US 3200005 A
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Description (OCR text may contain errors)
Aug. 10, 1965 G. c. BAUER 3,200,005
PAPER PRODUCTS COATED WITH VINYL; RESIN AND WAX Filed May 28. 1962 ANTIBLOCKING POLYVINYL W AGENT I REsIN EMULSION-DISPERSION p p OR COATING PAPERBOARD STEP WET COATED PRODUCT DRYING STEP COATED PRODUCT OF REDUCED MOISTURE CONTENT BAKING STEP BAKED PRODUCT COOLING STEP FINISHED PRODUCT FIGURE I wAx AND ANTIBLOCKING AGENT 2- POLYVINYL REsIN LAYER 3- PAPER OR PAPERBOARD SHEET INVENTOR.
2 GERALD 0. BAUER A TTORNE Y a corporation of Michigan Filed May 28, 1952, Ser. No. 193,073 Claims. (Cl. 117-15) The present invention relates to novel coating compositions, fibrous cellulose sheet materials coated therewith, and to a process for producing the said coated fibrous cellulose sheet materials, and is especially concerned with the use of a chlorine-containing polyvinyl resin, wax and anti blocking agent in a multi-step process for the production of glossy, non-adhering, send-resistant, moistureproof products having a two-layer coating on one or more surfaces thereof.
Frozen foods, e.g., frozen poultry and ice cream, are often retailed in paper or paperboard packages. In processing, these products are usually introduced into the containers in an unfrozen state and frozen therein. After retailing, the frozen foods are usually removed from their containers while still frozen, either to be served or thawed. It is highly desirable that such paper or paperboard containers have non-blocking (non-adhering) properties, so that no part of the package will adhere to the food and adversely affect the appearance, texture, flavor or purity thereof. Nonblocking properties are also desirable to prevent the containers from sticking together when shipped or stored in lots. Numerous other solid and liquid products, such as asphalt, sealants, caulking compositions, and the like, are also shipped or stored in such containers which advantageously have similar non-blocking properties.
In addition to non-blocking qualities in such food and other containers, it is desirable that they be moistureproof in order to prevent the flow of moisture from the product to the outside of the package, from the air to the product, or from either into thep aper or paperboard of the package, and for the package to have a pleasing, glossy, scuffresistant appearance which will aid in retailing of the product.
It is already known from Quarles et al., U.S. Patent 2,391,620 that paper may be moistureproof by coating with a non-homogeneous mixture of wax and polyvinyl resin and subjecting the coated product to baking. When this process is employed, either a single film composed of both resin and wax is formed, or two filmsan inner film composed of wax and an outer film composed of resin are formed. These results create several problems: only paper of low porosity may be used directly in the method, since the wax tends to enter the paper and cause blemishes and, if an antiblocking agent which is not compatible with the resin is used, it will not be on the surface where it is most useful. In addition, this method requires large amounts of wax and polyvinyl resin to impart satisfactory moistureproof qualities to the paper coated therewith.
It is an object of the present invention to provide a method for the production of glossy, non-adhering, scuffresistant, moistureproof coated fibrous cellulose and other products. Another object is to provide an improved method for coating fibrous cellulose sheet materials, including paper and paperboard products of relatively higher porosity. Yet another object is to provide less costly moistureproof paper and paperboard products. An additional object is to provide novel coating compositions which are useful according to the invention, and coatings produced therefrom. Other objects will be apparent to one skilled in the art and still other objects will become apparent hereinafter.
The foregoing and additional objects are achieved by United States Patent 3,210,015 Patented Aug. 10, 1965 ice providing an aqueous emulsion-dispersion of a particular type of polyvinyl resin, wax, and antiblocking agent, and by coating a material, especially a fibrous cellulose sheet material, e.g., a paper or paperboard sheet, therewith, and thereafter drying, baking, and cooling the coated material according to the method of the invention.
This procedure leads to several unexpected results: A two layer coating is formed, the inner layer being composed of the polyvinyl resin and the outer layer being composed of wax and antiblocking agent. Moreover, only a very thin coating is required to impart waterproofness, which greatly reduces the cost of the product.
The antiblocking agent used in the invention is any one, or a mixture, of a number of polysiloxane polymers commonly used as antiblocking agents, e.g., polydimethylsiloxane, polymethylhydrogensiloxane, or the like. Best results have been obtained using a polydialkylsiloxane, e.g., polydimethylsiloxane, polydiethylsiloxane, or the like, or a polyalkylhydrogensiloxane, e.g., polymethylhydrogensiloxane, or the like. The use of the stated antiblocking agent is critical. To achieve the same antiblocking properties without the said antiblocking agent, it would be necessary to increase the wax content by a factor of at least four. Such an increase would be uneconomical, would result in a much softer outer layer reducing scuffproofness and antiblocking qualities of the product, and would permit only a much thinner vinyl film for the same total thickness of coating. In addition to providing antiblocking properties, the polysiloxanes apparently assist the moistureproof qualities of the product. To achieve the same moistureproof properties without the polysiloxane antiblocking agent, it appears necessary to increase the thickness of the entire coating which accordingly increases the cost of the product substantially. The process of the invention may, however, employ any known antiblocking agent which is wax compatible and polyvinyl resin incompatible, as will become apparent hereinafter, although the polysiloxanes are in any event much preferred.
The vinyl resins employed according to the present invention are polymers formed from monomers containing a vinyl group or copolyrners formed predominantly from monomers containing a vinyl group, said monomers in any event comprising a chloroethylene having from one to two chlorine atoms on only one of its carbon atoms, i.e., vinyl chloride or vinylidene chloride. In referring to copolymers, it is intended to include copolymers of more than two reactants. The preferred resins are those composed of more than fifty percent by weight of vinyl chloride or vinylidene chloride. Representative polymers and copolymers are described in U.S. Patents 2,431,745 and 2,636,870, the disclosures of which patents are herein incorporated by reference.
The vinyl resins which may be employed in the invention, then, are those prepared by the polymerization of monomeric materials comprising a chloroethylene having from one to two chlorine atoms on one only of its car- I bon atoms. Latices thereof may be prepared by dispersing the solid, finely divided polymer in water or by polymerizing the monomeric material in aqueous emulsion. More specifically the latices may be prepared by polymerizing in aqueous emulsion vinyl chloride, vinylidene chloride, mixtures of these two materials with each other, or mixtures of one or both of these materials with other monomers copolymerizable therewith in aqueous emulsion, such as vinyl acetate or vinyl propinate, vinyl butyrate, methyl acrylate, methyl methacrylate, ethyl methacrylate, methyl ethacrylate, maleic acid or anhydride, esters of maleic acid or of chloromaleic acid, and other similar materials. Particularly preferred are the resin latices prepared by polymerization in aqueous emulsion of vinyl chloride, Vinylidine chloride,
like derivatives of chlorinated napthalene.
starch, for neutralization purposes.
monomeric materials in which the chloroethylene is the predominantconstituent, i.e., amounts to at least 50% by weight of the starting monomers.
Suitable vinyl polymers and copolymers of which the foregoing are representative are available under the trademark Geon. These Geons are latexes, usually in water dispersion, which upon drying even at room temperature form a strong flexible film or coating. They usually neither contain nor require a plasticizer, being internally plasticized. They exhibit low moisture vapor transmission in addition to the considerable chemical, moisture, and grease resistance typical of vinyl latices. Of these Geons, the one identified as Geon latex 652 is especially preferred. It is an internally plasticized polyvinyl chloride resin of the type just described, and available as a dispersion having total solids of about 49-51 percent, having negatively charged spherical resin particles, having a particle diameter of about 0.2 micron, and having an 'jexcellent mechanical stability. Further physical properties of the Geon 652 resin and latex are as follows:
color-white; mechanical stability-excellent; pH (initial) 6.0 minimum; total solids 49 to 51; specific gravity (latex)--1.24 to 1.25; specific gravity (resin)-1.60; surface tension '(dynes/cm.)34 to 38; viscosity (Brookfield at room temperature) (cps.)9 to 14; particle size (micron)--0.2.
The waxes used in the present invention include any waxes commonly used in moistureproofing, e.g., parafiin wax, ceresin wax, Japan wax, spermaceti Wax, or the wax- In order to allow sufficient' time for fusing of the polyvinyl film duralthough sometimes none is necessary asthe polyvinyl d the polyvinyl resin in dispersion is stable under such conditions. Although an excessively acid surface may cause agglomeration of a thin vinyl coating, exact neutrality is not always essential since thicker coatings are relatively unalfected by usual residual acidity of the stock to be coated. An suitable paper or paperboard may be used as the starting uncoated sheet, e.g., single or multi ply paper or paperboard, such as cylinder board or Fourdrinier paper and paperboard, preferably such base materials having a thickness. of 0.005 to 0.5 inch, preferably 0.005 to 0.4 inch, and a weight of at least about 25 pounds per ream (3,000 square feet).
The procedures which may be used for preparing the aqueous emulsion-dispersion of the present invention are well known in the art. The Wax and its emulsifying agent are mixed and heated together and then added to the water with vigorous agitation. The antiblocking agent and polyvinyl resin, each with its respective emulsifying and dispersing agent, are then added'with further agitation, preferably in that order. When to be used for packaging of foods, itis preferred to use Federal Food and Drug Administration approved emulsifying and dispersing agents, e.g., with the wax, oleic acid, morpholine, or the like; with the antiblocking agent, polyoxyethylene monooleate, sorbitan monostearate,.rnono-fatty-acid esters of polyethylene glycol or the like; and with-the vinyl resin, sodium 'oieate, sodium salt of dodecane-l-sulfonic acid, lauryl amine hydrochloride, or like dispersing agents. Other polyvinyl resin dispersing agents listed in column 41of US. Patent 2,636,870 may alsobe used,
resin is relatively stable except under acid conditions. if the emulsion-dispersionis on the acid side, it should be adjusted to basic to about neutral pH, as with alkali or usual bufferlsystems, e.g., a phosphate buffer system,
- due to the fact that excessive acidity tends to unstabilize ing processing without interference due to heat attraction I of the wax, and to avoid blocking and streaking during shipment or storage of the coated products of the invention, it is necessary to use wax melting above about 150 Fahrenheit and preferred to use wax melting from about 170 to 180 Fahrenheit, or even higher. Examples of preferred waxes are refined mineral waxes, e.g., ceresin wax, refined animal waxes, e.g., beeswax, microcrystalline waxes, e.g., those of Louisiana, Pennsylvania or mid-continent origins, highly refined paraffin waxes,
mixtures thereof, and the like. When the coated product.
is intended primarily for use in food packaging, it is preferred to use Federal Food and Drug Administration approved waxes, e.g., highly refined paraffin wax.
The base materials coated according to the present invention may be and preferably are fibrous cellulose sheet materials, including folded or wound sheet materials, e.g., carton blanks or convolute tubes, including various types of paper or paperboard, parchment, non-Woven textiles, virgin or regenerated cellulose, and the like. Preferably the starting base material will be paper or paper- 'board in such sheeet form and have a smooth, about neutralpH surface with a good fiber laydown. The fiber 'laydown is essential only where the coating is to be sufficiently thin that it would otherwise not penetrate through 4 the erect fibers to give complete coating of the paper or paperboard along its entire surface. In order to have a desirable smooth surface, either calendered or precoated, preferably hard sized, paper or paperboard is advantageously'used. However, hard sized paper or paperboard has an acid surface so that lt'lS sometimes advantageous to pretreat it with a slightly basic material, e.g., borated stock may even be or'be made somewhat basic, since The surface of the the polyvinyl resin dispersion and sometimes results in undesirable agglomeration of the resin particles which interferes with production of an integral film of the polyvinyl resin at a later stage in the process.
The thus-formed emulsion-dispersion is composed of about fi 'ty to seventypercent, preferably sixty to seventy percent, by weight of water and about thirty to fifty, preferably thirty to forty, percent by weight of solids. Advantageousiy, the solids may be about 35 percent and the water about percent by weight of the composition. The solids are in turn composed of wax, resin, and antiblocking agent in the ratio, by weight, of about one part of Wax to five to fifteen parts of resin and 0.001 to 0.0001 part of antibloclcing agent. The emulsifying and dispersing agents are included in the weight of each componcnt. mentioned. A preferred range of ratios is about sevento twelve parts resinand 0.0602 to 0.0008 part polysiloxane antiblocking agent to one part wax, and optimum results appear to be obtained using about nine parts resin and about 0.0006 part polysiloxane antiblocking agent for each part of wax. The polyvinyl resin is in dispersed form and the wax and antiblocking agent are in -rnonomers containing a vinyl group and copolymers formed from monomers containing a vinyl group, said vinyl monomers including a chloroethylene having from one to two chlorine atoms on only one of 'its carbon atoms, (b) wa'x'having a melting point of at least about degrees Fahrenheit, and (c) an antiblocking agent which is wax compatible and polyvinyl resin incompatible, (2) subjecting the coated product to a dryingstep at a temperature and for a periodof time sufiicient to remove up to aboutone-half of the moisture in the coated prodnet and draw the wax and antiblocking agent to the surface of the coating without fusing of the polyvinyl resin layer as an integral film to the surface of the fibrous cellulose sheet material, (3) substantially immediately subjecting the thus-coated product of reduced moisture content to a baking step at an increased temperature and for a period of time sufficient to fuse the polyvinyl resin as an integral film to the surface of the fibrous cellulose sheet material and further reduce the moisture content of the thus-coated product to not greater than about ten percent, whereby two films are formed on each surface of the product coated, an outer film of wax and antiblocking agent and an inner film of polyvinyl resin, and (4) cooling the thus-coated product to set the coating on the surface or surfaces thereof.
The resin (a) is preferably a polymer formed from a vinyl monomer which is a chloroethylene having one to two chlorine atoms on only one of its carbon atoms and any copolymer is preferably predominantly formed from such a monomer. The wax preferably has a melting point of about 170 to 180 Fahrenheit and is preferably refined parafiin wax. The antiblocking agent is preferably a polysiloxane, especially a polydialkylsiloxane or polyhydrogenalkylsiloxane. Other preferred components and preferred operating procedures and ranges are given elsewhere in this specification.
Thus, one or both surfaces of the fibrous cellulose sheet material, e.g., a carton blank or a sheet of paper or paperboard, may be conveniently finished or coated according to the present invention, usually at or about normal room temperatures, in a four step process, the number of surfaces coated depending upon various factors, such as the intended end use of the product. Illustratively for paper, the paper sheet is coated with a thin uniform layer of the emulsion-dispersion, preferably by a continuous web or dip process, the web process being used primarily for sheet materials to be coated on one side only and the dip process being used primarily for items, e.g., sheets, carton blanks, or tubes, to be coated on both sides.
The amount and composition of the emulsion-dispersion coated onto the paper controls the thickness of the coating in the final product. In general, when about five pounds of solids are contained in the amount of emulsiondispersion coated onto 2,000 square feet of paper, the coating will be about .0001875 inch thick. The thickness of the coating will vary in direct proportion to the amount of solids coated on the paper. To maintain thickness control, an air knife may be conveniently used to remove excess coating from the sheet when using a dip process or from the web when using a web process.
After the coating step, and before the coating can become uneven through drying, coagulation or dripping, the wet coated product is placed in an enclosed area where unrestricted dry air at a temperature of from about 150 to 200 Fahrenheit is allowed to evaporate up to about fifty percent, usually about forty to fifty percent, by weight of the moisture both in and on the product. A preferred temperature range is from about 160 to about 185 Fahrenheit. Prior to this step, the dispersed resin usually appears as fine particles floating at or near the surface of the coating. During the drying step, the wax melts and migrates to the surface of the coating, carrying with it the antiblocking agent since they are compatible and since both are incompatible with the vinyl resin, and the previously finely dispersed polyvinyl resin forms a film on the surface of the material, e.g., paper, being treated. It is essential that the vinyl resin does not fuse into an integral film at the surface of the paper during this step, since it is necessary for the paper to be able to breathe in order for its internal moisture to escape. Still speaking illustratively for paper, if the moisture does not escape at this stage, the paper may rupture from internal pressure during the subsequent fusion of the vinyl resin as an integral film to the surface of the material coated, which usually occurs if the moisture content is reduced much below fifty percent or if the temperature is much above 200 Fahrenheit. The period required for the drying step is usually from about four to about twelve seconds depending upon the temperature and the exact type and thickness of the coating and the thickness of the fibrous cellulose sheet material. Excellent results have been obtained by using a period of about eight seconds and a temperature of about 175 Fahrenheit, and by evaporating about 50% of the moisture.
The dried product, before cooling, is placed substantially immediately in an enclosed area where it is brought substantially instantaneously to a temperature of about 275 to 325 Fahrenheit. A preferred range of temperature is about 285 to 310 Fahrenheit, and the optimum temperature is about 175 Fahrenheit. At this point several things occur: the high temperature dissipates no longer needed emulsifying and dispersing agents, the layer of previously dispersed polyvinyl resis is fused as an integral film to the surface of the material coated, and the way-polysiloxane film on the surface of the resin film is cured in a manner which improves its antiblocking properties. This temperature is maintained until the moisture content of the coated paper is reduced to about ten percent or less, preferably to between about six and eight percent or, in other words, until about to 90 percent of the remaining moisture is removed from the coating. It is advantageous that the coating reach the baking temperature substantially instantaneously so that the vinyl resin layer fuses into an integral film before the wax has time to draw back into the paper product and cause blemishes and/ or corresponding Weaknesses in the vinyl layer and/or total coating. Instantaneous heat may be most readily developed by the use of infra-red rays. This baking step usually requires a period of from about two to six seconds. The best results from the baking step have been achieved using a period of about four seconds and a temperature of about 300 degrees Fahrenheit, and by removing about percent of the remaining moisture from the coating. A final moisture content of about 7.5 percent is considered optimum. Substantially immediately after the baking process is complete, the baked paper product is cooled either by a cool water bath, as is most convenient when the product is coated on both surfaces, or by cool air, as is most convenient when it is coated on one side only, to set the coating on the surface thereof.
For a better understanding of the process of the present invention, reference is made to the accompanying FIGURE 1, which is a flow sheet illustrating the method of the present invention and which is self-explanatory.
The fibrous cellulose product produced by the process of the present invention is non-blocking, moistureproof, glossy, and scuff-resistant. On each of one or more surfaces it has a coating composed of two films; an outer film composed of wax and antiblocking agent and an inner film composed of the polyvinyl resin. This coating may be of any desired thickness but is usually from about 0.000125 to 0.0005 inch thick. The lower boundary of this range is fixed at where moistureproof properties begin and the upper boundary is fixed by cost factors. The coating is preferably between about .000125 and .00025 inch thick, and very satisfactory re sults have been obtained using a coating approximately 0.0001875 inch thick. The ratio between the thicknesses of the outer and inner layers or films is from about 1:15 to 1:5, preferably from about 1:12 to 1:7, and appears to be best at about 1:9. 7
Reference is made to the accompanying FIGURE 2 which is an enlarged fragmentary cross-sectional elevational view illustrating a coated fibrous cellulose product produced according to the invention. The drawing shows paper or paperboard sheet material (3), polyvinyl resin .used for coating other base materials, e.g., wood, metal,
or the like, 'to give a superior coated product, the procedural details of the coating being .thesame. This is of special interest when the base material, e.g., wood or metal, is to be used to contain or contact food orthe like, since FDA approved materials may be employed for all of the coating ingredients, rendering the coated product much more acceptable for such purpose.
The following examples are given to illustrate the process of the present invention but are in no way to be construed aslimiting. Allparts are by weight.
Example 1 An aqueous emulsion-dispersion is prepared from fifteen parts water, nine parts of an equal blend of two tripolymers (1) a tripolymer prepared from 77 parts vinylidene chloride, 11.5 parts vinyl chloride, and 11.5 parts ethyl acrylate, and (2) a tripolymer prepared from 90 parts vinylidene chloride, 5 parts vinyl chloride, and 5 parts methyl methacrylate, and its dispersing agent sodium oleate, one part of highly refined parafiin wax melting at 175 Fahrenheit and its emulsifiers, oleic acid and .morpholine, and 0.0006 part of polydimethylsiloxane and its emulsifier, s orbitan monostearate.
The composition is applied to one surface of a sheet of 0.005 inch calendered paper by a continuous web process, coating the paper with 1.65 pounds of solids for every one thousand square feet ofpaper. An air knife is used to control the amount of composition distributed on the web. Thecoa-ted paper is then placed in an enclosed area where it is exposed to unrestricted dry air at a temperature of 175 Fahrenheit for a period of eight seconds, whereby about fifty percent of its moisture content is evaporated. The paper is then placed in another enclosed area, which is maintained at 300 Fahrenheit by direct infra-red rays, and baked for a period of four seconds. The paper is then immediately cooled by subjecting it to cool air. 7
The product is a sheet of calendered paper 0.005 inch thick having on one surface a 0.000125 inch coating composed of two films, an outer film composed of wax and polydimethylsil-oxane antiblocking agent and an inner film. composed of polyvinyl resin. 7 scuff-resistant, non-blocking, and semi-moistureproof.
The product is glossy,
Example 2 A sheet of 0.01 inch calendered paper is coated accord ing to the process of Example 1. The polyvinyl resin is a dipolymer prepared from 90 parts of vinylidene chloride and ten parts methyl methacrylate. 'The product is a sheet of 0.01 inch calendered paper coated substantially The product is a sheet of 0.02 inch calendered paper coated substantially the same as the product of Example 1 and has similar properties.
Example 4 A sheet of 0.03 inch calendered paper is coated according to the process of Example 1. The paperis coated to theextent of 2.5 pounds of solids per thousand square feet of paper. The product is a sheet of calendered paper 0.03 inch thick, coated on one side to a thickness of 0.0001875 inch. It'is waterproof and water vapor proof methand otherwise has properties similar to'those given for the product of Example 1.
' Example 5 An emulsion-dispension is prepared according to Example lusing nineteen parts of water, seven parts of polyvinyl resin, one part of Wax, and 0.0006 part of'polydimethylsiloxane. A carton blank is dippedinto this emulsion and coated to the extent of 2.5 pounds of solids per thousand square feet per side. The blank is. then treated bytheprocess of Example 1 wherein the temperature in the first enclosure is 150 degrees Fahrenheit and in the second 275 degrees Fahrenheit. The product, whenfolded' properly, is a carton with both outer and inner surfaces coated as indicated for the one surface of the product of Example'4 to a thickness of 0.0001875 inch. It is'moistureproof and otherwise has properties similar to those of the product of Example 4.
Example 6 An emulsion-dispersion is prepared according to Example 1 using 19.5 parts water, twelve parts'of polyvinyl resin, one part wax, and: 0.0006 part of polydimethylsiloxane. Both surfaces of a sheet of 0.4 inch paperboard sheet Wound into the form of a convolute tube are coated with this emulsion to the extent of about 6.25 pounds per thousand square feet of paperboard per side. The paperboard tube is then treated by the process of Example 1 wherein the tempera-ture of the first enclosure is 200 degrees Fahrenheit and of the second 325 :degrees Fahrenheit. The product, after being cooled by a water bath, is a convolute tube'of paperboard sheet 0.4 inch thick having on each surface a coating as in Example 1 which is 0.0005 inch thick. It is waterproof and moisture vapor proof and otherwise has properties similar to those given for the product of Example 1.
In each case, when the sheet paper products from the above examples arecut into carton blanks and formed into cartons or other containers, the products exhibit a high degree of moisture-proofness and resistance to moisture-vapor transfer.
Various modifications and equivalents will be apparent to one skilled in the art'and may be made in the method, compositions, and products of the present invention without departing from the spirit or scope thereof, and it is therefore to be understood that the invention is to be lmiited only by the scope of the appended claims;
1. A process for the coating of a base material comprising the steps of (l) coating the base material with an aqueous emulsion-dispersion of (a) a resin selected from the group consisting of polymers formed. from monomers containing a vinyl group and copolymers formed predominantly'from monomers containing a vinyl group, said vinyl monomers includinga chloroethylenehaving from one to two chlorine atoms on only one of its carbon atoms, (b) wax having a melting point ofat least'about 150 degrees Fahrenheit, and (c) a polysiloxane antiblocking agent which is wax compatible and polyvinyl resin incompatible, (2) subjecting the coated product to a idrying step at a temperature and for a period of time sufiicient to remove at least some and up to about one-half the moisture inthe coatedproduct and draw the wax and antiblockin'g agent tothe surface of the coatingwithout fusing of the polyvinyl resin layeras an integralfilm to the surface of the base. material, (3) substantially im- I mediately subjecting the thus-coated product of; reduced moisture content to a baking step at an increased temperature and for a period of'time sufficient: to fuse the poly- 7 vinyl resin as an integral filmto the surface of the base material and further reduce the moisturecontent of the thus-coated product to not greater than about ten percent, whereby two films are formed onthe surface'ofthe prodnot, an outer film of wax and' antiblockingagentand an 9 inner film of polyvinyl resin, and (4) cooling the thuscoated product to set the coating on the surface thereof. 2. A process for the coating of fibrous cellulose sheet materials to render the same more Waterproof andscutfresistant, comprising the steps of (1) coating a fibrous cellulose sheet material with an aqueous emulsion-dispersion of (a) a resin selected from the group consisting of polymers formed from monomers containing a vinyl group and copolymers formed predominantly from monomers containing a vinyl group, said vinyl monomers including a chloroethylene having from one to two chlorine atoms on only one of its carbon atoms, (b) wax having a melting point of at least about 150 degrees Fahrenheit, and (c) a polysiloxane antiblocking agent which is wax compatible and polyvinyl resin incompatible, (2) subjecting the coated product to a drying step at a temperature and for a period of time suflicient to remove at least some and up to about one-half the moisture in the coated product and draw the wax and antiblocking agent to the surface of the coating without fusing of the polyvinyl resin layer as an integral film to the surface of the fibrous cellulose sheet material, (3) substantially immediately subjecting the thus-coated product of reduced moisture content to a baking step at an increased temperature and for a period of time suffieient to fuse the polyvinyl resin as an integral film to the surface of the fibrous cellulose sheet material and further reduce the moisture content of the thus-coated product to not greater than about ten percent, whereby two films are formed on the surface of the product, an outer film of Wax and antiblocking agent and an inner film of polyvinyl resin, and (4) cooling the thus-coated product to set the coating on the surface thereof.
3. The process of claim 2, wherein the temperature in the drying step (2) is about 150 to about 200 degrees Fahrenheit and the temperature in the baking step (3) is about 275 to about 325 degrees Fahrenheit.
4. The process of claim 3, wherein the baking step 3) is effected by subjecting the coated product from the drying step (2 to the action of infra-red rays.
5. The process of claim 3, wherein said polymer is formed from a monomer which is a chloroethylene having from one to two chlorine atoms on only one of its carbon atoms and said copolymer is predominantly formed from such a monomer.
6. The process of claim 5, wherein the aqueous emulsion-dispersion contains about to percent by weight of water and about 30 to 50 percent by weight of solids, the solids being present in a ratio of about one part by weight of wax to about five to fifteen parts by weight of resin and 0.001 to 0.0001 part by weight of antiblocking agent.
7. The process of claim 6, wherein the period of drying is about four to twelve seconds and the period of baking is about two to six seconds.
8. The process of claim 6, wherein the resin (a) is a vinyl chloride-vinylidene chloride copolymer, wherein the wax (b) is a refined paraffin wax having a melting point between about and degrees Fahrenheit, and wherein the antiblocking agent (c) is selected from the group consisting of polydialkylsiloxanes and polyhydrogenalkylsiloxanes.
9. The process of claim 8, wherein the aqueous emulsion-dispersion contains about 60 to 70 percent by weight of water and about 30 to 40 percent by weight of solids, the solids being present in a ratio of about one part by weight of wax to about seven to twelve parts by weight of resin and 0.0002 to 0.0008 part by weight of antiblocking agent.
10. The process of claim 9, wherein the temperature of the drying operation is about 160 to degrees Fahrenheit and the temperature of the baking operation is about 285 to 310 degrees Fahrenheit.
References Cited by the Examiner UNITED STATES PATENTS 2,306,046 12/42 Duggan et al. 117-76 2,391,620 12/45 Quarles et al. 117-76 2,431,745 12/47 Flanagan.
2,636,870 4/53 Connors et al. 260-296 2,869,722 1/59 Marander et al. 117-155 XR 2,983,622 5/61 Biskup et al. 117-76 3,062,678 11/62 McCluer 117-76 RICHARD D. NEVIUS, Primary Examiner.