US2119480A - Covering material and process of treating same - Google Patents

Description

May 31, 1938. P. w. CODWISE COVERING MATERIAL AND PROCESS OF TREATING SAME Filed Feb. 20, 1955 Patented May 31, 1938 UNITED STATES PATENT OFFICE COVERING MATERIAL AND PROCESS OF TREATING SAIKE Application February 20, 1935, Serial No. 7,347

6 Claims.

This invention relates to the treatment of fibrous materials in sheet form and more especially to the impregnation of panels or of wall boards of felted fibrous structure. The invention particularly relates to ,the process and to the product resulting from the process of impregnation of such fibrous panels with sizingmaterial.

Sheets of paper of various kinds and of various compositions and fibre wall boards and other panels heretofore have been coated upon their surfaces or have been treated with sizing materials of different kinds for the purpose of producing different kinds of finish of the surface of the sheet or panel and for the purpose of preventing entrance into the sheet of water, air or other elements. In the manufacture of wall boards of fibres of various kinds the fibres themselves also have been sized and, as well, sizing has been applied upon the surface of the panel.

The sizing materials heretofore used have been of various compositions and have included oils, Waxes, starches and varnishes, some of which are of such character as to be retained by the fibrous structure by capillary attraction or by absorption into the fibre. Others which are capable of setting, such as waxes, varnish, starch, glue and similar sizes are retained for the most part while liquid between the fibres, by capillary attraction and upon setting act to stiffen the fibrous structure or to harden the surface of the sheet. Particularly in the sizing of sheets of paper or of wall board of fibrous composition heretofore it has been difficult, even with the sizes of highly penetrating character, to secure more than substantially a surface penetration of the size into the felted structure of the sheet or panel. I account for this difiiculty of obtaining as great a depth of penetration as would be desirable by the fact that the penetration of the size beyond the initial depth is limited because the capillary attraction, which is effective to produce the initial penetration, also is effective to retard further penetration unless a suitable process and means are utilized to force the size further into the fibrous structure.

while heretofore sizes and sizing material have been applied to sheets of paper, to fibre wall boards and to other felted fibrous structures by passing the sheet over or in contact with a roll, while simultaneously feeding the sizing material to the surface of the sheet, the process has not been so carried out as to bring pressure upon the sheet or the panel, while applying sizing thereto, in such a way that the sizing is forced into the fibrous structure of the sheet or panel. In the process of my invention I so apply sizing to the sheet and so apply pressure to the size covered surface of the sheet that the sizing material which is absorbed by the surface portions of the fibrous structure may be partially or wholly squeezed therefrom and forced into the inner portions or layers of the fibrous structure of the sheet while additional sizing material is applied to the surface of the sheet to be absorbed by the surface portions or layers thereof. Or stated in another way I apply the sizing material in excess of that whichwould be absorbed by the capillary action alone of the outer portions of the fibrous structure and carry out sub stantially simultaneously the forcing of the sizing into the inner layers or portions of the structure while maintaining the penetration of the outer portions or layers.

In its broad aspect, therefore, my invention comprises the application of sizing material and of pressure of such degree and in such relation to the application of the sizing as to force the sizing further into the sheet or into the fibrous structure of the panel than the depth to which it would penetrate under the absorption by capillary action alone. In orderto accomplish the desired practical penetration preferably I carry out my processby repeated applications of sizing and pressure. Moreover, preferably in order properly to effect the penetration of the sizing into the deeper layers of portions of the fibrous structure I repeatedly apply the sizing while simultaneously applying the pressure upon the sheet, preferablyeach time with the sizing in excess of the amount to be absorbed by capillary action-alone for the depth of penetration being reached, and each time also with pressure in excess of that which would effect only capillary penetration.

In the practice of my invention in connection with sheets or panels in which it is desired to provide a relatively hard surface and a relatively stiff body structure when sized, I utilize certain materials in order to obtain the desired penetrating characteristics of the sizing and in order to provide a structure which has the desired degree of penetrabilityto said sizing. Such panels usually must provide a body structure through which may be driven a fastening such as a nail or screw. Particularly in the manufacture of wall boards of fibrous materials I may utilize boards which are formed with fibres capable of felting. The fibres in condition for felting are of such character and are of such size in relation'to each other as to form a pulp or mass with a degree of freeness which is suitable for obtaining the desired penetrability or absorptiveness of the felted structure. A free stock as compared with a slow stock is preferable for the purposes of the invention.

The degree of freeness is determined in common practice by means of a sedimentation tester. This instrument in one type consists of an open glass tube 10 /2" long and "/8" inside diameter. At one end of this tube is fitted a wire mesh screen of '70 mesh which is held in place by a device providing a stopper of suitable type for stopping and starting the flow. In testing a given fibre stock the stock is first brought to a. definite consistency of mixture with water, this consistency usually.being .2%, that is 2 grams of air dry fibre stock per 1,000 grams of 'water, and the stock being maintained at a temperature of Fahrenheit. with the stoppered and screened end down, the instrument in vertical position is filled with said stock to overflowing. The stopper is removed and the time required for the head to fall 7", that is, within 3 of the screen, is determined with a stop watch. As the stock is filtered out of the water a mat of fibre forms upon the screen and the flow becomes slower as the head drops and the resistance increases. With a relatively free stock the rate of drop through the 7" is faster than with a less free" stock.

With an open or free" stock suitable for the purpose of the present invention as applied to wall boards, preferably the time necessary to drop the head 7" is between 50 seconds and 100 seconds when testing stock at a consistency of 2% and at a temperature of 80 Fahrenheit. Thus this characteristic of the stock suitable for wall board panels to which the invention is applied as a freeness of 50 to 100 invention is not limited specifically to this range of freeness" I have found, especially for the purpose of sizing wall boards of fibrous materials and particularly those made from or containing ground wood or ground wood may be designated seconds. While the pulp, that stocks having a "freeness of this degree are most suitable for the desired degree of penetration, In order to secure the desired degree of freeness" and to modify the degree of the freeness of the ground wood itself or of other fibre in some cases I utilize sulphite stock mixed with the ground wood. The sulphite stock preferably utilized is the unbeaten pulp which is not highly hydrated fiber stock. As tested by the method of test above described, the sulphite stock is much freer than the ground wood. A certain percentage of t e sulphite stock, therefore, may

be utilized to modify and to control the freeness of the mixture.

The degree of freeness" however is not the only factor determining the depth of penetration which may be obtained with a given sizing. I have found that other factors, such as the character of the fibre and its method of manufacturemay have an influence upon the amount or degree of penetration obtained. As a practical measure therefore I have developed a method of test in order to determine the penetration quality or absorptiveness of a fibrous structure of the type suitable for the present invention.

For the purposes of this test I utilize a mixture of 13 ounces of amylacetate and ounce of one-half second cotton solution as a test'liquid to apply to the surface of the fibrous structure to be penetrated. The test may be made by placing a spot of 4 drops of this solution upon the surface to be tested and noting the time required for complete absorption of the solution by the fibrous structure so that the solution is not apparent upon the surface. For example, with a stock which has been found satisfactory in the manu-. facture of fibre board and which includes in its composition a considerable percentage of ground wood which may be designated as free stock, the spot may be completely absorbed by the fibrous structure in about 5 seconds. On the other hand, when the test is made with a sheet of thoroughly hydrated or slow stock such as is provided in sheets composed substantially entirely of manila" pulp, the solution absorbs very slowpart, disappear but the surface retains a somewhat moist appearance. For the purposes of the invention, particularly in the manufacture of fibrous wall board, a degree of absorptiveness as expressed by the absorption of 4 drops in from about 3 to seconds indicates a fibrous structure in the wall board or other material which will be suitable for the absorption and penetration of the sizing materials which will provide the desired finish and surface for the material while also securing a material which may be fastened in the usual manner to the building structure as by nailing.

The cotton solution which forms a part of the test mixture is composed of nitrated cellulose dissolved in suitable solvents and is a well known commercial product.

In order to secure the desired surface hardness while also obtaining the penetrability of the sizing material into the fibre and fibre layers or portions of the sheet or panel, preferably I utilize a'sizing material which is capable of-setting or hardening in the air. This sizing material, however, when being applied, is in a substantially liquid condition and has a viscosity of suitable degree properly to penetrate the deeper layers or portions of the sheet or panel when pressure is applied thereto. In the particular application in connection with the invention being described,

namely, the manufacture'of fibre wall board, I have utilized a so-called varnish size thinned by suitable solvents. While I have found that cer- .50 seconds to seconds, and the range of absorptiveness of 3 seconds to 90 seconds, as described above. Certain sizing materials are of such character as to be capable of setting and capable of being thinned by solvents or by heat or by other means to have a Saybolt viscosity of ,7 to 15 seconds at a temperature of to Such sizes may be applied under pressure upon the sheet or upon the panel or wall board and they may have the proper consistency, viscosity and relative capillary action upon the fibrous structure and will remain sufficiently liquid for a sufiicient time before setting so that the process referred to above of forcing the sizing into the deeper fibre structure of the sheet or panel maybe carried out before setting of the sizing.

In order to make clear the process of my invention the following description may be taken in connection with the drawing in which Figure 1 shows in cross section the apparatus for carrying out the process of the invention; and

Figure 2 shows an enlarged cross section of a part of a wall board panel treated in the manner of the invention.

In Figure 1 is shown a table I supported upon suitable struts 2. The table I serves as a support for the panel 4 of wall board, bearing upon its upper surface 3, to be treated according to the process of the invention. At I is shown a roll positioned to contact the upper surface 5 of the panel 4. At 8 is shown a counter or anvil roll substantially tangent to the upper surface 3 of the table I and against which the undersurface 6 of the panel 5 may bear when the panel passes between the rolls 1 and 8. By suitable means not shown rolls I and 8 are driven to turn in the direction of the arrows so as to feed the panel 4 from the table I, between the rolls I and 8 and toward the table I0, the upper surface II of the table I0 being substantially tangent to the roll 8. Thus the panel 4 may be moved between the rolls I and 8 and supported upon the surface II, the table I0 being mounted upon the struts I2.

The roll 8 may be journaled in the lower portion of a stand I4 and the roll I may be arranged to slide in a slot I5 while being capable also of turning movement upon its axis. By means of a bearing piece II, against which acts the spring I8 which may be forced downwardly by the T-piece I9 when the nuts 2| are turned upon the bolts 22, the roll I may be forced into contact with the upper surface 5 of the panel 4. As the panel 4 passes between the rolls I and 8 it is thus squeezed between said rolls with substantial pressure which may be of the magnitude of about 40 to 60 pounds per inch of width.

To the size box 25 may be fed, so as to maintain a substantially constant level therein, the sizing material of suitable composition. The size box is so mounted with respect to the roll I that an orifice opening or slot 26 lengthwise of the roll I is provided through which the sizing material may fiow, under the head of the sizing maintained in the box 25, as the roll 1 turns in the direction of the arrow. Theopening between the size box and the roll is small and insuflicient to permit substantial fiow unless the roll I is turning. As the roll turns sizing material may be delivered continuously to the upper face 5 of the sheet or panel 4 and may pass, together with the panel 4, between the rollers I and 8. In this treatment the sizing material may not only be absorbed by the natural capillary action of the fibrous structure but, sufficient or excess sizing material being present, by the pressure of the rolls I and 8 it may be forced into a deeper portion or layer of the fibrous structure. To insure that sufficient excess of the sizing material is present and available for forcing into the fibrous structure the opening 26 may be such as will maintain the roll always wet with a substantial amount of the sizing.

ile at first thought it might appear that the sizing taken up by the fibrous structure under its capillary action would be forced out of that structure when the pressure is applied to the board, I have found that such is not the case and that, as stated above, the sizing material is forced deeper into the fibrous structure providing that the sizing is kept at the proper consistency and the fibrous structure of the board is suitable as described above and that the pressure is properly applied with the rolls kept wet. Moreover, by the method and with apparatus capable of producing the action being described, I may produce a substantially uniform application of the sizing material over the surface of the sheet or panel and may force it into the fibrous material of the panel to substantially a uniform depth of penetration and to any desired depth.

An important part of my invention consists in the repeated application of the sizing material to the fibrous panel in the manner just described. For this purpose in a simple method of carrying out the process I may, by tables or other transfer means placed alongside of the sizing apparatus, shift the panel 4 from its dotted position upon the table I 0 around again to table I, from which table it again may be fed in the direction of the arrow through the size rolls 1 and 8 to have applied thereto an additional application of the sizing material and to have this sizing material forced deeper into the structure than the depth of the first application of sizing.

If this repetition of the sizing step is carried out before substantial setting of the sizing material has started or has progressed to any substantial degree I have found that the sizing may be forced into the sheet or into the panel to depths depending upon the number of the repetitions of the sizing operation. Moreover, I have found that the ultimate depth of the penetration secured is substantially proportional to the number of repetitions. For example, as illustrated in Figure 2, which may be considered an enlarged cross section of a portion of the panel 4, the first application of the sizing may afford a penetration thereof in the structure of the panel of .0025", with a sizing of given composition and a wall board of particular fibre structure, this penetration being illustrated by the portion or depth numbered 30 in Figure 2. The second application of the sizing by the method of my invention may cause the sizing to penetrate to a depth of .005", that is, to the depth shown by the portions 30 and 3|. Similarly, with addi tional applications of the sizing under pressure, greater depth of penetration is secured and the portions numbered 30 to 35 in Figure 2 are intended to show the penetration secured in six successive applications of sizing and pressure, so that the full depth of penetration would be substantially .015". If ten applications were made then the depth of penetration of the sizing in the particular case being described would be .025. It will be understood that these depths of penetration are merely illustrative and may be different with sheets or panels of difierent fibrous structures as well as being different with different types of sizes. Figure 2 is merely a diagrammatic showing, in somewhat distorted and enlarged proportions of the degree of penetration produced by the repeated applications of sizing under pressure.

While the dimensions of the successive depths of penetration in the particular example illustrated in Figure 2 are of the degree of a few thousandths of an inch, the invention contemplates and includes within its scope the carrying out of the process as described to eifect penedescribed. The space between lines 38 and 40 may represent the next ply of the outer layer or lamination and the total thickness of the layer or lamination of which these two plies are a part is shown between the lines 36 and 48, there being six plies in the outer layer or lamination. The next layer or lamination below the outer layer or lamination may be illustrated in part by the portion below the line 48, and the plies in this inner layer or lamination may be illustrated by the lines ill-"-44, etc. Thus it will be clear that the sizing may be applied so as to penetrate into the outer ply to the desired depth and to pass entirely through the outer ply or if desired through the outer layer. In ordinary practice, as the layers or laminations are made up of plies which are felted together on the paper machine and in some cases are made of different-qualities of stock or pulp, penetration of the sizing material by the method of the invention into the deeper plies will depend upon the character of the fibrous stock in the deeper plies as to its freeness and absorptiveness"'as has been described above. The invention contemplates such penetration of these inner plies when the character of the fibrous stock is suitable for the penetration of the selected sizing and particularly when such stock, meeting thetest of freeness and of absorptiveness which have been set forth above, is treated with sizing of the character above described. Penetration of the sizing beyond the first layer or lamination, however, in v the usual case may not be expected because in usual practice, as indicated by the heavy line 48, such layers or laminations are caused to adhere together by means of an adhesive, such as silicate of soda, which resists the penetration of the sizing. Such adhesives frequently are non-absorptive and in fact may be substantially impervious to fluids. If an adhesive can be used which itself has the desired absorptiveness, then penetration of the inner layers or laminations may be accomplished.

In the above description the operation is set forth as applying the sizing and causing penetration thereof into the board from one surface only, that is, the upper surface of the panel 4. It is equally possible and practical, however, to apply the sizing material and cause a penetration thereof into the fibrous structure of the panel from both faces, that is, from face] as well as from face 5. In order to apply the sizing material to the lower face 6, I may provide the pan 28 as shown in Figure 1 of the drawing. The pan may be suitably supported between the table I and the table III as by cross members 29 spanning between strut '2 and the strut l2. The roll 8 may dip into the sizing material contained in the pan 28 and upon rotation of the roll the sizing material may be carried up to the face 8 of the panel 4 as said panel 4 passes between the rolls 1 and 8 as described above. It will be understood that the pressure due to squeezing the panel between the rolls I and 8 is applied to the lower face 8 by roll 8 in like degree to the pressure applied to the upper face 5 by the roll 1. While the simultaneous application of the sizing material to both faces of the panel is not necessary for the practice of the invention, it may constitute the preferred method because of the saving of time and of power consumption and the avoidance of extra handling of the panel required to pass it through the rolls for the separate application of the sizing to the second face of the panel.

While the invention has been described in the application of sizing to one face, that is face 5 of a wall board panel, or simultaneously to both faces 5 and 6, it will now be obvious that the face 6 of the panel may be treated by running the panel through the rolls I and 8 with the face 8 uppermost after treatment of face 5 is coinpleted. Moreover, it will be understood by those skilled in the art that instead of repassing the panel 4 through the same setof rolls, if desired, additional apparatus may be provided in series or in line with the apparatus for carrying out the operations described in connection with Figure l, the particular arrangement of and the particular type of apparatus for carrying out the sequence and repetition of the operation being subject to variations without departing from the spirit of the invention.

The apparatus utilized with the invention is capable not only of suitably applying the sizing to the surface of the sheet but also of so applying pressure to said surface, at the point of application of the sizing or upon the previously ap plied sizing, that said pressure is of such degree as to be capableof forcing the sizing into the inner portions'of the fibrous structure. In the particular type of apparatus illustrated the pressure utilized upon the rolls is of the degree of about 2,500 to 3,000 pounds upon a. panel of 48 inches in width or about 50 to 60' pounds per inch of width of the panel. Preferably, for the purposes of the invention in connection with fibre wall board a pressure greater than 25 pounds per inch of width is utilized and this pressure usually may be in the range of 40 to 60 pounds per inch of width of the panel or sheet passed through the rolls I and 8. As has been stated above, this pressure may be secured and controlled by means of the springs l8 pressing upon the bearing piece l1 and reacting against the T piece I 9, there being a spring and a set of said parts on each end i of the roll I.

As a sizing material with whichto secure the resultsobtainable by my invention in sizing fibre wall board panels made of ground wood orof mixtures of ground wood and sulphite stock I have found a composition comprising varnish, kerosene, parafllne oil and gasoline highly suitable for securing a hard surface on the fibre board and a surface capable of receiving paint and other surfacing materials while being penetrable' for nailing to studding. Moreover, in some cases the sized surface itself may provide a sufliciently finished surface so that the wall board may be fastened to the studding without further'applicw,

tion of paint or other covering material. The composition referred to may be prepared in the following manner: A varnish may be made in a varnish kettle with the following formula: 1,000 pounds of rosin, 50 pounds of lime and 10 gallons of linseed oil. This varnish then may be thinned with solvents in the proportions of 50 gallons of mineral spirits of about 50 Baume and 97 ill iii

' bituminous saturants.

gallons of gasoline, these amounts of the mineral spirits and gasoline being those which are suitable to be used with the amounts of the materials forming the varnish as just described.

In order to form the particular sizing composition I utilize:

Gallons Varnish of the composition given above 75 Kerosene 20 Parafiin oil of about 20 Baum Gasoline (60 to 65 Baum) 5 The kerosene is added to secure a softer film upon the sized surface and the kerosene and the paraffin oil assist in securing the desired penetrating quality of the sizing. The gasoline being more volatile aids the setting of the size in the board by its evaporation. While these material are preferable because a varnish containing them is prevented from becoming too hard and too brittle especially during the process of impregnation, other materials may be used as solvents for thinning down and to modify the properties of the varnish. For example, gasoline and mineral spirits oi a density of about 50 Baum may be used. Moreover, other materials may be utilized instead of the varnish size of the composition above described, it being understood that preferably the size should have a viscosity and a penetrating quality in relation to the fibrous structure and to the freeness test of the stock from which it is made which would be advantageous for securing a deep penetration by the repeated application of sizing and of its application under pressure, as has been described.

In addition to material composed of ground wood or of ground wood and sulphite pulp, and as another specific example of the fibrous material utilized in my invention soda pulp has the desired fibre characteristics and may be felted to form an open structure of the type desired for the present invention. In my prior Patent No. 1,948,979, I disclosed my discovery that soda pulp because of its softness and bulking properties has a high absorption capacity for asphalt and In the present invention I may utilize this high absorptive capacity of soda pulp for the absorption of a sizing material which is capable of setting and which more particularly for securing a finished surface will present a hard surface which may be substantially impervious to water. In this way I secure a material which is capable of resisting disintegration through abrasion or by contact with water or in other ways, the sizing and the absorptive felted soda pulp structure cooperating to provide a solid resistant material. It will be understood also that these physical characteristics are obtained with other fibrous materials as well as with the ground wood fibrous structure described above.

The invention is not limited to the specific embodiments shown in the drawing and described above and within the scope of the invention variations from these embodiments may be made in the use of different sizing materials and of different base materials of fibrous structure while utilizing sizing material which is capable of setting and an absorptive fibrous base, the penetrative character of the sizing and the absorptive character of the fibrous structure of the base being so related as to secure a deep penetration of the sizing. Such modifications and variations may be made to secure the most desirable results in particular cases with the process of the invention which utilizes repeated applications of the sizing under pressure.

Having now described my invention, what I claim is:

1. Process of sizing a sheet formed with a plurality of plies of felted fibers, at least the outer or surface ply having a freeness test substantially of the range of fifty to one hundred seconds, which comprises applying to the surface of said sheet a coating of sizing capable of setting, subjecting the coated sheet to pressure to force the sizing into the fibrous sheet, and repeating the applications of sizing and of pressure while said sizing is substantially unset until the sizing has penetrated to a depth of not substantially less than .015 inch.

2. Process of sizing a sheet formed with a plurality of plies of felted fibers, at least the outer or surface ply having afreeness test of between fifty and one hundred seconds, said sheet having an absorptiveness substantially of three to ninety seconds, which comprises applying to the surface of said sheet a coating of sizing capable of setting, subjecting the coated sheet to pressure to force the sizing into the fibrous sheet, and repeating the applications of sizing and of pressure while said sizing is substantially unset until the sizing has penetrated to a depth of not substantially less than .015 inch.

3. Process of sizing a sheet formed with a plurality of plies of felted fibers, at least the outer or surface ply having a freeness test substantially of the range of fifty to one hundred seconds, said sheet having an absorptiveness of substantially three to ninety seconds, which comprises applying to the surface of said sheet a coating of sizing having a viscosity of substantially seven to fifteen seconds at 129 Fahrenheit, said sizing being capable of setting, subjecting the coated sheet to pressure to force the sizing into the fibrous sheet, and repeating the applications of sizing and of pressure while said sizing is substantially unset until the sizing has penetrated to a depth of not substantially less than .015 inch.

4. Process of sizing a fiber wall board containing a plurality of laminations, at least an outer one of said laminations being formed of a plurality of plies of felted fibers, at least the outer or surface ply having a freeness test substantially of the range of fifty to one hundred seconds, which comprises applying to the outer surface of said outer lamination a coating of sizing capable of setting, subjecting the coated board to pressure to force the sizing into said lamination, and repeating the application of sizing and of pressure while said sizing is substantially unset until the sizing has penetrated to a depth of not substantially less than .015 inch.

5. The product of the process claimed in claim 1.

6. The product of the process claimed in claim 2.

' PHILIP W. CODWISE.

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