JPH0611776B2 - Method for producing solid resole type phenol resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a shell mode, a grindstone, a brake lining,
The present invention relates to a method for producing a solid resol-type phenol resin used as a binder or molding material for various organic or inorganic materials such as paper, pulp, and felt.

(Prior art and its problems) Solid resol type phenol resin which is a solid substance of resol type phenol resin (hereinafter, abbreviated as solid resol)
Was produced by a method in which phenols and aldehydes were usually subjected to a resolization reaction in the presence of an alkaline catalyst in a molar ratio (aldehydes / phenols) of 1 to 3 and then dehydrated and concentrated. .

In such a method for producing a solid resol, it is difficult to stably dehydrate and concentrate the reaction liquid produced by the resolization reaction, and in the dehydration-concentration step, stirring may be impossible or gelation may occur due to a rapid increase in viscosity. It was difficult to obtain a solid resol of stable quality, because the solidification was insufficient due to insufficient resolization reaction. Moreover, since this solid resol has a low softening point, blocking (caking) is likely to occur during storage, and there is a problem in handleability. It also has a problem in long-term storage stability.

Thus, there have been various technical problems in the production of solid resol.

(Means for Solving Problems) The inventors of the present invention have achieved the present invention as a result of intensive studies to solve the problems of the solid resol as described above.

That is, in the method for producing a solid resol type phenolic resin of the present invention, aldehydes are 1.1 to 1 mol per mol of phenols.
It is characterized in that after performing the novolak-forming reaction in an acidity of 2.5 mol ratio, an alkaline catalyst is added and the resol-forming reaction is carried out at pH 7.5 to 9.

The present invention will be described in more detail.

When phenols and aldehydes are reacted in an acidic manner, a novolac type resin in which molecules mainly grow linearly is produced, but in the novolac reaction, the reaction of 1 mole of aldehyde to 1 mole of phenol is the limit.

Therefore, when the process proceeds to the next alkaline resolization reaction, the unreacted aldehydes are added to the already formed linear novolac resin and converted into a so-called resol type resin.

That is, in the present invention, a linear condensate is first produced by a novolac reaction, and then a cross-linking point is imparted by a resolization reaction. Therefore, the molecular weight and the cross-link density are determined by the novolak reaction and the resol reaction, respectively. , Can be adjusted independently.

In the conventional technique, since the resolization reaction is carried out using an alkali catalyst from the initial stage of the reaction, the crosslink density increases with the increase of the molecular weight as the reaction progresses, so that it is an essential requirement for the solid resol to "melt easily by heating" Say
The resolization reaction has to be stopped within the range of the crosslink density required to maintain the properties, and the resulting solid resol has a low molecular weight and thus a low softening point and is easily blocked.

In order to make the molecular weight as high as possible, the reaction density has to be controlled within the limit of the cross-linking density, and due to its difficulty, the uniformity of quality and the storage stability are lacking. Provoke. On the other hand, according to the method of the present invention, since the crosslink density can be appropriately adjusted despite the high molecular weight, the solid resol obtained by the method of the present invention can have a high softening point and is therefore difficult to block.

Furthermore, in the final step of the resolization reaction and the dehydration concentration step, the reaction rate does not become abnormally fast, so that the reaction control becomes easy, and a solid resol with stable quality and excellent long-term storage stability can be obtained. Can be done.

In the present invention, the pH during the novolak reaction is preferably 1.5 to 3.5. If the pH is less than 1.5, the rate of the novolak reaction is increased, and the reaction control becomes difficult, which is not preferable. In addition, the amount of the alkaline catalyst added during pH adjustment during the next resolization reaction increases, and the amount of salts produced increases, leading to a decrease in the physical properties of the solid resol, which is not preferable.

When the pH exceeds 3.5, the novolak-forming reaction rate becomes slow, and a partial crosslinking reaction also occurs, which diminishes the effect of the present invention.

The pH during the resolization reaction is important and must be in the range 7.5-9. If the pH is less than 7.5, the resolization reaction is slow and the reaction time is long, and solidification after dehydration and concentration is extremely difficult. If the pH exceeds 9, the reaction rate will be too fast and control of the reaction will be difficult, and a solid resol cannot be obtained stably.

In the present invention, the molar ratio of phenols to formaldehyde is 1.1 moles of aldehydes to 1 mole of phenols.
The range is from to 2.5 mol. When the molar ratio is less than 1.1, the crosslinking density is low, solidification of the resole becomes difficult, blocking is likely to occur even if solidification is forcibly solidified, the gel time becomes long, and the practicality is poor. If the molar ratio exceeds 2.5,
Crosslink density becomes too high.

Further, the aldehydes may be added all at once at the start of the novolak reaction, or may be added separately at the start of the novolak reaction and at the start of the resole reaction. However, in the case of divided addition, the amount of aldehyde added at the start of the novolak reaction is 1
0.7 mol or more is necessary with respect to mol. When the amount is less than 0.7 mol, unreacted phenols in the novolak reaction increase, and the amount of resole in the next resol reaction increases, which is not preferable.

The concentration of the reaction liquid is preferably 60 to 90% by weight as the total amount of phenols and aldehydes. If it is less than 60% by weight, the evaporation amount of water in the subsequent dehydration and concentration step increases,
Not only is it a loss of energy, but the dehydration and concentration step is lengthened and the condensation proceeds too much, which is not preferable. If it exceeds 90% by weight, the viscosity increases and it becomes difficult to control the resolization reaction. The concentration of the reaction solution is preferably adjusted by adding the concentration of aldehydes supplied to the reactor and the dilution water.

Phenols which can be used in the present invention include phenol, cresol, xylenol, resorcinol, catechol, hydroquinone and the like, but may be a mixture of two or more of them. As aldehydes,
Formalin, paraformaldehyde, glyoxal, trioxane and the like having various concentrations may be used, and a mixture of two or more thereof may be used.

As the acidic catalyst added during the novolak reaction, hydrochloric acid, sulfuric acid, formic acid, oxalic acid, paratoluenesulfonic acid, phenolsulfonic acid and the like can be used.

Examples of the alkaline catalyst used in the resolization reaction include caustic soda, caustic potash, calcium hydroxide, sodium carbonate, alkali metal or alkaline earth metal hydroxides or oxides, alkali metal carbonates and bicarbonates, and the like. Inorganic alkali compounds, various amines, ammonia water,
One or more organic alkali compounds such as hexamethylenetetramine are used.

Immediately after the resolization reaction, dehydration concentration is performed.

The dehydration concentration is usually carried out under reduced pressure of 5 to 50 Torr while heating by a known method such as thin film evaporation in a batch system or a continuous system until the water content becomes 1 to 2% by weight.

The evaporation temperature is about 35 to 40 ° C initially, but gradually rises as the dehydration progresses. Since the water content of the reaction solution correlates with the evaporation temperature, the water content of the reaction solution is
When the temperature of 80 to 90 ° C. corresponding to 2% by weight is reached, the dehydration concentration operation is stopped and immediately cooled.

The rapid cooling is carried out by a known method such as discharging to a moving steel belt or a vat cooled to 40 ° C. or lower after completion of the dehydration / concentration operation and putting it into a cooling chamber as a plate.

Since the rapidly cooled resol is solidified in a plate shape, it is crushed to a size of about 5 to 20 mm for easy handling. The crushing is performed by a conventionally known method using a yawer type crusher, a jaw crusher, or the like.

(Examples) Hereinafter, embodiments of the present invention will be specifically described with reference to Examples and Comparative Examples.

In the examples and comparative examples, all percentages are by weight unless otherwise specified.

Example 1 940 g of phenol and 1000 g of formalin having a formaldehyde concentration of 37% (aldehydes / phenols = 1.23)
Was placed in a reactor equipped with a thermometer, a reflux condenser, a stirrer, a heating and cooling jacket, and a vacuum concentrator, and the temperature was gently raised to avoid bumping while stirring. % Hydrochloric acid was added dropwise to adjust the pH to 2.5, and the temperature was raised to 100 ° C. After the temperature was raised, a novolak reaction was carried out for 2 hours while maintaining the temperature at 98 to 102 ° C. During this period, the pH of the reaction solution was always 2.5. Next, the temperature was lowered to 80 ° C and caustic soda with a concentration of 40% was slowly added dropwise to adjust the pH to 8.5.
Adjusted to. During the pH adjustment, the liquid temperature rises due to the heat of neutralization, so the heating amount was adjusted so that the liquid temperature did not exceed 90 ° C.

When the pH reached 8.5, the liquid temperature was maintained at 90 ° C and the resolization reaction was performed. The resolization reaction was terminated when the viscosity of the reaction solution measured at 40 ° C. reached 5.0 poise. Then, the pressure was set to 30 Torr and the heating medium temperature was set to 90 ° C. to perform dehydration concentration, and the dehydration concentration operation was stopped when the liquid temperature reached 80 ° C. After the completion of the dehydration concentration operation, the liquid was immediately discharged into a vat outside the system to form a plate having a thickness of about 10 m / m.
Then, the whole vat was put into a refrigerator and cooled to 30 ° C. or lower to be solidified. After the solidified resol was roughly broken with a hammer, it was coarsely crushed with a Nara type free crusher with the screen removed to obtain a small granular solid resol having a diameter of 5 to 10 m / m.

As shown in Table 1, the obtained solid resol had good softening point and good blocking resistance.

Example 2 Softening according to the physical properties shown in Table 1 was carried out under the same conditions as in Example 1 except that 1220 g of xylenol, 710 g of formalin having a formaldehyde concentration of 42% and 145 g of glyoxal (aldehydes / phenols = 1.24) were used. A solid resol having good points and good blocking resistance was obtained.

The resolization reaction was completed when the viscosity measured at 40 ° C. was 8.0 poise.

Example 3 Same as Example 1 except that formic acid was used as the acidic catalyst, and 40% concentration of sodium carbonate aqueous solution and 25% concentration of ammonia water were premixed at a weight ratio of 8 to 2 as the alkali catalyst. By operating under the conditions, a solid resol was obtained. As for the physical properties of the obtained solid resol, as shown in Table 1, both the softening point and the blocking resistance were good.

Comparative Example 1 A solid resol resin having the physical properties shown in Table 1 was obtained by operating under the same conditions as in Example 1 except that the acidic reaction was omitted, but blocking was apt to be a practical problem.

Comparative Example 2 A solid resol was obtained by operating under the same conditions as in Example 1 except that 810 gr of formalin having a formaldehyde concentration of 37% was used (aldehydes / phenols = 1.00), but blocking was likely to be a practical problem. .

Comparative Example 3 The same operation as in Example 1 was carried out except that the pH during the resolization reaction was 6.8. It does not solidify even after rapid concentration after vacuum concentration,
No solid resol could be produced.

Comparative Example 4 The procedure was carried out under the same conditions as in Example 1 except that the pH was 10 during the resolization reaction, but a sharp increase in the viscosity of the reaction solution occurred 45 minutes after the start of the resolization reaction, making reaction control difficult. At the end of dehydration and concentration, the fluidity of the reaction liquid was almost lost, and it was extremely difficult to remove it from the reactor.
It was virtually impossible to produce a solid resol.

(Remarks) Measurement conditions (1) Gel time and flow were measured according to the method of JIS K-6910.

(2) The softening point was measured by the method of JIS K-2531.

(3) Blocking resistance was measured by applying a load of 0.1 kg / cm ^{2 to} the sample in an atmosphere of 30 ° C. and a relative humidity of 75%, and measuring the number of days until blocking of the sample occurred.

(Effects of the Invention) As described above, the present invention is a method of producing a solid resol by first performing an acid novolak reaction and then performing an alkaline resol reaction, which results in quality stability which has been a problem in the past. The present invention provides a method for obtaining a product having excellent blocking resistance and long-term storage stability. The present invention significantly expands the demand and use of solid resole.

Claims (1)

[Claims] 1. A novolak reaction of phenols and aldehydes at a ratio of 1.1 to 2.5 moles of aldehydes to 1 mole of phenols and a pH of 1.5 to 3.5. Then, a method for producing a solid resol-type phenol resin, which comprises adding an alkaline catalyst to carry out a resolization reaction at a pH of 7.5 to 9.