INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1955
Table X. Boundarv Tensions and Soreading Coefficient of Built 1.0% 1s;-octyl Phenyl NknaethGene Glycol Ether at 25-26’ C. Builder Conon.,
%
Surface Tension, Dynes/Cm.
Interfacial Tension u s . Paraffin Oil, Dynes/Cm.
Spreading Coefficient on Paraffin Oil Ergs/Sq. CI;.
NaB04 0.3 0.6 0.9 1.5 2.0
30.1 30.0 30.0 29.9 30.0
2.3 2.2 2.1 2.2 2.2
-2 4 -2 2 -2 1 -2 1 -2 2
XasPsOm 0.3 0.6 0.9 1.5 2.0
30.1 30.0 30.0 30.0 30.0
2.3 2.4 2.3 2.3 2.3
-2.4 -2.4 -2.3 -2.3 -2.3
30.1 30.1 30.1 30.1 30.1
2.3 2.3 2.3 2.3 2.3
-2.4 -2.4 -2.4 -2.4 -2.4
30.1
2.2
-2.3
0.3 0.6
0.9 1.5 2.0
Zero
2181
Table XI. Calculation of Orange O T Solubilization by Built 1% Solutions of Iso-octyl Phenyl Nonaethylene Glycol Ether (0. &hour interaction, 23-26’
Aggregation
Builder PH 11.25 11.9
C.) Solubilization, Molecules Orange OT/Micelle IOPNG Exptl. Calcd. 2.126 2.121 2.254 2.220
135
Builder 0 . 3 % NazCOa 0 . 4 5 % NaaPO4.HaO
151
O.Q’% NaGOa
0 . 8 3 % 1\TeaPOa.H20
11.45 12.2
2.503 2.585
2.493 2.609
168
1 , 2 8 % NazCOs 1 . 4 6 % NaZOa.Ha0
11.5 12.4
2.857 3.015
2.862 3.001
NO.
ACKNOWLEDGMENT
Acknowledgment is made of the cooperation and advisory assistance of fellow workers at the Paint and Chemical Laboratory, Aberdeen Proving Ground, Md., C. F. Pickett, chief, and Myer Rosenfeld; also of the help of Rebecca Fliclcinger and R. D. Hemenway in obtaining many of these data. LITERATURE CITED
builders investigated, and for which the ratio of the solubilizations is constant a t fixed micellar sizes, i t seems possible to estimate Orange O T solubilizations, provided the builder p H is linown. I n built 1.0% solutions of fixed micellar size the ratios of the total sodium ion concentrations (moles per liter) and anion concentrations (equivalents per liter) are constant. This suggests t h a t for anionic surfactants of this type, ionic concentration ratios could also be key variables in estimating micellar solubilization in solutions of fixed micellar size.
IT.,J . Phys. Colloid Chem., 55, 664 (1951). (2) Harkins, W. D., “Physical Chemistry of Surface Films,” pp. 32& 1, Reinhold, New York, 1952. (3) Harkins, W. D., and Jordan, H. F., J. Am. Chem. Soc., 52, 1761 (1930). (4) Mankowich, A. M., IND.ENG.CHEIM., 44, 1151 (1962). (5) Mankowich, A. M., J . Phus. Chem., 58, 1027 (1954). (6) L‘utting, G. C., Long, F. A., and Harkins, W. D., J . Am. Chem. SOC.,62, 1496 (1940). (I) Debge, P., and Anacker, E.
RECEIVED
for review April 5 , 1955
ACCEPTEDJuly 11, 1955.
Uniformity in the Formation of Latex Paints MAX KRONSTEIN, RALPH W. MUSCHETT, JR., EDWARD J. DYPA, AND ARTHUR H. STAHELI Research Division, College of Engineering, N e w Y o r k Uniuersity, University Heights, N e w Y o r k 53, N . Y .
I
of various pigmentations in latex paints, a means was needed for comparing the distribution of the pigment particles in the dry paint film. Henson, Taber, and Bradford ( I ) had shown in 1952 how in ideal and unpigmented latex films, or in the binder part of a very diluted paint, the individual latex emulsion particles are ordered in a dense pattern. It was evident that the inclusion of pigmentation would affect this close orientation, or delay a final state which the authors described as the “fusion of the film.” They had used the electron microscopic method of investigation, which requires the use of very diluted specimens and the preparation of extremely thin films on the instrument screen. Their method shows a very small area of the film, in the case of the photographs ( 1 ) covering an area of about 5 X 6 microns or about 0.030 square inch. I n another electron microscopic study, Kienle and Maresh ( 2 ) studied cases where pigment particles had been drawn together into clusters in latex paint Elms to such an extent t h a t areas in the film were devoid of pigment particles. The need for the present investigation arose when i t was observed that, under certain conditions, white latex paints on pine panels produced, under Weather-Ometer exposure, globular discolorations t h a t must have been caused by chemical changes in the latex matter itself. The question wm: whether or not there ?; STUDYING the behavior
was a n y connection between the condition of the latex and the pigment distribution in these paint films, and between the condition of the paint film and its behavior under twin arc exposure. For these studies, i t appeared desirable to study larger area? of applied latex paint films. PHOTOGRAPHIC TEST METHOD
A photographic method for studying the applied films has been used, based on an application of the following considerations. Assuming with Henson and others that in an ideal condition a latex film is formed by a uniform lining up of the globular emulsion polymer particles, such a film can be expected to transmit the light of a strong light source in some kind of uniform manner. If the latex is pigmented with one or more different pigment materials, these particles will be embedded in this film, when dispersed, in some uniform manner so as t o transmit the light in a uniform manner of dispersion. T h a t is, if the test latex paint is applied on a thin glass plate and this plate is illuminated from the back by a strong light source, this light may be expected t o illuminate the paint film in such a manner t h a t i t will be possible to observe, from in front, whether or not the paint film is uniform in its formation and whether the light passes through a uniformly or a nonuniformly packed paint film.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2182
Such disorientation might be due t o a lack of fusion, or t o chemical effects, such as the formation of slight gel conglomerations in the paint film, or t o local cracks in the paint film, Visual observation indicates the existence of such conditions. T o obtain quick and indicative results about the condition of the films, it is possible t o apply the test paints on glass plates and set them on such concentrated and available light sources as, for instance, the search unit of a Photovolt Glossmeter. The observation will show whether or not the paint film is uniform or cracks are present.
Vol. 47, No. 10
ferent paints, study the paint film photographically, and compare this with the behavior of the paint films under selected conditions. APPLICATION ON TWO BASIC LATEX PAINT FORMULATIONS
For the study, two latex materials were chosen: high styrenebutadiene copolymer latex and poly(viny1 acetate)copolymer latex. Two different stabilizer materials were used for each of the two latices: a casein compound and methylcellulose, 400 cp. Three foam-controlling agents were used, selected from the industrial field. 1. An ester of high molecular weight derived from coconut oil. 2. A polyethylene glycol monolaureate. 3. A dimethyl polysiloxane (with small percentage of colloidal silica).
Two general formulations were applied t o both latices:
-m
GLASS PANELt
I
1
I
1. A formulation generally used in the practice for each type of latex, as shown in Table I. 2. These two formulations reversed with respect t o the latex used-that is, the formulation recommended for one type was used with the other type of latex and vice versa.
SUPPORT BOARDL I n order t o study the influence of the hiding power of the pigmentation, two types of pigmentation were used in these paints in varying proportions:
I 5Em I
BOARD FRONT SHOWING CUT-OUT
s1
1. Pigmentation of high hiding power, such as rutile titanium dioxide alone or with lithopone. 2. Extender material, such as wet-ground mica, 325-mesh.
These pigments mTere used in different ratios, as shown in Table 11.
=---L
="I
1
I
1
7WEATHEROMETER
QUARTZ LAMP
80
Figure 1.
Schematic diagram of photographic setup
A
\
I
I
I
150
200
\
I
It was desirable t o supplement this method of observation by the use of a photographic camera, whereby the image produced on photographic film could be enlarged and used as a permanent record for comparative studies, This photographic test setup is shown in Figure 1. Exposures were made by mounting the glass panels in a frame in front of two 500-watt photoflood lights, 3 inches away from the lights, without the use of a reflector. The camera was 10 inches away from the specimens. Exposure time was 0.1 second at f 8, 11, or 16, depending upon the amount of transmitted light. A 126-mm. lens was used with a No. 3 pprtrait lens. The filni was Kodak XX620. The area shown in the photographs 1s 2.75 X 1 inch. The photographs were printed in actual size. Figure 3 indicates the general types of paint films studied. A shows a uniform film with a uniform pigment distribution. This film is based on a poly(ving1 acetate)copolymer latex with a methylcellulose stabilizer and pigmentation consisting of 82% rutile titanium dioxide and 18% mica, 325-mesh. The irregularities in this film are due t o slight variations in film thickness. B shows a film with a tendency t o form small cracks. This paint was a high styrene-butadiene copolymer latex with a casein stabilizer and with 100% titanium dioxide pigmentation. c shows the same vehicle with different pigmentation consisting of 2770 titanium dioxide and 73% mica. Figure 4 shows examples of latex paints having a low degree of fusion. The great difference in the latex paint films shown in Figures 3 and 4 made i t advisable t o prepare a systematic group of dif-
0 PAINT 1 (8446MICA)I
M
IO0
250
TIME, HOURS
Figure 2.
Effect of light source on change of reflectance
Two groups of test panels were prepared, one on white pine panels and one on glass panels. The size of the wooden panels was selected to fit into the exposure racks of the Weather-Ometer. T h e wooden panels viere lightly rubbed with steel wool, 0-fine, and two coats of paint were applied by brush. T h e first coat was allowed to airdry for 3 days and the second for 4 days, before testing. The glass panels were prepared by washing the glass with sulfuric acid-dichromate cleaning solution, removing this with water, cleaning the glass again with soap and water, giving the glass a final water rinse and drying in warm air. The paints were applied in a wet-fiim thickness of 0.01 inch, using an eye dropper and film applicator. They were allowed t o air-dry for 3 days before testing. On some specimens R shellac undercoat was used before the test paints were applied.
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1955
Table I.
Basic Paint Formulations
Formulation 1 (Generally Recommended for High Styrene-Butadiene Latex Paints) Material Parts 251.0 Titanium dioxide rutile 71.5 Lithopone 35.7 Mica, 325-mesh 3.8 Lecithin, water-disp~rslble 190.0 Distilled water 78.5 Casein solution 3.5 Foam-controlling agent 37.0 Funzicide 0 Latex 447.2 Formulation 2 [Generally Recommended for Poly(viny1 Acetate) Copolymer Latex] Parts I.’ermula t ion 1 5% 400-cp. methylcellulose solution 100.0 2 Tetrasodium pyropliospha.te 1.5 3 Distilled water 180.0 4 Titanium dioxide rutile 225.0 5 Mica, 325-mesh 50.0 6 Latex 333.0 7 Dihutyl phthalate 14.0 8 5Y0 400-cp. methylcellulo-e solution 63.0 9 Diethylene glycol monoethylene ether 46.0 5.0 10 Oleic acid 11 26 B ammonia ( 2 9 . 4 % ) 3.5 I n preparing Formulation 1 materials 1, 2, 3, 4, a n d 5 were mixed. Some of t h e latex of 9 a n d some of t’he water of 5 were added until enough fluidity was obtained t o allow douhle grinding on the roller mill. Then t h e other materials were added under continuous electrical mixing, a n d the mixing was continued for 30 minutes. In preparing Formulation 2, materials 1 2 3 4 and 5 were mixed a n d double-mound on the roller mill, No. 7 wa$ disdersed in ?io. 6 bv addina it slowly ’& the emulsion using a~high-speedagitator. It was allowed t o stand for 24 hours, then added t o the paste of 1 t o 5, with electric mixing. T h e mixing was cont.inued for 2 hours, then materials 8 t o 11 were gradually added as t h e mixing continued. T h e mixing was continued for 2 hours more. ~~
~
~~~~~
2183
Table 11. Variations in Pigmentation Used in Paint Formulation 1
Paint a h 4
(High styrene-butadiene copolymer latex) Pigmentation, % Hiding pigment
Mica
10 (from different sources) 20 30 44 50 55 73 84 100
...
100% Ti02
I
~
BEHAVIOR O F PAINT FILMS UNDER ULTRAVIOLET LIGHT EXPOSURE
The evaluation test method is based on studying the relationship between the film uniformity and the effect of ultraviolet light exposure. Two different ultraviolet light sources were used.
1. T h e twin carbon arcs of the Weather-Ometer, used without water spray. Here it was observed that the two carbon arcs
Figure 4.
Paints of low fusion
I. Hiding pigment 9 0 7 mica 1 0 7 11. H/djng pjgment 70%: mica 3 0 d 111. Hldmg pigment 50%, mica 50%
affect the panels in the upper and lower brackets of the instrument differently. Generally, the position of the panels had to be changed periodically to avoid these differences. B u t in other studies, where a difference in intensity of the ultraviolet light was desirable for the current studies, the same position of the panels was maintained throughout the investigation. 2. A Hanovia burner, Type SH. For exposure, the painted glass panels, 2 X 3 inches in size, were placed inside a wooden case 10 inches from the lamp in a n arrangement whereby they received, as far as possible, equal amounts of radiation. The positions of the panels were changed a t 24-hour intervals.
Figure 3.
Different types of latex paint films A.
B.
Uniform pattern Film showing slight oraoks
C. Same latex as B without oracks
The two setups differ in their energy output, in the distance between light source and test specimens, and in the temperature inside the exposure chambers. Figure 2 indicates t h a t the loss in reflectance of identical paints under the two light sources differs widely, and t h a t the quartz lamp has a more rapid effect on the paint films. Figures 3 and 4 show paints applied on glass and photographed under the light setup of Figure 1. Figure 3 shows paints which have a good state of fusion, SO that the pigment is visible without the appearance of the conglomerates. Within the pigment the titanium dioxide appears generally as white particles. The sparkling of the mica particles is best seen in Figure 3. Figure 4 shows paints which have a low degree of fusion. The pigment particles are spread throughout the system, with the conglomer-
INDUSTRIAL AND ENGINEERING CHEMISTRY
2184
Vol. 47, No. 10
primarily with the study of the relatiomhip between film structure and ultraviolet light resistance and not with the study of the paint formulations themselves, no ultimate answer has been sought as t o the decisive factor for the different types of film formation. One question has been studied t o some extent-the influence of changing the foam-controlling agent without changing the rest of the composition or the method of paint preparation. The photographic pattern shows t h a t t o a certain extent the degree of fusion of the film changes with the selection of the foam-controlling agent, but this change was not decisive enough t o change the behavior of the paint under the exposure tests (Figure 6). . I n applying the various test paints t o wooden panels it was found that paints with similar pigmentation can have similar tri-green reflectance values, although they may differ in their film structure under the photographic method. I n respect t o gloss, the selection of the stabilizer is important. The paints formulated with methylcellulose had less initial gloss than those with
A
Effect of variation in formulation on film pattern
Figure 5 ,
A. Styrene-butadiene latex with methylcellulose compounded according to Formulation 1 B . Styrene-butadiene latex with methylcellulose compounded according t o Formulation 2 C. Poly(viny1 acetate) latex with casein compounded according t o Formulation 1
ates appearing as black arem in the film, This darkness is caused by the fact that the conglomerates allow less light to pass than the rest of the film. It was desirable t o study the conditions under which such different types occur and the relation of the type of film to the behavior of the coating under ultraviolet light. J t was found that one particular type of latex does not always produce one specific type of film and another latex another type, and that the same Bind of stabilizer, such as casein or methylcellulose, does not always produce, with one or the other type of latex, the same kind of film. This is shown in Table 111. Figure 5 , A , shows a paint film where there is a slight degree of coagulation using Formulation 1 with methylcellulose stabilizer. I n B, where Formulation 2 and the same stabilizer were used, the latex particles are well fused and do not interfere with the uniform distribution of the pigment in the film. C shows the state of coagulation of a poly(vinyl acetate)latex film with casein and Formulation 1.
Table 111. Types of Paint Films Obtained from Combinations of Components in Latex Paints Latex used
I
I I1
Uniform Pattern Stabilizer Formulation used used A 2
B A
2
Latex used
I I
2 I1 ir B 2 I1 I. High styrene-butadiene latex. 11. Poly(viny1 acetate) copolymer latex. A. Casein. B. Methylcellulose, 400 CP.
__
~
Low FuRed Stabilizer Formulation used used A 1 B 1 A 1 B 1
Variations in the ratio of hiding pigmentation and extender do not cause this difference in the film. The differences between the two formulations consist of certain components used in the one formulation and not in the other and of a different procedure in compounding the various materials. As this paper is concerned
Figure 6.
Effect of changing foam-controlling agent A.
Formulated with foam-controlling agent 1
B. Formulated with foam-controlling agent 2 C. Formulated with foam-controlling agent 3
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
October 1955
2185
casein. The ratio of hiding pigment and extender has a similar effect on the appearance of paint films having uniform film structure and those of lesser fusion. Here, the appearance is a factor of the hiding power of the paint. Table I V indicates that paints having the same basic formulation vary in their initial appearance according t o t h e hiding characteristics of the pigmentation. Table V shows t h a t uniformly formed, well fused films have a slow change in reflectance under both ultraviolet light sources. RZoreover, paints having lower hiding power showed a faster rate of change than those having greater hiding power, but the change which occurred on well fused films of low hiding power was generally less than the change on low fused paint films of greater hiding power. The effect of ultraviolet radiation was considerably greater on paint films having a low degree of fusion than on uniformly formed films; and this effect increased with any considerable decrease in hiding power, or increase in t h e transmittance characteristics of these paint films. The kind of effect differed with the source of ultraviolet radiation (Table VI).
Tnhle IV.
Reflectance Values of Test Paints Applied on Wood (Using tri-green filter) ReflecReflecPainta tance Paint tance
Pigmentation, % Hiding C-2 YO 0-1 80 h-2 50 h-1 72.0 65.0 1-2 16 1-1 a Kumerals inzpaint designations refer to types
Table V.
Paint
Reflectance
C-2 h-3
80 0 71.0 63.5
1 80.0 71.0 67.0
1-3
of foam-controlling agents.
Reflectance and Gloss Measurements on Uniformly Fused Paint Films
[Poly(vinyl acetate)Ilatex, methylcellul!xe stabilizer, 82% hiding pigment, Formulation 21 On Wood (Carbon Arc Exposure) =lass (Quartz Lamp Exposure) -Reflectance Gloss Reflectance Gloss 0 Iir. 426 hr. 0 hr. 425 hr. 0 hr. 230 hr. 0 hr. 230 hr. 81 0 84.0 3.0 5.0 87.5 80x0 3.0 2.0
'Table VI.
Results of Exposure of Paint Films to Quartz Lamp Uniform Pattern Heflectance Gloss ______ _ 0 110 0 110 hr. hr. hr. hr.
Paint Mica, yo 50 .. .. I-.4-1 I-A-2 18 80 75 7.4 3.0 I-€3-1 50 .. .. I-R-2 18 81 81 4:o 2 . 0 11-A-1 10 , . .. 11-4-2 50 73 64 1610 5 . 0 11-8-1 10 .. 11-B-2 18 8715 80 3:0 2 . 0 I . High styrene-butadiene latex. 11. Poly(viny1 acetate) copolymer lstex. A . Casein. E . Rlethylcellulose, 400 cp. 1. Formulation 1, Table I. 2 . Formulation 2, Table I. I
.
Low Fused Reflectance Glow 0 110 0 110 hr. hr. hr. hr. 76 62 6.9 3.0
..
71
..
57
3.0
82
73'
8.0 2 . 0
8::2
78:O
9 . 0 3.0
4.0
I .
..
..
..
..
Table VI1 shows the behavior, under quartz lamp exposure, of three paints of Formulation 1 with different ratios of hiding pigment and extender and three different foam-controlling agents. Considerable color changes occur and the degree of these color changes follows the ratio between hiding pigment and extender, or the transmittance characteristics of these paints. Slight initial differences between paints of the same pigmentation but using different foam-controlling agents disappear after a relatively short time of exposure. The difference betn-een these paints and the well dispersed paints of Formulation 2 which have initially less gloss, but retain this gloss, is very characteristic. The uniformly formed paint film has a high initial whiteness and retains
2
Figure 7.
Typical test series
T o p . Well fused latex paint viewed through glass. Poly(viny1 acetate) copolymer latex with methylcellulose,sttlbilizer, compounded according to Formulation 2 Bottom. Same paint on wood (1) before and (2) after 425-hour exposure to carbon arc ultraviolet light. Same paint on glass (3) before and (4) after 400-hour exposure to quartz lamp
this whiteness t o a very high degree. I t is a n indication that the type of film which is formed and the consequent pigment distribution are of greater importance than changes in the ratio between hiding pigment and extender. If t h e ratio between hiding and nonhiding pigment is increased t o a 50 :50 range, t h e transmittance of the paint increases far enough t o overshadow the difference in the film formation, and discolorations might be observed in both groups of Table VI. The most interesting effects were those under the slower-acting ultraviolet exposure of the twin carbon arcs in the WeatherOmeter. The films with uniform pigment dispersion show, besides certain color changes which are indicated in Table V, little change in appearance when exposed for about 400 hours t o the ultraviolet light sources. Figure 7 shows t h e typical appearance which has been observed in several test series made in test groups of five panels each a t different times. Figure 8 is a result of repeated tests. The paints with a low fused film formation show on glass as well as on wood very interesting chemical effects, which appear t o be directly related to t h e existence of t h e conglomerations in the film. Figure 8 shows the photographic patterns of four paints when viewed on glass against a strong light source, and the results of exposure of the films t o ultraviolet light. Paint 1 (panel 1)is the paint with 100% titanium dioxide pigment, which shows the tendency t o cracking in Figure 3 B. This tendency disappeared when the pigmentation was changed t o 90% hiding pigment and 10% wet-ground mica. But with increasing transmittance, and especially when used with a n extender content of 50% and above, the light penetration caused chemical changes around the conglomerates, perhaps in the form of oxidation under ultraviolet light, perhaps in t h e form of more complex reactions. These formations became permanently visible on the surface of the paint films in a network pattern similar t o t h a t which may be assumed t o exist in the film formation of these loosely fused films. This pattern is shown in paints2 t o 4 (panels 2 t o 4) in Figure 8.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2186
Panel 1
Figure 8. A.
Panel 3
Panel 2
Vol. 47, No. 10
Panel 4
Influence of fusing condition of film on behavior under ultraviolet exposure
Photographic transparencies of paint films compounded according t o Formulation 1 b u t using different proportions of hiding pigment t o extender. Left. Titanium dioxide 100%. Rzght. Titanium dioxide 27%, mica 73%
B. Results of exposure with different degrees of hiding power in pigmentation. 200-hour exposure t o carbon arc ultraviolet light
C.
Same panels as B , with subsequent 320-hour exposure to quartz l a m p Panel 1. Ti02 loo’% Panel 2. Ti02 90%, mica 10%
The panels of Figure 8 are shown after 200 hours’ exposure t o the twin carbon arcs in the Weather-Ometer. At that time a part of each panel was cut off and this section was exposed t o the quartz lamp for 320 hours longer. The lower part of the photographs shows the increased intensity of these chemical formations under this additional ultraviolet light exposure. The same effect has been found on similar paint compositions on wood, and the effect is increased when the paints are applied on certain undercoats such as shellac. The globular color formations have not been found on any of the uniformly formed paint films. There appears t o be, therefore, a direct relationship between the film structure a8 shown in the photographic method and the formation of these visual discoloration effects under ultraviolet light exposure under the described conditions. It can be seen as caused by a lack of uniform interlinkages in the not well fused films which exposes the latex in these films more t o the chemical effect of ultraviolet radiation.
Panel 3. Panel 4.
Ti02 27%, mica 73% Mica 100%
SUMMARY
A photographic study of the film formation of latex paints shows two different film patterns on latex paints: (1) a uniform distribution of the pigment in a well fused, uniform film, and ( 2 ) globular conglomerates throughout the film. These patterns are typical neither of one particular type of latex nor of one particular combination of a latex with a stabilizer. The difference is caused by differences in general formulation or in the process of compounding. Films of one pattern are not changed into the other pattern by changing in the pigmentation the ratio between hiding pigment and extender. Films of uniform conditions change slowly in appearance under ultraviolet light exposure; loosely fused films change more rapidly. Films with 100% titanium dioxide showed a tendency t o slight cracking, which films with 90% titanium dioxide and 10% or more wet-ground mica did not show. Extensive increase in transmittance of a film increases the rate of effect of ultraviolet radiation, Table VII. Effect od? Exposure of Test Paints on Glass Panels to especially when the ratio between hiding pigment Ultraviolet Lamp and extender is 50:50, or when a greater propor(Formulation 1) tion of extender is used. Gloss Readings Reflectance As ultraviolet light sources a quartz lamp and 0 50 145 230 400 0 50 145 230 400 Mica, % Paint hr. hr. hr. hr. hr. hr. hr. hr. hr. hr. the twin carbon arcs in the Weather-Ometer have 10 e-1 8.0 4.1 3.0 2.0 2.0 81 .o 72.4 71.0 70.0 74.0 been used. 3.0 3.0 86.0 71.2 68.0 65.0 69.0 0-2 10.5 7 . 0 4.5 84.7 71.2 68.0 65.0 69.0 2.0 2.0 3.0 0-3 10.0 6.5 I n repeated tests, uniform films show very little h-1 50 5.5 66.0 2.0 2.0 2.0 73.5 2.9 59.0 55.0 59.0 66.0 62.0 4.0 2.0 2.0 76.0 h-2 2.4 58.0 63.0 2.0 change on exposure t o ultraviolet light. Loosely 67.0 62.0 66.0 2.0 61.0 6.9 3.0 2.0 76.0 h-3 3.8 48.0 45.0 1-1 6.0 3.0 2.0 56.7 fused films developed on the paint surface dis2.0 65.6 45.0 84 3.4 51.0 57.8 51.5 2.0 67.0 47.0 1-2 6.0 3.0 2.0 3.9 coloration areas of a pattern similar t o that 66.0 52.0 52.0 58.0 48.5 1-3 4.0 2.0 6 . 8 4.1 2.0 in the transparent film of the same paint.
October 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
The type of film formation of latex paints and the paint behavior under ultraviolet light exposure are closely related.
2187
LITERATURE CITED
ACKNOWLEDGMENT
(1) Henson, W. A., Taber, D. A., and Bradford, E. B., IND.E m . CHEM., 45,735-9 (1953). (2) Xienle, R. H., and Maresh, C . , J. Oil Colour Chemists’ Assoc., 36, 61948 (November 1953).
Appreciation is expressed t o the Wet Ground Mica Association for assistance in this study.
RECEIVED for review June 7, 1954. ACCEPTED June 8, 1955, Division of Paint, Plastics. and Printing Ink Chemistry, 125th Meeting ACS. Kansas City, Mo., 1954.
Electrical Conductance of Porous Plugs ION EXCHANGE RESIN-SOLUTION SYSTEMS M. C. SAUER, JR., P. F. SOUTHWICK, K. S. SPIEGLER,
AND M. Gulf Research 6;: Development Co., Pittsburgh, P a .
EASUREMENTS of the electrical conductance of porous aggregates saturated with a conducting electrolyte are of considerable importance t o the oil industry, Such measurements offer a convenient means of characterizing the pore structure of sedimentary rocks; they are widely used both for electric log interpretation and calculation of permeability. h summary of these applications has been given by Wyllie and Spangler (19). Analogous measurements have been made by Stamm ( I d ) to characterize the structure of wood fibers. The conductance of porous aggregates is also of importance to the soil scientist (10). The conductivity of an aggregate of electrically nonconductive particles saturated with a conductive electrolyte has been shown by Archie ( 1 ) t o depend upon the conductivity of the electrolyte and a dimensionless geometrical factor, analogous t o a cell factor in conventional conductometry, which is now widely termed “formation resistivity factor,” F . I n such a system the plot of the electrical conductance of the porous plug against the conductance of the saturating solution is a straight line through the origin; the reciprocal value of the slope of the line is F. Attempts have been made t o calculate F as a function of porosity for aggregates of spheres (11), but even for aggregates having a relatively simple geometry great difficulty is experienced. Accurate experimental data have been published ( 1 7 ) for the relationship between F and porosity, 9, for aggregates composed of spheres, cubes, cylinders, disks, and triangular prisms. These data refer t o aggregates composed of particles t h a t are electrically nonconductive. The analogous problem of the conductivity of saturated aggregates composed in whole or in part of particles which are themselves conducting is more complex. When the electrical conductance of the plug is plotted against the conductance of the saturating solution, a curve concave with respect t o the abscissa results; this is shown in Figures 4 and 5. Wyllie and Southwick (18) have given some attention to this problem in the context of electric log interpretation. It appears, however, t h a t the nature of the conductance of saturated aggregates of conducting particles and solutions of electrolytes is of interest not only in electric log interpretation but in other fields of chemical engineering also-for instance, in problems of soil conductance or in the electrical regeneration of beds of ion exchange resins. The latter has been studied by Heymann and O’Donnell ( 7 ) and Spiegler and Coryell ( I S ) and has been used in conjunction with ion exchange membrane electrodialysis by Walters, Weiser, and Marek (15) for the case of porous aggregates containing both anion and cation exchange beads. It is the object of this paper t o examine the nature of the conductance of columns of ion exchange resin spheres saturated
R. J. WYLLIE
with solutions of electrolytes of different concentration, t o explain these data and, in particular, to re-examine and confirm, if possible, the basic equations proposed by Wyllie and Southwick (18) which describe the change of the net specific conductance of the porous plug with the specific conductance of the saturating solution. PREPARATION O F RESIN
The sulfonated polystyrene cation exchange resin Amberlite IR-120 (Resinous Products Division, Rohm & Haas Co Philadelphia, Pa.) was selected. The material used was obtained by dry-sieving about 1300 ml. of the resin previously dried at 100’ C. for 2 hours. Particles passing a No. 32 and retained by a KO. 35 U. S. standard screen were collected and conditioned in the following way: A column of resin 0.813 inch in diameter in the sodium form was backwashed with 3 liters of distilled water a t a flow rate of roughly 100 ml. per minute in order t o elutriate impurities and small particles. One Liter of 2.5N hydrochloric acid was then passed through the resin column over a period of 20 minutes t o convert it t o the hydrogen form. The column was backwashed with about 2 liters of distilled water and the washing was followed by the passage of 1.5 liters of 1.6N sodium chloride solution a t a slow rate t o convert the resin t o the sodium form. The washing and sodium chloride treatment was repeated three times, about 1.5 liters of water being used for each backwashing. The procedure adopted had two purposes: t o continue the removal of nonhomogeneous and incompletely formed particles from the resin, and to ensure complete conversion of the resin to the sodium form. The resin was then taken from the column and dried at 100” C. for 3 hours. Broken spheres not removed by elutriation were eliminated by allowing the resin particles t o roll down an inclined plane slanted sufficiently for spherical particles only to roll; broken particles remained behind. After this procedure, an examination under a microscope showed that the resin contained only four or five broken particles per 100. DESCRIPTION OF APPARATUS
The following general procedure was used to determine the conductance of a column of the uniformly sized Amberlite IR-120. The Plexiglas cell shown in Figure 1 was filled with the resin particles between the perforated platinum electrodes, A and B. The system was then rinsed with distilled water by connecting side arms C and D t o a circulating system consisting of two conductance cells leading to C and D, a solution reservoir, and a circulating pump as shown in Figure 2. Rinsing was continued until the specific conductances of the water entering and leaving mho the resin column were identical and less than 5 X cm-1. For purposes of these experiments, a specific conductance less than 5 x 1 0 - 6 mho cm.-l was considered to be negligible. The resistance of the resin column was then measured with the movable electrode adjusted to various settings before and past the point a t which contact with the resin particles was just made.
