RSS 1X
The grade must be produced under conditions wherein all processes are carefully and uniformly controlled. Each bale must be packed free of mould but very slight traces of dry mould on wrappers or bale surfaces adjacent to wrapper found at the time of delivery will not be objected to, provided there is no penetration of mould inside the bale. Oxidized spots of streaks, weak, heated, under-cured, over-smoked, opaque and burnt sheets are not permissible. The rubber must be dry, clean, strong, sound and evenly smoked, and free from blemishes, specks, resinous matter (rust), blisters, sand, dirty packing and any other foreign matter. Small pin-head bubbles, if scattered, will not be objected to. No master or official international sample has been established for this grade. RSS 1
Each bale must be packed free of mould but very slight traces of dry mould on wrappers or bale surfaces adjacent to wrapper found at the time of delivery will not be objected to, provided there is no penetration of mould inside the bale. Oxidized spots of streaks, weak, heated, under-cured, over-smoked, opaque and burnt sheets are not permissible. The rubber must be dry, clean, strong, sound and free from blemishes resinous matter (rust), blisters, sand, dirty packing and any other foreign matter except slight specks as shown in the sample. Small pinhead bubbles, if scattered will not be objected to. RSS 2
Slight resinous matter (rust) and slight amounts of dry mould on wrappers, bale surfaces and interior sheets, found at the time of delivery will not be objected to. Should “rust” or “dry mould” in an appreciable extent appear on more than 5% of bales sampled, it shall constitute grounds for rejection. Small bubbles and slight specks of bark to the extent as shown in the sample will not be objected to. Oxidized spots of streaks, weak, heated, under-cured, over-smoked, opaque and burnt sheets are not permissible. The rubber must be dry, clean, strong, sound and free from blemishes, resinous matter (rust), blisters, sand, dirty packing and all other foreign matter other than those specified above are permissible. RSS 3
Slight resinous matter (rust) and slight amounts of dry mould on wrappers, bale surfaces and interior sheets, found at the time of delivery will not be objected to. Should “rust” or “dry mould” in an appreciable extent appear on more than 10% of the bales sampled, it shall constitute grounds for rejection. Slight blemishes in colour, small bubbles and small specks of bark are permissible to the extent shown in the sample. Oxidized spots or streaks, weak, heated, under-cured, over-smoked, opaque and burnt sheets are not permissible. The rubber must be dry, strong and free of blemishes, blisters, sand, dirty packing and all other foreign matter other than those specified above as permissible. RSS 4
Slight resinous matter (rust) and slight amounts of dry mould on wrappers, bale surfaces and interior sheets, found at the time of delivery will not be objected to. Should “rust” or “dry mould” in an appreciable extent appear on more than 20% of the bales sampled, it shall constitute grounds for rejection. Medium sized bark particles, bubbles, translucent stains, slightly sticky and slightly over-smoked rubber are permissible to the extent as shown in the sample. Oxidized spots or streaks, weak, heated, under-cured, over-smoked (in excess of the degree shown in the sample) and burnt sheets are not permissible. The rubber must be dry, firm and free of blemishes, blisters, sand, dirty packing and all other foreign matter other than those specified above as permissible. RSS 5
Slight resinous matter (rust) and slight amounts of dry mould on wrappers, bale surfaces and interior sheets, found at time of delivery will not be objected to. Should “rust” or “dry mould” in an appreciable extend appear on more than 30% of the bales sampled, it shall constitute grounds for objection. Large bark particle, bubbles and small blisters, stains, over–smoked, slightly sticky rubber and blemishes of the amount and size shown in the sample are permissible. Slightly under dried rubber is permissible. Weak, heat, burnt, oxidized spots or streaks are not permissible. The rubber must be dry, firm, and free of blemishes except to the extent shown in the samples. Dirty packing, sand and all other foreign matter other than specified above is not permissible. Packing and Baling
The sheets after grading are packed in 50 kg bales. The grades are marked on the bales and marketed. Technically Specified Rubber (TSR)
Technically specified rubber (TSR) is a modern marketable form of natural rubber produced from latex and field coagulum. The production of TSR started only during the 1960’s, prior to which raw natural rubber was marketed in conventional forms like sheet and crepe for which only visual grading was done. From 1950’s onwards well packed and scientifically characterized synthetic rubbers became commercially available in bulk quantities. To compete with synthetic alternatives, TSR was developed.
TSR is produced in almost all NR producing countries. In India, TSR production started in the year 1973. It is marketed with quality certification from the Bureau of Indian Standards, under the name Indian Standard Natural Rubber (ISNR). Production
Several commercial processes are being used for the production of TSR. Unit operations in the process of manufacture are 1) Size reduction, 2) Dewatering, 3) Dirt removal, 4) Drying, 5) Blending and 6) Grading. The important parts of machinery being used for the said operations are slab cutter, coagulum crusher, pre-breaker, macerator/crepe roller, hammer mill/shredder driers and baling press. TSR bales produced are packed in low-density polyethylene (LDPE) bags. Each bale shall have a weight of 25kg and will have an identification number such as lot/batch number marked on the cover. Specification and Grading
In India six grades of TSR are being produced. The Bureau of Indian Standards (BIS) specifications for each grade of rubber are given below. |
Crepe Rubber
Crepe rubbers are processed from fresh latex coagulum, field coagulum or cuttings of RSS. When any of these materials, after necessary preliminary treatments, is passed through a set of crepe making machines, crinkly, lace-like rubber is obtained. This, when dried, is called crepe rubber. Crepe rubbers are classified into latex crepe and field coagulum crepe, depending on the starting material used. Latex Crepe
Pale latex crepe (PLC) and sole crepe are the two latex grade crepe rubbers. Latex to be used for the production of PLC and sole crepe shall be free from yellow pigments as far as possible. Also the coagulum shall not undergo enzymic discolouration. 1. Pale Latex Crepe
Starting Material: Fresh Field Latex
It is produced from latex of which the yellow colouring pigment is removed by either fractional coagulation or by bleaching or a combination of the two. The latex is sieved, diluted, bulked and treated with sodium bisulphate to avoid enzymic discolouration. Fractional coagulation is then effected by adding acetic or oxalic acid to remove the undesired colouring matter present in latex. The coagulum containing the colouring matter in the latex due to partial coagulation is removed by sieving. In the bleaching process, the colouring matter is bleached using certain bleaching agents such as tolyl mercaptan or its sodium/potassium salts.
After fractional coagulation and or bleaching, the final coagulation is done using formic or oxalic acid. The coagulum is then passed through a creping battery. The thin crepe is then dried, graded and packed. Pale latex crepe is generally graded into four groups viz; IX, 1, 2 and 3.
Different grades of PLC are used for high quality products such as pharmaceutical articles, light coloured and transparent goods, adhesives, tapes, tubings and derivatives such as chlorinated rubber. 2. Sole Crepe
Starting Material: Dried PLC
The dried PLC is cut into proper sizes and lamination is done with hand. A table, which can be heated, and machines that can press the laminated crepes are the additional requirements for the production of sole crepe. Sole crepe is marketed in different sizes and thickness. The thickness of the various types of sole crepes, specified by the consumers is 1.5, 3.2, 4.7, 6.3 and 9.5 mm and the size of laminated piece is generally 90 x 30 cm. A variation of 0.4 mm in thickness is allowed. The sole crepe after sizing is packed in bales. The maximum weight of the crepe in each bale shall be 101.7 kg and the minimum 72.6 kg.
Sole crepe is used primarily for the production of translucent shoe soling materials. 3. Field Coagulum Crepe
The unit operations involved in crepe production from field coagula are soaking of the coagulum in water, crepe making, drying, grading and packing. For the production of crepe rubbers from field coagulum, the minimum set of machinery required consists of a macerator, crepe roller and one finishing machine.
The crepe prepared from field coagulum materials fall into five types. i. Estate Brown Crepe (EBC)
Starting material: Cup lumps and other higher grades offField coagulum
The preprocessing consists of soaking the coagulum in water for 24 h and washing the cup lumps and scraps to remove dirt. The washed materials are passed through a creping battery. The crepe thus obtained is air-dried, graded and packed. Three different grades of EBC are produced viz, IX, 2X and 3X. ii. Thin Brown Crepe (Remills)
Starting material: Wet slab coagulum, unsmoked sheets and cupLumps
The materials are washed and milled in the creping battery. The crepe obtained is air-dried, graded and packed. three different grades are produced: 1, 2, 3 and 4. iii. Thick Blanket Crepe
Starting material: Wet slabs, unsmoked sheets or other high grade Scraps
The processing consists of milling the material in the creping battery, air drying and packing. Four different grades are viz, 2, 3 and 4. iv. Flat Bark Crepe
Starting material: All types of low grades scrap including earth Scrap
The details of processing are the same as that of estate brown crepe. v. Smoked Blanket Crepe
Starting material: Smoked rubber derived exclusively from ribbed smoked sheet or cuttings
The processing consists of milling the materials in the creping battery, air drying and packing. The crepe from field coagulum grade is packed in bales as specified in the Green Book.
Different grades of field coagulum crepe are used in appropriate proportions in blends with other forms of natural rubber to make products such as tyres, footwear, retreads, mechanical goods, extruded items, etc. |
