I
D. E. WINKLER Shell Development Co., Emeryville, Calif.
New and Modified Epoxy Stabilizers Epoxides themselves are excellent stabilizers for chlorine-containing compounds used on steel. But with certain cadmium or strontium soaps, they exert a remarkable synergistic effect in most poly(viny1 chloride) compositions T H E epoxides repregent a class of compounds which are capable of reacting with hydrogen chloride and which do stabilize a variety of chlorine-containing compounds. Their effectiveness is believed to be more deep-seated than the reaction with hydrogen chloride (8). The epoxides which will be considered are: Epon 834, a condensation product of bisphenol A and epichlorohydrin; Epon 562, a glycidyl ether of glycerol; and an experimental material, poly(ally1 glycidyl ether). Epon resins are the epoxy polymers of Shell Chemical Corp. These epoxides are soluble in the resin at concentrations normally employed for stabilizers and hence can be used in clear stocks (Table I).
dibutyl tin dilaurate. After 0.5 hour the coating which contained the cadmium soap and the control without stabilizer had failed-Le., the panels were black. After 1.0 hour the coatings which contained the strontium soap and dibutyl tin dilaurate were black. After 2.0 hours all three of the panels containing the epoxide stabilizers were still clear and light colored. This is remarkable because iron is a well known catalyst for decomposing chlorinated compounds. Other chlorine-containing polymers were evaluated in a similar manner. Vinylite (VYHH) and Saran F-120 containing 20 and 10 p.h.r., respectively, of di(2-ethylhexyl) phthalate plasticizer and 5 p.h.r. of stabilizer were used to
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Table I.
Epoxide Stabilizers
Visc. ,a Name Poise 3.5-9b Epon 834 0.9-1.5 Epon 562 6 Poly(ally1 glycidyl ether) 5 2.5' C. 70% solution in butyl Carbitol.
Stabilizers for ChlorineContaining Surface Coatings One of the outstanding properties of the epoxide stabilizers is their ability to protect chlorine-containing polymers when applied as surface coatings on steel. To demonstrate this, clean steel panels were dip-coated in various resin solutions containing a small amount of plasticizer and stabilizer. One of the resins tested was a low viscosity grade of Parlon, a chlorinated natural rubber. The resin was dissolved in a methyl isobutyl ketone-xylene solvent containing 15 p.h.r. (parts per hundred of resin) of dibutyl phthalate and 5 p.h.r. of various stabilizers. After the panels were dry they were heated in an air oven at 160' C . for 0.5, 1.0, and 2.0 hours. T o ensure a uniform temperature the air in the oven was circulated at a high velocity. The stabilizers evaluated included besides the three epoxide compounds, a strontium soap, a cadmium soap, and
Color (Gardner)
Av. Mol. Wt.
100
469 319 424
5c
7
Epoxide Content Equiv./100 G . 0.35-0.44 0.61-0.71 0.72
Maximum.
coat steel panels and then aged at 160' C. as previously described but for shorter periods of time. Vinylite without stabilizer failed in 15 minutes, the cadmium soap and dibutyl tin dilaurate failed in 30 minutes, and the strontium soap and Epon 834 failed in 60 minutes. Epon 562 and poly(ally1 glycidyl ether) afforded the greatest protection. Saran F-120 without stabilizer or with cadmium soap failed in 10 minutes, The strontium soap and dibutyl tin dilaurate failed in 20 minutes, while poly(ally1 glycidyl ether) and Epon 562 failed in 30 minutes. Epon 834 offered the greatest protection. Outdoor weathering tests were run on aluminum panels coated with Vinylite of the same composition as previously described. Exposure was at Modesto, Calif., for a 60-day period beginning on March 29. All samples failed-i.e., showed severe pitting and some discoloration, except those which contained any one of the three epoxides or dibutyl tin dilaurate.
Stabilizers for Poly(viny1 Chloride) Stabilizers for the high molecular weight homopolymers of vinyl chloride, as well as copolymers of vinyl chloride and vinyl acetate of high vinyl chloride content, were considered. Many papers (3, 5-7) have been written on this subject. Emphasis here will be placed on the role which epoxides can play. Several methods have been used to measure polymer degradation-e.g., measuring the evolution of hydrogen chloride and also changes in intrinsic viscosity as a function of time at high temperatures (7) ; measuring changes in ultraviolet light transmission (4); and using both ultraviolet and infrared to determine changes in the polymer structure ( 2 ) . These measurements are fine for elucidating the processes involved in polymer degradation; however, for screening a large number of stabilizers changes which can be observed by sight and touch are sufficientfiamely, discoloration and changes in modulus or stiffness. Although stabilizers can be rated by manual inspection, an attempt has been made to remove the human element and to give numbers based on physical measurements to changes which are readily observed. Discoloration was measured by determining the extinction coefficient using light of 5000 A. Stiffness was determined using the Olsen stiffness tester which bent the sample at a constant angular velocity. Measurements of the force moment applied to the sample were made a t predetermined bending angles. Samples for testing had the following composition : Resin Di(2-ethylhexyl) phthalate Stabilizer
100 parts 50 parts 2 or 5 parts
The standard batch consisted of ,456 grams of resin, plasticizer, and stabilizer. This was milled for 15 minutes on a 6 x 12 inch roll mill with roll temperatures of 132' and 158' C. Regular tensile sheets were molded to a thickness. of 0.075 inch for 2 minutes at 160' C. Smaller samples were then cut from these molded sheets for the various tests. VOL. 5 0 , NO. 6
JUNE 1958
863
Air Aging at 160' C. Samples, 1 X 11/2 X 0.075 inch, were exposed for 1.0 and 2.0 hours in a hotpack oven with partial fresh air make-up and rapid circulation. Since many of the samples were distorted in this treatment, they were repressed at 160' C. before determining extinction coefficient (color) and stiffness (Table 11). The epoxide stabilizers are compared with cadmium and strontium stabilizers, separately, and combined, in two resin systems. Generally the epoxide compounds afford better protection than the cadmium or strontium compounds when used separately, but marked advantages, especially in color retention, are obtainable when the epoxides are used in conjunction with the cadmium or strontium compounds. For further comparison data are presented on dibutyl tin dilaurate, a recognized high-quality standard, and on tribasic lead sulfate, a typical lead stabilizer which imparts opacity. Aging in Artificial Light. An Atlas single arc Weatherometer was used without the rain cycles but under conditions of high humidity. The carbon electrodes were changed and the globes were cleaned at the end of each 17 hours of operation. Samples were exposed for 170 and 340 hours. Since relatively thick (0.075 inch) samples were used, they did not become stiff and brittle as would be the case with films. Degradation was observed by change in color and surface effects, mainly pitting (Table 111). The epoxides are fairly good light stabilizers by themselves and they are not improved by adding cadmium or strontium compounds as was the case in the heat stability tests.
Table II.
Outdoor Exposure Tests. Outdoor exposure tests were made during 3 summer months a t Modesto, Calif. Samples (2 X 2 X 0.075 inch) faced south at an angle of 45'. The exposed samples were given a numerical rating from 1 to 6 based on visual inspection (Table IV). A rating of 1 indicates no
Table 111. Effect of Stabilizers on Exposure in a Fadeometer
Extinction Coeff after 170 hr. 340 hr.
noticeable change in the surface or color of the resin when compared with the unaged portion; 2 indicates very little change-Le., one or two scattered pits; 6 indicates severe discoloration accompanied by gross surface changes. I t may be concluded that the Epons are fair light stabilizers in Geon 101 at 2 p.h.r. and become quite good a t 5 p.h.r. The combinations of Epons with cadmium or strontium compounds are also good a t the higher loading.
I
Stabilizer, 2 P.H.R.
Geon 101 None Epon 834 Epon 562 PAGE Dibutyl tin dilaurate Tribasic lead sulfate Cd soap Sr soap Epon 834-Cd soap" Epon 834-Sr soap" Epon 562-Cd soap" PAGE-Cd soapa
0.8 B P 0.4 0.5
0.7 0.3 0 ; SP 1.0 0.5 0.4 0.6 0.6 0.3
1.1 B P 0.4 0.4 0.9 0.4 0; SP 0.8 0 . 5 SP 0.4 0.3 0.5 SP 0.3
VYKW None Epon 834 Epon 562 PAGE Dibutyl tin dilaurate Cd soap Cd soap Epon 834-Cd soapa Epon 834-Sr soapa Epon 562-Cd soap"
1.2 BP 0.6 0.6 1.0 0.3 1.6SP 0.8 SP 0.6 P 1.6 P 0.7
9.2 B P 2.3 P 1.0 S P 1.4 SP 0.4 9.4BP 1.3 P 0; P 0;P 1.9 P
PAGE = poly(ally1 glycidyl ether) : SP = slightly pitted; P = pitted; BP = badly pitted; 0 = opaque. a 1p.h.r. of each.
Air Aging - - of Vinyl Compounds (160' C.)
Stiffness in Flexure, P.S.I. 1 hr. 2 hr,
Extinction Coefficient stabilizer, 2 P.H.R.
0 hr.
1 hr.
2 hr.
Epon 834 Epon 834a Epon 562 Epon 56Za PAGE PAGE" Cd soap Epon 834-Cd soap* Epon 562-Cd soapb PAGE-Cd soap* Sr soap Epon 834-Sr soap* . Dibutyl tin dilaurate Tribasic lead sulfate
0.8 1.2
2.5 3.5
0.5
1.5
1.1 0.5 0.7 0.5 0.4
1.4 3.4 0.8 5.7 0.5 0.6
3.5 4.0 2.9 1.9 5.8 1.2 0 0.6 0.7 0.7 8.6 2.0 1.2 0
0 hr.
Table IV. Effect of Stabilizers on Outdoor Exposure
Loading, P.H.R.
Stabilizer
Rating
Geon 101
None Epon 562 Epon 834 Sr soap Cd soap Dibutyl tin dilaurate Tribasic lead sulfate Sr soap Epon 834 Epon 834-Sr soapa Epon 834-Cd soapa
VYNW None Epon 562 Epon 834 Cd soap Cd soap Dibutyl tin dilaurate Sr soap Epon 834-Sr soapa Epon 834-Cd soapa 2.5
... 2 2 2 2 2 2 5
5 5 5
6 3 3 6 2 1 5 5 2 2 2
... 2 2 2 2 2 5 5 5
p.h.r. of each
I n VYSW the above combinations are far superior to any of the components used separately and approach the effectiveness of tin stabilizers in protecting this resin against degradation by sunlight.
Gem 101
0.5
0.4 0.9 0.5 0.4 0
0.5 3.3 1.1 0.7 0
1700 1500 1600 1270 1450 1140 1760 1860 1350 1810 1590 1790 1530 1950
1650 1980 2530 2100 2700 1780 3950 2900 2690 2760 2740 2570 3200 1900
4020 3200 7000 5900 8350 3290 7500 3650 6900 9000 8200 3850 8500 1980
Literature Cited
1360 1230 1330 1430 1220 1500 1500
1780 2200 2500 2620 1440 2000 1540
4210 4100 9400 8500 2290 3500 2970
(1955). (8) W;nkIe;, D. E., 132nd Meeting, ACS
VYKW 2.1 1.3 2.9 1.6 2.4 1.3 0 0 0 2.2 0.5 0 0.8 3.0 0.8 1.5 1.6 PAGE = poIy(aIIy1 glycidyl ether); 0 = opaque.
Epon 834 Epon 562 PAGE Cd soap Epon 834-Cd soap* Sr soao Epon S34-Sr soap* a
5 p.h.r.
864
0.6 0.8 0.8 0.6
1 p.h.r. of each.
INDUSTRIAL AND ENGINEERING CHEMISTRY
(3) Mack, G. P., Modern Plastics 31, No. 3 , 150 11953). Scarbobgh, L., Kellner, W. L., Rizzo, P. W., Ibid., 29, No. 9, 111 (1952). Smith, H. V., Brit. Plastics 29, No. IO, 373 (1956). Swern, D., Paint Varnish Production 46,No. 6, 29 (1956). Vennels, W. G., Plastics (London) 20, 93 New York, September 1957. RECEIVED for review September 20, 1957 ACCEPTED March 10, 1958 Division of Paint, Plastics, and Printing Ink Chemistry, Epoxy Plasticizers-Stabilizers Symposium, 132nd Meeting, ACS, New York, September 1957.
