DD242219A1 - METHOD FOR PRODUCING CEMENT-LINED FIBER PLATES - Google Patents

Abstract

The invention relates to a method for producing cement-bonded fiberboard, which are used as self-supporting elements for ceilings, cladding and the like in construction. The object of the invention is to provide a process according to which a fibrous board can be produced which is inexpensive to use and which is made from inferior wood productions and by integrating the process steps of pulp production and processing. The object of the invention is to improve the known processes for the production of cementitious fiberboard in such a way that the processing of the fiber components can be done without high excess of water and the associated disadvantages. According to the invention, this object is achieved by the fact that, according to a known digestion process, at temperatures above 170 ° C. B. in a defibrator energieoekonomisch produced from wood chips pulp is intensively mixed with cement after a possible intermediate storage with cement, so that a free-flowing mixture is formed.

Description

Field of application of the invention

The invention relates to a method for producing cement-bonded fiberboard, which are used as self-supporting elements for ceilings, panels and the like in construction. The fiberboards produced according to the invention have the high specific strength required for their intended use, low thickness swelling and good surface and narrow surface quality.

Characteristic of the known technical solutions

Are known methods for the production of cementitious building materials containing as reinforcing elements organic fiber or chip materials in which the fibers or chips and the binder are present in aqueous or pasty suspension and then due to the plastic deformability of the organic materials relatively easy to to form a fleece.

A disadvantage of these methods with excess water is the expulsion of the excess water by vacuum and mechanical pressing, since it causes additional expense and limits the parameters of the fiberboard.

Thus, the density is increased by the pressing. In addition, due to the poor drainability of non-wovens with high heights, only thin sheets can be produced economically. Another major disadvantage of this method is the required purification of the wastewater.

Also known is a production process for an asbestos-free building board using cellulose fibers and / or waste paper instead of asbestos, but in order to achieve similar properties as asbestos in terms of their filterability, the cellulose fibers and / or the waste paper prior to their addition to the rest Ingredients of the building board leading wet mass to a freeness of 30 ° to 70 ° SR (Shopper Riegler) must be ground, which requires additional energy.

Information Source:

DE-AS No. 28 54506, Int. Cl. ² : C04 B 31/36

C 04 B 43/16

"After the winding process for a non-asbestos shell board" With a substantial excess of water, a building board made of a fiber-binder mixture of wood chips and cement is produced with the addition of chemicals It is stated that this simplifies the production, in particular the admixture additional fibers, such as glass fibers and / or cellulose fibers and / or synthetic fibers and / or rockwool fibers, facilitated, however, with the greatly increased water content, there is a risk of segregation.

Information Source:

DE-OS No. 30 07 012, Int. Cl. ³ : C04 B 31/36

C04B31 / 06

"Plywood"

According to another known method, wood pulp is placed in a liquid slurry of cement, which may additionally contain cellulose fibers to improve the properties. However, the increase in the proportion of cellulose fibers in the total fiber content and the increase in the fiber content of the mixture as a whole is only possible to a certain extent due to the mixing and shaping difficulties. The feasibility of the solution described is extremely complicated at the high fiber content and the targeted low water-cement value smaller than 1, since the fibers would withdraw all the water from the pulp, so that a mixture in the proposed manner would be difficult. Information Source:

DE-OS No. 2737 058, int. Cl. ² : C04B31 / 36

C04B43 / 12 C04B31 / 40 C 04 B 29/04 B28B 1/52

"Cementitious building material reinforced with fibers and method of making the same"

Object of the invention

The object of the invention is to provide a method according to which, using cost-effective fibrous materials produced from inferior wood assortments and by integrating the process steps of pulp production and processing, it is possible to produce a cement-bonded fiber board which can be widely varied in its properties.

Explanation of the essence of the invention

The object of the invention is to improve the known methods for producing cementitious fiberboard in such a way that the processing of the fiber components can be done without high excess of water and the associated disadvantages.

According to the invention the object is achieved in that the according to a known pulping process at temperatures above -f-170 ° Cz.B. In a defibrator energy-economically produced from wood chips pulp, immediately after leaving the defibrator, a humidity of 100% to 150%, depending on the input moisture of wood chips and Vorordämpfbedingungen and a fiber length of 1 mm to 6 mm, after a possible intermediate storage damp with

Cement in the ratio Faser.Zement = to, preferably until intensively mixed, so that a

100 100 100 100

free-flowing mixture is formed. '

By directly following the pulp production subsequent processing in the wet state eliminates the very costly drying. The water required for the setting of the cement extracts this from the wet pulp. Another important advantage of this method is that even higher fiber cement ratios can be processed without problems at low water-cement values. It can also plates with greater thickness produced by this method, without the web formation is deteriorated.

The addition of chemicals to improve the cement bond can be carried out in such a way that they are added in dissolved form to the pulp or the pulp-cement mixture. The proportion of water can be varied so that sets an optimal wood moisture.

The required to achieve a good plate quality intensive mixing of pulp and cement can be achieved in a known manner by counter-rotating brush or spiked rollers, which can be combined with the spreader in one unit.

It is also possible to use difficult-to-process fibers of organic or inorganic material, such as e.g. Glass fibers, cut synthetic fibers or mineral wool fibers to the wet pulp prior to web formation depending on the additional fibers up to 10% based on the cement weight, without the need for major technological changes.

The scattered nonwoven has a low bulk density and has immediately after compression still great spring forces, which are gradually reduced by the solidifying cement.

It has been found that by restoring dry cement or in particular by applying a cement suspension, the restoring forces are lower and therefore the pressing time can be shortened. At the same time, the surface quality is improved and a sandwich structure is achieved. Other favorable properties of the plates are the homogeneous cross-sectional structure and the associated good narrow-surface quality and the good strength properties, even at lower fiber content due to the relatively large specific surface area of the wood pulp.

embodiment

The invention will be explained in more detail by way of example in the following.

586 g atro of an air-dry pulp produced industrially on defibrators were sprayed with water by means of a laboratory spray-bonding machine. The spray water contained 10% MgCl ₂ , based on the mass of wood pulp atro.

1760 g of cement were then added to the moist pulp and mixed thoroughly. The scattering of a single-layer fleece was carried out by hand in a mold frame measuring 350 × 350 mm ² . A thin layer of cement was sprinkled on the plates as a topcoat. The compression of the fleece to a thickness of 16mm was carried out in one

Laboratory press with a specific pressure of about 3 MPa. After 6 hours, the plates were removed from the press and stored wrapped in polyethylene films until testing after 28 days. Improved technology (mixing, spreading) further improves the properties

 The plates produced according to the invention had the following parameters:

Fiber content: 33% Moisture content: 120% density: 1.3 kg / m ³ Bending strength: 15,1MPa Modulus of elasticity: 4,2GPa Thickness swelling after 2 hours: 1.3% nach24Stunden: 1.7%

Claims (4)

Invention claim: 1. A process for the production of cement-bonded fiberboard using wood pulp, which is produced by a known thermo-mechanical pulping process (eg Asplund process) from wood chips, characterized in that, due to the pulping process, still moist pulp {U = 100% to 150%) after a possible intermediate storage and after addition of known, the cement degradation reducing chemicals and other organic or inorganic fibers so intense with cement in the Ratio fiber cement = --- to, preferably --- to --- mixed that a homogeneous free-flowing Mixture is formed, which is formed by suitable spreaders into a nonwoven, covered with a cement suspension and then pressed until the restoring forces of the pulp are lifted by the hardening cement. 2. A process for the production of cementitious fiberboard according to item 1, characterized in that the cement degradation reducing chemicals are added to the pulp in dissolved form, the amount of chemicals, based on the cement, is constant, the amount of water, however, is varied depending on the moisture content , so that an optimal wood moisture content of U = 120% to 170% is established after chemical addition depending on the fiber content. 3. A process for producing cement-bonded fiberboard according to item 1, characterized in that the other organic or inorganic fibers consist of glass fibers, synthetic fibers or mineral fibers. 4. A process for the production of cementitious fiberboard according to item 3, characterized in that the proportion of other organic or inorganic fibers to 10%, based on the mass of the binder is.