1. Field of the Invention:

Preparation of Rubber sheets.

2. Background of the Invention:

Natural rubber is an important raw material used for the manufacture of thousands of products including automobile tyre. It is obtained from rubber trees in the form of latex with 20 to 45% dry rubber content. 80% of the rubber produced in India is processed into rubber sheets by the producers. Rubber sheets are conventionally prepared by coagulating latex obtained from rubber tress in aluminum dishes and the coagulum size is 27x3 7cm with 4cm thickness. Only one sheet per dish can be prepared at a time. The process is time consuming; as field latex is first sieved into a bulking tank, then diluted with required quantity of water, diluted acid is then added, mixed well, four liters of the mixture is then poured into each dish quickly and carefully, each dish is placed in a perfect flat surface and the froth is removed carefully from each dish. Long rectangular tanks with vertically inserted partitions are also in use but the sheets will be of uneven thickness as rubber particles in the latex, being lighter than water, migrate upwards resulting in a coagulum with thicker upper portion, this in turn leads to uneven drying and consequent lower grade sheets. Another disadvantage of the existing coagulation tank is that only full capacity can be processed in it (in a 120 sheet tank 110 sheets or any quantity less than 120, cannot be processed).

3.Summary of the invention:

A new coagulation tank with horizontally placed partition plates, with four sheets in each layer, has been invented, in which up to 60 sheets can be prepared much faster than dish coagulation and without any defect of long tank with vertical partition.

4. Brief Description of the Drawings.

Fig. 1 shows the elevation of the coagulation tank with a stand.

Fig.2 shows section A-A with partition plates.

Fig.3 shows section A-A with details of spacing between partition plates. The height of
the ridge can vary from 25 to 50mm and same will determine the volume of latex/weight of sheets in each layer.

Fig.4 shows plan of the coagulation tank.

Fig.5 shows plan of the partition plate with cross ridge.

Fig.6 shows part of cross ridge with hole. Plates are taken out of the tank by inserting a hook into the hole on the ridge.

All the figures are of tank and partition plates with sharp corners.

5. Description of the invention:

a) Coagulation tank -measurements, 54cm wide X 74cm long X(10 to 70) cm deep with + or- 10cm variation or multiples or fractions of any dimension; material, any material. The coagulation tank can be made with or without a stand; also with or without a tap on bottom. Corners of the tank can be sharp(90degree) or smooth curved.

b). Partition plates- measurements, 53.80cm wide X 73.80cm long X 2mm thick plate (length and breadth can vary up to + or- 1cm and thickness can vary from 0.5mm to 4mm) with a cross ridge of 3.5cm height(can vary from 2.5cm to 5cm) (fixed or removable)on one side of the plate divide the plate into four equal quarters so as to prepare 4 coagula in each layer. Corners of the plate can be sharp (90degree) or smooth curved.

The partition plates are placed horizontally one above another. Number of partition plates used in a tank can vary from 1 to 20. Field latex( quantity required for making 4 to 60 sheets) is directly sieved into the new coagulation tank, required volume of water and diluted acid is added, mixed well, froth is removed from the top, partition plates are pressed down and placed horizontally one above another, each plate will rest on the cross ridge of the plate below. The new coagulation tank can be used for preparation of lesser number of sheets than its full capacity Minor variations in length, breadth or thickness or changes in the number of layers/number of sheets per layer will not affect the usefulness of the new design , so protection is sought over such variants also.

6. Claims:

I claim

1. In the newly invented coagulation tank horizontally placed partition plates prevent vertical migration of rubber particles and the coagulum will be of uniform thickness and results in best grade sheets.

2. The present invention results in time & labour saving. 60sheets can be prepared in the new device when 6 sheets are prepared in the conventional dish coagulation.

3. The present invention results in better quality of the product. Sheets prepared in old coagulation tanks fall in RSS-4 where as the new gives RSS-1/1X grade. As coagulum is formed one above other only the top layer is exposed to air.

4. The present invention occupies less space compared to aluminum dishes.

5. The present invention results in the uniformity of the product. In dish coagulation, volume of latex poured into each dish very often varies, consequently sheet to sheet variation in dry weight is common, whereas in the newly invented coagulation tank, partition plates with identical ridges ensure formation of identical coagulum and identical sheets without any variation.

On testing, the coagulum prepared in the new tank is found similar to conventional dish coagulum but preparation is much faster and uniform in size; at the same time suitable for further processing in existing infrastructures like sheeting rollers and smoke houses.