FR3036397A1 - PROCESS FOR SOLID SHAPING OF GRANULAR MATERIAL - Google Patents

Abstract

The present invention relates to a solid forming method of a granular material comprising the following steps: - providing a granular material whose particle size is between 100 μm and 750 μm, - preparing a hardening resin composition whose viscosity is lower at 800 mPa.s at a temperature of 23 ° C, - mixing the granular material with the hardening resin composition, - forming of the resulting mixture, - allow the hardening of the resin.

Description

The present invention relates to a method of solid forming and solidification of granular product, sand type, in the form of plate, paver, slab or solid block formed or molded. The solid shape obtained can then be machined, cut or even finely bored with a high level of detail in any desired shape and without modification of its external appearance or its strength.

We now know objects, such as slabs, made of reconstituted stone. The manufacture of such reconstituted stone objects begins with the mixing and pouring of stone mortar into molds or formwork. It is based on the use of crushed limestone and hydraulic binders such as white cement and hydraulic lime. A "standard" base composition of a limestone mortar comprises 3 volumes of crushed limestone 0/4 or 0/6, 1 volume of white cement, added with a water-repellent mass such as a silicone derivative (for the 20 exterior slabs and stones exposed to permanent moisture), natural pigments and water. The reconstituted stone thus obtained contains only naturally occurring mineral materials, unlike many of the counterfeit and reconstituted stones of the market which contain resins, fibers and other constituents and adjuvants. Slabs or other objects of reconstituted stone are intended for masonry, architecture and interior or exterior decoration, siding, cornices, pillars and walls, fountains and other stone objects and objects around the house or garden. Although the appearance and feel of the objects thus formed are close to natural stone, they are not suitable for cutting, boring, boring and fine fitting. Indeed, as soon as you cut, size, mill or plant such parts, the mineral matrix tends to crumble in the corners. Thus the making of small articles with fine details is not possible. Polymeric concretes, which are composite materials resulting from the polymerization of a monomer mixture within a mixture of aggregates and cement, are also known. The properties of polymeric concrete differ greatly depending on the preparation conditions. For a given type of polymeric concrete, the properties are dependent on the resin-type polymeric binder as well as the content and distribution of the aggregate particles. The most commonly used resins for polymeric concrete are unsaturated polyester resin, methyl methacrylate, epoxy resins, polyurethane resins and urea formaldehyde resin.

Generally, more than 75-80% volume in the polymer concrete is occupied by the aggregates. Typically, the aggregates are composed of particles of two sizes, on the one hand particles of size of the order of 5 mm and more, and on the other hand of fine particles, as well as microparticles of silica and cement, and this to fill the voids left between the large particles. The amount of resin generally varies between 10 and 20% by weight of the composition and the mechanical strength is dependent on the amount of resin. In addition, the more the composition comprises fine particles of cement, the more the amount of resin will have to be increased because of the increase in the specific surface area associated with the use of such materials (M. C. Ribeiro S., P. R.

3036397 3 Nôvoa, A.J. M. Ferreira, and A. T. Marques, "Flexural performance of polyester and epoxy polymer mortars under severe thermal conditions," Cement and Concrete Composites, vol. 26, no. 7, pp. 803-809, 2004).

The objects formed of polymeric concrete have the particularity of a high hardness and a strong adhesion to the supports once dry and hard. In addition, the curing phase of these concretes is generally quite long. These concretes are well adapted to the masonry but little to the manufacture of parts to be reworked, that is to say drilled, cut, bored. In addition, the surface and touch of objects made of polymer concrete are very smooth and without any texture. Obtaining a textured surface requires chemical or mechanical processing which makes the processes for obtaining textured parts complex and expensive. The artificial stones are made of marble particles or silica particles mixed with a resin-type binder. A method of manufacturing slabs or blocks is described in document WO2006079585 and provides for the mixing of aggregates with a polymeric binder associated with very fine quartz particles (ie 400 mesh or 37 μm), the rolling on a plane support followed by vacuum compression associated with vibratory motion. The resins described are polyester and epoxy resins or methacrylate. Due to the presence of fine particles increasing the specific surface to be coated by the resin, in order to obtain an acceptable mechanical strength, the amount of resin is of the order of at least 10% by weight of the finished product . In addition, various problems are associated with the resins which, on the one hand, age poorly in terms of discoloration or present risks of solvent emanation. In addition, as with polymeric concrete objects, artificial stones have a smooth, untextured surface. Finally, the method described in WO2006079585 is complex because it requires heating, vacuum compression and a vibratory motion system. Products called "carpet of stone" exist and consist of aggregates coated with a binder resin type.

However, since these products are intended for floor coverings, they are permeable and porous, which is not desirable for all applications in which it is desired to protect the product from impregnation with liquids. Finally, the particle size of the particles prevents any fine cutting, machining or drilling. Finally all these processes relate to inorganic particles or aggregates and nothing provides for the agglomeration and the solid forming of organic granular composition. Finally, in none of the products of the prior art, the texture of the granular product is retained on the finished product in solid form and it is difficult to recognize the product both visually and to the touch. Thus, there is a need for a process for quickly and easily granulating a granular material, particularly in the form of a slab or slab, in such a way that on the one hand the mechanical strength of the finished product is acceptable, that the finished product can be cut, drilled, reamed, adjusted and finely while maintaining a surface roughness that allows to recognize both the sight and the touch the granular material implemented.

Thus, the present invention relates to a method for solid shaping of a granular material comprising the following steps: providing a granular material having a particle size of between 100 μm and 750 μm; preparing a composition of hardening resin whose viscosity is less than 800 mPa.s at a temperature of 23 ° C, - mixing the granular material with the hardening resin composition, - forming of the resulting mixture, - allow the hardening of the resin. The granular material used in the process according to the invention may be a mineral material and may be siliceous in nature, such as quartz, granites, porfides, basalt, quartzites, siliceous or calcareous sand such as marbles, dolomites, colored stones, for example. The granular material is used in the form of sand or granulate. The nature, the dimensions and the granulometric scale of the granular material are chosen according to the aesthetic aspects and the physico-mechanical characteristics that one intends to obtain in the finished products.

In a particular embodiment, the granular material is sand, in particular sea or river sand, in particular rinsed and washed sea sand. Such a granular material has been rinsed and washed repeatedly to remove any traces of organic debris or mineral salts that may interfere with the curing of the resin. The washing can be carried out with a natural soap or a commercial surfactant. The washing may be preferably with demineralised water. In a particular embodiment, the granular material has a particle size greater than 100 μm and less than less than 750 μm, more particularly less than 650 μm, more particularly still less than 500 μm, and even less than 400 μm. In a particular embodiment at least 60%, particularly at least 75%, more particularly at least 80%, more particularly at least 90% of the particles of the granular material have a particle size of less than 750 μm, more particularly less than 650 pm, more particularly also less than 500 pm, or even less than 400 pm.

In a preferred embodiment, at least 60%, especially at least 75%, more particularly at least more preferably at least 90% of the particles have a particle size of between 50 and more particularly between 50 and 400%, more particles and 500 μm. more particularly between 100 and 400 μm. In a preferred embodiment, at least 80% of the particles have a particle size of between 50 and 500 μm, more preferably between 50 and 400 μm, more particularly between 100 and 400 μm. In a preferred embodiment, at least 90% of the particles have a particle size of between 50 and 500 μm, more preferably between 50 and 400 μm, more particularly between 100 and 400 μm. The percentages given with respect to the granulometry of the granular material are percentages by weight. They correspond to the mass ratio of the rejection of one or more sieves relative to the total mass of the sample tested, when measuring the particle size, as explained below. The particle size is determined by a test consisting in classifying the different grains constituting the sample using a series of sieves, nested one on the other, whose opening dimensions are decreasing from top to bottom and range from 1 mm and 50 μm in increments of 100, 150 or 250 μm. The granular material studied is placed in the upper part of the sieves and the classification of the grains is obtained by vibrating the sieve column. The dried material, of mass M, is poured onto a series of sieves selected such that the progression of the openings increases from the bottom of the column upwards. In the lower part, there is a sieve of 50 pm surmounting a sealed bottom to recover the fine elements that pass through the latter sieve. Sieving is considered to be complete when the rejections (part of the material retained on a sieve) do not vary by more than 1% between two sieving sequences. The mass percentage of refusal is determined as the ratio, expressed as a percentage, of the mass of dry material retained by one or more sieves, to the total initial mass of dry material passing through the mesh sieve. It is notable that the granular material is free of what is commonly referred to as fine particles such as those which can be found in polymeric cements or artificial stones and which serve to fill the interstices between them. particles of larger size. These fine particles, whose particle size is such that 80% of the particles are smaller than 20 μm, increase the surface area and involve the use of a larger amount of resin-type binder. This is not the case in the context of the process according to the present invention since the granular material used is virtually devoid of such fine particles. The granular material can also be an organic material. A suitable organic granular material may be selected from the group consisting of ground coffee, ground spices, seeds, semolina. Among the spices can be mentioned pepper, cumin, saffron, pepper for example. Among the seeds we can mention the seeds of poppy, linseed, sesame for example. Semolina includes wheat semolina, cornmeal or rye semolina, for example. It is appropriate that the particle size of such an organic granular material corresponds to the ranges specified above. When using granular, inorganic or organic material, it is preferable that it be as dry as possible. A moisture content of less than 2% by weight, particularly less than 1% by weight, is preferable for the mixing step with the resin and hardener assembly. The curing resin composition may be a composition comprising a resin and a curing agent (or crosslinking agent) or a thermosetting resin. Thus, the conditions used in the step of allowing the resin to cure may depend on the nature of the hardening resin composition. If the composition comprises a resin associated with a curing agent (or crosslinking agent), this step will consist primarily of allowing the crosslinking reaction to take place for the time and temperature required, as indicated by the method. manufacturer's instructions, in order to ensure hardening. This step can be facilitated by raising the temperature above room temperature to speed up the process but is not essential. In the case of using a curing resin composition composed of thermosetting resin, the curing step will consist mainly of ensuring a temperature suitable for the polymerization and solidification or curing of said resin. Regarding the determination of the viscosity of the resin composition, it is carried extemporaneously at the time of its implementation. In the particular case of a resin composition comprising a curing agent (or crosslinking agent), it is the viscosity of the mixture (resin + hardener) which is measured just after obtaining said homogeneous mixture and before it is incorporated into the granular material; without allowing the crosslinking to begin, which would result in increasing the viscosity. The hardening resin may be an epoxy or "epoxy" resin obtained by polymerization of epoxy monomers with a hardener (crosslinking agent) which may be based on acid anhydride, phenol or, more often, on amine (polyamine, aminoamide): these are three-dimensional polymers. The best-known representative of epoxy polymers is Araldite®. Epoxy (or epoxy) resins harden (irreversible reaction) in the presence of a hardener under the effect of heat. The hardening resin may be a polyester resin, particularly an unsaturated polyester (UP) resin. This is a liquid thermosetting resin to which a crosslinking agent (hardener) is added. The polyester resins are obtained by polycondensation of one or more glycols on one or more diacids, at least one of which contains an ethylenic double bond. The polycondensate obtained is soluble in certain vinyl, acrylic or allilic monomers capable of reacting later with the double bonds of the polycondensate. This solution is capable of copolymerizing under the action of heat. This hardening is ensured, in practice, by the provision of a catalyst (usually an organic peroxide), which leads to a three-dimensional crosslinking which is usually accompanied by an exotherm.

In the case of using an epoxy or polyester type hardening resin requiring the use of a crosslinking agent, it is added to the resin composition extemporaneously before the mixing step with the material. granular. The weight ratio of crosslinking agent (or hardener) / resin depends on the nature of the resin and is indicated by the manufacturer. Typically it can vary from 1/5 to 1/2 for example. The hardening resin may also be an acrylic resin such as polymethylmethacrylate which is a transparent thermoplastic polymer obtained by polyaddition whose monomer is methyl methacrylate (MMA). The resin composition may also be a polyisocyanate resin composition for example. In order to ensure adequate mixing and uniform coating of the granular material particles by the resin composition, optionally comprising a crosslinking agent, the viscosity of this composition is less than 800 MPa.s, especially less than 600 MPa. s, more particularly still less than 500 MPa.s, measured at 23 ° C approximately, just after extemporaneous preparation and preliminarily at the time of its mixing with the granular material. Such viscosity allows easy and intimate mixing of the resin composition with the entire granular material. In addition, the choice of this viscosity associated with the granulometry of the granular material and the resin / material ratio makes it possible to avoid phase shift and sedimentation of the resin in the bottom of the forming mold. Preferably, the step of mixing the granular material with the resin composition is carried out at room temperature, at about 22 ° C or below, in order to allow stirring, kneading and prolonged mixing while limiting the too early curing of the resin.

The amount of the resin composition relative to the amount of granular material may depend on the nature and viscosity of the resin as well as the nature and granulometry of the granular material.

For a granular material having a particle size such that at least 80% of the particles, in particular 90%, have a size of between 100 and 400 μm, the amount of resin composition may be between 3 and 6% by weight relative to to the total mixture, more particularly between 4 and 6% by weight, more particularly around 5% by weight.

The forming step allows the blend to be shaped into a form that can either be used directly after curing or be cut, machined, drilled, and modified after curing.

The forming may consist of casting and forcing the mixture obtained in the previous step into molds of various shapes and sizes, such as blocks, pucks, cubes of any size. The molds may advantageously be silicone molds for example.

Alternatively, the forming may consist of rolling the mass of the mixture between a roll and a plate or between two rollers in order to obtain a plate of desired thickness. The plate obtained may have a thickness of between 0.5 cm and 5 cm, particularly between 0.5 cm and 3 cm for example. After forming, curing is achieved by polymerization of the monomers of the resin in the presence of the hardener or crosslinking agent, or by the action of heat in the case of thermosetting resin.

Typically, the curing step is carried out by heating at a temperature between room temperature and 50 ° C for example, by steaming in a thermostatically controlled enclosure for example. In the case of using a thermosetting resin composition, without a crosslinking agent, it is the only heating at the appropriate temperature that will allow the resin to harden. The duration of this curing step depends on the nature and amount of the resin and is generally from 1 hour to 12 hours. The plates or shapes obtained can then be used as such or cut with a saw or jet of high pressure water for example or shaped using appropriate tools. The combined choice of a particle size of the granular material, particularly in a narrow range of particle size as hereinbefore indicated, combined with a viscosity resin as indicated and used, as specified above, allows the obtaining cured finished products which have a hardness and a mechanical strength quite satisfactory but while maintaining the appearance, the color and the texture of the granular material used. This choice makes it possible to ensure a compromise between a marked texture while allowing shaping by machining, boring, drilling, sanding, planing or cutting the product obtained in any shape while preserving a finishing detail of the angles and shapes. hollow quite satisfactory. This avoids obtaining a smooth resinous block and without relief. Thus, at the mere sight of the resulting slab or block product, the granular material used can be recognized because it is not embedded in an excess of resin or in an excess of fine particles forming a continuous phase. Conversely, it also avoids a friable block which could not be reworked, carved, chiseled, machined or which, if it were, would have coarse edges as can be the case with stone. reconstituted or stone carpet type products. It is thus particularly interesting to note that the blocks or plates of granular material solidified according to the process of the present invention can be shaped into individual pieces or into spare parts which can be used for making objects or decorative utensils such as handles. knives, forks, spoons for example, pen body, branches or frames 3036397 14 glasses or plates, knife holders, picture frames, jewelry for example. Thus the present invention is directed to a solidified granular material block obtained or obtainable by a process according to the present invention. In another embodiment, the present invention is also directed to the use of a solidified granular material block obtained or obtainable by a method according to the present invention for forming decorative objects or utensils. For the purposes of the present invention, the expression "shaping" is understood to mean machining, boring, drilling, milling, sanding, polishing, planing and / or cutting operations in order to obtain decorative object with 15 reliefs, aspects and textures fine and attractive. An advantage of the present process according to the invention, in particular in the context of the implementation of organic granular material is that the aromas and fragrances inherent in said material are preserved and somehow encapsulated by the resin and are then diffused slowly over a much longer period than if said materials were in the open air. It is thus possible to envisage odor release devices consisting of a solidified material according to the invention in which the granular material is an organic fragrant material. This is particularly remarkable in the case of use of fragrant seeds, fragrant seed powders, ground coffee, for example, or spice powders.

EXAMPLE SANDIFICATION OF SEA SAND Sea sand is used: it is rinsed three times with clear water to rid it of organic debris, then washed twice with industrial soap and finally rinsed with water. The sand obtained is sieved on a succession of sieves ranging from 1.4 mm to 50 μM. The sample retained has a particle size such that 95% of the grains have a size of between 100 and 400 μm. An epoxy resin composition is prepared by mixing resin (RESOLTECH 1070 S) with a suitable hardener (RESOLTECH 1074) according to the manufacturer's recommendation. The viscosity of the composition thus prepared is 400 MPa.s at 23 ° C. The sand is poured into the resin composition (resin + hardener) at a rate of 5% resin composition, by weight, based on the total weight.

The whole is kneaded at room temperature until a homogeneous mixture is obtained and molded into 15 cm x 2 cm x 2 cm silicone molds. The molds are put in an oven at 40 ° C for 6 hours. The bars obtained have the visual appearance and feel of sand without resinous appearance, without phase shift (that is to say without sedimentation of the resin at the bottom of the mold). These bars can be machined, cut and drilled without crumbling. The angles of the cuts and bores are sharp and do not show any burrs. Decorative pieces and utensils such as knife handles, pen bodies, key holders can be obtained by cutting, drilling, grinding. The granular aspect of the sand is preserved and the mechanical resistance is also ensured in order to support the classic manipulation of this type of objects.

Claims (9)

REVENDICATIONS1. To provide a solid-state granular material forming step: granular material having a particle size of 100 μm and 750 μm, - preparing a hardening resin composition having a viscosity of less than 800 mPa.s at a temperature of 23 μm. ° C, - mixing the granular material with the hardening resin composition, - forming of the resulting mixture, - allow the hardening of the resin. 2. Method according to claim 1, characterized in that the granular material has a particle size less than 650 pm, more particularly still less than 500 pm, or even less than 400 pm. 3. Method according to one of claims 1 or 2, characterized in that at least 90% of the particles have a particle size of between 100 and 500 pm, more particularly between 100 and 400 pm, more particularly between 100 and 400 pm . 4. Method according to preceding claims characterized in that the granular material has a moisture content of less than 2% by weight, particularly less than 1% by weight. 5. Method according to one of the preceding claims, characterized in that the resin composition is selected from the group consisting of epoxy resin compositions and polyester resin compositions, and comprise a crosslinking agent. 6. Method according to one of the preceding claims characterized in that the resin composition has a viscosity of less than 600 MPa.s, more particularly less than 500 MPa.s, measured at 23 ° C, at the time of its mixture with the granular material. 7. Method according to one of the preceding claims characterized in that the amount of resin composition is between 3 and 6% by weight relative to the total mixture, more particularly between 4 and 6% by weight, more particularly around 5% by weight. Block of solidified granular material obtained by a method according to one of claims 1 to 7. 9. Use of a block of solidified granular material according to claim 8 for the shaping of objects or decorative utensils.