156
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 20, No. 2
Protective Paint from Rubber’ Harold Gray THEB. F. GOODRICH COMPANY, AKRON,OHIO
A protective paint has been prepared from rubber UBBER has long been high as 10 to 20 per cent and which can be used commercially. The chief features considered for use in still be within the range of the paint i n d u s t r y . of the new Paint are: (1) good adhesion to metals: goodbrushingproducts. The Certain of the physical prop(2) resistance to acids, alkalies, corrosive Bases, and chief difference between there r t i e s of s u i t a b l y corncorrosive chemicals in general; (3) low permeability m o p r e n e p a i n t and those to moisture, salt solutions, salt spray, etc. ; (4) the pounded rubber-such as repreviously made with a rawsilience, resistance to shock, film is tough and can be bent without injury at subrubber vehicle is that the forlow permeability to moisture, zero temperatures: ( 5 ) the film does not flake when Cut, mer resembles a lacquer in high resistance to abrasion, and rust spreads very slowly from an exposed area. that it needs no vulcanizing and its characteristic strength O n account of its unusual set of Properties, this paint or curing operation. -make it a very promising should have a wide range of usefulness, particularly in Properties Of Rubber Paint starting material. S e v e r a l chemical and other plants where metal parts are subattempts have been made to jected to excessive corrosive conditions. RESISTANCE TO CHEMICAL utilize its unusual properties. AcTIoN-The resistance to For instance, a small amount of rubber has sometimes been acids, alkalies, corrosive gases, and corrosive chemicals in dissolved in the oil in regular lead and oil paints. No doubt general is very good. Examples are sulfuric acid, sulfur in some cases this was for advertising purposes only, but in dioxide, sulfur trioxide, hydrochloric acid, hydrogen sulfide, others a determined effort was made to utilize the physical sodium hydroxide, sodium hypochlorite, and calcium hypoproperties of the rubber to give an improved product. De- chlorite. T O MOISTURE PENETRATIOS-LOWpermearivatives of rubber have also been tried, but without much RESISTANCE success. The chlorinated product is apparently the only one bility to moisture, desirable in any paint, is shown to a rethat has found any commercial application, and that is very markable degree by films of thermoprene. A molded sheet limited.* (7 by 7 by I / ~ Oinch or 18 by 18 by 0.13 cm.) gained 0.365 A number of patents have been issued dealing with paints per cent in weight when immersed in water a t +1 O to +2” C. or not for 345 days. (Chart 1) Panels covered with the paint and varnishes made from hard r ~ b b e r . Whether ~ any of them ever reached the market, they did not achieve and immersed in water show practically none of the disany considerable commercial success. coloration caused by moisture penetration. The importance Heretofore the use of the rubber hydrocarbon as such has of this very useful property is shown by the remarkable been impractical, for a number of reasons. Solutions of results obtained with the paint in salt water, salt spray, and rubber in organic solvents. so-called “cements,” are very under moist conditions in general. viscous and it is necessary to use low concentrations. Dilute ADHEsIox-Any paint to be of value must adhere firmly solutions-say 2 to 5 per cent-are difficult to handle as far to the surface it covers. The high degree of adhesion of the as brushing, spraying, dipping, etc., are concerned. After a new paint is one of its most important properties. It is film has been deposited, it is not satisfactory, owing to its practically impossible to separate the film from the undertacky nature, until it is vulcanized. This could be made an lying surface without actually cutting it. This property is air-curing process, but a t least several days would be re- valuable in a number of ways. For exampIe, if a thermoquired. Small objects could be cured in heaters, as is now done with baking paints, but such a process would limit the use of the paint too closely. Even were it possible to obtain a smooth, even coat wherever desired, there would be difficulty in obtaining a proper cure, as frequently considerable trouble is encountered in vulcanizing films deposited from a cement. In the course of an extended series of investigations started by Fisher,4 there has been perfected i n the Goodrich laborac ~ a v ~ * z - i m m r r r e ~n d Sea Water i’c tories a technic for modifying the properties of rubber hydrocarbon by means of a change other than vulcanization. A series of products ranging from a tough, horny, balata-like substance to a brittle, pulverizable material resembling C h a r t 1-Resistance to M o i s t u r e Shown b y R u b b e r P a i n t shellac is made available by this treatment. The hydrocarbon (which throughout this paper ivill be designated 8s prene film on iron is ruptured, the exposed surface will rust “thermoprene”) is very pure and has many unusual proper- very quickly. The rust, however, will spread very Slowly ties which make it a promising starting material for paints. from the exposed area, because the film adheres so firmly to The outstanding point of interest to the paint chemist is that the metal that it will not Strip back. When the film iS Cut the concentration of thermoprene in the solvent can be as with a knife it does not shatter or flake. The cut or scratch is clean and only the portion actually in contact with the cut1 Presented as a part of the Symposium on Lacquers, Surfacers, and ting device is affected’ Thinners before the Section of Paint and Varnish Chemistry a t the 73rd ELASTICITY-The film is very elastic, as sh0m-n by the fact Meeting of the American Chemical Society, Richmond, va , April 11 t o 16, 1927 inch or 10 by 5 by 0.16 that a piece of steel (4 by 2 by K0llotd-Z 29, 150 2 Lamble, Od Color Trades J , 57, 1250 (1920). em.) covered with three coats of thermoprene and cooled to (1921), Caoutchouc b gutta-percha, 16, 9811 (1919) - 18”to - 170 can be bent without injury to the 8 British Patent 243,966 (1925) on India-rubber varnishes is an example A sharp blow with a hammer results in nothing more than 4 I n d Eng. Chem , 19, 1325 (1927).
R
9
the ciittiiig of the film a t the point of contact. Some of the films liere tested at temperatures as low ils -46" to -51" C. and showed up as well as at 0" C . Cutting the film when cold results in a separation only at the cut portion, with no Elmitering or flaking. I~CSISTAKCETO '~MVEFLATURE CWAXGES-hOthCl' rather u1111~un1feature of the pnint is its resistance to sudden tr1rrper:tture change.;. In one series of experiments the filiiii (on steel) w x e cooled in an ice-salt bath and tlicn put.
on a hot phte st 115" C. After 15 minutes on-the hut plate the panels were plunged into the ice wat.or again. This cycle was repeated ten to fifteen times with no apparent effect on t.he films. PIGMEST~TIOX PRoPEmIEs-----Anydesired pigment can be used in the paint and any color except a pure white can be obtained. The amount of pigment can be varied widely. The possible range extends from no pigment a t all to ss high as 250 or 300 volumes of pig~nentto 100 volumes of thermoprene. The practical range is yet to he determined. Good results are obtained vith 70 volumes of pigment. Color may be imparted by organic dyes, using a white pigment as the filler. A very wide range of oils and softeners can be used. I n some cases where a baking paint, is desired, drying agents may be used. SOLVEKT I'Ropwms-The paint should probably be classed as a lacquor, since a solvent is used which does not remain as a part of the film. I n general, the ordinary rubber solvents are used-.--such as gasoline, toluene, benzene, carbon tetrachloride, turpent.ine, kerosene, etc. 'We solvents are varied aerording to the use for which the paint is inteiided~L i. e.l hruiliing, spraying, or dipping.
Testing Program
In tiixkiiig those tests on composition and general pruperties, three p:inels (4 by 12 inches or 10 by 30 cirr.) were made in each case, always with three coats and sometimes with four of paint. Of each set, one panel was exposed on the roof on a rack facing south at an angle of 45 degrees from the vertical, one wits c,iit up for laboratory tests, :mi one was stored for reference.
Crnerd properties of films were studied in a long series of laboratory tests. These properties included: (I) Tack, warm, and cold.
(2) Color, origiiial, aiter wcatlicring, arid after treatment with various chemicals. ( 3 ) Adhesion, a t room temperature, rrt - 1U" C. and in some casesat -46"10--51"C.
( 7 ) Corrosion resistance toward various ciicnricals arid iii the salt-spray test. (8) \Veather resistance; the panels on the roof werc rnamiired from time to time to observe such effects as checking, chalking, rusting, color changcs, etc.
Laboratory Tests
Cunrprelrensive ksts have heen conducted to determine the general characteristics of the paint. With respect to composition, the following factors were &died: Variations in physical properties of thermoprenr. (2) Effect of pigments. The inore common ones were aluminum, asbesthie, barytes, blanc fire, chromic oxide, d a y , gas black, graphite, iron oxide, lead chromiltc, lithopone, red lead. sienna, Titanor, ultramarine bhtc, white lead, whiting. zinc oxide, and 8 series of crgauic dyes. (3) Variations in pigment concentration ill under-coat and in top-coat. (4) Eirect of oils and softeners. ( 5 ) Effect of driers in the drybig oils. (6) Time and temperature (compounds used for baking mamcls) (7) Surface. All the paints wtre tested on steel. A representative series was also tried on niimerous other surlaces ineluding aluminum, brass, and bronze (4 types), copper. Duralomin, iron (4types), lead, nickel, tin, leaded tin, galvanized iron, zinc, magnesium, red oak, and white pine. Some tests were also made an hard and soft rubber. (1)
7 ~ L r s dm d Oil paint 0 -~Thcrrnoprmcpaint Plate It- Steel Panels Exposed Five Months in Salt Works
The eliihoration of this program uf testing required more than tu-o years. At one time there were over twelve hnndred weather-exposure panels under observation. The conclusions drawn from this testing program are briefly summarized its follows: (1)
Phvsical "rollerties of the themonrene are uniform.
subject to-accuraie manufacturing control. -
(2) Ordinary paint pigments can be successfully incorporated into these paints over a wide volume range.
I X D C S T H I S L A5U IWGINEERING CHEMISTRY
158
Although oils BIKIdriers mix well witli the paints, there advsutigc to lie rained from tlieir usc. (4) As in tlie case of orditiary paints, baking hardens tlic film. (Si Both air-dried and baked films show mod adhesion to most metallic and other surfaces. This adl&sion persists at temperatarcs as low as -51" C. (6) Direct ~xposurcto weather and sunlight reveals a pre-
(3)
is
\-,
vailing tendericy toward chalking, occasional checking, and
some rusting in spots. (7) Exposure to acid and alkali and to salt spray indicates
that thermoprene has exceptional protective properties.
Small-Scale Commercial Tests
The laboratory and roof experiments were siippleniented by a series of semicommercixl test.s tending to sliow the type of service for which the paint is best adapted. For example, there tias always been a great deal of trouble in obtaining a pairit which would protert the metal in a salt works. Several test panels and test sections of metal work in such a factory showed that the thermoprene paint stood up much better than commercial paints that had been used before. In R a t e I1 two panels are shown that had been exposed for
A Modified Weighing Pipet' Graham Edgar E r x n G ~ s o ~ rCOXPORAIION. r;~ 25 ~ R O * D W I Y , NEWYORZ,N. Y .
frequent,ly desirttble analytical work that aiiaiyscs Iand'I'beISinmade upon a nearly coristmt qimitity of material, the case of corrosive liquids or other liquids not iii
readily ineasurablc in ordinary volumetric apparatus, this procediire may be inconveiiieiit. There bas been devised in this laboratory a modified Lunge weighing pipet wliich ba,s proved very useful, and it is described here as being of possible interest to other laboratories where routine analyses are carried out. The apparatus, illustrated in the accompanying sketch, consists essentially of a Lunge pipet containing three bulbs I
Received December 28, 1927
Vol. 20, No. 2
five months. I'and 7 was covered with a lead ;and oil paint, and is complet,ely rusted. There are a few small rust spots on panel 6, wliich was protected by a thermoprene paint. These rust spots are due to pigment aggLmerates, which have now beeii eliiniiialed by improsixl methods of manufacture. The effect oS salt spray is fiirther brought out iii Plate 111. These panels were cut from a 4 by 12 inch (10 by 30 cm.) panel and tlre edges are raw. Tlie edges were left this way purposely to sliow how well the films would prevent rustspreading. There is practically 110 spread of ruet from tlre edge of the tbennoprene paint panels 72 and 5'3. In a cooling tower where the spray of steam and cooling water from tire vulcanizers was hloaii against. a series of louvres in a fine spray, a t the end of nixie niont,lis the commercial paints were practically a11 destroyed, while a few thernroprene paints OS a particular composition were in good condition at, the end OS sixteen months. Tlirse preliminary development tests are now being augmented by paintiiig tests iir chcmical plants.
of iiefiiiit,e voluiiie with gradua t i o n marks between them. 'The base is flattened and is of s u ~ l diiriensiorrs i tbat the pipet will ,stand comfortably on tlre ordiiinry balnnce pan. By tlie use of this pipet duplicate or triplicate n,eighiiigs of nearly bho same quant,ity of material may be conveniently mndc. The apparatus may be made with two bulbs instead of three a n d t h e dimensions of the bulbs may be changed to suit individual needs. Tlie pipet has been made by the Yonkers Laboratory Supply Co., 549 West 132nd St., New York, N. Y.
