WO1998016617A1

WO1998016617A1 - Environmentally safe bromopentane composition for cleaning metallic, electrical and plastic materials

Info

Publication number: WO1998016617A1
Application number: PCT/US1997/019136
Authority: WO
Inventors: Richard G. Henry
Original assignee: Advanced Chemical Design, Inc.
Priority date: 1996-10-17
Filing date: 1997-10-17
Publication date: 1998-04-23
Also published as: AU4915197A

Abstract

An environmentally safe non-ozone depleting solvent with and without stabilizing agents for use in the cleaning of metallic and non-metallic surfaces. 1-bromopentane is used as the principal component instead of such highly ozone depleting substances as Freon and 1,1,1 Trichloroethane. 1-bromopentane is used either by itself or mixed with at least one of the following specific groups of stabilizing agents which prevent the mixture from becoming acidic or releasing bromine into the atmosphere: (1) nitromethane; (2) 1,2-butylene oxide; (3) 1,3-dioxolane; (4) 1,4-dioxane; (5) butyl alcohol; (6) tert-butyl alcohol; (7) sec-butyl alcohol; (8) dimethoxymethane; (9) 1,3-dioxolane and nitromethane; (10) nitromethane, 1,2-butylene oxide and 1,3-dioxolane; (11) nitromethane, 1,2-butylene oxide and 1,4-dioxane; and, (12) 1,2-butylene oxide, butyl alcohol and dimethoxymethane.

Description

ENVIRONMENTALLY SAFE BROMOPENTANE COMPOSITION FOR CLEANING METALLIC, ELECTRICAL AND PLASTIC MATERIALS

Cross-Noting to Related Applications

This application claims the benefit of U.S. Provisional Application No. 60/028,667, filed October 17, 1996.

Background of the Invention

This invention relates to the art of cleaning compositions and more particularly to cleaning compositions using 1-bromopentane .

This invention is particularly applicable to 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 other cleaning solvents and techniques, and in other applications such as a solvent in adhesives and the like.

Heretofore, non-flammable solvents or cleaning compositions are widely used in cold cleaning applications such as immersion cleaning, ultrasonic cleaning, wipe cleaning, and aerosol cleaning. Cold cleaning using nonflammable solvents involves exposing contaminated metallic articles to a solvent which dissolves and removes the contaminants .

In aerosol cleaning, a solvent is dispensed from an aerosol container which has within it a propellant which forces the solvent out through a nozzle. This pressurized solvent is very effective in breaking up and then dissolving a grease or dried rosin flux and thereby cleaning the article.

Defluxing of soldered circuit boards by this method is very common in industry. If a small bit of rosin flux is left on a circuit board, it is sprayed with the solvent and then wiped with a clean cloth.

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. However, the Kauri butanol value may not be too high so as to attack plastic components, electronic components or various construction materials of the contaminated articles, such as found in printed circuit boards.

Alcohols have been used as cleaning solvents in the past; however, their use is limited because of the danger of fire. Non-flammable solvent materials employed in the past include CFC-113, 1,1,1 trichloroethane and various hydrochlorofluorocarbons such HCFC-141B. However, the problem with these solvents and others is that they are now listed by the Environmental Protection Agency as ozone depleting chemicals and have been or are being phased out of production. 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. Brominated hydrocarbons are also effective cleaning compositions. However, they readily decompose on use and release bromine into the air. Further, most brominated hydrocarbons are too aggressive for many plastics, elastomers and the like.

A primary 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 provide solvent compositions which are non-flammable and non-ozone depleting.

Another object of the present invention is to provide environmentally-safe "drop in" substitutes for wipe, aerosol, ultrasonic and immersion cleaning apparatuses and techniques which currently employ environmentally unsafe, overly strong or unstable solvents such as 1,1,1 Trichloroethane and CFC or HCFC.

Summary of the Invention

The present invention contemplates a new and improved composition and method which overcomes all of the above referenced problems and others while economically and effectively cleaning contaminated articles. In accordance with the present invention, there is provided a cleaning composition having an ozone depletion factor of less than 0.1 and Kauri butanol value at or between about 40 and 80. The cleaning composition comprises about 80-96.8%, by volume, 1-bromopentane . Further, the cleaning composition comprises about 3.2- 20.0%, by volume, of a stabilizer. The amount of the stabilizer is effective to inhibit the release of bromine from the 1-bromopentane into the atmosphere. The stabilizer comprises at least one of the following groups : (1) nitroalkane;

(2) 1,2-butylene oxide;

(3) 1, 3-dioxolane;

(4) 1,4-dioxane;

(5) butyl alcohol; (6) tert-butyl alcohol;

(7) sec -butyl alcohol;

(8) dimethoxymethane;

(9) 1, 3-dioxolane and nitromethane;

(10) nitromethane, 1,2-butylene oxide and 1, 3-dioxolane; (11) nitromethane, 1,2 -butylene oxide and 1,4-dioxane; and,

(12) 1,2-butylene oxide, butyl alcohol and dimethoxymethane . In accordance with a more limited aspect of the invention, the composition comprises, by volume of the composition: approximately 0.1-5% nitromethane; approximately 0.1-5% 1,2 -butylene oxide; and, approximately 3-10% 1 , 3 -dioxolane or 1,4-dioxane. In accordance with another more limited aspect of the invention, the composition comprises, by volume of the composition, approximately 1-3% of one of tert-butyl alcohol and sec-butyl alcohol.

In accordance with a yet another more limited aspect of the invention, the composition comprises, by volume of the composition, approximately 0.1-0.5% butylene oxide, approximately 0.1-1.0% butyl alcohol, and approximately 0.01%-0.5% dimethoxymethane.

In accordance with another aspect of the invention, a method of cleaning hydrocarbon-soluble contaminants from an article comprises applying to the article a cleaning composition having an ozone depletion factor of less than 0.1 and Kauri butanol value at or between about 40 and 80. The cleaning composition comprises about 80-96.8%, by volume, 1-bromopentane and about 3.2-20.0%, by volume, of a stabilizer. The amount of the stabilizer is effective to inhibit the release of bromine from the 1-bromopentane into the atmosphere. The stabilizer comprises at least one of the following groups: (1) nitroalkane;

(2) 1,2 -butylene oxide;

(3) 1, 3 -dioxolane;

(4) 1,4-dioxane;

(5) butyl alcohol; (6) tert-butyl alcohol;

(7) sec-butyl alcohol;

(8) dimethoxymethane;

(9) 1 , 3 -dioxolane and nitromethane; (10) nitromethane, 1,2 -butylene oxide and 1 , 3 -dioxolane ;

(11) nitromethane, 1,2 -butylene oxide and 1,4-dioxane; and, (12) 1,2 -butylene oxide, butyl alcohol and dimethoxymethane .

In a more limited aspect of the invention, the step of applying comprises immersing the article in a liquid state of the cleaning composition. In another more limited aspect of the invention, the method of cleaning comprises, after the step of immersing, transmitting ultrasound into the liquid state of the cleaning composition.

In another more limited aspect of the invention, the method comprises, after the step of immersing, agitating one of the article and the liquid state of the cleaning composition.

In another limited aspect of the invention, the step of applying includes spraying the cleaning composition onto the articles.

A principal advantage of the invention is it provides effective cleaning compositions for removing hydrocarbon soluble contaminants from metal and electronic articles . Another advantage of the invention is that it has a low ozone depletion potential.

Still another advantage is that the compositions are non-flammable at room temperature and/or are self- extinguishing at operating temperatures. Another advantage of the invention is that it prevents decomposition and concurrent release of bromine into the air.

Yet 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 to the apparatuses .

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 Embodiments

By way of background, a modern cleaning solvent should have certain characteristics for proper cleaning of metal, plastic, elastomers, circuit boards, and the like. Preferably, the solvent should: 1) be properly stabilized if it should come into contact with metals; 2) be nonflammable at least at room temperature; 3) have an ozone depletion potential of less than 0.1; 4) have a high solvency with Kauri-Butanol value above 40 for effective cleaning but below 80 to safely clean plastics, elastomers, etc.; 5) have an evaporation rate of at least 3 and on evaporation leave no residue. Under these standards, the brominated hydrocarbon 1-bromopentane is a desirable cleaning solvent. As such, it is a very appropriate material for use in aerosol cans, and for wipe, immersion, or ultrasonic cleaning of metals, plastics, and electronic materials.

An advantage of 1-bromopentane is that it has no flash point at room temperature, although its flash point is 88 degrees Fahrenheit. In testing its flammability at or above its flash point, it was discovered that 1- bromopentane was able to self-extinguish due to the presence of bromine at the molecular level. In contrast, 2 -bromopentane and 3 -bromopentane were flammable at room temperature and thus unacceptable for cleaning applications. This self-extinguishing nature or "non- flammability" of 1-bromopentane makes it acceptable for many conventional cleaning apparatuses and techniques. It is noted, however, that 1-bromopentane solvent compositions should not be used in vapor phase cleaning where the solvent is boiled and the vapors are used to clean an article.

To prevent it from turning acidic and releasing bromine in the air, 1-bromopentane is stabilized, with 3.2-20% by total volume of any of the following groups of low boiling solvents:

(1) nitroalkane;

(2) 1,2 -butylene oxide; (3) 1, 3 -dioxolane ;

(4) 1,4 -dioxane;

(5) butyl alcohol;

(6) tert-butyl alcohol;

(7) sec-butyl alcohol; (8) dimethoxymethane;

(9) 1, 3 -dioxolane and nitromethane;

(10) nitromethane, 1,2 -butylene oxide and 1 , 3 -dioxolane ;

(11) nitromethane, 1,2 -butylene oxide and 1,4-dioxane; and,

(12) 1,2 -butylene oxide, butyl alcohol and dimethoxymethane. In addition, these low boiling point solvents reduce attack by 1 -bromopentane upon metal aerosol cans . In a preferred embodiment, the appropriate ratio of the components, by volume of the entire cleaning composition, is 80-96.8%, by volume, 1 -bromopentane and about 3.2-20.0% of a mixture of the following stabilizers: nitroalkane, such as nitromethane or nitroethane; 1,2 butylene oxide; and, 1,3 dioxolane or 1,4 dioxane . In another embodiment, the stabilizers are of the amounts: approximately 0.1-5% nitromethane; approximately 0.1-5% 1,2 -butylene oxide; and approximately 3-10% 1 , 3 -dioxolane or 1,4 -dioxane. In still another embodiment the amounts of the stabilizers are: approximately 0.5% nitromethane; approximately 0.5% 1,2 -butylene oxide; and approximately 3-4% 1, 3 -dioxolane or 1,4 -dioxane.

As indicated above, other stabilizing agents which can prevent decomposition of 1 -bromopentane within an aerosol can are tert-butyl alcohol and sec-butyl alcohol at amounts of 1-3% of the total volume of the mixture. In addition, 1,3 dioxolane and/or nitroalkane, such as nitromethane or nitroethane, can be used to increase stability in contact with the metal of aerosol cans. A preferable stabilized composition contains 3% 1,3 dioxolane and 0.25-0.50% nitromethane. Another preferable stabilized composition comprises 0.1-3% dioxolane or 0.1- 0.5% nitroalkane, such as nitromethane or nitroethane.

Another preferred embodiment comprises a mixture of 1-bromopentane, approximately 0.1-0.5% butylene oxide, approximately 0.1-1.0% butyl alcohol, and approximately 0.01%-0.5% dimethoxymethane. The stability of the compositions was verified by adding the above-mentioned compositions to an aerosol can and heating the can to 100 degrees F. for 2 weeks. Below is a table listing the cleaning compositions and the results of such stability testing:

PRODUCT STABILITY

1-bromopentane/l, 3 dioxolane/l, 2 butylene Stable oxide/nitromethane

1-bromopentane/l, 4 dioxane/1,2 butylene Stable oxide/nitromethane

1-bromopentane/l , 2 butylene oxide/butyl Stable alcohol/dimethoxymethane .

1-bromopentane/l, 3 dioxolane Stable

1-bromopentane/l, 4 dioxane Stable 1-bromopentane/nitromethane Stable

1-bromopentane/l, 3 dioxolane/nitromethane Stable

1-bromopentane/tert-butyl alcohol Stable

1-bromopentane/sec-butyl alcohol Stable

1-bromopentane Unstable

When used by itself or more preferably with stabilizing agents, 1-bromopentane may be utilized as a cleaning solvent in a variety of methods such as aerosol, wipe, immersion, and ultrasonic cleaning. In ultrasonic cleaning, stabilized and unstabilized 1-bromopentane compositions are used to clean metallic, plastic and electrical materials. In one preferred method, a bath of one of the stabilized bromopentane compositions is prepared. A contaminated article, such as a printed circuit board, is immersed in the bath. Ultrasound is transmitted into the bath which causes cavitation in the composition at the surface of the article thereby dissolving and dislodging the contaminants. The article is then removed from the bath and dried.

Another preferred method of cleaning contaminated articles includes submerging the articles in an immersion tank containing one of the above-described cleaning compositions. The articles are left in the bath until the contaminants have dissolved. Agitation of the bath or of the articles hastens the cleaning process. The article is then removed from the bath and dried.

In aerosol cleaning, an aerosol can is charged with approximately 200 grams of 1-bromopentane and pressurized with carbon dioxide or HFC type propellant. The propellant effectively discharges the 1 -bromopentane from the can. A circuit board having approximately 1 gram of rosin flux is then sprayed with this mixture. The rosin flux is then seen to dissolve and is easily wiped off with a clean cloth. If the cleaning composition should remain in contact with the aerosol can for a long time, it is preferable to use only stabilized mixtures of 1 -bromopentane . In another preferred method of the present invention, an aerosol can is charged with 200 grams of a mixture of 99.5%, by volume, 1-bromopentane and 0.5% nitromethane. The can is pressurized with carbon dioxide or HFC type propellant. A piece of steel is coated with mineral oil and then sprayed with this mixture. The mineral oil is then seen to dissolve and is easily wiped off with a cloth. In yet another preferred method of the present invention a mixture of 95% 1 -bromopentane, 0.5% 1,2 butylene oxide, 0.5% nitromethane and 4% 1,3 dioxolane is added to a Crest ultrasonic cleaning tank. An aluminum panel is coated with molybdenum grease and immersed into the cleaning chamber with agitation. The aluminum panel is cleaned of the grease and leaves no signs of corrosion. Substituting 1,4 dioxane for 1,3 dioxolane produces the same results. 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 .

Claims

Having thus described the preferred embodiment, the invention is now claimed to be:

1. A cleaning composition having an ozone depletion factor of less than 0.1 and Kauri butanol value at or between about 40 and 80 comprising: about 80-96.8%, by volume, 1 -bromopentane; about 3.2-20.0%, by volume, of a stabilizer, the amount of the stabilizer being effective to inhibit the release of bromine from the 1 -bromopentane into the atmosphere, the stabilizer comprising at least one of the following groups: (1) nitroalkane;

(2) 1,2 -butylene oxide;

(3) 1, 3 -dioxolane;

(4) 1,4 -dioxane;

(5) butyl alcohol; (6) tert-butyl alcohol;

(7) sec-butyl alcohol;

(8) dimethoxymethane;

(9) 1, 3 -dioxolane and nitromethane;

(10) nitromethane, 1,2 -butylene oxide and 1, 3 -dioxolane ;

(11) nitromethane, 1,2 -butylene oxide and 1,4-dioxane; and,

(12) 1,2 -butylene oxide, butyl alcohol and dimethoxymethane .

2. The composition of claim 1 wherein the composition comprises, by volume of the composition, approximately 0.1-5% nitromethane; approximately 0.1-5% 1,2-butylene oxide; and approximately 3-10% 1, 3-dioxolane or 1,4 -dioxane.

3. The composition of claim 2 wherein the composition comprises, by volume of the composition, approximately 0.5% nitromethane; approximately 0.5% 1,2- butylene oxide; and approximately 3-4% 1 , 3 -dioxolane or 1,4 -dioxane.

4. The composition of claim 1 wherein the composition comprises, by volume of the composition, approximately 1-3% of one of tert-butyl alcohol and sec- butyl alcohol .

5. The composition of claim 1 wherein the composition comprises, by volume of the composition, approximately 3% 1,3 dioxolane and approximately 0.25- 0.50% nitromethane.

6. The composition of claim 1 wherein the composition comprises, by volume of the composition, approximately 0.1-0.5% butylene oxide, approximately 0.1- 1.0% butyl alcohol, and approximately 0.01%-0.5% dimethoxymethane .

7. A solvent mixture comprising 1-bromopentane and a stabilizer, the stabilizer present in the composition in an amount effective to inhibit decomposition of the 1-bromopentane, the stabilizer selected from one of the following groups :

(1) nitroalkane;

(2) 1,2 -butylene oxide;

(3) 1, 3 -dioxolane ;

(4) 1,4 -dioxane; (5) butyl alcohol;

(6) tert-butyl alcohol;

(7) sec-butyl alcohol;

(8) dimethoxymethane;

(9) 1 , 3 -dioxolane and nitromethane; (10) nitromethane, 1,2 -butylene oxide and

1 , 3 -dioxolane ;

(11) nitromethane, 1,2 -butylene oxide and 1,4-dioxane ; and, (12) 1,2 -butylene oxide, butyl alcohol and dimethoxymethane.

8. The solvent mixture of claim 7 wherein the stabilizer comprises, by volume of the solvent mixture, approximately 0.1-5% nitromethane; approximately 0.1-5% 1,2-butylene oxide; and approximately 3-10% 1, 3-dioxolane or 1,4-dioxane.

9. The solvent mixture of claim 8 wherein the stabilizer comprises, by volume of the solvent mixture, approximately 0.5% nitromethane; approximately 0.5% 1,2- butylene oxide; and approximately 3-4% 1, 3 -dioxolane or 1,4 -dioxane.

10. The solvent mixture of claim 7 wherein the stabilizer comprises, by volume of the solvent mixture, approximately 1-3% of one of tert-butyl alcohol and sec- butyl alcohol.

11. The solvent mixture of claim 1 wherein the stabilizer comprises, by volume of the solvent mixture, approximately 3% 1,3 dioxolane and approximately 0.25- 0.50% nitromethane.

12. The solvent mixture of claim 1 wherein the stabilizer comprises, by volume of the solvent mixture, approximately 0.1-0.5% butylene oxide, approximately 0.1- 1.0% butyl alcohol, and approximately 0.01%-0.5% dimethoxymethane .

13. A method of cleaning hydrocarbon-soluble contaminants from an article comprising: applying to the article a cleaning composition having an ozone depletion factor of less than 0.1 and Kauri butanol value at or between about 40 and 80 comprising about 80-96.8%, by volume, 1-bromopentane and about 3.2-20.0%, by volume, of a stabilizer, the amount of the stabilizer being effective to inhibit the release of bromine from the 1 -bromopentane into the atmosphere, the stabilizer comprising at least one of the following groups :

(1) nitroalkane;

(2) 1,2 -butylene oxide;

(3) 1, 3 -dioxolane ; (4) 1,4 -dioxane;

(5) butyl alcohol;

(6) tert-butyl alcohol;

(7) sec -butyl alcohol;

( 8 ) dimethoxymethane ; (9) 1, 3 -dioxolane and nitromethane;

(10) nitromethane, 1,2 -butylene oxide and 1 , 3 -dioxolane ;

(11) nitromethane, 1,2 -butylene oxide and 1,4 -dioxane; and, (12) 1,2 -butylene oxide, butyl alcohol and dimethoxymethane .

14. A method according to claim 13 wherein the step of applying comprises: immersing the article in a liquid state of the cleaning composition.

15. A method according to claim 14 further comprising: after the step of immersing, transmitting ultrasound into the liquid state of the cleaning composition.

16. A method according to claim 14 further comprising : after the step of immersing, agitating one of the article and the liquid state of the cleaning composition.

17. A method according to claim 16, wherein the step of applying includes spraying the cleaning composition onto the articles.

18. A method according to claim 17 further comprising: placing the cleaning composition into an aerosol container; charging the aerosol container with a propellant .

19. A method according to claim 13 wherein the step of applying comprises: wiping the cleaning composition across the article .

20. The method according to claim 13 wherein the article includes one of a metal, a plastic and an elastomer.