Resin bonded sand

In the reclamation of chemically or resin bonded sands, the system employed must be able to break the bond between the resin and sand and remove the fines that are generated. The systems most commonly employed are wet washing and scrubbing for silicate bonded sands, or dry scrubbing/attrition and thermal (rotary drum or fluidized bed) systems for resin bonded sands. 

Foundries utilise mechanisation and automation depending on the need for reproductivity and on the series sizes. The most flexible installation is typically the jobbing foundry. This produces a variety of products in small numbers (<100). In general, this type of foundry applies manual moulding techniques with resin-bonded sand moulds. The melting furnace works batch wise to allow an easy change of alloy. This implies the use of induction or rotary furnaces. 

Table 3.46 Emission factors for iron casting in cold-setting resin-bonded sand moulds [110, Vito, 2001]...

This technique applies for pol5mrethane (cold-box) and fliran resin-bonded sands. Other binders do not allow this technique. 

Castings are produced by different molding processes green sand, air-set sand, resin-bonded sand, rammed graphite, investment, etc. The corrosion resistance of an as-cast surface is a function of the moulding process, pouring temperature, and mold surface treatments or mold washes. Carbon pick-up and mold reactions are just two of the factors that influence corrosion resistance. The corrosion resistance of most machined surfaces will be independent of the molding process provided that 1/16-1/8 in. of material is removed. 

Hexa, which is not suppHed with the resin, is usuaUy added either with the water as a solution or just before or immediately after the water addition. By quenching the mix with water, the resin-coated sand is cooled to a point where there is no significant reaction with the curing agent. Any reaction between the resin and the hexa in the muller affects the bonding properties of the coated sand. As the batch cools and begins to break up, more lubricant may be added, which remains on the outside of the coated grains where it is most effective. 

The mold is formed by surrounding the pattern with a shell of hardened sand.To eliminate pattern distortion from ramming, a cold setting(resin bonded or cement bonded) casting sand should be used. I have cast simple pieces from patterns rammed up in damp green sand, with only a slight amount of pattern damage. This method is acceptable for pieces that will be later machined to final shape. 

Urethane adhesives were introduced to the foundry industry in 1965 by ADM Chemicals, which is now part of Ashland Chemical Company. The product was an immediate success, and within two years more than 10 million pounds of urethane adhesive was being sold into the U.S. foundry industry. Ashland Chemical introduced a second urethane adhesive to the industry in 1968 and a third in 1970. These unique products were highly successful. On a worldwide basis, growth rate for the use of urethane adhesives by the foundry industry has averaged 20% per year over the period 1970 to 1980. Over 125 million pounds of urethane adhesives were used by the foundry industry throughout the world in 1979. U.S. use in 1979 was about 75 million pounds. The foundry industry uses urethane adhesives to bond sand. Typically, one to two percent adhesive is used in combination with a clean, dry sand. The resin-sand mixture is shaped into a core or mold and cured. 

Moulding and core-making with chemically-bonded sand 4.3.3.1 Minimisation of binder and resin consumption... 

Modem civilization would not be possible without bonded abrasive products. By the year 1825 sand, emeiy, and even diamond were being bonded together with shellac for use in abrasive sticks and wheels. Rubber bonded wheels were introduced in 1857, the sodium silicate and the vitrified bond just after the Civil War, and the phenolic resin bond in 1923. The metal bond was introduced for diamond wheels in 1940. 

Foundry Resins. In the foundry industry, phenoHc resins are used as the binder for sand in the manufacture of sheU molds and cores. The two mating halves are joined by clamps or a bonding agent to form a sheU mold into which the molten metal is poured for castings. The sheU is formed by depositing a resin—sand mix on a hot metal pattern plate. After a certain period the pattern is inverted and the excess resin sand is removed. The sand particles are bonded by an oven cure, and the sheU is ejected from the pattern plate. 

A cement slurry additive consisting of methylcellulose, melamine-formaldehyde resin, and trioxane has been proposed for better bonding of cement to the casing string [20]. Bisphenol-A epoxide resins, with amine-based curing agents, sand filler, and a mixture of n-butanol and dimethyl benzene as a diluent, have been proposed as additives to increase adhesion properties of cement [572]. 

Phenolic-isocyanates (phenolic-urethanes). The binder is supplied in three parts a phenolic resin in an organic solvent (0.8%), methylene diphenyl diisocyanate (MDI) (0.5%), and a liquid amine catalyst. When mixed with sand, the amine causes a reaction between the resin and the MDI, forming urethane bonds, which rapidly set the mixture. The speed of setting is controlled by the type of catalyst. The optimum cure temperature is 25 to 30°C. Compression strength is typically over 4000kPa (600psi). 

Natural stone, such as granite, sandstone, limestone, and slate, is a very limited resource but provides a very durable building material. Reconstituted stone products are made using stone dust from quarrying operations, bonded with cement or synthetic resins. Synthetic stone is made from minerals such as sand and ash bonded with synthetic resins. More energy is required to produce a reconstituted or synthetic product than to use stone in its natural state, and the production of the resins used can cause pollution. 

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