PROCEEDINGS
OF THE TOMSK ORDER OF THE OCTOBER REVOLUTION AND ORDER OF THE RED BANNER OF LABOR POLYTECHNIC INSTITUTE named after S. M. KIROV

Vol. 250 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1975

STUDY OF ISSUES IN THE INTENSIFICATION OF SHEET RUBBER COOLING AFTER CALENDERING

I. P. CHASHCHIN, S. M. YUDINSKIKH

(Presented by the scientific seminar of the departments of PMKhP and OKhT)

The manufacture of rubber products is a major branch of industry, whose output is used in all areas of the national economy.

The main raw materials for making rubber are rubbers of various grades with the addition of a variety of organic and inorganic substances, vulcanizing agents, accelerators, antioxidants, plasticizers, etc. In the process of manufacturing semi-finished products and articles, the ingredients impart to rubber compounds the required technological properties [1].

According to the existing technology, the rubber compound obtained in rubber mixers successively passes through the stages of plasticization, calendering, cooling, cutting, rubberizing fabrics with adhesives, extrusion, and vulcanization [2].

In this entire technological line, the “bottleneck,” in particular at the Tomsk Rubber Footwear Plant, is the cooling of rubber after calendering. The need for effective cooling of rubber on cooling drums is caused by many reasons. During the passage of the rubber strip over the cooling drums, the rubber, simultaneously with cooling, undergoes shrinkage. If, without cooling the rubber to the temperature required by the technology (+25 °C), it is cut and stacked on carts, much time and space will be required; the rubber will have to be held for a long time for the necessary shrinkage to occur. In addition, during storage, uncooled rubber sheets stick together, which leads to rejects. Effective cooling of rubber on cooling drums is also necessary to eliminate the process of prevulcanization, since in connection with this process the rubber loses some of its valuable properties: it becomes less plastic, and its adhesive capacity deteriorates.

The cooling drums installed at the plant (Fig. 1) after the calenders ensure effective cooling of rubber only under winter conditions, since the coolant in the drums is river water, which has different temperatures at different times of the year. Thus, the Tomsk Rubber Footwear Plant uses water from the Tom River; in the winter period the temperature of the water in the Tom is +2–5 °C, while in summer the water temperature is +20–25 °C.

Therefore, we were faced with the task of intensifying heat exchange during the cooling of rubber on cooling drums. In connection with this task, we considered several variants.

In the first variant, we propose preliminary cooling of the water entering the cooling drums by means of a refrigerating machine to \(+2^\circ\mathrm{C}\), which ensures effective operation of the drums year-round. For this purpose, the refrigeration capacity of the refrigerating machine was calculated according to generally accepted equations, taking heat losses into account [3]. We calculated that, to cool \(951\ \mathrm{kg/hour}\) of rubber after the calenders at the Tomsk Rubber Footwear Plant, it is necessary to remove \(13370\ \mathrm{kcal/hour}\) of heat from the rubber sheet. On the basis of the calculated refrigeration capacity, an KhMAV-22 refrigerating machine was selected [4].

Fig. 1. a) installation of cooling drums; b) motion of the cooling water. Legend: 1 — cooling drums, 2 — rubber sheet, 3 — drain pocket

In view of the fact that there is a water well on the grounds of the Tomsk Rubber Footwear Plant, in the second variant we calculated heat exchange under the condition that the water for cooling is taken not from the Tom River, but from the well. The temperature of the water in the well is \(+7 \div 8^\circ\mathrm{C}\). For this variant, thermal and hydraulic calculations were performed. According to the calculations carried out, in order to ensure circulation of the existing water flow rate of \(60\ \mathrm{l/min}\), a centrifugal pump of type \(1\,1/2\) K-6 was selected [5].

The next variant calculated was cooling the rubber by means of precooled air. Since, on the installed cooling drums after the calenders, the rubber in the summer period is cooled only to \(+30^\circ\mathrm{C}\), we proposed additional cooling of the rubber with cold air \((+13^\circ\mathrm{C})\) to the temperature required by the technological standards \((+25^\circ\mathrm{C})\). Using the principal, generally accepted equations, we calculated and selected an AKFV-12 refrigerating machine [4] for cooling the air and an MTs-series fan to provide blowing and cooling of the rubber sheet [6].

All three variants were calculated under the condition of incomplete filling of the cooling drums with water (Fig. 1). In this connection, only part of the surface of the cooling drum participated in the heat exchange. To select the most advantageous variant from the standpoint of economy and simplicity of equipment design, work is continuing in the following directions.

1. Under the condition of the existing flow rate of cooling water \((216\ \mathrm{l/min})\), and without changing the design of the cooling drums installed at the plant, intensify the heat-exchange process by completely filling the drums with cooling water.

2. For the purpose of greater intensification of heat exchange in cooling the rubber after calendering, change the design of the cooling ...

drums, ensuring turbulent motion of the cooling water in the cooling drums.

REFERENCES

1. Kh. E. Malkina. General Principles of Rubber Production Technology. Goskhimizdat, Moscow, 1960.

2. F. F. Koshelev, M. S. Klimov. General Technology of Rubber. Goskhimizdat, Moscow, 1960.

3. K. F. Pavlov, P. G. Romankov, A. A. Noskov. Examples and Problems for the Course on Processes and Apparatuses of the Chemical Industry. Goskhimizdat, Moscow, 1961.

4. Catalog of Refrigeration Equipment. Leningrad, 1963.

5. Pumps. Handbook. Mashgiz, Moscow, 1960.

6. Fans. Reference Material. Moscow, 1960.