CA1053086A - Method of preparing powder particles by control of the particle shape - Google Patents

Abstract

Abstract of the Disclosure The process of preparing powder particles having a desired particle shape, comprising the steps of: providing a paint solution having a film-forming portion and a first solvent portion, forming droplets containing the film-forming portion and the solvent portion, by contacting the paint solution with a second solvent which is partially miscible with the first solvent and in which the film-forming portion in non-soluble, the second solvent being substantially saturated with the first solvent, diluting said droplets with a sufficient quantity of a third solvent which is at least partially miscible with the first solvent and in which the film-forming portion precipitates as powder particles, and controlling the shape of the powder particles by regulating the dilution of the first solvent in the droplets.

Description

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Background of the 'Invention ',' ,' Powder particles have become highly desirable as a means ,~
of coating'various substrates. For a description of powder paints and methods of application see Iron Age, November 16, 1972, pages 67 to 74, and Chemical'Engineering, July 12, 1971, pages ,, ,, ~;
36 to 38. Use of the particles has becomè of interest primarily ~ - , .: . .: , .
as powder paint. In other words, powder paint relates to the ,,, application of-film-forming_materials_on,~o~,a substrate in order ' , to coat that substrate to give a desired finish wit~out the presence , '''~
of a solvent. The particles contain the film-forming substances ~' -,':' :
and pigments. ~ , .: :
rJ.S. Patent ~,737,401 teaches'the method of preparing " ' : ' ' ' ~ ~ '' ~6P 7210~-lM

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powder paint by physically dividing a liquid paint, in the presence of a coagulating liquid, to minute d~oplets o uniform composition and subsequently diluting said droplets ~, to remove the solvent.
It has been determined that the co~trol of the shape of the particle that is produced by ~he process of Patent 3,737,401 is desirable in order to control the film characteristics of the coated materials as well as the application of the powder to form the fil~. It is an object of the present case to prepare powder particles of con-trolled shape by modifying the conditions of preparation.Summary of the Invent~on The invention is concerned with the preparation of pow~er particles having a desired particle shape by em-ploying the principle of mutual solubility. Droplets of a paint solution will be formed con~aining the film-for~ing portion and the solvent portion by contacting the liquid ~aint with a sol~ent that is mutually soluble with the solvent for the paint and subsequently diluting the drop-lets, removing the solvent for the film-forming portion and controlling the shape of the powder particles. The powder particles may remain dispersed in the final liquid medium which would be the product of the process, or the powder par~icles may be subsequen~ly separa~ed from the 1 - : .
solution, dried and packaged.

This invention is an impro~ement of the pr~cess . .
for preparing powder particles descri~ed in U. S. Pa~ent 3,737,401. ~ -~

The particles produced according to this in~ention may have one, two or three dimensions.

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:, Brief Description of *he Drawin~s ~
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Fig.lis a schematic diagram of the process of :, the present invention relating to the preparation of uni~ ~' ' dimensional powder particles; r Fig. 2 is a schematic diagram of the process of the present invention relating to the preparation of powder particles having only two dimensions; ..
Fig. 3 is a schematic diagram of the process of ~;
the present invention relating to the preparation of spherically shaped powder particles;
Fig. 4 is a schematic diagram of the process of -:' :, .
the present invention relating to the preparation of ,~?~ ~, irregularly shaped powder particles; and '~.. , . ' :
Fig. 5 is a schematic diagram of the process of the present invention relating to the use of a sonic particle, ~';,,,:,' ~.
dispersing unit and various solvent separation and recovery `.'' , .:
steps. ' , '; .':.
Description of Preferred Embodiments The invention of the present case is concerned with ''!, the method of preparing powder particles having a desired particle shape comprising the steps of: ` .'.
(1) providing a paint solution having ~ film-forming "s,,~, portion and a first solvent portion, said first solvent substantially dissolving the film-forming portion, `'' : -~ . .

(2) forming droplets containing the film-forming portion and the first solvent portion by contacting said paint -.~.:.. ' ' solution with a second solvent which is partially miscible ~`.'':
wi~h the first solvent and in which the film-forming portion is not soluble, the second solvent being substantially, ,.,"' saturated with the first solvent, (3) diluting said droplets .'~'..~ '.-:
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with a suf~icient qu~nti-ty of a third solvent which is miscible with the first solvent and in which the film-forming portion precipitates as powder paxticles, and (4) controlling the shape of the powder particles by regulating the xate of dilution of the first solvent in the droplets.
While applicant does not wi~h to be tied to any particular theory as to the operability of the invention, the particle shape is controlled following the below described principles, it is believed.

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10When applicant refers to "one, two or three `
dimensions", it is meant that the particles formed according to the process of the present invention may have any one of the desired physical dimensions of substantially ,.: :
only length (one dimension), length and width (two dimen~
sions) or length, plus width plus depth (three dimensions).
Particles that can be considered substantially one dimensional are fibrous or filamentary in nature much like ' a wire or thread, where the length is substantially greater than the width, so that it can be said that there 20 is substantially no width. ;'' Particles that can be considered two dimensional are much like plates or flat disks. The shapes may not ' be a fixed geometric shape, such as squara, triangular, rectangular,'polygon, etc. but may be irregular with the ;-only provision being that there is but two dimensions of 'length and width. ' The particles that can be considered three dimen- ~ -sional have an appearance that can be considered spherical, ~ multifacetea~irregular, symmetrical, and the like.
Other parameters must also be taken into consider-_ y_ :

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ation when applicant's mutual solvent system is employed to fox~ particles of desired shape. When a solution of film~forming compounds and solvent (hereinafter called Solvent A) for the film-forming components is mixed with another solvent (hereinafter called Solvent B), which is a non-solvent for the film-orming components but whiah is mutually solvent with Solvent A, fine droplets are formed : i . . . - .
of Sol~ent A and film-forming components. If a suffiaient period of time is permitted to pass, a spherical droplet ;
will be formed because this is the posture of the minimum surface energy effected by sur~ace tension (interfacial tension) between the droplet and Solvent B. This i5 the `
minimum energy level for the droplet.
It is believed that prior to applicant's invention, there was no widespread commercially available way to obtain powder paint particles of a substantially uniform composition, other than irregular shaped particles which are obtained from grinding dried paint drops or like processes. Some processes, -such as the so called "Spray Dry" technique produced in ~ -2~ limited amounts powder particles of a material composition which is not heat sensitive, otherwise the drying at high temperatures would deteriorate the desired compositions.
By engaging applicant's process one can obtain a substantially uniform consistency of powder particles of the shape desired.
It should be pointed out that the powder compositions produced according to ap~licant~s process have unique proper-ties. If a substantially all spherical powder compositiOn is employed, then the physical flowing properties of the com-position will be improved since there is su~stantially less friction involved as there would be for a substantially all _ 5~

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irregular shaped powder composition.
In addition it is believed that the rharacteristics of film buildup and ability of particle to carry electrical charge vary with the physical dimensions of the particle.
Therefore the film buildup is related to the ratio of surface area of the particle to volume of the particle.
It is believed that a particle substantially spherical will ~-take less charge during the electrostatic spraying of the particle but that it also loses less charge during the passage of the particle from the charging area (usually spray gun) to the desired substra e. Conversely, an irregular shaped paxticle will take more initial charge but loses more charge, as compared to the spherical particles.
The all spherical powder composition when e~ectro-statically sprayed may keep the charge entirely too long for certain powders and will gather dust thereon due to ;
static electrcity. Also an all irregular shaped powder composition when electrostatically sprayed will dissipate its charge so rapidly that the powder particle may not have sufficient charge to adhere to the desired substrate and therefore cannot be electrostatically sprayed. This is pre- ~-cisely the situation with respect to powdered polyvinyl chloride currently available. The particle shapes are nat sufficient to hold the charge for electrostatically spraying `~
the particle.
By employing applicant's process of preparing the powder of varying desired shape~ film forming dielectric, such as a PVC powder composition~can be electrostaticallY
sprayed resulting after cure in very ~ine film having a ~.
30 thickness of about 0.5 to about 5 mils, or lesg, to 3 mils. ~ :

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This can be accomplished by producing a powder composition that is substantially spherical.
It can be seen that by following applicant's `
process, one now has the ability to vary another parameter ;~
(particle shape) in the application of a film former to a substrate. If, for example, one has found that an all spherical composition has certain undesirable results, such as, holding static electricity, then one can vary the shape from spherical, but yet, not totally irregularly shaped. As can be seen, all of this can be done without varying the film forming composition. It should be appre~ ;~
ciated however, that one may wish to design a film forming composition which is to be used to produce a powder particle.
It is to be appreciated that applicant can produce powder compositisns that are not necessarily limited to powder paint ~Dmpositions but preferably are so limited.
Applicant can produce powder compositions which allow the formation of the appropriate dimensional powder particle to obtain the desired film property~ such as thickness, 20 hardness, color, hue, pigmentation, and the like. ~-In view of the abo~e it can be seen that one may be able to control the thickness of the paint film and therefore overcome the dielectric or insulati~e nature of the film because a higher charge can be held by spherical particles than irregular shaped particles. Also one can var~ the flow !`. ~' particles of the film by ~arying the particle shape.
Irregular shaped particles will flow at lower temperatures than spherical shaped~ Therefore by merely altering the ;

particle shape one can alter the properties of the film (fusion temperature, film thicknes~, and thP like).

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The first step of the process for preparing the powder particles is providing a solution having a film-forming portion and a first solvent portion. (Solvent A) It is preferred that the solution be a paint prepared in the normal processing techniques. In other words, the paint would be a liquid paint containing a solution of the film-forming portion which can be any one of a number of compositions ~uch as various resins as alkyd, urethanes, polyesters, polyamides, epoxies, vinyls, such as from monomers as vinyl chloride, acrylic acid or esters, methacrylic acid or esters, acrylamide and N-substituted acrylamides, styrene, vinyl toluene, copolymers thereof and the like, hydrocarbon resins, varnishes, such as oleoresinous and spirit varnishes, and the like. Of the above enumerated film-forming portions it is preferred that an acrylic acid or ester or methacrylic acid or estex resin be employed with the epoxy~ vinyl chloride and polyester resins most preferred of the other enumerated resins.
Other resins may also be used in applicant's process to produce the desired powder composition. Any film form-ing resin may be used, such as, polyolefins, such as, poly-ethylene, polypropylene, and copolymers thereof, and the like, polycyclopentadiene, polydienes, as, butadiene, is oprene and copolymers thereof such as, styrene - butadiene ~SBR), acrylonitrile - styrene - butadiene (ABS3, and the like, polyimides, organic~silicones, and the like.
The solution in which the film-forming portion is dissolved is a solvent for the film-forming portion (solvent A). In order to control the shape of the particle the solution ha~ing the film-portion is contacted with a 3~6 B&P 72104-lM

second solvent (solvent B~ thereby forming droplets. The droplets that are formed in this separate solution are of a composition substantially similar to that o$ the first solution. In other words, the droplets that are present in solvent B have substantially the same ratio of the film-forming portion to the solvent A portion as was present in the solution of the first step. Solvent B
that is used is one that is partially miscible with the ~-first solvent but is substantially non-soluble with respect to the film-forming portion. The basis for this condition is that solvent B is usually a stable medium for the first `~
~. .
solvent. Solvent B is a liquid medium in which the droplets -will be formed of the film-forming portion but the relative content of solvent A in these droplets is substantially the same, for solvent B is substantially unable to dissolve ~ ;
substantial portions o~ solvent A so that the content of solvent A in solvent B (or vice versal is not substantially altered.
In some instances solvent B may be able to dissolve some additional amount of solv~nt A. But this is generally because the solvents ha~e not been agitated sufficiently for equilibrium to be reached. All that is required for solvent B is that it be a stable medium into which solvent A
plus film former may be added so that the droplets of film former may be formed. When one employ~ solvents that are partially miscible, two l~yers of solvent may form. When the relati~e quantities of the two components (solvent A
and solvent ~) are such that the two liquid layers coexist, one of the layers is a saturated solution of A in B while the other is a saturated solution of B in A. The two liquid .,. ~.
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layers and phases in equilibrium are called conjugate solutions. Outlined in Table I are representative solvents are partially miscible in each. Therefore while the ratio of solvent A to film former may vary slightly when the droplets are formed in solvent B, nonetheless, the droplets are formed due to the insolu-bility of the film former in solvent B.
After the droplets are formed, the powder particles may then be formed by removal of ~he solvent A from the droplets. The various powder shapes are formed by the dilution of the solvent A into a third solvent as well as by mechanical or physical treatments of the droplets.
The principle being employed in the direct contact ~;
of the solvents is one that permits control of the removal of solvent A from the film-forming portion.
Preparation of Unidimensional Powder Particles Referring nvw to Figure 1, liquid paint 12, a solution of solvent and film former, is contained in tank 10 and is pumped or is flowed via line 14 into tank 16 having agitator 18. After a sufficient size of droplets 20 are ob~ained, due ~o the agitation, the solu~ion is then passed via line 22 through a venturi 24 which is a lead to a pipe through which solvent C is flowing. Due to the swift movement of solvent C past the outlet of the venturi, the solvent A is rapidly removed from ~he droplet and from solvent B by being dil~ted into solvent C at the same tLme the film former of the droplet is precipitated, thereby being stretched into a fibrous of filamentary form 28 shown at the outlet of pipe 26 l~

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.~ , PreDaration of Two Dime~sional Powder Particles . ~:
The same procedure for unidimensional powder ,~ ::
preparation is followed with respect to the initial tanks that are i'dentified as tank 10' and 16' with no substantial ~ `
difference in'the handling of the droplets formed in tank 16' This is expresed in Figure 2. The droplets 33 from tank '~
16' are slowly dropped or sprayed onto a liquid surface 31 (solvent C~ in tank 30, having weir 32 and agitator 34 1 "
which allows for very slow movement of solvent C in tank 30 10 mexely sufficient to provide a surface of solvent C. :~:
Therefore once the disks or plates are formed at ~he surface 36 of solvent C then no further solvent A may be removed ~ :
therefrom and the powder particles remain in their shape as was formed when they hit the surface o~ solvent C~
For practical purposes, solvent C should be one that has a high surface tension, such as water, which can rapidly precipitate ;~
the powder by rapidly removing solvent A from the droplet. : ' Preparation of Three Dimensional Powder ~ .
Particles - Spherical Shaped Following the same procedure for preparation of uni~
' ' '' ` "
dimensional powder particles with respect to employing the :, first two tanks identified in Figure 3 as 10' and 16', after ':
agitation of the droplets to obtain satisfactory size and spherical shape, the solution is then passed from tank 16' ~',' into tank 40 containing solvent C (42). The particles 44 that are formed are of ve~y fine ~ize r generally sphericalO
The solvent C is agitated by agitator 46 to allow for complete removal of solvent A from the particles. To allow uniform removal or dilution of solvent A into solvent C ~
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the droplets are passed into 501 ution C under the surface : . , , ~: . .

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. , of solvent C at outlet 48 of pipe 22.
Formation of I~reg~lar Shaped Particles -, Figure 4 schematically shows the formation of irregularly shaped three dimensionally shaped particles.
Using the same liquid as in Figure 1 ~rom the first tank, identified also as 10', a solution of solvent A and film ormers is fed through line 50 directly into tan~ 52 con-taining solvent C t54~ which immediately removes solvent A
from the droplets which are formed rather quickly. However `
before a spherical shape could be formed, the shaping is interrupted and therefore irregularly shaped particles 56 result. The solution C in tank 52 is agitated by means of agitator 58 in order to eliminate or remove as quickly as possible, solvent A and dilute or dissolve it into solvent C. The agitator also allows for physical means of ,' dividing the aroplets as the solvent A is being removed therefrom. As can be seen from above, solvent C is a ~ilution solvent. The function of this third solvent is `;
, to remove in a controlled ~ashion solvent A thereby pre-" 20 cipitating the powdered particles.
As can be appreciated, solvent C may vary from the solvent B simply to the extent of the amount that the `~
, solvent A is present in the third solvent i.e. solvent B -~
and C may be comprised of the identical chemical compounds or entities. In other words, since the solvent A is partially soluble with the second and third solvent, one can vary the content of the first solven~ in the third or diluting solvent. Since the exten~ o~ dilution tor miscibility) of one solvent in another is reasonably well known to one of skill in the art, one may control the rate ~ha~ solvent A

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~ill leave the film-formln~ portion. Therefore, solvent C
may have substantially no solvent A in lt when it (the `
dilution solvent) first contacts or dllutes the droplets.
Suitable examples of solvents that may be employed see j Table I. ~lso indicate~ is that amount that each is soluble in the other. Therefore to control the rate of `
dilutlon of solvent A into solvent C, one therefore varies the concentration of solvent A in solvent C.
Preferably sol~ent C has little or no solvent A therein. ~ ;
Most preferably solvent C is water. It should be appreciated that one would select solvent A based on the amount necessary Z to achieve conjugate solutions for in designing a complete system~ one would separate such as by distillation, solvent A
from solvent C. The separation is designed to achieve minimum energy requirements.

TABLE I - ;
i % by Weight S by Weight I of Solvent A of ~2 Example~ of Sol~ent A in H20 in Solvent A
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Alcohols 1 - Butanol 7.7 20 ` 20 2 - Butanol 20 36.3 Isobutanol 8.5 15 1 - Pentanol 2.6 9.5 2 - Pentanol 4.9 11 --Amyl Alcohol tmixed Isomers~ 1.7 9.2 ;
1 - Hexanol 0.58 7.2 2 - Ethyl Butanol 0.43 4.56 2 - Ethyl Hexanol 0.07 2.fi 2,6 - Dimethyl -4-Heptanol 0.06 . 0~99 ~sters .
MethyI Acetate 24.5 8.2 Ethyl Acetate '~ 8.7 3.3 ` Butyl Acetate 0.68 1.2 Isopropyln~cetate 2.9 1.8 Cellosolv~rAcetate ~CH3COOC2H4OC2H5) 22c9 6.5 Butyl Carbitol Acetate Ethyleneglycol Diacetate 16 r 4 7 ~ O
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TABLE I (Contlnued~
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: Ketones :- .
Met~y~r-~thyl Ketone 26,8 11.8 i .
Methyl propyl ketone 4.3 3.3 : : `
Methyl isobutyl ketone 1.9 1.6 .
;, Methyl-butyl ketone 1.42.1 Cyclohexanone 2.5 8.0 Glycol Ethers .
', C~H90 - CH2CH(CH3~ O~ 6.4 15.5 As is outlined above and in ~. S. 3,737,401, a slurry of powder particles results from the process f ``
which may subsequently be filtered, washed, divided into desired particle sizes and packaged as a slurry or dried ~;' 10 for dry powder packaging. An example of a slurry in which the particles could be employed is described in U. S. ~ ' ~'` Patent No. 3,787,230. .
~'. . It can be appreciated here that the particles resulting from this process may be used for a desirable number of end uses, such as dry particles for electro- `~
~i. static spraying, ~orming slurries for application to a .. substrate such as metal and the like. It should also be - ~;
appreciated that the film-forming portion may include . .
. pigments which are normally used in liquid paints as well : 20 as flow control agents to improve the flowing properties ::
. of the film formers during curing, catalysts to accelerate -~` the curing of the:film and other agents to impart other - desixable properties to the film. ~
In Figure 5 there is an a}ternate way of producing ~.
`-, the powders of controlled shape, Following the noxmal paint .` manufacture, composed of solvent ~ and piyment and film formers, a solution is prèpared in tank 60. As the liquid is passed to diaphragm pump 62, soivent B is passed into :

, the line 64 upstream o~ the pump, thereby producing droplets ~` .30 66,~which are then passed to tank 68. :
y _ :~ , ~53~36 - :. ` ``. :.

; Tank 68 is composed of an upper and lower portion ..
separated by a slotted V-shaped trough 74 through which : ~
the droplets pass. Solvent C 70 is present in the lower . . .......... .
portion. By means of a sonic dispersing means 76 the particles ~ `
78 are physicall.y divided as they are precipitated. The .
entire unit 68 is available from Sonic Engineering Corp. of Norwalk, Conn. After passing from the sonic dispersing uni~
-I the finely divided particles are passed to a separation tan~
80 via line 79 which may be maintained at a sufficient le~el ;~
10 to allow the majox porti~n of particles to flow to subsequent .~ `;.
filtration via exit 8~. A good por~ion of the liquid may . .
then pass through filter 84 for subsequent separation and reuse.

The powder particles produced according to the , .
process of the present invention generally range in size from about 0.1 microns to about 150 microns, preferably for ;.~ .
electrostatic spraying having an average particle size of -~ 35 microns or less. The fibrous particles may have a length of up to 1,000 microns, although a length of 100 - 200 is : ;
. preferred and a cross-section of about 5 microns. .- ~: .
20 One ca~ also make oval shaped particles by the aboYe ..
:~ process for fibers wherein the length is about 1.5 times the . diameter. ` `
~ ~ - ' : : . ;' ;
., .While having described the invention above in its .... ~
.`. .. general aspects, listed below are examples that further amplify .. :. ;
the invention wherein temperatures are given in degrees Fahrenhei~ . ...
~ .and percentages are percentages by weigh~ unless otherwise ~ : .;.
. ~ndicated. ;
~ .Example5 1-3 . A.green pigmented vinyl coating was prepared by lO dissblving a.mixture of ~inyl powders: a) gO~ Ba~elite EZOOO : :
~inyl chloride resin of.medi~m molecular weight and melting - lS ~

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. i i l~S3~6 range o 120-135c) and b) Union Carbide VMCH (copolymer of ~inyl chloride (86~) and vinyl acetate (13%) with 1% of an interpol~nerized dibasic acid (0.7-0.8 carboxyl) in methyl ethyl ketone (solvent A). Solvent B was methyl ethyl ketone ~ saturated in water while solvent C was deionized water. Table ;; II indicates the various amounts of components.
TABLE II (All Parts by Weight) i Film former 20 35 40 Solvent A 80 65 60 Solvent B800-1200 800-1200 500-1500 Solvent c5600-17000 5500-16000 3200-200,000 -~
The particles were processed according to the steps outlined in Fig. 3 so that they ~ere substantially spherical having an average diameter of about 25 microns. The particles ~, were separated from the water and dried. They were then electro-statically sprayed at 45 KV onto a metallic panel. The treated ~-panel was subjected to heat of 350F for 5 minutes whereupon a smooth film of 1.5 mils was produced which can be characterized as flexible, having a high tensile strength file with a tukon hardness of 3-10.
The satio of solvent C to solvent ~ may be as low as 5-1 with no real upper limit. The practical upper limLt is dictated by overall system design in optimi2ing the process ~~
~:` 1 .;
parameters, in particular, quality of powder, ability to ~` separate and reuse solvents~ and the like.
; It is to be appreciated that solvent C may~-be com- i pletely miscible with solvent A. This may facilitate the di-lution of solvent A from the dxoplets r Conversely, solvents .,. :, ;30 B ~,C may be comp~ised o~ substantially identical chemical entities. In the latter case~ solvents A ~ B should be only partlally miscible.

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Substantially equivalent results are obtained when `
a pigment, such as Tio2 is employed wi-th the film-former. ~' Examples 4-12 Various solutions were prepared with the compo5ition shown in Table III. The procedure for forming the particles is as follows: Components No. 1 and 3 were added to No. 11 and then 2, 4, 8 and 10. Then Components 5 or 6 and 9 were added. Just before precipitation, No. 7 is added. -Solvent B (10% ethyl acetate, 90% water, by volume) was prepared. The procedure shown in Figure 3 was followed. ~
After various solutions (4-12) were prepared, the pump in `
container 1~' was turned on and operated at 5,000 RPM. ~hen each paint solution was pumped at about 100 pounds per inch2 gage through nozzels having an orifice diameter of 0. 012 I!
(nozzle with zero degree solid stream tip) into container 16' -near the rotating agitator. Solvent B in container 16' amounted to 10,000 ml. Fine droplets of spherical shape are formed. After each solution was passed into container 16', the total contents were then passed into a 55 gallon drum (40) containing 30 gallons of deionized water which was agitated.
The contents of container 16' were pumped under the surface ;~
of the water in the drum and entered the drum near the agitator and were allowed to wash for 1 to 2 hours. The particles pro-duced had a composition substantially similar to the starting liquid paint composition except the solvent was substantially removed therefrom. The particles subsequently were separated from the solution and dried. They were substantially spherical and ranged in diameter from 5 to lS0 microns, which after drying had a range of size of 10 to 75 microns.

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TABLE I I I

Component Number 4 5 6 7 8 9 10 11 12 EPON-201 266 266266 ~ --0- 1~ 110 110 100 3 OEX-1615 26.5 50 50 75 305 75 75 75 75

4 VMCA 78 31 Trimellitic Anhydride -O- 35 -0-6 A~alic Acid 51 47 25 25 25 25 7 SnO2 4 ~~ ~~ ~~
8 Moda10w 3 3 3 3 3 3 3 3 3 9 Cab-o-sil 1.5 1.51.5 1.5 1.5 1.51.5 -O- -0-Ferro 840 5 11 Ethyl Acetate Adjusted to have 30% solids content Epon -201 and Eponol 55-B-40 are trademarks of Shell Oil Company for epichlorohydrin/bisphenol A type epoxy resin generally of the structure C ~2 ~ -CH2-~ ~ $ ~ 0-CH2CH-CH2]n-0 ~ -C ~ O CH C ACH
C~I3 CH3 OEX-1615 is a trademark of Union Carbide for a modified vinyl , chloride resinous product. VMCA is a trademark of Union Carbide for a vinyl resin having the composition parts by weight, of vinyl, vinyl acetate and maleic acid (81/17/2). Modaflow is a trademark Monsanto of/and is a comple~ polymeric plasticizer and is soluble in benzene, toluene, xylene, kerosene, petroleum ether, carbon ~ r tetrachloride, mineral oil, approximately 2-3% by weight in iso-propyl alcohol and increasingly soluble in higher alcohols, `~ insoluble in water. Cab-o-sil is a trademark of Cabot Inc. and ~ is a thickening and thixotropic agent of a fumed silica type ., :
, which is produced by the hydrolysis of vaporized silicon tetra-. " ~
chloride in a flame of hydrogen and oxygen. Ferr~ 840 i~ a trade- ~
mark of Ferro Chemical Corporation and is an alkyl tin heat ;
stabilizer having a specific gravity of 1.11 and a viscosity , of A-l Garner.
;~` It is to be appreciated that the liquid paint solids may also range up to 30 to 75% solids, if desired.

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~53~ 6 Example 13 A solution (34% solids~ of the components of Table IV
was prepared and weighed 8.2 lbs. per gallon with a viscosity of 64.2 seconds Ford Cup No. 4. The procedure for preparing the droplets and particles was that of Examples 4-12, except 7.5 gallons of paint were used with 75 gallons of Solvent B
and the agitator in container 16' was operating at 1,000 RPM.

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TABLE IV

Parts By Weight 1 OEX-1615 53.94 2 VMCH 5.1 -3 Cellulose Acetate Butyrate 4.0 `
4 Modaflow O4

5 Ferro 840 .8

6 EPON-201 2.0

7 Triisodecyl Trimellitate 7.84 ),~
, .

8 1,2,4-~Trioctyl Formate) Benzene 7.84

9 Ethyl Acetate 192.91 J,'~ , .

10 Carbon Pigment 1.65 See Table III for definition of the marks. -~
' After separation and drying, the particles obtained were substantially spherical in shape and ranged in size ~' from a diameter of 10 microns to about 75 microns. The composition of the particles is substantially the same as ~` the starting liquid paint composition except the sol~ent has . :
been removed therefrom.

Example 14 ~i Spherical shaped acrylic powder was prepared following `,;i the procedure of E~amples 4-12. One part of liquid paint was used with 10 parts of Solvent B (26.8% methyl ethyl kotone ~y ~l volume in water). The washing in the drum containing water `~ lasted about 1 hour. The liquid paint had the composition of , Table V. `~
i` 1 7 _ ` ~
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1053~6 B~P 7210~
TABLE V
. Parts By Weight Thermoplastic acrylic film-former having hydroxyl functionality347.8 Cross-linking agent (isophorone diisocyanate blocked with methyl isobutyl ketoxime (equimolar) and product reacted (equimolar) with 1,6-hexanediol) 34.0 ~odaflow 2 Tio2 60 10 Methyl ethyl ketone 128 OH/NCO ratio (acrylic film-former/
cross-lin~ing agent) : For a further description of the cross-linking agent reference may be made to Canadian patent application Serial No.
.
229,729, filed June 19, 1975.
The particles produced according to this process were substantially spherical in shape and ranged in diameter from about S to 150 microns in the wet state and about 10 to about 75 microns in tbe dry state. `
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

A process of preparing particles of a film-forming polymer comprising providing a solution having a film-forming portion and a first liquid portion in which the film-forming portion is soluble; forming droplets containing the film-forming portion and the first liquid portion by contacting the solution with a second liquid which is at least partially miscible with the first liquid and in which the film-forming portion is non-soluble, the second liquid being saturated with the first liquid; and diluting said droplets with a quantity of a third liquid which is at least partially miscible with the first liquid and in which the film-forming portion precipitates as particles, whereby the first liquid is removed from the droplets by the third liquid, the quantity by weight of the third liquid employed being at least five times that of the first liquid, thereby producing powder particles of a side of 0.1 to 150 microns or fibers from 100-1,000 microns with a cross-section of about 5 microns.

The process of claim 1 further comprise controlling the shape of the powdered particles to produce substantially unidimensional particles by passing the formed droplets through a venturi to a moving body of the third liquid.

The process of claim 1 further comprising controlling the shape of the powdered particles to produce substantially two-dimensional powders by contacting the droplets formed with a surface of the third liquid.

The process of claim 1 wherein the second and third solvents are comprised of substantially identical chemical entities and wherein the amount of the first solvent present in the second solvent is substantially greater than the amount present in the third solvent.

The process of claim 1 wherein the dilution of the first solvent in the droplets into the third solvent is obtained by uniformly contacting the droplets with the third solvent.

The process of claim 5 further comprising forming spherical shaped droplets in the second solvent, prior to the dilution with the third solvent.

The process of claim 1 further comprising passing the droplets onto a surface of the third solvent thereby diluting the first solvent from the droplets.

The process of claim 4 wherein the third solvent is comprised of a minor amount of the first solvent and wherein irregularly shaped three dimensional particles are formed by contacting the solution with the third solvent.

The process of claim 1 wherein the solution provided is a pigmented paint solution.

The process of claim 1 wherein the third solvent is water.