Method for preparing a mold for manufacturing an engineered stone, a mold for manufacturing an engineered stone and a method for manufacturing an engineered stone

Abstract

A method for preparing a mold (1) for manufacturing an engineered stone (20) that comprises the steps of: - providing a mold (1) for manufacturing the engineered stone (20); - coating at least one surface, preferably all of the surfaces, of the mold (1) with a precursor (11, 17) of a release film (10); - forming the release film (10) from said precursor (11, 17); wherein said step of forming the release film (10) from said precursor (11, 17) occurs at a temperature below 100°C, preferably at room temperature.

Description

[0001] Method for preparing a mold for manufacturing an engineered stone, a mold for manufacturing an engineered stone and a method for manufacturing an engineered stone

[0002] The invention relates to a method for preparing a mold for manufacturing an engineered stone, a mold for manufacturing an engineered stone and a method for manufacturing an engineered stone. In particular, the engineered stone of the invention is often known on the market as quartz.

[0003] Within the context of the present invention, an engineered stone is a material that comprises an inorganic filler like crushed stones, sands or other minerals but also recycled ceramic or glass, bonded by means of a cured resin, most preferably a thermosetting resin like unsaturated polyester resin. More in detail, with engineered stone is intended a composite material formed by an inorganic filler or a stone like material bonded together by means of a cured binder that it is cured at low temperature, wherein with low temperature is intended a temperature below 500 °C.

[0004] Therefore, in the past years methods for manufacturing engineered stones were developed in order to reduce costs and provide a more environment friendly product. A well-known example of such methods is represented by the so called Bretonstone® technology described, for example, in the document, WO 2007 / 138529. Said document discloses a method for manufacturing an engineered stone which comprises the step of: providing a inorganic filler, for example by grinding sand or quartz; mixing the stone or stone like material with a binder, for example a resin powder, in order to obtain a mixture; depositing the mixture in a mold of a press, having shape and dimension similar to those of the final article; press the mixture applying vacuum, with the accompanying application of a vibratory motion at pre-established frequency; the semi-product obtained is then hardened by means of a heat curing process to obtain the engineered stone; the engineered stone is then subjected to finishing steps like cutting or polishing.

[0005] During manufacturing the mixture for forming the engineered stone is loaded into a mold made of rubber and comprising a container body and a lid to cover the container body. The mixture remains inside the mold at least during the compacting phase, i.e. during the application of vacuum and vibration, and during the curing step. In order to avoid undesired interaction between the mold and the mixture during curing, a release film is provided inside the mold, to cover the surface thereof, and to prevent the contact between mold and mixture. Normally, said release film can be formed by a PVA (polyvinyl alcohol) film coating the inner surfaces of the container body and the inner surface of the lid. The PVA film is formed by providing a water based PVA solution on the surfaces to be coated and by subsequently drying the mold. Each mold can be reused, but after a certain number of manufacturing cycles the mechanical performances of the rubber forming the mold can deteriorate thereby causing defects in the engineered stone. A typical defect caused by this deterioration is the so called “waves”, i.e. deep depressions on the surface of the engineered stone, probably due to an excessive deformation of the bottom of the container body during the compaction step. In order to limit the deterioration of the mold, US 10,195,795 B2 proposes to coat the surfaces thereof with a solid releasing film. Nevertheless, during private research the inventors have found that by means of the solid film it could be difficult to obtain a good coating of all the surfaces of the mold, in particular at the corners between the bottom side and the lateral wall of the cavity. In addition, for the application of the solid film, it may be necessary to use complex machinery requiring continuous maintenance.

[0006] Thereto, the present invention, in its various independent aspects, is directed to solve one or more of the problems of the prior art described above.

[0007] According to its first independent aspect, the invention relates to a method for preparing a mold for manufacturing an engineered stone, the mold comprising at least a main body having outer walls defining an open cavity adapted to receive a mixture for forming said engineered stone, the method comprising the steps of: providing a mold for manufacturing an engineered stone; coating at least one internal surface of said cavity, preferably all the internal surfaces of said cavity, with a precursor of a release film, preferably in liquid form; forming a release film from said precursor; wherein said step of forming release film from said precursor occurs at a temperature below 120°C, preferably below 100°, even more preferably below 90°C, for example at room temperature. During private research, the inventors have found that by subjecting the molds to multiple heating cycles it is possible to observe a reduction of the hardness of the mold. Thereto, by avoiding excessive heat exposure during preparation of the mold, the life of the mold can be prolonged. It is noted that within the context of the present invention, the temperature at which said forming of the release film occurs is at least the temperature at the surface of said cavity to be coated and / or the temperature of said precursor during the step of forming the release film.

[0008] Said step of forming the release film can be performed according to several measures, that can be performed either alone or in combination each other, some of which are described below.

[0009] According to a first measure said precursor of a release film comprises a radiation curable substance and the method comprises the step of radiation curing said precursor of a release film. By radiation curing the precursor of a release film is possible to reduce the exposure of the mold to heating steps and prolonging the life of the mold, as this curing can easily be performed at room temperature without stressing the mold. In the preferred embodiment of this first measure, the radiation curable substance can be a UV radiation curable substance. UV curing, occurring at room temperature, may help prolonging the life of the mold. Alternative radiation can involve electron beam or excimer radiation. According to the first measure, the precursor of release film can be a liquid substance comprising at least monomer and / or oligomer, and optionally additives, like catalysts, antifoaming agents, wetting agents, initiators. Said monomer and / or oligomer can be adapted to polymerize under the action of said radiation for forming a solid polymeric material that forms the release film. In the preferred embodiment of this first measure, the radiation curable substance can be a silicone-based substance. Silicone can show good release properties with the substances of the mixtures of the engineered stone and, in particular, with the binder thereof, especially when the binder comprises unsaturated polyester resin. According to its second measure, said precursor of a release film is a fluid substance, preferably liquid, for example a solution of the release film in a solvent or a suspension of the release film in a suspending vehicle, said release film can be formed by drying said fluid substance and wherein said drying is performed at a drying pressure below atmospheric pressure, i.e below 1013,25 mbar, for example said drying pressure can be below 750 mbar, for example below 500 mbar, even more preferably below 250 mbar. By reducing the pressure under the atmospheric pressure, the evaporation temperature of the solvent and / or of the suspending vehicle of the fluid substance can be reduced so that the impact of the drying step on the life of the mold can be limited.

[0010] In the preferred embodiment according to this second measure, said fluid substance is a water-based solution or a water-based suspension. In some embodiments of this second measure, the drying pressure can be selected so that the boiling temperature of water can be below 90°C, preferably below 80°C, more preferably below 60 °C. For example, said boiling temperature of water can be between 40°C and 80°C. In some embodiments, the drying pressure can be below 701 mbar, preferably below 473 mbar, more preferably below 208 mbar. For example, said drying pressure can be between 72 mbar and 473 mbar. According to said second measure, said drying can be performed by IR (Infra-Red) radiation and / or by hot air convection and / or by microwave radiation.

[0011] According to its third measure, said precursor of a release film is a fluid substance, preferably liquid, for example a solution of the release film in a solvent or a suspension of the release film in a suspending vehicle, said release film can be formed by drying said fluid substance and wherein said drying is performed by microwave drying. The liquid substance has to comprise one or more components, preferably the solvent and / or the suspending vehicle thereof, being adapted to interact with microwave to heat up the liquid substance and perform the drying. Thereto, in the preferred embodiment, the liquid substance is preferably a water-based solution or suspension. Microwaves interacts with the water molecules while the material forming the mold can be transparent to microwaves so that heat exposure of the mold can be limited. It is noted that in the preferred embodiments according to the second and third measure, the release film can comprise PVA (polyvinyl alcohol).

[0012] In a special embodiment of the invention, said precursor of the release film can be or comprise one or more recycled components. For example, the PVA contained in said precursor can be a recycled PVA. Most preferably, said recycled PVA can derive from a starting release film used in a method for manufacturing an engineered stone. Thereto the method according to any of the preceding measures, can comprise the steps of: collecting a starting release film; shredding said starting release film; forming a precursor of a release film, preferably by suspending or dissolving said shredded releasing agent into a suspending agent or a solvent to obtain a liquid substance. In this way, it could be possible to improve the circularity of the method of the invention thereby reducing its environmental impact. The starting release film to be recycled can be according to several possibilities that can be performed alone or in combination each other, two of which are herein described:

[0013] According to the first of said possibilities the starting release film has been formed in the mold starting from a precursor, for example in a method according to the first independent aspect.

[0014] According to a second of said possibilities, the starting release film is a solid release film that has been provided in the mold already in the solid state, for example taken from a roll, or a mixture thereof. It is noted that a starting release film according to said second possibility can have a higher molecular weight than the starting release film according to the first possibility and / or a molecular weight higher than the molecular weight of the final release film. Starting from a release film having a higher molecular weight the final one, can provide the advantage of leading to the desired molecular weight in the final release film at the end of the method, thereby compensating any possible risk of deterioration that can happen during the process, for example because of heating during curing of the engineered stone. Preferably, in the preparation of said liquid substance it is preferably added a surfactant, for example glycerol, with the aim of improving the surface tension of the liquid substance so that the application of the liquid substance in the mold is improved. This is particularly beneficial in case the starting release film is according to the second possibility and comprises a relatively high molecular weight. Preferably the surfactant represents between 0.5 and 2.5% by weight of the liquid substance.

[0015] Preferably, the precursor, in the form of a liquid substance, can comprise the releasing agent, preferably in the form of the shredded starting release film, in an amount of at least 70% by weight of the liquid substance, for example between 75 and 90% by weight of the liquid substance itself. Said liquid substance comprises the solvent or suspension liquid, most preferably water, in an amount of at least 10% by weight of the liquid substance, for example between 10 and 20% by weight of the liquid substance. The liquid substance can additives like leveling agent and / or antifoam agent.

[0016] In case the liquid substance is a solution, the method can preferably comprise the step of stirring a mixture of at least the release film, in particular the shredded starting release film, and the solvent at a temperature comprised between 70 and 90 °C.

[0017] It is noted that in some embodiments according to any of the preceding measures, the method can form release film with a weight above 40 g / sqm (grams per square meter), preferably equal or above 50 g / sqm.

[0018] In some embodiments according to any of the preceding measures, the coating step can be performed by spraying. Spraying can provide for a homogeneous distribution of the precursor on each internal surface of the cavity and also in the corners.

[0019] In accordance with any of the measures of the first independent aspect, the mold can preferably comprise a container body and a lid. The container body can comprise bottom wall and lateral walls defining the cavity of the mold wherein said lateral walls surround an opening of said cavity. The lid can preferably be substantially flat and adapted to close the opening of the cavity. The mold is preferably made of rubber, preferably EPDM rubber. In some embodiment, said rubber made mold can comprise fiberglass reinforcement, for example a fiberglass mold in the bottom wall and in the lid.

[0020] The method of the first independent aspect can be part of a method for manufacturing an engineered stone. Thereto according to its second independent aspect the invention can relate to a method of manufacturing an engineered stone can comprise the steps of preparing a mold, preferably as per the method of the first independent aspects in any of the described measure and / or embodiments; providing a mixture for forming an engineered stone in the prepared mold; compacting the mixture in the mold; curing the mixture in the mold.

[0021] In the preferred embodiments the inorganic filler comprises mineral material like any kind of stone, sands, siliceous mineral material, for example quartz, silica sand, clay, feldspar cristobalite granite, talc or calcareous mineral material, for example, calcium carbonate, marble, gypsum. The inorganic filler can also comprise ceramic, glass, metals and other inorganic material, for example recycled materials. The filler can be in form of powder, granules, shards, grains, aggregates or any other particulate form although granules and powder forms are preferred. Preferably the filler is in powder form having an average particle dimension lower than 45 pm, preferably lower than 20 pm. The filler is preferably at least the 80% by weight of the mixture, preferably more than the 85% and more preferably more than 90%. According to another embodiment of the invention the filler can be in form of aggregates, grains and / or granules having a particles size distribution between 0,1 and 6,5 mm, preferably between 0,1 and 2mm, 0,1 and 0,7 mm. In the most preferred embodiment, the filler is composed by a combination of powder and grains, for example said combination can comprise at least 60 wt% of grains and / or granules and between 20 to 35 wt% of powder form wherein, for example, the granules have a particles size distribution between 0, 1 and 6,5 mm and the powder have an average particle dimension lower than 45 pm, preferably lower than 20 pm. In the most preferred embodiment of the invention the filler is composed for its majority, i.e. at least 50%weight, and more preferably mainly consist, of an inorganic material that is based on silicon (Si). Silicon based material like siliceous minerals and glass show a good affinity with the binder so that the final bonding can be improved. In some embodiments, crystalline silica, feldspar or kaolin can constitute preferred choice for the inorganic filler, or at least for a majority of the filler, as they can show a relatively white color. In some embodiments, glassy and / or amorphous inorganic fillers can be preferred for forming the majority of the inorganic filler as they can reduce the amount of free crystalline silica dust in manufacturing and / or working of the decorative element.

[0022] The binder is a curable substance that is configured to be cured thereby bonding together the particles of the stone or stone like material. The binder can be in any form, i.e. liquid, solid, gel or any form that is suitable to be mixed with the filler and to be homogeneously dispersed within. In some embodiments, powder form can be preferred as reduce the possibility of contamination of the mixture from other substance, that can occur using wet form of binders. The binder can be an organic substance, for example a resin. In the most preferred example the binder can be a thermosetting resin.

[0023] In the most preferred embodiment the binder comprises, preferably substantially consists of, polyester resin preferably unsaturated polyester resin. Less preferred alternative solutions for the binder comprise acrylic resin, epoxy resin, polyurethane, rubber, vinyl ester resin or the like. The binder is preferably less than the 20% by weight of the mixture, preferably less than the 15% and more preferably less than 10%. Polyester resins have shown a very high coupling capability with the inorganic filler.

[0024] It is noted that the mixture can also comprise additives, like for example coupling agents, catalyst or reagents to activate or speed up hardening of the binder, and / or temporary bonding agent like glues or thermoplastic resins that temporarily bonds the stone or stone like material. In the most preferred example, the additives comprise at least a silane- based coupling agent to further enhance the bonding between silicon-based filler and the binder, preferably the unsaturated polyester binder. Moreover, the additive can comprise crosslinkers and / or catalysts to activate and / or accelerate curing of the binder. It is noted that in the any of the embodiments of the method, it is preferable that the step of compacting the mixture can involve a vibro-vacuum compaction step.

[0025] After the compacting step, the mixture in the mold is carried to a curing station. The cure of the binder can be obtained by means of radiation, heat, chemical curing or other suitable techniques. In the preferred embodiment, the curing step is conducted at a temperature below 500°C, for example below 200°C, for example at room temperature. In particular, in the preferred example the curing step can be thermally activated and continues in an exothermic reaction. The activation of the curing of the binder can occur at a temperature below 100°C.

[0026] In some embodiments, during the curing step the film of releasing agent sticks to the engineered stone.

[0027] After the step of curing, the engineered stone is extracted from the mold. After the engineered stone is extracted from the mold the method can comprise one or more finishing step, preferably calibration, polishing and / or squaring. In some embodiments, during one or more of said finishing steps said release film is removed from the engineered stone.

[0028] In some embodiments, the method can comprise a step of restoring the mold for a new preparation method. Said restoring step can comprise the step of cleaning the mold and / or remove residues of the film of releasing agent. Said residue can be collected and recycled for preparing a new precursor.

[0029] It is noted that that the fact that the precursor is obtained starting from a recycled used release film can represent an inventive aspect independently from how the release film is generated, and in particular from the temperature at which the release film is formed form a precursor. Thereto, the present invention according to its third independent aspect, relates to a method for forming a precursor of a release film for being used in the manufacturing of engineered stone, that comprises the steps of: collecting a starting solid release film; shredding said starting release film; forming a precursor of a solid releasing agent, preferably by suspending or dissolving said shredded releasing agent into a suspending agent or a solvent to obtain a liquid substance. Two important characteristics of preferred embodiments of the third independent aspect are that: said starting solid release film ; starting release film is a solid release film that has been provided in the mold already in the solid state, preferably said starting release film has a molecular weight being higher than the final release film to be obtained and / or the step of forming said precursor comprises adding a surfactant to the obtained liquid substance, for example glycerol, preferably to represent between 0.5 and 2.5% by weight of the liquid substance. Preferably said starting release film has been used in a first line for manufacturing an engineered stone, and the obtained precursor is used on a second line for manufacturing a release film. It is noted that said precursor can be used in a method for preparing a mold or in a method for manufacturing an engineered stone according to any of the first and second independent aspects. It is further noted that the precursor, liquid substance and the lines or the method for manufacturing engineered stone of said third independent aspect can comprise one or more of the features described in relation to the first and second independent aspect.

[0030] With the intention of better showing the characteristics of the invention, in the following, as an example without any limitative character, several preferred forms of embodiments are described with reference to the accompanying drawings, wherein:

[0031] Figure 1 shows a mold for manufacturing an engineered stone in an axonometric view; Figure 2 shows some steps of the method for preparing the mold of figure 1 according to a first embodiment the first independent aspect;

[0032] Figure 3 shows some steps of the method for preparing the mold of figure 1 according to a second embodiment;

[0033] Figure 4 shows some steps of the method for preparing the mold of figure 1 according to a third embodiment;

[0034] Figure 5 shows some steps of a method for manufacturing an engineered stone.

[0035] Figure 6 shows a some steps in a method for recycling a releasing film according to another independent aspect of the invention. Figure 1 shows a mold 1 to be used for manufacturing an engineered stone. The mold 1 comprises a container body 2 having a bottom wall 3 and a plurality of side walls 4 defining an open cavity 5. The mold 1 further comprises a lid 6 for closing said open cavity 5. The mold is made of EPDM and fiberglass and is adapted to configured to shape the engineered stone in the form of a slab.

[0036] Figure 2 shows some steps in a method for preparing the mold 1 according to a first embodiment of the invention. The method comprises a first step SI of applying a precursor of a release film 10 in the internal cavity 5 of the mold 1. In step SI said precursor in form of a liquid substance 11 is sprayed by one or more dedicated nozzles

[0037] 12 on all the internal surfaces of the cavity.

[0038] The liquid substance 11 is a water-based solution of PVA (polyvinyl alcohol) comprising 84.5% weight basis of PVA, 14.5 % weight of water and 1 % weight of glycerol.

[0039] The method of figure 2 further comprises a step S2 of drying the liquid substance 11 to form the release film 10 of PVA. The step of drying is performed in a drying environment

[0040] 13 provided with means 14 for reducing the pressure inside said drying environment 13, for example a vent, so that drying is performed at a pressure below atmospheric pressure, preferably below 701 mbar. In these conditions the drying temperature of the water contained in the liquid substance 11 is below 90 °C. In the example drying is performed by means of IR (infrared) lamps 15.

[0041] After drying step S2 the water contained in the liquid substancel l is removed and the releasing film 10 made of PVA is obtained.

[0042] Figure 3 shows some steps of the method according to a second embodiment. Said second embodiment differs from that in figure 2 in that the drying step S2 is performed by means of microwave radiation generated by means of microwave emitters 16. As the EPDM rubber forming the mold 1 is transparent to microwaves, the mold 1 itself doesn’t heat up to a temperature causing deterioration of the rubber. In addition, since the microwaves acts substantially only on the water contained in the liquid substance 11, said drying can be performed at a temperature at 100°C or above and it is not needed to reduce the pressure in the drying environment 13 below the atmospheric pressure.

[0043] Figure 4 shows some steps of the method according to a third embodiment. In this embodiment the precursor of the release film 10 is a liquid substance 17 that comprises a silicone monomers and UV curing initiators. The method of this third embodiment comprises a step S3 of curing the precursor for forming the releasing film 10. The S3 is performed at room temperature by means of UV (ultraviolet) radiation emitted by UV lamps 18.

[0044] It is noted that figures 2, 3 and 4 show some steps on a line for preparing the container body 2 of the mold 2. Nevertheless, although not shown in the figure the same steps are performed on the lid 6 on the same line or on a separate, preferably parallel line.

[0045] Figure 5 shows some steps of a method for manufacturing an engineered stone 20 using the mold 1 prepared in any of the methods of figure 2 to 4. The method of figure 5 involves a first step S4 of depositing a mixture M comprising inorganic filler, for example silica oxide, and a binder, for example unsaturated polyester resin, inside the container body 2 of the mold 1.

[0046] Subsequently the lid 6 is placed on the container body 2 to close the mold 1. The mold 1 is placed in press 21 for performing a compacting step S5 under the action of vibration vacuum.

[0047] After compaction the mold 1 containing the mixture M is placed in an oven 22 for curing the binder at a temperature below 200°C, in a curing step S6.

[0048] After curing the engineered stone 2 is removed from the mold 1. The releasing film 10 normally remains attached to the engineered stone 20, but a part of it can remain attached to the mold 1 and the mold is then cleaned. Figure 6 shows some steps of a method for preparing the liquid substance 11 by recycling a used releasing film 30.

[0049] The method of figure 6 starts with some steps for manufacturing the engineered stone substantially identical to the steps S4, S5 and S6 illustrated in figure 5 with the sole difference that the mold 1 is prepared by means of a solid releasing film 30, made of PVA, taken from a roll 31.

[0050] After curing, the engineered stone 20 is extracted from the mold 1 and the used release film 30 is collected in a collecting step S7. The used release film 30 is then shredded into a particulate material 32 in a shredding step S8.

[0051] The method then continues with a step S9 wherein the particles 32 of the shredded release film 30 are solubilized in water 33 at a temperature between 70 and 90 °C and mixed with glycerol to obtain the liquid substance 11 with the composition described in relation to figure 2. The obtained liquid substance can then be used in steps SI and S2 of figures 2 and 3.

[0052] The present invention is in no way limited to the hereinabove described embodiments, but such solution may be realized according to different variants without leaving the scope of the present invention.

[0053] Further, as is clear from the content of the description, the present invention relates to one or more of the items as listed below:

[0054] 1. A method for preparing a mold for manufacturing an engineered stone that comprises the steps of: providing a mold for manufacturing an engineered stone; coating at least one surface, preferably all of the surfaces, of the mold with a precursor of a release film; forming the release film from said precursor; wherein said step of forming the release film from said precursor occurs at a temperature below 100°C, for example at room temperature.

[0055] 2. The method according to item 1, wherein said precursor of the release film comprises a radiation curable substance and wherein the method comprises the step of radiation curing said substance promoter of a release film.

[0056] 3. The method according to item 2, wherein the radiation curable substance can be a UV radiation curable substance.

[0057] 4. The method according to item 2 or 3, wherein the radiation curable substance can be a silicone-based substance.

[0058] 5. The method according to item 1, wherein said precursor of a release film can comprise a water-based solution of a release film, wherein said release film can be formed by drying said precursor and wherein said drying occurs under at a drying pressure below atmospheric pressure, for example said drying pressure can be below 750 mbar.

[0059] 6. The method according to item 5, wherein the drying pressure can be selected so that the boiling temperature of water can be below 90°C, preferably below 80°C, more preferably below 60 °C.

[0060] 7. The method according to item 5 or 6, wherein said boiling temperature of water can be between 40°C and 80°C.

[0061] 8. The method according to any of items from 5 to 7, wherein the drying pressure can be below 750 mbar, preferably below 50 mbar, more preferably below 250 mbar.

[0062] 9. The method according to any of items from 5 to 8, wherein said drying pressure can be between 72 mbar and 473 mbar.

[0063] 10. The method according to any of items from 5 to 9, wherein said drying can be performed by IR (Infra-Red) radiation and / or by hot air convection. 11. The method according to item 1, wherein said precursor of a release film can comprise a water-based solution of a release film, wherein said release film can be formed by drying said precursor and wherein said drying occurs via microwave drying.

[0064] 12. The method according to any of items from 5 to 11, wherein the release film can comprise PVA (polyvinyl alcohol).

[0065] 13. The method according to any of the preceding items, wherein the precursor is in liquid form.

[0066] 14. The method according to any of the preceding items, wherein the precursor comprises a leveling agent.

[0067] 15. The method according to any of the preceding items, wherein said release film is formed with a weight above 40 g / sqm (grams per square meter), preferably equal or above 50 g / sqm.

[0068] 16. The method according to any of the preceding items, wherein the coating step can be performed by spraying.

[0069] 17. The method according to any of the preceding items, wherein the mold can comprise a lower body and an upper body.

[0070] 18. The method according to item 17, wherein the lower body can comprise a container body having a bottom wall and lateral wall, whereas the upper body can comprise a lid, for example a flat lid.

[0071] 19. The method according to any of the preceding items, wherein the mold can be made of rubber, preferably EPDM rubber.

[0072] 20. The method according to any of the preceding items, wherein said rubber made mold can comprise fiberglass reinforcement, for example a fiberglass mold in the bottom wall and in the lid. 21. The method according to any of the preceding items being part of a method for manufacturing an engineered stone.

[0073] 22. The method according to any of the preceding items, comprising the steps of collecting a starting release film; shredding said starting release film; forming the precursor of the release film preferably by suspending or dissolving said shredded releasing agent into a suspending agent or a solvent to obtain a liquid substance.

[0074] 23. A method for manufacturing an engineered stone comprising the steps of: preparing a mold as per the method according to the preceding items; providing a mixture for forming an engineered stone in the prepared mold; compacting the mixture in the mold; curing the mixture in the mold.

[0075] 24. The manufacturing method according to item 23, wherein the mixture comprises an inorganic filler and a binder, the binder being preferably a resin.

[0076] 25. The manufacturing method according to item 24, wherein the filler is preferably at least the 80% by weight of the mixture, preferably more than the 85% and more preferably more than 90%.

[0077] 26. The manufacturing method according to item 24 or 25, wherein the binder is a is a thermosetting resin, preferably unsaturated polyester resin.

[0078] 27. The manufacturing method according to any of items from 24 to 26, wherein the binder is preferably less than the 20% by weight of the mixture, preferably less than the 15% and more preferably less than 10%.

[0079] 28. The manufacturing method according to any of items from 24 to 27, wherein mixture can also comprise additives, like for example coupling agents, catalyst or reagents to activate or speed up hardening of the binder.

[0080] 29. The manufacturing method according to any of items from 23 to 28, wherein the step of compacting the mixture can involve a vibro-vacuum compaction step. 30. The manufacturing method according to any of items from 23 to 29, wherein the curing step is thermally activated and continues in an exothermic reaction, preferably said activation occurs at a temperature below 200°C.

[0081] 31. The manufacturing method according to any of items from 23 to 30, wherein during the curing step the film of releasing agent sticks to the engineered stone.

[0082] 32. The manufacturing method according to any of items from 23 to 30, wherein the step of curing, the engineered stone is extracted from the mold.

[0083] 33. The manufacturing method according to item 32, wherein the method comprises one or more finishing step, preferably calibration, polishing and / or squaring.

[0084] 34. The manufacturing method according to item 33, during one or more of said finishing steps said release film is removed from the engineered stone.

[0085] 35. The manufacturing method according to any of items from 23 to 34, that comprises a step of restoring the mold for a new preparation method.

[0086] 36. The manufacturing method according to item 35, wherein said restoring step can comprise the step of cleaning the mold and / or remove residues of the film of releasing agent.

[0087] 37. A method for manufacturing engineered stones that comprises:

[0088] - preparing a mold in a first mold preparation line configured for placing a solid release film, for example taken from a roll, in a first mold;

[0089] - manufacturing a first engineered stone in said first mold;

[0090] - collecting used solid release film from said first mold and / or said first engineered stone;

[0091] - forming a precursor of a release film, preferably in form of a liquid substance, from said used solid release film;

[0092] - using said precursor for forming a release film on a second mold in a second mold preparation line, wherein second mold is preferably prepared in a method according to any of the items from 1 to 21.

Claims

Claims1. A method for preparing a mold (1) for manufacturing an engineered stone (20) that comprises the steps of: providing a mold (1) for manufacturing the engineered stone (20); coating at least one surface, preferably all of the surfaces, of the mold (1) with a precursor (11, 17) of a release film (10); forming the release film (10) from said precursor (11, 17); wherein said step of forming the release film (10) from said precursor (11, 17) occurs at a temperature below 100°C, preferably at room temperature.

2. The method according to claim 1, wherein said precursor (17) of the release film comprises a radiation curable substance (17) and wherein the method comprises the step of radiation curing said radiation curable substance to obtain the release film (10).

3. The method according to claim 2, wherein the radiation curable substance (17) is a UV radiation curable substance (17).

4. The method according to claim 2 or 3, wherein the radiation curable substance (17) is a silicone-based substance.

5. The method according to claim 1, wherein said precursor of a release film comprises a water-based liquid substance (11) containing a release film forming substance, wherein said release film is formed by drying said precursor and wherein said drying occurs at a drying pressure below atmospheric pressure, preferably said drying pressure being below 750 mbar.

6. The method according to claim 5, wherein the drying pressure is selected so that the boiling temperature of water is below 90°C, preferably below 80°C, more preferably below 60 °C.

7. The method according to claim 5 or 6, wherein said pressure is selected so that the boiling temperature of water is between 40°C and 80°C.

8. The method according to any of claims from 5 to 7, wherein the drying pressure is below 750 mbar, preferably below 50 mbar, more preferably below 250 mbar.

9. The method according to any of claims from 5 to 8, wherein said drying pressure is between 72 mbar and 473 mbar.

10. The method according to any of claims from 5 to 9, wherein said drying is performed by IR (Infra-Red) radiation and / or by hot air convection and / or microwave drying.

11. The method according to any of claims from 5 to 10, wherein the release film (10) comprises PVA (polyvinyl alcohol).

12. The method according to any of the preceding claims, wherein the precursor is in form of a liquid substance (11, 17).

13. The method according to any of the preceding claims, wherein said release film is formed with a weight above 40 g / sqm (grams per square meter), preferably equal or above 50 g / sqm.

14. The method according to any of the preceding claims, wherein the coating step is performed by spraying.

15. The method according to any of the preceding claims, wherein the mold (1) comprises a container body (2) and a lid (6).

16. The method according to claim 15, wherein the container body (2) comprises an internal cavity (5), and wherein said precursor (11, 17) is coated on the surfaces of said cavity (5) and on a surface of said lid (6) closing said cavity (5).

17. The method according to any of the preceding claims, wherein the mold (1) is made of rubber, preferably EPDM rubber.

18. The method according to any of the preceding claims, comprising the steps of collecting a starting release film (30); shredding said starting release film (30); forming the precursor (11) of the release film preferably by suspending or dissolving said shredded releasing agent into a suspending agent or a solvent to obtain a liquid substance.

19. A method for manufacturing an engineered stone (20) comprising the steps of: preparing a mold (1) as per the method according to the preceding claims; providing a mixture (M) for forming an engineered stone in the prepared mold (1); compacting the mixture in the mold; curing the mixture in the mold.

20. A method for manufacturing engineered stones that comprises:- preparing a first (1) mold in a first mold preparation line configured for placing a solid release film (30), for example taken from a roll (31), in a first mold (1);- manufacturing a first engineered stone (20) in said first mold;- collecting used solid release film (30) from said first mold and / or said first engineered stone;- forming a precursor of a release film, preferably in form of a liquid substance (11), from said used solid release film (1);- using said precursor for forming a release film on a second mold in a second mold preparation line, wherein second mold is preferably prepared in a method according to any of the claims from 1 to 18.

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