L.G.Gerasimova, Doctor of Technical Sciences,
A.I. Nikolaev, Doctor of Technical Sciences,
Deputy director (Chemistry Institute of the Kola Scientific Center
of the Russian Academy of Sciences)

Building industry consumes a considerable amount of varnish and paint materials (VPM) of different purpose - about 60 % from their total production.

At the same time, for the finishing of surfaces inside accommodation VPM on water basis are mainly used, as a rule, and for outer works, VPM on organic basis are used more vastly. The positive effect (social-economic and esthetic) from the use of VPM is difficult to overestimate. That is why, one can hope that the amount of VPM and their assortment for construction will keep increasing in the future (1, 2).

The composition of VPM includes the pigment, the filler ad the linking agent, on the whole. Each of these components performs its functions. For example, the pigment gives the paint a frosting effect, the filler plays the role of the regulator of rheological attributes (flow property, ductility and so on), the linking agent creates a flowing dispersion with the following formation on the painted surface a film, dried for a certain time.

Recently, there have appeared a considerable amount of works dedicated to the synthesis of such pigment compositions-PC (white, coloured) which improve the paint and technical characteristics of varnish and paint coverings. Titanium, iron, aluminum, silicon and calcium compounds are more often included into such compositions (3, 4).

Researches at the Chemistry Institute of the Russian Academy of Sciences together with the "Apatite" Ltd. are being held in this direction. Apatite, nepheline and sphen concentrates, produced at the "Apatite" Ltd., contain all components necessary for the synthesis of PC, which is a very important factor for receiving cheap and high-qualitative varnish and paint production.

The nepheline is a mineral of a grey colour, containing aluminum, silicon and alkaline metals oxides (Na, K2O, Al2O3, 2SiO2)-a natural aluminum silicate, which can be used as the filler for fillings and primings after microdisintegration, similar to kaolin and talc. Aluminum silicates received on its basis refer to active fillers (AF) and the main effect from their use is the improvement of the distribution of pigment particles in the covering and the creation of microareas with different indices of retraction, which rises light scatter and improves spreading capacity. The positive effect of the AF's influence on the spreading capacity of enamel allows to reduce in the composition of the latter the content of pigment (titanium dioxide) by 15 % on average. Synthetic AF also increase stability of the varnish and paint covering to abrasion and water influence at the expense of its reinforcement. The reinforcement is provided by structuring of the linking agent with the active centers of AF. All abovementioned attributes of VPM, whose composition includes AF, allow to use paint systems both inside and outside accommodation. The coverings possess good decorative and technical attributes. Table 1 shows the conditions of AF receiving and its main attributes.

One of the variants of the AF synthesis is the following. The nepheline concentrate is gradually inserted into the sulphuric acid solution with the observation of conditions close to the formation of gel (5), dehydration of which is carried out with the help of 10-% ammonia solutions (op.1, 1a) or lime milk (op.2-4). The influence on concretion degree and suspension (V) pH filtration speed and concretion temperature has been researched. On finishing the process, the suspension has been filtered, the sediment washed from the soluble salts of alkaline metals and put to heat treatment at the temperature of 250-850 Co. At the same time, the white mass of the intermediate product turned into a slightly beige baked material, which has been disaggregated with the help of a vibration mill. The intensity of the beige shadow of AF goes up with the baking temperature increase, which can be explained with the increase of the degree of oxidation of iron (II), present in their composition, to iron (III). The deletion of the shadow, that is the rise of the filler whiteness can be achieved by adding before baking a phosphoric acid into the semiproduct at a rate of 1-1.5% P2O5 to the sediment weight.

Table 1. Receiving of active aluminum and silicate fillers

Composition of samples, % mass:
1. SiO2 - 39.54; CaO - 0.3; Al2O3 - 57.1; P2O5 - 0.34
2. SiO2 - 15.56; CaO - 15.4; Al2O3 - 20.0; P2O5 - 0.035

Under the heat treatment of sample 1, minor parts aggregation at the expense of their agglomeration takes place, and the structure thickens. Aggregated parts do not destroy under their decomposition. Their size changes in the broad interval from 10 to 100 mkm. The presence in Sample 2 of a considerable amount of hydrated calcium sulfate (mainly, gypsum) hinders parts' agglomeration under their baking. There takes place sediment structure loosening with the formation of labile aggregates, consisting of a considerable amount of monoparts, measuring 1-2 mkm. The availability of a considerable amount of pores on the surface of the aggregates increases its activity with regard to organic substances (oil absorption) and to water (water absorption) and hence, rises the spreading capacity index.

Analyzing what has been mentioned above, one can make a conclusion that, choosing AF synthesis conditions, one can regulate its attributes and, correspondingly, the attributes of VPM prepared on its basis (dispersive ability, stability to exposure, ductility, gloss and so on).

At the same time, AF is a filler and can be used together with a pigment only. The authors have researched the possibility of receiving such a composition in which an aluminum and silicate material serves as a core for a pigment coat. A thin ash fraction of heat stations has been taken as such a material, % mass.: SiO2 - 54-55; Al2O3 - 16-17; Fe2O3 - 15-17; MgO - 2.5-3.0. Ash, activated by a mechanical and chemical way, has been used for the synthesis:

-ash pounded to the size of parts (40-60 mkm) - a mechanical activation;

-ash treated with a sulphuric or hydrochloric acid solution - a chemical activation;

Under the chemical activation, for example, in the sulphuric solution with the concentration of acid 100-150 % g/l at the temperature of 65-75 Co, there takes place the lixiviation of iron compounds (III) by 20-25 % from the original one, as well as the destruction of agglomerates, which ash parts consist of, including parts with microvoids. At the expense of this, the specific surface area and free energy of parts raises (6). A hydrated iron (III) coat is put on the sediment activated in such a way. The process goes in a ferric sulfate solution (II) with an inconsiderable amount of free sulphuric acid at the oxidative regime at the temperature of 65-70 Co for 10-12 hours. After thorough cleaning, the received sediment is baked. At the same time, at the temperature of 100 o C, the sediment has a yellow or a light-yellow colour, at the to of 500-550 o C - red-brown, at 800-850 o C - yellow-brown. The researches of the development types of the pigment fillers in the compositions of serial VPM have given positive results (Table 2).

Table 2

Owing to the low content of water-soluble compounds in the ash pigment and the specific structure of its parts, it can also be used for receiving masonry paints on the latex basis. The coverings have good decorative attributes and are distinguished with a high stability to atmosphere influences.
The AF and ferrooxide pigment technology has passed a stage of experimental and industrial researches and is ready for launching. As for receiving of pigment products described above accessible and cheap raw materials are used (nepheline and the wastes of cogeneration plants), one can hope that VPM on their basis will also be much cheaper than serial building paints.

List of literature

1. State of the World Varnish and Paint Industry in 1997 (according to the materials of the press-conference SERE) // 
Varnish and Paint Materials and Their Use. 1998. №12. P. 26-27.
2. Saprykin M.V., Konin S.A. The Economic Aspects of the Development of the Consumer Market of Varnish and Paint Materials in 1999. Varnish and Paint Materials and Their Use. 1999. №9. P. 6-8.
3. Gerasimova L.G. Researches in the Sphere of Pigment and Fillers. // Varnish and Paint Materials and Their Use. 1997. №3. P. 12-15.
4. Gerasimova L.G., Nikolaev A.I. Composition and epipolar pigments - New opportunities of Synthesis and Use. // Varnish and Paint Materials and Their Use. 1999. №4. P. 3-7.
5. Zakharov V.I. and others. Physical and Technical Foundations and Development of New Trends of the Complex Processing and Use of Alkaline Aluminium Silicates. Apatity, the Publishing House of the RAS. 1995. Part I. P.175.
6. Gerasimova L.G. and others. Pigments and Fillers from Heat Powers’ Ash Taking Away. //. 1998. V.71. № 8. P. 744-748.

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