US2375450A - Manufacture of surface-hardened fiberboard - Google Patents

Description

Patented.

NT OFFICE MANUFACTURE OF SURFACE-HARDENED FIBERBOARD Henry E. Walter, Clo net, Mlnm, assignor to Wood Conversion Company, Cloqnet, Minn., a corporation of Delaware No Drawing.

3 Claims.

The present invention relates to the manufactureof artificial fiber board, and more particularly to one with a hardened surface, which is water-resistant,.washable, resistant to scar and scuff, yet which presents a distinct fibrous texture.

Heretofore, artificial board has beenmade from aqueous slurries of fiber in which water-resistant materials such as drying oils as emulsoids have been incorporated. These produce boards which are more Or less uniform throughout as to the effects of the oil. In order to obtain great surface hardness and water resistance, very large amounts of oil are needed for such a process.

Also, heretofore, attempts have been made to limit the hardening to the surface by adding drying oil to the surfaces of dry board. The penetration is deep, and again, for great surface hardness, too much oil is required. a

The present invention is directed to the pro- Application February 3, 1940, Serial'No. 817,105

added with the same oil. I

duction of oil-hardened surfaces with a fibrous texture, using a minimum of oil.

One object of the invention is to apply oil to board in the process of manufacture, when the stock for the board, in mat form, is already wet with water, thus resisting penetration of oil.

Another object of the invention is to apply oil to wet-board-forming mats in the form of an oil-in-water emulsion, further to limit the penetration of oil.

Still another object of the invention is to add drier to the oil, and to dry? the board and harden the oil simultaneously by the application of heat in the presence of oxygen in such a way as to eifectsetting of the oil while the board is still wet and in process of drying.

The invention may be carried out in numerous ways, and with numerous materials. Vegetable oils are known in both drying and non-drying form. Recently, drying oils have been made from non-drying vegetable oils, such as dehydroxylated castor oil, and also from petroleum and other hydrocarbon bases, such as Puro-Resin, a trademarked product which is an unsaturated petroleum derivative having double bonds in the molecule which dry as do the double bonds in dry-, ing oils, giving an oxidized solid resin-like product. These and the natural drying oils, such as I Perilla, linseed, soya bean, China-wood, oiticica,

and many others, may be used. They are emulsified in water with a minimum of other material, except emulsifying agent and drier. Incorporation of other solids, for example starch, merely adds filler to absorb oil. The preferred absorbent forthe oil is the surface layers of the The following composition is a suitable one to illustrate the invention:

Percent by weight Water I 69.4 China-wood oil 27.8 Japan drier 2. Sodium carbonate .4 Dyestuffs (for coloring) .4

Water, 011 and drier are the chief constituents, and the proportion of each is not at all critical. They are used in such proportions as'will provide a stable useful emulsion for the practical method of application adopted. The choice of an emulsifying agent, such as the sodium carbonate has some place in determining the oil concentration, where a low content of agent is used. Compounding is efiected largely with reference to oil usage and consistency of emulsion for the particular method of application. In the above example the sodium carbonate and water at to F. are used as a vehicle to receivethe mixed drier and oil with emulsifying agitation. The emulsion may be sprayed or roll-coated onto a wet mat of fibers.

In making board theslurry of fibers, as of wood or other vegetable form, is ordinarily flowed onto a wire, through which water drains. The wet mat passes through squeeze rolls or other press to remove excess water and provide a mat capable 01 being dried with or without pressure to provide a board. Such a wet mat may be used as a base to receive the emulsion as a surface coat. The mat may .then be dried directly after receipt of the emulsion, or it 'may be subjected to further pressing. However, for the economic limitation of penetration it is preferred to dry it without pressing sion.

Where the board is treated to mark its surface, as by a marking net, as described in my application Serial No. 220,355, filed July 20, 1938, now

Patent No. 2,369,092, issued February 6, 1945, the preferred point of'applying the emulsion depends upon the manner of application. A net of loose heavy cordsextending generally parallel, tied is pulled taut, and the cords lie haphazardly to make a pleasing non-repetitive pattern. This device, or any other impression device, is forced into a wet mat permanently to deform the surface,

without destroying a continuous felted connection betweenthe surface fibers. An open mesh after applying the oil em'ul-- 1 bath, principally to backing sheet. of fabric may be used for mounting the cords, or any other impression members. In such case, a felt may be used in back of the fabric to absorb surface of 'the mat matis being continuously formed, as in a Four-.

any water expressed from the being marked. Where thedrinier type of machine, a flexible impression device and felt, in endless belt form are preferred.

The returning stretch of the marking'device may as by running through a cleaning prevent accumulation ofso1- ids-and fibers by continuous use. Squeeze {rolls provide the marking pressure. In a machine coinbining structures such Patent No. 1,690,152 and Streeter No. 1,712,852, the marking device and the felt need not be flexible for use in the fiat platen press of Ziska.

A net capable of forming a multitude of wavy becleansed,

grooves running close'together'f in the same general direction, is a patterffbvhich may be successfully coated with aidl'l', after impression, with an emulsion of oil to produce a uniformly tough surface- The'final board after drying and surface flattening exhibits intaglio depressionsfrom .005- to .04 incht deep, with a predominant depth from tion. The surface described in detail is rollcoated in practice with the composition as given. Hence it is not necessary to apply the emulsion before forming depression or intaglio designs on the mat. It is preferred to apply the emulsion after the formation of impressions or intaglio designs, in order to avoid removing emulsion in the marking step. Such a mat marked or plain, with oil emulsion coated thereon, is passed into an oven for drying, wherein air is present, the temperature .being well above 212 F. to boil out the water in the mat. A common temperature range is from 310 Fhto 345 F., and in some cases it is common to have fiat platens or feet to contact the board as it dries, thus to reduce the high parts thereof to a common level or callper, as described in Frost No. 2,154,201.. A high heat of the oven is particularly desirable in order that the direct heat of the oven or the platens hasten the setting of the oil by oxidation before the board inside is dry. Thus the oil is localized and set at the surface to give most efficient use of oil.

The desired oil-skin effect on a boardof density about 16-pound per cu. ft. with a hi h degree of localization, begins at about 7 pounds of oil per 1000 sq. ft. It may be used up to 30 pounds of oil per 1000 sq. ft. Common practice for uniform results calls 'for a usage from 11 to 22 pounds, with preference for lowest usages in that range.

' Usage below 7 lbs. per 1000 sq. ft. fails to give sufficient depth to the skin for practical resistances in Wainscot uses.

The board presents a fibrous texture, rather than an oil-skin texture, but it has properties akin to an oil-skin. The surface fibers are oil-sized and bound together by the dried oil. The surface is free from fuzz. It is water-resistant, washable like paint, hard, and resistant to maras shown in th Ziska ring and scufiing. It is excellent for use as Wainscot, and in this use it is desirably decorated with impressions as set forth in my said prior applications. The usage Ofoilis verylow, and the maximum benefit of th I-oil." btained'. The process described permits somerset penetration to give more than a thin shell at the surface of the board. The penetration may be modified by many changes in-co'nditions, and the thickness of the hardened layer may be increased bya greater quantity of oil.

Any desired color may be obtained by. addin dyestuffs, either oil-soluble or water-soluble, to color the oil, or to color the fibers, or both. Pigments and fillers are preferably absent since they tend to filter out on the fibers to coat them,

I and may be rubbed oif in cleaning operations.

The'oil and 'color at the surfac enter the fibers and the oil hardens the fibers. individually and as afelt.

A variant of the invention forboards' already made is to wet the board with water at the surface to be hardened, then to apply the emulsion, and then subject to heat toharden the oil and dry out the water. The application to wet board prevents striking in of oil, and the use of an emulsion gives uniform distribution of the oil,

' which otherwise would be repelled by the wet oil over the surface.

.. companying claims.

fibers. The drying of the oil is to be effected before the drying of the under-layers of fibers.

in order to prevent striking in of the oil. This is simply accomplished by the use of boiling drying temperatures, and by the use of driers in accordance with the needs of the oil selected.

The compounding of the emulsion is of course effected to include a high content of oil, thereby in part to limit the amount'of water to be dried out, and in part to provide a suitable thick emulsion to give a uniform distribution of the In forming a felt the fibers of surface layer and of the wire-face are in continuous felted relation. The impression of a design with depressions into a wet mat preserves this continuous felted layer. The presence of oil in the layer with or without a design makes a continuous resistant surface. Heretofore, designs have been cut into dry, fiber boards, but this breaks the surface continuity-of the web and exposes fiber ends at the under-cut parts. Where the entire surface with a design is to present uniform resistant properties, it is very important that the hardening agent and the design be applied while the board is wet and while the continuous felted connections at the surface are shiftable, and then to dry the mat to set the surface connections, and hence the design, and also to set the hardening agent.

The oil-surface snakes an excellent base for paints, varnishes or lacquers, acting as a size to prevent penetration of such coating materials.

Thus, where it is desired 'to'redecorate a board and economically.

vention, and these are contemplated in the ac- Iclaim: pg '1. The method of making an a" tificialfiber insulation board which comprises. .,;forming ,a slurry of vegetable fibers into a wetin'at, squeezing water from the mat to form' a wet-'insula tion-board-forming mat, applying an emulsion in water of dispersed liquid phase-consisting sub- Various changes and modifications will be 'apparent from the foregoing description of the in--' with the wet mat, thereafter exposing the set oil to an oil-hardening atmosphere while effecting hardening of the oil and while continuing the drying of the mat as to water, and completing the drying of the mat as to water,. whereby the hardened oil is localized at the surface of the dry mat.

, 2. The method of making an artificial fiber insulation board which comprises forming a slurry of vegetable fibers into a wet mat, squeezing water from the mat to form a wet-insulation-boardforming mat, applying an'emulsion in water of dispersed liquid phase consisting substantially entirely of a setting and hardenable drying oil together with a small quantity of drier therefor tothe surface of the wet mat in quantity to use 'I to BQ pounds of said oil to 1000 sq. ft. of mat surface, heating the wet coated mat in the presence ofan oil-drying and oil-setting atmosphere at a temperature in excess of the boiling point of water and boiling water out of the coatin and themat while pressing mechanically on the coated wet mat to reduce the overall thickness mere drying of the wet-surfaced mat produces I of the resulting board to a uniform'caiiper, and

while eflecting setting of the oil to a non-flowing the Wet mat, thereafter condition in contact with exposing the set oil to an oil-hardening atmosphere while eflfecting hardening of thefoil and while continuing the drying ofthe mat as to water, and completing the drying of the mat as to water, whereby the hardened oilis localized at the surface of the dry mat.

3. The method of producing a coated board which comprises applying to the wet surface of a mat of vegetable fibers of character such that a vegetable flber board, an emulsion in water of dispersed liquid phase consisting substantially entirely of a setting and hardenable drying oil together with a small quantity of drier therefor in quantity of emulsion to provide from '7 to 30 poundsof oil per 1000 sq. ft. of surface-of the mat, subjecting the coated surface of the mat to a boiling heat in the presence of oil-setting atmosphere while removing water from the coating and eflecting setting of oil to anon-flowing condition in contact with the wet surface of the mat, and continuing exposureof the said oil to an oil-hardening atmosphere while effecting hardening of the oil, and completing the drying of the mat as to water after the setting of the oil, whereby to produce a dry board with said hardened oil as a coat localized at-the surface of the mat.

HENRY E. WALTER.