WO1999052836A1

WO1999052836A1 - Gypsum fiber plates and their manufacturing process

Info

Publication number: WO1999052836A1
Application number: PCT/FI1999/000304
Authority: WO
Inventors: Martti PERÄLUOMA
Original assignee: Peraeluoma Martti
Priority date: 1998-04-09
Filing date: 1999-04-09
Publication date: 1999-10-21
Also published as: FI980829A0; FI980829A; AU3422999A

Abstract

The invention relates to a method of making building blocks, according to which method fibre-containing blocks, suitable for building, are made out of a mix of waste gypsum and short-fibred reject mass obtained from a deinking process of recycled paper. Advantageously, the gypsum used is so-called power plant gypsum. The invention further relates to a building block, which is made of waste gypsum and short-fibred reject mass. The fibres of reject mass act as a reinforcing material in the block, and at the same time, they make the block lighter.

Description

Gypsum fiber plates and their manufacturing process

The invention relates to a method of making building blocks, according to which method a mix containing gypsum and water is prepared, from which mix are formed building blocks which can be used for providing various wall surfaces, for instance.

The invention further relates to a building block which comprises means for connecting the block to other similar blocks such that by connecting the blocks it is possible to provide desired structures, such as indoor walls and other wall surfaces. Traditionally, building blocks and similar elements for providing wall surfaces have been produced by burning stone material and by moulding bricks from lightweight concrete, sandiime and from gypsum alone. Apart from bricks, waste gypsum is used as a raw material for various gypsum boards. However, waste gypsum is produced all the time much more than what is cur- rently possible to utilize as board material. So gypsum has to be stored in waste heaps in the vicinity of production plants or it is transported to a dumping site. Like other refuse materials, also waste gypsum causes environmental problems and increases production plant costs, for instance, due to waste management fees, transportation and multiple handling. DE publication 35 36 013 discloses use of straw as strengthening fibres when making building blocks of waste gypsum obtained from smoke deposition. Further, DE publication 43 00 428 discloses shredded paper, sawdust or straw to be mixed with gypsum. Furthermore, DE publication 23 65 161 discloses manufacture of gypsum boards by using waste gypsum and long- fibred reject of pulp industry as a raw material for boards. Long-fibred reject like this is not actually waste material, but it is also utilizable in paper industry.

The object of the present invention is to provide a method by which various blocks suitable for building can be produced from two different waste materials in a simple and cost-effective manner, and a further object of the invention is to provide a low-cost block that is made by said method and that has advantageous properties.

The method of the invention is characterized in that waste gypsum is used for preparing said mix and to the mix is further added short-fibred reject mass, obtained from the deinking process of recycled paper, which is generally unsuitable for papermaking. 2

The building block in accordance with the invention is further characterized by being mainly made of waste gypsum and short-fibred reject mass, obtained from the deinking process of recycled paper, which is generally unsuitable for papermaking. The basic idea of the invention is that two materials, waste by definition, are used for making desired blocks which are well suited for building and out of which it is possible to build wall surfaces and support structures mainly for indoor use. The blocks in accordance with the invention are made of waste gypsum and short-fibred reject mass, obtained from the deinking proc- ess of recycled paper, both of which are waste materials from production processes and as such only a burden on the production plants concerned. However, by mixing said two ingredients in a suitable proportion, it is surprisingly possible to achieve a block which is strong and whose surface is good in quality without any necessary binders or fillers. If necessary, various fillers can still be added to the raw material, for a special purpose, for instance. Block making can also be accelerated by using a suitable accelerator.

The invention has an advantage that waste gypsum and fibre reject need no longer be hauled to the dumping site, whereby the load of dumping sites naturally reduces. At the same time, both waste materials can be utilized effectively and rationally. Moreover, other alternative raw materials can thus be saved. Currently, the handling of said waste materials causes only trouble and costs to the production plants, but by utilizing the present invention these wastes can be used in an environmentally friendly manner as a good building- block raw material, which the production plants can sell to block manufacturers and thus make some extra profit thereby. From the viewpoint of the production plants, even the fact that the block manufacturers take care of the management and transportation of said waste materials is economically feasible, even though the production plants would not get actual sales profits. Furthermore, the building blocks in accordance with the invention have the advantage that they do not form noxious gases in indoor air, they have good acoustic and thermal insulation capacity, they are easy to process, and thanks to gypsum, they are also fire-proof. The fibres of reject mass in turn ensure the strength of the blocks. In addition to strength, the use of fibres has the advantage that the blocks are light, thanks to the high fibre content in the mix, in comparison with the blocks made of gypsum alone, but their strength and other required properties, such as the quality of surface, are nevertheless adequate to building. 3

The blocks made of waste material have a further advantage that, since the price of raw material may consist of the mere transportation costs, or at least the remuneration for material calculated per one block is relatively low, the blocks in accordance with the invention can be manufactured at low costs. So, when the technical properties of the building blocks of the invention are good and the price is low, they are very competitive. Moreover, since the use of gypsum in the form of building boards has become familiar to the public, the fibre-containing building blocks of the invention will have an extensive market. The invention will be described in greater detail in the attached drawing, wherein

Figure 1a is a schematic end view of one building block in accordance with the invention and Figure 1 b is a top view of said block, and

Figures 2a and 2b are schematic end views of alternative building blocks in accordance with the invention. Figure 1a is an end view of one building block in accordance with the invention. The block shown in the figure is a solid piece made of gypsum and reject fibre, whose first surface, i.e. the upper surface in the figure, is provided with a protruding part 1 , and correspondingly, a second block surface, i.e. the lower surface, is provided with a recess 2, whose size and shape is compatible with the protruding part of the first surface. Thanks to a protrusion- recess arrangement, these blocks have an automatic mutual fit, when they are positioned on top of each other. Consequently, it is relatively easy to build straight and even wall surface even with a minimum of experience. It is also possible to provide corresponding connecting means in the block ends. The block thickness is advantageously arranged to correspond to commonly used wall thicknesses, whereby the structures built with these blocks can be combined without trouble with other structures implemented in other manners, for instance, in renovation projects. A first face 3 and a second face 4 constitute the exposed portion of the block. If desired, the faces can be decorated by grooving, for instance, whereby it is possible to produce impressive, pre- decorated surface. The superimposed and abutting blocks are connected to one another, for instance, by means of thin plaster, adhesive, such as wallpaper paste, or some other suitable binder. The blocks are advantageously connected by using so-called bricklaying with thin joints or gluing, when the gaps between the blocks are narrow. Thus it is easy to fill the narrow gaps between the blocks while finishing the wall, for instance, by means of plaster or some 4 other suitable filler. Further, a vertical channel 5 can be seen in Figure 1b. This kind of a channel 5 is advantageously provided in the middle portion of the block and half-channels 5a and 5b at both ends of the block such that two abutting blocks form together a channel at the joint of said blocks. When the blocks are typically arranged to form a half-block bond with respect to the previous and following courses, vertical channels are provided in the wall structure with regular half-block spacing. In this manner it is simple to lay pipes, cables, and so on, concealed also in the vertical direction of the wall.

The making of building blocks in accordance with the invention comprises mixing of raw materials, in which gypsum and reject fibres, serving as fibrous raw material, are mixed together in the desired proportion. In order that recycled paper could be used as a raw material in paper industry, it has to be deinked first. From the fibre pulp are then removed, for instance, ink and other impurities, and with various screens and similar separating devices, short and other unsuitable fibres, which form reject mass, are separated from the actual pulp to be used in papermaking. Thus the deinking process produces deinked, long-fibred pulp, which is suitable for a raw material for paper, and short-fibred reject, i.e. so-called fines, which is unsuitable for papermaking. The reject mass comprises exceptionally short fibres and other fibrous material that is poorly suited to papermaking or not suited at all. Fibre length is generally less than 1 mm, mostly in the order of 0.1 to 0.7 mm. Paper mills cannot technically process reject mass of this kind, or it is not economically feasible to use it as a raw material for paper. Reject mass is produced in large amounts all the time, and currently it is mainly dumped or used as a landfill. The mass involves considerable handling and transportation costs. Moreover, the waste management fees charged by the dumping sites are also a considerable cost item. Some plants have started burning the mass for producing energy, but that has not been a satisfactory solution to the reject mass problem either, because the mass is very moist on leaving the plant, and conse- quently, the burning of the mass requires that it is first dried, which in turn decreases the efficiency of the process. Furthermore, the burning of the mass requires costly investments, whereby the economical profit from burning is questionable. High moisture content of the mass which comes from the production plant does not cause any problems to block making in accordance with the invention, because preparing a mix from gypsum requires a given moisture content, in any case. Consequently, the reject mass can be used as such in 5 most cases as one main ingredient in the raw material mix of the blocks. When determining the moisture content of the mix, the moulding method to be used is naturally considered.

Even though it is not necessary to add a separate binder or any other admixing material, it is possible to add to the mixture, for special conditions and special needs, e.g. colour pigments, anti-mildew compounds and moisture barriers, if so desired. The other basic raw material, i.e. gypsum, can be, for instance, power plant gypsum obtained from flue gas desulphuration or any other gypsum suitable for the purpose, preferably waste gypsum, how- ever. Further, the gypsum to be used as raw material can be waste gypsum produced in connection with plaster board manufacturing. The waste gypsum is regenerated, i.e. it is processed by heating to gypsum powder suitable for block making. Heating is performed at a suitable temperature, in general at about 190 °C, when the gypsum releases crystal water which evaporates in the course of heating. After said treatment the gypsum is again in such a state that by adding water thereto a mix will be obtained, which is easy to shape and which hardens into a strong piece while drying. Furthermore, it is possible to use natural gypsum, titanium oxide gypsum, phosphoric gypsum or synthetic gypsum. When reject mass is mixed with the gypsum, the blocks to be made become stronger, and at the same time, lighter. The mix proportion of gypsum and reject mass can be selected on the basis of desired characteristics. The mix proportion preferably varies between 1 :3 to 3:1 , expressed in volume fractions. However, it is quite possible to use other mix proportions as well. Even though the fibres of deinked mass are short, they still act as an efficient rein- forcing material in the mix. In addition, the short fibres mix better with the gypsum than the long ones, and if desired, the structure provided will be more compact. Further, it is easier to treat the mass and to mould blocks out of said mass as compared with a mass with long fibres. The quality of the surface can also be better, thanks to short fibres. The mix proportion of gypsum and reject mass can be selected to suit the use. Naturally, a block containing a large amount of gypsum is heavier than a block containing a large amount of fibres. When the volumetric proportion of reject mass is, for instance, 3:1 on the total block material, the blocks are light, which enables easier handling. Despite the lightness, the blocks containing large amounts of reject mass are surprisingly strong. Furthermore, if the mass contains particularly large amounts of reject mass, the surface of 6 the building blocks may be somewhat uneven, which can even be a desired characteristic when more decorative wall surfaces are built.

The tests conducted show that it is advantageous to make building blocks out of a mass having 10% starch on the dry solids content, and gypsum and reject mass substantially in the same proportion.

The mass mix is shaped wet into mass cakes. The blocks can be shaped by mould casting, mould pressing, and for instance, by continuously extruding a long bar having a suitable cross-sectional shape, from which blocks are cut to size as desired. After shaping, the mass is dehydrated. Dry- ing can be accelerated, for instance, in a drying kiln or by using steam for drying. Naturally, the shaped blocks can be allowed to dry freely. After drying, the blocks have achieved their final strength and they can be subjected to a finishing treatment, if necessary.

Figure 2a shows an end view of a second building block in accor- dance with the invention. Here the block's first surface, i.e. the upper surface in the figure, comprises a plurality of minor protruding parts 1 and the surface opposite thereto correspondingly comprises a plurality of minor recesses 2. It further appears from the figure that a longitudinal channel 6 is provided in the block. Figure 2b shows an end view of a third building block in accordance with the invention. As appears from the figure, the recess 2 can be designed larger than required by the protruding part 1 , whereby a space 7 remains between the protruding part of the lower block and the recess bottom of the superimposed block, which space can be utilized, for instance, when laying con- cealed electric cables and telephone cables. By making said space sufficiently large, it is possible to place even water pipes and air ducts therein.

The drawing and the specification relating thereto is only intended to illustrate the inventive idea. The details of the invention may vary within the scope of the claims. If desired, the produced blocks can be finished such that substantially ready-made surface can immediately be obtained therefrom. It is possible to finish the blocks in controlled conditions at the production plant with various paintings, coatings and protective treatments. Furthermore, the blocks can even be shaped after moulding and drying. For instance, they can be subjected to a kind of calibration rubbing or milling, which gives them very precise measurements and the desired, even and smooth, or suitably profiled surface. It is also easy to provide in the blocks both transversal and longitudi- 7 nal drill holes, channels and other necessary apertures. Waste material produced in a finishing process like this, as well as surplus products and imperfect products can be recycled to production to be used again as raw material. The building block in accordance with the invention can deviate in shape from the examples described in the figures of the application. The shape of the blocks or the elements can thus well be more complex than what is depicted in the figures. In moulding step, it is also possible to arrange so-called inserts in the mould, whereby necessary connecting, bearing and supporting parts and the like can be pre-connected to the blocks. Apart from building blocks, it is also possible to make advantageously similar elements out of the mass, and for instance, children's toy bricks that are light and can be combined in a variety of ways.

Claims

8CLAIMS

1. A method of making building blocks, according to which method a mix containing gypsum and water is prepared, from which mix are formed building blocks which can be used for providing various wall surfaces, for in- stance, characterized in that waste gypsum is used for preparing said mix and to the mix is further added short-fibred reject mass, obtained from the deinking process of recycled paper, which is generally unsuitable for papermaking.

2. A method as claimed in claim 1, characterized in that prior to the preparation of the mix, waste gypsum is regenerated by heating it at a predetermined temperature for a predetermined time.

3. A method as claimed in claim 1 or 2, characterized in that the gypsum used is waste gypsum obtained from flue gas desulphuration of power plants.

4. A method as claimed in any one of preceding claims, characterized in that the reject mass mainly comprises short fibres whose length is less than 1 mm.

5. A method as claimed in any one of preceding claims, characterized in that the building blocks are made of raw material mix, in which the volumetric mix proportion of the gypsum and the reject mass is within the range of 1:3 to 3:1.

6. A building block which comprises means for connecting the block to other similar blocks such that by connecting the blocks it is possible to provide desired structures, such as indoor walls and other wall surfaces, char- acterized in that the building block is mainly made of waste gypsum and short-fibred reject mass, obtained from the deinking process of recycled paper, which is generally unsuitable for papermaking.

7. A building block as claimed in claim 6, characterized in that the gypsum used as a raw material for the building blocks is waste gyp- sum obtained from flue gas desulphuration of power plants.

8. A building block as claimed in claim 6 or 7, characterized in that the reject mass mainly comprises short fibres whose length is less than 1 mm. 9

9. A building block as claimed in any one of claims 6 to 8, c h a r - acterized in that the volumetric mix proportion of the gypsum and the reject mass is within the range of 1:3 to 3:1.