Abstract:
Improved article drying compositions which effectively remove water from the surface of non-absorbent articles to be dried, are provided. The solvents used to formulate the additive modified compositions are azeotropic binary mixtures, comprised of isobutanol and trichlorotrifluoroethane; and n-butanol and trichlorotrifluoroethane. The non-volatile additive, dissolved in the binary systems comprises a phosphate ester free acid type. These additives characterized as complex phosphate ester-free acid surfactants of the ethylene oxide type, which are commercially available, are preferred.

Description:
The invention relates to water removal composition. More particularly, the invention relates to improved compositions for drying water wet articles in which the residue left on the dried article using the water removal composition is substantially reduced. 
     The wettability is enhanced through the presence of iso-butanol or n-butanol as one of the components of the azeotropic mixtures used in these formulations. 
     BACKGROUND OF THE INVENTION 
     Various drying compositions are known in the prior art. These compositions contain various kinds and various amounts of surfactants and other additives. Specifically, the concentration of surfactants added to chlorocarbon and chlorofluorocarbon solvents, such as, methylene chloride or 1,1,2-trichloro-1,2,2-trifluoroethane typically used in amounts of 500 ppm or greater, such as in U.S. Pat. Nos. 3,386,181; 4,401,584 and 4,438,026 are known. Such levels of surfactant leave substantial residue on dried parts from the drying solvent and require relatively long rinse times. Moreover, the inclusion in the drying composition of such relatively large amounts of surfactants hinders phase separation in that water becomes more miscible and hence more difficult to remove. It is thus apparent that a need exists for an improved drying composition characterised as an azeotrope which can function at a low additive level and maintain higher solvency power and enhanced wettability. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the invention to provide a water removal composition that functions at a low additive level and enhanced wettability. It is a more particular object of the invention to provide an azeotropic drying composition of 1,1,2-trichloro-1,2,2-trifluoroethane and n-butanol or isobutanol which leaves minimal residue on articles dried with these compositions and which because of the low solubility of water therein permits a more complete phase separation. 
     The presence of n-butanol or isobutanol in the base solvent contributes to water removal by improving solvent wettability in a manner similar to a surfactant, but without increasing non-volatile residue; hence not contributing to rinse sump contamination or process time. This is an advantage over the prior art. The azeotropic nature of the volatile components of the composition of the invention provides increased wettability to both liquid and vapor, hence constituting an advantage over prior art surfactant/solvent systems. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the invention, any water immiscible organic solvent may be employed. Such solvent should have a boiling point of 21°-75° C., a density of at least 1.1 at 20° C., and should not form an azeotrope containing more than 2% by weight water. &#34;Water-immiscible solvent&#34; is intended to include solvents in which water is not more than 0.1% by weight soluble. Preferably, the solvent has a boiling point of about 35°-49° C., a density of about 1.4 to 1.6 weight percent at 20° C., and does not form an azeotrope containing more than about 0.5% of water. Suitable solvents include trichloromonofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane and azeotropic mixtures of the latter solvent with n-butanol or isobutanol. The isobutanoltrichlorotrifluoroethane mixture is preferred. 
     The solvent generally contains a surfactant to aid in displacement of water from articles to be dried. Preferably, the surfactant is soluble in the solvent and virtually insoluble in water. Any solvent-soluble surfactant which provides for displacement of water by the solvent may be used. Suitable surfactants include long chain carboxylic acids containing an amidomethyl group such as a oleoyl sarcosine or alkyl phosphate esters neutralized with saturated aliphatic amines such as the 2-ethyhexyl amine salt of di-n-octyl phosphate or an ethylene oxide-adduct type complex phosphate ester free acid. The latter is preferred. Such phosphate ester free acid surfactants are commercially available and contain a mixture of both mono and di-esters. The hydrophobic base may be aromatic or aliphatic, preferably aromatic. 
     Typical of the complex phosphate ester-free acid surfactants are those of the ethylene oxide adduct type. These anionic products are mixtures of mono and diesters, e.g. ##STR1## wherein R is an alkylaryl radical and introduces a hydrophobic property; n has a value that signifies 2-10 moles of ethylene oxide reacted with one mole of hydrophobe. Preferably 3-5 moles of ethylene oxide are reacted with one mole of hydrophobe. 
     The hydrophobe or hydrophobic group R is comprised of an alkyl group of three to nine carbon atoms, attached to aromatic nuclei such as benzene or naphthalene. The preferable hydrophobe is an aromatic alkyl phenol preferably nonyl phenol. The preferred surfactants of this type are thus mixtures of the free-acids of mono- and di-phosphate esters having polyethylene oxide adducts having a hydrophobic terminal group. 
     Such surfactants include GAFAC RM-410 or GAFAC RL-210 (GAF Corp.); GAFAC RM-410 is preferred. 
     Surfactant concentration may range from 150 ppm to 500 ppm, but a concentration between 50 and 500 ppm is preferred. It is further preferred that surfactant concentration be 100 ppm. 
     The presence of certain alcohols (n-butanol or isobutanol) improves the wettability of the solvent and hence aids in the removal of water without contribution to non-volatile residue in the solvent. It is also preferred that the alcohol form a constant-boiling composition with the solvent. 
     The constant-boiling composition should contain between 0.1 and 3.0% by weight of alcohol and preferably between 0.1 and 1.0% by weight of alcohol. The constant-boiling behavior is desired to maintain wettability characteristics in both liquid and vapor phases of the solvent composition during use (and to avoid build-up of alcohol in the boiling sump of a typical solvent dryer). It is further preferred that the alcohol be n-butanol at a composition between 0.5 and 0.75% by weight or isobutanol at a composition between 0.2 and 0.5% by weight. 
     In order that the invention may be more fully understood, the following examples are set forth for purposes of illustration. The specific enumeration of details therein should not be interpreted as a limitation except as expressed in the amended claims. 
    
    
     EXAMPLE 1 
     Constant boiling behavior of 1,1,2-trichloro-1,2,2-trifluoroethane and n-butanol, isobutanol. 
     In order to maintain the contribution of wettability provided by a volatile additive such as an alcohol, throughout the liquid and vapor zones of a typical drying apparatus, the volatile additive and base solvent must form a constant boiling mixture. Thus, 1350 grams of a mixture of 3.0% by weight n-butanol in 1,1,2-trichloro-1,2,2-trifluoroethane was charged to a 3 liter boiling flask fitted with a 21&#34; Vigreaux column and Allihn reflux head. The mixture was allowed to reflux for one hour before distilling over any material. The boil-up rate was 15 ml/minute. The first overhead cut, 170 ml in volume, was discarded. A 30 minute period of total reflux was provided between cuts. The next three cuts were combined and retained to serve as starting material for a second distillation. Cut size, head temperatures, and barometric pressure are given in Table 1. 
     
                       TABLE 1______________________________________First Distillation of n-butanol and1,1,2-trichloro-1,2,2-trifluoroethaneCut #    Cut Weight, grams                  Head Temperature °C.______________________________________2        262.3         47.53        267.3         47.54        285.8         47.5______________________________________ Barometric Pressure = 743.0 mm Hg at 28.1° C. 
    
     The bottom portion was discarded. The recombined cuts 2, 3 and 4 were charged to the same apparatus as above and a second distillation performed in the same manner. Analysis of the distilled cuts was performed by gas chromatography. Results appear in Table 2. 
     
                       TABLE 2______________________________________Analysis of Distillation Cuts, Second Distillation ofn-butanol and 1,1,2-trichloro-1,2,2-trifluoroethaneCut  Grams Weight,            Head        Cut Composition, % wt.#    grams       Temperature %                        n-butanol______________________________________2    154.4       48.0        0.333    153.5       48.0        0.384    152.5       48.0        0.45______________________________________ Barometric Pressure = 753.5 mm Hg @ 24.0° C. 
    
     A third distillation was performed where 176.2 grams of a mixture containing 0.3% weight n-butanol served as starting material. This composition was formulated as the average of the cuts from the second distillation. Table 3 gives the composition of the cuts that resulted. 
     
                       TABLE 3______________________________________ Cut Weight           Head         Cut Composition, % wt.Cut # grams     Temperature °C.                        n-butanol______________________________________2     152.4     48.0         0.223     153.3     48.0         0.234     153.0     48.0         0.28______________________________________ Barometric Pressure = 749.2 mm Hg @ 26.5° C. 
    
     Tables 2 and 3 of this example illustrate the constant boiling behavior of n-butanol in 1,1,2-trichloro-1,2,2--trifluoroethane through successive distillation at a n-butanol concentration of about 0.2 to 0.5% by weight. 
     Similarly, isobutanol and 1,1,2-trichloro-1,2,2--trifluoroethane were distilled. Data in Tables 4, 5 and 6 establish the constant boiling behavior of this pair. 
     
                       TABLE 4______________________________________First Distillation of isobutanol and1,1,2-trichloro-1,2,2,-trifluoroethane mixture,Charge Composition - 3% weight isobutanol in1,1,2-trichloro-1,2,2-trifluoroethane Charge Weight = 1632 grams       Cut Weight,                  HeadCut #       grams      Temperature °C.______________________________________2           342.1      47.53           350.6      47.54           345.6      47.5______________________________________ 
    
     
                       TABLE 5______________________________________Analysis of Cuts, Second Distillation of Isobutanoland 1,1,2-trichloro-1,2,2-trifluoroethane mixtureCharge Weight - 1028.9 gramsCut  Cut Weight,           Head         Cut Composition, % wt.#    grams      Temperature °C.                        isobutanol______________________________________2    170.8      47.9         0.583    175.0      47.9         0.634    228.0      47.8         0.74______________________________________ Barometric Pressure = 750.54 mm Hg @ 26.1° C. 
    
     
                       TABLE 6______________________________________Final Distillation of Isobutanol in1,1,2-trichloro-1,2,2-trifluoroethaneCharge composition: 0.65 weight percent isobutanol in1,1,2-trichloro-1,2,2-trifluoroethaneCharge Weight = 1028.9 gramsCut  Cut Weight,           Head         Cut Composition, % wt.#    grams      Temperature °C.                        n-butanol______________________________________2    156.6      47.0         0.513    157.0      47.0         0.544    154.6      47.0         0.60______________________________________ Barometric Pressure  749.2 mm Hg @ 26.5° C. 
    
     It can be seen from date in Tables 4, 5 and 6 that isobutanol forms a constant-boiling composition with 1,1,2-trichloro-1,2,2-trifluoroethane at about 0.5 to 0.75% by weight of isobutanol. 
     EXAMPLE II 
     The ability of a solvent to preferentially wet a substrate that is already wet with water was characterized using the method below. A deionized water droplet of measured volume was expressed from a 10 microliter syringe with the resulting droplet adhered to the end of the needle. The needle was immersed just beneath the surface of given solvent composition and held in a beaker at 99° F. Immediate removal of the needle followed. The process required a smooth motion of one second duration. The droplet volume that would release to the solvent composition surface was recorded. It is apparent in Table 7 of the example, that the addition of certain alcohols to 1,1,2-trichloro-1,2,2-trifluoroethane increases the ability of the solvent to wet a substrate already wet with water. 
     
                       TABLE 7______________________________________Enhanced Wettability of1,1,2-trichloro-1,2,2-trifluoroethaneUsing Certain AlcoholsSolvent Composition% Weight       Water Droplet Volume Released, ml.______________________________________(1) 1,1,2-trichloro-              0.20    1,2,2-trifluoroethane    (Solv. A)(2) 0.54% isobutanol in              0.05    Solv. A(3) 0.22% n-butanol in              0.10    Solv. A(4) 0.5% isopropanol in              0.10    Solv. A______________________________________ 
    
     EXAMPLE III 
     Water Removal Effectiveness 
     The method used to determine water displacement times given in Table 7 is described below. Clean stainless steel screws, 1&#34;×1/8&#34;, roundhead, were used as received. Alumina ceramic slides, 11/2&#34;×11/2&#34;, were found to be 100% water wettable as acquired, hence were not cleaned prior to use. To ensure a 100% water wettable surface on 1&#34;×3&#34; glass slide, said slides were soaked overnight in a mixture of water, ammonia, methanol, and detergent. The slides were then rinsed consecutively, with deionized water, acetone, and methanol and finally allowed to air dry. 
     A 600 ml glass beaker was charged with 400 ml of drying solvent and heated to boiling on a ceramic hot plate. Parts to be dried were first immersed in deionized water and then in boiling drying solvent. The time required to remove water from the part was recorded. In Table 8, four additive packages were evaluated for their ability to impart water displacement capabilities to base solvent, in this case, 1,1,2-trichloro-1,2,2-trifluoroethane. In the case of the latter two additive packages, each when combined with 1,1,2-trichloro-1,2,2-trifluoroethane constitute commercially available water displacement solvents as noted in Table 8 under solvent compositions. The commercial materials were used in this evaluation. Table 8 of this example shows that water displacement from glass, alumina, ceramic and stainless steel is demonstrated for the composition of the invention in time frames comparable to existing commercial formulations. 
     
                       TABLE 8______________________________________Effectiveness of Water Removal          Time Required to Remove Water,Solvent Composition          Seconds______________________________________1,1,2-trichloro-          Stainless Steel1,2,2-trifluoroethane          Screws      Alumina Ceramicwith . . .     Trial 1 Trial 2 Trial 1                                 Trial 2______________________________________100 ppm phosphate          3       2        9     10ester free acidsurfactant (2) and0.54% isobutanol100 ppm phosphate          5       5       15     15ester free acidsurfactant (2) and0.22% n-butanolalkyl phosphate ester          2       2       10     10neutralized withsaturated aliphaticamine (3)(Commerciallyavailable asDu Pont Freon ® TDFC)0.25% sarcosine (4)          5       5        105 (1)                                  195 (1)surfactant anddemulsifiers (Availablecommercially asGENESOLV ® DRMfrom Allied-Signal Corp.)______________________________________1,1,2-trichloro-1,2,2-trifluoroethane          Glass Slideswith           Trial 1   Trial 2   Trial 3______________________________________100 ppm phosphate          20        25        26ester free acidsurfactant (2) and0.54% isobutanol100 ppm phosphate          26        20        21ester free acidsurfactant (2) and0.22% n-butanolalkyl phosphate ester           5        10         5neutralized withsaturated aliphaticamine (3)(Commercially asDu Pont Freon ® TDFC)0.25% sarcosine (4)          85        195        240 (1)surfactant anddemulsifiers(Commercially as AlliedGENESOLV ® DRM)______________________________________ (1) No drying detected, the test was interrupted at this point. (2) GAFAC RM410 surfactant (GAF Corporation). (3) 0.05 to 3.0% by weight of a mixture of monooxo-octyl and dioxo-octyl phosphates or a mixture of mono(tridecyl) and bis(tridecyl) phosphates or a mixture of mono and din-octyl and mono and din-decyl phosphates neutralized with 2ethylhexylamine or other suitable amines as disclosed i U.S. Pat. No. 3,386,181. (4) N--lauryl sarcosine. However, N--cocoyl sarcosine or N--oleoyl sarcosine, and mixtures, may also be used as disclosed in U.S. Pat. No. 4,401,584. 
    
     EXAMPLE IV 
     Solubility of Water in Water Removal Compositions 
     Increased solubility of water in water removal solvents affects drying and dryer performance by prohibiting complete phase separation of water from solvents, increasing the tendency to form emulsions and necessarily allowing more water to inhabit the vapor zone of a dryer. Table 9 of this example illustrates the solubility of water in various drying solvent compositions. In Table 9 of this example, as in Table 8 of Example III, the combination of 1,1,2-trichloro-1,2,2-trifluoroethane with each of the four listed additive packages were tested for water displacement ability. In the case of the latter two additive packages, their combination with 1,1,2-trichloro-1,2,2-trifluoroethane produces a result comprable to commercially available water displacement solvents. These two commercial solvents, as given in Table 9 under Solvent Composition, were used as such in testing. A microburet was used to titrate deionized water into 50 ml of drying solvent at room temperature. The buret tip was held beneath the solvent surface. The solvent was stirred using a magnetic stirrer. The volume of water added that caused cloudiness was taken to be the limit of solubility. 
     
                       TABLE 9______________________________________Solubility of Water Removal Compositions             Volume of Deionized             Water RequiredSolvent Composition             to Generate Cloudiness, ml.______________________________________1,1,2-trichloro-1,2,2-trifluoroethane with100 ppm phosphate ester             0.4free acid surfactant (1)and 0.54% isobutanol100 ppm phosphate ester             0.4free acid surfactant (1)and 0.22% n-butanolalkyl phosphate ester,             0.5amine salt (2)(Du Pont Freon ® TDFC)0.25% Sarcosine   1.2surfactants (3)(Allied GENESOLV ® DRM)______________________________________ (1) GAFAC RM410 surfactant (GAF Corp.) (2) 0.05 to 3.0% by weight of a mixture of monooxo-octyl and dioxo-octyl phosphates or a mixture of mono(tridecyl) and bis(tridecyl) phosphates or a mixture of mono and din-octyl and din-decyl phosphates neutralized with 2ethylhexylamine or other suitable amine as disclosed in U.S. Pat. No. 3,386,181 (3) N--lauryl sarcosine. However, N--cocoyl or N--oleoyl sarcosine and mixtures may also be used as disclosed in U.S. Pat. No. 4,401,584. 
    
     Various changes may be made in the reactants, proportions, and conditions within the disclosure is set forth and therefore the invention is not to be limited except as set forth in the claims which follow.