JP2005232199A - Novolak type phenol resin for refractory binder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novolak type phenol resin for a refractory binder as a result of studies so as to solve various problems of the conventional novolak type phenol resin for the refractory binder and affording a refractory providing good working environment during handling and having excellent mechanical strength. <P>SOLUTION: The novolak type phenol resin for the refractory binder is characterized as follows. The novolak type phenol resin has (a) ≤1 wt.% content of unreacted phenols, (b) ≤10% content of binuclear components, (c) ≤5 dispersity of molecular weight distribution and (d) 300-1,000 number-average molecular weight. The novolak type phenol resin is obtained by reacting the phenols with aldehydes and phosphoric acids. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novolac type phenol resin for a refractory binder.

  In recent years, in converters, electric furnaces, ladles, etc., the amount of non-fired brick containing graphite using phenolic resin as a binder is increasing. As a phenol resin used as a binder for such a refractory, a liquid or powder phenol resin of novolac type and resol type is used alone or in combination.

In the case of a novolak type phenol resin, a typical example of the use of a phenol resin is that a powder resin containing hexamethylenetetramine is used together with a wetting agent such as ethylene glycol, glycerin or a modified alcohol, or a resol type liquid phenol resin. They are used in combination.
Further, a liquid resin obtained by dissolving a novolac type phenol resin in a solvent such as ethylene glycol in advance is often used in combination with hexamethylenetetramine at the time of kneading.
On the other hand, in the case of a resol type phenol resin, an aqueous solvent type liquid resin or a solvent type liquid resin using a solvent such as ethylene glycol is used alone, or these liquid resins are used in combination with a novolac type powder resin. (For example, refer nonpatent literature 1.).

  When a novolac type phenol resin is used as a binder, the required properties of the novolac type phenol resin include high fluidity during heating and low viscosity when dissolved in a solvent or liquid resin. The fluidity during heating is related to the mechanical strength of the refractory brick after drying, and when the fluidity is low, the coating on the surface of the refractory aggregate is insufficient and the adhesion between the refractory aggregates becomes insufficient, There is a problem that the mechanical strength is lowered. Further, regarding the viscosity when dissolved in a solvent or a liquid resin, if the viscosity becomes high, the coating on the refractory aggregate may be insufficient, and the mechanical strength after drying may similarly decrease.

Various proposals have heretofore been made for methods of obtaining novolak-type phenolic resins that have high fluidity when heated, or have low viscosity when dissolved in a solvent or liquid resin.
For example, a method of reducing the molecular weight of a novolac type phenol resin can be mentioned. However, in this case, the number of moles of phenols must be excessive with respect to the number of moles of formaldehydes when the resin is synthesized, and the content of unreacted phenols and binuclear components increases. When such a resin is used, the irritating odor such as phenols becomes strong, resulting in a problem that the working environment is deteriorated. In addition, in the case of a resin having an excessively low molecular weight, the strength of the brick before the drying process in which the resin is cured may be reduced.
For this reason, a novolak type phenol resin having a low content of low molecular weight components such as unreacted phenols and dinuclear components, high fluidity during heating, or low viscosity when dissolved in a solvent, and having an appropriate molecular weight. It is desired.

Funabiki Shinpei and two others, "Phenolic resins and their use in refractories", Refractories, Refractory Technology Association, February 10, 1979, No. 277, vol33, p8-24

The present invention has been made as a result of studies to solve various problems of conventional novolak type phenolic resins for refractory binders, has a good working environment during handling, and has excellent mechanical strength. It is intended to provide a novolac type phenolic resin for a refractory binder that can be obtained.

Such an object is achieved by the following present inventions (1) to (3).
(1) (a) The content of unreacted phenols is 1% by weight or less, (b) the content of dinuclear components is 10% or less, (c) the degree of dispersion of molecular weight distribution is 5 or less, and (d ) Novolak type phenolic resin for refractory binders having a number average molecular weight of 300 to 1,000 and obtained by reacting phenols and aldehydes with phosphoric acids.
(2) The novolak-type phenol resin for refractory binders according to (1) above, wherein 0.2 mol or more of the phosphoric acid is used with respect to 1 mol of the phenol resin.
(3) The novolac type phenol resin for a refractory binder according to (1) or (2), wherein the phosphoric acid is phosphoric acid.

  In the present invention, (a) the content of unreacted phenols is 1% by weight or less, (b) the content of dinuclear components is 10% or less, (c) the degree of dispersion of molecular weight distribution is 5 or less, and ( d) A novolak type phenolic resin for refractory binders having a number average molecular weight of 300 to 1,000 and obtained by reacting phenols and aldehydes with phosphoric acids. It is possible to obtain a refractory having a good working environment and excellent mechanical strength.

Below, the novolak-type phenol resin for refractory binders of this invention is demonstrated.
The novolak-type phenolic resin for refractory binder of the present invention (hereinafter sometimes simply referred to as “phenolic resin”) has (a) a content of unreacted phenols of 1% by weight or less, and (b) a binuclear component. Content of 10% or less, (c) the degree of dispersion of molecular weight distribution is 5 or less, and (d) the number average molecular weight is 300 to 1000, and phenols and aldehydes are reacted with phosphoric acids. It is obtained.

  Although it does not specifically limit as phenols used as the raw material of the phenol resin of this invention, For example, cresol, such as phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2 , 5-xylenol, 2,6-xylenol, 3,4-xylenol, xylenol such as 3,5-xylenol, ethylphenol such as o-ethylphenol, m-ethylphenol, p-ethylphenol, isopropylphenol, butylphenol, Butylphenol such as p-tert-butylphenol, p-tert-amylphenol, p-octylphenol, p-nonylphenol, alkylphenols such as p-cumylphenol, fluorophenol, chlorophenol, bromophenol, iodine Halogenated phenols such as phenol, monovalent phenol substitutes such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol and trinitrophenol, and monovalent polycyclic phenols such as 1-naphthol and 2-naphthol, Examples thereof include polyphenols such as resorcin, alkylresorcin, pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, phloroglucin, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. These can be used alone or in combination of two or more. Usually, phenol, cresols, and bisphenol A are often used for refractory binders because high mechanical strength of refractories is easily obtained.

Although not particularly limited as aldehydes, for example, formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde Benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like. These can be used alone or in combination of two or more. Usually, formaldehyde and paraformaldehyde are often used for refractory binders because of their high reactivity during synthesis.

Although the reaction molar ratio (F / P) of phenols (P) and aldehydes (F) is not particularly limited, it is preferably 0.4 to 1.0, more preferably 0.5 to 0.00. 8.
Thereby, the phenol resin which has the molecular weight suitable for a refractory binder can be obtained. When the reaction molar ratio is less than the lower limit, the yield tends to be low, and the molecular weight of the resulting phenol resin may be small. On the other hand, when the reaction molar ratio exceeds the above upper limit, the molecular weight of the phenol resin tends to increase, the softening point becomes high, and sufficient fluidity may not be obtained during heating. Moreover, it is sometimes difficult to control the molecular weight, and depending on the reaction conditions, gelation or partial gelation tends to occur.

  The reaction method for synthesizing the phenolic resin of the present invention is not particularly limited. For example, a method in which all phenols and aldehydes are collectively charged into a reaction vessel at the start of the reaction and a catalyst is added to react, or In order to suppress heat generation at the initial stage of reaction, a method in which phenols and a catalyst are added and then aldehydes are sequentially added and reacted is included.

The content of unreacted phenols and dinuclear components in the phenolic resin of the present invention is 1% by weight or less for unreacted phenols and 10% or less for dinuclear components.
Thereby, the generation amount of gas which worsens the working environment at the time of handling resin can be reduced.
When the content of unreacted phenols and dinuclear components is higher than the above upper limit, when kneading with a refractory aggregate, these components become strong irritating gases, which may lead to deterioration of the working environment. In addition, the molecular weight of the phenol resin is reduced, and the mechanical strength of the refractory may be reduced.
For such purposes, it is more preferable that the content of unreacted phenols is 0.5% by weight or less, and the content of the binuclear component is 7% or less.

The degree of dispersion of the molecular weight distribution of the phenol resin of the present invention is 5 or less.
Thereby, good fluidity is exhibited during heating, the solution viscosity when dissolved in a solvent can be lowered, and good mechanical strength can be imparted to the refractory.
If the degree of dispersion exceeds the above upper limit, the fluidity and solution viscosity increase, and the refractory aggregate surface becomes insufficient when kneading phenolic resin into the refractory aggregate, which reduces the mechanical strength of the refractory. May end up.
For such purposes, the degree of dispersion is more preferably 3 or less.

The phenol resin of the present invention has a number average molecular weight (Mn) of 300 to 1,000.
Thereby, high mechanical strength can be provided to the refractory.
When the number average molecular weight exceeds the upper limit, the fluidity and the solution viscosity are increased, and the mechanical strength of the refractory may be lowered. Moreover, if it is less than the said lower limit, adhesive force may fall and the mechanical strength of a refractory may fall.
For such purposes, the number average molecular weight is more preferably 400 to 900.

The content of unreacted phenols in the phenolic resin of the present invention is a value measured by an internal standard method using 2,5-xylenol as an internal standard substance using a gas chromatography method in accordance with JIS K 0114. is there.
In addition, the number average molecular weight and the dispersity of the molecular weight distribution were measured using a GPC (gel permeation chromatography) method, tetrahydrofuran was used as an elution solvent, the flow rate was 1.0 ml / min, and the column temperature was 40 ° C. Under the conditions, a differential refractometer was used as a detector, and the molecular weight was converted with standard polystyrene. The content of the binuclear component is determined from the corresponding area ratio from the molecular weight distribution curve. The device
1) Body: "HLC-8120" manufactured by TOSOH
2) Analytical column: Two "G1000HXL" manufactured by TOSOH, one "G3000HXL"
It was used.

  The phenol resin of the present invention is obtained by reacting phenols and aldehydes with phosphoric acids.

  Here, as the phosphoric acid, a phosphoric acid compound that can be dissolved in water to form a phosphoric acid aqueous solution can be used, and is not particularly limited. For example, phosphoric acid (orthophosphoric acid), diphosphoric acid, triphosphoric acid, etc. In addition to linear polyphosphoric acid, cyclic polyphosphoric acid, diphosphorus pentoxide, phosphorous acid, hypophosphorous acid and the like, various phosphoric acid ester compounds can be mentioned. These can be used alone or in combination of two or more.

  Of these phosphoric acids, phosphoric acid is preferred. Phosphoric acid can be easily adjusted in concentration and can be obtained at low cost.

  Although it does not specifically limit as a density | concentration of phosphoric acid at the time of using phosphoric acid in the form of aqueous solution, It is preferable that it is 20 to 99 weight%, More preferably, it is 40 to 99 weight%. By setting the concentration of phosphoric acids to the above lower limit or higher, the reaction between phenols and aldehydes can be efficiently advanced.

The amount of phosphoric acid used here is not particularly limited, but is preferably 0.2 mol or more with respect to 1 mol of phenols. Thereby, in the system which makes phenols and aldehydes react using phosphoric acids, distribution of the organic phase which has phenols as a main component and the water phase containing phosphoric acids can be stabilized.
The amount of the phosphoric acid is more preferably 0.3 to 1.0 mol, and particularly preferably 0.4 to 0.9 mol, with respect to 1 mol of phenols. Thereby, the phenol resin with little content of unreacted phenols can be obtained efficiently.

  Increasing the amount of phosphoric acid tends to increase the effect of obtaining a phenol resin with a low content of unreacted phenols in a high yield, but it exceeds 1.0 mol with respect to 1 mol of phenol. Even if the amount is used, this effect may not be substantially changed, so it may not be economical. On the other hand, if the amount is less than 0.2 mol, the phosphoric acid concentration in the aqueous phase is too low to stably distribute the organic phase and the aqueous phase, so that the reaction rate decreases.

  Although it does not specifically limit as reaction conditions at the time of synthesize | combining the phenol resin of this invention, It is preferable that reaction temperature is 40-150 degreeC. More preferably, it is 90-140 degreeC. By making reaction temperature more than the said lower limit, reaction with phenols and aldehydes can be accelerated | stimulated and content of unreacted phenols can be reduced. Moreover, it can make phosphoric acid aqueous solution into a preferable viscosity, and can avoid that a catalytic action falls. On the other hand, the decomposition of the phenol resin can be suppressed by setting it to the upper limit value or less.

Moreover, it is although it does not specifically limit as a moisture content rate in the reaction system at the time of reaction, It is preferable to set it as 1 to 40 weight%. More preferably, it is 1 to 30% by weight.
Here, the moisture content in the reaction system is the weight ratio of the total amount of moisture present in the reaction system to the total amount of phenols, aldehydes, phosphoric acids, phenol resins, etc. present in the reaction system. Point to. The water present in the reaction system includes water derived from the raw material to be added, such as water contained in an aqueous solution of phosphoric acid, water contained in aldehydes, and condensed water generated during the reaction.
The water content in the reaction system can be calculated by taking the sum of the water content in the charged raw material and the amount of condensed water produced by the reaction as the water content in the reaction system, and dividing this by the total amount charged. Also, when the reaction is carried out by distilling off water, the water content in the reaction system is reduced by subtracting the amount of water distilled off from the total amount of water content in the raw material and the amount of condensed water produced by the reaction. Can be calculated.

By carrying out the reaction preferably within the above range for the water content, a phenol resin having a small content of unreacted phenols and a narrow molecular weight distribution can be obtained in a high yield.
By setting the water content in the reaction system to the above lower limit value or more, it is possible to prevent the phosphoric acids from becoming highly viscous or solidified. Moreover, since the fall of reaction rate can be suppressed by setting it as the said upper limit or less, reaction of phenols and aldehydes can be advanced efficiently.

Such reaction conditions are effective for selectively reacting not only unreacted phenols but also low molecular weight components such as dinuclear components, and can narrow the molecular weight distribution of the resulting phenolic resin. .
That is, the reaction of unreacted phenols proceeds sufficiently even outside the range of the reaction conditions described above, but for the selective reaction of low molecular weight components such as dinuclear components, the reaction conditions are within the range of the reaction conditions described above. It is effective to do.

  In addition, there is no restriction | limiting in particular about reaction time, According to the kind of phenols and aldehydes, reaction molar ratio, the kind and usage-amount of a catalyst, reaction conditions, etc., it can select suitably.

When synthesizing the phenol resin of the present invention, for example, the reflux temperature in the range of 20 to 40% by weight of water is approximately 102 to 110 ° C., and normal pressure reaction is a preferable condition for controlling the temperature and moisture. is there. As other reaction methods, for example, a solvent reflux dehydration reaction using a non-aqueous solvent such as butanol or propanol, a high pressure reaction, or the like can be applied.
In addition, a reaction method in which aldehydes are sequentially added and condensed water to be generated is removed by distillation or the like can be carried out under preferable reaction conditions because the amount of water in the reaction system is constant. However, when unreacted phenols are easily removed together with moisture, the reaction is performed under the condition that unreacted phenols are not distilled until the unreacted phenols become a certain amount or less. It is preferable to continue the reaction after removing or after removing.

  In the synthesis of the phenolic resin of the present invention, phosphoric acids are used as a catalyst. In addition to this, acidic catalysts such as oxalic acid, sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid are usually used in the production of novolak type phenolic resins. It can also be used together. The combined use of these acidic catalysts is effective for accelerating the reaction, particularly when a high molecular weight component having four or more nuclei is required, and is an effective means for controlling the molecular weight distribution.

Although it is not particularly limited in the production method of the present invention, after synthesizing the phenol resin by the method described above, the reaction system is washed with water, and the concentration of phosphoric acids contained in the phenol resin is 3.0% by weight or less. It is preferable to make it. More preferably, it is 0.1 weight% or less.
Thereby, decomposition | disassembly of a phenol resin can be suppressed when performing atmospheric distillation or vacuum distillation after water washing.

  Although it does not specifically limit as a method to wash with water here, For example, the organic phase containing a phenol resin and the aqueous phase containing phosphoric acid aqueous solution are isolate | separated by centrifugation. Subsequently, the obtained organic phase is washed with pure water or ion-exchanged water, whereby the concentration of phosphoric acids contained in the phenol resin can be reduced to 3.0% by weight or less. Moreover, the concentration of phosphoric acids can be reduced to 0.1% by weight or less by performing this water washing a plurality of times.

  Further, after washing with water until the concentration of phosphoric acid is not more than the above upper limit, 0.8 to 1.5 equivalents of alkaline substance is used for 1 equivalent of phosphoric acid remaining in the reaction system. Can be neutralized. Thereby, since the catalytic activity which phosphoric acids have can be deactivated, even when performing a dehydration reaction at high temperature by the subsequent process, decomposition | disassembly of a phenol resin can be suppressed.

  Although it does not specifically limit as an alkaline substance used here, For example, calcium hydroxide, sodium hydroxide, a triethanolamine etc. can be used. Although it does not specifically limit as a form of an alkaline substance, It is preferable to use with the form of aqueous solution.

  After synthesizing the phenol resin by the method described above, if necessary, in order to remove water, organic solvent, and unreacted phenols, atmospheric distillation, vacuum distillation, steam distillation, etc. are performed in combination. You can also

  In the present invention, by reacting phenols and aldehydes with phosphoric acids, a phenol resin having a small content of unreacted phenols and binuclear components and a low molecular weight distribution is obtained. The reason for this can be considered as follows.

Phosphoric acids are very water-soluble compounds, but phenols have low solubility, and phenol resins have the property of increasing their molecular weight and further reducing solubility.
By using these phosphoric acids, the reaction system at the start of the reaction is phase-separated into an organic phase mainly composed of phenols and an aqueous phase containing phosphoric acids. In this liquid-liquid heterogeneous reaction system, low molecular weight components such as phenolic monomers and dinuclear components are relatively easily eluted in the aqueous phase, and the eluted components are separated from the added aldehydes by the catalytic action of phosphoric acids. react. The phenol resin produced by the reaction is rapidly extracted into the organic phase, but the phenol resin having a high molecular weight to some extent does not elute into the aqueous phase.

  Also, by setting the water content and reaction temperature in the reaction system preferably within the above ranges, low molecular weight components such as dinuclear components and trinuclear components generated by the reaction are eluted into the aqueous phase containing phosphoric acids. And the reaction in the aqueous phase can easily proceed. And since the ion concentration in a water phase is maintained in the state where it is high, the interface of a water phase and an organic phase isolate | separates more firmly, and the polymeric reaction on the organic phase side can be prevented.

  As described above, when synthesizing the phenol resin of the present invention, the low molecular weight component and the high molecular weight component of the phenol resin cause a difference in reaction rate due to the difference in solubility in the aqueous phase. While low molecular weight components, such as a nucleus component, react selectively, it can suppress that the produced | generated phenol resin becomes high molecular weight too much.

  In the synthesis of the phenol resin of the present invention, by performing such a liquid-liquid heterogeneous reaction, the content of unreacted phenols and dinuclear components is less than or equal to the above upper limit, and further, the increase in high molecular weight components By suppressing the above, it is possible to obtain a phenol resin having a number average molecular weight within the above range and a molecular weight distribution having a dispersion degree of not more than the above upper limit.

Although the phenol resin of the present invention is not particularly limited, hexamethylenetetramine, a resol type phenol resin, or the like can be used as a curing agent. You may use these individually or in mixture of 2 or more types. For example, when hexamethylenetetramine is used as the curing agent, it is usually blended in an amount of 5 to 15 parts by weight with respect to 100 parts by weight of the phenol resin.
In addition to these, a lubricant, a silane coupling agent, and the like can be blended as a modifier, if necessary.

As explained above, the phenol resin of the present invention has a low content of unreacted phenols and dinuclear components. Thereby, the generation amount of gas which worsens the working environment at the time of kneading with a refractory aggregate or heat drying can be reduced.
Further, it has a specific number average molecular weight and a degree of molecular weight distribution. Thereby, since it has high fluidity | liquidity, the coating to a refractory aggregate can fully be performed at the time of kneading | mixing a phenol resin and a refractory aggregate, and high mechanical strength can be provided to a refractory.

  When the phenol resin of the present invention is used as a refractory binder, a usual method can be applied. That is, a kneaded material is obtained by kneading refractory aggregates such as alumina, magnesia, and scaly graphite, the phenolic resin of the present invention, and hexamethylenetetramine as a curing agent in a predetermined composition. A refractory can be obtained by filling the obtained clay into a mold or the like, pressurizing and molding, heating to a predetermined temperature, and firing as necessary.

  Hereinafter, the present invention will be specifically described with reference to examples. “Parts” described herein means “parts by weight”, and “%” means “% by weight” except for the content of the binuclear component.

1. Synthesis of phenolic resin
<Example 1>
In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 1000 parts of phenol and 1000 parts of 85% aqueous phosphoric acid solution (corresponding to 0.82 mol per mol of phenol) were charged. After the internal temperature was raised to 130 ° C., 277 parts of 92% paraformaldehyde (reaction molar ratio F / P = 0.80) was added over 30 minutes, followed by refluxing reaction for 1 hour.
Next, 500 parts of pure water was added and mixed to remove the aqueous phase separated from the resin phase. Such a water washing process was performed 3 times. When the amount of phosphoric acid remaining in the phenol resin after washing with water was measured, it was 0.07 part. To this, 0.06 part of 50% aqueous sodium hydroxide solution (1.2 equivalents relative to 1 equivalent of the remaining phosphoric acid) was added, and the dehydration pipe was switched again to perform normal pressure dehydration to an internal temperature of 130 ° C. Vacuum dehydration was performed at 9500 Pa to a temperature of 150 ° C.
Thereafter, 450 parts of ethylene glycol was added, and the resulting resin was taken out of the reaction vessel to obtain 1470 parts of a phenol resin solution. The molecular weight of the obtained resin by GPC measurement was Mn = 515, Mw = 720, and dispersity (Mw / Mn) = 1.40. The amount of unreacted phenols was less than the detection limit (0.1%), and the amount of dinuclear components was 2%.

<Example 2>
In a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, 1000 parts of phenol and 1000 parts of 85% aqueous phosphoric acid solution (corresponding to 0.82 mol per mol of phenol) were charged. After the internal temperature was raised to 130 ° C., 243 parts of 92% paraformaldehyde (reaction molar ratio F / P = 0.70) was added over 30 minutes, followed by refluxing reaction for 1 hour.
Next, 500 parts of pure water was added and mixed to remove the aqueous phase separated from the resin phase. Such a water washing process was performed 3 times. When the amount of phosphoric acid remaining in the phenol resin after washing with water was measured, it was 0.07 part. To this, 0.06 part of 50% aqueous sodium hydroxide solution (1.2 equivalents relative to 1 equivalent of the remaining phosphoric acid) was added, and the dehydration pipe was switched again to perform normal pressure dehydration to an internal temperature of 130 ° C. Vacuum dehydration was performed at 9500 Pa to a temperature of 150 ° C.
Thereafter, 450 parts of ethylene glycol was added, and the resulting resin was taken out of the reaction vessel to obtain 1430 parts of a phenol resin solution. The molecular weight of the obtained resin by GPC measurement was Mn = 425, Mw = 540, and dispersity (Mw / Mn) = 1.27. The amount of unreacted phenols was 0.1%, and the amount of dinuclear components was 8%.

<Example 3>
In a reaction vessel equipped with a stirrer, a condenser tube and a thermometer, 1000 parts of phenol and 429 parts of 85% phosphoric acid aqueous solution (corresponding to 0.35 mol per mol of phenols) were charged. After the internal temperature was raised to 130 ° C., 277 parts of 92% paraformaldehyde (reaction molar ratio F / P = 0.80) was added over 30 minutes, followed by refluxing reaction for 1 hour.
Next, 500 parts of pure water and 2000 parts of methyl isobutyl ketone were added, and the aqueous phase separated from the resin phase was removed. Further, 2000 parts of pure water was added, and a water washing step for removing the aqueous phase separated from the resin was performed three times. When the amount of phosphoric acid remaining in the resin after washing with water was measured, it was below the detection limit. This was again switched to a dehydration pipe, and normal pressure dehydration was performed to an internal temperature of 130 ° C., followed by vacuum dehydration at 9500 Pa to an internal temperature of 150 ° C.
Thereafter, 450 parts of ethylene glycol was added, and the resulting resin was taken out of the reaction vessel to obtain 1460 parts of a phenol resin solution. The molecular weight of the obtained resin by GPC measurement was Mn = 525, Mw = 745, and dispersity (Mw / Mn) = 1.42. The amount of unreacted phenols was 0.1%, and the amount of dinuclear components was 4%.

<Comparative example>
A reaction vessel equipped with a stirrer, a condenser tube and a thermometer was charged with 1000 parts of phenol and 10 parts of oxalic acid, heated to an internal temperature of 95 ° C. at normal pressure, and then added with 621 parts of 37% formalin over 1 hour. . Furthermore, after refluxing reaction at 98-100 degreeC for 1 hour, it heat-dehydrates at atmospheric pressure, raises internal temperature to 140 degreeC, depressurizes to 9500 Pa, and also heats internal temperature to 180 degreeC, Then, ethylene glycol 450 parts was added and taken out from the reaction vessel to obtain 1455 parts of a phenolic resin solution.
The molecular weight of the obtained resin by GPC measurement was Mn = 460, Mw = 986, and the dispersity = 2.14. The amount of unreacted phenols was 3.0%, and the amount of dinuclear components was 13%.

2. Practical tests as refractories Obtained in an experimental universal kneader with 650 parts of magnesia clinker coarse particles (1 to 3 mm), 200 parts of magnesia clinker fine powder (0.3 mm or less), 150 parts of scaly graphite, Examples and Comparative Examples 28 parts of phenol resin (in terms of solid content) and 2.8 parts of hexamethylenetetramine were added and kneaded at 40 ° C. for 30 minutes.
Next, 120 g of the kneaded product was placed in a 15 mm × 25 mm × 100 mm mold, molded by applying a pressure of 9.8 × 10 ⁷ Pa, and the obtained test piece was dried at 200 ° C. for 3 hours.
Furthermore, this test piece was heat-treated at 1000 ° C. for 3 hours under a reducing atmosphere to produce each test piece.

  Table 1 shows the molecular weight, the degree of dispersion, the amount of unreacted phenol, the amount of the binuclear component, and the characteristic measurement results of the refractories obtained in Examples and Comparative Examples.

The characteristic evaluation method of a phenol resin and a refractory is as follows.
(1) Content of unreacted phenols: This is a value measured by an internal standard method using 2,5-xylenol as an internal standard substance using a gas chromatography method in accordance with JIS K 0114.
(2) Number average molecular weight, weight average molecular weight, dispersity of molecular weight distribution: measured using GPC (gel permeation chromatography) method, using tetrahydrofuran as an elution solvent, flow rate 1.0 ml / min, Measurement was performed using a differential refractometer as a detector at a column temperature of 40 ° C., and the molecular weight was converted with standard polystyrene. The device
1) Body: "HLC-8120" manufactured by TOSOH
2) Analytical column: Two "G1000HXL" manufactured by TOSOH, one "G3000HXL"
It was used.
(3) Content of binuclear component: It was calculated from the corresponding area ratio from the molecular weight distribution curve obtained by the GPC measurement.
(4) Bending strength: Tensilon UTM-III-500 manufactured by Toyo Baldwin Company was used. The span was 80 mm and the head speed was 5 mm / min.
(5) Irritant odor: The odor generated during kneading was confirmed by sensory test. On the basis of the comparative example, there were cases where there was a similar irritating odor, and cases where there was no case.

  Examples 1 to 3 are all phenolic resins of the present invention, and in a practical test as a refractory using the same, compared with a comparative example that is a conventional phenolic resin, mechanical properties after drying at 200 ° C. Both strength and mechanical strength after firing at 1000 ° C. could be improved. In addition, the irritating odor generated during kneading could be reduced.

  The novolak type phenolic resin for refractory binders of the present invention is suitably used as a refractory binder because the working environment during handling is good and the mechanical strength of the refractory can be improved.

Claims (3)

(A) The content of unreacted phenols is 1% by weight or less, (b) the content of binuclear components is 10% or less, (c) the degree of dispersion of the molecular weight distribution is 5 or less, and (d) the number average A novolak type phenol resin for a refractory binder, which has a molecular weight of 300 to 1,000 and is obtained by reacting phenols and aldehydes with phosphoric acids. The novolak-type phenol resin for refractory binders according to claim 1, wherein 0.2 mol or more of the phosphoric acid is used with respect to 1 mol of the phenol resin. The novolac type phenol resin for a refractory binder according to claim 1 or 2, wherein the phosphoric acid is phosphoric acid.