CS213938B1 - A method of preparing artificial stone for sculptural and stonework objects - Google Patents

Abstract

The method of preparing artificial stone for sculptural and stone-making objects consists in adding 0.5 to 5 wt. % of the compound RSi /ORz/^, where R is amino or epoxyalkyl with C-^ to Cg and R^ alkyl with C to Cg, to quartz sand with a grain size of 10"® to 3 mm, in an organic solvent, e.g. toluene, acetone or ethanol, after which the mixture is homogenized and left to stand for 3 to 72 hours at a temperature of 0 to 30 ° C. Then 5 to 15 wt. % of epoxy resin in a concentration of 25 to 100 wt. % in an organic solvent, e.g. toluene and a hardener in an amount of 7 to 10 wt. % per weight of epoxy resin are added to the mixture. The resulting malleable mixture is then processed in a conventional manner. The method according to the invention can be used advantageously in sculptural and stone-making practice, e.g. in the restoration and reconstruction of sculptural objects, honeycombs of buildings and stone elements made of sandstone and marl. The essence of the invention is explained by three examples.

Description

The present invention relates to a process for the preparation of artificial stone for concrete objects.

Natural stone is very often the main building material of historically and monumentally important buildings. The choice of natural stone, especially for sculptural and stonecutting elements, was heavily governed by its effort to treat and therefore various types of sandstone and the marlwood in the Prague area are most often used for this purpose. However, the easy workability of these types of stones also results in their low resistance to weathering.

Natural stone exposed to masonry or sculptural objects g of stone elements to weathering for centuries has been damaged in various ways. It has changed the surface of the stone and its structure, there has been a more or less rapid transformation of the physical and mechanical properties of the stone, or even its aesthetic appearance. Especially the last time the intensity of the spawning has multiplied. In addition to natural influences, stone objects are also damaged by the carelessness of people. For restoration and refinement of missing parts, in the restoration practice cements made of classical materials containing uncoupled original material, lime and cement are still used.

The main disadvantage of this classical sealant lies mainly in the different chemical composition of the sealants, so that the joint of the old and new material does not disturb, the formation of cracks and eventually the seal falls off with a part of the original material. The alkalinity of the binder of the seal changes the color of the pigments in a short period of time and, moreover, white colored efflorescence forms on the surface of the sealant and cannot be removed by water migration. As a result, white objects appear on the objects, which aesthetically disturb the effect of the work of art.

A significant improvement is the use of a new type of artificial stone, where the lime binder component is replaced by an epoxy resin (U.S. Patent No. 139,733). The advantages of this sealant are indisputable. However, long-term experience in exterior application has shown that this type of artificial stone is to a minor extent disturbed by the action of UV rays by the interaction of water on the interface between the epoxy binder and the silicate material where there is only adhesion by physical forces. Substantially more advantageous properties of artificial stone could be achieved by replacing relatively weak physical forces with Chemical bonding, which guarantees the durability of composite materials. For this purpose, organosilicon compositions may be used which, on the one hand, form a chemical bond between the silicate material and the organosilicon coupling agent, such as aminopropyltriethoxysilane.

The chemical bond is formed after hydrolysis of the alkoxy groups to the silanols and their subsequent condensation with the hydroxyl groups of the silicate materials. On the other hand, the linker has the ability to react with its organofunctional groups with the chemically active groups of the epoxy resin to form a chemical bond. The formation of real chemical bonds is evidenced not only by theoretical assumptions, but also by practical tests of physical properties carried out in the laboratory where the compressive strength was 46% higher than without the use of an organosilicon composition. Another important advantage that indicates the use of an organosilicon binder is the increased hydrophobicity of the binder as well as the sealant. This will also limit the water absorption and the course of the chemical reactions leading to decomposition.

SUMMARY OF THE INVENTION The present invention provides a process for preparing an artificial stone for sculptural and masonry objects, wherein 0.5-5% of RSi (OR 2 ^z ) p is added to silica sand of 10 "to 3 mm grain where R is amino or epoxialkyl and up to C 8 and R * is an alkyl of up to C 8, in an organic solvent such as toluene, acetone, ethanol, the mixture is homogenized and aged for 3 to 72 hours at 0 to 30 ° C, then 5 to 15% is added to the mixture wt. epoxide resins in a concentration of 25 to 100% in an organic solvent, e.g.

The following is an example of an embodiment of the process for preparing an artificial stone according to the invention.

Example 1

Kg 1 kg of quartz sand with a particle size of 0.02 to 0.6 mm was added 20 g of fine 6 2 silica with a particle size of "ZLO" mm and a specific surface area of 100 in / g and 2 g of aminopropyltriethoxysilane. After 15 minutes of vigorous stirring and a technological break of 48 hours, during which the chemical reactions take place, to the treated mixture was added §0 g of epoxy resin with 7 g of diethylenetriamine as a hardener. Four cubes with an edge length of 5 cm were prepared from the ductile mixture as test pieces by not blowing into a decomposing metal mold on a surface treated with a micro-layer release agent (methyl silicone oil having a viscosity of 200 cP). Compressive strength was measured on test specimens and compared to samples without the use of an organosilicon bonding agent made of the same material by the same procedure.

compressive strength of samples without fastener

MPa average value of 23.8 MPa compressive strength of samples with fastener

MPa average value 35.0 MPa

From the above table, it is clear that the samples prepared using an organosilicon binder had a 46% higher compressive strength.

Example 2

To 10 kg of loose material consisting of 6 kg of silica sand with a grain size of 0.03 to 0.2 mm and 4 kg of sand with a grain size of 0.2 to 0.6 mm was added 150 g of very jean silica of particle size 10 ^- ? mm, 10 g of aminoethoxypropyltrimethoxysilane and 3 g of red iron oxide pigment. The mixture was stirred for 20 minutes and then left to stand for 2 days. After a technological break, 750 g of epoxy resin with 50 g of diethylenetriamine as a hardener were added. The thoroughly kneaded ductile mixture was infused into a three-part gypsum form of a baroque plug, which was treated with a microlayer release agent (methyl silicone oil with a viscosity of 2.00 cP). At a technological break of about 24 hours at a temperature of 18 ° C, the ductile mixture cured and the plug was removed from the mold. After retouching, removal of joints and filling of insufficiently compressed spots, the plug was exposed to weather conditions. No defects were observed after 4 years of outdoor exposure;

Example 3

1 g of epoxipropyltributoxysilane was added to 500 g of a bulk mixture consisting of 400 g of silica sand with a grain size of 0.05 mm to 0.2 mm and 100 g of sand with a grain size of 0.2 to 0.6 mm,

1.5 g of silica with particle size 10 " mm and 0.1 g of black iron oxide pigment. The mixture was stirred for 15 minutes and then left to stand for 2 days. Then the bulk mixture was mixed with 50 g of epoxy resin and 4 g of diethylenetriamine as a hardener. A well with a diameter of 15 cm and a depth of 3 cm in a sandstone block was first soaked with a 1% solution of N-aminopropyltriethoxysilane in ethanol and after 24 hours a freshly prepared ductile mixture was infused therein. After curing, which took about 48 hours, the sandstone bleach was exposed to the weather. After 4 years there were no cracks between the seal and the original material and no aesthetic defects.

The method according to the invention can be used advantageously in sculpture and stoning practice, for example in the restoration and reconstruction of sculpture objects, building shells and sandstone and marl stone elements.

Claims (1)

Způdob preparation of artificial stone and stone for sculptural objects, characterized in that the silica sand having a grain size of 10 * ^- ^ to 3 mm, are added 0.5 to 5 wt. % of the compound RSi (OR '4, where R is amino- or epoxy-alkyl to C8 and R * is alkyl to C8, in an organic solvent such as toluene, acetone or ethanol, the mixture is homogenized and allowed to stand for 3 to 72 5 to 15% by weight of epoxy resin in a concentration of 25 to 100% by weight in an organic solvent such as toluene and a hardener in an amount of 7 to 10% by weight % of the epoxy resin and the resulting malleable mixture is processed in a conventional manner.