JPS6123806B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a liquid phenolic resin composition for organic self-hardening molds, and more specifically, it is a resol-type organic resin composition with a low content of free phenol and free formaldehyde, a low viscosity, and a high flash point. The present invention relates to a method for producing a liquid phenolic resin composition for hard molds (hereinafter simply referred to as phenolic resin). This type of phenolic resin is produced by heating and polymerizing phenol and formaldehyde in the presence of an alkaline catalyst, and then dehydrating the condensate to remove water, unreacted phenol, unreacted formaldehyde, and other volatile components. can get. When used for casting, it goes without saying that the foundry sand must have sufficient strength as a mold by adding a phenolic resin and an acid curing agent, but it must also be used for sand mixing work, mold making work, etc. In view of pouring work, it is required to have a low content of free phenol and free formaldehyde, a low viscosity, and a high flash point. The reason for this is that when the content of free phenol and free formaldehyde is high, a severe odor or irritating odor is emitted during sand mixing, mold making, and pouring, which can cause skin irritation such as rashes on the worker's body. This is because it significantly worsens the working environment, and if the content of free phenol is high,
This is because, especially when molding a large casting mold, internal hardening of the thick portion is insufficient. Furthermore, the viscosity of this type of phenol release is 90
~135cp/30℃, but in conventional manufacturing methods, lowering the content of free phenol and free formaldehyde increases the viscosity of the resin, so methanol or a similar organic solvent must be mixed in to lower the viscosity value. In this case, of course, the point of attraction is lowered to, for example, about 35 to 58°C, and the flammability increases, creating the inconvenience that special storage equipment is required. By the way, the phenol content of conventionally known phenolic resins of this type is about 11.4wt.% by company S in West Germany, and 11.7wt.% by company D in the United States.
%, which is quite high. Also, the free formaldehyde is from Company S in West Germany.
It is 0.69wt.%, and that of Company D in the United States is about 0.78wt.%, which is also usually an extremely high percentage. In any case, nothing less than these values has been obtained. The cause lies in the conventional method of producing this type of phenolic resin itself. In other words, the conventional method for producing phenolic resin is to charge phenol, formaldehyde, and an alkaline catalyst into a 50 to 10,000 liter reactor equipped with a stirring device, reflux device, vacuum dehydration device, and heating/cooling device, and then stir the mixture under heat. This is a method in which water and unreacted components are removed by condensation polymerization while heating and dehydration under reduced pressure (hereinafter referred to as batch dehydration method). In this method, it takes a long time to remove the water and unreacted components in the can, so the phenolic resin undergoes thermal history and becomes a polymer, making it difficult to produce the low-viscosity phenolic resin of the present invention. I don't get it. For this reason, in order to lower the viscosity of conventional phenolic resins, the dehydration temperature was suppressed, making it impossible to remove unreacted components. In view of the conventional manufacturing method of this type of phenolic resin as described above, the present inventors conducted various studies to reduce the content of free phenol and free formaldehyde. When dehydrating the condensation product obtained by the above reaction, contrary to the purpose of dehydration, after artificially adding an appropriate amount of water to the condensation product, the dehydration temperature is much higher than that obtained by conventional production methods. The water is continuously fed into a long dehydration treatment tube heated to a high temperature, and the water vapor is flushed into a connected evaporator under reduced pressure while preventing the condensation product from burning onto the inner wall surface of the tube. By performing continuous dehydration treatment while removing unreacted phenol, unreacted formaldehyde, and other volatile components from the evaporator as much as possible, a phenolic resin that solves the problems of conventional phenolic resins can be obtained. This discovery led to the present invention. That is, the gist of the present invention based on such a new concept is as stated in the claims in the header, and the purpose of the present invention is to
Provides a method for producing a phenolic resin that has good internal curing ability, significantly improves the working environment, has a low viscosity, substantially does not require organic solvents, and therefore has low risk of ignition when storing the liquid resin. It's about doing. The method for producing a phenolic resin of the present invention will be explained in more detail below. Condensation polymerization of phenol and formaldehyde is carried out in the presence of an alkaline catalyst by a conventional batch method to obtain a polycondensation product having a resin concentration of 30 to 75 wt.%. Then, before entering the dehydration step, water is added to the condensation product in advance so that the resin concentration is 5 to 45 wt.%. Next, the condensation product to which water has been added is continuously fed into a long dehydration treatment tube to which an evaporator is connected at the end of the tube to perform continuous dehydration treatment. This long tubular dehydration treatment tube is set so that the ratio of the length L of the tube to the inner diameter D of the tube, that is, L/D, is about 1000 to 2500, preferably about 1500, and the temperature inside the tube is 100. Heated to ~130℃. Furthermore, the evaporator is maintained at a reduced pressure of 50 to 200 mmHgAb. The water vapor generated by heating the water-added condensation product that is continuously fed into a long dehydration treatment tube heated to 110 to 150℃ removes unreacted phenol, unreacted formaldehyde, and other substances in the phenolic resin condensation product. Since the volatile components of the condensate are washed away and the fluid flows through the tube in a highly turbulent state, burning of condensation products on the inner wall surface of the tube is also prevented. The water vapor and liquid phenolic resin that have passed through the dehydration treatment tube are flushed into an evaporator maintained at a reduced pressure of 50 to 200 mmHgAb. Here, the liquid phenolic resin is separated from water vapor, unreacted phenol, unreacted formaldehyde, and other volatile components. In this way, the phenolic resin condensate passes through the dehydration treatment tube, which is heated to a higher temperature than the dehydration temperature of the conventional batch method, but because it passes through the tube together with high-temperature water vapor in a short period of time, it is not subject to thermal history. Therefore, polymerization can be suppressed. In other words, it is dehydrated without thickening and is obtained as a low-viscosity product. After dehydration, the phenolic resin is taken out from the evaporator, water is added to the resin to give a moisture content of 9 to 42 wt.%, and after uniform mixing, it is used as the desired organic self-hardening phenolic resin for molds. The content of phenol formaldehyde resin in the phenol resin obtained by the present invention is 50 to 50%.
The reason for limiting the value to 80 wt.% is that if it is less than 50 wt.%, the residual moisture in the mold will increase, making drying necessary, and the hardening speed inside the mold will also be slow. On the other hand, if it is more than 80wt.%, the wettability to sand will be poor and the mold performance will not be good.
Furthermore, since the viscosity of the resin increases, the fluidity of the coated sand mixed with the sand deteriorates, resulting in defects. Also, the reason why the free phenol content was limited to 5wt.% or less is that when the content is higher than 5wt.%,
It is subject to extremely severe restrictions in terms of occupational safety and health due to the Regulations for Prevention of Hazards Due to Specified Chemical Substances and the Poisonous and Deleterious Substances Control Law. In addition, phenol gas is generated during kneading, molding, and pouring, which is likely to have an adverse effect on the human body, such as rashes. Furthermore, the reason why free formaldehyde is limited to 0.5 wt.% or less is that, like free phenol, formaldehyde gas is generated during sand mixing and molding, which significantly deteriorates the working environment. That is, the irritating odor is so pronounced that it has a very negative effect on the health and hygiene of workers. Further, as described above, the resin content and the amount of free monomer are adjusted within a predetermined range, the resin viscosity is adjusted to a range that is easy to use, and an appropriate amount of water is added to eliminate the flammability of the resin. Water content is 42wt.
If it is more than 9wt.%, the resin content and water will separate easily, and if it is less than 9wt.%, the viscosity will be high, making it difficult to use, and the flash point will be low. In addition, the resin concentration as used in the present invention refers to the residual content expressed in wt.% after placing the resin in an aluminum foil container, heating it on a hot plate at 180±1°C for 1 hour, and then allowing it to cool to room temperature. Phenol was measured by HLC, free formaldehyde was measured by the hydrochloric acid hydroxyamine method, water was measured by the Karl Fischer method, viscosity was measured by a B-type viscometer, and flash point was measured by a tag method. Example 1 550Kg of phenol, 568Kg of 38% formalin, 1.65Kg of NaOH as a catalyst, 6.6Kg of water, 6.6Kg of water as a catalyst
Batch operation was carried out using a mixture of 3.85 kg of Ca(OH) ₂ and 15.4 kg of water. In the reaction vessel, within 1 hour from the initial temperature of 30℃
The temperature was raised to 70°C, maintained at that temperature for 6.5 hours, and then cooled again to 30°C within 1 hour. After cooling, 22.7 kg of paratoluenesulfonic acid and 34.1 kg of water were added to the above raw materials as neutralizing agents. This condensation product had a resin concentration of 49 wt.% and a pH of 4.5. 145 kg of water was added to this to create a stock solution with a resin concentration of 43.7 wt.%. A dewatering step was then carried out in continuous operation. The liquid flow rate at the pipe inlet is 100Kg/h, and the temperature inside the pipe is 120Kg/h.
Processed at ~130°C. Heating steam pressure is 2.5
~3.4Kg/ ^cm2 . Also, the evaporator is 100-120mm
The patient was under reduced pressure due to HgAb. The processing time was 13.5 hours. 700 kg of distillate thus obtained
The resin concentration was 80wt.%. Also, the viscosity is
It was 550cp/30℃. By adding some water to this,
A product composition was obtained having the following properties. Resin concentration……………72wt.% Viscosity…75cp/30℃ Free phenol…5wt.% Free formaldehyde…0.2wt.% Moisture: 17.7wt.% Flash point: No ignition Comparative example 1 As a comparative example, the above raw materials were dehydrated using a batch method. The dehydration temperature of 60mmHg Ab. under reduced pressure could only be raised to 80℃. The reason for this is that the resin component becomes polymeric and the viscosity increases. In addition, the properties of the product in that case were as follows. Resin concentration......72wt.% Viscosity...155cp/30℃ Free phenol...13wt.% Free formaldehyde...1wt.% Water Minutes…………………………9wt.% Flash point…………………………Not flammable In other words, even if water is added in the same way, the free content is much higher and the There is no difference from the conventional product in this respect. In other words, it is clear that this was not simply due to the effect of diluting it with water. Comparative Example 2 Free phenol was added to 5 wt. in the same manner as Comparative Example 1.
% or less, dehydration was performed by raising the temperature to 95°C under a reduced pressure of 20 mmHgAb. The resin concentration at this time is
It had a viscosity of 75,000 cp/30°C at 87 wt.%. By adding methanol to this, a product composition with the following properties was obtained. Resin concentration……………70wt.% Viscosity…120cp/30℃ Free phenol…5.0wt.% Free formaldehyde…0.2wt. % Moisture……………………4.2wt.% Flash point……………………37℃ In other words, free phenol is added in batches.
If it is less than 5.0wt.%, a large amount of methanol must be used to lower the resin viscosity, which lowers the flash point. In producing the resin composition of the present invention, in the dehydration step, for example, in a pilot plant, the inner diameter of the pipe is D = 12 mm, the length L = 22 m,
L/D was 1833. In the plant under actual operation, the inner diameter D = 35.7 mm, the length L = 39.6 m, and L/D was 1109. In this way, when L/D is at least 1000, preferably 1500, and the maximum value is about 2500, a kind of flushing phenomenon is introduced in the dehydration process, and excessive condensation polymerization can be prevented even if the temperature is raised to a certain extent. It is believed that Example 2 Phenol 550Kg, 38% formalin 568Kg,
NaOH 1.65Kg, water 6.6Kg, Ca(OH) ₂ 3.85Kg, water
The raw materials were adjusted at a ratio of 15.4 kg to carry out the condensation polymerization reaction. The temperature conditions for heating and cooling were the same as in Example 1. After the reaction, add 22.7 kg of paratoluenesulfonic acid to water.
A solution of 34.1 kg was added under stirring to neutralize. The pH was 4.5. Also, the resin concentration in this case is
It was 49wt.%. To the above stock solution, 325 kg of water was added to make the resin concentration 38.6 wt.%. The resin content was 1527Kg. Next, to perform the dehydration operation, the flow rate of the stock solution was increased to 100Kg/h.
operated on. The temperature inside the tube was 110-120°C, the steam pressure was 2-3 Kg/cm, and the evaporator was under reduced pressure of 100-120 mmHgAb. The operation was carried out continuously. In this case, the resin discharge temperature was 35 to 40°C, and the amount of resin (yield) was 680 kg. The composition in this case is: Resin concentration......81wt.% Free phenol...6.7wt.% Free formaldehyde...0.2wt.% Residual moisture...... ……7.0wt.% Viscosity…………………………650cp/30℃. In order to commercialize this into the required product, 422 kg of water was added to make the resin concentration 50 wt.%. The composition of this product is: Resin concentration: 50wt.% Free phenol: 4.1wt.% Free formaldehyde: 0.12wt.% Water content: 50wt.% ……42.0wt.% Viscosity…………………………35cp/30℃. Example 3 The raw material ratios were selected as in Example 2, and the condensation product reaction conditions and stock solution preparation were the same as in the previous example, but 1604 kg of water was added, the resin concentration was 21 wt.%, and the resin The amount was set as a proportion of 2806Kg. Next, the above stock solution was dehydrated in the same manner as in the previous example. The conditions are: Stock solution temperature: 30℃ Stock solution flow rate: 100Kg/h Tube temperature: 120-130℃ (steam pressure: 2.5-3.5Kg/cm) Evaporator pressure (Reduced pressure)...Continuous operation at 100-120mmHgAb. Resin discharge temperature......30-35℃ Resin amount (output)......651Kg of discharged material Obtained. The characteristics of the discharged resin composition thus obtained are as follows: Resin concentration: 82wt.% Free phenol: 3.6wt.% Free formaldehyde: 0.19wt.% Residual moisture was 7.5wt.% and viscosity was 860cp/30°C. In order to commercialize this into the required product, for the composition made in this way,
16 kg of water was added to make the resin concentration 80 wt.%.
The composition of this product is: Resin concentration......80wt.% Free phenol...3.5wt.% Free formaldehyde...0.18wt.% Water content... ………9.7wt.% Viscosity…………………………700cp/30℃. Table 1 shows the results of Examples 1 to 3 and Comparative Examples 1 and 2. As is clear from Table 1, the phenolic resin composition according to the present invention has a lower content of free phenol (5 wt.% or less) and free formaldehyde (0.5 wt.% or less) than conventional phenolic resins. It is excluded from legal restrictions such as the Ordinance on Prevention of Hazards from Substances, etc. and the Poisonous and Deleterious Substances Control Law, and because its flash point is 70°C or higher, it must be classified as at least Class 4, Class 3 Petroleum, etc. when handling hazardous materials based on the Fire Service Act. It is treated in the same way as heavy oil, glycerin, etc., and legal regulations have been relaxed, such as increasing the specified quantity (or storage quantity), or completely excluding it (if it does not have a flash point), which cannot be obtained with conventional phenolic resins. It has the greatest feature that no one has.

[Table] Next, gases generated during kneading and molding of the phenolic resins obtained in Example 1 and Comparative Example 1 of the present invention are shown below.

[Table] Formaldehyde was measured using a Kitagawa detection tube at the location of the worker's face. )
Conditions: High-speed mixer (continuous mixer) used Product...0.8wt.% (based on sand) Hardening agent...50wt.% (based on phenolic resin) Very small amounts of formaldehyde may be detected during kneading and molding. However, in general, there was no problem as long as the concentration was below the permissible level. The concentrations of other gases were too low to be measured with a detector tube. Next, the mold strength (stretch strength and standing strength) when organic self-hardening sand is coated with the phenolic resin obtained in Example 1 and Comparative Example 1 of the present invention and used as a mold will be shown. Conditions: Using a high-speed mixer Sand: Frimantle new sand Resin: 0.8% (based on sand) Hardener: 50% (based on phenolic resin)

[Table] The stick strength was measured using a stick strength meter manufactured by Jiyoji Fisher Co., Ltd. after one hour of molding, the mold was removed. Snagging strength is measured by the depth of the teeth sunk in by rotational force, and the smaller the value, the higher the mold strength. This result shows that resins with less free phenol have stronger internal strength, and therefore resins with less free phenol have better moldability.

[Table] The test piece used was 50φ x 50h. From the above, it can be seen that the mold strength is also equal to or higher than that of the conventional mold. As explained above, it can be seen that the performance of the mold using the phenolic resin obtained by the present invention is normal or better.

Claims (1)

[Scope of Claims] 1. Polycondensation of phenol and formaldehyde in the presence of an alkaline catalyst is carried out, and an appropriate amount of water is added in advance to the polycondensation product obtained in the dehydration step, and the resulting product is heated in the form of a long tube. The water, unreacted phenol, and unreacted water are continuously fed into the dehydration treatment tube, and while the generated water vapor prevents the condensation product from being burned onto the inner wall of the tube, water, unreacted phenol, and unreacted water are removed by flushing action in the evaporator. A phenol formaldehyde resin characterized by continuous dehydration treatment while removing formaldehyde and other volatile components as much as possible.
50 to 80 wt.% Free phenol 5 wt.% or less Free formaldehyde 0.5 wt.% or less Water An organic compound with a composition of 9 to 42 wt.%, substantially free of organic solvents, and with a flash point of 70°C or higher. A method for producing a liquid phenolic resin composition for hard molds.