CH317986A - Process for manufacturing an artificial board and artificial board obtained by this process - Google Patents

Description

Process for manufacturing an artificial board and artificial board obtained by this process The present patent comprises a process for manufacturing an artificial board <B>ä</B> from a wet layer of fibrous and coarse pulp, and an artificial board obtained by this process.

It is known that an artificial board can be produced by carrying out a process comprising the decomposition into fibers and the refining of a fibrous material such as wood chips, these operations being followed by forming operations. and lowering the water content of a wet layer of said material, on a Fourdrinier machine, and solidifying by application of heat and pressure, to obtain a hard and compact fibrous mass 1i6e by the hemi -celluloses, lignins and other natural binding constituents of the wood.If desired, additional ingredients may be added, such as, for example, baits consisting of various waxes and additional binding materials such as - less than synthetic resins, for example phenol-formaldehyde resin.

A board produced in the manner described above has certain disadvantages in view of what is currently required of such boards. The fibers form tiny holes <B>ä</B> in the surface of the board, thereby increasing the number of coats of paint needed to achieve a good quality painted surface. In addition, the smooth surface of the board has a dark appearance and is frequently marked with spots or dots very close to each other, <B>to</B> make it difficult to obtain a clear finish. . The smooth surface of the board is that which is in direct contact with a flat platen of a press, during the final solidification. Its rough surface receives the imprint of a supporting metallic wire screen, during said solidification. For most applications of such a board only the surface appearance of said smooth surface is of importance.

During the past few years, the demand for artificial boards with an improved surface has increased in importance. The increasing cost of lumber and structural modifications RTI ID="0001.0273" WI="18" HE="4" LX="1368" LY="1966"> greater proportion of scrap wood than before, more more broken wood and even less suitable species and mime of bark and made it essential to increase the operating speed of the machines, and hence the rate of lowering the water content to as high a point as possible. In order to accommodate increased machine speeds and to compensate for decreased drainage rates resulting from the presence of bark particles, coarser, freer-draining fibers have been used. Bark particles also contribute <B>ä</B> to darkening the surface. Therefore, the demand for artificial boards having an improved surface has effectively coincided with a deterioration in the surface appearance of the artificial boards produced.

One possibility to improve the surface appearance of the smooth surface of an artificial board would be to <B>ä</B> use finer fiber and<B>ä</B> 6Ihnine all the bark particles from the wood chips used. However, this would significantly increase the cost of the wood used and the refining of that wood. In addition,<B>there</B> is a limit <B>ä</B> to the freedom of the fiber and this freedom should not be reduced to the point at which the thick hardened plank mat no longer forms well in the usual wet process. <B>11</B> it is obvious that such a possibility is unsatisfactory because it is contrary <B>ä</B> to the modern tendency to use more scrap wood and coarser fibers. res.

Another solution which has been adopted previously is to <B>ä</B> use a coating process in which a secondary tea can is used to allow a thin layer of specially fine fibers to flow. prepared as an aqueous suspension and on the partially formed wet layer. The top layer of higher quality fibers covers poor quality fibers and bark stains and gives the board <B>ä</B> an improved appearance and surface qualities. This coating process presents. serious limitations <B>ä</B> because of the addition of relatively large volumes of water which is necessary to cleanly flow the secondary coating material and to shape it properly. Water is difficult <B>ä</B> to remove. Special equipment is needed to supply the muddy feedstock. Secondary feedstock also tends <B>ä</B> to fill depressions in the underlying surface and<B>ä</B> to flow <B>ä</B> from the protrusions. gaps from this surface, so it is necessary RTI ID="0002.0276" WI="13" HE="4" LX="1248" LY="343"> to use a coating of Notable thickness to obtain the desired surface regularity. It is expensive. Another solution which has also been adopted previously consists in laying down a thin board having good surface qualities on a solidified base sheet formed of coarser fibers. A sheet of paper can be used as a surface layer. This way of proceeding has the disadvantage of requiring a large quantity of adhesive to ensure a good bond between the base sheet and the surface sheet. Even with a large amount of adhesive, the face sheet may peel off under certain conditions. Considerable additional equipment is also required <B>ä</B> to obtain a veneer which, in fact, presents a smooth surface.

According to the process forming the subject of one of the inventions, the water content of the wet layer of fibrous and coarse pulp is lowered until this layer comprises approximately one-third by weight of solid matter, applies a sheet of paper on. the surface of said wetted layer which corresponds <B>ä</B> to a smooth surface of the finished board, and the wetted layer and the sheet of paper are solidified by the application of heat and pressure, so as to < B>ä</B> form a bond between the paper and the rest of the artificial board by the action of the natural binding constituents of the pulp and by an interlacing of the fibers of the paper and the pulp.

It has been found that a board is thus obtained having considerably improved surface qualities due to the fine fibers of the paper, and in which the bond obtained between the paper and the underlying layer of fibers coarser is such that the paper forms an integral part of this layer. In addition, the board thus obtained is inexpensive because a thin surface layer is used and the modifications of the basic process required are small. The artificial plank object of the other invention is characterized in that it comprises a solidified fibrous mass whose fibers are mainly bonded to each other by natural binding constituents, and a sheet of paper making integral part of one of the surfaces of the said mass<B>ä</B> which it is united by interlacing the fibers of the fibrous mass and the fibers of the paper and by the said natural binder constituents.

The appended drawing illustrates,<B>ä</B> by way of example, an implementation of the claimed process and represents an embodiment of the artificial board obtained by this implementation of the process. fig. <B>1</B> is a schematic view illustrating said implementation of the method. fig. 2 is a sectional view of a plank section.

A preferred implementation of the process will be described with reference to <B>ä</B> the production of a hard board <B>3.2</B> mm thick in the volume of a rev# ment made of newsprint, obtained by using a binder <B>ä</B> linseed oil.

A filling consisting of a mixture of hard and soft woods in approximately equal proportions is formed by separate treatment of wood chips in disintegration apparatus into fibers <B>A,</B> respectively <B><I> A2</I></B> and in secondary refiners B, and B.. This trim is sent to storage bins <B>C,</B> and C,. The wood is treated with steam before and during the process of disintegration into fibres. The consistency of the pulp entering the storage chests is characterized by about 4.5 ()/o by weight of solid matter. Hardwood and softwood pulps are mixed in approximately equal amounts in a mixing box <B>D</B> where the consistency of the material is regulated so that it is characterized by approximately <B>3</B> % by weight of raw material. <B>At</B> this stage, priming materials, such as Wax Emulsion, are added. The pulp is transported <B>ä</B> a box <B>of</B> head <B>G ä</B> through a conduit <B>E</B> and by means of a pump F.<B>At</B> from this head, it is brought onto a metal wire screen of a Fourdrinier machine H. The wet layer then presents a thickness of approximately <B> 7.6</B>cm. A part of the skin is removed by free drainage along a section <B>J</B> and another part of the skin is removed by means of one or more boxes RTIID="0003.0274" WI="18" HE="4" LX="1497" LY="430"> suction roller K and one or more sets of suction rollers L. The wet layer then passes <B>ä</B> through a or'several pairs of cold pressure rollers M. Only one pair of <I>M</I> rollers is shown, however, preferably, several pairs of such rollers are used, with a pinging pressure varying between<B> 18</B> and 134 kg/cm. The wet layer comes out with a thickness of about <B>19 to 25</B> mm and with a water content of about <B>65</B>% and is transferred to the section of a table <B>ä</B> rollers <B><I>N.</I> At</B> at this point the coating paper is applied. Ort passes newsprint weighing approximately 0.054 kg/m2 <B>ä</B> from a <B>0</B> roll and between a P adhesive backing roll and a <B>Q</B> back-up roller and this paper is then applied to the wet layer by means of an R-roller. pressure in a heated press <B><I>S</I></B> where it is subjected <B>-ä</B> to a pressure varying between<B>3.5</B> and 45.6 kg/cm2 <B>ä</B> at temperatures of approximately 2000<B>C</B> during a pressing cycle of approximately <B>8</B> minutes of total hardness.<B>A</B> From there, the board is sent to a furnace <B>ä</B> to cook <I>T</I> where it is treated <B>ä</ B> a temperature between 145 and <B>1650 C</B> for about <B>3</B> hours or longer to vulcanize the binder. After that, said board is moistened until it contains approximately <B>7</B>% humidity.

As represented <B>ä</B> in FIG. 2, the product obtained comprises a base sheet consisting of a solidified fibrous mass <B>U</B> which is integrally joined <B>ä</B> to a covering sheet V, along a line W. Along the Egne W, the fibers are crisscrossed which ensures a solid connection. In addition, this bond is further ensured by the effect of the natural binders <B>of</B> the pulp and the drying oil. Some of the drying oil is near the W line and is available for bond formation. Another part of the drying oil is driven outwards by the migration of binder constituents and moisture <B>ä</B> from the wet layer, so <B>ä</B> to form a resistant barrier <B>ä</B> Skin indicated at <I>X.</I> For purposes of illustration, barrier X is shown as well defined. In practice, it has no clearly defined limits.

The product represented <B>ä</B> in fig. 2 exhibits good <B>ä</B> abrasion resistance due to <B>ä</B> drying oil, a pleasing translucent appearance and superior bending properties to form small radius curves and having smooth surfaces. The fibers of the coating are short and do not tend <B>ä</B> to protrude <B>ä</B> outside the surface, and the coating acts <B>ä</B> the way #re of a reinforcing sheath for the underlying base sheet. The product should be free of spots or dark spots and close together. In addition, it has been found that the improved surface of the product makes it possible to remove approximately one layer of paint compared to <B>ä</B> what is necessary with ordinary planks. Since the cost of the paint application is several times the cost of the impregnated coating, a considerable saving is achieved. The surface effects of said product are comparable <B>ä</B> to those obtained with boards treated by immersion or by application by means of rollers, with a quantity of drying oil between 2 and <B>8</B > % by weight of the board. <B>11</B> is therefore evident that the written process is more economical than those known hitherto. This process can also be compared favorably with the mud surfacing process, in which a surfacing between 0.122 and <B>0.488</B> kg/m2 of board is normally used and for which, in addition, the equipment costs are more 61ev#s.

From the foregoing, it will be seen that the specified process and product provide a significant improvement in surface qualities, <B>ä</B> at extremely low cost. <B>11</B> is preferable to use a sheet of skhe paper in order to obtain RTI ID="0004.0278" WI="4" HE="4" LX="1556" LY="247" > increased absorbency <B>ä</B> of the binder constituents <B>ä</B> of the wet diaper.

Ort can obtain an additional reinforcement <B>of</B> the bond between the paper and the underlying mass by using a thin layer of an additional binder, although the use of such a binder is not obligatory. Said binder tends <B>to</B> to provide a more uniform bond by filling depressions which the base sheet may have and by providing a bond where the base sheet has such depressions.

Particularly good results have been obtained using a drying oil <U>as</U> the binder. It has been found that, while contributing <B>ä</B> to bind the sheet of paper to the base mat, said drying oil further <B>-</B> gives <B>ä</B> the plane - for surface properties comparable <B>ä</B> to those that can be given to it by treating it by applying a siccative coating to its surface, by soaking or by means of a roller, the consumption of drying oil being, however, considerably less. Some of the drying oil also forms a water-resistant 6eran adjacent <B>ä</B> the surface of the paper, so that it is <B>ä</B> emp-kher the appearance of water stains which could otherwise form during hot <B>ä</B> pressing. These water stains are probably due <B>ä</B> to the water <B>ä</B> in its liquid state and<B>ä</B> to substances dissolved in it and which are forced towards the surface, the water evaporating and becoming steam on contact with the hot plate. Sugars and other water-soluble substances thus cause discoloration. It has also been found that oils give the surface of the board a pleasing translucent appearance but that, despite this translucent appearance, darker stains of the board surface base sheet are well covered and concealed.

The sheet of paper used as a cover can have very different qualities, thicknesses and other properties. Currently, cheap paper with good absorption qualities is used, such as newsprint. Other suitable papers include semi-chemical sulphite, sulphate and neutral sulphite sheets. A preferred grade of newsprint has a weight of 0.054 kg/m2.

The binder may be a drying oil such as linseed oil or the product labeled <B> </B> Velsicol <B> 929</B> which is believed to be a mixture of drying oils. and petroleum polymers. Other drying oils include hn oil, soybean oil, tung oil and china oil. Alternatively, many other binders can be used, <B>including</B> including synthetic resins of compositions such as phenolic resins, urea formaldehyde-based resins, and vinyl resins. Rubber-like networks such as butadiene-styrene and animal or vegetable glues and other binders can also be used. Ideal liarit is inexpensive and effective in small quantities and forms bonds that are <B>ä</B> resistant to water, weather and<B>ä</B> heat. The binder should not stain the coating. The amount <B>ä</B> to be used varies with the nature of the binder and other factors, but generally considerably less than that required with an ordinary sheet is used, since the binder is not used. as a primary binding agent but only as a complement to the natural binding obtained by the interlacing of fibers and by the natural binding constituents of the base material. In the case of linseed oil, <B>0.0073</B> kg/m2 is a recommended amount of binder. The amount of binder used is generally between 0.0049 and 0.0245 kg/m-' but can be between 0.00245 and 0.049 kg/m2. An amount of binder greater than 0.0098 kg/m2 does not significantly improve the adhesion of the paper <B>to</B> the base sheet but can be used to obtain a smooth surface. more resistant. An amount of<B>0.0073 kg</B> of phenolic resin or styrene-butadiene per m2 is also effective. Modifiers, catalysts and driers can be added to the binders. Thus, in the case of certain driers, it may be desirable to add a drier such as manganese, cobalt, lead or iron naphthenate. RTI ID="0005.0278" WI="8" HE="4" LX="1536" LY="209"> In the case of linseed oil, it has been found that when this oil is added before solidification of the plank, the heat applied during the pressing and during the subsequent cooking hardens the oil sufficiently.

The wet diaper should be treated to remove water until it has a consistency of <B>ä</B> #60-75% moisture content or <B>ä</B> approximately one third of solid matter, before applying the sheet of paper to this layer. In order to obtain this consistency, the water content is first reduced by free drainage <B>ä</B> through wire meshes of a Fourdrinier machine and then drainage is carried out by suction and then apply cold pressure rollers. The wet layer emerging from between the pressure rollers presents a smooth surface which facilitates bonding <B>ä</B> this layer to the sheet of face paper, <B>ä</B> this manufacturing stage. In addition, most of the water that needs to be eliminated has already <I>6t6</I> 6hmin6e <B>ä</B> at this time. The coating therefore brings only a minimum impediment <B>ä</B> to the removal of water from the pulp. The coating can be applied by means of rollers, after calendering by means of cold <B>ä</B> pressure rollers and before solidification in a heated press. When a binder is to be reused, it can be applied to the surface of the paper intended <B>to</B> to come into contact with the wetted layer, before this paper is applied to this layer. In the case of binder such as linseed oil and other drying oils, it has been found that the binder can alternatively be applied to the outer surface of the paper, after the board has solidified in a heated press. Drying in the heated press renders the paper sufficiently absorbent for the binder to penetrate <B>ä</B> through the paper backing and into the surface layer of the base sheet. When the board is baked, the binder forms a bond between the paper and the base sheet. <B>11</B> is however preferable to apply the binder before solidification by application of heat and RTI ID="0005.0557" WI="13" HE="4" LX="1509" LY="2287" > pressure, because part of the binder then forms a water-resistant barrier<B>to</B> preventing the formation of water spots.

Claims (2)

CLAIMS: <B>1.</B> Process for manufacturing an artificial board<B>from</B> from a wet layer of fibrous and coarse pulp, characterized in that the content of water of this layer until it comprises approximately one-third by weight of solid material, in that a sheet of paper is applied to the surface of said wet layer which corresponds<B>to</B> a smooth surface of the finished board, and in that the wet layer and the sheet of paper are solidified by the application of heat and pressure, so as<B>to</B> form a bond between the paper and the rest of the artificial board by the action of the natural binding constituents of the pulp and by an interlacing of the fibers of the paper and the pulp. <B>II.</B> Artificial board obtained by the process according to claim<B>1,</B> characterized in that it comprises a solidified fibrous mass whose fibers are mainly bonded to each other, by natural binding constituents, and a sheet of paper forming part of a surface of said mass <B>to</B> which it is united by interlacing the fibers of the fibrous mass and the fibers paper and by said natural binder constituents. SUB-CLAIMS <B>1.</B> Process according to claim<B>1,</B> characterized in that said sheet of paper is dried immediately before applying it to said wet layer. 2. Method according to claim I, characterized in that a layer of a binder is applied<B>to</B> said sheet of paper, and in that this binder is vulcanized to reinforce the bond obtained. between the paper and the board by the action of the natural binding constituents of the wet layer. <B>3.</B> Method according to claim 1 and sub-claim 2, characterized in that one of the surfaces of the said sheet of paper is coated with a binder, and in that one brings the surface of the paper thus coated in contact with said wetted layer. 4. Method according to claim I and sub-claim 2, characterized in that said wet layer and said sheet of paper are solidified by application of heat and pressure, in that binder is then applied to the covered side of paper from the solidified board, and in that said board is treated in order to vulcanize said binder. <B>5.</B> A method according to claim 1 and sub-claim 2<B>,</B> characterized in that approximately<B>0.0073 kg</B> of solid binder is used per m2 of board. <B>6.</B> A method according to claim 1 and sub-claim 2, characterized in that said binder is a drying oil. <B>7.</B> Process according to claim<B>1</B> and sub-claims 2 and <B>6,</B> characterized in that said binder is linseed oil . <B>8.</B> Process according to claim I, characterized in that the water content of the said pulp is lowered by applying pressure, so as<B>to</B> give a smooth surface and plane <B>to</B> said pulp. <B>9.</B> Board according to claim II, characterized in that it comprises a layer of an additional binder to reinforce the bond between the paper and the adjacent surface of the said fibrous mass. <B>10.</B> Board according to claim<B>II</B> and sub-claim <B>9,</B> characterized in that said additional binder is a drying oil used<B> >at</B> approximately<B>0.0073 kg</B> of solid material per m2 of board. <B>11.</B> Board according to claim <B>11</B> and sub-claim <B>9,</B> characterized in that a part of said additional binder is constituted by a layer <B></B> water-resistant protective film adjacent<B>to</B> the outer surface of said paper, and in that said outer surface is substantially free of water spots.