GB1572019A - Heat-softenable thermoplastic partitioning agent and preparation of crumb rubber coated therewith - Google Patents

Description

(54) HEAT-SOFTENABLE THERMOPLASTIC PARTITIONING AGENT AND PREPARATION OF CRUMB RUBBER COATED THEREWITH (71) We. THE GOODYEAR TIRE & BR< RUBBER COMPANY, a corporation organised under the laws of the State of Ohio.

United States of America. of 1144 East Market Street. Akron. Ohio. United States of America. do hereby declare the invention for which we pray that a patent mav be granted to us and the method by which it is to be performed to he particularly described in and by the following statement: Neubert U.S. Patent Specification No.

3,813,259 discloses the use of resinous butadiene-styrene copolymer and polymethyl methacrylate as partitioning agents, indi vidually. but does not suggest that any mixture of them be emploved It is well known that elastomers including natural rubber and synthetic rubbers, e.g.

polyisoprenes, polybutadienes, or copolymers of styrene and acrylonitrile with isoprene or butadiene, made by emulsion, solution or suspension processes. are tacky. When coagulated form the latex form in which they occur naturally or in which they are polymerized, the elastomer particles tend to agglomerate unless they are agitated vigorously. When dry they are even more tacky and special means must be emploved if it is desired to maintain the elastomer in the form of discrete particles.

It is an object of this invention to coat elastomeric crumb particles with a heatsoftenable thermoplastic partitioning agent to prevent agglomeration during drying, storage, shipping and handling. The word "crumb" is used herein to refer to the individual particles or agglomerates formed in coagulation processes, or to pellets formed by cutting extruded clastomers, or to particles formed by grinding larger masses of the elastomers. The crumb particles produced by coagulation or grinding may usuallv be considered as having diameters of I to 15 mm.: and it produced trom an extruded strand may measure as much as 50 mm. in anv direction.

Various resinous polymers may be emploved as heat-softenable thermoplastic partitioning agents for elastomeric crumb materials, e.g. polystyrene. polymethyl methacrvlate. polvacrvlonitrile. polyvinyl chloride.

polyethylene. and various copolymers and terpolymers of styrene. butadiene, acrvlonitrile. or methvl methacrvlate. The satis factorv use of a resinous polymer for the purpose of this invention depends on its agglomeration temperature. The agglomer- ation temperature is that temperature at which particles of the resin dispersed in water will soften and mass together. For the process for applying the coating of thermoplastic resin to the rubber crumb in aqueous slurry as included herein to be practical and economical it should be conducted at slurrv temperatures below about 99"C. Higher temperatures may be used but they require the process to be conducted in a pressure vessel under pressure.The coating is best applied at a slurrv temperature at or near the agglomeration temperature of the resinous coating material.

The above-mentioned Neubert patent refers to the use of polymethyl methacrvlate as a partitioning agent. Polymethyl methacrvlate. alone. with an agglomeration temperature over 1000 C. can be applied to a powdered rubber (e.p. up to I mm in diameter) at temperatures under the boiling point of water or slurries of a rubber crumb.

However. when it is attempted to apply the polymethyl methacrvlate resin as a coating to larger-size crumb particles of the elastomer. under conditions such as included herein. much of the resin coagulates by itself and forms free resin particles rather than forming the desired coating on the crumb rubber.

Neubert refers to the use of a resinous styrene-butadiene copolymer with a styrene content of 80-99 per cent bv weight. He refers to it os a preferred partitioning agent.

Such copolymer may be used in the blend described herein. Copolymer of a lesser styrene content. e.g. 80-85 per cent, is preferred for blending with polymethyl methacrylate. Any such copolymer resin with an agglomeration temperature such as 55-70 C. may be applied very readily as a partitioning agent to the surface of crumb particles. However. its agglomeration temperature is so low that the resulting resincoated crumb particles must be dried at rather low temperatures to avoid their sticking together during drying A drving temperature significantly higher than 6(i C.

would cause the rubber crumb particles coated with such copolymer to stick together. The use of a low drying temperature. e.g. 6(1 C.. is uneconomical. however.

because of the slow rate of evaporation of the water held in the crumb. On the other hand. polvmethvl methacrylate resin. while not adhering to the surface of the particles as well as the stvrene-butadiene copolvmer, will permit the crumb coated with it to be dried at a much higher temperature of. for example 95 C. or higher. without sticking together to any appreciable extent. due to its very high agglomeration temperature.

Whereas polymethyl methacrvlate is apreferred ingredient to be used in the partitioning agent of this invention. it is possible to use in its place certain other resins of high agglomeration temperature.

which we define for the purposes of the present description and claims as comprising polymers and copolymers of styrene and vinyl chloride. Thus one may use, for example. polystyrene. or polyvinyl chloride.

or a copolymer of stvrene and acrvlonitrile.

The resin blend cif this invention is applied is a partitioning agent in a hot slurrv of the crumb. The slurry may be formed bv coagulation of the elastomeric latex or by dispersing pellets or ground crumb in water.

This slurry must contain a coagulant. either an excess from the coagulation of a rubber latex, or that added when a slurry of pellets or ground crumb is prepared. The coagulant ma. tor example. be aluminum sulfate, magnesium sulfate. calcium chloride, calcium oxide. or barium hydroxide. or a mixture of sodium chloride and sulfuric acid used most often for SBR coagulation. The concentration of the rubber crumb and the nature and concentration of the coagulant in the slurry will vary, and may be anything which is usual in the industry.In the case of a crumb slurry prepared by coagulating a rubber latex the coagulation and the formation of the resin coating may be carried out either batchwise or continuously.

it has been discovered that blends of polymethyl methacrvlate resin and styrenebutadiene copolymer resin have agglomeration temperatures intermediate between those of the individual components. There- fore. a blend ratio may be selected which will give a coating of all or nearly all of the resin blend on to the surface of the crumb particles at a reasonable slurry temperature of, for example. 9()-95 C., and provide a coating with a high enough softening temperature that the coated crumb may be dried at a high temperature of, for example, 85 C. or higher. Thus. advantages of both blend components are obtained.

According to one aspect of the present invention. we provide a partitioning agent which is a heat-softenable mixture of (a) 50 to 80 parts, by weight. of a styrenebutadiene copolymer with a styrene content of 80 to 99 per cent. bv weight. and (b) 50 to 20 parts of a polymethyl methacrylate or another resin of high agglomeration temperature. as herein defined. The heatsoftenable mixture is preferably composed of (a) substantially 70 parts of the copolvm- er and (b) substantiallv 30 parts of the polymethyl methacrvlate. or other resin of high agglomeration temperature. as herein defined. and has an agglomeration temperature which usuallv will be in the range of 85 to 95 C and which preferably is substantially 90 C.

The invention also includes a process of producing a coated polymer crumb. which process comprises coating a tackv polymer crumb with a blend of (a) 5() to 8il parts. by weight. of a stvrene-butadiene copolymer resin with a stvrene content of substantiallv 80 to 99 per cent and (b) 5() to 2(1 parts. by weight. of a polymethyl methacrvlate resin, or another resin of high agglomeration temperature, as herein defined. and drying the coated crumb at a temperature not in excess of substantiallv 110 C.

The invention further includes a process for preparing elastomeric particles coated with a partitioning agent which comprises preparing a latex blend of (a) 5() to 8() parts, by weight. of a styrene-butadiene copolymer resin with a stvrene content of substan tally XO to 99 per cent and (b) 50 to '() parts, bv weight. of a polvmethvl methacrylate resin. or another resin of high agglomera- tion temperature. as herein defined, said latex having a concentration of 0.1 to 10 per cent: coagulating a latex of elastomeric particles in an aqueous medium containing coagulant ill slight excess of that necessarv to agglomerate the elastomeric particles: mixing the two resin latices to produce the blend. using sufficient of the latex blend to coat the elastomeric particles sufficientlv to prevent the agglomeration of the coated particles during drying. and drying at a temperature not in excess of substantially 110 C. Preferably the partitioning agent is a blend of substantially 70 parts of the copolymer and 30 parts of the polymethyl methacrylate, or other resin of high agglomeration temperature, as herein defined, and the final drying temperature does not exceed substantially 90 C.Preferably also the con centration of the components in the latex of the partitioning agent is not over 2 per cent by weight.

The polymer from which the ahovementioned tacky polymer crumb is produced may for example be a butadienestyrene rubber,and furthermore this crumb may have a black masterbatch composition, or an oil masterbatch composition, or an oil-black masterbatch composition.

The present coated polymer crumb producing process may include the steps of extruding the polymer crumb as a strand measuring no more than substantially 50 mm. in the largest dimension, dividing the strand into lengths no more than substantially 50 mm. in length, forming an aqueous slurry therefrom, and coating the resulting crumb particles with the blend. It is also possible for the said process to include the steps of obtaining the crumb by grinding.

foriiiing a slurry from the ground particles and coating the particles.

In the practice of the invention, a slurry of the rubber crumb particles concerned, with coagulant present, may be heated to a temperature near or above the agglomera- tion temperature of the blend constituting the partitioning agent. The two resinous components of the blend. in the form of aqueous latices, can be blended and diluted to any usable concentration, for example, 0.1 per cent to 10 per cent of the weight of the latex, more or less, and preferably 2 per cent by weight total solids, and heated to a temperature near thnt of the slurrv of the coagulated rubber crumb. Then the hot dilute resin latex is added slowly to the hot rubber crumb slurry with mild agitation.

Under these conditions the resins in the latex blend are coagulated by the coagulant in the rubber crumb slurry and adhere to the surface of the rubber particles. Because the slurry temperature is near or above the agglomeration temperature of the resin blend, the components of the resin soften, but, surprisingly instead of the polymethyl methacrylate particles cohering to one another the resin blend adheres to the surface of the rubber particles. The concentration of the blend in the slurrv mav varv widelv and should he regulated so that the amount of the blend present is sufficient to coat substantially the entire surface of the elastomeric particles.

The resin coating thus fornied on the surface of the otherwise tacky rubber crumb particles is an effective partitioning agent.

When the water is drained or filiered from the slurry of the coated crumb particles and thev are dried. the particles resist sticking together if they are not held at too high a temperature after becoming essentially dry.

The wet particles may enter a tunnel drier at a temperature considerably above the agglomeration temperature, e.g. 110 to 115 or 120 C, or thereabout, provided that as the water is removed the temperature is lowered, and the final drying may be accomplished at a temperature not over 85 C or 95 C or thereabout: depending upon the partitioning agent. Tunnel drying is not necessary, and in any method of drying the final temperature is critical and should not exceed, in a typical case. 8() to 95 C'.. or somewhat higher depending upon the composition of the partitioning agent, etc.

Usually the ratio of the weight of the coating resin to the weight of the clastomeric particles would be in the range of perhaps 1 to 25 per cent or thereabout, and prefer ahlv 7 to 1() per cent. depending on the particle size and the particle surface area.

Six examples follow, of which Examples 1 and 2 relate, respectively, to the prior-art use of polymethyl methacrylate and styrenebutadiene copolymer alone.

Example 1 an SBR 1502 type latex is coagulated with salt and acid. To 300 g. of agitating latex containing 60 g. dry weight of rubber, 60 ml. of a solution containing 15 g. of NaCl is added and enough of a 1 per cent solution of H2SO4 to lower the pH to about 5. This forms a slurry of elastomeric crumb particles of perhaps 1-10 mm. diameter in water. This slurry is heated to 95 C.An aqueous latex of polymethyl methacrylate (RHOPLEX B85 manufactured by Rohm & Haas) with an agglomeration temperature of > 100 C of 3 g. dry weight (5% of weight of rubber) is diluted to 2 per cent total solids, heated to 85 C. and added slowly to the agitated slurry of rubber crumb. Under these conditions the polymethyl methacrylate resin is coagulated by the residual solt and acid in the slurry and a portion fuses on the surface of the crumb particles. When this is dried at 95 C. the coated rubber particles do not stick together hut a considerable portion of the polymethyl methacrylate coagulates separately and makes the product dusty.

This partially fused coating is not ncarlv as effective in partitioning the rubber crumb as if all the resin were fused on the surface of the crumb particles.

Example 2 A coagulated slurry of SBR rubber crumb is prepared as in Example 1 and heated to 70 C. Eight ml. of a stvrene-butadiene resin latex with 38 per cent total solids, a styrene content of 82.5 per cent, and an agglomeration temperature of 65 C. is diluted with water to 2 per cent solids and added slowly to the agitating slurry. The resin coagulates and almost all of it fuses together on the surface of the elastomer crumb particles.

When this is dried at 65 C. no free resin is evident but the rubber particles stick together.

Example 3 A slurry of rubber particles is prepared as in Example 1 and heated to 9() C. A blend of resinous latices of polvmethvl methacrylate with an agglomeration temperature of > 1(1(1 C. and a styrene-butadiene copolymer with a styrene content of 82.5 per cent and an agglomeration temperature of ó5 C.

is made and dilute to 2 per cent with water.

The ratio of polymethyl methacrylate to the copolymer resin is 30/70 and the agglomeration temperature of the blend is 90 C. The dilute latex blend containing 3 g. dry weight of resin is heated to 850 C. and added slowlv to the agitating rubber crumb slurrv. The resins coagulate and fuse on the surface of the crumb particles. When the particles are dried at a temperature not over 90 C.. there is little or no sticking of the particles. and little or no free resin present.

Example 4 A bale of 171' SBR-type oil exteiided rubber is ground to give a crumb of about 1 S-l 4 inch in particle size. Two pounds of this ground crumb is slurried in ten pounds of water containing 27 grams of MgSO4.7H2O coagulant. The slurry is heated to 90 C. A two per cent latex of a 70/30 mixture by weight of styrene-butadiene copolymer and polymethyl methacrylate latices containing four parts of resin per 100 parts of rubber crunib is prepared as in Example 3 and added to the rubber crumb slurry. The resin coats the surface of the ground rubber to serve as a partitioning agent. The water is drained off and the coated crumb is dried at 85 C.

Example 5 To a cold NBR latex with 32 per cent bound acrylonitrile and 68 per cent butadiene: a Mooney siscosity. M/L-at 212 F.

of SA: and a solids content of 20.5 per cent is added ail aqueous dispersion of a finely ground SRF (ASTM N762) carbon black.

The black amounts to 75 per cent by weight of dry rubber solids. A 1 per cent solution of sulfuric acid is added to coagulate the black masterbatch in the form of a crumb. If needed to complete the coagulation of the NBR latex and clear the serum a coagulation aid such as Polvamine H. made bv Union Carbide, is added. The rubber/black crumb is washed and fed to an extruder dryer. It is extruded through a die with holes 1/16-inch in diameter and cut with a cutter into dry pellets of 1/X-inch diameter and about liX-ínch length. Fortv pounds of these pellets are put into 250 pounds of water, and eight pounds of sodium chloride and 33 grams of concentrated sulfuric acid are added. The slurrv is heated to 9() C.The 70/30 styrene-butadiene/polmethyl methacrylate resin blend in the form of a hot 2 per cent latex is prepared as in Example 3 to give 4 parts/100 parts of the rubber black masterbatch. It is added to the hot rubber pellet slurry and the resin coats the surface of the pellets. The pellets are dried at 850 C.

without sticking together and resist massing during storage.

Example 6 A rubber latex is coagulated continuouslv and the resulting rubber crumb particles are coated continuously with a fused thermoplastic partitioning agent in this example.

Two thousand nine hundred seventy pounds of a cold SBR 1713 latex with a solids of 19.9 per cent. a M/L-4 at 212 F. of 135. and a bound stvrene content of 23.5 per cent is put into an agitated vessel. Five hundred ninety pounds of a 50 per cent emulsion of a naphthenic, non-staining processing oil and a suitable antioxidant is added to the latex.

This is 5(1 parts of oil/100 parts of rubber solids. The latex/oil blend is heated to 55 C.

In another vessel a (1.7 per cent solution of Al2(SO4)3.18H2O (alum) is prepared and heated to 60 F. In a third vessel 260 gallons of water are heated to 93 C. with steam.

Ninety seven pounds of a styrene-hutadiene copolymer latex with 36.2 per cent solids.

and 39 pounds of a polymethyl methacrvlate latex of 38.3 per cent solids are added. This makes a 2.3 per cent solids latex of the 70/30 blend of the two resin partitioning agents.

This dilute latex is maintained at a temperature of 82 C. or higher. T he oil, rubber latex mixture is run continuously to a 70-gallon coagulation tank at a rite of 0.95 gallons/ minute, or a drv rubber rate of 130 pounds/ hour. Alum solution and dilution water are also run continuously into the coagulation tank at I and ().') gallons/minute. respective ly. The contents of this tank are kept at (0t)(050 C. The alum coagulates the rubber latex and forms a slurry of the rubber crumb in water which overflows to a 400-gallon tank.In this second tank the slurry is heated to 90 C. with steam, and the hot 2.3 per cent resin latex is added continuouslv at a rate of 3.8 pounds/minute which will give four parts/100 parts of the oil extended rubber. The hot slurry overflows to another 4(X)-gallon tank where it is maintained at about 90 C. and another four parts of the resin partitioning agent latex is added continuously at a rate of 3.8 pounds/minute of the dilute latex. The slurry of the coated rubber particles then overflows to a 100- gallon tank where the coagulation of the resin latex is completed. Substantiallv all of the resin adheres to the surface of the particles. The slurrv overflows to a con tinuous vacuum filter where the water is drained of the crumb and washing takes place.The wet rubber particles are then fed to a continuous apron or tunnel dryer with an air temperature of 85 C. There is some sticking together of the resin-coated crumb on the apron of the dryer. but the dry material crumbles apart easily to a freeflowing rubber crumb.

WHAT WE CLAIM IS: 1. A partitioning agent which is a heatsoftenable mixture of (a) 50 to 80 parts, by weight, of a styrene-butadiene copolymer with a styrene content of 80 to 99 per cent.

by weight, and (b) 50 to 20 parts of a polymethyl methacrylate or another resin of high agglomeration temperature, as herein defined.

'. A partitioning agent of claim I in which the heat-softenable mixture is composed of (a) substantially 7() parts of the copolymer and (b) substantially 30 parts of the polymethyl methacrylate, or other resin of high agglomeration temperature, as herein defined, and has an agglomeration temperature of substantially ()() C.

3. The process of producing a coated polymer crumh. which process comprises coating a tacky polymer crumb with a blend of (a) 50 to 80 parts, by weight, of a styrene-butadiene copolymer resin with a styrene content of substantially 80 to 99 per cent and (b) 50 to 20 parts, by weight, of a polymethyl methacrylate resin, or another resin of high agglomeration temperature, as herein defined, and drying the coated crumb at a temperature not in excess of substantially 110 C.

4. The process for preparing elastomeric particles coated with a partitioning agent which comprises preparing a latex blend of (a) 50 to 80 parts, by weight, of a styrenebutadiene copolymer resin with a styrene content of substantially 8() to 99 per ceilt and (b) 50 to 20 parts, by weight, of a polymethyl methacrylate resin, or another resin of high agglomeration temperature, as herein defined, said latex having a concentration of 0.1 to 10 per cent: coagulating a latex of elastomeric particles in an aqueous medium containing coagulant in slight ex cess of that necessary to agglomerate the elastomeric particles: mixing the two resin latices to produce the blend, using sufficient of the latex blend to coat the elastomeric particles sufficientlv to prevent the agglomeration of the coated particles during drying, and drying at a temperature not in excess of substantially 110 C.

5. The process in claim 3 in which the polymer from which the crumb is produced is a butadiene-styrene rubber.

6. The process of claim 3 in which the polymer from which the crumb is produced has a black masterbatch composition.

7. The process of claim 3 in which the polymer from which the crumb is produced has an oil masterbatch composition.

8. The process of claim 3 in which the polymer from which the crumb is produced has an oil-black masterbatch composition.

9. The process of claim 4 in which the partitioning agent is a blend of substantially 70 parts of the copolymer and 30 parts of the polymethyl methcarylate, or other resin of high agglomeration temperature, as herein defined, and the final drying temperature does not exceed substantially 90 C.

10. The process of claim 4 in which the concentration of the components in the latex of the partitioning agent is not over 2 per cent by weight.

II. The process of claim 3 which includes the steps of extruding the polymer crumb as a strand measuring no more than substantiallv 50 mm. in the largest dimension. dividing the strand into lengths no more than substantially 5(1 mm. in length, forming an aqueous slurry therefrom. and coating the resulting crumb particles with the blend.

12. The process of claim 3 which includes the steps of obtaining the crumb by grinding. forming a slurrv from the ground particles and coating the particles.

13. The process of claim 3 in which the polymer crumb is coated and dried in a continuous process.

14. The process of claim 3 in which the polymer crumb is obtained in a continuous coagulation process and is then coated and dried in a continuous process.

15. A process as claimed in claim 3 substantiallv as described in Example 3. 4, 5 or 6.

16. Coated polymer crumb produced by a process as claimed in any of claims 3 to 15.

17. Coated polymer crumb wherein the crumb coating comprises a partitioning agent as claimed in claim I or 2.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. cent resin latex is added continuouslv at a rate of 3.8 pounds/minute which will give four parts/100 parts of the oil extended rubber. The hot slurry overflows to another 4(X)-gallon tank where it is maintained at about 90 C. and another four parts of the resin partitioning agent latex is added continuously at a rate of 3.8 pounds/minute of the dilute latex. The slurry of the coated rubber particles then overflows to a 100- gallon tank where the coagulation of the resin latex is completed. Substantiallv all of the resin adheres to the surface of the particles. The slurrv overflows to a con tinuous vacuum filter where the water is drained of the crumb and washing takes place.The wet rubber particles are then fed to a continuous apron or tunnel dryer with an air temperature of 85 C. There is some sticking together of the resin-coated crumb on the apron of the dryer. but the dry material crumbles apart easily to a freeflowing rubber crumb. WHAT WE CLAIM IS:

1. A partitioning agent which is a heatsoftenable mixture of (a) 50 to 80 parts, by weight, of a styrene-butadiene copolymer with a styrene content of 80 to 99 per cent.

by weight, and (b) 50 to 20 parts of a polymethyl methacrylate or another resin of high agglomeration temperature, as herein defined.

'. A partitioning agent of claim I in which the heat-softenable mixture is composed of (a) substantially 7() parts of the copolymer and (b) substantially 30 parts of the polymethyl methacrylate, or other resin of high agglomeration temperature, as herein defined, and has an agglomeration temperature of substantially ()() C.

3. The process of producing a coated polymer crumh. which process comprises coating a tacky polymer crumb with a blend of (a) 50 to 80 parts, by weight, of a styrene-butadiene copolymer resin with a styrene content of substantially 80 to 99 per cent and (b) 50 to 20 parts, by weight, of a polymethyl methacrylate resin, or another resin of high agglomeration temperature, as herein defined, and drying the coated crumb at a temperature not in excess of substantially 110 C.

4. The process for preparing elastomeric particles coated with a partitioning agent which comprises preparing a latex blend of (a) 50 to 80 parts, by weight, of a styrenebutadiene copolymer resin with a styrene content of substantially 8() to 99 per ceilt and (b) 50 to 20 parts, by weight, of a polymethyl methacrylate resin, or another resin of high agglomeration temperature, as herein defined, said latex having a concentration of 0.1 to 10 per cent: coagulating a latex of elastomeric particles in an aqueous medium containing coagulant in slight ex cess of that necessary to agglomerate the elastomeric particles: mixing the two resin latices to produce the blend, using sufficient of the latex blend to coat the elastomeric particles sufficientlv to prevent the agglomeration of the coated particles during drying, and drying at a temperature not in excess of substantially 110 C.

5. The process in claim 3 in which the polymer from which the crumb is produced is a butadiene-styrene rubber.

6. The process of claim 3 in which the polymer from which the crumb is produced has a black masterbatch composition.

7. The process of claim 3 in which the polymer from which the crumb is produced has an oil masterbatch composition.

8. The process of claim 3 in which the polymer from which the crumb is produced has an oil-black masterbatch composition.

9. The process of claim 4 in which the partitioning agent is a blend of substantially 70 parts of the copolymer and 30 parts of the polymethyl methcarylate, or other resin of high agglomeration temperature, as herein defined, and the final drying temperature does not exceed substantially 90 C.

10. The process of claim 4 in which the concentration of the components in the latex of the partitioning agent is not over 2 per cent by weight.

II. The process of claim 3 which includes the steps of extruding the polymer crumb as a strand measuring no more than substantiallv 50 mm. in the largest dimension. dividing the strand into lengths no more than substantially 5(1 mm. in length, forming an aqueous slurry therefrom. and coating the resulting crumb particles with the blend.

12. The process of claim 3 which includes the steps of obtaining the crumb by grinding. forming a slurrv from the ground particles and coating the particles.

13. The process of claim 3 in which the polymer crumb is coated and dried in a continuous process.

14. The process of claim 3 in which the polymer crumb is obtained in a continuous coagulation process and is then coated and dried in a continuous process.

15. A process as claimed in claim 3 substantiallv as described in Example 3. 4, 5 or 6.

16. Coated polymer crumb produced by a process as claimed in any of claims 3 to 15.

17. Coated polymer crumb wherein the crumb coating comprises a partitioning agent as claimed in claim I or 2.