Method of cleaning waste water and recovery of contaminants therefrom

A method of cleaning waste water and removing contaminants therefrom with respect to compositions exhibiting water solubility behavior which is pH dependent. The method includes the preliminary step of applying the composition at a pH at which the composition is water insoluble, then removing excess composition from application equipment with a wash solution having a pH at which the composition is water soluble or washable, changing the pH of the wash solution to a pH at which the composition is water insoluble to thereby precipitate the composition and removing the composition by filtration or other separation techniques. The invention also relates to a shop towel clean up method.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to the field of waste water 
treatment and more particularly to a method of cleaning waste water 
containing contaminants and the recovery of such contaminants therefrom. 
The present invention is applicable to a broad range of contaminants, but 
has particular application to the clean up of waste water from coating 
processes, and in particular, oil based coating processes such as 
lithographic or other printing processes, paint or varnish application 
processes or the like in which the oil based coating composition is water 
insoluble at first pH levels and water soluble or washable at second pH 
levels. 
2. Summary of the Prior Art 
Water treatment in general has grown significantly over the past several 
years. Treatment methods which result in clean water with minimal chemical 
or energy input are highly desirable. This is particularly true with 
industrial waste water effluents containing contaminants resulting from 
the clean up of various coating processes including lithographic or other 
ink printing processes and paint or varnish application processes. Waste 
water effluents from such processes often contain organic wash solvents 
which are needed to clean up application or processing equipment and 
tools. The laundering of shop towels and other cleaning aids containing 
such contaminants and organic wash solvents are also a source of pollution 
since the laundering medium containing such contaminants is commonly 
disposed of into the sewer system. 
In a lithographic printing process which utilizes both an oil based ink 
composition and an aqueous fountain solution, printing plates and/or inks 
need to be periodically changed as one job is completed and another 
started. Whenever this occurs, the blanket cylinder and/or the entire 
print train including the application rollers, the print plate, etc. must 
be cleaned. Such cleaning is commonly accomplished using organic or other 
non aqueous wash solvents which dissolve the oil based ink for removal. 
This creates a waste solution comprised of the organic or other non 
aqueous wash solvent and the dissolved oil based contaminant as well as 
shop towels saturated with such materials. 
Such a clean up process gives rise to several sources of both air and water 
pollution. First, many of the wash solvents needed to acceptably clean the 
oil based inks or other coating materials contain various volatile organic 
compounds (VOCs) which are ultimately dispersed into the atmosphere. 
Secondly, the organic or other non aqueous wash solvents and the dissolved 
oil contaminants cannot be discharged into the sewer system without 
extensive and costly processing and separation of the contaminants. In 
fact, many are considered hazardous wastes whose disposal is tightly 
controlled. Thirdly, the laundering of shop towels or other clean up aids 
and materials results in laundry waste water containing finely dispersed 
particles of the wash solvents and oil based contaminant which are 
difficult to separate through common filtration. Although technology such 
as reverse osmosis, distillation or other membrane processes will, in 
theory, function to separate the finely dispersed wash solvent and 
contaminant particles from the laundry waste water, such processes are 
energy intensive and require substantial maintenance and upkeep. As a 
consequence, few industries are able to economically clean such waste 
water and most continue to discharge such untreated water to the sewer 
system. The Clean Water Act and various other state and federal 
legislation, however, will force those responsible for polluting 
discharges to treat the effluent and to remove the contaminants regardless 
of treatment costs. As an alternative, many printers have gone to 
disposable towels which create disposal problems of their own. 
Accordingly, a need exists for a method of cleaning waste water and 
recovering the contaminants therefrom. More particularly, a need exists 
for a method of cleaning waste water from various coating processes such 
as lithographic and other printing processes, paint or varnish application 
processes and the like. A need also exists for a method of recovering such 
contaminants from the waste water and from laundering solutions used to 
clean shop towels and other clean up aids. 
SUMMARY OF THE INVENTION 
The present invention relates generally to a clean up process for a 
composition or contaminant and more particularly, to a method of cleaning 
waste water containing a coating composition and the recovery of such 
composition in a manner which overcomes many of the problems in the prior 
art. Although the method of the present invention has applicability to a 
variety of compositions, both oil based and non oil based, it has 
particular applicability to certain coating compositions which exhibit 
water solubility behavior which is dependent on the pH of the solution to 
which they are exposed. In other words, the present invention is 
applicable to compositions or contaminants which are generally water 
insoluble at first pH levels and water washable or water soluble at second 
pH levels. Examples of such compositions include those identified in 
applicant's co-pending application Ser. No. 07/946,762, filed Sep. 17, 
1992, the entirety of which is incorporated herein by reference. However, 
the scope of the present invention is not intended to be limited to these 
particular compositions. 
The method of the present invention is also applicable to the clean up and 
recovery of compositions which are comprised of components not generally 
water soluble at any pH level, but which are combined with one or more 
compatible solubility controlling components whose water solubility is pH 
dependent and which is present in a quantity sufficient to provide the 
entire composition with pH dependent water solubility or washability 
behavior. Preferably this solubility controlling component or all or a 
part of the composition is a water reducible resin or other composition 
which exhibits the desired pH dependent water solubility behavior. 
A step which is preliminary to the clean up or recovery steps is the 
application of the coating composition to a substrate. This is 
accomplished using various application or processing equipment and tools 
(hereinafter sometimes referred to as "application equipment" or 
"application equipment and tools"). The application is at a pH falling 
within the first pH levels at which the composition is generally water 
insoluble. 
Following such application, the application equipment and tools are cleaned 
using an aqueous solution having a pH falling within the second pH levels 
at which the composition is water soluble or washable. This results in the 
composition dissolving in, or being rendered washable by, the aqueous wash 
solution. The cleaning and removal of the composition from the application 
equipment and tools can be aided with the use of shop towels, brushes and 
other cleaning aids. Completion of the cleaning step results in a spent 
wash solution containing dissolved or finely dispersed particles of the 
composition and shop towels, brushes or other cleaning aids also 
containing the aqueous wash solution and dissolved or finely dispersed oil 
based composition. 
Clean up of the spent wash containing dissolved or finely dispersed 
composition involves changing its pH to a pH falling within the first pH 
levels. Because the composition is generally water insoluble under these 
conditions, a solubility shift occurs. This causes the composition to 
become water insoluble. Once insoluble, the composition is no longer 
stable in the generally aqueous wash solution. As a result, the particles 
of such composition become hydrophobic or oleophillic, and begin to 
precipitate out and form larger particles of a filterable size as more and 
more of the contaminants contact each other and stick together. In 
addition, these particles have sufficient dimensional stability to 
facilitate separation by low cost separation technologies. Following this 
conversion of the oil based composition to particles of a filterable size, 
they are removed from the spent wash solution either by conventional 
filtration or by centrifugation or other separation techniques known in 
the art. 
Removing and recovering the composition from the shop towels and other 
cleaning aids involves first washing the same in a wash solution having a 
pH falling within the second pH levels or a conventional or modified 
laundering medium to remove the composition. This resulting wash solution 
or laundering medium is then treated as described above by changing the pH 
to a level corresponding to or falling within the first pH levels. This 
causes the dissolved or finely dispersed composition particles to 
precipitate out of solution and combine to produce particles of an 
adequate size capable of removal using conventional filtration or other 
separation techniques. 
Accordingly, it is an object of the present invention to provide a method 
of cleaning waste water containing certain compositions and recovering 
such compositions therefrom. 
Another object of the present invention is to provide a method of cleaning 
waste water from a coating process in which the waste water comprises 
coating compositions such as lithographic or other ink compositions and 
paint or varnish compositions. 
A further object of the present invention is to provide a clean up and 
recovery method for a coating composition such as an oil based coating 
composition which is water insoluble at first pH levels and water soluble 
or washable at second pH levels. 
A still further object of the present invention is to provide a method of 
cleaning shop towels or other cleaning aids containing contaminants 
including the cleanup of the laundering or wash medium and the removal of 
the contaminants therefrom. 
These and other objects of the present invention will become apparent with 
reference to the description of the preferred method described below.

DESCRIPTION OF THE PREFERRED METHOD 
The present invention relates to a method of cleaning waste water 
containing certain compositions or contaminants and a method of recovering 
such contaminants therefrom. More specifically, the present invention 
relates to a method of cleaning waste water containing compositions which 
are generally water insoluble at first pH levels and water soluble or 
water washable at second pH levels. Accordingly, those compositions to 
which the present invention is applicable are those described in 
applicant's co-pending application Ser. No. 07/946,762, filed Sep. 17, 
1992, the entirety of which is incorporated herein by reference, as well 
as various other oil based or non oil based compositions or components 
which, either themselves or because of their combination with other 
solubility controlling components, exhibit water solubility/insolubility 
behavior which is pH dependent. 
It is contemplated that the method of the present invention is applicable 
to the clean up and/or recovery of any composition whose water solubility 
is pH dependent, but has particular applicability to oil based coating 
compositions and more specifically to oil based ink, paint or varnish 
compositions which exhibit such behavior. The description of the preferred 
method will be with reference to the clean up and/or recovery of oil based 
lithographic printing inks. 
Oil based compositions which exhibit the above described pH dependent water 
solubility behavior are those in which their acid functionality is 
sufficient to result in such behavior. Preferably, the compositions which 
exhibit sufficient acid functionality and thus also exhibit the pH 
dependent water solubility are those which have an Acid Number greater 
than 25. The Acid Number (or AN) of a particular material is one accepted 
measure of acid functionality. Acid functionality in turn is a measure of 
the amount of "free acid", or the amount of acid groups available for 
reaction, in the material. The Acid Number is defined as the amount of 
potassium hydroxide (KOH) in milligrams (mg) which is required to 
neutralize one gram of the material being tested. Thus, the Acid Number is 
a measure of the "free acid" groups or ends which are not tied up or 
hindered by some other component in the system. Normally, Acid Numbers of 
conventional lithographic inks are minimized to reduce ionic behavior of 
the composition. This in turn increases the overall stability and water 
insolubility of the ink. For a particular composition or contaminant to 
exhibit the necessary water solubility/insolubility pH dependency, the 
Acid Number should preferably be above about 25, more preferably above 
about 30 and most preferably above about 40. Below these threshold levels, 
the composition tends to be water insoluble regardless of the pH. 
The extent to which the composition is required to have a maximum Acid 
Number will depend upon the particular environment in which the method is 
practiced. In a lithographic printing environment, a maximum Acid Number 
is required because of the criticality of maintaining a stable separation 
between the oil and water components of a lithographic system. In 
contrast, for non lithographic ink compositions and for paints, varnishes 
and other coating compositions, no maximum Acid Number exists. In such 
cases, however, the Acid Number will, to some extent, dictate the 
efficiency with which the water solubility of the composition can be 
converted between a water soluble and a water insoluble form. In general, 
the greater the Acid Number, the more acid will be required to convert the 
composition to a water insoluble form. 
In a lithographic printing environment, the oil based ink composition 
should exhibit acid functionality defined by an Acid Number preferably in 
the range of about 25-150, more preferably in the range of about 30-100 
and most preferably in the range of about 40-60. Compositions with Acid 
Numbers below these ranges will tend to not exhibit the necessary pH 
dependent water solubility for practicing the present invention, while 
compositions with Acid Numbers above these ranges will tend to exhibit 
insufficient stability for lithographic printing. In all cases, the 
particular Acid Number which is preferred will depend on the particular 
composition being used. 
The method of the present invention is applicable to compositions which 
themselves individually exhibit pH dependent water solubility/insolubility 
behavior as well as compositions which alone do not exhibit such behavior, 
but which when combined with certain solubility controlling components 
will exhibit at least limited water solubility or washability behavior as 
a function of pH. 
It has been found that certain compositions when combined with a sufficient 
quantity of a compatible solubility controlling component such as a water 
reducible alkyd, polyester or other resin, or a blend of such compounds, 
will result in the entire combined composition exhibiting pH dependent 
water solubility behavior sufficient to practice the method of the present 
invention. Preferably, the composition with which the method of the 
present invention is applicable should include at least 5% by weight, or 
about 5-60% by weight, of a solubility controlling component which is 
water insoluble at certain first pH levels and water soluble or washable 
at certain second pH levels. More preferably, such solubility controlling 
component should be present in an amount of at least about 10% or about 
10-40% by weight. It has been shown that certain water reducible alkyds 
(Cargill's short oil alkyds 74-7450, 74-7451; Cargill's long oil alkyd 
74-7416; Cook Composites short oil alkyd 101210), certain water reducible 
polyesters (Cargill's polyester 72-7203), certain water reducible 
polyolefins (Cargill's modified polyolefin 73-7358), certain water 
reducible modified oils (Cargill's modified linseed oil 73-7319) and 
certain water reducible epoxy esters (Cook Composites styrenated epoxy 
ester 100453) exhibit the desired characteristics and are capable of 
providing the required pH dependent solubility to the system provided they 
are compatible with the other components of the oil based composition and 
are present in an amount sufficient to cause such other components to 
exhibit similar characteristics. All of the above water reducible resins 
except the 73-7319 and the 73-7358 are available in a solvent diluted 
form. For those resins in a solvent diluted form it is preferable that 
they be solvent stripped. 
For the water reducible compositions or other solubility controlling 
components exhibiting water solubility which is pH dependent and for ink 
compositions or other coating compositions incorporating such compounds, 
water solubility or washability characteristics depend on the pH of the 
aqueous solution with which the material comes into contact. Preferably 
the first pH level at which the above mentioned solubility controlling 
components or the composition are water insoluble are acidic pH levels 
less than 7.0 and the second pH level at which the solubility controlling 
components are water soluble or washable are alkaline pH levels greater 
than 7.0. It is contemplated, however, that the method of the present 
invention will also work in an alkaline system in which the composition is 
generally water insoluble at certain alkaline pH conditions and water 
soluble or washable at certain acidic pH conditions. 
The method steps involved in the present invention include the preliminary 
step of applying the oil based coating or ink composition to a substrate 
at an application pH corresponding to or falling within the first pH 
levels described above. This is followed by removing the coating or ink 
composition from at least a portion of the application equipment and tools 
using shop towels, brushes or other cleaning aids and an aqueous wash 
solution having a solution pH falling within the second pH levels. This 
results in a spent wash solution containing dissolved or finely dispersed 
particles of the oil based composition and soiled shop towels and other 
cleaning aids containing similar materials. Next, the pH of the spent wash 
solution or the resulting wash or laundering medium from the shop towels 
cleaning process is lowered to a precipitation pH corresponding to the 
first pH levels. This converts the composition to a water insoluble form 
and causes it to precipitate out and combine to form particles which are 
sufficiently large for separation. Such particles are then separated and 
recovered via filtration, centrifugation or other known separation 
techniques. The filtrate from the separation process is a clear aqueous 
liquid substantially free of any of the composition or other contaminants, 
while the filtered material is comprised substantially of the separated 
composition or other contaminants. 
The preliminary application step is dependent upon the particular 
composition being used and the particular environment in which such 
composition is being applied. In a lithographic printing application in 
accordance with the preferred method, the oil based ink composition, 
together with an aqueous fountain solution, are applied to a lithographic 
printing plate via application rollers. The ink is then transferred either 
directly to an image receiving substrate or to an intermediate blanket 
cylinder which then subsequently transfers the ink to the receiving 
substrate. During this process, the entire print train including the 
application rollers, the print plate and the blanket is exposed to the oil 
based ink composition. 
In other printing processes, either oil based or non oil based ink 
compositions may be applied to a printing plate or the like, without an 
accompanying fountain solution, and thereafter transferred to an ink 
receiving substrate. Oil based or non oil based paints, varnishes and 
other coating compositions may also be applied to substrates using 
conventional application equipment and tools. Application may be via 
roller means as in lithographic printing or via spray, brush or other 
application techniques known in the art. 
Regardless of the particular application environment, the application 
equipment and tools must be cleaned. In the lithographic printing 
application, all or part of the print train including the application 
rollers, the print plate and the blanket must be thoroughly cleaned to 
accommodate a change in the printing plate and/or ink. This is 
accomplished by flushing or wiping the application equipment with, or 
otherwise exposing it to, an aqueous wash solution with a pH level 
corresponding to the second pH levels defined above. Such flushing or 
wiping should be continued until the entire ink train and/or the blanket 
are clean. In the preferred procedure, the aqueous wash solution is 
applied in a manner such that the wash solution is mixed with or milled 
into the oil based composition on the application equipment. In the 
lithographic printing application, the wash solution is applied to the 
front end rollers of the print train and then cycled for about 100 cycles. 
Such mixing can also be accomplished via brushing, wiping or other similar 
techniques. Preferably the surfaces of the application equipment are then 
wiped with a shop towel or the like to finally remove any remaining 
composition contaminant. 
Because the aqueous wash solution is at a pH level corresponding to the 
second pH levels (i.e., above 8.5 for the preferred method), the oil-based 
ink composition on the application equipment and tools becomes water 
soluble or water washable, thus facilitating its removal from the 
application equipment or tool surfaces. This is done either by the 
flushing action or by wiping such surfaces with a shop towel, brush or the 
like, or by both. For the lithographic printing application, this removal 
step produces a resulting spent wash solution containing dissolved or 
finely dispersed particles of the composition and soiled shop towels, 
brushes or other cleaning aids containing similar materials. 
The particular efficiency of the removal or cleaning step in the 
lithographic printing application will depend upon various factors 
including, among others, the pH of the aqueous wash solution, the 
temperature of the wash solution, the amount of wash solution used and 
whether or not surfactants or other additives are used. In the preferred 
system, an increase in the pH of the wash solution will result in an 
increase in the speed with which the oil based composition will be removed 
from the surfaces and a decrease in the volume of wash solution which must 
be utilized. Preferably, the pH of the wash solution should be greater 
than 8.5, or in the range of 8.5-14, and most preferably greater than 
about 10.5 or in the range of 10.5-13. Increase in temperature will also 
tend to increase the efficiency of the removal or cleaning step by 
speeding up the conversion of the ink composition to a water soluble form 
and thus removal from the equipment. However, it is contemplated that most 
of the removal or cleaning steps will be performed at or about ambient 
temperatures. 
Various additives can also be used to alter, and in particular to improve, 
the efficiency of the removal or cleaning step. For example, the use of 
various surfactants, cosolvents and other additives common to the industry 
may be used as part of the wash solution. Selection of the appropriate 
surfactant will depend on the particular composition. Examples of 
surfactants which have been found to be useful with oil based lithographic 
ink compositions include a nonionic surfactant made by Mazer Chemical and 
sold under the trade name Mazawet 77, a nonionic surfactant made by Air 
Products and sold under the trade name Surfonyl 104 and a cationic 
surfactant made by PPG Industries and sold under the trade name M Quat. 
Various other nonionic, cationic and anionic surfactants may also be used. 
While not necessary to the practice of the present invention, surfactants 
provide additional surface wetting and dispersion characteristics during 
the cleaning (or solubilization) step. Of equal importance is the fact 
that the surfactants do not interfere with, but in fact appear to aid, the 
water clean up (or insolubilization) step as described below. This appears 
to result from the ability of the surfactants to surround the growing 
particles as they are formed. This in turn enhances the filterability of 
the resulting mixture. 
If desired, the removal step may also include preapplication to the 
equipment of a clean up composition which is compatible with the 
composition to be removed and whose water solubility is pH dependent. 
Initial application of clean up composition will react with the ink 
composition thereon and render the same more readily water soluble at 
certain pH levels. Such a clean up composition may include a solubility 
controlling component and can be applied directly or, because of viscosity 
or other reasons, can be combined with one or more diluents compatible 
therewith. Virtually any of the water reducible alkyds, polyesters or 
other resins can be used as the solubility controlling component for this 
purpose provided they are compatible with the composition to be cleaned 
and exhibit the desired pH dependent water solubility behavior. Diluents 
which include fatty acids (such as oleic and steric acids), vegetable oils 
(such as soya, caster and linseed oils) and mineral oils may be used to 
reduce the viscosity of the solubility controlling component provided they 
are compatible both with the composition to be cleaned and the solubility 
controlling component. Thus, a precoating or preapplication, together with 
a mixing or milling in, of a compatible solubility controlling component 
or a clean up composition containing the same will improve the efficiency 
of the removal by reducing the amount of wash solution needed and the 
removal time. 
Following removal of the oil based ink composition from the application 
equipment and tools as provided above, the composition exists as a 
dissolved portion, or as finely dispersed particles, within the spent wash 
solution. A portion of the removed oil based composition is also contained 
within the shop towels or other cleaning aids either as dissolved portions 
or as finely dispersed particles within the spent wash solution. 
For that portion of the oil based composition existing in a dissolved or 
finely dispersed form within the spent wash solution, recovery of the 
composition involves first changing the pH of such spent wash solution to 
a pH corresponding to the first pH levels and then removing or recovering 
the composition by filtration, centrifugation or various other separation 
techniques known in the art. 
In the preferred system, lowering the pH of the spent wash solution causes 
such composition to become water insoluble. This in turn causes the 
composition to precipitate out, thereby facilitating its separation by 
filtration, centrifugation or the like. Even compositions which normally 
exist as liquids are separated as discrete particles to further enhance 
the separation efficiency. The conversion to a water insoluble form also 
results in the precipitated particles having an affinity for one another 
so that agglomeration of particles occurs. This further improves the 
ability to separate the precipitated particles of the ink composition from 
the spent aqueous wash solution. 
Both the rate and extent to which the composition comes out of solution or 
combines to form particles large enough to filter is dependent upon the 
amount of acid (or free protons) in the wash solution and thus the pH 
level to which the spent wash solution is lowered. This in turn is 
determined by the amount and strength of the particular acid being used 
and the Acid Number of the particular composition. During the process of 
lowering the pH, acid is consumed as it reacts with the acid functional 
groups to render it nonionic. At a pH of 6, the acid is relatively dilute 
and the chance for neutralization is reduced since the available acid is 
not in great supply. Thus, at a pH of 6, the extent of precipitation is 
diminished and the time for precipitation to occur is longer. As much as 
several hours may be required for the precipitation to reach its maximum 
levels. In contrast, if the pH of the spent wash solution is lowered to a 
pH of 2, excess acid is available and the conversion occurs to a greater 
extent and very rapidly, on the order of a few seconds to several minutes. 
Preferably, for complete precipitation and separation of the composition 
particles from the aqueous solution to occur, a pH below 5 or in the range 
of about 4-5 is preferred. At pH levels above 5, insufficient acid exists 
to fully neutralize the material. This results in incomplete separation. 
At pH levels below 4, excess acid is present. This will not necessarily 
improve the overall separation, but will speed up the process. Thus, below 
a pH level of 4, economic analysis will determine whether increased speed 
justifies the excess acid for a given application. 
It has been shown that various additives can improve the conversion of the 
ink composition from a water soluble or washable form to a water insoluble 
form, and thus its precipitation. For example, certain salts, specifically 
sodium chloride and potassium chloride, have been shown to have such an 
effect. It is believed that this is due to the equilibrium shifting effect 
of the excess ions which reduces the ionic effect of the acid groups and 
shifts the solubility of the material down. The presence of a salt will 
not appreciably impact the ultimate extent of separation, but will tend to 
speed up the process. 
After the pH of the spent wash solution has been lowered and the 
composition precipitated, such precipitated particles can be removed 
through various separation techniques such as filtration, centrifugation 
and the like which are known in the art. Filtration will normally be the 
most efficient separation technique which can be improved with the use of 
various filter aids known in the art. If the density difference between 
the particles and the water is sufficiently large, separation via 
centrifugation is also a viable alternative. It may also be desirable, in 
certain cases, to preconcentrate the contaminants in the wash solution 
(prior to lowering the pH) via reverse osmosis or other processes known in 
the art. 
With respect to shop towels which contain portions of the ink composition, 
either in a dissolved or finely dispersed form as part of the spent wash 
solution, the separation and recovery of such composition is similar to 
the separation and recovery of the composition from the spent wash 
solution. However, a first step with respect to shop towels or other 
cleaning aids requires the removal of such composition from the shop 
towels themselves. This can be accomplished by washing, soaking or rinsing 
the shop towels in a washing pH solution failing within the second pH 
levels. An alternate procedure is to launder the shop towels in a 
conventional or modified manner using conventional or modified laundering 
detergents or other compositions for the purpose of cleaning the 
composition from the towels. In both situations, the ink composition ends 
up as dissolved or finely dispersed particles in the wash or laundry 
solutions. Following this removal or cleaning procedure, the resulting 
spent wash or laundry solution is treated in a manner similar to that 
described above by changing the pit to a level corresponding to the first 
pH level. When this is done, the previously dissolved or finely dispersed 
ink composition will become insoluble. This in turn causes the composition 
to precipitate out and combine with one another to form into larger 
particles capable of separation by filtration or the like. 
In a conventional or modified laundering process which normally includes 
the presence of surfactants and detergents, such materials actually 
improve the precipitation process. During the conversion of the 
composition from a water soluble to a water insoluble form, such 
surfactants and detergents surround the particles and maintain them as 
discrete particles. This promotes larger particles and easier separation. 
Having described the details of the preferred method, the following 
examples will demonstrate the applicability of the method of the present 
invention to a wide range of compositions and to various mixtures and 
materials generated during a clean up process. Throughout the application, 
and in the examples, percentages are based upon weight unless otherwise 
indicated. Further, in all examples, the water reducible alkyd or other 
resin was first solvent stripped to remove petroleum or other solvents. 
PROCEDURE OF EXAMPLES 1-6 
Examples 1-6 below were conducted to show application of the method of the 
present invention to an oil based lithographic ink composition 
(hereinafter referred to as Deluxe Ink #H32) having the following 
composition: 
______________________________________ 
Rosin (Arizona Chemical SLYVAROS R) 
30.14% 
Alkyd (Cargill 74-7451) AN 47-53 
13.80% 
Castor Oil (USP-United Catalyst) 
15.53% 
Oleic Acid (EMERSOL 213 NF, Henkel Inc.) 
15.53% 
Black Pigment (REGAL 400R, Cabot Inc.) 
25.00% 
______________________________________ 
The above ink composition is an oil based ink composition exhibiting water 
solubility/insolubility behavior as a function of pH. Specifically, such 
composition is water insoluble at acidic pH levels and preferably pH 
levels below about 7.0 and is generally water soluble or washable at 
alkaline pH levels and preferably pH levels above about 8.5. The alkyd is 
a commercially available, water reducible short oil alkyd which has been 
solvent stripped. 
In each of Examples 1-6, an aqueous waste water or spent wash solution was 
simulated and produced by combining known quantities of the above ink 
composition in a known quantity of an alkaline wash solution containing 
NaOH at a pH of 12.7. This was mixed with an impeller for about five 
minutes to achieve complete dispersion A standard Buchner funnel was 
fitted to a one liter filter flask and the flask was attached to a vacuum. 
Standard Whatman #2 filter paper was added to the Buchner funnel. In 
examples 1-5, 54 g of Hyflo Super-Cel filter aid was added to the funnel 
to complete the filter apparatus. In example 6, 54 g of the filter aid was 
added to 1 liter of the mixture. Following pretreatment by addition of an 
acid as set forth in Examples 2-6, but without pretreatment as provided in 
Example 1, each of the samples was passed once through the filter 
apparatus described above, under vacuum, and the filtrate was collected 
for analysis. Pretreatment with acid included adding the acid over a 
period of about 30 seconds until the desired pH was reached. Analysis of 
oils, greases and fats in the filtrate after separation was conducted 
using USEPA Method 413.1. Color evaluation of filtrate was conducted using 
visual qualitative analysis. Theoretical ink concentration and separation 
were calculated. 
EXAMPLE 1 (NO PRETREATMENT) 
Waste water sample: 0.1066% ink in solution at pH of 12.7 
Ink concentration: 1066 mg/l 
Pretreatment: None 
Filtrate analysis: No effective separation 
Oils, greases, fats analysis: 633.7 mg/l 
Color: Dense black 
##EQU1## 
EXAMPLE 2 (PRETREATMENT BY pH REDUCTION) 
Waste water sample: 0.1066% ink in solution at pH 12.7 
Ink concentration: 1066 mg/l 
Pretreatments: Addition of concentrated HCl to pH 2 
Filtrate analysis: Effective separation 
Oil, greases, fats: 2.6 mg/l 
Color: Clear 
##EQU2## 
EXAMPLE 3 (PRETREATMENT BY pH REDUCTION AND HIGH INK CONCENTRATION) 
Waste water sample: 1.000% ink in solution at pH 12.7 
Ink concentration: 10,000 mg/l 
Pretreatment: Addition of concentrated HCl to pH 3.4 
Filtrate analysis: Effective separation 
Oils, greases, fats: 25.0 mg/l 
Color: Clear 
##EQU3## 
EXAMPLE 4 (DROP pH TO 6.0) 
Waste water sample: 1.000% ink in solution at pH 12.7 
Ink concentration: 10,000 mg/l 
Pretreatment: Addition of concentrated HCl to pH 6.0 
Filtrate analysis: Partial separation 
Oils, greases, fats: 863 mg/l 
Color: Slightly pigmented 
##EQU4## 
EXAMPLE 5 (DROP pH TO 6.0 AND ADD 5% KCl) 
Waste water sample: 1.000% ink in solution at pH 12.7 
Pretreatment: Add concentrated HCl to bring pH to 6. Also add 5% KCl to 
speed separation. 
Filtrate analysis: Partial separation 
Oils, greases, fats: 506 mg/l 
Color: Very slightly pigmented 
##EQU5## 
EXAMPLE 6 (PRETREATMENT BY pH REDUCTION AND PREADDITION OF FILTERAID) 
Waste water sample: 1.000% ink in solution at pH 12.7 
Ink concentration: 10,000 mg/l 
Pretreatment: Addition of concentrated H.sub.2 SO.sub.4 to pH 4.0 
Filtrate analysis: Effective separation 
Oils, greases, fats: 33 mg/l 
Color: Clear 
##EQU6## 
Example 1 demonstrated no effective separation of the ink from the waste 
water by the filtration procedure. Because of the USEPA Method 413.1 
procedure used, a prefiltering step was performed on all samples. During 
the prefilter step, a certain amount of pigment, with absorbed oil, is 
trapped and removed from the system. Thus, the 20.7% theoretical 
separation for example 1 is misleading because much of the contaminant was 
removed as part of this procedure, not as part of the initial separation. 
In reality, little, if any, of the oils, fats, and greases would be 
removed during the filtering step if USEPA Method 413.1 procedure is not 
performed. The result of Examples 2, 3 and 6 demonstrated effective 
separation and recovery, while Examples 4 and 5 demonstrated partial 
separation and recovery. 
EXAMPLES 7-11 
The procedure of Examples 7-11 was similar to that of Examples 1-6, but 
different ink and other coating compositions were tested. The details are 
as follows: 
EXAMPLE 7 
In Example 7, the Deluxe #H32 ink composition identified in Examples 1-6 
was mixed in a 5:1 ratio (Deluxe #H32: Multigraphic PS-274) with 
conventional oil based lithographic ink identified as Multigraphic PS-274 
made by AM Multigraphic. This lithographic ink did not exhibit water 
solubility/insolubility behavior as a function of pH. 
Waste water sample: 1.010% ink in solution at pH 12.7 
Ink concentration: 10100 mg/l 
Pretreatment: Add concentrate HCl to pH 4.0 
Filtrate analysis: Complete separation 
Oils, greases, fats: 33mg/l 
Color: Clear 
##EQU7## 
EXAMPLE 8 
In Example 8, the composition used was a water-based latex enamel 
identified as a Glidden Ultra Hide low lustre enamel exhibiting water 
solubility behavior as a function of pH. 
Waste water sample: Enamel paint at 1.038% in solution at pH 12.7 
Paint concentration: 10380 mg/l 
Pretreatment: Treat with concentrated HCl to pH 2.1 
Filtrate analysis: Complete separation 
Oils, greases, fats: 194 mg/l 
Color: Clear 
Note: Theoretical separation unknown due to no knowledge of paint formula. 
EXAMPLE 9 
Example 9 involved a Handschy water-based black flexo ink identified by the 
tradename Hanco #50688 exhibiting water solubility as a function of pH. 
Waste water sample: 1.005% ink in solution at pH 12.7 
Ink concentration: 10050 mg/l 
Pretreatment: Treat with concentrated HCl to pH 2.1 
Filtrate analysis: Complete separation 
Oils, greases, fats: 37 mg/l 
Color: Clear, slight blue tint 
Note: Theoretical separation unknown due to no knowledge of ink formula 
EXAMPLE 10 
Example 10 involved tests conducted on the clear varnish of the Deluxe #H32 
ink composition identified in Examples 1-6, with pigments deleted. 
Waste water sample: 1.016% dear varnish in solution at pH 12.7 
Varnish concentration: 10160 mg/l 
Pretreatment: Treat with concentrated HCl to pH 2.05 
Filtrate analysis: Complete separation 
Oils, greases, fats: 52 mg/l 
Color: Clear 
##EQU8## 
EXAMPLE 11 
In Example 11, a series of experiments was conducted to determine the 
behavior of all of the ink compositions identified in the Examples 1-19 of 
applicants co-pending application Ser. No. 07/946,762, filed Sep. 17, 
1992. The specific formulations of such ink compositions are incorporated 
herein by reference. All such ink compositions exhibited water 
solubility/insolubility behavior as a function of pH. For all such 
compositions, 10,000 mg of the ink composition was combined with one liter 
of a NaOH solution adjusted to a pH of 12.7. Each sample was pretreated 
with concentrated hydrochloric acid to a pH of about 2.0. In all samples, 
a noticeable precipitation was observed upon addition of the acid. The 
resulting mixture was filtered in accordance with the procedure described 
in Examples 1-6. In all instances, the filtrate was determined by visual 
observation to be a clear liquid with no noticeable traces of the ink 
composition. 
EXAMPLES 12-19 
Lithographic ink (Deluxe #H32) was applied to the rollers of an A. B. Dick 
375 offset lithographic press until a consistent film of 0.007 inch was 
measured using an ink film thickness gauge. 
In Examples 12-18, 10 milliliters of a solution of a preapplication clean 
up composition comprised of 10% by weight of a solubility controlling 
component (SCC), 87% by weight of a diluent (either oleic acid or castor 
oil) and 3% by weight of surfactant was applied to the rollers and allowed 
to mill in to the ink train for 100 press revolutions. A washup tray was 
then fitted on the press and the press rollers started. An aqueous wash 
solution of water/sodium metasilicate adjusted to pH 12.5 was sprayed on 
the rotating rollers until all ink was removed. A stopwatch was used to 
time the entire operation from the time where the wash up blade was 
attached to the press. 
The test of Example 19 involved the evaluation of press clean up without 
the above preapplication solution. In Example 19, the exact procedure 
above was followed except the aqueous solution at pH 12.5 replaced the 
preapplication solution. 
______________________________________ 
% Time 
Ex # SCC Diluent Surfactant 
SCC Result 
(min.) 
______________________________________ 
12 74-7416 Oleic Acid 
Mazawet 77 
10 Clean 4:30 
13 74-7495 Oleic Acid 
Mazawet 77 
10 Clean 4:10 
14 73-7358 Oleic Acid 
Mazawet 77 
10 Clean 3:40 
15 10-1210 Oleic Acid 
Mazawet 77 
10 Clean 3:45 
16 10-0453 Oleic Acid 
Mazawet 77 
10 Clean 3:25 
17 74-7451 Oleic Acid 
Mazawet 77 
10 Clean 3:50 
18 74-7451 Castor Oil/ 
Oleic Acid 
Mazawet 77 
10 Clean 3:45 
19 -- -- -- -- Clean 5:40 
______________________________________ 
In the above examples, 74-7416 is a Cargill water reducible long oil alkyd 
(AN 53-58); 74-7495 is a Cargill water reducible chain stopped alkyd (AN 
33-38); 73-7358 is a Cargill water reducible modified polyolefin (AN 
25-30); 10-1210 is a Cook Composite water reducible short oil alkyd (AN 
32); 10-0453 is a Cook Composite water reducible styrenate epoxy ester (AN 
65) and 74-7451 is a Cargill water reducible short oil alkyd (AN 47-53). 
The table above illustrates a reduction of cleaning times of about 20%-40% 
with the use of a preapplication clean up composition. 
EXAMPLES 20 
Shop towels soiled with Deluxe #H32 ink were placed in an alkaline water 
bath at room temperature. One liter of water was used and the soiled 
towels were agitated for five minutes. The dirty water was drained and the 
shop towels wrung out. One liter of tap water was introduced (at room 
temperature) and the towels were agitated for another five minutes. The 
rinse water was collected. An additional rinse cycle was used and the 
resulting towels were clean. 
The collected water (including both the wash and rinse) was then lowered to 
a pH of 3.0 using hydrochloric acid and filtered though a Whatman #2 
filter. Clear filtrate was obtained. 
EXAMPLES 21 
The procedure in Example 20 was followed except 10 gm of Surf laundry 
detergent was added per liter of wash water. Again clean towels resulted 
and the waste water was successfully treated. 
Although the description of the preferred method have been quite specific, 
it is contemplated that various modifications could be made without 
deviating from the spirit of the present invention. Accordingly, it is 
intended that the scope of the present invention be dictated by the 
appended claims rather than by the description of the preferred method.