JP2003137948A - Method for producing resol resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a resol resin, which is a method for producing a resol resin substantially not containing unreacted monomers or containing an extremely small amount of unreacted monomers and with which environmental loading is reduced and physical properties of excellent curability and heat resistance can be obtained while keeping water solubility. SOLUTION: This method for producing a water-soluble resol resin comprises reacting an aldehyde with phenol in the ratio of [aldehyde]/[phenol] of 0.3-0.6 (molar ratio) to give a novolak resin (A) and reacting the novolak resin (A) with an aldehyde.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a resole resin in which the amount of residual phenol (residual unreacted monomer) is reduced.

[0002]

2. Description of the Related Art Phenolic resin has excellent heat resistance,
Utilizing adhesiveness, mechanical properties, electrical properties, price advantage, etc., molding materials of various base materials, binders for friction materials, binders for abrasives, adhesives for wood, binders for laminated materials, for molds Widely used as a binder, coating agent, epoxy resin curing agent, etc. As the phenol resin for reacting phenols with aldehydes, an alkali resol resin using a hydroxide of an alkali metal or an alkaline earth metal as a catalyst, an ammonia resol resin using ammonia, or a high ortho type resin using a divalent metal salt is used. Novolak resins using acids as catalysts are generally known. In recent years, unreacted phenols in phenolic resin from the viewpoint of atmospheric environment protection or human body environment protection,
There has been a demand for reducing pollution due to volatilization of aldehydes or mononuclear components. With the above novolak resin, a product having an unreacted monomer content of 0.1% or less can be produced.

However, in the case of the resol resin, the situation is different from this, and since it has thermosetting property, it is difficult to remove the phenol monomer at high temperature. Further, it has been attempted to extract the unreacted monomers and the mononuclear component with a solvent, but there are many problems such as the method of treating the solvent used at that time. Furthermore, reduction of monomer has also been studied by selecting reaction conditions. Therefore, under certain conditions,
For example, it is possible to reduce the amount of phenolic monomers by reacting under a condition where the molar ratio of phenols to aldehydes is 2.5 or more and a relatively large amount of catalyst is used. Even in this case, a large amount of unreacted aldehydes often remains, and it is difficult to obtain a product in a practical range except for some uses. Further, not only unreacted monomers but also mononuclear components in which aldehydes react with phenols are present in the resin in a large amount, and therefore volatilize during processing of the phenol resin to pollute the environment. To avoid these, phenols such as bisphenol A, bisphenol F,
It is also possible to obtain a phenol resin containing substantially no phenol monomer by using a binuclear body such as bisphenol S. However, it is difficult to obtain a water-soluble resin using these phenol dimers, and it is necessary to dissolve them in alcohols and ketones, and they have been put to practical use only in limited applications such as paints. In many cases.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a resole resin, which is substantially free of unreacted monomers or can be greatly reduced in producing the resole resin. Moreover, it is possible to maintain water solubility like conventional resole resins, and it is possible to obtain resole resins with a wider range of application in various product forms, and the products not only reduce the environmental load, It is to find a method for producing a resole resin capable of significantly improving curability and heat resistance and obtaining excellent physical properties.

[0005]

Means for Solving the Problems The present inventor has conducted extensive studies as a method for producing a resole resin, which substantially does not contain unreacted monomers or significantly reduces unreacted monomers. Using a specific novolak resin with controlled amount and molecular weight as a part or all of the raw material of phenol, unreacted monomer is reduced by reacting with aldehydes, and it was found that a resole resin with excellent physical properties can be obtained. The invention has been completed.

That is, according to the present invention, aldehydes and phenol are represented by [aldehydes] / [phenols] =
Provided is a method for producing a water-soluble resol resin, which comprises reacting a novolak resin reacted with an aldehyde at a ratio of 0.3 to 0.6 [molar ratio].

Further, in the present invention, aldehydes and phenol are represented by [aldehydes] / [phenols] = 0.3
The novolak resin (A) obtained by reacting at a ratio of ˜0.6 [molar ratio] is reacted with aldehydes and phenol, and the residual amount of phenol is 5% by weight or less of the obtained resole resin. A method for producing a resol resin is also provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a resole resin of the present invention is a method of reacting the novolak resin (A) with an aldehyde in the presence of a catalyst. The novolak resin (A) can be obtained by reacting phenols with aldehydes. At that time, the one in which the content and molecular weight of the unreacted phenols remaining in the resin are controlled is used.

The above specific novolac resin is, for example,
It can be manufactured through the following steps. Phenols,
Charge aldehydes and acid as a catalyst,
Allow to react for ~ 5 hours. After that, the unreacted phenol remaining in the novolac resin is removed at a temperature of 180 to 230 ° C. through normal pressure dehydration and reduced pressure dehydration steps. At that time, the content of the above-mentioned residual unreacted phenol monomer in the novolac resin is preferably as low as possible, and most preferably removed up to 0%, but substantially 1.0% by weight or less is preferable. , 0.1% by weight or less is more preferable. Further, it is particularly preferable to reduce the amount to about 0.01% by weight. Further, the reaction ratio of phenols and formaldehyde is preferably [formaldehyde] / [phenols] = 0.3 to 0.6 [molar ratio]. The production is possible even if the molar ratio is less than 0.3, but the yield is deteriorated as the molar ratio decreases, which is not economically preferable. On the other hand, if it exceeds 0.6, it becomes difficult to adjust the molecular weight to an appropriate value for use in the present invention, which is not preferable.

The phenols used as the raw material are not particularly limited, and include, for example, phenol, alkylphenols such as cresol, xylenol, ethylphenol, butylphenol and octylphenol, polyhydric phenols such as resorcinol and catechol, and halogens. Phenol, phenylphenol, aminophenol and the like. In addition, these phenols are not limited to one kind in use, and two or more kinds can be used in combination. In order to obtain a water-soluble resol resin as a product here, resorcin and a usual phenol monomer are preferable, but in order to obtain an inexpensive product, a phenol monomer is preferable.

As the aldehydes of the present invention, formaldehyde, paraformaldehyde, formaldehyde such as trioxane, acetaldehyde, etc., which are commonly used in the production of phenol resins, are effective, and urotropin can also be used.

Acids used as a catalyst in the present invention include:
Acids commonly used in the production of novolac resins can be used, for example, oxalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, paratoluenesulfonic acid, phenolsulfonic acid, or zinc acetate, octyl which is a catalyst for high ortho novolac resins. Zinc acid or the like is used.

As the novolak resin used in the present invention, a so-called modified novolak resin obtained by reacting phenol with, for example, an epoxy resin or a triazine at an arbitrary ratio in the process of synthesizing the novolak resin can be used.
When the novolac resin modified with these is used as a raw material in the production of the resole resin, it is possible to impart water resistance and heat resistance to the resole resin produced by the method of the present invention.

The method for producing a resol resin using the above novolak resin as a raw material is provided by the following method.

1. As a method for producing a resol resin that does not substantially include a mononuclear component having 1 to 3 phenol monomers or methylol groups bonded to a phenol nucleus, an aldehyde, an alkali metal catalyst, and an alkaline earth are prepared using only the above novolak resin as a raw material. It can be obtained by reacting with a metal oxide, amines, ammonia, zinc acetate or the like. These catalysts may be reacted in one kind or in combination of two kinds. Further, for the purpose of neutralizing the catalyst, sulfuric acid, hydrochloric acid, phosphoric acid, paratoluenesulfonic acid, etc. may be used.

2. In order to obtain a resin in which the amount of unreacted monomer and mononuclear component is less than that of a conventional resole resin, the low molecular weight novolak resin and the phenol monomer are used in combination, and the reaction is performed using an aldehyde and the same catalyst as above. Just do it.

The ratio of the novolak resin to the aldehyde in the production of the resole resin of the present invention is [aldehyde] / aldehyde as the bond molar ratio of the resin measured by C-13 NMR.
[Novolak resin] is 0.5 from the viewpoint that unreacted novolac resin component does not remain and physical properties such as curability are improved.
The above is preferable, and 4.0 or less is preferable from the viewpoint that unreacted formaldehyde does not remain and it is preferable in terms of environmental measures. Furthermore, [aldehyde] / [novolak resin] = 1.
0 to 2.5 (molar ratio) is particularly preferable.

The amount of alkalis or alkali metals used as a catalyst is preferably 0.01 times or more moles of the catalyst with respect to the total number of moles of the novolak resin or the novolak resin and phenol used as a raw material, from the viewpoint that the reaction proceeds smoothly. Further, the molar ratio is preferably 1.0 times or less because the reaction can be easily controlled, the storage stability of the product is not deteriorated by the catalyst, or the obtained resin does not become brittle.

Examples of the method for producing the phenolic resin of the present invention include the following methods. First, as a method for producing the raw material novolac resin, phenol and 37%
Oxalic acid was added as a reaction catalyst to a mixture of formaldehyde aqueous solution having a concentration, and the temperature in the reaction system was set to 100 ° C.
After reacting for 5 hours, distillation was carried out under atmospheric pressure up to 200 ° C., and further vacuum distillation was carried out, and the amount of residual phenol in the resulting novolak resin was 1.0 wt.% Or less, preferably 0.1.
% Or less of novolak resin (A) is obtained.

Next, the novolak resin (A) obtained in the above reaction and a 37% strength formaldehyde aqueous solution were mixed with [aldehydes] / [phenols] = 0.3 to 0.6.
As a catalyst, 4 was added to the mixture mixed at a ratio of [molar ratio].
Sodium hydroxide having a concentration of 8% was added, and the mixture was reacted at a temperature of 50 to 80 ° C. for 1 to 5 hours, and the amount of residual phenol in the obtained resole resin was 1.0% by weight or less based on the resin.
Preferably, 0.1% or less of the resole resin (B1) is obtained.

Further, phenol and novolac resin (A)
As a method for obtaining a resole resin in which the residual amount of phenol in the obtained resole resin is 5% by weight or less, the novolak resin (A) obtained by the above reaction, phenol and 37% 48% sodium hydroxide was added to a mixture of formaldehyde aqueous solution having a concentration and reacted at a temperature of 50 to 80 ° C. for 1 to 5 hours, and the amount of residual phenol in the obtained resole resin was 5% by weight or less, preferably 3% by weight. It is possible to obtain a resole resin (B2) having a content of not more than%.

As the form of the resol type resin obtained by the above-mentioned production method, the following various types can be produced. 1. Resol resin aqueous solution: the one obtained by the above reaction. 2. Resol resin solution: Resol resin solution obtained by the above reaction, after removing water from the resol resins (B1) and (B2), and then dissolved in a solvent such as alcohols such as methanol, ketone ethers such as methyl ethyl ketone and the like. Is easily obtained. 3. Water-dispersible resin: When a novolac resin (A) and an aldehyde are reacted with each other, or a novolac resin (A), an aldehyde and a phenol are reacted in the presence of a catalyst, for example, dispersion of a phenol resin such as polyvinyl alcohol. If a dispersant suitable for is used, a water-dispersed resol resin can be obtained. 4. Solid resin: When novolak resin (A) and aldehydes are reacted with each other, or when novolac resin (A), aldehydes and phenol are reacted in the presence of a catalyst, respectively, a high molecular weight is obtained by using ammonia or hexamethylenetetramine as a catalyst. It is possible to remove water and solvent to obtain a solid form, and it is easy to obtain a crushed product. In particular, in this case, the conventional method had a large amount of residual phenol and it was difficult to raise the melting point.However, according to this method, the residual phenol is very small, a resin having a high melting point is obtained, and blocking after pulverization occurs. A small amount of high molecular weight resole resin powder is obtained. 5. Powder resin: The product reacted as described above can be directly powderized by a spray drying method, and in this case also, a high molecular weight resol powder substantially free of residual phenol or mononuclear body can be obtained.

[0023]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. In the examples, “part” and “%” are parts by weight and% by weight, respectively. Further, the number average molecular weight means a molecular weight converted into polystyrene having a known molecular weight by GPC (gel permeation chromatography). The residual phenol was measured by GPC when the residual phenol was 1% or more, and by gas chromatography when the residual phenol was less than 1%. The present invention is not limited to these examples.

Example 1 A 2 liter four-necked flask was equipped with a stirrer and a thermometer, and 941 g of phenol and 40.3 g of 37.2% formalin were added.
Was charged and 8.82 g of oxalic acid dihydrate was added, the temperature was raised to the reflux temperature (100 ° C.), and 37.2% formalin 36 was added.
2.9 g was added dropwise over 1 hour. After reacting at reflux temperature for 3 hours, distillation was started and the temperature was raised to 180 ° C. After that, the temperature was raised to 220 ° C., and vacuum distillation was carried out at 50 torr (6.65 kPa) for 1 hour, the softening point of B & R method was 75 ° C., and the amount of free phenol measured by gas chromatography was 0.3.
%, A novolac resin (Ia) having a number average molecular weight of 780 by GPC was obtained. 80% solid content of the novolac resin
Novolac resin (I
The methanol solution of a) was tested as follows. Then, the methanol solution 13 of the novolak resin (Ia) obtained above
1.3g and 37% formalin 60.8g were mixed well, and 48% sodium hydroxide 10.5g was added to this, 70
The temperature was raised to ℃. After reacting at 70 ° C. for 4 hours, the mixture was cooled to obtain a resol resin (IIa) aqueous solution. 135 of this resin
The nonvolatile content at 50 ° C was 50.8%, and the gel time at 150 ° C was 68 seconds. Miscibility of this resin with water (Measurement method;
The added amount which causes turbidity when g is added is expressed in%.
The same applies hereinafter) was 320%, and free phenol measured by GPC was below the detection limit. The amount of free phenol measured by gas chromatography is 0.
It was 02%. The bond molar ratio of this resin measured by C13-NMR was 1.49.

Example 2 A 2-liter four-necked flask was equipped with a stirrer and a thermometer, and 941 g of phenol and 40.3 g of 37.2% formalin were added.
Was added and 8.82 g of oxalic acid dihydrate was added, the temperature was raised to 100 ° C. under reflux, and 202.7 g of 37% formalin was added.
Was added dropwise over 1 hour. After reacting at reflux temperature for 5 hours, distillation was started and the temperature was raised to 180 ° C. Then increase the temperature to 2
The temperature is raised to 20 ° C., and vacuum distillation is performed at 50 torr (6.65 kPas) for 1 hour to obtain a softening point of 45 ° C. by the ring and ball method (B & R method)
The amount of residual phenol measured by gas chromatography is 0.1%, the number average molecular weight by GPC is 610, and C1
A novolak resin (Ib) having a bond molar ratio of 0.75 determined by 3-NMR was obtained. The novolac resin (Ib)
Was diluted with methanol to a solid content of 80% and tested. Methanol solution 1 of the novolak resin (Ib) obtained above
Mix well 31.3g and 37% formalin 36.5g,
To this, add 10 g of 48% sodium hydroxide,
It was heated up to. After reacting at 70 ° C. for 4 hours, it was cooled to room temperature to obtain a resol resin (IIb) aqueous solution. The resin has a viscosity of 1020 mPa · s (25 ° C.), a gelling time at 150 ° C. of 110 seconds, and a nonvolatile content at 135 ° C. of 68.
%, Miscibility with water was 250%. The content of residual phenol measured by GPC was below the detection limit.
The free phenol measured by C (gas chromatography) was 0.01%. The bond molar ratio of this resin measured by C-13 NMR was 1.20.

Example 3 131.3 g of the methanol solution of the novolak resin (Ib) obtained in Example 2 and 36.5 g of 37% formalin were thoroughly mixed, and 3.15 g of 25% aqueous ammonia was added thereto. Thereafter, the temperature was raised to 75 ° C. and maintained for 3 hours, and then vacuum distillation was continued by vacuum distillation until the resin temperature reached 85 ° C. 105 g of methanol was gradually added into the flask to obtain a methanol solution of resol resin (IIc). 13 of this resin
Nonvolatile matter measured at 5 ℃ is 50.8%, 150 ℃
Gelation time at 92 seconds and viscosity at 37 mPa · s (25
℃). The residual phenol measured by the GC method was 0.01%. The bond molar ratio determined by C-13 NMR was 1.18.

Example 4 131.3 g of the novolak resin (Ib) obtained in Example 2 in methanol and 36.5 g of 37% formalin (0.1%).
(45 mol) was thoroughly mixed, 0.5 g of zinc acetate was added thereto, the temperature was raised to 100 ° C. and maintained for 3 hours, and then water was removed by vacuum distillation until the temperature in the flask reached 90 ° C., 105 g of methanol was added to obtain an alcohol solution of the resol resin (IId). The nonvolatile content of this resin measured at 135 ° C. was 50%, and the gel time at 150 ° C. was 5 minutes and 20 seconds. The amount of free phenol measured by the GC method was 0.01%. The pH of this resin was 4.6. The bond molar ratio determined by C13 NMR was 1.19.

Example 5 131.3 g of a methanol solution of the novolak resin (Ib) obtained in Example 2, 94.1 g of phenol and 182.4 g (2.25 mol) of 37% formalin were mixed, and 4 parts thereof were mixed.
After adding 15.93 g (0.14 mol) of 8% potassium hydroxide solution and reacting at 80 ° C. for 4 hours, the viscosity was 1100 mP.
After dehydration under reduced pressure until the temperature became a · s (25 ° C.), the mixture was cooled to obtain a resole resin (IIe) aqueous solution. This resol resin (I
Ie) The non-volatile content of the aqueous solution measured at 135 ° C. is 68%,
Gelation time at 150 ° C 69 seconds, miscibility with water 19
It was 0%. The residual phenol determined by the GPC method was 3.5%. The bond molar ratio determined by C-13 NMR was 1.45.

Example 6 131.3 g of a methanol solution of the novolak resin (Ib) obtained in Example 2 and 36.5 g of 37% formalin (0.1%).
45 mol) was mixed, 5 g of 25% aqueous ammonia was added thereto, the temperature was raised to 70 ° C., and then the mixture was kept for 3 hours. Distillation under reduced pressure was continued until the water content of the reaction product reached 0.8%, and the solid resole resin (I
If) was obtained. The melting point (MP) of this resin is 78 ° C, 15
The gelation time at 0 ° C. was 80 seconds. The residual phenol amount determined by the GC method was 0.01%. C-
The bond molar ratio determined by 13 NMR was 1.21.

Comparative Example 1 94.1 g of phenol and 3 in a 1 liter 4-necked flask
After thoroughly mixing 121.6 g of 7% formalin and adding 4.71 g of 48% sodium hydroxide solution and reacting at 80 ° C. for 3 hours, the viscosity at 25 ° C. was 650 mPa.
After adjusting to s, it was cooled to 25 ° C. to obtain a resole resin (IIg). The nonvolatile content of this resin is 73%, 1
Gelation time at 50 ° C is 85 seconds, miscibility with water is 280
%. The residual phenol of this resin measured by GPC was 8.1%. The bond molar ratio determined by C-13 NMR was 1.39.

Comparative Example 2 A 2-liter four-necked flask was equipped with a stirrer and a thermometer, charged with 941 g (10 mol) of phenol and 40.5 g (0.5 mol) of 37% formalin, and oxalic acid dihydrate of 8.82.
g (0.07 mol) was added, the temperature was raised to the reflux temperature (100 ° C.), and 527.0 g (6.5 mol) of 37% formalin was added dropwise over 1 hour. After reacting at reflux temperature for 3 hours, distillation was started and the temperature was raised to 180 ° C. Then 50to
Distillation under reduced pressure for 1 hour at rr (6.65 kPa), softening point 88 ° C. by B & R method, amount of free phenol 2.1% measured by gas chromatography, number average molecular weight 910 by GPC, and binding determined by C13-NMR The molar ratio is 0.
A novolak resin (Ih) of 76 was obtained. As in Example 1, the solid content was diluted to 80% with methanol. 131 g of a methanol solution of the novolak resin (Ih) obtained above
35.7g (0.44mol) of 37% formalin and 10% (0.12g) of 48% sodium hydroxide.
Mol) was added and the temperature was raised to 70 ° C. After reacting at 70 ° C. for 3 hours, it was cooled to 25 ° C. to obtain a resole resin (IIh) aqueous solution. 135 of this resol resin (IIh) aqueous solution
Non-volatile content at 5 ℃ is 59.0%, gelation time is 110
Second, free phenol measured by GC (gas chromatography) was 0.5%. The miscibility with water was 20%. The bond molar ratio in C-13 NMR is 1.
It was 18.

Comparative Example 3 105 g of the novolak resin (IIb) obtained in Example 2
And 12.1 g of 37% formalin are mixed well, and 4
10 g of 8% sodium hydroxide was added, and the temperature was raised to 70 ° C. After reacting at 70 ° C. for 4 hours, it was cooled to 25 ° C. to obtain a resol resin (IIi) aqueous solution. 1 of this resol resin
Non-volatile content at 35 ℃ 82%, gelation time is 76
Sec., Miscibility with water was 10%, and residual phenol measured by GC (gas chromatography) was 0.02%. The bond molar ratio of this resin measured by C-13 NMR was 0.91.

Comparative Example 4 94.1 g of phenol and 3 in a one-liter four-necked flask
After thoroughly mixing 97.3 g of 7% formalin and adding 4.71 g of 25% aqueous ammonia solution and reacting at 80 ° C. for 3 hours, the mixture was dehydrated under reduced pressure until the water content was 1% or less, and taken out as it was. The gelling time of the obtained resol resin (IIj) was 115 seconds, the melting point was 65 ° C., and the residual phenol amount measured by GPC was 8.2%. The bond molar ratio determined by C-13 NMR was 1.05. Tables 1 to 3 show a summary of the property values of the resins obtained above.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

In Examples 1 and 2 and Comparative Example 1, the miscibility with water was the same as the conventional one and the residual phenol was extremely small, and in Example 4 the present invention was effective at pH 4 or higher. Indicates. In Comparative Examples 2 and 3, the molecular weight of the novolac used was high, so that water miscibility was not obtained, and Example 5 shows that even when the novolac resin of the present invention and phenol are used in combination, residual phenol is less than that of the conventional product. Example 6
And Comparative Example 4 show that the resin produced by the method of the present invention has a high melting point and the solidification when pulverized is small.

Application Examples Next, methods and results for evaluating the physical properties of the resins obtained in the above Examples and Comparative Examples are shown below.

(1) Yield measurement of resin: Resin concentration 5
Diluted with methanol to 0% and filter paper (Toyo Roshi No. 65)
It is impregnated with 60% of resin solid content / 40% of filter paper weight, left at room temperature for 12 hours, dried at 80 ° C. for 1 hour, and then weighed. After that, 150 ℃, 200 ℃, 2
The sample was left in a drying oven at 50 ° C. for 30 minutes and weighed. The yield was measured from the weight before and after drying. Table 4 shows the obtained results.
Shown in.

(2) Measurement of curing rate; resin concentration 50%
Was diluted with methanol and impregnated with filter paper (Toyo Filter Paper No. 65) to a resin solid content of 60% / filter paper weight of 40%,
After leaving at room temperature for 1 hour, preliminary drying is performed at 90 ° C. At this time, the pre-drying condition is important to obtain the optimum curing condition, which is a measure of the goodness or badness of the drying property of the resin. After drying under optimum pre-drying conditions, the curing rate was measured at 120 ° C. using a curast meter (Curlastometer V type, manufactured by Nigo Shoji Co., Ltd.), and the results were compared. The curing speed was obtained from the obtained torque curve. That is, the torque value at 90% curing time of the maximum torque minus the torque at 10% curing time is shown as the slope divided by that time. The results obtained are shown in Table 5.

(3) Measurement of heating loss: 180 ° C. of resin
After curing for 4 hours, the particles were sized to a size of 75 μm to 106 μm, and the weight loss on heating was measured under the conditions of an atmosphere in air and a heating rate of 10 ° C./min. The obtained results are shown in Table 6.

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

The resole resin obtained by the production method of the present invention can be obtained not only with residual phenol but also with substantially no mononuclear component of the resole resin, and the volatile matter even at a high temperature of 250 ° C. It is seen that the yield is very small and the yield is improved by about 10% as compared with the conventional product. Furthermore, due to the fact that it does not contain low molecular weight substances, the curing speed is significantly faster than conventional products, and workability can be improved. It should be further noted that the resole resin of the present invention exhibits a dramatically low heating loss as compared with those produced by the conventional technique. INDUSTRIAL APPLICABILITY The present invention can be applied to fields in which these properties can be utilized, that is, various uses of phenolic resins such as friction materials, abrasive cloth paper, grinding wheels, various impregnation chemical treatments, wood processing, refractory materials, castings, heat insulating materials, paints and FRP Is.

[0046]

EFFECTS OF THE INVENTION The resole type phenol resin of the present invention is a low free phenol, has a low volatile content, is environmentally friendly, has a high curing speed and excellent workability, and has a very high heat resistance of the cured product. It has an epoch-making characteristic that has never existed.

Claims (12)

[Claims] 1. A novolak resin (A) obtained by reacting an aldehyde and a phenol at a ratio of [aldehyde] / [phenol] = 0.3 to 0.6 [molar ratio] and the aldehyde. A method for producing a water-soluble resol resin, which comprises reacting with 2. The production method according to claim 1, wherein the residual phenol amount of the novolac resin (A) is 1% by weight or less. 3. The production method according to claim 1, wherein the novolak resin (A) has a number average molecular weight of 500 to 800 as measured by GPC. 4. The ratio of the bond between the novolak resin (A) obtained by C-13NMR and the aldehyde in the resole resin is [aldehyde] / [novolak resin] =
The production method according to claim 1, which is 1.0 to 4.0 (molar ratio). 5. The method for producing a resol resin according to claim 4, wherein the novolac resin (A) and the aldehyde are reacted in the presence of a catalyst under the conditions of pH 4 to 12. 6. The production method according to claim 5, wherein the residual phenol content of the water-soluble resol resin is 1% by weight or less. 7. A novolak resin (A) obtained by reacting an aldehyde and a phenol at a ratio of [aldehyde] / [phenol] = 0.3 to 0.6 [molar ratio] and an aldehyde A method for producing a resol resin, wherein a phenol residual amount is 5% by weight or less of the obtained resol resin by reacting a phenol with a phenol. 8. The production method according to claim 7, wherein the residual phenol amount of the novolac resin (A) is 1% by weight or less. 9. The production method according to claim 7, wherein the number average molecular weight of the novolac resin (A) measured by GPC is 500 to 800. 10. The ratio of the bond between the novolak resin (A) obtained by C-13NMR and the aldehyde in the resole resin is [aldehyde] / [novolak resin].
The manufacturing method according to claim 7, wherein: 1.0 to 4.0 (molar ratio). 11. The method for producing a resol resin according to claim 10, wherein the novolac resin (A) and the aldehyde are reacted in the presence of a catalyst under the conditions of pH 4 to 12. 12. The method according to claim 10, wherein the residual phenol content of the water-soluble resol resin is 1% by weight or less.