Phenol resin composition, binder coated refractory product, and phenol resin molding material

Abstract

To provide a phenol resin composition which can reduce environmental contamination by ammonia and formaldehyde and has a high cure rate.SOLUTION: In order to reduce contamination by ammonia and formaldehyde, when a novolac-type phenol resin and a dimethylene ether-type phenol resin are used in combination as phenol resins, an ammonia resol-type phenol resin is further used in combination, whereby curing characteristics of the dimethylene ether-type phenol resin can be improved and a cure rate can be increased. In addition, blending hexamethylene tetramine can further increase a cure rate of the dimethylene ether-type phenol resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a phenolic resin composition, a binder-coated refractory material coated with a binder containing the phenolic resin composition, and a molding material containing the phenolic resin composition. [Background technology]

[0002] Phenolic resins are used in a variety of applications. For example, resin molded articles for electrical appliances and the like are produced by using a phenolic resin composition prepared mainly from a phenolic resin as a molding material and molding the composition by transfer molding or the like.

[0003] In addition, binder-coated refractories (commonly called resin-coated sand) are prepared by coating refractory aggregate such as silica sand with a binder whose main component is phenolic resin, and this binder-coated refractory is then filled into a mold and heated to produce a casting mold in which the refractory aggregate is bound with the binder. This type of mold has been widely used since it allows for casting with good dimensional accuracy using the shell mold method.

[0004] Phenolic resins are classified into novolac-type phenolic resins and resol-type phenolic resins, and novolac-type phenolic resins are often used as the phenolic resins for the above-mentioned molding materials and binder-coated refractories. Novolac-type phenolic resins are thermoplastic and do not harden even when heated, making them easy to handle. However, novolac-type phenolic resins require the addition of a curing agent to harden them, and hexamethylenetetramine is typically used as this curing agent (see, for example, Patent Documents 1 and 2).

[0005] When a binder-coated refractory prepared using a novolac phenolic resin containing hexamethylenetetramine as a curing agent is used as a binder and this binder-coated refractory is supplied to a molding die to manufacture a casting mold, the hexamethylenetetramine is decomposed into formaldehyde and ammonia by heating during molding. Most of the formaldehyde reacts with the novolac phenolic resin, hardening it to an infusible state, while most of the ammonia is volatilized into the atmosphere, although some of it reacts with the novolac phenolic resin. As a result, the working environment in which the casting mold is made may be contaminated with ammonia.

[0006] On the other hand, resol-type phenolic resins are self-curing and can be cured by heating alone without the need for hexamethylenetetramine, so there is no problem of contamination by ammonia produced by decomposition of hexamethylenetetramine. However, because resol-type phenolic resins have a high content of free formaldehyde, formaldehyde is emitted when preparing resol-type phenolic resins or when preparing binder-coated refractories using resol-type phenolic resins as binders, and there is a risk of formaldehyde contamination of the working environment.

[0007] Dimethyl ether phenolic resin, which is a type of resol phenolic resin, can be cured without the need for a curing agent such as hexamethylenetetramine, and is characterized by the fact that it contains a small amount of formaldehyde, thereby suppressing contamination by formaldehyde.

[0008] Therefore, the combined use of a novolac-type phenolic resin and a dimethylene ether-type phenolic resin as the phenolic resin has been investigated (see Patent Document 3). As mentioned above, novolac-type phenolic resins have the problem of ammonia contamination, but the problem of formaldehyde contamination is small. On the other hand, dimethylene ether-type phenolic resins are free from ammonia contamination and can also suppress formaldehyde contamination. Furthermore, even if formaldehyde is generated during the reaction process when the dimethylene ether-type phenolic resin hardens, the novolac-type phenolic resin reacts with this formaldehyde, thereby further reducing the release of formaldehyde. Therefore, by using a novolac-type phenolic resin and a dimethylene ether-type phenolic resin in combination as the phenolic resin, it is possible to reduce contamination by ammonia and formaldehyde. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-265750 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-170244 [Patent Document 3] Japanese Patent Application Publication No. 2017-109206 Summary of the Invention [Problem to be solved by the invention]

[0010] As described above, by using a novolac type phenolic resin and a dimethylene ether type phenolic resin in combination as the phenolic resin, it becomes possible to prepare a phenolic resin composition that is less susceptible to contamination by ammonia and formaldehyde.

[0011] However, because dimethylene ether-type phenolic resins are resol-type resins, they have a problem of slow curing speed. This not only causes problems in productivity during molding, but is particularly problematic in applications requiring high initial strength. For example, when molding a mold using a binder-coated refractory, if the binder's curing speed is slow, after the mold is filled with the binder-coated refractory and heated to form the mold, the mold is removed from the mold before the binder has fully cured, resulting in deformation and collapse of the mold and a decrease in mold yield.

[0012] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a phenolic resin composition, a binder-coated refractory material, and a phenolic resin molding material which are capable of reducing environmental pollution caused by ammonia and formaldehyde and which have excellent curing properties. [Means for solving the problem]

[0013] The phenolic resin composition according to the present invention is characterized by containing a novolac-type phenolic resin, a dimethylene ether-type phenolic resin, an ammonia-resol-type phenolic resin, and hexamethylenetetramine.

[0014] In order to reduce contamination by ammonia and formaldehyde, when a novolac type phenolic resin and a dimethylene ether type phenolic resin are used in combination as phenolic resins, an ammonia resol type phenolic resin is further used in combination. The ammonia resol type phenolic resin has a fast curing rate, which compensates for the slow curing of the dimethylene ether type phenolic resin, thereby improving the curability of the phenolic resin composition. Furthermore, by adding hexamethylenetetramine, the curing rate of the dimethylene ether type phenolic resin can be further increased, and a phenolic resin composition with excellent curing properties can be obtained.

[0015] In addition, in the present invention, the ammonia resole phenolic resin is characterized in that it is produced by using, in addition to the catalyst for preparing the ammonia resole phenolic resin, a catalyst selected from the oxides and hydroxides of alkali metals and alkaline earth metals.

[0016] By using an ammonia resol type phenolic resin prepared in combination with a catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals, it is possible to further improve curing properties such as curing speed.

[0017] In addition, in the present invention, the blending amounts of the novolac type phenolic resin and the dimethylene ether type phenolic resin are characterized in that the blending amount of the dimethylene ether type phenolic resin is in the range of 10 to 100 parts by mass per 100 parts by mass of the novolac type phenolic resin.

[0018] By setting the blending amounts of the novolac type phenolic resin and the dimethylene ether type phenolic resin within this range, it is possible to obtain a high effect of reducing contamination by ammonia and formaldehyde.

[0019] In the present invention, the amount of the ammonia resol type phenol resin blended is characterized by being in the range of 50 to 300 parts by mass per 100 parts by mass of the dimethylene ether type phenol resin.

[0020] By setting the blending amounts of the dimethylene ether type phenolic resin and the ammonia resole type phenolic resin within this range, the slow curing rate of the dimethylene ether type phenolic resin can be compensated for by the fast curing rate of the ammonia resole type phenolic resin, thereby achieving a significant effect of improving the curing rate of the phenolic resin composition.

[0021] In the present invention, the blending amount of hexamethylenetetramine is characterized by being in the range of 1 to 10 parts by mass per 100 parts by mass of the total of the novolac type phenolic resin, the dimethylene ether type phenolic resin, and the ammonia resol type phenolic resin.

[0022] By setting the blending amount of hexamethylenetetramine within this range, it is possible to achieve a good balance between sufficient curing of the novolac type phenolic resin, an improvement in the curing rate of the dimethylene ether type phenolic resin, and a reduction in ammonia contamination.

[0023] The present invention is also characterized in that an acid is contained as a curing accelerator for the dimethylene ether type phenolic resin.

[0024] The acid can accelerate the curing rate of the dimethylene ether type phenolic resin.

[0025] The binder-coated refractory according to the present invention is characterized in that the surface of a refractory aggregate is coated with a solid coating layer containing the above-mentioned phenolic resin composition as a binder.

[0026] The phenolic resin composition forming the binder of the binder-coated refractory has a fast curing rate as described above, and after a mold is filled with the binder-coated refractory and heated to form a casting mold, the mold can be removed from the mold in a state in which the binder has sufficiently cured, thereby reducing the occurrence of deformation or collapse of the mold and improving the yield of the casting mold.

[0027] The phenolic resin molding material according to the present invention is characterized by containing the above-mentioned phenolic resin composition.

[0028] As described above, the phenolic resin composition has a fast curing rate, and when molding using the phenolic resin molding material, it is possible to speed up the molding cycle, thereby increasing molding productivity. [Effects of the Invention]

[0029] According to the present invention, when a novolac-type phenolic resin and a dimethylene ether-type phenolic resin are used in combination as phenolic resins, the ammonia-resol-type phenolic resin is further used in combination. The ammonia-resol-type phenolic resin has a fast curing rate, which compensates for the slow curing of the dimethylene ether-type phenolic resin, thereby improving the curability of the phenolic resin composition. Furthermore, by adding hexamethylenetetramine, the curing rate of the dimethylene ether-type phenolic resin can be further increased, and a phenolic resin composition with excellent curing properties can be obtained.

[0030] Since the phenolic resin composition has a fast curing rate, a binder-coated refractory prepared by covering the surface of a refractory aggregate with a coating layer containing the phenolic resin composition as a binder can improve the yield when molding a casting mold, and a phenolic resin molding material prepared by containing the phenolic resin composition can increase the productivity when molding. [Brief explanation of the drawings]

[0031] [Figure 1] 1A to 1C are cross-sectional views showing an example of a method for manufacturing a mold according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described.

[0033] The dimethylene ether phenolic resin used in the present invention is a type of resol phenolic resin obtained by reacting phenols with aldehydes at a temperature of 100 to 140°C using a divalent metal naphthenate, a divalent metal carboxylate, or a divalent metal hydroxide as a reaction catalyst, and can be prepared in liquid, semi-solid, or solid forms. For example, by reacting phenols with formaldehyde and then dehydrating the mixture under reduced pressure to 100°C or below, the dimethylene ether phenolic resin can be easily prepared in a solid form at room temperature (25°C) in a relatively heat-stable state.

[0034] Here, the above-mentioned phenols refer to phenol and phenol derivatives, and examples thereof include, in addition to phenol, trifunctional phenols such as m-cresol, resorcinol, and 3,5-xylenol, tetrafunctional phenols such as bisphenol A and dihydroxydiphenylmethane, and difunctional o- or p-substituted phenols such as o-cresol, p-cresol, p-terbutylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, and 2,4- or 2,6-xylenol.Halogenated phenols substituted with chlorine or bromine can also be used.Of course, one of these phenols can be selected and used, or multiple phenols can be used in combination.

[0035] As the aldehyde, formalin, which is an aqueous solution of formaldehyde, is most suitable, but forms such as paraformaldehyde, trioxane, and tetraoxane can also be used, and it is also possible to use formaldehyde by replacing part of it with furfural or furfuryl alcohol.

[0036] The blending ratio of the phenols and aldehydes is not particularly limited, but it is preferable to set the molar ratio of the phenols to the aldehydes in the range of 1:1 to 1:3.5.

[0037] Further, examples of naphthenic acids of divalent metals as reaction catalysts include lead naphthenate, zinc naphthenate, magnesium naphthenate, calcium naphthenate, barium naphthenate, etc., examples of divalent carboxylates include zinc acetate, lead acetate, magnesium acetate, barium acetate, calcium acetate, etc., and examples of hydroxides of divalent metals include magnesium hydroxide, barium hydroxide, etc. Furthermore, zinc borate can also be used as a reaction catalyst.

[0038] In the present invention, the novolac phenolic resin is not limited to a specific one and any one can be used, that is, a phenolic resin prepared by reacting a phenol with a formaldehyde in the presence of an acid catalyst can be used.

[0039] The phenols and formaldehydes that can be used are those mentioned above. The blending ratio of the phenols and formaldehydes is preferably set so that the molar ratio of the phenols to the formaldehyde falls within the range of 1:0.6 to 1:3.5.

[0040] As the acidic reaction catalyst, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, etc., organic acids such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, etc., and zinc acetate, etc. can be used.

[0041] In the present invention, the ammonia resol phenolic resin is prepared by reacting phenols and aldehydes with an alkaline catalyst, using an amine catalyst selected from ammonia, hexamethylenetetramine, primary amines, and secondary amines as the alkaline catalyst. Specific examples of these include ammonia, hexamethylenetetramine, ethylenediamine, diethylenetriamine, triethylenetetramine, N-(2-aminoethyl)ethanolamine, and N-(2-aminoethyl)propanolamine. These can be used alone or in combination with two or more. Among these, ammonia and hexamethylenetetramine are preferred.

[0042] The phenols and formaldehydes that can be used are those mentioned above. The blending ratio of the phenols and formaldehydes is not particularly limited, but it is preferable that the molar ratio of the phenols to the formaldehyde is set to a range of 1:1 to 1:3.5.

[0043] The phenolic resin composition of the present invention is prepared by using the above-mentioned volac-type phenolic resin, dimethylene ether-type phenolic resin, and ammonia-resole-type phenolic resin in combination as phenolic resins, and further blending this with hexamethylenetetramine as the main component.

[0044] In the phenolic resin composition according to the present invention, the blending amounts of the novolac type phenolic resin, dimethylene ether type phenolic resin, and ammonia resol type phenolic resin contained as the phenolic resins are not particularly limited, but it is preferable to set the blending amount of the dimethylene ether type phenolic resin in the range of 10 to 100 parts by mass per 100 parts by mass of the novolac type phenolic resin, and to set the blending amount of the ammonia resol type phenolic resin in the range of 50 to 300 parts by mass per 100 parts by mass of the dimethylene ether type phenolic resin.

[0045] As mentioned above, dimethylene ether phenolic resin is a type of resol phenolic resin, but among resol phenolic resins, it generates relatively little aldehyde during curing. However, as shown in the following chemical formula, a small amount of formaldehyde (HCHO) is produced during the curing reaction of dimethylene ether phenolic resin.

[0046] [ka]

[0047] In contrast, in the present invention, since a dimethylene ether phenolic resin and a novolac phenolic resin are used in combination, the formaldehyde produced when the dimethylene ether phenolic resin cures acts as a curing agent for the novolac phenolic resin. In other words, even if formaldehyde is produced when the dimethylene ether phenolic resin cures, it reacts with the novolac phenolic resin and is consumed, preventing formaldehyde from volatilizing and polluting the work environment. Furthermore, because this formaldehyde acts as a curing agent for the novolac phenolic resin, the amount of hexamethylenetetramine used as a curing agent for the novolac phenolic resin can be reduced, thereby reducing the amount of ammonia generated by decomposition of hexamethylenetetramine.

[0048] As described above, the phenolic resin composition of the present invention uses a novolac-type phenolic resin and a dimethylene ether-type phenolic resin in combination to suppress the generation of ammonia and formaldehyde, thereby reducing environmental pollution. By setting the blending ratio of the novolac-type phenolic resin and the dimethylene ether-type phenolic resin in the range of 10 to 100 parts by mass of the dimethylene ether-type phenolic resin per 100 parts by mass of the novolac-type phenolic resin, as described above, the generation of ammonia and aldehyde can be effectively suppressed in a balanced manner. If the blending amount of the dimethylene ether-type phenolic resin exceeds this range, the effect of suppressing the generation of aldehyde decreases. Furthermore, if the blending amount of the dimethylene ether-type phenolic resin falls below this range, the blending amount of the novolac-type phenolic resin increases relatively, requiring a larger amount of hexamethylenetetramine, the curing agent for the novolac-type phenolic resin, and therefore the effect of suppressing the generation of ammonia decreases.

[0049] Furthermore, dimethylene ether-type phenolic resins have a slower curing rate than novolac-type phenolic resins, resulting in poor curing characteristics for the phenolic resin composition. Therefore, the present invention uses an ammonia-resol-type phenolic resin in combination. The ammonia-resol-type phenolic resin has a fast curing rate, which compensates for the slow curing rate of the dimethylene ether-type phenolic resin and improves the curing rate of the phenolic resin composition.

[0050] By setting the blending amount of the ammonia resole type phenolic resin in the range of 50 to 300 parts by mass per 100 parts by mass of the dimethylene ether type phenolic resin as described above, the effect of improving the curing rate of the phenolic resin composition can be sufficiently achieved. If the blending amount of the ammonia resole type phenolic resin is less than this range, the effect of improving the curing rate by the ammonia resole type phenolic resin may be insufficient. Conversely, if the blending amount of the ammonia resole type phenolic resin exceeds this range, the effect of reducing environmental pollution may be reduced due to the generation of aldehyde from the ammonia resole type phenolic resin and the generation of a small amount of ammonia from the catalyst, such as ammonia remaining in the resin.

[0051] Here, the ammonia resol type phenolic resin may be prepared by using, as a catalyst for reacting phenols with aldehydes, a catalyst for preparing an ammonia resol type phenolic resin, i.e., an amine catalyst selected from ammonia, hexamethylenetetramine, primary amines, and secondary amines, in combination with a catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals.

[0052] Examples of the catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, and barium hydroxide.

[0053] The ratio of the amine catalyst for preparing the ammonia resol type phenolic resin to the catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals is not particularly limited, but it is preferable to set the mass ratio at 1:0.1 to 1:2.

[0054] An ammoniacal resole phenolic resin prepared by using an amine catalyst for preparing an ammoniacal resole phenolic resin in combination with a catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals has a faster curing rate than a general ammoniacal resole phenolic resin prepared using only an amine catalyst, and can further improve the curing properties of a phenolic resin composition.

[0055] In order to prevent a decline in the curing properties of the phenolic resin composition due to the slow curing rate of the dimethylene ether phenolic resin, in addition to the use of an ammonia resol phenolic resin as the phenolic resin as described above, the present invention further blends hexamethylenetetramine. Hexamethylenetetramine has the effect of accelerating the curing of the dimethylene ether phenolic resin, thereby accelerating the curing rate of the dimethylene ether phenolic resin and further improving the curing properties of the phenolic resin composition.

[0056] Hexamethylenetetramine also functions as a curing agent for novolac-type phenolic resins. The amount of hexamethylenetetramine added depends on the blending ratio of the dimethylene ether-type phenolic resin, novolac-type phenolic resin, and ammonia-resole-type phenolic resin, but is preferably in the range of 1 to 10 parts by mass per 100 parts by mass of the total amount of the dimethylene ether-type phenolic resin, novolac-type phenolic resin, and ammonia-resole-type phenolic resin. If the amount of hexamethylenetetramine is small, below this range, the effect of improving the curing properties of the phenolic resin composition may be insufficient. Conversely, if the amount of hexamethylenetetramine is greater than this range, there is a risk of problems with the working environment due to ammonia generation.

[0057] In addition to blending hexamethylenetetramine into the phenolic resin composition, an acid may be blended into the phenolic resin composition as a curing accelerator for the dimethylene ether type phenolic resin to improve the curing properties.

[0058] The acid may be an inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid, etc., or an organic acid such as benzoic acid, salicylic acid, paratoluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, etc. The amount of acid added varies depending on the type of acid and conditions such as the curing temperature, but is generally preferably in the range of 0.1 to 30 parts by mass per 100 parts by mass of the dimethylene ether phenolic resin.

[0059] The binder-coated refractory according to the present invention is formed by covering the surface of a refractory aggregate with a coating layer containing the above-mentioned phenolic resin composition as a binder.

[0060] The refractory aggregate to be used is one having a sandy form, and is not particularly limited, but examples thereof include silica sand, pit sand, alumina sand, olivine sand, chromite sand, zircon sand, mullite sand, and other artificial sands. These may be used alone or in combination of two or more types.

[0061] The coating layer is solid at the ambient temperature (e.g., 20-30°C) where the binder-coated refractory is stored and used, and the binder-coated refractory is in a free-flowing granular form and has good fluidity.

[0062] To improve the fluidity of the binder-coated refractory, the coating layer may contain a lubricant. Examples of lubricants that can be used include aliphatic hydrocarbon lubricants such as paraffin wax and carnauba wax, higher aliphatic alcohols, aliphatic amide lubricants such as ethylene bis(stearic acid amide) and stearic acid amide, metal soap lubricants, fatty acid ester lubricants, and composite lubricants. Metal soap lubricants are preferred. Examples of metal soap lubricants that can be used include calcium stearate, barium stearate, zinc stearate, aluminum stearate, magnesium stearate, and combinations of these.

[0063] The coating layer of the binder-coated refractory may further contain a carbonaceous material. Examples of such carbonaceous materials include natural graphite, artificial graphite, kish graphite, mesophase carbon, petroleum pitch coke, coal pitch coke, carbon black, resinous carbon, anthracite, precursor, exfoliated graphite, charcoal, and carbonized organic materials. Silicon carbide, a carbon compound, may also be used as the carbonaceous material.

[0064] Because carbonaceous materials have poor wettability with molten metal, molds manufactured using binder-coated refractories containing a carbonaceous material in the coating layer can be protected from the molten metal, and the effectiveness of preventing penetration or seizure of the molten metal into the mold can be highly achieved. Furthermore, it is generally known that the wetting of refractory aggregate such as sand with molten metal (molten iron) is promoted by the presence of iron oxide, and carbonaceous materials can maintain a reducing gas atmosphere in the mold, preventing the formation of iron oxide and maintaining poor wettability with the molten metal.

[0065] The amount of coating layer applied to the refractory aggregate varies depending on the components and application, and cannot be generally determined, but it is generally preferable to set the amount of binder in the coating layer to be in the range of 0.5 to 6.0 parts by mass per 100 parts by mass of the refractory aggregate.

[0066] Methods for producing binder-coated refractories by applying a solid coating layer to the surface of refractory aggregate include the hot coating method, cold coating method, semi-hot coating method, and powder solvent method.

[0067] The hot coating method involves adding a solid binder to refractory aggregate heated to 110 to 180°C and mixing the mixture, melting the solid binder with the heat of the refractory aggregate, so that the molten binder wets and coats the surface of the refractory aggregate, and then cooling the mixture while maintaining the temperature to obtain a granular, free-flowing binder-coated refractory. Alternatively, a binder-coated refractory can be obtained by mixing a binder dissolved or dispersed in a solvent such as water with refractory aggregate heated to 110 to 180°C, coating the aggregate, and then volatilizing the solvent.

[0068] The cold coating method is a method in which a binder is dispersed or dissolved in a solvent such as water or methanol to form a liquid, which is then added to and mixed with refractory aggregate particles, and the solvent is evaporated to obtain a binder-coated refractory material.

[0069] The semi-hot coating method is a method in which a binder dispersed or dissolved in a solvent such as water or methanol is added to and mixed with refractory aggregate particles heated to 50 to 90°C, and the solvent is evaporated to obtain a binder-coated refractory material.

[0070] The powder solvent method is a method in which a solid binder is crushed, the crushed binder is added to particles of refractory aggregate, and then a solvent such as water or methanol is added, and the mixture is mixed to volatilize the solvent, thereby obtaining a binder-coated refractory material.

[0071] In any of the above methods, the surface of the refractory aggregate is coated with a solid coating layer to obtain a granular, free-flowing, binder-coated refractory material with good fluidity, but the hot coating method is preferred in terms of workability, etc. When mixing the binder with the refractory aggregate as described above, other materials to be contained in the coating layer can also be blended, if necessary, such as a hardener, various coupling agents such as a silane coupling agent for improving the affinity between the refractory aggregate and the binder, or carbonaceous materials such as graphite.

[0072] The binder-coated refractory of the present invention obtained as described above can be used as a material for casting molds, firebricks, wall materials, ceramics, etc., but is particularly suitable for use as a casting mold.

[0073] When manufacturing a casting mold using a binder-coated refractory, the binder-coated refractory is supplied to a heated mold, for example, filling the cavity of the mold with the binder-coated refractory, and the binder in the coating layer of the binder-coated refractory is melted and hardened by the heat of the mold, thereby binding the refractory aggregate with the hardened binder, thereby manufacturing the casting mold.

[0074] Here, the phenolic resin composition used as the binder in the coating layer of the binder-coated refractory material uses a combination of a novolac-type phenolic resin and a dimethylene ether-type phenolic resin as the phenolic resin, as described above, to reduce ammonia and aldehyde emissions, thereby preventing contamination of the mold manufacturing environment with ammonia and aldehydes. Furthermore, the use of an ammonia-resol-type phenolic resin as the phenolic resin improves the curing properties of the phenolic resin composition by compensating for the slow curing rate of the dimethylene ether-type phenolic resin. Furthermore, the inclusion of hexamethylenetetramine increases the curing rate of the dimethylene ether-type phenolic resin. Because of the high curing properties of the phenolic resin composition, the mold develops strength quickly after molding, reducing deformation and breakage of the mold when it is removed from the mold, thereby improving mold yield.

[0075] In the above embodiment, a method for producing a casting mold has been described in which a binder-coated refractory is supplied to a heated mold and heated by heat transferred from the mold, but a casting mold can also be produced by heating the binder-coated refractory with steam. That is, a casting mold can be produced by filling a mold with the binder-coated refractory, then supplying and passing steam through the mold, and heating the binder-coated refractory in the mold with the latent heat of condensation and sensible heat of the steam, thereby causing an addition-condensation reaction of the phenolic resin in the coating layer to harden.

[0076] An example of such a method for manufacturing a casting mold using steam will be described with reference to FIG. 1. As shown in FIG. 1(a), mold 1, which has a cavity 3 formed therein, has an inlet 4 on its top surface and an outlet 6 on its bottom surface, which is blocked with a mesh 5 such as a wire mesh. This mold 1 can be split vertically or horizontally. The binder-coated refractory 2 is stored in a hopper 7, to which an air supply pipe 9 with a cock 8 is connected. After aligning the nozzle opening 7a at the bottom of the hopper 7 with the inlet 4 of mold 1, the cock 8 is switched from closed to open, blowing air into the hopper 7 to pressurize it. The binder-coated refractory 2 in the hopper 7 is then blown into mold 1, filling the cavity 3 of mold 1 with the binder-coated refractory 2. Because the outlet 6 is blocked with the mesh 5, the binder-coated refractory 2 does not leak out of the outlet 6. When a plurality of injection ports 4 and discharge ports 6 are provided in the mold 1 as in the embodiment of FIG. 1, the binder-coated refractory material 2 may be poured into one or more of the injection ports 4 .

[0077] Here, the binder-coated refractory 2 according to the present invention is formed by covering a refractory aggregate with a coating layer containing a phenolic resin composition as a binder, and since the coating layer is solid, the binder-coated refractory 2 does not have adhesiveness on the surface and has good fluidity. Therefore, when filling the mold 1 with the binder-coated refractory 2 as described above, the binder-coated refractory 2 can be smoothly poured into the cavity 3 of the mold 1, and the binder-coated refractory 2 can be filled into the mold 1 with good packing properties, thereby preventing the occurrence of filling defects.

[0078] After the binder-coated refractory material 2 has been filled into the mold 1 as described above, the hopper 7 is removed from the injection ports 4 of the mold 1, and air supply pipes 10 are connected to each injection port 4 as shown in Figure 1(b). The air supply pipes 10 are designed to be able to supply steam, and a cock 11 of the air supply pipes 10 is opened to blow steam into the cavity 3 of the mold 1.

[0079] Here, saturated steam can be used as is as the water vapor, but superheated steam is preferably used. Superheated steam is water vapor in a completely gaseous state obtained by further heating saturated steam to a temperature above its boiling point, and is dry steam at 100°C or higher. Superheated steam obtained by heating saturated steam may be expanded at a constant pressure without increasing the pressure, or may be pressurized steam obtained by increasing the pressure without expanding. The temperature of the superheated steam injected into the mold 1 is not particularly limited; since the temperature of superheated steam can be increased up to about 900°C, it may be set to a temperature between 100 and 900°C as needed.

[0080] When steam is blown into and passed through the mold 1 in this manner, the steam comes into contact with the surface of the binder-coated refractory 2, and the steam condenses as the latent heat is absorbed by the binder-coated refractory 2. However, because steam has a high latent heat, the temperature of the binder-coated refractory 2 is rapidly raised to around 100°C by the latent heat transferred when the steam condenses. The time required for the binder-coated refractory 2 to be heated to around 100°C by the transfer of the latent heat of the steam varies depending on the temperature of the steam, the flow rate of the steam blown into the mold 1, the amount of binder-coated refractory 2 packed in the mold 1, etc., but is usually a short time of around 3 to 30 seconds. The steam blown into the mold 1 through the injection port 4 heats the binder-coated refractory 2 in the mold 1 and then is exhausted through the outlet 6.

[0081] When steam is blown into the mold 1 as described above, the latent heat transferred when the steam condenses can rapidly raise the temperature of the binder-coated refractory 2 to around 100°C, but to further raise the temperature above 100°C, the condensed water must be evaporated. This condensed water is then evaporated by heating due to the latent heat and sensible heat of the steam blown into and passing through the mold 1, and the temperature inside the mold 1 rapidly rises to near the temperature of the steam, allowing the binder-coated refractory 2 to be heated to a temperature above 100°C, at which the phenolic resin binder can be hardened.

[0082] In this way, the temperature of the binder-coated refractory material 2 can be raised to 100°C or higher in a short time after the start of blowing steam into the mold 1, and the speed at which the temperature inside the mold 1 is raised to a temperature above the temperature at which the phenolic resin in the coating layer of the binder-coated refractory material 2 undergoes an addition condensation reaction and hardens can be increased.

[0083] The steam and heated gas supplied into the mold 1 pass between the particles of the binder-coated refractories 2 in the mold 1 and are discharged from the outlet 6, so that the binder-coated refractories 2 are simultaneously heated by the steam at all locations in the mold 1. Therefore, the binder-coated refractories 2 in the mold 1 are heated with a uniform temperature distribution, making it possible to manufacture a homogeneous mold with no difference in strength between the surface and the interior of the mold.

[0084] The time for blowing steam into the mold 1 varies depending on the temperature of the steam, the flow rate of the steam blown into the mold 1, the amount of binder-coated refractory 2 packed in the mold 1, the amount of condensed water in the mold 1, and the like, but is usually a short time of about 5 to 40 seconds. Therefore, it is possible to manufacture a casting mold in a short time of about 10 seconds to 1 minute after starting to blow steam into the forming mold 1.

[0085] As described above, by supplying steam to the mold 1 to heat the binder-coated refractory 2, the binder-coated refractory 2 can be instantly heated by the high latent heat and sensible heat of condensation of the steam, thereby hardening the phenolic resin in the coating layer, making it possible to stably manufacture molds in a short time without the need to preheat the mold 1 to a high temperature, thereby improving mold productivity. Furthermore, even if ammonia or aldehyde is generated during heating, it can be absorbed by the condensed water of the steam, thereby reducing environmental pollution.

[0086] Furthermore, by blending various additives with the phenolic resin composition of the present invention and mixing or kneading them, phenolic resin molding materials that can be molded for various applications can be obtained. Additives that can be blended depending on the application include fillers such as graphite, wood flour, pulp, and fiber, plasticizers, stabilizers, colorants, mold release agents, and lubricants.

[0087] The phenolic resin molding material according to the present invention prepared in this manner can be molded by any method, such as transfer molding or compression molding, and the molded products can be used in various fields, such as electrical parts, automobile parts, building materials, and daily necessities.

[0088] Furthermore, the phenolic resin composition according to the present invention can be dissolved in a solvent and used as an adhesive, etc., and the uses of the phenolic resin composition are not particularly limited. [Example]

[0089] Next, the present invention will be specifically described with reference to examples.

[0090] (Preparation of Dimethylene Ether Phenolic Resin A) A reactor equipped with a stirrer was charged with 170 parts by weight of phenol, 106 parts by weight of 92% paraformaldehyde, 0.7 parts by weight of zinc acetate, and 33 parts by weight of water. The mixture was brought to a boil over approximately 60 minutes and allowed to react at the boil for 4 hours. The mixture was then deliquified at atmospheric pressure over 60 minutes until the temperature reached 115°C, and then deliquified at 105°C for a further 6 hours to remove unreacted phenol. This deliquification was carried out by steam deliquification under a reduced pressure of -90.5 kPa while adding 70 g of water dropwise per hour. After deliquification was complete, the liquid temperature in the reactor was lowered to 100°C, and the contents of the reactor were then poured onto a stainless steel tray and cooled to room temperature, yielding 202 parts by weight of solid dimethylene ether-type phenolic resin A.

[0091] This dimethylene ether type phenolic resin A was pulverized using a power mill pulverizer with a screen having openings of 2.5 mm in diameter, and then fine powder was removed using a fluidized bed dryer to prepare granules having a diameter of about 1 mm.

[0092] (Preparation of Dimethylene Ether Phenolic Resin B) A reactor equipped with a stirrer was charged with 80 parts by weight of phenol, 100 parts by weight of bisphenol A, 60 parts by weight of 92% paraformaldehyde, 0.2 parts by weight of zinc acetate, and 8 parts by weight of water. The mixture was brought to a boil over approximately 60 minutes and allowed to react for 160 minutes while maintaining the boiling state. The mixture was then dewatered at atmospheric pressure over 15 minutes until the temperature reached 113°C, and then dewatered at atmospheric pressure for another 9 hours while maintaining the temperature at 113±2°C. The pressure inside the reactor was then reduced to -93.5 kPa, and unreacted phenol was removed by dewatering over approximately 20 minutes while maintaining the temperature at approximately 98°C. After dewatering was completed, the liquid temperature inside the reactor was lowered to 100°C, and the contents of the reactor were then poured onto a stainless steel tray and cooled to room temperature, yielding a solid dimethylene ether-type phenolic resin B in a yield of 234 parts by weight. Thereafter, the resin was pulverized in the same manner as in the case of the dimethylene ether type phenolic resin A, and the dimethylene ether type phenolic resin B was prepared into granules having a diameter of about 1 mm.

[0093] (Preparation of ammonia resol type phenolic resin C) A reaction vessel equipped with a stirrer was charged with 140 parts by weight of phenol, 65 parts by weight of 92% paraformaldehyde, 16 parts by weight of hexamethylenetetramine, and 120 parts by weight of water. The mixture was heated to 60°C over approximately 40 minutes and allowed to react at this temperature for approximately 120 minutes. The mixture was then heated to 70°C and allowed to react for approximately 80 minutes. The mixture was then dehydrated under reduced pressure of -86.7 kPa until the internal temperature reached 58°C. The contents of the reaction solution were then poured onto a stainless steel tray and stored in a -10°C freezer to cool, yielding a frozen and solidified ammonia resol phenolic resin C.

[0094] Next, the frozen ammonia-resol type phenolic resin C was pulverized using a power mill pulverizer with a screen having openings of φ2.5 mm, and then the pulverized material was dried by heating with hot air at 60°C for 120 minutes using a fluidized bed dryer (freeze-drying).The pulverized material was then cooled to room temperature, yielding 180 parts by mass of granular solid ammonia-resol type phenolic resin C with a diameter of approximately 1 mm.

[0095] (Preparation of ammonia resol type phenolic resin D) A reaction vessel equipped with a stirrer was charged with 120 parts by mass of phenol, 50 parts by mass of 92% paraformaldehyde, 13 parts by mass of hexamethylenetetramine, 0.4 parts by mass of 48% caustic soda, and 88 parts by mass of water, and the mixture was heated to 70°C over approximately 60 minutes and reacted at this temperature for approximately 20 minutes.The mixture was then heated to a boil over an additional 20 minutes and then reacted at the boil for approximately 9 minutes.

[0096] The mixture was then dehydrated under reduced pressure of -86.7 kPa until the internal temperature reached 58°C, and then, in the same manner as in the case of the above ammoniacal resol-type phenolic resin C, it was cooled in a freezer to freeze-solidify, yielding ammoniacal resol-type phenolic resin D. Then, in the same manner as in the case of the above ammoniacal resol-type phenolic resin C, it was pulverized in a power mill pulverizer, freeze-dried in a fluidized bed dryer, and cooled to room temperature, yielding 170 parts by mass of granular solid ammoniacal resol-type phenolic resin D with a diameter of approximately 1 mm.

[0097] (Preparation of ammonia resol type phenolic resin E) Solid ammonia resol phenolic resin E was obtained in a yield of 170 parts by mass in the same manner as in the case of the above ammonia resol phenolic resin D, except that the amount of 48% caustic soda added was changed to 0.7 parts by mass.

[0098] (Preparation of ammonia resol type phenolic resin F) Solid ammonia resol type phenolic resin F was obtained in a yield of 170 parts by mass in the same manner as in the case of the above ammonia resol type phenolic resin D, except that 0.4 parts by mass of 48% caustic potassium was used instead of caustic soda.

[0099] (Preparation of ammonia resol type phenolic resin G) Solid ammonia resol phenolic resin G was obtained in a yield of 170 parts by mass in the same manner as in the case of the above ammonia resol phenolic resin D, except that 0.4 parts by mass of lithium hydroxide was added instead of caustic soda.

[0100] (Preparation of Novolac Phenolic Resin H) A reactor equipped with a stirrer was charged with 162 parts by weight of phenol, 45 parts by weight of 92% paraformaldehyde, 0.6 parts by weight of oxalic acid, and 26 parts by weight of water. The mixture was brought to a boil over approximately 60 minutes and allowed to react at the boil for 120 minutes. The mixture was then deliquified at atmospheric pressure over 130 minutes until the temperature reached 175°C. The pressure in the reactor was then reduced to -93.5 kPa, and unreacted phenol was removed by deliquification over approximately 15 minutes. After deliquification was complete, the contents of the reactor were poured onto a stainless steel tray and cooled to room temperature, yielding 165 parts by weight of solid novolac phenolic resin H.

[0101] The molecular weight, softening point, and gel temperature of the phenolic resins A to H obtained as described above were measured. The results are shown in Table 1.

[0102] Here, molecular weight measurements were performed using gel permeation chromatography (GPC) (HLC-8400GPC manufactured by Tosoh Corporation), and the number average molecular weight (Mn) and weight average molecular weight (Mw) were determined in terms of polystyrene. The softening point and gel time were measured in accordance with JIS K 6910, and the gel time was determined as the time it took for gelation at 150°C. The gel time was measured by mixing each phenolic resin with hexamethylenetetramine in the mass % shown in Table 1.

[0103] [Table 1]

[0104] Dimethyl ether phenolic resin is a resol type and has self-curing properties, so there is no need to use a curing agent such as hexamethylenetetramine, but as can be seen in the "Gelation Time" column in Table 1, blending a small amount of hexamethylenetetramine, about 5% by mass, into the dimethylene ether phenolic resin significantly shortens the gelation time. This demonstrates that blending hexamethylenetetramine with the dimethylene ether phenolic resin can increase the curing speed by several times.

[0105] Ammoniacal resole phenolic resins are typically prepared by reacting phenols with aldehydes using an amine catalyst. A comparison of ammoniacal resole phenolic resin C, prepared using only an amine catalyst, with ammoniacal resole phenolic resins D to G, prepared using both an amine catalyst and a catalyst composed of an oxide or hydroxide of an alkali metal or alkaline earth metal, reveals that ammoniacal resole phenolic resins D to G have a shorter gelation time, as shown in Table 1. Thus, the combined use of a typical amine catalyst for the production of ammoniacal resole phenolic resins with a catalyst composed of an oxide or hydroxide of an alkali metal or alkaline earth metal can produce ammoniacal resole phenolic resins with a fast curing rate. Furthermore, as seen in the comparison of ammoniacal resole phenolic resin D and ammoniacal resole phenolic resin E, the curing rate tends to increase with increasing the amount of catalyst composed of an oxide or hydroxide of an alkali metal or alkaline earth metal.

[0106] Example 1 10,000 parts by weight of ACI-G silica sand heated to 140-145°C was charged into a Whirl mixer. The following phenolic resins were added: 60 parts by weight of dimethylene ether-type phenolic resin A, 60 parts by weight of ammonia resol-type phenolic resin C, and 80 parts by weight of novolac-type phenolic resin H. The mixture was kneaded for 45 seconds. 10 parts by weight of hexamethylenetetramine dissolved in 150 parts by weight of water was then added and kneaded until the sand particles were disintegrated. Next, 10 parts by weight of calcium stearate was added and kneaded for 30 seconds. The mixture was then removed from the Whirl mixer and aerated to cool, yielding a binder-coated refractory (resin-coated sand: RCS). The binder-coated refractory thus obtained had a solid surface coating and consisted of particles with good fluidity.

[0107] Example 2 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 70 parts by mass of dimethylene ether type phenolic resin A, 30 parts by mass of ammonia resol type phenolic resin C, and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins.

[0108] Example 3 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin C, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0109] Example 4 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 30 parts by mass of dimethylene ether type phenolic resin A, 70 parts by mass of ammonia resol type phenolic resin C, and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins.

[0110] Example 5 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin D, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0111] Example 6 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin E, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0112] Example 7 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin F, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0113] Example 8 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin G, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0114] Example 9 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin B, 50 parts by mass of ammonia resol-type phenolic resin D, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins.

[0115] Example 10 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 30 parts by mass of dimethylene ether type phenolic resin B, 70 parts by mass of ammonia resol type phenolic resin D, and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins.

[0116] Example 11 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether type phenolic resin A, 50 parts by mass of ammonia resol type phenolic resin C, and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins, and that 2 parts by mass of salicylic acid was added as a curing accelerator for the dimethylene ether type phenolic resin A simultaneously with hexamethylenetetramine.

[0117] (Comparative Example 1) A binder-coated refractory material was obtained in the same manner as in Example 1, except that 200 parts by mass of novolac type phenolic resin H was used as the phenolic resin and the amount of hexamethylenetetramine added was 30 parts by mass.

[0118] (Comparative Example 2) A binder-coated refractory material was obtained in the same manner as in Example 1, except that 200 parts by mass of novolac type phenolic resin H was used as the phenolic resin.

[0119] (Comparative Example 3) A binder-coated refractory material was obtained in the same manner as in Example 1, except that 100 parts by mass of dimethylene ether type phenolic resin A and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins.

[0120] Comparative Example 4 A binder-coated refractory material was obtained in the same manner as in Example 1, except that 100 parts by mass of dimethylene ether type phenolic resin B and 100 parts by mass of novolac type phenolic resin H were used as the phenolic resins.

[0121] (Comparative Example 5) A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin C, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins, and hexamethylenetetramine was not used.

[0122] (Comparative Example 6) A binder-coated refractory material was obtained in the same manner as in Example 1, except that 50 parts by mass of dimethylene ether-type phenolic resin A, 50 parts by mass of ammonia resol-type phenolic resin D, and 100 parts by mass of novolac-type phenolic resin H were used as the phenolic resins, and hexamethylenetetramine was not used.

[0123] The flexural strength, strength at high temperatures, bend amount, and amount of generated gas were measured for the binder-coated refractories obtained in the above Examples 1 to 11 and Comparative Examples 1 to 6. The results are shown in Tables 2 and 3.

[0124] The bending strength was determined as follows. Each of the binder-coated refractories described above was filled into a mold and fired at 250°C for 60 seconds in accordance with JIS-K-6910 (1999) to prepare a 10 x 10 x 60 mm test piece. The test piece was then released from the mold and allowed to cool to room temperature, after which the bending strength was measured at room temperature in accordance with the JACT test method (SM-1).

[0125] The warm strength was determined as follows. Each of the binder-coated refractories described above was filled into a mold and fired at 250°C for 60 seconds in accordance with JIS-K-6910 (1999) to prepare a 10 x 10 x 60 mm test piece. Ten seconds after releasing the test piece from the mold, the strength was measured in accordance with the JACT test method (SM-1). The warm strength was determined by evaluating the strength of the mold immediately after it was filled with the binder-coated refractory and formed. The higher the warm strength, the faster the binder in the binder-coated refractory hardens, and the less likely the mold is to deform or distort when removed from the mold.

[0126] The bending amount was determined according to the JACT test method (SM-3). Each binder-coated refractory material was filled into a mold and fired at 250°C for 30 seconds. After 10 seconds, a 500g load was applied to the center of the specimen, which was then released from the mold. The specimen was then supported on a support and left for 3 minutes. The amount of bending was then measured at the center. When the binder cured more rapidly, the strength of the specimen increased, resulting in a smaller bending amount. When the binder cured more slowly, the strength of the specimen decreased, resulting in a larger bending amount. In Table 3, an "x" indicates that the specimen was not strong enough to support the load. The bending amount evaluated here evaluates the ease of mold removal (handling) after the mold was filled with the binder-coated refractory material and molding. The smaller the bending amount, the faster the binder curing rate of the binder-coated refractory and the easier it was to remove the mold from the mold without deformation or distortion.

[0127] The amount of gas generated was measured by spreading 1 g of each of the binder-coated refractories on a hot plate at 250°C, covering it with a 20-liter container, and after 30 seconds, inserting a Kitagawa-type detector tube ("Tube No. 105SC" manufactured by Komyo Rikagaku Kogyo Co., Ltd.) into the container and measuring the ammonia concentration for 60 seconds. The obtained concentration value (ppm) was converted to mass (μm) and displayed.

[0128] [Table 2]

[0129] [Table 3]

[0130] The following can be concluded from Tables 2 and 3. When a dimethylene ether-type phenolic resin and a novolac-type phenolic resin are used in combination as the phenolic resin, and an ammonia resol-type phenolic resin is further used in combination with hexamethylenetetramine as a curing agent as in Examples 1 to 11, the strength at high temperature is improved and the amount of bending is reduced, confirming that the binder in the binder-coated refractory material has a fast curing rate. That is, although Comparative Examples 3 and 4 use only a combination of a dimethylene ether-type phenolic resin and a novolac-type phenolic resin as the phenolic resin, the strength at high temperature and the amount of bending of Examples 1 to 11 are significantly improved compared to Comparative Examples 3 and 4, confirming that the curing rate of Examples 1 to 11 is fast.

[0131] In Comparative Examples 1 and 2, in which only a novolac-type phenolic resin was used as the phenolic resin, when the amount of hexamethylenetetramine curing agent was small, curing was insufficient, resulting in poor hot strength and bend amount, as in Comparative Example 2, and when the amount of hexamethylenetetramine was increased to speed up the curing rate, a large amount of ammonia gas was generated, as in Comparative Example 1. Even when a combination of a dimethylene ether-type phenolic resin, an ammonia resole-type phenolic resin, and a novolac-type phenolic resin was used as the phenolic resin, without adding hexamethylenetetramine, the generation of ammonia gas was reduced, but the hot strength and bend amount were poor, as seen in Comparative Examples 5 and 6, confirming that adding hexamethylenetetramine is necessary to speed up the curing rate.

[0132] Furthermore, the ammonia resol type phenolic resin C used in Examples 1 to 4 is a general ammonia resol type phenolic resin prepared using only an amine-based catalyst, while the ammonia resol type phenolic resins D to G used in Examples 5 to 8 are special ammonia resol type phenolic resins prepared using an alkali metal hydroxide in addition to an amine-based catalyst. As is clear from a comparison of the hot strength and bend amount between Examples 1 to 4 and Examples 5 to 8, it is confirmed that the use of an ammonia resol type phenolic resin prepared using an alkali metal hydroxide in addition to an amine-based catalyst increases the curing rate of the binder in the binder-coated refractory.

[0133] In Example 11, salicylic acid was added as a curing agent for the dimethylene ether type phenolic resin A to the composition of Example 3. As is clear from a comparison of the strength at high temperature and the bend amount between Example 3 and Example 11, it was confirmed that the curing rate of the binder in the binder-coated refractory material was increased.

[0134] (Examples 12 to 22, Comparative Examples 7 to 12) Dimethyl ether type phenolic resins A and B, ammonia resol type phenolic resins C to G, novolac type phenolic resin H, hexamethylenetetramine, and salicylic acid were charged into a crush mixer and pulverized and mixed in the same amounts as in Examples 1 to 11 and Comparative Examples 1 to 6 above, and 40 parts by mass of this resin mixture was blended with 60 parts by mass of cellulose ("KC Flock W-200" manufactured by Nippon Paper Industries Co., Ltd.) as a filler to prepare the phenolic resin molding materials of Examples 12 to 22 and Comparative Examples 7 to 12.

[0135] Curastometer measurements were carried out on the phenolic resin molding materials obtained in Examples 12 to 22 and Comparative Examples 7 to 12, and the results are shown in Tables 4 and 5. "Curastometer" is a registered trademark of ENEOS Material Corporation.

[0136] Curastometer measurements were performed using a "VPD" model Curastometer manufactured by Nikko Shoji Co., Ltd. 7.5 g of each molding material was placed in the measurement section of the Curastometer at a temperature of 150°C and a vibration frequency of 100 cpm. The Curastometer (registered trademark) uses a temperature-controlled die as the measurement section. The sample is filled into the hollow section of the die, and while heating, repeated strain is applied. The resulting stress is measured as torque. This measurement allows the calculation of the time required for 10% cure (T-10), 50% cure (T-50), and 90% cure (T-90). The shorter these times, the faster the cure rate and the shorter the molding time required for molding the molding material.

[0137] [Table 4]

[0138] [Table 5]

[0139] As can be seen in Tables 4 and 5, when comparing each Example with Comparative Examples 7-8, which used only a novolac-type phenolic resin as the phenolic resin, the initial cure time, T-10, at 10% cure, was short in all cases, and it was confirmed that each Example had a fast cure speed, similar to Comparative Examples 7-8. On the other hand, Comparative Examples 9-10, which used a combination of a dimethylene ether-type phenolic resin and a novolac-type phenolic resin, and Comparative Examples 11-12, which did not contain hexamethylenetetramine, had a longer T-10 time and a slower cure speed.

[0140] Furthermore, while Comparative Examples 7-8 have short T-50 times (50% cure), which is the middle stage of curing, and T-90 times (90% cure), which is the final stage of curing, it is expected that the resin will harden too quickly in the mold during molding, resulting in molding defects such as poor filling and voids. In contrast, the T-50 and T-90 times of the Examples are longer than Comparative Examples 7-8 but shorter than Comparative Examples 9-12, confirming that molding times can be shortened while preventing molding defects. [Explanation of symbols]

[0141] 1 mold 2. Binder-coated refractories

Claims

1. A phenolic resin composition comprising a novolac-type phenolic resin, a dimethylene ether-type phenolic resin, an ammonia-resol-type phenolic resin, and hexamethylenetetramine.

2. The phenolic resin composition according to claim 1, characterized in that the ammonia resole type phenolic resin is a phenolic resin which is prepared by using, in addition to a catalyst for preparing the ammonia resole type phenolic resin, a catalyst selected from oxides and hydroxides of alkali metals and alkaline earth metals.

3. 3. The phenolic resin composition according to claim 1, wherein the amount of the dimethylene ether phenolic resin is in the range of 10 to 100 parts by mass per 100 parts by mass of the novolac phenolic resin.

4. 3. The phenolic resin composition according to claim 1, wherein the amount of the ammonia resol type phenolic resin blended is in the range of 50 to 300 parts by mass per 100 parts by mass of the dimethylene ether type phenolic resin.

5. 3. The phenolic resin composition according to claim 1, wherein the amount of hexamethylenetetramine blended is in the range of 1 to 10 parts by mass per 100 parts by mass of the total of the novolac type phenolic resin and the dimethylene ether type phenolic resin.

6. 3. The phenolic resin composition according to claim 1, further comprising an acid as a curing accelerator for the dimethylene ether type phenolic resin.

7. 3. A binder-coated refractory material, comprising a refractory aggregate having a surface coated with a solid coating layer containing the phenolic resin composition of claim 1 or 2 as a binder.

8. A phenolic resin molding material comprising the phenolic resin composition according to claim 1 or 2.

Images