Shell Moulding - Supra NL - 502 and Supra NL - 502 - A

Description

Supra phenolic resins Supra-NL 502 and Supra-NL 502-A are phenolic novolacs dissolved in solvent. It is used for pre-coating sand used for shell moulding. It is to be mixed with hardener in the ration of 100:18 by weight.

Supra-NL 502 and Supra-NL 502-A can be used to prepare coated sand in a wide range of foundry mixers including both muller types such as the August-Simpson, Mix-Muller, Neville Mill, Pioneer mill etc. and bladed mixers such as the Fordath Sand Coating Plant.

Supra NL-502-A gives a lower mulling time compared to Supra NL-502 because of its low viscosity. The rest of the properties are same for both the grades.

Typical Properties

Product: P.F. Liquid Resin for Coated Sand

Supra NL-502 Supra NL-502-A a. Appearance Clear Light Brown Clear Light Brown b. Solid content @ 1500C  - 1 hour 70% ± 1% 70% ± 1% c. Viscosity by cup @ 300C by Ford Cup No.6B 80 sec ± 120 sec. (2500 – 4500 centistokes) 60 sec ± 10 sec. (2000 – 4000 centistokes) d. Cure time @ 1500C 150 ± 10 sec. 150 ± 10 sec. e. PH 2.5 – 3.0 2.5 – 3.0 f. Solvent Methanol Methanol g. Shelf Life 6 months in cool and dry place 6 months in cool and dry place h. Packing 200 kgs. nett in M.S. drums 200 kgs. nett in M.S. drums

Properties of Precoated Sand

The following is the typical coated sand properties with Supra-NL 502 and Supra-NL 502 and Supra-NL 502-A when a dry AFS (55-65) – clean silica sand containing less than 0.5% clay is coated with 5% clay is coated with 5% resin and 18% of catalyst based on resin is used.

Properties Results Stick Point (0C) 96-100 Hot Tensile Strength/2350C 6 mm thick (kg./cm2) 4 mts./2 sides heating 27 Gas content/9800C (ml/gm) 26 maximum

Note: Whilst the above information is based on the result of experimental work in our laboratories and is correct to the best of our knowledge, users are recommended to establish for themselves that the process and materials are satisfactory for their requirements. Freedom from patent rights must not be assumed. No liability is accepted by us for any damage, injury or loss resulting from the use of this information.

Product: Hardener for Coated Sand

a. Hexamine 75% b. Fineness @ 1500C – 1 hour +200 mesh B.S.S. – Nil c. Shelf Life 6 months in cool & dry place

Precautions:

The only precaution to be observed are to see that the containers are well sealed to prevent loss of solvent by evaporation and to exercise the care normal to the handling of materials with low flash point.

Process:

Any dry sand normally used in the shell moulding process is suitable for use in the preparation of coated sand by the solvent process. The “Clay grade content” should not exceed 0.75%.

The appropriate amount of sand is charged to the mill and the mixed resin and hardener is added whilst mixing is continued. After mixing for one minute, air at temperatures up to 150⁰C is blown over the charge or, as in the case of mixers equipped for it, through the charge. The end of the coating cycle is shown by the hard lumps, formed consequent upon the evaporation of the solvent, breaking down either into small lumps in the case of bladed mixers, or into a free flowing material in the case of muller type mixers. The product is discharged on to vibrating screens and is bagged ready for use or may be conveyed pneumatically to storage hoppers.

The total cycle time varies between 6-15 minutes depending on the type mixer and the temperature of air used.