USRE22812E - Plasticization of plastics - Google Patents

Description

Reiesued Dec. 3, 1946 PLASTICIZA'I'ION F PLASTICS John D..I

scum.

The preunt invention relates to the preparation and use of plastic compositions and notably to those containing compatible plasticizers.

One object of the invention is to provide a simple and economical process of uniformly dispersing compatible plasticizers with plastic materials in which they are employed as modifiers.

A second object of the invention is to provide a fluid composition comprising a high concentration oi plastic material, and a plasticizer therefor suitable for spraying, brushing or like applications. without recourse to expensive solvents for the plastic.

These and other objects or the invention will be apparent irom consideration of the following specification and the appended claims.

Plastics such as vinyl resins.'cellulosic plastics and the like are customarily compounded with modiiiers termed plasticizers. which enhance plasticity, toughness, flexibility and homogeneity. If the plastic is to be molded, sheeted. extruded. or otherwise shaped, the plasticizer may be incorporated by milling. which is a relatively laborious operation.

In the preparation of coating compositions suitable ior spraying, brushing, dipping, or for application by other methods well understood by the art. it is customary to dissolve the resin plastic and such plasticizers as are required therefor in a suitable solvent in such proportions as to obtain a requisite fluidity of the composition. Upon application of the composition to the bodies to be coated, the solvents soon evaporate leaving the plastic. plasticizer and other modifiers as continuous adherent films. One objectionable feature of such process is that many of the desirable plastlcs are soluble only in certain relatively active solvents which can only be obtained at substantial expense.

Furthermore, plastics. in dissolving in solvents, tend to produce solutions oi high viscosity and unless the concentration is kept low. the solutions may be so viscous as to make it diiiicult to apply themasfilmstobodiestobe coated. Low concentration of plastic in the solvent necessitates use of excessive amounts of solvent and application of an undesirably large number of coats to obtain desired film thickness.

It has also been proposed to disperse solutions of resins with water or other non-solvent for the resins, to provide emulsions that can be suitably applied to a surface to be coated. The suspending medium and the solvent for the plastic evaporate from a him of such material and the particles of resin solution coalesce to form a solid. continuous film. Either process requires the use of solvents for the plastic.

In accordance with one feature oi the present invention it is proposed to disperse a plastic ma terial in finely-divided or powder form in an inenkim, Milwaukee, Wis. assign to Pittsburgh Plate Glass Company, Al or county, Pa, a corporation of DIIIIIIIINNO. 2,385,920. dated Octolegllelly Pennsylvania 024, December iii,

expensive medium which is a non-solvent there- 'for, and which contains in solution a plasticizer for the plastic, to provide concentrated suspensions that can be sprayed or brushed or otherwise applied to a body to be coated in much the same manner as ordinary coating materials, without recourse to solvents.

Any suitable finely-divided plastic material may be employed in practicing the invention. They include any of the usual synthetic or natural resins or plastics commonly used for molding or for forming coatings, which by themselves at ordinary temperatures may be obtained as non-tacky powders. Plastics considered to be especially suitable for the purpose included Vinylite X, a form of resin particularly designed for use in safety glass and considered to embody a polymerization product of polyvinyl alcohol and an aldehyde such as butyraldehyde. which polymerization is carried sufllciently iar to obtain a product which is substantially insoluble in water, but is not conducted to the stage in which the resin loses its solubility in all solvents.

Another form oi resin suitable for many purposes comprises the product sold under the trade name oi "Vinylite 1-1." This product is understood to comprise a copolymer of approximately 87% of vinyl chloride and 18% of vinyl acetate. If desired. the copolymer may be replaced by a simple polymer of either or its components. namely, of vinyl chloride or vinyl acetate.

Vinyl resins may be replaced by cellulosic plastics including cellulose acetate. cellulose ethers of the type of ethyl cellulose, cellulose aceto-propionate and cellulose acetobutyrate. Phenol resins, namely the polymerized products oi' phenol and formaldehyde, especially straight or unmodified phenolic resins in the intermediate or B stage of p lymerization may be employed. Similarly, soluble urea resins obtained by condensing urea or thiourea and mixtures of urea and thiourea with formaldehydes. such as formaldehyde are contemplated. These resins may be modified by additions of certain amounts of alkyd resins obtained by condensing and polymerizing phthalic anhydride or other dicarboxylic acid with a polyhydroxy alcohol. such as glycerol. These alkyd resins may themselves include such modifiers as fatty acids. e. g, oleic acid, stearic acid. or glycerides. such as drying oils from linseed or the like source. The alkyd resins in general are relatively soft and soluble and constitute plasticizers for the other resins. Any other thermoplastic resin or plastic. that may be obtained in finely-divided. non-agglomerating solid form, may be employed.

The preparation of powders of the resins suitable for use in the practice of the invention may be efiected by various methods. The most obvious method of course includes grinding or mechanicaiattrition. However. the material employed in the practice 01' the invention is reduced to a particle size or 200 mesh or less. The above method is not always satisfactory for producin such finely-divided materials, notably where the materials are relatively tough and rubbery plastics of the type of vinyl resins. Accordingly, it may be desirable in many instances to resort to precipitation of the plastic materialirom a solvent in order economically to obtain a pulverulent body suitable tor dispersion, in accordance with the provisions of the present invention. One such process is disclosed in British Patent 498,396. This method involves projecting the resin while in solution as a very fine spray and precipitating the resin while the solution is still finely divided. Another method especially applicable to polyvinyl acetals is disclosed in British Patent 481,532, and involves dissolving the resin in a water immiscible solvent, such as chloroform or methylene chloride. This solution is then emulsified at high speed in water and in the presence of a dispersing agent such as sodium butyl naphthalene sulionate. The solvent is removed by steam distillation. A further method is disclosed in German Patent 670,212 and involves dissolving the resin in a liquid under pressure, which liquid is gaseous at ordinary temperatures. Sulfur dioxide and methyl chloride are suggested for the purpose.

A preierred method for purposes or the present invention involves dissolving the plastic material, e. g., a polyvinyl acetal or a copolymer oi vinyl acetate and vinyl chloride. vinyl acetate, methyl methacrylate, or the like in a solvent, adding a non-solvent to the solution approximately to the point of incipient precipitation oi the plastic, and then cooling and agitating the solution in order to eflect gelling, and subsequent separation of the plastic as a finely-divided solid which can be removed from the solvent by washing or other methods. to increase the concentration or nonsolvent.

Examples of the method are as follows:

Example A About 150 parts or the resin obtained by partial condensation oi polyvinyl alcohol with butyraldehyde was dissolved in 050 parts of synthetic methanol. To this solution under agitation at room temperature was added 90 parts of water. The resin was partially precipitated during this addition but redissolved upon continued agitation to a clear fluid solution. The charge was continuously agitated and was gradually cooled. At 18' C. the charge became translucent and started gelling and at 5 C. the gel was quite heavy and viscous. Very strong agitation was required to keep the solution homogeneous at this point. At -8 0. some syneresis occurred and at 10 C. the gel began breaking and precipitation started. At C. the resin had precipitated and the product was in fluid suspension. It was further cooled to C. and an additional 2000 parts or water was added at this point to harden theresin. The mixture was poured into 3000 parts oi water at room temperature and the product was isolated by nitration. It was dried in a current of air at 25 C. to yield a very light flufly powder, 94.7% of which readily passed a 200 mesh sieve. Under the microscope the particle size appeared to be very unii'orm and in the'neiehborhood of 1000 mesh.

Theiilteredresinmaybedriedetenytemperature below its softening point without serious coalescence or the resultant powder. A tempera- 4 ture of 45-50 C. has been found generally most satisfactory for polyvinyl acetal resins.

Example B A solution was prepared by dissolving under agitation at room temperature, 100 parts of the resin obtained by copolymerizing, 8'! parts or vinyl chloride and 13 parts of vinyl acetate in 900 parts of acetone. To this solution under agitation were added 320 parts oi 88% isopropanol. Particles oi resin precipitated during this addition but redissolved readily upon continued agitation. There resulted a slightly hazy but very fluid solution which was gradually cooled. At 5 C. the solution had become very hazy and quite viscous. At -4' C. the resin precipitated in very finely divided form to yield a fluid suspension. Cooling to i0 C. brought no further change in the appearance oi the suspension.

An additional 700 parts oi 88% isopropanol were added at -40 C. and immediately thereafter 1500 parts 01 water raising the temperature to 24 C. The charge was then dropped into 1000 parts of water at room temperature. After filtering and drying, less than 2% of the powder failed to pass a 200 mesh sieve.

Example C Fii'ty parts of a commercial polymerized methacrylic resin known as "Acryloid -27" were dissolved in 450 parts or acetone. To this solutim under agitation at room temperature were added 75 parts oi water. The resulting clear bolution was gradually cooled. At 9 C. it was viscous and haziness appeared. At 2 C. it was very hazy and viscous and required strong agitation to keep the mixture homogeneous. Between 0 .and -5 C. the viscosity decreased very rapidly indicating that the gel had broken and the resin precipitat-ed. At -8 C. an additional 500 parts 01 water were added alter which the charge was dropped into 6000 parts of water at room temperature.

Ai'ter mixing 1 hour the resin was filtered and was subsequently dried. It was then obtained as a fine powder the major portion of which readily passed a 200 mesh sieve.

Example D A sample of polyvinyl alcohol was prepared by the hydrolysis of low viscosity polyvinyl acetate by the method described by Blaikie and Crozier, J. Ind. and Eng. Chem. 28 1158 (1936). According to this method 50 parts 'of the polyvinyl acetate known commercially as Vinylite AYAA" were dissolved in 100 parts at synthetic methanol. A solution of 0.25 part 01 caustic potash in 10 parts or. methanol was added. After several hours, the solution had set to a gel and after 10 hours, a rubbery gel remained covered by a clear mixture 0! methyl acetate and methanol. The solvent was decanted and the gel was dissolved in water. The resulting solution was held at 90-100 C. until the residual methanol and methyl acetate had been distilled. Additional water was then added so that the dual concentration corresponded to the addition of 330 parts oi water.

To this solution under agitation was added 330 parts 0! acetone by volume. It was then chilled gradually to 10 C. where it gelled. At 20', the gel started synerizing and at -25' the gel was definitely broken and the product had precipitated. At 25 to 30 C. 1000 parts of acetone were added and the resulting suspension was allowedtowarmtoroomtemperatureandwas filtered. The filter cake was washed with 1000 parts of i'resh acetone and was then dried in an oven at 65 C.

The product was thus obtained in dry lumps which were readily crushed under light pressure to a ilne powder. All but '1 oi the product readily passed a 200 mesh sieve.

Example E Forty parts of a commercial resin obtained by polymerizing ethyl methacrylate were dissolved in a mixture consisting of 316 parts of 99.5% alcohol and 60 parts of acetone by volume. The solution was agitated at room temperature and there was added a. solution consisting of 40 parts of water in 100 parts of alcohol. The solution became slightly cloudy but no precipitation occurred. It was then gradually cooled. At 15 C., the solution had become quite cloudy and 12 C. it began to gel. At C. the gel started to break and at 5 C. the gel had broken and there was a very fluid suspension. The charge was cooled to -15 C. and was there diluted with 140 parts of water. It was then poured with 2500 parts or water to form a fine suspension.

The suspension was filtered and the cake was washed with water. It was then dried in an oven at 50 C. to form soft lumps which broke readily into a flufly powder. Essentially all of the powder passed a. 200 mesh sieve.

For purposes of forming suspensions of the plastic which suspensions embody a plasticizer for the final films or other bodies, the finelydivlded plastic is incorporated with a liquid medium which is essentially non-solvent for the plastic, but which is a solvent for the plasticizer to be incorporated with the plastic. It will be apparent that if the precipitation method above described is employed to disperse or break up the plastic, the original precipitation or drowning medium may be employed as a medium for eil'ecting the incorporation oi the plasticizer. Thus in Example 13, as above given, the plasticizer may be added to the resin suspended in finely-divided form in isopropanol.

A preferred method in many instances, however, involves removal or the precipitant by filtration, or filtration and evaporation and subsequent addition of an inexpensive organic nonsolvent such as mineral spirits, petroleum ether or the like, which can be obtained at an expense of but a few cents a. gallon. The plasticizer can then be added and soon dissolves in the nonsolvent for the plastic.

Simultaneously any plasticizers, which are reasonably soluble in the non-solvent dispersing medium for the specific plastic contemplated, may be employed. A few suitable combinations of non-solvents and plasticizers for certain plastics are tabulated as follows:

NITROCELLU LOSE Non-solvent Plasticizers M inoral spirits Glycol other plasticizers Toluene 'lricresyl phosphate Carbon tetrachloride, etc. Castor oil CELLULOSE ACETATE Mineral spirits Carbon Ietrachlorille Turpeni inc, etc.

Dimethyl phthalnte Phtlialic acid ester of monomoihyl ether oi ethylene glycol, etc.

CELLULOSE AOETO-PRDPIONATE or BUTYRATE Petroleum naphtha Dlbutyl phthalatc UREA-FORM ALDEHYD E M inoral spirits Petroleum naphtha Turpentine, ctc.

Soft alkyd resins VINYL ACETATE POLYMER M incrnl spirits Turpentine, etc.

Dihntyl phthalate 'irlcresyl phosphate VINY L CHLORIDE .Nlincral spirits 'lurpenline, vic.

Dibutyl phthalate Tricresyl phosphate PARTIAL POLY-VINYL ACETAL 0R BUTYRAL Petroleum na htha Dibutyl phthalete l i yrirogenate naphtha (etano Triethylenc glycol dlhexoate COPOLYMER 87% VINYL CHLORIDE 13% VINYL ACETATE 'letrahydro naphthalene Dipentcne, petroleum spirits,

hntyl alcohol Propyl alcohol Dlhutyl phthalate Tricresyl phosphate C11 LORINATED RUBBER Petroleum naphtha Chlorinated diphenyi 'lricrcsyl phosphate M E'IHYL ME'IHACRYLATE RESIN Dibutyl phthalate M incral spirits SH ELLAC M incral spirits Dibutyl phthalato MANILA GUM Mineral spirits Dibutyl phthalate STYRENE RESIN M incral splriis Dibutyl phthalate CO UMARONE-INDENE Butanol Linseed all For most purposes, a range of non-solvents of about 30 to 90% with a preferred range or about 50 or 60% upon the basis or the complete formula is satisfactory. though for special purposes lower and higher proportions may be employed.

same

The plasticizers may be added in any amount less than that at which the resin tends strongly to gel in the non-solvent. For most purposes about 25 to 100%, based on plastic content is satisfactory.

Pigments such as carbon black, titanium dioxide, white lead and others may be added in appropriate amounts (2 to 300% more or less) based on plastic content of the formula. The pigments may be dispersed in the suspension or may be dispersed in the plastic or resin solutions prior to comminution of the resin.

It will be evident that mixtures, in practically any proportion, e. 5. equal parts by weight oi any two or more oi the plastics herein disclosed. may be plastlclzed simultaneously, or two or more compatible pulverized and plasticized plastics may be admixed. Drying or semi-drying oils (scya bean, etc.) and resins may be added. Similarly compatible plasticizers may be admixed.

For example, suspensions of "Vinylite H, i. e. copolymer of vinyl chloride and vinyl acetate, may be modified with appropriate amounts (10 to 50%, more or less) or normal butyl methacrylate resin, Bakelite modified with ester gum, or simply with ester gum. Nitrocellulose may be modified with glycerol phthalates, ethyl cellulose, vinyl acetate, gum damar or ester gum modified phenolic resin. Ethyl cellulose may be modified with methyl acrylate resin, cellulose acetate, phenolic resin, coumar, damar, rosin, alkyd resins, etc.

The modifiers may be added to the base Plastic at any time, e. g. beiore solution preparatory to precipitation of the powder, or to the solution, prior to precipitation. In some cases suspensions of the two plastlcsmay be admixed or in event that the added resin is soluble in the non-solvent tor the base resin, a suspension oi the base resin in a solution of the added resin may be formed.

Alkyds, notably the soft, modified alkyds, may be dissolved in suspensions of vinyl acetals or vinyl acetate-vinyl chloride copolymers, in mineral spirits or other non-solvents. When the liquid evaporates the dissolved resin sets either as a binder about the particles of solid resin or forms a compatible mixture therewith, It is, or course, desirable that the proportion of dissolved resin be not so great as to induce gelation of the suspension. In most cases, 5 or based on total resin content or more can be added safely.

Solvents in limited amounts may be added to suspensions of plastics in non-solvents. A par- .ticularl interesting system involves a combination of a relatively volatile non-solvent and a solvent oi lower volatility. As the non-solvent evaporates, the concentration of solvent increases to such extent that the plastic becomes so softened as to induce cohesion of the particles into a, homogeneous mass. Subsequent fusion of films of such material by heat may not be required.

A typical system of this type would comprise a suspension of nitrocellulose plasticized with dibutyl phthalate and suspended in high test gasolene to which was added amyl acetate as a solvent ior the nitrocellulose. A typical formula of this type might be approximately as follows:

Example I Per cent Nitrocellulose (powder) 20 Dibutyl phthaiate 10 Suspension medium 70 The suspension medium comprising:

Amyl acetate 10 Examples in which the low volatility solvent is omitted are:

Example 1'] Per cent Partial poly-vinyl butyral powder 14 Dlbutyl phthalate 6 Titanium dioxide pigment 20 Petroleum spirits Example III Per cent Partial polyvinyl butyral powder 21 Dibutyl phthalate 9 Petroleum spirits '70 Example IV Per cent Partial polyvinyl butyral or acetal powder 14 Dlbutyl phthalate 6 Carbon black 3 Petroleum spirits 77 Example V Per cent Copolymer of vinyl chloride and acetate powder 20 Dibutyl phthalate '1 Tricresyl phosphate 3 Normal butyl methacrylate l0 Mineral spirits 60 Example VI Per cent Copolymer of vinyl acetate and vinyl chloride (powder) 20 Ethyl cellulose (powder) l0 Tricresyl phosphate 'l Dibutyl phthalate 3 Mineral spirits 60 The composition was applied by spray to metal panel and baked for 20 minutes at C. to provide a hard and strongly adherent film.

In any of the examples as well as in other applications of the invention dispersing agents such as sulfonated castor oil or sodium salt of dibutyl naphthalene sulfonate in small percentages may be added to promote and maintain dispersion of the plastic particles.

It will be apparent that films after drying may be simply sprayed with a volatile solvent to provide homogeneous films. Objects coated with the dispersed plastics may be passed through chambers filled with solvent yapors or mists to produce softening. Thus films of the material in Examples I to V1, instead of being baked to induce plastic flow and coalescence oi the particles, may be merely wet with acetone or other solvent or exposed to vapors thereof, or subjected to heat and/or pressure as by a roll.

Suspensions of partial polyvinyl acetal resin the grade used in safety glass in mineral spirits and about 30% of a compatible plasticizer such as triglycol dihexoate may be spread upon glass plate and dried. The plates may then be superposed without cements and subjected to a temperature of 100 C. or upward and to direct fluid pressures of 10 or 15 atmospheres to cause them to adhere, thus providing safety glass of high strength. v

Suspensions of plastics in solution of plasticizers in non-solvents for the resin, for instance those of Example III, or any of the plastics contemplated for suspension, may be spread upon the traveling surfaces of drums or bands of polished chromium or other stripp ng surfaces and baked to provide films that may be removed by stripping and used as a reinforcement ior'safety glass or for other purposes. Suspensions of resins without plasticizers may also be employed to form films.

Suspensions of the plas ics may be added to paper pulp as a size or may be spread upon sheets of paper to give a surface finish.

Example VII Percent Partial polyvinyl butyral resin (powder) i 21 Dibutyl phthalate 9 Kerosene 70 The suspension was spread with a blade upon a, sheet of paper. The sheet was baked at 100 C. to evaporate the kerosene and to provide an adherent, water-resistant, low gloss coating excellently adapting the paper for use as a wrapping for food products, such as cheese and the like.

Cloth, such as cotton or linen or rayon, may be coated or sized with vinyl chloride acetate copolymer, vinyl acetal or other resin in similar manner, or fabrics may be dipped in a thin suspension and then wrung. Loosely woven fabrics such as are used as liners in collars or neckties may be permanently sized with a permanently thermoplastic resin of the type of partial polyvinyl acetal as described in Example VII, or of the copolymer of vinyl chloride and vinyl acetate as disclosed in Example V, to provide a product that will withstand repeated laundering and ironing and will bond the inner and outer layers together.

Suspensions. such as herein described, may be applied as coatings over films of regenerated cellulose, cellulose acetate, cellulose nitrate, casein. rubber hydrochloride and the like impermeable fims, and the particles dried and coalesced by flash heating or by application of solvents or solvent vapors to increase resistance to moisture, solvent vapors, or to provide surfaces that can be united by heat or solvents to provide wrappers for food products or other merchandise. The suspensions should be made in non-solvents for the films to be coated.

In a further application of the invention, suspensions of plastics with or without fillers such as wood flour, paper pulp or the like in nonsolvents as herein described may be applied to porous moulds of appropriate contour. The liquid medium is absorbed in, or drained out of the mould to leave films of resin that follow the contour of the mould. The resin may be consolidated by heat. The mould may be removed, or retained as a reinforcement in the finished body.

10 Example VIII A mould may be formed of plaster of Paris or the like and illed or partially filled with a paste or slurry of a finely-divided, thermoplastic resin su'eh as Vinyl 2:" (partial polyvinyl butyral) in mineral spirits. A plasticizer such as dibutyl 'phthalate in appropriate amount, e. g., 20 or 30%, based on resin, fillers such as wood pulp in amounts of for example 40 or 60, based on total solids may be added. The slurry in proper amount is poured into the mould and let stand a few minutes. The excess is then poured off. The mould with the desired coating therein is left to stand for an hour or longer and the article in it is then sprayed with ethyl alcohol. After it has stood a further period of several hours the moulded article is removed and baked at 100 C. or thereabout to form a coherent homogeneous mass.

In order to provide an improved flatted varnish, resins. such as a Vinyi.ite X" or Vinylite H" or ethyl cellulose in suspension in a nosolvent, as herein described, may be admixed with drying oils or other paint or varnish-forming material which is a non-solvent for the suspended plastic in amounts of about i to 20%. based on the total non-volatile content. Films of oils or varnishes so treated are of excellent, non-glossy appearance. They possess excellent strength and adhesion. They may be baked without loss of the flatting effect and are in other respects highly satisfactory. The suspensions of resins as herein described, for instance in Examples I to V1, are highly suitable for use as flatting agents in drying oils, either alone or when compounded with pigments, modifiers, etc.

For purposes of preparing a printing ink, a very finely-divided thermoplastic plastic, e. g., ethyl cellulose or the like, most of which will pass a screen of 200 to 1000 mesh, or even finer, is suspended, preferably along with a plasticizer, in a non-solvent for the plastic. Coloring matter, such as carbon black. dye, etc., may be incuded in amounts of and upward, based upon plastic content. Drying oils, such as linseed, tung and the like may be included in amountsof 20% or more upon a like basis. The formulations given in Examples IV and VI. to which carbon black or other coloring matter in appropriate amount has been added may be employed. These inks, with enough non-solvent to give proper fluidity, are applied to paper, e. g., newspaper stock byconventional presses. The porous paper immediately absorbs much of the 55 dispersing liquid, leaving the particles oi plastic adhering to the paper in the desired pattern.

The print is quickly passed over hot rolls or under radiant heaters to rapidly evaporate the solvents and to fuse down the plastic into adherent 60 homogeneous state upon the paper. The paper may then be cooled by blasts of cold air or by passing it over cold rollers.

Drying of the film in printing is very rapid and at most requires but a few seconds. This is 65 of great advantage in high speed printing because it admits of high production with relatively small drying apparatus. It also reduces blurring of print.

It is to be understood that webs of paper, cloth 70 or other material, after printing, coating or im pregnation, may be passed through chambers filled with vapors of a volatile solvent designed temporarily to soften the plastic the point at which particles will cohere to eacl ...her and ad- 75 here to the Pap In some instances the use of a plasticizer for resin is not required. For example, it may not always be required in the production of plastic suspensions suitable for use as prin i inks. as coatings for paper or cloth, or other surfaces; a suspension oi finely-divided resin such as vinylite "X" orljH" in a volatile, plasticizer free, nonsolvent for xthe resin may be applied to porous bodies or other surfaces and then freed oi soivents and the resin sintered down to coherent state, by application of heat.

What I claim is: I

1. A coating composition comprising a finely pulverulent thermoplastic organic plastic, a. volatile liquid which is a non-solvent for the plastic in which the particles of the plastic are suspended and a permanent, compatible plasticizer for the plastic dissolved in said liquid, said plastlcizer being present in substantial amount but less than an amount at which said plastic tends strongly to gel in said liquid non-solvent.

2. A coating composition as defined in claim 1 in which the plastic is a vinyl acetal.

3. A coating composition as defined in claim 1 in which the organic plastic i cellulosic.

4. A coating composition as defined in claim 1 in which the organic plastic is a polymer of a polymerizable vinylic compound.

5. \A method oi. coating 9. surface which com-- pr applying thereto a film o! a coatingcomr .tion comprising a finely pulveruient thermoplastic organic plastic, a volatile liquid which is a non-solvent tor the plastic in which the particles oi the plastic are suspended and a permanent, compatible plasticizer tor the plastic dissolved in said liquid, said plasticizer being present in substantial amount but less than an amount at which said plastic tends strongly to gel in said liquid non-solvent.

6- A method of coating is surface which comprises applying to the surface a. film o! a suspension of finely divided thermoplastic organic plastic material in suspension in an organic liquid medium which is a non-solvent tor the plastic, said medium containing dissolved therein a compatible plasticizer for the plastic. the liquid medium being present in an amount within the range of to per cent based on the complete formula and the plasticizer being present in an amount within the range of 25 to per cent based on the content 0! said organic plastic material therein.

'7. A method as defined in claim 6 in which the liquid medium is present in an amount within the range or 60 to 60 per cent of the complete formula.

8. A method as defined in claim 6 in which the organic plastic material is ceilulosic.

9. A method as defined in claim 6 in which the organic plastic material is a vinyl compound.

JOHN D. JENKINS.

Disclaimer Re. No. 22,812.-Joim D. Jenkins, Milwaukee, Wis. PLABTICIZATION or PLASTICS. Patent dated Dec. 3, 1946. Disclaimer filed Mar. 15, 1948, by the assignee, Pittsburgh Plate Glass Company.

Hereby disclaim all coatinglcompositions covered b claims 1 to 4 inclusive of said patent except those in whic the combination of pu verulent lastic and plasticizer, but for the presence of the non-solvent, would result in the ge ling of the plastic particles to the point of coherence;

And disclaims all methods of coating covered by claim 5 except those involving the application of a film of a coating composition in which the combination of pulverulent p astic and plasticizer, but for the presence of the non-solvent, would result in the gelling of the lastic particles to the point of coherence;

And further disclaims all methods of coating covered by claims 6 to 9 inclusive except those involving the application of a film 0 a suspension in which the combination of finely divided lastic and plasticizer, but for the presence of the non-solvent, would result in the gelling of the plastic particles to the point of coherence.

[Oflicial Gazette April 13, 1948.]

Images