Abstract:
Blends of chlorinated polyvinyl chloride and chlorinated polyethylene and methods for preparing extruded profiles such as a window spacer, a glazing bead, a window lineal, and a track for lighting, having smooth surface characteristics are disclosed. The blends comprise 100 weight parts CPVC containing from 62% to 72% chlorine, preferably 65% to 71% chlorine and from 10 to 30 weight parts, preferably 15 to 25 parts of chlorinated polyethylene containing from 25 to 45% chlorine and extruding the blend. The preferred embodiments of the invention are further defined by a particular combination for the chlorine content of CPVC, the real weight average molecular weight of CPE (M w ) and polydispersity (M w  /M n ), defined as the ratio of the weight average to number average molecular weight, and extrusion shear rate.

Description:
This is a continuation of application Ser. No. 08/365,338, filed Dec. 28, 1994, now abandoned, which is a continuation of application Ser. No. 08/023,542, filed Feb. 26, 1993 now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention pertains to blends of post-chlorinated polyvinyl chloride (CPVC) and chlorinated polyethylene (CPE), and methods for making extruded rigid profiles from the blends and exhibiting smooth satin surface appearance. 
     BACKGROUND OF THE INVENTION 
     Combinations of polyvinyl chloride and chlorinated polyethylene are established in the art, for example, flexible wire and cable cladding. Blends of PVC and chlorinated polyethylene are recognized as contributing both impact modifying characteristics as well as ease of melt processing. Chlorinated polyethylene is not particularly efficient when utilized as the sole impact modifier with PVC, hence an amount needed to boost notched Izod Impact strength to at least about 10 lb.-ft./inch notch will lead to appreciable loss in rigidity, measured as tensile of flexural modulus. 
     There have been suggested graft copolymers of chlorinated polyethylene and PVC. Ludwig Beer, in 1962 suggested in U.S. Pat. No. 3,268,623 that improvements in properties could be obtained by dissolving CPE in vinyl chloride monomer and suspension polymerizing to yield an improved combination compared to mechanical blending of the two resins. 
     In U.S. Pat. No. 4,481,333 Fleisher et al. disclosed the combination of PVC, CPE, and fluoropolymer. There it was taught that if prior to combining with PVC, fluoropolymer and CPE are first combined, a 10-fold lesser quantity of fluoropolymer (PTFE) provided the same magnitude of reduction in extruder torque compared to a ternary mixture. 
     Hankey disclosed in Canadian Patent No. 636,534 that on the addition of 19 weight parts of CPE &#34;per 100 weight parts of PVC&#34; (phr), room temperature notched Izod impact strength improved to 24 ft.-lb./inch notch. Hankey showed that at this level of CPE, the flexural modulus of PVC was lowered from 400,000 psi to 270,000 psi, while in a combination 5 parts of CPE, 5 parts of a rubbery diene type polymeric impact modifier and 90 parts of PVC, room temperature notched Izod impact was comparable but rigidity was not sacrificed to the same degree. The samples demonstrated were milled and compression molded, with no teaching to extrusion characteristics. 
     Frey and Klug disclosed in U.S. Pat. No. 3,940,456 that extruded PVC blends with chlorinated high pressure polyethylene may, in certain instances, exhibit coarseness, i.e., rough extrusion characteristics. They proposed to solve this problem by employing a CPE which had been chlorinated in the presence of a finely-divided silicic acid and siloxane oil. The CPE described was of high molecular weight characterized by a specific viscosity and methylcyclohexane swell. The swell number indicated the &#34;through&#34; chlorination, i.e., the degree to which all chains were chlorinated. 
     Klug and Frey disclosed in U.S. Pat. No. 4,280,940 the combination of PVC and two CPE&#39;s to provide improved transparency for weatherable blends. They noted that the incorporation of CPE with methylcyclohexane (MCH) swell of more than 10% lead to reduced transparency. Klug and Frey also noted that the combination of CPE and PVC with K value 70 is difficult and can lead to rough extrudate. They proposed a combination of PVC (K=55-65) and two CPE&#39;s, one having a low MCH swell, and both containing 37-42% chlorine. 
     With respect to CPVC/CPE blends, Jennings and Kliner of the B. F. Goodrich Co. disclosed in U.S. Pat. No 3,299,182 the combination of impact improvement and processing enhancement of CPVC with small amounts of homogeneously chlorinated low pressure, high density polyethylene at usage levels of from 2 to 10 phr. Processing aids, plasticizers and impact modifiers were preferably avoided. The examples illustrated a variety of chlorinated polyethylene base polymers combined at 5 parts per 100 parts CPVC (phr), the CPVC having a density of 1.57 g/cc, corresponding to a chlorine content of about 66%. CPE and CPVC were precipitated from cements, dried, milled and pressed for determination of heat distortion temperature (HDT) and IZOD impact strength. The CPE chlorine content from 30-40% was preferred and impact strength was maximized using most types of base polyethylene having about 35% chlorine content. Exceptions to this trend occurred with a copolymer of ethylene and butene having a relatively high melt index. The preferred Zeigler type polyethylenes chlorinated to about 30-32% always gave higher impact strength than those with higher chlorine content. It was noted that extrusion speed and appearance of the extrudate was best at 7 phr CPE, while at 10 phr and higher, chemical resistance and HDT were detrimentally altered. 
     Dreyfuss and Tucker also of the BFGoodrich Company disclosed in U.S. Pat. No. 3,453,347 that enhanced melt flow rate and processing stability of CPVC/CPE blends can be obtained by the addition of 0.25 to 2.5 phr of rubbery amorphous polyalkylene mono-epoxide. One aspect of the &#39;347 patent was to obtain a combination of HDT and impact resistance with from 5 to 10 phr CPE. A small effective amount, on the order of 1 to 2 phr of the amorphous rubbery epoxide imparted higher melt flow rates. The working examples were prepared by milling and compression molding, while melt flow rate was measured by a small extrusion rheometer. The best melt flow rate/HDT/impact strength balance was observed at CPE use levels of 7.75 phr. 
     Buning, et al have taught in U.S. Pat. No. 3,459,692 that due to the higher crystallinity of stereo-regular CPVC and the tendency of a cooling melt to re-crystallize, molded articles from a blend of CPE and stereo-regular CPVC are more brittle than blends with atactic CPVC. They found that milled, pressed sheets of a blend of CPE and CPVC, where the CPVC was derived from 55 to 85% syndiotactic PVC were shown to exhibit toughness, no re-crystallization tendency and had higher corresponding Vicat softening temperatures than with the atactic CPVC blend. 
     More recently, G. Wear in U.S. Pat. No. 4,213,891 disclosed the use of a combination of high and low molecular weight chlorinated polyethylene with CPVC for calendared sheets having improved thermoforming characteristics. Another object of Wear was the use of PVC/acrylate based impact modifier for compounds with reduced smoke emission. CPVC having 66% chlorine was combined with 15 phr CPE (36% Cl and m.w. greater than 1,000,000) and 7.5 phr CPE (22% Cl and mw less than 100,000). The blend was fluxed on a Banbury/mill then fed into a calendar stack to produce a uniform 0.010-0.017 inch sheet. 
     There have been found no detailed published reports systematically studying the extrusion characteristics of CPVC/CPE blends in which CPE is present above 10 phr. Blends of PVC and CPE exhibit more consistent melt characteristics than blends of post-chlorinated PVC and CPE. Although at low levels of 1 to 5 phr, CPE imparts improved impact strength and processibility under low shear extrusion, the behavior of extrudates containing more than 10 phr CPE under higher shear conditions is different. The differences with PVC can not be extrapolated to CPVC blends. Good processibility suggests lower viscosity, torque and work input, hence processing stability, however this does take account of the variations in extrusion quality observed over varied conditions, varying chlorination level or molecular weight of CPE and CPVC. 
     Compared to PVC, chlorinated PVC exhibits higher density, higher Tg, improved resistance to solvent and chemical attack, requires higher extrusion temperature with greater susceptibility to degradation, higher melt viscosity and brittleness, these properties vary with different chlorine content of CPVC. The heat distortion temperature for homo-PVC is about 75° C. whereas it is 80° C. to 180° C. for chlorinated PVC, and is proportionate with chlorine content. Likewise, Vicat softening point for PVC is at least about 30° C. lower for chlorinated PVC. As the temperature of processing increases with CPVC chlorine content, blend morphology with CPE varies. 
     As illustrated below relatively 63-65% chlorine content CPVC is observed to behave differently with CPE than CPVC with relatively high chlorine content due in part to changing morphology with temperature. Whereas homo-PVC has a characteristic viscosity range for given molecular weight, its structure is uniform, made up of repeating units having the following structure: ##STR1## whereas chlorinated PVC is a combination of three structures, one of which corresponds to the repeating unit of PVC (I), and two other repeating unit types: ##STR2## The proportion of structures I, II and III for CPVC varies with chlorine content, the higher the chlorine content the higher proportion of structures II and III and the lesser proportion of structure I. Correlation between chlorine content and proportion of structures I, II and III in non post-chlorinated and chlorinated PVC is set forth in Table A below: 
     
                       TABLE A______________________________________   % Chlorine           Structure   Content (I)        (II)   (III)______________________________________PVC       56.6      100        0    0CPVC      57.5      97.2       2.8  0&#34;         61.2      81.1       17.5 1.4&#34;         63.2      71.1       26.8 2.1&#34;         69.5      31.1       49.9 19.0&#34;         72.6      5.5        60.5 34.0______________________________________ 
    
     On the basis of Table A, chlorinated PVC with a chlorine content of about 61% contains about 80% of structure I that corresponds to non post-chlorinated PVC, about 17% of structure II, and about 1% of structure III whereas at 72% chlorine content, chlorinated PVC contains about 5% of structure I, more than 60% of structure II, and more than 35% of structure III. Thus, there is no simple extrapolation of properties obtained in blends of PVC and CPE to blends of CPVC and CPE. 
     DIFFERENTIAL SCANNING CALORIMETRY 
     In the following table CPVC, tin stabilizer and chlorinated low molecular weight polyethylene was evaluated using differential scanning calorimetry method to confirm that two distinct phases exist for this blend: 
     
         ______________________________________Sample     phr CPE   Tg CPE °C.                            Tg CPVC °C.______________________________________CPE (35% Cl.)      neat      -12.9       --*CPVC 68.5% CL      --        --          143.0&#34;          10        -16.5       132.9&#34;          15        -18.6       132.8&#34;          20        -18.7       132.7&#34;          25        -16.9       132.5______________________________________ *no tin stabilizer present 
    
     By way of this method it is evident that with 68.5% chlorine CPVC a non-miscible two-phase blend exists with no shift in the glass transition temperature of either polymer beyond the plasticization effect of the tin stabilizer present. 
     Scanning electron microscopic observation of cross sections of extruded blends also confirms that at a discrete dispersed CPE domain exists and has a domain size of one micron and smaller. There are significant differences in extrudability observed across blends of CPVC/CPE with Varying molecular weights and chlorine levels of each. The varying quality of extrudate is unexplained by any general theory. It has also been observed that a specific blend may extrude well within a certain range of shear rate, for instance, 100-500 sec -1  yet when one increases the output rate, the extrusion undergoes melt fracture, giving a rough surface appearance. 
     The prior art recognizes that chlorinated polyethylene can be combined with CPVC in small amounts less that 10 phr to obtain processing improvements. The art also teaches the combination of PVC and lower amounts of chlorinated polyethylene with a core/shell impact modifier to obtain impact strength with less loss in HDT. 
     The prior art recognizes the maximum impact strength improvement for CPVC with CPE containing 30-32% chlorine, and that good appearance and extrusion speed are obtained when the CPE is present at about 7 phr. 
     It has been observed that as the chlorine content of CPVC is increased, the extrusion processing window for combination with CPE changes considerably. The incidence of rough extrusion occurs with increasing frequency using a variety of differently chlorinated polyethylenes of varying molecular weight as one increases the chlorine content of CPVC. 
     While it would be desirable to utilize CPVC containing at least 65% by weight chlorine for its high HDT, the limited processing window with CPE presents a problem in obtaining smooth extrudates under Varied processing shear conditions. The inclusion of conventional core/shell impact modifier with CPE, as suggested by Hankey for PVC, did not achieve an improvement in surface smoothness. Also, it was been observed that the appearance of extruded profiles from CPVC containing conventional core/shell impact modifier alone exhibits less desirable gloss and tactile characteristics. 
     Among the published art, there has been little disclosure of the use of CPE with CPVC for rigid profile extrusion of appearance articles such as window spacers, gaskets, glazing beads, window lineals, track lights, and the like. The designs used in commercial applications often require intricate cross-section shapes for profiles and the localized shear forces at the interface of the die and extrudate may vary widely as with the part geometry. Such rigid profiles having varied geometry formed in extruders under relatively high shear rates, exhibit more sensitivity towards melt fracture loss of shape and/or waviness. 
     It would thus be desirable to obtain the smooth extrudate surface and tactile characteristics under with high extrusion output rates. It would also be desirable to achieve high output rates for extruded profiles having any intricate cross-sectional shape while also maintaining dimensional stability and low percent die swell. 
     In a systematic study of immiscible but mechanically compatible CPVC/CPE blends, extrusions were obtained under varying processing conditions. With the use of rheological equations for Newtonian fluids, the apparent viscosity of non-Newtonian rod shaped extrudate was used with quantified output to calculate the instantaneous shear rate of the extrudate independent of shape. The surface characteristics under each condition were visually rated and compared. The general equations used for a rod-shaped die, are: 
     
         S.sub.D =9.8×10.sup.-3 Q/p r.sup.3 and P=2.9×10.sup.-5 S.sub.D VL/r 
    
     wherein: 
     S D  =shear rate, s -1   
     Q=flow rate, lb./hr. 
     p=melt density, g/cc 
     r=radius, in inches 
     P=pressure, psi 
     L=land length, in inches and 
     V=viscosity in poise. 
     In studies with a small extruder equipped with a 0.046 inch rod die, under varying conditions, there were found particular combinations of CPVC and CPE types extruded under particular conditions that exhibited excellent appearance characteristics and low die swell. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide specified blends for rigid profile extrusion of appearance parts such as window spacers, glazing beads, window lineals, and track lights, having smooth surface characteristics. The object is achieved by a method of extruding blends in a specified range of shear rate generally from about 100 sec -1  to about 4,000 sec -1 , the blends comprising 100 weight parts of CPVC having an I.V. of the precursor PVC of from about 0.4 to about 1.6, preferably 0.5 to 1.2 and most preferably from 0.7 to 1.0, and a CPVC chlorine content of from 62% to 72%, preferably greater than 65% up to 71%, in combination with from about 10 phr to about 30 phr of a single chlorinated polyethylene. 
     Another object of the invention is defined by a method of preparing an extruded profile from a blend comprising 100 weight parts CPVC containing from 62% to 72%, preferably greater than 65% up to 71% chlorine and 10 to 30 weight parts chlorinated polyethylene containing from 25% to 45% chlorine and extruding the blend in a specified range of shear rate depending on the specific CPVC and CPE present. The preferred embodiments of the invention are further defined by the particular combination wherein the chlorine content of CPVC, the real weight average molecular weight of CPE (M w ) and polydispersity (M w  /M n ), defined as the ratio of the weight average to number average molecular weight, and shear range are as follows for embodiments (a) through (m): 
     
         ______________________________________     CPE M.sub.wCPVC Cl level     × 10.sup.3               CPE M.sub.w /M.sub.n                           shear range (S.sup.-1)______________________________________(a) 62%-64%      90-130   4-8         100-600(b) 62%-64%     150-200   3-8         100-500(c) 64.1%-66%      90-130   4-8         100-4,000(d) 64.1%-66%     170-220.sup.1               6-9         100-500(e) 64.1%-66%     170-210.sup.2               8-11        100-550(f) 66.1%-69%      90-130   4-8         100-4,000(g) 66.1%-69%     150-200   3-8         100-1,300(h) 66.1%-69%     290-330   8-14        100-650(i) 66.1%-69%     170-220.sup.1               6-11        100-1,800(j) 69.1%-72%      90-130   4-8         100-3,500(j) 69.1%-72%     150-200   3-8         100-1,000(k) 69.1%-72%     290-330   8-14        100-500(l) 69.1%-72%     170-220.sup.1               6-9         100-3,500(m) 69.1%-72%     170-210   8-11        100-2,300______________________________________ .sup.1 38%-44% chlorine content .sup.2 33-37% chlorine content 
    
     More preferred embodiments are specified by the following: 
     
         ______________________________________     CPE M.sub.wCPVC Cl level     × 10.sup.3               CPE M.sub.w /M.sub.n                           shear range (S.sup.-1)______________________________________(a) 62%-64%      90-130   4-8         300-600(b) 62%-64%     150-200   3-8         400-500(c) 64.1%-66%      90-130   4-8         350-4,000(d) 64.1%-66%     170-220.sup.1               6-9         400-500(e) 64.1%-66%     170-210.sup.2               8-11        350-550(f) 66.1%-69%      90-130   4-8         400-4,000(g) 66.1%-69%     150-200   3-8         400-1,300(h) 66.1%-69%     290-330   8-14        500-650(i) 66.1%-69%     170-220.sup.1               6-11        400-1,800(j) 69.1%-72%      90-130   4-8         350-3,500(j) 69.1%-72%     150-200   3-8         300-1,000(k) 69.1%-72%     290-330   8-14        350-500(l) 69.1%-72%     170-220.sup.1               6-9         500-3,500(m) 69.1%-72%     170-210   8-11        400-2,300______________________________________ .sup.1 38%-44% chlorine content .sup.2 33-37% chlorine content 
    
     Still more preferred embodiment of (a) contains a chlorinated polyethylene having a real average molecular weight of from 115,000 to 125,000 and a polydispersity of from 5-7. The more preferred embodiment of (b) contains a chlorinated polyethylene having a real average molecular weight of from 175,000 to 195,000 and a polydispersity of from 5-6. The more preferred embodiment of (c) contains a chlorinated polyethylene having a real average molecular weight of from 115,000 to 125,000 and a polydispersity of from 5-7. The more preferred embodiment of (d) contains a chlorinated polyethylene having a real average molecular weight of from 190,000 to 205,000 and a polydispersity of 6-9. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative of a very smooth surface appearance. 
     FIG. 2 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative a smooth surface appearance. 
     FIG. 3 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative of a semi-smooth surface appearance. 
     FIG. 4 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative a slightly rough surface appearance. 
     FIG. 5 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative a rough surface appearance. 
     FIG. 6 is a photomicrograph at 15× magnification of a section of a 0.046 in. extruded rod which is representative a very rough surface appearance. 
    
    
     DETAILED DESCRIPTION 
     The rigid thermoplastic CPVC/CPE compounds specified herewith are defined as compositions having a modulus of elasticity, either in flexure or in tension, greater than 700 Mpa (100,000 psi), and preferably greater than 1,400 MPa at 23° C. and 50% relative humidity when tested in accordance with ASTM Method D747, Test for Stiffness of Plastics by Means of a Cantilever Beam, ASTM Methods D790, Test for Flexural Properties of Plastics and Electrical Insulating Materials, ASTM Method D638, Test for Tensile Properties of Plastics, or ASTM Methods D882, Test for Tensile Properties of Thin Plastic Sheeting. As a semi-rigid extrudate, the compounds herein may exhibit a modulus of from 70 to 700 MPa (10,000 to 100,000 PSI). Rigid versions are most preferred. 
     The articles of manufacture are extruded profiles in any shape comprising CPVC as the major component and chlorinated polyethylene as the second component. There can be included preferably in minor amounts less than the weight of CPVC present, one or more other halopolymers selected from the group consisting of homopolymers and copolymers of: polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, and polyvinylidene fluoride. These halopolymers enumerated above are commercially available from sources listed in Chemical Week Buyers&#39; Guide, October-1990, Vol. 147 No. 18, New York. In addition, other halopolymer materials are described in detail in the following U.S. Patents: polyvinylidene fluoride--U.S. Pat. No. 4,585,701; polyvinyl chloride--U.S. Pat. No. 5,036,121; chlorinated polyethylene--U.S. Pat. No. 3,299,182 and U.S. Pat. No. 4,749,751; and polyvinylidene chloride--U.S. Pat. No. 4,362,834. 
     Post-chlorinated PVC is available commercially worldwide from a variety of sources including Atochem S.A., The B. F. Goodrich Co., Nippon Carbide Industries, Co., Ltd., and Tokuyama Sekisui Industry Co., Ltd. 
     Post-chlorinated PVC for use herein is preferably prepared by the post-chlorination of suspension polymerized PVC. Suspension polymerization techniques are well established in the art and set forth in the Encyclopedia of PVC, pp. 76-85 published by Marcel Decker, Inc. (1976) and need not be discussed in great detail here. 
     Chlorinated polyvinyl chloride is obtained by chlorinating homopolymers or copolymers containing less than 50% by weight of one or more copolymerizable comonomers. Suitable comonomers for vinyl chloride include acrylic and methacrylic acids; esters of acrylic and methacrylic acid, wherein the ester portion has from 1 to 12 carbon atoms, for example methyl-, ethyl-, butyl-, ethylhexyl acrylates and the like; methyl-, ethyl- , butyl methacrylates and the like; hydroxyalkyl esters of acrylic and methacrylic acid, for example hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate and the like; glycidyl esters of acrylic and methacrylic acid, for example glycidyl acrylate, glycidyl methacrylate and the like; alpha, beta-unsaturated dicarboxylic acids and their anhydrides, for example maleic acid, fumaric acid, itaconic acid and acid anhydrides of these, and the like; acrylamide and methacrylamide; acrylonitrile and methacrylonitrile; maleimides, for example, N-cyclohexyl maleimide; olefin, for example ethylene, propylene, isobutylene, hexene, and the like; vinylidene halide, for example, vinylidene chloride; vinyl ester, for example vinyl acetate; vinyl ether, for example methyl vinyl ether, allyl glycidyl ether, n-butyl vinyl ether and the like; crosslinking monomers, for example diallyl phthalate, ethylene glycol dimethacrylate, methylene bis-acrylamide, tracrylyl triazine, divinyl ether, allyl silanes and the like; and including mixtures of any of the above comonomers. Comonomers as well as crosslinking comonomers are preferably absent. That is, preferred are homopolymers and uncrosslinked CPVC polymers. 
     The molecular weight as measured by I.V., of precursor polyvinyl chloride for the post-chlorinated polymer will range from about 0.4 to about 1.6, preferably 0.5 to 1.2 and most preferredly from about 0.7 to 1.0 I.V.. The inherent viscosity is a representative measure of the molecular weight of a polymer and is obtained in accordance with ASTM procedure No. D-1243-66. The choice of molecular weight is made by considering the shape and intricacy of the profile, the processing conditions and the physical property balance desired. If the molecular weight is too low, there may be insufficient melt strength and dimensional stability of the hot extrudate will suffer, and if the molecular weight is too high, the compound may not be processible under the desired conditions. Excellent results are obtained under a variety of conditions and cross-sectional shapes using an I.V. of the PVC precursor of about 0.85 to 0.95. 
     Chlorination of PVC can be carried out in any conventional manner as known to the art and to the literature to obtain a chlorinated base polymer having higher than 57 percent by weight chlorine up to about 74 percent by weight based upon the total weight of the polymer, however, in the practice of the invention, the use of a major amount of CPVC having a chlorine content of greater than 65% and up to 74% is preferred, and more preferably from 67% to about 71% chlorine. 
     The preferred method of post-chlorination is by the aqueous suspension chlorination method. There are considerations relative to this method wherein the preferred mode of chlorination employs a relatively concentrated aqueous suspension of the precursor PVC. The most preferred method results in a CPVC resin having a density which does not deviate more than about 20 percent from the mean density, and a surface area which does not deviate more than 30 percent from the mean surface area is more desirable. A concentration of about 15 to about 35 weight percent of solids in the suspension is preferred. Generally a concentration of the suspension higher than the specified range results in less uniform chlorinated product, while concentrations below 15 percent yield uniform product, but are not as economical. By &#34;aqueous suspension&#34; of PVC base polymer we refer to a slurry-like mixture of base polymer macrogranules suspended in water. This process is particularly directed to a batch process. 
     It is desired that oxygen be removed from the aqueous suspension before chlorination is initiated. This may be effected in any convenient manner, and assisted with agitation. Heating as may be required is preferably done after Cl 2  is sparged into suspension from a liquid Cl 2  cylinder until the pressure in the reactor reaches about 25 psig, at which point the suspension is saturated with Cl 2 . It is preferred that this pressure be somewhat higher, that is in the range from about 35 psig to about 100 psig, to get the optimum results, though a pressure as low as 10 psig and higher than 100 psig may be employed. The amount of Cl 2  charged to the reactor is determined by weight loss in the Cl 2  cylinder. The reactor is preferably brought up to a &#34;soak&#34; temperature in the range from about 60° C. to about 75° C. at which soak temperature the suspension is maintained under agitation for a soak period in the range from about 1 minute to about 45 minutes. Excessive pressure adversely affects the porosity of the macrogranules to the detriment of the stability of the chlorinated product. 
     It is desirable to complete the chlorination reaction under photo-illumination, preferably with ultraviolet light, or the desired conversion of base polymer to chlorinated base polymer product does not occur. Chlorination proceeds at a rate which depends upon the pressure and temperature within the reactor, higher rates being favored at higher temperature and pressure. It is most preferred to adjust the soak temperature, the mass of resin, and the level of photo-illumination so that the temperature is &#34;ramped&#34; by the heat of reaction until it levels off at a finishing temperature of about 100° C. After chlorination has proceeded to the desired degree, the suspension is preferably not cooled but dumped to be centrifuged and the chlorinated polymer freed from the aqueous phase, after which Hcl is removed from the product, preferably by neutralizing with an aqueous solution of an alkali metal hydroxide. The product is then washed with water to free the chlorinated polymer of residual alkali, and dried, all in a conventional manner, except that the temperatures at which the operations are carried out may be in the range from about 60° C. to about 100° C., which are higher than conventionally used. 
     Chlorinated polyethylene used herein has a specific gravity of from about 1.13 to 1.4, preferably about 1.16, a residual crystallinity of from about 0 to about 25%, preferably 0 to 10%, and a chlorine content from about 25% to about 45%, preferably 35% to 44%. The chlorination can be either homogeneous or heterogenous, preferably to a small extent. Surface appearance of extrudates depended on CPE molecular weight and polydispersity as measured by gel permeation chromatography and on the extrusion conditions used as illustrated below. Chlorination methods for CPE include aqueous suspension, solution, or gas phase methods, with the preferred method by way of suspension chlorination. CPE is commercially available from Dow Chemical Inc. The amount of CPE present ranges from about 10 to about 30 phr, preferably from about 12 to about to 25 phr, still more preferred are levels from 15 to 25 phr. The particular combination of CPVC and CPE within the scope of the present invention will be described below. 
     The core/shell type impact modifiers can be present but are preferably absent. These include acrylonitrile butadiene styrene terpolymers (ABS), methacrylate, acrylonitrile, butadiene, styrene (MABS) polymers and methacrylate butadiene styrene polymer (MBS). Other impact modifiers are disclosed in Plastics compounding, November/December, 1983: &#34;Update: Impact Modifiers for Rigid PVC,&#34; by Mary C. McMurrer. Various commercial MBS grades include Paraloid® KM-653, BTA-733 from Rohm and Haas, or Kanegafuchi Inc. B-56 and B-22; Commercial polyacrylate impact modifiers include KM®-323B, and KM®-330, from Rohm and Haas, Inc.; ABS grades are commercially available from GE Plastics, Inc, for example, Blendex® 336. 
     Thermal stabilizers are employed in the compounds herein and can be selected from various organic compounds, for example dibutyltin-S-S&#39;-bi-(isooctylmercaptoacetate), dibutyl tin dilaurate, di-butyltin di-2-ethylhexyl thioglycolate dimethyl tin di-isooctyl-thioglycolate, and the like. Tin compounds are generally used at from 1 to 5 phr, preferably about 2.0 to 4.0 phr. Secondary stabilizers may be included for example a metal salt of phosphoric acid, polyols, or epoxidized oils. Specific examples of salts include water-soluble, alkali metal phosphate salts, disodium hydrogen phosphate, orthophosphates such as mono-,di-, and tri-orthophosphates of said alkali metals, alkali metal polyphosphates, -tetrapolyphosphates and -metaphosphates and the like. The most preferred secondary stabilizer is disodium hydrogen phosphate (DSP) and is used by treating the CPVC resin. Polyols such as sugar alcohols, and epoxides such as epoxidized soya oil can be used. Typical levels of secondary stabilizers can range from about 0.1 wt. parts to about 7.0 wt. parts per 100 wt. parts halopolymer (phr). In addition, commercially available antioxidants are used such as phenolics, BHT, BHA, various hindered phenols and various inhibitors like substituted benzophenones. 
     Other auxiliary components are contemplated. Antistats may be used and are commercially available under the Glycolube® trademark of Lonza Corp. Exemplary lubricants are the various hydrocarbons, such as paraffins, paraffin oils, low molecular weight polyethylene, oxidized polyethylenes, fatty acids and their salts such as stearic acid and calcium stearate, fatty alcohols such as cetyl, stearyl, or octadecyl alcohol; metal soaps such as calcium or zinc salts of oleic acid; fatty amides of organic acids such as stearamide, ethylene-bis-stearamide; preferred fatty esters and partial esters such as butyl stearate, polyol esters such as glycerol monostearate, hexaglycerol distearate; and fatty ester waxes such as stearyl esters. The most preferred lubricant is oxidized polyethylene. Henkel Co. produces a variety of preferred fatty ester formulations under the Loxiol® mark. Combinations of internal and external lubricants may also be used. Lubrication of the halopolymer compounds of the present invention is a complex art. Since several lubricants can be combined in countless variations, the total amount of lubricant may vary generally from about 2 to 10 phr, preferably from 2 to about 6 phr. Optimization of particular individual lubricant formulations is beyond the scope of the present invention, and can be achieved as one skilled in the art prefers. 
     Adjustment of melt viscosity can be achieved as well as increasing melt strength by optionally employing commercial acrylic process aids such as those from Rohm and Haas under the Paraloid® Trademark, for example Paraloid® K-120ND, K-120N, K-175. 
     Exemplary fillers are optional and include clay, wollastonite, mica, barytes, calcium carbonate and silica including precipitated silicas, silica gels, metallic silicates, pyrogenic or fumed silicas and the like. These have the general formulae: SiO 2 , M n  (SiO 3 ) x . The values of n and x can vary with the oxidation state of the metal associated with the SiO 3  ion. The values n and x are usually integers from about 1 to about 4. 
     Preferred pigments are the various titanium dioxides (TiO 2 ) and carbon blacks which are commercially available. Preferred TiO 2  types are coated or uncoated, rutile titanium dioxide powder. An exemplary commercial grade is Ti-Pure® R-100 from E. I. DuPont De Nemours and Co. Inc. (DuPont). If used, pigments such as TiO 2  are present in an amount ranging from 1 to 25 phr, more typically 3 to 15 phr, and most typically from 3 to about 8 phr. Optional coloring pigments can be used. 
     The method of compounding is straightforward as any high intensity method to uniformly mix and fuse the components into a homogeneous compound such as with a Banbury/mill, followed by sheeting, slitting or extrusion into pellets, or cubes. The differences in process handling of CPVC compared with polyvinyl chloride-based compounds relate mainly to the temperature and viscosity differences and care must be taken to avoid too much work and shear burning. In the preparation of compounds, the components can be combined and mixed with a Banbury and milled on a heated roll mill. The fused compound can be extruded and chopped into cubes. Alternatively, the components can be combined in a compounding twin screw extruder. The compounds are extruded into final form at conventional stock temperatures from about 175° C. to about 235° C. and preferably from about 200° C. to about 225° C. The extruder characteristics applicable to melt processing of the compounds of the present invention include: 
     Head pressure rating of at least 7500 psi (51.7 Mpa). 
     Extruder drive/gearbox capable of generating high torque at low rpm. 
     Vacuum venting to remove volatile components, moisture and entrapped air. 
     A barrel L/D of at least 16/1 for twin screw; generally at least 20/1 for single screw. 
     Temperature controllers able to control within 5° F. or preferably +/-2° F. 
     Accurately controllable powder metering screw for powder compounds. 
     A ramped barrel temperature profile is advisable with a zone nearest the hopper set at 180° C. and the zone nearest the die at about 195° C. for 0.75 inch diameter screw. There can be used calibrating blocks at the exit end to assist in proper dimension sizing as the hot profile is cooled. Air streams can be used to improve heat loss, and for more close tolerances, vacuum water sizing devices can be used. The extent to which one chooses to employ calibrator blocks and air or water sizing will depend on dimension tolerances for the particular profile shape, the intended output volume of any one profile article and the number of different profiles made with a particular production set. These considerations are beyond the scope of the disclosure. 
     EXAMPLES 
     In the examples below, compounds were prepared as listed below. The components were combined in a Banbury/mill and extruded in a Brabender extruder equipped with a 0.046 inch rod die. The extrusion conditions were controlled by varying the rpm from 5 to 50 rpm. The actual shear rates were calculated for each example using quantitative extrusion volume output rates. For each rpm series the calculated shear rates were grouped as follows: 
     
         ______________________________________SCREW             (S.sup.-1)RPM               SHEAR RANGE______________________________________ 5                 400-50010                 800-100015                1000-130020                1200-180025                1500-220030                1700-330040                2200-330050                2700-4100______________________________________ 
    
     The compounds used in the examples contained one of the following CPVC resins. 
     
         ______________________________________    ResinResin    Chlorine      Resin   Wt.No.      Content, %    I.V.    Amount______________________________________1        63.1          0.92    1002        65.2          0.92    1003        68.3          0.92    1004        70.3          0.92    100______________________________________ 
    
     The examples contained either of the following components: 
     
         ______________________________________                    Real           %Number Type     Wt. PHR  AVE. MW.sup.2                             M.sub.w /M.sub.n                                   chlorine______________________________________A      CPE      20       120,000  5.7   36B      CPE      20       188,000  6.6   36C      CPE      20       317,000  11.6  36D      CPE      20       197,000  7.4   42E      CPE      20       192,000  9.5   35F.sup.x  CPE      20       180,000  --    25G.sup.x  CPE      20       180,000  --    40H      Acrylic  20       --       --    --I      MBS      20       --       --    --______________________________________ X estimated 
    
    
     column set: PLgel 10 μm, 1 guard column+3 mixed bed columns+a 100 Å column. 
     Mobile phase: Trichlorobenzene 
     Flow rate: 1.0 ml/minute 
     Temperature: 135° C. 
     sample size: 200 μl @ ca. 0.3% 
     Intensities: 64×8 
     The following formulation was used in evaluating extrudates: 
     
         ______________________________________Component         Amount______________________________________CPVC              100Component (A-J)   20tin thioglyocolate             2.25Oxidized polyethylene             1.5Glycerol ester    1.0Antioxidant       0.25TiO.sub.2         5.0Carbon black      0.25______________________________________ 
    
     The Brabender extruder barrel zones were maintained at the following temperatures (°C.): 
     
         ______________________________________Zone 1    Zone 2        Zone 3  Die______________________________________180       185           190     195______________________________________ 
    
     Percent die swell measurements were taken by comparing the actual diameter of the extrudate after cooling and the die diameter. The following results were reported as (extrudate dia.-die dia.)/die dia.×100. 
     
         ______________________________________% DIE SWELL  RPMEXAMPLE  5      10     15   20   25   30   40   50______________________________________1-A      41     35     30   39   43   46   48   501-B      39     41     41   43   46   46   43   431-C      57     48     48   48   52   50   52   501-D      61     54     50   55   74   57   54   Fail*1-E      52     48     50   55   40   57   59   Fail*1-F      50     43     46   44   96   49   50   501-G      70     59     54   55   97   59   61   Fail*1-H      33     33     33   33   77   39   39   391-I      35     37     37   33   99   37   35   33______________________________________ *too irregular to measure  Lumpy flow 
    
     Example 1-A exhibits a desirable reduced level of swell. 
     
         ______________________________________% DIE SWELL  RPMEXAMPLE  5      10     15   20   25   30   40   50______________________________________2-A      33     33     33   37   39   41   48   502-B      39     39     39   41   43   46   58   482-C      43     43     48   50   57   57   57   592-D      52     52     54   57   62   61   65   652-E      46     46     48   50   54   59   61   612-F      37     35     37   39   41   46   48   502-G      54     52     52   57   57   61   63   652-H      33     37     43   50   54   59   61   592-I      33     35     43   48   54   52   52   503-A      28     28     28   30   33   35   37   413-B      37     35     35   37   41   43   46   483-C      46     50     48   50   50   52   57   593-D      50     57     54   54   54   57   59   633-E      41     41     41   41   46   48   54   573-F      28     30     30   30   35   37   41   463-G      48     52     50   52   52   54   61   673-H      43     67     80   87   91   91   96   933-I      57     61     63   65   67   70   67   634-A      43     37     26   26   26   24   26   304-B      33     30     28   30   30   33   41   434-C      41     41     39   37   39   39   41   464-D      48     48     43   41   41   43   46   504-E      50     50     46   46   41   37   41   434-F      28     24     24   26   26   28   30   354-G      46     41     37   39   39   39   43   464-H      65     76     78   78   80   83   89   894-I      59     57     54   57   59   65   65   70______________________________________ 
    
     It can be seen from the above die swell measurements taken at the indicated RPM, among resin series 1 through 4, that the degree of die swell varies widely as between CPE resins of different chlorine content as well as molecular weight. However it is observed that die swell is comparatively less among the examples exhibiting the best surface smoothness. 
     The following actual shear rates were calculated: 
     
         __________________________________________________________________________SHEAR RATE, SEC -1RPMEX. 5    10  15  20  25  30  40  50__________________________________________________________________________1-A 409  754 1084            1373                1685                    2034                        2647                            32371-B 396  718 1072            1406                1735                    1982                        2694                            32781-C 405  768 1114            1390                1719                    2017                        2577                             31691-D 466  791 1254            1574                1983                    2357                        2964                             3379*1-E 440  779 1105            1407                1668                    1983                        2552                             31611-F 367  626  994            1243                1478                    1679                        2230                            29551-G 386  719 1004            1327                1621                    1940                        2640                             3288*1-H 388  782 1112            1542                1844                    2267                        2877                            37091-I 364  739 1088            1420                1785                    2092                        2754                            33592-A 382  727 1007            1320                1642                    1976                        2558                            32042-B 386  691 1010            1365                1650                    1987                        2710                            32552-C 399  723 1095            1477                1780                    2085                         2658!                             3271!2-D 452  784 1227            1598                1987                    2355                        3106                             3709!2-E 417  786 1165            1482                1813                    2126                        2661                            23142-F 349  625  937            1173                1436                    1673                        2225                            27842-G 414  766 1153            1480                1786                    2062                         2665!                             3346!2-H 468  774 1188            1605                1943                    2404                        3173                            40472-I 381  726 1093            1539                1905                    2294                        2937                            36473-A 486  772 1129            1421                1792                    2060                        2654                            32113-B 450  807 1158            1430                1728                    2048                        2287                            432943-C 539  867 1266            1569                1840                    2175                        2711                            34783-D 487  994 1428            1739                2144                    2497                        3008                            37173-E 487  878 1202            1510                1823                    2103                        2638                            33423-F 354  676  977            1219                1531                    1735                        2196                            25983-G 476  896 1248            1590                1901                    2192                        2788                            34963-H 443  767 1220            1673                2097                    2451                        3231                            39713-I 391  795 1174            1570                1901                    2270                        2889                            34804-A 409  573  855            1433                1713                    2019                        2690                            33214-B 440  826 1208            1533                1867                    2173                        2819                            34244-C 513  966 1357            1769                2149                    2463                        2991                            36834-D 535  914 1365            1818                2260                    2687                        3338                            41174-E 482  958 1299            1626                1906                    2184                        2821                            34804-F 389  738  967            1234                1499                    1762                        2236                            27194-G 519  1000        1349            1677                1930                    2228                        2884                            35114-H  453@     910*         1297&#39;             1652&#39;                 2083&#39;                     2427&#39;                         3233&#39;                             4120&#39;4-I 374  747 1078            1348                1654                    2004                        2697                            3293__________________________________________________________________________ @ Slightly Lumpy *  Lumpy &#39; Very Lumpy ! Fail   Slightly Spiral 
    
     BRABENDER TORQUE 
     The equilibrium torque for the above series of compounds was evaluated in a Haake Rheomix Model No. 600 under the following conditions: 
     
         ______________________________________Mixing Bowl Temp °C.              210RPM                 35Sample Weight      65 gms.______________________________________ 
    
     3 minute load and heat soak at 10 rpm before testing. 
     The following table lists the torque reading under controlled conditions and each compound can be compared. The general trends show that torque is directly proportional to CPVC chlorine content and the average molecular weight of the impact modifier. The MBS impact modifier exhibited the highest torque while CPE-A exhibited the lowest torque. 
     
         ______________________________________BRABENDER TORQUE (m-g)ADDITIVE     CPVC TYPETYPE         1      2          3    4______________________________________A            1230   1500       1540 1690B            1530   1800       2000 2030C            1570   1780       2080 2070D            1480   1650       1980 1920E            1420   1600       1820 1910F            1640   1700       2000 1970G            1620   1690       2000 2070H            1590   1880       2220 2500I            2000   2220       2680 2920______________________________________ 
    
     SURFACE APPEARANCE 
     Series 1-4 with additives A-I were extruded with the aforementioned single screw extruder equipped with a 0.046 in. circular die. Each example was compared to an established appearance criteria using six categories and illustrated in FIGS. 1-4 for the standards. The figures show photomicrographs made at 15× magnification of rods which were representative of each appearance classification category. The categories are as follows: 
     SMOOTH RODS 
     1. Very smooth/silky feeling rods with no texture visible. 
     2. Smooth feeling rods with a slight texture visible. 
     3. Smooth feeling rods with some texture visible 
     ROUGH RODS 
     1. Some texture can be felt and seen. 
     2. Rough to the touch and lots of visible texture. 
     3. Very rough to the touch and extremely coarse texture seen. 
     In a preferrd embodiment, CPVC resin is used which has been pre-treated with a phosphate salt. The following compounds illustrate the significant improvement with the use of this type of resin for improving the processing stability. 
     
         ______________________________________Component          Example A Example B______________________________________Untreated CPVC     100 (parts)                        --DSP treated CPVC   --        100Tin stabilizer     2.25      2.25Chlorinated PE     20        20lubricant          2.5       2.5TiO.sub.2          5         5Antioxidant        0.25      0.25Brabender stability (minutes)              6.5       13.7Torque (m-g)       2100      1800Temperature (°C.)              222       225______________________________________ 
    
     Table A below represents the extrusion appearance ratings of the compound containing CPVC with a chlorine content of 63.1; Table B illustrates the appearance of extrudate from compounds made with a 65.2% chlorine level; Table C illustrates the appearance of extrudate from compounds made with 68.3% chlorine level, and table D illustrates the appearance of extrudates from compounds made with 70.3% chlorine CPVC. The preferred embodiments are made with a CPVC containing from 67 to 72% chlorine, with the most preferred CPVC contains from 67% to 70% chlorine. The most preferred chlorinated polyethylene contains from 35% to 37% chlorine and has a real weight average molecular weight of from 90,000 to 130,000, more preferably 115,000 to 125,000 and most preferably about 120,000, with a polydispersity of from 5 to 7 as in CPE number A above. 
     
                                           TABLE A__________________________________________________________________________5 rpm  10 rpm      15 rpm          20 rpm              25 rpm                  30 rpm                      40 rpm                           50 rpm__________________________________________________________________________1-A   semi  sl. sl. semi              sl. sl. sl.  sl.   smooth  rough      rough          smooth              rough                  rough                      rough                           rough                  lumpy                      lumpy                           lumpy1-B   very  very      very          very              very                  very                      very very   rough  rough      rough          rough              rough                  rough                      rough                           rough1-C   rough  very      very          very              very                  very                      very very  rough      rough          rough              rough                  rough                      rough                           rough                           lumpy1-D   semi  sl. rough          rough              rough                  rough                      rough                           very   smooth  rough                    rough                           lumpy1-E   very  very      very          very              very                  very                      very very   rough  rough      rough          rough              rough                  rough                      rough                           rough                      lumpy                           lumpy1-F   rough  very      very          very              very                  very                      very very  rough      rough          rough              rough                  rough                      rough                           rough                           lumpy1-G   rough  sl. very          very              very                  very                      very very   lumpy  rough      rough          rough              rough                  rough                      rough                           rough                      lumpy                           wavy1-H   smooth  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth1-I   smooth  very      very          smooth              smooth                  smooth                      very smooth  rough      rough           smooth  lumpy      lumpy__________________________________________________________________________ 
    
     
                                           TABLE B__________________________________________________________________________5 rpm  10 rpm      15 rpm          20 rpm              25 rpm                  30 rpm                      40 rpm                           50 rpm__________________________________________________________________________2-A   smooth  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth2-B   very  very      very          rough              rough                  rough                      rough                           rough   rough  rough      rough2-C   very  very      very          very              very                  very                      very rough   rough  rough      rough          rough              rough                  rough                      rough                           wavy                      wavy2-D   very  sl. rough          rough              rough                  rough                      sl.  sl.   smooth  rough               rough                           rough                           wavy2-E   smooth  rough      very          very              very                  rough                      rough                           rough      rough          rough              rough2-F   semi  very      very          very              very                  very                      rough                           rough   smooth  rough      rough          rough              rough                  rough2-G   smooth  sl. rough          very              very                  very                      rough                           rough  rough   rough              rough                  rough                      wavy wavy2-H   very  very      very          very              very                  smooth                      semi sl.   smooth  smooth      smooth          smooth              smooth  smooth                           rough2-I   very  very      very          very              very                  very                      very very   smooth  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth__________________________________________________________________________ 
    
     
                                           TABLE C__________________________________________________________________________5 rpm  10 rpm      15 rpm          20 rpm              25 rpm                  30 rpm                      40 rpm                           50 rpm__________________________________________________________________________3-A   very  very      very          very              very                  very                      very very   smooth  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth3-B   semi  smooth      semi          sl. sl. sl. rough                           sl.   smooth  smooth          rough              rough                  rough    rough3-C   smooth  rough      rough          very              very                  very                      rough                           rough          rough              rough                  rough3-D   very  smooth      semi          semi              sl. sl. sl.  sl.   smooth  smooth          smooth              rough                  rough                      rough                           rough3-E   smooth  smooth      sl. sl. sl. rough                      rough                           rough      rough          rough              rough3-F   very  very      very          very              very                  very                      very very   smooth  rough      rough          rough              rough                  rough                      rough                           rough3-G   smooth  semi      semi          sl. sl. sl. sl.  sl. rough  smooth      smooth          rough              rough                  rough                      rough                           lumpy3-H   semi  sl. rough          very              very                  very                      very very   smooth  rough   rough              rough                  rough                      rough                           rough          lumpy              lumpy                  lumpy                      lumpy                           lumpy3-I   very  very      very          very              very                  very                      sl. rough                           sl. rough   smooth  smooth      smooth          smooth              smooth                  smooth                      lumpy                           lumpy__________________________________________________________________________ 
    
     
                                           TABLE D__________________________________________________________________________5 rpm  10 rpm      15 rpm          20 rpm              25 rpm                  30 rpm                      40 rpm                           50 rpm__________________________________________________________________________4-A   semi-  smooth      very          very              very                  very                      very very  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth4-B   smooth  semi-      sl. rough              rough                  rough                      rough                           very  smooth      rough                rough4-C   semi-  rough      very          very              very                  very                      very very   smooth  rough          rough              rough                  rough                      rough                           rough4-D   smooth  smooth      smooth          smooth              smooth                  smooth                      semi sl.                      smooth                           rough4-E   smooth  smooth      smooth          smooth              smooth                  semi                      rough                           rough                  smooth4-F   very  smooth      rough          very              very                  very                      very very   smooth      rough              rough                  rough                      rough                           rough4-G   smooth  sl. sl. rough              rough                  rough                      rough                           rough  rough      rough4-H   very  rough      very          very              very                  very                      very very   smooth  lumpy      rough          rough              rough                  rough                      rough                           rough      lumpy          lumpy              lumpy                  lumpy                      lumpy                           lumpy4-I   smooth  very      very          very              very                  very                      very very  smooth      smooth          smooth              smooth                  smooth                      smooth                           smooth__________________________________________________________________________