during cross linking by ultraviolet radiation than by high energy electrons. Other Fluorine-Containing Polymers
S e t degradation occurred when T F E resin and poly(ch1orotrifluoroethylene) were irradiated in a nitrogen atmosphere at 250” C. with high energy electrons. This behavior parallels that when these resins are irradiated at room temperature. However, there are indications that the rate of degradation of’ T F E resin is reduced. The importance of environment on the degradation of T F E resin by high energy radiation has also been demonstrated by Wall and Florin ( 8 ) . who reported that less degradation occurs in the absence of oxygen than in air. Exposure of T F E resins at 315” to 328” C. and poly(ch1orotrifluoroethylene) at 250” C. to ultraviolet radiation in an atmosphere of nitrogen also did not produce net cross linking. Minor degradation of the T F E resin was noted, while the poly(chlorotrifluoroethy1ene) degraded appreciably. Obviously. in end use applications the effects of ultraviolet radiation at elevated temperatures can be mitigated by use of light weight opacifying agents and/or ultraviolet screens, a mode of protection not so readily applicable to high energy electrons. Conclusions
FEP resin cross-links when exposed above its glass I transition temperature to high energy radiation. With doses greater than 2.6 Mrads, ultimate elongation and resistance to deformation under load a t elevated temperatures are improved, and the yield stress is increased. The improvements are accompanied by some loss in toughness. When irradiated less than 0.9 Mrad, FEP resin retains its flow characteristics at high
stresses, while at lower stresses there is an advantageous decrease in flow rate. T F E resin and poly(chlorotrifluoroethy1ene) degrade \vhen exposed to high energy radiation at elevated temperatures, although in the T F E resin the rate of degradation may be decreased from that observed at room temperature. FEP resin is also cross-linked by ultraviolet radiation at elevated temperatures, while T F E resin is slightly degraded and poly(chlorotrifluoroethy1ene) is extensively degraded. Acknowledgment
The authors express their gratitude to T. R. \Vallingford for assistance in irradiating and evaluating the polymer compositions. literature Cited
(1) Bovey, F. A., “The Effects of Ionizing Radiation on Natural and Synthetic High Polymers,” pp. 151 ff., Interscience, New York, 1958. (2) Florin, R. E., Wall, L. A., Division of Polymer Chemistry, 134th Meeting, ACS, Chicago, Ill., September 1958. (3) Florin, R. E., Wall, L. A., J . Research Natl. Bur. Standards 65A, 375 (1961). (4) Larsen, H. A., DeHoff, G. R., Todd, N. W., Modern Plastics 36,89 (1959). (5) McCrum, N. G., Makromol. Chem. 34, 50 (1959). (6) Mallouk, R. S., Siegle, J. C., Straw, H. S., “Properties of a Copolymer of Tetrafluoroethylene and Hexafluoropropylene. Comparison with Other Fluorine-Containing Polymers,” Am. SOC. Mech. Em.. December 1957. (7) Mallouk, R. S., Thompson, W. B., Jr., Materials in Design Eng. 47, 171 (1958). ( 8 ) Wall, L. A,, Florin, R. E., J . Appl. Polymer Sci.2, 251 (1959). RECEIVED for review January 22, 1962 ACCEPTED April 9, 1962 Division of Industrial and Engineering Chemistry, 140th Meeting, ACS, Chicago, Ill., September 1961.
RIGID URETHANE FOAMS DERIVED FROM CRUDE TALL OIL P. G . G E M E I N H A R D T , W. C. D A R R , A N D J.
H. SAUNDERS
Mobay Chemical Co., New Martiwville, W . Va.
Rigid urethane foams have been prepared from crude diphenylmethane diisocyanate and resin blends containing up to 75% of crude tall oil. These foams have properties close to those obtained from the more familiar rigid foams derived from tolylene diisocyanate and polyethers, but are significantly cheaper. Some variations have been encountered with regard to the closed cell content and shrinkage, which must be overcome before the system is suitable for commercial foaming. Research designed to correct these deficiencies is under way.
HE
commercial development and growth of flexible ure-
Tthane foams are unprecedented in this country ( 8 ) . I n a
short span of 6 years flexible foams have become a mainstay for the automotive engineer, the furniture upholsterer, and the textile manufacturer. In addition, flexible foams are making rapid gains in a variety of other applications, many of which have not previously been satisfied by cellular materials. 92
l & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
Rigid urethane foams which are chemically similar to flexibles have not developed so phenomenally. Although rigid foams have unique and outstanding physical characterreason for the rapid acceptance of flexiblesistics (5, &‘-a high costs have retarded their wide scale acceptance and use. Previous research in the industry has led to the development and use of less expensive foaming techniques involving low
boiling, chemically inert blowing agents-e.g., trichloromonofluoromethane (9) and the low-cost polyether resins (6). An additional cost-saving step has now been realized. Crude tall oil, a “tonnage” chemical in terms of price quotations, has been used in amounts up to 38% by weight of the final polymer for the preparation of low-density rigid urethane foams. The saving in foam raw material cost is significant.
Experimental Raw Materials. The work described involved crude tall oil, a material not previously used in urethane foams, and a crude form of @,@I-diphenylmethanediisocyanate. C r u d e Tall Oil. Tall oil is a natural product obtained as a residue from the alkaline or sulfate process of wood pulp manufacture (7). The primary source of this material is the soft resinous-type woods, such as pine and fir, which are used for kraft paper. T h e tall oil is produced by acidifying the black liquor skimmings which are separated from the fiber after the digestion step of the kraft paper process. I t is composed primarily of a mixture of rosin acids related to abietic acid and of fatty acids related to oleic acid, as well as other nonacidic materials. This material has long interested the chemical industry because of its very low cost and its chemical activity through the carboxylic groups and unsaturation of the various components. Table I lists the range of properties which might be expected from crude tall oil from various sources and areas. The crude tall oil can be used as is for certain chemical applications, burned for its fuel value, or purified to obtain the more valuable rosin and fatty acids. T h e crude material, as well as certain purified fractions of tall oil, has been used to produce rigid foams; however, a “synthetic” crude designated as Emtall 672-65 (Emery Industries, special crude tall oil) is the most successful product tested so far. The physical properties of this product are also given in Table I . The major active components of tall oil are: Abietic (I) and related acids (11) which have the empirical formula Cl,Hz,COOH. CH? COOH
CHa
COOH
Table II.
Physical Properties of Crude p,p’-Diphenylmethane Diisocyanate
Boiling pt., initial, 1 mm. Hg, Freezing pt., ’ C. Specific gravity, 20” C. Viscositv. CDS.. 25” C. Assay, % NCO, % Hydrolyzable chloride, % Total chloride, % ’ Solids content, yo Table 111.
C.
O
170 8 1.25 50-60 .4pprox. 88-90 Approx. 30-31 Approx. 0 . 2 Approx. 0 . 2 Approx. 1 .O
Typical Formulations for Rigid Foam from Crude Tall Oil
(Parts by weight) 1 2 3 Recipe 75 75 75 Crude tall oil 25 25 25 Ouadrol“ Mondur E-1 72 70 70 70 Refrigerant 11 25 15 5 1 Silicone stabilizer L-520b 1 1 100 100 Index number 100
4 75 25
70
70
80
_.
1
100
5
25
6 65 35 90 25
1 100
1 100
30
a Wyandotte Chemical Co. .47,.\r,A!J’.V’Tetrakis (2-hydroxypropyl)ethylenediamine. Union Carbide.
Oleic acid (111), which has the empirical formula C18H3402, and related acids (IV and V). 111. CH~(CHZ)~CH=CH(CH~)&OOH. Oleic acid IV. CH,(CHJ ~CH=CHCHZCH=CH(CH~);COOH. Linoleic acid V. CHICH~CH=CHCH~CH=CHCH~CH=CH(CH~)~C O O H . Linolenic acid The nonacid materials, which may be alcohols, hydrocarbons, or esters of the alcohols and the various acids, will vary, depending on source and treatment of the raw tall oil. C r u d e p,p’-Diphenylmethane Diisocyanate. Crude p,p’diphenylmethane diisocyanate, designated developmentally as Mondur E-172 (Mobay Chemical Co.), is composed chiefly of the diisocyanate (VI) but also contains a polyisocyanate (VII).
OC N-- D - C H VI
OCN-0-C 1
-
-
~
~
AH-O-SCO Abietic Acid I
Pimaric .4cid I1
VI1
Typical Properties of Crude Tall Oil Emtall Property General Range 672-65
Table I.
Density .4cid number Saponification number Iodine number .4sh,, % Moisture, % Material insoluble in pet. ether,
%
Fatty acids, % Rosin acids, % Nonacid bodies, % ._ Viscosity, cps. 25” C. 18’ C. l o o o c. Color, Gardner
0.95-1.024 107-174 142-185 135-2 16 0.4-4.62 0.39-7.2 0.1-8.5 18-60 28-65 5-24
... 130-i 50 ... ,.. , . .
48-62 20-30 16-25
150-1 200
...
13
The crude diisocyanate is a dark-colored liquid containing a small amount of finely suspended solid believed to be dimer. The most important physical properties of the diisocyanate are summarized in Table 11. Since the crude diisocyanate is subject to freezing a t 8’ C. or below, care was exercised in its storage. When freezing occurred, the diisocyanate was reliquefied by heating to about 65’ C. for a time depending on the volume of the material frozen. Heating for several hours (4 to 5) a t the suggested temperature did not affect the activity of the diisocyanate. Storage for long periods above about 40’ C. was avoided, to limit the formation of additional insoluble solid material. Foaming. Rigid foams were prepared from a select mixture of crude tall oil, crude p,p ’-diphenylmethane diisocyanate, certain nitrogen-based polyols, trichloromonofluoromethane, and foaming stabilizer. Some typical brmulations are shown in Table 111. VOL.
1
NO. 2
JUNE 1 9 6 2
93
Free-rise foaming of the formulations given in Table 111 was straightforward on the Mobay M F (stationary head) foam machine (4) under the following machine conditions (Table
IV). The handling of the foaming ingredients presented no particular problem. A separate catalyst was not found necessary, since the Quadrol promoted foaming. In practice. when foaming on the machine, the system was divided into two components. One of the components was the resin mixture formed by combining the crude tall oil, Quadrol, Refrigerant 11, and L-520 and was fed to the mixing head of the foam machine by gear pump. When preparing this mixture it was found convenient first to mix the crude tall oil and Quadrol. Slight exotherm to about 40' to 45' C. resulted from this mixture, due to the acid and base character of the two chemicals. The age of this mixture did not appear to affect the foaming. A mixture 1 hour old and a mixture aged 2 months were used for foaming with no apparent differences in foaming characteristics. Also, the viscosities of three different mixtures of crude tall oil and Quadrol were followed over a 3-month period. The initial viscosities, measured with a Brookfield viscometer a t 25' C., were 22,400 cps. for the 75% tall oi1-25% Quadrol blend, 33,600 cps. for the 70/30 blend, and 40,000 cps. for the 65/35 blend. These values did not change significantly during a 3-month storage period. The mixture was completed by then adding the L-520 and Refrigerant 11. Best control of fine cell size was obta'ned when this complete resin mixture was used fresh. Somewhat coarser cells were formed when the complete resin mixture had aged several hours, but the properties of the foam appeared unaffected. The viscosities of the complete resin mixture for recipes 1, 5, and 6 (Table 111) were 3700, 3900, and 4100 cps., respectively. Mondur E-172, the second component, was metered to the mix head by a Bosch fuel injection pump. One outstanding feature of the use of Mondur E-172 is its low vapor pressure. which results in essentially no fumes and consequently no odor. Thus the degree of exposure to irritating fumes when foaming is much reduced. The two components (resin mixture and E-172) on mixing formed a very fluid prefoam mixture facilitating the filling of complicated shapes. The foaming characteristics for the recipes given in Table 111 are summarized in Table V. A very short time after mixing, the foaming began and continued in a very stable manner. Foaming exotherm temperatures, as might be expected, were lower than those of typical one-shot polyether fluorocarbon blown foams. The rise in exotherm for three different ratios of crude tall oil and Quadrol foamed according to recipes 1, 5, and 6 (Table 111) are shown in Figure 1. Testing. Whenever possible, testing was effectvd according to ASTM methods (2). Thus density (ASTM D 1622-59T), tensile strength (ASTM D 1623-59T), compression strength, and compression modulus (ASTM D 1621-59T) were measured by standard procedures. The per cent closed cells was determined by the gas volume displacement method on equipment manufactured by Ace Glassware, Inc. (7). The K factor was obtained using the heat line source method (DowCorning probe manufactured by Custom Scientific Co.) ( 3 ) . Retention of K was determined at regular intervals by remeasuring K after a period of aging under normal room temperature conditions of 23' C. and 50% relative humidity. Dimensional stability was measured as a change in volume of a specimen having initial dimensions of 4 inches square by 1 inch 94
l & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
-
120 I
c
ci 100
1
d
E
80
I-
:
60
w
I
40 W
2o
t
01 0
I
I
5
IO
I
I
I
30
35
I
I
20 25 TIME, min.
IS
I 40
Figure 1, Exotherms of rigid foam systems using tall oilQuadrol ratios shown
thick, after aging for extended periods of time under the follow ing conditions: 100' C. and ambient humidity, 70' C. and 95 to 100% relative humidity, and -40' C. and ambient humidity. Dimensional stability was also noted for foams aged under normal room temperature and humidity conditions, Water absorption as given in grams of water absorbed per cubic inch of foam was measured by submerging a 4 X 4 X 1 inch foam specimen under 1 inch of water for 24 hours. Results. Rigid foams having 85 to 95% closed cells with low thermal conductivity and excellent dimensional stability under a variety of accelerated aging conditions were prepared from the select mixtures containing crude tall oil. In Table V I are summarized physical properties for foams containing different amounts of crude tall oil (38, 34, and 30% by weight of the total polymer) which were prepared according to recipes 1, 5, and 6 (Table 111), a t a density of about 2 pounds per cubic foot. These data show that these foams, containing large amounts of what one would presume to be an undesirable foam constituent, have promise for low temperature insulation and other applications. If an application demands greater foam strength,
Table IV.
Machine Conditions for Preparing Rigid Foam from Crude Tall Oil
Machine type R a i n rate, g.p.m. Resin temp., O C. Isocyanate temp., ' C. Agitator type Agitator speed, r.p.m. Mixer sizes. mm. Diameter Length Nozzle orifice, diamrter, mm. Nozzle extension, length, mm.
Table V.
MF (stationary mixer) 3800 22-24 22-24 Low shear (pin-type) rotor 6000 50 100 24 100
Foaming Characteristics for Rigid Foam from Crude Tall Oil
Recipe Cream time, sec. Rise time, sec. Tack-free time, sec. Max. exotherm, C.
1 1
2 0 65
3
5 6 6 6 90 80 100 85 75 120 90 120 120 120 90 90- 110- 105- 110- 100- 110110 120 115 120 120 120 6
4
5
5
m lo'
.-
'i
H.
d
-
a 3001 iv)
0' 2 0 0 -
I 0 u
100 01
I
2
4
6
I
*-COMP.
MOD.
- 2
A-COMP.
STR.
- io3
I
I
I
,
I
8 IO 12 14 16 FOAM DENSITY, p.c.f.
I
I
18
I
20
Figure 2. Relations among foam density, compressive modulus, and compressive strength Foams prepared from 7 5 / 2 5 ratio of tall oil to Quadrol
merely increasing the density by reducing the amount of blowing agent will result in stronger foam. This is shown in Figure 2 for foams prepared with a 75/25 ratio of crude tall oil and Quadrol. respectively, and varying amounts of Refrigerant 11.
Discussion
A break-through in the cost of rigid urethane foam has been achieved by the use of crude tall oil priced a t about $50 per ton as a major foam ingredient. The investigation of crude tall oil is far from complete, however. Many interesting phenomena which have been observed since this work began require further study. Chief of these is the inconsistency of dimensional stability which has occurred with some foams when stored under room temperature conditions. The shrinkage in these cases developed very slowly, so that several weeks elapsed before the distortion became noticeable. The amount of crude tall oil in the foam appears to influence the room temperature stability. I n Table V I it is shown that foams from the 75/25 resin ratio are more prone to undergo this secondary shrinkage than are those from 65/35 or 70130 ratios. Also there has been indication that a slight excess (5%) of the E-172 is helpful in making the foam more dimensionally stable under this mild storage condition. So far the use of tolylene diisocyanate (Mondur TD-80, 80/20 ratio of 2,4 and 2,6 isomers) in place of E-172 for the preparation of closed cell rigid foams has been unsuccessful. When TD-80 was substituted for the E-172 in the recipes shown in Table 111, the foams were dimensionally unstable, resulting in severe shrinkage within a n hour from preparation. Neither have conventional polyether resins containing no tertiary nitrogen been successfully substituted for the Quadrol. When such substitution was made, even with greater amounts of the conventional polyol, the closed cell content of the foam was seriously affected and foam having predominantly open cells was produced. Examples of formulations that have produced foam having greater than 95% open cells are given in Table V I I . The open cell foams resulting from these formulations exhibited high K factor (0.25) and excellent dimensional stability, and absorbed large amounts of water that flowed right through it. Although the work described thus far involved free rise foaming, the moldability of the system is being investigated. Molded panels measuring 24 X 24 X 1 to 3 inches have been prepared
Table VI.
Physical Properties of Rigid Foams from Crude Tall Oil
Recipe 1 5 6 Crude tall oil, % by weight of total polvmer 38 30 34 Density, lb./&. ft. 2.2 2.2 2.0 Tensile strength, p.s.i. 25-35 25-35 25-30 Comp. strength at yield, psi. 15-20 15-20 20-25 Comp. modulus, p.s.i. 300-400 350-450 400-500 Closed cells, % 85-95 85-95 85-95 K factor, B.t.u./hr. sq. ft., O F./inch, 23' C., 50% R.H. Initial 0.13-0.14 0.13-0.14 0.14-0.15 After 50 days 0.14-0.15 0.14-0.15 0 . 1 5 4 . 1 6 Dimensional stability, vol. change, % 100' C., ambient humidity 2 weeks 5-10 5-10 5-1 0 4 weeks (-5)-10 (-7)-10 5-1 5 70' C., 95-100% R.H. 2 weeks 0-5 0-1 0 0-1 0 4 weeks (-5)-5 5-1 5 5-1 5 Ambient temp. and humidity, vol. change, yo 1 week 0-20 0-1 0 0-5 0-1 0 24 weeks 0-40 0-20 -40' C . , ambient humidity, length change, % 3 weeks 0 0 0 Water absorption, g./cu. inch 0.5-0.8 0.5-1.0 0.5-1.0 55-70 Cell size, cell/inch 55-70 55-70 Cell uniformity Excellent Excellent Good
Table VII.
Formulation for Open Cell Rigid Foam from Crude Tall Oil
Recipe Crude tall oil, parts by weight Selectrofoam 6402a Mondur E-1 72 Mondur TD-80 Refrigerant 11 Silicone stabilizer L-520 Catalyst C-lbb Catalyst T-9C Index number a Pittsburgh Plate Glass Co. lyst, Metal and Thermit Co.
Table VIII.
7 50 50 76 ... 32
1 .o
1.5 0.2 100
...
47 32
1 .o
1.5 0.2 100
Catalyst, Mobay Chemical Co.
Cata-
Recipe for Molded Rigid Foam from Crude Tall Oil
Recipe Crude tall oil, parts by weight Quadrol Mondur E-1 72 Refrigerant 11 Silicone stabilizer
Table IX.
8 50 50
9 75 25 70 35 1
Physical Properties of Molded Rigid Foam from Crude Tall Oil
Density, lb./cu. ft., core Comp. str., p.s.i. at yield K factor, initial, B.t.u./hr., sq. ft., ' F./inch Closed cells, %
VOL 1
2.1 15 0.126 87
NO. 2
JUNE 1 9 6 2
95
according to the formulation of Table V I I I . Best results were obtained when the mold was preheated to 130’ to 140’ F. The panels foamed between polyethylene sheeting for effecting release had core densities of about 2 pounds per cubic foot and have been characterized by small uniform cell structure throughout the foam core. Of particular note has been the relatively uniform cell structure adjacent to the foam-mold interface through the height of the panel. Physical properties of molded foam using recipe 9 are summarized in Table I X . The work reported herein is very new and in certain respects incomplete ; however, considerable effort is being extended to improve foams and reduce the cost of this type of foam system. Acknowledgment
The authors are grateful for the physical testing conducted by the Physical Testing Group during the course of this work under the direction of Samuel Steingiser and Harold Staley
and for the assistance of C. D. Ferrell and J. L. Wharton in carrying out the experiments. literature Cited (1) Agnello, L. A., Barnes, E. O., Ind. Eng. Chem. 59, 726 (i960). (2) Am. SOC. Testing Materials, Philadelphia, Pa., ASTM
Standards,” 1961. (3) D’Eustachio, D., Schreiner, R. E., A m . Soc. Heating Ventilating Engrs. Trans. 58, 331 (1952). (4) Hoppe, R., tveinbrenner, E., Muhlhauser, C., Breer, K. (to Farbenfabriken Bayer), U. S. Patent 2,764,565 (Sept. 25, 1956). 15) Khawam. A,. Plastics Technol. 5 . No. 6, 31-35 and 50 (1959). ( 6 ) LeBras, L. R.’, S.P.E. Journal 16; 420 (1960). (7) Remington, FV. J., Pariser, R., Rubber World 138, 261 (1958). (8) Rill, J. C., Div. of Chemical Marketing Economics, 139th Meeting, ACS, St. Louis, March 1961. (9) Rill, J. C., Kesling, K. K. (to General Motors Corp.), U. S. Patent 2,962,183 (Nov. 29: 1960). RECEIVED for review October 5, 1961 ACCEPTED February 26, 1962 Division of Organic Coatings and Plastics Chemistry, 140th Meeting, ACS, Chicago, Ill., September 1961. ~I
A R S E N I C PENTOXIDE C U R E OF A N ORGANIC A D H E S I V E f l e w Route to Semi-inorganic Adhesive Polymers HAROLD H . LEVlNE Narmco Research and Development, A Division of Telecomputing Corp., San Diego, Calif.
The reaction of arsenic pentoxide with an epoxy novolak-silicone-phenolic resin system was investigated. The epoxy novolak was polymerized to a polyether, while the silicone-phenolic resin reacted to form a polymer containing Si-O-As+5 linkages. This study points to a new route to semi-inorganic, heat-stable polymers b y reaction of heat-resistant organic polymers with selected inorganic reagents. It may b e possible to avoid difficulties in semi-inorganic polymer synthesis, such as low molecular weight due to insolubilily and hydrolytic instability. Improved adhesive and sealant systems use arsenic trisulfide as the curing agent. HE major obstacle to achieving a heat-stable adhesive is Toxidation sensitivity. Even at 538’ C. (1000’ F.) the thermal energy input is far below the 80 kcal. per mole required to rupture a carbon-carbon bond. Oxidative degradation of an adhesive is even more severe on stainlesssteel than on aluminum, probably because of iron present in the steel ( 5 ) (Figure 1). This company attempted to find a means of reducing oxidation of adhesives. If some substance could be added to the adhesive which would either act as a catalytic poison or insolubilize iron ions migrating into the adhesive, deterioration of the adhesive would be curtailed or eliminated. The use of arsenic pentoxide was suggested because arsenic compounds were known to act as catalyst inhibitors and because iron arsenate is a n insoluble salt. Effective removal of iron ions from the system was observed in trial experiments. Further work (9) provided the first adhesive containing an arsenic compound in its formulation (Figures 2 and 3). The arsenic pentoxide became an integral part of the adhesive,
96
I & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
because it was the sole curing agent. Optimum high temperature tensile shear strength was obtained at an arsenic pentoxide concentration of 32 parts per hundred parts of total resin. The most interesting assumption made about this adhesive was : If the arsenic pentoxide was becoming a part of the polymer, this might result in the formation of a semi-inorganic adhesive polymer. Experimental
In addition to arsenic pentoxide, the adhesive consisted of an epoxy novolak, a silicone-phenolic resin synthesized by condensation of bisphenol A with a poly(ethoxyphenylsi1oxane), and aluminum powder. Model compounds were selected to study reactions of the various functional groups. Phenyl glycidyl ether and 1,2epoxydodecane were selected to study the reactions of the oxirane moiety, 1- and 2-octanol and 1,3-diphenoxy-2-propanol to study the reaction of primary and secondary hydroxyl
