DK168020B1 - PROCEDURE FOR THE PREPARATION OF FORM STABLE ARTICLES FROM A FLUIDIZED CELLULOSE FIBER MATERIAL - Google Patents

Description

DK 168020 B1

The present invention relates to a method for making mold-stable articles by depositing a fluidized cellulosic fibrous raw material on a shaping substrate by aspirating a pulp of the fibrous raw material onto this substrate.

By a fluidized cellulose fiber raw material is meant a suitable starting material which can be present in wet form and which is fibrous in nature. As such a starting material, reference may be made, for example, to a fiber pulp material, such as is used, for example, for trays and cartons for packaging fragile and delicate objects such as fruits, flowers, eggs and articles, for example glass. The pulp material then comprises the rule of a slurry, fibrous cellulose.

For this purpose, it is known to employ a manufacturing technique in which the starting material in the form of a pulp is applied, in a deposition process, to the contour-giving exterior of a mold which is permeable to allow an gaseous working medium to influence the material 20 through suction. the material of the mold, thereby sucking the material in contour on the mold.

The object of the invention is to indicate how this, in itself suitable manufacturing technique, can be used not only for the production of relatively small and light objects, but also for the production of large, relatively heavy, and extremely sustainable elements which are distinguished by a shape stability. which is substantially based on a corresponding thickness of the material layer deposited on the forming substrate. In comparison, the material thickness of said small and light objects is rather low, and the practically necessary stiffness is usually provided by a deliberate design of wall portions which, for example, provide support for said objects, the walls producing a relatively rigid overall subject by mutually supporting 35 each other.

The stated object is achieved according to the invention in that DK 168020 B1 2 produces from the fluidized cellulose fiber raw material a pulp which, using a long-fiber starting material, has improved dewatering properties, that this pulp is applied to the substrate in such an amount and that the suction is carried out in a controlled manner. in such a way that a fiber raw material layer of such thickness is deposited on the substrate upon suction to provide the desired shape stability for the article, after which the article is completed.

GB-A-1,589,077 discloses a molding of articles composed of different thickness parts, which is achieved by varying the concentration of the suction holes of the mold to remove the liquid phase from a fibrous suspension. mold surface.

SE Patent Laid-Open No. 324,498 discloses a web 15 having a varied mesh pattern to provide variations in the wall thickness of articles molded by suction of a fibrous web onto the web.

U.S. Patent No. 3,325,349 discloses measures for controlling the pulp quantity required to produce a certain amount of pulp by reducing the thickness of certain portions of the article. For nap purposes, a specific perforation of the suction mold used is made.

U.S. Patent No. 2,079,667 discloses measures that aim at uniform layer thickness of the molded article, which must be achieved by a special design of the mold used.

Contrary to this prior art, it is essential for the invention to use a pulp that can be dewatered particularly easily so that a substantially increased thickness of the deposited fiber raw material layer is provided by increasing the pulp's fluid delivery capacity, which is again achieved by using a pulp material. long-fiber starting material.

Hereby, it will be possible to make use of the aforementioned manufacturing technique to produce sustainable elements such as pallets and building elements which, in contrast to the mentioned packaging examples, can exhibit relatively smooth and smooth outer surfaces and which in themselves exhibit a large form stability. The deposition of a fiber raw material layer of the defined thickness means that, under the suction pressure applied to the suction material, a material density can be provided which is greatest at the outer surface of the material layer facing the mold surface and which will act as reinforcing material. , being at a distance from the central median plane of the deposited object.

Example

As the starting material, in the example "recycled paper" which has a large, in the example approx. 80% content of cellulose fibers with a length up to 3.5 mm (conifer), approx.

18% shorter fibers, and approx. 2% small particles.

In a dry process treatment e.g. in a shredder, followed by a dry process treatment in a hammer mill, a loosening of the starting material's fiber structure is carried out in its constituents, which is checked, for example, by selecting the hole size and luminous area of a screen built into the hammer mill.

The fibers thus exposed are fed dosed to a pulper, as is known from the paper manufacture, and in which they are processed for approx. 3 minutes, and the resulting pulp is then ready for application to the shaping substrate. This processing time amounts to approx. 10-20% of the processing time which may be used for the preparation of a finished pulp of the same starting material which has not been subjected to said dry process treatment.

In the overall treatment described, a significant improvement in the dewatering properties is obtained, since the dewatering rate during suction of the pulp on the shaping substrate was increased 4 times over a suction process carried out with a pulp made without the use of the previous dry process treatment. .

The increase in the drainage rate also means that products which, for the sake of shape stability, must have a large mass, e.g. a plate blank of 1.2 x 0.8 m and a weight of 3 kg has been produced at a suction time of 30 seconds.

Utilizing the layer thickness of the article thus produced, its mold stability as set forth in claim 2 can also be enhanced by providing one or more variations in the layer thickness by distributing the suction effect during a common suction process for the layer thickness thereof. the amount of fiber pulp needed for the whole article is similarly varied locally. In this way, during one and the same work operation, i.e. The deposition of the fiber raw material on the shaping substrate could be shaped both at the final outer surface desired for the article and, utilizing the thickness of the material layer, a molding stability increasing the shaped structure of the article material forming itself. Such a structure, as stated in claim 3, can, for example, be designed as a coherent structural pattern with a greater layer thickness relative to the other areas of the object.

A convenient method for carrying out the method according to the invention is set forth in claim 4 and characterized in that a gaseous pulp of the fibrous raw material of the desired thickness is used for a gaseous working medium under pressure. easy-to-mold form having a permeable surface permeable to the working medium, the permeability of which is adapted to the thickness of the fiber raw material layer to be deposited by suction of the pulp on this surface.

In this way, such an interaction can be achieved between the pulpability 30 of the pulp 30 and the suction surface of the mold surface, that also elements having a high fiber layer thickness due to the desired shape stability can be produced rationally.

In order to obtain local variations in the layer thickness of the element raw material layer, as indicated in claim 5, a mold whose shape surface has a permeability which varies according to the layer thickness of the local variation or localities of or the associated structural pattern of the easily degradable fiber pulp film deposited on the mold surface.

This means that the deposition of fibrous raw material on the mold surface will be different according to the permeability of this surface itself, whereby the suction effect will vary locally, so that in areas where the mold surface permeability is poor, a reduced deposition of fibrous material on the mold surface will occur. while the deposition will be large in areas where the permeability of the mold surface is high.

For the preparation of a pulp which is to be easily degradable, as indicated in claim 6, as a fiber raw material, a starting material containing long fibers can be used which is processed into a pulp using a cutout 15 in a pulp and partly by a pulp. prior, separately, controlled dry milling, in which the starting material is divided into dosed quantities and comminuted into its fibers, after which the article is made of the pulp thus formed.

The use of a pulp as an essential machining step of the fiber raw materials to form a pulp from which the desired articles are to be made, inter alia in cases where the fiber raw materials are received as dry masses in bales, for example as paper waste.

In the pulper a vigorous vortex is produced, whereby the individual parts of the material rub against each other, thereby being finely divided, whereby the raw materials are divided into fibers.

Especially with heterogeneous materials such as waste or recycled paper, it is to be expected that this division takes place successively, so that the fibers that are first released are subjected to further substantial processing over the later released fibers. In other words, the machining of the pulper in its course will thus be uncontrolled, and thus uneven. Said further machining results in both the degree of grinding (° SR-Schopper-Riegler) and thus the mucus formation in the pulp being increased, which has a negative effect on the later dewatering of the pulp made article, DK 168020 B1 6 and increases the shrinkage of the article. during the dewatering and drying of its material.

By the method of claim 6, it is achieved that at least partially a fiber raw material is supplied to the pulper, the fibers of which are already substantially divided into single fibers, which is why they are more immediately and simultaneously susceptible to the self-grinding effect provided in the pulper. and mixing effect. As the pulper processes a more uniform feedstock, the degree of grinding provided in the pulper 10 can also be controlled to be more uniform, and the aforementioned bonding of water in the pulp exiting the pulper will thus be better controllable.

However, the same approach will also bring other benefits which are particularly valuable in recycling paper waste.

Recycled paper waste is available in many different grades and grades. If this material is subjected to a separate controlled dry grinding prior to the pulverization, it will often be possible to use a poorer, and thus cheaper, material quality than if the partitioning process was carried out solely as a pulverization.

It is within the scope of the invention to carry out the aforementioned, separate dry milling process as a multi-stage process, whereby the starting material can be divided into dosable quantities in a particularly effective manner.

In this way, for example, a waste paper material containing plastics, wet-strength paper, plastic laminated cardboard and paper can also be divided into fibers and other particles to the desired extent. Non-paper split components may then be separated prior to delivery to the pulper or, as they are in finely divided condition, these components may be included in the subsequent production process.

In one embodiment of the aforementioned method, a separately controlled dry grind subjected to long-fiber starting material may be added to a pulp already formed in the pulper and subjected to a common time-limited extinction thereof.

In this way, an article can be produced, the fiber material of which is mainly bonded by hydrogen-bonded fiber, and partly mixed with air-suspended fiber material, to which bonding is usually used glue.

It has been found that in this way a traditional, completely hydrogen bonding of the whole pulp can be dispensed, which means that the dewatering, and thus the production time of the object, can be significantly shortened. Furthermore, the method allows for close control of the stabilizing strength properties desired for the object, which can be controlled precisely by the addition of glue.

These advantages are essential to a rational "and thus economically industrial manufacture" also of 15 large, shape-stable objects using the described suction technique.

For example, a multi-stage dry milling can be carried out using a blender, also called shredder, followed by a treatment in a hammer mill which can thus receive the material from the shredder in dosed quantities and subject the material to a further comminution effect. before, if desired, also in especially dispensable amounts, the pulper is fed to the actual knockout operation.

25 The aforementioned separate, controlled dry milling of the fiber raw materials prior to their scraping in the pulper also opens up the possibility of reuse waste paper in cases where the articles to be manufactured must be shrink-free and target-proof. A starting material with a high content of wood-containing fibers causes less shrinkage than if the fibers were cellulose fibers. It has been found that by applying the method of the invention to a wood-containing paper raw material, a substantial amount of affordable recycled waste paper can be added, including cardboard waste, which is not necessarily wood-containing, because of the prior separate , controlled dry grinding of the raw material will be able to produce a pulp which does not cause any unwanted shrinkage of the manufactured articles.

In principle, it is known to produce articles of a fluidized fibrous material to use adjuvants in the form of fillers and chemicals, as well as binders. The adjuvants determine whether the manufactured articles should be more or less strong, hard and transparent, or weak, soft and absorbent. The present invention 10 also provides advantages in using such auxiliaries.

Namely, the division of the manufacturing process into several manufacturing stages allows for increased additives at various stages of the overall manufacturing process. The resultant open structure of the final pulp obtained by the machining of the invention even makes it increasingly available to the auxiliaries, so that, for example, a binder can be applied more or less integrally in the surface of the manufactured articles 20 to provide an increased wall strength. The addition of the adjuvants during the preceding separate controlled dry milling may, in a particularly good way, promote a very uniform distribution of the adjuvants in the produced pulp. Of course, the auxiliaries 25 can also still be added to the pulper.

Furthermore, it is within the scope of the invention that the knockout in the pulper is carried out as a processing process controlled in dependence on the prior separate milling. In other words, the degree of self-grinding provided in the pulper can be adjusted to the degree of grinding which has been carried out according to the conditions at the preceding grinding step (s). For example, a paper pulp divided into the pulper to a normal grinding degree of 60 "SR (Schopper-Riegler), 35 can be added to a dry grinding fiber material, after which the mixture is processed in the pulper for a further 5 to 16 minutes. . Objects made from such blending pulp can be given a particularly large thickness, porosity and permeability. This means that the products can have good dewatering properties and therefore can also be manufactured with large thicknesses of material.

A readily degradable pulp made for use in the process of the invention allows for a uniform application of the fiber suspension over the mold, even in the case of the manufacture of articles of high wall thickness.

10 Waste paper, also called recycled paper, can be very complex and contain fibers of many different lengths. Nevertheless, it has been found that the average fiber length is so large that the above mentioned dewatering and structural advantages can be obtained when this paper material 15 forms part of the manufacturing process.

The process according to the invention can be used for processing also so-called virgin material.

Claims (9)

A process for making mold-stable articles by depositing a fluidized cellulosic fibrous material on a shaping substrate by aspirating a pulp of the fibrous raw material onto this substrate, characterized in that a pulp is produced from the fluidized fibrous material using a pulp. long-fiber starting material has improved dewatering properties that this pulp is applied to the substrate in such an amount and that the suction is made guided in such a way that a fiber raw material layer of such thickness is deposited on the substrate to provide the desired object. shape stability, after which the object is completed. 2. A method according to claim 1, characterized in that one or more variations in the layer thickness are distributed over the fiber raw material layer in that the suction effect during a common suction process for the fiber pulp quantity required for the whole article is varied locally. . Method according to claim 2, characterized in that the deposition of the fiber raw material with a thickness corresponding to the desired shape stability is provided as a coherent structural pattern with a layer thickness greater than the other areas of the article. Method according to any one of claims 1-3, characterized in that a pervious form permeable to a gaseous, suppressed working medium having suctionable pulp of the fibrous raw material in the desired thickness is used. the medium pervious mold surface, the thickness of which is adapted to the thickness of the fiber raw material layer to be deposited by suction of the pulp on this surface. Method according to claim 4, for carrying out the method according to claim 2 or 3, characterized in that a mold is used whose mold surface has a permeability which varies according to the layer thickness in DK 168020 B1 of the local or local variations, respectively. of, or the desired associated structural pattern of, easily degradable fiber pulp sheets deposited on the mold surface. Process according to any one of the preceding claims, characterized in that as a raw material, a starting material containing long fibers is used and which is processed into a pulp using a cutout in a pulper and a previous one separately. controlled dry milling, in which the starting material is divided into 10. dosed quantities and comminuted into its fibers, after which the article is made from the pulp thus formed. Process according to claim 6, characterized in that the preceding separate dry milling is carried out as a multistage process. Process according to any one of claims 6 and 7, characterized in that a separate, controlled dry milling subjected to long-grained starting material is added in dosed amounts to a pulp already formed in the pulper and subjected to a common time-limited extinction thereof. Process according to any one of claims 6-8, characterized in that an auxiliary substance is added during the re-use of the formed pulp.