Method for obtaining a foundry body from a granular mixture comprising a modified polycondensed resin and a formaldehyde scavenger

According to the Invention)

Resin: Urea—formaldehyde resin comprising vanillin, which was synthesized in an acid medium with a formaldehyde / urea molar ratio of 2.37, and to which vanillin was added in a urea / vanillin molar ratio of 4.5.

The vanillin content with respect to the resin is 11.3% by weight.

This resin was used at 2% with respect to the sand.

Catalyst: Catalyst constituted by 1.4% hydroxylamine in solution at 50%, 1.7% p-toluene sulphonic acid in solution at 65%, 15.1% carbohydrazide, 2.2% hydroxylamine sulphate and 79.7% water.

This catalyst was used at 0.4% with respect to the sand.

Box Temperature: 120° C.

Hot air temperature: 100-120° C.

Hot bending strength on removal from the box: respectively at 30, 60 and 120 seconds: 15, 30 and 45 daN / cm2

Cold bending resistance, respectively at 30, 60 and 120 seconds: 55, 60 and 65 daN / cm2

The hot and cold bending strengths are sufficient to allow, respectively, handling of the formed bodies and casting of the metal.

Formaldehyde on

According to the Invention)

[0113]Resin: Urea-melamine / formaldehyde resin, which was synthesized with a formaldehyde / urea molar ratio of 2.95 and to which melamine was added in a formaldehyde / melamine molar ratio of 3.45 then to which was added 3% Fintan 737B modified tannin, a commercial product from the company Indunor (modified condensed tannin originating from Schinopsis lorentzii or Quebracho colorado in powder).

This resin was used at 2.2% with respect to the sand.

Catalyst: Catalyst containing 14% hydroxylamine sulphate, 20% carbohydrazide and 66% water.

This catalyst was used at 0.3% with respect to the sand.

Box Temperature: 130° C.

Hot air temperature: 100-120° C.

Hot bending strength on removal from the box: respectively at 30, 60 and 120 seconds: 15, 24 and 42 daN / cm2

Cold bending resistance, respectively at 30, 60 and 120 seconds: 75, 84 and 95 daN / cm2

The hot and cold bending strengths are sufficient to allow, respectively, handling of the formed bodies and casting of

According to the Invention)

[0114]Resin: Urea / formaldehyde modified tannin, which was synthesized with a formaldehyde / urea molar ratio of 2.37, and to which was added 25% Fintan 737C modified tannin, a commercial product from the company Indunor (stabilized condensed tannin originating from Schinopsis lorentzii or Quebracho colorado in solution at 45%).

This resin was used at 2% with respect to the sand.

Catalyst: Catalyst containing 14% hydroxylamine sulphate, 20% carbohydrazide and 66% water.

This catalyst was used at 0.3% with respect to the sand.

Box Temperature: 130° C.

Hot air temperature: 100-120° C.

Hot bending strength on removal from the box: respectively at 15, 30 and 60 seconds: 6, 13 and 21 daN / cm2

Cold bending resistance, respectively at 15, 30 and 60 seconds: 31, 40 and 45 daN / cm2

The hot and cold bending strengths are sufficient to allow, respectively, handling of the formed bodies and casting of the metal.

Formaldehyde on mixing: less than 0.2 ppm (undetectable)

Formald