US2260557A - Method of making low density water resisting fibrous products - Google Patents

Description

Patented Oct. 28, 1941 METHOD OF MAKING LOW DENSITY WATER -RESISTING FIBROUS PRODUCTS John 0. Burton, International Falls, Minn., as-

signor, by mesne assignments, to Minnesota and Ontario Paper Company, a corporation of Minnesota No Drawing.

Application March 20, 1939,

Serial No. 263,066

4 Claims.

This invention relates to improved structural fibrous material and to a process for producing the structural insulating material.

An object of the invention is to produce a fibrous material which is light and porous'and has improved heat and sound insulating properties. The term structural units as used throughout the specification and claims relates to blocks, boards, sheets or other desirable forms of material suitable for the formation, covering or lining of walls, floors, buildings, containers, or other structures where it is desirable that they be resistant to either heat or sound or sound absorbing.

A further object of the invention is to produce porous structural units from materials consisting primarily of pulp or fibers, such as wood pulp, cor'n stalks, bagasse, jute, flax, peat or other fiber cellulose material, or asbestos fibers, hair, rock wool or similar inorganic fibrous materials alone or in combination with lignocellulose fibers.

It has been discovered that highly porous fibrous structures may be produced by incorporating into a pulp or fiber mass an amount of waste liquor resulting from Ckil'lg cellulosecontaining materials, such as wood, bagasse, corn stalks, etc. and aerating the mixture.

In practice of the invention, there is prepared a pulp composed of fibers of substantially uni-- form degree of fineness (and of substantially uniform size). The pulp is mixed with sufficient amount of water or other liquid to render the pulp sufliciently fluid for satisfactory handling. To the pulp mass thus formed, there is incorporated waste liquor resulting from cooking lignocellulose material, for example synthetic-lumber black liquor, kraft black liquor, sulphite waste liquor, soda liquor, etc. The pulp mass and waste liquor are thoroughly aerated and then formed into the desired shape and dried. Drying may take place at any suitable temperature but the best results are obtained when using a drying temperature of about 300 to 350 F. or higher; 7

It is to be understood that any waste or other liquor resulting from cooking ligno-cellulose material may be used. Waste liquor as used throughout specification and claims means liquor resulting from cooking ligno-cellulose material.

When producing semi-chemical pulp there results in what may be termed black liquor waste which contains about to 20% of the original the cellulose material is satisfactory as a frothmaterial of the ligno-cellulose material cooked.

chiefly resins, sugars and degradation products of lignin and cellulose.

When using waste liquor resulting from producing semi-chemical pulp, the following process may be used to obtain highly porous and light structural units.

The fibers are suspended in water at a consistency of about 1 to 3%, and are placed in an aerating apparatus to which is added waste liquor in a ratio of liquor to fibers of about 30:1 to 4:1, depending upon whether a density of from about .75 to about 5 pounds per cubic foot is desired. It is preferred and generally deemed necessary that if the waste liquor is alkaline that a suitable acid or acid reacting salt be added which results in stiffening and stabilizing the frothy mass resulting from aerating. The mixture is thoroughly agitated resulting in the formation of a frothy mass containing relatively small bubbles. The frothy mass is then passed to a suitable forming device and thereafter passed to a suitable dryer.

When using kraft black Waste liquor which contains 40 to of the original material in the lignocellulose material, it is preferred that the waste liquor be diluted to about a Baum of 5. The best results have been obtained by varying the ratio of liquor to fibers from 15:1 to 1:1 in order to obtain a density in the finished structural unit of from about 1 to about 5 pounds per cubic foot. It is necessary when using kraft black waste liquor to add thereto some acid to obtain a stiff and stable froth. In general it may be stated that any acid or acid reacting salt capable of lowering the pH between 4.0 to 6.0 will serve as a froth stabilizer. This relates particularly to synthetic lumber black liquor, kraft black liquor,.and glue. It may be stated generally that any material which reduces solubility of stabilizer, and the amountof such material which should be used is the amount which will reduce the colloidal components to their minimum solubility.

Waste liquor resulting from acid cooking (sulphite or the like) of ligno-cellulose material usually contains about 40% to about 50% the original ligno cellulose material. 'It is preferred to dilute waste-sulphite liquor to a Baum of about 4. This waste liquor when mixed with pulpy material and thoroughly agitated, produces a froth which is fairly stable.

It is believed that the bulk of the constituents of waste liquor are in colloidal form. Colloids of this nature have the property of lowering the on the fibers.

surface tension of water and result in frothing when air is introduced. However, they cause greatest lowering of the surface tension, and hence more frothing when the 'pH is that at which the colloids are the least soluble. The adjusting of the pH to the point where the optimum amount of froth is formed results in the colloidal material and resins being precipitated The precipitated. material results in imparting greater strength and water resistance to the finished products. It is believed that the precipitated material acts as a binder and waterproofing agent.

The best results are obtainable when thefolthe lowing pI-Is are employed:

. pH Synthetic lumber black liquor 4.0 to 6.0 Kraft black liquor 4.0 to 6.0

Sulphite waste liquor 9.0 to 12.0

The process may be carried out at pHs varying from the above, but the best results and the most economical are obtained within the range above indicated.

After the pulp and froth forming materials have been thoroughly aerated, the surplus water may be removed from the formed product by suction, suction and pressure, etc.

If suction is applied to the surface of the formed product'to remove the surplus moisture the bubbles in the material adjacent that face collapses, resulting in a denser surface. Thus a dense surface may be formed on one or more of the surfaces of the product.

When using lignocellulose pulp there may be used mechanically, semi-chemically, and chemically produced pulp depending upon the type of end product desired.

As animal glue is a known colloid, such glue may be employed as the froth-forming material. When glue is used it is essential that the pH be adjusted to about 4 to 4.5 to obtain a stiff, stable froth. To produce a light colored board of about 4 pounds per cubic foot, 1 part of glue is added to about 4 parts of light colored produced pulp.

If it is desired that the finished product have a more decorated effect, the froth-fiber mixture is stirred and/or agitated. The finished product will contain the fibers in a whorly and wavy formation.

The fibers may be proofed by .a process which makes a product not incompatible with the froth-forming material employed. Fireproofing 0f the fibers may be accomplished by various known methods.

d If greater water resistance is desired, the fibers may be treated by any of the known methods for waterproofing.

A mixture of waste liquors may be used as the frothing agent such as an acid and an alkaline waste liquor,

While there has been specifically described the sion,

preferred embodiment of the invention, it is to be understood that the invention is not limited to the details described, or sequence of steps, but may be otherwise embodied and practiced within the scope of the claims. Cognate subject matter not here claimed is claimed in my application, Serial No. 263,067, filed March 20, 1939.

What I claim is:

1. A process of producing a vegetable fiber structural unit having a density of about .75 lb. to about 5 lbs. per cu. ft. which comprises adding to vegetable fibers in a water suspension alkaline kraft ligno-cellulose waste cooking liquor, said waste cooking liquors added in a ratio to the fibers of 30:1 to 4:1, adding an acid as a froth stabilizer, a colloid insolubilizer, and to adjust the pH of the fiber suspension to within a range of 4 ,to 6, agitating and aerating the mixture; forming a structural unit in which the fibers are distended and drying the unit.

2. A process of manufacturing low density structural units comprising adding alkaline kraft waste ligno-cellulose cooking liquors to fibers in a water suspension, said waste cooking liquor added in a ratio to the fibers of about 30:1 to about 4:1, adding an acid reacting salt to adjust the pH of the fiber suspension to within the range of 4 to 6, to stabilize froth and insolubilize colloids, agitating and aerating the mixture, forming a structural unit from the distended fibers and drying the unit without substantially compacting thereof.

3. A process of manufacturing low density structural unit of a density of .75 to about 5 lbs. per cut. ft., comprising adding to vegetable fibers in a water suspension waste cooking liquor resulting from alkaline cooking of ligno-cellulose materials, adding an acid to adjust the pH of the suspension in a range of about 4 to 6 and insolubilize the colloids of the cooking liquor, I

-of about .75 lb. to about 5 lbs. per cu. ft. comprising adding waste cooking liquors resulting from the alkaline cooking of ligno-cellulose materials to vegetable fibers in a water suspensaid cooking liquors added in a ratio to the fibers of about 30:1 to about 4:1, adding an acid reacting salt to adjust the pH of the suspension to within a range of 4 tov 6, to stabilize foam and insolubilize colloids of the waste cooking liquor, agitating and aerating the mixture whereby the fibers are-distended, forming a unit from the distended fiber mass and drying the unit at a temperature of about 300 F. to about 350 F. without substantially consolidation thereof.

JOHN O. BURTON.