JP2003112231A - Novolak type phenolic resin for shell mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novolak type phenolic resin for a shell mold which is good in working environmental characteristics and is excellent in workability and the strength of a casting mold. SOLUTION: This novolak type phenolic resin for the shell mold is characterized in that (a) unreacted phenols are <=1 wt.%, (b) the binuclear body components calculated from the area ratios of respective peaks by GPC analyses are <=10%,(c) the degree of dispersion of molecular weights is <=5 and (d) the number average molecular weight is 300 to 1,000. More preferably the novolak type phenolic resin is the novolak type phenolic resin for the shell mold, as described above, obtained by reacting phenols and aldehydes by using an organic phosphonic acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novolac type phenol resin for shell mold.

[0002]

2. Description of the Related Art The production of a mold by the shell mold method is
This is performed by filling a resin-coated sand in a heated mold and curing it. Resin-coated sand is prepared by adding a binder to preheated refractory aggregate, kneading with a mixer, coating the surface of the refractory aggregate with the molten binder, and then using a novolac-type phenol resin. Is obtained by adding a curing agent such as hexamethylenetetramine, and further cooling while kneading. Normal,
As a binder, storability in resin coated sand,
Novolac-type phenolic resins are used for reasons such as high strength of molds, high dimensional stability, and disintegration of molds after pouring.

The properties of the novolac type phenolic resin required here include that there are few low molecular weight components such as unreacted phenols and that the fluidity at the time of heating is high. Unreacted phenols and the like become a strong irritating gas due to heat when used as a binder by molding a novolac type phenol resin as a binder of resin coated sand to form a mold, which is a problem in the working environment. Further, if the fluidity during heating is low, the coating on the surface of the fire-resistant aggregate during the production of the resin-coated sand will be insufficient, or the adhesion between the fire-resistant aggregates will be poor when the resin-coated sand is molded into a mold. There is a problem that it becomes sufficient and the strength decreases.

Regarding a method for obtaining a novolac type phenol resin in which unreacted phenols and the like are reduced,
Various proposals have been made so far. For example, when a novolac type phenol resin is produced by a usual method, a method of removing unreacted phenols by a method such as solvent fractionation or distillation of the resin can be mentioned. However, in the case of solvent fractionation, there is a problem that the amount of waste increases with the use of solvent. Also, in the case of distillation, there is a cost disadvantage due to an increase in the number of processes and an increase in energy cost. On the other hand, various proposals have been made for a method of obtaining a novolac phenol resin having high fluidity when heated. For example, a method of adding a fluidizing agent such as acetanilide, which has the effect of lowering the molecular weight of the resin or increasing the fluidity of the resin, can be mentioned. However, when lowering the molecular weight of the resin, the number of moles of phenols must be excessive with respect to the number of formaldehydes at the time of reaction, and unreacted phenols increase. For this reason, the reaction yield rate is reduced, which is disadvantageous in terms of cost. Further, when a fluidizing agent is added, the adhesive temperature of the resin coated sand is lowered, and as a result, a blocking phenomenon of the resin coated sand is likely to occur, which causes a problem in storage stability.

Therefore, rather than removing unreacted phenols, which increases waste and is disadvantageous in terms of cost, unreacted phenols are reacted by reacting phenols with formaldehyde at a high reaction rate. There is a demand for a novolac type phenol resin for a shell mold, which has a reduced amount, has high fluidity when heated, and has good resin-coated sand storage stability.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of studies to solve various problems which have been problems in the conventional novolak type phenol resin for shell mold, and has a good working environment. The present invention provides a novolac-type phenol resin for shell mold, which is excellent in workability and mold strength.

[0007]

The present invention provides (1) (a)
Unreacted phenols are 1% by weight or less, binuclear components calculated from the area ratio of each peak by GPC analysis are 10% or less, (c) polydispersity of molecular weight is 5 or less, (d) number average molecular weight is 300 to Novolak type phenolic resin for shell mold, which is 1000, (2) Novolak type phenolic resin is obtained by reacting phenols and aldehydes with organic phosphonic acid (1) The novolac type phenol resin for shell molds according to the item (1) or (2), wherein (3) the organic phosphonic acid is represented by the general formula (I). Resin, R-PO (OH) ₂ (I) (R contains a carbon atom, and -COOH, and / or-
It is a group containing PO (OH) ₂ .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Phenols used as a raw material for the novolac type phenol resin of the present invention are not particularly limited, but include phenol, o-cresol, m-cresol, p-cresol, xylenol, bisphenol A and p-tertiary. Examples include, but are not limited to, butylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, other alkylphenols, catechol, resorcin, bisphenols, and the like. Moreover, you may use these individually or in mixture of 2 or more types. Usually, for shell molding, phenol, cresols, and bisphenol A are used because high strength is easily obtained when molded into a mold.

The aldehydes are not particularly limited, but include formaldehyde, paraformaldehyde, benzaldehyde and the like, substances that are the source of generation of these aldehydes, or solutions of these aldehydes, and are particularly limited to these. Not a thing. Also,
You may use these individually or in mixture of 2 or more types. Usually, for shell molds, formaldehyde and paraformaldehyde are used because of their high reactivity during phenol resin production.

Aldehydes (F) and phenols (P)
The reaction molar ratio (F / P) with is not particularly limited, but can be 0.
It is preferably 1 to 3.0, and more preferably
It is 0.75-0.95. By reacting at such a molar ratio, a novolac type phenol resin having a molecular weight suitable for resin coated sand can be obtained. If the reaction is carried out under the condition that the reaction molar ratio is lower than the lower limit value, the yield tends to be low, and the resulting novolac type phenol resin may have a low softening point since the molecular weight is low. On the other hand, when the reaction is carried out under the condition that the reaction molar ratio exceeds the upper limit value, the molecular weight of the novolac type phenol resin is likely to be high, the softening point is high, and sufficient fluidity may not be obtained during heating. . In addition, it may be difficult to control the molecular weight, and depending on the reaction conditions, gelation or partial gelation is likely to occur.

As the reaction method, phenols and aldehydes may be charged in a batch at the start of the reaction into a reaction vessel, and a catalyst may be added to carry out the reaction. In order to suppress heat generation at the initial stage of the reaction, phenols may be added. You may make it react by adding an aldehyde sequentially after charging with a catalyst.

The content of the unreacted phenols and the binuclear component in the novolac type phenol resin of the present invention is preferably 1% by weight or less of the unreacted phenols,
It is more preferably 0.5% by weight or less. Also, GPC
The binuclear component calculated from the area ratio of each peak by analysis is preferably 10% or less, more preferably 7%.
It is the following. If the contents of unreacted phenols and binuclear components are higher than the above upper limits, when the resin coated sand is molded into a mold, these components become a strongly irritating gas due to heat, which leads to deterioration of working environment. Sometimes. Further, the softening point of the novolac type phenol resin is lowered, and the phenomenon of blocking of the resin coated sand is likely to occur, which may affect storage stability. In addition, in the present invention, the amount of unreacted phenols is a value measured by an internal standard method using 2,5-xylenol as an internal standard substance using a gas chromatography method according to JIS K0114. Further, the amount of the binuclear component is measured by GPC (gel permeation chromatography), and is 2 with respect to the total area of each peak.
It is obtained from the area ratio of the nuclear component.

In the novolak type phenolic resin of the present invention, the polydispersity of molecular weight (hereinafter, simply referred to as polydispersity) is the ratio of polystyrene-reduced number average molecular weight (Mn) and weight average molecular weight (Mw) measured by GPC ( Mw / Mn)
It is a value represented by. Generally, in a high molecular weight compound having a molecular weight distribution, Mw> Mn and the dispersity is greater than 1. The smaller this value, the lower the degree of dispersion and the narrower the molecular weight distribution. When Mw = Mn, it means a single compound.
The novolak type phenolic resin of the present invention preferably has a dispersity of 5 or less. More preferably, it is 3 or less. This is because the novolac type phenolic resin having such a dispersity exhibits good fluidity in the vicinity of its softening point, and is suitable for resin coated sand applications. When the dispersity exceeds the upper limit value, the fluidity at the time of heating the resin decreases, so that the coating of the refractory aggregate surface becomes insufficient during the production of the resin-coated sand, or when the resin-coated sand is molded into a mold. In addition, the adhesion between the refractory aggregates may deteriorate, and the mold strength may decrease. In the present invention, GPC analysis was used to measure the content of the binuclear component, the number average molecular weight, and the weight average molecular weight. GPC
The analysis uses tetrahydrofuran as the elution solvent,
The flow rate was 1.0 ml / min, and the column temperature was 40 ° C. As for the device, the main body: Tosoh HLC-8020, the analytical column: Tosoh TSKgel G1000HXL 2
, One G3000HXL was used. The measured value of the molecular weight is a polystyrene conversion of the obtained value using a calibration curve prepared using a polystyrene standard substance.

The number average molecular weight (Mn) of the novolac type phenol resin of the present invention is 300 to 1000.
Is preferable, and more preferably 400 to 90.
It is 0. By using the one having such a number average molecular weight, it is possible to achieve both the preservability as a resin coated sand and the mold strength. If the number average molecular weight exceeds the upper limit, the fluidity at the time of molding may be lowered to lower the mold strength. On the other hand, if the number average molecular weight is less than the lower limit, the blocking phenomenon may easily occur.

The softening point of the novolac type phenol resin of the present invention is not particularly limited, but it is preferably 85 ° C. or higher. When the softening point is less than 85 ° C, a problem may occur in storage stability such that the resin coated sand easily causes a blocking phenomenon.

The novolac type phenolic resin of the present invention is
Although not particularly limited, it is preferable to use an organic phosphonic acid as a catalyst during the production. The organic phosphonic acid referred to here is an organic compound containing a phosphonic acid group —PO (OH) ₂ , and any compound can be used, but the organic phosphonic acid represented by the general formula (I) is an unreacted phenol. Is preferable in order to obtain a novolac type phenol resin having a small amount and a narrow dispersion in a high yield. R—PO (OH) ₂ (I) (R contains a carbon atom, and —COOH, and / or —
PO (OH) ₂ -containing group) Examples of the organic phosphonic acid represented by the general formula (I) include aminopolyphosphonic acids such as ethylenediaminetetrakismethylenephosphonic acid, ethylenediaminebismethylenephosphonic acid, aminotrismethylenephosphonic acid and β. -Aminoethylphosphonic acid-N, N-diacetic acid, aminomethylphosphonic acid-N, N-diacetic acid, 1-hydroxyethylidene-1,1'-diphosphonic acid, 2-phosphonobutane-1,
2,4-tricarboxylic acid and the like. Among these, aminotrismethylenephosphonic acid, 1-hydroxyethylidene-1,1′-diphosphonic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid, which are industrially mass-produced and inexpensive in view of the object of the present invention, are used. It is preferable to use an acid.

The amount of the organic phosphonic acid added is not particularly limited, but it is 0.00 per 1 mol of the phenols.
The amount is preferably 1 to 4.0 mol, and more preferably 0.01 to 0.5 mol. The larger the amount of the organic phosphonic acid added, the greater the effect of obtaining a high yield of a novolak type phenolic resin having a small amount of unreacted phenols and a small degree of dispersion, but if the amount of the catalyst added exceeds 4.0 mols. The effect does not change, and if it is less than 0.001 mol, the effect as a catalyst is not sufficiently exhibited. Also, with the above phosphonic acid as a catalyst, oxalic acid, sulfuric acid,
Other acidic substances such as hydrochloric acid and p-toluenesulfonic acid can be used in combination. The combined use of these acidic substances is particularly effective in promoting the reaction in the high molecular weight region of tetranuclear or higher.

The novolac type phenolic resin of the present invention is
The reason why the amount of unreacted phenols and binuclear components is small and the molecular weight distribution is narrowed is considered as follows. Organic phosphonic acid is a compound having a property of being extremely water-soluble and easily hydrated. And, it has a low solubility in phenols, and the novolac-type phenol resin has a property that the solubility becomes smaller as the molecular weight increases. Therefore, at the time of the reaction, the catalyst is separated into an aqueous layer containing a large amount of an organic phosphonic acid as a catalyst and an organic layer in which a catalyst composed of phenols and novolac resin is scarcely present. Low molecular weight components such as phenols and binuclear bodies are relatively easily eluted in the aqueous layer, and the eluted portion reacts with aldehydes, but high molecular weight components hardly elute and the reaction does not proceed. Further, the low molecular weight novolak type phenol resin eluted in the aqueous layer reacts with the aldehyde to have a high molecular weight and is rapidly extracted into the organic layer, and the reaction does not proceed any further. In this way, a reaction rate difference occurs between the low-molecular weight component and the high-molecular weight component, resulting in a small amount of unreacted phenols, etc., and a high yield of a novolac type phenol resin having a narrow molecular weight distribution. It becomes possible.

The novolac type phenol resin used in the present invention may also contain a lubricant, a silane coupling agent and the like as a modifier, if necessary.
As the lubricant, ethylene bis-stearic acid amide, methylene bis-stearic acid amide, oxystearic acid amide, stearic acid amide, methylol stearic acid amide and the like can be used, and as the silane coupling agent, aminosilane, epoxysilane, vinylsilane and the like can be used.

As described above, the novolac-type phenol resin used in the present invention has a small amount of unreacted phenols and the like, so that when the resin-coated sand is molded into a mold, a gas that deteriorates the working environment is generated. The amount can be reduced. In addition, since the molecular weight distribution is narrow and has a specific molecular weight, it has an appropriate softening point and exhibits high fluidity in the vicinity of the softening point, so it is possible to sufficiently coat the refractory aggregate during the production of the resin coated sand. It is possible to provide sufficient strength when molding the mold.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. All "parts" and "%" described herein indicate "parts by weight" and "% by weight".

Example 1 In a reaction vessel equipped with a stirrer, a cooling pipe and a thermometer, 1000 parts of phenol, 1-hydroxyethylidene-1,1'-diphosphonic acid (1-1-
Hydroxyethylidene-1,1'-diphosphonic acid (monohydrate) 95% or more, 600 parts of Kishida Chemical Co., Ltd.) was added, and after raising the internal temperature to 120 ° C, 278 parts of 92% paraformaldehyde was added. Was added over 30 minutes, and then refluxed for 1 hour. Then, after adding 500 parts of water and stirring at an internal temperature of 100 to 103 ° C for 30 minutes, the internal temperature was cooled to 60 ° C and left standing for 30 minutes. After standing, from the bottom of the reaction vessel 1
The -hydroxyethylidene-1,1'-diphosphonic acid aqueous solution was separated and removed. After the separation was completed, 1000 parts of water was added to wash the remaining catalyst. After standing for 30 minutes, the washing water was removed from the upper part of the reaction vessel. The system was again switched to the dehydration pipe to carry out atmospheric pressure dehydration up to an internal temperature of 130 ° C., and then vacuum dehydration up to an internal temperature of 150 ° C. at 5000 Pa to remove water in the system. Then, add ethylene bis-stearic acid amide 11
Parts were added, and the obtained resin was taken out from the reaction vessel into a vat to obtain 1070 parts of novolac type phenol resin A.

<Example 2> 600 parts of phenol, 400 parts of bisphenol A, 1-hydroxyethylidene-1,1 'were placed in a reaction vessel equipped with a stirrer, a cooling pipe and a thermometer.
-Diphosphonic acid (1-1-hydroxyethylidene-1,
After 95% or more of 1'-diphosphonic acid (monohydrate) and 1000 parts of Kishida Chemical Co., Ltd. was added and the internal temperature was raised to 120 ° C, 265 parts of 92% paraformaldehyde was added to 3 parts.
After adding for 0 minutes, a reflux reaction was performed for 1 hour. After that, 500 parts of water is added, and the internal temperature is 100 ° C to 103 ° C for 30 minutes.
After stirring for a minute, the internal temperature was cooled to 60 ° C., and the mixture was left standing for 30 minutes. After standing still, 1-hydroxyethylidene was removed from the reaction vessel.
The 1,1′-diphosphonic acid aqueous solution was separated and removed. After the separation was completed, 1000 parts of water was added to wash the remaining catalyst. After standing for 30 minutes, the washing water was removed from the upper part of the reaction vessel. The system was again switched to the dehydration pipe to carry out atmospheric pressure dehydration up to an internal temperature of 130 ° C., and then vacuum dehydration up to an internal temperature of 150 ° C. at 5000 Pa to remove water in the system. Thereafter, 11 parts of ethylenebisstearic acid amide was added, and the obtained resin was taken out from the reaction vessel into a vat to obtain 1060 parts of novolac type phenol resin B.

Comparative Example 1 1000 parts of phenol and 10 parts of oxalic acid were placed in a reaction vessel equipped with a stirrer, a cooling pipe and a thermometer.
Part, and after raising the internal temperature to 95 ° C at atmospheric pressure, 37%
621 parts of formalin was added over 1 hour. 9 more
After carrying out a reflux reaction at 8 to 100 ° C. for 1 hour, it is heated and dehydrated at atmospheric pressure to raise the internal temperature to 140 ° C. and 5000 k
After reducing the pressure to Pa and further heating the inner temperature to 180 ° C., 11 parts of ethylenebisstearic acid amide was added and taken out from the reaction vessel to obtain 1055 parts of novolac type phenol resin C.

Comparative Example 2 1000 parts of phenol and 10 parts of oxalic acid were placed in a reaction vessel equipped with a stirrer, a cooling pipe and a thermometer.
Part, and after raising the internal temperature to 95 ° C at atmospheric pressure, 37%
720 parts of formalin was added over 1 hour. 9 more
After carrying out a reflux reaction at 8 to 100 ° C. for 1 hour, it is heated and dehydrated at atmospheric pressure to raise the internal temperature to 140 ° C. and 5000 k
After reducing the pressure to Pa and further heating the internal temperature to 180 ° C., 11 parts of ethylenebisstearic acid amide was added and taken out from the reaction vessel to obtain 1065 parts of novolac type phenol resin D.

<Preparation of Resin Coated Sand> Using the novolac type phenolic resins obtained in Examples and Comparative Examples, resin coated sand was prepared for each. After adding 8000 parts of flattery sand heated to 130 ° C to the mixer, 1 piece of novolac type phenol resin was added.
60 parts were added and kneaded for 45 seconds. Next, an aqueous solution prepared by previously dissolving 30 parts of hexamethylenetetramine in 88 parts of water was added and kneaded while air cooling until the coated sand collapsed, and further 8 parts of calcium stearate was added and kneaded for 20 seconds. Then, it was discharged from the mixer to obtain resin coated sand. This was similarly performed for four types of novolac type phenolic resins.

The number average molecular weight, weight average molecular weight, dispersity, unreacted phenol amount, binuclear component amount, softening point, and resin coated sand using the novolac type phenol resins obtained in Examples and Comparative Examples Table 1 shows the measurement results of the characteristics of

[Table 1]

<Method for measuring characteristics of resin coated sand> (1) Bending strength: Bending strength was measured according to JIS-K6910. (Firing conditions 250 ° C./60 seconds) (2) Stimulating odor: 25 g of resin coated sand 25 g
It was heated for 60 seconds on a hot plate of 0 ° C., and the produced odor was confirmed.
When Comparative Example 1 was used as a reference, the case where there was a similar pungent odor was marked with X, and the case where there was no similar odor was marked with ◯. (3) Storability: A resin coated sand was placed on a copper rod having a temperature gradient (80 to 120 ° C.), and after 60 seconds, air was blown from a certain distance at a certain pressure. This time,
The lowest temperature at which the resin coated sand remained on the copper rod was used as the sticking point, and was used as an index of storability. The higher the temperature of this sticking point, the more difficult the resin coated sand is to block and the better the storage stability.

From Table 1, the novolak type phenolic resins used in Examples 1 and 2 are obtained by reacting phenol and formaldehyde at an appropriate molar ratio using an organic phosphonic acid as a catalyst. On the other hand, the novolac type phenolic resins used in Comparative Examples 1 and 2 were prepared by using oxalic acid as a catalyst instead of the organic phosphonic acid, and contained a large amount of unreacted phenol and binuclear component as compared with those in Examples. The comparative example 2 has a large degree of dispersion. As a result of using these in the resin coated sand, Examples 1 and 2 were able to reduce the generation of irritating odor during the production of the resin coated sand while maintaining the storability of the resin coated sand and the sufficient mold strength. On the other hand, Comparative Examples 1 and 2 both had an irritating odor during the production of the resin coated sand, and Comparative Example 2 had a low degree of fluidity due to its high degree of dispersion and a decrease in mold strength.

[0030]

INDUSTRIAL APPLICABILITY The present invention is a novolac-type phenol resin obtained by reacting phenols and aldehydes, preferably using an organic phosphonic acid, containing 1% by weight or less of unreacted phenols by GPC analysis. The binuclear component calculated from the area ratio of each peak is 10% or less, the dispersity is 5 or less, and the number average molecular weight is 300 to 1,000. By using the novolac type phenolic resin of the present invention for the shell mold, the resin-coated sand has excellent storage stability, reduces the amount of pungent odor gas generated during the production of the resin-coated sand, and retains the strength during the production of the mold. be able to. Therefore, the present invention is preferably used for mold production by the shell mold method which is excellent in workability and environment.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4E092 AA47 BA04 BA12 BA20 CA03                       CA04                 4E093 LC01 LC10                 4J033 CA02 CA03 CA04 CA11 CA12                       CA13 CA19 CC08 HA02 HA12                       HB05

Claims (3)

[Claims] 1. (a) 1% by weight or less of unreacted phenols, (b) 10% or less of a binuclear component calculated from the area ratio of each peak by GPC analysis, and (c) a polydispersity of molecular weight of 5 Hereinafter, (d) a novolac-type phenol resin for shell molding, which has a number average molecular weight of 300 to 1000. 2. The novolac type phenolic resin for shell mold according to claim 1, wherein the novolac type phenolic resin is obtained by reacting phenols and aldehydes with an organic phosphonic acid. 3. The novolac type phenol resin for shell mold according to claim 1, wherein the organic phosphonic acid is represented by the general formula (I). R-PO (OH) ₂ (I) (R is a group containing a carbon atom and containing -COOH and / or -PO (OH) ₂ )