ENVIRONMENTALLY-SAFE SOLVENT COMPOSITIONS UTILIZING
1-BROMOPROPANE THAT ARE STABILIZED, NON-FLAMMABLE, AND HAVE
DESIRED SOLVENCY CHARACTERISTICS
Cross-Noting to Related Applications
This application is a continuation-in-part of U.S. Patent Application 08/598,798 filed February 9, 1996; claims the benefit of U.S. Provisional Patent Application No. 60/046,799, filed May 2, 1997; is a continuation-in-part of U.S. Patent Application 08/818,971 filed March 14, 1997; is a continuation-in-part of U.S. Patent Application 08/932,724 filed September 18, 1997; and is a continuation-in-part of U.S. Patent Application 09/022,779 filed December 2, 1997.
Background of the Invention
This invention pertains to the art of solvent compositions and more particularly to solvent compositions that are stable, non-flammable, and environmentally safe.
The invention is particularly applicable to cleaning compositions for removing hydrocarbon-soluble contaminants, such as oil, grease, and rosin, from articles using conventional cleaning techniques and will be described with particular reference thereto. However, it will be appreciated that the invention may be advantageously employed with inks, coatings, and adhesives and in lubricant-carrying, spot -free, water drying as well as other environments and applications .
Heretofore, solvent or cleaning compositions have been widely used in immersion cleaning, ultrasonic cleaning, wipe cleaning, aerosol cleaning and vapor degreasing. These techniques involve exposing contaminated articles to a solvent to dissolve and removes contaminants. The contaminants often consist of oil, grease, flux or other
hydrocarbon-soluble material. In addition, contaminants can include any unwanted non-soluble particles adhering to the hydrocarbon-soluble contaminants .
Ozone Depleting Solvents In recent past, solvents of choice for vapor degreasing and ultrasonic cleaning were 1, 1, 1-trichloroethane and trichloroethylene. Other solvents for cleaning were chlorofluorocarbon solvents such as CFC-113, and various hydrochlorofluorocarbons such HCFC-141B. However, the problem with these solvents and others is that they are now listed by the United States Environmental Protection Agency as ozone-depleting chemicals and have been or are being phased out of production. In this regard, they all have ozone depleting potentials of 0.1 or greater which makes them dangerous to the earth's ozone layer and subject to regulation.
Volatile Organic Compounds
Another problem with many hydrocarbon-based solvents is that they form ground-based ozone which can turn into smog. More particularly, upon evaporation, certain highly-reactive hydrocarbon-based solvents combine with hydroxyl radicals in the presence of ultraviolet (UV) light. When this occurs very close to the ground, it can produce photochemical smog. Smog is harmful and sometimes dangerous in part because it reduces visibility for drivers of vehicles. Some cities with severe smog actually issue "alerts" to warn drivers. Although smog is partially caused by hydrocarbon emissions from cars, another major contributor is industrial use of hydrocarbon-based solvents such as hexane and toluene .
The difference between solvents that form ground- based ozone and those that do not is defined by the reaction
rate of ethane. If a compound has a reaction rate with the hydroxyl radical and UV light that is faster than ethane, the compound is deemed to react too close to the ground such that it forms ozone and smog. These "highly-reactive" compounds are termed volatile organic compounds (VOCs) . On the other hand, if a compound has a reaction rate that is slower than ethane, the compound reaches higher into the atmosphere before reacting with the hydroxyl radical and UV light. In such instances the non-VOC compound does not contribute to the formation of ground based ozone and smog.
Flammable Solvents
Other solvents that have been used for cleaning are alcohols. These types of solvents can have sufficient solvency power to completely dissolve unwanted oil, grease or hydrocarbon-soluble contaminants. However, alcohols have limited use because they are flammable.
Unstable Solvents
Still another problem with certain solvents is their lack of stability. In this regard, many halogenated solvents decompose in the presence of water and certain metals. The decomposition creates corrosive acids which can attack cleaning apparatuses and articles that the solvents were intended to clean. Further, the decomposition can release harmful gases into the air. The stability is even more of a concern with flammable solvents .
Weak Solvents
Still other solvents are less effective because they have low solvency power. Hydrofluorocarbons (HFCs) such as 2,3-dihydroperfluoropentane are non-flammable and exhibit good environmental and toxicological characteristics . This particular HFC solvent has been granted approval under the
Significant New Alternatives Program (SNAP) by the U.S. Environmental Protection Agency. However, this solvent and HFCs generally have low solvency compared to the chlorinated or brominated solvents. This drawback significantly limits the use of HFCs . One solution has been to mix the HFC with trans-dichoroethylene; however, trans-dichloroethylene can only be added in very low amounts to avoid flammability.
Alcohols such as methanol and isopropanol have also suffer from low solvency power. Hydrochlorofluorocarbon (HCFC) have been added to alcohols in the range of 3.5-7 percent by volume to improve solvency for inorganic flux residue. However, HCFC solvents have been banned under the Montreal Protocol for their inherent ozone depletion potential.
Overly Aggressive Solvents
Each solvent has an associated Kauri butanol which is a measure of its solvency power. The higher the Kauri butanol value (kb) the stronger the solvent. Preferably, the Kauri butanol value is high enough to completely dissolve the unwanted oil, grease or hydrocarbon-soluble contaminant. The brominated solvents such as 1-bromopropane and chlorobromomethane have very high Kauri butanol values of around 126-132 which make them particularly effective cleaning agents for metallic materials. A problem arises if it is desired to clean articles such as printed circuit boards and medical devices which contain plastic or solvent-sensitive material. Cleaning agents such as 1-bromopropane and chlorobromomethane are far too powerful to clean materials containing plastic. For example, 1-bromopropane by itself damages most plastics because of its high Kauri butanol value of 126.
In the past, this problem was addressed by using "gentler" solvents such as the chlorofluorocarbons CFC-113
and HCFC-141b. These chlorofluorocarbons have Kauri butanol values of only 30 and 70, respectively. These solvents remove flux and oils from solvent sensitive substrates without attacking and dissolving the substrates or removing identifying markings used in the printed circuit board industry. However, these chlorofluorocarbons are environmentally unsafe in that their ozone depleting potentials are greater than 0.1.
U.S. Patent No. 5,403,507 to Henry discloses cleaning compositions of dibromomethane and stabilizing agents. The compositions have a boiling point of 210 degrees. Although the compositions are effective cleaning agents, their solvency is too high for solvent-sensitive materials. Further, the compositions are no longer considered environmentally safe. They all have ozone depleting potentials of 0.1 or greater which makes them dangerous to the earth's ozone layer and subject to regulation. Still further, the boiling point is too high to clean some heat-sensitive articles.
Other Art
Other art attempts to address these concerns without arriving at a practical solution. For example, U.S. Patent No. 4,193,838 to Kelly et al . describes a method in which a pool of hot saturated vapors of a halogenated solvent are used to remove thermoplastic resin. In practice, the method would be very dangerous because the halogenated solvents, which are unstabilized, would become very acidic within minutes . The acidic solvent would then damage the cleaning apparatus and probably any article being cleaned. U.S. Patent No. 4,115,461 to Archer et al. describes a method for stabilizing non-flammable trichloroethane using a mixture of three stabilizing agents. The agents include 1,4-dioxane, 1,2-butylene oxide, tert-amyl
alcohol, nitromethane and 1, 3-dioxolane. Although these agents may be effective stabilizers with tricloroethane, they are not necessarily effective with other solvents. More importantly, if the solvent is self-extinguishing rather than non-flammable, the range of stabilizers taught in Archer et al . would make the solvent mixture flammable. This would bar the solvent mixture from being used in many cleaning applications, especially in vapor degreasing.
U.S. Patent No. 5,403,507 to Henry discloses cleaning compositions of dibromo ethane and stabilizing agents. The compositions have a boiling point of 210 degrees. Although the compositions are effective cleaning agents, their solvency is too high for solvent-sensitive materials. Further, the compositions are no longer considered environmentally safe. They all have ozone depleting potentials of 0.1 or greater which makes them dangerous to the earth's ozone layer and subject to regulation. Still further, the boiling point is too high to clean some heat-sensitive articles. U.S. Patent No. 4,056,403 issued to Cramer et al . describes a method and composition for cleaning polyurethane foam generating equipment. The composition includes methylene chloride or other halogenated hydrocarbon and a monohydric alcohol . These compositions have solvencies too high for solvent-sensitive materials. Further, the compositions have ozone depleting potentials of 0.1 or greater making them subject to regulation.
U.S. Patent No. 3,924,455 to Bergishagen discloses a method and composition for stripping brittle lacquer coatings from plastic models without damaging the plastic. The composition comprises halogenated solvents, glycol ethers and mineral spirits. This method and composition has several drawbacks. The composition is not stabilized and therefore must be handled carefully to prevent water- and/or metal-
initiated decomposition. Further, the composition is not environmentally safe. Regarding the method, before applying the stripping composition, the coated plastic must be cleaned with alcohol and allowed to dry for about \4 hour. These additional steps diminish the value of the method.
Objects of the Invention
A desired solvent or cleaning composition has the following characteristics: 1) stabilized from decomposition in the presence of water and/or metals; 2) non-flammable at room temperature and/or at temperatures of vapor degreasing; 3) an ozone depletion potential of less than 0.1; 4) a Kauri- Butanol value below 92 so that it will not damage plastics or other solvent-sensitive materials; 5) an evaporation rate of at least 3; and 6) leave no residue on evaporation. Thus, an object of the present invention is to provide effective cleaning compositions which are suitable for removing hydrocarbon-soluble contaminants from electronic, plastic and metallic materials.
Another object of the present invention is to reduce the Kauri Butanol Value of stabilized and unstabilized cleaning solvents.
Another object of the present invention is to provide solvent compositions which are non-flammable and non- ozone depleting. Another object of the present invention is to provide a safe "drop in" substitute for cleaning apparatuses and techniques which currently use environmentally unsafe or overly strong solvents.
Summary of the Invention
The present invention contemplates a new and
improved compositions and methods which overcome all of the above referenced problems and others .
In accordance with the present invention, there is provided an environmentally-safe, low volatile organic compound (VOC) , non-flammable or self-extinguishing, solvent composition. The composition contains: 10-99.99999 %, by total volume of the composition, 1-bromopropane; and one of a stabilizing agent and solvency-adjusting agent.
In accordance with a more limited aspect of the invention, the composition contains approximately 4.0-6.4 %, by total volume of the composition, n-propanol, to sufficiently increase a Hansen solubility parameter.
In accordance with another more limited aspect of the invention, the solvency-adjusting agent contains approximately 30-90 %, by total volume of the composition, hydrofluorocarbon .
In accordance with yet another more limited aspect of the invention, the stabilizing agent is selected from the group consisting of: pyridine; triethylamine; morpholine; n- alkylmorpholines in which the alkyl group has 1-7 carbon atoms; diisoalkylamine having 3-4 carbon atoms; dicyclohexylamine; aliphatic alcohols having 1-10 carbon atoms; propargyl alcohol; glycerol; 3-methyl-pentyn-3-ol; ephichlorohydrin; epibromohydrin; butylene oxide; furan; phenol and its derivatives; ethers having 1-5 carbon atoms; nitroalkanes having 1-7 carbon atoms; and cyclohepto-1, 3 , 5- triene.
A principal advantage of the invention is a solvent that is non-flammable, low- or non-VOC and has an ozone depletion potential of less than 0.1.
Another advantage of the invention is an effective cleaning composition for cleaning hydrocarbon-soluble contaminants from articles without damaging those that are solvent-sensitive .
Another advantage of the invention is that it may be used in place of solvents such as CFC-113 and HCFC-141b in current cleaning apparatuses and techniques without any changes thereto . Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.
Detailed Description of the Preferred Embodiment
The cleaning compositions as herein described and as set forth in the claims are expressed in terms of percentages by volume unless clearly indicated to the contrary.
In a preferred embodiment of the present invention, an effective solvent or cleaning composition contains mostly 1-bromopropane also known as n-propyl bromide ("NPB") . This solvent has high solvency power, a low-ozone-depletion potential and is non-VOC.
However, full industrial acceptance of 1- bromopropane would remained limited because it easily decomposes in contact with water and certain metals, which causes it to generate corrosive amounts of hydrogen bromide. This decomposition can occur even when the solvent is used in a cold liquid phase, although the decomposition reaction is more likely to occur at high temperatures and especially in the hot vapor phase. Accordingly, 1-bromopropane should be stabilized.
Further, 1-bromopropane has certain other disadvantages which require the addition of other components depending on the application. More particularly, l- bromopropane is flammable and overly aggressive with solvent- sensitive articles such as plastics. Accordingly, various
preferred embodiments described below address one or more of the disadvantages of 1-bromopropane.
Non-flammable or self-extinguishing embodiments containing 1- bromopropane That Have a Higher Hanson Solubility Index 1-bromopropane has a boiling point of 71° C and a flash point at 22-24° C. Flash point tests have been performed which show that 1-bromopropane is self- extinguishing at temperatures up to its boiling point. Self- extinguishing means that the solvent has flammable limits in air. 1-bromopropane is self-extinguishing in an open cup test in which it has a flash point but not a fire point. In closed cup flash point tests, 1-bromopropane still ignites. Because 1-bromopropane is not completely non-flammable, there are some safety concerns with use of this solvent . In one non-flammable embodiment, a solvent mixture includes 1-bromopropane and n-propanol. N-propanol is flammable. Accordingly, n-propanol is preferably in an exact amount to decrease the mixture's solvency while still keeping the mixture self-extinguishing. Very small amounts of stabilizing agents may also be added if necessary.
In Table 1 below, n-propanol is added to 1- bromopropane in very precise amounts. At each amount, the flammability is measured by a TAG Closed Cup method. In addition, the Hansen solubility parameter is shown in the table. The Hansen solubility of a solvent is an indication of the solvents relative polarity. The lower the Hansen solubility parameter the more a solvent can dissolve non- polar hydrocarbon materials such as rosin or paraffin oil . The higher the Hansen solubility parameter the better the solvent is able to dissolve inorganic materials such as a salt. The Hansen solubility range is usually 6-13 where 6 is the parameter for a compound such as a mineral spirit and 13 is for a compound such as ethanol .
Table 1. Test Summar For N-Pro anol Plus 1-Bromo r
Accordingly, a preferred embodiment includes
1-bromopropane and 4.0-6.4 vol. % n-propanol. In the above chart, this mixture is shown to have a sufficiently increased Hansen solubility parameter while remaining self- extinguishing. In contrast to other mixtures, this embodiment does not create a fire hazard upon extended boiling in a vapor degreaser. The preferred combination would have the proper amount of n-propanol to give the required increase in solubility for inorganic flux residue found on circuit boards for example. In another preferred embodiment, a solvent composition comprising 4 percent by volume of n-propanol and 96 percent of stabilized 1-bromopropane is prepared. After a flash point measurement is made it is seen to be self- extinguishing. It is then placed in a standard sump type vapor degreaser and brought to a boil. A circuit board which has been coated with inorganic flux residue is then placed in the vapors. After 2 minutes of exposure time the flux residue is seen to be removed.
In another preferred embodiment, a solvent composition comprising 6.4 percent by volume of n-propanol and 93.6 percent of stabilized 1-bromopropane is prepared. After a flash point measurement is made it is seen to be
self-extinguishing. It is then placed in a standard sump type vapor degreaser and brought to a boil . A circuit board which has been coated with inorganic flux residue is then placed in the vapors. After 1 minute of exposure time the flux residue is seen to be removed.
Lower-solvency and Non-flammable Embodiments Containing 1-bromopropane
1-bromopropane is very aggressive on plastic substrates where it causes crazing, etching and sometimes dissolves the plastics. This is not acceptable in many sensitive applications such as in electronics where very solvent sensitive plastics are common.
In a preferred embodiment, a hydrofluorocarbon (HFC) , which contains only hydrogen, fluorine, and carbon atoms, is mixed with 1-bromopropane in an amount sufficient to make the mixture non-flammable by Tag Closed Cup testing.
In another preferred embodiment, an HFC is mixed with 1-bromopropane in an amount sufficient to make the 1- bromopropane safe for use on plastics substrates . These and additional embodiments are more particularly shown in the table below. Various mixtures of 1-bromopropane and the HFC were tested for attack on polycarbonate plastic. The plastic was dipped into the solvent mixture for 1 hour and then examined for crazing or etching. The various mixtures were also tested for their flash points by the Tag Closed Cap method.
Table 2.
Test Summary for Hypdrofluorocarbon (HFC) Plus 1-Bromopropane (NPB)
Effective cleaning can be done in less than 1 hour, i.e., the test described above represents prolonged immersion in the cleaning composition. When using the cleaning composition, a higher amount of NPB may be added than indicated in the test. Accordingly, desired cleaning embodiments contain the following:
Table 3
In another preferred embodiment, a mixture contains 40% by volume of hydrofluorocarbon solvent and 60% by volume
of 1-bromopropane. A Tag Closed Cup flash point test was performed and the mixture was found to have no flash point. Thus, the embodiment would be classified as non-flammable. In still another preferred embodiment, a mixture contains 70% by volume of a hydrofluorocarbon solvent and 30% by volume of 1-bromopropane. A piece of polycarbonate plastic was immersed in this mixture for 1 hour and was examined for crazing, etching or dissolving of the plastic. No solvent attack was observed. In yet another preferred embodiment, a mixture contains 40% by volume hydrofluorocarbon solvent, 4% 1,3- dioxolane, 0.5% 1,2 butylene oxide, 0.5% nitromethane and 55% 1-bromopropane is prepared. A Tag Closed Cup flash point test was performed and the mixture was found to have no flash point. Thus, the embodiment would be classified as nonflammable.
These lower-solvency and non-flammable solvents are useful in aerosol, immersion, or wipe cleaning, lubricant carrying, spot-free water drying and other applications.
Stabilized Embodiments Containing 1-Bromopropane
In a preferred stabilized solvent composition, 1- bromopropane is mixed with a stabilizing mixture comprising nitromethane, 1,2-butylene oxide and 1, 3-dioxolane . The stabilizing mixture prevents or inhibits the 1-bromopropane from turning acidic and releasing bromine into the air. Each of the components of the stabilizing solvent mixture is selected to have a low boiling point, preferably around the boiling point of 1-bromopropane.
In another preferred embodiment, the cleaning composition contains about 95% 1-bromopropane, 4% 1,3- dioxolane, 0.5% 1,2 butylene oxide and 0.5% nitromethane. It is not necessary to have these exact values to obtain the advantages of the present invention.
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0.2% p-tert-amyl phenol 0.3% 3-methyl-l-pentyn-3-ol
Example 2 Stabilizer system: 0.1% 5, 6,7, 8-tetramethyl-5, 6,7, 8-tetrahydro-2-napthol
0.3% 3-methyl-l-pentyn-3-ol.
Examples 1-2 utilized a combination of a tertiary acetylenic monohydric alcohol and a phenolic compound.
Example 3 Stabilizer system
0.09% furfuryl alcohol
Example 4 Stabilizer system:
0.012% furfuryl mercaptan
Examples 3-4 utilized a small amount of either a cyclic carbinol or a corresponding mercaptan. Concentrations of 0.05-0.5 % by volume provide significant inhibition.
Example 5 Stabilizer system: 2.0% 1,4-dioxane
0.03% styrene oxide
Example 6 Stabilizer system:
2.0% 1,4-dioxane 0.03% phenyl glycidyl ether
Example 7
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Stabilizer system:
3.0% 1, 3-dioxolane
0.5% nitromethane
0.5% phenyl glycidyl ether
Examples 6-7 utilize a primary stabilizer such as styrene oxide, phenyl glycidyl either and mixture thereof and a second stabilizer from the group of a primary, secondary or tertiary alkanol, a 1-3 carbon atom aliphatic nitro compound, 1,4-dioxane or 1, 3-dioxolane. Below are additional preferred embodiments described in percent by volume. One preferred embodiment includes approximately: 1-bromopropane 90-98%; 0.5-6.4% tert- butyl alcohol or n-propanol; 0.1-4% dimethoxymethane or diethoxymethane ; 0.1-3% of a mixture of 2 or more epoxides selected from the group: butylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, and epibromohydrin.
Another preferred embodiment includes approximately: 1-bromopropane 90-98%; 0.5-6% 1, 3-dioxolane; 0.1-4% nitromethane or nitroethane; 0.1-3% of a mixture of 2 or more epoxides selected from the group: butylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, and epibromohydrin.
Yet another preferred embodiment includes approximately: 90-98% 1-bromopropane; 0.5-6% 1, 3-dioxolane; 0.1-4% nitromethane or nitroethane; 0.001-2% n-ethyl morpholine or n-methyl pyrollidone; and 0.1-3% of a mixture of 1 or more epoxides selected from the group : butylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, and epibromohydrin. Still another preferred embodiment includes approximately: 90-98% 1-bromopropane; 0.5-6.4% tert-butyl alcohol or n-propanol; 0.1-4% dimethoxymethane or diethoxymethane; 0.1-3% of a mixture of 2 or more epoxides
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Additional embodiments are described in Table 5 below. Column 1 provides a list of stabilizing agents which can be used in combination with 1-bromopropane to provide an improved cleaning composition. Only a quantity of stabilizer sufficient to retard or to stop the reaction of metals and water with 1-bromopropane needs to be used. The stabilizing agent can be used alone or in combination with the additional component or components listed directly across from it in the third column of Table 5 to form a mul i-component stabilizing agent .
The cleaning solution of this invention includes about .00001-10 vol . % of one or more of the stabilizing agents listed in Table 5, with the remainder of the solution being 1-bromopropane . Optimum concentrations of the one or more stabilizing agents range from about 0.1 vol% to about 1.5 vol% . When a stabilizing agent is used in combination with one of the additional components, the total concentration of the stabilizing agent and additional components ranges from about .00001 vol . % to about 10 vol . % and preferably from about 0.1 vol . % to about 1.5 vol%.
Table 5.
Stabilizing Agents Used for the Stabilization of 1 -bromopropane
Stabilizing vol . % Additional vol . % Agent Components pyridine 0.001-0.3 butylpyrocatechol 0.001-0.3 triethyla ine 0.01-0.3 butylene oxide 0.001-0.3 morpholine 0.1-1.0 phenol 0.001-1.0 n-alkylmorpho- 0.001-0.1 alkyl phenols in 0.001-1.0 lines in which which the alkyl the alkyl group has 1-7 group has 1-7 carbon atoms carbon atoms
n-alkylmorpho- 0.001- alkyl phenols in which 0 001- lines in which 0.1 the alkyl group has 1-7 1 0 the alkyl group carbon atoms has 1-7 carbon atoms n-alkylpyrroles 0.001- tetrahydrofuran, or 0.01-1.0 in which the 1.0 mono- or bicyclic epoxy alkyl group has compounds 1-7 carbon atoms diisoalkylamine 0.001- alkylphenol, in which 0.001- s having 3-4 1.0 the alkyl group has 1-7 1.0 carbon atoms carbon atoms, or aliphatic alcohols having 1-10 carbon atoms, straight chain or branched chain ketones having 1-10 carbon atoms dicyclohexyla- 0.001- mono- or bicyclic epoxy 0.01.10 mine 0.5 compds . or phenol aliphatic 0.1- nitro compds. or phenol 0.05-1.0 alcohols having 4.0 and its derivatives 1-10 carbon including napthols atoms propargyl 0 001- epichlorohydrin, 0.001- alcohol 1 0 nitromethane , N-methyl 0.5 pyrrole or 1,1- dialkylhydrazine in which the alkyl group has 1-10 carbon atoms glycerol 001- phenol and its 0.001- 0 derivatives, mono- or 1.0 bicyclic epoxy compds., diisopropyl-amine
3 -methyl - 0.3- epichlorohydrin, 0.05-1.0 pentyn-3-ol 1.0 dihydrooxybutane, or phenol epichlorohydrin 0.002- aliphatic amines having 0.001-
0.5 1-5 carbon atoms, 0.5 propargyl alcohol, or nitroalkanes having 1-7 carbon atoms, or phenol
19 -
epibromohydrin 002- n-methylmorpholine or 0.001-
5 allyl glycidyl ether in 0.5 which the allyl group has 1-10 carbon atoms butylene oxide 0.25- phenols and its 0.001- 0.5 derivatives, lactams, 1.0 oximes, hydrazones, disulfides, acetals, amines furan 1.0- phenyl glycidyl ether, 0.005- 10.0 aliphatic nitro compds. 0.5 having 1-7 carbon atoms or acetals phenol and 0.02- amines having 1-7 0.0001- derivatives 1.0 carbon atoms, aliphatic 10.0 alcohols having 1-10 carbon atoms, or epichlorohydrin ethers having 0.05- diethylethanolamine 0.1-5.0 1-5 carbon 5.0 atoms nitroalkanes 0.01- pyrrole and its 0.1-5.0 having 1-7 5.0 derivatives or phenol carbon atoms cyclohepta- 0.01- unsaturated tertiary 0.03-0.6 1,3, 5-triene 5.0 amines having 1-10 carbon atoms
1, 4-dioxane 1.0- styrene oxide or phenyl 0.001- 10.0 glycidyl ether 5.0
Additional preferred embodiments are listed below as examples. These examples inhibit the decomposition of 1- bromopropane . All examples include 1 -bromopropane as the balance of the mixture .
Example 1 Stabilizer system:
selected from the group: butylene oxide, propylene oxide, cyclohexene oxide, epichlorohydrin, and epibromohydrin.
Another preferred embodiment includes 1- bromopropane and approximately 0.00001 vol% to about 10 vol% of at least one multi-component stabilizing agent consisting essentially of:
(a) tert butyl alcohol;
(b) one or more of dimethoxymethane and diethoxymethane ; and,
(c) one or more of:
(i) one or more of butylene oxide, propylene oxide and cyclohexene oxide; and,
(ii) one or more of epibromohydrin and epichlorohydrin .
Another preferred embodiment includes 1- bromopropane and approximately 0.00001 vol% to about 10 vol% of:
(a) tert butyl alcohol;
(b) one or more of dimethoxymethane and diethoxymethane ; and,
(c) one or more of :
(i) one or more of butylene oxide, propylene oxide and cyclohexene oxide; and,
(ii) one or more of epibromohydrin and epichlorohydrin .
Another preferred embodiment includes 1- bromopropane and approximately, by total volume of the composition:
(a) 1-10% tert butyl alcohol;
(b) 0.1-10% one or more of dimethoxymethane and diethoxymethane ; and,
(c) one or more of:
(i) 0.1-5% one or more of butylene oxide, propylene oxide and cyclohexene oxide; and,
(ii) 0.001-2% one or more of epibromohydrin and epichlorohydrin.
Another preferred embodiment includes 1- bromopropane and approximately, by total volume of the composition:
(a) 1% tert-butyl alcohol or isopropyl alcohol or propyl alcohol;
(b) 0.1% one or more of dimethoxymethane and diethoxymethane ; and,
(c) 0.5% or more of a mixture of butylene oxide and cyclohexene oxide .
Another preferred embodiment includes 1- bromopropane and approximately 0.00001 vol% to about 5 vol% one or more of epibromohydrin, epichlorohydrin and n-ethyl morpholine.
Another preferred embodiment includes 1- bromopropane and approximately 0.1-5 vol% one or more of epibromohydrin, epichlorohydrin and n-ethyl morpholine.
Another preferred embodiment includes 1- bromopropane and approximately 0.001-2%, by total volume of the composition, one or more of epibromohydrin, epichlorohydrin and n-ethyl morpholine.
Another preferred embodiment includes 1- bromopropane and approximately 0.01 %, by total volume of the composition, one or more of epibromohydrin, epichlorohydrin and n-ethyl morpholine.
Another preferred embodiment includes 1- bromopropane and approximately, by total volume of the composition:
0.01 % epibromohydrin or epichlorohydrin; and
0.2 % n-ethyl morpholine.
Another preferred embodiment includes 1- bromopropane and approximately, by total volume of the composition:
0.01 % epibromo or epichlorohydrin;
0.2 % n-ethyl morpholine; and
0.1-1 % propargyl alcohol.
In another preferred embodiment, a stabilized solvent mixture contains 1-bromopropane and a stabilizer mixture of, by total volume, approximately 0.5-3% alcohol such as isopropyl alcohol, 0.01-0.1% cyclohexene oxide, 0.1- 1% butylene oxide, 1-5% 1, 3-dioxolane, and 0.1-1% dimethoxymethane .
Other preferred embodiments of the 1-bromopropane mixtures include one or more of n-propanol and hydrofluorocarbon to adjust the solvency of the mixture. In addition, the stabilizing agents described above are added to the mixtures to prevent decomposition of the 1-bromopropane.
The 1-bromopropane mixtures can be used to clean metals, plastics, elastomers and circuit boards using various known cleaning apparatuses and techniques . One example technique is vapor degreasing which is described in U.S. Patent No. 5,403,507 to Henry. Another example technique combines vapor cleaning with agitation of the articles as described in U.S. Patent No. 4,193,838 to Kelly et al . Another example is immersion cleaning in which articles are immersed in a bath of the cleaning composition. The bath or articles or both may be agitated to hasten the cleaning process. Another example is ultrasonic cleaning. Other examples are wipe cleaning and aerosol cleaning.
More particularly, in a preferred method of the present invention, the preferred cleaning composition described above is used to clean contaminated printed circuit boards . Other compositions described herein as well as those
encompassed by the present invention may be used with this preferred method. The boards are contaminated with solder flux composed of epoxy resin. The flux as well as unwanted materials embedded in the flux must be removed. The boards themselves as well as the electronic components on the boards contain plastic or solvent-sensitive materials which must be preserved. Further, the boards and components have various identifying ink markings on them which must be maintained.
The preferred cleaning composition is introduced into a sump of a standard vapor degreaser of the kind described in U.S. Patent No. 5,403,507 to Henry. The composition is brought to a boil by heating to 156 degrees Fahrenheit . The contaminated boards are immersed in the vapor layer of the degreaser for approximately 5 minutes . The boards are then removed from the vapor layer. The solvent of the cleaning composition does not crack, pit, leach or otherwise attack the boards or the components . Further, the solvent does not remove or fade the ink markings. Nevertheless, the board and components are cleaned of all the solder flux.
However, when a mixture of only 95% 1-bromopropane, 0.5% butylene oxide, 0.5% nitromethane and 4% 1, 3-dioxolane is used in the degreaser, the high solvency mixture damages the printed circuit boards. Specifically, although the mixture removes the flux, the mixture causes cracking and peeling of the plastic on the board. Moreover, all of the identifying ink markings are removed. The circuit boards are no longer useful for their original purpose.
In another preferred method, a stabilized solvent composition of 90% 1-bromopropane, 0.5% 1,2 butylene oxide, 0.5% nitromethane, 4% 1, 3-dioxolane and 5% glycol ether is used to clean motion picture film. The film is contaminated with fingerprints and other oil. The composition is introduced into the sump of a film cleaning machine. The
sump heats the solvent to a boil. Motion picture film made of cellulose acetate is immersed in the vapor layer of the boiling sump for approximately 60 seconds. In this time, a conventional solvent would attack the film by, for example, bending and/or blurring the film. However, the cleaning composition does not damage the film. Moreover, the cleaning composition removes fingerprints and other oil on the film.
Analogously, the same composition is also suitable for cleaning plastic articles or substrates in ultrasonic cleaning units. In this technique, contaminated articles are immersed in a bath of the cleaning composition. Ultrasound, i.e., high-frequency sound, is transmitted into the bath to clean the articles by causing cavitation in the cleaning composition at the surface of the contaminated articles.
In another preferred method of the present invention, a cleaning composition encompassed in the above disclosure is charged into an aerosol can or other aerosol delivery system. If the can or system is susceptible to attack, it is preferable to use one of the stabilized cleaning compositions. The composition is sprayed onto a contaminated article such as a printed circuit board contaminated with rosin. The spray dissolves and completely removes the rosin. This technique does not damage printed circuit boards, or components or markings thereon.
The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof .