JP5491382B2 - Phenolic resin composition for shell mold, resin coated sand for shell mold, and mold obtained by using the same - Google Patents

Description

  The present invention relates to a phenol resin composition for a shell mold, a resin-coated sand for a shell mold, and a mold using the same, and in particular, generation of a thermal decomposition product (hereinafter simply referred to as “anim”) generated during casting. The present invention relates to a phenol resin composition for a shell mold capable of suppressing the amount and simultaneously solving the problems of thermal expansion and randomness, a resin-coated sand obtained using the same, and a mold formed using the same It is.

  Conventionally, in shell mold casting, a resin-coated sand (hereinafter referred to as “hereinafter referred to as“ resin coated sand ”) obtained by kneading a refractory particle (casting sand) and a phenolic resin (binder) and, if necessary, a curing agent such as hexamethylenetetramine. In general, shell molds have been commonly used that are heat molded using abbreviated RCS ”to form the desired shape.

  However, among these types of molds, in particular, in the case of a mold having a complicated shape for casting a cast product such as a cylinder head of an internal combustion engine, in the casting operation using the mold, There is a problem that it is easy to cause "cracking"). Further, as the shape of the mold becomes complicated, the number of vent holes tends to decrease. For this reason, the occurrence of burrs derived from the binder has become a serious problem during casting.

  By the way, in order to prevent the cracking of the mold, it is considered that the thermal expansion coefficient of the mold should be lowered and the property should be increased. However, in Patent Document 1, bisphenol A is used as a binder component. It has been clarified that by using bisphenols such as bisphenol E and low bisphenol E, the rapid thermal expansion coefficient can be reduced and thus low thermal expansion can be realized. However, in such a technique, the problem of cracking of the mold can be sufficiently solved, but a problem that a generation amount of spear increases at the time of casting is newly generated.

  Patent Document 2 proposes a method in which polyethylene glycol having a number average molecular weight of 1500 to 40000 is present in RCS, thereby preventing cracks in the mold. However, the improvement in sex was not sufficient, and there was still room for improvement.

JP 59-178150 A JP 58-119433 A

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is that there is a small amount of spear generation during casting and a low thermal expansion coefficient. An object of the present invention is to provide a phenol resin composition for a shell mold that can advantageously provide a mold having higher properties, an RCS obtained by using the phenol resin composition, and a mold obtained by molding using the RCS.

Then, the present inventors have, to attempt to resolve the such problems described above, the shell mold phenolic resin composition, was intensive studies, to the phenolic resin, by blending the polymer of propylene glycol In the mold molded by RCS obtained by using the same, it has been found that the amount of dust generation is advantageously suppressed, the coefficient of thermal expansion is low, and the characteristics with higher properties are advantageously realized, The present invention has been completed.

That is, the present invention is to solve the problems to above, with a phenol resin, a polymer of propylene glycol, a phenol resin composition for shell molds, characterized by containing as essential components, This is the gist.

Note that according to one preferred embodiment of the shell mold phenolic resin composition according to according the present invention, the polymerization of the propylene glycol is used in the proportion of 1 to 30 parts by weight per 100 parts by weight phenolic resin In the present invention, the polymer of propylene glycol has a number average molecular weight of 300 to 3,000.

  Furthermore, in the present invention, there is also provided an RCS for shell mold characterized in that a coating layer made of a phenol resin composition for shell mold as described above is formed on the surface of predetermined fire-resistant particles. It is a summary.

  In addition, in the present invention, a mold obtained by molding using the RCS for shell mold as described above and heat-curing is also the object.

Therefore, according to such a phenol resin composition for a shell mold according to the present invention, since a predetermined polymer of propylene glycol is an essential constituent component together with the phenol resin, a coating layer made of the predetermined polymer is formed as a predetermined component. By forming the RCS for shell molds on the surface of the refractory particles and forming a mold using the RCS, the amount of spear generated from such a mold can be advantageously reduced. At the same time, the coefficient of thermal expansion of the resulting mold is low, and the properties of the mold can be sufficiently improved, so that there is a problem of gas defects due to the occurrence of spears during casting. In addition, the casting defect problem of vaning can be solved at the same time.

It is explanatory drawing which shows the measurement form of more sex as measured in the Example.

By the way, the phenol resin composition for shell molds according to the present invention is formed by combining a predetermined polymer of propylene glycol as an essential component together with a phenol resin, as described above.

  The phenol resin that can be used there is in the form of a solid or liquid obtained by reacting phenols and aldehydes in the presence of an acidic catalyst and / or a basic catalyst (for example, varnish or emulsion). And a phenol resin that exhibits thermosetting properties by heating in the presence or absence of a predetermined curing agent or curing catalyst, specifically, a novolac-type phenol resin, resole Type phenolic resin, nitrogen-containing resol type phenolic resin, benzyl ether type phenolic resin, and the like. These may be used alone or in combination of two or more.

  Moreover, when manufacturing such a phenol resin composition for shell molds, examples of phenols used as a raw material of the phenol resin include phenols, alkyl-substituted phenols such as phenol, cresol, xylenol, bisphenol A, bisphenol F, etc. And aldehydes include formalin, paraformaldehyde, trioxane, acetaldehyde, paraaldehyde, propionaldehyde, and the like. Of course, these phenols and aldehydes are not limited to those exemplified, and any other known resin raw materials can be used as appropriate. In addition, such phenols and aldehydes may be used alone or in combination of two or more raw materials.

  The method for producing the phenol resin used in the present invention is not particularly limited, and various conventionally known methods can be employed. For example, oxalic acid, hydrochloric acid, sulfuric acid, A method of reacting phenols with aldehydes using acidic substances such as phosphoric acid, basic substances such as ammonia, sodium hydroxide, calcium hydroxide, and catalysts such as organic acid metal salts and divalent metal salts Are advantageously employed.

  In addition, when the phenol resin is produced, the compounding molar ratio (F / P) of the aldehydes (F) and the phenols (P) can be appropriately selected according to the type of reaction catalyst used, Preferably, it will be set within the range of 0.55 to 0.80. In addition, by making this compounding molar ratio 0.55 or more, the target phenol resin can be obtained in a sufficient yield, while by using 0.80 or less, it is formed using the resulting phenol resin. In the RCS for shell mold thus formed, the strength of the mold obtained by molding it can be advantageously improved.

  The phenol resin thus obtained is in the form of a solid or liquid (eg, varnish or emulsion), for example, in the presence of a curing agent such as hexamethylenetetramine or a curing catalyst, or In the absence, it is thermosetting by heating. In the present invention, a phenol resin having a number average molecular weight obtained by gel permeation chromatography (GPC) analysis in the range of 400 to 900 is preferably used. When the number average molecular weight of the phenol resin is too small, in the RCS for shell mold formed by coating the resin composition containing the resin, the filling property at the time of molding is impaired, and the obtained mold has sufficient strength. On the other hand, if the number average molecular weight of the phenol resin is too large, the fluidity of the resin during heating is impaired, and sufficient strength may not be ensured in the resulting mold. There is.

  In the present invention, such a phenolic resin is appropriately preliminarily prepared with various additives conventionally used for the purpose of improving the physical properties of the mold. In particular, silane coupling agents such as γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, lubricants such as ethylene bis stearic acid amide and methylene bis stearic acid amide, etc. It is desirable to blend.

In the phenol resin composition for a shell mold according to the present invention, a polymer of propylene glycol (hereinafter abbreviated as “PG” ) is combined as an essential component together with the phenol resin as described above. Among them, in the present invention, in particular, a predetermined polymer of PG is preferably used because it has a high boiling point and hardly volatilizes.

  More specifically, in the present invention, among the PG polymers, in particular, a polypropylene glycol (hereinafter abbreviated as “PPG”) having a number average molecular weight of 300 to 3000 obtained by gel permeation chromatography analysis. .) Is preferably used. When the number average molecular weight of such PPG is 300 or more, the boiling point thereof is considerably higher than the temperature at which the mold is formed, and it is difficult to volatilize. Therefore, the effect of PPG as described above is further enhanced. It will be used advantageously. Moreover, when the number average molecular weight of PPG is 3000 or less, it becomes possible to suppress advantageously the strength fall of the obtained shell casting_mold | template. Various types of PPG having such a number average molecular weight are commercially available, and can be appropriately selected from such commercially available products in the present invention.

Further, the blending ratio of the polymer of PG to the phenol resin in the present invention is not particularly limited, but is generally used in a ratio of 1 to 30 parts by mass with respect to 100 parts by mass of the phenol resin. Is desirable. When the mixing ratio of the polymer of P G is 1 part by mass or more is than the effect of preventing the generation of cracks in the resulting shell mold is a more be more sufficiently exhibited, The polymerization of P G When the compounding ratio of the product is 30 parts by mass or less, the strength reduction of the shell mold can be advantageously suppressed.

The polymer of such P G are combined by mixing or the like to the phenolic resin, whereby although the so that the one form of the shell mold phenolic resin composition according to the present invention can be realized In the present invention, the method for combining the polymer of PG with the phenol resin is not particularly limited, and the phenol resin is produced, the reaction between the phenol and the aldehyde is started, during the reaction, Alternatively, it can be realized by appropriately blending a polymer of PG at any time after completion of the reaction. Further, after the production of the phenolic resin, and phenolic resin, or a method of mixing and grinding the polymer of PG, and the phenol resin by a mixer such as extruder, also such a method of melt-mixing the polymer of P G, as appropriate Is where it can be adopted. Furthermore, it is possible to add a polymer of PG during the production process of RCS. When blending in the production process of RCS, it may be performed before or after the addition of the phenol resin, or at the same time. Further, the polymer of PG may be blended as it is, or may be dispersed or dissolved in any medium and blended.

  By the way, when manufacturing RCS for shell molds according to the present invention, refractory particles are further kneaded with the phenol resin composition for shell molds as described above. Therefore, the blending amount of the phenol resin composition for the shell mold in the RCS of the present invention is determined in consideration of the type of resin used, the required mold strength, etc. In general, it is within the range of about 0.2 to 10 parts by weight, preferably 0.5 to 8 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of refractory particles. Within the range of parts by mass.

  Further, the kind of the refractory particles kneaded with such a phenol resin composition for a shell mold is not particularly limited in the present invention. Since such refractory particles serve as a base material for a mold, any inorganic particles having a particle size suitable for casting and mold formation (molding) can be used for shell mold casting. Any known inorganic particles that have been produced can be used. Examples of such refractory particles include, in addition to commonly used silica sand, special sand such as olivine sand, zircon sand, chromite sand, and alumina sand, ferrochrome slag and ferronickel slag. Slag-based particles such as converter slag, mullite-based porous particles such as Niiga Cera beads (trade name, ITOCHU CERATECH Co., Ltd.), or regenerated particles recovered and regenerated after casting, etc. Or in combination of two or more.

  And when manufacturing such RCS for shell molds, the manufacturing method is not specifically limited, Conventionally well-known methods, such as a dry hot coat method, a semi-hot coat method, a cold coat method, a powder solvent method, etc. However, in the present invention, in particular, after kneading the preheated refractory particles and the resin composition for the shell mold in a kneader such as a whirl mixer or a speed mixer, A so-called dry hot coating method is recommended, in which an aqueous solution of methylenetetramine (curing agent) is added, the bulk content is disintegrated into particles by cooling with air blowing, and calcium stearate (lubricant) is added.

  Furthermore, when molding a mold using the RCS for shell mold as described above, the heating molding method is not particularly limited, and any conventionally known various methods can be advantageously used. Will get. For example, RCS as described above is filled in a mold heated to 150 ° C. to 300 ° C. having a desired shape space for giving a target mold by a gravity drop method, a blowing method, or the like and cured. Thereafter, the cured mold can be removed from the mold to obtain a casting mold. And in the casting_mold | template obtained in that way, the outstanding effect as mentioned above will be able to be exhibited advantageously.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the specific description described above. It should be understood that improvements and the like can be added.

  In the following description, “parts” and “%” mean “parts by mass” and “% by mass”, respectively, unless otherwise specified. Moreover, each characteristic of manufactured RCS for shell molds is measured according to the following test method.

-Measurement of mold strength-
Using the manufactured RCS for shell mold, a JIS type test piece (width: 10 mm × thickness: 10 mm × length: 60 mm) according to JIS-K-6910 (Baking condition of specimen: 250 ° C. for 60 seconds) The mold strength (N / cm ² ) of the prepared JIS test piece (hereinafter also simply referred to as “test piece” or “TP”) was measured in accordance with JACT test method SM-1.

-Measurement of amount of spear generation-
After placing four test pieces for mold strength measurement (size: 10 mm × 10 mm × 60 mm) in a glass test tube (inner diameter 27 mm × length 200 mm), weighed glass wool in the vicinity of the opening of the test tube (2.5 g) was inserted to make a device for measuring the amount of spear generation. Next, the measurement apparatus was placed in a tubular heating furnace maintained at 700 ° C., subjected to heat treatment for 6 minutes, taken out, and allowed to cool to room temperature. Then, the glass wool was taken out from the measuring device and its mass was measured. In addition, the value (mg) was calculated by subtracting the glass wool mass (mg) before the explosion heat from the glass wool mass (mg) after the explosion heat.

-Evaluation of the nature of mold
First, a mold piece (120 mm × 40 mm × 5 mm) using each RCS as a mold for evaluating the nature is produced under firing conditions: 250 ° C. × 40 seconds, and the mold is left to room temperature. And cooled.

  Next, as shown in FIG. 1, the mold piece obtained above was set on a support base, and then the heating element (elema rod) was gradually heated from 200 ° C. and heated up to 800 ° C. The laser displacement meter was set at a position 10 mm from the tip of the mold piece, and the data was directly taken into a personal computer. As the displacement behavior, first, the mold piece is warped on the basis of the expansion behavior due to the heating of the mold piece, and then begins to bend, and finally, the mold piece is almost at the center, that is, the heating of the heating element. Break at the part. “Nariyori” as used herein is expressed by the maximum amount of bending obtained until fracture, and the larger the value, the easier the mold is deformed and the greater the flexibility. In addition, this measurement was performed in consideration of a measurement cycle in which measurement of the next mold piece is started when the temperature of the heating element reaches around 200 ° C.

-Evaluation of thermal expansion coefficient-
The test was performed according to the rapid thermal expansion measurement test method described in JACT test method M-2 thermal expansion coefficient measurement test method. Firing temperature: 280 ° C., Firing time: 120 seconds in a test piece (28.3 mmφ × 51 mm L, approximately ¼ cut of the circumference) in a high-temperature foundry sand tester adjusted to a furnace temperature: 1000 ° C. And was taken out after 1 minute. And the thermal expansion coefficient was computed from the test piece length before and after heat exposure according to the following formula.
Coefficient of thermal expansion (%) = {(post-heat-pre-heat) test piece length} / (test piece length before heat exposure) × 100

-Production of phenol resin A-
A reaction vessel equipped with a thermometer, a stirrer and a condenser was charged with 940 parts of phenol, 428 parts of 47% formalin, and 2.8 parts of oxalic acid. Next, the temperature of the reaction vessel was gradually raised, and after reaching the reflux temperature, the reaction was refluxed for 90 minutes, and further, the mixture was heated and concentrated under reduced pressure until the reaction solution temperature reached 170 ° C., thereby obtaining a phenol resin A. .

-Production of phenol resin B-
A reaction vessel equipped with a thermometer, a stirrer, and a condenser was charged with 650 parts of phenol, 350 parts of bisphenol A, 270 parts of 47% formalin, and 3 parts of oxalic acid. Next, the temperature of the reaction vessel was gradually raised, and after reaching the reflux temperature, the reaction was refluxed for 70 minutes. Further, the reaction solution was heated and concentrated under reduced pressure until the reaction solution temperature reached 170 ° C., thereby obtaining a phenol resin B.

- Experimental Example 1
After 100 parts of phenol resin A is heated and melted, 3 parts of PPG (trade name: Hiflex D-2000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) having a number average molecular weight of 2000 are mixed, cooled and solidified. Thus, a phenol resin composition was obtained. Next, 105 parts of the obtained phenol resin composition and 7000 parts of refractory particles (regenerated cinnabar) heated to 130 to 140 ° C. were put into a laboratory whirl mixer and kneaded for 60 seconds. Furthermore, what melt | dissolved 23 parts of hexamethylenetetramine in 105 parts of water was added, air cooling was carried out, Then, 7 parts of calcium stearate was added, and RCS was obtained.

- experimental example 2～6-
The number average molecular weight: instead of 3 parts of PPG 2000, In Experiment Examples 2 and 3, it has the added amount of 5 parts, 10 parts, In Experiment Example 4, for the use of 5 parts of PG, in experiment example 5, the number-average molecular weight: 400 for using 5 parts of PPG, in experiment example 6, the number-average molecular weight: except for using 4000 PPG, the same procedure as experiment example 1 RCS was obtained.

-Experiment example 7-
The number average molecular weight: except that it was decided not added 3 parts of 2000 PPG, in the same manner as Experiment Example 1, to obtain a RCS.

-Experimental example 8-
The number average molecular weight: instead of 3 parts of PPG 2000, the number average molecular weight: except for using 5 parts of 2000 polyethylene glycol (PEG), in the same manner as Experiment Example 1, was obtained RCS .

-Experimental example 9-
Instead of the phenol resin A, using phenol resin B, further, except that the it is not added the PPG, by performing the same procedure as described above Experiment Example 1, to obtain a RCS.

-Evaluation-
With respect to the obtained RCS, according to the test method described above, the mold strength was measured, the amount of spear generation was measured, and the properties of the mold and the thermal expansion coefficient were measured. The results are also shown in Table 1 below.

As apparent from the results of such Table 1, in the experimental examples 1 to 3 and 5, which is a RCS according to the present invention, together with those generated amount of tar is small, low coefficient of thermal expansion, than it and The nature was great. On the other hand, RCS of Experimental Example 7 in which propylene glycol and / or its polymer is not added to the phenol resin, and Experimental Example 8 in which polyethylene glycol is added instead of propylene glycol and / or its polymer. In this case, the coefficient of thermal expansion was high, and it was much less likely. Furthermore, in the RCS of Experimental Example 9 using a conventional low thermal expansion phenol resin, there were many stains and the thermal expansion was suppressed, but the properties were smaller.

Claims (7)

With a phenolic resin, a polymer of propylene glycol, Ri Na contained as essential components, and polymers of the propylene glycol is characterized that you have a number average molecular weight of 300 to 3000 Shell A phenolic resin composition for molding. The polymer of propylene glycol is, for the shell mold phenolic resin composition according to claim 1, characterized in that used in the proportion of 1 to 30 parts by weight per 100 parts by weight phenolic resin. The phenol resin reacts with aldehydes (F) and phenols (P) using a predetermined catalyst such that their blending molar ratio (F / P) is 0.55 to 0.80. The phenol resin composition for a shell mold according to claim 1 or 2 , wherein the phenol resin composition is obtained. The phenol resin composition for shell molds according to any one of claims 1 to 3 , wherein the phenol resin has a number average molecular weight within a range of 400 to 900. A resin coating for a shell mold, wherein a coating layer made of the phenol resin composition for a shell mold according to any one of claims 1 to 4 is formed on a surface of the refractory particles. sand. The resin-coated sand for shell mold according to claim 5 , wherein 0.2 to 10 parts by mass of the phenol resin composition for shell mold is used with respect to 100 parts by mass of the refractory particles. A mold obtained by molding using the resin-coated sand for shell mold according to claim 5 or 6 , followed by heat curing.

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