Method for making dimensionally stable composite products from lignocelluloses
First Claim
1. A method of making a dimensionally stable composite product from lignocellulosic material, comprising:
- a) bringing the lignocellulosic material in divided form into contact with high pressure steam at a temperature high enough to decompose and hydrolyze hemicellulose and lignin contained in said lignocellulosic material without carbonization thereof;
b) maintaining the lignocellulosic material in contact with high pressure steam for a time sufficient only for the decomposition and hydrolysis of hemicellulose and lignin into low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids and low molecular weight lignins and other lignin decomposition products, with negligible degradation of cellulose;
c) drying the hydrolyzed lignocellulosic material;
d) forming the residue of the lignocellulosic material, in comminuted form, and including low molecular weight lignins and other lignin decomposition products formed in step b), together with low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids derived from decomposition and hydrolysis of one or more of hemicellulose and cellulose, into a mat or web; and
e) compressing the said mat or web at a temperature and a pressure for a sufficient time to polymerise, cross-link, and thermoset the water-soluble resin material and lignin decomposition products into an adhesive which forms a bond “
in situ”
yielding a reconstituted composite product.
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Abstract
This invention relates to a process for making dimensionally stable reconstituted composite products from lignocellulosic material. By treating lignocellulose with high pressure steam to decompose and hydrolyze the hemicellulose, cellulose and lignin fractions of the lignocellulose and using those decomposition products as both a bonding and bulking agent, it converts, under heat and pressure in a molding operation, the treated lignocellulose into molded composite products such as panel boards and molded articles. The composite products thus produced possess good physical and mechanical properties. Specifically, the dimensional stability in terms of the thickness swelling and linear expansion of panel boards such as fiberboards and particleboard, can be minimized to very low levels when the panel boards are made in high density. The adhesive bond developed from thermosetting of the decomposition products of hemicellulose, cellulose and lignin is strong and stable, and resistant to boiling water and acid hydrolysis, and is free of formaldehyde emissions. Thus, the reconstituted panel boards and molded products are suitable for exterior and particularly for indoor applications. The absence of free formaldehyde emissions makes the product very suitable for interior applications. The manufacturing cost for the reconstituted products is significantly lower in comparison to the conventional process because expensive synthetic resin is not used.
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Citations
14 Claims
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1. A method of making a dimensionally stable composite product from lignocellulosic material, comprising:
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a) bringing the lignocellulosic material in divided form into contact with high pressure steam at a temperature high enough to decompose and hydrolyze hemicellulose and lignin contained in said lignocellulosic material without carbonization thereof; b) maintaining the lignocellulosic material in contact with high pressure steam for a time sufficient only for the decomposition and hydrolysis of hemicellulose and lignin into low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids and low molecular weight lignins and other lignin decomposition products, with negligible degradation of cellulose; c) drying the hydrolyzed lignocellulosic material; d) forming the residue of the lignocellulosic material, in comminuted form, and including low molecular weight lignins and other lignin decomposition products formed in step b), together with low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids derived from decomposition and hydrolysis of one or more of hemicellulose and cellulose, into a mat or web; and e) compressing the said mat or web at a temperature and a pressure for a sufficient time to polymerise, cross-link, and thermoset the water-soluble resin material and lignin decomposition products into an adhesive which forms a bond “
in situ”
yielding a reconstituted composite product. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of making a composite product from lignocellulosic material, comprising:
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a) bringing the lignocellulosic material in divided form into contact with high pressure steam at a temperature high enough to decompose and hydrolyse hemicellulose and lignin contained in said lignocellulosic material without carbonization thereof; b) maintaining the lignocellyulosic material in contact of hemicellulose and lignin into low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids and low molecular weight lignins and other lignin decomposition products, with negligible degradation of cellulose; c) drying the hydrolyzed lignocellulosic material; d) forming the residue of the lignocellulosic material, in comminuted form, and including low molecular weight lignins and other lignin decomposition products formed in step b), together with low molecular weight, water-soluble resin material including pentose and hexose sugars, sugar polymers, furfural products, dehydrated carbohydrate and organic acids derived from decomposition and hydrolysis of one or more of hemicellulose and cellulose, into a mat or web; and e) compressing the said mat or web at a temperature and a pressure for a sufficient time to polymerise, cross-link, and thermoset at least the water-soluble resin material into an adhesive which forms a bond “
in situ”
yielding a reconstituted composite product, lignin decomposition products not forming the bond being available for further bonding on further compressing of the product at a temperature and pressure and for a sufficient time to polymerise, cross-link and thermoset such products.
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Specification