JP5429545B2 - Resin composition for shell mold and resin coated sand - Google Patents

Description

  The present invention relates to a resin composition for shell mold and a resin-coated sand (hereinafter referred to as RCS) useful for producing a casting mold. More specifically, the present invention relates to a resin-coated sand for a shell mold that has a good disintegration property after pouring and maintains a mold strength in the manufacture of an aluminum casting having a low pouring temperature.

  There are various methods for producing resin-coated sand for shell molds, but in general, from the standpoint of productivity and quality, hot-merling, that is, heated new sand, recycled sand or artificial sand, and phenol resin are melted. After that, a hexamethylenetetramine aqueous solution as a curing agent is added and mixed. The obtained RCS is blown into a predetermined mold, and the phenol resin is cured to be used as a mold.

  However, recently, aluminum parts have been used for the purpose of weight reduction in automobile-related parts and the like, and castings of low-temperature pouring (about 700 ° C.) such as aluminum alloys are increasing. When manufacturing castings using aluminum alloys with low melting temperatures, conventional molds using phenolic resins are less prone to decomposition and deterioration of the resin, and the mold itself does not collapse after metal solidification and remains in the casting. was there. As countermeasures, there have been a method in which the casting after pouring is heat treated again in a high temperature furnace to remove the remaining mold and a method in which a physical impact is applied to the casting to remove it. Both methods require considerable energy and have a problem that a secondary load is applied to the cast product. In order to solve such a problem, for example, an additive for accelerating the decomposition of the resin binder during casting, weakening the strength of the mold and improving the disintegration, specifically, phosphate esters (Patent Documents) 1), aromatic condensed phosphate esters (see Patent Document 2), and the like have been proposed. However, a mold material using this type of additive shows good mold disintegration at a location where a sufficient amount of heat is supplied from the molten metal to the mold (where the ultimate temperature of the mold is high), but a sufficient amount of heat. However, there is a disadvantage that the mold disintegration is insufficient at a place where molten metal is not supplied to the mold (a place where the temperature reached by the mold is low).

JP-A-58-3745 JP 2007-275988 A

  The present invention overcomes the drawbacks of such conventional mold materials for shell molds and is excellent in the mold moldability, particularly the main mold used in the shell mold casting method of non-ferrous castings such as aluminum alloys. Resin coated sand and resin coated sand for use in the manufacture of cores (hereinafter referred to as molds), where sufficient heat is not supplied from the molten metal to the mold, that is, good mold disintegration even at low temperatures Is intended to provide.

The present invention is as follows.
(1) A resin composition for a shell mold containing a phenol resin and a polyoxyalkylene phosphate ester , wherein the phenol resin is a novolak type phenol resin, a resol type phenol resin, a nitrogen-containing resol type phenol resin, or a benzyl ether type phenol. Any of resins, alkyl-modified phenolic resins, or modified by mixing or reacting these phenolic resins with epoxy resins, urea resins, melamine resins, xylene resins, polyamide resins, epoxy compounds, melamine compounds, urea compounds phenol is any one of resin, the polyoxyalkylene phosphoric acid ester is, for the shell mold resin composition which is a compound represented by formula (I).

((I) where R ¹ And R ² Is a methyl group and R ³ And R ⁴ Is a hydrogen atom and n is 1. )

(2) The said resin composition for shell molds characterized by including 1-30 mass parts of polyoxyalkylene phosphates with respect to 100 mass parts of phenol resins.
(3 ) Resin coated sand comprising at least the resin composition for shell mold and a refractory granular material.

  According to the present invention, by using a polyoxyalkylene phosphate ester as a disintegrant, a bending strength can be maintained, and a location where a sufficient amount of heat is not supplied from the molten metal to the mold (a location where the ultimate temperature of the mold is low) ), A resin composition for a shell mold having good disintegration and a resin-coated sand using the same can be provided.

The resin composition for shell molds according to the present invention contains a phenol resin and a polyoxyalkylene phosphate (disintegrant).
The phenol resin contained in the resin composition for shell molds of the present invention is generally used as a binder for RCS used in the production of casting molds for shell molds such as cast iron, cast steel, and aluminum. Of the materials used for producing the phenol resin, phenol, cresol, xylenol, catechol, resorcinol, hydroquinone and the like are used as the phenol, and paraformaldehyde, formalin and the like are used as the aldehyde.

The phenol resin is not particularly limited as long as it is a resin mainly composed of a reaction product of phenols and aldehydes and has a property of being heat-cured in the presence or absence of a curing agent. Specifically, novolac-type phenol resins, resol-type phenol resins, nitrogen-containing resol-type phenol resins, benzyl ether-type phenol resins, alkyl-modified phenol resins and these phenol resins, for example, epoxy resins, urea resins, melamine resins, xylene resins, Examples thereof include a modified phenol resin obtained by mixing or reacting with a polyamide resin, an epoxy compound, a melamine compound, a urea compound, or the like. These may be used alone or in combination of two or more. In addition, when using a novolak-type phenol resin alone, it usually imparts thermosetting properties in combination with a curing agent such as hexamethylenetetramine during the production of the mold material.
Moreover, the phenol resin may contain a novolac type phenol resin and a resol type phenol resin. Moreover, it is preferable to contain a novolak type phenol resin more than 0 mass part and 100 mass parts or less with respect to 100 mass parts of resol type phenol resin, More preferably, it is 40-70 mass parts. When the novolac type phenol resin exceeds 100 parts by mass, the curing rate tends to be slow.

As a disintegrant in the resin composition for shell molds of the present invention, polyoxyalkylene phosphate is effective. In the resin composition for shell mold, the blending amount of the polyoxyalkylene phosphate is preferably 1 to 30 parts by mass, more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the phenol resin. When the blending amount of the polyoxyalkylene phosphate (disintegrant) is less than 1 part by mass, the disintegrating effect is reduced. On the other hand, when the amount exceeds 30 parts by mass, the softening point of the resin composition is remarkably lowered, and when the RCS is produced, the fusion point is lowered to cause blocking, and the mold strength is lowered and the curing rate tends to be slow. It is in.
As the disintegrant, a phosphate ester other than the polyoxyalkylene phosphate ester may be used in combination. For example, aromatic condensed phosphate ester, aliphatic phosphate ester, etc. are mentioned. A good disintegration effect is exhibited even in a mixture or a mixture of two or more of a polyoxyalkylene phosphate and an aromatic condensed phosphate or an aliphatic phosphate.

  For example, the phosphate ester that can be used in combination is trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, trischloroethyl phosphate, trischloropropyl phosphate, triphenyl phosphate, Tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, xylenyl diphenyl phosphate, trilauryl phosphate, tricetyl phosphate, tristearyl phosphate, trioleyl Orthophosphate such as phosphate, trimethyl phosphite, triethyl phosphite, tributyl phosphite, triphenyl phosphite, tridodecyl phosphite, trisnonylphenyl phosphite, Phosphorous acid triesters such as chloroethyl phosphite and tristridecyl phosphite, phosphite diesters such as dimethyl phosphite, diethyl phosphite and dibutyl phosphite, butyl phosphonate, di (2-ethylhexyl) 2-ethylhexyl phosphonate And the like.

  For example, as an aromatic condensed phosphate ester, CR-741 (α-diphenoxyphosphoryl-ω-phenoxypoly (n = 1 to 3) [oxy-1,4-phenyleneisopropylidene-1,4-phenyleneoxy (phenoxy) Phosphoryl)]), CR-733S (phenylenebis (phenylcresol phosphanote)), CR-747 (2,2-bis {4- [bis ((mono or di) methylphenoxy) phosphoryloxy) Phenyl} propane), PX-200 (1,3-phenylenebis (dixylenyl) phosphate) (both trade names manufactured by Daihachi Chemical Industry Co., Ltd.), and the like.

  The method for adding (mixing) the disintegrant to the phenol resin is not particularly limited, but it is desirable to add the disintegrant at a temperature of 130 ° C. or higher, more preferably 150 ° C. or higher. The mixing time after the addition is not particularly limited, but it is desirable to mix for 1 hour or more. The polyoxyalkylene phosphate is added when the RCS is produced by kneading the resin composition for the shell mold (binding agent) and the refractory granular material (sand) after producing the resin composition for the shell mold. You can also

  As the polyoxyalkylene phosphate ester in the present invention, for example, a compound represented by the following formula (I) can be used.

In the formula (I), R ¹ and R ² represent a hydrogen atom, an alkyl group, an alkenyl group, an optionally substituted aryl group, an alicyclic hydrocarbon group, or an aralkyl group, and R ¹ and R ² are the same. But it can be different. Preferred R ¹ and R ² are methyl groups. R ³ and R ⁴ represent a hydrogen atom or an alkyl group, and n is an integer of 1 to 9. R ³ and R ⁴ are preferably a hydrogen atom, and n is preferably 1.

Examples of usable polyoxyalkylene phosphates include DAIGUARD-600 (manufactured by Daihachi Chemical Industry Co., Ltd.). Moreover, as a mixture of polyoxyalkylene phosphate and aromatic condensed phosphate, DAIGUARD-580 and DAIGUARD-610 (both manufactured by Daihachi Chemical Industry Co., Ltd.) can be used.
Further, polyoxyalkylene phosphates may be synthesized and used by a known synthesis method (see, for example, JP-A-57-125259 and JP-A-2000-327690).

  The polyoxyalkylene phosphate ester according to the present invention is made of 100% fresh sand, 100% reclaimed sand, 100% artificial sand, or new sand / recycled sand / artificial sand. Even a mixed system of the above shows a good disintegration effect.

  To the resin composition for a shell mold of the present invention, a lubricant, a silane coupling agent, and the like that are commonly used in the art may be added, if necessary, as long as the essential effects of the present invention are not impaired. A lubricant is preferable because it provides improved mold strength and improved blocking resistance. As the lubricant, ethylene bis stearic acid amide, ethylene bis oleic acid amide, methylene bis stearic acid amide, oxystearic acid amide, stearic acid amide, palmitic acid amide, oleic acid amide, methylol amide, calcium stearate, polyethylene wax, paraffin wax , Montan wax, carnauba wax, etc. can be used.

  As for the addition amount of a lubricant, it is desirable to use 0.3-5 mass parts with respect to 100 mass parts of phenol resins. If it is less than 0.3 part by mass, the effect of improving the strength and blocking resistance is small, and if it exceeds 5 parts by mass, the curing rate is slowed and the adhesive force between the sand grains is hindered. The method of blending the lubricant is not particularly limited, but it is desirable to add at a temperature of 150 ° C. or higher. The mixing time after the addition is not particularly limited, but it is preferable to mix for 1 hour or more. The lubricant may be added when the RCS is produced by kneading the resin composition for the shell mold (binding agent) and the refractory granular material (sand) after the production of the resin composition for the shell mold.

  The silane coupling agent is usually added to increase the adhesive force between the refractory granular material (sand) and the phenol resin. Although it does not specifically limit as a silane coupling agent which can be mix | blended with the resin composition for shell molds of this invention, An aminosilane coupling agent is preferable. As the aminosilane coupling agent, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, or the like is used. . Although the compounding quantity of a silane coupling agent is not specifically limited, It is desirable to use 0.05-5 mass parts with respect to 100 mass parts of phenol resins. If it is less than 0.05 parts by mass, the effect of improving the strength by the coupling agent is small, and if it exceeds 5 parts by mass, there is a risk of blocking the phenol resin, which is not preferable.

  The resin-coated sand according to the present invention is produced from a refractory granular material which is an aggregate for a mold and the above resin composition for a shell mold. Here, as the refractory granular material, silica sand, chromite sand, zircon sand, olivine sand, mullite sand, synthetic mullite sand, magnesia, alumina artificial sand (for example, trade name ESPARL, Yamakawa Sangyo) Co., Ltd.), sun pearl sand, recovered sand, recycled sand, and the like. In the present invention, various refractory granular materials can be used without particular limitation, such as fresh sand, recovered sand, reclaimed sand, or a mixture thereof. In addition, the particle size distribution and particle size of the refractory granular material can be selected without particular limitation as long as the refractory granular material is suitable for casting and forming a mold.

  The RCS can be produced by putting a fire-resistant granular material heated to a predetermined temperature into, for example, a mixer and kneading the above-described resin composition for shell mold so as to melt-coat the fire-resistant granular material. As an example, the refractory granular material is heated to, for example, 130 to 160 ° C., the heated refractory granular material and the shell mold resin composition are kneaded, and then an aqueous solution containing, for example, hexamethylenetetramine is added as a curing agent. Then knead until the lump of refractory granular material is broken. Further, for example, calcium stearate is added and dispersed as a lubricant to obtain RCS.

Hereinafter, based on an Example, this invention is demonstrated further more concretely. The present invention is not limited to the following examples.
Example 1
In a four-necked flask equipped with a stirrer, reflux condenser and thermometer, 891 g of phenol (manufactured by Mitsui Chemicals), 127 g of 92% paraform (manufactured by Formol), 244 g of 37% formalin (manufactured by Wako Pure Chemical Industries, Ltd.) and 2.6 g of oxalic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was blended, heated on an oil bath with stirring, and reacted until the reaction solution was emulsified at reflux temperature. Thereafter, concentration was performed under reduced pressure, and when the softening point reached 90 ° C., the end point was set to produce a phenol resin. 10 parts by mass of polyoxyalkylene phosphate (disintegrant) was added to 100 parts by mass of the phenol resin to obtain a resin composition for shell mold.
In addition, the used polyoxyalkylene phosphate ester has a structure shown in the formula (I), R ¹ and R ² are methyl groups, R ³ and R ⁴ are hydrogen atoms, and n is 1. In addition, after synthesizing by a conventionally known method, the structural formula was obtained by mass spectrometry, infrared analysis or the like.

Example 2
A resin composition for a shell mold was obtained in the same manner as in Example 1 except that the blending amount of the polyoxyalkylene phosphate was 1 part by mass.

Example 3
A resin composition for a shell mold was obtained in the same manner as in Example 1 except that the blending amount of the polyoxyalkylene phosphate was 3 parts by mass.

Example 4
A resin composition for a shell mold was obtained in the same manner as in Example 1 except that the blending amount of the polyoxyalkylene phosphate was 15 parts by mass.

Example 5
A shell mold resin composition was obtained in the same manner as in Example 1 except that the blending amount of the polyoxyalkylene phosphate was 30 parts by mass.

Example 6
A shell mold resin composition was obtained in the same manner as in Example 1 except that the amount of the polyoxyalkylene phosphate ester was changed to 0.5 parts by mass.

Example 7
A shell mold resin composition was obtained in the same manner as in Example 1 except that the blending amount of the polyoxyalkylene phosphate was 35 parts by mass.

Example 8
In a four-necked flask equipped with a stirrer, reflux condenser and thermometer, 891 g of phenol (manufactured by Mitsui Chemicals), 127 g of 92% paraform (manufactured by Formol), 244 g of 37% formalin (manufactured by Wako Pure Chemical Industries, Ltd.) and 2.6 g of oxalic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was blended, heated on an oil bath with stirring, and reacted until the reaction solution was emulsified at reflux temperature. Thereafter, concentration was performed under reduced pressure, and when the softening point reached 90 ° C., the end point was set to produce a phenol resin. Next, a mixture (mixing mass ratio; polyoxyalkylene) of polyoxyalkylene phosphate and phenylenebis (phenylcresol phosphate) (trade name: CR-733S, manufactured by Daihachi Chemical Industry Co., Ltd.) which is an aromatic condensed phosphate ester Phosphate ester: aromatic condensed phosphate ester = 80: 20) was produced. 10 parts by mass of the mixture was added to 100 parts by mass of the phenol resin to obtain a resin composition for shell mold.
The mixed polyoxyalkylene phosphate ester is the same as in Example 1.

Example 9
A shell mold resin composition was obtained in the same manner as in Example 8 except that the mixture mass ratio of the mixture was changed to polyoxyalkylene phosphate ester: aromatic condensed phosphate ester = 75: 25.

Comparative Example 1
Shell mold as in Example 1 except that polyoxyalkylene phosphate ester was changed to triphenyl phosphate (trade name TPP, manufactured by Daihachi Chemical Industry Co., Ltd.) which is an aliphatic phosphate ester as a disintegrant. A resin composition was obtained.

Comparative Example 2
The same procedure as in Example 1 was conducted except that polyoxyalkylene phosphate ester was changed to dibutylhydroxymethyl phosphate (trade name CR-707, manufactured by Daihachi Chemical Industry Co., Ltd.), which is an aliphatic phosphate ester, as a disintegrant. The resin composition for shell molds was obtained.

Comparative Example 3
As a disintegrating agent, polyoxyalkylene phosphate ester is replaced with α-diphenoxyphosphoryl-ω-phenoxypoly (n = 1-3) [oxy-1,4-phenyleneisopropylidene-1, aromatic condensed phosphate ester. A resin composition for a shell mold was obtained in the same manner as in Example 1 except that 4-phenyleneoxy (phenoxyphosphoryl)] (trade name CR-741, manufactured by Daihachi Chemical Industry Co., Ltd.) was used.

Comparative Example 4
A resin composition for a shell mold was obtained in the same manner as in Comparative Example 1 except that the amount of triphenyl phosphate (trade name TPP, manufactured by Daihachi Chemical Industry Co., Ltd.) was changed from 10 parts by mass to 1 part by mass.

Production of Resin Coated Sand (RCS) As a refractory granular material, 10 kg of fresh sand (trade name: Flattery) heated to 150 ° C., 130 g of each shell mold resin composition obtained in the above-mentioned Examples and Comparative Examples was speed mixer. After mixing for 45 seconds, 119.5 g of hexamethylenetetramine aqueous solution in which 19.5 g of hexamethylenetetramine (manufactured by Changchun Plastics Co., Ltd.) and 100 g of water are mixed and dissolved is added until the lump of sand is broken. After kneading, 10 g of calcium stearate (manufactured by NOF Corporation) was added and mixed for 20 seconds, and then discharged from the mixer to obtain RCS. Using the obtained RCS, the bending strength, fusion point, arbitrary temperature (300 ° C., 350 ° C., 400 ° C.), and the bending strength after heat treatment for 15 minutes were measured.
Tables 1 and 2 show the composition (formulation) and RCS characteristic measurement results of the shell mold resin composition used.

  The bending strength was measured according to JIS K 6910 (Phenolic resin test method). That is, the fired RCS test piece was supported at both ends, and the maximum bending stress when a concentrated load was applied from the top to the center was defined as the bending strength (MPa). The molding conditions of the test piece are a mold temperature of 250 ° C. and baking for 60 seconds.

  The fusion point was measured by JACT test method C-1 (fusion point test method). That is, a RCS to be measured is quickly sprinkled on a metal rod having a temperature gradient, and a nozzle having a diameter of 1.0 mm that moves along the guide rod at a position 10 cm away from the metal rod 60 seconds later. The RCS on the metal rod is blown off by reciprocating one turn from the low temperature part to the high temperature part at an air pressure of 0.1 MPa. The fusion point (° C.) was determined by reading the temperature of the boundary line between the blown-off RCS and the non-blowed RCS up to 1 ° C.

  The collapse rate was calculated from the difference between the bending strength at normal temperature (25 ° C.) and the bending strength after heat treatment at an arbitrary temperature (300 ° C., 350 ° C., 400 ° C.) and 15 minutes (see the following formula).

・芳香族縮合リン酸エステル；α−ジフェノキシホスホリル−ω−フェノキシポリ（ｎ＝１〜３）［オキシ−１，４−フェニレンイソプロピリデン−１，４−フェニレンオキシ（フェノキシホスホリル）］（商品名ＣＲ−７４１、大八化学工業株式会社製）
・混合物；ポリオキシアルキレンリン酸エステル：芳香族縮合リン酸エステル

Aromatic condensed phosphate ester: α-diphenoxyphosphoryl-ω-phenoxypoly (n = 1 to 3) [oxy-1,4-phenyleneisopropylidene-1,4-phenyleneoxy (phenoxyphosphoryl)] (trade name) CR-741, manufactured by Daihachi Chemical Industry Co., Ltd.)
・ Mixture; Polyoxyalkylene phosphate ester: Aromatic condensed phosphate ester

As is apparent from the results of Tables 1 and 2, in the Examples, it can be seen that the resin composition for shell mold exhibits good mold disintegration by adding polyoxyalkylene phosphate. In particular, in Examples 1 and 4 in which the blending amount of the polyoxyalkylene phosphate is 10 parts by mass or more (with respect to 100 parts by mass of the phenol resin), the bending strength is also good, and the disintegration at a treatment temperature of 400 ° C. The rate is 67% or more, and even when the disintegrating treatment temperature is changed from 400 ° C. to 350 ° C., the decrease in the decay rate is small (4%), indicating the same level of decay rate as 400 ° C. In addition, if the compounding amount of the polyoxyalkylene phosphate is 30 parts by mass or more, the bending strength is somewhat low, but the disintegration rate of RCS is 60% or more even at a processing temperature of 300 ° C., which is extremely good. Show good disintegration.
In contrast, in Comparative Examples 1 to 4, in which no polyoxyalkylene phosphate is used, the disintegration rate is 46% or less even at a treatment temperature of 400 ° C., and the disintegration treatment temperature is changed from 400 ° C. to 350 ° C. The disintegration rate is reduced by 13% or more, and it can be seen that the disintegration property is insufficient at a place where the temperature reached by the mold is low.
In Examples 8 to 9, polyoxyalkylene phosphate ester and aromatic condensed phosphate ester are used in combination, and even in this case, good disintegration is shown.
From this, it was found that by adding a polyoxyalkylene phosphate, it is possible to provide a resin composition for a shell mold having excellent low-temperature decomposability. In particular, RCS disintegration is sufficient if polyoxyalkylene phosphate is used as a disintegrating agent even at locations where the ultimate temperature of the mold is low, such as good disintegration even at 350 ° C. and even lower temperatures of 300 ° C. I understand.

Claims (3)

A resin composition for a shell mold comprising a phenol resin and a polyoxyalkylene phosphate ester , wherein the phenol resin is a novolac type phenol resin, a resol type phenol resin, a nitrogen-containing resol type phenol resin, a benzyl ether type phenol resin, an alkyl Any of modified phenolic resins, or modified phenolic resins formed by mixing or reacting these phenolic resins with epoxy resins, urea resins, melamine resins, xylene resins, polyamide resins, epoxy compounds, melamine compounds, urea compounds A shell mold resin composition , wherein the polyoxyalkylene phosphate is a compound represented by the formula (I):

(In the formula (I), R ¹ and R ² are methyl groups, R ³ and R ⁴ are hydrogen atoms, and n is 1.)   The resin composition for a shell mold according to claim 1, comprising 1 to 30 parts by mass of a polyoxyalkylene phosphate with respect to 100 parts by mass of the phenol resin. A resin-coated sand comprising at least the resin composition for a shell mold according to claim 1 or 2 and a refractory granular material.