This disclosure relates generally to plastic vapor degreasers and methods of cleaning using vapor degreasing.
Vapor degreasing is an important operation in many major industries such as aerospace, micro-mechanics, optics, electronics and others where a high reliability and low failure rate is required. In these industries, significant initial capital investment is often required for vapor degreasing and, thus, may be a significant barrier to entry and/or to changing an existing cleaning process. Moreover, current trends in modern manufacturing to move to production cells, where all tools necessary for a job are within arm's reach to improve efficiency, may be frustrated by the capital investment requirements currently needed in conventional vapor degreasing.
With these production cells, it is important to be able to have the cleaning process portable and/or small enough to fit near the worksite. The solvent will also need to have the right safety properties such a low toxicity and non-flammability so that it can be safely used in the production area and ideally, would also have a low global warming potential.
Materials for current degreasers are limited to those which can withstand the high operating temperatures of aggressive solvents. Many conventional degreasers therefore are constructed of metals, such as stainless steel, which makes them expensive due to material price, labor hours, and necessary tools/processes for their manufacture. The weight of these machines when built from metals also reduces their portability and increases their transport cost.
A low cost, portable and durable degreaser capable of being used with low boiling point solvents is needed.
The present disclosure provides a degreasing apparatus which may be made at least partially, or substantially, of at least one plastic material, for use with solvents having relatively low boiling points that are chemically compatible with certain plastic materials, such as 1233zd (1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl).
As used herein, the term “substantially” when used in conjunction with a degreasing apparatus made of a plastic material, includes degreasing apparatuses where any or all solvent-wetted parts that are non-heat transfer parts are made at least partially, or entirely, of at least one plastic material. As used herein, “non-heat transfer parts” include any part not specifically dedicated to a heat transfer purpose, including, for example, sumps, pipes for solvent transport, sidewalls, bottom walls, and partitions as disclosed herein.
In various embodiments, the degreasing apparatus itself, including its tank(s), structures within its tank(s) and any immediately surrounding or integrated components such as fittings, but not including external supporting structures or external, attached components such as pumps or filters, may comprise at least 25% plastic by weight, at least 50% plastic by weight, or at least 75% plastic by weight, such as 25% to 100% plastic, 50% to 100% plastic, 75% to 100% plastic, 50% to 95% plastic, 70% to 95% plastic, and 75% to 95% plastic. The various plastic components of the degreasing apparatus may be made of the same type of plastic, or may be made of different plastics.
As used herein, the term “relatively low boiling point” or “low boiling point” include solvents or mixtures of solvents with boiling points below 40° C., below 35° C., below 25° C., and below 20° C., such as boiling points within the ranges of 15° C. to 25° C., 15° C. to 35° C., 15° C. to 40° C., 17° C. to 40° C., 17° C. to 25° C., and 17° C. to 20° C.
Also, as used herein, the term “chemically compatible”, or plastics that are chemically “compatible” with solvents, include plastics that experience at least one of: less than a 5% change in weight and less than a 5% change in volume after being immersed in the solvent for a period of two weeks at room temperature (between 20° C. to 23° C.). In further embodiments, a chemically compatible plastic may experience at least one of: less than a 3%, 1%, 0.5%, or 0.2% change in weight and less than a 3%, 1%, 0.5%, or 0.2% change in volume after being immersed in the solvent for a period of two weeks at room temperature (between 20° C. to 23° C.). Furthermore, chemically compatible plastics may also exhibit no substantial no color change by visual inspection after being immersed in the solvent for two weeks.
Advantageously, the use of low boiling point and plastic compatible solvents, such as 1233zd (1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl) and more preferably trans-1233zd (trans-1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl), in turn allows for the use of plastic materials for the degreaser, as opposed to the use of more expensive metal or metal alloy materials which are otherwise necessary for high boiling point, plastic incompatible solvents of the type currently used in degreasing applications. Additionally, 1233zd is also environmentally preferable, having a low Global Warming Potential (GWP) of 1, has low toxicity, and is non-flammable according the ASTM E-681.
In various embodiments, degreasing apparatuses may include a tank having a side wall and a bottom wall, a partition coupled to a lower portion of the tank, dividing the tank into an immersion sump and a vaporizing sump, a vaporizing element associated with the vaporizing sump, and a condensing element positioned above the lower portion, wherein at least one of the side wall, the bottom wall, and the partition is made of a plastic material according to various embodiments.
The present disclosure also provides methods of degreasing an article that may include the steps of providing a degreasing apparatus formed at least in part from a plastic material and containing a degreasing solvent, vaporizing the degreasing solvent to provide a vapor space, disposing an article in the vapor space, and condensing the vapor in a vapor recovery space according to various embodiments.
The above mentioned and other features of the invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring first to
For example, in
The solvent can be vaporized using any known methods for vaporizing a solvent including means for altering the temperature of the solvent and/or the pressure of the system. For example, the solvent may be heated by an electrical heating element, gas heater, solar heater, or via a fluid heat transfer system, such as heating element 50.
The solvent can also be recovered through any known method of recovering vapor, such as condensing with solvent condenser 30. Condensing may be accomplished through changes in pressure and/or temperature, such as cooling the vapors. For example,
In some embodiments, the cooling coils may be maintained at temperatures below the boiling point of the solvent. Exemplary cooling coil temperatures include temperatures less than 10° C., temperatures less than 5° C., temperatures less than 0° C., temperatures less than −10° C., and temperatures less than −15° C., such as temperatures within the ranges of −25° C. to 10° C., −25° C. to 5° C., −25° C. to −10° C., −25° C. to −15° C., 10° C. to −15° C., 5° C. to −15° C., and 4° C. to −10° C.
With reference to
As illustrated in
The geometry of the degreasing apparatus 100 is not particularly limited. Various portions of the degreasing apparatus (e.g., side wall 112, tank 105, partition 125, immersion sump 111, and a vaporizing sump 120) may be shaped into various suitable geometries, as would be recognized by a skilled artisan. For example, the degreasing apparatus may be rectangular as exemplified in
Degreasing apparatus 100 may also include a vaporizing element associated with the vaporizing sump 120. For example, the vaporizing element may be located within the vaporizing sump 120, such as heating coil 150, which is exemplified in
In various embodiments, by constructing the heating coil 150, first condensing element 130, and/or second condensing element 140 with thermally conductive materials, such as a metal, heat transfer can be improved. The thermally conductive material is not particularly limited and may be any known thermally conducive material. Exemplary metals include at least one of iron, copper, aluminum, nickel, chromium, titanium, molybdenum, tungsten, ruthenium, silver, gold, cadmium, zinc, alloys thereof, or combinations thereof. Thus, in some embodiments the metal may be a nickel-chromium based alloy, such as INCONEL 78. In other embodiments, the metal may comprise iron, such as steel pipes (e.g., stainless steel).
Advantageously, with the use of a low boiling point solvent such as trans-1233zd, compositions of which are disclosed in U.S. Pat. No. 8,772,213 entitled SOLVENT COMPOSITIONS INCLUDING TRANS-1-CHLORO-3,3,3-TRIFLUOROPROPENE AND USES THEREOF which is incorporated herein by reference in its entirety, tank 105 may be constructed partially or entirely of at least one plastic material. By constructing all or part of tank 105 with at least one plastic, the degreasing apparatus may be more insulated for reducing ambient heat loss through the degreaser. In various embodiments, at least one of the side walls 112, bottom 110, or partition 125 may comprise a plastic.
In various embodiments, the plastic may include a thermoplastic and/or a thermoset plastic. The type of plastic is not particularly limited, provided that the plastic is not adversely affected by the solvent being used.
Exemplary thermoplastics include at least one of acrylonitrile butadiene styrene (“ABS”), nylon, polycarbonate (“PC”), polyethermide (“PEI”), polyethylene (“PE”) (e.g., high-density polyethylene (“HDPE”)), polyvinyl chloride (“PVC”), polytetrafluoroethylene (“PTFE”), polyvinylidene fluoride (“PVDF”), polyoxymethylene (“POM”), polyethylene terephthalate (“PET”), or mixtures thereof. In various embodiments, the polyvinyl chloride may be a chlorinated polyvinyl chloride (“CPVC”).
In the prior art, plastics have conventionally been considered to be incompatible with conventional degreasers due to the incomparability of plastic with the solvents of conventional degreasers. However, certain new solvents, such as trans-1233zd, commercially available under the SOLSTICE® brand from HONEYWELL INTERNATIONAL INC., a Delaware corporation, advantageously facilitate the use of plastic degreasers.
Trans-1233zd (trans-1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl) is a new solvent that has recently been introduced to the cleaning market. Trans-1233zd is compatible with various polymers such as polyoxymethylene (e.g., DELRIN®, a registered trademark of E. I. DuPont Nemours and Company, a Delaware corporation), HDPE, polycarbonate, polyethermide (e.g., ULTEM®, a registered trademark of SABIC Global Technologies, a corporation of the Netherlands), polyvinylidene fluoride (e.g., KYNAR®, a registered trademark of Atofina Chemicals, Incorporated, a Pennsylvania corporation), polytetrafluoroethylene (e.g., TEFLON®, a registered trademark of E. I. DuPont Nemours and Company, a Delaware corporation), polypropylene, PVC and PET. By utilizing a plastic that is compatible with trans-1233zd the weight, cost to manufacture and cost to operate can be reduced significantly. A degreaser was fabricated from PVC for the examples below. PVC is available from many industrial suppliers and other commercial sources.
Typical plastics such as polyoxymethylene, HDPE, polycarbonate, polyethermide, polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, PVC and PET are ideally suited for use with the preferred solvents of the present invention, including particularly those preferred solvents having a boiling point below 40° C., such as trans-1233zd (trans-1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl). For example the boiling point of trans-1233zd (trans-1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl) is 19° C., which is well below the temperature at which the mechanical strength of PVC begins to deteriorate, e.g., by dissolving or swelling (around 45° C.). Aside from chemical incompatibility, other, higher boiling solvents could not be used with PVC as they boil at temperatures that would structurally degrade the material when at normal atmospheric pressures.
Operating heaters below 35° C. for vaporizing the fluid may be desirable to maintain adequate mechanical strength of the degreaser. Processes such as fluid distillation may be accomplished with heaters that run at temperatures and pressures within the acceptable range of many plastics, such as PVC. As a result of the heating values when using 1233zd (1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl), distillation may be accomplished at atmospheric pressures and temperatures within the acceptable range of plastics, while still maintaining a sufficient turnover rate of clean fluid.
Providing a plastic degreasing apparatus containing a degreasing solvent (step 310) is not particularly limited, and may include providing solvent from an inlet stream 312 (shown in
The solvent in the immersion sump 111 may rise over partition 125 and flow into the vapor sump (120 shown in
The vapor in contact with coils 135 and 145 may then condense 342 in a vapor recovery space (step 340). Condensed solvent returns to immersion sump 111 (flow path 346) from a collecting tube/water separator box 280 (shown in
In view of the fact that the boiling point of trans-1-chloro-3,3,3-trifluoro-propene (1233zd) is near room temperature, containing and processing it within a material that helps shield it from the environment is beneficial. Plastics, such as PVC also have insulating properties that prevent heat loss from the solvent used, reducing heat flux from the external environment through the walls of the apparatus or pipes. Therefore, a further advantage of using plastic materials for the tank is the reduction of undesired solvent evaporation as well as facilitating minimized energy/heat input for increased efficiency.
An additional cost benefit of manufacturing a degreaser from a plastic material such as PVC is the ease with which the components of the degreaser can be fabricated relatively quickly and easily with shop tools, such as shop tools that are common to basic wood working. For example, table saws and miter saws may be used to cut the plastic material effectively, leaving surfaces that have a smooth finish, which facilitates downstream, secondary assembly of the individual plastic degreaser components. Chemical welding of the plastic parts with standard PVC cement is facilitated by cleanly finished cuts, and significantly reduces required labor hours as opposed to heated plastic welding. Other manufacturing operations similar to those used in metal working, such as threading holes for various fittings, can still be performed in the same manner with plastic components with a regular drill and tap set. In this manner, the use of plastic for the components of the degreaser disclosed herein facilitates manufacture without the need of specialized tools.
Chemical compatibility of the solvent with the materials of construction is an important consideration in the design of a vapor degreaser, and the combined effects of chemical, thermal, and mechanical loading on a material will inform a proper construction of a degreaser. To this effect, a series of soak tests of PVC samples were performed using solvents including in VERTREL® SDG (a registered trademark of E. I. DuPont Nemours and Company, a Delaware corporation), n-Propyl Bromide, and trans-1233zd. Pieces of PVC were solvent welded together and allowed to soak in the boiling solvent for approximately 1 day. Table 1 below summarizes the results of the compatibility test, which illustrates the compatibility of trans-1233zd with PVC.
As can be seen in Table1, PVC was not compatible with 1-Bromopropane (“nPB”) or VETREL® SDG, a trans-1,2-dichloroethylene (t-DCE) and hydrofluorocarbon mixture commercially available from Dupont®. However, trans-1-chloro-3,3,3-trifluoro-propene (trans-1233zd) was found to not adversely affect the PVC.
A degreaser, shown in
The degreaser in as exemplified in
The temperature of the cooling coils was then lowered to −10° C. and the temperature of the heating coils maintained at ˜24° C. to study the effect of loss rate versus coil temperature. The loss rate was reduced to 0.09 lbs/hr with a turnover rate of 8.9 lbs/hr. Lowering the coil temperature to −10° C. yielded a 75% greater turnover with only 50% the losses while using smooth cooling coils. Without being limited to any theory, it is believed that finned coils may allow for an even lower loss rate due to the increased surface area for heat transfer. After running trans-1233zd for 1 month in the PVC degreaser there was no sign of visual attack or degradation of the PVC. The PVC degreaser did not form any leaks or show any sign of deterioration.
Commonly used plastics were immersed in trans-1233zd for 2 weeks. The weights and volumes of the plastics were measured before and after the 2 week immersion. Many of the plastics saw a weight and volume change of less than 5% which was determined to be acceptable. Both HIPS and acrylics were greatly affected by trans-1233zd in this application and were determined to be unacceptable for use as a construction material for a plastic degreaser when using trans-1233zd as the solvent.
As can be seen in Table 2, trans-132zd was compatible with numerous polymers, including polyamide (Nylon 66), polyethermide (ULTEM®, a registered trademark of SABIC Global Technologies, a corporation of the Netherlands), PET, PVC, PVDF, POM (DELRIN®, a registered trademark of E. I. DuPont Nemours and Company, a Delaware corporation), HDPE, PTFE (TEFLON®, a registered trademark of E. I. DuPont Nemours and Company, a Delaware corporation), ABS, polycarbonate, and polypropylene. However, HIPS and acrylics were seen as having a significant weight and volume change (greater than 5%).
Thus, a plastic degreasing apparatus may be used as a vapor degreaser when combined with an appropriate solvent, such as trans-1233zd (1-chloro-3,3,3-trifluoro-propene, CF3CH═CHCl). Accordingly, plastic degreasing apparatuses when used with the aforementioned appropriate solvents provide compatible, low-cost, reasonably durable degreasers that are more portable and that are capable of widespread use in production cells.
While this invention has been described as relative to exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/333,532, filed on May 9, 2016 and entitled PLASTIC VAPOR DEGREASER AND CLEANING METHODS, the entire disclosure of which is hereby expressly incorporated by reference.
Number | Date | Country | |
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62333532 | May 2016 | US |