US2161224A - Manufacture of articles molded from cellulosic fibrous pulp - Google Patents

Description

Patented June 6, 1939 PATENT OFFICE MANUFACTURE OF ARTICLES MOLDED FROM CELLULOSIC FIBROUS PULP Ivar Bjarne Berghoff, Stockholm, Sweden No Drawing.

Application February 15, 1937,

Jfierial No. 125,928. In Sweden February 18,

5 Claims.

My present invention relates to a process for the manufacture of molded articles, particularly plates or boards for building, furnishing and/or insulating purposes, and especially of molded 5 articles which have great porosity and small specific weight. The plates-have good heat and sound insulating properties but in spite of their great porosity they show little or no absorption or adsorption of liquid, when immersed into for instance water. The invention also includes articles manufactured according to my new process. iAccording to myinvention the articles are manufactured by forming and drying to sheets or webs of finely divided mixture of a cellulosic fibrous material and a binding agent, subjecting said sheets or webs to such a mechanical treatment as to cause the fibres to be re-loosened from each other, wholly or in part, while forming a wool-like product, mixing said product with a binding agent or a'mass containing such an agent, for instance original un-dried mixture, and forming the mass'thu's obtained into desired shape, preferably under supply of heat and ap- 5 -plication of small pressure.

. 'As basic material I may use any suitable cellulosic fibrous material, e. g., grass, straw, esparto, reed, bark, cork and the like, which has been subjected to a defibrating operation before said treatment, or which is defibrated during same. In order to obtain a porous product I prefenhowever, to use pulp obtained by chemical or mechanical treatment of wood, as for instance mechanical wood pulp in the form of second-rate wood pulp, such as brown wood pulp. As binding agent I may use any suitable substance having binding properties, but as in most cases the choice of said agent is dependent of the price obtainable for the product produced, I prefer to use as binding agent lime, preferably in the form of-lime milk, alum and/or resin, either each per se or two or more thereof admixed with each other. In the manufacture of highly porous plates having small specific weight the lime may be dispensed with and only alum and/or resin be used, the latter substance having in addition to its binding properties also hydrophobe character which is of advantage 'for obtaining a product having water repelling character.

My invention will be described in the following as applied to the manufacture of highly porous plates from brown wood pulp .or other second-rate wood pulp as basic material, it being observed, however, that my invention may also be applied to the manufacture of plates or boards of harder nature from the same or other basic material.

In a mixing apparatus, which preferably consists of an edge-mill but also may be a grinding machine, defibrator or similar apparatus, I mix brown or other second-rate wood pulp with alum (for instance potassium aluminium sulphate) in a quantity amounting for instanceto 5 to 10% of the dry weight of the basic material. Before being mixed with the alum the basic material may have been subjected 'to a preliminary defibration in an edge-mill or similar apparatus. The alum may be added in solid state or in the form of a water solution. In the same edge-mill but preferably after the addition of the alum, or more preferably in a following edge-mill, when using a number of such apparatuses, resin is incorporated into the mixture in a quantity varying with the content of the basic material of resins and/or lignines and amounting for instance to 5% of the'dry weight of the material. In addition to any water added together with the alum I may add during the mixing operation additional water into one or more of the edge-mills dependent of the water content of the basic material. The water content should be kept at a value so as to prevent the rollers of the edgemill from cutting through the material while simultaneously ensuring an effective grinding action. When using second-rate or brown wood pulp in the form in which said pulp leaves the drainage-drums the water content may be 90% but for the purpose of my invention it should preferably be at most 80% or still lower, for instance to 50%. ing the mixing operation should be so adapted as to obtain a final mixture of a water content of at most preferably still lower, e. g., between 70 and 50%.

When the ingredients are thoroughly mixed the mixture is formed and dried to sheets or webs in any known manner. The drying may be carried out in an ordinary drying press.

According to the invention I subject the dried product thus obtained to such a mechanical treatment as to cause the product to be defibrated, that is the fibres thereof to be reloosened from each other, wholly or in part. This treatment may be carried out in any suitable manner asfor instance by subjecting the sheets or webs to the action of brushes or other grinding members. By this mechanical treatment a woollike product is obtained in which all of the fibres are impregnated by the binding agent or agents added during the preceding mixing operation.

The addition of Water durdried mixture of the basic material and bindin agent of a suitable water content or together with water, which mixture may be added' by being sprayed onto the dried product or in any other suitable manner. The mass thus obtained is then ready for molding which may be efiected in a mold or on a plane sieve. i

According to another embodiment of my in-' vention the wool-like product is mixed with undried mixture in a stirring vat or similar apparatus, water being added in such a quantity as to obtain a mixture of a consistency of about 1 to 5, preferably about 2% by weight of dry substance. Then the molding operation is carried out in molds or on a plane sieve while removing the water as completely as possible. 1

The addition of the un-dried mixture to the wool-like product may also take place in any suitable mixing apparatus while keeping the addition of water as low as possible soas to obtain a mass of a dough-like consistency, 'Then the mass is molded by being pressed out-through a nozzle.

The proportion between the dried re-defibrated wool-like product and the un-dried product may be to parts by weight of the former to 20 to 10 parts by weight of the latter.

The plates or boards obtained by'the molding operation are then dried. This may be carried out in such manner that every separate board is introduced between two hollow pressing plates of metal such as aluminium or steel which are heated in any suitable manner, e. g., by means of steam. The pressure required may be executed by the own weight of the over-lying pressing plate, or by additional pressure applied in suitable manner to one or both of the pressing plates. Preferably, several pairs of such pressing plates are provided one above the other so as to form interspaces between them, into which the fibre boards are introduced. By providing stopping studs between the pressing plates all of the fibre boards may be pressed to one and the same desired thickness.

In the embodiment described the magnitude of the pressure should be relatively low, and I also prefer to applyzthe pressure gradually, for instance by providing springs around the stopping studs. The pressure of the steam may originally amount to about 6 kgs. per sq, cm., but when the desired thickness of the boards is attained, I may gradually reduce the pressure to about 2 kgs. per sq. cm. thereby preventing the boards from being burnt.

After the boards have been sufficiently dried under supply of heat and application of suitable pressure, they are removed from the press and are then ready for use.

Boards manufactured according to my invention have a very low specific weight of .12 to .10 and still lower, for instance .085 as well as good heat and sound insulating properties.

articles, which comprises mixing a cellulosic fibrous material with alum and a binding substance having hydrophobe character so as to form a finely divided mixture, forming sheets of'said mixture and drying said sheets, subject- 7 ing said dried sheets to such a mechanical treatment as to cause the fibres to be re-loosened, at least in part, while forming a wool-like product, mixing a quantity of said product with a quantity of a binding agent, and forming the mass thus obtained into desired shape under heat.

2. A process for the manufacture of molded articles, which comprises mixing a cellulosic fibrous material first with alum and then with resin so as to form a finely divided mixture, forming sheets of said mixture and drying said sheets, subjecting said dried sheets to such a mechanical treatment as to-cause the fibres to be-re-loosened, at least in part, while forming a wool-like product, mixing a quantity of said product with a quantity-of a binding agent, and forming the mass thus obtained into desired shape under heat.

3. A process for the manufacture of molded articles, which comprises mixing a cellulosic fibrous material with alum and resin so as to form a finely divided mixture, forming sheets of said mixture and dryingsaid sheets, subjecting said.

articles, which comprises mixing a cellulosic fibrous material with lime, alum and resin so as to form a finely divided mixture, forming sheets from said mixture and drying said sheets, subjecting said dried sheets to such a mechanical treatment as to cause the fibres to be re-loosened from each other, at least in part, while forming a wool-like product,.mixing a quantity of'said product with a quantity of a binding agent, and forming the mass thus obtained into desired shape under heat.

5. A process for the manufacture of molded articles, which comprises mixing a oellulosic fibrous material with lime, alum and resin so as to form a finely divided mixture, forming sheets from said mixture and drying said sheets, subjecting said dried sheets to such a mechanical treatment as to cause the fibres to be re-loosened from each-other, at least in part, while forming a wool-like product, mixing a quantity of said product with a quantity of the original un-dried mixture, and forming the mass thus obtained into desired shape under heat.

IVAR BJARNE BERGHOFF.