US3779843A Expired / Lapsed US ⏱️ 0.0 years remaining

Continuous process for producing consolidated lignocellulosic material

Assignee: Individual

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Filing: 1971-01-21

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Granted: 1973-12-18

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Expires: 1991-01-21

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Abstract

Abstract Hardboard and particleboard is continuously made by a continuous multi-stage press which allows humidified consolidated fibrous material to exit from the press without blisters or delamination and without the need of a subsequent humidification process. A control system is provided to insure that the end product has uniform properties. A preformed mat of moist fibrous material to which wax or other water repellent sealer and a thermosetting resin have been added is fed into a precompresser of conventional design wherein the mat is consolidated to an intermediate density without cure of the resin therein. From the precompresser the precompressed mat is fed into the nip of a continuous multi-stage press having multiple heat and pressure zones therein. Initially the mat is pressed momentarily to a pressure of up to 1,000 pli and then passed through subsequent sections of the press wherein the temperature and pressure are modified while the board is progressing through the press to (1) cure the resin in the consolidated material, and then (2) cool the consolidated mat while under pressure to prevent formation of gas pockets or blisters in the board. The cooling stage of the press is so designed to permit pressure release with sufficient moisture control in the board equal to the equilibrium moisture content control usually attained in a subsequent conventional humidification process. By this means it is possible to form a fiber mat with higher moisture content than feasible in a conventional curing cycle thereby obtaining better board properties because of the increased plastic flow under pressure. After formation of the mat, after precompression, and at the exit end of the press sensing means are provided to continuously measure properties of the board, particularly mass density, moisture content and thickness. The output values are compared with predetermined values and the amount of fiber, wax, resin, moisture, and the press conditions varied to obtain predetermined properties in the board.

Inventors

👤 H Knapp

Bibliographic Details

Application Number —

Jurisdiction US

Data Source google_patents

Last Synchronized 2026-10-25 16:27

CPC Classifications

B; B27; B27N; B27N3/00

Claims Analysis

Total Claims: 4

Claim 1

Independent Claim 278 words

A process of making continuous sheets of consolidated lignocellulosic material comprising, forming a continuous mat of indefinite length of moist wood fiber coated with a thermosetting resin and a water repellant sealer, continuously measuring the mass density and moisture content of the formed mat, comparing the measured values of mass density and moisture content to predetermined values, controlling the amount of fiber used to form the mat and the amount of resin, sealer and moisture added to the wood fiber relative to the predetermined values, feeding the mat into the nip of a continuous multi-stage press between opposed endless caul belts, the press having multiple temperature and pressure zones therein and a predetermined press cycle relating pressure, pressing temperature and press speed, applying heat and pressure to the mat in the press sufficient to consolidate the mat to a predetermined density and to establish a temperature and vapor pressure gradient between the interior of the mat and the outer surfaces thereof in a first heating and pressure zone, continuing the application of heat and pressure on the mat in the press to complete cure of the resin throughout in one or more subsequent heating and pressure zones, cooling the outer surfaces of the mat under pressure in a cooling zone to reverse the temperature and vapor pressure gradients, the consolidated mat remaining under pressure with cooling to allow flow-back of moisture within the mat to dried out areas near the outer surfaces thereof and reduction of the vapor pressure within the mat to less than the internal bond strength thereof so that, on pressure release, the mat retains sufficient moisture content to eliminate the need for subsequent humidification.

Claim 2

Dependent Claim 50 words

The process of claim 2 including monitoring the consolidated mat on exit from the continuous multi-stage press to detect blows and delaminations therein, and controlling the pressing cycle of the press, the relative amounts of resin, sealer and moisture added to the wood fiber to eliminate such blows and delaminations.

Claim 3

Dependent Claim 60 words

The process of claim 2 including continuously measuring the modulus of rupture and thickness of the board on exit from the continuous multi-stage press, comparing the measured values to predetermined values, and controlling the pressing cycle of the continuous multi-stage press and the relative amounts of resin, sealer and moisture added to the wood fiber relative to the predetermined value.

Claim 4

Dependent Claim 232 words

A process of making continuous sheets of hardboard comprising, forming a continuous mat of indefinite length of moist wood fiber coated with a thermosetting resin and a water repellant sealer, compressing the mat to impart sufficient strength thereto for cauless transfer thereof, feeding the compressed mat into the nip of a continuous multi-stage press between opposed endless caul belts, the press having multiple temperature and pressure zones therein and a predetermined pressing cycle relating pressure, pressing temperatures and press speed, applying heat and pressure to the mat, sufficient pressure being applied to compress the mat to a predetermined density and sufficient temperature applied to establish a temperature and a vapor gradient between the interior of the mat and the outer surfaces thereof in a first heating and pressure zone, continuing the application of heat and pressure in one or more subsequent heating and pressure zones to complete cure of the resin throughout the mat, cooling the outer surfaces of the mat under pressure in an integral cooling zone of the continuous multi-stage press to reverse the heat and vapor pressure gradient therein, and maintaining the mat under pressure in the multi-stage press with cooling of the mat until the vapor pressure within the mat is reduced to lEss than the internal bond strength thereof so that, on pressure release, the mat retains sufficient moisture content to eliminate the need for subsequent humidification.

References Cited (Backward Citations)

US2830924A Cited

US2907071A Cited

US3021244A Cited

US3098781A Cited

US3521552A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-12-17	1977-06-18	1977-12-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-12-17	1981-06-18	1981-12-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-12-17	1985-06-18	1985-12-18	$7700.00	Window Closed / Lapsed

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