FR2477947A1 - Direct feeding of differently constituted fibre-contg. suspensions - into separate depositing zones for asbestos cement structure prodn. - Google Patents

Abstract

The direct feeding of the suspensions for the prodn. of a multi-layered building material based on fibrous cement, takes place simultaneously in at least two wash depositing zones, sepd. from each other. The fibre-contg. suspensions may be of different or of similar consistency; a layer which assists filtration being produced in the first depositing zone. For pref. in the second depositing zone, and the,if any, following additional depositing zones, suspensions contg. fibre of a high consistency are delivered. At least one of the suspensions contains a binding agent, and the suspensions differ both as regards the fibrous material and the binding agent qualitatively and quantitatively. At least one suspension contains thermoplastic, organic, synthetic fibrous material, which, after the building material has set, is melted to give a layer protecting against corrosion. A binding agent which can be dispersed in water is added and is polymerised after the layer has set, to give protection against corrosion. To remedy the failings of the first feeding method, that the fibrous material is not distributed statistically satisfactorily, and that a great deal of material goes through the gauze. The invention gives a product with a multi-layered fleece structure and good mechanical characteristics, esp. resistance to bending, tension and impact.

Description

 The invention relates to a method and an apparatus for the manufacture of a product obtained from suspensions containing fibers by influx of material, in particular for the manufacture of a laminated building material based on fiber cement.

 Up to now, in order to manufacture products drawn from suspensions containing fibers, we have most often used direct inflow machines comprising an atflow inflow box, but also short and long felt machines.

Compared to the YO cylindrical taxi machines, direct inflow machines are distinguished above all by a simple mechanical structure, less sensitivity to disturbances, hence a lower maintenance cost, and also by a more universal aspect (as for the thickness of the fiber layer and at the production speed). However, the direct inflow machine with a material inflow box has certain disadvantages: the treated fibrous materials are distributed in a relatively less statistical manner, the layer formed by the direct influx offers a homogeneous structure but with a single layer. , since immediately or shortly after deposition, the deposition region is dehydrated, the proportion of filler or binder which passes through the felt without being used is much greater than in a machine with several cylinders in which the fiber layer is made up of a number of layers corresponding to the number of cylindrical screens.

 The aforementioned drawbacks of the direct inflow process cause a net decrease in the strength of the web or, in the manufacture of fiber cement material, of the material removed from the format cylinder or the pipe mandrel.

 The object of the present invention is to indicate a process of the type defined above which appreciably improves the yield of material and which makes it possible to manufacture a product with several layers of good mechanical properties, in particular a high resistance to the tract in flexion and to shock.

 According to the invention, this problem is solved as indicated in the characterizing part of claim 1.

 The organization of the process is further indicated in subclaims 2 to 5.

 For the implementation of the method according to the invention, an apparatus is indicated, the characteristics of which appear in claims 6 and 7.

The advantages obtained thanks to the invention essentially lie in the fact that it is possible to manufacture a laminated building material, having advantageous mechanical properties, by using a direct inflow machine.

This machine offers here the possibility of treating in the same system suspensions containing fibers and having a different composition, the retention power and the yield of material being significantly improved by the formation of an auxiliary filtration layer.

A material inflow apparatus suitable for implementing the method according to the invention is presented diagrammatically using the appended figure, and described more precisely below.

 The material inflow apparatus has two separate inflow or outflow boxes 1 and 2 each of which is provided with a special material inlet 1a, 2a and a special material outlet 1b, 2b. The deposit boxes 1 and 2 successively supply one side with a rotating endless sieve felt band 3 on the other side of which suction devices are provided in the form of suction boxes 1c, 2c. The sieve felt strip, the direction of travel of which is indicated by an arrow, is guided by idler rollers 4.

In the example below, the composition of the material suspensions and the implementation of the process are presented.
Suspension I 1 pp (part by weight) of short cut polyethylene fibers 0 to 100 pp of portland cement PZ35F 10 to 30 pp of polyacrylate dispersion and 100 to 500 pp of water
Suspension Il 1 pp of asbestos mixture 10 pp of portland cement PZ35F 10 to 40 pp of water
The suspension I is brought to the material inflow box 1 and the sieve felt strip which runs at around 4C m / min is supplied with this suspension.

The sheet which forms in the region of the suction boxes 1c constitutes an auxiliary filtration layer for the suspension II which is brought from the material inflow box 2. The sheet, now formed of two layers, is then introduced into the molding part not shown so as to be wound around a steel core (format or mandrel cylinder) until the desired thickness of the product is reached.

Claims (7)

 1 - Method for manufacturing a product obtained from suspensions containing fibers by influx of material, in particular for the manufacture of a laminated building material based on fiber cement, characterized by the fact 1.1 that the influx of material is carried out simultaneously in at least two separate deposition regions, 1.2 that suspensions containing fibers having a different or equal consistency are used, 1.3 that in the first deposition region, an auxiliary filtration layer is produced.  2 - A method according to claim 1, characterized in that in the second deposition region and in the deposition regions which may follow it, suspensions containing fibers are brought in and having a higher consistency.  3 - Process according to claims 1 and 2, characterized in that at least one of the suspensions brought into the deposition regions contains binder.  4 - Process according to claim 3, characterized in that the suspensions have different compositions qualitatively and quantitatively, both as regards the fibrous materials as the binder.  5 - Process according to claim 3, characterized in that the influx of material takes place in two or more deposition regions with suspensions of material having the same qualitative and quantitative composition.  6 - Material inflow apparatus for implementing the method according to claims 1 to 5, characterized in that it comprises at least two inflow or deposit boxes (1,2), following one another, each provided with a special material inlet (1a, 2a) with an overflow and a material outlet (lob, 2b), and each feeding one side with a strip of felt or endless sieve ( 3) on the other side of which are provided suction devices (tick, 2c).  7 - Apparatus according to claim 6, characterized in that the material inflow boxes (1,2) can be connected in series and that the material outlet (lob) of the box (1) is then connected to the 'enter material (2a) from the body (2).