WO2002036531A2

WO2002036531A2 - Stabilizer and solvent compositions

Info

Publication number: WO2002036531A2
Application number: PCT/US2001/030854
Authority: WO
Inventors: Isabelle Riff
Original assignee: Dow Global Technologies Inc.
Priority date: 2000-11-03
Filing date: 2001-10-02
Publication date: 2002-05-10
Also published as: AU2001296504A1; WO2002036531A3

Abstract

A stabilizer composition comprising a) an olefinic amine with a boiling point of from 5 °C to 80 °C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms. The stabilizer composition is useful for stabilizing a C1-3-haloalkane against degradation.

Description

STABILIZER AND SOLVENT COMPOSITIONS

The present invention concerns a stabilizer composition, particularly a stabilizer composition for Ci-₃-haloalkanes, such as methylene chloride, and a solvent composition comprising a Ci-₃-haloalkane as the main component.

Ci-s-haloalkanes, such as methylene chloride, are extensively used for degreasing, cleaning and/or drying of metals in view of their solvating power, their low boiling point and their non-inflammability. Methylene chloride is very frequently used because of its greater stability than other chlorinated hydrocarbons, such as perchloroethylene or trichloroethylene, and its low boiling point, which renders it particularly suitable in the vapor degreasing of metals. However, it is well known that methylene chloride can react with aromatic and aliphatic compounds in the presence of metals, metal halides or combinations thereof, such as aluminum or its alloys or magnesium or its alloys. The reaction products are typically high boiling tarry substances of a brown to black color and acids, such as hydrochloric acid or phosgene, which render the methylene chloride unsuitable for further use.

Therefore, it is common in the industry to add a stabilizer to d-.₃- haloalkanes, such as methylene chloride.

The published European patent application EP— A-0 Oi l 658 discloses a stabilizer composition for methylene chloride which comprises methyl formate and/or ethyl formate and optionally propylene oxide.

The published European patent application EP— A-0256 903 discloses a stabilizer composition for methylene chloride which comprises at least an epoxide, such as propylene oxide or butylene oxide, at least a ketone, such as acetone, and at least an ether and/or ester, such as methyl formate. Unfortunately, in several applications this stabilizer composition does not provide sufficient corrosion protection in metal degreasing operations.

U.S. patent No. 4,032,584 discloses a stabilizer composition for methylene chloride which comprises mixed amylenes, propylene oxide, butylene oxide and tertiary butylamine. U.S patent No. 5,739,090 discloses a methylene chloride composition which is stabilized with an 1,2-epoxy alkane, such as 1,2-epoxybutane, and an acetal, such as dimethoxymethane. The stabilized methylene chloride composition can also comprise additional additives chosen from amines, such as dimethylethylamine, methyldiethylamine, or rimethylamine, amino alcohols, such as triethanolamines, ketones, such as acetone or methyl ethyl ketone; or ethers, such as diethyl ether or tetrahydrofurane.

The published European patent application EP-A-0 001 670 discloses methylene chloride which is stabilized with hexamethylene tetramine.

The published British patent application GB-A-2 069 995 discloses the use of methyl alcohol and small amounts of diisopropyl amine and/or benzylethyl amine and/or triethylamine as a stabilizer for methylene chloride against the danger of explosion during degreasing.

Unfortunately, most of the amines disclosed in the above-mentioned publications are quickly consumed by contaminants which are introduced in metal degreasing processes, such as cutting fluids and metal fines. Accordingly, the stabilizing amine is not preserved in the methylene chloride composition over an extended period of time.

In view of the above-mentioned disadvantages of the known stabilizers for methylene chloride, it is desirable to find a new solvent composition which comprises a Ci- ₃-haloalkane, such as methylene chloride, as the main component and which is stable over an extended time period in the presence of light metals, such as aluminum or its alloys. It is particularly desirable to find such a solvent composition which can easily be regenerated by distillation, that means which preserves the stabilizer additives to a large extent during distillation. A solvent composition has now been found which meets the above- mentioned object.

One aspect of the present invention is a solvent composition which comprises a Ci-₃-haloalkane as the main component and which additionally comprises a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms. Another aspect of the present invention is a method of cleaning, degreasing or drying metal components wherein the metal components are contacted with the above- mentioned solvent composition.

Yes another aspect of the present invention is the use of the above-mentioned solvent composition for cleaning, degreasing or drying metal components.

Yet another aspect of the present invention is a stabilizer composition which comprises a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

Yet another aspect of the present invention is a method of stabilizing a Ci-₃- haloalkane against decomposition which method comprises incorporating in the Q-₃- haloalkane an effective amount of a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

Yet another aspect of the present invention is the use as a stabilizer for a . ₃-haloalkane of a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

The accompanying Figure 1 illustrates the decrease of alkalinity of methylene chloride stabilized according to the present invention during distillation and recycling of the distillate in the presence of contaminants over an extended period of time.

The accompanying Figure 2 illustrates the extent to which various amines are present in the vapor phase of distilled methylene chloride.

The solvent composition of the present invention comprises a d-₃- haloalkane, such as n-propyl bromide, isopropyl bromide, bromomethane, chloromethane, methylene chloride or chloroform. Methylene chloride is the most preferred C^- haloalkane. The C^-haloalkane is the main component of the composition. Its amount generally is at least 90 percent, preferably at least 95 percent, more preferably at least 97 percent, based on the total weight of the solvent composition.

The solvent composition of the present invention additionally comprises an olefinic amine a) with a boiling point of from 5 °C to 80 °C, preferably from 10 °C to 60 °C, more preferably from 30 °C to 60 °C at atmospheric pressure. Preferred olefinic amines a) contain from 2 to 6 carbon atoms and a single carbon-carbon double bond. Exemplary thereof are vinyl amine, allyl-dimethylamine or allyl-methylamine. The most preferred olefinic amine a) is allyl amine. The concentration of the olefinic amine a) preferably is from 1 to 600 ppm, more preferably 5 to 200 ppm, most preferably from 10 to 100 ppm, based on the weight of the d-₃-haloalkane. The pKa of the olefinic amine a) preferably is from 7 to 12, more preferably from 7 to 11, most preferably from 7 to 10.

The solvent composition of the present invention further comprises b) an aliphatic, acyclic ester of 2 to 6 carbon atoms or an aliphatic, acyclic formate of 2 to 6 carbon atoms. The ester or formate b) preferably contains from 2 to 4 carbon atoms. Preferred esters or formates b) are compounds of the formula I

R' - C(O) - O -R² (I), wherein R is hydrogen or a Cι-₂-alkyl group, such as methyl or ethyl, and R is a Cι-₂-alkyl group, such as methyl or ethyl. Suitable examples of an ester or formate b) are methyl formate or ethyl acetate. The most preferred compound b) is methyl acetate. The concentration of the ester or formate b) preferably is from 500 to 20,000 ppm, more preferably from 1,000 to 12,000 ppm, most preferably from 4,000 to 8,000 ppm, based on the weight of the Cι-₃-haloalkane.

The solvent composition of the present invention optionally comprises c) an epoxide, preferably isoamylene oxide, propylene oxide or, more preferably, 1 ,2-butylene oxide. If present, its amount preferably is from 500 to 20,000 ppm, more preferably from 1,000 to 10,000 ppm, most preferably from 2,000 to 6,000 ppm, based on the weight of the Q-₃-haloalkane.

Furthermore, the solvent composition of the present invention optionally comprises d) a saturated aliphatic amine with a boiling point of from 5 °C to 80 °C, preferably from 10 °C to 60 °C, more preferably from 10 °C to 50 °C at atmospheric pressure. Exemplary of such saturated aliphatic amines d) are methyl amine, n- propylamine, isopropylamine, sec-butyl amine, isobutylamine, isopropyl-methylamine, diethylamine, ethyldimethylamine, diethylmethyl amine or dimethylpropylamine. The most preferred saturated aliphatic amine d) is tert.-butyl amine. If present, the amount of the saturated aliphatic amine d) preferably is from 1 to 500 ppm, more preferably from 5 to 200 ppm, most preferably from 20 to 100 ppm, based on the weight of the Cι-₃-haloalkane.

Furthermore, the solvent composition of the present invention optionally comprises an antioxidant e), for example a cyclic alkane, such as cyclohexane, or preferably an amylene, such as 2-methyl-l-butene, 3-methyl-l-butene or, more preferably 2-methyl-2- butene. If present, its amount preferably is from 1 to 500 ppm, more preferably from 5 to 200 ppm, most preferably from 10 to 50 ppm, based on the weight of the C^-haloalkane.

The compounds a) and b) and the optional compounds c), d) and e) can be added individually or as a stabilizer composition to the C].₃-haloalkane. They are incorporated in effective amounts in the Ci-₃-haloalkane, generally in amounts indicated further above.

It is understood that the solvent composition of the present invention can comprise one or more types of olefinic amines a), esters or formates b), optional epoxides c), optional saturated aliphatic amines d) and optional antioxidants e). However, their total amount is preferably within the weight ranges indicated above.

Another aspect of the present invention is a stabilizer composition which comprises an above-mentioned olefinic amine a), an above-mentioned aliphatic, acyclic ester or formate b), optionally an epoxide c), optionally an above-mentioned saturated aliphatic amine d), optionally an antioxidant e) and/or optionally an organic diluent f). The organic diluent f) is preferably a hydrocarbon. The organic diluent preferably has a boiling point above 150°C, more preferably a boiling point above 160°C measured at atmospheric pressure. Preferred hydrocarbons are aliphatic linear or cyclic hydrocarbons with a boiling point above 200°C.

When a stabilizer composition is prepared, it preferably comprises from 10 to 90 percent, more preferably from 20 to 80 percent, most preferably from 30 to 70 percent of the olefinic amine a), preferably from 90 to 10 percent, more preferably from 80 to 20 percent, most preferably from 70 to 30 percent of the ester or formate b), preferably from 0 to 100 percent, more preferably from 0 to 90 percent, most preferably from 0 to 80 percent of the epoxide c), preferably from 0 to 100 percent, more preferably from 10 to 90 percent, most preferably from 20 to 60 percent of the saturated aliphatic amine d), preferably from 0 to 50 percent, more preferably from 5 to 40, most preferably from 5 to 30 percent of the antioxidant e), and preferably from 0 to 3000 percent, more preferably from 20 to 1000 percent, most preferably from 50 to 800 percent of the organic diluent f), based on the total weight of a) and b). It is understood that the stabilizer composition of the present invention can comprise one or more types of olefinic amines a), esters or formates b), optional epoxides c), optional saturated aliphatic amines d), optional antioxidants e) and optional organic solvents f). However, their total amount is preferably within the weight ranges indicated above. The stabilizer composition may contain minor amounts of other components, but the sum of the components a) and b) and the optional components c), d), e) and f) preferably amounts to at least 80 percent, more preferably at least 90 percent, most preferably at least 95 percent, based on the total weight of the solvent composition.

The solvent composition of the present invention is useful for cleaning, degreasing or drying metal components in a known manner. The solvent composition is stabilized against the build-up of acidic compounds over an extended period of time. Accordingly, the metal parts to be cleaned and the cleaning equipment do not tend to corrode to a substantial degree when treated with the solvent composition of the present invention. Furthermore, the solvent composition of the present invention can easily be regenerated by distillation and preserves the olefinic amine a) and aliphatic, acyclic ester or formate b) to a large extent. The invention is illustrated by the following examples which should not be construed to limit the scope of the present invention. Unless stated otherwise all parts and percentages are given by weight.

Example 1

Technical methylene chloride and an initial concentration of 60 ppm of allyl amine, 0.6 percent of methyl acetate, 40 ppm of tert.-butyl amine, 50 ppm of amylene are introduced into a pilot distillation device simulating the solvent cycle in a closed cleaning apparatus. Coupons of 90 mm x 10 mm x 1 mm of aluminum, iron and brass are placed in the vapor phase of the distillation device. Methylene chloride is distilled and subjected to recycling within the cleaning apparatus. The steps of distillation and recycling of methylene chloride are carried out continuously. During the distillation trial, an oil used in the metal working industry, commercially available from Blaser under the trademark Blasomill DEC 80 is added in portions to the distillation bottom to simulate the increase of the oil concentration in the distillation bottom in metal degreasing trials. Samples are taken on a regular basis from the condensed vapor. The content of allyl amine and tert.-butyl amine in the methylene chloride vapor phase in each sample are determined and expressed as ppm, based on the weight of stabilized methylene chloride. The total distillate alkalinity is expressed as ppm NaOH according to ASTM D-2106. The content of allyl amine and tert.- butyl amine and the alkalinity in the condensed vapor are an indication of the stabilization level of the methylene chloride in the cleaning apparatus. The oil content is expressed as percent, based on the total weight of the distillation bottom. The results are illustrated in Figure 1 wherein the content of the allyl amine and the tert.-butyl amine in the condensed methylene chloride vapor, the total alkalinity of the condensed methylene chloride vapor and the oil content the distillation bottom are plotted versus the reflux time in days. The thinnest trend-line in Fig. 1 illustrates the decrease in tert.-butyl amine content, the dotted trend-line illustrates the total distillate alkalinity and the thickest trend-line illustrates the decrease in allyl amine content over time. A higher contaminant concentration in the distillation bottom increases the allyl amine content in the vapor phase. Off-line measurements are caused by the non-homogeneity of the solvent system upon addition of the oil contaminant.

Fig. 1 illustrates that upon addition of oil contaminant starting at the seventh day of the experiment, the concentration of allyl amine in condensed methylene chloride vapor decreases at a slower rate than the concentration of tert.-butyl amine.

Example 2

The extent to which various amines are present in the vapor phase of distilled methylene chloride is studied in a lab distillation device. Three different types of methylene chloride solutions are prepared, the first type contains tertiary-butyl amine, the second type contains allyl amine and the third type contains dimethylpropyl amine. Of each type several samples are prepared with varying concentrations of the amine. The methylene chloride solutions are distilled continuously and the distillate alkalinity is expressed as ppm NaOH according to ASTM D-2106. The distillate alkalinity is plotted in Fig. 2 versus the alkalinity of the liquid methylene chloride solutions, that means the distillation bottoms. Fig. 2 illustrates that both tert.-butyl amine and allyl amine are present in the vapor phase of the methylene chloride to a large extent, which enables an efficient distillation and recycling of contaminated methylene chloride. However, a large amount of dimethylpropylamine, which is used for comparative purposes, remains in the distillation bottoms during distillation. For example, even at a concentration of 70 ppm dimethylpropylamine in liquid methylene chloride, expressed as ppm NaOH, a distillate alkalinity of only 4 ppm is achieved.

Example 3 to 12

A stabilized methylene chloride is prepared which contains 30 ppm of allyl amine, 0.6 percent of methyl acetate, 0.4 percent of butylene oxide, 50 ppm of amylene and 40 ppm of tert.-butylamine, based on the weight of methylene chloride. The stabilized methylene chloride and 20 percent of various contaminants, based on methylene chloride in the distillation bottom, as listed in Table I below are introduced in a lab distillation device as in Example 2. The alkalinity of the condensed vapor is expressed as ppm NaOH according to ASTM D-2106. The butylene oxide concentration of the condensed vapor is measured by gas chromatography and expressed as percent, based on the weight of methylene chloride. These data as well as the pH of the condensed vapor and of the distillation bottom are listed in Table II below.

Table II below illustrates that the thus stabilized methylene chloride has a good stability over seven days of continuous distillation and recycling.

Table I

Table II

Claims

Claims:

1. A solvent composition comprising a Cι-₃-haloalkane as the main component and additionally comprising a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

2. The solvent composition of Claim 1 wherein the Cι-₃-haloalkane is methylene chloride.

3. The solvent composition of Claim 1 or Claim 2 wherein the olefinic amine a) contains from 2 to 6 carbon atoms and a single carbon-carbon double bond.

4. The solvent composition of Claim 3 wherein the olefinic amine a) is allyl amine.

5. The solvent composition of any one of Claims 1 to 4 wherein the ester or formate b) is a compound of the formula I

R' - QO - O -R² (I) wherein R¹ is hydrogen or a C[.₂-alkyl group and R² is a Cι-₂-alkyl group.

6. The solvent composition of Claim "5 wherein the ester b) is methyl acetate.

7. The solvent composition of any one of Claims 1 to 6 comprising additionally one or more compounds selected from c) epoxides, d) saturated aliphatic amines with a boiling point of from 5°C to 80°C and e) antioxidants.

8. The solvent composition of any one of Claims 1 to 7 comprising from 1 to 600 ppm of the olefinic amine a) and from 500 to 20,000 ppm of the ester or formate b), based on the weight of the Cι-₃-haloalkane.

9. A method of cleaning, degreasing or drying metal components wherein the metal components are contacted with the solvent composition of any one of Claims 1 to 8.

10. Use of the solvent composition of any one of Claims 1 to 8 for cleaning, degreasing or drying metal components.

11. A stabilizer composition comprising a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

12. The stabilizer composition of Claim 11 comprising a) the olefinic amine and b) the aliphatic, acyclic ester or formate and additionally one or more compounds selected from c) epoxides, d) saturated aliphatic amines with a boiling point of from 5°C to 80°C, e) antioxidants and f) organic diluents.

13. The stabilizer composition of Claim 12 comprising from 10 to 90 percent of the olefinic amine a), from 90 to 10 percent of the ester or formate b), from 0 to 100 percent of the epoxide c), from 0 to 100 percent of the saturated aliphatic amine d), from 0 to 50 percent of the antioxidant e), and from 0 to 3000 percent of the organic diluent f), based on the total weight of a) and b).

14. A method of stabilizing a Cj-rhaloalkane against decomposition which method comprises incorporating in the d -haloalkane an effective amount of a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.

15. The method of Claim 14 wherein the C_!-₃-haloalkane is methylene chloride.

16. The use as a stabilizer for a Cι-₃-haloalkane of a) an olefinic amine with a boiling point of from 5°C to 80°C and b) an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms.