MC824A1 - Artificial stones and their manufacturing process - Google Patents

Description

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.70.824

. 368 DEC 2 £ &

PATENT FOR INVENTION

Artificial stones and their manufacturing process

MEDIL S.p.A.

The present invention relates to artificial stones and their manufacturing process.

It is known to manufacture artificial stones using, as filler, powder, grains, flakes, or chips of natural stone, and, as binders, cement, hydraulic lime, or gypsum. The mixture of filler and binder is molded and extracted from the molds after it has hardened.

(i) The resulting artificial stones are generally fragile, highly hygroscopic, not very compact, and it is difficult to machine and polish them to a high sheen. Their resistance to decomposition in air and light leaves much to be desired.

The processes known until now do not allow for the production of artificial marble slabs that exhibit the attractive veining and luster of genuine marble. The present invention aims to provide a process for manufacturing artificial stones that are resistant to decomposition in air and light and that can be easily machined and polished to a high sheen.

The products obtained with this process surpass in resistance and beauty not only known artificial stones, but also many natural stones. In its later development, the process allows the production of artificial marble, which reproduces the colors, veins and bands, as well as the luster of precious marbles, in such a perfect way that it

25. In practice, it is almost impossible to distinguish them from these.

The process according to the invention consists of the operations of intimately mixing crushed natural stones, thermosetting resins and, if coloring the mixture is desired, pigments, optionally with the addition of a catalyst for the resin and a dispersant for the pigments; filling molds with the mixture thus obtained; heating the mixture under pressure until it has completely hardened; and extracting the artificial stones thus obtained from their molds.

35 and, if necessary, their subsequent machining.

In a further development of the process for creating artificial marbles, a number of the aforementioned mixtures are used, corresponding to the color components that the finished artificial marble must exhibit. Therefore, each of the aforementioned mixtures forms a color component in the finished artificial stone.

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whose color is determined by the pigment that has been added to it.

These color components are mixed together only to the point where they still appear in the composition as more or less clearly discernible bands. To achieve the effects of veining and marbling characteristic of natural marbles, changes in the layers and shapes of these component bands are produced in the composition by transferring the composition one or more times. The best results were obtained with color components comprising, by weight percentage, 70 to 90%, preferably 82 to 85%, of natural stone powder, advantageously limestone powder; 28 to 9%, advantageously 15 to 11%, of resin, for example a mixture of melamine resin with another aminoplastic resin in the ratio 60:40 to 90:10.

Advantageously 80:20, or better still a melamine resin, using para-toluenesulfonic acid, oxalic acid, phthalic anhydride, or preferably zinc sulfite as a catalyst. For coloring, on average 2 to 20%, preferably 0.20 to 1.66%, of pigments with dispersants are used.

For hardening the composition poured into molds, pressures of between 140 and 180 kg/cm² are used, with an initial temperature of between 10 and 30°C, a hardening temperature of between 145 and 160°C, after which the extraction of the finished artificial stones is carried out after their cooling to a temperature of between 25 and 40°C.

To facilitate understanding of the process, we will describe below the example of the production of artificial marbles 30 having a white base component.

For the production of this component, 85% by weight of powdered white limestone is mixed with approximately 15% powdered melamine resin and 0.15% zinc sulfite as a catalyst for the resin, until a homogeneous mixture is formed. Advantageously, the limestone is derived from the grinding of saccharoidal limestones to a particle size where, on a 400 mesh sieve, no residue remains, and on a 16,400 mesh sieve, a maximum residue of 10% remains. The limestone must have a moisture content below 4%. For the preparation of each color component, one mixes...

intimately 83.5% by weight of white limestone of the aforementioned maximum particle size and moisture content, with 15% by weight of powdered melamine resin, 0.15% by weight of powdered zinc sulfite as a catalyst, 0.5% by weight of a mineral oxide as a pigment, and approximately 0.3% by weight of the sodium salt of naphthalene sulfonic acid as a dispersant. The pigment particle size is advantageously chosen so that, on a sieve of 16,400 meshes per cm², the residue does not exceed 0.1%. Each color component is mixed until it achieves a uniform color.

The doses of color components needed to create the desired type of marble are poured into a mixer, the bottom of which narrows into a funnel. After a brief stirring, the mixture, with its components forming clearly discernible colored bands and veins, is discharged through this bottom into another container.

* - s of a funnel-shaped base, and of this into molds. Here the color components have already taken, thanks to repeated transfers, the conformation of the veins and marbling of real marbles— 20 bres.

The molds are placed in a hot press. The pressure increase in the press is regulated so that the maximum pressure of 155 lcg/cm² is reached only when the temperature of the hot press plate has risen to approximately 25°C. At constant pressure, the hot plates are now heated to 150°C. This temperature is maintained for the entire duration of what is known as the "firing" of the product. This duration depends on the thickness of the artificial stone article to be produced, and it must be taken into account that at the aforementioned temperatures and pressures, the composition in the molds undergoes a thickness loss of 35 to 40%. Once the "firing" is complete, the hot press plates are cooled to approximately room temperature, after which the press is opened and the marble slabs are removed from their molds.

For easier separation of artificial stones from their molds, it is advantageous to coat or spray the molds with a separating agent before filling them with the mixture. Experience has shown that an aqueous emulsion of oaraffin and natural wax solutions are particularly suitable.

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and artificial? Butylphthalate, isobutylphthalate, chlorophthalate, paraffin oil diluted with eutoluene or benzene, mixtures of paraffin and carnauba oils diluted with benzene or eutoluene. The plates thus obtained can be easily cut.

The machine and polish to a reflective sheen. Their resistance, compared to that of natural stones, is as follows:

- resistance to bending 21.3 kg/cm^ (limestones with a granular structure, eue u ;cçf/ cm4- , a 10' granular structure 140 kg/cm^)

- impact resistance 0.30~0.70 kg/m (natural marbles 0.20-

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- Wear resistance with a 4 mm thickness loss (limestone)

•' • a compact structure S mm; with structure—

•''15 (granular structure 10 mm, granite 4 mm)»

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It goes without saying that the process described above is by no means limited to the production of artificial stones that must give the impression of natural stones. On the contrary, the process can be generalized for the production of agglomerates which, by their color combinations and the contours of their color components, can create entirely new aesthetic effects. Since the mixture of the filler with its binders and pigments is so complete in the color components that, by firing and pressing, they already provide agglomerates with the desired mechanical resistance, one can abandon the imitation of natural marbles in favor of other effects, and yet one can replace the mixture and the...

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successive changes in the layers of the components through these process operations tending towards the realization of other designs. If desired, each color component could also be poured directly into the molds. To extend the coloring possibilities, for certain colors, inorganic pigments can be replaced by organic pigments.

It is understood that the process of the invention is not limited in any way to the production of artificial stones in the form of slabs, since it can also be applied to other forms of agglomerates.

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starting from natural stones .r. -Jz.—: •. ■'*-• ;• -". '"... ; ' in s and using a binder for these pl..r..;_e .v.: being

D characterized by .13 eaee eue. cc.. ..." and .. /..r Cw pouero or these grains of natural stones, on -rn! rie 1 :e rc-sines therrr.odur— cissabi.es advantageously ce —^ e^„—_• — ~,..,„.eçuOs

2. Process for the production of artificial stones. They are characterized by the following operations:

10 — preparation of a possible solution by intimately mixing these natural particles in gravy, this thick or granular 5 of thermosetting resins and a catalyst for these 5,.;

- filling molds with the mixture thus obtained5

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until the resins harden and a solid agglomerate forms?

- extraction of the resulting agglomerate after cooling®

20 3» Process according to claim 2, characterized in that it contains the mixture, in addition to natural stone seeds or powder, artificial resins and catalyst; also contains pigments and, optionally, a means of dispersing them

25 4® A method according to claim 1, characterized in that it comprises the following operations 2

_

preparation of

'a number of these components of that one ^

each

component consisting of a singular mixture... - as possible

homogeneous, made of natural stones in powder or grain form,

30

of therrriodur cisable resins with a catalyst for these resins

born in the shape of powder ir s r, c cha eue c c- r.i posing Gts-n'c co j. wax by the ad-

edition of a pigment;

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transferring the desired components into a mold;

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heating of the color components* contained in the rnou-

35

the pressure at the imperial ciradue-i.j-errvan*c c_rc

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until the obt

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harden it-

sow this -^a. resin;

- extraction of the: ag ~ iomer after its r o :: r o i d i s s e rr. e n t • ®

5. Procedure, according to the .... e on r<ûc%.iriôé by the

40. The fact that between the preparation of the color components and their

filling in molds - these; or. interposed the following operations

— rupture-iissage cvzc ...zs • ts ~e "; sa :a '. - color. cans 2g

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"These components are connected."

10 o.«Procedure suivcr/c _ ®unî çu— aancua. aes revanc.icat_or.s pre—

ceoen-ces ; caractérisa sr. c j eut cnaque c o z, z z z >—~ ce cou_cur compris /O a S a% en p-oics ^ uvanaagauwement oa a gs7j en poacs y es poudre ou. grains de pierres naturelles • ce préférence de calcine;1* 28 to 9% en'weight-, advantageously li a 11% an pid„, de resin A5 thermocurcissabla en poudra, do préférence poudre de resin mé-1 ami ni que 5 .un catalyst, pour la resin., de préféreras de zinc sulfite; 2. à O- 20% en ocras, ca préférence 113 L 0.11% en

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poicls<, de pagmenus avec des a-" u~.es casasrsanas zz'zzzz ceux—aa*

'7» Process following lsune eu al designed a- cas r avand_eations 2, 20 4- or 5 y characterized by ^.s rare au a- — e ma„anga contained cans the mold is heated from an initial temperature of 10-00 Cj a 'ceirroercL'cure ae curcassee.ant -ae ^osj°G sous ores —

sion crO—eo*> aases * c-c.^cverrar.^ du aa.rcassement ae a-* ag—

the resulting agglomerate is then allowed to cool to 25-4G°C

25 before? its extraction from the mold

8. The process according to claim 7, characterized in that the treatment is carried out by increasing the pressure exerted on the mixture to a maximum pressure of 140-180 kg/cm², and this maximum pressure is maintained throughout the treatment.

9. A method according to claim S, wherein the pre-

Maximum pressure is exerted on the contents of the mold only when these contents have reached a temperature of 70-100°C, or advantageously 90°C*.

35-101 A method according to any one of the preceding claims

cédentes ,• characterized by the fact that it is used as a separating agent? to spray or scrape the molds before filling them with the mixture, :_s natural waxes of silicones iiciiiuGs5 eu .oun tw ^ ac ..1 n_.a... a_'_pnta„aae j 40 du dioct yipnt^ici.t e ^ ce r * n e i 1 o ce parcirrana a-— a e ^ et ae ore®

30

Claims (4)

xerenca une enuiSion aquavs-s c.o "1. i. © I?n.i ^ 3 G.i- w--L.— c-.i -•... 1. o, to one of the revenà.icatisnà .1 u "jrocvCo conxornu en J. containing .'added word 4 A 1. $0 ... (crossed-out word references) José C uJR A U .Industrial Property Consultant!® 58, Bou!. Princess Charlotte, 28 MONTE-CARLO By proxy of tf£ï& Il $j $