Plastic and nonmetallic article shaping or treating: processes – With step of cooling to a temperature of zero degrees c. or...
Reexamination Certificate
1998-07-22
2002-04-30
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of cooling to a temperature of zero degrees c. or...
C264S050000, C264S054000, C264S115000, C264S320000, C162S218000
Reexamination Certificate
active
06379594
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a process for producing blanks or molded bodies with similar characteristics as wood from one or more cellulose-containing, fibrous raw material, e.g. pure cellulose, but also crude fibers or the complete plant or other constituents of hemp, flax, reed, cotton, straw, etc., as well as old cardboard and waste paper, through specific processing of said fibers to form a microfiber pulp which is then dried, if necessary after first draining and forming it, as well as the diverse use of said microfiber pulp as bonding or matrix material for taking up filler materials.
The objective is an economical production of the aforementioned materials, bodies and molded parts having good technical properties, if possible based on ecological criteria.
2. Description of the Related Art
In the patents CH 254243, DE 4207233 A1, EP 402866 A2, U.S. Pat. No. 3,935,924 A, as well as GB 2066145 A, it is suggested using beaten cellulose or microcellulose pulp as bonding agent, filter, speaker membrane or as thickening and reinforcing agent for paper products. These patents appear to oppose individual claims of the patent under consideration. The process suggested in the CH 254243, however, requires extremely long, uneconomical processing times and the resulting, gelatinous slime has a consistency that makes the drainage of water very difficult. In addition, higher densities and strength can be obtained with this process only by using pressure (at least 4 kg/cm
2
) and heat (above 100° C.).
Basically, considerably lower strengths are achieved on the basis of this Swiss patent and other already known processes than with our process.
Thus, according to the DE 4207233 A1, waste paper is beaten and stirred and, following the introduction of air, is dried to filtering bodies with low strength. It is significant that the inventor considers it necessary to admix the fiber pulp with calcium oxide powder, as is mentioned several times in this patent, in order to obtain firmness and stability for the filter block through a post-curing. The introduction of air into the fiber pulp thus refers to an obviously hardly processed base material with extremely low bonding properties.
The word “microcellulose” by itself generally does not define either the degree of shortening, squeezing, fibril removal, hydration or the adjusted fractional composition of the fibers, which are critical for the internal cross-linkage, matting and bonding properties.
It is significant that the EP 402866 A2 also does not address the fineness via these bonding properties, but via the filtering characteristics of the material, that is to say whether the material is adjusted finely enough to prevent certain particles (e.g. bacteria and the like) from passing through the filter.
The fact that the use of polymers as raw material is also suggested for these filters, in the cited examples as well as the claims, serves as further proof that the refinement function has another purpose as well as has a very different qualitative and quantitative cause. Thus, the processing clearly does not serve to increase the hydrogen bonding between fibers.
The U.S. Pat. No. 3,935,924 A appears to deal only with carbon-fiber reinforced fine paper with somewhat increased bonding properties for speaker membrane production.
All the aforementioned patents use only pure cellulose, but not cheap crude fibers or other plant constituents. Refiners are used only for shortening of cellulose fibers to make these suitable for further processing, e.g. in a “high pressure homogenizer.” This high-pressure pulping in an expansion nozzle results in totally different fractional compositions and defibration degrees. The same is true for the GB 2066145 A. The pulp produced with this process has considerably lower bonding properties. It is significant that the suggestion is only for using this pulp as reinforcement for paper, but not for the bonding of wood replacement products such as furniture panels or, following the drying, as synthetic material replacement. Adding approximately 40% highly processed micro pulp, produced according to our process, as suggested in table IX of this patent specification, provides the paper with the properties of wood veneer, which is too hard for paper, is brittle and unusable in this function. The conclusion can be drawn from this as well that substantial differences to the present patent exist.
SUMMARY OF THE INVENTION
In contrast to the processes suggested in said patents, the process in the present patent permits an economical realization for the intended applications. This concerns the processing expenditure as well as the options for the raw material selection, the drainage times and the suggested processing paths for a product realization. Beyond that, the microfiber pulp produced with this process results in work pieces with higher strength values, which can surpass those of hardwood, without having to use bonding and flux agents or external pressures, given a suitable raw material selection and corresponding processing. Specific gravities of up to 1.5 can be achieved in this way. The light-weight and porous variants also have excellent strength values.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This is achieved through a continuous grinding, chopping and defibration of the cellulose fiber or cellulose-containing fiber in the refiner, wherein a total energy expenditure of at least 0.5 kWh/kg, but ideally 2-2.5 kWh/kg are necessary with a laboratory refiner RO-Escherwys. (In order to determine the actual grinding capacity, the no-load capacity must be deducted from the total energy consumption. Thus, a different ratio between no-load capacity to grinding capacity results if machines with a higher capacity or other suitable fiber chopping and defibration machines are used, and the above-defined total energy consumption must be adapted accordingly.) In this way, a moldable microfiber pulp with very diverse fiber lengths and the tiniest fibril sizes develops, which pulp has the characteristic of hardening to form an ecological, subsequently deformable fiber material with high density (up to a specific gravity of 1.5) and strength without the admixture of adhesives or chemical additives and without the use of pressure, simply through drying and the associated shrinkage.
External pressures and forces applied after the grinding above all serve to effect a quick preliminary drainage, the forming and holding of the form and do not represent a premise for achieving high material strengths. Furthermore, the strengths and densities of the material, as well as the structural fiber arrangements of the work pieces are controlled by varying the raw fiber material used, the amounts of grinding energy and the selected grinding tools, but also the processes used for the prior drainage, forming and drying.
Strength, hardness and formability of the material increase with increasing refinement of the cellulose fiber structure. However, if the fibers are chopped to be extremely small, the strength can be further increased through reinforcement with longer fibers (addition of preferably less than 15% dry substance). The highest strengths can be achieved with an extremely fine-ground microfiber pulp, which is reinforced with a thin net of fibers with varied lengths in a balanced fiber-length distribution. In this case, the extremely fine-ground microfiber pulp provides good bonding—but also good flux—and thus forming characteristics; the reinforcement distributes the pressure, pull, or shear forces onto larger areas and prevents a short break over a small area.
Processing:
The plastic properties of the microfiber pulp depend directly on its water content.
The microfiber dry substance content between 1-15% is very suitable for pumping into water-permeable forms (step
1
). Microfiber pulps with this consistency can also be pressed into rigid, impermeable forms, stamped or rolled. In particular, fiber pulps with higher material density are predestined for these processes (step
2
).
The following o
Bramsteidl Robert
Döpfner Horst
Ernegg Martin
Kuhns Allan R.
Spencer George H.
Venable
Wells Ashley J.
Zellform Gesellschaft m.B.H.
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