Composition for protective coating and method of reception

 

(57) Abstract:

Use: protective coating of large equipment in shipbuilding, building, automotive, hydraulic engineering. The inventive composition includes a solution of polymethylphenylsiloxane in toluene (calculated on dry substance) 25 34; tetrabutoxide 5 - 11; silicate 42 60; a metal oxide 1 5; silicon carbide 3 10. Get composition by mixing a solution of polymethylphenylsiloxane in toluene with tetraethoxysilane, the introduction of the mixture of silicate, metal oxide, silicon carbide and machining the resulting suspension in a ball mill. Drying time to degree 3 0.5 h, the adhesion of the coating by the method of cross-hatch test 1 score, the strength of the coating at the impact of 3.5 to 4.0 N * m) bending strength 1 to 3 mm, the hardness unit M 3 0,4 0,6. 2 S. p. f-crystals, 2 tab.

The invention relates to the field of materials science of coatings, in particular to compositions based polyorganosiloxanes curing at ambient temperature. The composition is intended to obtain a weather-resistant anticorrosive coatings on metal surfaces and can be used in cases where it is impossible to education coverage in terms of viewcommentar, supply engineering.

Known compositions based polyorganosiloxanes consisting of three components: a polymeric binder, silicates and oxides [1] After curing, the composition forms a single spatial-linked structure, which can be considered as a system of thin polymer films, fixed between the particles of the other components. The set of properties to ensure reliable application of coatings, largely achieved through the introduction of silicate components forming the polymer siloxaneimide communication, as well as oxides catalyzing this process and to improve adhesive performance.

Gap siloxane bonds in the silicate lattice and the polymer molecule is under the influence of external energy influences, including mechanical:

Si-OSi + Si-OSi __ surface silicate (C) the molecule of the polymer (p)

__

Reaction

__+H2O< / BR>
i-OH+R-i __ i-O-Si + RH proceed with sufficient weight when heated or in the presence of crosslinking agents and are primarily related to the stage of spatial crosslinking (curing) of the composition based on polyorganosiloxanes.

When producing the e most probable reaction, flowing through the first scheme, the formation of primary chemical bonds between the polymer base and silicate components. Subsequent cross-linking, leading to the formation of a common spatial patterns, is in the process of curing the composition under the influence of high temperatures or in the presence of crosslinking additives at a temperature of 10-30aboutC.

In the case of the known curing the composition under the influence of high temperatures is possible to obtain high quality coatings with high physical-mechanical properties. However, the formation of such coatings is the process is labor - intensive, as it requires heat treatment in a special program: temperature rise at the rate of 1,5-2aboutWith a minute to 270aboutWith isothermal holding at that temperature for 2.5-3 hours and subsequent cooling rates up to 5aboutWith in a minute. Failure mode heat treatment leads to the formation of internal defects and bubbles through the allocation and intramolecular condensation of water, which causes the degradation of polyorganosiloxanes and, as a consequence, the degradation of physical and mechanical properties. The disadvantages of the compositions are also limited is rasiwasia bulky parts and hardware.

Closest to the composition according to the invention is known composition for the protective coating comprising a solution of polymethylphenylsiloxane in toluene, tetrabutoxide (0.6), the silicate and metal oxide. A method of manufacturing the composition provides for the introduction of tetraethoxysilane in the composition that was used only as an independent composition. This hardener in it injected directly before coating [2]

However, obtained on the basis of known composition, the coating has low mechanical strength, hardness and adhesion to the substrate and on the physico-mechanical properties inferior to the coatings on the basis of compositions, curable under the influence of high temperatures.

An object of the invention is the improvement of physical and mechanical properties of the coating, which consists in increasing the strength characteristics, hardness and adhesion to the substrate.

The increase in strength characteristics, hardness and adhesion of the coating to the substrate is achieved in that the composition for the protective coating comprising a solution of polymethylphenylsiloxane in toluene, tetrabutoxide, silicate and metal oxide optionally contains a carbide, PU glue is,

dry ve - society 25-34 Tetrabutoxide 5-11 Silicate 42-60 the metal Oxide 1-5 silicon Carbide 3-10

The increase in strength characteristics, hardness and adhesion to the substrate is achieved by the fact that in the method of manufacturing the composition, which consists in mixing a solution of polymethylphenylsiloxane in toluene, tetramethoxysilane and inorganic components and machining the resulting suspension in a ball mill according to the invention, first, a mixed solution of polymethylphenylsiloxane in toluene with tetraethoxysilane, and then the mixture is injected inorganic components.

It is an unconventional sequence of mixing the components of the composition when used in its tetraethoxysilane in significant concentrations leads to the formation of a homogeneous gel and final processing in a ball mill provided quality compositions with typical paint consistency.

A high concentration of tetraethoxysilane in the composition after its application to the metal surface as volatilisation of organic solvent provides a more active passage of interesterification reactions of tetraethoxysilane polymethyl the binding of Oh-groups, located on the surface of silicates and oxides. As a result of such chemical interactions formed with high physical and mechanical properties of highly structured coating with a high content of compounds of the formula: MexTimSinOm+n+ .

Using tetraethoxysilane in high concentrations is an obvious solution, as before, the concentration of tetraethoxysilane limited, seeking to avoid what is happening when blending tetraethoxysilane with a suspension containing polymethylphenylsiloxane, silicate and oxide gelation. It was believed that the gelation of making the composition unsuitable for its intended use. However, the use of tetraethoxysilane in high enough concentrations, possibly due to the special way of mixing components in the manufacture of the composition. Adding in the process of mixing the inorganic components in a pre-prepared mixture of tetraethoxysilane with a solution of polyorganosiloxane in toluene leads to uniform gelation of the suspension without formation trudnoobrabatyvaemyh clots and guarantees after machining in a ball mill, obtaining Y, which, if the machining is capable of not be ground to particle size of 10-20 microns as, for example, silicate, and up to 1-2 microns, provides uniform distribution of the filler in the smallest cavities spatial-linked structure of the resulting layer, increasing its hardness.

It is established that the optimum content of tetraethoxysilane in the composition should be 5-11 wt. When the content of tetraethoxysilane less than 5 wt. the composition dries slowly and the resulting coatings have a low hardness. The increase in the concentration of tetraethoxysilane more than 11 wt. leads to the formation of a very hard coating with large internal stresses that have poor adhesion to the substrate.

Exceeding the upper limit of the recommended range of concentrations of polymethylphenylsiloxane in the composition increases the drying time and reduces the hardness of the coating. When the concentration of polymethylphenylsiloxane less than 25 wt. significantly deteriorate the strength characteristics of the coating, reduces its hardness and adhesion to the substrate.

Limitations in the composition concentration of silicate and silicon carbide on the upper limit of respectively 60 and 10 wt. obpl is thinned content component in the composition for the silicate 42 wt. and for silicon carbide 3 wt. explained on the basis of maintaining a sufficient hardness of the coating.

The limits of the content of the metal oxide is selected in accordance with the practice of its introduction in organosilicate materials to impart color. When the content of the oxide of the metal is less than 1 wt. the composition does not have a pronounced colour. With the introduction of metal oxide in excess of 5 wt. the effect of dyeing remains at that level, in addition, the coating becomes less elastic, resulting in the decrease of Flexural strength.

The composition was prepared as follows.

Ball mill load solution polymethylphenylsiloxane in toluene and with mild stirring into it tetrabutoxide. Then the mixture was added in powder form other components. The formed gel was processed in a ball mill for 1-3 days. After machining, the composition is ready and has a characteristic to paint consistency. It is bottled in a tightly closed glass or metal bowl.

In the laboratory studies have been conducted of the properties of coatings obtained from compositions, distinguished for the quantitative content of comparity was 100 μm.

P R I m e R s 1-14. The compositions of examples are given as described above. Formulations of compositions according to the examples given in table. 1, properties of coatings based on them in the table. 2.

The use of the composition according to the invention and the manner of its reception allows to produce curable at ambient temperature coatings, comparable in its physical and mechanical properties physical and mechanical properties of the coatings cured at high temperatures. In addition to the high strength characteristics, hardness and adhesion to the substrate of the coating based on the composition of the invention also possess good electrical and physical properties.

1. Composition for protective coatings, vlychada solution polymethylphenylsiloxane in toluene, tetrabutoxide, silicate and metal oxide, characterized in that it further contains silicon carbide in the following ratio, wt.

The solution polymethylphenylsiloxane in toluene calculated on the dry matter 25 34

Tetrabutoxide 5 11

Silicate 42 60

The metal oxide 1 5

Silicon carbide 3 10

2. A method of obtaining a composition for a protective coating, which consists in mixing a solution of polymethylphenylsiloxane in toluene the mill, wherein the first mixed solution polymethylphenylsiloxane in toluene with tetraethoxysilane, and then the mixture is injected inorganic components, and the components are taken in the following ratio, wt.

The solution polymethylphenylsiloxane in toluene calculated on the dry matter 25 34

Tetrabutoxide 5 11

Inorganic components:

Silicate 42 60

The metal oxide 1 5

Silicon carbide 3 10

 

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