Continued Development of FEA-1100: a Zero ODP and Low GWP Foam Expansion Agent with Desired Properties

Transcription

1 Continued Development of : a Zero ODP and Low GWP Foam Expansion Agent with Desired Properties GARY LOH, JOSEPH A. CREAZZO, MARK L. ROBIN DuPont Company 711 Chestnut Run Plaza, Wilmington, DE Tel: , Fax: ; gary.loh@usa.dupont.com ABSTRACT DuPont has developed a 4th generation foam expansion agent,, for polyurethane foam applications. As a liquid foam expansion agent, is characterized by a unique combination of desirable properties, including an excellent environmental profile (zero ODP and low GWP), nonflammability, low vapor thermal conductivity and a boiling point of 33 o C. Internal testing of has provided promising results and our development program has been expanded to include customer testing and evaluation. This paper will provide an update on our program and discuss studies based on customer interest and feedback, including insulation performance, foam properties and optimization. Introduction Fluorocarbon foam expansion agents (FEAs or blowing agents) are widely used for polyurethane insulation production. CFC- 11 and HCFC-141b were once the FEAs of choice, but their use is being phased out due to their non-zero ozone deletion potentials (ODPs). The currently employed hydrofluorocarbon (HFC) and hydrocarbon FEAs are characterized by zero ODPs, but these agents now face challenges due to their effects on climate change (e.g., global warming) and energy efficiency. Consequently, the industry is searching for a FEA that is environmentally sustainable (zero ODP, low GWP) while maintaining the properties desired in a FEA. DuPont has conducted extensive research and developed a novel Fourth-Generation foam expansion agent,. (CF 3 CH =CHCF 3 ) has an excellent environmental profile. It contains no chlorine or bromine and hence is characterized by a zero ozone depletion potential (ODP). It is also characterized by a short atmospheric lifetime of 22 days, and a low global warming potential (GWP) of 8.9 (NOAA 2011). is non-flammable based on testing in accordance with ASTM E Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases) carried out at temperatures of 60 o C and at 100 o C. The nonflammable nature of allows its safe use in a broader range of applications. is characterized by a boiling point and vapor pressure that are very suitable to polyurethane foaming processing technology. has a vapor pressure very close to that of HCFC-141b, and therefore it can be used with the optimal FEA level in formulations, providing desired foam properties without concern for high B-side pressure or flammability. has low vapor thermal conductivity, providing excellent insulation performance in foams. In our previous publications, we reported laboratory application studies including stability, reactivity and the performance of in generic foam formulations for the manufacture of polyurethane foams. Equimolar quantities of were dropped in to generic formulations without optimization to compare the relative insulation performance of with commercially available FEAs (HCFCs, HFCs and hydrocarbons).the results indicate that may be employed as a drop-in replacement for other liquid foam expansion agents, providing improved insulation performance with low conversion costs. Our recent work has focused on providing data required for customer testing. Additional toxicity evaluations have been completed and an exposure limit has been established. A study was also conducted to evaluate the impact of on ground level ozone (i.e., smog) formation. To verify the results of laboratory studies, samples were provided to customers for large scale testing in various end use applications. In this paper, we update properties and discuss customer drop-in evaluation results. Exposure Limit

2 The available toxicological data indicate that can be safely used in foam expansion applications. In standard toxicological tests, has been shown to be characterized by very low acute and repeat inhalation toxicity. No adverse effects have been observed on genetic materials and the developing fetus is not a target for toxicity. As a consequence of its highly favorable toxicity profile, the DuPont Allowable Exposure Limit (AEL) for is 500 ppm (8 & 12-hr time-weighted average, TWA). Table 1 compares the exposure limits of with commercially available FEAs. Table 1 Comparison of Exposure Limit with Commercially Available FEAs FEAs HCFC-141b HFC-365mfc Cyclopentane Methyl Formate TLV, OEL or AEL a (ppm) 500 a a a: DuPont Allowable Exposure Limits (8-12 hr TWA) Impact on Ground-level Ozone Formation A number of commercially available foam expansion agents (e.g., hydrocarbons) are classified as volatile organic compounds (VOCs) due to their contribution to the formation of ground-level ozone (the primary component of urban "smog") Within the US, VOCs are commonly characterized by their Maximum Incremental Reactivity (MIR) relative to that of ethane. Chemicals with MIR values equal to, or greater than, the MIR of ethane are considered VOCs for regulatory purposes. Table 2 compares the MIR of with ethane and other FEAs. The MIR of is only 14% of that of ethane (W.P.L Carter personal communication, 2011), and hence is expected to be classified as a "non-voc" at both the Federal and State level. The European Union employs a different but related measure of atmospheric reactivity, the photochemical ozone creation potential (POCP), to characterize ground-level ozone formation. MIR and POCP values are correlated based on recent studies [2], and therefore is expected to have a much lower POCP value than ethane. Table 2 Comparison of Maximum Incremental Reactivity (MIR) [1] Foam Expansion Agent MIR (g O 3 /g) 0.04 Methyl Formate 0.06 HFO-1234ze 0.10 HFO-1234yf 0.28 Ethane 0.28 Dichloroethylene 1.70 Cyclopentane 2.39 CUSTOMER DROP-IN EVALUATIONS samples were provided to customers for testing in various applications. In these tests was substituted for HCFC-141b, HFC-365mfc and in existing formulations without optimization and employing a weight of identical to the weight of HCFC-141b, HFC-365mfc or employed in the existing formulations. Bench scale studies confirmed the comparable reaction profile and stability of with foam systems. Large scale testing in foam machines and commercial spay foam equipment demonstrated that superior insulation performance and comparable dimensional stability and mechanical properties were afforded by the use of. Despite the higher molecular weight of compared to or HCFC-141b, customers were able to achieve improved insulation performance in formulations employing a weight of identical to the weight of or HCFC-141b employed in the existing formulations. Customer Panel Foam Evaluation (Equal Weight Substitution for HCFC-141b and HFCs) A. Reaction Profile and Stability Panels are widely used in the construction industry. In developing countries, HCFC-141b is still used due to its good insulation performance and low flammability. Developed countries have moved to zero ODP options (HFCs and hydrocarbons). HFCs are often chosen for their superior insulation performance and non-flammability. In this example, a customer dropped into a HCFC-141b panel formulation containing polyether and polyester polyols, surfactant,

3 catalyst, flame retardant and water. Identical weight quantities of foam expansion agents were employed in the same formulation to compare the relative performance with HCFC-141b, and HFC-365mfc. Figure 1 provides a comparison of the reaction profile (cream, gel and rise time) for, HCFC-141b, and HFC-365mfc during the foaming process. Even though these FEAs have different boiling points, little difference in the FEA reaction profiles is observed, consistent with the results of our previous studies. Calculations indicate that the heat requirement to vaporize these FEAs during the foaming process is very similar [3]. Figure 1. Reaction Profile Comparison Reactivity (Second) 140 Cream Time Gel Time Rise Time HCFC-141b (29.5kg/m3) (30.9kg/m3) HFC-365mfc (33.3kg/m3) (34.6kg/m3) Table 3 compares the storage stability of, HCFC-141b, and HFC-365mfc in the same B-side formulation. Tests were conducted at 20 o C for 14 days. Hand-mix foams were prepared to identify any changes in density and reaction profile (cream time gel time and rise time). did not exhibit any increase in reaction profile or foam density after 14 day storage, indicating its stability with this generic panel foam system. The results are consistent with our previous stability study conducted in generic polyether and polyester formulations at 50 o C for 6 months [3]. Table 3 Storage Stability for Panel Foam Formulation Changes relative to day 0 after 14 day HCFC-141b HFC-365mfc storage at 20 o C Cream time +5.9% +7.7% +12.5% -5.9% Gel time +1.3% -1.2% -1.3% +1.3% Rise time +1.6% +4.9% +2.5% -4.1% Density -1.0% -2.6% -9.6% -0.6% B. Table 4 compares the properties of foams produced with 10% overpacking in a mold with a temperature setting of 45 o C. afforded comparable foam properties and lowest initial when equal weights of compared to the weight of HCFC-141b, or HFC-365mfc were dropped into the panel formulation. After 28 days of aging, foams produced with maintained the lowest compared to foams produced with HCFC-141b and HFCs, and provided an 8 percent improvement compared to HCFC-141b. The results are consistent with our previous stability study conducted in sucrose based polyether formulations [3].

4 Table 4. Panel (Drop-in Comparison with HCFC-141b and HFCs) HCFC-141b HFC-365mfc Foam density (kg/m 3 ) Core density (kg/m 3 ) at 23 o C (mw/mk) - initial Relative vs HCFC-141b control (initial) Control +1% +3% -3% at 23 o C (mw/mk) - 28 days Relative initial vs HCFC-141b control (28 days) Control -3% -1% -8% Closed cell % 91% 93% 93% 94% Dimensional Stability (% Volume change) Cold(-30 o C/48H) - parallel -0.10% -0.07% -0.02% -0.21% Cold(-30 o C/48H) - perpendicular -0.32% -0.10% -0.05% -0.02% Hot(70 o C/48H) - parallel -0.38% 0.0% 0.00% 0.07% Hot(70 o C/48H) - perpendicular 0.75% 0.2% 0.52% 0.72% Hot Humid (70 o C/95%RH/48H) - parallel 4.6% 5.0% 4.4% 4.3% Hot Humid (70 o C/95%RH/48H) - perpendicular 12.4% 9.1% 8.5% 10.0% Mechanical Properties Compressive strength -parallel (kpa) - parallel Bending strength (kpa) Customer Spray Foam Evaluation A. Drop-in Comparison with (Equal Weight Substitution of ) In this example, a customer evaluated in a spray foam formulation optimized for. An equal mass of was substituted for in the formulation containing polyether and polyester polyols, surfactant, catalyst, flame retardant and water. The B-side formulations were stored at room temperature for 6 months to compare their physical and chemical stability. Visual observation for FEA separation from B-side mixture was conducted during the storage to evaluate physical stability. Chemical stability was evaluated by making hand-mix foams to produce foam reaction profiles after storage. A Graco H2035 spray machine was used to spray the foams. Tables 6 and 7 indicate the spray equipment conditions and foam properties. Foams produced with exhibited good physical and chemical stability following six months of storage. Substitution of with an equal weight of afforded slightly improved s and improved mechanical properties. Table 6. Spray Conditions (Drop-in Comparison with ) Spray equipment Spray foam equipment Graco H2035 Spray gun Fusion Process temperature ( o C) 54 o C

5 Table 7. (Drop-in Comparison with ) FEA and water level (pbw) based on 100 pbw Polyol FEA (pbw) 9 9 water (pbw) Foam System Stability (6 months at room temperature) Physical Stability Chemical Stability No separation Stable Identical to Identical to relative to Density (kg/m 3 ) % at 23 o C (mw/mk) % Close cell % 98% 99% Dimensional stability (% volume change) Cold(-29 o C/14 days) 0.17% 0.23% Hot (93 o C) 5.9% 1.8% Hot and Humid (70 o C/95%RH/28 days) 19% 17% Compressive strength -parallel(kpa) % Tensile strength (kpa) % B. Level Impact (Equal Weight Substitution of and HCFC-141b) In this example, the customer compared the impact of levels using formulations optimized for HCFC-141b and. Equal quantities (mass basis) of were substituted for HCFC-141b and, and foams were sprayed using the same condition listed in Table 6. As shown in Table 8 and 9, provided improved s in formulations optimized for HCFC-141b and, however, the relative improvement was more significant in the HCFC-141b formulation where a higher level of FEA was used. Since the level of in formulations is limited by its low boiling point, provides the flexibility to use higher levels of FEA for significant relative improvement (Table 9). Customer evaluations are consistent with our previous laboratory studies [3].

6 Table 8 - FEA Level Impact on (Equal Weight Substitution of and HCFC-141b) in in HCFC-141b HCFC-141 formulation formulation formulation formulation (High level FEA) (Low level FEA) (High Level FEA) (Low level FEA) FEA and water level (pbw) based on 100 pbw Polyol FEA (pbw) H 2 O (pbw) Moles of FEA Moles of H 2 O Total moles Mole % FEA 91% 87% 40% 35% Foam density (kg/m 3 ) Initial at 23 o C (mw/mk) relative to control Control -4% Control -2% Closed cell % 93% 94% 98% 99% Compressive strength - parallel(kpa) Table 9 -FEA Level Impact on ( in HCFC-141 formulation vs ) FEA and water level (pbw) based on 100 pbw Polyol formulation (Low level FEA) in HCFC-141 formulation (High Level FEA) FEA (pbw) 9 19 H 2 O (pbw) Moles of FEA Moles of H 2 O Total moles Mole % FEA 40% 87% Foam density (kg/m 3 ) Initial at 23 o C (mw/mk) relative to % Closed cell % 98% 99% Compressive strength parallel (kpa) Customer Appliance Evaluation A. Drop-in to a Formulation (Equal Weight Substitution of ) was dropped into a commercial appliance formulation. Identical weights of and were added to the same formulation to compare the relative performance. The reaction profile and flow were compared and showed no significant difference. The B-side systems were then stored at room temperature for 6 months. Physical stability was checked by identifying any FEA separation from the B-side system. Chemical stability was checked by measuring the

7 density and reaction profile from hand-mixed foams. produced no difference in the physical or chemical stability of the foam compared to (Table 10). Table 10. Foam System Reactivity and Stability (Equal Weight Drop-in Comparison with ) Relative to Reaction profile and flow Cream time (second) 12 Identical to Gel Time (second) 85 Identical to Flow index 1.3 Identical to B-side system stability ( 6 months at room temperature) Physical stability No phase separation Identical to Chemical stability No reactivity and density change Identical to Foams were made from these formulations using a high pressure machine at 10% overpacking. Table 11 provides a comparison of the foam properties. afforded improved, compressive strength, adhesion and dimensional stability when an identical weight of was dropped into the appliance formulation without optimization. Table 11. (Equal Weight Drop-in to a Formulation) relative to (10% Overpacking) Mold density (kg/m 3 ) Control +1.5% Compressive strength (kpa) Control +6.4% Adhesion (kpa) Control +16.4% Dimensional Stability(% volume change) Control 10 o C (mw/mk) Control 23 o C (mw/mk) Control -1.3% b. Level Impact (Equimolar Substitution of ) In this example a customer evaluated the level effect of and in hand-mixed foams. was dropped into a appliance formulation at 10% overpacking. The mole percent of and was increased from 54 to 75 mole percent to evaluate the impact on foam properties and FEA efficiency. The first 3 columns of Table 12 show the results at 54 mole percent FEA level. In this case, afforded 4 percent lower and 1 percent higher s at 23 o C and 1.7 o C, respectively, resulting in a 2 percent improved average k factor compared to. However, afforded a 25 percent lower FEA efficiency due to its higher molecular weight. The next 3 columns of Table 12 show the results at 75 mole percent FEA level. As the FEA mole percentage was increased from 54 to 75 mole percent the impact on at 1.7 o C for and was significantly different. Higher FEA level resulted in a positive impact for, but a negative impact for. Even though foams produced with had a higher compressive strength compared to those produced with, the average for foam produced with was 4 percent higher. In addition, FEA afforded a 25 percent lower FEA efficiency due to its higher molecular weight. Table 13 compares foam properties and FEA efficiency at 54 mole percent level and 75 mole percent level. Reducing the level from 75 to 54 mole percent improved the average and FEA efficiency, narrowing the property gaps between and. The compressive strength was also significantly improved compared to. Customer evaluations confirm our laboratory observations [4]: there is an optimal level of at a given application temperature. Optimization based on application needs is required to improve the FEA efficiency and insulation performance.

8 Table 12. FEA Level Impact on (Equimolar Substitution of ) (54 mole% FEA) (54 mole% FEA) relative to (75 mole % FEA) (75 mole% FEA) relative to FEA and water level based on 100 pbw Polyol and Additives FEA (pbw) % % H 2 O (pbw) Moles of FEA Moles of H 2 O Total moles of FEA and H 2 O Mole % FEA in FEA and H 2 O 54% 54% 76% 75% % Overpacking 9-12 % 9-12 % 9-12 % 9-12 % Packed density (kg/m 3 ) o C (mw/mk) % o C (mw/mk) % % Ave (mw/mk) % % Compressive strength (kpa) % % Closed cell% Table 13. FEA Level Impact on (75 mole % vs 54 mole% FEA- (75 mole % FEA) (54 mole% FEA) relative to FEA and water level based on 100 pbw Polyol and Additives FEA (pbw) % H 2 O (pbw) Moles of FEA Moles of H 2 O Total moles of FEA and H 2 O Mole% FEA in FEA and H 2 O 76% 54% % Overpacking 9-12 % 9-12 % Packed density (kg/m 3 ) o C (mw/mk) o C (mw/mk) % Ave (mw/mk) % Compressive strength (kpa) % Closed cell% Optimization Based on Application Temperature Performance: Laboratory Study Our previous laboratory studies [3, 4] and customer evaluations summarized in Table 9 and 13 indicate that for a given application temperature, there is an optimal level of which provides maximum insulation performance and FEA

9 (mw/mk) efficiency. Figure 5 shows the impact of level on the as a function of temperature. In this example, the relative levels of and water (mole percent) were varied in an appliance formulation while maintaining the total moles of and water constant. K-factors were measured to compare the level impact on s at different temperatures. As shown in Figure 5, higher mole percentages of can be used to achieve the lowest k- factor at 23 o C, however, the mole percent of should be reduced at 1.7 o C. The level should be optimized based on the required application temperature for FEA efficiency and insulation performance. Figure 5. K-factor vs Level Effect of Level (Generic Appliance Formulation) Poly. ( C) Poly. ( - 10 C) Poly. ( C) % 25% 35% 45% 55% 65% 75% Mole% of Tables 14, 15 and 16 show the loss for foams produced using different mole percentages of. Even though foams using lower mole percentages of contain more CO 2 in foam cells, the higher level of CO 2 does not seem to affect the loss. All the foams show good dimensional stability after 169 days aging. Table 14. Comparison of (1.7 o C) Loss during Aging at Different Mole% of Aging days (40 mole% FEA- % loss (40 mole% FEA- (60 mole % FEA- % loss (60 mole % FEA- (73 mole % FEA- % loss (73 mole % FEA % % % % % % % % % Table 15. Comparison of (10 o C) Loss during Aging at Different Mole% of Aging days (40 mole% FEA- % loss (40 mole% FEA- (60 mole % FEA- % loss (60 mole % FEA- (73 mole % FEA- % loss (73 mole % FEA % % % % % % % % %

10 Table 16. Comparison of (23.9 o C) Loss during Aging at Different Mole% of Aging days (40 mole% FEA- % loss (40 mole% FEA- (60 mole % FEA- % loss (60 mole % FEA- (73 mole % FEA- % loss (73 mole % FEA % % % % % % % % % CONCLUSIONS is a zero ODP and low GWP foam expansion agent. Recent studies also show that has a negligible impact on ground-level ozone formation, and is expected to be classified as a non-voc. The results of drop-in customer evaluations are very promising and confirm our laboratory study results. The results also demonstrate the potential for FEA optimization to achieve foam expansion agent efficiency and insulation performance. DuPont is conducting further study to maximize the performance of. DuPont is currently in the process of commercializing, and a SNAP (Significant New Alternative Policy) application and PMN (Pre Manufacturing Notification) are being prepared. Commercialization of in other regions of the world is also underway. REFERENCES 1. The California Consumer Products Regulations 127pp. California Environmental Protection Agency, Air Resource Board, Publication November Derwent R.G. Reactivity scales for Volatile Organic Compounds using the SAPRC-07 and MCMv3.1 Chemical Mechanisms, J. Air & Waste Manage. Assoc, 60, , Loh, G., Creazzo J., Robin, M.L., Further Development of Low GWP Foam Expansion Agent with Improved Insulating Performance vs Commercially Available Options Today, Proceedings of 12th Blowing Agents and Foaming Process, Cologne, Germany (2010). 4. Loh, G., Creazzo J., Robin, M.L., Further Development of : a low GWP Foam Expansion Agent, Proceedings of Polyurethanes 2010 Technical Conference, Houston, TX USA DISCLAIMER The information set forth herein is furnished free of charge and based on technical data that DuPont believes to be reliable. It is intended for use by persons having technical skill, at their own risk. Since conditions of use are outside our control, we make no warranties, expressed or implied and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate under, or a recommendation to infringe any patents or patent applications.