US2550232A

US2550232A - Method of coating metallic articles with vinyl resin dispersions

Info

Publication number: US2550232A
Application number: US754045A
Authority: US
Inventors: John W Donnell; Tator Kenneth
Original assignee: Industrial Lining Engineers Inc
Current assignee: Industrial Lining Engineers Inc
Priority date: 1947-06-11
Filing date: 1947-06-11
Publication date: 1951-04-24
Anticipated expiration: 1968-04-24

Description

April 24, 1951 J. w. DONNELL ETA METHOD OF COATING L METALLIC ICLES WITH ART VINYL RESIN DI RSIONS Filed June 1947 l5 3m. Q I 2 in. g ,l5 (in.

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' John W. Donnell 8 Kenneth Tater w W a 53 Patented Apr. 24, 1951 assert OFFiCE METHOD OF COATING METALLIC ARTICLES WITH VINYL RESIN John W. Donnell, East Lansing,

DISPERSIQNS Mich and Kenneth Tator, Sewickley, Pa., assignors to Industrial Lining Engineers, corporation of Pennsylvania,

Application 'June 11, 1947, Serial No. 754,045

7 Claims.

This invention relates to articles of manufacture having corrosion-proof coatings thereon and to the process for producing resinous corrosion-proof coatings on metallic articles of manufacture;

I-Ieretofore, films of corrosion-proof materials have been applied to metals in many different ways, the commonest being tobuild up a desirable thickness'by applying successive layers of the corrosion-proof material and heating such layers to remove solvents therefrom and to convert the corrosion-proof materials to their final form. Such practice is unsatisfactory as it is time consuming and the final product may have poor adhesion between layers or porosity in the thin individual layers.

An object of this invention is to provide an adherent corrosion-proof coating of a vinyl compound on metal articles of manufacture.

Another object of this invention is to provide for producing in a single application a corrosion-proof coating of predetermined thickness between 1% inch and inchof a vinyl compound.

; A further object of this invention is to provide for immersinga metal article in a supply of unheated viscous vinyl compound and solidifying a layer of predetermined thickness of the vinyl compound on the immersed metal article without detrimentally affecting the remainder of the supply;

A more specific object of this invention is to provide, in a process of producing corrosionprcof coatings on metal articles, for heating the metal article to a predetermined temperature and immersing the heated article in a supply of unheated viscous solvent-free vinyl base plastisol for a predetermined period of time to effect a solidification of the plastisol adjacent the v heated article to produce an of predetermined thickness of the solidified vinyl compound thereon, the solidified coating being adherent coating free of seams and flaws.

' Other objects of this invention will become apparent from the following description when taken in conjunction wit the accompanying drawing, in which:

Figure 1 is a schematic illustration of apparatus utilized in practicing the teachings of this invention,

Fig. 2 is a graph, the curves of which illustrate the relationship between the thickness of the coatings produced at different temperatures in practicing this invention and the eifect of the relationship of the volume to the surface area of the article on such coatings, and

rm, Sewicklcy, Pa, a

3 is a graph, the curves of which illustrate the effect of time on the thickness of the coatings produced at different temperatures for a given article of constant volume to surface area ratio.

In practicing this invention the articles to be coated are first cleaned as by sand blastingto remove scale, rust and the like from the surface thereof. The sand blasting also functions to etch the surface to thereby render it more receptive for receiving and retaining a coating thereon. After the surfaces of the article are thoroughly cleaned, a thin coating of a suitable primer is applied thereto as by dipping the article in a supply of the primer or brushing the primer thereon.

Different primers are well known in the art and can be successfully employed. For example, the primer may be a chlorinated rubber solution, or a solution of either vinyl resins or'vulcanized, natural or synthetic rubberor a coinbination thereof. In a preferred form for cooperating with the coating to be applied as described hereinaftenthe primer is a solution of vulcanizable synthetic rubber of the acrylonitrile type and vinyl resin.

The primer applied to the cleaned surface of the article bonds with the etched surface thereof being reacted when subjected to heat to provide a thin, solid coating. For example, the coating of the primer last referred to can be completely reacted by heating the primer coated article at a temperature of about 300F. for about 2 hours or may be only partially reacted by heating it for a shorter period of time to drive off the solvents thereof, the reaction being completed during the application of a corrosion-proof coating to be next described. v

The corrosion-proof coating of this invention is formed from a synthetic resinous thermoplastic composition such as vinyl plastisol. The vinyl plastisol is a dispersion of high molecular weight .resins, essentially vinyl chloride, in a suit thereto, there is a change in phase in that the as carried by the conveyor Referring to Figure 1, there is a diagrammatic illustration of apparatus employed in applying the plastisol to the articles which are provided with the primer coating. As illustrated, the apparatus generally comprises a furnace l0, and a continuous conveyor belt or chain 14 having hooks l6 thereon in spaced relation for holding the articles 18 which are to be coated. The furnace I is of sufficient size and length so that a number of the articles l8 will be contained therein at any given time.

The conveyor belt M is disposed for intermittent operation to be so lowered as it leaves the furnace I0 that an article 18 carried by the belt 14 may be dipped and held immovable within the supply l2 of vinyl plastisol as will be de scribed hereinafter. The articles [8 are so spaced belt 44 that as one supply I2, the next held in the furnace article is immersed in the and succeeding articles are In accordance with this invention, the articles l8 having the primer coating (not shown) thereon are carried into the furnace i0 where they are subjected. to sufficient heat to develop heat in the articles of between 225 F. and 350 F. depending on the size and shape of the articles H]. The relation of the volume to the surface area of the article being coated and the temperature to which the article is heated determines the thickness of the coating formed thereon for any given time of immersion.

During the heating of the articles in the furnace II] the primer coating is at least more completely reacted to give a solid film of the primer. When the required temperature is developed in the article 18, the belt H3 is intermittently actuated to advance one of the heated articles 18 directly from the furnace I0 into the supply 12 of the unheated viscous vinyl plastisol where the heated article I8 is held immovable for a period of time of from minute to 7 minutes depending upon the temperature of the article and the thickness of the coating to be produced.

When the heated article 18 is dipped into the vinyl plastisol and maintained immovable therein, it is found that the heat of the metal effects a more complete reaction of the primer if not heretofore completely reacted, and simultaneously therewith causes the adjacent layer of the vinyl plastisol to convert to the solid stage in adhering relation to the heated article. The conversion is outward from the surface of the article l8 so that by controlling the time of immersion the thickness of the adhering layer or coating 20 of converted plastisol can be controlled. During the immersion, it is thought that the heat of the metal causes the plasticizer to go into the vinyl resin to change its phase and that thereafter the heat causes a coalescence of the discrete particles of resin by natural fusion process.

By maintaining the article immovable in the supply I2 of vinyl plastisol, smooth, uniform coatings 20 are produced which are free from any detectable swirls, voids, overlaps or the like.

After the predetermined layer 29 of converted plastisol is formed on the article 18, the conveyor belt 14 is actuated to remove the coated article from the supply l2 and to advance another one of the heated articles l8 forward from the furnace l0 into the supply [2. As the coated article is removed from the supply 12, any excess 4 of unconverted plastisol is readily removed from the coated article by wiping such article leaving a smooth seamless and adherent coating 20 on the article.

Referring to Figure 2, the curves therein illustrate the efiect of the temperature of the metal articles on the thickness of the coating 20 of the converted plastisol for different volume'to surface area ratios as found in working with many different shaped and sized articles with a constant dip or immersion time of 2 minutes. The curves of Fig. 2 are self-explanatory and clearly show that as the volume to area ratio (V/A) increases, the heat content of the article so increases that for a given time of immersion the thickness of the coating formed on the article increases. Thus for any given metallic article having a predetermined volume to area ratio the thickness of the coating formed can be closely controlled by controlling the temperature developed in the article.

Referring to Fig. 3 of the drawing, the effect of the temperature of the heated article on the thickness of the coating formed on an article having a predetermined volume to area ratio of .1875 is illustrated for different lengths of time of immersion as indicated. Thus by developing a temperature in the article of 300 F. and dipping the heated article in the vinyl plastisol for 1 minute a coating having a thickness of .14 inch can be produced whereas if the time is extended to 6 minutes, a coating having a thickness of .20 inch is obtained. Little, if any, advantage is obtained by extending the dipping time beyond this period as the heat content is apparently dissipated or is so low at this point that it fails to convert additional plastisol to a solid.

On the other hand, if a thicker coating is required, then the article should be initially heated in the furnace to develop a higher temperature therein. Thus when a temperature of 350 F. is developed in the primer coated article which is then immersed and maintained immovable in the vinyl plastisol for about 5 minutes, it is possible to produce a coating of .25 inch thickness on the article.

In practice, it is desired-to maintain the heat of the article at not less than 225 F., as temperatures below that temperature will produce coatings of insufficient thickness. However, it is also necessary to maintain the temperature of the heated articles at not more than 350 F. as the coatings formed at higher temperatures have poor adhesion and contain voids resulting in uneven coatings. Preferably the heating temperature should be-maintained between 275 F. and 325 F. for best results.

After the adhering coating is thus formed on the article, the coated article is subjected to a further heat treatment or baking at a temperature between 350 F. and 375 F. for a period of time ranging from 4 min. to 4 hrs. depending upon the thickness of the coating and the article coated to effect the fusing of the solids of the film or coating and to impart strength to the resulting resilient coating. It has also been found that this latter heat treatment is also effective for completing the reaction of the primer if such reaction had not heretofore been completed.

In ourcopending application Serial No. 754,044, filed simultaneously herewith, there is a disclosure of the process of producing the resinous corrosion-proof coatings on metallic articles of large surface area. As disclosed therein the articles, such as plate stock, vessels and other metal covered thereby,

articles of manufacturewhich have largesurface areas have. the surfaces which are to be coated cleaned as by sand blasting to remove scale,

rust and the like, after which, a primer of the type disclosed herein is applied as by spraying or brushing. The large surfaces are preferably designated into smaller areas and marked with a heat responsive temperature indicating means, such as a temperature responsive crayon having a definite range of melting temperature. Heat is then applied as by means of a direct flame to one of the smaller designated areas until the temperature responsive crayon marks indicate that the metal of the designated area is heated to a temperature in the range of 275 F. and '350'F., which heating effects the reaction of the primer to a relatively solid layer. The-vinyl plastisol is then applied to the heated area, the heat of the metal converting the plastisol to the solid stage in adhering relation to the heated article. The adjacent small areas are similarly treated until the entire surface which-is to be coated is given a uniform coating, the adjacent areas being coated with a layer of the solidified plastisolwhich is free from detectable joints, marks or flaws. A further heat treatment of the coated article at a temperature between 350. F. and 375 F. is found to effect the fusing of the solids of the vinyl coating and to impart strength to the resulting resilient coating. This latter heat treatment also completes the reaction of the primer if not completed heretofore.

Corrosion-proof coatings ranging from to /2 inch can be readily formed on articles by following the teachings of this invention. Such coatings are also abrasion resistant, resilient and strong being very adherent to the surface of the article.

We claim as our invention:

1. The process of producing a corrosion-proof coating on a surface facture comprising, in. combination, applying a primer consisting of a solution of at least one substance selected from the group consisting of rubber and vinyl resins to the surface of the article to be coated, heating the article to develop a temperature therein between 275 F. and 355 F., immersingthe heated article while the article retains a temperature between 275 F. and 350 F. in a supply of unheated viscous compound comprising a solvent-free dispersion of vinyl chloride-acetate copolymer in a liquid plasticizer for a period of time of between minute and 7 minutes, the heat in the phase of the viscous compound closely adjacent to the metal to solidify a layer of the compound in adhering relation to the primer and removing the coated article from the supply, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer,

2. The process for producing a corrosion-proof coating on the surface of a metallic article of manufacture comprising, in combination, applying a polymerizable primer consisting of a solution of at least one substance selected from the group consisting of rubber and vinyl resins to the surface of the article to be coated, heating the article to' develop a temperature therein between 225 F. and 350 F. and at least partially polymerize the primer, immersing the primer coated surface of the heated article while the article retains a temperature between 225 F. and 350 F. ina supply of unheated viscous solventof a metallic article of manu F. and 350 of the metal effecting a change t 6 free vinyl compound consisting of a dispersion of vinyl chloride-acetate copolymer having 96% vinyl chloride in a plasticizer therefor, maintaining the heated article stationary in the unheated vinyl compound for a period of time of between minute and 7 minutes during which the heat of the metal effects the completion of the polymerization of the primer and simultaneously therewith effects a change in the phase of the vinyl compound adjacent the primer to solidify alayer of the compound in adhering relation to the primer and metal covered thereby, removing the coated article from the supply, thereafter removing unsolidified vinyl compound carried on the surface of the solidified layer when the coated article is removed from the supply to produce a smooth, seamless, tightly adhering, corrosionproof coating having a thickness of between 1% inch and inch on the metal article, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer.

3. The process for producing a corrosion-proof coating on the surface of a metallic article of manufacture comprising, in combination, applying a primer consisting of a solution of at least one substance selected from the group consisting of rubber and vinyl resins to the surface of the article to be coated, heating the article to develop a predetermined temperature between 225 F. therein, immersing the primer coated surface of theheated article while the article retains a temperature between 225 F. and 350 F, in a supply of viscous solvent-free vinyl compound consisting of a dispersion of vinyl chloride-acetate copolymer having about 96% vinyl chloride in a plasticizer therefor for a period of time of between minute and 7 minutes to eifect a change in phase of the vinyl compound adjacent the heated article to solidify a predetermined layer between inch and inch thick of the vinyl compound in adhering relation to the primer and metal covered thereby, removing the coated article from the sup ly, and thereafter heating the coated article at a temperature between 350 F. and 375 F. to fuse the solidsof the solidified layer. 7

' 4. The process for producing a corrosion-proof coating on the surface of a metallic article of manufacture comprising, in combination, applying a primerconsisting of a solution of vulcanizable synthetic rubber of the acrylo-nitrile type and vinyl resin to the surface of the article to be coated, heating the article to develop a temperature therein between 225 F. and 350 F. and

at least partially react the primer, immersing the primer coated surface of the heated article while the article retains a temperature between 225 F. and 350 F. in a supply of unheated viscous vinyl compound consisting of a dispersion of vinyl chloride-acetate copolymer having 96% vinyl chloride in a plasticizer therefor for a time of between minute and 7 minutes, the heat of the metal completing the reaction of the primer and simultaneously therewith effecting a change in the phase of the vinyl compound adjacent the primer to solidify a layer of the compound in adhering relation adjacent the primer and metal covered thereby, removing the coated article from the supply, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer.

5. The process for producing a corrosion-proof coating on the surface of a metallic article of manufacture comprising, in combination, applying a primer consisting of a solution of vulcanizable synthetic rubber of the acrylo-nitrile type and vinyl resin to the surface of the article to be coated, heating the article to develop a temperature therein between 225 F. and 350 F. and at least partially react the primer, immersing the primer coated surface of the heated article while the article retains a temperature between 225 F. and 350 F. in a supply of unheated viscous solvent-free vinyl compound consisting of a dispersion of vinyl chloride-acetate copolymer havin 96% vinyl chloride in a, plasticizer therefor, maintaining the heated article stationary in the unheated vinyl compound for a period of time of between A; minute and '7 minutes during which the heat of the metal effects the completion of the reaction of the primer and simultaneously therewith effects a change in the phase of the vinyl compound adjacent the primer to solidify a layer of the compound having a thickness of between inch and /2 inch in adhering relation to the primer and metal covered thereby, removing the coated article from the supply, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer.

v 6. The process of producing a corrosion-proof coating on the surface of a metallic article of manufacture comprising, in combination, applying a primer consisting of a solution of vulcanizable synthetic rubber of the acrylo-nitrile type and vinyl resin to the surface of the article to be coated, heating the article to develop a temperature therein between 225 F. and 350 F. and at least partially react the primer, immersing the primer coated surface of the heated article while the article retains a temperature between 225 F and 350 F. in a supply of unheated viscous solvent-free vinyl compound consisting of 50 parts by weight of vinyl chloride-acetate copolymer having 96% vinyl chloride and 50 parts by weight of a plasticizer therefor for a time of between A minute and '7 minutes, the heat of the metal completing the reaction of the primer and simultaneously therewith effecting a change in the phase of the vinyl compound adjacent the primer to solidify a layer of the compound in adhering relation adjacent the primer and metal covered thereby, removing the coated article from the supply, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer.

'7. The process of producing a corrosion-proof coating on a surface of a metallic article of manufacture, comprising, in combination, applying a primer consisting of a solution of at least one substance selected from'the group consisting of rubber and vinyl resins to the surface area of the article to be coated, heating a portion of the area to be coated to develop a temperature therein between 225 F. and 350 F., applying 'a layer of unheated viscous compound comprising a solvent-free dispersion of vinyl chloride-acetate copolymer in a liquid plasticizer to the heated portion of the area to be coated while the heated portion retains a temperature between 225 F. and 350 F., the heat of the metal effecting a change in the phase of the viscous compound to solidify the layer of the compound from the metal outwardly in adhering relation to the primer and metal covered thereby, and thereafter baking the coated article at a temperature between 350 F. and 375 F. to fuse the solids of the solidified layer.

JOHN W. DONNELL. KENNETH TATOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Powell, Vinylite Resin Dispersions, Off. Digest N0. 263, D80. 1946, pgs. 696-702.

Claims

1. THE PROCESS OF PRODUCING A CORROSION-PROOF COATING ON A SURFACE OF A METALLIC ARTICLE OF MANUFACTURE COMPRISING, IN COMBINATION, APPLYING A PRIMER CONSISTING OF A SOLUTION OF AT LEAST ONE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF RUBBER AND VINYL RESINS TO THE SURFACE OF THE ARTICLE TO BE COATED, HEATING THE ARTICLE TO DEVELOP A TEMPERATURE THEREIN BETWEEN 275* F. AND 350* F., IMMERSING THE HEATED ARTICLE WHILE THE ARTICLE RETAINS A TEMPERATURE BETWEEN 275* F. AND 350* F. IN A SUPPLY OF UNHEATED VISCOUS COMPOUND COMPRISING A SOLVENT-FREE DISPERSION OF VINYL CHLORIDE-ACETATE COPOLYMER IN A LIQUID PLASTICIZER FOR A PERIOD OF TIME OF BETWEEN 3/4 MINUTE AND 7 MINUTES, THE HEAT OF THE METAL EFFECTING A CHANGE IN THE PHASE OF THE VISCOUS COMPOUND CLOSELY ADJACENT TO THE METAL TO SOLIDIFY A LAYER OF THE COMPOUND IN ADHERING RELATION TO THE PRIMER AND METAL COVERED THEREBY, REMOVING THE COATED ARTICLE FROM THE SUPPLY, AND THEREAFTER BAKING THE COATED ARTICLE AT A TEMPERATURE BETWEEN 350* F. AND 375* F. TO FUSE THE SOLIDS OF THE SOLIDIFIED LAYER.