Compositions: coating or plastic – Coating or plastic compositions – Molds and mold coating compositions
Patent
1980-10-27
1983-07-05
Morris, Theodore
Compositions: coating or plastic
Coating or plastic compositions
Molds and mold coating compositions
106 3825, 106 74, 106 80, 106214, 106 385R, 106162, 524791, 524842, B28B 736, C08L 100
Patent
active
043916422
DESCRIPTION:
BRIEF SUMMARY
This invention relates to alkali metal silicate binder compositions, particularly for use in the production of foundry moulds and cores.
It is common practice to use alkali metal silicate aqueous solutions, particularly sodium silicate solutions as binders for sand for the production of foundry moulds and cores. These solutions usually contain 40-50% by weight of a sodium silicate having a SiO.sub.2 :Na.sub.2 O ratio of from 2.0:1 to 3.0:1. In one process the sodium silicate solution is mixed with sand, and the resultant mixture is formed into a mould or core. Carbon dioxide gas is then blown through the mould or core, and due to chemical reaction between the sodium silicate and the carbon dioxide a bonded mould or core results. In another process a so-called hardener, which may be for example, a mixture of diacetin and triacetin, is mixed with sodium silicate and sand, and the mixture is formed into a mould or core which on standing hardens due to chemical reaction between hardener and the sodium silicate.
A disadvantage of both processes is that after casting the moulds and cores are difficult to break down and remove from the solidified cast metal. This can be particularly disadvantageous in the case of cores of complex shape, or when the moulds and cores are used for the production of castings in metals which are cast at high temperatures, e.g. steel castings. Accordingly numerous proposals have been made in the past to add materials, so-called breakdown agents, to the mixture of sand and sodium silicate, which will aid the breakdown or disintegration ability of the sand mould or core after casting.
Among the breakdown agents used is a variety of carbohydrate-containing materials such as cellulose derivatives, starches, and sugars, e.g. sucrose and dextrose.
It has now been found that improved results can be obtained in the production of foundry sand moulds and cores bonded with an alkali metal silicate binder by using a binder composition which contains in addition in the alkali metal silicate and a carbohydrate, a phenolic compound which is miscible with or soluble in an aqueous alkali metal silicate solution.
According to the invention there is provided a binder composition in aqueous solution obtained by mixing:
(i) an alkali metal silicate
(ii) a substantially water soluble carbohydrate selected from monosaccharides, disaccharides, polysaccharides and derivatives of any of these and
(iii) a phenolic compound selected from monohydric phenols, dihydric phenols, trihydric phenols, phenols of polynuclear hydrocarbons and phenolic acids, which is miscible with or soluble in an aqueous solution of an alkali metal silicate.
According to a further feature of the invention there is provided a method of making an article of bonded particulate material such as a foundry mould or core, which comprises forming to the desired shape a mixture comprising particulate material and a binder composition in aqueous solution obtained by mixing:
(i) an alkali metal silicate
(ii) a substantially water soluble carbohydrate selected from monosaccharides, disaccharides, polysaccharides and derivatives of any of these and
(iii) a phenolic compound selected from monhydric phenols dihydric phenols, trihydric phenols, phenols of polynuclear hydrocarbons and phenolic acids, which is miscible with or soluble in an aqueous solution of an alkali metal silicate.
The preferred alkali metal silicate is sodium silicate. The SiO.sub.2 :Na.sub.2 O ratio of the sodium silicate may vary widely, e.g. from 2.0:1 to 3.5:1 but sodium silicates having a ratio of from 2.0:1 to about 2.5:1 are preferred.
Examples of suitable monosaccharides include glucose, mannose and fructose, and examples of suitable disaccharides include sucrose, maltose and lactose.
Polysaccharides, also known as glycans, are polymers of monosaccharides with or without reducing terminal groups.
The monosaccharide constituent may be an aldose or a ketose. Examples of glycans are glucans (polymers of glucose), xylans (polymers of xylose) and gluco-xylans (copolymers of glucose
REFERENCES:
patent: 1048536 (1912-12-01), Horn
patent: 1171905 (1916-02-01), Tompkins
patent: 1498270 (1924-06-01), Harris
patent: 3615780 (1971-10-01), Kim et al.
patent: 3816145 (1974-06-01), Melcher
patent: 4070196 (1978-01-01), Kraak et al.
patent: 4131477 (1978-12-01), Kagan et al.
patent: 4194918 (1980-03-01), George et al.
Anderson John G.
Cross Alan
Stevenson John
Foseco International Limited
Morris Theodore
LandOfFree
Alkali metal silicate binder compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Alkali metal silicate binder compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Alkali metal silicate binder compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1438545