Accelerated Tests for the Settling of Pigments in Paints. I1 S. WERTHAN, R. H. WIEN, AND E. A. FATZINGER, The New Jersey Zinc Company, Palmerton, Pa.
T
HE first requisite in the Of any test is a clear conception of
I n 1928 the Jirst paper1 of this series reported a n inoestigation Of the settling tendencies of paints during shelf storage and described acceleraled tests for determining this property. I n confinuing this study, the variables encountered during shelf aging and their influence o n settling tendencies are considered. The ralue and limitations of accelerated tests f o r duplicating shelf slorage are presented. A recording penetrometer f o r determining the degree and characteristics ?f the settled mass is described.
the properties to be evaluated and of the variables involved. The appearance of a supernatant layer of clear vehicle during Storage iS not a measure of the settling tendencies of a paint. The separation of clear liquid if not accompanied by packing of the pigment is not detrimental. The degree of hard-settling or caking of the pigment is the significant factor. paint manufacturer, in determining the aging properties of his product, will set aside cans of freshly prepared paint which will be held at a fairly uniform temperature and not be disturbed, except t o be examined after what he considers a suitable lapse of time. On the other hand, under commercial conditions the packaged product may be frequently disturbed and undergo severe temperature variations during its journey from the labeling table t o the consumer. A satisfactory test should predict the probable condition of the paint when it reaches the ultimate consumer.
EFFECTOF STORAQE CONDITIOXS A number of tests were undertaken t o determine the influence of storage conditions on the degree and the nature of the settling. The variables considered were temperature, agitation, and the kind and size of the container. Previous work indicated that the influence of these factors varies with the type of paint. Based on consistency characteristics, paint may be divided into three types: 1
~ ~ ~ i l : ! i Yi ~ merit suspension is dependent on
the specific gravities of the pigment and the vehicle, the viscosity of the vehicle, and the ~ ~ e t n h e , s ~ i ~ ~ l Pof t &dispersion g’ee
11. Paints possessing marked t h i x o t r o p i c properties-that is, yield values which decrease with agitation and tend to return when agitation ceases. This type of consistency is usually due to metallic soaps, added during manufacture or subsequently formed by chemical reaction between pigment and vehicle. 111. P a i n t s possessing artificially produced high yield values or “false bodies,” which if broken down generally do not reform. This type of consistency is usually due to emulsions produced by water solutions.
-4simple lithopone flat \Val1 paint, which possessed moderate settling tendencies, Iqras prepared as representative of the first type. The same formula R’ith one pound (0.45 kg.) of aluminum stearate per hundred pounds (45 kg.) of pigment resulted in a paint of the second type. A paint of the third type was obtained by stirring a %Teak water soap solution into the first paint in the ratio of one to one hundred gallons (3.79 to 379 liters). A large number of 6-ounce (180-cc.) glass containers were filled with each of the three paints and stored under each of the following conditions:
R’erthan a n d W e n , IND.ENQ.CHEM., 20, 729 (1928).
1. On a cabinet shelf under conditions simulating shelf storage in a store
a. Undisturbed b. Moderately agitated once a week c. Moderately agitated once a day 2. Exaosed under various temaerature conditions with and wit‘hout daily agitation
TABLEI. EFFECTOF CONDITIONS DURING STORAGE os SETTLIXG OF PIGMEST IN PAINTS EXPOSURE CONDITIONS Room conditions: Not disturbed: 6-0s. (lSO-cc.)bottle 0.5-pt. (0.47-liter) can 1-pt. (0.95-liter) can 1-gal. (3.79-liter) pail Agitated weekly Agitated daily Maintained a t 28’ C.: Not disturbed -4gitated daily Maintained a t 52’ C.: Not disturbed Agitated daily
Ratinga
TYPEI PAIXT Description
4
Layer, inrreasing in hardness with depth
4 5
5 5
Layer, increasing in Layer, increasing in Thinner and harder Thinner and harder
4 5
7
Cycle-8 hrs. a t 52‘ C. and 16 hrs. a t 4’ C.: Kot disturbed Agitated daily On steam radiator: Not disturbed Agitated daily Continuous light: Not disturbed Agitated daily Continuous dark: Not disturbed Agitated daily Diffused light of rocim, not illuminated a t night :Not disturbed 4 Agitated daily 5 Degree of settling based on the penetrometer
TYPEI1 PAINT Description
2
5
Soft sediment Soft sediment Soft sediment Thin stringy layer Gummy layer Tough cake
Layer, increasing in hardness with depth Thinner and harder cake
1 None 2 Slight soft sediment
3 5
Soft stringy sediment Tough cake
Thin, very hard cake
3
Almost imDenetrable cake
5
hardness with depth hardness with depth cake cake
1 1 1 1
TYPEI11 PAINT Ratinga Description
None Kone None None 1 None 1 None
4 Layer, increasing in hardness with depth
10
Ratingn
Thick soft layer, slightly packed a t bottom Soft with thin, hard-Dacked layer
2 2
3
4
8 Very tough hard cake 10 Very hard almost impenetrable cake
Soft cake Soft cake
None None
Gummy sediment Gummy sediment
Layer, increasing in hardness with depth Thin cake
S!igh: soft 3ediinerit Slight soft sediment
Thin gummy layer Thin hard cake
Layer, increasing in hardness with depth Thin cake
Sone Snne
Soft sediment Tough cake
Layer, increasing in hardness with depth Thin cake
Sone Sone
Soft sediment Tough hard cake
2 Soft sediment 1 None Layer, increasing in hardness with depth 5 Tough cake Thin cake 1 None graphs, rated from 1 to 10, 1 denoting none and 10 very hard and objectionable settling.
1288
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I N D IJ S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
November, 1933
a. Maintained at 82' F. f27.8" C.\ b. Maintained a t i25"F.'(5
