.
Quantitative Thinning of Hot Varnishes APPARATUS AND PROCEDURE A quantitative study of the thinning step in varnish manufacture on plant-size batches is difficult because of the practical impossibility of controlling all essential factors within the desired limits. Laboratory studies of the relative merits of various solvents available for the thinning of varnishes have been greatly handicapped by the lack of suitable equipment and procedures. In the past investigators have resorted to studies of cold cuts in an effort to obtain some indications of the properties of various varnish solvents. This procedure, however, differs so widely from actual practice that the practical significance of the results obtained may be very uncertain. A quantitative laboratory procedure simulating plant conditions is sorely needed. Such a method and the necessary apparatus have been developed and are described in some detail.
W. P. COLIO, N. T. PHELPS, W. T. HARVEY, S. S. KURTZ, JR., AND COOPERATORS1 Philadelphia Paint and Varnish Production Club, Philadelphia, Penna.
the customary manner. When the cook is finished, the whole batch of base is poured into a sampling pot (Figure l), equipped with a ball valve and four nozzles. The ball valve is lifted and a predetermined volume of varnish allowed to flow into each of four beakers. The weight of the sample is determined, and the beakers are placed on a dilution apparatus (Figure 2) having stirring paddles and reflux con1 Those cooperating were GI. R. Henry, J. C. Moore, E. C. Hainen, J. C. Whiteway, Jr., A. Skett. X.Kreah. E. 8. Esposito, E. H. MoArdle, and E. L. Baldesohwieler.
HE study of the relative merits of various Solvent6available for the thinning of varnishes has been complicated the fact that (a) uniform sampling is difficult owing to continued bodying while sampling and (a) in commercial practice varnishes are thinned while still at 400-500° F., with a solvent having a 400410” F. end point. I n the plant it is not easy to cook and thin two batches of varnish so that they are identical, even when the same solvent is used. Comparison of solvents on the basis of thinning plant batches is expensive and is uncertain unless many batches are involved. Small differencm in cooking of the varnish can affect the varnish viscosity as much or more than the differences in the solvent used for thinning. In laboratory studies of the dispersion of resins and varnishes, considerable work has been done with cold cuts of resins and varnishes (f-8). These studies have already raised the question, “Would the same conclusions have been obtained if the varnishes had been thinned hot, in accordance with commercial practice?” The present work was undertaken to provide a procedure for the study of varnish thinning which would make it possible to thin varnishes quantitatively while still hot. In order that the only variable should be the solvent, it was also necessary that the procedure should make it possible to thin simultaneously several portions of the same batch of varnish. The procedure developed involves cooking 0.75 to 1 gallon of varnish base in a 1- or %gallon laboratory varnish kettle in 1413
L > tr) *
- - 6 - A9 2 SALE IN INCHES
FIGURE 1. Two VIEWS OF
THI
SAMPLING POT
1414
VOl. 33, No. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
densers. Solvent is added to each mix gradually and simultaneously. Two thinning procedures have been developed, depending on whether or not it is desired to obtain a quantitative check on the amount of solvent lost by evaporation. The details of these procedures follow.
TABLE I. TESTOF DILUTION APPARATUS TO SHOW UNIFORMITY OF FOURDILUTIONS OF AN ESTERGUM VARNISH^ PREPARED SIWJLTANEOUSLY Wt. % Nonvolatile
Dilution No.
BY A, S. T. M.
Rapid Method for Dilution of Varnish
Intended 50 50 50 50 50
1 2 3 4
Approximately 0.75 gallon of varnish is cooked in a laboratory varnish kettle of 1- to 2-gallon capacity. When the varnish is finished, it is poured immediately into the dividing pot (Figure 1). The ball valve is lifted long enough to allow approximately 200 grams of hot varnish solids to flow into each of four one-liter-tall form Pyrex beakers (Pyrex Catalog No. 1040) which have previously been weighed to 0.1 gram on an accurate pan balance (Arthur H. Thomas Company's No. 1907 or the equivalent), The beaker and hot varnish are weighed to the nearest 0.1 gram and placed on the mixing apparatus. When all four beakers have been weighed and put on the apparatus, a few small pieces of ice are added to the water in the condenser cups and the stirrer drive is started. Before the varnish is cooked, 75 per cent of the anticipated quantity of spirits needed for each mix is weighed out in a one-quart narrow-mouth bottle marked with its tare weight. The whole anticipated amount of spirits is not weighed out in advance, since it is easy to run out from the sampling pot 10 per cent more or 10 per cent less varnish base than was intended. The 75 per cent of spirits weighed out in advance may turn out to be 65 or 85 per cent of the spirits actually needed.
method D-154-38 49.5 49.4 49.5 49.3 49.4
Viscosity
Specific Gravity b
Fenske, oentistokes 189 192 190 194 191
GardnerHoldt
G
0.888 0.888 0.858
G G
G
0.888
+ '/&B 4-'/4B + 1/4B
Av. Av. *o. 1 deviation 30-gallon oil length: tung oil 20,linseed 10. b Determined with long hydrometer and correoted t o dz6.
a3
(1
poured into the bottle in which the spirits was weighed out. The bottle is tightly corked and shaken to ensure mixing of the small amount of fipirits which did not drain out of the bottle in the mixing operation. The weights (in grams) which must be taken for each mix are as follows: A = weight of beaker B = weight of beaker unthinned varnish C = weight of unthinned varnish = B A D = total weight of final mix = wt. of unthinned varnish/ % solids in final mix E total weight of spirits t o add, D - C F = weight of empty-bottle G = weight of bottle approx. 75% of spirits
+
-
E
+
i
I
I
c
I
.523/e" 0
3
6
9
1
2
SCALE IN INCHES
FIGURE 2. DILUTION APPARATUS
The spirits for each of four mixes is added gradually, and as nearly as possible simultaneously, through the funnels. When the initial quantity of spirits has been added, a new tare weight is obtained on each bottle, and additional spirits is weighed in to give the correct concentration based on the actual weight of varnish in the beaker. After the final increment of spirits has been added, the thinned varnish is
H
= weight of approx. 75% of spirits weighed out in advance
zgkt
$K z= weight $ ~ ~ ~ ~ i ~ c ~ ofm ~e n of bottle + final increment of spirits = J + I
This procedure involves six determined weights and is suitable for routine use, but does not give a direct quantitative check on the evaporation loss, if any.
t
~
INDUSTRIAL AND ENGINEERING CHEMISTRY
November, 1941
Complete Method When a Quantitative Figure fox Evaporation Loss Is Needed The complete dilution procedure is carried out in exactly the same manner as the rapid procedure until 80 to 85 per cent of the spirits actually needed has been added. The remaining 15 to 20 per cent of spirits is reserved for rinsing. Solvent addition is stopped after approximately 85 per cent of the total spirits has been added and stirring continued until the varnish is well mixed and cooled nearly to room temperature. The beakers are then lowered, and the varnish is allowed
1415
suitable when we desire to determine and adjust for vaporization loss. The precision obtainable with the rapid procedure is shown in Tables I and 11. When using one batch of varnish and one solvent, four simultaneous dilutions of equal concentration and viscosity can be prepared (Table I). The concentrations agree within *O.l per cent. The viscosities checked within bubble by the Gardner method and within 1.5 per cent by precise kinematic measurements. Table I1 gives data for six varnishes thinned with four spirits. The deviation of any synthetic resin is 0.1 per cent. Accordingjo
~~
TABLE 11. WEIQHTPERCENTNONVOLATILB IN VARNISHES PREPARED BY RAPID DILUTION PROCEDURE Resin
Super Beokacite 1001 ester gum 25 Dehydrated oastor 75.2
Amberol F-7
+
Oil length, gal. Oil Wt. % of solids Av. in 4 solvents (A. 8. T. M. procedure) % deviation from av. Solvent A para5nio) Solvent B naphthenic) Solvent C aromatic solvept p intermediate) AI. deviation Max. deviation
Amberol 801
Ester gum
25 Dehydrated oastor
10 Tung 50 bodied 1insee)d 50
25 Tung 72, bodied linseed 28
15 Dehydrated castor
15 Dehydrated castor
76.4
75.4
75.7
74.7
74.8
0.0 0.0 0.0
-0.1 0.0 -0.1
0.0
+o. 1
-0.9 +0.7 +0.9 -0.6 0.70 0.90
I
0
-0.1 0.02 0.1
0.0 0.05 0.1
0.0
0.0 -0.1 0.02 0.1
Batu
-0.0 +0.4 +0.2 0.3" 0.0"
Congo
The higher percentage variation in the case of these Varnishes waL) at least partially caused by the presence of some insoluble material.
to drain from the stirrers. The stirrers are cleaned with a spatula, and both the spatula and stirrers are rinsed with the remaining spirits. The evaporation loss is now computed on the basis of the following data:
L = weight of beaker + unthinned varnish + spirits M - weight of unthinned varnish + spirits (L- A ) N = weight of bottle and residual spirits o = weight of spirits added (G - J ) + (K - N)
+
+
P = theoretical weight of unthinned varnish spirits = C 0 & = loss of spirits and varnish = P - M (if stirring apparatus and spatula are well rinsed, this will represent vaporization loss only, and in any case represents maxim possible vaporization loss) R = % vaporization of spirits = (&/0)100 spirits to obtain desired concentration, D - M or s = D +added A - L S = T = final wei ht of beaker varnish spirits = L D+fz;
+
+
+
Then adjust beaker to weight T on balance. This complete procedure involves nine determined weights and is more time consuming than the first procedure, but is
Table 111,vaporization losses by the complete dilution method are only about 0.7 per cent by weight, and the viscosities of the varnishes thinned by both procedures check. The data of Tables I, 11, and I11 show that the apparatus (working drawings for the construction of this apparatus can be obtained from the Philadelphia Paint and Varnish Production Club) and procedure described in this paper are adequate for the simultaneous and quantitative dilution of varnishes to obtain thinned varnishes of equal concentration. This procedure eliminates many of the uncertainties inherent in the older methods of preparing varnish dispersions in connection with the study of solvents.
Acknowledgment This work was carried out under the auspices of the Mineral Spirits Committee of the Philadelphia Paint and Varnish Production Club. The committee is indebted to the Sun Oil Company for the construction and initial testing of the equipment.
Literature Cited DeGray, R. J., and Easer, A. J., IND.ENQ. C H ~ M .33, , 525 (1941).
Huff, R. H., et al., Paint, Oil. Chem. Rev.,
TABLE 111. COMPARISON OF RAPIDAND COMPLETE DILUTION PROCEDURE^
Varnish Batch No. 1 2
Method of Dilution Complete (No. 2) Rapid (No. 1) Complete N o 2 Rapid h o : 11
Wt. % Loss of Solventb 0.75
Kinematie Viscosity Centistokeso 173 178
0.7
145 146
... ...
Ester gum varnish IO-gallon oil len th spirits D 50% nonvolatile. Average of two dederminations whic%check withk -0.1. Determined with Fenske-type recision visoometer Eaoh viscosity is average of two dilutions for which &e viscosities check 'within 2%. a
b
101, No. 3, 90-4, 96-8 (1939). Huff, R. H., et al., meeting of Federation of Paint and Varnish Production Clubs, Oot., 1940. Kurtz, S. S., Jr., Harvey, W. T., and Lipkin, M. R., IND.ENQ. CHQM.,ANAL.ED., 11, 476 (1939). McArdle, E. H., Mool'e, J. C., Terrell, H. D., Haines, E. C., and cooaerators. Ibid.. 11. 248 (1939). Mantill, C. L., and Skett, A., IND. ENQ. CHEM.,30, 417-22 (1938). Philadelphia Paint and Varnish Production Club, Natl. Paint, Varnish Lacgusr Assoc., Sei. Sect., Circ. 568 (1938). Ware, V. W., and Teeters, W. O., IND. ENQ.CHEM.,31, 738 (1939).
e
PRSSH~NTRD before the Division of Paint, Varnish, and Plastics Chemistry at the 102nd Meeting of the Amerioan Chemical Sooiety, Atlantic City, N. J.
