Alkali metal silicate binder compositions

• US 4,329,177 A
• Filed: 10/27/1980
• Issued: 05/11/1982
• Est. Priority Date: 02/27/1979
• Status: Expired due to Term

• Current Assignee: Foseco International Limited (Vesuvius Plc)
• Original Assignee: Foseco International Limited (Vesuvius Plc)
• Inventors: George, Raymond D.
• Primary Examiner(s): Hayes, Lorenzo B.
• Application Number:
  US06/205,957
• Time in Patent Office: 561 Days
• Field of Search: 106/38.35, 106/38.5 R, 106/80, 106/84, 106/162, 106/213, 106/214
• US Class Current: 106/38.35
• CPC Class Codes: B22C 1/167 Mixtures of inorganic and organic binding agents
• CPC Class Codes: B22C 1/20 of organic agents
• CPC Class Codes: B22C 1/26 of carbohydrates; of distillation residues therefrom
• CPC Class Codes: C04B 22/0013 Boron compounds
• CPC Class Codes: C04B 24/008 Aldehydes, ketones
• CPC Class Codes: C04B 24/02 Alcohols; Phenols; Ethers
• CPC Class Codes: C04B 24/10 Carbohydrates or derivatives thereof
• CPC Class Codes: C04B 24/12 Nitrogen containing compounds organic derivatives of hydrazine hydrazine C04B22/00
• CPC Class Codes: C04B 24/38 Polysaccharides or derivatives thereof C04B24/243 takes precedence
• CPC Class Codes: C04B 28/26 Silicates of the alkali metals

Abstract

A binder composition in aqueous solution, suitable for use in the production of foundry sand moulds and cores is obtained by mixing

(i) an alkali metal silicate

(ii) a substantially water soluble carbohydrate selected from monosaccharides, disaccharides, polysaccharides and derivatives thereof and

(iii) urea.

The composition may also contain an oxyanion such as a borate which is capable of forming a water soluble complex with the carbohydrate. The preferred carbohydrate is a stabilized starch hydrolysate whose reducing power has been removed by a process such as hydrogenation.

Moulds and cores bonded using the composition may be hardened by injection of carbon dioxide gas, or a chemical hardening agent for the alkali metal silicate may be added to the sand.

Claims

1. In a binder composition obtained by mixing, in aqueous solution, an alkali metal silicate and a hydrogenated starch hydrolysate, the improvement comprising including urea in said composition.

2. A binder composition according to claim 1 characterised in that it contains 15-47% by weight of alkali metal silicate, 2-45% by weight of the starch hydrolysate, 0.1-10% by weight of urea and balance water.

3. A binder composition according to claim 1 characterised in that it contains 26-45% by weight of alkali metal silicate, 3-27% by weight of the starch hydrolysate, 0.4-4% by weight of urea and balance water.

4. A binder composition according to any one of claims 1 to 3 characterised in that it also contains furfuryl alcohol.

5. A binder composition according to any one of claims 1 to 3 characterised in that it also contains formaldehyde.

6. A binder composition according to any one of claims 1 to 3 characterised in that the alkali metal silicate is sodium silicate.

7. In a method of making an article of bonded particulate material which comprises forming to the desired shape a mixture comprising particulate material and a binder, and causing or allowing the mixture to harden;

the improvement comprising, as the binder, the composition according to any one of claims 1 to 3.

8. In a binder composition obtained by mixing, in aqueous solution, an alkali metal silicate, a substantially water soluble carbohydrate selected from monosaccharides, disaccharides, polysaccharides and derivatives thereof and an oxyanion salt, the improvement comprising including urea in said composition.

9. A binder composition according to claim 8 characterised in that it contains 15-47% by weight of alkali metal silicate, 2-45% by weight of carbohydrate, 0.5-5% by weight oxyanion salt, 0.1-10% by weight of urea and balance water.

10. A binder composition according to claim 8 characterised in that it contains 26-45% by weight of alkali metal silicate, 3-27% by weight of carbohydrate, 0.5-2% by weight oxyanion salt, 0.4-4% by weight of urea and balance water.

11. A binder composition according to any one of claims 8 to 10 characterised in that it also contains furfuryl alcohol.

12. A binder composition according to any one of claims 8 to 10 characterised in that it also contains formaldehyde.

13. A binder composition according to any one of claims 8 to 10 characterised in that the alkali metal silicate is sodium silicate.

14. A binder composition according to any one of claims 8 to 10 characterised in that the oxyanion salt is an alkali metal borate.

15. A binder composition according to any one of claims 8 to 10 characterised in that the carbohydrate is a monosaccharide selected from glucose and fructose.

16. A binder composition according to any one of claims 8 to 10 characterised in that the carbohydrate is a disaccharide selected from sucrose, maltose and lactose.

17. A binder composition according to any one of claims 8 to 10 characterised in that the carbohydrate is a hydrogenated starch hydrolysate.

18. In a method of making an article of bonded particulate material which comprises forming to the desired shape a mixture comprising particulate material and a binder, and causing or allowing the mixture to harden;

the improvement comprising, as the binder, the composition according to any one of claims 8 to 10.