CN1313876A - Expandable thermoplastic polymer particles and method for making same - Google Patents

Abstract

An improved process for manufacture of expandable polymer particles is provided. The continuous process disclosed produces expandable polymer pellets in a single step while eliminating many of the dangers inherent in processes of prior art employed for the same. The polymers produced herein are of uniform size, and may be molded into various articles of manufacture using existing equipment and techniques known to those skilled in the art.

Description

Expandable thermoplastic polymer particles and process for their preparation

This application claims U.S. nonprovisional patent application 09/158189 filed September 22, 1998, U.S. nonprovisional patent application 09/122512 filed July 24, 1998, and PCT application PCT filed July 24, 1998 /US98/15446 as the priority basis, they are still pending. The entire contents of these patents are hereby incorporated by reference.

The present invention relates to a new method of producing expandable thermoplastic particles. More specifically, the present invention relates to expandable polymer particles which can be advantageously produced using atomization techniques. The pellets thus produced can be expanded and melted in a manner well known to those skilled in the art, so that various molded articles can be formed from these pellets.

background

The prior art provides methods for producing expandable thermoplastic polymer materials including both crystalline and amorphous polymers. Expandable thermoplastics made from crystalline polymers are produced by heat-plasticizing a normally solid polymer resin and mixing the heat-plasticized resin with a volatile blowing agent under heat and pressure A flowable gel is formed which is then extruded into a zone of lower pressure and temperature to expand and cool the gel to form the desired solid polymer foam product. 1,2-Dichlorotetrafluoroethane has been widely used as this blowing agent because it imparts sufficient dimensional stability to the bulk of the foamed product during curing. However, due to the use of stability control agents, such as those long-chain fatty acid/polyol partial esters described in U.S. Patent 3,644,230 and the esters of higher fatty acids described in U.S. Patents 4,214,054 and 4,395,510, other blowing agents, such as pentane and the like The hydrocarbons of alkanes have been successfully utilized at present, and the contents of the above-mentioned patents are hereby incorporated by reference into the present invention. Consequently, a wide variety of expandable thermoplastics, even including crystalline polymers, can now be produced using conventional techniques. In known methods, blowing agents are compounded into the starting polymer resin blend in proportions to produce the desired degree of expansion in the resulting foamed honeycomb product, typically up to about 60 times volume expansion, to produce aged foam Product with a material density down to about 9.6 kg/m3 (about 0.6 lb/ft3). Foamable compositions can be made by heat-plasticizing an olefinic polymer resin, then mixing the resin with a stability control agent and a blowing agent, and finally activating the blowing agent to expand the mixture. Typical methods of producing these materials are outlined in US Pat. Nos. 4,694,027, 4,894,395, 5,304,580 and 5,605,937, the entire contents of which are hereby incorporated by reference. However, known methods of producing expandable thermoplastics result in pellets with suboptimal properties. For example, expandable polyolefin particles such as polyethylene must be pre-expanded prior to impregnation with the blowing agent, and this pre-expansion requirement is well known to those skilled in the art. This necessary pre-expansion equates to a corresponding increase in the storage space required to store the final expandable particles. Furthermore, it is well known to those skilled in the art that the shelf life of pre-expanded thermoplastic foamable materials made from normally crystalline polymers is much less than ideal.

On the other hand, the production of foamable compositions comprising amorphous polymers, such as polystyrene materials, involves the usual batch process in which various raw materials (including those containing styrene mono- body, surfactant, catalyst, and an aqueous suspension of other additives) to obtain spherical polystyrene beads with a diameter of about 0.3-1.5 mm. Subsequently, these beads are impregnated with a hydrocarbon or other blowing agent (usually pentane or halogenated hydrocarbon), that is, about 100 parts (by weight) of polymer particles, 100 parts of water, and 1 part of concentrated surfactant (or A mixture, such as a mixture of aralkyl polyether alcohol and dodecylbenzenesulfonate) is charged into the autoclave along with about 3-10 parts of pentane. The mixture was heated under pressure to about 170 degrees Fahrenheit for 3 hours and then cooled to room temperature to obtain expandable polystyrene beads which were rinsed, dried and stored until use. In general, in such batch systems, bead size can be controlled by advantageous selection of process conditions including: time, agitation, temperature, pressure, and reactant concentrations. But this method of producing expandable polystyrene beads inherently has several disadvantages, one of which is that large amounts of water are required to suspend the polystyrene beads during both the polymerization and impregnation steps. This is actually a double disadvantage. First, at the end of the impregnation, if the water is discharged into the environment, the energy input into the water to achieve the required temperature is lost. Second, prior to discharge, the water must be treated at additional expense to meet stringent regulations imposed by various government entities. These combined energy and disposal costs represent a substantial portion of the cost of expandable polystyrene that must be passed on to the polystyrene end user.

Another disadvantage is that stirred tank reactors in which the suspension is reacted are susceptible to failure of the reactor agitator by a variety of factors, including power and equipment failure. These failures can mean catastrophic consequences, i.e., the coalescence of monomer droplets can lead to the formation of individual, large, reactive clumps of feedstock which, in the absence of effective heat removal in this case, undergo Uncontrollable, strongly exothermic reaction. In addition to contaminating the equipment, this situation clearly represents a safety hazard.

Expandable thermoplastic polymer materials, including expandable polystyrene containing a propellant prepared as previously described, are known to be expanded by heating under conditions such that the propellant evaporates and forms a large amount of Cells. (U.S. Patents 4,174,427, 5,000,891, 5,240,657, 5,525,637, and 5,573,790 all describe their production methods, the contents of which are hereby incorporated by reference.) The foamable A variety of articles are produced from polymeric materials, regardless of whether these materials are in pellet or bead form. The present invention relates to an alternative method of preparing expandable crystalline and amorphous particles, including polyolefin and polystyrene beads, which avoids the disadvantages associated with the prior art processes and properties described above. The present invention also relates to a method of producing expandable polymer particles having considerable size uniformity, which reduces or even eliminates the need for multi-step size sizing of spheroids. The resulting spheroid particles in the present invention may contain various additives including, but not limited to, flame retardants, nucleating agents, and other chemicals known to impart desirable properties to polymers. These other chemicals are well known to those of ordinary skill in the art.

Summary of the invention

The present invention provides a continuous process for producing expandable thermoplastic spheroid particles, which is suitable for crystalline polymers such as polyolefins and amorphous polymers such as polystyrene. In the case of expandable polyolefins, those materials produced according to this method contain more gaseous blowing agent than when produced using prior art methods. In the case of amorphous polystyrene, this production does not pose hazards due to the formation of bulky exothermically reactive materials, nor does it entail the added expense of enforcing environmental or other regulatory standards to deal with large volumes of water.

The method of the present invention involves providing a molten mixture comprising a thermoplastic polymer and at least one blowing agent and then forming pellets from the thermoplastic polymer. Immediate rapid thermodynamic quenching of the formed particles holds the blowing agent dispersed throughout the polymer melt in place within the solid matrix. In one method, a process comprising atomizing the thermoplastic with a blowing agent is advantageously performed to deeply thermodynamically quench the nascent particles, which fixes the blowing agent within the particle matrix. Such formation of particles avoids the foaming gas repelling problems normally associated with polymer crystallization, since this cooling is more rapid than using prior art methods. In accordance with the present invention, polymers such as isotactic polypropylene and polyethylene are quenched by adiabatic cooling, which occurs immediately after particle formation at the atomizing nozzle, as described elsewhere herein. In addition, pellets can be formed from thermoplastic polymers using an extrusion technique in which the fluid polymer is immediately quenched in a liquid cooling bath as it emerges from the die in extrudate form, wherein the liquid cooling bath is selected from cold water, Liquid nitrogen, or liquid helium, and the process is similar to that used to produce lead pellets or gemstone casting pellets. The process is preferably, but not necessarily, carried out under pressure in a controlled atmosphere comprising a blowing agent. Under these conditions, the rate of crystallization of thermoplastics can be substantially delayed or inhibited when using normally crystalline materials, which would otherwise occur almost instantaneously. Pellets may be formed by surface cutting action on extrudate formed from a conventional polymer extruder die, and these pellets fall within the meaning of the word "pellets" as used in this specification and the appended claims. within the meaning. In the case of normally crystalline materials, rapid cooling of the polymer under conditions that inhibit or retard the rate of polymer crystallization substantially limits the ability of the gaseous blowing agent to diffuse out of the bulk of the particle as it cools. Thus, the blowing agent is bound within the particles. This concept is a common idea shared by the methods disclosed herein.

The most preferred method for forming particles is to convey a molten mixture comprising a blowing agent to an atomizing nozzle under conditions sufficient to atomize the molten mixture, thus forming droplets comprising the molten mixture, and then subjecting the droplets to sufficient While cooling, polymer particles with blowing agent bound in them are formed. These particles are then collected for later use. This method is applicable to both crystalline and amorphous polymers.

In a preferred embodiment, expandable polystyrene spheroids can be produced by first providing a stream or reservoir of molten polymer material at temperature and pressure conditions sufficient to ensure that the gaseous phase does not exist in the melt The bottom contains at least one uniformly distributed blowing agent. It is also equipped with an atomizing nozzle for fluid contact with the melt. Molten material remaining in the polymer stream or reservoir is diverted through holes in the nozzle to an area at a lower pressure than the reservoir or stream. The pressure changes encountered, combined with the physical configuration of the nozzle and the effect of the atomizing gas, result in atomization of the molten polymer containing the blowing agent uniformly distributed therein. Joule/Thompson cooling with expansion of the atomizing gas upon atomization, and any external cooling if desired, causes the molten polymer to form spheroids containing the blowing agent uniformly distributed therein. After collection, these spheroids are suitable for molding into various articles using various techniques known to those of ordinary skill in the art.

A brief description of the drawings

The accompanying drawing is a cross-sectional view of an atomizing nozzle which can be used to produce expandable thermoplastic polymer particles according to the invention.

Detailed description of the preferred embodiment

The invention is a process for producing expandable thermoplastic particles from a polymer melt comprising at least one blowing agent. Pellets are produced from this melt by extrusion techniques combined with rapid cooling, or most preferably by an atomization process which itself includes adiabatic or external cooling. The resulting particles are spheroids which can then be used in molding processes well known to those of ordinary skill in the art. Typically, the polymer spheroid particles comprise polypropylene, polyethylene or polystyrene.

In the preferred method of the present invention for forming thermoplastic particles, a polymer melt stream comprising a blowing agent is fed to an atomizing nozzle under conditions sufficient for rapid particle formation, which is then rapidly cooled either simultaneously or immediately. Using this method, particles can be formed from crystalline polymers such as polypropylene and polyethylene, as well as amorphous polymers such as polystyrene.

In another method according to the invention, an extrusion technique is used to form pellets from the mixture, including, but not limited to, directing a stream of molten thermoplastic material into a quench in a manner similar to the production of lead pellets or gemstone casting pellets. The entire quenching process is preferably carried out under pressure in a controlled atmosphere containing a blowing agent in a bath such as cold water, liquid nitrogen, or liquid helium. Preferably, the pressure within the controlled atmosphere is sufficient to substantially reduce any tendency of the blowing agent to separate from the melt. Under these rapid cooling conditions, which can mean that the polymer changes from 250 degrees Celsius to minus 78 degrees Celsius in less than 1 second, the rate of crystallization of thermoplastics that would otherwise occur when the polymer solidifies can be substantially delayed or inhibited , these polymers are generally considered to crystallize under normal conditions. Pellets or cylinders of polymer formed by the cutting action of a surface acting on the extrudate formed by the die of a polymer extruder fall into the word "pellet" as used in this specification and the appended claims within the meaning of This granulation process can be carried out using water as the cooling medium in contact with the extrudate, or using a cooling bath of other liquid materials such as liquid nitrogen, liquid helium, or metallic mercury. Although the inventors do not wish to be bound by any particular theory, it is speculated that the rapid cooling of the polymer under conditions that inhibit or retard the rate of polymer crystallization substantially limits the diffusion of the gaseous blowing agent from the bulk of the particle upon cooling. ability. Thus, the blowing agent is bound within the particle and remains bound within the particle even after normal subsequent crystallization of the polymer. This normal subsequent crystallization of the polymer in the pellets occurs as a result of the increase in polymer temperature from the quench temperature to ambient temperature.

Polymer crystallinity is usually measured by its intrinsic property called heat of fusion, which is routinely determined by test methods ASTM D-3417 or ASTM E-793-85. In general, for thermoplastic polymers, the measured crystallinity value for a given sample of a commercial grade material is only a fraction of that for a pure isotactic material. This is due to the many production variables that affect the total amount of crystallinity for a given material sample, with the net result that the amount of crystalline material, generally considered highly crystalline, present in the material is only about 40-60%. Therefore, the heat of fusion for a given sample is only a fraction of the heat of fusion that occurs in the pure material. Thus, each sample of a polymer has a characteristic heat of fusion value which directly represents the value of crystallinity present in that sample. For the present invention to work as intended, the crystallinity of freshly prepared (aged less than 1 minute) expandable pellets must be less than 90% of the crystallinity of the polymer prior to melting and injection or mixing with blowing agent. This reduced crystallinity is a result of the molten polymer stream having been rapidly cooled in accordance with the teachings herein and is directly indicative of an effective inhibition or retardation of polymer crystallization. Of course, eventually after storage, especially at room temperature, of pellets made according to the invention, the crystallinity of the pellets should increase to that normally observed for the polymer in question (after correcting for the presence of blowing agent). However, this crystallization does not have the same detrimental effect on the support of the gaseous blowing agent in the polymer as if the polymer were completely crystallized in accordance with its natural tendency when the polymer was changed from the molten state to the solid state, because the gaseous blowing agent is trapped. Effectively bound within the pellet body. This reasoning does not apply to amorphous polymers that retain a gaseous blowing agent upon solidification.

Blowing agents are generally known to those of ordinary skill in the polymer art. Blowing agents as used herein include any blowing agent known in the art of foamable polymers to be useful therein, including but not limited to gases including: hydrocarbons, nitrogen, carbon dioxide, halogenated hydrocarbons, fluorocarbons, chlorocarbons, fluorine Chlorocarbons. In this context, solid substances suitable as blowing agents, such as azodicarbonamide and other well-known compounds which similarly evolve gas when subjected to thermal energy, are also meant to be suitable blowing agents for inclusion in the polymer melt. For the purposes of the present invention, however, the blowing agent preferably comprises n-pentane, butane, or isobutane. The blowing agent most preferably comprises n-pentane. The amount of blowing agent in the melt is preferably about 0.5-7.0% by weight, and if n-pentane is selected as blowing agent, then it is in an amount of 1.0-10% by weight, most preferably 5.0% by weight of the total polymer. The molten polymer stream is maintained at a temperature and pressure in the absence of gaseous pentane, and the blowing agent is then uniformly distributed within the melt of the polymer stream. Any various stirring methods known to those skilled in the art can be used to promote the uniform dispersion of the foaming agent in the melt.

The atomizing nozzle to which the blowing agent-laden polymer stream is fed can be of various configurations so long as the polymer stream is sufficiently atomized such that by cooling the atomized polymer, particles of about 0.3-1.5 mm in size can be formed. particles.

According to the present invention, the most preferred nozzles for atomizing the polymer melt use the mechanism of impinging a gas stream on a stream or film of molten polymer to atomize the stream or film. Such gas atomizing nozzles are disclosed in US Pat. Nos. 4,619,845 and 5,228,620, the entire contents of which are hereby incorporated by reference. Referring to the accompanying drawings, there is shown a cross-sectional view of an atomizing nozzle which may be used to prepare expandable polymer particles of the present invention. In this figure, 75 denotes a polymer particle product. 83 denotes the coextensive structure contained within the tubular conduit 71 through which the molten polymer stream 26 is conveyed to the atomization zone 69. 42 is the structure defining the apertures through which the atomizing gas and molten polymer stream pass. The molten polymer stream is atomized by the interaction of the high velocity atomizing gas 17 with the molten polymer stream as it passes through the aperture. At high pressure, atomizing gas 17 is fed at subsonic velocity into the atomizing nozzle, which then acts on the molten polymer stream to atomize it. The portion 30 where the atomized particles are formed is a region of low pressure (preferably atmospheric pressure). As the pressure of the atomizing gas drops, the atomizing gas and the polymer particles are simultaneously cooled adiabatically. Since the molten polymer stream 26 contains blowing agent, this cooling of the particles will ensure that the blowing agent is encapsulated within the product particles 75 themselves.

Adiabatic cooling or Joule-Thompson cooling is a phenomenon well known to those skilled in the art of physical chemistry, the mathematical and practical details of which are given in the book entitled "Physical Chemistry" by Peter W. Atkins , 3rd Edition, published by W.H. Freeman and Company, New York, 1985 (ISBN-O-7167-1749-2), the entire contents of which are incorporated herein by reference.

The atomization mechanism is described in detail in the book entitled "FluidFlow Phenomena in Metals Processing" (J. Szekely, published by Academic Press, New York City, New York (1979), page 340 onwards) , the entire contents of which are incorporated herein by reference. Other atomizing equipment suitable for use in the method of the invention may include, for example, rotating atomizing disks or plates, single-material or multi-material nozzles with or without auxiliary energy supply (e.g., mechanical oscillation), and internal or external mixing Mixing nozzle. An article in "Materials World (Materials World)" magazine (Volume 5, No. 7, July 1997, page 383 onwards) proposes and describes another kind of nozzle that can be used in the present invention, hereby its entirety The content is incorporated herein by reference.

Another requirement for the production of polymer particles according to the invention is the feeding of a stream of molten polymer to the above-mentioned atomizing means. This can be accomplished by free flow from a pressurized vessel or by use of a suitable pump, extruder, or other melt delivery device known in the art. The combination of temperature and pressure required to deliver the polymer melt to the atomizing nozzle at the desired flow rate is readily calculated from temperature-viscosity dependence data for the polymer or polymer mixture used. Preferably, the pressure within the conduit is greater than atmospheric pressure and most preferably about 200 psig. The temperature of the polymer melt is preferably at least 10 degrees Celsius above the melting point or glass transition temperature of the polymer. If the polymer used is polystyrene, the preferred temperature for the melt is 180 degrees Celsius using 5.0% pentane (in the melt).

Once the liquid stream comprising the polymer melt is fed to the atomizing nozzle, atomization can be effected by the interaction of the atomizing gas with the polymer melt and the resulting pressure change. Preferably, the pressure outside the nozzle is atmospheric pressure, but pressures other than atmospheric pressure may be used as long as the pressure experienced by the polymer melt differs by at least 5 psig from the external pressure. The resulting particles preferably have a diameter of about 0.3-1.5 mm. The preferred size of the particle varies depending on the end application in which it is desired to be used, typically 1.0 mm in diameter.

In addition, in order to suppress the gas generation of the blowing agent during the formation of polymer spheroids, so that there is no significant net expansion of the particles, and in order to promote the retention of the blowing agent in the solidified particle The polymer particles are sufficiently cooled.

Example 1

A continuous batch polymerization plant for the production of molten polystyrene at 8000 kg/hr was assembled such that a stream of molten polymer could be taken from the output stream of the plant at a rate of 50 kg/hr using a gear pump. A gear pump delivered the polymer to a static mixer equipped with an injection device through which volatiles, such as 5.0% pentane (by weight, based on polymer weight), could enter the molten polymer and dissolve therein. The polymer leaving the static mixer was maintained at 210 degrees Celsius by heat transfer oil circulating in a jacket around the static mixer. The polymer was passed from the static mixer into the feed throat of the cooling extruder, which cooled the molten polymer to 170 degrees Celsius. The polymer exiting the extruder was passed through an atomizing die consisting of a heated vertical filling tube with an internal diameter of 10 mm. The molten polymer forms a free-settling beam from the lower end of the filling tube, which then impinges on and is atomized by the nitrogen stream. A stream of atomized nitrogen was delivered at a pressure of 17 bar through a plurality of holes arranged in an annular array (the center of the filling tube being the center of the annular array). The nitrogen flow from each hole impinged on the polymer at an angle of 15 degrees (relative to the axis of the polymer flow). Inside each nitrogen delivery conduit is a resonant chamber capable of generating 50 kHz pressure and velocity oscillations in the nitrogen flow. The nitrogen flow rate was set at 5 cubic meters per hour (calculated at standard temperature and pressure). The pentane-loaded polymer was atomized by impinging gas to form spherical particles with an average diameter of 1 mm. A sample of these particles was heated in boiling water, which swelled to give low-density expanded polystyrene particles with a closed-cell structure, indicating that an effective amount of pentane was retained in the primary polymer particles obtained by atomization to expand the particles . In a pre-expansion machine of the type commonly used for the production of expandable polystyrene from suspension-polymerized gas-impregnated polymer beads, large quantities of the particles in batches of about 100 kg are exposed to steam for pre-expansion. The foamed beads were aged for 5 hours, and then molded into a thermal insulation board with a density of 40 kg/m3 and a thermal conductivity of 0.03 W/m·°C.

While the invention has been shown and described in terms of certain preferred embodiments, it is apparent that equivalents and modifications will occur to those skilled in the art upon the reading and understanding of this specification and the appended claims. The present invention includes all such modifications and alterations, and is therefore limited only by the scope of the following claims.

Claims (28)

1. method of producing expandable thermoplastic particles comprises:

A) provide a kind of molten mixture that comprises thermoplastic polymer and whipping agent;

B) form particle by this thermoplastic polymer;

C) described particle is cooled under its fusing point; And

D) collect described particle.

2. according to the process of claim 1 wherein that described cooling carries out being enough to described whipping agent is included under the described intragranular speed.

3. according to the method for claim 2, the amount that wherein is included in described intragranular described whipping agent can make described particle be expanded to about 2 times of its green diameter effectively when standing to be higher than 95 degrees centigrade temperature.

4. according to the method for claim 2, wherein form the described step of particle and refrigerative and all in less than 1 second, carry out.

5. according to the method for claim 2, the described cooling of wherein said particulate proceeds to effective low temperature to suppress the crystallization of described polymkeric substance basically with effective speed, obtains 90% the material that a kind of degree of crystallinity is lower than the normal observation value of described polymer crystallization degree.

6. according to the process of claim 1 wherein that described particle is the spherule that is of a size of about 0.3-1.5 millimeter.

7. method of producing expandable thermoplastic particles comprises:

A) provide a kind of molten mixture that comprises thermoplastic polymer and whipping agent;

B) provide a kind of atomizing gas;

C) described molten mixture and described atomizing gas are being enough to atomize described molten mixture and form under the condition of the drop that comprises described molten mixture and be sent to atomizing nozzle;

D) described drop cooling is formed solid polymer particle; And

E) collect described particle.

8. according to the method for claim 7, wherein atomizing gas is fed to described atomizing nozzle.

9. method according to Claim 8, wherein said atomizing gas is selected from rare gas, nitrogen, oxygen, air and carbonic acid gas.

10. method according to Claim 8 wherein uses whipping agent as atomizing gas.

11. method according to Claim 8, wherein said whipping agent is selected from: hydrocarbon, chlorocarbon, fluorochlorohydrocarbon, carbonic acid gas, nitrogen and air.

12. method according to Claim 8, wherein said whipping agent is a Cellmic C 121.

13. method according to Claim 8, wherein said whipping agent is selected from pentane and Trimethylmethane.

14. method according to Claim 8, wherein said thermoplastic polymer comprises the polymkeric substance that is selected from polystyrene, polyethylene and polypropylene or its mixture.

15. method according to Claim 8, wherein said thermoplastic polymer comprises the C of ethene, propylene and vinylbenzene or its mixture ₂-C ₄Multipolymer.

16. method according to Claim 8, wherein said thermoplastic polymer comprise a kind of polymer materials of crystalline generally.

17. method according to Claim 8, wherein said thermoplastic polymer comprise unbodied basically polymer materials.

18. method according to Claim 8, wherein said cooling are to utilize the expansion of atomizing gas to carry out.

19. according to the method for claim 18, wherein said molten thermoplastic particle is lower than 25 degrees centigrade temperature being enough to the degree of crystallinity of crystalline polymer material suppressed be cooled to 90% speed of the normal observation degree of crystallinity that is lower than described polymkeric substance.

20. according to the method for claim 19, wherein said thermoplasticity integument is cooled to and is lower than 25 degrees centigrade, slowly returns to 25 degrees centigrade then.

21. according to the method for claim 18, wherein said expansion is an adiabatic basically.

22. method according to Claim 8, the temperature of wherein said molten mixture is about 40-300 degree centigrade.

23. method according to Claim 8, the pressure that wherein said molten mixture stood is greater than normal atmosphere.

24. method according to Claim 8, the concentration of wherein said whipping agent in described polymkeric substance melt are about 0.5-7.0% weight of polymkeric substance melt gross weight.

25. method according to Claim 8, wherein said atomizing gas comprise a kind of can be with the reactive materials of described functionalization of polymers.

26. according to the method for claim 25, wherein said reactive materials is selected from halogen, hydrogen halide, interhalogen compound, nitrogen oxide, ozone, maleic anhydride, amine, oxygen, sulphur trioxide and air.

27. method according to Claim 8, the difference of the pressure outside pressure that wherein said polymer melt stood and the described atomizing nozzle is greater than 5psig.

28. 1-27 and the polymeric articles produced by any method.

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