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INTEROFFICE COMMUNICATION

MIDWEST RESEARCH INSTITUTE July 11, 1984

To: Pro jec t F i l e No. 7705-L

From: Barbara W. D u l e t s k y p

Subject: Use o f E l e c t r o s t a t i c Spray Techniques f o r the Surface Coating o f P l a s t i c Parts f o r Business Machines

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The most common type o f coat ing equipment use by f a c i l i t i e s t h a t coat p l a s t i c par ts f o r business machines i s m u a l a i r atomizc?spray. E l e c t r o s t a t i c spray methods have been demonstrated t h a t appear t o achieve higher t ransfer e f f i c i e n c i e s than conventional a i r s p r a y 7 T f o s e o f t h i s memorandum i s t o present informat ion gained through indus t ry contacts about e l e c t r o s t a t i c spray technology, and t o draw conclusions about i t s a p p l i c a b i l i t y t o the surface coat ing o f p l a s t i c pa r t s f o r business machines.

ELECTROSTATIC SPRAY

A. Theorv

The basic mechanism o f e l e c t r o s t a t i c spray i s the d i f fe rence i n po ten t i a l energy o f the coat ing and the p a r t t o be coated, which causes an e l e c t r o s t a t i c force t o e x i s t between them. and prope l led toward the p a r t by means o f a h igh pressure airstream. grounded p a r t i s opposi te ly charged, the a t t r a c t i o n o f the coat ing p a r t i c l e s f o r the p a r t overcomes the momentum o f the p a r t i c l e s . around" the p a r t ra the r than being l o s t as overspray. e f f i c i e n c y i s g r e a t l y improved over conventional a i r spray methods. have estimated t r a n s f e r e f f i c i e n c y f o r e l e c t r o s t a t i c guns t o be anywhere f r o m 30 t o 90 percent, depending on the method o f atomizat ion ( i . e . , a i r , a i r l ess , a i r -ass is ted/ a i r l ess ) . 1 - 5

Typ ica l l y , the coat ing i s given a p o s i t i v e charge a t the gun Since the

Consequently, the coat ing "wraps By t h i s method, t rans fe r

Indus t ry contacts

When the p a r t t o be coated i s a nonconductive substrate such as p l a s t i c , i t i s necessary t o prov ide a conductive surface t h a t can bleed o f f the e l e c t r i c a l charge r e s u l t i n g from the accumulation o f charged p a i n t pa r t i c l es . This may be done by apply ing a conductive s e n s i t i z e r t o the surface t o be coated, grounding the e lec t ro - magnetic in te r fe rence/ rad io frequency in ter ference (EMI /RF I ) sh ie ld ing layer , grounding a conductive f i x t u r e o r image behind the target , using a p l a s t i c t h a t i s i t s e l f conductive, o r spraying an e l e c t r i c a l l y conductive topcoat ing such as a waterborne coat ing.

1. Conductive sens i t i ze r . The most common method o f prepar ing p l a s t i c f o r e l e c t r o s t a t i c spraying i s spray app l i ca t i on o f a conductive sens i t i zer . A t y p i c a l sens i t i ze r contains 1 t o 8 percent by volume hydroph i l i c s a l t i n so lu t i on w i t h an organic solvent o r water. It can be appl ied by spraying, mis t ing, hand-wiping, o r dipping. As the so lvent evaporates, the s a l t expands by absorbing water molecules

2

from the air and forms a continuous, conductive film on the part. described in a vendor brochure, is shown in Figure 1.6

This process, as

Sensitizers dissolved in organic solvents such as isopropyl alcohol are being used more frequently than waterborne sensitizers. application of this type of conductive sensitizer is a source of VOC emissions. There are no data available on whether or not the overall VOC emissions are reduced by using a conductive sensitizer prior to electrostatic spray, but preliminary estimates and calculations show that emissions may be reduced by as much as 63 percent. Table 1 shows the approximate tradeoff between emissions from air atomized spray application of a conductive sensitizer and emission reductions achieved by using electrostatic spray for subsequent topcoats. isopropyl alcohol is assumed, since this would contain the highest expected proportion of VOC. since this represents the highest level of VOC emissions for the 1,500 to 2,000 ft2/gal range supplied by the manufacturer.

Since isopropyl alcohol is a VOC,

A l-percent solution of sensitizer in

The coverage for 1 gallon of sensitizer is assumed to be 1,500 square feet,

2. Grounded EMI/RFI shielding. In order to attenuate EMI/RFI signals, plastic business machine housings should be effectively shielded by a layer of conductive material. This is most commonly achieved by zinc-arc spraying or by application of conductive coatings using conventional air atomized spray guns. Other EMI/RFI shielding techniques include electroless plating and the use of conductive plastics.

For zinc-arc spraying and air atomized spraying.of conductive coatings, a layer o f conductive material is applied to the interior surface of each housing. grounding this layer, the exterior surface can be coated electrostatically. plastic acts as an insulating barrier between the conductive layer and the spray gun, the charged paint particles are still attracted toward the grounded E M V R F I - shielded surface. Attraction may be uneven, however, depending on the uniformity of the shielding coating. This is a disadvantage, since a nonuniform electrostatic force does not provide a good basis for an even surface finish.

By Although

In the case of electroless plating, the part is dipped in a conductive solution, thus making both interior and exterior surfaces conductive. surface, the topcoating can be applied electrostatically.

By grounding the metal

In the same way that charged paint particles can be applied electrostatically to a metal surface, they can also be applied to conductive plastics. Plastic can be made conductive by the use of molded-in metal flakes or carbon particles.

electrostatic sprayi ng.

Depending on the surface resistivity, this type of substrate can be an effective base for i

3. Grounded image. A conductive fixture or image may be placed behind the part and then grounded to facilitate electrostatic spraying. the plastic part does not prevent the attraction of the coating for the grounded surface. in potential, the charged paint particles are deposited on the part.

Like the previous method,

Since the plastic part lies within the force field created by the difference

4. Waterborne coatings. Waterborne coatings can be charged at the gun and sprayed electrostatically onto a plastic part. film on the grounded part, the surface is rendered conductive. coating remains wet, it continues to bleed off the charge and maintains a difference

Once the coating forms a continuous As long as the

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TABLE 1. EMISSIONS FROM ELECTROSTATIC SPRAY COATING (FOLLOWING APPLICATION OF A CONDUCTIVE SENSITIZER) COMPARED TO CONVENTIONAL A I R ATOMIZED SPRAY COATING

Sens i t i zer App l ica t ion

VOC content o f sens i t i ze r VOC dens i ty ( isopropyl a lcohol ) = 6.56 lb /ga l So l ids content o f sens i t i ze r = 1% by volume, as app l ied

= 99% by volume, as app l ied

Coverage a t 100% t rans fe r e f f i c i e n c y = 1,500 f t2 p l a s t i c per 1 gal sens i t i ze r = 0.667 gal sensitizer/1,000 f t 2 p l a s t i c = 0.00667 ga l solids/1,000 ft.2 p l a s t i c

Sens i t i ze r usage a t 25% t r a n s f e r e f f i c i e n c y ( a i r atomized spray guns) = coverage t 0.25

= 0.0267 gal solids/1,000 ft2 p l a s t i c

VOC emissions a t 25% t r a n s f e r e f f i c i e n c y ( a i r atomized spray guns) = 0.0267 gal solids/1,000 ft2 p l a s t i c

= 17.3 l b VOC/l ,OOO f t 2 p l a s t i c

x 99 ga l VOC/gal so l i ds x 6.56 l b VOC/gal VOC

Coating App l ica t ion

VOC content o f coat ing VOC dens i ty (average) So l ids content o f coat ing

= 68% by volume, as app l ied = 7.36 lb /ga l = 32% by volume, as app l ied

Coverage a t 100% t rans fe r e f f i c i e n c y = 5 m i l x 1 ft2 s o l i d s / f t 2 p l a s t i c = 720 in3 solids/1,000 f t2 p l a s t i c = 3.12 gal solids/1,000 ft2 p l a s t i c

Coating usage a t 25% t rans fe r e f f i c i e n c y ( a i r atomized spray guns) = coverage + 0.25 = 12.5 gal solids/1,000 ft2 p l a s t i c

VOC emissions a t 25% t rans fe r e f f i c i e n c y ( a i r atomized spray guns) = 12.5 gal solids/1,000 f t 2 p l a s t i c

'x 68 gal VOW32 gal so l i ds x 7.36 1 b VOC/gal VOC

= 196 l b VOC/ l ,OOO f t2 p l a s t i c

(continued)

5 TABLE 1. (continued) -

VOC emissions and emission reductionsa for electrostatic spray:

Trans fer e f f i c i ency 50 70 90 - - - 30 -

Coating usage (gal solids/1,000 ft2): (coverage i transfer efficiency)

VOC emissions for electrostatic spray ( l b VOC/l,OOO ft2): (Coating usage x 68 gal V O W 3 2 gal solids x 7.36 l b VOC/gal VOC)

10.4 6.24 4.46 3.47

163 97.6 69.8 54.3

VOC emissions from application of 17.3 17.3 17.3 17.3 conductive sensitizer (1 b VOC/l, 000 ft2)

VOC emissions for electrostatic spray following application of conductive sensitizer ( l b VOC/l,OOO ft2)

( l b VOC/l,OOO ft2) VOC emissions for air atomized spray

Emission reductiona ( l b VOC/l,OOO ft2) 16 81 109 124

Emission reductiona (percent) a 41 56 63

Emission reduction achieved by using electrostatic spray following application of a conductive sensitizer instead of conventional air atomized spray.

a

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i n po ten t i a l between the p l a s t i c p a r t and the p a i n t p a r t i c l e s . decreasing VOC emissions and coat ing consumption, t h i s method a lso reduces the f i r e hazard caused by spraying h igh volumes o f VOC.

I n add i t i on t o

6. Appl icat ions i n Indus t ry

1. Equipment and conductive coatings/substrates vendors. E lec t ros ta t i c spray equipment and conductive coatings/substrates are r e a d i l y ava i l ab le through many d i f f e r e n t vendors. Some o f these vendors were contacted f o r in format ion on the use o f t h e i r products i n the surface coat ing of p l a s t i c p a r t s f o r business machines. Table 2 summarizes the in format ion gathered from these contacts.

2. Surface coaters o f miscellaneous p l a s t i c par ts . Surface coat ing i ndus t r i es

The ef fect iveness

F o r instance, par ts w i t h recessed and louvred areas are par t i cu- On the

t h a t are using t h i s technique for p l a s t i c products such as safety helmets, automobile fasc ia , window shutters, etc., are l i s t e d i n Table 3. The t r a n s f e r o f t h i s techno- logy t o business machine par ts may not be made d i r e c t l y , however. o f t h i s spray method depends, t o a la rge extent, on the s i ze and complexity o f the p a r t t o be coated. l a r l y d i f f i c u l t t o cover e l e c t r o s t a t i c a l l y due t o the "Faraday Cage'' e f fec t . o ther hand, e l e c t r o s t a t i c spraying o f coat ing onto a la rge f l a t t a r g e t would approach 100-percent t rans fe r e f f i c i e n c y and provide complete and uni form coverage.

3. Surface coaters o f p l a s t i c pa r t s f o r business machines. It i s uncommon f o r f a c i l i t i e s t h a t surface coat p l a s t i c business machine pa r t s t o employ e l e c t r o s t a t i c spray methods. c a l l y about t h e i r use o f t h i s method. O f the 19 companies surveyed, 5 have used e l e c t r o s t a t i c spraying on a product ion basis, and 4 others have experimented o r in tend t o experiment wi th it. be l ieve t h a t t rans fe r e f f i c i e n c y has been improved, on ly one was able t o provide s p e c i f i c support ing data. 30

Table 4 shows the names o f t he companies t h a t were contacted s p e c i f i -

While the companies t h a t use t h i s method i n product ion

Many contacts o f fe red poss ib le reasons fo r the in f requent use o f t h i s method i n the industry. A major f ac to r i s the i n i t i a l c a p i t a l cos t o f the equipment. An e l e c t r o s t a t i c hand-held gun costs $2,000, which i s 10 times the cos t o f a conventional a i r atomizing gun.17 the savings i n coat ing consumption, most coaters would not r e a l i z e t h i s savings wi thout i n c u r r i n g p r i o r losses common t o incorpora t ing new equipment. the small job shops do no t have the resources ava i l ab le t o experiment w i th t h i s technology. Even i f the i n i t i a l c a p i t a l investment were not a b a r r i e r , they would not have the p l a n t capaci ty t o maintain t h e i r product ion r a t e wh i le r e t r a i n i n g the spray gun operators.

Although the vendors adver t ise a shor t payback per iod due t o

Many o f

I n add i t i on t o manual spray guns, automat ica l ly con t ro l l ed systems are ava i l ab le from various equipment vendors. The c a p i t a l cos t of an automated system i s much greater than t h a t o f manual guns, bu t the consis tent and e f f i c i e n t spraying i t provides has the p o t e n t i a l t o improve t rans fe r e f f ic iency. l a r l y bene f i c ia l f o r f a c i l i t i e s t h a t coat la rge quan t i t i es o f s i m i l a r parts. the coat ing l i n e has been programmed t o spray a c e r t a i n rack o f par ts , large quan t i t i es can be coated w i t h l i t t l e o r no adjustments t o the contro ls . of t h i s technique inc lude improved t r a n s f e r e f f i c i e n c y , increased production ra te , and consistency i n q u a l i t y o f t he f i n a l products.

Automation i s par t i cu- Once

Advantages

Improved t rans fe r e f f i c i ency has

TABLE 2. ELECTROSTATIC SPRAY ( E S ) COATING--EQUIPMENT AND CONDUCTIVE COATING/SUBSTRATE VENDORS __I - - - -- _-_ - -- - __ . - . _ . __---__- .-. - - ___ __ ______--

Comments Company, address Product Method of ES coating

Advanced Chemicals and Coatingss Temple City, Calif.

Celanese Corp. Charlotte, N.C

Coatings

Carbon fibers

Deft. Inc.'O Irvine. Calif.

Chemicals

Grounded E M V R F I - Grounding the EMI/RFI shielding has been used with polyurethane topcoat applications.

Conductive carbon fiber mesh nonwoven veil of conductive carbon fibers.

woven aesh.

- Ford Motor Co. had been involved in ES using

- International Paper Co. manufacturers the non-

Conductive coatings

Electro-Cote Chemicals, 1nc.I' Chemicals (conductive Conductive sensitizer Noblesville, Ind. sensitizer)

Electro Kinetic Systems, Inc. l 2 EM1 shielding coatings Grounded EHI/RFI Wilmington. Oel.

Enthone. Inc. Bridgeview. 1 1 1 .

Graco, Inc.' Minneapolis, Minn.

Enshield@ EMI/RFI shielding process

Spray equipment

Grounded EMI/RFI

Deft sells mostly to aerospace industry, but they are working with Beckman Instruments to develop coatings with ES potential.

* Business machine coaters may not have the re- sources to experiment with costly new technolo- gies such as ES.

Sensitizers are in isopropyl alcohol solution. Effectiveness increases with humidity. Up to four top coats can be applied by ES.

* IBM and A m c o are involved i n ES coating using conductive sensitizers. Ransburg and Air Power manufacture ES equipment. 4

- EM1 shielding can be sprayed onto exterior surfaces and used as a base for ES coating. - Solvents In EM1 and top coat must be compatible for a good surface finish.

* Leida Finishing may be using this method of ES coating.

* Most peo le use two-component urethanes over the Enshielde electroless plating. - Coaters hat may be doing ES coating over the Enshiel 8 plating: Genron, Furniture City, E/M Lubricants.

No surface pretreatment * ES centrifugual atomizer, CA-1000, can achieve transfer efficiencies of 85% on conductive or nonconductive substrates. Also manufacture automatic and manual ES air spray guns.

_ _ _ _ ~ (continued)

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TABLE 2. (continued) _ _ _ _

~ -- _ _ _ - - _._. .- - ____ Company, address Product Method o f ES coat ing C m e n t s

Kremlin, lnc. ' ' Addison, Ill.

LeaRonal, I n c . I s Freeport, N.Y.

Nordson Corp. l 6 Matthews, N.C.

Nordson Corp. Amherst, Ohio

Ransburg Corp. Indianapolis, Ind.

Transmet Corp.I9 Columbus, Ohio

Udy l i t e P la t i ng Systems2" Warren, Hich.

Arv id C. Walberg & C O . ~ ' Oowrier ' s Grove, I 1 1.

Spray equipment Grounded metal hangers - Uneven coverage since p a i n t i s a t t rac ted unevenly. On metal, a i r -ass is ted/a i r less ES gets 38% b e t t e r t rans fe r e f f i c i e n c y than air-atomized ES.

Vest', vapor etch Grounded EHI/RFI Shielding process involves vapor etch ing sh ie ld ing technology followf!d by e lect rop lat ing. - The surface may be conductive enough a f t e r vapor

etch ing f o r ES coating. - The p l a t i n g i s a good base f o r ES coating. Xerox has experimented w i t h t h i s technique.

Spray equipment Conductive sens i t i ze r

Grounded image

Grounded metal rack

Grounded EMI /RFI

Conductive p l a s t i c s

Spray equipment General

Spray equipment Conductive sens i t i ze r

Aluminum f i l l e r f o r Conductive p l a s t i c s conductive p l a s t i c s

A t tenup 1 ate' EM1 /RF I shie ld ing process

Grounded E M I / R F I

Spray equipment Waterborne coatings

- Rendered nonconductive i f heat i s applied. Otherwise a good method.

* Not as e f f e c t i v e as using a conductive sensi t izer .

* Coating i s a t t rac ted only t o po ints o f contact w i t h metal.

* Causes uneven a t t r a c t i o n due t o nonuniform shielding. C a l l Eastnan or Celanese f o r more information. 03

* Cost i n h i b i t s most small coaters from using ES. Hewlett-Packard i n the San Francisco area i s spraying waterborne coatings by ES.

- Ransburg manufactures manual and automatic ES A i r ES guns achieve 50-75 percent t rans fe r e f f i c i e n c y .

* H igh ly u n l i k e l y tha t pa r t s could be coated by E S , since most o f the aluminum i s concentrated near the center and the surface i s res in - r i ch .

e - Attenuplate process can be used as a base f o r E S coating, although it provides surfaces w i t h much higher conduct iv i ty than needed by ES. E/M Lubricants r a y be involved w i t h ES coat ing by t h i s method.

* Walberg manufactures both automatic and hand-

- Waterborne coatings are conductive, so no

* Hetamora to . i s using a Walberg system.

he ld ES equipment.

sens i t i ze r i s needed.

~ _____ -_-r-_- ____-_I___ - _- - . _ _ . . _ _ -. - ______P-=.== ~ - _ ___ ____

TABLE 3. ELECTROSTATIC SPRAY (ES) COATING-MISCELLANOUS P L A S T I C COATERS __ -____ - -_ . _- --_ __ ___- __

Type o f experience Method o f ES coat ing Product coated Comments Company. address

Arthur Fulmer C O . ~ * Production Conductive p l a s t i c s Safety helmets - Conductive gel i s molded-in w i t h f iberg lass and Miami. Fla then coatings are appl ied by Ransburg ES rec ipro-

ca t i ng disc.

Davidson Rubber Co. Production Grounded image, P l a s t i c pa r t s f o r - Research w i t h e l e c t r o s t a t i c b e l l s t o determine

Experimented w i t h several types o f ES primers. Dover, N H conductive sens i t i ze r automobiles standard t e s t for t r ans fe r e f f i c i ency .

Ford Motor Co.’ Production Carbon f i b e r mesh Automobile hood * Doing research i nvo l v ing co lan inat ion o f nonwoven scoops v e i l o f carbon f i b e r nesh, fol lowed by ES coating.

Guide D iv i s ion o f GM2 Production Grounded aluminum Automobile Six Graco ES guns i n each booth t r iggered auto- f i x t u r e behind p a r t fascias n a t i c a l l y .

* System i s computer con t ro l l ed and TE = 60 t o 70%.

Jay Plast ics23 Mansfield, Ohio

Production M e t a l l i c layer Miscel laneous - A f t e r base coat, products receive sput ter ing app l i ca t i on o f a decorative me ta l l i c layer. Outer coat ing i s sprayed automatical ly w i t h Ransburg ES guns.

Metamora Products Corp.24 Production Waterborne coatings Window shutters - Using Walberg system for ES coating. Metamora, Mich. * About t o i n s t a l l DeVilbiss system.

-

TABLE 4. ELECTROSTATIC SPRAY (ES) COATING--SURFACE COATERS OF P L A S T I C PARTS FOR BUSINESS MACHINES - -- -___ - -_ - . _.____-- - . - _ - . _ _ _ _

Company, address Type of experience Method of ES coating Comments

A I - I ~ C O ~ ~ Hartford City, Ind

None N/A They do not coat their own business machine parts, and the contractors who coat the parts do not use ES.

Parts are coated by Cashiers Plastics, Structural Plastic Systems, Northwest Molded Products, and Kaiser-Haskin Co.

* ES lends itself to a high degree of automation, long runs, and requires an increased capital investment.

* As the company grows and volume increases, they will reconsider ES.

* One-percent of the plastic coated is done by ES. This probably will not increase because plastic is difficult to ground. A negligible amount of €5 coating is done on plastic, mainly for research purposes.

- Transfer efficiency data indicate 50 to 60% for automatic ES, and 30 to 40% for manual ES.

E/H has not been involved with E 5 coating.

Beckman Instruments26 Fu I 1 erton , Cal i f .

None N/A

Cashier's Structural Foam D ~ V . * ~ None Chandler, Ariz.

N/A

No surface preparation Component F i ni s h i ngZ8 Santa Clara, Calif.

Limited production

E - Sy s t ems Oallas, Tex.

Eastman-Kodak Co. 30 Rochester, N.Y.

Experimental

Production

E/M Lubricants, I ~ c . ~ ' W . Lafayette, Ind.

FCM Plastics D ~ V . ~ * Grand Rapids, Mich.

None

Past production

N/A

Grounded electroless p 1 at i ng

* Their electroless coating is a good base for ES. but presently no jobs specify E S coating.

than for conventional. * Transfer efficiency is greater for ES

- ES coating of metal parts is done here. - The company has some conductive sensitizer with which they plait to test ES coating of plastics in the near future.

1 equipment . - Using conventional (manual air spray)

Finishing Technology, Inc.33 Tempe, Ariz.

Planned experimental Conductive sensitizer

None

Past production

N/A

?

Foam Molding Company o f Arkansas, Inc.34 Rogers, Ark.

Lexington, Ky. 1BM Corp.35 VOC ES was discontinued in June 1981, and

waterborne ES was discontinued in July 1983.

(continued)

Structura l P las t i cs Torrance, C a l i f .

T i mespec4 San Carlos, Ca l i f

Xerox Corp. 4 1 Webster. N.Y

None

Past experimental

N/A

Conductive sens i t i ze r

TABLE 4. (continued) ____ .__-____

Company, address Type o f experience Method o f ES coat ing Comen t s

Leida F i n i ~ h i n g ~ ~ None N/A * Leida coats metal pa r t s by ES, bu t no t

- Number o f batches t o be coated would have t o be large enough t o j u s t i f y the pur- chase o f ES equipment and the setup t i n e f o r each run.

Wall i ngford, Penn. p l a s t i c .

Premix, lnc.37

Storage Technology3*

- According t o the p l a n t engineer, Premix N. K ingsv i l l e , Ohio has never done ES coating.

L o u i s v i l l e , Colo. s i m i l a r par ts , there would be a good For f a c i l i t i e s t h a t coat h igh volumes o f

payback. * The technique i s not good f o r Storage

Technology, since they specify low quan t i t i es o f var ied par ts .

SPS has no t used ES or a i r l e s s equipment due t o the c a p i t a l expenditure involved. Manual a i r -spray i s su i tab le f o r most o f t h e i r jobs.

- ES coat ing o f p l a s t i c i s not possible because o f the need f o r a conductive surface.

* Xerox coats = t a l pa r t s by ES. P l a s t i c i s nonconductive and a conductive sens i t i ze r would need t o be applied. The biggest problem would be overcoming the Faraday e f f e c t when coat ing complex shapes.

t.L - Tinespec uses manual a i r guns. c-’

None N/A

None

None

N/A

N/A

Conductive sens i t i ze r Conf ident ia l Contact No. 1 Experimental - Need f l e x i b l e coat ing systems because o f the wide assortment o f pa r t s coated.

* I n s t a l l i n g an ES system would requi re a spray booth f o r sens i t i ze r appl icat ion.

Conductive sens i t i ze r Conf ident ia l Contact No. 2 Production There i s a t rade-of f i n ES coating: whi le t rans fe r e f f i c i e n c y increases by 3W. t o t a l VOC emissions may decrease since the sens i t i ze r i s almost a l l solvent.

~ - _ __c ______- - -- -- _ _ . - - - - ______ ~ ._ - . -____I__ __ _________--- - . _ - _ _ - -

12

the consequent effects of decreasing VOC emissions, decreasing coating consumption, and decreasing booth maintenance costs.

Automation is not economically beneficial for facilities that perform a wide variety of low-volume coating jobs. to set up and fine tune the automatic controls would not be justified.by the rela- tively short run of parts through the coating line. The savings in paint consump- tion would be small compared to the cost of production time lost while programming the controls.

For these facilities, the amount of time needed

Whether automatic or manual electrostatic spray equipment is used, touch-up spraying with air atomized spray guns is usually necessary, especially for complex parts with many recesses. production rate and the VOC emission reduction that are gained by switching to electrostatic spray systems.

The manual touch-up step would limit both the increase in

C. Conclusions

While electrostatic spray technology appears to achieve higher transfer efficiency than air atomized spray for the surface coating of plastic parts for business machines, little data are available from actual testing to quantify the improvement. If there is an economic payback in using the methods presented herein, it has not been dramatic enough to convince most coaters serving the business machine industry to begin using them. their facilities, but most do not have the resources to install new equipment while maintaining their current levels of production.

Some coaters have been experimenting with electrostatic systems for use in

According to the information received from industry contacts, electrostatic

The infrequent use of the tech- spray coating technology is readily available and is applicable to the surface coating of plastic parts for business machines. nology for this purpose reflects the difficulty of coating a nonconductive surface electrostatically and the high capital cost of implementing this technology in an existing plant.

References

1. Wilson, Ayjay. Methods for Attaining VOC Compliance. Pollution Engineering. April 1983. pp. 34-35.

2. Poll, Gerard, H . , Jr. New System at Guide Paints Bumper Fascias. Products Finishing.

3. Telecon. Duletsky, E., MRI, to Conner, G., 1984. Transfer efficiency test results.

4. Vendor brochure. Graco CA-1000: The Centr Finishing System. Graco, Inc. Minneapolis

5. Telecon. Duletsky, E., MRI, to Comfort, E. Transfer efficiency test results.

November, 1983. - pp. 38-44.

Davidson Rubber Company. April 2,

fuga1 Atomizer Electrostatic Minnesota.

Centec Corp. April 17, 1984.

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6.

7.

8.

9.

10.

11.

12.

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Vendor brochure. Conductive Sensitizers. Electro-Cote Chemical Company, Inc. Detroit, Michigan.

Telecon. Duletsky, B., MRI, to Panzer, J., HSC Corp. June 1, 1984. Coverage achieved by conductive sensitizers.

Letter and attachments from Hughes, T., Advanced Coatings and Chemicals, to Newton, D., MRI. May 23, 1984. p. 2. Information on EMI/RFI shielding coating.

Telecon. Duletsky, B. , MRI, to Carvoni, T., Celanese Corporation. 1984. Use o f carbon fibers in electrostatic spray coating.

May 4,

Telecon. Duletsky, B., MRI, to Garrett, T., Deft, Incorporated. March 9, 1984. Information on electrostatic spray coating.

Telecon. Duletsky, B., MRI, to Stephens, D., Electro-Cote Chemical Company, Inc. March 8, 1984. Information on conductive sensitizers.

Telecon. Duletsky, B., MRI, to Proulx, D., Electro Kinetic Systems, Inc. March 12, 1984. coating.

Telecon. Information on use of Enshield as a base for electrostatic spray coating.

Use o f EM1 shielding coating for electrostatic spray of top-

Larson, J., MRI, to brulik, G. , Enthone, Inc. March 23, 1984.

Telecon. Duletsky, B., MRI, to Burke, J., Kremlin, Inc. May 24, 1984. Infor- mation on spray equipment.

Telecon. N wton, D., MRI, to McCaskie, J. , LeaRonal , Inc. March 20, 1984. Use of VES + as a base for electrostatic spray coating. Telecon. Duletsky, B. , MRI, to Beck, G. , Nordson Corporation. April 18, 1984. Methods of electrostatic spray coating of plastic.

Telecon. Duletsky, B., MRI, to Gunsel, S. , Nordson Corporation. May 14, 1984. Information on electrostatic spray equipment.

Telecon. Maurer, E., MRI, to Utterback, L., Ransburg Corporation. January 9, 1984. Information on air ES guns.

Telecon. Newton, D. , MRI, to Crossman, R., Transmet Corporation. April 3, 1984. Information on aluminum-filled plastic.

Telecon. Duletsky, B., MRI, to Oberle, D. , Udylite Plating Systems. March 5 and 30, 1984. Use o f Attenuplate as a base for electrostatic spray coating.

Telecon. Duletsky, 6. , MRI, to Walberg, A. , Arvid C. Walberg & Co. March 9, 1984. Information on electrostatic spray coating.

Telecon. Newton, D., MRI, to Sewell, R., Arthur Fulmer Co. February 24, 1983. Information on coating usage at Arthur Fulmer Co.

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Telecon. Newton, D., M R I , t o B e l l , J., Jay P las t ics . March 1, 1983. Coating methods used a t Jay Plast ics .

Telecon. Duletsky, B. , M R I , t o Schiedegger, C., Metamora Products Corp. March 20, 1984. Use o f Walberg system a t Metamora Products Corp.

Telecon. Duletsky, B., M R I , t o Sales Manager, Armco. March 8, 1984. Use o f e l e c t r o s t a t i c spraying a t Armco.

Telecon. Duletsky, B., M R I , t o Simpson, D., Beckman Instruments. March 22, 1984. Use o f e l e c t r o s t a t i c spraying a t Beckman Instruments.

Telecon. Larson, 3. , M R I , t o Harman, C., Cashier 's S t ruc tura l Foam Div is ion . Use o f e l e c t r o s t a t i c spraying a t Cashier 's P las t ics .

Telecon. Duletsky, 6. , M R I , t o V ier ra, J., Component Finishing. May 23, 1984. Use o f e l e c t r o s t a t i c spraying a t Component Finishing.

Telecon. Larson, J., M R I , t o Pyle, N . , E-Systems. March 16, 1984. Use of e l e c t r o s t a t i c spraying a t E-Systems.

L e t t e r from Cushman, D., Eastman-Kodak Company, t o Duletsky, B., M R I . May 25, 1984. Transfer e f f i c i e n c y f o r surface coat ing o f p l a s t i c parts.

Telecon. Duletsky, B., MRI , t o Fick, R. , E/M Lubr icants, Inc. May 10, 1984. Low-VOC-emi t t i n g techniques used a t E/M Lubr icants , Inc.

Telecon. Larson, J. M R I , t o Gross, R., FCM P las t i cs Div is ion. March 26, 1984. Use o f FCM-CS as a base f o r e l e c t r o s t a t i c spraying. 03

Telecon. Duletsky, B. , M R I , t o Mabante, M., F in ish ing Technology. May 7, 1984. Use o f e l e c t r o s t a t i c spraying a t F in i sh ing Technology.

Telecon. Larson, J., M R I , t o Jensen, D., Foam Molding Co. o f Arkansas. March 14, 1984. In format ion on coat ing process a t Foam Molding Co.

L e t t e r from W i t t , Z., I B M Corp. A p r i l 17, 1984. Surface coat ing operations a t I B M l s Lexington, Kentucky f a c i l i t y .

Telecon. Duletsky, B., M R I , t o Wix, D., Leida F in ish ing. March 12, 1984. Informat ion on surface coat ing a t Leida Finishing.

Telecon. Larson, J., M R I , t o Ha l l , D., Premix, Inc. March 29, 1984. Use o f e l e c t r o s t a t i c spraying a t Premix, Inc.

Telecon. Duletsky, B., M R I , t o Kajewski, S. , Storage Technology. May 15, 1984. Low-VOC-emitting techniques a t Storage Technology.

Telecon. Duletsky, B. , M R I , t o Reis inger, 6. , St ruc tura l P las t i cs Systems. March 26, 1984. Surface coat ing process a t S t ruc tura l P las t i cs Systems.

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40. Telecon. Duletsky, B . , M R I , t o Spencer, P . , Timespec. March-26, 1984. Surface coat ing process a t Timespec.

41. Telecon. Newton, D . , M R I , t o Maynard, G . , Xerox Corp. March 28, 1984. Information on e l e c t r o s t a t i c spraying a t Xerox.