ELASTOMERS-Latex Commercial Low Temperature Latices. Figures 15 and 16 depict stress-strain properties of several 50” F. latices which have been produced commercially or have been made available as samples t o the trade. The values for tensile st’rengthof several of the 70-30 butadienestyrene polymers were widely divergent, even though the latices had been made under conditions intended to give equivalent properties (Figure 15). The ultimate elongations of all the cold rubbers were markedly higher than for their hot rubber counterparts (Figures 2, 4, 10, and 14). The tensile products of the cold commercial latices n-ere sufficiently high to make them extremelj- interesting for industrial utilization. CONCLUSIONS
perior to those of any of the synthetic rubber latices tested to date. Cold rubber latices now in production are an improvement over high temperature latices, for example, in wet gel strength, but do not approach natural rubber latex in stress-strain properties. ACKNOWLEDGMENT
The authors are grateful to J. B. Lfitchelson, J. A. Gotshall, and C. T Winchester, Chemical Engineering Division, and R. W Hobson, Research Division, for assistance in preparation of latex samples. They are also grateful to Goodyear Tire and Rubber Co. for permission t o publish this paper. LITERATURE CITED
Borders, A. M., and Pierson, R. >I., IND. ENG.C m x , 40, 1473 (1948).
.
When test.ed in a single standardized procedure for cast latex films, the type of synthetic rubber latex employed in latex blends containing 70% or more natural rubber latex had little effect on the stress-strain properties of the mixture. Cold rubber latices imparted higher stress-strain values to blends wit,h natural rubber than did the corresponding hot rubber latices. The improvement was particularly noted on coldparison of tensile product values. Low conversion synthetic polymers produced higher stressstrain properties, than high conversion polymers in blends with natural rubber, even t,hough their tensile strengths in 1 0 0 ~ syno thetic stocks were approximately equal. Optimum physical properties were obtained by use of blends with synthetic polymers of medium Mooney viscosity. I t is believed t h a t the appearance of an optimum Mooney viscosity is tied in with the necessit,y of having quite high molecular weight on the one hand, and, on the other, the ability of the part>iclesto knit well, the latter in turn requiring a comparative freedom froin tight gel. Tensile product values increased with increasing styrene content in the synthetic polymer, but, correspondingly, the lo^ temperature stiffening increased. The physical properties of a natural rubber stock are far su-
Clayton, W. J . , U. S. Patent 2,444,869 (July 6 , 1948). Firestone Tire and Rubber Co., private communication to the Reconstruction Finance Corp., Synthetic Rubber Division. Flint, C. F., “The Chemistry and Techno!ogy of Rubbcr Latex,” New York, D. Van Nostrand Co., 1938.*, Gehman, S. D., Woodford, D. E., and Milkinson, C. S.,Jr., IND.ENG.CHE~I., 39, 1108 (1947). Gehman, S. D., Woodford. D. E., and Wilkinson, C. S..Jr., “Tentative Method of Measuring Low Temperature Stiffening of Rubber-Like Materials by the Gehman Torsional Apparatus,” ASTM D 1053-49T. Maron, J. H., Elder, M. E., and Ulevitch, I. K., private com, munication to Office of Rubber Reserve. (8) Rogers, T. H., Jr., U. S.Patent 2,469,894 (hlay 10, 1949). (9) Rubber Reserve Release, abstracted in Rubber Age, 69, 215 (1951); India Rubber World, 124, 446, 587 (1951). (20) Smith, H. S., Werner, H. G.. Rladigan, J. C., and Howland, L. H., IND.E N o . CHCY.. 41, 1584 (1949). (11) Talalay, L., paper presented befoie Rubber Division, 120th Meeting, AM. C H m f . SOC., Xew York; abstracted i n Rubber A g e , 6 9 , 3 3 1 (1951).
(12) Willson, E. A., U. S.Patent 2,357,861 (Sept. 12, 1944). (13) Woh!er, L. A , , Ihid., 2,537,615 (Jan. 9 , 1951). RECEIVED for review September 17, 1931. ACCEPTEDJanuary 11, 1952. Contribution 190 from the Goodyear Tire a n d Rubber Go., Research Division. Work was sponsored by the Office of Rubber Reserve, Reconstruction Finance Corp., in connection with the government synthetic rubber program.
LATICES OF FLEXIBLE SYNTHETIC POLYMERS B. M. G. ZWICKER,
B. F. Goodrich Chemical Co., Cleveland, Ohio
During the past ten years there has been rapid progress i n manufacture and use of flexible synthetic polymers. There are now nearly two hundred synthetic rubber, plastic, or plasticizable polymer latices commercially available in the United States, which have been grouped into fifteen classes according to reported polymer composition. General properties of synthetic latices are discussed, including the effect of particle size on stability and viscosity ; characteristics of typical emulsifiers and dispersing and thickening agents and their influence on stability, coagulatability, and application ; and wet and dry film strength properties of typical synthetic polymers. The adoption of soap requirement titration for control of synthetic latex compounds is recommended. Each class of polymer is discussed with reference to inherent polymer properties and how these are related to principal applications. Certain deficiencies in existing materials are pointed out. New products entering the market in-
774
clude water-dispersible polymers (for hydrosols), watersoluble polymers (polyelectrolytes and hydrophilic compounds), and plastisols (resins dispersed in plasticizers). The first two types are classified by composition, and general properties of each class are summarized.
S E of the earliest uses of a flexible high polymer latex was as an adhesive. The value of certain plapt saps as flexible and shock-resistant glues and lacquers a as recognized very early in the developnient of manufacturing technology. The art of making articles by dipping rubber latex is more recent, but as early as 1736 de la Condamine ( 4 3 ) reported such a practice by the natives of Peru. The first report of an attempt to make an artificial water dispersion of natural rubber was in 1836 (171). The art of polymerization was discovered about the same time (158, I r a ) , but emulsion polymerization to a synthetic latex was not described until 1012 ( 2 7 ) . Many commercial synthetic lubbers and plastics
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 4
ELASTOMERS-Late-
*
are now produced almost exclusively as emulsion-polymerized latices, and their use BB such has assumed considerable industrial importance (33). Many of today’s commercial applications for synthetic high polymer latices were first developed with natural plant fluids, especially natural rubber latex, However, in many instances the use of a water dispersion was simply the best way to make a new article from the special nynthetic polymer. The general advantages of handling natural rubber in the form of latex ($6, 139, I @ ) apply equally well to synthetic polymersfluidity a t high concentration, low cost and nonflammability of the volatile diluent, and control over polymer deposition. In addition, many unique advantages exist for specialty uses of synthetic latices-for example, the recent availability of water dispersions of the refractory polyfluorinated resins has made their application to intricately shaped articles much easier. The use of minor quantities of Hevda to impart flexibility to many articles represents a substantial commercial market for latex, and one that has attracted many flexible synthetic materials which are far less elastic than natural rubber. There is no sharp dividing line between elastic and rigid high polymers; therefore the word “plastic” has been used to describe this broad transition group. I n a strict sense, all high polymer materials possess a degree of high elasticity under proper temperature and stress conditions and this can be controlled by selection of certain compounding materials. The scope of this review has been arbitrarily restricted to water dispersions of synthetic elastic and plastic materials commercially available in the United States, the compounded dry films of which display a useful degree of elastic recovery within the temperature range of liquid water. Water-soluble thermosetting resins are treated only as compounding ingredients for the more flexible linear polymers. GENERAL PROPERTIES OF SYNTHETIC LATICES
The technology of synthetic plastic and rubber latices is expanding rapidly. The possibilities of tailoring unique polymer compositions increase factorially with each new polymerizable material and the discovery of a new polymerization technique offers a possible variation for each polymer composition. Physical properties of a given polymer composition can be modified over a wide range of plasticity by varying the molecular weight or degree of branching, or by use of plasticizers. Strikingly different latices of the same polymer can be obtained by variation of the particle size, surface active agents, and water-soluble ingredients. The proprietary compounder can make hundreds of distinct latex blends from any one of these basic raw materials. It is not surprising that consumers of latex compounds find i t difficult to keep informed and to take full advantage of the increasing numbers of commercial synthetic latices; hence this attempt to rationalize and classify. Some general properties of synthetic polymer latices require a different technical approach from that usually applied to natural products such as Hevea rubber latex. Disappointing results have often been due t o failure to recognize these new parameters. Particle Size. Particle size and its influence on latex stability are probably the most universally important subjects t o be considered in compounding and using any synthetic latex. Particle diameters of synthetic latices can be varied over a wide range of size and distribution (34, 188). For the most part, this is determined in the polymerization or dispersion process and is characteristic of each commercial material. On the average, the particle size of synthetic polymer latices is much smaller than that of Hevea latex. This fact requires the compounder t o set up a new yardstick for stabilizing synthetic latices for commercial use. There is an enormous increase in hydrophobic surface as particle diameter of a rubber or plastic latex is reduced. This has April 1952
been calculated for hypothetical systems a t several unifprm particle diameters and listed in Table I. Stability of the heterogeneous system requires that some minimum quantity of protective agent be associated with this surface. The last column in the table shows the milliequivalents of saturated fatty acid soap per hundred parts of dispersed polymer that would be required to cover the surface of each particle completely with a condensed monomolecular soap film (theoretically 21 square A. per soap molecule).
Table I . Variation of Latex Surface with Particle DiaGeter (Hypothetical latices of uniform particle size; polymer speaific gravity = 1.0) Total Surface, Theo. Me. Soap No..of Particles Sq. Meters/ per 100 Parts per Kg. Polymer Kg. Polymer Polymcrb 2.39 X 1 0 3 0 236 300,000
Particle Diameter, Micronsa 0.02 0.06 0.20 0.6 2.0 6.0
8.84 X 1018
2.39 x
1017
8.84 X 10’6 2.39 X 10’4 8.84 X 101%
100 000
78.6
10,000
3,000
23.6 7.9 2.4
1,000
0.8
30:OOO
1 micron = 10,000 A. b Theoretical milliequivalents of saturated soap re uired for condensed monomolecular film per hundred parts of polymer soli%. a
Experience with G R S latex has shown that the actual saturation requirements are much less (188),and that a latex with 40 to 6OY0 of its actual saturation soap requirements satisfied possesses adequate stability for shipping and handling. This is not enough for some of the oil-resistant rubber and plastic latices, nor for many commercial compounding, coating, or impregnation processes. Although a latex of larger particle size requires less stabilizer, many applications take specific advantage of the very small particle size of some synthetic latices. The affinity between the surface of the polymer particle and the surface active agent is very great. I n a typical soap-stabilized GR-S latex of 0.1-micron average particle diameter, approximately 7 parts of emulsifying agent are present per hundred parts of polymer. At 4Oy0 total solids, there is less than 0.04oJ, soap in the water phase, representing only 60% of practical saturation. I n other words, of the total soap in the latex, 99% is on the particles; furthermore, over 4 more parts of soap can be added on the polymer before there will be an appreciable increase of soap concentration in the water phase. Hevea rubber latex can be saturated with very little added soap. Failure fo recognize this fundamental difference between many synthetic latices and Hevea will lead compounders into serious difficulty. The addition of a perfectly good compounding d i s persion to a soap-starved synthetic latex can result in microflocculation and poor dispersions. The stabilizers on the com‘pounding ingredients simply transfer to the latex particles. The use of nonsurface active polymeric dispersing agents such as polyalkylaryl sulfonates (small effect on surface or interfacial tension) for the compounding dispersions will minimize this difficulty. The potassium hydroxide number so commonly used to characterize different lots of Hevea latex helps ensure uniformly stable compounds. This technique, which indicates protein and ammonium soap content of Hevea latex, is of no value in characterizing most synthetic latices. A new laboratory tool is needed, and soap requirement titration appears t o be worthy of serious consideration. It is a practical analysis of the particle size and soap content of the raw latex, and can be useful in prescribing type and amount of additive to meet factory compounding and stability requirements. Several techniques are available, but the end-point determination that is common to all depends on the fact that many soaps form micelles in water solutions above a critical concentration. The unsaturated surface of latex particles keeps the soap con-
INDUSTRIAL AND ENGINEERING CHEMISTRY
175
-ELASTOMERS-Latex centration in the aqueous phase below this critical concentration until its requirements are satisfied. Variations in the techniques arise from the fact t h a t a number of peculiaritjes occur a t the point of micelle formation (120): minimum surface tension (19, 108), discontinuity in electrical conductivity, salubilization of dyes (39, 40) and other hydrophobic materials (41), change in foam structure, gellation, or viscofiity changes, change in light scattering (44), and many others. The conductivity technique I
m
300
I
I
I
I GR-S LATEX VISCOSITY I
I
I
I
I
3OoC
I
RUBBER CONTENT, %
Figure 1.
Influence of Latex Concentration on Viscosity (Private comrnunicetionlfrom S. H. Maron)
of Maron (194) for lat,ex is summarized in a recent publication (188), and is perhaps the best developed laboratory technique. The use of surface tension titration is simpler and offers advantages for control work; however, t'he method is not so generally applicable as conductance. The dye solubilization technique (117) is also simple, but is not satisfactory for latex. Any selected t'echnique would have t o be correlated with factory experience to be of value to the latex compounder and consumer. Determination of actual particle size by light scattering (44), electron microscope (187, 188), or other techniques is of importance to the latex manufacturer in controlling product uniformity. Knodedge of particle size of synthetic latices can also be valuable to the consumer in developing specific products and processing techniques. From Table I i t can be seen that a h e particle synthetic latex (0.06-micron diameter) would have nearly forty times as many particles in a pound of latex solids as there would be in a typical synthetic latex of large particle size (0.20micron diameter), and over a thousand times as many particles as there are in a pound of Hevea latex solids. Surface Active Emulsifiers. I n most Synthetic latices, surface active materials such as soaps arc used in the emulsion polymerization or dispersing process and prevent agglomeration of the particles by maintaining a hydrophilic surface that is usually electrically charged by ionization. There is a minimum protection requirement for storage latex stability, a higher one for transfer stability and a still higher one for stability of thin films under pressure (roll coaters, squeeze rolls, etc.). Stability is usually varied by changing the amount of surface active material in a given latex. T o meet the maximum number of requirements, latex manufacturers usually limit stabilizer content of t,heir products to the minimum for static or dynamic stability. Stabilizer requirements for a specific application and latex depend primarily on particle size and manner of use, but are also affected by type of polymer, type of stabilizer, pH, and compounding ingredients.
776
Control of latex stability and coagulability requires investigntion by the consumer for each type of synthetic product. Because most stabilizers are of low molecular weight and water-soluble, they are subject to natural laws of adsorption and equilibrium; addition of a stabilizer with greater affinity for the latex particle than that in the original latex may displace it and result in uneconomical or unsatisfactory compounds. Discussion of the many types of commercial surface a&ve materials and their use in manufacture and compounding of synthetic latices is beyond the scope of this paper. Although no published review covers the broad subject, a number of pu1)lic.ations describe the commercial emulsifiers (68,177, 182) and eyiithetic polymer emulsion polymerization (38, 79, 107, 131, 268, 173, 176). There are four types of emulsifiers commonly used in synthetic latex manufacture: fatty acid soaps; rosin wid soaps; alkyl aryl sulfonates, alkyl sulfates or other anionic agents with broad p H range; and nonionic agents st,able to a wide range of chemical compounds. There are a few latices on the market with cationic soaps. Nonelectrolytic agents are not only used alone by some manufacturers but are useful additives to increase sbability of any latex t o electrolytes and compounding agents. Most ionizable stabilizers are affected by electrolyte content of the lat,cx (37, 222, 178); stabilizer efficiency can often be improved b y judicious use of such materials, polyelectrolytes such as polyalkylar.)-l sulfonates being particularly useful. The latices containing fatty acid or rosin acid soaps are sensitive t o pH (as), polyvalent metallic ions (calcium, magnesium, etc.), and compounding pigments which liberate such ions in water solution. This eensitivity can be controlled soniewhat by use of alkaline bufiers (weak bases such as ammonia and amines or strong base salts of weak polyvalent acids such as sodium pyrophosphate) together with a strong sequestering agent such as the sodium salt of diaminoethyltetraacetic acid, or by addition of an auxiliary eniulsifying agent that is stable t o these chemical conditions. I t is usually advisable to use softened or deionized water for all latex technology unless adequate technical control is developed for use of service water for a particular process. Viscosity and Total Solids. Viscosity of a latex increaws as concentration increases (115, 1@), and a critical paste-forming concentration is characteristic of each commercial material. These properties are determined primarily by the particle size of the latex, including its adsorbed soap and water film, h u t tire influenced by type and amount of emulsifier, electrolyte, conieiit, and temperature ($9). .4 pasty synthetic latex may frequently be unstable to mechanical agitat'ion, but can be fluidized without coagulation by careful reversal of the cause for thiokeriirrg (concentration, low temperature, etc.). This is not true of ii s d t flocced latex (227), where irreversible coalescence of the particles has occurred. Under controlled conditions, some fiynthotic latices can be increased in average particle size withont IUIIIP coagulation by this technique. Such latices are then sat)ur:ite(i with soap and have limited commercial ut,ility. blaron and coworkers (188) have investigated the vis& t y and thickening properties of a number of GR-S latices and h w 7 v described a number of intereflting phenomena. Typical limiting concentrations for fluid GR-S latices of various average particle sizes are summarized in Table 11. Typical viscosity curvcp as a function of latex concentration are shown in Figure 1. IGxperimental latices of 0.03-micron diameter have become pasttls a t 25% total solids. Table 11.
Limiting Concentrations of Fluid GR-S Latices
Type of Lstex
I1 I11 V
Av. Particle Size, Micron 0.06 0.11 0.22
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Max. Concn. for 100 Cy. Visoobity a t 30' C., 70Rubber 39 53 56
Vol. 44, No. 4
ELASTOMERS-LateThe use of natural products such as casein, glue, starch, gums, and alginates as thickeners and humectants to simplify manufacturing operations is well known to the latex industry. Many synthetic polymers have been developed in recent years that are particularly valuable additives to synthetic latices. Among the more popular types are cellulose derivatives (ethers and esters), polyacrylic and methacrylic acid salts, and polyvinyl alcohols of low acetate content. These materials are generally watersoluble or dispersible high polymers and some are useful as the primary flexible-base polymer in the compound. The general development of water-soluble polyelectrolytes is progressing rapidly and deserves serious consideration as a growing factor in water-based high polymer technology. Coagulation and Wet Film Strength. A latex is only an intermediate in the fabrication of the end product. There are very few instances where the coalescence of the latex particles and elimination of water are not a fundamental part of the ultimate consumer’s process. There are two recognizable extremes : 1. Complete gellation of the latex compound and subsequent elimination of water from the heterogeneous solid gel. 2. Evaporation of the water to essential dryness prior to coalescence or fluxing of the latex particles.
Practical applications utilize both procedures, and usually involve a compromise. Irreversible coagulation of most synthetic latices is not difficult in itself, but its control usually presents a practical problem. Some films will not dry rapidly or will not deposit thick films by the anode coagulant dip process. This property of insulation is apparently due to failure of the wet latex deposit to retain aqueous permeability because the emulsifier is isolated or squeezed out of the polymer film. The proteins and carbohydrates present in EIevea latex are believed to be important in imparting these properties, although the small particle size of the synthetic materials probably contributes to the problem. Hydrophilic compounding ingredients improve these properties, especially with the synthetic latices of larger particle size. Proteins such as casein are very useful, but their preparation and addition require careful technical control, as they are often antagonistic to the synthetic latex system. Absence of easily fermentable materials in synthetic latex compounds is often an advantage worth retaining. Even with compounding to give uniform gellation, films from many synthetic latices develop cracks, porosity, and generally poor properties during drying. Maron and Madow have proposed a carbon dioxide atmosphere t o avoid this difficulty (196). Hevea films dried from coagulant processes are similar to airdried products; polychloroprene latices are the only commercial synthetic rubbers which display this valuable property. This is because most synthetic elastomers and plastics have less cohesive tendency than do the cis-polyisoprene units in Hevea rubber or the trans-polychloroprene units in neoprene. Dry rubber technologists refer to this property as “tack”; latex t’echnologists see it as high wet strength of the gelled rubber film. Synthetic rubber latex manufacturers recognize this practical deficiency in their products and are striving to correct it, Meanwhile compounders can do something for themselves by selecting stabilizers and thickeners of high wet strength (polymeric materials, casein, etc.) and by taking advantage of the thermoplasticity of the polymers in designing their operations. The use of softeners, even in small quantities, is an especially effective device. Dry Film Properties. Once a homogeneous dry product is obtained, the fundamental properties of the compounded polymer predominate. These may still be affected markedly by the surface active materials in the latex compound. As larger amounts of these hydrophilic materials are present in many synthetic latices than in Hevea latex, their removal by leaching April 1952
or their neutralization by chemical action may assume considerable practical importance. In many applications such as paper or textile treatment or pigment binding, the emulsifiers may be wicked away from the polymer film and have little if any influence on the properties of finished article. However, in general, the selection of stabilizers for latex manufacture and compounding to minimize water sensitivity in the final product is an important technical problem for both producer and consumer. The synthetic latex industry is actively following the new synthetic emulsifier developments in search of an ideal latex stabilizer. Volatile based soaps are interesting and useful, but have many practical limitations. The ultimate reason for selecting a special synthetic latex for a given application is to use the inherent physical or chemical properties i t imparts to the final product. Synthetic elastomers and plastics offer many properties not easily obtainable from natural products such as Hevea. These are discussed in more detail in the following section, but include fire, oil, and chemical resistance, oxidation and abrasion resistance, adhesion properties, thermoplwticity, appearance, and cost advantages. With the exception of extenders based on economy or supply problems, synthetic latices are specialty products and most of them should not be considered as replacements or extenders for Hevea, but rather as new raw materials from which new or improved articles of commerce may be prepared. However, one property is almost universally characteristic of present commercial synthetic polymers-relatively high modulus at low elongations as compared with Hevea vulcanizates. I n many applications this is an advantage; in others it is a disadvantage. The use of softeners or special low modulus polymers usually results in general reduction of ultimate tensile properties of the synthetic materials. I n rubber technology it is an axiom that a vulcanized Hevea latex film represents the peak of ultimate tensile strength of a high elastic material. It is true that its 50,000 to 60,000 pounds per square inch tensile strength a t break (based on actual crosssectional area a t the 900 to 1100% elongation, 196) is exceeded by few elastic organic compounds with the exception of fibers. So far, synthetic flexible polymers commercially available in latex form fall short of Hevea in this ultimate proparty. However, some classes of synthetic materials give products from latex that compare favorably in ultimate tensile with dry mixed rubber vulcanizates, and this is adequate for the majority of practical applications. CLASSIFICATION OF COMMERCIAL SYNTHETIC FLEXIBLE LATICES BY POLYMER~COMPOSITION
Manufacturers are understandably reluctant to disclose specific polymer compositions, emulsifier types and amounts, manufacturing techniques, and other confidential information about their commercial products. However, the need for some type of classification of the large number of comniercial latices now being sold is generally recognized and the author received splendid cooperation from the various suppliers in preparing and editing the list of products shown in Table 111. In such a rapidly growing field, it is obvious that there are already changes in the list from the June 1, 1951, assembly date, and that each manufacturer has new or improved experimental products in the field which he does not yet consider to be commercially established. I n some instances the manufacturer requested that the listing of his commercial products merely include typical grades of a given class rather than the complete group. No attempt is made here to describe the individual commercial products more fully, as the suppliers will furnish this information upon request. The general properties of each class are summ* rized to indicate the special characteristics of the polymer type which have resulted in its development as a commercial latex. Suggested fields of application are also indicated.
IN D U S T R I A L A N D E N G IN E E R IN G. C HE M I S T R Y
777
ELASTOMERS-Latex Table 111.
Classification of Commercial Synthetic Latices of U. S. Manufacture (Uncompounded plastic and elastic niaterials, June 1, 1951)
I.
Class and Group Acrylic rubbers
11. Butadiene rubbers Acrylic copolymers
Trade Name Hycar 4501 Polyco 319 Polyco 1010-32 Polyco 434 Polyco 435 Rhoplex F R N Rhoplex WC-9 Butaprene h-F Butaprene N L Butaprene N I Butaprene NXM Chemigum 235 Cheniigum 245 Chemigum 200 Herecrol NL-40 Hycar 1561 Hycar 1562 Hycar 1552 Hycar 1502-X-392 Nitrex 2612 Polyco 422 Polyco 423
Supplier Reference
High acrylic comonomer Medium acrylic comonomer Medium styrene 71/29 BD-styrene 501'50 BD-styrene 50/50 BD-styrene 70/30 BD-styrene, tough 55/45 BD-styrene 80/20 BD-styrene 50/50 BD-styrene 5 0 / 5 0 BD-stvrene soft 53/47 BD-stcrene' 71/29 BD-styrene 70/30 BD-styrene, cold Rx 71/20 Same, tough 71/29 Same touoh 70/30 Same: t o u i h Pnlvbutsdiene tough tough
Styrene copolymers
iMiscellaneous 111.
Chloroprene rubbers
IV.
Isobutylene rubbers
V.
Polysulfide rubbers
VI.
VII.
VIII. IX.
Acrylic plastics
Polyamides
Polyesters Polyfluorinated plastics
Styrene plastics Unplaaticized
% T.S. 48-52 40 40 40 40 40 40 28-32 43-47 38-42 43-47 30-45 30-45 53-57 27-31 38-41 38-42 50-54 31-35 38-40 3 8-40 3 8--40 54-58 26-28 37--39 39-42 >59 60-63 60-63 >50 37-39 45-49 26-28 60 >50 4 >4 >4 >4 >4 >4 18.5 >8.5 >8.5 >8.5
9.5-10.5 9.5-10.5 9.5-10.5 >8.5 >8.5
>8.5
>8.5
2-13 >9.5 6-10
5-10
9.5-12.0
8.5-12.0 8.6-12.0 8.5-12.0 8.5~12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-11.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 8.5-12.0 >10 2-10
__
,R
2-10 2-10 2-12 >9.5 >9. 5 >9.5
Av. Part. Size, Microns 0.18 0.18 0.18 0.18 0.18 Large 0.10 0.05 0.08 0.06 0.15 0.10-0.15 0.10-0.15 0.20-0.25
0.0g
0.10
0.10 0.22 0.20 0.20 0.15 0.10 0.15 0.06 0.15 0.05 0 05 0.20
0.20 0.20 0.20 0.22 0.22 0.22 0 22 0.22
Tougher than 571
49-51
>9. 5
0.18
Modified low compression set Crystallization resistant Creamed 842 Creamed 8428 Creamed 571 High wet extensibility Soft polynier
49-51 49-51 58-60 58-60 58-60 34-38 49-51
>9.5 >9.5
0.18 0.18 0.22 0.22 0.22 0.12 0.18
Loxite 8500 Loxite 8502 (94) (180, 181) (180, 181) (180, 181) (180, 181)
Aerotex 120 Aerotex 133 Polyco 177 Polyco 1677-7c Polyco 1677-35C Rhoplex WN-75 Rhoplex WN-80 PA resin suspensoid A-001X PA resin suspensoid A-003 PA resin suspensoid A-006 Aerotex 110 Aerotex 7513 Kel-F N-1
Dow latex 579 Dow latex 580 Koppers polystyrene emulsion F Kopuers polystyrene emulsion &I Latex B K S 90 Lustrex X600C Lustrex X601-40 Polyco 220 N S Polvco 220 R S Waiters 19-60
>9.5
>9.5
Butyl rubber disp. Polyisobutylene disp.
58
...
Polyethylene polysulf. High solvent resistance Same plus soft Medium solvent resistance Odor-free, very low freeze point
65
6-14 6-14 6-14 6-14 6-14
Copolymer Copolymer Copolymer Acrylio type resin Acrylic type plastic
50
50 60 50 50 25 25 40 40 40 55 40
7-8 6.5-8.6 3-11
3-1 1 3-1 1 3-1 1
0.20
0.18 0.18 0.18
... ...
1-4 20-60 20-60 40-80 80-1 50 16 70° C. Polyamine-pol) fatty acid
35-42
3-11 1-7
3842
1-7
1
Same as above
35-42
4-7
1
1
45 9-10 9-10 45 (nonaqueous)
10 10 0.1-3
>330° C. Same as above >225O C. Polytetrafluoroethylene, seal >350° C.
(nonaqueous) 45-48 3.5-10 5
0.1-3 0.2-3
Polystyrene, devolatilized Polystyrene Polystyrene, freeze-thaw stable
40 42 40-44
>9 >9 6.8-9.2
Polystyrene
40-44
6.S9.2
30-33 39-41
>6
Modified alkyd Modified alkyd Polytrifluorochloroethylene, seal
...
40 40 40
8--9
-
0.18
Neoprene Neoprene hieoprene Neoprene hleoprene Neoprene Neoprene
>9.5 >9.5
0
0.06
Neoprene 572
>9.5
-
0.06 0.18 0.18 0.18 0 29-0 30
BAG latex GEX-TAC Neoprene 571 842 842A 601 601A 60 735 700
Particle Charge
0.06
1/30 BD-styrene )O/O BD-styrene Medium styrene Contains pyridyl proupe Same as above Chloroprene polymer
Kel-F NW-25, Teflon dispersion X.
Polymer Description Polyacrylic ester Acrylic copolynier Acrylic copolymer Copolymer, perm. tacky Copolymer, perm. tacky Acrylic type polymer Acrylic type polymer Lorn acrylonitrile Medium acrylonitrile High acrylonitrile High acrylonitrile High acrylonitrile hIedium acrylonitrile Medium acrylonitrile Hieh acrvlonitrile
...
0.10 0.10 0.26-25
%io >8 ...
... (Continued on p a w 779)
778
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 4
ELASTOMERS-bateTable 111. Classification of C o m m e r c i a l S y n t h e t i c Latices of
U. S.M a n u f a c t u r e (Continued)
(Uncompounded plaetic and elastic materials, June 1, 1951) Class and Group Plasticized
Copolymers
XI.
Vinyl butyral plastics
XII.
Vinyl chloride plastics Unplasticized Preplasticized Copolymers
XIII.
XIV.
XV.
Vinyl ester plastics (polyvinyl acetate)
Vinylidene chloride plastics
Trade Name Latex BKS 92 Lustrex X-62Od
160,
Lustrex X-630 Walters 16-42 Butaprene SLF Darex BOOS Darex 3L Darex 9L Darex X34L Darex X44L Darex X70L Dow latex 512K Dow latex 513K Dow latex 546 Dow latex 529K Dow latex 737K Dow latex 762K Kralac 2714 Marmix 4950 Marmix 7345 Polyco 376 Polyco 380 Polyco 398-20 NS Polyco 398-20 RS Polyco 335-30 NS Polyco 335-30 R S Polyco 350 Polyco 350-35 NS Polyco 3509 Polyco 350N Pliolite 150 Pliolite 170 Pliolite 190 Merlon R R Merlon BRS Geon 151
160 High st rene resin ca. 60$styrene ca. 70 o styrene Like 3L, no antioxid. ca. 85% styrene Like X34L, no antiox. ca. 95% styrene Med. styrene Med. styrene, antiox. Med. styrene, unstripped High styrene High styrene antiox. Harder t h a n 512K High styrene High styrene High styrene High styrene Med. styrene kutadiene utadiene 0 butadiene 30% butadiene 35% butadiene 35% butadiene butadiene 0 butadiene Inter. between 170-190 High styrene, filming High styrene, reinforcing plasticizer 0 plasticizer 175' C. fusion
+ +
2?2$
::F
'$
Geon 576 Geon PX45 Dow latex 744B Geon 351 Geon 352 Geon 251 Polyco 446 Aerotex 160 Darex X52L Darex X53L Darex X56L Darex XT90
Polyco 1673-37B Vinylite vinyl acet a t e resin dispersion W-125 Geon 652 Geon 653 Polyco 453 Saran latex F122A15 Saran latex F122A20
% T.S.
Polymer Descriution
37-40 39-41 39-41 47 34 44-46 44-46 44-46 44-46 44-46 54-58 45 45 45 45
...
5i154 33 50 40 50 45 45 45 45 45 45 45 45 33-39 33-39 33-39 50 50 52-55
Stable p H Range 8-10 8-9
Av. Part. Size, Microns
...
.
.
0.05
... ... ... .... .. ... 0.20
>9 >9
0.20 0.20 0.20
>10
0.22
... ...
... ...
0.5-13 0.5-13 1-13 >7 1-13 >7 >7 rn 1-13 >7 1-13 9. 5-10.5 9. 5-10.5 9.5-10.5 >9 >9 8-11
... ...
... ... ... ...
...
...
0.08-0.10 0.os:o. 10 0.08-0.10 0.50 0.50 0.19
2-12 2-12 2-12 2-12 2-12 2-12 4-7 2-12 2-12 2-12 2-12 2-12 3.5-8.5 3.5-8.5 3.5-10 3.5-10 3.5-10 3.5-10 3.5-10 3.5-10
54-56 50
3.5-10 2-12
2.3
2-8 2-8 2-1 1 6.5-7.5
0.17 0.17
(67)
49-51 49-51 45 51.653
(67)
51.5-53
6.5-7.5
0.20
(88, 89,96) 25" C. fusion (88,90, 96) 105O C. fusion 25' C . fusion
-
>9 I
>8.5 >8.5 >8.5 >8.5 >8.5 >8.5 28.5 >9 >9
54-56 54-56 50 54-56 54-56 54-56 45 53 53-56 53-56 53-56 50-53 38-40 55-57 55-57 55-57 55 55 55 55 35 55 55 50 55 55 36 55 55 55 55 55 56 56-57 55 45 55
140' C. fusion 110' C. fusion 100" C. fusion 140' C. fusion 140' C. fusion 100' C. fusion 25' C. fusion Med. mol. weight Med. mol. weight High mol. weight Similar t o X53L unstripped Similar to X56L, stable to b,orax Low mol. weight Medium viscosity Medium viscosity Low viscosity Medium viscosity Medium viscosity Low viscosity Medium low viscosity Low viscosity High viscosity Med. viscosity Med. viscosity Tou h 91' C. softening Plia%le 104O C. softening Brittle 104' C. softening Pliable 85O C. softening Brittle, hard resin 7 2-i2 2-12 2-12
0.19 0.19 0.20 0.19 0.19 0.19 1-2 2-3 1 1 1 Colloidal 1-3 1-3 0 . 5 -1.5 1.75-2 0 . 5 -1 2-2.5 0.25 2-3.5 2-3.5 I
0.5-1 0.2 2-3 1.5-2
...
ilio
2-10 1-7 0.5-2 150 O C.) for brief periods, although continuous films can be formed at lower temperatures (125' C.). Even the preplasticized materials require heat to develop maximum tensile and low block properties, although they film at lower temperatures (50 O C. 1. Copolymers also require plasticizer addition and high temperatures (100" to 150" C.) to develop good films. The high tensile and abrasion resistance of vinyl chloride plastics is fundamentally dependent on the molecular orientation accompanying high temperature fusion and annealing. Polyvinyl chloride materials tend t o discolor in light unless special stabilizers are used; when properly stabilized, light stability is adequate for many applications as decorative coatings on paper and fabric. Such coatings also have functional utility, being resistant to grease, water, and chemicals, and flameretardant. Plasticized materials are only fair moisture vapor barriers, and this is an advantage for wallpaper coatings and textile fiber binding applications. The flame resistance of plasticized polyvinyl chloride is substantially better than that of hydrocarbon or ester-type polymers, and relatively flameresistant plasticizers such as phosphate esters can be used to improve it further. The water and heat resistance of the vinyl chloride plastics is sufficient to provide sterilizable finishes for medical fabrics. Abrasion resistance is one of the outstanding properties of plasticized polyvinyl chloride and vinyl chloride copolymers. This, combined with excellent gloss for an elastomeric material, has resulted in commercial applications in floor finishes and other abrasion protective coatings. XIII. Vinyl Ester Plastics. Polyvinyl acetate latex is one of the first commercial synthetic plastic materials marketed in the United States, It is available from a number of sources over a wide range of particle size and molecular weight. Some degree of hydrolysis to alcohol groups takes place during manu-
INDUSTRIAL AND ENGINEERING CHEMISTRY
781
-ELASTOMERS-Latefacture, and this, together with differences in degree of polymerization, affects the utility of the various products for specific applications. Without plasticizer, the materials of higher molecular weight form continuous films under heat and pressure, and, because of the chemical nature of the polymer, strong heatsealing adhesives for cellulose, protein, and some inorganic pigment products. With plasticizer, room temperature drying yields flexible continuous films, commercially applied as wet adhesives, paper coatings, and impregnants and textile finishes. The polymer is stable t o light. Polyvinyl acetate can be thermoset with reactive chemicals such as melamine and dimethyl01 urea. This increases the polymer's limited resistance to water and steam and also increases its stiffness. The dried or cured films of polyvinyl acetate are oil- and greaseresistant, and thus of use in foodpackaging materials as coatings and adhesives. A new interesting use is developing for these latices as a concrete compounding agent (76). Cuied concrete properties can be varied from a resilient insulating flooring mastic (high polyvinyl acetate content) to s highly shock-resistant structural concrete, including the new foamed light weight variety. XIV. Vinylidene Chloride Plastics. These latices form films a t room temperature but require heat treatment to develop maximum gloss, toughness, and flexibility. Properties of fused unplasticized films are generally similar to plasticized polyvinyl chloride films; resistance to some oils is better and light resistr ance to discoloration is inferior. Resistance to gas permeability and moisture vapor transmission is superior to polyvinyl chloride plastic latex films and is unusually low for films made from waterbased system. Therefore thrse latices are used in paper coatings for packaging materials. Flame resistance of vinylidene chloride copolymers is better than that of vinyl chloride plastics, and this property makes such latices of interest in flame-retardant saturants and finishes for textiles, paper products, and building finishes. XV. Rubber-Plastic Blends. The use of compatible rubbers as nonmigratory and vulcanizable plasticizers for thermoplastic resins has assumed commercial importance in recent years. Several commercial latices are now available which differ by technique of manufacture from those obtainable by physically blending separately available latices. Films prepared from these preblended latices are relatively easier to flux t o maximum tensile properties. The nitrile rubber-polyvinyl chloride latex blend combines the unique properties of high oil and grease resistance and adhesion to hydrophilic materials with the gloss and thermoplasticity of the plasticized vinyl. As such, these materials are of special use in paper, leather, and textile 6nishing and in pigment and fiber binding. The nitrile rubber-styrenc+acrylonitrile resin latex blends are elastic over a temperature range t h a t is somewhat higher than that of the nitrile rubber-plasticized polyvinyl resin plastics. Resistance to chemicals and oils also differs to some extent. The styrene rubber-styrene plastic blends compare in oil resistance and physical strength to the latex films discussed above The use of polymer blends t o develop compounds r i t h unique properties not obtainable from either component is a new and growing industrial technology that challenges the latex compounder. The commercial materials already available plus the large number of experimental materials being developed by the suppliers offer a broadly open field for development of specific properties t o meet the technical needs of new and improved elastic and plastic latex products. X V I . Miscellaneous. I n addition to the materials classified above, a large number of flexible polymer latices are designed for specific applications such as textile finishes, wood glues, and adhesives. Composition information is not available and many products involve compounded materials which are outside the scope of this discussion.
782
WATER-DISPERSIBLE MATERIALS
Shipment of latex involves several practical problems such as protection from freezing, coagulation during handling, and excess weight. For this reason two new cechniques have been devised t o handle flexible polymers which still avoid the disadvantages of dry mixing or forming of solvent-based s y s t e m : (1) paste resin technology for plasticized resins, and (2) waterdispersible powders. I n the first case there is little or no volatile product to be eliminated during fabrication, a n obvious advantage, and this technology is becoming increasingly important. With some materials i t competes directly with, and has already displaced, some latex applications (164). A discussion of the current state of this technology requires separate treatment. Materials of the second class deserve consideration in a discussion of commercial latex technology, because they directly compete with or are compatible with synthetic and natural latices and involve similar fabrication technology. There are two classes of synthetic materials-water-dispersible and watersoluble-with no precise dividing line, as many such materials develop true colloidal dispersions (10 t o 100 A. diameter). Materials of one chemical class have been arbitrarily excluded from this discussion, although they are of major commercial importance in water-based adhesives and coatings. These are t h r aldehyde condensation polymers with phenols, resorcinol, urea, melamine, and other reactive compounds. In general, these products develop rigid three-dimensional resin networks in their final cured state and thus are not properly part of a discussion of elastic polymer latices. However, it is possible, through use of compatible elastic polymers-e.g., nitrile rubbers with special phenolic resins and GR-6 or neoprene with special resorcinol resins-to increase the shock resistance and flexibility of the thermoset resin, and such techniques have become very important in latex technology as well as solventrbased systems. The use of smaller quantities of these thermosetting or air-curing resins mith elastic latices also offers a useful method of curing, stiffening, and decreasing the thermoplasticity of the flexible films. Latex and water solution blending is a very convenient method for mixing the two polymers intimately, as dry blending is difficult with the heat-sensitive resins. There are a large number of essentially linear synthetic high polymers which are soluble or dispersible in water. The list in Table IV includes the commercially important chemical classes. Some do not have direct use as flexible or elastic structural materials, but all are useful and important in flexible polymer latex technology. I n addition t o these synt,hetic materials, there are many naturally occurring proteins, starches, resins, and gums with which theee synthetic materials compete but which are not proper subjects for this discussion. I. Acrylic Polymers. The polyacrylic and polymethacrylic acid salts are usually furnished as water solutions of either fixed or volatile alkalies. They are used as film-forming thickener additives for other synthetic and natural latices, although they also have utility by themselves as special pigment binders. Being polyelectrolytes, solutions of these materials display a wide range of interesting colloidal and viscosity change in the presence of other electrolytes, over a range of pH, and in presence of polyvalmt cations (185). These properties, plus excellent light snd heat stability, make polyacrylate acid salts and copolymer modifications useful as thickeners and stabilizers for other latices, oilresistant seal coats for masonry, adhesives, and pigment binders. R a t e r sensitivity of the final film can be reduced by addition of pigments which liberate polyvalent cations or plasticizers containing acid reactive groups, followed by heat treatment. Chemical reactivity with many natural fiber products makes such materials of special value in fiber binders, textile finishes, and pigment dyeing. 11. Vinyl Ether Polymers. Polyvinyl methyl ether is aunique high polymer. It is soluble in cold water but precipitates above
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 4
,-,ELASTOMERS-LateTable IV.
Classification of Commercial Water-Soluble and Dispersible Flexible Sy’ntheticr Materials of U. S. Manufacture Regrence Su plier
1.
Clam and Group Acrylic polymers
11. Vinyl ether polymers 111.
IV.
V.
Vinyl alcohol polymers
Vinyl ohloride plastics Cellulose derivatives Methyl cellulose
Trade Name Acrylic polymer 101 Acrylic polymer 201 Acrylic polymer 301 Acrysol A-1 Acrysol GS-new Good-rite TS-20 Polyco 296 Polyco 296BT Polyco 296-N Polymethacrylio acid size PVM, unmodified
(161) (06 (01
(78,74)
EM”
Darex X-551 Elvanol72-51 Elvanol 50-42 Elvanol 32-70 Elvanol 20-105 Elvanol 71-24 ElvanoI 64-22 Elvanol 52-22 Elvanol 31-31 Elvanol70-06 Elvanol 51-05 Geon J26 Vinylite resin NV.4
Low viso. PVA, 1 aoetate Low visc. PYA, 1% acetate Polyvin 1 chloride Vinyl c&oride copolymer 27-31 % methoxyl(2 groups/anhydroglucose) ’ methoxyl(2 groups/anhydro27-31 % glucose) 27-31 % methoxyl(2 groupsjanhydroglucose) 27-31 % methoxyl(2 groups/anhydro. glucoae) 27-31 % methoxyl(2 graups/anhydroglucose) 27-31 % methoxyl (2 groups/snhydro-
Methocel 15 Methocel 25 Methocel 100 Methocel400 Methocel 1600 Methocel 4000
Hydroxethyl cellulose
Sodium carboxymethylcellulose
VI.
Misoellaneous
Methocel HG 15 Methocel HG 26 Methocel HG 400 Methocel HG 4000 Methocel CAM Methocel AS 1500 Cellosize WSLL Cellosize WSLM Cellosize WSLX Cellosize WSLH Carbose I Cellulose gum CMC-70L Cellulose gum C M C 4 0 M Cellulose um CMC-7OH Sod/um C%lC-lOW Sodium CMC-1OD Sodium CMC-11 Sodium CMC-12 Sodium CMC 2WXH Lustrex X-810 Lustrex X-820 PVM/MA
Commercial Form
water solution Powder, alkali-soluble Balsamlike, water-soluble 80 sirup in water 60g water solution 16-36% water solution Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Water-soluble powder Powder, water dispersible Powder, ball Ioil1 dispersible Powder, wter-sol. Powder, water-sol. Powder, water sol. lowder, water-sol. Powder, water-sol. Powder, water-sol. Powder. water-sol.
(140, 148) (141 (811
Polyco 328 Polyco 329 Polyco 330
35” C.; upon cooling, i t is again soluble. The addition of alcohols of lower molecular weight increases the solubility in aqueous solutions and raises the precipitation temperature. It is soluble in 1 N inorganic acids and in weak bases, and is compatible with a variety of rubbers and plastics. These properties make i t useful as a thickening heat-sensitizing agent for latex coagulation, a tackifying agent for adhesives, a binding agent for textiles and pigments, a sizing agent for paper afid leather, and a plasticizer for certain resins and plastics. Higher homologs of the polyvinyl ethers are water-insoluble tacky materials which are not yet commercially available in latex form. 111. Vinyl Alcohol Polymers. Polyvinyl alcohol is prepared by hydrolysis of polyvinyl acetate, and the large number of commercial grades results from variations of both molecular weight and degree af hydrolysis. Because of its high hydroxyl content, polyvinyl alcohol is sensitive to water and steam; this property reaches a maximum a t low molecular weight and a t about 88% hydrolysis of the acetate. High tensile strength and toughness are outstanding properties of dry polyvinyl alcohols, reaching a maximum a t the highest molecular weight and complete hy-
April 1952
Polymer Description Modified sodium polyacrylate Modified sodium polyasrylate Modified sodium polyaorylafe Polyacrylic acid Sodium polyaor late Polyacrylia s a d Sodium polyacrylate, high viscosity Sodium polyaorylate, medium vgoosity Sodium olyacrylate, low viscosity Polymet%acrylis asid Polyvinyl methyl ether Polyvinyl methyl ether Polyvinyl methyl ether
20 viscosity 100 viscosity 500 viscosity 1000 visoosity Low viscosity Low visoosity Med. visoosity High viscosity Low viscosity Low viseosity Low visoosity, contains buEers Low viscosity, contains buffera High viscosity, oontains buffers Copolymer resin Copolymer resin, contains maleio 1:1 molar maleic anhydride: vinyl methyl ether Sodium salt of high polymer acid Same exoept ammonium Same except anhydrous
107 water solution 10.90 water solution 8 7 wafer solution 8.90 water solution Dry powder, water-sol. Dry powder, water-sol. Dry powder, water-sol. Dry owder, water-sol. 4 7 . 6 8 damp crumb 62% powder of 1OW 36.5% h m p 58.0% d r y powder of 11 58% d r y powder Alkali soluble Alkali soluble Water- and alkali-soluble powder
&
2 6 9 water solution
2 5 d water so1,ution Powder, alkali-soluble
drolysis (22,000pounds per square inch dry, 12,000 pounds per square inch, a t 50% relative humidity). Adhesion to smooth nonabsorbent surfaces decreases with degree of hydrolysis, and films from the completely hydrolyzed grades are “dry” and have excellent grease and oil resistance and low gas permeability. Resistance to aromatic oils, chlorinated solvents, esters, ethers, and ketones is outstanding. Although films are hygroscopic, they remain dry and nontacky, even a t high humidity. Polyvinyl alcohol can be vulcanized to reduce its water sensitivity (dimethylolurea and other aldehydes, and chromic compounds). These properties make certain grades of polyvinyl alcohol useful as wet and rewettable adhesives and binders for paper and cloth and for ceramics, papier-mach6, sand cores, and pigments. Fugitive textile sizing based on polyvinyl alcohol i p abrasion resistant and oil resistant. Paper sizing based on Golyvinyl alcohol yields increased wet and dry strength, grease resistance, and transparency, and coated papers are of value in p?ckaging applications. By a technology similar to latex, plasticized polyvinyl alcohol is used to produce oil- and solvent-resistant dipped goods, tubing, and a m , Being incompatible with many elastomers and plastics, its use as dispersing agent, thickener,
INDUSTRIAL AND ENGINEERING CHEMISTRY
783
-ELASTOMERS-Latex and protective colloid in latex compounding requires technical examination for the specific application, but’ in many cases polyvinyl alcohol is a useful additive to such systems. IV. Vinyl Chloride Plastics. As in the case of vinyl chloride plastic latices, the water-dispersible vinyl chloride plastic powders in Table IV require plasticizer and heat treatment t o produce continuous films. Final product properties are similar to those of the latex products. The use of such materials is relatively new, and proper dispersion manufacture is important t o success of the process. Pebble mill grinding with plasticizer and other conipounding ingredients is a typical piocedure. Properly used, this “hydrosol” technique offers the compounder greater latitude for hiq formulations. V. Cellulose Derivatives. Alpha-cellulose is a linear polyglucoride with water sensitivity and flexibility, especially when n e t Because of its tendency to foim hydrogen-bonded crystallites, the introduction of small side groups in varying amounts (thiough partial esterification or etherification) changes its propel ties significantly. Cellulose nitrate and cellulose acetate are 17 ell-known thermoplastic materials with commercially valuable properties. More reccntly the alkyl ethers such as ethylcellulose have also assumed commercial importance, as they ale alkali resistant. These materials are usually handled as plasticized dry materials or i n solvent aolution. If finely ground, they can be dispersed in water to form stable hydrosols, but commercial dispersions of this type are not n o x marketed in uncompounded form. Ethylcellulose and Cellulose Esters. Water dispersions can be made in a manner similar to that desciibed for the vinyl chloride plastics. Cellulose nitiate and the higher homolog esteis such as cellulose propionate require the presence of some dispelsing aid, and it is usually bettei t o use solvent swollen or eniulsion techniques (109, 179). Because of the more hydrophilic properties of ethylcellulose and cellulose acetate, it is not necessary to have additional dispersiiig agent present, although the use of a thickener such as metliylcellulose reduces settling and iinpoves flow. Fusion temperatures of 140’ t o 180’ C. are nt’cetisary for homogeneous film formatioii, dependent on amount and type of plasticizer used. Ethylcellulose plastics are resistant t o hydrocarbon oils but less so t o animal and vegetable fats. Useful temperature range is broad and low temperature flexibility is good. Light stability and transmission are excellent. These properties make the hydlosols of value in flexible protective coatings for fabrics, paper, and leather. They are also of interest in heat-sealing adhesives and binders for pigments and fibers. Water absorption is more than for the cellulose esters (except acetate) and wax compounding is desirable where water resistance is important. Cellulose esters (acetate, nitrate, acetate-propionate, acetatebutylate) are not alkali-resistant, and the acetate is somewhat hygroscopic. They are more resistant t o animal and vegetable oils than the ethers and have higher softening points (200” t o 260” C. unplasticized) but lower flexibility. Light resistance t o discoloration is very good, with the exception of the nitrate. These properties make the hydrosols of interest in nonblocking protective and decorative coatings and in heat-sealing adhesives If tlie size of the “plasticizing” substituent is small, or if i t also has hydrophilic properties, very interesting water-soluble or colloidally dispersible flexible plastics result. Three types of coinniercial products are shown in Table IV, all representative of cellulose ethers. The degree of etherification ia one t o two groups per anhydroglucose unit, but variation of this ratio is one means for changing colloidal and film properties; another method is degradation of the cellulose to lower molecular weight. METHYLCELLULOSE. Like polyvinyl methyl ether, methylcellulose is soluble in cold but not in hot water. Solutions will gel in the temperature range of 40 to 75’ C., depending on viscosity type and concentration. The mildly plasticized (humidified) or dry films from metliylcelliilose are oil and grease resistant,
784
very tough but pliable (6000 t o 15,000 pounds per square inch a t 50 to 12% elongation), and can be insolubilized by further chemical reaction with the remaining hydroxyl groups. Unlike most of the other products discussed in this paper, methylcellulose is not thermoplastic. These properties make methylcellulose of interest in wet adhesives for paper, textiles, leather, pigments, and fibers; binders for sand and ceramics, nonthermoplastic mold release agents and oil-resistant protective coatings; and in tough unsupported sheet and film where water sensitivity and solubility are desirable features. HYDROXYETHYLCELLULOSE. Hydroxyethylcellulose differs from methylcellulose in water solution because its solubility increases with increasing temperature. The dry film is very resista n t to organic solvents and is hygroscopic but does not become tacky a t high humidity. This property is of value in preventing build-up of electrostatic charges. The film is soluble in water, but it can be insolubilized by compounding with hydroxylreactive materials (glyoxal, urea-formaldehyde, melamine-formaldehyde, or chromates). These properties make the material generally suitable for greaseproof paper sizing and coating, temporary textile sizing, and pigment printing, and as thickeners and binders for adhesives, emulsions, latices, water paints, cosmetics, and ceramic clay slips. SODIUM CARBOXYMETHYLCELLULOSE. Chemically this is an a-carboxy ether derivative of cellulose. As such, its application and film properties differ somewhat from those of the other watersoluble cellulose ethers It is stable in highly alkaline solution but can be insolubilized by strong acid. It has a substantial tolerance for polyvalent metal cations but can be insolubilized by large amounts of them. Films are oil- and grease-resistant, adhesive to hydrophilic materials, and moderately compatible with the oil-resistant rubbers and vinyl plastics. These properties lead to uses in latex formulation, adhesives, pigment and clay dispersions, and textile and paper sizing and finishing. VI. Miscellaneous. Among the miscellaneous water-solublp flexible high polymers, the use of maleic anhydride copolymers is increasing. A variety of properties can be obtained by varying the comonomer. An interesting feature of such materials is the tendency to obtain regularly alternating units of the two monomers along the polymer chain. These materials can be further modified by solution in alcohol instead of water or alkali, resulting in half esters with properties dependent on the nature of the alcohol used. Further modifications result from reactions with secondary amines or ammonia (amphoteric cationic-anionic derivatives). The chemical versatility of these new materials offers a wide field of utility in the field of latex and water-based plastic technology Both improvements in established uses and entirely new products can come with full exploitation of this new class of high polymers. BIBLIOGRAPHY
(1) Abernathy, H. H., Rubbe? A g e , 52, No. 2, 125 (1942). (2)
(3) (4)
(5) (6)
(7) (8) (9) (10)
Amalgamated Chemical Corp., 3400 Rover St., Philadelphia, Pa., private communication, April 25, 1951 American Cyanamid Co., Textile Resin Dept., Bound Brook, N. J., “Acrylic Polymers,” March 3, 1950. American Cyanamid Co., Textile Resin Dept., Bound Brook, N. J., private communication, April 13, 1951. American Polymer Corp., Chem. W e e k , 68,KO.17, 1 (May 12, 1951) American Polymer Corp., 101 Foster St., Peabody, Mass., Tech. Bull. P-16. American Polymer Corp., Tech. Data Sheet P-4 (Sept. 30, 1949). I b i d . , P-6 (Nov. 15, 1949). I b i d . , P-8 (Nov. 15, 1949). I b i d . , P-11 (Jan. 5 , 1949).
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 4
ELASTOMERS-Latex(11) (12) (13) (14) (15) (16) (17)
Ibid., P-12. Ibid., P-13. Ibid., P-19 (Feb. 1, 1950). Ibid., P-20. Ibid., P-21. Ibid., P-23. Ibid., P-24. Ibid.. P-25 (Feb. 1. 1951). Antonoff, G., “Colloid Chemistry,” ed. by J. Alexander, Vole VII, New York, Reinhold Publishing Corp., 1950. Bakelite Co., Thermoplastics Dept., Union Carbide and Carbon Corp., Tech. B u l l . W-125. Bakelite Co., Union Carbide and Carbon Corp., Thermoplastics Dept., Tech. Release and Supplement, 10 (April 1949). Bakelite Co., Union Carbide and Carbon Corp., Thermosetting Dept., 30 East 42nd St., New York 17, N. Y., Tech. Bull. 146 (April 1950). Ibid., 147 (April 1950). Ibid., 148 (April 1950). Barron, H., Brit. Plastics, 11, 464-7 (1940). Barrows, R. S., and Scott, G. W., paper presented a t meeting of Division of Rubber Chemistry, AM. CHEM.SOC., May 26, 1947. Bayer & Co., Ger. Patent 254,672 (Jan, 26, 1912). Bennett, H., “Emulsion Technology,” Brooklyn, N. Y . ,Chemical Publishing Co., 1946. Borders, A. M., and Pierson, R. M., IND.ENG. CHEM.,40, 1473-7 (1948). (30) Brenneck, R. A., Oficial Digest Federation P a i n t & V a r n i s h Production Clubs, No. 317, 352-70 (1951). (31) Burr, W. W., and Matvey, P. R., Oficial Digest Federation P a i n t & V a r n i s h Production Clubs, No. 304, 347-58 (May 1950) (32) Carbide & Carbon Chemicals Corp., Union Carbide and Carbon Corp., 30 East 42nd St., New York, 17, N. Y., Tech. Information F-5339 (October 1945). (33) Chem. Inds., 67, 713-14 (1950). (34) Chittenden, F. D., McCleary, C. D., and Smith, H. S., IND. ENG.CHEM.,40, 337-9 (1948). (35) Clayton, R. E., Rubber A g e , 59, 334 (1946). (36) Conant, F. S., and Wohler, L. A., I n d i a R u b b w W o r l d , 1211 179-84 (1949). (37) Corrin, M. L., J . Colloid Sci., 3, 333 (1948). (38) Corrin, M. L., J . P h y s . and Colloid Chem., 54, 265 (1950). (39) Corrin, M. L., and Harkins, W. D., J . Am. C h m . Soc., 69, 679-83 (1947). (40) Corrin, M. L., Klevens, H. B., and Harkins, W. D., J . Chem. Phys., 14, 216-17, 640-1 (1946). (41) Ibid., pp. 480-6. (42) Dales, B., I n d i a Rubber World, 102, No. 1, 43-5 (1940). (43) Davis, C. C., and Blake, J. T., “Chemistry and Technology of Rubber,” p. 619, New York, Reinhold Publishing Corp., 1937. (44) Debye, P., J . Applied Phys., 15, 233 (1944); J. Phys. and Colloid Chem., 53, 1 (1949). (45) Dewey & Almy Chemical Co., Organic Chemicals Division, Cambridge 40, Mass., Latex D a t a Sheet L-2 (January 1948). (46) Dewey & Almy Chemical Co., Organic Chemicals Division, Cambridge 40, Mass., private communication, April 16, 1951. (47) Dewey & Almy Chemical Co., Organic Chemicals Division, Tech. Data Sheet E-1 (Jan. 1, 1949). (48) Ibid., Y-2 (Feb. 1, 1950). (49) Dow Chemical Co., Midland, Mich., Tech. BUZZ., C.S. 1-5c 1143. (50) Ibid., ME-1-2M-443. (51) Ibid., ML-1-U-1249. (52) Dow Chemical Co., Plastics Division, Midland, Mich., private communication, April 11, 1951. (53) Dow Chemical Co., Plastics Division, Midland, Mich., Tech. Bull., 498-V-550 (1950). (54) Ibid., 580. (55) Ibid., CTS-1-1M-450. (56) Ibid., CTS-6-15C-650. (57) Ibid., CTS-18-15C-1150. (58) Ibid., CTS-64-2M-950. (59) Ibid., PL-147-S-449 (1949). (60) Du Pont de Nemours & Co., E. I., Electrochemical Dept., Wilmington 98, Del., Tech. Bull. A-2446 (1946). (61) Ibid., A-5408-10 M (December 1947). (62) Du Pont de Nemours & Co., E. I., Electrochemical Dept., V i n y l Products B u l l . V3-249 (1949). ,
April 1952
I
(63) Ibid., A430 (1950). (64) Du Pont de Nemours & Co., E. I., Organic Chemicals Dept., Rubber Chemicals Division, Rept. BL 184 (Dee. 9, 1944). (65) Ibid., BL 201 (Aug. 11, 1945). (66) Ibid., BL 217 (Aug. 16, 1946). (67) Ibid., 42-2 (1942). (68) Ibid., 47-4 (May 1947). (69) Ibid., 48-1 (June 1948). (70) Ibid., 48-3 (September 1948). (71) Ibid., 50-3 (August 1950). (72) Ibid., 51-1 (January 1951). (73) Du Pont de Nemours & Co., E. I., Polychemicals Dept., Memo, Aug. 4, 1949. (74) Ibid., Bull. 2 (April 6, 1950). (75) Farmer, N. W., Plastics ( L o n d o n ) , 15, 89 (1950). (76) Fettes, E. M., and Jorczak, J. S.,IND.ENG.CHEM.,42,2217-23 (1950). (77) Firestone Industrial Products Co., Akron, Ohio, Bull. M 607644 (1946). (78) Fox, K. M., I n d i a Rubber W o r l d , 117, 487-91 (January 1948). (79) Fryling, C. F., and Harrington, E. W., IND.ENG.CHEM.,36, 114 (1944). (80) General Aniline & Film Corp., Central Sales Development Dept., Easton, Pa., Data Bull. 110-R (July 10, 1948). (81) General Aniline & Film Corp., Product Development Dept.. N e w Product Bull. P-103 (Jan. 3, 1951). (82) General Mills, Inc., Chemical Dept., Modern Packaging, 24, No. 7,111 (March 1951). (83) General Mills, Inc., Chemical Dept., Minneapolis 13, Mlnn., N e w Product Data Sheet Revision E>(Feb.15, 1951). (84) General Mills, Inc., Chemical Dept., Polyamide R e s i n Tech. B u l l . (April 1951). (85) General Tire & Rubber Co., Akron, Ohio, technical information, Feb. 7, 1951. (86) Goodrich Chemical Co., B. F., Cleveland 15, Ohio, Service Bull. H-5 (December 1949). (87) Ibid., H-6 (August 1950). (88) Ibid., L-1 (April 1950). (89) Ibid., L-la (April 1950). (90) Ibid., L-lb (April 1950). . (91) Ibid., L-2 (April 1950). (92) Ibid., L-3. (93) G,oodrich Chemical Co., B. F., Tech. Bull. Geon 126. (94) Ibid., P.E.P.S. (95) Ibid., TS-20. (96) Goodrich Chemical Co., B. F., Tech. Chart, Latices, April 1950. (97) Goodyear Tire & Rubber Co., Chemical Division, Akron 16, Ohio, Bull. A-9414-K (September 1948). (98) Ibid., 1501. (99) Ibid., 1701. (100) Goodyear Tire & Rubber Co., Chemical Division, Tech. Bull. Supplement to Bull. 1901. (101) Goodyear Tire & Rubber Co., Chemical Division, TechnG Guide 1901. (102) Ibid., C-101. (103) Ibid., (2-200 X-47-1. (104) Ibid., C-235 E-50-1. (105) Ibid., C-245 E-50-1. (106) Hahn, F. J., Oficial Digest Federation P a i n t &? V a r n i s h Production Clubs, No. 317, 332-9 (1951); P a i n t , Oil Chem. Reu., 114, 14-28 (1951). (107) Harkins, W. D., J . Polymer Sci., 5, 217 (1950). (108) Hartley, G. S., Paris, Hermann et Cie., 1936. (109) Hercules Powder Co., Cellulose Products Dept., Wilmington, Del., private communication, April 26, 1951. (110) Hercules Powder Co., Cellulose Products Dept., Tech. Bull., 500-87A 5M 9-49 57304. (111) Heresite Chemical Co., Manitowoc, Wis., private communication, April 30, 1951. (112) Howland, L. H., Peaker, C. R., and Holmberg, A. W., India. Rubber W o r l d , 109, 579-81, 584 (1944). (113) I n d i a Rubber W o r t d , 113, 237 (1945). (114) Irvin, H. H., Ibid., 114, 660-2 (1946). (115) Jordan, H., Brass, P., and Roe, C., IND.ENG.CHEM.,ANAL.ED., 9, 182 (1937): 11, 377 (1939). (116) Kellogg, W. M., Chemical Mfg. Division, 4 Barclay St., New York. N. Y.. Tech. Bull. 3-50. (117) Klevens, H. B., J . Colloid Sci., 2, 365 (1947). (118) Koppers Co., Inc., Chemical Division, Pittsburgh 19, Pa., private communication, May 7, 1951.
I N D U S T R I A L A N D EN G I N E E R I N G CHEMISTRY
785
-ELASTOMERS-Latex Ludwig, L. E., Oficial Digest Federation P a i n t & V a r n i s h Production Clubs, No. 276, 114 (1948). McBain, J. W., “Colloid Chemistry,” ed. by J. Alexander, Vol. V, New York, Reinhold Publishing Carp., 1944. McBain, J. W., and Searles, J., J.P h y s . Chem., 40,493-9 (1936). Marbon Carp., 1926 West Tenth Ave., Gary, Ind., Tech. Rept. MX-1. Ibid., MX-3 (Nov. 14, 1950). Maron, S. H., Elder, M. E., and Vlevitch, I. N., Division of Rubber Chemistry, 112th Meeting AM. CHEW SOC., New York, 1947. Maron, S. H., and Madow, B., A n a l . Chem., 20, 545 (1948). Maron, S. H., Madow, B., and Triaastic, J. C., IND.ENG. CHEM.,40, 2220-2 (1948) : Ibid., submitted for publication. Maron, S. H., Moore, C., Kingston, J. G., Vlevitch, I. N., Trinastic, J. C., and Borneman, E. H., Zbid., 41, 156 (1949). Maron, S. H., et al., J . Colloid Sci., in press. Mast, W. C., and Fisher, C. H., IND. ENG.CHEM.,40, 107-12 (1948). Ibid., 41, 790-6 (1949). Mast, W. C., Smith, L. T., and Fisher, C. H., Zbid., 37, 365-9 (1945). Mattiello, 3. J., “Protective and Decorative Coatings,” Vol. IV, pp. 345-6, New York, John Wiley & Sons, 1944. Mighton, C. J., I n d i a Rubber W o r l d , 115, No. 5, 659-60 (1947). Monsanto Chemical Co., Merrimac Division, Boston 49, Mass., Tech. Bull. T-15 (March 1, 1948). Ibid., T-16 (March 1, 1948). Ibid., T-17 (April 15, 1948). Monsanto Chemical. Go., Plastics Division, Springfield 2, Mass., Development B u l l . B165-5C-12-47. Ibid., B175-5C-4-48. Monsanto Chemical Co., Plastics Division, Springfield 2, Mass., private communication, May 16, 1951. Monsanto Chemical Co., Plastics Division, Product Development Dept., bulletins, May 9, 1949. Monsanto Chemical Co., Plastics Division, Tech. Data Sheet, May 25, 1949. Monsanto Chemical Co., Plastics Division, Tentative Data Sheet, May 1, 1948 Mooney, M., and Ewart, R., Physics, 5, 350 (1934). Muhlstein & Co., Inc., H., GO East 42nd St., New York 17, N. Y . ,private communication, May 15, 1951. Nassaro, R. T., Z?zdia Rubber W o r l d , 106, 345-6 (1942). National Casein Go., 601 West 80th St., Chicago 20, Ill., private communication, April 30, 1951. Naugatuck Chemical, Division of U. S.Rubber Co., Naugatuck, Conn., BtdZ. 100. Naugatuck Chemical, Division of U. S. Rubber Co., Naugatuck, Conn., private communication, April 18, 1951. Naugatuck Chemical, Division of U. 8. Rubber Co., Tech. Bull., Sept. 20, 1950. Ibid. (June 13, 1949). Zbid. (April 25, 1950). Nopco Chemical Co., Harrison, N. J., private communication, ApriI 11, 1951. O’Conner, H. F., and Sweitzer, C. W., Rubber A g e , 54, 423-7 (1944). Partridge, E. G., and Jordan, G. O., Ibid.. 67, No. 5, 553-60 (1950). Reconstruction Finance Carp., Office of Rubber Reserve, Washington 25, D. C., “Classified List, Current GR-S Polymers and Latices,” April 16, 1951. Reconstruction Finance Carp., Office of Rubber Reserve, Washington 25, D C.. “ G R S Type 111 and IV Latices,” March 1948.
Reconstruction Finance Carp., Office of Rubber Reserve, Washington 25, D. C., “GR-S Type V Latex,” June 1947. Regnault, R., Ann. chim., (2) 69, 157 (1838). Rehberg, C. E., and Fisher, C. H., Division of Paint, Varnish and Plastics Chemistry, 109th Meeting AM. CHEM.SOC., Atlantic City, N. J. Rohm and Haas Co., Resinous Products Division, Philadelphia 5, Pa., private communication, Feb. 1, 1951. Rohm & Haas Co., Resinous Products Division, Tech. Bull. MR-1-50. Ibid., MR-5-49. Ibid., MR-6-49 (rev. June 1951). Ibid., MR-7-49. Ibid., MR-8-49 (rev. July 1950). Ryden, L. L., Britt, N. G., and Visger, R. D., Oficial Digest Federation P a i n t & V a r n i s h Production Clubs, No. 303, 292301 (1950). Semegen, C. T (to B. F. Goodrich Chemical Co.), U. 9. Patent 2,411,899 (Dec. 3, 1946). Semon, TV. L., Chem. Eng. N e w s , 24, 2900 (1946) Shawinigan Products Corp., 350 Fifth Ave., New York 1, N. Y., Tech. B u l l . 1948. Sheppard, S. E., and Geddes, A. L , J C h ~ mPhys., 13, 63 (1945). Sievier, R. W., Brit. Patent 7015 (1836). Simon, E., Ann., 31, 265 (1839). Smith, H. S., Werner, H. G., Madigan, J. C., and Howland, L. H., IND.ENG.CHEM.,41, 1584-7 (1949). Smith, H. S., Werner, H. G., Westerhoff, C. B., and Howland, L. H., I n d i a Rubber W o r l d , 121, 689 (1950); Rubber A g e , 66, 671 (1950). Smith, H. S.,et al., IND.ENG.CHEW,43, 212 (1951). Starkweather, H. W., Carter, A. S., Hill, F. B., Sanders, P. A., Walker, H. W., Youker, M. A,, and Hurka, V. R., Ibid., 39, 210 (1947). Sutheim, G. M., “Introduction to Emulsions,” p. 55, Brooklyn, N. Y., Chemical Publishing Co.. 1946. Tartar, H. V., Sivertz, V.,and Reitmeier, R. E., J . Am. Chem. Soc., 62, 2375-80 (1940). Tennessee Eastman Carp., Division of Eastmali Kodak Co.. Kingsport, Tenn., Tech. B u l l . 50-848. Thiokol Corp., Trenton, N. J., Tech. Bull. (Nov. 1, 1948). I b i d . (Nov. 15, 1948). Van Antwerpen, F. J., IND. ENQ.CHEM.,35, 126 (1943). Wall, F. T., and deBults, E. H., Jr., J.Chem. Phys., 17, 1330-4 (1949). Walsh, R. H., Rubber A g e , 61, 187-93 (May 1947). Walters Chemical Corp., Avon-by-the-Sea, N. J., private communication, April 23, 1951. Wendt, M. E., and Aiken, W. H., T a p p i 34,49-56 (February 1951). Williams, R. C., and Wycoff, R. W. G., J Applied Phys., 15. 712 (1944). Willson, E. A., Miller, J. R., and Rowe, E. H., J . P h y s . and Colloid Sci., 53, 357-74 (1949). Wintersteiner, Oskar, and Ruigh, W. L. ( t o E. R. Squibb Q. Sons), U. 9. Patent 2,411,177 (Nov. 19, 1946). Wyandotte Chemical Carp., Wyandotto, Mich., Tech. BuU. (March 22, 1950). I b i d . (April 24, 1950). I b i d . (May 4, 1950). Xylos Rubber Go., Akron 1, Ohio, private communication, May 28, 1951. Yost, D. M.,and Aiken, W. H., T a p p i , 34,40-8 (January 1951). RECEIVEDfor review September 17, 1951.
ACCEPTED January 19. 1952.
,
786
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 44, No. 4
