US2200650A

US2200650A - Composite board

Info

Publication number: US2200650A
Application number: US136208A
Authority: US
Inventors: Arthur R Welch
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-04-10
Filing date: 1937-04-10
Publication date: 1940-05-14
Anticipated expiration: 1957-05-14

Description

11 4 A. R. WELCH 2,200,650

COMPOSITE BOARD Filed April 10, 1957 Fig. 3

Wpfimm (lttorneg Patented May 14,1940

UNITED STATES; "PATENT OFF-ICE 4 Claims.

The present invention relates to a board which hasqualities of lightness, adequate strength'for many structural purposes, and which constitutes a sound-proof material which can be incorporated in light partitions, doors, and the like. It may also incorporate a fireproof or fire-resistant material.

It is one of the objects of my present invention to devise a board having the characteristics indicated, and one which can be made up in part from materials which are largely waste in the lumber industry, such as wood chips or sawdust, and which can therefore be made inexpensively.

It is a further object to provide a board of the character indicated, which can be made up conveniently by the process described in my copend-'- ing application Serial No. 123,551, filed February 1, 1937.

In a specific application of the principles of this invention it is an object to provide a board having many characteristics of plyboard in that it is formed with two faces of wood veneer, and

which has between the faces a filler of compressed wood particles with a resin binder incorporated, so that the board may be formed in a single operation by the application of heat and pressure.

Not all resins will serve as a binder in conjunction with the fireproofing agent which has been found suitable, hence it is a further object to provide a composite board, or materials for use in such a board, which incorporates both a fireproofing material and a binder which will work properly under the conditions encountered in the manufacture and use of such a board, when such fireproofing material is incorporated therein.

It is a further object to provide such a board in which may be incorporated spacer element's between the two faces or outer sheets, suflicient to give structural strength and rigidity, but with the lighter and more sound-proof filler material filling a considerable part of the space between the two faces.

It is an object to provide a board, and a process of making the same, wherein because the several components are assembled in the dry state, the harmful effects of steam formation in manufacture are eliminated, and subsequent conditioning is rendered unnecessary.

With these and other objects in view, as will appear hereafter, my invention comprises the novel board shown in the accompanying draw-- ing, described in this specification, and as will be more particularly defined by the claims.

In the accompanying drawing I have illustrated various forms of the board, and the process of making the same.

Figure 'l is a perspective view of a corner of a representative board, a part of the top face being broken away to show the interior.

Figure 2 is a similar view of a modified form of board.

Figure 3 is a sectional view through such a board and associated press parts, showing an initial step in the formation of such a board, and Figure 4 is a similar view showing a further step.

Figure 5 is a similar view showing the process of manufacturing a sheet of aggregated material such as is formed in accordancewith my process.

The board is usually formed of two continuous sheets, I and 2, forming the opposite faces of the board, which sheets are conveniently of wood veneer.. It should be borne in mind, however, that other materials may be employed than wood veneer, for instance paper or pulp board might be employed, or indeed, one or both faces may be omitted. These two faces are held spaced apart, and preferably the spacing is rendered definite and the entire composite board is stiffened and strengthened by spacer means which in one form constitutes a marginal frame 3, which may be of wood. Such a frame, in addition, may serve as part of a mold in the pressing step, later described, even though it becomes a part of the finished board. Within the marginal frame, and between the sheets i and 2, is placed a mass of discrete wood particles, in the dry state, having incorporated and thoroughly mixed therewith discrete particles, in the dry state, of a binder which sets under heat and pressure, as for instance a resin. When I speak of wood particles I have in mind wood chips or sawdust, but similar particles having some compressibility, in themselves or relatively to other particles, may be employed. This mass is indicated at 8.

As may be seen in Figure 3, the mass 4, when placed within the marginal frame 3, is of a thickness in excess of that which it is intended to occupy in the finished board. The initial thickness depends upon' the degree of density desired, the compressibility of the filler, the amount of pres sure to be used, etc. The lower face 2 may be placed upon a press plate 5, the marginal frame put in place, the mass of particles 4 placed within the frame, the face I placed on top of the mass, and then a press plate 6 is placed on top of the face I, and the press plates 5 and 6 are moved together to compress the face I down upon the marginal frame 3. The mass 4 of mixed wood particles and binder particles is thus compressed,

A and when the press plates I and i are heated the entire board is aggregated and held in thiscondition by the setting of the binder under the influence of heat and pressure, the heat and pressure being such in amount, and continued for such time, as may be required by the conditions (as thickness), or by the particular binder, a number of which are known to be suitable. The formation of the board may be accomplished by the process and apparatus described in my companion application referred to above. This single operation not only solidifies the particles of the mass 4, but binds the faces I and 2 to the compressed mass, and the latter to the marginal frame 3. It will be observed that the margins of the sheets I and 2 are extended to or beyond the marginal frame 3, and thus pressure is transmitted directly to the marginal frame and this is strengthened during the compressing operation, although the particles of the mass 4 tend to compress in the direction of the pressure rather than transversely thereto. At final compression the board is in a form as shown in Figure 4.

Instead of employing a marginal frame the spacer means may take some other form, as shown in Figure 2, wherein the faces I and 2 are spaced apart by blocks or spacer elements I, which may be arranged in any desired pattern, preferably interspersed through the entire space between the faces. However, a substantial part of the space between these faces is open, and is filled with the mass of particles at 4. A marginal frame may be used or may be omitted, as is preferred, in this form.

A board which is satisfactory for some purposes may be made up with only a single face, or indeed both faces may be omitted, and the mass of particles, as shown in Figure 5 at 8, may be enclosed within a frame composed of the press plate 9 and the marginal frame I0, and may be compressed by movement toward the plate 8 of a press plate II which fits closely within the marginal frame I0, and thus the mass 8 may be compressed and heated and bound into a solid sheet under the influence of heat and pressure acting upon the binder incorporated with the mass of wood particles.

It is at times desirable to render such a board fireproof or fire-resistant, for while its lightness and cheapness recommend it, it is almost entirely of wood, and there are places where a more fireproof material is desirable. I have found that this can be done by incorporating among the discrete particles a fireproofing material. That which I have used is monoammonium phosphate. To obtain the most intimate mixture thereof with the wood particles, I dissolve the flakes of fireproofing material in water, and then moisten the wood particles with the solution. Care should be taken that they are only moistened, otherwise an excessive amount of steam is formed at pressing. Monoammonium phosphate of about 6% to 7% of the whole mass has been found adequate, and a higher percentage has been found not to improve the results materially.

When the fireproofing material is employed it has been found that certain resins or binders will not operate satisfactorily, at least, within the limits of the process of pressing employed. That which has been found most satisfactory is Laucks urea resin, commercially available as such, although certain resins manufactured by General Plastics, Inc., designated 120 and 470 resins, have been found suitable.

The fire-proofing treatment may or may not be employed, as the manufacturer or user may prefer. If the iireproofingmaterial is omitted, I do not know any resin of the general type setting under heat and pressure that can not be used, provided the limiting conditions, for instance, time, pressure, and temperature, can be met without injury to the wooden components of the board.

Such a composite board is light, yet may be given adequate strength for the purpose desired by the marginal frame or spacer members. It can be sawed and nailed like ordinary plywood. It has been found to have excellent properties for the manufacture of doors, and doors made of this composite board do not permit the penetration of sound to any considerable degree. Similarly partitions can be built of this board, such partitions being light, comparatively thin yet soundproof to a considerably higher degree than partitions made of ordinary plyboard or other composite boards.

Because the particles of wood and binder are mixed in the dry state, especially if the fireproofing material is not used, there is no excess moisture which must be eliminated, at an expense of power (in the form of heat) or time. Even more important, perhaps, is the fact that the formation of steam within the interior of the board is minimized or prevented, hence steam pockets which destroy the homogeneity of the final board, or which may blow out or bulge upon release of pressure, are not formed. By reference to wood in a dry state I mean wood which has not been subjected to soaking or wetting (other than such as naturally and unavoidably occurs in usual handling and milling processes), and which therefore is in a natural state, although, if a given wood or mass of particles is found to contain (from natural or artificial causes, or'because of the fireproofing step) an excess of moisture, it is not outside the scope of my invention, nor of the term dry state," to reduce the moisture content, before mixing or pressing, by any suitable process. It is preferred that the wood contain some moisture while being pressed, for a board incorporating moisture is lessbrittle or friable than one wherein the moisture content is unduly or unnaturally low. If the moisture content of the particles, or of the pressed board, is too low, it may be necessary to condition the board by supplying moisture to it, and if the latter can be avoided by leaving the normal moisture content in the particles, an additional step with its consequent expense and delay can be avoided.

What I claim as my invention is:

1. A process for manufacturing composite boards or the like which comprises mixing in a dry state discrete wood particles or the like with a resin binder, placing in a mold, as a first layer, a sheet of plywood or the like, next placing spacer strips of wood substantially at the margins of the first layer, adding as a second layer, and within the spacer strips, said mixture of wood particles and binder, covering the second layer and marginal strips with a sheet of plyboard and then applying heat and pressure to the mass, in the mold, for a time and to a degree necessary to aggregate the same into a solidified sheet or composite board.

2. A process for manufacturing composite boards or the like which comprises mixing in a dry state discrete wood particles with a resin binder, placing in a mold, as a first layer, a sheet of plyboard, next placing on the first layer spaced blocks of wood or the like, then filling in the spaces between the blocks with the said mixture of wood particles and binder, covering this second layer with a sheet of plyboard and then applying heat and pressure to the mass, in the mold, for a time and to a degree necessary to aggregate the same into a solidified sheet or composite board.

3. A process for manufacturing composite boards or the like which comprises mixing in a dry state discrete wood particles or the like with a resin binder, placing in a mold, as a first layer, a sheet of plyboard or the like, next placing spacer elements of wood on the aforesaid sheet,

adding as a second layer, intimately associated with the spacer elements, said mixture of wood particles and binder, covering the second layer and spacer elements with a sheet of plyboard or the like, and then applying heat and pressure to the mass, in the mold, for a time and to a degree necessary to aggregate the same into a solidified sheet or composite board.

4. A process for manufacturing composite boards which comprises mixing in a dry state discrete wood particles or the like with a resin binder, laying up a composite board with a sheet of plyboard or the like as a first layer, next placing wooden spacer elements on the aforesaid sheet, adding as a second layer, intimately associated with the spacer elements, said mixture of wood particles and binder, covering the second layer and spacer elements with a sheet of plyboard or the like, and then, with the composite board in place in a mold, applying heat and pres-v sure thereto for a time and to a degree necessary to aggregate the same into a solidified board.

ARTHUR R. WELCH.