FI67108C - FILTER PRESSES AND CUTTING MEDELTAET LIGNOCELLULOSAFIBERSKIVA MED MEDELDENSITET OCH HOEG STYRKA SAMT ANORDNING FOER DESS FRMSTAELLNING - Google Patents

Description

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Patent and Registration Board

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Sao Paulo, Sao Paulo, Brazil (BR) (72) James R. Roberts, Palatine, Illinois, USA (7 * i) Leitzinger Oy (5 * i) Stretched, pressed and dried medium density high strength 1ignocellulose fiber board and The present invention relates to a padded, compressed and dried medium-density high-density lignocellulosic fibreboard having a density of at least 0.2 g / l of high density lignocellulosic fibrous material having a method of making the same.

Construction requires composite boards, especially wood fiber boards, which have an average density and higher strength and have other necessary and desirable properties of the fiberboard in terms of dimensional stability, thickness change, water absorption, uniformity, and the like. If such a fibreboard product were to be commercially available, it would replace substantially higher density fibreboards as a building material. This would result in significant raw material savings and further important benefits in construction material and transportation costs.

Accordingly, it is a general object of the present invention to provide a composite board having a medium density, a remarkably strong strength of 6771 08, and further having acceptable properties such as dimensional constant, thickness stability, water resistance and uniformity.

It is a further object of the present invention to provide a low cost composite board that can be produced with high efficiency over the original starting materials.

It is a further object of the present invention to provide a composite sheet which does not require a considerable amount of expensive rare binder with its original fibrous lignocellulosic component.

It is a further object of the present invention to provide a composite sheet product having an inexpensive binder which in addition acts as a dispersant for the lignocellulosic fibrous component of the sheet, as a particle retention agent and also as a density control agent for the sheet.

It is a further object of the present invention to provide a rapid and economical manufacturing process for sheets having the above-mentioned properties of medium density and high strength.

It has now been found that the above and other objects of the present invention are achieved by providing a medium density compound sheet generally consisting of a dry base, 60 to 95% by weight of lignocellulosic fiber and 5 to 40% by weight of a particular cellulose gel binder. As described in detail below, the cellulose gel binder used is fully hydrogenated so that its gel conditions are characterized by a TAPPI leakage time of at least 350 seconds, more preferably 900 seconds, and most preferably 900-2000 seconds.

The sheet product according to the invention has an average density of 0.27 to 0.69 3 g / cm 3. However, its strength properties are similar to those of higher quality fibreboards of the prior art. For example, the average fiber density of the invention of 0.41 g / cm corresponds to the current product standards of the American Hardboard Association1 for exterior and interior design.

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wood fiber board cores of a density of 0,58 g / cm used for the work. The standards for fracture moment, torsional stiffness, change in thickness and water absorption are further met. The savings in raw material use, transportation costs, and production costs resulting from the use of the medium-density product described herein for construction purposes are immediately noticeable.

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The observed improvement in strength has been achieved, without, however, sacrificing any of the other important properties imposed on fibreboard products.

This desired result is achieved as a direct result of the fully hydrogenated cellulose gel binder introduced in connection with the fibreboard products described herein, which is the largest involved in the manufacture of the board. In molding the sheet product, the gel component not only acts as an effective binder for the rapid extrusion operation to bind the lignocellulose particles into a unitary sheet, but also acts as a fiber dispersant to provide a unitary sheet without accumulated fiber particles. It also shrinks during drying of the board with the result that it compacts and unifies other components of the board. Being water resistant per se, it increases the water resistance properties of the finished sheet product.

The high-strength, high-strength ligno-cellulose sheets according to the invention are generally and recommended in the following and the percentages are expressed as a percentage by weight of the dry weight base:

General mixture __ (%) Recommended mixture (%)

Lignocellulosic particles 60 to 95 70 to 90

Hydrogenated Cellulose Gel Binder 5-40 10-30 The main structural component of the medium density composite sheets disclosed herein, lignocellulose, can be obtained from a wide variety of sources. Representative sources include bagasse and trees such as eucalyptus, American poplar, willow, alder, douglas spruce, and pine.

When wood materials are used, they must be used as wood chips, planed chips, flakes or sawdust. Regardless of its source, the size of the material is first preferably reduced by breaking it down into lignocellulosic fibers or fiber bundles. This is done with a suitable device, such as Bauer or Sprout-Waldon mechanical decomposers, in which the pieces of wood are subjected to a decomposing action in steam 2 at a pressure of 2.9 to 10.8 kg / cm. If desired or necessary, the fibrous product of the Asplund machine can be subjected to yet another crusher, such as an Asplund cleaner, to achieve extreme reduction in particle size with a maximum size greater than 10% over screen hole size 12, U.S. Pat. Sieve Series.

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Another primary ingredient in the medium density lignocellulosic composite sheets described herein is a fully hydrogenated cellulose gel binder used in an amount of 5 to 40 weight percent, more preferably 10 to 30 weight percent of the dry sheet base.

This material differs from previously known hydrogenated cellulose gels in that it is fully hydrogenated to a state where it has substantially no fibrous structure. The difference becomes clear when the gels are subjected to the traditional Schopper-Riegler determination of the degree of grinding or the TAPPI standard T221-OS-63.

According to TAPPI standard T221-OS-63, which standard is used. To measure the degree of powder coating of the various slow wood pulps discussed here, the pulp sample is formed into a 158 mm diameter sheet in a William board mold. The molded plate contains 1.2 g of dry mass or gel. The drying time required to form the board is measured and expressed by the degree of hydrogenation of the raw material.

Using this test, it is possible to distinguish the highly hydrogenated cellulose gel binders described herein from prior art cellulose gel products, such as those used in the manufacture of glassine paper and those used in the manufacture of prior art composite sheet products disclosed in Roberts U.S. Pat. 3,379,608-9 together. Both of these use hydrogenated cellulose gels with a run time of about 300 seconds as measured by the above-mentioned TAPPI standard T221-OS-63.

However, it has been found that it is possible to hydrogenate a cellulose gel to a much higher degree than is characteristic of gels used either in glassine paper or in composite sheets according to the above-mentioned patents. Thus, where said prior art gels have a TAPPI standard grinding degree with a draining time of 300 seconds, the gels of the invention have a draining time of at least 350 seconds, more preferably more than 900 seconds and most preferably 900-2000 seconds.

Other test methods can be used to identify and characterize the highly hydrogenated cellulose gel binder disclosed herein.

One is to determine the shrinkage in the plate obtained by the TAPPI test described above. The suitably hydrogenated gel forms a sheet, which shrinks during drying to a diameter at least 35% smaller than its original diameter.

In the third method, the plate is dried and the underside is heated with a slight flame. If the cellulose is sufficiently hydrogenated, the flame will instantly form a blister to the plate.

In the fourth test method, 250 ml of this pulp is dried into a uniform sphere. If the gel is sufficiently hydrogenated for the present purpose, the ball sinks when dropped into water and then remains hard without swelling for an indefinite immersion time.

The use of thoroughly hydrogenated cellulose gel binders of this nature in the medium density composite sheets of the invention is critical for a variety of reasons.

First, the gel acts as a very effective binder that binds the lignocellulosic fibers together in a unitary product. During drying, the gel binder materially shrinks, pulling the particles together and permanently locking them in their uniform state. This factor is paramount in determining the increased strength of a sheet product.

The gel also acts as a binder that quickly determines the thickness and density of the padded sheet as it is transported to the press. This allows for a fast pressing operation, i.e. requires a pressing time of only 10 seconds to 3 minutes, most preferably 10 to 60 seconds. This is quite economical, requiring only a relatively inexpensive single-hole press that can be easily connected to traditional production lines.

A few other important advantages arise from the use of the new cellulose gel binder described above. The binder increases the water resistance of the board for which it is used. As mentioned, such products contain from 5 to 40% by weight of binder and the binder is hydrogenated to such an extent that it is substantially insoluble in water. In this way, a high water resistance is obtained in the sheet product with the binder. The gel binder is superior in this respect compared to traditional fiberboard binders such as thermosetting urea-formaldehyde resins.

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Furthermore, the gel is a very effective dispersion aid in forming the fibrous porridges from which the sheets are made. In this use, it breaks down into individual fibers the wood fiber clumps that may be present in the "porridge." It also reinforces the "porridge" so that when it passes through the wire at a consistency of about 5%, there are few symptoms that the light particles of the "porridge" will float or heavy sink. And yet it is causing a very uniform mixture of porridge, which then turns into a completely homogeneous cross-section in the final sheet product.

Fourth, the gel acts as a sludge retention agent. This is of particular importance in vacuum forming a plate from a pulpwood web to a washer. During this process, the fine particles in the "porridge" tend to leave the plate formed by the excess runoff water. As a preservative, the gel performs a valuable function by retaining these particles in the plate, thus preserving the raw material, improving the properties of the plate and minimizing the waste problem.

Hydrogenated cellulose gels suitable for the desired purpose are products in which hydrogenation water is added to the cellulose molecules by substantially complete mixing or purification of the cellulose in an aqueous medium. Thus, the cellulose is converted from a fluffy, fibrous state to a gelatinous state depending on such variables as the duration of purification, the nature of the cleaning agent, the presence or absence of external chemicals, etc.

The cellulosic pulp required to make the gel can be obtained from any of several sources, such as bleached or unbleached pulp of wood or bagasse made by a conventional method of making sulphate or sulphite paper. If bagasse is used as the extreme raw material, it is recommended to remove the kernel before making it into pulp. Pulps are largely commercially available in the form of dried pulp sheets.

In the manufacture of the gel products described herein, the cellulosic pulp is purified and thoroughly hydrogenated to a high degree, whereby the fibrous structure is almost completely destroyed. This is accomplished by crushing the 7 67108 cellulosic pulp sheets into their original elements, discrete fibers or fiber agglomerates, most preferably by placing the dry sheets and water in a conventional hydropulper and treating them at a pulp content of 1 to 10%, most preferably 6 to 8%. This takes about 30 minutes.

The resulting pulp is then pumped into a storage tank and fed in a controlled flow to a selected plate or cone type primary cleaner. Most preferably, three such purifiers are arranged in series with a flow restrictor valve after the last purifier to ensure a uniform residence time in the purifier. This cleanses the pulp and hydrates it to a high degree.

The resulting partially purified and hydrogenated pulp is transported to a second storage tank which feeds a secondary purifier of the same general type as the primary purifier but which is effective to supplement purification and size reduction in the pulp to values of at least 350 seconds, preferably more than 350 seconds. . This is accomplished by a frictional action that destroys the fibrous structure of the pulp almost completely and hydrates it thoroughly. This additional and thorough purification greatly improves the properties of the pulp as a binder, disintegration factor, and cohesive when used in the manufacture of the medium-density high-strength composite sheets described herein.

In particular, it makes the gel an unopenable binder. This means that composite sheets made with the well-purified gel binder described herein can be exposed to boiling water for a few hours, with little softening or loosening observed in the binder between the bonded fibers. If the plate is dried after such a cooking experiment, it will be exactly as strong as before cooking. This same property is manifested in phenolic resins when used as a binder. It is undoubtedly causing the water resistance of the composite board according to the invention.

In addition to the lignocellulosic fiber and hydrogenated cellulose gel binder of the base materials of the composite sheets described herein, the sheets may contain various amounts of additives, such as a calibrating agent, used in an amount necessary to develop the desired properties in the sheet product. In particular, the boards may contain 0.5 to 3% by weight of traditional wax materials such as Petrolatum or Hercules Paracol to improve the water resistance of the boards.

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Other additives that can be used are fire retardants such as borax, boric acid and ammonium phosphate? additional fibers such as sisal or fiberglass are used in amounts of 5 to 15% to increase hardness and compressive strength? pigments? and additional binders such as starch and phenolic resin binders used in the amounts required for the desired properties in each case.

In the production of the high-strength, medium-density sheets according to the invention, three different structural components are combined: ligno-cellulose fiber pulp, hydrogenated cellulose gel and wax emulsion and / or other additives.

Lignocellulosic pulp is prepared as described above. In typical operation, pulp logs - peeled or unpeeled are reduced to chips in a conventional chipper. The chips are fed to an Asplund diffuser, followed by a conventional Asplund-type cleaner that reduces the chips to a pulp having a particle size of up to 10% greater than 12, U.S. Pat. According to the Sieve Series. The consistency of the pulp is about 40% after the diffuser and about 30% after the purifier.

hydrogenated :; the preferred provision of the cellulose gel component is accomplished by feeding the sulfate cellulose pulp to a conventional hydro-pulper where it is broken down into a fibrous porridge having a consistency of 1 to 10%, most preferably 6 to 8%.

The resulting porridge is fed to a series of three or four conventional purifiers, such as JOnes or shaped Jordan purifiers with straight steel blades or, preferably, lava coatings. The charge goes from one of these cleaners to another and finally to a plate-type cleaner such as the Jones dual-circuit disc cleaner. The flow through the purifier row is controlled by a special valve system that provides sufficient filling or holding time effective to form a hydrogenated cellulose gel product having a flow time of at least 350 seconds in the TAPPI casting test T221-OS-63 described above, more preferably at least 900 seconds. and most preferably 900 to 2000 seconds.

The additional emulsion is prepared by emulsifying in water a traditional industrial wax such as Hercules Paracol or Petrolatum and mixing in predetermined amounts any other selected additive.

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The three basic substances mentioned above, i.e. the lignocellulosic fibrous pulp, the cellulosic gel pulp and the additional emulsion, are fed together as measured streams to a mixing tank, where they are thoroughly mixed together in the desired proportions.

The charge of the mixing tank is then transferred to the front of a shaping machine, which is preferably of the Fourdrinier type and has a strong suction to remove water from the charge. In the forming machine, the charge is conveyed to a wet sheet having a compressed thickness of about 3.81 cm, compressed in a rotary press cycle and cut to length. The resulting sheet is then rapidly pressed to a thickness of 0.63 to 2.54 cm on the pressing surfaces of a heated planar press, depending on the desired final sheet thickness.

A particular feature of the invention is that the use of the novel cellulose gel binder described herein enables a pressing operation with a relatively inexpensive single orifice press. This is because the gel adjusts the density and thickness of the sheet in the press in a very short pressing time from 10 seconds to 3 minutes, more preferably between 10 and 60 seconds at a pressure between 3.62 and 10.8 kg / cm 2 and at a surface temperature between 66 and 149 ° C.

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Exemplary compression conditions are 7.25 kg / cm at 116 ° C for 30 seconds.

Other advantages arise from the use of a rapid compression process.

Rapid pressing dries the water to a moisture content of about 35% by weight, while the conventional level is 55% so that less drying time is required. This is achieved without altering the properties of the gel binder.

Rapid pressing also preheats the plate so that even less time is required for the actual drying. Further, it forms a fine surface on the board, which surface remains when the board is dried.

Furthermore, rapid compression allows the density of the finished sheet to be controlled in the range of 0.27 to 0.69 g / cm 3. By using a gel binder, the plate can be removed without breaking it as it returns from the press. This result is clearly characteristic of the effective adhesive properties of the gel binder.

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This is followed by drying oven drying, which takes place in three zones with successive zone temperatures of 260 to 315 ° C, 205 to 260 ° C and 149 to 204 ° C, with the highest temperatures being on the main side of the drying oven. Drying is continued to a final degree of dryness of the sheet of less than 2%, most preferably 1/2% by weight. Drying removes not only free water from the plate, but also most of the cellulose gel hydrogenation water-

The resulting sheets are cooled, matched, finalized to a specified product, if necessary, and packaged ready for shipment.

Example The newly described medium-density, high-strength composite sheets and their manufacturing method are described in the following example: 2

Eucalyptus wood chips were decomposed in an Asplund diffuser at a pressure of 10.8 kg / cm, followed by purification in an Asplund-type cleaner up to a fiber size of up to 10% over 12 as measured in U.S. Pat. According to the Sieve Series. The fibers were mixed with a sufficient amount of water to form an amount of fibers with a consistency of 4%.

The fully hydrogenated cellulose gel was obtained by hydropulping unbleached sulfate cellulose pulp to a consistency of 8%. The resulting pulp was transferred through a series of three Jones Fibermaster No. II conical cleaners, followed by a Jones Duo Flow friction type disc cleaner. During operation, they were controlled by their drain valve valves to achieve operating times in which the purifiers were able to uniformly produce three types of gel, one with a run time of 350 seconds, another 1200 seconds, and a third 1800 seconds, all measured by TAPPI test according to T221-OS-63.

The above ingredients were mixed in a mixing tank with 1% Hercules Paracol wax.

The three structural components were mixed evenly, transported to the front end of a Fourdrinier-type forming machine, and run into a plate. The plate was compressed to thickness, dried and tested for its refractive index.

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Three sets of plates were then prepared and tested using gels with run times of 350, 1200, and 1800 seconds, respectively. In each set of tests, three plates were prepared with a gel content of 10, 15 and 20% by weight of the dry plate base, respectively.

When the first two groups of plates were pressed, the pressing pressure was 10.8 kg / cm 2 and the pressing temperature was 116 ° C, and the pressing time was 40 seconds. The third group of plates had a compression pressure of 7.25 kg / cm, a compression temperature of 116 ° C and a compression time of 25 seconds.

The results are in the table below:

Eg Plate Plate Gel Gel Mass Fracture No. thickness density drainage use flow factor _ (mm) (g / cirr) time (s) (%) time (s) (kg / cm2) 1 13.13 0 .33,355 10 10 63.05 2 12.92 0.37 355 15 14 78.64 3 12.59 0.40 355 20 30 106.54 4 13.33 0.43 1200 10 20 83.35 5 13, 41 0.41 1200 15 55 137.71 6 12.70 0.45 1200 20 123 181.20 7 12.82 0.41 1800 10 63 117.41 8 12.95 0.41 1800 15 97 184.82 9 12.57 0.41 1800 20 220 221.78

It will be appreciated from the foregoing that the incorporation of a fully hydrogenated cellulose gel binder in certain proportions will provide a major and most significant beneficial effect in the compositions of the invention. Thus, as seen in Example 9, the inclusion of a 20% gel with a run-off time of 1800 seconds provides a plate with a density of only 0.41 g / cra but a refractive index above 221 kg / cm. This particularly high refractive index is not normally characteristic of 3 plates with a density of the order of 0.41 g / cm, but of plates with a much higher density of 3, such as plates with a density of 0.62 g / cm.

The resulting savings in raw material costs, transportation costs, and plate production costs are significant. These have been achieved while maintaining other properties such as lightness, dimensional constant, uniformity, water resistance and workability, which must necessarily be characteristic of 12 67108 structural composite panels to enable them to be suitable for their various uses.

Claims (13)

13 671 0 8 1. quilted, pressed and dried medium-density high-strength O lignocellulosic fibreboard with a density of at least 0.27 g / cm, characterized in that its dry base contains 60 to 95% by weight of ligno-cellulosic fibers, based on hydrogenated cellulose pulp-based cellulose 5-40% by weight and that the hydrogenated cellulose gel binder is characterized by a TAPPI drainage time of at least 350 seconds. Composite board according to Claim 1, characterized in that the lignocellulosic fibers are fibrous wood. Composite board according to Claim 1, characterized in that the lignocellulosic fibers are fiberized bagasse. Composite board according to Claim 1, 2 or 3, characterized in that the particle size of the lignocellulosic fibers, defined as the degree of grinding of the TAPPI-CSF fibers, is less than 750. Composite board according to one of the preceding claims, characterized in that it contains 70 to 90% by weight of lignocellulosic fibers and 10 to 30% by weight of hydrogenated cellulose gel binder. Composite sheet according to one of the preceding claims, characterized in that the hydrogenated cellulose gel binder is characterized by a TAPPI drainage time of at least 900 seconds, preferably 900 to 2000 seconds. Composite sheet according to one of the preceding claims, characterized in that the sheet has a density of 0.27 to 0.69 g / cm 3 and a refractive index of at least 144.96 kg / cm 3. A method of making a composite board according to claim 1, characterized in that a) the cellulose pulp is ground and comminuted in an aqueous 14 671 08 material into a hydrogenated cellulose gel binder with a TAPPI bleeding time of at least 350 seconds, b) an aqueous pulp with lignocellulose particles 60 to 95 is formed. by weight, 5-40% by weight of hydrogenated gel binder and water in an amount predetermined to give the pulp a sheet-forming density; . Process according to Claim 8, characterized in that the lignocellulose particles consist of wood fibers with a TAPPI-CSF degree of grinding of less than 750. Method according to Claim 8, characterized in that the atus-bleeding time of the gel is at least 900 seconds. Method according to Claim 8, characterized in that the ΤΑΡΡΙ-bleeding time of the gel is at least 900 to 2000 seconds. Process according to Claim 8, characterized in that the pulp is dried while being compressed to a density of 0.27 to 0.69 g / cm 3. Process according to Claim 8, characterized in that the pulp is dried by rapid compression at a pressure of 3.62 to 10.88 kg / cn \ 2 and a temperature of 65 to 149 ° C for 10 seconds to 3 minutes, followed by oven drying to obtain the plate is dried to a predetermined humidity. 15 67108