3.2 Technology of compositions preparation

The widespread way of preparation of powder, paste, liquid synthetic detergents is the mixture of liquid and firm components. A homogeneous mix of components making detergent is named a composition. The quality of synthetic detergents depends on uniformity and stability of structure. The composition contains 60-70 % of firm substances, thus, it represents suspension, in which dispersive medium is the water solution of salts and washing substances, and disperse phase is inorganic salts. Stability of such system depends on dispersive action of corresponding components. Uniformity of structure is defined by degree of dispersion and quality of hashing.

Most of all the technology of preparation of compositions containing significant amount of firm particles depends on viscosity of system. High viscosity of suspensions interferes effective mixture of components and leads to increase of energy spent on hashing.

Firm components of synthetic detergent are characterized various solubility and ability to formation of crystal hydrates. The majority of inorganic salts at sufficient content of water during preparation of compositions are passed in crystal hydrates. Solubility of crystal hydrates basically defines viscosity of compositions.

Very important value is the content of sodium tripolyphosphate, which can achieve 50% (weights). During manufacturing compositions sodium tripolyphosphate is changed into hydrate, forming a viscous product. Rise in temperature promotes reduction of viscosity, but during too time reduces speed of hydration. As compositions are received at temperatures about 90⁰С, insufficiently hydrating and consequently hygroscopic product is formed. It has bad flow ability and can form lumps. For this reason the hydration of sodium tripolyphosphate is carried out before loading of other components.

The influence of water content, temperature and duration of preparation on compositions viscosity are shown in table 1.

It is necessary to note, that at loading of loose raw material in liquid phase air is brought, and hashing leads to formation of foam. These two factors influence on density of composition. The air content is reduced at processing by vacuum or ultrasound. Ultrasonic or mechanical processing reduces also the sizes of firm particles and improves fluidity of composition. Machining is carried out in homohenizators or pumps, thus particles in size 0,2-0,3 mm are received.

Process of preparation of a composition includes the following stages: 1) batching of liquid and loose raw material; 2) mixture of components in reactors with mixers; 3) filtration; 4) removal of air; 5) homogenization. Compositions are prepared in periodic or continuous ways.

Table 2. Dependence of SD properties from technological parameters.

Parameter	Viscosity, Pa. s	Washing action, %
Temperature of preparation, 0С
60	3,93	30,5
70	2,95	29,6
80	2,81	29,2
90	2,66	29,7
Time of preparation, minute
10	2,95	26,6
20	3,77	27,4
30	6,79	27,6
40	6,3	29,4
Water content in a composition, % (mass)
40	9,2	30,7
50	2,95	29,6
60	1.03	29,3
70	0,544	30,5

Periodic process is applied for preparation of liquid, paste synthetic detergents and powders at installations by productivity 30-100 thousand tons in year. Periodic way of preparation of compositions:

- differs reliability and simplicity of hardware registration;

- allows to load the components in the reactor-amalgamator in any sequence.

Liquid glass, water and solutions of washing substances are loaded first of all. For preparation of powder with high density the received mix is heated up to 70-90⁰С, then it is mixed at simultaneous consecutive loading of powder sodium carboxyl methilcellulose, optical bleach, sodium sulfate, sodium carbonate and sodium polyphosphate. Loading of raw material in return sequence leads to preparation of powder with low density. At periodic preparation of composition components are consistently loaded into the reactor-amalgamator, from it the received mix by pump or by gravity is directed to account reactor, homogenizator, and filter and submitted on packaging or on drying.

Continuous process is carried out in the cascade of reactors working on the following circuit. Components as parallel streams are submitted to the first reactor from which the mix flows in the following reactors. Time of stay in one device makes 4-5 minutes. The reactor-amalgamator represents the enameled or from stainless steel device in volume of 1-14 m³ with a shirt and a mixer (24-300 rev/min). At continuous process of synthetic detergents production reactors in volume of 1 m³ are applied.

For homogenization of compositions homogenizator is used. Working parts of this device represent the disks with ledges which rotate in opposite sides. The distance between surfaces of disks does not exceed 2 mm. The composition is submitted on the center of disks then homogenizative suspension is deduced on periphery.

In the number of synthetic detergents compoundings soap is entered. It is prepared at neutralization of synthetic alkylcarbon acids by solution of sodium hydroxide in reactor-neutralizer. For preparation of homogeneous composition neutralization is carried out in solution of SAS.

The received mass from reactor is given on the filter of rough clearing for removal of firm impurity then the homogeneous composition passes the pump-homogenizator and again is filtered through the special filter. In this filter the particles in size more than 2 mm are removed from composition. The productivity of such circuit makes 3 kg/s.