Disclosure of Invention
Therefore, it is necessary to provide a method for preparing a semi-solid thermosetting phenolic resin aiming at the technical problem that phenolic resin and hexamethylenetetramine are required to be added in the preparation of the existing phenolic moulding compound.
The technical scheme provided by the invention is as follows:
a preparation method of a semi-solid thermosetting phenolic resin comprises the following steps:
1) adding phenol, paraformaldehyde and an alkali catalyst into a reaction kettle, heating, stirring and heating to 60-70 ℃, adding a first batch of resorcinol, heating to 70-80 ℃, starting to dropwise add an aldehyde aqueous solution, and carrying out a first-stage constant-temperature reaction;
2) cooling to 60-70 ℃, adding a second batch of resorcinol and paraformaldehyde, heating to 75-80 ℃, and continuing to perform constant-temperature reaction;
3) after the aldehyde aqueous solution in the step 1) is completely dripped, heating to 80-105 ℃ for second-stage constant-temperature reaction.
In the invention, the reaction trend of phenols and aldehydes is regulated and controlled by sectional temperature control, and the phenolic reaction process can be divided into two steps of addition reaction and polycondensation reaction. Wherein, the addition reaction means that when the aldehyde phenol is reacted, ortho-position and para-position of phenolic hydroxyl group are substituted to generate a plurality of hydroxymethyl phenols, and a mixture of monohydric phenol alcohol and polyhydric phenol alcohol is formed. The polycondensation reaction mainly refers to the polycondensation reaction of hydroxymethyl compounds, namely monohydric phenol alcohol, polyhydric phenol alcohol or dimer and the like are subjected to continuous polycondensation reaction under certain conditions, so that the relative molecular weight of the resin is continuously increased, and a network structure is gradually formed to obtain the thermosetting resin.
Several alternatives are provided below, but not as an additional limitation to the above general solution, but merely as a further addition or preference, each alternative being combinable individually for the above general solution or among several alternatives without technical or logical contradictions.
Preferably, the alkali catalyst is selected from one or more of ammonia water, triethylamine, barium hydroxide and metal oxide.
Preferably, the alkali catalyst is a composite alkali catalyst, and comprises ammonia water and magnesium oxide.
Preferably, the phenol in the step 1) is one or more selected from phenol, m-cresol, cardanol, resorcinol, bisphenol A and p-cresol.
Preferably, the aqueous aldehyde solution in the step 1) is an aqueous formaldehyde solution.
Preferably, the reaction time of the first-stage isothermal reaction in the step 1) is 1-1.5 h.
Preferably, the reaction time of the isothermal reaction in the step 2) is 0.5-1 h.
Preferably, the reaction time of the second-stage isothermal reaction in the step 3) is 1-3 h.
Preferably, the preparation method of the semi-solid thermosetting phenolic resin comprises the following steps:
1) adding 530-550 g of phenol, 5-6 g of paraformaldehyde and an alkali catalyst into a reaction kettle, heating, stirring and heating to 60-70 ℃, adding a first batch of 25-35 g of resorcinol, heating to 70-80 ℃, starting to dropwise add 590-600 g of formaldehyde solution, and carrying out a first-stage constant-temperature reaction; the mass fraction of the formaldehyde aqueous solution is 35-40 wt%;
2) cooling to 60-70 ℃, adding a second batch of 25-35 g of resorcinol and 5-6 g of paraformaldehyde, heating to 75-80 ℃, and continuing to perform constant-temperature reaction;
3) after the aldehyde aqueous solution in the step 1) is completely dripped, heating to 80-105 ℃ for second-stage constant-temperature reaction.
Preferably, the preparation method of the semi-solid thermosetting phenolic resin comprises the following steps:
1) adding 530-550 g of phenol, 5-6 g of paraformaldehyde and 35-60 g of ammonia water solution into a reaction kettle, heating and stirring to raise the temperature to 60-70 ℃, adding a first batch of 25-35 g of resorcinol, raising the temperature to 70-80 ℃, starting to dropwise add 590-600 g of formaldehyde water solution, and carrying out a first-stage constant-temperature reaction; the mass fraction of the formaldehyde aqueous solution is 35-40 wt%;
2) cooling to 60-70 ℃, adding a second batch of 25-35 g of resorcinol and 5-6 g of paraformaldehyde, heating to 75-80 ℃, and continuing to perform constant-temperature reaction;
3) after the aldehyde aqueous solution in the step 1) is completely dripped, heating to 80-105 ℃ for second-stage constant-temperature reaction.
Preferably, the preparation method of the semi-solid thermosetting phenolic resin comprises the following steps:
1) adding 530-550 g of phenol, 5-6 g of paraformaldehyde, 35-50 g of ammonia water solution and 10-12 g of magnesium oxide into a reaction kettle, heating and stirring to raise the temperature to 60-70 ℃, adding a first batch of 25-35 g of resorcinol, raising the temperature to 70-80 ℃, starting to dropwise add 590-600 g of formaldehyde water solution, and carrying out a first-stage constant-temperature reaction; the mass fraction of the formaldehyde aqueous solution is 35-40 wt%;
2) cooling to 60-70 ℃, adding a second batch of 25-35 g of resorcinol and 5-6 g of paraformaldehyde, heating to 75-80 ℃, and continuing to perform constant-temperature reaction;
3) after the aldehyde aqueous solution in the step 1) is completely dripped, heating to 80-105 ℃ for second-stage constant-temperature reaction.
The invention also provides the semi-solid thermosetting phenolic resin prepared by the preparation method.
The invention also provides application of the semi-solid thermosetting phenolic resin in preparation of low-temperature curing phenolic molding plastic.
The invention has the following beneficial effects:
(1) the phenolic resin obtained by the preparation method is thermosetting phenolic resin, does not need to add a curing agent urotropine, can be self-cured without overhigh temperature, and has small damage to the service life and the performance of a product.
(2) The thermosetting phenolic resin obtained by the preparation method is in a thermosetting state or a semi-solid state, is more convenient to transport, transfer and store than a liquid state, has high transport efficiency, and is convenient for process blending and processing molding.
(3) The preparation method regulates and controls the reaction trend of phenols and aldehydes by sectional temperature control, the obtained thermosetting phenolic resin can be cured without overhigh temperature, has short curing time, high curing speed and certain fluidity, and can be used as the adhesive of phenolic molding plastic required by special industries such as precise electric appliances, instruments and meters.
Detailed Description
For the convenience of understanding, the present invention will be described below by way of examples. It will be understood by those skilled in the art that the examples are merely for the purpose of further illustrating the invention and should not be taken as limiting the invention in any way, as many variations and modifications of the invention are possible without departing from the scope of the invention and are intended to be covered thereby.
Example 1
(1) 540 g of phenol, 5.78g of paraformaldehyde and 35.36g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, wherein the paraformaldehyde not only participates in the reaction and plays a role of a curing agent to a certain extent, a small amount of paraformaldehyde is added to be beneficial to reducing the curing temperature, the curing efficiency is improved, the curing time is shortened, and excessive addition is not beneficial to reaction control and cost increase. Heating and stirring to uniformly mix the raw materials, adding a first batch of 30g of resorcinol when the temperature rises to 65 ℃, slowly raising the temperature, starting to dropwise add 594g of 37 wt% of formaldehyde aqueous solution when the temperature rises to 73-78 ℃, carrying out a first-stage reaction, wherein the first-stage reaction mainly comprises small molecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, cooling to 65 ℃, adding a second batch of 30g of resorcinol and 5.78g of paraformaldehyde, raising the temperature to 75-78 ℃, continuing the constant-temperature reaction for 0.5-1.0 hours, and adopting the dropwise adding form of the formaldehyde aqueous solution to mainly carry out the addition reaction in the stage to form a mixture of monohydric phenol alcohol and polyhydric phenol alcohol. As the formaldehyde content increases, a small portion of the polycondensation reaction occurs while the addition reaction occurs.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 85 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 2
(1) 540 g of phenol, 5.78g of paraformaldehyde and 35.36g of ammonia solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly raised, a first batch of 30g of resorcinol is added when the temperature is raised to 65 ℃, the temperature is slowly raised to 73-78 ℃, 594g of 37 wt% formalin is dropwise added for a first-stage reaction, the reaction in the stage is mainly a small molecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added after the temperature is lowered to 65 ℃, the temperature is raised to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 3
(1) 540 g of phenol, 5.78g of paraformaldehyde and 46.67g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly increased, a first batch of 30g of resorcinol is added when the temperature is increased to 65 ℃, the temperature is slowly increased to 73-78 ℃, 594g of 37 wt% formalin is dropwise added for a first-stage reaction, the reaction in the stage is mainly a small molecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added after the temperature is reduced to 65 ℃, the temperature is increased to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 4
(1) 540 g of phenol, 5.78g of paraformaldehyde and 52.33g of ammonia solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly increased, the first 30g of resorcinol is added when the temperature is increased to 65 ℃, the temperature is slowly increased to 73-78 ℃, 594g of 37 wt% formaldehyde aqueous solution is dropwise added to carry out the first stage reaction, the reaction in the stage mainly comprises small molecule addition reaction, the constant temperature reaction time is 1.0-1.5 hours, the second 30g of resorcinol and 5.78g of paraformaldehyde are added after the temperature is reduced to 65 ℃, the temperature is increased to 75-78 ℃, and the constant temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 5
(1) 540 g of phenol, 5.78g of paraformaldehyde and 56.57g of ammonia solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly raised, a first batch of 30g of resorcinol is added when the temperature is raised to 65 ℃, the temperature is slowly raised to 73-78 ℃, 594g of 37 wt% formaldehyde aqueous solution is dropwise added to carry out a first-stage reaction, the reaction in the stage is mainly small molecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added after the temperature is lowered to 65 ℃, the temperature is raised to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 6
(1) 540 g of phenol, 5.78g of paraformaldehyde and 11.88g of magnesium oxide powder are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly increased, a first batch of 30g of resorcinol is added when the temperature is increased to 65 ℃, the temperature is slowly increased to 73-78 ℃, 594g of 37 wt% formalin is dropwise added for a first-stage reaction, the reaction in the stage is mainly a small molecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added after the temperature is reduced to 65 ℃, the temperature is increased to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 7
(1) 540 g of phenol, 5.78g of paraformaldehyde and 35.36g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, 11.88g of magnesium oxide powder is added after stirring for 5 minutes, heating and stirring are carried out, the temperature is slowly increased, a first batch of 30g of resorcinol is added when the temperature is increased to 65 ℃, the temperature is slowly increased to 73-78 ℃, 594g of 37 wt% formaldehyde water solution is dropwise added to carry out a first-stage reaction, the first-stage reaction mainly comprises a micromolecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, after the temperature is reduced to 65 ℃, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added, the temperature is increased to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Example 8
(1) 540 g of phenol, 5.78g of paraformaldehyde and 46.67g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, 11.88g of magnesium oxide powder is added after stirring for 5 minutes, heating and stirring are carried out, the temperature is slowly increased, a first batch of 30g of resorcinol is added when the temperature is increased to 65 ℃, the temperature is slowly increased to 73-78 ℃, 594g of 37 wt% formaldehyde water solution is dropwise added to carry out a first-stage reaction, the first-stage reaction mainly comprises a micromolecule addition reaction, the constant-temperature reaction time is 1.0-1.5 hours, after the temperature is reduced to 65 ℃, a second batch of 30g of resorcinol and 5.78g of paraformaldehyde are added, the temperature is increased to 75-78 ℃, and the constant-temperature reaction is continued for 0.5-1.0 hour.
(2) After the formaldehyde is completely dripped, the temperature is raised to 90 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Comparative example 1
PF-8203 solid thermoplastic resin for phenolic molding compound is commercially available.
Comparative example 2
(1) 570 g of phenol and 35.36g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly raised, 625g of 37 wt% formaldehyde water solution is dropwise added into the mixture when the temperature is raised to 73-78 ℃ to carry out a first-stage reaction, the first-stage reaction is mainly a small molecule addition reaction, and the constant-temperature reaction time is 1.5-2 hours.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 85 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Comparative example 3
(1) 540 g of phenol and 35.36g of ammonia water solution are sequentially added into a reaction kettle provided with a stirrer, a thermometer, a vacuum meter, a condensing and refluxing device and a heating and cooling device, the mixture is heated and stirred, the temperature is slowly raised, 60g of resorcinol is added when the temperature is raised to 65 ℃, the temperature is slowly raised, the mixture is heated and stirred when the temperature is raised to 73-78 ℃, 625g of 37 wt% formaldehyde water solution is dropwise added into the mixture to carry out a first-stage reaction, the first-stage reaction is mainly a micromolecule addition reaction, and the constant temperature reaction time is 1.5-2 hours.
(2) After the formaldehyde aqueous solution is completely dripped, the temperature is raised to 85 ℃ for the second stage reaction, and in the stage, the monohydric phenol alcohol and the polyhydric phenol alcohol are continuously subjected to polycondensation reaction under the conditions of heating and alkalinity, so that the relative molecular mass of the resin is increased, and a cross-linked network is formed. And (3) carrying out constant-temperature reaction for 1.5-2.5 hours, and dehydrating to obtain the phenolic resin.
Basic performance test:
the test is carried out by adopting a ring and ball method, and the basic performances of the examples 1-8 and the comparative examples 1-3 are shown in the table 1:
TABLE 1 basic Performance test results
Serial number
|
Softening point/. degree.C
|
Solids content/%
|
Residual carbon rate/%)
|
Example 1
|
60.5
|
93.53
|
54.23
|
Example 2
|
65.0
|
92.87
|
54.45
|
Example 3
|
62.0
|
93.52
|
55.34
|
Example 4
|
62.25
|
93.63
|
54.55
|
Example 5
|
65.25
|
92.39
|
54.7
|
Example 6
|
57.5
|
93.68
|
56.24
|
Example 7
|
56.25
|
93.55
|
55.88
|
Example 8
|
56.5
|
92.97
|
55.82
|
Comparative example 1
|
103.0
|
98.33
|
51.64
|
Comparative example 2
|
65.5
|
90.76
|
51.51
|
Comparative example 3
|
67.0
|
92.67
|
52.55 |
According to the test data, the phenolic resin and the preparation method thereof provided by the invention have the advantages of low softening point, high curing speed, high carbon residue rate, good fluidity during molding and processing, and are beneficial to processing and molding.