Document 15nkoVvq1mmy188KBB4Qp2dEo

Reprinted from Tappi, The Journal of the Technical Association of the Pulp and Paper Industry, Vol. 50, No. 1, January 1967. Copyright, 1967 by TAPPI, and reprinted by permission of the copyright owner Vinyl Plastisol and Organosol Coatings for Paper ARNOLD C. WERNER URL 14502 Many familiar products in the home and in industry are fabricated from vinyl plastics or use vinyl in tbeir con* struction In combination with other materials. Some of these are listed in Table I. The bulk of vinyl plastics is processed through heavy duty equipment such as Banbury mills, two roll mills, extruders, calenders, injection molders, etc. This equipment must be powerful to knead the various components of a vinyl plastic together into a homogenous state. This equipment is necessarily quite ex pensive. In each case considerable beat is required to bring the vinyl to a thermoplastic state so that it can be squeezed or molded into a useful shape. However, a technique is available, that utilizes the various components of a vinyl plastic in such a way that a fluid material is formed at room tem perature. These fluid vinyl systems are known as plastisols and organosols. COMPONENT PARTS OF VINYL PLASTIC The basic vinyl formulation consists of two major components, the vinyl polymer itself and a softening agent (plasticizer), which when fluxed with the vinyl polymer acts to separate the polymer chains. The amount of plas ticizer present controls the hardness and rigidity of the product. Vinyl polymer are of two types: straight PVC (polyvinyl chloride) homo polymers and copolymers, in which vinyl chloride is copolymerized with several other comonomers such as vinyl acetate, vinyl maleate, and others. The level of comonomer may go as high as 15% in the plastic grades of vinyl resin. Vinyl plastics are formulated into products varying in hardness from very hard, such as pipe, conduit, home siding, credit cards, to very' soft products, such as dolls, toys, and stocks used for upholstery and clothing. In the former instance little orno plasticizer is present. In the latter instance quantities of plasticiser equal to the weight of the PVC resin itself are used. Vinyl plastics are processed at ele vated temperatures to take advantage of their thermoplastic nature in forming them into useful shapes and a consider vT.*ien*eahelaudie>waolCemSWeornvnicwreeH,uni.C, ShPeermnoidoicuraoGlt rDoDueivpv,e,LlooUapdmtueerro,nytMmalin--rdo. S. Rubber Co., Nauratuek, Conn. The use of vinyl plostisols and orgonsok as coolings for doth, paper, and flooring substrotes has grown to be a substantial portion of several industries. This paper summarizes the technology involved in the use of these liquid vinyl systems and in* eludes a discussion of the basic components of a vinyl compound; its room tempera* lure rheology; its changes in rheology os it proceeds to gelation; and its ultimate development of useful physical properties as it is fused with heat. Compounding and application techniques are also covered. Keywords: Webs paper Cloth Fabrics Organosols * Coatings Dispersions Plastisols Vinyl resins Viscosity Temperature Physical properties able exposure to heat is involved. Without some chemical assistance, the vinyl polymer itself would rapidly darken and decompose. Fortunately there are many stabilizing materials available that work well with vinyl in maintaining its thermal stability. These are organic compounds based princi pally on barium, cadmium, sine, and lead. As each metal serves a special stabilising function, a balanced stabi liser system contains two or more of them. As in other products, pigments are used for coloration and fillers are used for cost reduction. When a cellular product is needed, any one of a number of chemical blowing agents is employed. Of course there are many other specialty materials used with this combination of PVC polymer, plasticizer, stabilizer, etc., each providing many essentia! process ing and application features. PLASTISOLS FROM VINYL DISPERSION RESINS A form of vinyl retin is available such that when simpiy mixed with the liquid plasticiser a stable fluid or paste is formed. Here, the vinyl retin particles are uniformly distributed throughout the continuous plasticizer phase much like particles in a latex. The vinyl particles are sufficiently fine to do this, e.g., 0.2 to 3 microns. They do not settle out and such mixture remains stable almost in definitely. The other vinyl components such as fillers, stabilizers, pigments, etc., are similarly included in the formulation. Liquids such as stabilizers are dissolved in the plasticizer. Pigments, fillers, etc., are dispersed in it, as is the resin. As expected, a soft vinyl plastic results ing from a high plasticizer level will be more fluid than a harder product with less plasticizer available to dilute the continuous liquid phase. Under suffi cient magnification the vinyl resin particles can be seen to be uniformly dispersed in the plasticizer phase as schematically shown in Fig. 1. PROPERTIES OF PLASTISOLS Ge/ofton and fusion After a plastisol is coated onto a sub strate, molded into a useful shape, or Pfdaetum Table L Applications of Vinyl CmSnutim fabricati'm In the home Shower curtain* Unsupported film Table cloths Film, unsupported or sup ported on cloth Flooring Film and/or foam on felt or asbestos Clothing (jackets, handbags, Film and/or foam, unsup hats, tiroes, belts) ported and supported on doth Dolls and toy* Hollow moldings Pipes, rain gutters, window Rigid /Iinnla Calender Calender or spread coated Spread coated Calender and spread coated Slush and rotatiouaUy molded Extrusion Conveyor belts Electrical wiring Ducts In industry Plies of vinyl on doth Vinyl coated on wire Vinyl ooated onto duct work Spread coating and press lamination Extrusion Spraying _ \lC*ri*veu PartidM \ FI Ditce*iiriirti* 80' \$7&\ {ROOM TEMPEWTUHt) &;*YO 1 t30#F ( FNC-8CIATI0N SWELLING OF MATICLCS} 180 "F (GELATION. VHrnML 0fSAFFMAftfiE OF UOUID PHASE) 280 *F (PARTIAL FUSION) 330F (FUSION) FiB. I. Flmtitol gMalion and fvtlonj ramparotiirM ahown very witb seb tpocifle fomtufafim. ports/100 ports resin Tttirtcipe: Marvinol SO--100; DOP--M abowo Fig. 2. Flolol vitcowly w. ploilkizar lava! Fig. 3. Plattiiol vtecMity MsbSty **, taraga tamparatwra fabricated in some other way, beat is applied to convert it into its solid state. This is called fusion. Although the fusion process takes but a minute or two in the usual industrial applications of a vinyl piastisol, a number of changes take place in the physical state of the material during this brief interval. The piastisol is heated in a convection oven, or by a bank of infrared lamps, or in a higbfrequency induction system. This causes the plasticiser to soften the vinyl resin particles, swelling them, until finally each swollen particle touches Its neighbor (Pig. 1). At this point most or all of the plasticiser has been absorbed by the resin particles; the plastic is dry, but it has virtually no physical strength. This is called the gel stage. It is a useful phenomenon in certain types of vinyl piastisol proc essing where the coating thickness of a dipped or molded vinyl is controlled in this fashion. Gelation temperatures vary with formulation, but most fall within the 150-200F range. As heat continues to penetrate the system, the PVC particles lose their identity, as such, as the plasticiser begins to separate the polymer chains. Now the polymer chains are in a sense dissolved in the plasticiser. This is fusion. Although varying with formu lation, fusion generally starts in the 280-3006F range, with complete fusion developing at 325-3S0F. On cooling, the plastic is characterised by useful tensile strength, abrasion and chemical resistance, plus all the other attributes associated with vinyl coatings. Viscosrfy at Room Temperature A piastisol may be held at room tem perature for a relatively long period of time before it is processed through a pump and applied to some substrate by a roller or knife coaler. Hence, its room temperature viscosity properties merit considerable attention. Figure 2 describes the viscosity of a piastisol at varying levels of plasticiser. As plasticiser is withdrawn from the system, viscosity increases. At first this viscosity change is slight, but it in creases rapidly at the lower plasticiser levels. When attempting to apply a low plasticiser level compound, its viscosity may be well above a coatable level. In such an instance, it is neces sary to dilute the plasticiser with a volatile diluent that will reduce com pound viscosity, yet flash off during fusion to maintain the proper PVC/ plasticiser ratio in the fused composi tion. Such sy*'.ems are known as or ganosols and will be covered in greater detail later. Although pl&stisols are quite stable in their liquid state, exposure to a slightly elevated temperature will cause partial gelation of the compound, mani festing itself in a gradual viscosity in 04 0 It 1* SO *4 TIME, min Fig. 4. Fro-gttalion vncoMty. lot* tamparotVT4> 130'F crease. The magnitude of this increase is dependent on storage temperature as depicted in Fig. 3. This strongly sug gests that care should be exercised in maintaining proper storage conditions in the day-to-day handling of piastisol com|x>unds. A maximum ambient stor age temperature of 90F is recom mended, although some exposure to higher temperatures for short periods will not be harmful. Prg-Gafafion V/seosfty A piastisol is generally exposed to fusion temperatures for a period of 1-2 min in most industrial applications. Thus, the amount of time in the socalled pre-gelation temperature range, i.e., between room temperature and gelation, is relatively short, perhaps l/ min or less, depending on formulation, fusion conditions, etc. The viscosity properties of a piastisol in this pre-gela tion temperature tone are quite different from its properties at room tempera ture. Figure 4 plots the viscosity of three compounds as a function of time. The time interval here is deliberately made longer than actually experienced during fusion as noted above, so that the changes in viscosity that occur can be examined in greater detail. This is done by exposing the piastisol to tem peratures considerably lower than full fusion conditions but sufficiently high to bring the piastisol through its pre gelation stage as shown. These changes in viscosity are par ticularly important in cloth coating work where the reduced viscosity of a piastisol during pre-gelation may cause the compound to strike through the interstitial spaces in the cloth. This temporary viscosity reduction is gen erally not a problem when the substrate is not porous. URL 14503 fusion Tempercrfure* need for Ion* viscosity and high yield cosity of the continuous phase without value, required for the projter applica solvating or swelling the PVC resin par As already described, the vinyl must tion of the compound, is met bv adjust ticles makes the aliphatic type naphtha be fused to develop useful properties. ing viscosity with high oil absorptive particularly useful in this work. Although a semblance of fusion may be fillers or gels and volatile diluents. The way in which the viscosity of ( detected at temperatures as low as 280CF for standard formulations, use In other cases, the need for hardness or rigidity in a product may call for a an organosol is brought into a useful range is shown in Table II. Here a ful properties do not develop until reduction in the plasticizer level, below plasticizer level of 25 parts per 100 pans about 325F. Figure 5 describes the which a sufficiently fluid paste may not resin is required for a hypothetical pa])er temperature-time-tensile strength rela be formed. Here adjustment with a coating application. Ten parts of dil tionship for an organosol compound small amount of volatile diluent is ade uent are needed for the initial mixing of with 35 parts of plasticiser per 100 quate to develop enough fluidity for the compound (Recipe A). Attempts parts of -resin (abbreviated 35 phr). application. The volatile diluent is to coat this formulation resulted in ex With oven air at 350 and 375F, the evaporated during fusion. Such formu cessive force being required for the high time to accomplish fusion is reduced. lations, generally referred to as modified speed coating of the paper and poor flow- The higher tensile values noted at plastisols, are commonly used in fabric out of flow lines that developed in the 400F result from a loss of plasticiser coating and rotational molding of rigid coating. The high high-shear and high from the him as a result of this exposure type plastisols. low-shear viscosity of this compound to excessive temperature. When the plasticizer level has been correlate with these two observed flow Copolymer resins and solvating plas reduced to the point where it is difficult phenomenon, respectively. An adjust ticisers, e.g., tricresvl phosphate, will or impossible to form a paste when ment with three additional parts of shift these curves downward with fusion mixed with resin, volatile diluents are diluent brought both the high- and low- developing in the 250-300F range. used in the initial mixing of the com diear viscosity down, as noted in the data The ultimate physical strength de pound. These compounds are known (Recipe B). The compound then coated veloped by copolymer resins is less than as organosols. satisfactorily but still flowed out poorly. that developed by homopolymers, when The high-shear viscosity was then ade each is fused at its respective optimum quately adjusted. A further adjustment fusion temperature. Where oven heat Dtfueni Selection in the low shear range was needed to capacities are limited or heat sensi eliminate the flow lines. The use of ad tive substrates are being coated, co Volatile solvents and diluents, such ditional quantities of diluent may result polymer resins do provide higher as ketones and aromatic and aliphatic in excessive fire hazard or the develop strength values at lower temperatures. hydrocarbons, are commonly used to ment of diluent blisters due to trapped Where sufficient oven capacity i* avail dissolve and disperse vinyls. Ketones naphtha in the film during fusion. able, standard PVC homopolymers and are good solvents for solution grade Therefore an alternate means of vis standard plasticizers, e.g. dioctyl phtha- vinyls and have a strong solvating effect cosity adjustment was used. A nonionic r late (DOP), are used. A on dispersion grade PVC resins. Con sequently, if they were used as the sole diluent in organosols, high viscosity and surfactant added to the compound brought its low shear viscosity to a satis factory level. This addition did not ORGANOSOLS poor viscosity stability would result. significantly alter the high-shear vis The aromatic hydrocarbons, although cosity. This compound, altered by the Because the plasticiser level of a nonsolvents for PVC, have a partial addition of naphtha diluent to adjust plastisol compound is determined by the solvating or swelling effect on dispersion high-shear viscosity and wetting agent end product requirement, the resultant resin intermediate to that of the ketones to adjust low-shear viscosity, provides plastisol viscosity is often not ideal for and aliphatics. a properly formulated organosol com ready application. In such cases, ad Aliphatic hydrocarbons, known in the pound for high-speed paper coating. justments are made with various formu paint field as petroleum naphthas, are Special polymeric plasticizers may lating ingredients to develop the re actually mixtures of paraffins, naph sometimes be used in a plastisol or or quired rheological properties. A spray thenes, and aromatics. These mate ganosol formulation to provide special or cold dip plastisol is a typical exam rials are available in a wide variety of properties, such as extraction resistance, ple. Here sufficient plasticizer is gen boiling ranges and aromatic-aliphatic in a vinyl film. These plasticizers are erally available in the formulation to content. Their ability to dilute the not soluble in aliphatic naphthas. Con provide a fluid paste. However, the plasticizer and thereby lower the vis sequently there have been instances URL U 504 Toble II. Viscosity Adjustment of on Organosol A3 c PVC dispersion grade resin Plasticizer Stabilizer Diluent--aliphatic naphtha Wetting agent--PEG400DO Formulation 100 100 100 25 25 25 3 33 10 13 13 1.4 Brookfield (low shear) C Severe (high shear) TIME, min Rg. 3. Ilaitil fwtlen progtrlitij plaiticlxar Iml 35 part* par 100 parts raun (phr}. Drag resistance Flow-out 21,800 31,500 High Poor Viscosity, cpi 10,700 11,800 Coating properties Low Poor 2,000 0,800 Low Good where adding naphtha diluent to such compounds raised viscosity. It is there* fore necessary to develop useful diluent systems for such compounds. Figure 6 describes the high* and lowshear viscosity properties of a polymer plasticiser-based compound using blends of aliphatic and aromatic hydrocarbon diluents. An all-aromatic diluent pro* duces a very dilatant compound, i.e., its high shear viscosity is many times its viscosity at low shear. A 50:50 blend appears optimum for low viscosity but is close to the insolubility point. From such a plot, a 60:40 aromatic:aliphatic blend appears useful. Rtfology of Pksstisoh and Organosols Because plastisols and organosols are liquid systems and are applied as such, their application performance is inex tricably tied to their rheological prop erties. A comprehensive knowledge of this subject is essential to the plastisol and organosol user. However, it is beyond the scope of this paper to discuss this in detail, and only a few fundamen tal concepts will be presented. First, unlike water, oil, and other common fluids, the vinyl systems de scribed above are non-Newtonian, i.e., their viscosity is a changing function de pendent on the shearing action and time associated with their application. If their viscosity increases with increasing shear, they are "dilatant"--an undesir able feature. If some force must be overcome before flow will occur, the material exhibits "plastic flow." The initial force necessary to initiate flow is called "yield value." If the viscosity of a compound is observed to decrease as a function of time, "thixotropy" is evident. There are other flow phenomena to be observed in these systems, but these are the essential ones. If we were to meas ure some of these properties in a single sample, as we frequently do using a rotational viscometer, a rheogram, as shown in Fig. 7, may be constructed from these data. A rheogram plots shear Stress, as measured by the deflection of the viscometer spindle, against shear rate as measured by the rate of rotation of the viscometer cup. These are plotted on the Y and X axes, respec tively. The lower values of downcurve shear stress compared with upcurve data ind cate the thixotropic nature of the compound. The finite value of shear stress at tero shear rate represents yield value. Viscosity per ee, or more accurately apparent viscosity, is represented by the slope of the line connecting the origin with any point on the curve. The two viscosity lines shown indicate the dila tant state of the compound, i.e., the higher viscosity associated with the higher rate of rotation. Test recipe: Msrviaol 50--100, Parepiek G&4-- SO. diluent bland--26 fig. 4. Orgsnwol diluent Wand. fig. 7. Dtaegrea el e ptoktoot Foamod Vinyls Up to this point the discussion of vinyl coatings on paper has been re stricted to a consideration of solid coat ings, both clear and pigmented. Foamed vinyl coatings on cloth have become so popular in recent years for clothing and upholstery that their use on paper should be considered as well. Pig. I. Slew tptad change con-type misar (photo courtesy C. toes & Son Co.}. Vinyl foam coatings may be produced by whipping air into specially formu lated plastisol compounds. Vinyl foam is also produced by incorporating chemi cal blowing agents into the compound. In the former technique, air is mechani cally whipped into a plastisol, com pounded with a wetting agent so that the resultant froth is reasonably stable. This froth is spread onto a substrate and passed through a fusion oven. Because it is difficult to force heat throught a foamed structure, the thick ness of foam must be maintained at a relatively low, but nevertheless useful, level. Foam thickness in this case may be increased by using the more sophis ticated induction heating techniques for plastisol fusion. This type of foam is open cell in nature, i.e., the cells connect with one another. Also, it is restricted to the softer stocks because a relatively high plasticiser level is required to main tain the low viscosities needed for ade quate frothing of the compound. Most vinyl foam is manufactured us ing chemical blowing agents in vinyl plastisols. The use of azodicarbonamide far outweighs the use of other blowing agents in this application. Here is a typical starting point formu lation for such a product: PVC1 resin DOP Epoxy plasticizer Azodicarbonamide Stabilizer 100 95 5 3 3 The use of a medium molecular weight resin is preferred. Activation of the blowing agent occurs at relatively high temperatures, i.e., 325-350F. At this point the vinyl is in its fluxed, hot-melt state. The medium molecular weight resin provides a less viscous hot-melt plastic, which is capable of more readily expanding into a fine cell structured foam under the influence of the activated blowing agent. Through compounding and fusion temperature techniques, it is possible to control the density of the foam, cell size, and the degree of poros ity. Plastisol Compounding Techniques The relative ease with which plastisol resin may be blended with plasticizers and other formulating ingredients par tially accounts for the rapid growth of this field. Consequently, a brief dis* cu&sion of the various-mixing techniques available is in order. For the bulk of plastisol and organosol work, the Change Can or Pony type mixer is quite adequate (Fig. 8). A normal mixing cycle would involve charging the mixer with sufficient plas- 1 A medium molecular weight PVC dispersion grade resin. Pig. 9. High ifid nli*r Ipboto courtwy HouKoum Cowl#* Co.). Pig. 10. A 4*arote* (photo cawty CoreeM Machine Work*. Inc). ticizer, or in the case of an organosol, plasticiser and diluent, to wet the resin into a fairly heavy paste, thus |emit ting effective transmission of shear forces throughout the mix. When all the resin has been thoroughly masti cated, the balance of the plasticizer or diluent and other formulating ingre dients can then be blended in slowly. From this point the batch may be fur ther processed through paint mills and deaerators, if necessary. This mixing technique may be satisfactorily applied to most types of plastisol and organosol compounds. In the manufacture of organosols and plastisols of the low-viscosity type, it is possible to utilise another type of mixer that eliminates the necessity of keeping the paste in a heavy stage for effective mixing. This mixer, shown in Fig. 9, operates at very high speeds. Because the high-shear mixing action takes place in the immediate vicinity of the rotating blade, it is necessary to have rapid circulation of the compound to prevent localised overheating and consequent gelation of the material, thus requiring compounds with low viscosity properties. Consequently, all the liquid ingredients are first blended in the mixer, after which the resin is added in increments. Itel) and pebble mills used exten sively in the paint field are frequently used to compound plastisols and organ osols. Because no real grinding action is required, only a deagglomeration of the soft resin clusters, considerably more latitude with respect to ball or pebble charges and compound loading Fig. >2. Kevene roll coater (photo cowrtey tended Fiber* Co.). Fig. 13. Schematic drawing of reveree roll end knife ceeter (bated on drawing* by J. Woldron Co.). may be tolerated than with paints. Frequently deaeration can be accom plished in the same mill by rigging it for vacuum. Occasionally, an operation cannot tolerate the presence of any undis[)ersed resin agglomerates in the finished com pound. In such instances a single, loose jiass through a three-roll paint mill is sufficient to disperse any resin clusters that may remain undispersed in the eompound. When deaeration is necessary, any one of a variety of vacuum setups may be used. Figure 10 illustrates a commercial apparatus available for this purpose. URL 14506 Fig. 11. Knife ever roll coeter (photo courtesy J. Waldron Co.). COATING TECHNIQUE Basically two types of coating equip ment are employed in coating paper and cloth substrates. These are knife over roll and reverse roll coftlprs. both highshear devices, as shown in Figs. 11 and 12. Figure 13 shows these devices schematically. In knife coating, the compound is metered onto the paper by controlling the gap setting or clearance between the knife edge and the backing roll, in reverse roll mating, the plastisol is first metered between two rolls before trans ferring to the paper. This latter tech nique provides accurate coating weights down to about 3 mils. After coating, the plastisol is fused in a conventional forced air convection oven. Although infrared radiation is occasionally used, it does not provide the uniform and reasonably close tem perature control needed to prevent either under- or over-fusion of the com pound. Under-fusion of the plastisol or organosol will result in a relatively weak film. Overexposure to heat may result in thermal degradation of the substrate and/or vinyl compound as well as volatilization of some plasticizer from the cast film with its subsequent change in the designed physical properties of the film. ^/ending Resins Up to this ]X)int the discussion has dealt with plastisols and organosol systems that are based on the fine par ticle size plastisol or dispersion grade PVC and pojTolymer resins. There is another type of PVC resin that has re cently found a place in this tyjie of work, known as plastisol blending resin. The major distinguishing character istic of a blending resin is its particle size, which is many times the particle size of a dispersion grade resin, ranging between 5 and 75 n and higher by com)rison with the 1 n size of a dispersion resin. Consequently, a blending resin is not capable of forming a jiasle with plasticizer, but it may be used in conjunction with the paste-forming dis persion resin. A 30-50% blend with disitersion resin is commonly used. Blending resins are used in plastisol and organosol com}x>unds primarily be cause they lower compound cost. They vary in cost, but are as much as ft^/lb lower than dispersion grade resin. In a 50:50 blend, average resin cost may be reduced up to 17%. The particle size determines the suit ability of a compound in paper coating as well as in other spread coating appli cations. Because of the manner in which a plastisol is spread, i.e., through knife and reverse roll coaters, large par ticles tend to lodge in the coating nip and gouge out a long channel in the coated paper before slipping through. Consequently, blending resins for spread coating must be well regulated for par ticle size. Blending resins vary in molecular weight. As with all PVC resins, the higher molecular weight blending resins provide higher physical strength by comparison with those polymerized to a lower molecular weight. When strength projierties, such as tensile or tear, are an important consideration, it may be i>ossible to compensate for the lower strength resulting from the use of a lower cost, lower molecular weight blending resin by reducing the plasti cizer level somewhat. In such a case, however, the selection of a higher molec ular weight blending resin is strongly indicated. Although such resins are generally more exjtensive, they still rep resent some saving compared with disl>ersion grade resins. Blending resins also lower the gloss of a plastisol or organosol comjxmnd by virtue of their relatively large particle size. For many products, this feature is of considerable value. CONCLUSION Much has been said in this pajier re garding vinyl dispersion resins and their use in plastisols and organosols with specific reference to their use as paper coatings. It is beyond the scope of this paper to develop the chemistry of vinyl resins, plasticizers, etc., or the use of vinyl resins other than the dispersion and blending resin grades. However, a projwr understanding of this subject necessarily includes these as well as other facets of vinyl technology. Such subjects are commended to the reader for future study. LITERATURE CITED 1. Marvinol 50 Bulletin, Uniroyal, U. S. Rubber Co., Naugatuck, Conn. 2. Werner, A. C., Mod. Plastics 36 (11): 126(1959). 3. Werner, A. C., "The Rheology of Plastisols," Naugatuck, Conn., U. S.r Rubber Co. 4. Werner, A. C., Mod. Plastics 34 (6): 137 (1957). 5. Lazar, L. T., Mod. Plastics 42 (9): 149(1965). 6. Werner, A. C., "Formulating Poly meric Plasticizers in Vinyl Plastisol Formulations," SPE presentation, February 1962. 7. Werner, A. C., "Rheological Require ments of Vinyl Dispersion Compounds for Fabric Coating--Part II," SPE presentation, April 1966. R. Greenhoe, J. A., SPE J. 17 12: 1314 (1961). 9. Heinrichs, A. J., Mod. Plasticu 41 (8): 164(1964). 10. Heinrichs, A. J., Mod. Plastics 44 (1): 181 (1966). 11. Wemer, A. C., Mod. Plastics 39 (2): 135(1961). .Received Aug. 22 1W66. Presented at the Slit Pltiiici*PtMr Conference of the Technical Asaoeiation of the Pulp and Paper Industry, held in New York. N. Y., Sept- 19-21. I960. URL 14507