US3085731A

US3085731A - Container with cleavable coating on interior surface

Info

Publication number: US3085731A
Application number: US589809A
Authority: US
Inventors: Wilkins Colbert William
Original assignee: Owens Illinois Glass Co
Current assignee: OI Glass Inc
Priority date: 1956-06-06
Filing date: 1956-06-06
Publication date: 1963-04-16
Anticipated expiration: 1980-04-16

Description

Apnl 16, 1963 c. w. wlLKxNs 3,085,731

CONTAINER WITH CLEAVABLE COATING ON INTERIOR SURFACE Filed June 6, 1956 INVENTOR l Www/M ATTORNEY CGNTAINER WHTH CLEAVABLE COA'HNG 0N NTERIQR SURFACE Colbert William Wilkins, lacksonville Beach, Fla., as-

signor, by mesne assignments, to Owens-Illinois Glass Company, Toledo, hio, a corporation of Ohio Filed .lune 6, 1956, Ser. No. 589,809 6 Claims. (Cl. 229--3.1)

This invention relates to cleavable release coatings and particularly pertains to coating compositions for application to the inside walls of fiber board containers, and to such containers having coatings -on the inner Walls.

A general object of the invention is to provide improved release coatings `and coating compositions, and specific objects include the provision of coatings and coating compositions Which are less costly, which are eifective in decreased thickness, which are highly heat resistant, both in that the coating itself is not adversely affected by high temperatures and in that the container itself is protected from damage from high temperatures of the contained material by the coating, which do not crack or peel away from the container Wall material, which are more easily applied to the container Wall material, which permit rolling or stacking of coated material on itself with minimized sticking of the coated face to the next layer of material, which do not undesirably contaminate the product which it is desired to package in the container, and which cle-ave within the coating to release the product from the container.

The invention nds special applicability to the art of packaging asphalt, and other materials which present similar packaging problems, for example, resins and bitumens generally, latex, and the like, such as may be termed meltable gummy solids, `and which are ordinarily melted at elevated temperatures for pouring into the containers and thereafter permitted to cool and solidify.

While fiber board cartons and drums seem presently to offer the most satisfactory and economic containers for asphalt and similar products, it will be understood that the coatings of this invention may be used on wooden barrels or on containers made of other materials and of other types of construction.

Many release coating mixtures have been heretofore proposed, among which are, for example, wax emulsions containing, typically, bentonite, emulsifying agents and graphite, and various starch-containing mixtures. The coatings formed of such prior art mixtures, however, have left much to be desired, in that clays of acceptable quality are expensive, in most instances considerable thickness of the coating has been necessary, the resistance to cracking and peeling away of the coating has been low, necessitating great care in handling of the coated containers, the coatings have been ditlicult and expensive to apply and often ineffective for the intended purpose, or the coating was itself destroyed by hot materials o-r proved ineffective to protect the container from damage from hot materials. A particularly diflicult problem has been the provision of a coating which will stand up and which will protect the container when the container is filled with hot dead-level asphalt.

The novel features which are believed to be characterf istie of this invention are set forth with particularity in the appended claims. yThe invention itself, hofwever, both as to its organization and method of operation, together with further objects and advantages thereof, may best be under.

3,085,731 PatentedA Apr. 16, 1963 stood by reference to the following ydescription taken in connection with the 'accompanying drawing, in which:

FIG. l is an isometric view of a container of -a type useful in this invention;

FIG. 2 is a fragmentary sectional view -of a portion of a container wall having a coating thereon in accord with this invention; and

FIG. 3 is a fragmentary sectional view of a portion of a container wall having a double coating thereon in accord With a modification of this invention.

As seen in FIG. l, container 1 comprises a kraft fiber box or carton adapted to contain asphalt or the like. In accord with the invention, the inner walls 2 of the container are coated with a cleavable coating, whereby the container may be torn away from a contained hard block of asphalt when it is desired to use the asphalt, as at a construction site. End Wall top flaps 3 and side wall top aps 4 are also preferably coated with the cleavable coating.

The container is typically formed of a double wall tluted kraft board 5 as seen in FIG. 2 and carries a coating 6 comprising, as later described in detail, a synthetic resin binder material having small solid particles dispersed therein. The exposed coating surface 6 has characteristic tackiness, at least at elevated temperatures, and bonds or adheres to the material to be contained by the container.

FIG. 3 discloses a modification of the invention wherein solid kraft ber board Wall 7 carries a base or bottom coat 8 of a synthetic plastic in which are dispersed small solid particles and, in overlying relation to the base coat, a top coat 9 of a synthetic resin having an exposed surface 9 which is presented to the material to be contained in the container yof which the Walls are formed of board 7 L The surface 9 is preferably non-tacky and hard -at room or atmospheric temperatures, but becomes tacky at elevated temperatures.

It has been found that certain substances heretofore employed in release coating formulations can be profitably employed in the present invention, but certain important departures from previous teachings have resul-ted in a much improved coating, which can be deposited at arate as low `as six pounds per one-thousand square feet and yet function effectively, which is substantially less costly than the most nearly comparable coating, and which will, in accord with preferred embodiments of this invention, operate satisfactorily not only to release hot dead-level asphalt poured into the container at about 400 F. but also to protect the container from damage from the high temperature of the contained asphalt.

'Either of two systems may :be employed in practicing this invention, a single coat system, as shown in FIG. 2,' or la double coat system, as shown in FIG. 3. In the former, .a single :coat 6 may be spread by any of several methods on the surface of the Wall material, Which may be, typically, either double `wall corrugated or solid kraft liber board. The coating material, yas spread, will cornprise a slurry wherein Water is employed to carry in emulsion a binder material, such as an acrylic resin, and in suspension, small particles of solid materials as further explained hereinafter. The material may also 'comprise subsidiary `chemicals for perform-ing, for example, wetting, -defoami-ng, thickening, coloring, rand plasticizing functions.

A preferred formulation for a coating material for single coat application to graft fiber board comprises the following in parts by weight:

Example l Iarts by weight Component Function Liquids Solids Water 80 Base uid carrier.

Polyp)hosphate (water solu- 2.6 4 Wetting agent.

tion

Calcium stearate Slurry stabilizer. Carbon black (water disper- 4.0 0 Coloring and cleavage.

sion). Green slate Tale (325 mesh) In the formula of Example I, the water acts as a carrier for the solids and the polyphosphate and calcium stearate dissolve in the Water, the resin binder emulsifies in the water, and the carbon black, green slate, talc and mica comprise discrete solid particles in the slurry, suspended in the water. The amount of water is, of course, variable to provided a more dense or less dense slurry, with more or less liow, as required in the particular method of applying the coat, and as may be appropriate to drying time and method, although sufficient water should be included to carry the solid particles in free suspension. Ihe water dries from the finished coating, and in the slurry the water serves primarily as a medium for retaining the other materials in mechanically spreadable form or condition.

The amount `of polyphosphate is governed primarily by the amounts yand nature of the solid particles which must be wetted to provide a suspension. Accordingly, in Example I, sufficient polyphosphate is included to insure wetting of the carbon black, green slate, talc and mica particles. It should be understood that in the preparation of slurries in accord with this invention only a sufficient amount of wetting agent should 'be employed to decrease the surface tension of the water to the point at which substantially Iall of the solid particles become wetted. The polyphosphate wetting agent actually employed in the formula of Example l was `a mixture off hexametaphosphate and heptametaphosphate, but sodium hexametaphosphate, sodium salt of alkyl aryl sulfonate plus sulphate, polyhydroxyaloohol, ammonia, and certain sulphates and phosphates of higher synthetic alcohols have been found entirely satisfactory when used alone, or in combination of two or more, in approximately equivalent quantities, that is, quantities that provide approximately the same reduction in surface tension of the solution. Since certain grades and :sizes of the solids employed in the formula may be more or less difficult to wet, it is appropriate to increase or decrease the amount of wetting agent accordingly as is Well known in the art. It will be understood that the wetting agents mentioned are typical, and that these or other wetting agents cornpatible with the other materials of the slurry may be employed as desired in the formula of Example I and in the slurries hereinafter specified.

The carbon black provides coloring which is particularly appropriate in the packaging of asphalt or Aother black or nearly black materials. It has been found also that carbon black 'assists the internal cleavage action of the coating, and if carbon black is omitted, as, for example, when a black color is not desired, it maybe found desirable slightly to increase the :amount of one or more of the other cleavage solids, such as the green slate, talc or mica. Alternatively, if increased blackness of the coating is desired, the quantity of Acarbon black may be increased and the quantity of one or more of the yother cleavage solids may be accordingly slightly decreased.

Economic considerations dictate that no more than the minimum amount of carbon black be employed to provide the necessary coloration, and economics may further require that some of the blackening function be performed by graphite, preferably in the form of small flakes of the order of 325 mesh. Thus it has little effect on the action of the coating if graphite fiakes are substituted for part or all `of the carbon black, or even if up to a few parts of graphite are substituted for a minor portion of one or more of the cleavage solids. A specific formula comprisin g substantial amounts of graphite and bentonite clay, for example, is given hereinafter in Example II.

The internal cleavage function yis obtained primarily 4because of the inclusion in the coating of what are herein referred to as cleavage solids, and these solids in the above `formula comprise green slate, mica and talc, although, as explained, the cleavage function 4is further raided by the carbon lblack and would be aided by any added or substituted ake graphite.

While the use of talc in release coatings has been previously suggested, the function of the talc in the present invention differs from that in previous proposals. Mica has been employed heretofore in certain wax coating formulations to increase the viscosity of the wax and to bridge over pores in the wax film. The primary functions of the muscovite mica (as distinguished from -phlogopite mica, for example, which has a different chemical structure and crystalline shape) in the present release coating, however, a-re to provide heat insulation and internal cleavage or lm splitting characteristics. Unexpectedly superior results have ybeen obtained with coatings comprising a high proportion of cheap green slate, which it has been found functions to assist the cleavage characteristics and the heat insulating characteristics 0f the mica and talc, while permitting a substantial reduc tion of the amounts of relatively costly talc and mica. The inclusion of green slate in the coating formulations herein described makes unnecessary the inclusion of the relatively much more expensive clay heretofore employed in many release coatings in relatively large proportions to give body and spreadability to the coating slurry. it has been found important that the amount of sand, even in `finely ground state, be maintained at a minimum in the coating, since even a very small percentage results in rapid ysettling out of the particles suspended in the slurry, thereby seriously reducing the internal cleavage of the resulting coating, and since small quantities of sand further result in severe erosion of the coating equipment. Sand-free clay is, of course, much more costly than the usual commercial grades. It is possible to formulate excellent release coatings, however, which contain sand` free clay to replace a few parts of any one of the three primary cleavage solids of the formula of the above table.

The theory of many prior release coatings has been to provide a coating to which the packaged material, such as resin, asphalt, or latex, will not adhere. The coatings of the present invention, however, are designed to adhere to the packaged material, at the upper face of the coating film, and to adhere strongly to the container wall at the undersurface of the film. Release action is obtained by cleavage within the film itself.

Unlike previous release coatings, the binder employed in this invention is both bendable and tacky after drying and after completion of any polymerization. The tack characteristics of the coating of Example I are imparted by the lacrylic resin, and a resin should be selected which exhibits tackincss at temperatures above about F. to F. but which has little tackincss below such temperature. A coating having the mentioned tackincss characteristics can be applied to the fiber board and dried thereon and the board may then be rolled without appreciable resultant sticking together of the turns of the roll, but when the container is formed and hot asphalt is introduced into the container, the coating is raised in temperature by the asphalt above the temperature at which the coating exhibits suflicient tackiness to adhere to the asphalt.

To prepare a coating composition in` accord with the formula given above, the wetting agent or `agents are first added to the proper amount of water, with slow agitation, and the carbon black is next added. With the addition of the green slate, mica and talc, the speed of the agitator is increased to between about 600 to 1000 rpm. for a commercial agitator, thereby to provide thorough mixing and smooth consistency. Finally the binder material is added with continued high speed agitation. A certain amount of foam is normally to be expected and this foam is preferably reduced or eliminated 'by spraying with antifoaming agents, such as a sulfonated oil or a naphtha. The amount of anti-foaming agent required will be negligible, has been found not to affect the final coating in any noticeable way, and its use is advisable only for making the handling of the slurry more convenient and to eliminate the waste and extra handling which would otherwise result from mechanical removal of the foam.

Coating material prepared in the specified manner in accord with the formula of Example I was spread by flowing on the upper surface of -a length of corrugated kraft fiber board, the board being fed under a Iwiper roll to limit the coating thickness. The coating material thickness was such as to contain substantially 8-10 pounds dry weight of material per one thousand square feet of coated surface. After drying for approximately two minutes at 300 F. and conditioning `at 72 F. at 50% relative humidity for two hours, the coating solids were measured, the coated fiber board was formed into containers and the containers were filled with Idead-level asphalt at about 400 F. The filled containers were then held for two hours at 250 F. and thereafter permitted -to cool. At attnospheric temperatures thereafter the containers were torn away from the solid asphalt blocks which had formed inside. The fiber board came away readily and completely from the asphalt andthe inner surface of the container walls was found to be still covered hy `a film of the coating. Even at corners of the container, no fibers of the kraft .paper board had become adhered .to the asphalt. The surfaces of the asphalt block were a dull very dark gray, almost black, indicating that a portion of the coating had become bonded to and remained on the asphalt.

It is believed, from the results of tests, from microscopic examinations and from theoretical analysis of the facts developed from the studies of lthe present and other coatings, that the muscovite mica which is included is primarily responsible for the excellent internal cleavage characteristics of the coating film 6. It is also clear that Ithe acrylic resin binds the coating securely to the ber board surface and tends to strengthen the surface by impregnation of the fibers, and that it causes adherence of the lm surface 6 to the lasphalt or other packaged material. Muscovite mica comprising very small plate-like particles so reduces the internal strength of the coating film that the lm may be cleft between its inner and outer surfaces. This cleavage action is aided appreciably by the inclusion of green slate as one of the solid components, although it would be expected that green slate, like sand, would greatly reduce the cleavage or release characteristics. It has been found that the amount of .green slate may not greatly exceed approximately the combined amount of mica and talc without-some reduction of desired cleavage characteristics. Green slate may be introduced up to approximately 70% ofthe total solids weight if the percentage of muscovite mica is maintained at at least 14% to produce a useful coating with good cleavage action. The introduction of green slate np to about 40% of the total weight of the total solids in suspension permits some reduction in the -amounts of much more costly talc required, thereby providing a substantial reduction in over-all costs over a coating with a high percentage of talc. Reduction in the proportion of talc may also be accomplished by the substitution of certain types of sand-free clay, and it has been found that the use of a kaolinite type of clay comprising particles in the form of flat plated crystals, such as that mined near McIntyre, Georgia, and sold by Edgar Brothers Company of Mc- Intyre, Georgia, as type ASP 900, having a particle size of about 2 micron, when used to replace part `or all of the green slate, permits a reduction in the amount of talc and a slight reduction in the amount of mica below the proportions given in Example I, as is more particularly exemplified hereafter in specic formulas.

The talc, green slate and mica yall contribute to the heat insulating properties of the film, which resulted in the avoidance of any damage to the fiber board in the hereinabove described experiment from 400 F. asphalt, for example. The green slate and talc seem to become oriented between plates of mica in a manner such that the heat insulation obtainable is comparable to that of a coating of equal thickness, and of the same total solids content, but in which mica was substituted for the talc and green slate.

Example II As a second example of a single release or cleavage coating material, a slurry may be prepared as outlined above having the following formula:

A third exemplary formula for a single coat material embodying this invention is as follows:

Example III Parts by Function weight Water Carrier. Sodium alkyl aryl sulfonate 3 Wetting agent. Sulfonated oil 1 Anti-foam.

Green slate 60 Filler and cleavage. Washed clay (AS 90 30 Do. Color 3 Color, Mica 22 Cleavage. Butadiene-styrene copolymer 1l Binder.

' Stabilizer.

Soap 1 It will be seen that the two formulas last set forth include somewhat less mica than the iirstformula, and that in each later instance a different binder resin is specified.

Thoroughly satisfactory results are obtained with the slurries of Examples II and III spread and dried as described above at a rate to forma coating of between 6 to about `12 or 14 pounds dry weight,l of solids per 1000 square feet of coated container wall surface. It will be seen, accordingly, that the m-inimumI weight of mica per 1000 square feet in a coating comprising between 7 and 8% of mic-a would be approximately 0.45 or 0.50 pound. More economic and higher quality coatings comprise from about 12% mica to 20% mica, giving labout one pound of mica per 1000 square feet of surface. As herein explained, the percentage of mica which can be employed with good results reaches a maximum practical limit of approximately 40%, and a coating of 12 or 13 pounds per 1000 square feet might, accordingly, comprise about 5 pounds of mica per 1000 square feet.

While coatings thicker than 12 pounds per 1000 square feet would be operative, economics dictates that the coating thickness should be no more than at this rate but should be as thin as experience may prove acceptably operative. Since from about 60% to 92% of the total solids weight may be cleavage, filler or release solids other than mica, the total weight per 1000 square feet for these materials may range from about 3.5 pounds to about l2 pounds.

For hot dead level asphalt the coating is generally somewhat thicker than `for mopping -asphalts, depending largely on the maximum temperatures involved. Thus, while a coating of only 3 or 4 pounds per 1000 square feet might suice if the coating contains at least about 14% mica for materials poured into `the container at 175 F.200 F., dead level asphalt introduced at 375 F., for example, would require a minimum of labout 8 or 10 pounds per 1000 square feet and the formula for the coating should comprise somewhat more than 8% of mica and should further comprises a resin which is not destroyed when heated to the region of 375 F. to 400 F. Double coats as described herein are generally preferred to single coats in high temperature dead level asphalt packaging.

While approximately 10 parts of resin emulsion is specified in each of Examples I, II and III, the parts of resin may be substantially increased, for example, to about parts, without thereby reducing the effectiveness of the coating. Increasing the parts of resin binder above about 10 parts may be found necessary or desirable to reduce any flaking of the coating which may be encountered.

The Mineralite mica of the muscovite type as employed in the coating compositions of this invention should be of very line mesh. Specifically, excellent heat insulation and cleavage characteristics of the coating and good spreading characteristics of the slurry are obtained with 1000 mesh mica, but appreciably less readily spread and less stable slurries and less effective coatings result from the use of mica having particle sizes greater than sizes corresponding to 325 mesh and particles as large as 250 mesh are not suitable, best results being obtained with particles of about 1000 mesh or smaller, such as 3000 mesh.

The Mineralite mica of the muscovite type is characterized by the fact that its individual particles are of a scale-like crystalline shape. It is believed that this physical characteristic is closely tied in with the excellent cleavage characteristics exhibited by the coatings under discussion. The chemical analysis of these mica flakes A specific mica which has proved highly satisfactory is mined near Kershaw, South Carolina, `and sold by Mineralite Sales Corp., 90 yPine Street, New York 5, N.Y., as -Mineralite 4X (1,000 mesh), Mineralite 3X (325 mesh) and Mineralite 5X (3000 mesh). Such mica is within the chemical requirements given above.

'Ihe clay Iprovided in Examples II and Ill is of the flat plated crystal type such as is found at and mined near McIntyre, Georgia, and which is commercially available as Edgar Brothers Company, Metuchen, NJ., type ASP-900 (2 micron size particles) and type ASP 400 (3 micron size particles). Example II shows the use of 80 parts of clay and only 9 parts of mica. It

has been found, as will be understood from a comparison of this example with others given herein, that this clay is superior to talc or other cleavage or filler materials in making the mica effective in the coating, both as to cleavage and heat insulating properties, and, while clay alone, without mica, does not provide the desired results, the amount of mica may be substantially reduced with use of substantial amounts of iiat plated crystal clay and ake graphite without thereby appreciably adversely affecting the action of the coating. In Example II, mica comprises only about 8% of the total solids. Because of economic considerations it is not practical to decrease the amount of mica to this minimum percentage, and better results are obtained and a less costly coating can be prepared if mica is included at not less than 10% or 12% of the total solids.

Green slate, sometimes called mineral stabilizer, useful in this invention comprises that mined near Fairmont, Georgia, of 325 mesh and sold by F. I. Funkhouser & Company, 138 W. Washington St., Hagerstown, Md.

Suitable tales are those of 325 mesh mined near Chatsworth, Georgia, and sold by Whittaker, Clark and Daniels, 260 Broadway, New York, 13, NY., as No. 1648 and No. 1767, and those mined near Alpine, Albama, and sold by Whittaker, Clark and Daniels, as Clatal Tale No. 2952 and No. 2953, the last mentioned, however, being of 200 mesh and somewhat less desirable in this invention.

Graphite No. 1132 sold by Jos. Dixon Crucible Co., Wayne & Monmouth Streets, Jersey City 3, NJ., is a commercially available 325 mesh graphite, and graphite No. 6580 is a 425 mesh graphite obtainable from the same source, each of which is adapted for use in this invention.

A carbon black which has been found suitable is that sold by Binney & Smith Company, Inc., of 380 Madison Ave., New York, N.Y., as Aqua Blak G, while Black B Paste sold by General Dyestutf Company of 2459 Wilkinson Blvd., Charlotte 1, N C., is a satisfactory black pigment. In the several specific exemplary formulas herein set forth, several diiferent wetting agents, anti-foam materials and stabilizers are mentioned, together with ranges of substitutes therefor. Such materials given in one formula may generally be substituted in the other formulas, although in slightly varying amounts depending upon the difficulty of wetting certain of the components, for example, although it will also be understood that ammonia should not be used as a wetting agent if the synthetic resin binder t0 be employed is incompatible with ammonia. Furthermore, it will be understood that the binder materials specified in any one formula may be substituted from one to another of the formulas in a single coat process. Particularly useful as the resin binder in any of the above examples are resin emulsions of the type comprising acrylate and methacrylate resin materials together with sufficient lower alkyl polyacrylate materials to provide tackiness in the final coat for temperatures above about to 170 F., but with the polyacrylate limited in amount whereby the coating is not tacky below the specified temperature. Also useful and satisfactory are butadiene-styrene copolymers, having relatively high butadiene content to provide tackiness of the coating above about F.

Somewhat to be preferred to the single coat film described hereinabove and shown in FIG. 2 is a double coat film as shown in FIG. 3 wherein the base coat composition applied to the fiber board, or other container material, comprise muscovite mica suspended in an aqueous emulsion of a binder material, such as an acrylic resin, in which mica alone may provide vthe release or cleavage characteristics, or in which up to a major portion of the mica may be replaced with a clay, bentonite, fullers earth, lampblack, talc, green slate, carbon black or graphite, or a combination thereof. In accord withI this invention, a base coat so constituted, as more particu larly set forth hereafter, may provide internal cleavage satisfactory for the release function, but it has been found -that the base coat may be much reduced in thickness, or in weight of solids per square foot of surface, by covering the base coat with a top coat 9 comprising a tough, flexible and pliable plastic material iilm. Suitable materials for this top film are vinylidene chloride-vinyl chloride copolymers, or acrylic-methylmethacrylate copolymers, or high styrene butadiene-styrene copolymers, or vinylidene chloride-acrylonitrile copolymers, as more particularly discussed hereinafter. The top film is preferably applied in emulsion form, and the emulsion preferably includes a thickening agent in suspension therein for the purpose of increasing the ease of handling.

Base coats 8 of a double coating may be generally similar to the single coats `6 provided in Examples I, II and III above. The following specific examples of base coat formulations have proved highly effective.

Example IV The preparation of this emulsion slurry is as described in connection with Example l, and an anti-foaming agent, as before, may be used in the course of mixing.

A base coat formulation yielding comparable excellent results is as follows:

Example V Parts by weight Component Function Liquids Solids Water 90 Carrier. Polyphosphate. 1. 76 0. 24 Wettmg agent. Protein dispersion. 4.1 0.9 Stabilizer. Lampblack 4 Coloring and cleavage. M" 35 Cleavage. Green slate (600 mesh). 80 Cleavage and filler. .Acrylic resin 6 4 Binder.

In the above Example V, in place of the 35 parts of mica and 80 parts of green slate, one may use 25 parts of mica, 25 parts of talc (425 mesh) and 67 parts of green slate, or one may use 35 parts of mica and 65 parts of talc.

As a further alternative the base coat formulation may comprise the parts of water, wetting agents, calcium stearate and resin binder specified in Example IV and Example V, but with 22 parts of carbon black dispersion (l1 parts of carbon black in l1 parts of water) and 55 parts of mineralite mica (1000 mesh). Since carbon black and muscovite mica are more expensive than talc or clay, and much more expensive than green slate, it will usually befound desirable to include at least 60 parts of green slate, and, in order to insure maintenance of the excellent cleavage characteristics, to include a minimum of approximately parts, or 412%, of mica.

Excellent cleavage characteristics of coating 8 are maintained with increased parts of muscovite mica in the formulas of Examples IV and V, with reduction of the parts of other solid constituents, but a noticeable and undesirable tendency of the mica to thicken the slurry to a dough-like consistency occurs when the proportion thereof is increased to more than approximately 40 parts,

or to more than approximately 40% of the total solids. The nature of the solids used may make possible slightly greater proportions of mica. For example, substantial increase in the amount of lampblack or carbon black may permit somewhat higher percentages of mica, but since lampblack and mica are high in cost, no practical purpose would be served by such increase in the amounts of these components. In formulations in accord with this invention, the maximum permissible percentage of muscovite mica to total weight of solids may, accordingly, be considered as approximately 40%, whereas the minimum percentage of the mica to obtain the cleavage action is substantially 7% to 8%. Lower percentages of mica, below approximately 17%, have been found to necessitate the inclusion of substantial amounts of costly graphite, carbon black, or talc, or combinations thereof, to replace, for example, the relatively inexpensive green slate, although it has also been found that greater percentages of ASP 900 clay may also permit reduction of the percentage of mica to approximately 12% or 14%. Example II gives a formula withk approximately 8% mica, but with high proportions of ASP 900 clay and graphite, whereas Example lll, with 18% mica, 52% green slate, 26% clay and 3% color, such as lampblack, and with no graphite, provides excellent cleavage characteristics with total solids costs considerably reduced. `lt has also been found that insuiiicent heat blocking characteristics of the coating result from the use of less than about 10% of mica and completely satisfactory heat blocking requires about 14% or more of mica, in percentage of the total solids, unless unecoriomically large percentages of clay or other expensive materials are employed.

Further specific examples of slurry compositions which are adapted for spreading on a container wall to form either a base coat for a double coat cleavable coating or a single cleavable coat are as follows:

Example VI Filler and cleavage.

Clay (ASPQOO)- 40 Muscovite mica 34 Cleavage. Calcium stearate l. Stabilizer. Butadiene-styrene copolymer emul- 20 Binder.

sion (Dow 512K) (48% resin).

l Solid weight.

In Example VI, the butadiene-styrene copolymer should be of the type having lower styrene percentages, that is, a styrene-butadiene ratio of `6 4 or 5.5-4.15. In the example given, the resin emulsion which is added forms a finished resin after setting and drying weighing 48% of the emulsion. As in the other examples given herein, the materials are listed in the preferred order of addition to the mixing vat, water being iirst placed in the vat and the remaining materials being thereafter introduced and mixed in the order indicated, although the order may be varied as desired. The wetting agents of Example VI will comprise, preferably, as added, a few parts of water, as may several other ingredients, whereby the final slurry may comprise some or 100 parts of water. The amount of Water may vary in different applications to produce a slurry of the desired ow characteristics for coating the specific container material with a coating of the desired thickness using the specific coating machine available. The amount of water specified is suiiicient to suspend, -dissolve and emulsify the specified quantities of the materials, however, and is appropriate to provide a slurry of substantially the correct spreadability for application to kraft paper board by means of a wiper roll spreading machine.

Example VII Parts by Function weight Water 80 Carrier. Polyphosphate l 0.1 Wetting agent. Sodium alkyl aryl sulfonate.- 1 0.3 Do. Clay (ASPQOO) 70 Filler and cleavage. Green slate 14 Do. Graphite 20 Coloring md cleavage. Muscovite mica 14 Cleavage. Calcium stearato 0.5 Stabilizer. Acrylic resin emulsion (40%) (Rohm l0 Binder.

& Haas IVN-80).

l Solid Weight.

Example VIII Parts by Function weight Water 80 Carrier. Polyphosphate 0. l Wetting agent. Polyoxethylene ether 0. 5 Do. Carbon blacl-: 4 Coloringr and cleavage. Green slate 65 Filler and cleavage. Muscovite mica.. 34 Cleavage. Calcium stearate. 1 Stabilizer. Acrylic resin emulsion (40%) (Rohm l0 Binder.

& Haas WN-80).

Several types of plastic or latex compositions have been found to be useful in base coat formulations for a double coat process and, in general, these types are useful in preparing a slurry for single coat application.

Specifically, in the single coat formulations of Examples I, Il and III, and in the base coats of Examples IV and V, the binder material may comprise acrylic resins, such as polymerizcd acrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, or mixtures thereof, or other polymerized acrylic resins of similar characteristics. The lower alkyl polyacrylates are generally softer than is desired, and polymethylmethacrylates are preferred. Binders having the desired characteristics for use in bottom or base coat formulations and for use in single coat formulations, may be prepared by the combining of an acrylate or methacrylate resin with sucient lower alkyl polyacrylates to provide a coating which exhibits tackiness at temperatures above about 170 degress F., but which, at lower temperatures, possesses the characteristic hardness of acrylate resins. As later explained acrylic-methylmethacrylate copolymers form suiciently hard films to be useful as top coats in a double coat application.

Single coats and base coats, in Examples I, II, III, 1V and V may comprise an acrylic resin combined with any of several other types of resins. Specifically, l part of a lower alkyl polyacrylate with parts of acrylonitrile-methacrylate copolymer is suggested in Example Il, and Vinylidene chloride-acrylonitrile copolymer is useful with plasticizers selected to reduce the film hardness. Care should be taken, however, that 4the plasticizer does not cause the material to be -destroyed by the temperatures of the material to be packaged. On the other hand, 4 parts of Vinylidene chloride to 1 part of acrylonitrile copolymer with little or no added plasticizer provides an excellent hard top coat.

Examples of acrylic resin copolymer and polyvinyl acetate copolymer emulsions which are commercially available and are suitable for bottom coats or single coats are AC-33, WN-77 and WN-SO manufactured by Rohm & Haas, Washington Square, Philadelphia 5, Pa. These emulsions may be employed with plasticizers to provide suicient softness and tack for bottom or single coats, but the AC-33 is suiciently soft and tacky without Vany added plasticizer, while the non-ionic acrylic resin emulsion WN-80 and polyvinyl acetate emulsion WN-77 may be used as the top coating material. Walpol-9301 supplied by Reichold Chemical Co., Inc., 525 N. Broadway,

12 White Plains, N.Y., is a polyvinyl-acetate homopolymer which provides a satisfactory base or single coat. This material should be combined, however, with a plasticizer to reduce brittleness and impart tackiness, for temperatures of about F. and above, such as dibutylphthalate or other compatible tacky alkyd resins.

It is important to control and limit the amounts of alkali salts in the slurry when using acrylate, methacrylate and some other acrylic resins, since it has been found that swelling of the resin may occur, and that a gel may be formed in the slurry, and, further, that a very soft film may result. Thus 4the mica, talc, clay, slate and other ingredients should be selected to comprise a minimum of alkali salts.

Example lll indicates that butadiene styrene copolymers are useful in single coats, and it has been found that they are also useful in base or bottom coats and in top coats. Top coats require materials of the higher styrene percentages, i.e. more than 60% styrene, but materials of lower styrene percentages, such as Plio 101A, Plio 102 and Plio 160, which are approximately 40% to 45% butadiene- 60% to 55% styrene emulsions supplied by Goodyear Tire and Rubber Co., 1144 E. Market Street, Akron 16, Ohio, are well adapted for use in bottom or single coats. 40% butadiene-60% styrene emulsions, as exempliiied by S12-K and 5l2-R of Dow Chemical Co., Midland, Mich., are satisfactory as bottom or single coats, as are the Chemigum 236 and Chemigum 246 butadiene-acrylonitrile emulsions of Goodyear Tire and Rubber Co.

Top coats 9 exhibiting desired characteristics include, in general, the resins previously mentioned. More speciically, suitable top coat resins are vinyl chloride, such as Pliovic 300 supplied by Goodyear Tire and Rubber Co., vinyl acetates, and vinyl chlorides, which polymerize to form suitably hard, non-tacky top coat films. If the lms formed of any of these resins are too brittle in the specic application, appropriate plasticizers may be added.

In the case of the specific exemplary commercial product Pliovic 300, the vinyl chloride should be polymerized in the presence of a catalyst to form a latex or resin prior to emulsiiication, and a highly effective top coat material comprises a high proportion, Le. 60%-65%, of vinyl chloride, with a relatively low proportion (40%- 35%) of Vinylidene chloride, plasticized with a modified polyacrylate. Excellent results are obtained with X-2l02 emulsion supplied by Dow Chemical Co., an emulsion of from about 50% to 35% Vinylidene chloride, with 50% to 65% vinyl chloride. Polyvinyl acetatevinylidene chloride copolymers are also suitable for top coats. Vinylidene chlorides provide medium hard films, and are most satisfactory as a top coat when mixed with a harder material, such as, for example, a vinyl material. Copolymers of polyvinyl acetate-acrylonitriles and of Vinylidene chloride-methylmethacrylates form suitably hard lm top coats, while acrylonitriles alone, which polymerize naturally, may be employed, as may polyvinyl acetates of low molecular weights. A commercial example of a suitable polyvinyl acetate is Rohm & Haas WN-77 emulsion, which it is believed, comprises, with the acetate, an acrylate copolymer.

With respect to the use of vinyl chloride-Vinylidene chloride resins in coatings in accord with this invention, it has been found that 50% to 70% vinyl chloride to 50% to 30% of Vinylidene chloride is an acceptable range for top coatings. The vinyl chloride tends to impart toughness or hardness and tensile strength to the lm, while more Vinylidene chloride tends to increase the ease of spreading at lower temperatures and increases the water resistance and tack of the nal coating. A top coat of not more than 40% Vinylidene chloride may be suitably plasticized with chemical and polymeric plasticizers such as tri-ethylene glycol di-2 ethylbutyrate, or with lower styrene butadiene-styrene copolymer emulsions, or with water-soluble plasticizers with high evaporative tendencies. In the last mentioned case, the heat of drying of the iilm facilitates evaporation and subsequent fusion of the copolymer. Examples of such soluble plasticizers are alcohols, such as glycerol or ethylene glycol, or their derivatives such as diethylene glycol monoethyl ether acetate. Approximately to 35 parts of the 100% plasticizer to 90 to 65 parts of the vinyl chloride-vinylidene chloride copolymer is generally appropriate.

In certain cases, it may be found desirable to harden the film and reduce its tackiness by the addition of a urea formaldehyde type of resin. Such addition might be desired, for example, with vinyl chloride-vinylidene chloride copolymers wherein the vinyl chloride is in the range of about 50%.

Vinyl chloride-vinylidene chloride may form a suitable base coat or single coat if plasticizer, for example, with synthetic latex.

An acetate resin material useful as a top coat is sold by Rohm & Hass as WN-77, and such material is exemplary of polyvinyl acetate-acrylate copolymers which form good top coats and which may, with suitable plasticizers, be used in a single coat or base coat formulation.

The high styrene butadiene-styrene copolymers, such as Pliolite 170 furnished by Goodyear Tire and Rubber Co. which comprises approximately 30% butadiene and 70% styrene, are useful either alone, or with other resins, as top coat materials.

Polyethylenes of molecular weights between about 1500 and 6000 may be emulsiiied for use in top coats, although polyethylenes of higher molecular weights are not readily emulsiable. Obtainable from Semet Solvay Petrochemical Division, Allied Chemical and Dye Corporation, 40 Rector Street, New `York 6, N.Y., are solid polyethylenes AC-6 (molecular weight 2,000), AC-7, AC-617 (molecular weight 1,500) AC-6l5 (molecular weight 5,000) which may be emulsiiied and which are useful as top coats.

Vinylidene chloride, 4 parts, to l part acrylonitrile copolymer, acrylic-methylmethacrylate copolymers, vinylidene, chloride-methylmethacrylate copolymers, and acrylonitrile are also useful as top coats.

While each of Examples VI, VII and VIII provide when applied an operable single coat on the container wall, a superior coating for the wall results from the application of a top coat to cover such single coat. A top coat emulsion for spreading on a base coat formed from the slurry of any one of Examples I through VIII, but which is particularly applicable to the base coating formed by the 'slurry of Example VI, comprises, as Example Vl(a), 250 parts water, 6 parts of starch, 1.5 parts sodium alginate, and 100 parts of 50% emulsion of vinylidene chloride-acrylonitrile copolymer. In this top coat mixture, the starch and the sodium alginate function only to thicken the mixture for more effective spreading, and neither of these materials perform any useful function in the finished coat. Upon kfilling a container so coated with hot dead-level asphalt it seems probable that the two thickening agents are destroyed, but whether or not destroyed, the top coat bonds satisfactorily to the asphalt and the base coat cleaves in the desired manner. Hence the small amount of starch present does not in any way Valter the cleavage function.

A top coat formulation specifically appropriate for application over a base coat formed from Example VII, but useful with the other base coats, if desired, comprises, as Example Vll(a), 250 parts water, 1.5 parts sodium alginate and 100 parts .polyvinyl acetate emulsion (Rohm & Haas WN-77).

A top coat mixture generally useful but specifically adapted for application to a base coat formed from Example VIII is as follows, Example VIII(a), 250 parts Water, 6 parts starch, 1.5 parts sodium alginate, and 100 parts acrylic resin emulsion (40%) (Rohm & Haas 14 WN-SO). As in Examples VI(a) and Vll(a), the starch and sodium alginate have no function in the iinished coating.

It will be understood that the resins herein mentioned as useful for single coats and for base coats are employed as binder materials emulsied in the slurriers containing suspended solids. The top coats as described herein may comprise a resin alone, without suspended solids. The top coats are preferably spread in emulsion form on top of the already formed and preferably dried or set bottom coat. It is practical with resins adapted for spraying, however, to apply the top coat by this method, rather than by a owing on of an emulsified resin, and other known methods of applying resin surface films could be employed if desired. As further indicated by the above examples, it is contemplated that various t-hickeners or other materials which have no function in the finished top coat may be utilized to provide an appropriate body to permit ready application of the top coat with the type of coating equipment to be used.

While the formulations and modifications thereof discussed above are intended for application by flowing the slurry onto a iiber board surface, to be smoothed, spread and limited in thickness by a wiper roll, it will be apparent to those skilled in the art that the viscosity of the slurry should be varied in accord with the desired method of application. A thicker material, for example, may be desired for brush coating, while a thinner material may be required for spray coating. Thinning is readily accomplished by the mere use of additional parts of water, and possibly by .a slight increase in the `amounts of wetting agents and of the calcium stearate. When the mixture is to be made thicker, however, further precautions are necessary to insure, with a reduction in the amount of water, that the solids will remain in suspension in the slurry.

While only certain preferred embodiments of this inrvention have been shown and described by Way of illustration, many modifications will occur to those skilled in the art and it is, therefore, desired that it be understood that it is intended in the appended claims to cover all such modications as fall within the true spirit and 'scope of this invention.

thetic resin binder material bonded to said wall, and further comprising, dispersed in said binder material, solid particles of between 200 and 3000 mesh of a material selected from the group consisting of clay substantially only of the kaolinite type, fullers earth, lamp black, liake graphite, green slate, carbon black and talc and mixtures thereof, said binder material being a anember of the group consisting of polymerized acrylic acid, polymerized ethyl acrylate, polymerized methyl acrylate, polymerized methyl methacrylate, polymerized ethyl methacrylate `and copolymerized mixtures thereof, and acrylonitrile-methacrylate copolymer, butadienestyrene copolymer, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer and polyvinyl acetate, and mixtures thereof, the solids content of said resin binder being present in proportions by weight between about 37.5% of the total solids content of the named substances Vand said mica being present in proportions by weight between substantially 7-40% of the total solids content of the named substances.

2. The container of claim 1, in which said resin binder is an acrylic resin.

3. A container for -hot dead level asphalt or the like having a wall the inner surface of which is protected by a sand-free cleavable coating consisting essentially of muscovite mica particles of between about 300 and 3000 mesh dispersed in an acrylic resin having sucient lower alkyl polyacrylate and higher alkyl acrylate copolymers incorporated therein to provide a tacky surface at temperatures above about 170 F. and a substantially nontacky surface below about 170 F., and further comprising dispersed solid particles of between 200 and 3000 mesh of a material selected from the group consisting of clay substantially only ofthe kaolinite type, fullers earth, lamp black, flake graphite, green slate, carbon black and talc and mixtures thereof, the solids content of said resin being present in proportions by weight between about 3-7.5% of the total solids content of the named substances and said mica being present in proportions by weight between substantially 7-40% of the total solids content of the named substances.

4. A fiber board container for dead-level asphalt or the like having a wall the inner surface of which is protected by a substantially sand-free cleavable base coat consisting essentially of a polymerized organic resin which is tacky at normal atmospheric temperatures and solid particle cleavage constituents comprising between substantially 740% by weight of plate-like shaped mica particles of particle size between substantially 300 and 3000 mesh, said resin being selected from the group consisting of polymerized acrylic acid, polymerized ethyl acrylate, polymerized methyl acrylate, polymerized methyl methacrylate, polymerized ethyl methacrylate and copolymerized mixtures thereof, and acrylonitrile-methacrylate copolymer, butadiene-styrene copolymer, vinylidene chloride-acrylonitrile copolymer, vinylidene chloridevinyl chloride copolymer and polyvinyl acetate, and mixtures thereof, the solids content of said resin being present in proportions by weight between about 3-7.5% of the total solids content of said resin and cleavage constituents combined and said wall being further protected by a top coat overlying said base coat and comprising a polymerized organic resin which is tacky at elevated temperatures of about 400 F. and above and which is substantially hard and non-tacky at temperatures below substantially 150 F.

5. A double coated fiber board container for asphalt or the like wherein the base coat on the inner surface of said fiber board consists essentially of a heat resistant substan tially sand-free internally cleavable coating containing muscovite mica particles, a particulate material selected from the group consisting of tlake graphite, carbon black, lamp black, clay substantially only of the kaolinite type, fullers earth, green slate, and talc, and mixtures thereof and a tacky binder selected from the group consisting of polymerized acrylic acid, polymerized ethyl acrylate, polymerized methyl acrylate, polymerized methyl methacrylate, polymerized ethyl methacrylate and copolymerized mixtures thereof, and acrylonitrile-methacrylate copolymer, butadiene-styrene copolymer, vinylidene chlorideacrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer and polyvinyl acetate, and mixtures thereof, said mica being present in the form of particles of a size between 300 and 3000 mesh, the solids content of said tacky binder being present in proportions by weight between about 3-7.5% of the total solids content of the named substances and said mica being present in proportions by weight between substantially 7-40% of the total solids content of the named substances, and wherein the top coat is disposed over said base coat and consists essentially of an asphalt-adherent coat selected from the group consisting of polymerized acrylic acid, polymerized ethyl acrylate, polymerized methyl acrylate, polymerized ethyl polyacrylate, polymerized methyl polyacrylate, polymerized vinyl chloride, polymerized vinyl acetate, polymerized vinyl alcohol, vinylidene chloride, acrylonitrile, polyethylene and polyvinyl acetate and copolymers thereof.

6. The container of claim 5 in which said top coat presents a tacky surface at temperatures above substantially 400 F. and presents a substantially hard and nontacky surface at temperatures below substantially F.

References Cited in the tile Vof this patent UNITED STATES PATENTS 1,916,970 Denning July 4, 1933 1,983,349 Dreyfus Dec. 4, 1934 2,183,711 De Witt Dec. 19, 1939 2,333,023 `Manor Oct. 26, 1943 2,396,633 Bernstein Mar. 19, 1946 2,426,316 Martin Aug. 26, 1947 2,453,880 Vanderbilt et al. Nov. 16, 1948 2,494,920 Warrick Jan. 17, 1950 2,518,359 Mohrer Aug. 8, 1950 2,525,071 Hardy et al Oct. 10, 1950 2,624,683 Bezman Ian. 6, 1953 2,626,941 Habeck Jan. 27, 1953 2,634,459 Irons Apr. 14, 1953 2,672,454 Rother et al Mar. 16, 1954 2,704,105 Robinson et al Mar. 15, 1955 2,751,366 Braendle June 19, 1956 2,804,205 Barton et al Aug. 27, 1957 OTHER REFERENCES Paint Manufacture, October 1942, XII, pp. 182-186. Paint Manufacture, December 1942, XII, pp. 224-225.

Claims

1. A CONTAINER FOR HOT DEAD LEVEL ASPHALT OR THE LIKE HAVING A WALL THE INNER SURFACE OF WHICH IS PROTECTED BY A SUBSTANTIALLY SAND-FREE CLEAVABLE COATING CONSISTING ESSENTIALLY OF PLATE-KIKE SHAPE MICA PARTICLES OF BETWEEN ABOUT 300 AND 3000 MESH AND DISPERSED IN A POLYMERIZED SYNTHETIC RESIN BINDER MATERIAL BONDED TO SAID WALL, AND FURTHER COMPRISING, DISPERSED IN SAID BINDER MATERIAL, SOLID PARTICLES OF BETWEEN 200 AND 3000 MESH OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF CLAY SUBSTANTIALLY ONLY OF THE KAOLINITE TYPE, FULLER''S EARTH, LAMP BLACK, FLAKE GRAPHITE, GREEN SLATE, CARBON BLACK AND TALC AND MIXTURES THEREOF, SAID BINDER MATERIAL BEING A MEMBER OF THE GROUP CONSISTING OF POLYMERIZED ACRYLIC ACID, POLYMERIZED ETHYL ACRYLATE, POLYMERIZED METHYL ACRYLATE, POLYMERIZED METHYL METHACRYLATE, POLYMERIZED ETHYL METHACRYLATE AND COPOLYMERIZED MIXTURES THEREOF, AND ACRYLONITRILE-METHACRYLATE COPOLYMER, BUTADIENESTYRENE COPOLYMER, VINYLIDENE CHLORIDE-ACRYLOONITRILE COPOLYMER, VINYLDENE CHLORIDE-VINYL CHLORIDE COPOLYMER AND POLYVINYL ACETATE, AND MIXTURES THEREOF, THE SOLIDS CONTENT OF SAID RESIN BINDER BEING PRESENT IN PROPORTIONS BY WEIGHT BETWEEN ABOUT 3-7.5% OF THE TOTAL SOLIDS CONTENT OF THE NAMED SUBSTANCES AND SAID MICA BEING PRESENT IN PROPORTIONS BY WEIGHT BETWEEN SUBSTANTIALLY 7-40% OF THE TOTAL SOLIDS CONTENT OF THE NAMED SUBSTANCES.