid (H2SO4) is less used as catalyst, and its catalytic ability is inferior to that of hanging acid. Because its residue remains in resin, it must be neutralized to generate inert sulfate, such as BaSO4, CaSO4, etc.
Oxalic acid is a kind of organic acid with weak ionization, which is seldom used. It is characterized by mild polycondensation and easy to control, but with a large amount and a long reaction time.
(2) Effect of raw material ratio
When phenol and formaldehyde are polycondensated, thermoplastic resin and thermosetting resin can be obtained even under the condition of pH < 7 due to the different proportion of ingredients. The higher the molar ratio of formaldehyde to phenol is, the higher the ratio of formaldehyde to phenol is
The higher the softening point is, the larger the average molecular weight is. The viscosity of the alcohol solution of the resin increases, the yield (yield) increases, and the content of free phenol decreases. See Table 1 for details.
Table 1 Effect of material ratio of formaldehyde and phenol on the performance of thermoplastic phenolic resin
Formaldehyde used in 100g phenol G
Resin yield
(based on phenol)
Dropping temperature
Temperature
Curing rate at 150 ° C (plus 10% Urotropine)
Viscosity of 50% ethanol solution MPa · s free phenol content
Twenty-four
One hundred and eight point nine
Ninety-seven point five
One hundred and sixty
Eighty-three
Eight point seven
Twenty-six
One hundred and nine point six
One hundred and three point three
Eighty
One hundred and thirty-six
Five point nine
Twenty-eight
One hundred and twelve
One hundred and twelve
Sixty-five
Three hundred and seventy
Four point seven
Twenty-nine
Proceed to phase II (phase B) resin
It can be seen from table 1 that the large amount ratio of formaldehyde to phenol in actual production is 28g formaldehyde to 100g phenol, or equivalent to 1.2mol formaldehyde to 1.2mol phenol. If it exceeds this limit, it is easy to enter the second-order resin in the reaction process. The appropriate dosage used in industrial production is 26.5-27.5g formaldehyde per 100g phenol.
（3） The influence of polycondensation and drying conditions
The resin formed in the polycondensation process is insoluble in the reactant, so the polycondensation can be judged by obvious emulsification and stratification. However, after delamination, the polycondensation process does not necessarily meet the requirements, and the polycondensation time needs to be extended. According to the experimental data, when the polycondensation time is extended, the reaction tends to be complete, and the average molecular weight and shrinkage of the resin are improved. The effect is shown in Table 2.
Table 2 Effect of extended polycondensation time on properties of thermoplastic resin
Condensation time
Min
Resin yield
%
Drop temperature change
Temperature
Viscosity of 50% ethanol
MPa. S
Mass fraction of free phenol
%
Fifty-five
One hundred and seven point six
One hundred and two
One hundred and six
Six point seven
Sixty
One hundred and seven point eight
One hundred and six
One hundred and nine
Six point four
Ninety
One hundred and seven point nine
One hundred and ten
One hundred and twenty-six
Six
One hundred and fifty
One hundred and eight
One hundred and eleven
One hundred and twenty-nine
Five point eight
Two hundred and seventy
One hundred and eight point two
One hundred and seventeen
One hundred and sixty-three
Five point two
The drying time and the final temperature of the resin have influence on the molecular weight of the resin, the viscosity of the solution, the softening point, the dropping temperature and the content of free phenol. The drop temperature or softening point of the resin can be increased by increasing the final drying temperature and the molar ratio of formaldehyde to phenol.
Source: Shandong yushiju Chemical Co., Ltd
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