2-AMINO-2-METHYL-1-PROPANOL IN PAINTS & COATINGS: A VOC EXEMPTION

STORY

1 Ruth Keiko Kuriyama, 2 Patrick E. Brutto,

1ANGUS Chemical Company, Alexandre Dumas 1671, São Paulo, SP Brazil

2ANGUS Chemical Company, 1500 E. Lake Cook Road, Buffalo Grove, IL 60089

1Ruth K.Kuriyama , rkkuriyama@dow.com , 55 11 51889833

2Patrick E. Brutto, pebrutto@dow.com, 847-808-3766

Abstract

A primary amine produced by ANGUS Chemical Company, 2-amino-2-methyl-1-propanol (AMP), has been used as a neutralizer, pH adjuster and co-dispersant in water-based architectural paints since the early 1970s. AMP has helped formulators meet a broad range of requirements including in-can stability, moisture and scrub resistance, gloss development and color stability. This unique amino alcohol has enabled reduction of other components, including primary dispersants, which can remain in the film and reduce moisture resistance. Finally, AMP helps paint producers and consumers avoid odor issues associated with ammonia.

Regulations in the U.S. have forced architectural paint manufacturers to reduce volatile organic compounds (VOCs) in their formulations below 50 grams/liter. In addition, consumer requirements have forced the industry to develop formulations containing less than five grams/liter VOC. This presents a tremendous challenge in maintaining the expected levels of film performance. Inorganic neutralizers, in particular sodium hydroxide and ammonia, have been the only alternatives available. However, performance in several areas including pH stability and moisture resistance is often less than optimal. Use of AMP would be much preferred, given its favorable impact on paint performance relative to inorganics, and effective June 25, 2014, AMP is exempted by the U.S. Environmental Protection Agency (U.S. EPA) from regulation as a VOC.

This presentation will review the VOC exemption petitioning process for AMP, and the

supporting information leading to the exemption.

Background: AMP in Architectural Coatings

AMP has been used in water based architectural paints for several decades, and is an industry standard neutralizer and co-dispersant for interior and exterior formulations; the

structure of AMP is shown in Figure 1. The pure material has a melting point of 30 °C, boiling point of 165 °C, vapor pressure of 0.34 mm Hg at 20 °C, and a pKa of 9.8. It is miscible in all proportions with water.

Figure 1. Structure of AMP.

Examples of the benefits provided by AMP versus another industry standard,

ammonium hydroxide (i.e. aqueous ammonia), are provided in Table 1 and Figures 1 and 2, for an interior low VOC semi-gloss paint formulation. The formulation with AMP exhibited higher gloss before and after heat aging, as well as better scrub resistance, relative to the paint with ammonia. Also, in a three cycle freeze-thaw test at -9°C (modified ASTM D2243), the formulation with AMP passed (KU viscosity change = 27) while that with ammonia gelled.

Table 1. Low VOC Interior Semi-Gloss Paint Formulation

2 - A m i n o - 2 - M e t h y l - 1 - P r o p a n o l ( A M P ) C A S : 1 2 4 - 6 8 - 5

H 2 N O H

Formulation AMP Ammonia

Grind lb/100 gal lb/100 gal

Water 44.80 44.82

Attapulgite Clay Thickener 2.99 2.99

Biocide, Benzisothiazolinone 20% 0.50 0.50

Dispersant, Sodium Salt of Hydrophobic Copolymer, 25% 5.97 5.98

Surfactant, Nonionic Alcohol Ethoxylate 90% 1.99 1.99

Surfactant, Anionic Sodium Sulfosuccinate 75% 1.99 1.99

Defoamer, Oil-Based 2.07 2.07

AMP, 95% 2.20

Ammonium Hydroxide (20% Ammonia) 2.83

Kaolin Clay, Fine Grade 35.18 35.12

Water 5.00 5.01

Grind Subtotal 102.70 103.30

Let Down Latex Resin, Acrylic 50% for Solvent-Free Applications 450.07 449.99 Titanium Dioxide Slurry, Rutile 76.5% 280.00 280.00 Water 54.21 55.11 Defoamer, Oil-Based 1.00 1.00 Rheology Modifier, HEUR 30.03 30.00 Water 118.86 115.71

Rheology Modifier, HASE 8.00 8.00

Defoamer, Oil-Based 0.50 0.50

AMP, 95% 0.08

Water 0.00 1.06

Total 1045.45 1044.67

pH, 1 Day 8.69 8.71

Solids by Volume, % 33.9 34.0

Pigment Volume Concentration, PVC % 25.2 25.2

Volatile Organic Content, grams/liter (calculated) < 10 < 10

Figure 2. Gloss at 60° before and after heat aging (ASTM D523).

Figure 3. Scrub resistance of fresh paint (ASTM D2486). Given the U.S. market trend toward lower VOC formulations, partially due to federal and

state regulatory limits, and in part due to consumer preferences, formulators have moved to reduce the use of VOC contributors where performance allows. Until recently, AMP was considered a VOC by U.S. EPA regulations and, although generally used in small amounts in a paint formulation, was identified for de-selection in the lowest VOC formulations (less than five grams/liter).

40

45

50

55

60

65

70

AMP Ammonia

Glo

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Initial (One Day) Three Months at 60°C

500550600650700750800850900950

100010501100

AMP Ammonia

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Drawdowns aged overnight at

25°C and 50% relative humidity

As downward pressure on VOCs was occurring, the College of Engineering Center for Environmental Research and Technology, at the University of California Riverside, was contracted by the California Air Resources Board to test several materials for their tendency to form ground level ozone, including AMP. This work was done under the direction of Dr. William P.L. Carter, using a specialized smog chamber apparatus.

VOC Exemption Story

In the U.S., a compound may be excluded as a VOC as a result of public petitions and new scientific data that demonstrate its negligible effect on the formation of ground-level ozone. Since 1977, EPA has removed 62 specific compounds or classes of compounds from the list of VOCs that contribute to ozone formation. Below is an excerpt of EPA’s VOC exemption policy.

[“Tropospheric ozone, commonly known as smog, is formed when VOCs and nitrogen oxides (NOX) react in the lower atmosphere in the presence of sunlight. Because of the harmful health effects of ozone, the EPA and state governments limit the amount of VOCs that can be released into the atmosphere. The VOCs are those organic compounds of carbon which form ozone through atmospheric photochemical reactions. Different VOCs have different levels of reactivity. That is, they do not react to form ozone at the same speed or do not form ozone to the same extent. Some VOCs react slowly or form less ozone; therefore, changes in their emissions have limited effects on local or regional ozone pollution episodes. It has been the EPA’s policy that organic compounds with a negligible level of reactivity should be excluded from the regulatory control efforts on compounds that do significantly increase ozone concentrations. The EPA also believes that exempting such compounds creates an incentive for industry to use negligibly reactive compounds in place of more highly reactive compounds that are regulated as VOCs. The EPA lists compounds that it has determined to be negligibly reactive in its regulations as being excluded from the regulatory definition of VOCs. (40 CFR 51.100(s)). The CAA requires the regulation of VOCs for various purposes. Section 302(s) of the CAA specifies that the EPA has the authority to define the meaning of ‘‘VOC,’’ and hence what compounds shall be treated as VOCs for regulatory purposes. The policy of excluding negligibly reactive compounds from the regulatory definition of VOCs was first laid out in the ‘‘Recommended Policy on Control of Volatile Organic Compounds’’ (42 FR 35314, July 8, 1977) and was supplemented subsequently with the ‘‘Interim Guidance on Control of Volatile Organic Compounds in Ozone State Implementation Plans’’ (70 FR 54046, September 13, 2005). The EPA uses the reactivity of ethane as the threshold for determining whether a compound has negligible reactivity. Compounds that are less reactive than, or equally reactive to, ethane under certain assumed conditions may be deemed negligibly reactive and therefore suitable for exemption from the regulatory definition of VOCs. Compounds that are more reactive than ethane continue to be considered VOCs for regulatory purposes and therefore are subject to control requirements. The selection of ethane as the threshold compound was based on a series of smog chamber experiments that underlay the 1977 policy. The EPA has used three different metrics to compare the reactivity of a specific compound to that of ethane: (i) The

reaction rate constant (known as kOH) with the hydroxyl radical (OH); (ii) the maximum incremental reactivity (MIR) on a reactivity per unit mass basis; and (iii) the MIR expressed on a reactivity per mole basis.”]1

We will focus our discussion on the MIR metric, since it was a critical element in EPA’s

decision to exempt AMP from regulation as a VOC. As already stated, the analysis of the MIR value of AMP was completed by Dr. Carter at the University of California.

Maximum Incremental Reactivity (MIR)

An essential element for evaluating the MIR value of AMP was to understand its

potential reactivity with hydroxyl (OH) and nitrate (NO3) radicals, as well as ozone (O3).

Reaction of AMP with Hydroxyl Radicals The rate constant for the gas-phase reaction of hydroxyl (OH) radicals with AMP has

been measured to be 2.8 x 10-11 cm3 mol-1 sec-1 at ~300 °K, giving it a relatively short lifetime in the atmosphere.2 In Dr. Carter’s analysis, it was proposed that the following reactions of AMP with hydroxyl radicals dominate, with [1] occurring ~80% of the time and [2] ~19% of the time3:

CH3C(CH3)(NH2)CH2OH + OH H2O + CH3C(CH3)(CH2OH)NH

CH3C(CH3)(NH2)CH2OH + OH H2O + CH3C(CH3)(NH2)CH(·)OH [2]

In the same reference it is theorized that if NOx are present, which is required for formation of O3, the following reaction occurs which terminates the radical and prevents formation of O3:

CH3C(CH3)(CH2OH)NH· + NO2 CH3C(CH3)(CH2OH)NHNO2

Another proposed reaction, from the product of [2] with oxygen, is shown in [4]; although this propagation reaction can generate O3, it has less influence than the radical termination reaction [3] because reaction [2] occurs less frequently than [1].

CH3C(CH3)(NH2)CH(·)OH + O2 CH3C(CH3)(CHO)NH2 + HO2· [4]

Reaction of AMP with NO3 Radicals

Carter estimated the rate constant for reaction of AMP with NO3 radicals as 5.9 x 10-14 cm3 mol-1 sec-1, based on measurement by Aschmann of the reaction rate for N-methyl-2-pyrrolidinone (NMP) with NO3 of 1.26 x 10-13 cm3 mol-1 sec-1.3, 4 The mechanism proposed by Carter for reaction of AMP with NO3 is shown below [5].

CH3C(CH3)(NH2)CH2OH + NO3 CH3C(CH3)(CH2OH)NH· + HNO3 [5]

The product of [5] reacts with NO2 radical forming nitramine [3].

Reaction of AMP with Ozone

Carter reported there are no rate constant data available for the reactions of ozone (O3) with AMP, although data are available for a few other amines.3 Based on kinetic and mechanistic considerations, the same reference estimates reaction at N-H groups is probably not as important as that of hydrogen atoms on carbons adjacent (alpha) to the amino group. Since AMP lacks alpha hydrogens, Carter estimated the reaction of AMP with O3 is negligible under atmospheric conditions. Although uncertain, it is unlikely that reaction with O3 would be an important fate of AMP compared to its reactions with OH radicals.

The predicted reaction mechanisms were tested by Carter at the University of California

Riverside, using a specially designed environmental chamber. The results of these studies will now be described. Environmental Chamber Experiments

Experiments with AMP conducted at the University of California, Riverside in an “EPA environmental chamber”, consisted of incremental reactivity experiments where the effects of amines on O3 formation and nitric oxide (NO) oxidation rates were measured during irradiation of a simplified VOC surrogate/NOx mixture. The VOC surrogate consisted of a mixture of ethylene, propylene, n-butane, trans-2-butene, toluene, n-octane and m-xylene, and the NOx mixture consisted of a fixed ratio of NO and NO2. This method has been employed extensively to evaluate mechanisms for a wide variety of other VOCs.5 Following is a description and diagram of the environmental chamber:

[The UCR EPA chamber consists of two ~85,000-liter Teflon® reactors located inside a 16,000 cubic ft temperature-controlled “clean room” that is continuously flushed with purified air. The clean room design is employed in order to minimize background contaminants into the reactor due to permeation or leaks. Two alternative light sources can be used. The first consists of a 200 KW argon arc lamp with specially designed UV filters that give a UV and visible spectrum similar to sunlight. This light source could not be used for this project because it was not operational during this period. Banks of blacklights are also present to serve as a backup light source for experiments where blacklight irradiation is sufficient, and this was used for the experiments for this project because of availability and because use of blacklights was judged to be sufficient to satisfy the project objectives. The interior of the enclosure is covered with reflective aluminum panels in order to maximize the available light intensity and to attain sufficient light uniformity, which is estimated to be ±10% or better in the portion of the enclosure where the reactors are located.]3

Figure 4. Schematic of EPA environmental chambers at University of California Riverside.3

Various reactivity scales were developed by Carter, representing different levels of NOx

availability; these include maximum incremental reactivity (MIR), representing relatively high NOx where O3 is most sensitive to changes in VOC, maximum ozone incremental reactivity (MOIR) representing moderate NOx conditions optimum for O3 formation, and equal benefit incremental reactivity (EBIR) representing lower NOx conditions where both NOx and VOCs have equal relative effects on reducing ozone.6

Incremental reactivity data comparing the impact of AMP versus ethane, calculated

based on 39 city-specific scenarios, are shown in Table 2 and Figure 5. The “Base” column in Table 2 shows the results without addition of AMP or ethane. As mentioned earlier, ethane is considered by U.S. E.P.A. as a threshold compound for VOC classification. The calculations show that greater or lesser amounts of O3 are generated with AMP vs. ethane, depending upon the reactive organic gas (ROG)/NOx ratio, which varies with the city scenario. Species such as AMP, which scavenge radicals, have greater variability associated with their MIR values than those which react more slowly. Radical scavengers react with NOx, and NOx is both necessary for ozone formation and capable of producing species which reduce ozone. The relative rates of the competing reactions depend on the nature of the radical scavenger and the environmental conditions. Since AMP scavenges radicals, its estimated MIR value is expected to vary depending on environmental conditions; this is corroborated by the chamber experiments and associated calculations.

The average MIR values were reported as 0.25 ± 0.57 gm O3/gm VOC for AMP, versus 0.28 ± 0.07 gm O3/gm VOC for ethane.7 With respect to MIR comparisons, EPA stated: “a comparison to ethane on a mass basis strikes the right balance between a threshold that is low enough to capture compounds that significantly affect ozone concentrations and a threshold that is high enough to exempt some compounds that may usefully substitute for more highly

reactive compounds.”8 Under the MOIR and EBIR scenarios, AMP on average becomes

inhibitory to O3 formation, relative to ethane.

Table 2. Incremental Reactivities Calculated for City Specific Scenarios7

Figure 5. Incremental reactivities of AMP and ethane vs. reactive organic gas / NOx ratio for averaged conditions and city-specific scenarios.7

Other Considerations

In addition to the potential contribution to O3 formation, U.S. EPA also considers other factors when deciding whether to grant a compound exemption from regulation as a VOC. These include an assessment of the way the material is typically used, as well as its overall impact on health and the environment, including its global warming potential. Following is a synopsis of some of the other information provided to EPA, in support of the VOC exemption petition:

AMP is a reasonably strong base, preferentially forming salts with acids at pHs below its pKa of 9.8. This is the pH environment present in most formulations where AMP is used, including paints and coatings, personal care products and metalworking fluids. AMP therefore exists predominantly in its ionic or salt form, and very little will evaporate to be available for atmospheric reactions. It is difficult to transfer even un-ionized AMP quantitatively into the air at normal usage temperatures. Also, due in part to hydrogen bonding of AMP in aqueous systems where its usage predominates, un-neutralized AMP is expected to evaporate slowly based on its estimated Henry’s Law Constant of 6.48 x 10-10 atm · m3/mole at 25 °C.9

AMP will also react with acids present in environmental media including soil, water and air. These reactions ensure that not all of the AMP present in a given system will be available to react in the atmosphere.10

Once in soil or water, AMP will be biodegraded as it has been shown to be readily biodegradable in OECD 301F (89.3% biodegraded after 28 days).11

AMP is estimated to have a relatively short atmospheric lifetime of about 14 hours, based on its reaction with hydroxyl radicals at 25°C.12 Its contribution to global warming, typically measured on a 100 year time scale, will be insignificant. This contribution to global warming is at most equal to that of the carbon dioxide (CO2) equivalent of its carbon content, assuming 100% atmospheric availability and conversion to CO2. A consideration of the relative amounts of CO2 from degradation of AMP to that from burning carbon, suggests that even this overestimate of AMP’s contribution to global carbon dioxide is insignificant.10

Any AMP which exists in the vapor phase has a relatively short lifetime, and because it does not contain chlorine or bromine, it does not contribute to the depletion of the stratospheric ozone layer and has an ozone depletion potential value of zero.10

AMP is not regulated as a hazardous air pollutant under Title III of the Clean Air Act. Nor is it listed as a toxic chemical under section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA).

AMP has the following toxicological related properties:13 o Low acute oral toxicity (LD50 > 2000 mg/kg in rat) o Low dermal toxicity (LD50 > 2000 mg/kg in rabbit) o Eye and skin irritant o Did not cause allergic skin reaction in guinea pigs o Non mutagenic in standard in-vitro and animal genetic toxicity tests o Does not interfere with reproduction in animal reproductive toxicity studies o Practically non-toxic to aquatic organisms (LC50/EC50/EL50/LL50 >100 mg/L in the

most sensitive species tested), o Low bioconcentration potential (BCF < 100 ; Log Pow -0.63).

Exemption Petition Filing & EPA Ruling

The ANGUS Chemical Company submitted a petition to U.S. EPA, to exempt AMP from regulation as a VOC, on October 3, 2012. The executive summary taken from this petition is detailed below:

[The ANGUS Chemical Company submits this petition requesting that EPA modify the definition of volatile organic compound (VOC) found at 40 CFR 51.100(s) to exempt 2-Amino-2-methyl-1-propanol (AMP) from regulation as a VOC. AMP is used to disperse pigments in water-based coatings and has significant performance advantages compared to available substitute materials. AMP also is used as an additive in metalworking fluids, as an intermediate in chemical synthesis, as an additive in the production of food contact paper, as a neutralizer in personal care products, and also into some other minor uses. AMP meets the criteria that have been used to grant prior VOC petitions. Specifically, the current

maximum incremental reactivity (MIR) value for AMP is 0.25 grams ozone per gram of VOC, which is below the MIR value of the benchmark chemical ethane, which is 0.28 gram ozone per gram of VOC. Older MIR values that are no longer accepted as valid, are addressed in the petition. Species which scavenge radicals tend to have higher variability associated with their MIR values. This is the case with AMP. The MIR value in fact is negative under many conditions, meaning that the presence of AMP inhibits ozone formation under those conditions. AMP also is a solid at ambient temperatures and has low volatility, such that less than 100 percent of emitted AMP is available to contribute to ozone formation. Modeling that assumes 100 percent availability tends to overstate AMP’s potential contribution to ozone formation. These points are explained further in the petition. AMP is not regulated as a hazardous air pollutant (HAP) under Title III of the Clean Air Act. Nor is it listed as a toxic chemical under section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA). ANGUS Chemical respectfully urges prompt consideration and action on this petition. Manufacturers and formulators of water-based coatings need access to AMP to meet VOC limits on their products without impairing performance of their products. For reasons explained in the petition, there is considerable urgency to the situation.]10

EPA reviewed the AMP exemption petition and issued its direct final ruling on March 27,

2014, approximately 18 months after the petition was submitted. Following is the summary of the EPA ruling, published in the Federal Register:

[Air Quality: Revision to the Regulatory Definition of Volatile Organic Compounds—Exclusion of 2-amino-2-methyl-1-propanol (AMP) AGENCY: Environmental Protection Agency (EPA). ACTION: Direct final rule. SUMMARY: The Environmental Protection Agency (EPA) is taking direct final action to revise the regulatory definition of volatile organic compounds (VOCs) under the Clean Air Act (CAA). This direct final action adds 2-amino-2-methyl-1-propanol (also known as AMP; CAS number 124–68–5) to the list of compounds excluded from the regulatory definition of VOCs on the basis that this compound makes a negligible contribution to tropospheric ozone formation. DATES: This rule is effective June 25, 2014 without further notice, unless the EPA receives adverse comment on this action by May 27, 2014. If the EPA receives adverse comment, we will publish a timely withdrawal in the Federal Register informing the public that the final rule will not take effect.]1

EPA did not receive any adverse comments on the direct final rule and it therefore became effective on June 25, 2014. Conclusion

U.S. EPA has exempted 2-amino-2-methyl-1-propanol (AMP) from regulation as a VOC, effective June 25, 2014, based on scientific evidence that it will not contribute more significantly to tropospheric ozone formation than ethane. Acknowledgment The authors would like to acknowledge John Quinn of ANGUS Chemical Company, for generating and compiling the data presented in Table 1 and Figures 2 and 3. References 1 40 CFR, Part 51, Vol. 79, No. 59 (2014) 2 Harris, G. and Pitts, J.N. Jr., Rates of Reaction of OH with N,N-Dimethylaminoethanol and 2-Amino-2-Methyl-1-Propanol in the Gas Phase at 300 +/- 2 °K, Environ. Sci. & Technol., 17, 50-51 (1983) 3 Carter, W.P.L., Reactivity Estimates for Selected Consumer Product Compounds (Contract No. 06-408, with California Air Resources Board) (2008) 4 Aschmann, S., Atkinson, R., Atmospheric Chemistry of 1-Methyl-2-Pyrrolidinone, Atmos. Environ., 33, 591-599 (1999) 5 Carter, W.P.L., Development of the SAPRC-07 Chemical Mechanism, Atmos. Environ., 44, 5324-5335 (2010) 6 Carter, W. P. L., Development of Ozone Reactivity Scales for Volatile Organic Compounds,” J. Air & Waste Manage. Assoc., 44, 881-899 (1994) 7 Carter, W.P.L., Atmospheric Ozone Reactivity Estimates for 2-Amino-2-Methyl-1-Propanol, unpublished (2012) 8 Interim Guidance on Control of Volatile Organic Compounds in Ozone State Implementation Plans, 70 CFR 54046 (2005) 9 EPISUITE, HenryWin v. 3.20 10 Troester, L., Fontaine, D., Peera, A., Petition to Exempt 2-Amino-2-Methyl-1-Propanol, CAS No. 124-68-5, from Regulation as a Volatile Organic Compound (2012) 11

AMP (2-Amino-2-Methyl-1-Propanol): Determination of Biodegradability According to OECD Guideline 301F; Manometric Respirometry, sponsored by ANGUS Chemical Company, a subsidiary of The Dow Chemical Company; unpublished (2010) 12 EPISUITE, AOPWIN v. 1.92 13 Safety Data Sheet, ANGUS Chemical Company (Oct 2014)