JPS64973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a binder for manufacturing molds used in manufacturing castings, and in particular to solid resol type phenolic resins (hereinafter simply referred to as solid resols) used in the shell molding method. Conventionally, this type of solid resol has been produced by directly discharging the B-stage concentrate (phenol condensate obtained by depressurizing and dehydrating) into the atmosphere, which solidifies at room temperature but remelts when heated. JP-A-56-15309) is known, but this method of obtaining solid resol in the form of a block is difficult to cool down inside the block, and there is a risk of gelation due to residual heat, making it unsuitable for mass production. It has some unsuitable aspects.
Furthermore, the resin properties differ between the surface and the inside of the lump after cooling, making it difficult to obtain a solid resol with uniform quality. Furthermore, a method is known (Japanese Patent Publication No. 12467/1983) in which the product is concentrated to the B stage, then an organic solvent such as methanol is added, the reaction is suppressed by cooling, and the product is granulated into granules or spheres using a special granulator. .
However, while this method is very industrially useful and suitable for mass production, it requires expensive equipment and the energy cost for using it is high, so it has economic disadvantages. Furthermore, in recent years, a cellulose compound (Japanese Patent Publication No. 53-42075) or an aqueous polymer compound (Japanese Patent Publication No. 51-62857) has been added to the A stage, that is, the initial condensate, to form a granular, almost solid, product without concentration and dehydration. A method for obtaining resols is provided. However, with this method, there is a large amount of residual monomer, making it difficult to control the properties of the solid resol, and when used in the shell molding method, the odor is extremely strong due to the large amount of formalin and phenol remaining, which seriously impairs the working environment. To contaminate. It is especially noticeable when mixed with sand grains. In addition, in terms of other properties, it is extremely poor in melting point and blocking resistance, making it difficult to put it to practical use. Furthermore, the disadvantage of this method is that the surface of the obtained granular solid resol is quite viscous, making it impossible to apply mechanical means such as filtration or centrifugation in the next step of water separation. It's difficult. Therefore, the solid resol obtained by this method is difficult to use in the shell molding method. Therefore, the purpose of this invention is to provide a solid resol that eliminates all of the above-mentioned drawbacks, and in particular, does not involve problems such as gelation during the production of solid resols, and does not require a special granulator for solidification. To provide a solid resol which has a small amount of residual monomer, does not generate bad odor during sand grain kneading, molding, pouring, etc., and does not have a sticky surface. The objects of the invention are achieved by carrying out the matters described in the claims. This invention will be explained in detail below. The phenols used as starting materials for this invention are not limited to phenols, so-called carbolic acids, but include all known phenols. For example, simple substances such as xylenol and cresol, as well as derivatives thereof such as meta-alkylphenol and meta-alkoxyphenol are all included. Aldehydes also include all known aldehydes, and preferred examples include formaldehyde in either form of formalin or paraformaldehyde, and furfural. In this invention, a catalyst consisting of a nitrogen-containing compound means that it contains at least nitrogen in a compound such as an ammonia component (including amines) or hexamine. An alkaline catalyst such as alkaline earth metal hydroxide such as magnesium hydroxide or magnesium hydroxide may be used in combination. Further, the cellulose compound which is an additive added during the reaction process may be either synthetic cellulose or natural cellulose, or may be a mixture. Specific examples of the cellulose compounds include ethylcellulose, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, starch, dextrin, gum arabic, gum Karaya, sodium alginate, and ester compounds of sodium alginate. Similarly, an aqueous polymer compound is one that has at least one hydrophilic group within the compound, and specific examples thereof include gelatin, casein, polyvinyl alcohol, polyvinyl acetate, polyethylene glycol,
These are polyacrylic acid, polyethylene oxide, polyacrylamide, etc., and copolymers of these compounds. In addition, to carry out the method of this invention, a PH regulator is required to adjust the PH of the reaction system after adding the additives to obtain the granulated product and cooling the reaction system to 5 to 30°C. I'll talk about this. First, the granulated product is obtained, and after cooling the reaction system to 5 to 30°C, the reaction system is turned to the acidic side, preferably at PH
Any well-known inorganic or organic acid can be used as a pH adjuster to adjust the pH to 1.0 to 3.0, and there are no particular restrictions. Specific examples include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, sulfonic acid, and Toluenesulfonic acid, etc. After the surface of the granulated material is hardened, any known basic substance can be used as a neutralizing agent to neutralize the reaction system, and there are no particular limitations. Specific examples of this include sodium hydroxide, potassium hydroxide and calcium hydroxide. Next, regarding the blending ratio of these starting materials and additives, the aldehyde is blended at a ratio of 1 mole or more to 1 mole of the phenol, and the catalyst consisting of a nitrogen-containing compound is selected from among the known catalyst amounts. Select and use the amount needed, and there are no particular restrictions. The amount of the cellulose compound or aqueous polymer compound added is 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the phenols.
Parts by weight. If the amount of these additives is less than 0.01 parts by weight, granulation will not be carried out sufficiently, and if it exceeds 10.0 parts by weight, performance such as strength and curing speed of the solid resol will deteriorate, which is not preferable. Further, as another additive used in the method of this invention, hot water is used after concentration and dehydration, and the amount of this hot water added is 20 to 400 parts by weight, preferably 50 to 200 parts by weight, per 100 parts by weight of the above-mentioned phenols. Parts by weight. here
If it is less than 20 parts by weight, granulation will be difficult, and if it exceeds 400 parts by weight, the yield of solid resol will decrease, which is not preferable. Next, to describe the method of this invention, first, phenols and aldehydes are mixed into a predetermined container such as a reaction can, and then a nitrogen-containing compound is added at the same time or after heating to a predetermined temperature. After condensing for a certain period of time to synthesize an initial condensate, it is concentrated and dehydrated to the B stage under a reduced pressure of 60 to 75 cmHg, and after removing most of the monomers from the reaction system, it is heated to about 60 to 90°C. When the cellulose compound is added at the above-mentioned ratio while maintaining the concentrate at a predetermined temperature and stirring, a granular solid is obtained together with water in the container. Next, after cooling the reaction system to 5 to 30°C, the above-mentioned acidic substance is added into this container, and the pH is adjusted to the acidic side, preferably until the reaction system falls to PH 1.0 to 3.0, and the mixture is stirred. However, he continued to react. At the end of the reaction, the surface of the particles becomes slightly gelled and no longer has viscosity, while the inside has viscosity. At this time, if the temperature of the reaction system is high, this operation is difficult, so before adding the acidic substance, the temperature of the reaction system is
Cool to 30°C. Thus the surface has no viscosity,
A solid resol with an uncured interior can be obtained, but if the surface is taken out of the reaction system while still acidic, the reaction will proceed and problems will occur. is added to neutralize the reaction system. After the water is separated, the water on the surface of the solid resol is further removed by using a filter, centrifuge, etc., so that the surface does not have viscosity. A solid resol is obtained which is extremely easy to handle. (Example 1) 3 flasks were charged with 1000 g of phenol, 1620 g of 37% formalin, and 100 g of 28% amphonia water, heated, and when the liquid in the flask reached 70°C,
This temperature was maintained for 90 minutes. Next, the supernatant liquid of the upper layer was removed, and the mixture was concentrated and dehydrated under reduced pressure at a reduced pressure of 68 cmHg. After the start of pressure reduction, the temperature of the liquid in the flask fell below 60°C, and when most of the water and monomers were removed from the reaction system, the temperature of the liquid in the flask began to rise. When this temperature reaches 80℃, use 80℃ hot water.
1000g was added, stirred and mixed, and this temperature was maintained. Next, gum arabic pre-dissolved in 40g of water.
10 g was added to obtain granules with an average diameter of 1.0 mm.
After cooling the liquid in the flask to 10℃, 1N hydrochloric acid was added dropwise into the reaction system (flask) to bring the pH to 2.0~
2.5, and the reaction was continued for an additional 6 hours to obtain a solid resol with no viscosity on the surface and B-stage inside the particles. At this time, before water separation, a 10% sodium hydroxide solution was added to neutralize the reaction system. (Example 2) 1000 g of phenol, 1050 g of 37% formalin, and 20% caustic soda were placed in the flask of No. 3 and gradually heated. At the same time, 70 g of hexamethylenetetramine was separately weighed and gradually added to the above-mentioned mixture which was being stirred. When the liquid in the flask reached 80°C, this temperature was maintained and a condensation reaction was carried out for 60 minutes to obtain an initial condensate. Thereafter, a granular solid resol having a particle diameter of 0.2 to 0.5 mm was obtained in the same manner as in Example 1.
However, after the completion of vacuum dehydration, that is, when hot water was added, the temperature of the liquid in the flask was 70°C, the amount of hot water was 600 g, and after the addition of hot water, the liquid in the flask was maintained at 75°C, and the reaction was further proceeded for 30 minutes. In order to harden the particle surface by adding 200g of 5% polyvinyl alcohol instead of the gum arabic aqueous solution, the temperature of the reaction system was set to 20%.
The temperature was maintained at 0.degree. C., the pH was adjusted to 1.5 to 2.0, and the reaction was continued in this state for 4 hours. (Example 3) 1000 g of phenol, 1460 g of 37% formalin, 10 g of ethylenediamine, and 150 g of 28% aqueous ammonia were placed in the flask of No. 3, and gradually heated.
When the liquid in the flask reached 70°C, this temperature was maintained and the condensation reaction was carried out for 80 minutes to obtain an initial condensate, and then the particle diameter was 0.5 to 1.0 mm in the same manner as in Example 1.
A granular solid sol was obtained. However, the amount of hot water added
After adding 1500g and reacting at 80℃ for 10 minutes, 200g of 5% hydroxyethylcellulose was added instead of the gum arabic aqueous solution, and the temperature of the reaction system was cooled to 20℃ to harden the particle surface. The reaction was carried out at pH 2.0 to 2.5 for 8 hours. (Comparative Example 1) 1000 g of phenol and 1295 g of 37% formalin were placed in the flask from step 3 and gradually heated. When the liquid in the flask reached 40°C, this temperature was maintained.
200 g of 25% aqueous ammonia was gradually added through a separating funnel. Then, the further heated liquid in the flask
When the temperature reached 75°C, the reaction was carried out for 90 minutes while maintaining this temperature to obtain an initial condensate. At this time, add 1.0 g of gum arabic dissolved in 30 g of water in advance, and then
The reaction was continued for 60 minutes to obtain a spheroidized resin. After cooling, the supernatant liquid was removed, and the spheroidized resin in the lower layer was washed with water and air-dried for one week to obtain a granular solid resol with an average diameter of 1.0 mm. (Comparative Example 2) 1000g of phenol and 1295g of 37% formalin were placed in the flask from step 3 and gradually heated. When the temperature of the liquid in the flask reached 40℃, this temperature was maintained and 25% ammonia was added. Add 200 c.c. of water and 7.5 cc of 6N caustic soda and further heat until the temperature of the liquid in the flask reaches 75°C. Maintain this temperature and react for 170 minutes to obtain an initial condensate. Ta. Next, 10 g of carboxymethylcellulose pre-dissolved in 500 g of water and 10 g of polyvinyl alcohol
(degree of polymerization 1725, degree of saponification 88%) was added. After this, the reaction was continued for another 30 minutes, and then 1 g of sodium alkylsulfonate was added, followed by cooling. After cooling and standing, the supernatant liquid was removed, and the powdered resin formed in the lower layer was taken out, washed with water, and air-dried for one week. 95% of the resulting powdered resin passed through a 270 mesh standard sieve. In order to examine the properties and performance of Examples 1 to 3 and Comparative Examples 1.2, the test results are shown in Table 1 below.

[Table] This method shows that the melting point and gel time are
Compliant with JISK6901. Free phenol is JISK−
0102, and the blocking resistance was 100.
Place each solid resol in a cc beaker and heat at 40℃ for 24 hours.
Those that were left to stand for a period of time and were blocked were marked with an ×, and those that were not blocked were marked with an ○. The amount of gas generated was based on JISK-0102 for formaldehyde and phenol, and JISK-0099 for ammonia. Furthermore, the values in Table 1 are expressed in terms of the amount of gas generated (mg) per gram of solid resol at 250°C. The strength of the odor is indicated by ○ if it is slight, △ if it has a slightly bad odor, and × if it has a strong odor. Next, the water separation test results using the solid resols obtained in Examples 1 to 3 and Comparative Example 1.2 are shown in Table 2 below.
Shown below.

【table】

[Table] Therefore, as is clear from the above description, the method of the present invention does not involve defects such as gelation in any manufacturing process of solid resol, and does not require a special granulator for solidification. , and as is clear from Table 1 above, when mixing the mold and the sand grains and solid resol for that purpose,
In addition, the present invention provides a solid resol that minimizes the generation of bad odors in any process during casting manufacturing and does not worsen the working environment. In addition, since we have a step of concentration and dehydration under heating and reduced pressure, free phenol remaining in the obtained solid resol,
The present invention provides a method for producing a solid resol which has a small amount of residual starting materials such as ammonia and formalin, and therefore has an improved melting point and has extremely good resin properties. Furthermore, the temperature of the reaction system on the surface of the solid resol is 5~5
Since the reaction is proceeding on the acidic side while being cooled to 30℃, the inside is kept in an unreacted state, and only the solid resol surface reacts and does not have stickiness, so when water is separated, Mechanical means can be applied, and therefore water can be separated more efficiently in a short time.The resulting solid resol has a low water content and is easy to handle, exhibiting extremely good properties, making it extremely practical for the shell mold method. We offer solid resols rich in

Claims (1)

[Claims] 1. A catalyst consisting of at least phenols, aldehydes, and a nitrogen-containing compound is blended, and the mixture is heated to undergo a condensation reaction to obtain an A-stage initial condensation product, followed by dehydration under reduced pressure. Warm water is added to the obtained concentrate, and the temperature is maintained at a predetermined temperature range, and a cellulose compound or an aqueous polymer compound is added to granulate it.Then, the reaction system is cooled to 5 to 30°C, and then the reaction system is Add an acidic substance to the reaction system and
The granulated product is maintained at an acidic pH of 1.0 to 3.0, and only the surface of the granulated product gels, and the interior is reacted to the state of a B-stage concentrate, and then washed with water or neutralized by adding an alkaline substance. , water separation,
A method for producing a solid resol type phenolic resin, characterized in that it is obtained by drying. 2 The addition ratio of the above hot water is 100% of the above phenols.
The method for producing a solid resol type phenolic resin according to claim 1, wherein the amount is 20 to 400 parts by weight. 3. The solid resol type according to claim 1 or 2, wherein the addition ratio of the cellulose compound or the aqueous polymer compound is 0.01 to 10.0 parts by weight based on 100 parts by weight of the phenol. Method for producing phenolic resin.