INDUSTRIAL AND ENGINEERING CHEMISTRY
324
(8) Burr, W.W., and Matvey, P. R., Ibid., 304,347-58 (1950). (9) Endres, H. A., Am. P a i n f J., 32,86, 88-92 (1947). (10) Fordyce, R. G., I n d i a Rubber W o r l d , 118,377-8 (1948). (11) FOX,K. M., Ibid., 117,487-91 (1948). (12) Gates, G. H. (to Wingfoot Carp.), Can. Patent 459,736 (Sept. 13, 1949). (13) Holt, C. R., Susie, A. G., and Jones, M.E., I n d i a Rubber World, 121, 416-18, 423 (1950). (14) Hoover, J. R., quoted in I n d i a Rubber J . , 116,595 (1949). (1.5) Irvin, H. H., I n d i a Rubbe7 W o r l d , 114, 680-2 (1946). (16) Jones, M. E., and Pratt, D. M., Ibid., 117, 609-10 (1948). (17) Koningsberger, C., and Salomon, G., J . Polymer Sci., 1, 353-79 (1946). (18) Konrad, E., and Ludwig, R., U. S. Patent 2,335,124 (Nov. 23, 1943). (19) Lindbeck, W.A., and TVoltz, F. E., private communication to Office of Rubber Reserve. Oct. 24. 1946. (20) Ludwig, L. E., Oficial Digest Federation P a i n t & V a r n i s h Production Clubs, 276, 122-4 (1948). (21) McIntyre, 0. R., Taber, D. A., and Young, A. E., Program, Chemical Institute of Canada, p. 29, Toronto, June 19-22, 1950. (22) RlacLean, D. B., Morton, M., and Nichols, R. V. V., IXD. ENG. CHEW.,41, 1622-6 (1949). (23) Illeehan, E. J., J . Polymer Sei., 1, 318-28 (1946). (24) Mitchell, J. M., and Williams, H. L., Can. J . Research, 27F,3546 (1949). (25) Ryden, L. L. (to Dow Chemical Co.), U. S. Patent 2,498,712 (Feb. 28, 1960). (26) Ryden, L. L., Britt, h-,G., and Visger. R. D., OJSiciaZ Digest Federation P a i n t & T'arnish Prodtaction Clubs, 303, 292-30 1 (1950).
Vol. 43, No. 2
( 2 7 ) Sell, H. S.,and McCutcheon, R. J., I n d i a Rubber World, 119,66-
68, 116 (1948). (28) Ibid., 121,687 (1950) (abstract). (29) Smith, W. C. (to Standard Oil Development Co.), U. S. Patent 2,396,293 (March 12, 1946). (30) Sparks, W.J., Gleason, A . H., and Frolich, P. K. (to Standard Oil Development Co.), U. S. Patent 2,477,316 (July 26, 1949); Brit. Patent 577,860 (June 4, 1946). (31) Standard Telephones and Cables, Ltd., Ibid., 345,939 (June 6, 1930); 357,624 (June 20, 1930). (32) Storey, E. G., and Williams, H. L., Program, Chemical Institute of Canada, p. 35, Toronto, June 19-22, 1950. (33) Susie, A. G., and Wald, W. J.. Rubber Age (S.Y . ) , 65, 537-40 (1949). (34) TeGrotenhuis, T. A , , U. S.Patent 2,457,097 (Dec. 21, 1948). (35) Thies, H. R., and Aiken, W.H., Rubber B g e (.V. Y . ) ,61,51-8 (1948). (36) Tschunkur, E., and Bock, W.,Ger. Patent 588,785 (Nov. 27, 1933). (37) Weatherford, J. A, and Knapp, F. J., India Rubber World, 117, 743-4, 748 (1948). (38) Wingfoot Corp., Brit. Patent 606,980 (Aug. 24, 1948). (39) Winkelmann, H. A., I n d i a Rubber W o r l d , 113,799-804 (1946). (40) Workman, R. E., Oficial Digest Federation Paint & V a r n i s h Production Clubs, 291, 177-87 (1949). REcElVED October 6, 1950. The greater portion of this payer was first presented a t the Rubber Chemistry Division lIeeting, Chemical Institute of Canada. Toronto, Ontario, J u n e 21, 1950. Contribution 183 from Goodyear Tire B- Rubber Co.
Polysulfide Liquid Polymers e
J. S. Jorezak and E. M. Fettes Thiokol Corp., Trenton, N . J. T h e development of the polysulfide liquid rubbers was begun with the aim of obtaining a compatible vulcanizable plasticizer for the polysulfide rubbers. I t developed that the liquid polymer produced was unique in being a solventfree flowable liquid which could be vulcanized even at room temperature to a rubber. The cured rubbers have the physical properties characteristic of the polysulfide polymers, but are useful in a wide variety of applications, owing to the ease of handling a liquid material. The liquid polymers can be used with soluble curing
agents for the impregnation of leather, fabrics, and wood. The polymers can be compounded on a paint mill, in a ball mill, or in an internal mixer with fillers and reinforcing pigments. In the compounded form, they can be used as adhesives, casting compounds, coatings, and sealers. The cured liquid polymers are substantially odorless and have a service temperature from -70' to 300' F. The polymers are resistant to oils, aliphatic and aromatic fuels, and most solvents. They have good electrical properties and excellent ozone and oxidation resistance.
T
temperature properties are inherent in the polymer and are not dependent on special compounding techniques.
HE polysulfide liquid polymers are a comparatively recent
development conceived a t the Thiokol Laboratories in 1943. The development was initiated by the problem of finding methods to reduce the molecular weight of a polysulfide rubber which was too tough to process upon conventional rubber milling equipment. T h e problem was solved by reduction of a few of the disulfide links present in the polymer chain. I t was soon found that the method was applicable to the preparation of polymers low enough in molecular weight to be liquids. The method produces dimercaptans (dithiols) of high purity which are extremely active in a wide variety of chemical reactions. Some formulations have been developed which depend on conversion from the liquid to rubber state at temperatures as low as 50' F. in a period of about 30 minutes. Most of the converting agents function through oxidation with hydrogen removal from the thiol and a linkage of sulfurs to reform the disulfide group. The converted polymer has the general properties of the polysulfide polymers: good solvent resistance to a wide range of solvents, low diffusion rate of gases, good resistance to oxidation, ozone, and weathering, and a service temperature range from -65" to +250° F. (Some compounds can withstand intermittent temperatures as high as +350' F.) The low
Preparation The preparation of polysulfide polymers by the reaction of organic dihalides and sodium polysulfide
ClCH*CH?CI
+ K a 8 , --+(CH,CH&). + 2NaCl
(5 varies
from 1.0 to 5.0)
has been known for some time ( 5 , 7 ) . If an excess of sodium polysulfide is used, rubbers of high molecular weight can be readily produced. It is popsible to prepare liquids of low molecular weight in many cases by using a deficiency of sodium polysulfide. The products have chlorine terminals which are not easily coupled to form products of high molecular weight. Thermal depolymerization has also been used to make liquid polymers (Q),but this reaction is not readily reversed t o reform the rubber. The most practical method found has been reductive cleavage of disulfide groups to yield products which have thiol terminals.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
(-CH2CH20CH20CH2CH2SSCH&H20CHZOCH2CH2SS-)n 2H
+-CH2CHpOCH20CH2CH2SH +'
+ Table 11.
HSCH~CHIOCH~OCHZCH~SSThe amount of depolymerization can be readily controlled and the liquid polymeric product can be reconverted to rubbers of high molecular weight by a wide variety of methods. As the disulfide group is usually present in polysulfide polymers, this type of depolymerization has a wide applicability. Treatment of a water dispersion of a polysulfide polymer with sodium hydrosulfide and sodium sulfite (8) is one method for controlled cleavage of high polymers. Depending upon the mole ratio of sodium hydrosulfide to polymer repeating segments, liquid polymers of varying molecular weights can be readily prepared. The sodium hydrosulfide splits a disulfide link to form a thiol and a sodium salt of a thiol. The extra sulfur atom is taken up by the sodium sulfite. -R-S-S-R-
+ NaSH + Na2S03--+ -RSNa
+ HSR- + NapSiO,
The addition of acid to coagulate the liquid polymer water dispersion converts the sodium salt back to the free thiol. While the commercial liquid polymers contain terminal thiol groups produced by the methods described, liquid polymers have been prepared experimentally with terminal alkyl, aryl, hydroxyl, allyl, and carboxyl groups. These materials can be produced by using a mixture of dihalide with the appropriate monohalide in the initial reaction with sodium polysulfide. T h e molecular weight of the product is easily controlled by the mole ratio of monohalide to dihalide. The structure of the repeating chain segment can also be varied to produce liquid polymers of different chemical structures. While dichloroethyl formal is used in the commercial polymers, it is possible to use all the other dihalides adaptable to the reaction with sodium polysulfide. Ethylene dichloride, propylene dichloride, dichloroethyl ether, and triglycol dichloride ( ClCH2CH2OCH&H20CH2CH&l) can all be used alone or in mixtures to form copolymers. By using dihalides containing other functional groups, which must be unreactive with sodium polysulfide, polymers can be prepared containing that group distributed along the polymer chain. Thus use of glycerol dichlorohydrin, a,@-dichloropropionic acid, or dichloroethyl amine places hydroxyl, carboxyl, or secondary amino groups in the liquid polymer molecule.
Properties The liquid polymers produced commercially are described in Table I.
Table I.
Commercial Liquid Polymers
hlolecular weight (average) Viscosity, poise gpHecific gravity (20/20)
LP-2 4000 460 6 to 8 1.27
LP-3 1000
10 5 to 6
1.27
325
LP-8 300 0 5 5 to 6 1.23
These polymers are composed of 98% (mole) dichloroethyl formal and 2% (mole) trichloropropane. The vulcanized product thus consists of long linear chains held together by the small amount of trifunctionality placed in the polymer by the trichloropropane. The polymers in the low molecular weight form are soluble in a wide variety of solvents. The lower the molecular weight, the higher the amount of solvent miscible with the polymer. Table I1 shows the amount of solvent which can be added to the liquid polymers, expressed as per cent by weight of solvent at the composition a t which two phases begin to form. There are no known solvents for the converted polymers of
Solubility of Solvents in Thiolrol Liquid Polymersa
Acids organic LP-2 F o k c acid 20 Acetic acid, glacial 0 Alcohols 0 Methanol 0 Ethanol 0 1-Butanol 0 Ethylene glycol 90 Furfuryl alcohol 0 Glycerol Aldehydes hl Benzaldehyde M Furfural Ethers Diethyl ether 0 >I Dioxane Ketones 50 Acetone 70 Methyl ethyl ketone 30 Methyl isobutyl ketone M Cyclohexanone Esters Methyl acetate 60 Ethyl acetate 50 Butyl acetate 50 Dibutyl phthalate M Tricresyl phosphate M hromatic hydrocarbons Benzene M M Toluene Xylene 50 Chlorinated hydrocarbons Carbon tetrachloride 70 M Ethylene dichloride go Ethylene ohlotohydrin M Chlorobenzene Nitro paraffins BO Nitromethane 90 Nitroethane 90 1-Nitropropane 80 2-Nitropropane a yo b y weight of solvent in liquid polymer. M signifies miscible in all proportions.
LP-3 20 0
LP-8 hl b 0
0
25 20
0
31 0
M
M
31 31
40
M
11 ,\I
80
31
0 0 0 M
M
80
25 0
BI Bl
I11
Ll
M M M BI M
Ll 31
M
31 31
M M M M
M M M
M M M
iu hl
M
I\I
M M
M
M
31
31 M
iv
high molecular weight. They will swell in solvents but cannot be put into solution without molecular weight reduction. Solutions can be made by addition of small amounts of agents such as thiols, which reduce disulfide groups, or strong acids which can sever formal linkages. I n a neutral pH, organic thiols are very resistant to conversion to disulfides by atmospheric oxygen. These polymeric thiols are therefore stable at room temperatures. High temperatures or an alkaline environment will cause a change in viscosity with time. For a specific polymer structure the viscosity of the liquid polymers depends entirely upon the molecular weight produced in the controlled splitting. The viscosity varies with temperature, as shown in Figure 1. The molecular weights of the polymers have been determined by cryoscopic methods, by titration for terminal thiol groups (1, S), and by measurement of the water produced on oxidation with excess lead peroxide, A suitable solvent has not as yet been found for conducting amperometric titrations (4). The odor of the liquid polymers produced from dichloroethj-1 formal is caused by the presence of low molecular weight dithiols ( 2 ) . Because of the distribution of molecular weight species present, even the liquid polymer of highest molecular weight has some dithiols present with high enough vapor pressure to cause odors. Conversion by oxidation to the high polymer eliminates volatile dithiols and also the odor.
Vulcanization The most useful reaction for conversion of the liquid polymers to the high polymer state is that of direct oxidation. This reaction results in a linking of the two thiols to form the polymeric disulfide with liberation of water as a by-product. The important problems are distribution of the oxidizer in the mix and adjustment of curing aids or inhibitors to control the rate of re-
INDUSTRIAL AND ENGINEERING CHEMISTRY
326
Vol. 43, No. 2
more active than the cobalt salts have been used euperimentally. Conversion is too fast and no practical formulations are known. Compositions which contain cobalt drier have limited package stability. Skinning occurs in about a week and progresses with aging. Recently, some very practical formulations have been developed to use oxygen from the air as the converting agent. Conversion on air drying a t ambient temperatures is rapid and life of the mix is 24 to 48 hours. The formulations and properties are discussed in the section covering typical application formulations. There are several other reactions which do not depend on oxidation. Furfural will react to form a thioacetal linkage. An acid environment is required for this reaction.
CHO HS-R-SH
L
I
I
EO
100
I
I
I
I
120
140
160
I80
+
2-RSH 2-RSH 2 -RSH
+
+ PbOs +-R-SS-R-
+ ZnO -+ -R-S-Zn-S-R-
H -S-R-S-C-S-R-S-
HC=C
+ H90 + PbO + HzO
organic
+ H20
+ peroxides --+--R-SS--RHO-Y-L - ~ - X - O H
-R-SS-R-
-+-
+ H?S=KH%
In some cases where conversion is desired for films of 5 to 50 mils, the oxygen can be supplied from the air. Paint driers are effective. The most active driers are cobalt, manganese, and iron derivatives. Cobalt is outstanding and will yield converted films in a temperature range of 50" to 150" F. Manganese and iron driers require heat to accelerate conversion. The necessary concentration of cobalt is about 0.25% for LP-2 and about 0.50% for LP-3. (LP-8 has been converted in materials such as leather and Transite by a cobalt drier solution followed by impregnation with LP-8.) Some chelate compounds of cobalt known to be
I
--+
i>o
Effect of Temperature upon Viscosity of Thiolrol LP-2
action. As would be expected, alkaline environment accelerates the oxidation. Heating d s o accelerates the reaction and, because the reaction is exothermic, once conversion has started i t will proceed a t a rapid rate. Typical reactions are: 2-RSH
+ HS-R-SIX
HC=CH
TEMPERATURE, OF Figure 1.
HC=C!
formic acid
I
+ H20
I
I >
HC=CH The liquid polymers will combine with phenol formaldehyde, resorcinol formaldehyde, furfuryl alcohol, epoxide, and related resins. T h e properties of products of combination are dependent on the ratio of liquid polymer to resin. The main values seem to lie in use of low concentration of resin to develop the toughness in the converted liquid polymers or to use fairly low concentrations of liquid polymers to develop flexibility in the resins. I n some conversion reactions the water content of the compound has a marked effect on the rate of conversion, as shown in Figure 2. The humidity a t which the compound is mixed and used has a similar effect on rate, as shown in Figures 3 and 4. Apparently traces of moisture act to catalyze the oxidation reaction. Because water is a normal by-product of the reaction, the major effect on rate is noted during the induction period. Lead peroxide is particularly sensitive to the presence of moisture. T o dkcrease the variations in rate of conversion a minimum concentration of moisture is desirable in the compound. For Bome applications it is desired to limit the ultimate molecular weight. I n the case of liquid polymers this can be controlled very easily by use of monofunctional thiol compounds. Typical compounds which have been used successfully are mercaptoethanol, xylyl mercaptan, and benzyl mercaptan (01toluenethiol).
,
3
0
3
0 0
Effect of Added Water on Cure Rate of Thiolrol LP-2 Lead peroxide conversion
1
I
I
I
I
50
55
60
65
70
% RELATIVE HUMIDITY
TIME,MINUTES Figure 2.
I 45
Figure 3.
Effect of Relative Humidity upon Cure Time of Thiokol LP-2 Lead peroxide oonversion
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
Compounding 120
Applications where maximum fluidity is required make use of uncompounded liquid polymer. Typical examples of these are casting and impregnation compounds. For casting compounds in particular a minimum of porosity is desired. Usually mixtures of LP-2 with ester-type plasticizer or mixtures of LP-2 and LP-3 are basic materials for casting and impregnation work. Amount of deposition in impregnation can be controlled through use of solvents. For casting. either accelerator pastes containing lead peroxide as the active ingredient or organic peroxides are added just prior to application. There is an induction period at the start followed by a n exothermic reaction, resulting in rapid increase in viscosity and molecular weight. For good results casting must be done prior t o the initiation of the conversion reaction. It is possible to delay the reaction somewhat after converting agents are added by storage under refrigeration. Impregnation permits greater leeway. The object to be impregnated-leather, for example-can be preimpregnated with a converting agent or catalyst and then followed by the impregnation dip in polymer or polymer solution.
Table 111.
Effect of Fillers upon Physical Properties of LP-2Vulcanizates Elongation,
Filler SRF black Thermax Titanium dioxide Zinc sulfide Calcene Alumina C730 Alumina C741
Parts 30 50 50 90 100 150 100 150 50 100 50 100
Tensile 575 870 388 790 620 600 570 600 455 475 505 390
%
460 470 420 490 540 570 490 320 490 590 600 600
Tear Index 127 169 63 226 105 112 70 155 38 114 50 79
Shore A Hardness 53 61 46 62 60 70 52 69 52 63 52 55
Basic Recipe LP-2 100 Stearic acid 1 Tech. lead peroxide 8 Samples were prepared for test by milling ingredients on a three-roll paint mill. Compounds were allowed to set 4 8 hours a t room temperature and were then ground and pressed out in a platen press for 10 minutes at 310° F.
Most uses require addition of reinforcing fillers, pigments, resins, or plasticizers. Fillers both strengt'hen and reduce cost of compounds. Resins are used to improve adhesive properties and plasticizers are used to reduce viscosity as well as to extend compounds. The most commonly used filters are medium thermal (MT), semireinforcing furnace (SRFj', and fine furnace (FF) blacks. Several white fillers can be used, although these result in somewhat more expensive compounds. Zinc sulfide, lithopone, and titanium dioxide have been used for specific applications. Zinc oxide is a good reinforcing filler, but must be used with special attention, because it also acts as a converting agent. Neutral fillers, such as calcium carbonate and aluminum oxide, have been found useful. These fillers are not as good for reinforcing properties as those mentioned previously, but serve in some compounds as low-cost extenders (Table 111). Inert dry pigments are stirred into the liquid polymers. Dispersion of pigments in the LP-2 can be accomplished by means of a three-roll paint mill, a ball mill, or an internal mixer. The type of compound required generally determines the most suitable mixing device. The conversion accelerator is prepared as a separate mix. Lead peroxide can be dispersed in dibutyl phthalate with a small amount of stearic acid to prevent rapid settling and caking of the lead peroxide. The organic peroxides which are used are soluble in the polymers and ran be added as supplied or in diluted form. One of the important uses for liquid polymers has been in caulking compounds which can be applied by means of a trowel or gun. The compounds shown in Table I V are intermediate in
1
327
I
TIME,MINUTES Figure 4.
Effect of Relative Humidity on Rate of Cure of Thiolrol LP-2 Lead peroxide conversion
cure rate properties. Compounds can be adjusted to convert in less than 1 hour and, by varying the accelerator or oxidizer used, conversion can be retarded so that heating at 150" to 200" F. is required. Casting compounds are designed for low viscosity. Only a minimum of thixotropy can be tolerated, or the resiltant products will have excessive porosity. Highly plasticized compounds have poor physical properties, but in many applications the compound is supported or contained and tensile strength properties are of relatively little importance (Table V). An interesting application for low viscosity compounds is in making plugs in electrical cables. The basic polymer has good electrical properties; volume-resistivity 5 X 1010 ohms per cm., power factor 0.0410, and dielectric constant 7.50. . Compounds can be used as cold setting adhesives for bonding glass, wood, and metals. Solvent cleaning is adequate for surface preparation. Typical compounds are shown in Table VI. is impregnation of one important use for liquid porous materials, followed by conversion in place t o a rubber of
Table IV. LP-2 Stearic acid SRF black Calcene Mauico brown Red oxide Zinc sulfide Titanium oxide Accelerator C-5.
Rheological properties Color
Formulations for Caulking Compounds 100 1 30
... ... ... ... ... 15
Fluid
100 1
100 1
100 1
20 3 2
20 ... .. 10 ... 15
.... ._ 80
...
... ...
15
Thixotropic
...
Thixotropic
... ... .. 15
Thixotropic
Black Red Tan Cream 2 to 3 Pot life hours 8 t o 16 Set timk 80' F 1, hours 1 to 2 Set time 1158' F.),hours a Lead peroxide (90% commercial) 7.5, stearic acid 0.75, dibutyl phthalate 6.75.
Table V.
Formulations of Casting Compounds
LP-2 100 100 100 Stearic acid ... 1 ... ... 3.0 Oleic acid 10 ... ... Dibutyl phthalate Santiciaer M-17° ... 50 ... Tributyl citrate ... ... 30 Sulfur 0.4 ... 0.5 MT black ... 100 .. Zinc sulfideh 50 ... Accelerator C-5 c 15 20 ii ' Pot life min. 15 to 30 4 to 6 hours 5 to 10 Set timk (68' F.),hours 2 to 4 24 t o 4 8 1 to 2 a Methyl phthalyl ethyl glycollate, Monsanto Chemical Co. b ZS 800 New Jersey Zinc Co. Lead &oxide (90% commercial) 7.5, stearic acid 0.75, dibutyl phthalate 6.75.
...
INDUSTRIAL AND ENGINEERING CHEMISTRY
328 Table VI.
a
h
Formulations of Thiolrol LP-2 Adhesives
Table VIII.
LP-2 100 100 S R F black 30 ... Phenolic resina 10 10 Stearic acid 1 1 Accelerator C-5 b 20 20 P o t life, hours 1 to 2 Set time (68' F.),hours 8 t o 16 Dures 10694 or Bakelite 6741. Lead peroxide (90% commercial) 7.5, stearic acid 0 75, dibutyl phthalate
6.75.
a
Table VII.
Formulations of Air-Drying Paints T74F
T74G 100 50
100 25' 25 3
'
....
104 104
....
'3" 27
....
98
2.3 3.45
1.75 2.65
0.72 2.88
0.55 2.20
Physical Properties T74F Tensile strength, lb./sq. inch 1400 Elongatiqn, % 550 Hardness Shore Type A 60 Winkelmann 320
T74G 900 275
L,
SR-6 fuel extraction0
5% loss Sea water, 2 years' immersion S o change So'change P o t life, hours 24 t o 48 Tack free, houra 2 to 4 Cure time (10 mils), d a y 1 Cure time (50 mils), days 5 a Vinylite VYHH dissolved in inethyl ethyl ketone. b -4.S.T.M. D 395-49T 2 hours a t 158O F. C Apparatus as a n A.S.k.41. D 297-43T. 20 hours refluxing.
high molecular weight. This method has been successful for filling voids in leather (e),wood, felt, fabric, Transite, and porous castings. The following examples listed show the methods used in impregnating leather. Hexogen Cobalt (2yo)Preimpregnation 1. 10-min. dip in cobalt solution in toluene
2. 30-min. drying to allow solvent evaporation 3. 1-hour drying at 158 F. to drive out residual solvent 4. 30-min. dip in 50% solution of LP-2a Cumene Hydroperoxide-Triphenylguanidine Cure 1. 10 min. in 5% triphenyl guanidine in methyl ethyl ketone 2. 30-min. drying at room temperature 3. 1-hour forced drying at 158' F. 4. 30-min. dip in: LP-2 100 100 Solvent a Cumene hydroperoxide* 7 Or
Air-drying coatings are one of the most recent developments and promise to be of considerable value to the consumer market in addition to industrial applications. The formulations are prepared at high solids (40 to 60%) and can be applied by brushing, spraying, or dipping. They are adjusted to paint viscosity and behave much like paints containing drying oils. Conversion takes place a t ambient temperatures and depends on oxygen from the air as the main vulcanizing agent. A combination of catalysts is used to promote the conversion. The film is serviceable over a wide temperature range ( - 6 5 " to +250" F.) and has excellent ozone, weathering, and solvent resistance. A novel characteristic of this paint is that it can be
0 30 50 45
60 0 3
-4ppearanc
O.K. O.K. O.K.
O.K.
O.K. O.K. O.K. O.K. Fair
60%
Fair Bad Bad
Nitric acid, 20% 2 months' immersion a t 80' F.
applied in one coat to any desired thickness up to 50 mils without flo~ even on vertical surfaces. This paint is now being invefitigated as a protective coating over wood, steel, aluminum, magnesium, and natural rubber. T o develop a bond, it is recommended that a primer be used on the surface to be coated. Suitable primers are EC-853 and EC776 (Minnesota Mining & Mfg. Co., Adhesives Division). The liquid polymers were developed and promoted for several fiervice applications during World War 11,but no effort was made to apply them to industrial problems until termination of hostilities. During the past 5 years, many established uses have developed for which the polymers have proved satisfactory. The major outlet for compounds is in cabin sealing and sealing integral fuel tanks in aircraft. However, considerable quantities are used in leather impregnation and in preparation of flexible molds. Several problems in the preservation of ships were answered through use of LP-2 compounds. The number of different liquid polymers which can be produced is unlimited. The products which are now manufactured can b e adapted by compounding techniques t o extend the fields of application. Special polymers can be prepared to meet application conditions which cannot be filled by present materials.
Acknowledgment The authors are indebted to the laboratory staffs of the Development and Technical Service Departments, who obtained much of the information upon which this article is based.
Literature Cited
50/50 toluene-methyl ethyl ketone.
6 70% solution.
10
E2
Sulfuric acid 20%
Q
Volume Swella, %
Chemical Resistance of Air-Drying Paints
Chemical Ammonium hydroxide, coned. Sodium hydroxide 10% 50% Aluminum sulfate, satd. Sodium carbonate, satd. Sodium chloride, satd. Formaldehyde, 37y0 Hydrochloric acid
LP-2 base paint
LP-2 Furnex Statex B Sterling 105 Zinc peroxide Toluene Cyclohexanone Methyl ethyl ketone Accelerator B Sulfur VYHH solution (207,)a Accelerator C Diphenyl guanidine Methyl ethyl ketone
Solvent Resistance of Air-Drying Paints
Solvent SR-6 fuel SR-10 fuel Acetone Methyl ethyl ketone Ethyl acetate Carbon tetrachloride E t h y l alcohol Water 1 month a t 80' F.
Table IX.
Vol. 43, No. 2
(1) Bond, G. R., IND. ENG.CHEM.,ANAL.ED.,5, 257 (1933).
(2) Fettes, E. M., and Jorczak, J. S., IND.ENG.CHEM.,42, 2217 (1950). (3) Kimball, J. W., et al., J . Am. Chem. 8oc., 43, 1199 (1921). (4) Kol thoff, I. M., and Harris, W. E., IND.ENG.CHEU.,ANAL.ED., 18, 161 (1946). (5) Martin, S. M., Jr., and Patrick, J. C., IND. EXG.CHEM.,28, 1146 (1936). (6) Oehler, R., and Kilduff, T. J., J . Research Natl. Bur. Standards, 42, 63 (1949). (7) Patrick, J. C., Trans.F a ~ a d a ySoc., 32,347 (1936). (~, 8 ) Patrick. J. C.. and Ferguson. H. R. (to Thiokol Corp.), U. S. Patent 2,466,963 (April 12, 1949). (9) Perkins, B. A. (to Rockwell Mfg. Co.), Ibid., 2,474,859 (July 5, 1949). RECEIVED October
14, 1950.
