I .

An Environmentally Acceptable Solvent Based On nomtal-Propyl Bromide

Ronald L. Shubkm, Ph.D. R&D Advisor

and Eric W. Limatta, Ph.D.

R&D Specialist

Albemarle Corporation

Presented In Part at the:

Eighth Annual International Workshop On Solvent Substitution

December 2-5, 1997 Scottsdale, Arizona

TM A L B E M A R L E C O R P O R A T I O N

Cleaning Solvents Based On normal-Propyl Bromide Ronald L. Shubkin, Ph.D.

normal-Propyl bromide (nPB) has begun to attract wide interest as an environmentally acceptable alternative to chlorocarbons, hydrochlorocarbons and chlorofluorocarbons. In addition to its aggressive cleaning performance, nPB has a very low Ozone Depletion Potential and a very low Global Warming Potential. It has no Flash Point by either the Tag Closed Cup or Open Cup methods. Applications for nPB-based cleaners include vapor degreasing, cold cleaning and ultrasonic cleaning of complex metal parts, circuit boards, electronic components, implantable prosthetic devices, optical equipment and others. A discussion of toxicological, environmental and regulatory considerations is included. Case histories will illustrate the broad applicability of nPB-based cleaners.

mroduc t io0

The introduction of chlorinated solvents provided manufacturers and fabricators a convenient and economical way to clean a host of difficult soils from strategic parts. Efficient cleaning, rapid drying, low flammability, residue free parts and relatively low solvent costs all contributed to the popularity of chlorocarbon fluids. However, many chlorine containing solvents have now been banned or restricted because of environmental and/or health considerations. In the search to find suitable alternatives, a wide variety of new solvents were developed'. Many of the new solvent cleaners do excellent jobs, but still suffer from one or more deficiencies relative to the overall costlperformance of the chlorinated materials they replaced. Even some of the newer solvents, such as some hydrochloroflouorocarbons (HCFCs), have been shown to have environmental problems and have been banned from usage in cleaning applications.

Background

In 1991, the total U.S. market for 1,1,1-trichloroethane (TCA) as a cleaning solvent was 700 MM Ibs. Another 200 MM Ibs was sold as an emissive solvent. TCA was very effective and very popular as a cleaning solvent, but it suffers from two important drawbacks relative to environmental considerations. It has a relatively high Ozone Depletion Potential and a relatively high Global Warming Potential. The manufacture of TCA was banned by the Montreal Protocol effective January 1, 1996.

task, have

Identification of an across the board replacement for TCA has proved to be a formidable and a fragmentation of the cleaning market has resulted.' Different products and procedures been developed for different applications, but not all of these have proven to be wholly

satisfactory. As an example, the hydrochlorofluorocarbon HCFC-141 b was introduced and seemed satisfactory for a number of niche applications, but it was banned from use as a cleaning agent effective January 1, 1997. It may still be used as a refrigerant.

A host of new cleaning systems have been introduced in recent years to meet the

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challenges presented by today's industrial cleaning requirements. All of the new systems offer advantages in specified niche applications, but none have met all of the requirements of the marketplace. Some of the important alternatives are: I

Alternative chlorocarbon solvents. Most chlorinated solvents are effective cleaning agents. However, most have either been banned from manufacture, restricted to specified uses, or scheduled for phase-out. Hydrocarbons and oxygenated hydrocarbons. These solvents have the obvious advantage of low cost. However, they are readily flammable and present serious hazards when used in cleaning operations. Hydrochlorofluorocarbons (HCFCs). As with many chlorocarbon solvents, the most popular of these (HCFC-14lb) has been restricted to non-cleaning applications. Other examples are too expensive, too volatile, or have only moderate cleaning ability. Fluorocarbons. Fluorocarbons are non-toxic, non-flammable and very safe to use. They are also very expensive and have poor solvency for most soils. Hydrofluorocarbons (HFCs). HFCs have moderate solvency but are expensive. They are excellent for niche applications that can tolerate the high price. Hydrofluoroethers (HFEs). HFEs are similar to HFCs in solvency and cost. Volatile methyl siloxanes (VMSs). VMSs, such as hexamethyldisiloxane, are low in toxicity and contain no halogen atoms. They are chemically very stable. On the other hand, they have flash points and only moderate solvency -- and they are expensive. Semi-aqueous systems. The problem of proper disposal of semi-aqueous systems is often overlooked. Because of the high organic content, it is not appropriate (or legal in most cases) to dispose of these systems down the drain. Separation and recycle of the organic phase is usually difficult and is not cost-efficient. Slow drying and potential corrosion problems may also come into play. Aqueous systems. Aqueous systems are very inexpensive in terms of cleaner cost, but they are not suitable for many applications. Slow drying and residues on the clean parts are two major problems. Corrosion of metal parts may also be a factor. Finally, electrical and electronic applications usually cannot tolerate the presence of any remaining traces of water. No clean systems. Some manufacturers have eliminated the need to clean at various stages of manufacture. Sometimes this requires a change in the manufacturing process or the order of assembly.

l e r iv 1 n i

A new solvent/cleaner based on normal-propyl bromide (nPB) has been developed to meet the needs of those who require the cleaning efficiency of the chlorinated solvents, but who must meet the strict environmental standards for a replacement solvent.* The new solvent/cleaner does not suffer from many of the short-comings of other alternative solvents that have been offered to the market. nF'B is an effective cleaning agent. It is safe to use under the proper conditions, has a low ODP and a low GWP, and it is not regulated under most environmental and worker safety

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Latent Heat of Vap., caVgm

Sol. in Water, g d 1 0 0 gms water

Sol. of Water, gmd100 gms solv.

Surface Tension, 25"C, dynedcm

Flash Point, TCC, "C

Flammability Limits, volume ?LO

rules. It is compatible with metals, has a low tendency to cause corrosion and may be used in most current vapor degreasing equipment. It is easily recycled and is moderately priced.

58.8 57.5 57.2 52.3 33

0.24 0.07 0.11 0.18 0.033

0.05 0.05 0.03 0.042 0.03

25.9 25.6 26.4 19.3 16.2

None None None None None

4-7.8 7-13 8-10.5 7.6-17.7 None

Physical Prop-

Table I compares the physical properties of nPB to two hydrochlorocarbons and two hydrochlorofluorocarbons. HCFC-14lb is CH3-CCI2F, and HCFC-225 is a mixture of the two isomers CF,-CF,-CHCI, and CF,CI-CF,-CHCLF. The physical properties of the nPB are similar to all four of these solvents, but particularly so to TCA.

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ng - Power

Indicators that relate to the cleaning ability of a solvent are the solubility parameters These are the Hildebrand Parameter, the Kauri Butanol Number and the Hansen Parameters As indicated by the data in Table 11, these values for nPB compare quite well to the common chlorocarbons.

Non-Polar"

Polar"

TABLE II

16.0 17.0 18.0 18.2 19.0

6.5 4.3 3.1 6.3 6 5

11 Hansen Parameters:

Hydrogen Bonding"

4.7 2.1 5.3 6.1 2.9

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performance in removing polyol esters This experimental results are consistent with the Hansen Parameters which show that nPB has a slightly lower value for non-polar materials and higher values for polar and hydrogen bonding compounds. I

The cleaning power of nPB based cleaners is clearly equivalent to the popular chlorinated solvents that have been banned or restricted. Comparisons to the new alternative solvents that have been introduced to replace the chlorinated materials are even more dramatic. Again, it is instructive to first compare the relative solvency power of nPB to some of the new solvents that are being offered in the cleaning market.

Table I11 compares the Kauri Butanol Number of nPB to decafluoropentane (DuPont Vertrelm XF), perfluorobutylmethyl ether (3M HFE 7100), dichloropentafluoropropane (Asahi Glass AK-225) and hexamethyldisiloxane (Dow Coming OS-10). By this one measure, superior performance is expected from the cleaning formulations based on nPB.

fiQka.u w t a n o l Numbe r

normal-Propyl Bromide /I (Albemarle ABZOLTM Cleaners) I

Dichloropentafluoropropane (Asahi Glass AK-225)

Hexamethyldisiloxane (Dow Coming OS-10)

125

31

17

Decafluoropentane I (Vertrel" XF) I 9

Perfluorobutylmethyl ether II (3M HFE-7100) I 10

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Ranking Relative to ABZOLTM VG Cleaner

4 . 7 AEZOLTM VG Cleaner

E4 1,1,1-Trichloroethane Trichloroethylene Perchloroethylene Methylene Chloride

Graoh 1. Relative cleaning performance of a klly formulated cleaning solvent based on nPB and some ~ of

ABZOL VG H Vertrel XF HFE-7100 AK-225 os-IO

Graph 2. Relative cleaning performance of a hlly formulated cleaning solvent based on nPB and a selection of other new alternative solvents.

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Cleaning of Electronics Components

The electronics industry faces some cleaning challenges not found in other types of cleaning applications. In particular, it is of utmost importance that ionic residues remaining on integrated circuit boards after soldering operations be removed to very low levels. Cleaners based on nPB and formulated for vapor degreasing have proven to be surprisingly good at the removal of ionics. However, a new formulation designed specifically for the electronics industry ha5 recently been introduced. ABZOLTM EG Cleaner is a narrow boiling range (azeotropic or near azeotropic) blend of nPB, a specifically selected alcohol, and the appropriate levels of stabilizers.

Two independent experiments have demonstrated the high efficiency of the ABZOLm EG Cleaner formulation for the removal of ionic residues from circuit boards. In one experiment, circuit boards were prepared by a potential customer. They were cleaned and evaluated for cleanliness at Detrex Corporation using an Omega Meter. In the second, circuit boards were prepared by Contamination Studies Laboratories (CSL). These boards were cleaned at the Albemarle Technical Center and returned to CSL for evaluation by the Omega Meter and by Ion Chromatography.

The circuit boards prepared by the potential customer were made of polyimide and were 6"x7" with solder mask on both sides. Each board contained twelve 20-pin LCCs (Leadless Chip Carriers) and two 68-pin LCCs. The LCCs had 50 mil pitch centers (distance between leads). The boards prepared by CSL were JPC-B-36 boards. First they were pre-cleaned to less than 0.1 microgradsqh of NaCl residues. Alpha Metals RA321 RA solder paste was hand applied to the test pads. The paste was reflowed in an oven in the usual fashion. M e r cooling, the boards were sprayed with Kester 1585-Mil RA flux and again reflowed.

The cleaning process at Detrex emulated an in-line process at the customer which included immersion in the boiling solvent for 100 seconds and the use of spray wands. The cleaning process at Albemarle employed a batch vapor degreaser with three minutes immersion in the boil sump. Three circuit boards were cleaned by each combination of cleaning process and evaluation. The levels of ionic contamination found on the boards were:

Detrex CSL CSL I2Qad.m Meter shmahwx Ion Chromatograp hy

1 4.4 pgms/in2 2.30 pgms/in2 2.87 pgms/in2 2 3.9 3.10 2.18 - 3 fiA m - 2.55 Ave. 4.9 pgms/in2 2.70 pgms/in2 2.55 pgms/in2

Standard Requirements Mil-C-28809 <14.0 pgms/in2 Mil-STD-2000 <14.0 NASA NHB 5300.4 (3A-7) <10.0

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Contamination Studies Laboratory noted in their report that the maximum historically acceptable level for ionic contaminants is 14.0 pgms/in2 (see Mil specs above). The report judges ABZOLTM EG Clemer to perform better than the Freon TMS benchmark.

Evaaoration Rates

From the standpoint of raw material costs, the most economical class of substitutes for chlorinated solvents are aqueous systems. These cleaning systems suffer from two major drawbacks. The first is that they employ non-volatile surfactants and thus have a potential for leaving a residue. The second is the slow drying. The latter can be improved only by the installation of specialized drying equipment. Cleaning systems based on nPB have drying rates that are comparable to the chlorinated solvents. To compare evaporation rates, loss of weight from 2 ml of solvent at room temperature (24°C) was measured after five minutes. Graph 3 compares the relative rate of evaporation of an ABZOLW Cleaner to four common chlorinated solvents.

Evaporation Rates Relative to l,l,l-Trichloroethane, RT

" Relative Rates

Evaporation rates from normalized weight loss of 2 mL of sobent afler 5 minutes at room temperature.

Graph 3 . Relative rates of evaporation for nPB based cleaners and chlorinated solvents

Thermal Stab ility

A knowledge of the thermal stability and thermal degradation products of a new solvent is important for safety considerations during use. Buildup of contaminants on heating elements, for instance, can cause localized hot spots that may degrade the solvent. It is important to know at what temperature this will occur and to insure that the products of the degradation are not dangerous or highly toxic. Two different approaches were taken to determine thermal stability.

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Thermal degradation studies were conducted by Columbia Scientific using the Accelerating Rate Calorimetry (ARC) method. This method identifies the temperature for the onset of degradation by detecting the accompanying exotherm. For ABZOLTM VG Cleaner (a hlly formulated commercial cleaner based on nPB), a significant exotherm occurred at 2265°C. The test was terminated at 347°C. For ABZOLTM PS (nPB containing no additives), no exotherm was reported up to 395°C. However, the final pressure of the bomb after it was cooled was considerably higher than for the VG sample. Scrutiny of the temperature and pressure data shows that the temperature curve for the ABZOLw PS Cleaner flattened briefly at 226.5"C and that the rate of increase in pressure increased simultaneously. A possible interpretation of the data is that nPB thermally degrades at 226.5"C, but the event is either endothermic or it is slightly exothermic and is not detected by the ARC instrument. In the case of the ABZOLm VG Cleaner, which contains stabilizers, the products of the degradation react exothermically with one or more of the stabilizers present.

The degradation products formed in the experiments described above were trapped in a stainless steel bomb and analyzed by gas chromatographyhass spectrometry ( G U M S ) . The products are essentially the same from both the stabilized and the unstabilized nPB, although the ratios of the products are somewhat different. No free bromine or HBr is detected. Although trace amounts of methyl bromide and benzene are found, no products of a highly toxic nature form in significant quantities. Unlike chlorinated solvents, it is impossible to produce an extremely toxic compound such as phosgene.

The second approach to determining thermal stability was to simulate a real world failure of a heating element in a vapor degreaser'. A coiled nichrome wire was immersed in ABZOLTM VG Cleaner in the bottom of a 250 ml flask. The flask was connected to a dry ice/acetone trap which was vented to a laboratory hood. Electric current was passed through the nichrome wire until the exposed part glowed red hot. The cleaning solution boiled vigorously. The vaporized products were collected in the trap and analyzed by GCMS Unlike the ARC experiment that was conducted in the absence of air, some of the products formed in this experiment contain oxygen.

The decomposition products detected after the two experiments were:

ARC Method Propane Isobutane Butane Methyl bromide 2-Methyl butane Pentane Ethyl bromide Branched C,H,, isomers Isopropyl bromide

Subme reed N ichrome Wire Propene Methyl bromide Ethyl bromide Benzene Toluene Dipropyl ether 1,3,5-Trioxacycloheptane 4-Bromo-2-butanol 4-Bromo- 1 -butanol

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Excessively high temperature “hot spots” on the interior walls of a vapor degreaser can occur if the heating elements short circuit. The thermal degradation studies show that the use of ABZOLW Cleaners creates no risks that are not normally encountered in the event of catastrophic equipment failure.

f HBr Qrrosmitv o . .

Because hydrolysis of nPB produces HBr, while hydrolysis of chlorocarbons produces. HCI, it was important to determine the relative corrosivity of the two acids. Corrosion tests were carried out on carbon steel (CS) and stainless steel (SS) under static conditions. Two concentrations (saturated and dilute) and two temperatures (25 and 53°C) were used. HJ3r is less corrosive under all four of these conditions. The results are given in Table IV:

TABLE IV

Hvdrolvsis of nPB

Laboratory tests show that nPB is subject to a small degree of hydrolysis when contacted with water for extended times, particularly at elevated temperatures. In laboratory tests, a hlly formulated nPB cleaning solvent was compared with a hlly formulated l , l , 1-trichloroethane (TCA) cleaning solvent. After refluxing with water for 164 Ius, the layers were separated and analyzed. The nPB formulation showed 2-3 times as much hydrolysis as the TCA. These results are something of a trade-off with the corrosion data. nPB is more susceptible to hydrolysis than TCA, but is less corrosive if hydrolysis takes place.

Mate rials of Con struction - Comoatih ‘ ili tv wi th Meta I s and Dr um Linin

ABZOLTM VG Cleaner was tested for compatibility with metals according to Mil-T- 81533A 4.4.9. This is a metal corrosion test that was originally designed to test the suitability of TCA for military applications, The metal coupon is held half-submerged in the refluxing cleaning fluid for 24 hrs. It is then examined for signs of corrosion All of the following metals passed this test:

Page 1 1

Nickel Inconel Titanium Brass Copper Zinc Monel Aluminum Taqtalum Stainless steel 3 16L

Fresh aluminum surfaces react immediately with 1, 1,l-trichloroethane. n-Propyl bromide is much less reactive towards aluminum. If an aluminum coupon is scratched beneath the surface of TCA which contains no metal passivators, there is an immediate formation of a dark, brownish red color. If the test is repeated using nPB, no color formation is observed for several hours. At reflux, some small dark spots are observed on the edges of the aluminum coupons after three to four hours. Fully formulated nPB is completely safe for use with aluminum and other active metals.

Carbon steel 1010

In addition to the corrosion test, two month immersion studies were carried out at 130°F with carbon steel 1010, stainless steel 316 and high baked phenolic linings. All of these materials were shown to be suitable for long-term storage of cleaning fluids containing nPB. Most perfluorinated plastics are also suitable for storage.

w b i l i t y With Plastics and E l a w

Plastics and elastomers that pass short term compatibility tests (immersion in boiling solvent for fifteen minutes) include the following:

l?!.wtk Elastomers

AcculamTM epoxy glass AdipreneTM polyurethane AlathonTM HDPE AflasTM PTFE DelrinTM acetal* Buna-NTM rubber KynarTM polyvinyl fluoride* KalrezTM fluorelastomer* NylonTM (6 and 6.6) NeopreneTM polychloroprene Phenolics* Viton-ATM fluoroelastomer** Polyester (filled & unfilled) Viton-BTM fluoroelastomer** Polypropylene Teflonm PTFE* T e f z e P ethylene/PTFE* XLPEm crosslinked PE

* These materials are also compatible for long term (2 months) immersion at elevated temperature (65°C). ** The WonTM fluorelastomers are marginal for long term (2 months) immersion at elevated temperature (65°C).

Plastics and elastomers that were found to be unsuitable (U) or marginal (M) for contact

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with nPB at elevated temperature for short periods (1 5 min.) include:

Plastics Elastomers I

Low density polyethylene (M) Butyl rubber (M) EPDM-60 (U) UltemTM polyether imide (M) NBR nitrile rubber (M) Silicone (U)

WOW - Acute

n-Propyl bromide is toxic, but can be handled safely if reasonable precautions are taken. Below is a compilation of the current acute toxicology for nPB:

. . m a l i a n Gene- - nPB is negative for dominant lethal activity in rats at 400 mg/kg/day given for 5 days to male rats prior to breeding once weekly for 8 successive weeks. No difference in mating performance was noted in treated males. Their frequency of fertile matings, mean numbers of corpora lutea, number of implants per female, number of live embryos per female, and the dominate lethal index was comparable to the negative control group at weeks 1,2,3,4,5,6,7 and 8 after treatment. The frequency of dead implants was higher at week 8 of treatment compared to the control group, but no increase was observed in the dominate lethal index at that or any other time. The frequency of dead implants in the treated group was comparable to the control group at weeks 1,2,3,4,5,6 and 7.

Mamma lian M- ' - The half-life of nPB in the rat is very short ( approximately 2 hours). The majority of the administered dose is eliminated rapidly in expired air as the unchanged parent compound. The remainder is metabolized and excreted in the urine (predominant route) or in the expired air as C02(minor route).

Following a single intraperitoneal dose (200 mg/kg), the initial rate of excretion of unchanged (14C)-labeled parent compound in the expired air of the rat was rapid. Two hours after administration, 56% of the administered dose was exhaled as the parent compound. After 4 hours, 60% had been exhaled: only trace amounts were detected in expired air after this time. An earlier study also reported the elimination of the unchanged parent compound in expired air. Oxidation to C02 occurred only to a minor extent. Only 1.4 % of the total dose (or 3.5% of the metabolized dose) was exhaled as C02 over 48 hours. Approximately 40% of the total IF'- administered dose was available for metabolism in the rat and excretion in the urine.

T x' - The solubility of nPB in is approximately 0.25gllOOml water at 20 C. The 96 hour LCSO in flathead minnows is 67300 w g L .

Toxicolom - Chronic

Ninety day inhalation studies with rats were used to set the Albemarle Workplace Exposure Guideline ( A W G ) for workers using nPB on an eight hour shift, five shifts per week.

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The AWEG has been set at 100 ppm. At this level, solventkleaners based on nPB can be used safely with modem vapor degreasers and in other applications with proper handling. By comparison, the exposure guideline (PEL) for trichloroethylene is only 50 ppm (25 ppm in California).

Environmental and Health Regulatory Status

Worker safety, public safety and environmental protection are paramount in the development of any new product. The current status of n-propyl bromide and solventhleaner systems based upon it is:

1. SARA - Supefind Amendments and Re-authorizaton Act. This act requires reporting of inventories and emissions of listed chemicals and groups. nPB is not regulated.

2. HAP - Hazardous Air Pollutant. A listing of chemicals that the EPA has declared hazardous. nPB is not on the list.

3 . NESHAP - National Emission Standard for HAP. Sets standards for use of HAPS. Since nPB is not a HAP, these standards do not apply.

4. RCRA - Resource Conservation Recovery Act. Defines hazardous wastes and how to manage them. nPB is not regulated under this act.

5. GWP and HGWP - Global Warming Potential, Atmospheric Lifetime and Ozone Depletion Potential calculations were carried out in a cooperative effort by Atmospheric and Environmental Research, Inc. and the Center for Chemical and Environmental Physics at Aerodyne Research, Inc.' GWP is calculated relative to CO,, while HGWP (Halocarbon GWP) is calculated relative to CFC-11. HGWP method, CFC-11 is ten thousand times more detrimental as a global warming agent than is nPB. By the GWP method, it is fourteen thousand times worse than nPB, and nPB is only one tenth as bad as CO,.

GWP calculations were done using different integration time horizons. By the

GWP GWP GWP (100 yrs) (500 yrs)

3400 1400 CFC-11 1 .o 4500 nPB 0.0001 1.01 0.31 0.1

ComPound- GaYKSJ

6 . Atmospheric Lifetime - Ozone Depletion Potentials (as well as GWP) depend on the atmospheric lifetime of the substance in question. Ozone depletion takes place in the stratosphere. In order for a substance to have a high ODP, it must be able to work its way to the stratosphere. The atmospheric lifetime ofnPB is only eleven days by the latest estimate.' In comparison, TCA has a lifetime of 5.4 years.

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7. ODP - Ozone Depletion Potential. Models for calculating ODPs have generally been based on the assumption that the chemicals are relatively long-lived in the atmosphere. Because of the short atmospheric lifetime of nPB, certain assumptions had to be made relative to the rate of transport of the molecules and the free radicals that are formed when they dissociate. In a recently published paper, two different models were used, resulting in ODPs of 0.0019 and 0.027.4 More recently, Professor Don Wuebbles and associates at the Department of Atmospheric Sciences, University of Illinois, has determined that the ODP for nPB is only 0.006.5 For comparison, TCA has an ODP of 0.1.

8. PEL - Permissible Exposure Limit. This is the concentration of a material in the air that a worker can be safely exposed to over a time weighted eight hour work day, five days per week. Albemarle has set an Albemarle Workplace Exposure Guideline (AWEG) of 100 ppm based on 90 day inhalation tests.

9. VOC - Volatile Organic Compound. All volatile organic compounds are classified as VOCs until there is experimental evidence that they do not contribute to the formation of smog. Therefore, nPB is currently classified as a VOC and must be used in accordance with local regulations regarding VOCs. Studies are currently under way at the Statewide Air Pollution Research Center, University of California, Riverside, to determine the degree of photo reactivity of nPB and the types of photochemical products formed. The EPA will review this data to determine if nPB can be declassified.

10. SNAP - Significant New Alternatives Policy. This is the policy under which EPA gives approval for the marketing of a replacement for an ozone depleting chemical. ABZOLTM Cleaners have been commercial since January, 1997, under the EPA S N A P guidelines. The EPA has indicated in writing that they will soon publish a Proposed Rule in the Federal Register giving SNAP approval for cleaning, aerosols and emissive solvent uses. A thirty day comment period will follow before EPA makes the final ruling.

The H&E regulatory status for ABZOLW Cleaners is summarized in Table V.

Summarv

Solvent/Cleaner systems based on n-propyl bromide have been introduced as replacements for chlorinated solvents in cleaning applications. nPB is an aggressive, fast drying solvent that is suitable for a variety of difficult cleaning and degreasing applications. The use of nPB based solvents is not regulated under S A R q HAP, NESHAP or RCRA, and they are approved for sale under SNAP (further review by EPA possible). nPB has low potentials for ozone depletion and for global warming, but it is currently classified as a VOC. The Alhemarle Workplace Exposure Guideline is 100 ppm, which makes it safe to use with the proper precautions for worker safety. In comparative performance testing, nPB based formulations have been demonstrated to be as effective as chlorinated solvents and more effective than hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluorocarbon ethers and volatile methyl siloxanes.

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Reeulatlon SARA

I1 TABLE V

ABZOLTM Cleaners 1.1.1-Trichloroethane Trichloroethvlene

No Yes Yes

11

RCRA

HGWP

II Environmental and Health Regulatory Status II

~

No Yes Yes

0.0001 0.023 Almost Zero?

PEL

voc SNAP

II HAP I No I Yes I Yes I1

IO0 ppm* 350 ppm 50 PPm

Yes No Yes

Rule to be published Unacceptable Acceptable in Federal Register

IINESHAP I No I Yes I ~ Yes 11

/I ODP I 0.0064 I 0.1 1 Almost Zero? 11 I] Atmospheric Lifetime I 11 days' I 5.4 years 1 - ?? 11

1. Electronic Equipment

A company that produces electronic components for clinical equipment used in biomedical applications had used CFC 113 blends in both liquid and vapor phase defluxing6. Exacting performance standards, rate of throughput, space limitations, limited capital equipment budget and lack of an adequate industrial water system were major constraints on a changeover to a new cleaning system.

The company attempted to switch to a system based on d-limonene. Residue from the cleaning agent, buildup of rosin flux and reactivity to produce assorted oxidation products made the electronic components unsuitable for use. An unacceptable green residue remained on the assemblies and there was an increase in product failures.

M e r switching to a cleaning solvent made from n-propyl bromide (ABZOLTM VG Cleaner), the company found that the new cleaner did a better job of removing flux than the CFC- 113 blend. There were no residue problems as there were with d-limonene. Some of the plastic components did show some discoloration, but this problem was solved by shortening the exposure

Page 16

time -- an added benefit by increasing throughput.

2. Implantable Body Parts

Smith & Nephew Orthopedics (Memphis, TN) manufactures artificial body parts, such as hip joints, for implantation. The parts consist of a titanium bone replacement and an Ultra High Molecular Weight Polyethylene W E ) cartilage replacement. Standards for cleanliness are, of course, very high. In addition, Smith & Nephew expressed concern about retention of solvent in the UHMWPE parts. A final criteria is that the cleaning solvent must kill at least 50% of the bacterial spores on an artificially inoculated UHMWPE part. There were two cleaning solvents that Smith & Nephew wished to replace in their process. The first was based on HCFC-14lb. The second was based on trichloroethylene.

The initial set of experiments were for part cleanliness, and these were performed at BaronBlakeslee, Inc. (Long Beach, CA). UHMWPE parts were exposed to ABZ0Lm Cleaner vapors for 90 seconds. Both cleaned and uncleaned parts were returned to Smith & Nephew, who found the cleaning to be satisfactory. Acetabular components and hip stems were contaminated with buffing compound. These were cleaned using the BaronBlakeslee AutoBatch vapor degreaser. The cycle consisted of 30 seconds in the vapor, 5 minutes immersion in the ultrasonic sump at 130"F, 2 minutes TopHat drying and 2 minutes freeboard dwell. The parts were reported to be completely dry with no solvent drag out. BaronBlakeslee returned the parts to Smith & Nephew, who determined that the cleaning was satisfactory. In a third experiment, a femoral with finger prints was exposed to vapor for 90 seconds. Evidence of fingerprints remained after this test.

The second Smith & Nephew concern was retention of the solvent by the UHMWPE parts. ABZOLTM VG Cleaner was compared directly with commercial cleaning grades of HCFC- 141b and trichloroethylene. The test procedure was to place five parts in the boiling solvent for three (3) minutes. The parts were removed and placed in the same solvent at ambient temperature for two (2) hours. The parts were then removed and placed in an open dish. The dish was left in a firme hood with the fan going until it was time to take the measurements. To obtain the quantity of headspace vapors, the parts were placed in a sealed glass chamber and allowed to equilibrate for one ( I ) hour. The vapors were then analyzed using Gas ChromatographylMass Spectrometry and quantified against a standard. Measurements were taken at 24 hrs. and 96 hrs. for the ABZOLTM VG. For the other two solvents, the measurements were at 24 hrs. and 106 hrs The amount of vapor in the headspace has been converted to ppm by volume.

Concentration of So lvent in H e a w 96 or 106 hrs

ABZOLTM VG

Trichloroethylene HCFC-14lb

30 PPm 3.7 ppm 169 ppm 4.4 ppm 469 ppm 27 PPm

Page 17

These experiments indicate that the AE3ZOLTM VG Cleaner is retained in the UHMWPE parts to a lesser extent than either the HCFC-141b or the trichloroethylene.

, The third criteria was that the solvent/cleaner reduce bacterial spore counts on the

UHMWPE parts by at least 50%. Smith & Nephew supplied two sets of parts (six parts each) contaminated with SpordexB Buciflus Subiilis (globigii) spores. Each set was divided into two sets of three parts each -- one set to be cleaned and one set as a control. The cleaning procedure WaS:

1. Tests parts were placed in the basket of a laboratory vapor degreaser and covered with a metal screen to prevent the parts from floating to the surface. The degreaser contained AE3ZOLm VG Cleaner.

2. The basket was lowered into the vapor zone and remained there until condensation stopped.

3. The basket was then lowered into the boil-up sump (71°C) for 3 minutes (Set A) or 1.5 minutes (Set B).

4. The parts were placed in the rinse sump for 1 min. followed by the vapor zone for 1 min. The basket was allowed to hang in the free board zone for an additional minute to assure that the parts were dry.

The two sets of cleaned parts along with the accompanying control sets were returned to Smith & Nephew for analysis. The bioburden validation was done at Axios, Inc. (Kennesaw, GA). The results were:

.saw!e Suore Cou nt % Reduction

Sample A Control 5.5 x lo6 Cleaned 1.5 x lo6 73%

Sample B Control 8.8 x lo6 Cleaned 2.8 x lo6 68%

3. Aluminum Parts for Optical Applications

A manufacturer of optical equipment that uses anodized aluminum components. The parts have lettering and other markings on them. The customer requested an evaluation to make sure that the markings would not be damaged in the normal cleaning process. They sent four sets of components, each set containing six different parts. Two sets were cleaned in ABZOLTM VG

. .

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Cleaner by immersing in the boil-up sump for ten minutes followed by one minute in the rinse sump. The other two sets were immersed for only three minutes in the boil-up sump and then one minute in the rinse sump. All twenty-four parts were returned to the customer for examination. No damage to the parts was observed.

4. Electric Motor Stators

The Galley Products Division of B E Aerospace had a need to clean bumt oils from used electrical motor stators. They sent two such stators for cleaning. One was clean and the other was covered in oil. Both were cleaned using ABZ0Lm VG Cleaner. They were first lowered into the vapor zone of a vapor degreaser and held there until condensation of the vapor on the parts ceased. This required about 5 minutes. They were then lowered into the ultrasonic bath for ten minutes and back into the vapor zone for 5 minutes. The parts were returned to B E for examination.

B E Aerospace reported that the parts were “perfect”. No residual oils or other contaminants were found, and there was no damage to the electrical wiring or casings.

References:

1. Kanegsberg, B., “Precision Cleaning Without Ozone Depleting Chemicals,” Chemistry and Industry, #20: 787,21, Oct., 1996.

2. Shubkin, R. L., “A New and Effective SolventKleaner with Low Ozone Depletion Potential,” 1996 International Conference on Ozone Protection Technologies, Proceedings and Presentation, Washington, D. C., October 21-23, 1996.

3. Shubkin, R. L. and Liimatta, E. W., “A New Cleaning Solvent Based on n-Propyl Bromide,’’ NEPCON West ‘97 Conference, Anaheim, CA, February 23-27, 1997.

4. Nelson, D; Wormhoudt, J; Zahniser, M, Kolb, C; KO, M; Weisenstein, D, “On Reaction Kinetics and Atmospheric Impact of 1-Bromopropane,” The Journal of Physical Chemistry A, VOI. 101,4987-4990, 1997.

5. Wuebbles, D. J., Jain, A. K., Patten, K. 0. and Connell, P. S., “Evaluation of Ozone Depletion Potentials for Chlorobromomethane (CH2ClBr) and 1 -Bromo-Propane (CH2BrCH2CH3)”, Atmospheric Environment, in press.

6. Kanegsberg, B., “Cleaning High Value Components for Biomedical and Other Applications,” 1996 International Conference on Ozone Protection Technologies, Proceedings and Presentation, Washington, D.C., October 21-23, 1996.