Abstract: To provide a polymer which can provide a water- and oil-proof paper with excellent water and oil resistance. A polymer comprising the following units a, and at least the following units b among the following units b and the following units c, wherein the ratio of units a to all the units in the polymer is from 28 to 70 mol %, the total ratio of units b and units c to all the units in the polymer is from 30 to 72 mol %, and the ratio of units b to the sum of units b and units c is at least 45 mol %: units a: units represented by —(CH2—CHRf)— (wherein Rf is a C1-8 perfluoroalkyl group), units b: units represented by —(CH2—CH(OH))—, units c: units represented by —(CH2—CH(OC(?O)R))— (wherein R is a C1-4 alkyl group).

Abstract: The present invention relates to a method of manufacturing a cellulose product having a flat or non-flat product shape by a pressure moulding apparatus comprising a forming mould. The forming mould has a forming surface defining said product shape, The method comprises the steps of: arranging a cellulose blank containing less than 45 weight percent water in said forming mould; heating said cellulose blank to a forming temperature in the range of 100° C. to 200° C.; and pressing said cellulose blank by means of said forming mould with a forming pressure acting on the cellulose blank across said forming surface, said forming pressure being in the range of 1 MPa to 100 MPa.

Abstract: An object of the present invention is to provide an inorganic board lighter in weight and excellent in strength and rigidity, and a method of producing the inorganic board. An inorganic board described in claim 1 for accomplishing the object comprises a hydraulic inorganic material, an inorganic lightweight material, a woody reinforcing material and a calcium silicate hydrate, wherein a ratio of the calcium silicate hydrate to the hydraulic inorganic material is 3-54 parts by mass: 100 parts by mass. Thus, by making an inorganic board, made of a hydraulic inorganic material, an inorganic lightweight material and a woody reinforcing material as main components, further contain a calcium silicate hydrate, an inorganic board which is lightweight and excellent in strength and rigidity can be obtained.

Abstract: Emulsions are provided which are useful in imparting water-resistance to gypsum wood fiber products. In one embodiment, the emulsions comprise a wax or a combination of waxes, an alkyl phenol, at least one surfactant, Polynaphthalenesulfonic acid, and an alkali metal hydroxide. In another embodiment, the emulsions comprise a wax or a combination of waxes, an alkyl phenol, at least one surfactant, polynaphthalenesulfonic acid, an alkali metal hydroxide, and a complexed starch.

Abstract: An improved method for making compressed structural fiberboard by extruding agricultural fibrous matter into a compressed structural fiberboard. The improved method includes providing a preselected volume of agricultural fibrous matter and preconditioning the agricultural fibrous matter to have a predetermined moisture level. The agricultural fibrous matter is separated and cleaned, and steam is added until a predetermined level of moisture is reached within the agricultural fibrous matter. Borax is also added to the agricultural fibrous matter to prevent the formation of bacteria. The agricultural fibrous matter is conveyed throughout the process on conveyors having variable drives, wherein the level of the agricultural fibrous matter on the conveyors is sensed such that a signal is provided to adjust the speed of the conveyors in order to provide a predetermined level of agricultural fibrous matter. The agricultural fibrous matter is then extruded to form a compressed structural fiberboard.

Abstract: The papermaking sheet member includes inorganic fibers, and the inorganic fibers include a lump-shaped cohered fiber which coheres as a lump.

Abstract: A method of forming a molding mat formed bundles of reinforcing fibers and bonding materials is provided. The reinforcing fibers are preferably wet use chopped strand glass fibers (WUCS). The bonding materials may be any thermosetting material having a melting point less than the reinforcing fiber. The molding mat may be formed by partially opening the wet use chopped strand glass fibers and filamentizing the bonding materials, blending the reinforcement and bonding fibers, forming the reinforcement and bonding fibers into a sheet, and bonding the sheet. During bonding, the sheet is heated to a temperature above the melting point of the bonding fibers but below the temperature of the glass fibers. The molding mat thus formed may be used as a reinforcement material in sheet molding compounds.

Abstract: A manufacturing process for a fire component by having a mixture containing expansion graphite powder, chemical fiber and paper fiber at a specific ratio to be bound by a process normally used for the non-woven fabric, and finally hot pressed into sheet, or the mixture is treated as a pulp to be dried for serving as a fire component; accordingly, the process of the present invention gives accurate control of the mixing ratio of the expansion graphite powder and allows to increase the containment of the expansion graphite powder in the fire component up to eighty-five percent (85%), thus to significant upgrade the performance of the fire component.

Abstract: A pulp molded article having a pulp fiber layer (2) of single layer structure which is formed by papermaking from a single raw material composition and has a density distribution in the thickness direction thereof. The pulp fiber layer (2) has such a density distribution that the density increases or decreases in the thickness direction thereof.

Abstract: The present invention is to provide a base material for a laminate having a high strength, reduced thickness, and light weight. In the present invention, a base material is prepared by incorporating a thermosetting resin binder into a non-woven fabric of para-aramid fibers prepared by a wet type paper making, and then heating a plurality of the resultant non-woven fabric sheets under pressure. The non-woven fabric sheet comprises 95 to 70 mass % of the para-aramid fibers and 5 to 30 mass % of the thermosetting resin binder.

Abstract: The present invention relates to the manufacture of a multi-layered board having a stable, and moisture-resistant surface. To accomplish this and other advantages of the invention, an improved binder system is used in the production of the surface layers of a multi-layered board which combines an. excellent resin penetration inside the wood constituents of the board's surface layers, with a strength, durability and resistance to ambient water and moisture. The improved binder system used in the production of the board surface layers according to this invention involves contacting wood pieces with a binder composition comprised of a curable powdery aldehyde resin and a curable isocyanate resin in the substantial absence of free water to provide a composite mixture that can be formed into a surface layer for assembly and lamination together with other wood and resin composite layers.

Abstract: In the manufacturing method of fluoro based polymer composite boards of the invention, which provides a fast process and high efficiency, a suitable amount of water soluble organic solvent is added to a fluoro based polymer suspension during the process of mixing ceramic powder and/or glass fiber to the fluoro based polymer suspension in order to improve the coagulation of the fluoro based polymer and ceramic powder, and to reduce the gelling time. During the process of mixing ceramic powder and/or glass fiber, the fluoro based polymer suspension and the organic solvent, a suitable amount of water can be added to control the ratio between the water and the organic solvent obtained from the mixture. The gelling time of the mixture can thus be reduced. By controlling the ratio between the water and the organic solvent obtained from the mixture, there is still enough time to allow homogeneous mixing after the gelling speed is increased.

Abstract: A method for improving the bondability of annual plant materials to a formaldehyde-based resin including the steps of: (a) providing a straw plant material having a plurality of fibers with each of the fibers surrounded by a waxy and silica layer; (b) extruding the straw plant material in a twin screw extruder while simultaneously subjecting the straw plant material to a thermal treatment with an aqueous solution containing a lignin modifying agent or steam, the thermal treatment being conducted at a temperature between about 40° C. and 120° C., the extruding subjecting the straw plant material to a sufficiently high shear force such that the extruding with simultaneous thermal treatment achieves a substantial defibration of the straw plant material with destruction of the waxy and silica layer and formation of individual fibers and (c) subjecting the treated material to heat and pressure in the presence of the formaldehyde-based resin to form a resin-bonded fiberboard or particleboard.

Abstract: A molded body is produced on the basis of a raw material, the main content of which is material which is left after remolding pulp from paper and extraction of fibers from the pulp mass for remanufacturing of paper. This raw material which mainly consists of water, short fibers, and fine, mineral particles is drained by pressing in a first pressing stage between filter belts for production of a coherent body, is dried partially in a first drying stage is pressed and in a second pressing stage, and dried finally in a second drying stage. The invention concerns a similar method for separation of fibers and particles from waste water which results from repulping paper and reclaiming of fibers from the pulp mass for remanufacturing of paper, whereby an enviromental problem is solved in a very suitable way.

Abstract: A board composed of a lignocellulosic material and the modification thereof as the substantial components and having good mechanical strength, even when the board does not contain any components derived from an additive, by utilizing the autoadhesion of a specified lignocellulosic substance. This board is produced by molding under heat and pressure a lignocellulosic substance containing at least 30 weight % of a malvaceae bast plant, being substantially free from any component derived from an adhesive, and has a strength value of more than 100 as defined by the following formula (I): 0.48.times.Y/X.sup.2, wherein Y is a bending strength (kgf/cm.sup.2) and X is a density (g/cm.sup.3). A particulaly preferable example of the plant is the kenaf.

Abstract: An inorganic board consisting of a cured base mat and a cured surface mat is manufactured by forming a surface mat by the dry method on a base mat formed by a paper making method, embossing the composite mat, and curing the embossed composite mat. Ridges each having an enlarged top are formed on the surface of the base mat when a plural number of single mats formed by the paper making method are rolled and laminated around a making roll having a surface on which a plural number of ring grooves are formed. The ridges of the base mat engage the surface mat since each ridge has an enlarged top to improve the interlaminate strength between a cured base mat and a cured surface mat of the resulting inorganic board.

Abstract: The specification discloses an unorthodox system for manufacturing strong, light-weight and weather-resistant cellulosic composite materials from discarded paper and newsprint, and papermill sludge--and from an unlimited variety of particulated fibrous lignocellulosics--without the use of an extrinsic adhesive. Both the matrix-forming resin and the fiber-substrate, which comprise the entire composite, are spontaneously created in situ at ambient conditions by the ammoniation of a mixture of a protein-containing material and a particulated cellulosic. Heating an article shaped from such a mixture to above 175.degree. C. polymerizes the resin and bonds the fiber-substrate into a cellulosic composite product. Also disclosed is a process for manufacturing reinforced and laminated composites as well as a composition which simplifies the production of both cellulosic composites and all-biomass thermosetting resins.

Abstract: Production of plasterboard includes spreading of a mixture formed of gyps fibers and water onto a continuously moving belt to form a spread layer subsequently precompressed to 110% to 180% of a final board thickness and successively wetted from both sides and thereafter compressing the wetted layer to the final board thickness.

Abstract: An oriented strand board product is provided. The board is comprised of a baseboard having three wood strand layers, the wood strands being oriented in space with respect to a board-forming machine such that a core layer is comprised of wood strands oriented generally in a random or cross-machine direction and each adjacent layer is comprised of coarse and fine wood strands oriented generally in the machine direction and wherein the wood strands comprising each adjacent layer are formed with the coarsest strands located nearest the core layer and the finest strands are located nearest the outer surfaces of each outer board layer. The OSB board product is clad with a dry felted wood fiber overlay on one planar surface of the baseboard.

Abstract: In manufacturing fiberboard, it is known to press mixtures of lignocellulosic material and binding agents to form a board product. In this invention, an improved process for manufacturing fiberboard is disclosed including the step of adding a solution of maleic anhydride and glycerol to the lignocellulosic material prior to refining thereof. The binder used is preferably phenolic-formaldehyde resin, in which case post-heating may be beneficial.

Abstract: An oriented strand board (OSB)-fiberboard composite structure is comprised of a baseboard having three wood strand layers, the wood strands being oriented in space with respect to a board forming machine such that a core layer is comprised of wood strands oriented generally in a random or cross-machine direction and each adjacent layer is comprised of coarse and fine wood strands oriented generally in the machine direction. In a preferred embodiment, the wood strands comprising each adjacent OSB layer are formed with the coarsest strands located nearest the core layer and the finest strands are located nearest the outer surfaces of each outer board layer. The OSB-fiberboard composite product is clad with a wood fiber overlay on one major surface of the baseboard. The composite board is manufactured without warping, by providing particular OSB layer thicknesses, such that the lower OSB layer is about 25% to about 35% thicker than the OSB layer bonded to the fiberboard.

Abstract: An oriented strand board product is provided. The board is comprised of a baseboard having three wood strand layers, the wood strands being oriented in space with respect to a board forming machine such that a core layer is comprised of wood strands oriented generally in a random or cross-machine direction and each adjacent layer is comprised of coarse and fine wood strands oriented generally in the machine direction and wherein the wood strands comprising each adjacent layer are formed with the coarsest strands located nearest the core layer and the finest strands are located nearest the outer surfaces of each outer board layer. The OSB board product is clad with a dry felted wood fiber overlay on one planar surface of the baseboard.

Abstract: Calcium hydrosilicate bound fiberboard, in particular double-deck board, is manufactured in a process wherein a fiber-binder-filler mixture having a water content of 40 to 45% by weight and a solids content of 55 to 60% by weight is prepared by digesting cellulose fibers in an amount of from 2 to 12% by weight of the solids content with water and mixing them with fillers and with a binder comprising cement and/or lime hydrate and substances containing reactive calcium silicates to form a thick pasty mixture, whereupon the thick pasty mixture is introduced in a predetermined amount into the frame of a bottom mold of a single-shot press which further includes a top mold. The mixture is essentially leveled out, formed by closing top and bottom mold, and, via dewatering fabrics and channels in the top and bottom molds, dewatered. Finally, the mixture is compacted and vented, whereupon the raw board is demolded and autoclaved.

Abstract: A sheet calendering method and apparatus including a calendering cylinder, a delivering cylinder, and a conveyor for transporting sheets between the calendering cylinder and the delivering cylinder; wherein the conveyor includes two flexible elongated members forming parallel endless loops around the calendering and delivering cylinders, a plurality of support members attached between the parallel loops, and a plurality of calendering plates each linked to an adjacent plate by the support members to form an endless belt.

Abstract: Preformed cellulosic linerboard as utilized in the manufacture of corrugated products is provided with enhanced crush strength by a combined lignin-coating and calendering treatment. The linerboard is coated with an aqueous lignin-containing solution and then, with the coating in a wet or dry state, subjected to at least one pass through a calender nip to substantially increase the CD crush strength of the treated linerboard over the CD crush strength of an untreated linerboard or a lignin treated but uncalendered linerboard. The linerboard may be laminated with a substantially air and moisture impervious sheet to inhibit bleeding of the lignin coating in high humidity conditions.

Abstract: A process for using shredded scrap or virgin fiber glass in combination with starch, water and other components to make ceiling tiles. The tiles are made by initially preparing a mixture of water, starch, boric acid and fire clay. That initial mixture is then heated to form a gel. Fiber glass is then added to the gel to form a pulp. The pulp is fed into trays to form slabs. The slabs are dried and finished into tiles.

Abstract: An installation for the production of sheet-like members from a mixture of plaster and fibrous material comprises, in addition to a device which prepares the raw materials and mixes them in the dry state in a desired ratio, as well as a device, which adds and mixes in an accurately dosed quantity of water, a spreading device, which spreads a mat of material on a forming line. The mat of spread-out material is compacted in a continuously operating belt press. The latter comprises in known manner two endless steel belts, which are guided around two movable press plates of the belt press, which are spaced apart. The mat of spread-out material is compacted between the forming line, on which it rests, and an endless-belt screen, which bears on the upper steel belt of the belt press and thus acquires a side marked by the endless-belt screen. After being cut up by a cutting device, the individual sheets are turned through 180.degree.

Abstract: Flash expansion of moist multi-layered boards wherein each layer comprises aramid floc bonded by aramid fibrid results in high strength, low density aramid boards.

Abstract: A rigid, self-supporting, acoustical mineral fiberboard comprising a mixture of about 50 to 70 weight percent of mineral fibers, 15 to 35 weight percent of perlite, 1 to 10 weight percent of cellulosic fibers, and 4 to 15 weight percent of a binder with the proviso that the board forming solids do not include any clay filler. A pattern is formed on the fiberboard after the fiberboard has been dried.

Abstract: A method to control the opacity of sheet formed of nonwoven material involves providing a computer with a steam pressure measurement from each of two steam heated palmer bonders. One pressure sensor from the first bonder drum and one from the second bonder drum provide signals used to control steam pressure and thus temperature of each bonder drum's surface. A signal indicating temperature of the surface of each drum and a measurement of speed are also collected by the computer/controller. The fundamental control signal is provided to the computer from an opacity sensor device which is compared to an opacity aim and then steam pressure to the bonder drum is adjusted to minimize any error signal between opacity aim measured opacity.

Abstract: A composition comprising epoxidized polyamide wet strength resin and lecithin. The composition provides wet strength to paper and molded pulp products and at the same time increases the internal bonding of the paper or molded pulp products.

Abstract: A sculptured structural fiberboard product is formed using a mold that includes porous forming areas which, in one embodiment, are porous forming mandrels movably mounted on the mold, and liquid impervious thimbles which removably cover the porous areas. A fiber network is formed as water is drained off through the porous areas and the thimbles are moved to gradually unveil the porous areas during the mat formation. When mandrels are used, the mandrels are withdrawn in cooperation with a pressing force applied to the mat to consolidate and dry the web. The porous areas can also act as heat and mass transfer means during consolidation and drying. An alternative embodiment permits formation of laminated products and another alternative embodiment permits close control over the product density during consolidation and drying.

Abstract: A method of and apparatus for producing gypsum fiber boards includes introducing shaped boards provided of a mash of calcium sulphate dihydrate and fibrous material and possibly additives after dewatering and shaping the mash into at least one pressure vessel and to heat the boards at saturated steam atmosphere to 120.degree.-160.degree. C. over a predetermined period. Thereafter, the boards are allowed to cool down within the pressure vessel to a temperature of about 100.degree. or less before being discharged therefrom.

Abstract: Panels of composite wood material are formed in a wet process which includes depositing a layer of wet composite wood material in a mat on a press wire screen mesh and moving the screen mesh to carry the mat into a pressing position between a pair of spaced apart pressure plates having generally matching, contoured facing surfaces for shaping the outer face and a smoothly contoured back face of the panel. The back face of the panel is not flat and generally follows or matches the shape or contour of the outer face so that regions of high fiber stress and dense, brittle areas of high fiber compression are generally eliminated. The resulting finished panels having excellent machining qualities, more uniform surface coating absorption characteristics, more uniform thickness and less rapid moisture absorption properties, along with a lower tendency to check, crack or split.

Abstract: The present invention relates to a material in sheet form, used in a process of moulding-stamping or heat-forming involving melting of the thermoplastics resin contained in said material, said material in sheet form being prepared by the papermaking technique and comprising from 20 to 95% of reinforcing fibres and from 80 to 5% of thermoplastics resin in powder form forming the basic mixture and, with respect to this mixture, from 5 to 25% of a polyolefin pulp, from 5 to 30% of a binding agent and from 0.2 to 10% of at least one flocculating agent. The invention also relates to the process for preparing said material in sheet form.

Abstract: A method for producing a fibrous board having a decorative, textured surface comprising the steps of:(a) forming a wet mat of entangled mineral fibers;(b) pressure molding said fibrous mat while it is still wet to create a decorative textured surface thereon; and(c) drying said board.

Abstract: An absorbent material comprising hydrocolloidal fibers provided in board form having substantial structural integrity both in the dry state and after being wetted with body fluids. The board comprising hydrocolloidal fibers is subjected to a heat treatment step whereby the board is heated, in a dry state to impart such stability.

Abstract: The production of hardboard by the wet press process is speeded up by the incorporation of finely divided fibers in an aqueous slurry of otherwise fast draining wood fibers and a thermosetting binder so that a barrier of said fine fibers is formed during hot pressing of the mat and steam pressure is built up in the mat. The high pressure permits a curing temperature of from about 300.degree. F. to about 350.degree. F. in the core of the mat and a concomitant acceleration of the cure of the binder.

Abstract: An incombustible material containing at least one mineral substance, and including a first ingredient composed of a plurality of pieces constituted by fibers of cellulose and/or chips of wood shavings, with the pieces forming a network, a mass of thermosetting synthetic resin gluing the pieces of the first ingredient together, and particles of calcium sulfate, boric acid and an at least partially glass or ceramic forming mineral adhering to the fibers and/or chips.

Abstract: A low-cost mineral-fiber board having a natural-appearing highly textured surface, and improved uniformity of density is produced by coating the wet-textured surface of a perlite-containing mineral-fiber mat to a depth at least equal to the peak height of the texture with a layer of silicone-coated perlite prior to press-forming the board. The perlite layer fills the voids on the textured surface and provides a buffer layer between the board and press roll, enabling uniform pressure to be applied to the board without disturbing the textured surface. The top perlite layer may be removed by vacuum units before or after drying the board.

Abstract: A versatile process and apparatus is presented for producing, in high yields, many different grades of pulp from a single wood specie or for pulping any specie or type of woody material, and for storage and recycling of the by-product liquid and gaseous materials. The process of this invention is virtually pollution free, and the reactant chemicals are recoverable from the by-products. In the alternative, the by-products themselves have a commercial value which may forestall recovery of the reactants. The lignin constituent extracted from the pulp is usable as a resin binder, a wood rehardening agent, or a glue.

Abstract: Disclosed is a hardboard with a smooth, highly-consolidated, dense surface and a method for making it. The method of this invention greatly reduces the need for surface sanding after molding because release from the molding caul is improved and results in a product having a surface more free of defects. According to a preferred embodiment, a dry mat of wood particles is sprayed with from 8 to 30 grams per square foot of a surface coating of a consolidating agent comprising from 50 to 95% water, from 4 to 25% ethylene glycol and from 1 to 25% polyvinyl acetate, prior to pressing at elevated temperature. These percentages are based on the weight of the consolidating agent. The preferred products will have at least one highly-consolidated, smooth surface layer which comprises from 0.5 to 4 grams of polyhydric alcohol and from 0.5 to 4 grams of polyvinyl acetate per square foot of surface.

Abstract: A process for improving the strengths and resistance to water absorption of wood fiber hardboard, along with a lessening in the number of conventional steps, is disclosed. Hardboad is thereby produced by a process wherein drying oil is added to the wood chips prior to the pulp preparation stage; and optionally an oxidation accelerator is added during the pulp preparation stage. The hardboard is then formed in the usual manner without requiring the conventional addition of binder ingredients in the stock chest, without requiring conventional baking following pressing and, in the case of "tempered" hardboard without requiring the subsequent addition of tempering materials and baking following the conventional press operation.

Abstract: A method of making fiberboard using a substantially closed white water system. One or more layers of separately prepared surface pulp is applied to a layer of base pulp at the wet sheet forming stage. Lignocellulose chips in a pressure-sealed defibrating zone under generation of steam. The steam is separated at the discharge end of the defibrating zone under atmospheric pressure. The atmospheric steam is utilized to presteam the raw chips. The presteamed chips are thereafter dewatered to a moisture content coordinated to the energy demand of the defibrating treatment and the desired generation of steam prior to entering the defibrating zone. The water removed at the dewatering stage is collected for use in preparing the surface layer pulp suspension. A small portion of the base pulp to be used for the surface layer pulp is diverted to a refiner and diluted with water.

Abstract: A medium density, high strength lignocellulose composition board comprises on a dry weight basis from 60 to 95% lignocellulose particles and from 5 to 40% exhaustively hydrated cellulosic gel binder, the gel binder being characterized in its gel condition by a TAPPI drain time of at least 350 seconds.

Abstract: This relates to the manufacture of wet process hardboard. The invention involves supplying additional heat curable resin to the mid-thickness regions of the panel by injecting additional resin into the moving mat as it is being formed on a forming surface. The region of injection of the resin is selected so that the bottom of the partially formed mat is sufficiently consolidated to resist the passage of resin therethrough while at the same time the top of the mat is still sufficiently liquid so that disturbances of the fibers of the partially dewatered mat caused by the injection of the resin have an opportunity to mend. The resin may be injected into the longitudinal marginal portions of the mat in continuous fashion such that, after the edges of the final board product have been trimmed, the resin treated areas are exposed to view. The additional resin reinforces the edge portions and assists in providing uniform caliper of the board across its width.

Abstract: A mineral board product is formed having a low density backing layer and a high density damage-resistant surface layer on conventional fourdrinier equipment in a continuous wet-laid process by initially forming a low density water-laid sheet by flowing a slurry of the board-forming materials onto the wire of a fourdrinier and, at that point on the wire where the mat has formed but at which the water content is between about 7.0 and 12.0 percent, a surfacing layer is applied by means of a secondary head box to the mat, the slurry forming said surfacing layer having a slurry consistency of between about 10 and 15 percent and a Canadian Standard Freeness of between about 150 and 300.

Abstract: A rigid building component such as a door, table top or the like, is formed of coarse wooden particles mixed with adhesive, and a solid wooden edge frame, positioned between a pair of damp, substantially parallel, cellulosic fiber webs. A heated press is employed to compact the combination, particularly between the edge frame and the cellulosic fiber webs where the coarse wooden particles are greatly compressed to provide a durable edge. Under the heat and pressure applied in the press the particles are consolidated into a solid structure, while the damp cellulosic fiber webs are converted to tough exterior skins bonded to the coarse wooden particles. The sides of the rigid building component are suitably deeply embossed to provide a decorative paneled appearance.

Abstract: A method of producing an inorganic substance board, wherein after preparation, such as by use of paper making process, the board is hardened in an autoclave with saturated steam at a high temperature, high pressure and for a suitable length of time, and after hardening, subjecting the board to one or more drying cycles comprising a vacuum treatment at 60 to 300 Torrs, for a suitable length of time to enable the core of the board to reach a suitable temperature, the application of saturated steam at 2 to 12 Kg/cm.sup.2 pressure and 120 to 190.degree. C temperature for a period of time sufficient to allow the core to reach a suitable temperature. The number of cycles is preferably 10 or less. Advantageously, the inventive drying treatment prevents efflorescence and warping of the boards.

Abstract: A high density insulating board is produced by a process which includes forming a wet multi-ply board of fibrous material, substantially free of resin, on the roll of a wet cylinder machine, drying the board, placing the dry board in a press, and then hot pressing the board at a differential temperature of about 15.degree. to about 40.degree. F across the board for at least 30 seconds.