Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
  • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
  • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • B22C1/226—Polyepoxides

Definitions

• the invention relates to epoxide or epoxide novolac resins mixed with a latent curing agent, with or without an accelerator, cured by heat for the production of foundry sand molds and cores. It is common practice to refer to these heat curable resin binders as “Hot Box” or “Warm Box” binders since the core box or pattern must be heated to affect curing of the sand, resin, curing agent and accelerator mixture.
• the "Hot Box” and “Warm Box” processes utilize sand coated with a thermosetting resin in liquid form and a latent curing agent in liquid or dry powder form. This mixing of sand, resin and curing agent is done at ambient temperature. A metal pattern or core box is then heated to a temperature of 200 to 300 degrees C. and the damp mixture of sand, thermosetting resin binder and latent curing agent is applied to it by dropping or by fluidization with air. After a period of a few seconds to several minutes, the pattern or box is inverted or opened. The sand, resin and curing agent mix has now sufficiently hardened so that the mold or core can be handled and stored for later use in the metal casting process. The "Warm Box” process operates at somewhat lower temperatures than the "Hot Box” process.
• Epoxide and epoxide novolac resins cured by dicyandiamide with or without an imidazole are used in the aerospace, automotive, electronic, coating and adhesive industries.
• the cured epoxies are inert, non-toxic polymers. They are not chemically reactive and remain as very stable compounds. There is no presence of formaldehyde or other toxic materials.
• a sand, resin, curing agent and accelerator composition comprising a medium to high molecular weight epoxide resin, an epoxide novolac resin, or, a mixture of the two, both having an epoxide equivalent weight of 150 to 250; a latent heat curable curing agent such as dicyandiamide or an imidizole; and possibly an imidazole accelerator.
• a latent heat curable curing agent such as dicyandiamide or an imidizole
• imidazole accelerator an imidazole accelerator.
• a flowable sand, resin, curing agent and accelerator mix it may be necessary to dilute or dissolve the resin, curing agent or accelerator in a solvent such as propylene carbonate, methylglycol, methoxypropanol, methyl lactate or butyl lactate.
• the resin/diluent solution is applied to the sand at 0.5 to 5.0 percent by weight of the sand.
• the heat curable latent curing agent and accelerator may be applied to the sand in liquid (with diluent) or powder form at 2.0 to 25.0 percent by weight of the resin.
• the resulting damp sand mixture is now ready for use by heating it to temperatures in excess of the curing agent and accelerator activation temperature.
• various accelerators can be used such as modified or unmodified imidazoles, including, but not limited to 2-methyl imidazole, 2-phenyl imidazole and 1-H-imidazole.
• a sand mixture was prepared having the following composition by weight: 98.2 % Silica Sand AFS Grain Fineness Number 90 1.5 % Liquid Resin - 80 % Dow DER 331 Epoxide Resin 20 % Propylene Carbonate Diluent 0.3 % Powder Curing Agent - 100 % Dicyandiamide
• the sand mixture was blown into an AFS Standard Tensile Strength Specimen Core Box which had been heated to 150 degrees C.
• the test core required 2 minutes of curing time after which it had sufficient strength to be removed from the core box. No odor or smoke were present during the curing cycle.
• the 24 hour tensile strength of the cured sand core was measured as being over 350 pounds per square inch (over 25 Newtons per square centimeter).
• the mixed sand was stable for over 1 week at room temperature with no loss of performance.
• a sand mixture was prepared having the following composition by weight: 98.2 % Silica Sand AFS Grain Fineness Number 90 1.5 % Liquid Resin - 40 % Dow DER 331 Epoxide Resin 40 % Dow DER 431 Epoxide Novolac Resin 20 % Propylene Carbonate Diluent 0.3 % Powder Curing Agent - 100 % Dicyandiamide
• the sand mixture was blown into an AFS Standard Tensile Strength Specimen Core Box which has been heated to 150 degrees C.
• the test core required 1 minute of curing time after which it had sufficient strength to be removed from the core box. No odor or smoke were present during the curing cycle.
• the 24 hour tensile strength of the cured sand was measured as being over 350 pounds per square inch (over 25 Newtons per square centimeter).
• the mixed sand was stable for over 1 week at room temperature with no loss of performance.
• a sand mixture was prepared having the following composition by weight: 98.3 % Silica Sand AFS Grain Fineness Number 90 1.5 % Liquid Resin - 40 % Dow DER 331 Epoxide Resin 40 % Dow DER 431 Epoxide Novolac Resin 20 % Propylene Carbonate Diluent 0.3 % Powder Curing Agent - 80 % Dicyandiamide 20 % 2-Methyl Imidazole
• the sand mixture was blown into an AFS Standard Tensile Strength Specimen Core Box which had been heated to 150 degrees C.
• the test core required only 30 seconds of curing time after which it had sufficient strength to be removed from the core box. No odor or smoke were present during the curing cycle.
• the 24 hour tensile strength of the cured sand was measured as being over 350 pounds per square inch (over 25 Newtons per square centimeter).
• the mixed sand was stable for over 8 hours at room temperature with no loss of performance.
• a sand mixture was prepared having the following composition by weight: 98.475 % Silica Sand AFS Grain Fineness Number 90 1.5 % Liquid Resin - 40 % Dow DER 331 Epoxide Resin 40 % Dow DER 431 Epoxide Novolac Resin 20 % Propylene Carbonate Diluent 0.075 % 1-H-Imidazole
• the sand mixture was blown into an AFS Standard Tensile Strength Specimen Core Box which had been heated to 150 degrees C.
• the test core required only 15 seconds of curing time after which it had sufficient strength to be removed fromt he core box. No odor or smoke were present during the curing cycle,
• the 24 hour tensile strength of the cured sand was measured as being over 350 pounds per square inch (over 25 Newtons per square centimeter).
• the mixed sand was stable for over 8 hours at room temperature with no loss of performance.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Epoxy Resins (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6391823

Family Applications (1)

Country Status (2)

Cited By (3)

Citations (4)

• 1989
  • 1989-10-20 DE DE19893934940 patent/DE3934940A1/de not_active Withdrawn
• 1990
  • 1990-10-18 EP EP19900119969 patent/EP0423780A3/en not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (2)

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