GB2193461A - Method of manufacturing agglomerated facing boards - Google Patents

Abstract

The present invention relates to a method for manufacturing covering panels based on hard materials, previously reduced into grains and powder, agglomerated using synthetic resins, the said covering panels being especially intended for outer-wall covering. According to the invention, two layers of binder 5 and 8, based on synthetic resins of different compositions are successively deposited on a continuously moving belt which has especially previously been coated with a demoulding agent, the outer coating face of the said covering panel being the face 27 in contact with the carpet 1. Two types of granulate 10 and 15 are then selectively distributed in the strip 22 thus formed by the two superimposed layers, the first 10 descending into the first layer of binder 5 and the second 15 occupying the second layer of binder 8. <IMAGE>

Description

SPECIFICATION Manufacturing agglomerated facing boards The present invention relates, to a method of manufacturing agglomerated facing boards.

More particularly, this invention is directed to provide a method of manufacturing facing boards from hard materials pre- viously reduced to grain and powder particles bonded by means of synthetic resins. This method is applicable notably to the building industry for making facing boards intended notably for exterior wall surfaces.

A number of methods are already known which permit of making boards from synthetic resins and stones, marmor, granite or any other hard materials previously reduced to grain or powder particles.

In some of these known methods the desired dimensions, width and thickness of the boards are obtained by molding. A paste having the desired color is prepared by adding charges and granules to the resin, whereafter the paste is molded under high pressure, the resulting boards being subsequently subjected to various treatments such as drying, glossing and grinding.

With a method of this type wear-resistant facing boards having a decorative appearance and capable of imitating natural stone, marmor or the like are obtained, but it is not possible to produce on a commercial scale boards that are at the same time thin, rigid and plane.

On the other hand, another known method permits of manufacturing facing boards from hard materials previously reduced to grain or powder particles bonded with synthetic resins, the plane and rigid boards being manufactured by a continuous commercial process. Moreover, with this method all problems arising from shrinkage of the material occurring notably during the resin polymerization are safely solved.

In this known continuous method of manufacturing facing boards the following procedure is adhered to: - a fine layer of a synthetic resin binder filled with hard pulverulent materials, which has a very regular thickness, is deposited onto a continuously moving endless belt coated beforehand with a suitable stripping agent, - granules of selected materials mixed in predetermined proportions are deposited upon this binder layer, - the granules are caused to penetrate into the binder layer, - the layer thus obtained is eventually covered with a sole-forming layer of granules which will thus adhere to the belt surface, and - the compound plate thus obtained is subjected to complementary treatments such as notably drying in a polymerizing over, cutting into separated boards, polishing the facing boards, etc.

The facing boards obtained with this method display very satisfactory mechanical properties, are extremely flat and therefore particularly suitable for flooring applications.

However, due to the use of granules of noble materials, which must fill the total thickness of the facing board, its cost is relatively high and thus its use for large surfaces such as exterior wall facings cannot be contemplated.

To reduce the cost of facing boards so that they can be used as exterior wall facings, materials cheaper than marmor or granite should be used but in this case the aesthetical quality of the end product is impaired considerably. A compromise might be imagined by using facing boards consisting of two layers, the first layer adapted to constitute the exterior facing comprising noble materials such as notably marmor, the second layer consisting of cheaper materials, such as common black marmors or granules resulting from the crushing of local stones.

However, in this case the above-described method cannot be used since the travelling endless belt must be fed continuously with the different types of materials.

Considering the present state of the art, it might have occured to specialists that the following method could be devised: forming a first binder layer into which a first type of hard material is distributed and forming a second binder layer in which a second type of hard material is distributed, these two layers being subsequently superimposed and eventually polymerized.

Apparently, this method cannot be carried out in actual practice for obviously no bond can be obtained between the two resin layers, so that final facing boards of poor quality would result.

Another line of argument could have been held by a man of the Art by forming facing boards as follows : a thick layer of binder is deposited continuously on a conveyor belt, then a first type of hard material, which is to constitute the exterior surface of the board, is distributed in the first layer, and a second type of hard material is spread to complete the layer, the product being eventually hardened by polymerization.

With a method of this type, agglomerated facing boards would be obtained with a selective distribution of the component materials in the band, but on the other hand no appreciable savings would be obtained as compared with the method using a single type of hard material since the fact of using a single thick layer of binder increases considerably the final cost, in spite of the savings on hard materials.

A last manufacturing method in which a mixture of granules of different grades are distributed through a thick binder layer cannot be contemplated since it would not be possible to orient the various types of hard materials in the layer.

It is therefore the primary object of the present invention to provide a satisfactory solution to the problem set forth hereinabove, namely forming facing boards containing hard materials previously reduced to grains or powder, agglomerated by means of synthetic resins and consisting of two superimposed layers of hard materials closely bonded to each other.

It is another object of the present invention to provide a commercial method of making facing boards of the above-defined type in a continuous process.

Another object of the present invention is to provide a method of manufacturing relatively thin facing boards with a good finish, a plane surface and a good mechanical strength, at a substantially lower cost as compared with hitherto known methods. A complementary object of the present invention is to manufacture facing boards having an attractive and decorative external aspect imitating notably marmor or other noble materials.

Other objects and advantageous features of the present invention will appear as the following description proceeds with reference to the accompanying drawings showing a typical form of embodiment of the invention, given by way of example, not of limitation.

According to the instant invention, the method of manufacturing facing boards from hard materials possibly in the form of grains or powder agglomerated by means of synthetic resins, said boards being intended notably for covering exterior walls, is characterised in that: (a) On a conveyor belt driven continuously and previously coated with a stripping agent, the following materials are deposited:: - a first layer of synthetic resin base binder of which the belt engaging face is intended to constitute the exterior or ornamental face of said facing board; - a second layer of synthetic resin base binder of which the composition differs from that of the first layer, the two layers being superimposed and providing an interface therebetween; (b) the following materials are distributed selectively in the continuous band consisting of the first and second binder layers - a first type of granules in the first binder layer, by accelerating the downward penetration of the granules through the second binder layer toward the first layer down to the exterior or ornamental face thereof; - a second type of granules in the second binder layer while avoiding the downward penetration of material into the first binder layer.

A clearer understanding of the present invention will be had when reading the following description with reference to the drawings.

FIGURE 1 is a diagrammatic synoptic general view of the apparatus for carrying out the method of the present invention, and FIGURE 2 is a fragmentary longitudinal sectional view showing on an enlarged scale the facing board during the making thereof.

In the apparatus illustrated in Figure 1, designed for carrying out the method of the present invention, a variable-speed edged endless steel band 1 of a length sufficient to enable all the sequential steps of the process to take place during the time necessary for the passage of one belt length, is used. In some specific manufacturing processes the endless belt 1 may be coated beforehand with a suitable stripping substance, for example at station 2.

Then, a plurality of sequential stations overlying the endless belt 1 are provided for delivering the products and performing the steps necessary for the manufacture of facing boards.

Firstly, a first distributor 3 is provided for supplying a binder containing notably a socalled noble synthetic resin for building the socalled "noble" binder layer.

Then, a second distributor 6 delivering notably another so-called "poor" synthetic resin 7 is provided for forming the second, so-called "poor" binder layer. As shown in the drawing, this second distributor is followed by a first dosing and dispensing hopper 9 containing a first type of hard material 10 consisting notably of so-called "noble" washed granules.

Underneath the hopper 10 are a distributor 11, comprising essentially a bundle of metal blades of gradually decreasing cross-section, and a pair of superimposed screens 12, 13 adapted to distribute and dust the granules homogeneously.

Next is a second dosing and dispensing hopper 14 delivering a second type of hard material 15 consisting notably of so-called "poor" washed granules. This hopper 14 is constructed somewhat like the first hopper 9 but comprises a distributor 16 and two screens 17, 18.

The hopper 9 is followed by a belt section responsive to the vibration of a vibrating platform 19.

At the downstream end of this belt section a dispensing hopper 20 containing sole-forming granules 21 is provided, for building up a bed of grains 23 consisting of two superimposed layers 5, 8 on the travelling belt 22.

Then, a vibrating and compression device 24 is provided for causing the sole-forming granules 21 to adhere to the surface 22.

The conveyor belt is then caused to pass through a polymerizing oven 25.

Finally, an exhaust system 26 is provided for recovering all the excess granules, that is, the granules not adhering to the band.

This band is subsequently directed to other working or treatment stations (not shown in Figure 1) wherein the finishing steps such as cutting, sand-blasting and polishing are performed.

This apparatus, as described hereinabove, is adapted notably to carry out the method of manufacturing facing boards according to the present invention.

According to this invention, the method of manufacturing facing boards from hard materials previously crushed to a granular, grain or powder state and agglomerated by using synthetic resins, said facing boards being intended more particularly for lining exterior walls of buildings or the like, comprises the following sequence of steps: Firstly, a first binder layer 5 made of synthetic resins 4 is deposited on the conveyor belt 1 driven with a continuous linear motion and coated beforehand with a stripping substance at station 2. The bottom face 27 of this layer 5, which contacts the belt 1, is intended for constituting the exterior or ornamental face of the facing board.

This first binder layer also called "noble" layer is spread on the belt surface by means of a first binder distributor 3 comprising essentially a pair of rollers having intermeshing, gear-forming cylindrical surfaces adapted to form and deliver a layer having a regular thickness.

The synthetic resin 4 implemented consists notably of pasty polyester resin of the iso phthaiic type. This resin is prepared at another station, not shown in Figure 1, wherein the resin, charges of hard pulverulent materials, catalysts and possibly coloring matters are mixed.

Then, a second binder layer 8 containing synthetic resins 7 having a composition differring from that of the first layer is deposited on top of the first or "noble" layer 5, both layers 5 and 8 having consequently a common interface 28.

This second binder layer 8 referred to herein as the "poor" layer, consists notably of an orthophthalic type polyester synthetic resin.

This resin is prepared at another station (not shown in Figure 1) where it is mixed with pulverulent charges,. catalysts and notably coloring matters.

The second "poor" binder layer 8 is laid on top of the "noble" binder layer 5 by means of a second binder distributor 6 having the same general structure as the first distributor 3 which permits notably of forming a layer of substantially constant thickness.

According to a preferred form of embodiment of the present invention, the two superimposed layers 5, 8 of synthetic-resin base binders 4, 7 respectively have a pasty consistency but different viscosities, and furthermore they are not miscible. On the other hand, the chemical compositions of these layers are quite similar and compatible to avoid shrinkages and bring about an interaction between them during the polymerization.

Then, the continuously travelling band 22 comprising the two binder layers 5, 8 is fed selectively with the hard materials notably in the form of washed granules.

Figure 2 illustrates the selective distribution of these materials in the band 22 of which the layers 5, 8 are magnified considerably for a clearer understanding of the invention.

Firstly, a first type of so-called "noble" granules 10 are deposited by the fist dosingdistributing hopper 9 on the hand 22.

These granules 10 penetrate by gravity into said second layer 8 of "poor" binder down to the first layer 5 of "noble" binder as the band 22 moves past on conveyor belt 1.

This downward movement of materials 10 through the layers 8 and 5 toward the ornamental face 27 may be accelerated by using for example a vibrating platform 19 disposed on the path of the travelling band.

Then, a second type of so-called "poor" granules 15 are deposited on top of the band 22 already containing the "noble" granules 10 of the first type.

These granules 15 are thus caused to penetrate into the so-called "poor" binder layer by gravity and also by the vibrations of platform 19.

According to the present invention, the granules 15 penetrate only into the second binder layer 8 but not into the first layer 5.

To prevent the granules 15 from penetrating into the lower layer 5 different parameters are resorted to, such as notably the speed of the conveyor belt, the frequency and amplitude of the vibrations, the granulometry, the viscosity of the resin layer and the relative arrangement of the various working station along the belt.

Similarly, these various parameters may also be used for distributing the first granules 10 in the "noble" binder layer 5.

It will be seen that to promote the penetration of the various granules into the binder layers, the granules are coated beforehand with a monomer of the styrene or acrylic type.

The band 22 thus obtained moves past the next station 20 to which sole-forming granules 21 are fed to form a bed 23. A vibrating and compressor unit 24 is provided for causing said sole-forming granules 21 to adhere to the surface of band 22. During this step, the granules are fed to saturation so as to form a heat-insulating layer thick enough to avoid the heat shock due to heating and cooling during the polymerization. By providing this insulating bed, the problems arising from shrinkage are minimized.

The endless belt 1 then causes the band 22 to move through the oven 25 and then to pass under a suction or vacuum device 26 which recovers all excess granules not adhering to the band.

It will be seen that the resins are polymerized in the cold state by adding catalysts and accelerators, this step being followed by a heating step to complete the polymerization.

At the end of this manufacturing cycle the band is fed to various conventional treatment stations for shaping and polishing the facing boards.

With this method facing boards, intended notably for facing exterior walls, are obtained, these boards being relatively thin, rigid, plane and economical.

By carrying out this method it is possible to manufacture facing boards and plates having a wide range of specific properties, and more particularly the product described hereinafter by way of example.

A first layer of "noble" binder 5 consisting of an isophthalic polyester base resin, having a very reduced thickness within the range of about a few tenths of millimeter to about one millimeter, is deposited onto the conveyor belt. It will be seen that when very thin layers are used the stripping agent may be incorporated in the layer instead of being deposited beforehand. On the other hand, the binder distributor or dispenser 3 may be used, but as an alternative this layer may be applied by using spray nozzles.

On top of this first binder layer 5 the "poor" binder layer 8 of greater thickness and consisting of orthophthalic type polyester base resins is deposited, this "poor" binder layer having for instance a thickness of the order of one to twenty millimeters.

These two different types of resins are prepared beforehand by adding hard pulverulent charges thereto, as well as catalysts, accelerators and possibly coloring matters.

The noble resin utilized in the method of the present invention has a particularly good ageing resistance but its cost is relatively high, in contrast to the second resin which has poorer properties but compensates this drawback by reducing appreciably the total cost of the resin layer.

The conveyor belt 1 travelling at a linear speed of the order of 0.5 to 2 m/mn subsequently transfers the band 22 made of two superimposed layers 5, 8 to the hoppers of the dosing-distributing devices 9 and 14.

The first hopper 9 delivers a first type of "noble" granules 1Q consisting for example of white or colored marmors of well-known and therefore expensive grades.

On the other hand, the second hopper 14 delivers a second type of "poor" granules 15 consisting notably of black marmors or crushed local stones, available at a considerably lower cost.

In order to produce facing beards or plates made of homogeneous materials, not of twolayer materials, and avoid the problems arising from shrinkage differences between the two layers during the polymerization step, the materials 10 and 15 should have about the same granulometry. Thus, the two layers will have substantially the same shrinkage, but it may be pointed out that the thinner the "noble" binder layer, the lesser the shrinkage prob lems.

One may also contemplate a mixture consisting of two-thirds of granules having a relatively coarse granulometry, that is, within the range of about five to about eight mm, and one-third of fine granules, that is, having a granulometry within the range of about two to about five mm, for constituting on the one hand the "noble" mixture 10 and on the other hand the "poor" mixture 15.

According to the thickness of the "noble" binder, one can reduce the granulometry of the noble materials 10. In this case, to prevent the material deposited on the layer from cropping out from the outer surface of the layer, that is, on the conveyor belt side, since a lower granulometry tends to facilitate the downward movement of the granules, the viscosity of the "noble" binder layer 5 will be increased.

Therefore, these two types of materials will be distributed selectively through the band by controlling the various parameters, such as notably the linear velocity of the endless belt 1, the viscosity of the binder layers 5 and/or 8, the belt vibration and the relative arrangement of the two distributing hoppers 9 and 14.

More particularly, the belt vibration following the dusting of grains will notably promote the fall by gravity of the granules and remove the bubbles possible trapped in the resin.

The relative spacing between the two hoppers 9 and 14 is subordinate notably to the weights of the "poor" granules 15 which permit of accelerating the downward travel of the "noble" granules 10 through the "poor" layer 8. On the other hand, the distance from the hopper 14 to the next working station is such that the "poor" materials 15 cannot penetrate into the layer 5 beyond the interface 28. In fact, it is a primary requirement of the method of this invention to prevent the two types of materials from mixing together in the "noble" binder layer 5.

As the band 22 proceeds through the apparatus it moves past the next stations thereof in which the bullding of the insulating bed, the heating in the polymerization oven and the exhaustion of the excess granules take place.

It will also be seen that the insulating bed 23 may consist of granules of expanded material such as expanded clay or schist, other suitable materials being resilient materials providing the additional feature of improving the sound- and heat- insulating properties of the facing board.

Besides, it would also be possible to eliminate this sole-forming granule deposit and in this case the insulating bed would consist of an excess or surplus deposit of "poor" granules 15 delivered for constituting the second layer 8. In this case, the viscosity of this layer should be so adjusted as to enable it to retain a layer of such granules, which has a predetermined thickness, flush.to the surface of said second layer 8.

With the method embodied in the abovedescribed example, facing boards having good mechanical properties can be made at a relatively low or at least advantageous cost, notably in the case of exterior wall facings intended for protecting a building or like construction against external weather conditions.

It may also be emphasized that according to the present invention it would also be possible, for producing facing boards of which the external or ornamental side has a decorative appearance, such as imitation marmor, notably a surface displaying irregular colored veins, to insert in the above-described method an additonal step consisting in forming such veins in the "noble" binder layer 5.

For this purpose, it would only be necessary, at the inlet end of the manufacturing line, to substitute a different resin distributing station for the first binder distributor 3, according to a vein-forming technique well known in the art.

This additional vein forming station would comprise notably an inclined spreading plane permitting of distributing the resin layer from a slot-type hopper extending throughout the width of the resin layer, said inclined plane leading to an inclined tongue or a horizontal recti-linear blade or lip movable toward the horizontal band supported by the endless conveyor for transferring the resin layers from the inclined plane to the belt.

During the downward movement of the resin layer on this inclined plane a liquid resin of a color other than that of the layer formed on the inclined plane is injected against the side which will eventually be the outer surface of the facing through a movable nozzle driven to form random patterns corresponding to the desired vein patterns.

Claims (16)

1. A method of manufacturing facing boards containing hard materials previously crushed to the size of granules or powder particles bonded by means of suitable synthetic resins, said facing board being intended notably for covering exterior walls of buildings and the like, this method being characterised in that it comprises the following steps: (a) binder layers are deposited on a conveyor belt to which a continuous linear motion is imparted, said layers being coated beforehand with a suitable stripping agent, said layers being as follows:: - a first synthetic resin base binder layer of which the belt engaging surface is to constitute the exterior or ornamental side of the facing board; - a second synthetic resin base binder layer of which the composition differs from that of the first layer, the two layers being superimposed and forming an interface therebetween; (b) the following materials are distributed selectively in the continuous band consisting of said first and second binder layers: - a first type of granules in the first binder layer, the downward penetration of the granules through the second binder layer toward the first binder layer down to the exterior or ornamental face thereof being accelerated; - a second type of granules in the second binder layer while avoiding the downward penetration of material into the first binder layer.

2. The method of manufacturing facing boards according to Claim 1, characterised in that: (a) on an endless conveyor belt driven with a continuous linear motion and coated beforehand with a suitable stripping agent, a first so-called "noble" synthetic resin base layer having a regular thickness throughout and charged with hard pulverulent material is formed by means of a binder distributor; (b) on top of this first "noble" binder layer a second, so-called "poor" layer of synthetic resin charged with hard pulverulent material and having a regular thickness throughout is deposited by means of a second binder distributor, the synthetic resin of the two superimposed layers being pasty, non-miscible and having different viscosities; (c) on top of said superimposed first and second layers the following materials are deposited in the form of washed granules:: - by means of a first dosing-distributing hopper, granules of the first so-called "noble" type, which pass by gravity through said second layer of "poor" binder down to said first "poor" binder layer; - by means of a second dosing-distributing hopper, disposed downstream of said first hopper with respect to the direction of travel of said endless belt conveyor, a second type of so-called "poor" granules which are thus caused to penetrate into said second "poor" binder layer without penetrating however into said first "noble" binder layer.

3. The method of manufacturing facing boards according to Claim 1, characterised in that the velocity of the conveyor belt, the viscosity of said binder layers, the granulometry of said first and/or second granules types are controlled to cause these two types of granules to penetrate into said superimposed binder layers, respectively.

4. The method of manufacturing facing boards according to Claim 2, characterised in that the endless conveyor belt portion located downstream of said granules distributing hoppers is vibrated to promote the penetration of said granules into said binder layers.

5. The method of manufacturing facing boards according to Claim 1, characterised in that the first binder layer has a very reduced thickness ranging from about a few tenths of millimeter to one millimeter, compared with the thickness of the second binder layer which ranges from about one nnillimeter to about twenty millimeters.

6. The method of manufacturing facing boards according to Claim 1, characterised in that the chemical compositions of the synthetic resins constituting said superimposed binder layers are akin and compatible to avoid shrinkage and produce any interaction during their polymerization.

7. The method of manufacturing facing boards according to Claim 6, characterised in that the binder layers consist of polyester resins, the resin of the first layer being of the isophthalic type, and the resin of the second layer being of the orthophthalic type.

8. The method of manufacturing facing boards according to Claim 6, characterised in that the resins are polymerized in the cold state by adding suitable catalysts and accelerators, with the application of heat for producing a total polymerization.

9. The method of manufacturing facing boards according to Claim 2, characterised in that the granules of the first or "noble" type consist of a mixture of two-thirds of coarse granules having a size of five to eight millimeters and one-third of fine granules ranging from two to five millimeters.

10. The method of manufacturing facing boards according to Claim 2, characterised in that the granules of the second or "poor" type consist of a mixture of two-thirds of coarse granules, ranging in size from five to eight millimeters, and of one-third of fine granules ranging in size from two to five millimeters.

11. The method of manufacturing facing boards according to Claim 2, characterised in that the first type of "noble" granules is selected among -choice and notorious white or color marmors, the second type of "poor" granules being selected among common black marmors or local crushed stones.

12. The method of manufacturing facing boards according to Claim 2, characterized in that the various granular materials are coated with a monomer of the styrene or acrylic type or the like to facilitate their penetration through the binder layers.

13. The method of manufacturing facing boards according to Claim 1, characterised in that the stripping agent is incorporated in the first binder layer.

14. The method of manufacturing facing boards according to Claim 1, characterised in that colored and irregular vein patterns are formed on the outer surface of the boards.

15. The method of manufacturing facing boards according to Claim 1, characterised in that said band containing the two types of granules is covered with a layer of sole-forming granules which are thus caused to adhere to the band surface, said sole-forming granule layer being relatively thick so as to act as a heat-insulating bed capable of withstanding heat shocks caused by successive heating cooling steps during the polymerization.

16. The method of manufacturing facing boards substantially as herein described.