THE COLDCUTTM PROCESS TO ELIMINATE THE USE OF HAZARDOUS MACHINING FLUIDS

Timothy Palmer Shamrock Industrial, Inc. Sierra Madre, CA 91024

ABSTRACT

It is estimated that between 260 and 800 million gallons of machining fluid (lubricant/coolant ap lied to metal parts being drilled, cut, or otherwise "machined") is

sulphur, or petroleum based and contain additives which make them hazardous. The Coldcut Process seeks to eliminate the need for hazardous machining fluids by substituting the use of cold air and a non-hazardous vegetable based lubricant. Coldcut Process units of varying characteristics were constructed and tested in various machining applications.

used annually by U. 8 . manufacturers. Most machining fluids used today are chlorine,

INTF3ODUCTION

PROJECT DESCRIPTION

7 It is estimated that between 260 and 800 million gallons annually of machinin fluid - lubricant/coolant applied to mostly metallic materials being cut on machine too s by machining processes such as drilling, tapping, milling, and turning. Most machining fluids used today are chlorine, sulphur, or petroleum based and contain additives which make them hazardous. These fluids are traditionally applied in large volumes by flooding or spray-misting the machining tools.

The Coldcut Process is an alternative lubricatinglcooling method using an extremely small amount of syntheticEvegetable-based cuttin tool lubricant combined

feedrates; cutting t d life by reducing machining temperatures; and geometrical tolerances by reducing thermal changes in the workpiece.

Uniaue Product Features

The Coldcut Process utilizes chilled air and a precision cutting tool lubricant delivery system. The chilled air replaces water or oil as the principal cooling agent. The application of the cutting tool lubricant is infinitely adjustable between zero and four ounces per eight hour shift. The cutting tool lubricant is a clean, non-hazardous synthetic/ vegetable-based oil; traditional coolants typically contain unhealthy or environmentally unfriendly components. A representative machine tool consumes

with cold air. The technology enhances: productivity throug a increased cutting tool

52

I s 0 benefit from a portable unit. Most scrap dealers currently and export it at minimum prices. Processing the cable into its

sale of the materials at a higher price t 6 e s t i c markets.

ng introduced into the industry; 4kS’;dable systems r aluminumclad cable will,Mome available for recycling.

/

Limitations

As scrap market pri minimized to maximize

red with various seatin compounds between the Some cable is man components which M e s them difficult to separate,

ndling and processing time must be

--.

%K leaves a residue. Another be added to separate and clean tkcomponents. Should this

non-hazardous solvent must be identibd so as not to utilize any create hazardous waste.

Undrground television cable is becoming more common. Its differentcomposition

‘1 renders it more difficult to recycle.

51

about 600 gallons of traditional coolants annually; the Coldcut system consumes about 12 gallons. This is a 98 percent reduction in the use of machining fluids and the elimination of all hazardous machining fluids.

The Coldcut applicator's precision delivery system combines a biodegradable cutting tool lubricant and chilled air. Ambient temperature air,is forced through a vortex tube (also known as a Hilch tube or cold air gun) which separates air molecules, generating cold air at one end and hot air at the other end. The cutting tool lubricant is contained in a reservoir which is above the Coldcut applicator. The lubricant is gravity fed into a pneumatic pump in which the pump's adjustable piston stroke controls the volume of lubricant. The pump is interfaced with an adjustable timer which controls the number of pump cycles per minute.

The lubricant and cold air travel in separate tubes within a hose to the nozzle. The lubricant and cold air are mixed at the nozzle which delivers the chilled airbubricant to the interface of the cutting tool and the workpiece (part). The nozzle must be within one inch of this interface.

The vegetable-based cutting tool lubricant is a highly lubricous fluid that can si nificantly reduce friction when the cutting tool is in the cut. However, the lubricant wi 7 I vaporize at the relatively low temperature 600" F. The lubricant's ability to last through the cutting process is greatly enhanced by the cold air. The chilled air cools the part and cutting tool, thus prolonging the life of the lubricant before vaporization occucs.

The output of lubricant is so small that only a little residue remains on the or workpiece; most of the lubricant is consumed in the cut. In traditional floodi

spray mist methods, more residue is left on the parts which may be more di 7 cult to clean.

With the Coldcut Process, the resulting scrap is dry and clean. In many cases, because the scrap is not contaminated by ingredients found in traditional coolants, the scrap can be sold at a higher value per pound.

Typical consumption of lubricant in the Coldcut Process is one to two ounces per ei ht hour shift. A thin molecular coating of the lubricant is delivered to the cutting tool e! ge while the edge is exposed outside of the cut. The vegetable-based cutting fluid's high lubricity factor reduces friction more than mineral oils or water based coolants, and eliminates the need for hazardous, extreme pressure additives containin chlorine or sulphur. The latter is a major advantage, as thousands of gallons o 3 hazardous spent coolants are eliminated which are d y to dispose.

53

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54

APPLICATION

Process and Products Replaced

The Coldcut Process can replace most traditional spray mist and flood systems. Each single nozzle spray mist system consumes several hundred gallons of coolants each year; a single nozzle Coldcut applicator would typicall consume only four gallons of vegetable-based cutting fluids in the same perioJ Coolants used in traditional systems may contain harmful chemicals, whereas the vegetable-based product is quite clean and fairly benign. Traditional spray misting systems can suspend chemicals in the air, causing potential inhalation problems. The vegetable-based fluid is heavier than air, and the minute amount which is not consumed in the machining process quickly settles to the ground.

much of which must be disposed of as hazardous or lands on the shop floor to be collected by absorbent materials and subsequently disposed. A Coldcut applicator, consuming only about five to ten gallons of vegetable lubricant each year, prevents this waste.

A typical machine tool sump consumes about 600 gallons of coolants per year,

Cross Seament Uses

The Coldcut application may be utilized to reduce wear on friction parts. It may also enhance assembl operations - for example, those dealing with rivets and similar functions. The vegeta i le lubricants may have several applications in food processing or other industries where cleanliness with high lubricity are needed.

PROCEDURE

DEMONSTRATION

Lubricant Selection

Several water-based coolants, synthetic fluids, mineral oils, and vegetable-based lubricants were evaluated for use in the Coldcut Process. The selection of a vegetable-based cutting tool lubricant was determined by the criteria described below:

Pour point Lubricity (pin and vee block tests) - Compatibility with workpiece material - Environmental cleanliness - Employee protection

Pour point is an issue, as the vortex tube can reduce the air temperature to below 0" F. Therefore, the cutting fluid must stay liquid below freezing. Water-based coolants were eliminated due to the high pour point - about 32" F. Mineral oils were not as clean nor were they as lubricous. Some synthetic fluids stayed liquid at low

55

temperatures and had good lubricity characteristics; however, they were not as clean, Vegetable-based fluids had the best combined characteristics considering the criteria described.

The vegetablebased product with the best performance and application data is supplied b Product Solutions. It is compatible with all materials and is safe to

mist or fog m the machine shop. The pin and w e block test, a national lubicity measurement standard, is 2100 bad value to foot pounds (test ASTM D3233A).

Test ParametersfQA Controls

humans. 8 our point is approximately 5" F. It is heavier than air so it will not create a

Tests compared the parameters of the following machining processes using

Cutting tod life. - Machine tool productivity - feedrate in inches per minute (IPM). Finish - geometrical tolerance and RMS finish of the machined product RMS is the Root Mean Square - a2+b2+c 2... - and is used to determine the smoothness of the surface finish by measuring the distance above and below

Keeping constant the cutting tool, machine tool, and workpiece as control factors, the cutti monitor 2 for increases or decreases. Machine tool productivity was measured by the metal removal rate to create the part - an increase or decrease in feed rate measured in IPM. Geometrical tolerance was determined by measuring instruments and comparing measurements af the control group to the Coidcut group. RMS finish of the product is quantitative.

either spray misting or flood cooling:

. the mean reference line.

tool life, feedrate, and finish were measured. Cutting tool Life was

RESULTS AND DISCUSSION

PERFORMANCE RESULTS

Described below are several machining applitims comparing the coldcut Process to traditional processes. Taaping

Application - Exeellent Material - 8/40 steel; 90,OOO PSI Coolant Replaced - Chlorinated mineral oil-based lubricant Tool Me - Increased 238 percent Feedrate - Sam Finish - Slightly *mproved Comment - One of the best applications Payback - 1-6 months

Taps are cylindrical or conical thread cutting tools used to produce intenral threads. Tapping combines rotary and axial motion to cut or form the thread. The

56

Coldcut Process works extremely well in thread cutting applications, but does not perform well in thread forming operations. In thread forming, threads are formed by

uses pressure rather than a cutting action, and the Coldcut Process cannot handle Formi? t e pushing metal into the desired shape rather than cutting the desired s;:ape.

internal heat generated in some forming applications. However, Coldcut may work in some forming operations such as with mild strength carbon steel.

Drilling

Application - Excellent Material - A286 stainless Coolant Replaced - Flood, water soluble Tool Life - Increased 700 percent Feedrate - Increased 100 percent Finish - Improved Comment - One of the best applications Payback - Approximately 4 weeks

Drilling is one of the most economical means of machining a hole. It is done with a tool with one or more cuttin lips that transcend to flutes for chip evacuation.

great difficulty accessing the cuttin tool’s point when the hole depth equals three or

Coldcut Process may prove to be.

Drilling is one of the best Col 8 cut applications, as traditional cooling methods have

more drill diameters. As a depth o B cut increases to this level, the more effective the

Boring

Application - Average Material - 15/5 stainless Coolant Replaced - Chlorinated, water soluble Tool Life - Increased Feedrate - Increased Finish - Constant Comment - A good Coldcut application Payback - Approximately 2 months

Bori is a machining function in which the internal diameter of a hole is generatain a true positron of the centerline of the machine tool spindle. Most boring is done with a straight single point cutting tool, and may inhibit the Coldcut Process. When the amount of material to be removed is not very thick (less than .002 inch thick metal chip), the metal chip is not thick enough to help draw heat out of the workpiece. In this situation, Coldcut relies more on the cold air than the cutting tool lubricant to remove heat

Milling

Application - Excellent Material - 15/5 stainless Coolant Replaced - Chlorinated, water soluble

-- Tool Life - Increased 100 percent Feedrate - Increased 40 percent

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Finish - Constant Comment - Excellent application Payback - Approximately 2 weeks

Milling uses a rotating, multiple tooth cutter which removes a small amount of metal with each revolution of the spindle. Important to the Coldcut Process is that the miller's cutting edge usually exits the workpiece for a short period of time, permitting reapplication of the lubricant before the tool again enters the cut.

Machinincl Center

Application - Good Material - 15/5 stainless Coolant Replaced - Chlorinated, water soluble Tool Life - Increased 100 percent Feedrate - Increased 80 percent Finish - Constant Comment - Tool changer hits nozzles Payback - Usually less than 6 months

Machining Centers are CNC (Computerized, Numerically Controlled) machining tools that provide multiple machinin operations. It can function unmanned, employing

drilling, tapping, and boring. while the Coldcut Process has great potential wi Machining Centers, it is currently a difficult application. When a tool change is made, the automatic tool changer usually knocks the Coldcut applicator nozzle out of position. The n o d e may also have to be repositioned to accommodate for the different cutting tool positions.

Bandsawinq

% an automatic tool changer. Typical % achining Center operations include milli

Application - Failure Material - stainless steel, 12" diameter Coolant Replaced - Flooded mineral oil Tool Life - No data Feedrate - No data Finish - No data Comment - N o d e could not get close enough to the intersection of the cutting tool/workpiece Payback - Not applicable

The horizontal bandsaw blade - a long circular band with teeth on the edge - submerges itself in the workpiece and does not allow room for the Coldcut mule to be close enough to the cutting tool/workpiece intersection. However, in many bandsaw applications, an ambient temperature applicator, not employing the vortex tube, is all that is necessary.

CNC (Computerized Numerical Control) Drillina and Taming

-- . Application - Excellent Material - Brass and stainless steel

58

Coolant Replaced - Flood, water soluble Tool Life - Doubled Feedrate - Improved Finish - Constant Comment - Nozzle could get close enough to the intersection of the cutting tool/workpiece and not be hit by the tool changer. Payback - 6 months

The CNC Drilling and Tapping machine is a simplified CNC Machining Center. Its tool changer system permits easier access and better placement of the Coldcut nozzles.

Surface Grinding

Application - Good Material - Tool steels and stainless steel Coolant Replaced - Sulphurized mineral oil Tool Life - Increased 23 times Feedrate - Constant

Payback - Improved finish/justified purchase . Finish - Improved

In surface grinding, minute metal chips are removed from the workpiece by the mechanical action of irregularly shaped abrasive grains. The Coldcut process works well with grinding, but various operational issues need to be considered. For example, the metal chips are very small and light, and if too much lubricant is used - 1 ounce per 8 hour shift is too much - some of the metal chips will stick to the grindin wheel causing a burn on the workpiece. 1/2 to 1/10 ounce of lubricant per 8 hour s Yl ift is sufficient. In another issue, traditional flood cooling flushes away the swarth (chips) to the coolant sump. With the Coldcut Process, there is not enough volume of liquid to carry the swarth away from the cutting tool and workpiece. A vacuum system could evacuate the grinding dust created during this operation.

Combination Drilling and Countersinking - Drivematic Wina Assemblv Machine - Aircraft

Application - Excellent Material - Aircraft aluminum Coolant Replaced - Freon Tool Life - Increased 100 percent Feedrate - Remained constant Finish - Improved to acceptable Payback - Immediate payback because of improved finish

This was one of the best successes of the Coldcut Process. When Freon - a chlorofluorocarbon which cools by rapid evaporation - was first replaced, the aircraft company had difficulty in attaining the desired part tolerance and finish. As the Coldcut applicator can be adjusted to deliver a precise amount of lubricant, no extra cutting tool lubricant residue remained on the part which would otherwise cause problems in the subsequent manufacturing processes.

59

CONDITIONS THAT IMPACT PERFORMANCE

The various factors discussed below impact performance of the Coldcut Process.

Air Qualitv and Supply

Clean, dry air delivered at the optimum pressure and volume are crucial to the performance of the Coldcut Process. Dirty air adds forei n particles to the process. Wet air ices and clogs the applicator nozzle, hampering 8 elivery of chilled air and cutting fluid. The Coldcut applicator needs a minimum air supply of 18 CFM (cubic feet per minute) delivered with a minimum of 90 PSI (pounds per square inch). At 90 PSI, 18 CFM in dry, mild weather conditions, the applicator usually produces chilled air in the low 40"s F.; at 100 PSI, 18 CFM, temperatures in the mid-30"s F. can be obtained. On hotter, more humid days, it is difficult to optimize cold air delivery.

Coolants and Lubricants

control the heat generated in the machining process by quenching with water or oil based coolants, usually containing sulphur, chlorine, or other additives. Lubricants reduc'e friction in machining, thus minimizing heat build-up.

Coolants and lubricants function differently in machining processes. Coolants

Vegetable based lubricants have different characteristics than traditional coolants. Clean vegetable fluids no not have any high temperature or extreme pressure additives, so the range of speeds and feeds in which they work is very narrow.

Cuttim Tool SDeed and Feedrates

Regulating cutting tool speeds (SFM) and feedrates (IPM) is different in the Coldcut Process than in flood or spray mist coolants. Relative to flood machining conditions, speed is usually no more than 50-70 percent, and feedrate is can be increased 30-200 percent in the Coldcut Process. Reducing cutting tool speed usually reduces its temperature; increasing feedrate usually reduces heat in the part.

Nozzle Positioning, Plumbing. and Adaptation

N o d e placement involves several key issues. The nozzle must be as close to

Flexible Machining Cells, CNC Machining Centers, and CNC Turning Centers pose

the cutting tool/workpiece interface as possible, ideally within one inch.

difficult plumbing issues, as their automatic moving components displace the Coldcut nozzles. The machine tool programmer must account for nozzle location, positioning, and automation.

The length of the hoselnouie extension from the vortex tube should be as short as possible. The chilled air warms rapidly after leaving the vortex generator, especially as the hoselnoule length increases over 5 feet; it should never be over 10 feet.

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Chip Evacuation

Flood cooling easily flushes metal chips away from the workpiece. Coldcut Process requires an air vacuum system. Applications where chip evacuation is critical negates the use of the Coldcut Process, because part quality is impaired.

Human Resources

Cutting Tool Usage/Day

Machining Time ($50/hour x 4 houdday) Maintenance (1 /3 hour x $1 2/hour) Coolant Use/Day

Machine tool operators' attitudes is a significant issue. Feedrate increase equals a productivity increase which may mean a loss of overtime pay, a primary concem to workers. Machine operators and programmers may not realize how critical and radically different speed and feed set-ups are, and may be reluctant to change these parameters. If speed and feed adjustments are not made, the Coldcut Process will fail, creating a negative image which is not easily overcome.

m.00 $200.00 $4.00 $0.50

COSTBENEFIT ANALYSIS

The economic viability of the Coldcut Process is best described in a "number of days".payback period - the number of days to earn the $2,OOO cost of the applicator through productivity rate increases, tool life savings, maintenance clean-up, and disposal costs. The following formula may be applied:

# days payback = Coldcut Cost Factors Savings

Coldcut Cost Factors = applicator cost + lubricants + air costs

machining time x feedrate increases) + (cutting tool life savings) + Savings = I maintenance clean-up and disposal savings)

The following example may be cited:

Milling 15-5 stainless on a Mori Seiki v40 Machining Center

-- Tool Life Increase 100%

- Feedrate Increase 40%

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Maintenance (5 min. x $12/hour)

Cutting Tool Lubricant $1 .OO

$1 .OO

Cutting Tool Usage (50% tool life improvement x tool costs) Machine Time (40% feedrate increase x 4 hours)

Clean-up Savings ($4 traditional vs. $1 Coldcut) Cutting Fluid Savin s (Traditional: $0.50 coolant + $2.00 disposal vs. 8 oldcut: $1.00 coolant + $1.50 air)

CONCLUSIONS

$25.00

$80.00 $3.00 $0.00

POLLUTION PREVENTION ASSESSMENT

Total Daily Savings Cost of Coldcut Applicator/Total Daiiy Savings = Number of Payback Days

Incentives

industrial manufacturing process. Cutting tool lubricants were discovered in the market place that lend themselves well to the Coldcut Process. The technology reduces cutting tool costs, increases productivity and product quality, and solves several costly environmental issues.

Machining industry potential is excellent for the following tooling operations: tapping, drilling, milling, countersinking, counterboring, spot surfacing, and surface rinding. Potential is verygoodfor: turning, boring, reaming, shaping, and planing considerin improved processes and the likely development of more appropriate

Coldcut Process is excellent however, dedicated machines probabl comprise less

potential is greater, but the application more challenging; further development is required to successfully replace traditional coolant delivery systems on complex tools.

A basic portable applicator was developed, manufactured, sold, and proven in the

9 machining 1 uids). For conventional machine tools performing dedicated tasks, the

than 10 percent of the machine tool market. For multi-function mac Yl ine tools, the

~~

$1 08.00

$2,000/$108 = 18.52 days

Barriers

To summarize, they encompass four key areas: The limitations of the Coldcut Process have been discussed throughout this report.

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. Air - Quantity, volume, pressure, and consumption.

Mechanical Location - Length of hose/nozzle from the vortex generator to the workpiece/cutting tool intersection; nozzle must be repositioned for multi-function tools.

Lubricants - Improved lubricants will enhance performance.

- Human Resources - A lack of understanding and resistance to change hinders implementation of the new technology.

Potential Solutions

Air - Measuring and tracking volume, pressure, temperature, and quality will optimize air consumption and Coldcut performance.

Mechanical Location - The applicator nozzle must be kept 1 inch or less from the workpiece/cuttin tool intersection. The length of the hose should be less

multi-function complex machine tool; a computerized robotic nozzle manipulator interfaced to the machine tool controller would optimize nozzle positioning and placement.

- Lubricants - Environmental concerns are causing development of new coolants and lubricants, some of which will significantly enhance the Coldcut Process.

than 5 feet. The Co 7 dcut Process can be integrated in the design of a

- Human Resources - A multi-level educational program on the Coldcut Process can inform machine tool operators, programmers, engineers, and management about the technology’s benefits.

Issues to be addresses include:

- Environmental and health concems - Productivity enhancements - Tool life increases - Nozzle location and placement requirements - Speed and feedrates - Traditional versus Coldcut techniques

63

RECYCLING RADIATION-CURABLE ORGANIC WASTE BY CASTING STRUCTURAL AND DECORATIVE OBJECTS

Harry Katz & Radha Argarwal Utility Development Corporation

Livingston, N J 07039

I ABSTRACT

Radiation curable coatings (e.g., overprint varnishes used by the printing industry) are replacing the old solvent based coatings and formulations in the chemical and printing industries. The production of radiation curable coatings generates liquid polymer waste that is difficult and expensive to dispose. Utility Development tested vanous chemical catalyst systems and fillers to produce useful molded decorative and structural products (e.g., park bench supports, parking lot bumpers) using liquid polymer wastes generated in the production of radiation curable coatings. During the research and development program, appropriate catal st systems were selected and

materials were determined. The strength and weathering properties of cured test samples were optimized, and large castings were made.

optimized. Type of filler, filler ratios, cure rate, type o Y molds, and mold release

INTRODUCTION

PROJECT DESCRIPTION

A current major focus in the chemical formulation and printing industries is the production of “radiation curable” coatings - overprint varnishes on various substrates - to be used as a substitute for the old solvent-based coatings. The production of radiation curable coatings enerates considerable quantities of liquid polymer waste that is difficult to dispose. This project tested various fillers and chemical catalyst systems for the purpose of producing useful molded decorative or structural products (lawn ornaments, parking lot bumpers) from these liquid poJymer wastes. Strength and weathering properties of cured samples were also determined.

Uniaue Product Features

Products were cast from liquid or anic wastes that would otherwise be disposed as hazardous. The waste was render €2 non-hazardous by polymerizing the unsaturated monomers and oligomers. The polymerization forms a very high molecular weight polymer that IS cross-linked, thereby making it stable and non-hazardous. The polymerization was accomplished through a selected method for catalyzing the curing material. The catalyzed materials were then cured in molds to make the castings. See Figure 1.

--

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Figure 1. Process for Converting UV-Curable Waste Into Decorative and Structural Castings

I Hix Thoroughly

I i I W-Curable I I Inert 1

I

I Wjste 1 [ Fillers 1 I Catalyst S y s r I

Pour Into Open Hold

I - I

Various Types of Molds Such as Aluminum Castings

--

* Ambient

Temperature Cure

Can Be Varied From, 1 to 16 Hours

r I i

Remove From Hold

Hold Usually Cons,ists of a Number of Assembled

65

APPLl CATION

Products Replaced

The products made from the scrap coating liquids are traditionally produced from concrete or plaster. Products such as park bench supports, highway markers or dividers, and lawn statues can be cast from organic W-curable mating liquids. These equivalent castings from waste, which usually require expense to remove or dispose, are much lower in cost than standard commercial products.

Wastes Prevented

Radiation curable coatings are reactive polymer systems that cure rapid1 by lamps or electron beams. h e exposure to radiation such as industrial ultraviolet (U

coatings may be used for a variety of applications, inc Y uding:

- - - These products are solvent-free, cure rapidly, and consume small amounts of

Waste coating materials result from stora e beyond the recommended shelf life,

Decorative coatings for paper, plastic, and wood Abrasion resistant coatings for lenses and optical fibers Solvent resistant coatings for labels Fluorescent coatings and many novelty coatings, such as for holograms

energy.

contamination, or error in coatings preparation. Bh ese waste coating liquids are

? Hers and a catalyst system for casting purposes eliminates the need (and the associated liability) for disposing of the waste.

pically disposed of as hazardous waste. Combining the. waste coating liquids with

Cross Seament Uses

Other industries that generate reactive liquid waste products can use this process technique, however the appropriate catalyst and filler materials must be selected. Companies that generate certain types of solid wastes (e.g., fiberglass molding) may be able to use an analogous process: pulverize the waste, and use an inexpensive thermoset or thermoplastic resin as a binder to make an end product. Moreover, the resin binder chosen could be a waste product itself.

PROCEDURE

DEMONSTRATION

Utility Development selected and studied various catalyst systems, fillers, and filler levels to determine the proper materials and formulation for a satisfactory casting and an acceptable cure time.

66

Catalvst Svstems

Malvern Minerals’325 Novakup 1 100 or 325 Novacite

Meadowbrook Inventions’ Silver IE (aluminum) Fibers

MEK peroxide was used as the main catalyst, as the waste coating is an unsaturated resin. Peroxide catalysts require an accelerator to provide a convenient room temperature, overnight cure.

A number of peroxides were studied, and most castin s were made with Lupersol DDM-9, manufactured by ATOCHEM of Buffalo, N?

57.0

2.0

Accelerators evaluated included Hex-Chem 977 and Nap-All (4 percent calcium), Mooney Chemical, Inc.; 15 percent potassium naphthenate (Nuodex, Inc.); and 6 percent cobalt naphthenate.

Initial catalysVaccelerator trials showed the best results with MEK peroxide and 6 percent cobalt. A catalyst system containing cumene hydroperoxide and 4 percent vanadium Hex-Chem was also effective, but produced a too rapid cure rate. Another system containing 4 percent Calcium Nap-All and MEK peroxide provided good results and eliminated the heavy metal cobalt from the process. Calcium naphthenate is not usually effective in this type of system; the presence of aluminum fiber in the filler may facilitate a suitable exothermic reaction with the calcium material.

This final combination provided a cured part in about ten hours at room temperature. This is sufficient time for air bubbles generated during the mixing and pouring of the material to rise to the surface of the casting before the cure is complete. This provides a stronger casting with fewer trapped bubbles and surface voids.

- Fillers

weathered mica, calcium carbonate Wollastonite G and Wollastokup; an dT Malvern Minerals’ 325 Nova 1, up 1100 and 325 Novacite. Fillers were added to the waste coating materials to the point where the material was still at pourable viscosity. The high filler content was necessary to minimize shrinkage cracks in large castings.

A typical formulation is shown in Table 1.

Fillers evaluated include Englehard ASP-1 70 clay; a -325 mesh Periodite hompson-Weinman Atomite ; Nyco’s

The main fillers for recent castings were 325 Novakup 11 00 and 325 Novacite.

Table 1. Casting Formulation

n 11 Radiation Curable Waste 38.0 11 Msdnev Chemical’s Ca NaDhthenate (4%) I 1.5 It

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Surface Coatings

the trace amount of unreacted monomers. Castings were coated to improve appearance and to provide an odor barrier for

Initial coating trials with commercial ac lic paint provided good cosmetic results

A number of water-based acrylics were then evaluated. These did not provide

but not a good permeation barrier for the resi 7 ual odor.

a good permeation barrier for traces of unreacted monomer as indicated by a slight residual odor. Talc filler was unsuccessfully added to improve barrier properties; adhesion quality was also compromised.

The focus tumed to epoxy-based coatings. To obtain an easily applied coating without the use of solvents, a reactive dilutent, Ciba Giegy 1,4 butanediol diglycedol ether, was added. Various colorants and talc filler were also added. The coating hides minor surface pitting and other defects. The main coating formulation is shown in Table 2.

Tab!e 2. Coating Formulation

Omamental castings were prepared using commercially available molds. Castings and their approximate weights are shown in Table 3.

Table 3. Omamental Castings and Approximate Weights

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Structural castings, including a hi hway marker and a parking lot bumper, were also made. One key requirement of SUC 3, products is a compressive strength of at least 2,000 pounds per square inch (psi). Utility Development castings have a compressive strength of 7,000 psi.

RESULTS AND DISCUSSION

PERFORMANCE RESULTS

Utility Development successfull developed a formulation to cast structural and decorative objects from radiation cura L le organic waste materials.

Product Qualitv Variance

Product casting) quali can vary, as the starting waste material is not the same from batc (n to batch an 2 will have different cure characteristics. Initial screening tests can allow the formulation to be adjusted to the appropriate ration of fillers and

and size, mo 'y ding process, and cure cycle also affect product quality,

Conditions That ImDact Performance

catalysts.

Filler pe and loading, catalyst system and configuration, additives, mold type

Formulations and moldings variations caused some initial problems in obtaining a quality product. Due to the multi-functional acrylates in the waste product, castings without the addition of fillers resulted in severe cracking due to cure shrinkage. The final cure rate was often influenced by the type of filler used. Also, some filler formulations exhibited oxygen inhibition of cure which resulted in a tacky surface after the bulk of the casting solidified. Of the fillers used, mica prevented curing, and clay considerably slowed cure rate; other fillers did not inhibit the cure.

During the final two months of the project, castings using the calcium accelerator were prepared which had only slight surface porosity and possessed good compressive strength. Initial surface hardness was low, and the surface could be indented by fingernail pressure. A slight surface tack was also noted. Alter one to- two weeks stora e at mom temperature, hardness increased such that the surface could not be rea 8 ily scratched and was non-tacky. When the casting was placed outdoors in the sun, the surface became scratch-resistant and tack-free within one to two hours. Compressive strength of these samples ranged from 6,000-7,000 psi.

CostBenefit Analvsis

The starting material is a waste product, and the fillers are low cost. The catalysts, although expensive, are used at very low concentrations. Molds can be purchased at moderate costs and are suitable for casting many parts.

Utility Development's sister company, Rad-Cure Corporation, disposed of

69

approximately thirty, 55-gallon drums of radiation curable waste in 1988 at a cost o $225 per drum for liquid waste and $900 per drum for gelled material.

The cost analysis per pound of finished material is shown in Table 4.

Table 4. Cost Analysis Per Pound of Finished Material

The cost for surface coating is shown in Table 5.

Table 5. Surface Coating Cost

Since only a thin layer of the coating is used, the following estimate is made:

Casting Material + Surface Coating Cost = $0.35./lb.

Labor Charges = $0.20/lb.

Total Labor + Material Cost = $0.55/lb.

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CONCLUSIONS

POLLUTION PREVENTION ASSESSMENT

Incentives

utility Development successfully demonstrated the practicality of recycling radiation curable waste. Additional development is necessary to define all parameters for efficient conversion of the variety of scrap materials being generated by the rapidly expanding radiation curable industry. The resulting product IS strong and of low cost. The product meets strength requirements (when such a comparison is necessary) of similar products, although it is not necessarily of superior qualiv. The main benefit is the beneficial use of a material that is normally disposed at a significant cost.

Large or small firms that produce or use radiation curable liquids can recycle their waste through this process. Little initial investment is required to begin such a recycling program.

Liability associated with the disposal of hazardous waste is eliminated.

Barriers

Because waste quality and characteristics vary widely, one specific formula or handling procedure cannot be established for all lots of radiation curable wastes. Incoming quality control and testing will allow catalyst systems and filler adjustment for suitable end results. For example, it ma be desirable to blend some liquid from a

surface. poorly reactive lot of waste with waste wr; ich readily cures to a hard and tack-free

71