GB2135324A - Process for manufacture of slates from waste slate - Google Patents

Abstract

A process for the manufacture of slates from waste natural slate comprises crushing and grinding the slatewaste, sorting the crushed and ground particles according to size, selecting certain quantities of the particles of different granulometry, optionally mixing these particles with a preselected quantity of sand and then of chalk, adding a suitable resin (e.g. a methacrylic resin) and hardening agent for the formation of a comparatively fluid paste, transferring the said paste to a suitable mould heated to about 40 DEG C, and withdrawing the resulting product from the mould after vibration of the latter and hardening of the paste. <IMAGE>

Description

SPECIFICATION Process for manufacture of slates and slate product The present invention relates to slates produced from ground waste slates with a synthetic resin as a binding agent. It also extends two covering elements of the slate type which by reason of their method of production show improvements by comparison with natural slates.

In the manufacture of natural slates the quantity of scrap generally ranges up to 4times the quantity of slates prnducedrthis being the reason forthe high cost of natural slates.

The purpose of the present invention isto enablethe said waste material to be utilized for the manufacture of slates, thus reducing the cost price of natural slate and at the same time providing slates of a new type.

According to a first aspect of the present invention it provides a process for themanufacture of slates which is characterized by the factthat it consists ofthe following stages: - crushing and g rindinqthe slate waste - Sorting the crushed and ground particles accordingto size.

- Selection of certain quantities of different granulometry.

- Possible mixing ofthis charge with a preselected quantity of sand and then of chalk.

- Addition of a suitable resin and hardening agentforthe formation of a comparatively fluid paste.

- Transferofthesaid paste to a suitable mould heated to about400C.

- Withdrawal from mould after vibration ofthe latterand hardening ofthe paste.

In one particularlyadvantageousembodimentof the invention the composition ofthe solid charge represented by the natural materials is as follows: - T8-24% by weight of slate particles in the granulometricrange 16-28 mesh.

- an14% by weight ofslatepaniclesin the grniiulometric range 28-35 mesh.

- 7-T3% byweightofslateparticles in the granulometric range 35-48 mesh.

- 6-12% by weightofslate particles in the granulometric rang e.48-65 mesh.

- 4-10% by weight ofslate particles in the granulometric range 65-100 mesh.

- 9-15% by weight of slate particles in the granulometric range 100-200 mesh, as well as 5-11 % by weight of sand.

- 19-25% by weight of powdered chalk, to which are added the following percentages in relation to the weight ofthe solid charge: 2-4% of Degussa hardener "HK", 15-18% of methacrylic resin of type 1370 from Degussa.

The composition of the solid charge is preferably as follows: 21 by weight of slate particles ranging from 16to 28 mesh in particle size.

11% by weight of slate particles ranging from 28to 35 mesh in particle size.

10% by weight of slate particles ranging from 35to 48 mesh in particle size.

9% by weight of slate particles ranging from 48to 65 mesh in particle size.

7% by weight of slate particles ranging from 65to 100 mesh in particle size.

12% by weight of slate particles ranging from 100to 200 mesh, as well as 8% byweightofsand.

3% byweightof Degussa hardener "HK" and 17,5% by weight of methacrylic resin of type 1370 35 from Degussa.

The mould is advantageously provided in advance with a preliminary coating consisting of a resin oftype 1000 from Degussa, intended to form the protective surface coating oftheslate.

The process covered by the present invention enables slates to be manufactured in every possible shape, whether traditional or special, as will be described hereinafter.

According to a further aspect ofthe present invention, it provides a slate characterized by the fact that it has a first surface which as a whole forms a rectangle, connected at its base to a second surface which as a whole forms a triangle, the said slate being provided, on at least one of its faces, in the position where it is overlapped by other slates after being placed in position with a projecting element serving to support the said further slates.

These slates may comprise, in particular, ribs and projections confined to one ofthefaces, in which case they can be produced buy a simple moulding operation.

In certain particular cases it may be of advantage for one face ofthe slate to be provided with projections, such as ribs designed to fit into corresponding hollowed out parts on the otherface of a second slate coveringthefirst. In such cases a moulding press may have to be employed.

Forreasonsoftheclaritytheapplicantfirm applies the terms "slate" and "natural slate", respectively, to the slate imitation according to the present invention and to thetraditional natural slate used for roofing purposesorforcovering more or less vertical sutructures and obtained by cleaving natural products of a schistous nature.

The use of a synthetic material according to the invention enables special slates such as those mentioned to be obtained with the use of a mould.

The synthetic material used will preferably consist of a mixture of synthetic resin with the addition of a suitable catalytic system and of crushed slate waste.

The present invention is obviously not limited to the synthetic material mentioned; use may be made of any otherjudiciously selected material capable of being moulded and hardened and enabling an imitation of natural slates to be obtained, such as a resin to which suitable pigments have been added.

In one particularly advantageous version the ratio of the charge to the resin and hardener is about 5. The charge, mainly consisting of crushed slate waste, may contain up to 25% of chalk, according to the quality of the resin used,that ofthe natural slate waste adopted and the characteristics desired in the paste and in the final product.

In a preferred method for the production of the slate according to the present invention the projecting element is symmetrical in relation to an axis of symmetry centered on the slate, partly covers the surface ofthe said triangle, forming a groove in the centre, in accordance with the axis of symmetry, and partly extends over the said first surface.

In a first embodiment ofthe slate according to the invention, that side of the first rectangular surface which is substantially parallel to the base of the triangle forming the second surface, is of a size similar to that of natural slates, preferably ofthe order of 20 cm.

In a furtherversion ofthe slate to which the present invention relates, that side of the first rectangular surface which is substantially parallel to the base of the triangle forming the second surface is of a size which is a multiple ofthe corresponding dimension of the traditional slates, the individual units being separated by a groove provided in the said first surface.

These slates may with advantage posses perfora tions in suitable places in order to enable them to be rr,ailed to the roof, the said perforations being overlapped by the adjacent slates after being placed in position.

The constructional versions ofthe slates according to the present invention offer numerous advantages enabling large surfaces to be covered more rapidly and economically.

The use of synthetic materials capable of being moulded enables projecting elements to be produced as elements supporting and overlapping the slates.

By the selection of a suitable shape forthese projecting elements (which are no longer visible after the slates have been placed in position) the contact surfaces ofthe slates can be reduced, in order to preventtheascentofwaterthrough capillary action.

The groove produced in accordance with the axis of symmetry of the slate drains offthe water atthe bottom of the covered surface, such as a roof.

The groove formed by a projecting element is preferablyshutofffrom the point of the second triangularsurface, in oderto preventthe ascent of water bythis route.

The reinforcement ofthe slate provided by the projecting element constitutes a supporting frameworkforthe slate, and it is in these parts that the perforations designed to give passage to nails can be provided.This reinfocementalso enables thinner slates to be used, so thattheirweight and also the amount of material requiredfortheirmanufacture is reduced. The weight being still further reduced by the use of lighter synthetic materials, it is therefore possible to consider the production of lighter frameworks and structures.

The present invention will be described in greater details by reference to the accompanying diagrams wherein: Figure 1 illustrates a first embodiment ofthe slate according to the invention and Figure 2 illustrates a second embodimentthereof.

The examples which follow and which refer to the aforementioned diagrams are obvious only given as illustrations ofthe invention, of which the scope is thus in no way limited thereto. Slate waste is crushed in a cone-type crusher and then ground in a ball mill.

The ground waste is sorted into different grain sizes by means of screen-type separators. Screens of 16,28,35,48,65,100 and 200 mesh, for example, are used forthis sorting operation. "16" mesh" means thatthere are 16 meshes or openings per linear inch.

The particles thus sorted are stored in silosforthe respective size categories mentioned above. An additional silo is provided which contains said of which the particles are about 150 mm in diameter.

Finally,anothersilocontainschalkin a pulverous state, of which the particles measure a few hundredths ofa mm.

The different solid charges and a hardening agent are then mixed together in a dry mixer. This solid charge is then stored in a silo of which the contents are themselves drained off into a wet mixer, in which the corresponding proportion of resin is added. The quantities are shown in the following table: MATERIAL DIMENSIONSOFPARTICLES % BYWEIGHT Slatewaste. 16-28 mesh 21%) 28-35 mesh 11%) 35-48 mesh 10%)100% of 48-65mesh 9%)solid 65-100mesh 7%)charge 100-200 mesh 12%) Chalk 8% Chalk 22% Hardening agent: 3% of solid charge Resin: 17,5% ofsolid charge.

It is ofadvantage to use sand, as this consists os spherical particles, ensuring betterfluidityandthus better distribution. The use of chalk as a filling and encasing means is advantageous by reason ofthe fineness ofthe particles. The addition of chalk, however, also influences the resin content, since it mitigates the harmful effectofthegraphiticmaterials included in the fines of natural slate. The chalk can obviously be replaced by any other charge ensuring the same properties.

Preference is given to the use of the HKtype of hardener marketed by Degussa and ot a methacrylic resin of type 1370, supplied by the same firm.

The pastethusformed after mixing is immediately introduced in the right proportions into a mould heated to 40"C. This temperatu re of 40"C is maintained by means of a current of pulsed air and also as a result ofthe exothermal reaction which accompanied the setting ofthe resin.

Afterthe paste has been introduced into the mould the latter is caused to vibratefor about 2 minutes in orderto rearrange the grains and expel the air contained therein. The surface is atthe same time smoothed e.g. with a scraper. If necessary suitable pressure is also applied by means of a press, in order to obtain more complex moulded shapes. Where the temperature measured gives reason to believe that the exothermic reaction has been completed (after about 20 minutes) the resulting product may be withdrawn from the mould.

The mould is then cleaned with a jet of compressed air and then dried. This drying process is assisted by the temperature of the mould i.e. 40"C.

The cycle recommences by the application of a separatortothe base ofthe mould, followed bya preliminary coating of a Degussa resin of type 1000.

This preliminary coating will serve as the protective surface coating of the slate. The duration ofa moulding cycle is about 35-40 minutes.

Slates of any shapes as well as the conventional shape, can obviously be obtained, according to the shape ofthe particular mould employed.

In a further embodiment of the invention, slates of the general shape shown in Figure 1 may be produced. In this case there are two different geometrical shapes which go to make up the slate marked "1" as a whole.

A first flat geometrical shape consists of the said first rectangular surface 2 attached to the base of a second surface 3, which is substantially triangular.

The slate also includes a projecting element 4 forming a groove in accordance with the axis ofthe slate, the said grooveS being shut off at the apex of the triangle. The said projecting element 4constitutes a reduced supporting surfaceforfurtherslates arranged in zigzag configuration and partly overlapping it and extends to a small extentoverthe rectangular surface. This advantageous shape for the projecting elements prevents the capillary ascent of water and forms a reinforcementforthe slate, enabling itto be limited to a thickness 6 of 3.5 mm and thus rendered lighter in weight. The perforation 7 designed to accommodate a nail, for example, is advantageously positioned at the apex of the triangular surface and, in fact, in the reinforced portion, providing a thickness of about 4.2 mm.

The surface of the slate may be comparatively rough orcomparativelysmooth, accordingtothe state of the surface of the mould, and form the closest possible imitation ofthe natural slate. Similarly, the edges may be cut or chamfered and the corners rounded.

The broken lines 8 indicate another slate placed in position.

Figure 2 shows a different embodiment of the present invention on a smaller scale. In this case the rectangular surface 2 is made up of a number of units 11,12,13, 12,13, separated from one another buy a groove 14 which imitates the joint between two slates ofthe usual sizes. The triangular surface 3 and the projecting element4 as a whole presentthe same configuration as in the previous case, exceptforthe difference in the dimensions. Furthermore, the projecting element is provided, in the portion extending over the rectangular surface on each side ofthe axis of symmetry of the slate with a hole 15 forming a supplementary securing means.

It should be notedthatthe invention is not confined to slates oftheshapes described and that the projecting element may be given any other desired shape providing the advantages offered by the present invention.

Claims (15)

1. Processforthe manufacture of slates, characte rized by the fact that it consists of the following stages: - crushing and grinding the slatewaste.

- sorting the crushed and ground particles according to size.

- selection of certain quantities of different granulometry.

- possible mixing of this charge with a preselected quantity of sand and then of chalk.

- addition of a suitable resin and hardening agentforthe formation of a comparatively fluid paste.

- transferofthesaid pastetoasuitablemould heatedto about40 C.

- withdrawal from mould after vibration of the latter and hardening of the paste.

2. Process in accordance with Claim 1, wherein the solid charge represented by the natural materials, has the following composition: - 18-24% by weight of slate particles in the granulometric range 16-28 mesh.

- 8-14% by weight of slate particles in the granulometric range 28-35 mesh.

- 7-13% by weight of slate particles in the granulometric range 35-48 mesh.

- 6-12% byweighhtofslate particles inthe granulometric range 48-65 mesh.

- 4-10% by weight of slate particles in the granulometric range 65-100 mesh.

- 9-15% by weight of slate particles in the granulometric range 100-200 mesh as well as 5-11 % byweight of sand.

- 19-25% by weight of powdered chalk, to which are addedthefollowing percentages in relation to the weight ofthe solid charge: 2-4% of Degussa hardener "HK", 15-18% of methacrylic resin of type 1370 from Degussa.

3. Process in accordancewith anyone of the preceding claims, wherein the solid charge has the following composition: - 21% by weight of slate particles ranging from 16to 28 mesh in particle size - 11% byweightofslate particles rangingfrom 28 to 35 mesh in particle size.

- 10% by weight of slate particles ranging from 35to 48 mesh in particle size.

- 9% by weight of slate particles ranging from 48 to 65 mesh in particle size.

- 7% by weight of slate particles ranging from 65 to 100 mesh in particle size.

- 12% by weight of slate particles ranging from 100 to 200 mesh in particle size, as well as 8% by weight of sand - 3% byweightofDegussahardener"HK"and - 17,5% by weight of methacrylic resin of type 137035from Degussa.

4. Process in accordancewith anyone of claims 1 and 2, wherein the mould is provided in advance with a preliminary coating consisting of a resin of type 1000 from Degussa, intended to form the protective surface coating of the slate.

5. Slate, having afirst surface which as a whole forms a rectangle, connected at its base to a second surfacewhich as a whole forms a triangle, the said slate being provided, on at least one of its face, in the position where it is overlapped by other slates after being placed in position, with a projecting element serving to supportthe said further slates.

6. Slate in accordance with Claim 5, further comprising on one face projecting elements or ribs designed to fit into corresponding hollowed-out parts of another face of a second slate.

7. Slate in accordance with anyone ofolaims 5 and 6comprising a projecting element which is symmetrical in relation to an axis of symmetry centered on the slate, the said projecting element partly overlapping the surface ofthe said triangle, forming a groove in the centre, in accordance with the axis of symmetry, the said projecting element partly extending overthe said first surface.

8. Slate, in accordance with any one of claims 5to 7, wherein that side of the first rectangular surface which is substantially parallel to the base of the triangleforming the second surface, is of a size similar to that of natural slates, preferably of the order of 20cm.

9. Slate, in accordance with any one of claims 5to 8, wherein that side of the first rectangular surface which is substantially parallel to the base of the triangle forming the second surface, is of a size which is a multiple ofthe corresponding dimension of the traditional slates, the individual units being separated by a groove provided in the said first surface.

10. Slate, in accordance with any one of claims 5 to 9, comprising perforations in suitable places in ordertoenableto be nailed to the roof, the said perforations being overlapped by the adjacent slates after being placed in position.

11. Slates, in accordance with any one of claims 5 to 10 having a thickness of 3,5 mm and wherein the projecting element extends by at least 0,5 mm, preferably 0,7 mm, beyond the surface ofthe slate.

12. Slate, in accordance with any one of claims 5 toll said slate consisting of a synthetic material made up as follows: - 17% byweightofslateparticlesinthegrain size range 16-28 mesh.

- 9% by weight of slate particles in the grain size range 28-35 mesh - 8% by weight of slate particles in the grain size range 35-48 mesh.

- 7% by weight of slate particles in the grain size range 48-65 mesh.

- 6% by weight of slate particles in the grain size range 65-100 mesh.

- 10% by weight ofslate particles in the grain size range 100-200 mesh.

- 6,5% byweightofsand - 19% byweightofsand - 19% byweightofpowderedchalk - 2,5% byweightof Degussa hardening agent "HK".

- 15% byweightofmethacrylicresinoftype 1370 from Degussa

13. Slate in accordance with anyone ofclaims 5 tc 11 said slate consisting of a synthetic material including a suitable pigment.

14. Processforthe maufacture ofslatessubstan- tally as hereinbefore described.

15. Slate substantially as hereinbefore described with reference to the accompanying drawings.