Binder composition for use in three dimensional printing
First Claim
1. A process for forming a three dimensional part, comprising:
- building up the part in layers, the formation of each layer comprising;
(a) providing a layer of powder in a bed;
(b) providing a binder composition comprising;
a fluid dispersing medium;
silica in a solid particulate form dispersed in the fluid dispersing medium;
a catalyst able to promote gelation of the binder composition when the binder composition is below a predetermined pH value; and
a base able to maintain the pH of the binder composition above the predetermined value at which the binder composition gels; and
(c) selectively depositing through a print head a binder composition onto the powder layer; and
altering the pH of the binder composition in the powder to below the value at which the binder composition gels, whereby the binder composition becomes immobilized in the powder.
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Abstract
A binder composition for three dimensional printing of parts is disclosed which is stable during storage and passage through a printhead, yet able to gel under the conditions existing in a powder bed. The binder composition comprises colloidal silica, a catalyst able to promote gelation of the composition when the composition is below a predetermined pH value, and a base able to maintain the pH of the composition above the predetermined value at which the composition gels. Preferably, the catalyst is polyethylene glycol or another ethylene oxide-derived polymer, and the base is triethanolamine. Upon impact with a powder bed, the pH of the binder composition is reduced, as by adding an acid such as citric acid to the powder, thereby causing the binder to gel in the powder.
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Citations
21 Claims
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1. A process for forming a three dimensional part, comprising:
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building up the part in layers, the formation of each layer comprising; (a) providing a layer of powder in a bed; (b) providing a binder composition comprising; a fluid dispersing medium; silica in a solid particulate form dispersed in the fluid dispersing medium; a catalyst able to promote gelation of the binder composition when the binder composition is below a predetermined pH value; and a base able to maintain the pH of the binder composition above the predetermined value at which the binder composition gels; and (c) selectively depositing through a print head a binder composition onto the powder layer; and altering the pH of the binder composition in the powder to below the value at which the binder composition gels, whereby the binder composition becomes immobilized in the powder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification