PLASTIC PELLETS COATED WITH PROCESSING AID AND METHOD OF COATING

Abstract: Plastic pellets showing improved behavior upon extrusion, comprising coating the pellets with a fused layer of certain waxes or polymeric materials; and a method of preparation, comprising heating the plastic pellets to a temperature just below the softening or fusing temperature of the additive while blending the pellet in a high intensity blender, introducing the additive and maintaining intense blending until the temperature is above the fusing temperature of the additive, and discharging the coated pellets from the blender.

Description: PLASTIC PELLETS COATED WITH PROCESSING AID AND METHOD OF COATING The present invention relates to pellets of a plastic having improved extrusion properties. It is well-known to form a variety of articles fabricated from plastic pellets. In the past, the practice generally was to extrude the plastic directly from the powder form in which it is recovered after polymerization. Because of the convenience of shipping and handling, it is desirable to form the plastic into pellets prior to final extrusion. With the increased demand for pellets, the processing conditions to which pellets are exposed has become more demanding. When melt processed, conven¬ tional plastic pellets have a tendency to generate particulate degradation products (i.e., carbonaceous material, gels or fish eyes) in the extrudate, partic¬ ularly when the plastic is exposed to relatively long residence times in the melt processing equipment. Processing aids are conventionally blended into the plastic prior to fabrication into a pellet, However, it has been found that a certain lag time period exists, after exposure to desirable processing temperatures, before the blended processing aids func¬ tion effectively. It is during the lag time period, that the plastic is particularly susceptible to decomposition upon exposure to desirable processing temperatures. In some instances, plastic pellets have had processing aids applied to their surfaces. Generally, such processing aids are applied by spraying droplets of processing aid on the pellet surface. While such techniques have had some success, these techniques do not consistently provide uniform pellet surface coating. Although conventionally coated pellets may be satisfactorily extrudable for a period, such pellets have not been found to be easily extrudable for commer¬ cially required periods. Specifically, when extruded, the non-uniform coating on the pellet surface causes variations in extrusion rate, torque within the extruder and pressure within the extruder. Moreover, the non- -fused coatings tend to flake off the pellet surface. It is desirable to produce a plastic pellet, having its surface coated with lubricant, which is capable of being extruded without causing variations in torque of the extruder screw, melt pressure or rate of extrusion of the pellet. It is to these goals that the present invention is directed. The present invention concerns a process for preparing a pellet having improved extrudability, which process comprises the steps of: (a) providing a plastic in pellet form, and a processing aid having a softening point between ambient temperatures and below the processing temperature of the plastic in pellet form; (b) charging the pellet into a high intensity blender, said blender having an impeller; (c) rotating the blender impeller at a speed and for a period of time effective to raise the temperature of the pellet surface to between about 5°C and 10°C below the softening point of the processing aid; (d) charging the processing aid into the blender such that the processing aid contacts the heated pellet surface; and (e) rotating the blender impeller at a speed and for a period of time effective to raise the temperature of the pellet surface to a temperature above the softening point of the processing aid, and to coat a portion of the pellet surface by fusing the processing aid thereto. Additionally, the present invention concerns a composition, in the form of an extrudable pellet, which comprises a plastic, said pellet having a processing aid fused on the surface thereof at a level effective to improve the extrudability of the pellet. Applicant has discovered that the process and composition according to the present invention improves the extrudability of the plastic pellets. The pellets are considered to possess improved extrudability, i.e., less carbonaceous material contamination on the melt processing equipment, e.g., on an extruder screw heel; and a lower mechanical energy to extrude than a pellet, which does not have processing aids coated on its sur¬ face in a manner according to the present invention. The plastics which may be employed according to the present invention include any plastic which may be pelletized. The plastic is formed by blending a poly¬ mer, prior to pelletization, with a variety of additives incorporated therewith to form a plastic. Exemplary of suitable polymers are the olefin polymers such as homopolymers and copolymers of α-mono- olefins (e.g., ethylene, propylene, butene-1, isobutyl- ene, 1-pentene, 1-hexene, 1-octene, and the like); and α-monoolefin/α-monoolefin copolymers (e.g., ethylene/propylene copolymers). Additional suitable polymers include those based on substituted α-monoolefins (e.g., α-monoolefins having from 4 to 12 carbon atoms wherein the substituents can be halo, alkyl or haloalkyl having from 1 to 12 carbon atoms; α-alkenyl having 2 to 12 carbon atoms; acyl having 1 to 12 carbon atoms; carboxylate having from 1 to 12 carbon atoms; alkoxyl having from 1 to 12 carboa atoms; and aryloxy having from 6 to 12 carbon atoms). Exemplary substituted α-monoolefins are vinyl chloride, vinyl bromide, vinylidene chloride, acrylic acid, methacrylic acid, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, diethyl acrylate, diethyl maleate, ethyl hydrogen maleate, methyl ethacrylate, dibutyl itaconate, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl ethyl ether, methyl vinyl ketone, acrylamide, acrylonitrile and the like. Other suitable polymers include those based on carboxylic acids having from 3 to 8 carbon atoms (e.g., ethylene vinyl acetate and ethylene acrylic acid), and partially hydrolyzed copolymers thereof (e.g., ethylene vinyl alcohol); alkyl or haloalkyl esters of carboxylic acid wherein the alkyl or haloalkyl has from 1 to 12 carbon atoms; α-alkenyls having 2 to 12 carbon atoms; acyls having 1 to 12 carbon atoms; carboxylates having from 1 to 12 carbon atoms; alkoxyls having from 1 to 12 carbon atoms; aryloxys having from 6 to 12 carbon atoms; rubbery ethylene-propylene-diene terpolymers; polyesters and copolyesters such as those polyesters and copolyesters whose synthesis employs at least one polyhydric alcohol and at least one dibasic acid (e.g., polyethylene terephthalate, and the like); the poly- etheramides; the polyamides (e.g., polycaprolactam); the polycarbonates (e.g., bisphenol A,); the polyester carbonates; the polyimides; the vinyl aromatics such as styrene; and polymers based on vinyl aromatics copolymerized with suitable monomers, including unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, and ethacrylonitrile) , and the conjugated 1,3-dienes (e.g., butadiene and isoprene). This invention is advantageous for those plas¬ tics which are commonly melt processed with processing aids, and most advantageous for the extrusion of ther¬ mally sensitive plastics which are melt processed with processing aids. For the purposes of this invention, it is understood that the term "thermally sensitive" refers to any plastic which exhibits an undesirable change in properties, particularly physical properties, upon exposure to desirable processing temperatures. Exemplary thermally sensitive plastics include polyvinylidene halide copolymers, polyvinyl halide copolymers and ethylene vinyl alcohol copolymers. Suitable additives include, for example, colorants, pigments, non-elastomeric reinforcing agents, fillers, antioxidants, stabilizers, etc., as long as these do not detrimentally affect the resulting uniformity of coating and completeness of surface cov¬ erage. The process comprises physically blending the interpolymer with the additives to form a mixture. Methods of forming the plastic into pellets are well-known to those skilled in the art. Any method capable of forming the plastic into pellets is suitable for use in the present invention. For the purposes of this application, the terms "pellet" or "pellets" refer to particles having a minimum cross-sectional dimension of at least 1/32 inch, preferably at least 1/16 inch and most preferably at least 1/8 inch, said pellets suitably have a maximum cross-sectional dimension of at least 1/2 inch, preferably at least 3/8 inch and most preferably at least 1/4 inch. Exemplary of a method suitable for use in forming the pellets of the mixture is extrusion through a strand die and pelletization by chopping the extruded strand into pellets. By "processing aid" is meant any component which is employed to improve extrusion performance. Although not intended to be bound by theory, it is believed that by applying the processing aid to the surface of the pellet the processing aid will, during melt processing, rapidly migrate to the metal surface of the melt processing equipment. Surface coated pro¬ cessing aids thereby provide relatively fast functioning compared to conventionally compounded processing aids, which require pellet melting prior to functioning. Consequently, a lower amount of the processing aid is necessary to achieve equivalent effects to the same processing aid blended with the plastic. Generally, the surface of the pellet will be coated with a processing aid, wherein the processing aid will be in an amount of between 0.001 weight percent to 2 weight percent, said weight percents based on the weight of the pellet; preferably in an amount of between 0.01 weight percent to 1.5 percent, said weight percents based on the weight of the pellet; and most preferably in an amount of between 0.1 weight percent to 0.7 weight percent, said weight percents based on the weight of the 10 pellet. Generally, within the suitable ranges, the higher the level of processing aid on the pellet sur¬ face, the more benefit one will see in terms of improv¬ ing extrudability of the plastic pellet. 15 Within the prescribed ranges, the choice of optimum amounts of processing aids will be dependent upon the the processing aid selected, the viscosity of the processing aid, the size of the pellet and the type and size of the equipment through which the pellet is 20 extruded. Generally within the prescribed weight per¬ centage ranges for coating processing aids on the pellet pc - surface, the inventor has found that the more processing aid which is coated on the pellet surface the more of a decrease in particulate degradation will be seen in the extrudate. Preferably, the pellet surface will be uniformly coated with the processing aid, that is to 30 say, when compared to an uncoated pellet, 50 percent coverage of a pellet surface will produce somewhat decreased particulate degradation of the extrudate; whereas 90 percent coverage of the same pellet will produce a still further improvement in decreasing the particulate degradation in the extrudate. Similarly, within the ranges discussed above, the thicker the surface coating, the more benefit one will see in terms of decreasing the particulate degradation in the extrudate. If, however, the processing aid is applied in quantities excessive for the processing aid selected, the viscosity of the processing aid, the size of the pellet and the type and size of the equipment through which the pellet is extruded, the feeding of the pellet into the melt processing equipment may be impaired because of insufficient friction in the feed zone; or the excess amount of processing aid may form globules on the pellet surface. The processing aids coated on the pellet sur- face are those generally used for the conventional melt processing of plastics in either powder or pellet form. The processing aid is selected to have a softening point between ambient temperatures and below the processing temperature of the plastic in pellet form. Preferably, the processing aid should have, within the preferred range, a softening point slightly above ambient temperatures to allow for rapid functioning and yet for easy handling, e.g., low pellet surface tackiness, Within the above parameters, the specific processing aid selected will be a matter of choice for the skilled artisan, depending upon the desired results. Exemplary processing aids include lubricants and olefin polymers. The choice of specific processing aids for specific plastics will -be a matter of choice well within the means of one skilled in the art. Exem¬ plary factors in selecting a processing aid, although not all factors are important for all polymers, include melt adhesion, fusion delay, viscosity reduction and an extrusion rate increase at a given rpm. Lubricants include both internal and external lubricants which improve extrusion performance of the 5 plastic. By "internal lubricant" is meant any of the classes of compounds that have heretofore been employed as internal lubricants in plastics. Although not intended to be bound by theory, the lubricants are _ l0 classified as "internal" because they increase the ease with which the polymer molecules slip past one another, resulting in reduced melt viscosity, better flow, and lower energy to extrude requirements for melt pro¬ cessing. The compositions may perform functions in 15 addition to that mechanism referred to as internal lubrication. By "external lubricant" is meant any of the class of compounds that have heretofore been employed as 0 external lubricants in plastics. Although not intended to be bound by theory, the lubricants are classified as "external" because they are believed to be at least partially incompatible with the molten polymer. The π lubricant will therefore migrate to the surface of the molten polymer and form a film between the polymer and the heated metal surface of the extruder, mill or other equipment used to process the polymer composition. This film significantly reduces the tendency of the polymer 0 to adhere to these metal surfaces and degrade. The compositions may perform functions in addition to that mechanism referred to as external lubrication. Exemplary lubricants include fatty acids (e.g., stearic acid); esters (e.g., fatty esters, wax esters, glycerol esters, glycol esters, fatty alcohol esters, and the like); fatty alcohols (e.g., n-stearyl alcohol); fatty amides (e.g., N,N'-ethylene bis stearamide); metallic salts of fatty acids (e.g., calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, sodium stearate, tin stearate, sodium lauryl sulfate, and the like); and polyole in waxes (e.g., paraffinic, nonoxidized and oxidized polyethylene and the like). 10 The term "olefin polymer" includes homopolymers and copolymers of α-monoolefins and substituted α-mono¬ olefins, particularly α-monoolefins or substituted α-monoolefins having from 4 to 12 carbon atoms. Exem¬ plary α-monoolefin polymers include polyethylene (e.g., 15 ultra-low density polyethylene, low density polyethyl¬ ene, linear low density polyethylene, medium density polyethylene, high density polyethylene); polypropylene; poly(butene-1) , poly(isobutylene); poly(1-pentene) ; polyO-hexene) and polyO-octene) . 20 Substituted α-monoolefins include those wherein the substituents can be halo, alkyl or haloalkyl having from 1 to 12 carbon atoms; carboxylic acid having from 3 p j- to 8 carbon atoms; alkyl or haloalkyl ester of car¬ boxylic acid wherein alkyl or haloalkyl has from 1 to 12 carbon atoms; α-alkenyl having 2 to 12 carbon atoms; acyl having 1 to 12 carbon atoms; carboxylate having from 1 to 12 carbon atoms; alkoxyl having from 1 to 12 30 carbon atoms; ' and aryloxy having from 6 to 12 carbon atoms. The α-monoolefins and substituted α-monoolefins may also be copolymerized with a variety of suitable comonomers such as carboxylic acids having from 3 to 8 carbon atoms (e.g., ethylene vinyl acetate, and ethylene acrylic acid); alkyl or haloalkyl esters of carboxylic acid wherein alkyl or haloalkyl has from 1 to 12 carbon atoms; α-alkenyls having 2 to 12 carbon atoms; acyls having 1 to 12 carbon atoms; carboxylates having from 1 to 12 carbon atoms; alkoxyls having from 1 to 12 carbon atoms; aryloxys having from 6 to 12 carbon atoms; and α-monoolefin/α-monoolefin copolymers (e.g., ethylene/propylene copolymers). 10 The processing aid is then charged into the blender for further mixing of the preheated pellet and processing aid until the processing aid fuses onto the pellet surface. 15 The pellets are prepared for coating by being mixed in a high intensity blender. By "high intensity" blender is meant mixers that can apply about 10 horse power per cubic foot of material with high shear rate, 20 with a maximum of 20,000 sec " . Exemplary high intensity blenders include Banbury mixers, Prodex- -Henschel mixers, and Welex-Papenmeier mixers. p ,- Such blenders typically have an impeller for mixing and applying energy to the batch, and a baffle for directing the motion of the product to the center of the vortex. Such blenders also have a jacket sur¬ rounding the mixing bowl so that cooling may be applied. 30 Generally, the blender impeller is run at a tip speed of between 2000 feet per minute (fpm) to 4000 fpm, preferably between 2500 fpm to 3000 fpm. The degree of deflection of the blender baffle may be adjusted from 45° to 0°, and preferably between 15° to 0°, where 0° refers to a radial orientation. The pellet surface will be heated to a tem¬ perature of at least about 10°C, preferably about 5°C, below the temperature at which the processing aid will soften and fuse. Persons skilled in the art recognize that mixing times will vary with the blending technique, apparatus and the choice of processing aid. The pellets will be mixed until their surface temperature is above that of the temperature required to soften the processing aid, but below the softening point of the plastic. Water may be passed through a water jacket to maintain control of the heating of the pellet surface at a temperature of between the softening point of the processing aid and below the softening point of the plastic. After being surface coated, the pellet then may be melt processed and extruded into any suitable final product. The process of the present invention can be used to form a variety of films or other articles. As is well-known in the art, the films and articles may be fabricated with conventional coextru- sion, e.g, feedblock coextrusion, multimanifold die coextrusion or combinations of the two; injection molding; extrusion molding and lamination techniques. Articles formed therefrom include blown and cast, mono and multilayer, films; rigid and foam sheet; tubes; pipes; rods; fibers and various profiles. Lamination techniques are particularly suited to produce multi-ply sheets. As is known in the art, specific laminating techniques include fusion, wet combining or heat reac¬ tivation. Fusion comprises bonding self-sustaining lamina together by applications of heat and pressure. Wet combining comprises laminating two or more plies by using a tie coat adhesive, which is applied wet; driving off the liquid and combining, by subsequent pressure laminating, in one continuous process. Heat reactivation comprises combining a precoated film with another film by heating and reactivating the precoat adhesive so that it becomes receptive to bonding after subsequent pressure laminating. The present invention is illustrated in further detail by the following examples. The examples are for the purposes of illustration only, and are not to be construed as limiting the scope of the present inven¬ tion. All parts and percentages are by weight unless otherwise specifically noted. Examples TABLE I Code Polymer Components PVdC A pellet of a polymeric composition compris¬ Pellet ing a 96.5 base resin, 1.5$ ethylene vinyl acetate, "1 .2% tetrasodium pyrophosphate and 0.8$ epoxidized soybean oil. The base resin is polymerized from a monomer mixture con¬ taining 80 weight percent vinylidene chloride and 20 weight percent vinyl chloride, said resin having a major melting point of 164°C, and a molecular weight of 80,000. L-1 An oxidized polyethylene commercially avail¬ able under the trade designation as Allied 629A from Allied Corp. The oxidized polyeth¬ ylene has a density (ASTM Test D-1505) of 0.93 grams per cubic centimeter § 20°C, a drop point of 104°C and a Brookfield Viscosity of 200 cps § 140°C. L-2 A polyethylene wax commercially available from Allied Corp. under the trade designation Allied 617A. The polyethylene wax has a density (ASTM Test D-1505) of 0.91 grams per cubic centimeter, a drop point of 102°C and a Brookfield Viscosity of 180 cps @ 140°C. L-3 An ethylene/vinyl acetate copolymer having polymerized therein 72 weight percent ethylene and 28 weight percent vinyl acetate, both percentages being based upon copolymer weight * The copolymer has a melt index (ASTM Test D-1238) of 22 to 27 decigrams per minute and a density (ASTM Test D-1238) of 0.98 grams per cubic centimeter. The copolymer is commercially available from DuPont under the trade designation Elvax 3180. Sample Preparation The pellets are placed in a high speed blender which is commercially available under the trade desig¬ nation Welex Model 35 from F. H. Papenmeier K.G. Com- pany. The mixer has a diameter of 35 cm, and a nominal capacity of 1 cubic foot. The baffle of the mixer is adjusted in the radial direction, the impeller is started and the tip speed is adjusted to about 2700 feet per minute (fpm). When the pellet temperature reaches 75°C, various processing aids, coded in Table I, are charged in the mixer in quantities set forth in Table II. The pellets and processing aids are blended for a period of about eight minutes and discharged. The discharged material is cooled to about 65°C, by circulating 20°C air. Fusion Testing Extrudability is determined by measuring the fusion time of the pellet as it is melt processed. The pellets are placed in the bowl of a Brabender ® torque rheometer. The bowl is maintained at a temperature of 170°C and the speed of the blades is about 60 rpm. A sample of coated pellets, weighing 80 grams is charged in the rheometer, and the fusion times are determined. The fusion time for the pellets is 60 sec¬ onds, and the maximum torque is 960 meters/gram. A relatively short fusion time will cause degradation and discoloration of the molten polymer, resulting from a prolonged exposure to heat while in the molten state. The maximum torque value, a measure of the mechanical energy necessary to cause fusion, should be from about 1800 to about 2500 meter grams. Higher torque values will result in an excessively high current demand and possibly damage to the extruder motor. The results are set forth in Table II. TABLE I Coating Exam- Pellet Processing Weight Fusion Fusion — = not measured. Pellet type as set forth in Table I. Coating = (a) processing aid and (b) amount of processing aid coating on pellet in weight percent. Fusion Time in sec. Fusion Torque in sec. "NF" means that no fusion occurs by the time the test is terminated after 600 seconds. Examples 8-16 The procedures of Examples 1-7, respectively, are repeated with the following exception: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of a polymeric composition comprising a 96.5 percent base resin, 1.5 percent ethylene vinyl acetate, 1.2 percent tetrasodium pyrophosphate and 0.8 percent epoxidized soybean oil. The base resin is polymerized from a monomer mixture containing 94 weight percent vinylidene chloride and 6 weight percent methyl acrylate, said resin having a major melting point of 164°C, and a molecular weight of 90,000. The pellets exhibited a relatively long fusion time and low fusion torque. Example 17 The procedures of Example 5, respectively, are repeated with the following exception: Instead of the vinylidene chloride-vinyl chloride copolymer, the pel- lets are made of a polyvinyl chloride copolymer. The pellets exhibited a relatively long fusion time and low fusion torque. Example 18 The procedures of Example 5 are repeated with the following exception: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of polyethylene terephthalate copolymer. The pellets exhibited a relatively long fusion time and low fusion torque. Example 19 The procedures of Example 5 are repeated with the following exceptions: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of polypropylene. The pellets exhibited a relatively long fusion time and low fusion torque. Example 20 The procedures of Example 5 are repeated with the following exceptions: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of a polystyrene. The pellets exhibited a relatively long fusion time and low fusion torque. Example 21 The procedures of Example 5 are repeated with the following exceptions: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of a high impact polystyrene. The pellets exhibited a relatively long fusion time and low fusion torque. Example 22 The procedures of Example 5 are repeated with the following exception: instead of the vinylidene chloride-vinyl chloride copolymer, the pellets are made of polycarbonate. The pellets exhibited a relatively long fusion time and low fusion torque. Although the invention has been described in considerable detail, with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be affected within the _.,- spirit and scope of the invention as described above and as defined in the appended claims. 20 25 30

Claims: 1. A process for preparing a pellet having 10 improved extrudability, which process comprises the steps of: (A) providing a plastic in pellet form, 15 and a processing aid having a softening point between ambient temperatures and below the processing temperature of the plastic in pellet form; 20 (B) charging the pellet into a high intensity blender, said blender having an impeller; (C) rotating the blender impeller at a speed and for a period of time effective to 25 raise the temperature of the pellet surface to between about 5°C and 10°C below the softening point of the processing aid; (D) charging the processing aid into the blender such that the processing aid contacts 30 the heated pellet surface; and (E) rotating the blender impeller at a speed and for a period of time effective to raise the temperature of the pellet surface _,,- to a temperature above the softening point of the processing aid, and to coat a portion of the pellet surface by fusing the processing aid thereto. 2. The process of Claim 1, wherein the plas¬ tic comprises a polymer formed from a monomer selected from the group consisting of α-monoolefins, substituted α-monoolefins and copolymers formed therewith; carbox¬ ylic acids having from 3 to 8 carbon atoms, and par¬ tially hydrolyzed copolymers thereof; alkyl or haloalkyl esters of carboxylic acid wherein the alkyl or haloalkyl has from 1 to 12 carbon atoms; α-alkenyls having 2 to 12 carbon atoms; acyls having 1 to 12 carbon atoms; carboxylates having from 1 to 12 carbon atoms; alkoxyls having from 1 to 12 carbon atoms; aryloxys having from 6 to 12 carbon atoms; rubbery ethylene-propylene-diene terpolymers; polyesters and copolyesters; the polyetheramides; the polyamides; the polycarbonates; the polyester carbonates; the polyimides; and the vinyl aromatics such as styrene, and copolymers formed therewith. 3. The process of Claim 1, wherein the pro¬ cessing aid is selected from the group consisting of lubricants and olefin polymers. 4. The process of Claim 3, wherein the lub¬ ricant is selected from the group consisting of fatty acids; esters; fatty alcohols; fatty amides; metallic stearates; and polyolefin waxes. 5. The process of Claim 1, wherein the blender Impeller in step (c) is run at a tip speed of between 1000 fpm and 6000 fpm. 6. The process of Claim 5, wherein the blender impeller in step (e) is run at a tip speed of between 1000 fpm and 4000 fpm. 7. The process of Claim 1, wherein the pro¬ cessing aid is coated on the pellet surface at a level of between 0.001 weight percent and 2 weight percent, said weight percents based on the total weight of the pellet. 8. The process of Claim 7, wherein the pro¬ cessing aid is coated on the pellet surface at a level of between 0.01 weight percent and 1.5 weight percent, said weight percents based on the total weight of the pellet. 9. The process of Claim 8, wherein the pro¬ cessing aid is coated on the pellet surface at a level of between about 0.1 weight percent and about 0.7 weight percent, said weight percents based on the total weight of the pellet. 10. A process for preparing a pellet having improved extrudability, which process comprises the steps of: (A) providing a plastic in pellet form, and a processing aid, said processing aid being selected from the group consisting of fatty acids; esters; fatty alcohols; fatty amides; metallic stearates; and polyolefin waxes; (B) charging the pellet into a high intensity blender, said blender having an impeller; (C) rotating the blender impeller at a speed of between 2000 fpm and 3000 fpm for a period of time effective to raise the temperature of the pellet surface to between 5°C and 10°C below the softening point of the processing aid; (D) charging the processing aid into the blender such that the processing aid contacts the heated pellet surface; and 10 (E) rotating the blender impeller at a speed of between 2500 fpm and 3000 fpm for a period of time effective to raise the temperature of the pellet surface to a _.,- temperature above the softening point of the processing aid, and to coat a portion of the pellet surface by fusing the processing aid thereto. 20 11. A pellet made by the process of Claim 1. 12. A pellet made by the process of Claim 4. 13- A pellet made by the process of Claim 10, 25 14. A composition, in the form of an extrudable pellet, which comprises a plastic, said pellet having a processing aid fused on the surface thereof at a level 30 effective to improve the extrudability of the pellet. 15. The composition of Claim 16, wherein the plastic comprises a polymer formed from a monomer selected from the group consisting of α-monoolefins, 35 substituted α-monoolefins, and copolymers formed there¬ with; carboxylic acids having from 3 to 8 carbon atoms, and partially hydrolyzed copolymers thereof; alkyl or haloalkyl esters of carboxylic acid wherein the alkyl or haloalkyl has from 1 to 12 carbon atoms; α-alkenyls having 2 to 12 carbon atoms; acyls having 1 to 12 carbon atoms; carboxylates having from 1 to 12 carbon atoms; alkoxyls having from 1 to 12 carbon atoms; aryloxys having from 6 to 12 carbon atoms; rubbery ethylene- -propylene-diene terpolymers; polyesters and copolyesters; the polyetheramides; the polyamides; the polycarbonates; the polyester carbonates; the poly- imides; and the vinyl aromatics such as styrene, and copolymers formed therewith. 16. The composition of Claim 15, wherein the processing aid is coated on the pellet surface at a level of between about 0.001 weight percent and about 2 weight percent, said weight percents based on the total weight of the pellet. 17- The composition of Claim 16, wherein the processing aid is coated on the pellet surface at a level of between 0.01 weight percent and 1.5 weight percent, said weight percents based on the total weight of the pellet. 18. The composition of Claim 17, wherein the processing aid is coated on the pellet surface at a level of between 0.1 weight percent and 0.7 weight percent, said weight percents based on the total weight of the pellet. 19- The composition of Claim 14, wherein the processing aid is selected from the group consisting of lubricants and olefin polymers. 20. The composition of Claim 19, wherein the lubricant is selected from the group consisting of fatty acids; esters; fatty alcohols; fatty amides; metallic stearates; and polyolefin waxes.

Inventors: LOUKS PAUL T, LOUKS, PAUL, T.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1989
Main classification: B05B7
IPC codes: B29B7, B29B9, B29K23, C08J3