JPS584063B2 - Hardening agent solution of resol type phenolic resin for hot box - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acidic curing agent solution for use in resol-type phenolic resins such as addition condensation resins of phenols and formaldehyde, and cocondensation resins of phenols, fatty acid esters, and formaldehyde.

A hot box method is widely known, in which silica sand and an acidic curing agent solution are blended with the above resin, and then heated to accelerate curing to create a mold.

When silica sand grains are coated with a resol-type phenolic resin using a conventionally used acidic curing agent solution, and then the coated sand is blown into a mold at 200 to 260°C and cured, the curing speed is slow. In order to increase the curing speed, a method has been used in which the amount of acidic curing agent solution added is increased.

However, according to this method, the coated sand hardens during storage, resulting in a significant decrease in strength, which is disadvantageous in that the pot life is short.

For this reason, there has been a desire for a curing agent solution that has a fast curing speed in a heating mold and can provide a sufficiently long pot life.

The present invention provides a curing agent solution that improves the curing rate without changing the composition of conventionally used resol type phenolic resins for hot boxes and without shortening the pot life.

As a result of various studies aimed at improving the above drawbacks, we found that xylene sulfonic acid and/or phenolsulfonic acid 30~
By using a hardening agent solution in which 3 to 25 parts by weight of urea and/or urea derivatives are dissolved in 100 parts by weight of a hardening agent solution consisting of 70 parts by weight of alcohol and 70 to 30 parts by weight of a mixture of alcohol and water. It has been found that the above drawbacks can be improved.

The xylene sulfonic acid and phenolsulfonic acid used in the present invention may contain 20 parts or less of sulfuric acid as a subcomponent based on 100 parts by weight of the main component (hereinafter referred to as "parts by weight").

Moreover, alcohols such as methanol and ethanol can be used as a solvent for dissolving these.

When using phenolsulfonic acid containing sulfuric acid, a mixed solvent of water and alcohol can be used as the solvent.

The amount of xylene sulfonic acid and/or phenolsulfonic acid in 100 parts of the curing agent solution before adding ureas is 30 to 70 parts, preferably 40 to 60 parts.

When the amount is more than 70 parts, ureas tend to precipitate.

When the amount is less than 30 parts, a large amount of curing agent solution is required.

The amount of sulfuric acid, which is a subcomponent, is 20 parts per 100 parts of the main component.
If the amount is less than 30%, it can be used without deteriorating the surface stability of the mold.

The amount of urea added is 3 to 25 parts per 100 parts of hardening agent solution.
Part can be used.

The amount is preferably 3 to 20 parts.

If the amount added is more than 25 parts, the curing speed, which is the objective of the present invention, will be slow.

If the amount is less than 3 parts, the effect on quick curing will be small and the pot life will not be long enough.

As urea derivatives that can be used in the present invention, polyhydric alcohol-modified ureas such as thiourea, ethylene urea, and propylene urea are used.

The present invention will be explained below based on examples.

Table 1 shows the synthesis method of resins A and B used in the examples and the composition of the curing agent solution before adding ureas.

Resin A In a four-loaf flask equipped with a thermometer, condenser, and stirrer,
Phenol 188g, formaldehyde 210g, 20
% sodium hydroxide lagoon aqueous solution was added, the temperature was raised while stirring, the reaction was carried out at 80°C for 2 hours, and the mixture was concentrated under reduced pressure to obtain a resol type phenol resin of 100CP730°C.

Resin B: 188 g of phenol, 56 g of dehydrated castor oil, 4.4 g of 20% p-toluenesulfonic acid, 100 g of methyl ethyl ketone, in a four-bottle flask equipped with a thermometer, condenser, and stirrer.
was added, the temperature was raised with stirring, the reaction was carried out at 90°C, and the mixture was concentrated under reduced pressure to obtain 240 g of a phenol-dehydrated castor oil adduct with a weight of 5.0P/30°C.

Next, 282 g of phenol, 225 g of 80% paraform
After adding 150 g of methanol and 20% NaOH Log, the mixture was reacted for 8 hours at 60°C and concentrated under reduced pressure.
A phenolic resin having a temperature of P/30°C was obtained.

Examples 1 to 3 Resin A and urea were added in amounts of 0 to 100 parts of acidic curing agent solution a.
A test piece was prepared using 30 parts of the solution added and dissolved under the conditions described above.

The measurement results of bending strength are shown in Table 2.

Note that Examples 1 and 3 are comparative examples.

Examples 4 to 6 Test pieces were prepared in the same manner as in Examples 1 to 3, except that curing agent solution b was used instead of a, and the results of measuring the bending strength are shown in Table 3.

In addition, Examples 4 and 6 are comparative examples.

Examples 7 to 9 Bending strength was measured in the same manner as in Examples 1 to 5 using 0 to 25 parts of resin B and ethylene urea added and dissolved to 00 parts of curing agent solution CI, and the results are shown in Table 4. Shown below.

Note that Example 7 is a control example. To prepare a test piece, 3000 g of Sanei No. 6 silica sand was placed in a marla, then 10.5 g of an acidic curing agent solution was added to coat the silica sand grains, and then 105 g of phenol resin was added and marling was performed for 1 minute to obtain a wet mixture.

The obtained wet mixture was heated to 230° C., sucked into a 2-inch mold at a pressure of 4 kg/art, and held in the mold for 10 to 30 seconds to prepare a test piece.

The bending strength was measured using a 200 kg Amsler tester 30 seconds after the test piece was removed from the mold.

As described above, the present invention provides an acidic curing agent solution that has a fast curing speed and a long pot life.

Claims (1)

[Claims] 1 Hardening agent solution 100 consisting of 30 to 70 parts by weight of xylene sulfonic acid and/or phenolsulfonic acid and 70 to 30 parts by weight of alcohol or a mixture of alcohol and water
A curing agent solution of a resol type phenolic resin for a hot box, characterized in that 3 to 25 parts by weight of urea and/or a urea derivative are dissolved therein.