Process for internal cleaning of extruders

Claim 2

A process according to claim 1 in which there are present, by weight, in said composition from about 5 to about 95 parts of said first polymer and from about 95 to about 5 parts of said second polymer.

Claim 3

A process according to claim 3 in which said first polymer is a highly crystalline, brittle, linear polyester resin having recurring cyclic structure in the polymer backbone, having a brittle temperature point above about 135*C., a melting point below about 315*C., and an intrinSic viscosity in phenol: chlorobenzene in about 60:40 weight ratio, of from about 0.2 to about 1.3 deciliters per gram determined at about 25*C. in a solution containing about 0.5 grams of polymer per 100 milliliters in phenol:chlorobenzene, and in which said second polymer is selected from the group consisting of polyethylene; amorphous polyester having an intrinsic viscosity of about 0.2 to about 1.3; polypropylene; copolymer of ethylene with a copolymerizable ethylenically unsaturated monomer; polyvinyl acetate; polyvinyl chloride; synthetic wax; polybutylene; and polyisobutylene.

Claim 4

A process for removing deposits of encrusted and decomposed organoplastic material from the interior surfaces of a screw-type extruder having a series of controlled heat zones arranged along the length of the extruder in ascending temperatures from the inlet to the outlet of the extruder, said heat zones including a feed heat zone, a transition heat zone, a metering heat zone and an outlet heat zone, said process comprising a. charging into the inlet of the extruder an effective amount of an extruder cleaning composition comprising (1) discrete, crushable particles of a highly crystalline thermoplastic first polymer having a high brittle point and (2) a thermoplastic second polymer which has a melting point below said brittle point and which upon heating above its said melting point, forms a fluid-phase carrier for said particles, said highly crystalline polymer having a melting point up to about 350*C; b. heating the feed heat zone and transition heat zone of the extruder to temperatures at least above the melting point of the second polymer and below the brittle temperature point of the first polymer; c. propelling the composition through the feed heat zone and the transition heat zone of the extruder; d. heating the outlet heat zone of the extruder at least to the melting point of the first polymer; e. heating the metering heat zone to a temperature intermediate to that of the transition heat zone and the outlet heat zone; and f. propelling the composition through said metering heat zone and said outlet heat zone until the composition leaving the extruder is substantially free of occluded deposits of the organoplastic material.

Claim 5

A process according to claim 5 in which said composition comprises a mixture containing from about 5 to about 95 parts of said first polymer and from about 95 to about 5 parts of said second polymer.

Claim 6

A process according to claim 6 in which said first polymer is a highly crystalline brittle linear polyester resin having recurring cyclic structure in the polymer backbone, having a brittle temperature point above about 135*C., a melting point below about 315*C., and an intrinsic viscosity in phenol: chlorobenzene in about 60:40 weight ratio of from about 0.2 to about 1.3 deciliters per gram determined at about 25*C. in a solution containing about 0.5 gram of polymer per 100 milliliters of phenol:chlorobenzene and in which said second polymer is selected from the group consisting of polyethylene; amorphous polyester having an intrinsic viscosity in phenol:chlorobenzene in about 60:40 weight ratio of about 0.2 to about 1.3 deciliters per gram determined at about 25*C. in a solution containing about 0.5 gram of polymer per 100 milliliters of phenol:chlorobenzene; polypropylene; copolymer of ethylene with a copolymerizable ethylenically unsaturated monomer; polyvinyl acetate; polyvinyl chloride; synthetic wax; polybutylene; and polyisobutylene.

Claim 7

The process according to claim 7 wherein the second polymer is a polyethylene having a melt index in the range from about 0.5 to about 15 g. per 10 minutes with ASTM test method D1238E and a melting point of about 80* to about 100*C.

Claim 8

The process according to claim 7 wherein the first polymer is a polyester resin selected from the group consisting of poly(ethylene terephthalate), poly(1,4-cyclohexylenedimethylene terephthalate), poly(ethylene isophthalate), poly(tetramethylene terephthalate), poly(ethylene naphthalane-dicarboxylate) and mixtures thereof.

Claim 9

The process according to claim 9 wherein the second polymer is a polyethylene having a melt index in the range of from about 0.5 to about 15 g. per 10 minutes with ASTM test method D1238E and a melting point of about 80* to about 100*C.

Claim 10

The process according to claim 10 wherein the first polymer is poly(ethylene terephthalate).