Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-06-23
2001-12-04
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S145000
Reexamination Certificate
active
06326418
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP98/03939 which has an International filing date of Sep. 3, 1998, which designated the United States of America.
1. Technical Field
The present invention relates to a refractory granular material composition for molding by acid-hardening which can particularly be used preferably in producing a self-hardening mold.
2. Background Art
A certain method of producing a self-hardening mold involves blending an acid-hardening resin and a hardener with a refractory granular material such as silica sand and mixing them to produce a mold at room temperature. The hardener used include inorganic acids such as sulfuric acid and phosphoric acid, and organic sulfonic acids such as toluene sulfonic acid and xylene sulfonic acid, but further improvement in mold strength is desired. That is, if higher mold strength can be achieved, the amounts of the acid-hardening resin and the hardener can be reduced to decrease gas generated, so the environment can thereby be improved and gas defects in the resulting mold can be reduced.
DISCLOSURE OF THE INVENTION
The object of the present invention is to improve the strength of an acid-hardening mold.
The present invention relates to a refractory granular material composition for molding by acid-hardening which comprises at least one solvent selected from the group of (1) alcohols, (2) ether alcohols and (3) esters shown below:
wherein:
R
1
represents a C3 to C12 straight-chain or branched aliphatic hydrocarbon group or a benzyl group;
R
2
represents a C1 to C10 straight-chain or branched aliphatic hydrocarbon group, a phenyl group or a benzyl group;
R
3
represents an ethylene group or a propylene group;
n is an integer of 1 to 12;
R
4
represents a phenyl group or a methyl group; and
R
5
is a C2 to C6 aliphatic hydrocarbon group or —(R
3
—O)n—R
2
That is, the present invention relates to a refractory granular material composition for molding by acid-hardening comprising a refractory granular material, an acid-hardening resin-containing binder, an acid-continuing hardener, and at least one of the above-described solvents.
Further, the present invention provides a method of producing an acid-hardening mold comprising mixing a refractory granular material, an acid-hardening resin-containing binder, and an acid-containing hardener and hardening the acid-hardening resin to produce a foundry mold, wherein at least one of the above-described solvents is added to harden the acid-hardening resin.
The present invention provides an acid-hardening mold additive comprising one or more of the solvents described above. The above solvents are used as an additive for production of the acid-hardening resin. The solvents may have a solubility parameter of 8.5 to 12.
The present invention provides a method in which the refractory granular material, the binder, and the hardener and the solvents described above are mixed and hardened to produce a mold for use in producing castings.
The estimated reason that the above-identified solvents contribute to improvement in mold strength may be that they act as mutual solvent for improving binder and hardener solubility.
JP-A 2-500,753 discloses a binder composition which consists of an aqueous alkaline solution of specific phenol resol and a modifier selected from the group of open-chain ether alcohols and ketone alcohols and which can improve mold tensile strength. However, this prior art invention relates to a molding method for hardening alkaline phenol resin by ester and is completely different from the technique of the present invention in which acid-hardening resin is hardened by an acidic hardener composition to form a mold.
MODE FOR CARRYING OUT THE INVENTION
The refractory granular material composition for molding provided by the present invention is prepared by mixing of a refractory granular material, a binder composition containing an acid-hardening resin, and a hardener composition containing an inorganic acid such as sulfuric acid and phosphoric acid, and an organic acid such as an aromatic type sulfonic acid, and it is used for producing a foundry mold by hardening the acid-hardening resin. The refractory granular material include a new or reclaimed material of sand such as silica sand based mainly on quartz, a chromite sand, a zircon sand, a olivin sand, a alumina sand and a artificial mullite sand. Usually the reclaimed sand includes that obtained ordinarily in a mechanical abrasion system or calcination system, and the sand reclaimed in the abrasion system is preferable because of high yield and generality and from an economical viewpoint.
Examples of the acid-hardening resin include furfuryl alcohol (which becomes resin through polycondensation at the time of curing by the action of a hardener), the so-called furan resins such as furfuryl alcohol-aldehyde-urea polycondensate, furfuryl alcohol-aldehyde polycondensate, furfuryl alcohol-aldehyde-melamine polycondensate, and furfuryl alcohol polymer, and phenol resins such as phenol-aldehyde polycondensate. Further, the so-called phenol-modified furan resins such as furfuryl alcohol-phenol-aldehyde polycondensate and furfuryl alcohol-phenol-urea-aldehyde polycondensate can also be used. One or more of these acid-hardening resins can be used in combination thereof. Out of these acid-hardening resins, furan resin and phenol-modified furan resin are preferable because these can achieve particularly significant effects according to the present invention. The acid-hardening resin is used preferably in an amount of 0.6 to 5 parts by weight relative to 100 parts of the refractory granular material in the granular composition for molding.
In the present invention, phenols used in production of the acid-hardening resin include alkyl phenols such as phenol, cresol and 3,5-xylenol, polyvalent phenols such as resorcinol and catechol, and bisphenols such as bisphenol A, bisphenol F, bisphenol C and bisphenol E. Further, aldehydes may be publicly known aldehyde compounds such as formaldehyde, glyoxal and furfural.
In the acid-hardening resin of the present invention, urea and urea compounds, amines such as melamine, amides and phenols such as resorcin and bisphenol A besides the above major components can be contained for the purpose of reducing formaldehyde generated at the time of molding. In particular, resorcin is preferably contained in an amount of 2 to 30 parts by weight relative to 100 parts of the acid-hardening resin.
Further, 2,5-bishydroxymethyl furan or the like can be preferably contained as a curing accelerator in an amount of 0.5 to 30 parts by weight relative to 100 parts of the acid-hardening resin, thus achieving the significant effect of the present invention.
Further, a silane coupling agent such as N-&bgr;-(aminoethyl)-&ggr;-aminopropylmethyldimethoxysilane or the like can be added for the purpose of improving mold strength.
The hardener composition used in the present invention includes inorganic acids such as sulfuric acid, phosphoric acid and organic acids such as aromatic sulfonic acid. Sulfuric acid may be contained as an unreacted material at the time of synthesizing organic sulfonic acid or incorporated into the hardener composition, and its content is preferably 2 to 50% by weight. In view of the effect of the solvent in the present invention, its content is more preferably 2 to 35% by weight, most preferably 2 to 20% by weight.
Phosphoric acid is contained for reducing the amount of sulfur dioxide gas generated from a mold at the time of molding and for improving a working atmosphere. The content of phosphoric acid in the hardener is preferably 5 to 85% by weight.
The organic acid includes publicly known organic sulfonic acids such as benzene sulfonic acid, toluene sulfonic acid, xylene sulfonic acid and phenol sulfonic acid. These organic sulfonic acids can be contained in the hardener to achieve relatively high mold strength, and the content thereof in the hardener is preferably 5 to 80% by weight for a working atmosphere.
In the present invent
Kato Masayuki
Nakai Shigeo
Sawa Masuo
Birch & Stewart Kolasch & Birch, LLP
Cain Edward J.
Kao Corporation
Wyrozebski-Lee Katarzyna
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