GB2178045A - Particulate nonrubber materials derived from serums resulting from treatment of natural rubber latexes and method of their production - Google Patents

Abstract

Particulate nonrubber materials derived from serums byproduced during coagulation of nayrual rubber latexes consist essentially of nonrubber components present in those serums and have an average particle size of 10 to 100 microns. The materials are suitable for instance for rubber products and pharmaceuticals manufacture, and may be produced by spray-drying the serums at 150 DEG to 250 DEG C.

Description

SPECIFICATION Particulate nonrubber materials derived from serums resulting from treatment of natural rubber latexes and method of their production This invention relates to particulate nonrubber materials obtainable from serums byproduced during treatment of natural rubber latexes and also to a method of producing such materials.

A wide variety of rubber-yielding-plants have. been found among which the rubber tree, Hevea brasiliensis, has recently been in extensive cultivation asian important source of natural rubbers.

A milky fluid or latex, collected from such a rubber tree, usually contains about 35 weight percent of rubber components (rubber hydrocarbons), about 5 weight percent of nonrubber components including proteins, fatty acids, saccharides and the like, and the balance of water. This latex is a hydrophobic sol in which the rubber ingredients are colloidally distributed as the disperse phase through an aqueous dispersion medium.

Generally, natural rubbers such as ribbed smoked sheet (RSS), brown crepe and the like are obtained by washing rubber tree latexes with water to remove impurities, coagulating the rubber ingredients with a coagulant such as formic acid, acetic acid, sulfuric acid or the like, and squeezing out serums, followed by dehydration and drying of the resulting coagula. The dried coagula are milled or rolled into rubber sheets which are then smoked to prevent degradation against attack by molds and other organisms.

What are meant by serums as used. herein are aqueous solutions remaining after coagulation and removal of all of rubber hydrocarbons from natural rubber latexes. Disposal of the serums as waste, as has.

been usual in the rubber industry, has often posed environmental pollution problems since they contain proteins and saccharides which readily decompose to develop strong malodors. Attempts have been made with added disposal equipment, but with little success.

It has now been found that nonrubber materials derived from those otherwise undesirable serums can be effectively utilised in certain fields of industry.

Such nonrubber materials find useful application not only to rubber additives such as modifiers, vulcanising accelerators and coatings as reinforcing fillers but also. to feed for the cattle and to pharmaceuticals. The materials are conveniently transportable for their adequate bulkiness and highly applicable for their good solubility in water and solvents.

It is therefore one object of the present invention to provide novel particulate nonrubber materials derived from serums resulting fr.om treatment of natural rubber latexes.

Another object of the invention is to provide a method of producing such nonrubber materials of desired particle size with utmost efficiency and at increased yield.

According to the invention, there is provided a particulate nonrubber material derived from a serum resulting from the coagulation of, and removal of rubber components from, a natural rubber latex, which material consists essentially of nonrubber components present in the serum and has an average particle size of 10 to 100 microns.

According to the invention, there is also provided a method of producing a particulate nonrubber material derived from a serum resulting from removal of all of the rubber components, by coagulation, from a natural rubber latex, which comprises spray-drying the serum at a temperature of 1500 to 2500C into a particulate form with an average particle size of 10 to 100 microns, and collecting the resulting particles.

Particulate nonrubber materials contemplated under the invention are those derived from serums remaining after all of rubber components are removed by acid coagulation from rubber tree latexes.

The materials are preferably substantially spherical in shape with an average particle size between 10 to 100 microns. Smaller particle sizes would induce hygroscopicity and hence re-coagulation, resulting in clods or dumpling-like coagula. Greater particle sizes would fail to dissolve in water and solvents.

The nonrubber materials of the invention vary in composition depending upon the rubber latexes to be used and hence are difficult to define with accuracy. The materials however are usually composed of nonrubber components including proteins such as a-globulin, hevein and the like, fatty acids, amino acids, saccharides, inorganic salts such as of potassium (K), magnesium (Mg), copper (Cu), iron (Fe), sodium (Na), calcium (Ca), phosphorus (P) and the like, and traces of other components.

The composition of a fresh field rubber latex and that of a particulate nonrubber material according to the invention are exemplified respectively in Tables 2 and 3.

A method according to the invention enables particulate nonrubber materials to be produced from serums already free of rubber components.

There is no particular restrictions imposed on the composition of serums which depend upon the corresponding rubber latexes. Generally, serums resulting from industrially treating natural rubber latexes contain rubber components in an amount of about 0.5 weight percent, and nonrubber components in an amount of about 2.0 to 5.0 weight percent, which may be centrifugally separated.

Starting serums may have a nonrubber solids content between 2 and 80 weight percent. With effi ciency, control and economy in view, solids contents are preferably in the range of 50 to 70 weight percent. Industrially derived serums are about 3 to 5 weight percent in solids content and therefore may be concentrated, where desired, as by evaporation, centrifuging or filtration, say to a solids content between about 50 to 70 weight percent. Smaller solid contents than 50 weight percent sould result in reduced drying efficiency. Excessive solids contents would cause the serum to be too viscous, leading to handling inconveniences.

According to an important aspect of the method of the invention, starting serums are spray-dried into a drying chamber maintained at 1500 to 250"C in which sprayed droplets are evaporated dry to give particles of a predetermined particle size between 10 and 100 microns. Spray drying of a closed system may be employed to this end in which upon mechanical spraying of the serums, the droplets are instantaneously brought into direct contact with hot air and dried into particles. This system of drying can be effected by the use of a nozzle type spray drier with a pressure nozzle or a two-fluid nozzle, or a disc type spray drier with a disc revolving axially at high speed. Disc type spray drying is particularly preferred.

Jet pressures and disc speeds are preferably in the range of 0.5 to 2.0 kg/cm2 and in the range of 10,000 to 30,000 rpm, respectively. Departures from the above specified ranges would fail to provide desired nonrubber materials whose particle size ranges from 10 to 100 microns. Smaller particle sizes would invite hygropcopicity and hence re-coagulation, leading to deposits on the inner wall of the spray drier and also to massive products, which would in turn result in reduced yield. Greater particle sizes would lead to inadequate bulkiness and hence handling inconveniences.

The drying chamber should preferably be maintained at a temperature of 1500 to 250"C, particularly with an inlet temperature of 250 to 15000 and an outlet temperature of 1300 to 5000. Greater drying temperatures would induce thermal degradation due to such nonrubber components as proteins and saccharides being susceptible to the influence of heat. Droplets sprayed from the drier usually enter the chamber at a temperature less by about 100"C than the inlet temperature. Too high drying temperatures should be avoided to preclude deteriorated product qualities. Smaller drying temperatures would be ineffective for sufficient drying, giving massive products.

The invention wili now be further described by way of the following examples.

Invention examples 7 - 5 and comparison examples 1 - 2 Five samples of particulate nonrubber materials according to the invention were prepared with use of rubber latexes and under processing conditions shown in Table 1. Also prepared were two samples of controls in which the disc speeds of revolution and drying temperatures exceeded the limits as above specified.

The respective samples were measured and inspected for their particle sizes, shapes, moistures, colours and appearance with results given also in Table 1.

The sample product obtained in Invention Example 5 was analysed at the Japan Food Analyses Centre with results shown in Table 3.

Preparations and measurements were made by the use of the following driers and testers.

Spray drying: Nozzle type drier: L-5 (DL-41), Yamato Kagaku Co.

Disc type drier: L-12, Ohkawara Kakoki Co.

Solids content: Automatic moisture meter, Kett Co.

Apparent viscosity: Brookfield viscosimeter Moisture: Automatic moisture meter, Kett Co.

It is to be noted that all the particulate nonrubber materials representing Invention Examples 1 to 5 are quite satisfactory in respect of both production efficiency and product qualities. Controls of Comparison Examples 1 and 2 caused insufficient drying or thermal degradation, leading to massive products or many deposits in the drier.

TABLE 1 Invention Example Comparaison Example 1 2 3 4 5 1 2 Starting latex Nonrubber solids content (%) 5.8 2.8 20.5 4.4 4.4 4.4 4.4 Apparent viscosity (cp) 4.3 3.9 4.5 4.2 4.2 4.2 4.2 Process Spray drying type nozzle disc disc disc disc disc disc Jet pressure (kg/cm)/disc 1.0 20,000 20,000 10,000 28,000 8,000 35,000 revolution (rpm) Drying temperature Inlet ( C) 250 200 250 170 170 135 250 Outlet ( C) 90 104 120 60 60 60 130 Nonrubber product Average particle measurement size ( ) 40 20-30 30-40 70-100 20-30 impossible 15-20 Shape spherical spherical spherical rice grain-like spherical amorphous spherical Moisture (%) 4.5 5.2 4.8 7.2 3.8 13.4 5.0 Colour pale yelow- pale yellow pale yellow pale yellow- pale brown pale yellowwhite white white Appearance good good good good good large mass many deposits and deposits in drier in drier TABLE 2 Composition Percent by weight Percent by weight in latex in dry rubber hydrocarbon Rubber hydrocarbon 35.62 88.28 Proteins 2.03 5.04 Acetone solubles 1.65 4.10 (fatty acids) Saccharides 0.34 0.84 Ashes 0.70 1.74 (inorganic salts) Water 59.66 TABLE 3 Ingredients Contents Method of analysis (wit. %) Proteins 23.6 Kjeldahl method *) Amino acids **) Arginine 0.33 Lysine 0.53 Histidine 0.18 Phenylalanine 0.26 Tyrosine 0.36 Leucine 0.51 Isoleucine 0.28 Methionine 0.09 Via line 0.30 Alanine 1.17 Glycine 0.87 Proline 0.33 Glutamic acid 1.39 Serine 0.47 Threonine 0.30 Aspartic acid 1.02 Tryptophane 0.29 Uitra liquid chromatography Cystine 0.51 Performic acid oxidation method *) Nitrogen-protein conversion factor: 6.25 **) Amounts by gramme of amino acids in 100 g of sample (No. 16090241-001 of Japan Food Analyses Centre)

Claims (9)

1. A particulate nonrubber material derived from a serum resulting from the coagulation of, and removal of rubber components from, a natural rubber latex, which material consists essentially of nonrubber components present in said serum and has an average particle size of 10 to 100 microns.

2. A method of producing a particulate nonrubber material derived from a serum resulting frorn removal of all of the rubber components, by coagulation, from a natural rubber latex, which comprises spray-drying said serum at a temperature of 150 to 250"C into a particulate form with an average particle size of 10 to 100 microns, and collecting the resulting particles.

3. A method according to claim 2 wherein said spray drying is effected with an inlet temperature of 250 to 1500C and an outlet temperature of 1300 to 50"C.

4. A method according to claim 2 or 3 wherein said spray drying is of a nozzle or disc type.

5. A method according to claim 4 wherein said nozzle type spray drying is performed at a jet pressure of 0.5 to 2.0 kg/cm2.

6. A method according to claim 4 wherein said disc type spray drying is performed at a speed of 10,000 to 30,000 rpm.

7. A method according to any one of claims 2 to 6 further including a pretreatment step, prior to said spray drying, in which said serum is concentrated to a predetermined solids content.

8. A particulate non rubber material substantially hereinbefore described with reference to any of the Invention Examples.

9. A method of producing a particulate nonrubber material substantially hereinbefore described with reference to any of the Invention Examples.