EP0605605A1

EP0605605A1 - Semi-aqueous cleaning process and solvent compositions

Info

Publication number: EP0605605A1
Application number: EP92920868A
Authority: EP
Inventors: Felipe A. Donate; James G. Papajesk; Joanna M. Farella; Laurence W. Lee; Nancy H. Morris
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1991-09-24
Filing date: 1992-09-24
Publication date: 1994-07-13
Also published as: WO1993006204A1; AU2678292A; CA2119646A1

Abstract

Composition et procédé de nettoyage semi-aqueux comportant certains éthers de glycol, notamment l'éther n-butylique de dipropylène-glycol; un hydrocarbure; et éventuellement un tensio-actif et des inhibiteurs.A semi-aqueous cleaning composition and process comprising certain glycol ethers, including dipropylene glycol n-butyl ether; a hydrocarbon; and optionally a surfactant and inhibitors.

Description

SEMI-AQUEOUS CLEANING PROCESS

AND SOLVENT COMPOSITIONS

The present invention is related to semi-aqueous cleaning processes and compositions useful therein.

Cleaning is required in the metal working and electronics industries to remove oils, greases, coolants, fluxes and various particuiates such as metal fines and shop soils.

Typically, chlorocarbon and chlorofluorocarbon solvents have been used m vapor αegreasmg equipment to provide the needed cleaning. However, environmental concerns and regulations nave been directed toward the jse of these solvents in recent years.

One alternative to the use of chlorocarbon and chlorofluorocarbon solvents is the use of a semi-aqueous cleaning process and cleaner. Semi-aqueous cleaners are hydrocarbon formulations containing emulsifying agents to ennance their abil ity to be rinsed Generally the formulations are not bulk liquid flammable, put nave vapors that can ignite under certai n conditions whicn results in potential problems n processing and equipment design. Semi- aqueous cleaners typically use their affinity to organic contaminants to solvate the

contaminants from the surface of the item to be cleaned and take them into solution The solution must be rinsed off the cleaned surface with water resulting in an effl uent containing the hydrocarbon contaminants and water.

Compounds currently augrt to be use ful semi-aqueous processes include various compounds such as terpenes -owever there remains a need for additional se mi- aqueous cl eaning methods and compositions Summary of the invention

In one aspect, the present invention is a cleaning composition consisting essentially of

0) 30 to 70 volume percent of a glycol ether selected from tne group

consisting of dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, and propylene glycol phenyl ether and mixtures thereof;

(2) 30 to 70 volume percent of one or more

C_12-13 hydrocarbons having a flash point greater than about 200°F, a viscosity of less than 3.0 cP at 25°C and a surface tension of less than 30.0 dynes/cm at 25°C; and

(3) zero to 10 volume percent of one or more surfactants with a hydrophile/lipophile balance (HLB) of from 1 to 8.5 or from 12 to 16; and

(4) zero to 5 volume percent of one or more innibitors, perfumes or dyes The various components of tne composition are selected so that the compositior has a boiling point greater than 200°C ana a freezing point less than 5°C; a flash point greater tnan 95ºC, ana water solubility of less tnan 1 g/100g

'n a second aspect, the present invention is a semi-aqueous cleaning process using the above described composition.

Detailed Description of the illustrative Embodiments

in the semi-aqueous clean ing process of the present invention, the part to be cleaned is typically (1) subjected to a solvent wash; (2) brown with air to control solvent carryover; (3) rinsed witn water: and (4) driec in a modification of this system, an emulsion stage 5 used in the modified system, the part is subjected to a solvent wasn and then mmersed emulsion of solvent and water prior to being blown with air, rinsed ana dried. Solvents are kept at a minimum in the emulsion stage and the water is continuously recycled by

recirculating the emulsion through a static tank or coalescer The emulsion must readily separate - the static tank to permit the recycling of the water and/or solvent. The cleaning process may be conducted at room temperature or at elevated temperatures to accelerate cleaning and separation of emulsion. One skilled in the art with recognize that elevated temperatures will be maintained below the rasn point for safety purposes

The semi-aqueous cleaner of the present invention includes the grycol ether one or more hydrocarbons, optionally one or more surfactants are optionally one or more

-- rv- '-. oer -imes. dve oOtn ' onve^_".O"a- aαsit ves ~->e ς , z ' e ^{r r} .s ore÷eraD , cioroDyie^e g yco- r.-o xv! etne^r crtr-Dropv e-e givco- r-D-_../ι et-er anc s mo^re orefe^radι , ΠIDΓOD_J e~e g-yce ^r,-Di-tvϊ ethe' A hydrocarbon or a blend of hydrocarbons may be used in the practice of the invention. The hydrocarbon may be linear, branched or cyclic with linear being preferred. Typically, the hydrocarbon will have from from 12 to 18 carbon atoms, with C _14-16 linear paraffins being preferred The cyclic hydrocarbons may contain inert substituents such as alkyi groups.

Surfactants useful in the composition of the present invention are non-ionic surfactants having an HLB of 1 to 8.5 or 12 to 16. The surfactants will typically comprise a C_{8-1 5} linear, branched or cyclic aliphatic hydrophilic chain and a hydrophobic chain containing between 2 and 10 mole percent degree of alkoxylation. Preferred surfactants are Cs-i 5 alkyoxylated alcohols having from 1 to 8 alkylene oxide units wherein the alkylene oxide 15 ethylene oxide, propylene oxide or butylene oxide with ethylene oxide being preferred More preferred surfactants are C_{9- 1 1} alkyoxylated alcohols having 5-7 ethyiene oxide units.

The semi-aqueous cleaner may also include inhibitors to prevent corrosion of metals such as steel. Examples of useful inhibitors inciude amines, phosphates,

polyphosphates, nitrides, molybdates, suifonates and quarternary ammonium salts

Antioxidants such as butylated hydroxy toluene are also useful in some applications, it may also be necessary or desirable to add perfumes, dyes or other additives.

The relative amounts of the various components of the cleaning formulation are any which results in a composition having tne desired properties. The glycol etner comprises from 30 to 70 volume percent of the comoosition, preferably from 30 to 60 volume percert, more preferably from 40 to 50 ana most preferably 40 to 45 volume percent. The hyarocarbon comp rises from 30 to 70 volume percent of the composition, preferably from 40 to 70 volume percent, more preferably from 50 to 65 and most preferably 50-55 volume percent The surfactant comprises from 0 to 10 volume percent of the composition, preferably from 1 to 5 volume percent. An inhibitor or inhibitors, perfumes, dyes or other additives comprises from 0 to 5 volume percent of the composition, preferably from 0 1 to 1 .5 volume oercent Of course, the total volume of components in the composition totals 100.

The semi-aqueous cleaner 's prepared by mixing the components in a suitable vessel typically used oy those witn the art Order of mixing s not critical the cleaner composition s tormulated to have a flash point of 95ºC or greater. point. of 200ºC or greater and a freezing point at or below 5°C; and to have water 100g the cieaner composition also nas certain soil oaσing capac.ty. the ability to break an

and cleaning capability The cleaning composition has soil loading capacity of at least 15 weignt percent at 60°C. This soil loading capacity is the weight percent of soil , i.e. grease or oii, wmcn when present in the cleaning composition causes the cleaning performance of the formuiation to decrease below 90 percent. Aprocedure foUowec to measure soil loading capacity is to soil a series of 2" x 1/2" x 1/16" 1010 steel coupons with grease or oil (soil) . The oil is applied by dipping the coupons in the oil, and then allowing the excess oil drip off before weighing the coupons. These coupons are placed in 1 -ounce bottles containing solutions of the αeaner containing various weight percentages of grease or oil, i. e. soil loading. The bottles are placed in an Eberbach shaker for 5 minutes at 25°C and 180 oscillations per minute Tne couponsare then removed from the bottles, hung from hooks in a support assembly, and rinsed under tao water at 25°C for 10 minutes at 110°C and allowed to cool in a open atmospnere for 20 minutes. Atthis point the coupons are reweigned, and cleaning performance is determined DV the oercent soil removed by each formulation The percentage of grease or oil present in the composition whicn causes cleaning performance to oe lowerthan ninety percent

Another important characteristic of the compositions ;s their aomty to form and breaK emulsions The compos.ttons of this invention, when emulsified with water, .vill preferably separate from water in five, more preferably three, minutes or less at temperatures of 60°C or above. The ability to separate from water is determined bymixing, at room temperature, thirty ml of the cleaning composition and 70 mi of deionizeα water in a graduated cylinder. Location of the initial meniscus is noted and the cylinder is inverted several times to insure mixing The cylinder's left undisturbed for a set period of time then the appearance of each layer and the location of the meniscus are noted. The same tests are repeated at 6C°C. in this instance, the cylinders were placed n a 60°C water bath for 30 minutes before shaking and then allowed to stand tn the path. Similar tests are conducted with constant observation to establish the actual time required for tne emulsion to separate into two distinct layers. The ability to quickly rinse from items to be cleaned is also an important characterstic of the cleaning composition it is preferred that cleaning compositions

n one minute or less. Rinsing capabil ties are determined by mmersing a cou pon in a cleaner to which has been added a dye and then immersing the coupon into a container of

water which is then mildly agitated the time which elapses from the m oment the coupon

ntroduced in the water until no more dye can be seen or considered the

sinse time The following examples are provided to more ful ly illustrate the invention and should not be considered as limiting it in any way. Example 1 -- Semi-aqueous Cleaning with No Emulsion Stage

Six commercial greases were used to evaluate the cleaning compositions of this invention. These were Conoco HD Calcium Grease from Conoco Incorporated, Prestige 741 Lithium Grease from Witco, Alemite CD-2 White Lithium Grease from Stewart- Warner and three greases from Sta-Lube Inc. identified as Sta-Lube Aluminum High Temperature Bearing Grease, Sta-Lube Fibrous Sodium Heavy Duty Grease and Sta-Lube Molybdenum Disulfide- Lithium Extreme Pressure Grease. Using a wooden applicator, approximately 100 mg _+_ 0 1 mg of grease was applied on 2 inch x 0.5 inch x 0.063 inch 1010 steel coupons which had been previously vapor degreased with inhibited 1 ,1 , 1 -trichloroethane and weighed. The coupons were neld in a grooved metal holder which facilitated the application of an even film of grease The greased coupons were weighed and then placed in 2-ounce pottles containing 50 ml of the test composition. The bottles were placed in a shaker bath at 25ºC and snaken for 1 5 minutes at 160 oscillations per minute. The coupons were then removed from the bottles, hung from hooks in a support assembly and rinsed at 25ºC for 10 minutes and then reweigned The percent grease removed by each composition provided an indication of cleaning performance. All tests were done in triplicate and the results averaged The results of these tests are summarized in Table 1.

TABLE I

Example 2 - Semi-aqueous Cleaning with Emulsion Stage

The 1010 steel coupons were greased as described in Example 1 with Prestige 74' Lithium Grease and placed in 1-ounce flint bottles containing 15 ml of an emulsion made by mixing 4.5 ml of the formulation with 10.5 mi deionized water (30/70 ratio). Each formulation contained dipropylene glycol n-butyl ether (DPnB), a C,. _.. linear hydrocarbon and the various surfactants shown in the amounts listed in Table 2 The bottles were placed in an Eberpach snakerand shaken at 180 oscillations per minute. The shaker was stopped every 1 minute so that the coupons could be visually inspected for cleanliness. The test was discontinued when grease could no longer be seen on the coupon. Each formulation was tested in tripilcate and the results averaged. Another test was conducted to establish the time required for tne emuision to separate into two distinct layers. Three ml of solvent or blend and 7 ml deionized water were pipetted into a small glass vial. The vial was snaken vigorously for 15 seconds and then allowed to stand until the emulsion separated to a maximum of 10 minutes. The same test was repeated at 6C°C in this case, tne vials were placed in a 60ºC water path for 10 minute. before snaking ana then allowed to stand in the bath Results from the cleaning and separation tests are summarized in Table 2

Example 3

Using a wooden applicator, approximately 0.1000 g of either a lithium or calcium based grease was applied on 1 inch x 0.5 inch x 0.063 inch 1010 steel coupons which had been previously vapor degreased with inhibited 1 , 1 , 1 -trichloroethane and weigned. The coupons were held in a grooved metal holder which facilitated the application of an even film of grease The greased coupons were weighed and then placed in 1 -ounce bottles containing 15 ml of the test composition. The test composition was 55 volume percent of a cydoaliphatic

hydrocarbon; five volume percent of a linear primary alcohol ethoxylate with an average

of 6 moles ethylene oxide per mole of alcohol ; and 40 volume percent of either dipropylene glycol n-butyl ether or tripropylene glycol n-butyl ether. The bottles were Placed in an Eberbach shaker at 25°C and shaken for 5 minutes at 180 oscillations per minute The coupons were then removed from the bottles, hung from hooks in a support assembly and rinsed under cold tap water for 5 minutes and then dried in an oven at 100ºC for ten minutes. All tests were done in triplicate and the results averaged. When the dipropylene glyco w as u sed 38 77 percent of the lithium and 99 47 percent bf the calcium grease was removed. When the tripropylene glycol was used, 90.64 percent of the lithium and 99.04 percent of the calcium grease was removed. Example 4

The procedure in Example 3 was followed with the exception that the test composition was varied as shown in Table 3 below

TABLE 3

Example 5

In this example, the coupons were greased as described previously with each of the commercial greases and placed in 1-ounce flint bottles containing 20 ml of an emulsion made by mixing 6 ml of heat solvent or formulation with 14 ml delonized water (30/70 ratio)

The bottles were placed in an Eberbach shaker for 10 minutes at 25°C and 180 oscillations per minute. The coupons were then rinsed. dried, and cooled as previously described. The coupons were reweighed, and cleaning performance was determined by tne percent grease removed by each solvent or formulation. Results obtained are shown in Table 4 below.

TABLE 4

Claims

WHAT IS CLAIMED IS:

1. A composition consisting essentially of (1 ) 30 to 70 volume percent of a glycol ether selected from the group

consisting of dipropyiene glycol n-putyl etner, trioropylene glycol n-butyl ether, propylene glycol pnenyl ether and mixtures thereof;

(2) 30 to 70 volume percent of one or more

C_12-18 linear, branched or cyclic aliphatic hydrocarbons having a flash point of greater than 200°F, a viscosity of less than 3.0 cP at 25°C, and a surface tension of less than 30.0 dynes/cm at 25°C;

(3) zero to 10 volume percent of at least one surfactant with a hydro- phile/lipophile balance (HLB) of from 1 to 8.5 or from 12 to 16; and

(4) zero to five volume percent of at least one inhibitor, perfume or dye, said composition having a boiling point greater than or equal to 200°C and a freezing point less than or equal to 5°C; a flash point greaterthan 95°C; and water solubility of iess than 1g/ 100g.

2. The composition of Claim 1 wherein the glycol ether is dipropylene glycol n-butyl ether. 3. The composition of Claim 1 wherein a surfactant is present

4 The composition of Claim 3 wherein the surfactant ii a ethoxylatec

alcohol having from 1 to 8 ethylene oxide units.

5. The composition of Claim 1 wherein tne glycol ether is present in the composition in from 40 to 50 volume percent and the hyαrocaroon is present in the composition in from 50 to 65 volume percent. 6. The composition of Claim 5 wherein the surfactant is a C_8-18 alkyoxylated alcohol having from 1 to 8 alkylene oxide units and is present in the composition in from 2 to 6 volume percent.

⁷ The composition of Claim 1 which is 40 to 45 volume percent dipropylene glycol n-butyl ether 50 to 55 volume percent C_14-16 hydrocarbon and 1 to 5 volume percent C_9-11 alcohol ethoxylate having 6 ethylene oxide units.

8. A process for cleaning metal parts comprising

(a) subjecting the parts to a solvent wash;

(b) blowing the wasned parts with air to control solvent carry over;

(c) rinsing it with water; and (d) drying it wherein the solvent is a composition consisting essentially of

(1) 30 to 70 volume percent of a glycol ether selected from the group

consisting of dipropyiene giycol n-butyl ether, tripropylene glycol n-butyl ether, and propylene glycol phenyl ether and mixtures thereof;

(2) 30 to 70 volume percent of one or more

C _2-18 linear, branched or cyclic aliphatic hydrocarbons having a flash point of greater than 200°F, a viscosity of less than 3.0 cP at25°C, and a surface tension of less than 30.0 dynes/cm at25°C;

(3) ootionally, zero to 10 volume bercent of at least one surfactant with a hydrophile/lipoph ile balance (H-LB) of from to 8.5 or from 12 to 16: and

(4) obtionaily, zero to five volume percent of at least one inhibitor, perfume or dve, said composition having a boiling point greater than or equal to 200°C and a freezing point iess than or equal to 5°C; a flash point greater than 95°C; and water solubility of less than 1g/100g.

9. The process of Claim 8 further comprising immersing the part in an emulsion of solvent and water prior to step (b).

10. The process of Claim 8 wherein the solvent is 40 to 45 volume percent dipropylene glycol n-butyl ether 50 to 55 volume percent C_{14-1 6} hy drocarbon and 1 to 5 volume percent C_{9-1 1} alcohol ethoxylate having 6 ethylene oxide units.