US3664912A - Self-bondable printing paper - Google Patents

Abstract

The invention is directed to coated papers, which has been coated with a new and improved coating composition for imparting thereto (1) the printing properties of typical clay-coated printing papers and (2) heat sealing properties found in plastic films and plastic film-laminated papers. This paper comprises a white opaque paper substrate and an applied white opaque coating composition comprising an aqueous dispersion of 5-20 percent resinous binder, 15-75 percent opaque pigment such as inorganic pigment, and 20-65 percent discrete thermoplastic resin particles with a coalescing range of at least 140* F., and preferably 140*400* F., in which the above-listed percentages of components are based on the dry weight of the total dry solids content of the coating composition.

Description

United States Patent Olson [45] May 23, 1972 [54] SELF-BONDABLE PRINTING PAPER 211 App]. No.2 828,974

[52] U.S.Cl ..161/161, 117/14, 117/155, 117/161 UZ, 156/308, 161/162, 161/165, 161/181, 161/251,161/253,161/254,161/255,161/256,

[51] Int. Cl. ..B32b 3/26, B32b 27/08, B32b 27/30 [58] Field of Search 156/308; 161/247, 250, 251, 161/252, 254, 268, 270, 87, 238, 238, 265, 266, 162,165,181, 255, DIG. 2; 162/124, 168; 281/21,

15; 117/15 T, 14, 161 UP; 260/233,3

[56] References Cited UNITED STATES PATENTS 2,306,400 12/1942 Menzel ..161/DIG. 2 2,759,847 8/1956 Frost et a1.. 117/156 X 2,923,707 2/1960 Wolff ..260/233 3 2,992,149 7/1961 Drelich 117/161 Ul-ll-l 3,028,258 4/1962 Rice ..117/156 X 3,047,427 7/1962 Dratz 1 17/156 X 3,256,138 6/1966 Welch et al.... ...162/124 3,313,803 4/1967 Roberts 260/233 3 3,351,479 11/1967 Fairchild ..117/156 X SHEETS AFTER APPLICATION OF PRESSUFE AND ENERGY THERMOPLASTIC RESIN IN COALESCE D FORM FOREIGN PATENTS OR APPLICATIONS 116,167 8/1940 Australia ..281/21 OTHER PUBLICATIONS Ellis, Carleton, The Chemistry of Synthetic Resins, Volume 1, 1935, Reinhold Publishing Corp. New York NY. pages 792 and 828.

Lohnaset al ..117/156X vanWestrenen ..1 17/156 X Primary Examiner--.Iohn T. Goolkasian Assistant Examiner-C. B. Cosby AttorneyChristen & Sabol [57] ABSTRACT The invention is directed to coated papers, which has been coated with a new and improved coating composition for imparting thereto (1) the printing properties of typical claycoated printing papers and (2) heat sealing properties found in plastic films and plastic film-laminated papers. This paper comprises a white opaque paper substrate and an applied white opaque coating composition comprising an aqueous dispersion of 5-20 percent resinous binder, 15-75 percent opaque pigment such as inorganic pigment, and 20-65 percent discrete thermoplastic resin particles with a coalescing range of at least 140 F and preferably 140400 F., in which the above-listed percentages of components are based on the dry weight of the total dry solids content of the coating composition.

20 Claims, 2 Drawing Figures REGION OF SEA L REG ION OF SEA L Patented May 23, 197.2

INVENTOR ROBERT A. OLSON SELF-BONDABLE PRINTING PAPER BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to novel and useful coated paper, methods of making this paper, and unique coating compositions employed therein. The coated paper of this invention through the unique properties of its coating composition not only permits the application of any conventional method of printing used on conventional clay-coated papers; but in addition, it permits the unique feature of bonding these printed sheets together by the combined application of heat and pressure to form a superiorly bound coated paper product such as a book, magazine, brochure, pamphlet, annual report, pad, envelope or similar product.

2. Description of the Prior Art Books and pamphlets are conventionally made by fastening paper together by sewing, stapling or adhesive binding. Each of these methods suffer from one or more of the following shortcomings: low binding strength, poor permanence, failure to lie flat when opened, and high labor and cost of manufacture. The limitations of these methods are largely due to the characteristics of conventional coated printing papers, methods of quality printing such as letterpress and lithographic, and methods of reducing large printed sheets to book size.

There are a number of materials that can be fastened together by bonding with heat and pressure, such as certain plastic films and plastic film-paper laminations, and used in certain packaging applications; but all these, in general, suffer from the same problem of not being able to be used for the high quality printing application that is common of coated printing papers. These materials are printed in less demanding applications by the use of special pretreatment, special inks and with specialized printing processes such as flexographic printing with rubber plates. These materials are not suitable for the production of high quality books and the like because of the above-mentioned printing quality shortcomings and the high cost of production.

This invention makes possible new methods of fastening quality printed paper which overcome all the previously mentioned objections simultaneously, by basically altering the heat and pressure response characteristics of conventional coated paper while still maintaining the desirable qualities of conventional coated paper.

It has been known to produce thermal or heat-sensitive copy paper by coating paper with a composition containing a resinous binder and opaque thermoplastic particles having a fusion or coalescing point above the drying temperature used when applying the coating to paper. US. Pat. Nos. 3,228,785 and 3,306,763 disclosed such coated papers. Coated copy papers of this type rely on the transparentization of the opaque thermoplastic particles by application of heat at selected areas sufficient to fuse or coalesce the thermoplastic particles. The addition of pigment particles which are infusible at the temperatures to which the paper is subjected defeats the purpose of the heat-sensitive coating and such pigment particles are specifically excluded.

SUMMARY OF THE INVENTION The coated paper of this invention through the nature of its unique coating composition produces a bound printed product which has a superior, more durable bond than can exist by using the binding processes such as stapling, sewing, adhesive binding and mechanical binding now used with conventional clay-coated printing papers since the bond formed with the novel coated paper extends over the entire area pressurized, for example, which could run the full length of the bound edge. At the same time, the bound printed product made from the coated paper in this invention produces a superior printed product at a lower cost than conventional heat sealing materials such as plastic films.

The coated paper of this invention obtains its unique printing and self-bonding properties through its unique combination of coating composition components. In this coating composition, the presence of 20 to 65 percent of discrete thermoplastic resin particles which remain as discrete particles through the drying operation when the coating is applied to the paper substrate, but which will coalesce under the combined application of sufficient heat and pressure to form a bond to itself or another similar sheet, gives this coated printing paper unique heat sealing properties not found in other coated printing papers. These discrete thermoplastic resin particles in combination in this coating composition with 15-75 percent of inorganic pigment(s) and 5-20 percent of resinous binder give this coated heat sealing paper printing properties not found in any other heat sealing materials. This combination of printing and heat scaling properties produces a coated paper which can be printed and formed into uniquely bound book and book-like products.

BRIEF DESCRIPTION OF THE DRAWING The drawings presented which form a part of our specification, are rendered self-descriptive by the suitable legends accompanying the drawings, wherein:

FIG. 1 is an enlarged diagrammatic cross-sectional view of two sheets of one-side coated paper of this invention showing the random distribution of discrete thermoplastic particles and inorganic pigment particles held together on the surface of a paper substrate by the resinous binder before the combined application of heat and pressure by a pressure and heat source also shown.

FIG. 2 is similar to FIG. 1 except after sufficient heat and pressure have been applied to one area of the sheets to seal them together. FIG. 2 shows that in the pressurized area, after the pressure has been removed and the sheet cooled below the coalescing temperature of the thermoplastic, there no longer exists discrete thermoplastic particles but coalesced thermoplastic masses common to both sheets of paper thus providing a bonded area between the two sheets.

DESCRIPTION OF PREFERRED EMBODIMENTS The coated paper of this invention obtains its unique heat and pressure-sensitive properties primarily through the incorporation in the coating composition of 20 to 65 percent, preferably about 30 to about 45 percent, discrete thermoplastic resin particles, such as poly(vinyl chloride) or polystyrene which have coalescing temperatures of at least about F. Because these thermoplastic resin particles do not coalesce at the temperatures used in drying the coating composition on the paper substrate, the thermoplastic acts as pigment"-like particles and assists in imparting microporosity to the coated sheet which is necessary for proper printing ink receptivity, ink setting, and ink drying characteristics, provided the resinous binder or adhesive portion of the coating composition is maintained at sufficiently low levels to avoid complete filling of the voids or porous nature of the coating.

The discrete thermoplastic particles used in this invention are not film-forming below their coalescing temperatures and, as particles, have little or no binding or adhesive power at room temperature as do many somewhat similar materials used in conventional clay coated printing papers for pigment binders, such as low fusing styrene-butadiene copolymers (60 percent styrene 40 percent butadiene). The discrete thermoplastic particles have a coalescing temperature of at least bout 140 F., preferably in the range of about 140 F. to about 400 F. This pennits the coating to be dried during production of the coated paper while retaining the particulate nature of the thermoplastic. Only when the coated paper of this invention is subjected to the necessary combination of heat and pressure during the bonding operation, which brings the sheets of paper into intimate contact, do these discrete thermoplastic particles soften and coalesce with other such thermoplastic particles in an adjacent coated sheet to form a strong, durable bond between the sheets upon cooling of the thermoplastic below its coalescing temperature. Conventional clay-coated printing papers will not form a sufficient bond under the application of heat and pressure because the level of thermoplastic binder is necessarily too low. However, if the amount of room temperature film-forming thermoplastic resins used as pigment binders were increased to the necessary level in conventional clay-coated printing paper to allow formation of an adequate bond under the application of heat and pressure, the printing properties would then be lost because the microporosity of the sheet necessary for printing would have been reduced too much or destroyed. Also, by the use of thermoplastic particles that are non-film forming at temperatures below about 140 F., the coated paper of this invention avoids premature or undesired bonding, sticking, blocking, or marking tendencies at temperatures and pressures under which the coated paper is manufactured, handled and/or used.

The thermoplastic particles of this invention remain as discrete particles during the drying of the applied coating, so long as the sheet temperature is not raised above the coalescing temperature of the particles. The average particle size preferably ranges from about 0.2 to about 5.0 microns. Because of these factors and the inherent light reflectance and refractive properties of the thermoplastic particles, they contribute significantly to the opacity and brightness of the resulting coating. Particles of thermoplastic smaller than about 0.2 micron were found to contribute very small opacity and brightness benefits to the coating while particles larger than five microns might contribute to print quality degradation.

Inasmuch as the thermoplastic resins suitable for use as the thermoplastic particles of the present invention comprise a broad group that does not readily lend itself to narrow and accepted chemical classification and have physical and chemical properties that are not common to every member of the group, the following method is provided to enable the easy determination of suitability and selection of thermoplastic resins for use in this invention. One method which was used to determine the coalescing temperature of thermoplastics was as follows: Aqueous dispersions of the thermoplastic, for example, in the general form supplied by the manufacturers at about 50 i 6 percent solids, were drawn-down on 16-inchthick black glass plates using an applicator bar which applied a 3 mil thickness wet coating. These coatings were dried in an oven at various air temperatures from about 75 F. through about 400 F. for 10 minutes and then observed to determine at what temperatures the coatings remained white and opaque, effectively hiding the black glass plate from view, and at what temperatures the coatings lost their opacity and turned translucent or transparent, allowing the black plate to show through the resulting film. Those thermoplastic coatings which remain opaque and do not form a transparent or translucent film at or below about 140 F. are considered to have remained particulate in form and are acceptable from this standpoint for use in the coating formulation.

Any thermoplastic particles can be utilized in the novel coating compositions so long as they remain as discrete particles and do not act as film-forming binder materials below about 140 F. but coalesce at temperatures above about 140 F., preferably in the range of about 140 F. to about 400 F. Included are those grades of polyvinyl chloride, polystyrene, styrene butadiene (80-99 percent styrene to l-20 percent butadiene), vinyl chloride-vinylidene chloride copolymer, vinylchloride-vinylacetate copolymer, terpolymer of styrene, butadiene and acrylonitrile, gum rosin, polymerized rosin, polymerized rosin glycerol ester, partially dimerized rosin, acrylic polymers and powdered polyethylene, having these characteristics.

In order to give the coated paper of this invention the desired properties of proper ink receptivity, ink holdout, ink drying and setting characteristics, permanent opacity (especially at those areas which are heated and pressurized to form the bond), and favorable economics, the novel coating composition contains about to about 75 percent, preferably about 40 to about 60 percent, of one or more inorganic or organic pigments. The average particle size of the pigment can range from about 0.2 micron to about 5.0 microns. For example, inorganic pigments, such as, coating grade clay, calcium carbonate and TiO having average particle sizes of 1.0, 0.20 and 0.25 microns, respectively, have been used as components in the novel compositions. When a combination of inorganic pigments are used, maximum desired properties can be obtained, although the pigments can be effectively used individually. The type of inorganic pigment or combination in the novel coating compositions has little influence on the bonds formed between the sheets when heat and pressure were applied. However, the higher the pigment level in the coating, (requiring a consequent lowering of the thermoplastic resin particle level), the more the coated sheets tend to become difficult to bond to each other, all other conditions being equal. Non-thermoplastic pigments or pigments which do not coalesce below 400 F. are employed.

If colored sheets are desired, colored pigments or dyes can be used to partially replace the white pigments mentioned above, the degree of replacement depending on the desired hue.

The thermoplastic resin particles do not have sufficient binding or adhesive power (before activation by pressure and heat) to be utilized without the addition of an additional binding or adhesive material to secure the resin and pigment together in the coating layer and to the paper substrate. To bind the inorganic pigment and the discrete thermoplastic resin particles together in the coating layer and to bind the coating layer to the paper substrate in order to produce a coated paper which has the necessary degree of surface strength to allow the paper to be printed, particularly by the more demanding lithographic printing process and which has the necessary flexibility to allow the paper to be folded without cracking or weakening at the fold during folding and binding operations, about 5 to about 20 percent, preferably about 10 to about 15 percent organic resinous binder is used in the coating composition. The microporosity needed in the coating of a coated paper to permit proper printing ink receptivity, holdout and drying characteristics is not only dependent upon the particulate thermoplastic portion and the particulate pigment portion of the coating composition, but is also dependent on the amount of film-forming resinous binder used in the coating. The binder must be used at sufficiently low levels to prevent complete filling of the voids or spaces in the coating. Thermoplastic resinous binders which are film-forming at or about room temperature, such as poly(vinyl alcohol) or styrene-butadiene copolymer (60 percent styrene-40 per cent butadiene), were found to enhance the ease of bonding together of the coated sheets when subjected to heat and pres sure and in fact permit the reduction of the amount of discrete thermoplastic resin needed in the coating composition. However, the organic resinous binder need not be thermoplastic in order to practice this invention. Any of the binders commonly used in the paper coating arts can be employed.

The following is a non-limiting list of resinous binders which have been utilized either singly or in combination with one another: poly(vinyl alcohol), styrene-butadiene copolymer (60 percent styrene40 percent butadiene), soya protein, and hydroxyethylated starch. Several others which can be utilized include poly(vinyl acetate), acrylic polymers, casein and various starch binders.

Inasmuch as the content of the pigment particles and the thermoplastic resin particles affects the microporosity of the resulting coated paper, the total content of these particles should be in the range of about to about 95 percent, preferably about to about percent, of the coating on the dry weight basis.

The aqueous coating composition described in this invention can be applied to both sides of a white opaque paper substrate, basis weight range between 32 and lb. (25X38-500 by any conventional coating method, such as blade coating at coat weight levels from about 3 to about 15 lb. per side per ream and subsequently dried at a temperature below the coalescing temperature of the thermoplastic particles by means of hot air or steam heated dryer cans or any other means which removes the water or other inert vehicle from the coating so that the final coated sheet has been 2 and 7 percent final moisture based on the dry weight of paper. The resulting coated paper product has a basis weight range from 40 to 120 lb. (25X38-500) and has all the appearances and printing properties of conventional clay-coated printing papers. In addition, the resulting coated paper permits a strong durable bond to be fonned between sheets thereof brought into intimate contact under the application of heat and pressure and consequently permits books, pamphlets, brochures, and similar miltiple paper forms to be readily produced. A unique feature of this coated paper is its ability to be bound to similar sheets or to compatible plastic films, brought into intimate contact, under the application of suffcient heat and pressure to soften the discrete thermoplastic particles therein causing these materials to flow together under pressure to form a strong durable bond in the pressurized zone after cooling the sheets below the coalescing temperature of the thermoplastic.

An important feature of the coated paper of this invention is that it is non-heat and pressure sensitive within the temperature ranges of practical use and handling and that is non-heat and pressure sensitive below the fusion or coalescing temperatures of the thermoplastic resin particles used in the coating composition. Also, this coated paper will not form a bond to other similar paper by the application of pressure alone in the absence of sufficient heat to raise the temperature of the thermoplastic resin above its coalescing temperature or by the application of heat alone in the absence of sufficient pressure to put such sheets into intimate contact whereby the thermoplastic resin can flow and form binding points between the adjacent sheets.

Various chemical additives, which are commonly used in coating formulations to produce specific coating or coated paper properties, can also be used in the coating composition of this invention at normal use levels without interfering with the desired printing and heat scaling properties. Such materials include defoamers, antifoamers, flow modifiers, lubricants, thickeners and insolubilizers. The solids content of the novel composition can be varied in the range of about 20 to about 60 percent, depending on the method of application. For blade coating a range of about 50 to about 60 percent solids is preferred, and for size press coatings about 20 to about 40 percent solids is preferred.

In preparing the coating compositions, two basic procedures can be followed. With natural resinous binders and some synthetic adhesives, it is necessary to solubilize the material in the well known manner through a heat or chemical treatment or a combination of both in order to obtain the binding properties of the material upon drying of the coating. With the first procedure, if a resinous binder of this nature is to be used, the material in the dry powder form is blended into an aqueous dispersion of a certain solids content of the pigment particles. The mixture of pigment particles, unsolubilized resinous binder, and water is then subjected to the necessary heat and/or chemical treatment, following procedures outlined by the manufacturer of the resinous binder, to achieve solubilization. After cooling the mixture to a temperature below the coalescing temperature of the thermoplastic resin, the thermoplastic resin particles, in aqueous dispersion form as received from the manufacturer, are blended into the above described mixture. If an additional resinous binder of the type that requires no solubilization to achieve binding properties is to be used, it is blended into the coating composition next. When additives to improve the characteristics of the coating composition are used, they are blended into the mixture last, usually in the sequence of flow modifiers first and insolubilizers last.

With the second basic procedure for preparing coating compositions, if a natural or synthetic resinous binder requiring solubilization is used, it is prepared by itself, independent of the pigment dispersion, by dispersing the binder in the dry powder form in a certain specified quantity of water and then subjecting the blend to the necessary heat and/or-chemical treatment to achieve solubilization. The aqueous, solubilized form of the resinous binder is then added to an appropriate amount of inorganic pigment dispersion and the additional components of the coating composition are then added in the sequence described above for the first basic procedure for coating make-up. If desired, other inert vehicles may be used in place of water, although water is by far preferred because of economy, ease of handling and availability.

While paper is the preferred substrate other substrates to which the selected resinous binder will adhere can be used. For example, paperboard, cardboard, plastic films, and the like can be employed. The thickness of the substrate also is not narrowly critical and can fall in the range of about 2.5 mil to about 8.0 mils thickness.

There are many acceptable methods of heat sealing which can be used with the coated paper of this invention. The four major factors which primarily influence the strength of the bonded area are: (l) the power input which is responsible for heating the coating to the coalescing temperatures of the thermoplastic resin particles which varies for the different chemical types of thermoplastic resin used in this invention from about 140 F. to about 400 F., for example, (2) the pressure applied during heating which varies with thermoplastic resin type and amount of thermoplastic resin in the coating used in this invention from about 30 psi. to about 2,500 p.s.i. (3) the unit of time over which the heat and pressure were applied which varies with type of thermoplastic resin and the amount of thermoplastic resin as well as the heat input and pressure applied from as little as about 0.25 second to several seconds, e.g., 60 seconds, and (4) the width of the bonded area formed which can be varied from about one-sixteenth inch or less to about 1/4 inch or more. Excellent seals have been made with the coated paper of this invention depending on the combination of the above mentioned variables using either impulse type heating or radio frequency (RF) type heating devices. Other methods of heat sealing can be used and the invention is not limited to these two heat sealing devices. In general, the seal strengths have been judged adequate when, upon stressing, bond failure occurred in the paper substrate and not in the bond or at the interface between bonded sheets along the entire area of the seal.

Several examples of coating compositions which were found to produce the desired printing and heat sealing properties, in which, unless otherwise designated, all temperatures are in F., all parts and percentages are by weight and all the percentages listed for coating components are based on dry weight percentages of the total dry solids content of the coating compositions, are presented.

EXAMPLE 1 A coating composition comprising:

Thermoplastic ResinPoly(vinyl chloride) as an aqueous latex, manufactured and sold as Geon 151 by the B. F. Goodrich Chemical Company, containing about 56% solids poly( vinyl chloride), having a coalescing temperature above 250 F. and an average particle size of about 0.2 microns Inorganic Pigments( 1) Clay Pigment (manufactured by Englehard Minerals and Chemicals Corp. and available as Ultra White having 92-94% of particles less than 2.0 microns (2) Calcium Carbonate Pigment (manufactured by Wyandotte Chemical and available as Purecal-O) having a particle size of 0. l0-O.35 microns Resinous BinderPoly( vinyl alcohol),

manufactured by E. l. DuPont and available as Elvanol 7l-30), having a molecular weight of 50% calcium stearate l.0 Binder lnsolubilizer-Glyoxal as an aqueous solution containing 40% glyoxal 0.25 Total: 100.05

was prepared by the previously described first basic procedure where the resinous binder is cooked in the presence of pigment and water sufficient to adjust the solids content to 50.6 percent solids. The composition was applied to both sides of 3.0 mil thick white base paper at 10 to 13 lbs. per ream (total of both sides) using a trailing blade coater and the coated paper was dried with forced hot air at 220 F. for seconds per side. The coated paper was rewound and sheeted. Some of the paper was supercalendared to enhance its gloss to a value comparable to other commercial glossy coated printing papers.

EXAMPLE 2 A coating composition comprising:

was prepared to 46 percent solids as described in Example 1. The composition was applied to both sides of 3.0 mil thick white base paper at a total of 8 to lbs. per ream (total of both sides) using a trailing blade coater. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

Table l represents a comparison of the papers of this invention with conventional coated printing papers and with a selected plastic "paper", and a plastic-coated paper. Coated papers of the invention were those made in Examples 1 (unsupercalendared paper), and 2. Papers A through D represent typical commercial coated printing papers. Paper A1 is a sheet of typical paper that has bound on it a layer of extruded polyethylene. Paper B1 is an imitation paper, made entirely from a plastic material and is known as Ucar, manufactured by Union Carbide.

T-480 respectively. The K & N Receptivity Test was performed similar to TAPPI Routine Control Method RC-l9, except that the dyed test ink was left on the paper being tested ,for only one minute instead of the prescribed two minutes.

After the test was completed, a G. E. Brightness value was obtained on the tested area of the paper and this value was divided by the original brightness of the paper and multiplied by 100, yielding a value known as the percent brightness retained by the test area. The lower this value, the more receptive the paper is to the ink.

Coated printing papers must achieve a balance between ink receptive and ink holdout properties. Too much ink holdout could result in ink drying problems that might cause set-off of ink to sheets placed on top of the printed sheet, or even more serious, the sheet may not even accept a normal printing ink. 0n the other hand, coated printing papers must exhibit a certain amount of ink holdout for glossy prints and good definition.

To further compare these papers for ink receptivity and ink set-off characteristics, an ink-set off test was performed using the lGT Printability Test in conjunction with the Westvaco mm. Printing Disc. The ink used was lPl Speed King Process Blue Litho Ink. Generally, this procedure consists of metering ink onto the Westvaco Disc, transferring this ink at 50 kg pressure and M speed setting using the IGT Printability Tester to the sample being tested, and then after a specified time (the samples in Table I were tested after min.), placing a sheet of the same paper on top of the printed paper, clamping both samples in the tester, and putting an impression on both samples using the IGT 20 mm Printing Disc at a pressure of kg. This impression pressure causes undried ink on the original printed sample to set-off to the superimposed sample. The degree of ink set-off was measured by using a Densichron, manufactured by W. M. Welch Scientific Company, Chicago, 111., with the red filter and obtaining a percent transmission reading on the set-off area first by setting the instrument to read 100 percent transmission on the unprinted paper and then obtaining the reading of the ink set-off area. Therefore, the higher this value, the more light is reflected from the paper surface and the less set-off of ink has occurred.

Heat seals were made with both a Radio Frequency (RF) and impulse heat sealer. With the Radio Frequency Sealer pressure of 2,300 p.s.i. and heat at a temperature range of 300-350 F. were applied over an area 4 in. X l/ 16 in. for 0.25 sec. With the impulse sealer, pressure of 233 p.s.i. and heat at a temperature of 300350 F. were applied over an area 1 in. X H2 in. for4sec.

Heat seal strength was measured by employing a peel-type tensile test on the sealed sheets. For sheets sealed by RF, a 3- inch width seal was measured; for sheets sealed with the impulse sealer, a l-inch width seal was tested. The test was conducted by clamping the ends furthest from the seal of the respective bonded sheets in special jaws of an Instron Tensile Tester and the force required to peel the sheets apart was measured in lbs. per inch.

TABLE I Papers of invention Conventional coated Plastic coated or printing papers plastic paper Example Example Tests 1 2 A B C D A1 B1 G. E. brightness 83. 7 76. 9 77. 8 82. 3 81. l 80. 5 74. 6 86 8 Opaci y 93. 0 88. 0 92. 1 93. 6 93. 5 95.0 91. 5 88 2 G 055 s. 18. 5 12.0 13. 0 8. 0 16. 0 68. 0 55. 0 35- 0 K and N ink receptivity (percent brightness retained) 67. 3 75. 8 68. 0 57. 0 61. 8 76. 3 98. 2 91. 7 Ink set-ofi (percent transmission) 97. 7 71. 5 89. 5 80.1 92.9 80. O 24. 8 41. 2 Heat seal strength RF sealinglbs./in 0. 46 0.62 None None None None 0 82 None Heat seal strength impulse sealing-lbs./in 0. 68 0.58 None None None None 1 34 1. 64

The G. E. Brightness, Opacity, and Gloss tests were run according to TAPPI Standard Test Methods T-452, T-425, and

From the results of Table I, it is apparent that the papers of the invention are comparable to the conventional coated printing papers in optical and ink receptive properties. The plastic coated and plastic paper vary in optical properties but could compare to conventional coated papers. However, the ink receptive and set-off characteristics of these papers is so poor that normal printing inks could not be used to print them conventionally.

The seal strengths of the papers of this invention are not as great as the plastic or plastic-coated papers. However, the seals of the papers of the invention are adequate for binding by nature of the seals fiber pulling ability when peeled apart.

was prepared by the previously described second basic procedure where the resinous binder is cooked in the presence of water only and then the ingredients blended together, and water was added to adjust the solids content to 42 percent solids. The composition was applied to both sides of 3.0 mil thick white base paper at 12 lbs/ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220' F. for seconds per side.

was prepared to 42 percent solids in the manner described in 5' Example 3 and was applied to both sides of 3.0 mil thick white base paper at 12 lbs/ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F for 5 seconds per side.

EXAMPLE 5 A coating composition comprising:

Thermoplastic Resin-Poly(vinyl chloride) as described in Example 1 20.0 Inorganic Pigment-Clay pigment as described in Example 1 60.0 Resinous Binder-Hydroxyethyl ether substituted starch as described in Example 3 20.0 Total: 100.0

was prepared to 45 percent solids in the manner described in Example 3 and was applied to both sides of 3.0 mil thick white base paper at 12 lbs/ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

EXAMPLE 6 A coating composition comprising:

Thermoplastic Resin-Poly( vinyl chloride) as described in Example 1. 20.0 Inorganic Pigment-Clay pigment as described in Example I. 75.0 Resinous Binder-Poly(vinyl alcohol) as described in Example 3 5.0 Total: 100.0

was prepared to 52 percent solids in the manner described in Example 3 and applied to both sides of 3.0 mil thick white base paper at 13 lbs/ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

TABLE II Test results of Examples H K and N ink receptivity, G. E percent Heat seal Opacbn'ghtbrightness strength, Example ity ness Gloss retained lbs/in.

Table II lists the test results of Examples 3-6. These Examples utilized the approximate limits set forth for the compositions of this invention. From the results given, it is evident that the coated papers of these Examples were very close in optical and ink receptive properties to the typical commercial coated printing papers listed in Table l.

Table II also illustrates that the coated papers of these Examples were heat sealable, using conditions of RF heat sealing described in respect to Table I. All seals resulted in fiber rupturing bonds and were fully adequate for binding purposes.

EXAMPLE 7 The same composition as in Example 2 was prepared except that it was prepared to 28 percent solids and applied at 8 to 9 lbs. per ream using a size press.

EXAMPLE 8 A coating composition comprising:

Thermoplastic Resin-Styrene-butadiene copolymer as described in Example 2 20.0 Inorganic Pigment-Calcium carbonate as described in Example 1 75.0 Resinous BinderPoly( vinyl alcohol) as described in Example 1 5.0

Total: 100.0

was prepared to 48.6 percent solids in the manner as described in Example 2 was applied to 12 lbs. per ream (total of both sides) to 3.0 mil thick white base paper using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

. 1. EXAMPLE 9 A coating composition comprising:

EXAMELE 12 Wt. Wt.

Thermoplastic Resin Swrenebutadiene. Thermoplastic Resin-Polystyrene as described in acrylonitrile terpolymer (manufactured by ExamPle 1 Marbon Chemical Co., and available as Marmix n? T I) f i fif d 16123) as a 52% solids aqueous dispersion of the ggg zg s gg f 't' z grade terpolymer comammg. 80-85% Polymcnzed coating clay, HT Predispersed slurry, having an Styrene and less, average particle size of 0.8 microns 57.0 than 5% acrylonitrile, having an average particle (2) calcium carbonate Pigment as described size of 0.1 microns and coalescing temperature of in Example 1 60 about Resinous Binder-Poly( vinyl alcohol) as described Inorganic Pigmem-Calcium carbonate pigment as 1 5 in Example 1 70 described in Example 1 50.0 Total: 1000 Resinous Binder-Poly( vinyl alcohol) as described in Example 3 7.5 Total: 100.0

was prepared to 45.6 percent solids in the manner described in Example I and applied to both sides of 3.0 mil thick white was prepared to 37 percent solids in the manner as described paper at 8 to 10 per ream (total of sldejs) 3 trailing blade coater. The coated paper was dried with forced in Example 3 and applied to both sides of white base paper at hot air at 220 F for 5 Seconds p Side 6 to 10 lbs. per ream (total of both sides) using a Time-Life Bench Coater. The coated paper was dried with forced hot air A P 13 at 220 F. for 5 seconds per side.

A coating composition comprising: EXAMPLE 10 Wt. A coating composition comprising:

wt Thermoplastic Resin-Polystyrene as described in Example 11 30.0

Inorganic Pigments( l Clay pigment as described in Exam le 1 49.5 Thennoplastic Res1n-Vinyl chloride copolymer as galcium carbonate p g as described a 56% solids aqueous dispersion having an in Example 1 5'5 pamcle Slze of mlcmns a Resinous Binder-Styrene-butadiene copolymer as coalescmg temperamre of aboYc 250 a 50% solid aqueous dispersion of copolymer (manufactured by B. F. Goodrich Chemical Co. consisting f 60 Paris polymerized styrene, 40 and avallfiblc as Gcon 1) 620 parts polymerized butadiene, and manufactured inorganic Pigment-Calcium carbonate pigment as by Dow Chemical Co and available as Dow described in Example 1 40 Latex 620 15.0 Resinous BinderPoly(viny1 alcohol) as described Total. 1000 in Example 3 5.0 Total: 100.0

was prepared to 60 percent solids in the manner described in g Example 3 and applied to both sides of 3.0 mil thick white was prepared to 46 percent solids in the manner described in base paper at 95 to 12 per ream (total of both Sides) using Examplc 3 and PP to both of thick f a Mayer Rod. The coated paper was dried with forced hot air base paper at l l-l 2 lbs. per ream (total of both sides) using a at 220 fo 5 Seconds per Side. Mayer Rod. The coated paper was dried with forced hot air at 5 seconds per side. 50 EXAMPLE [4 EXAMPLE H A coating composition comprising: A Coatmg composmon compnsmg:

Wt. Wt. '77

Thermoplastic ResinPoly( vinyl chloride as Thermoplastic Resin-Polystyrene as a 50% sol ds described in Example 1 29 aqueous dispersion and havng an Inorganic Pigments( l Clay pigment as described particle size of 0.2 microns and a coalescing in Example I 51.50 temperature of about 300 F. (manufactured by (2) C l i carbonatc pigment as d ib d Dow Chemical Co., and available as Dow Latex in Example I 8.50 586) Resinous Binders( l) Poly(vinyl alcohol) as Inorganic Pigments( 1) Calcium carbonate described in Example 1 4.45

pigment as described in Example I 25.0 (2) Styrene-butadiene as a 50% solids (2) Clay pigment as described in Example 1 25.0 dispersion of copolymer consisting of 60 Resinous Binder-Poly(vinyl alcohol) as described parts polymerized styrene and 40 parts in Example 1 5.0 polymerized butadiene, and manufactured Total; [000 by the Sinclair-Koppers Co., and available as SinclaiFKoppers Latex K-55 E 4.45 Flow Modifiers( l) Carboxymethyl cellulose, manufactured by Hercules, Inc., and available as Cellulose Gui-n, grade 7 m, and having 0.65 to was prepared to 46 percent solids in the manner described in 0.85 carboxymethyl groups per Gum Example 1 and applied to both sides of 3.0 mil thick white anhydroglucose unit, molecular weight 10,000, base paper at 8-10 lbs. per ream (total of both sides) using a fg gfliz gzgigg cfiggersion as described 0.25 Time-Life Bench Coater. The coated paper was dried with in Example 1 L00 forced hot air at 220 F. for 5 seconds per side. 7 Insolubilizer-Glyoxal as described in Example 1 0.25

Total: 100.00

was prepared to 53 percent solids in the manner described in Example 1 and was applied to both sides of 3.0 mil thick white base paper at l l to 12 lbs. per ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for seconds per side.

EXAMPLE 15 A coating composition comprising:

was prepared to 56 percent solids in the manner described in Example 1 and was applied to both sides of 3.0 mil thick white base paper at 12-13 lbs. per ream (total of both sides) using a Time-Life Bench Coater. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

EXAMPLE 16 The same procedure as described in Example 15 was carried out except the 4.6 percent soybean protein was replaced with 4.6 percent hydroxyethyl ether substituted starch, as described in Example 3.

EXAMPLE 17 A coating composition comprising:

Thermoplastic Resin-Glycerol ester of polymerized rosin, as a 40% aqueous dispersion of said polymer which has a molecular weight of l 100, with 90% of particles having a particle size of 1 micron and a maximum particle size of 3 microns and a coalescing temperature of about 250 F manufactured by Hercules, lnc., and available as Dresinol 155 Inorganic PigmentClay pigment as described in Example 1 Resinous Binder-Poly( vinyl alcohol) as described in Example 3 7.0 Total: 100.0

was prepared to 42.5 percent solids in the manner described in Example 3 and applied to both sides of 3.0 mil thick white base paper at 13 lbs. per ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

EXAMPLE 18 A coating composition comprising:

Thermoplastic Resin-Powdered polyethylene,

average particle size 30 micron, melt index 5,

having a coalescing temperature of 300 F manufactured by U. S. 1. Chemicals, and available as Microthene FN 510 Microfine Polyethylene Powder 30.0 Inorganic Pigment-Clay pigment as described in Example 1 63.0 Resinous Binder-Poly( vinyl alcohol) as describe in Example 1 7.0 Total: 100.0

was prepared to 42-43 percent solids in the manner described in Example 1 and applied to both sides of 3.0 mil thick white base paper at 13 lbs. per ream (total of both sides) using a Mayer Rod. The coated paper was dried with forced hot air at 220 F. for 5 seconds per side.

The coated papers produced in Examples 7 through 18 were each very close in optical and ink receptive properties of typical conventional coated printing papers such as those listed in Table l. The coated papers of Examples 7 through 18 were each heat scalable, using conditions of RF heat sealing described in respect to Table l and the seals formed were all fully adequate for binding purposes.

What is claimed is:

1. Coated printing paper characterized by printing properties which are characteristic of clay-coated printing papers and in being bondable to itself by application of heat and pressure in selected areas to form a bound coated paper product such as a book, magazine, brochure, pamphlet, annual report, pad, envelope, or other printed paper products having bonded on at least one of its surfaces a coating comprising,

A. about 20 to about 65 percent discrete thermoplastic particles which are capable of forming an opaque coating from a dispersion thereof and remain discrete when dried at temperatures below about F. and which coalesce at temperatures of not less than about 140 F., the

average particle size of said discrete thermoplastic particles being less than about thirty microns,

B. about 75 to about 15 percent opaque pigment particles of an average particle size in the range from about 0.2 to about 5 microns, and

C. about 5 to about 20 percent binder which is film-forming between about room temperature and a temperature below about 140 F. for binding said thermoplastic particles and pigment particles together and to said paper,

said percentages being based on the total dry weight of said coating, the coat weight level of said coating being in the range from about 3 to about 15 pounds per side per ream (25X38-), said coated paper being bondable by pressure and heat sufficient to coalesce discrete thermoplastic particles and at temperatures below the temperature at which the paper deteriorates.

2. Coated paper as claimed in claim 1 wherein said thermoplastic particles coalesce at about 140 to about 400 F.

3. Coated paper as claimed in claim 1 wherein said pigment particles are calcium carbonate particles.

4. Coated paper as claimed in claim 1 wherein said pigment particles are titanium dioxide particles.

5. Coated paper as claimed in claim 1 wherein said pigment particles are clay particles.

6. Coated paper as claimed in claim 1 wherein said thermoplastic particles are poly(vinyl chloride) particles.

7. Coated paper as claimed in claim 1 wherein said thermoplastic particles are styrene-butadiene copolymer particles.

8. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are styrene-butadiene-acrylonitrile terpolyrner particles.

9. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are vinyl chloride-vinyl acetate copolymer particles.

10. Coated aper as claimed in claim 1 wherein said discrete thermoplastic particles are polystyrene particles.

11. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are polymerized rosin glycen'de particles.

12. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are polyethylene particles.

13. Coated paper as claimed in claim 1 wherein said binder is poly(vinyl alcohol) which is film forming at a temperature below about 140 F.

14. Coated paper as claimed in claim 1 wherein said binder is hydroxyethyl ether substituted starch which is film forming at a temperature below about 140 F.

15. Coated paper as claimed in claim 1 wherein said binder is styrene-butadiene copolymer which is film forming at a temperature below about 140 F.

16. Coated paper as claimed in claim 1 wherein said binder is protein which is film forming at a temperature below about 140 F.

17. A paper article comprising a plurality of sheets of coated paper as claimed in claim 1, the thermoplastic particles of the coating of one of said sheets being coalesced with the thermoplastic particles of another of said sheets.

18. Method of manufacturing coated paper which is printable and bondable by heat and pressure comprising the steps of applying to paper a composition comprising in an inert vehicle a mixture containing A. about to about 65 percent discrete thermoplastic particles which are capable of forming an opaque coating from a dispersion thereof and remain discrete when dried at temperatures below about 140 F. and which coalesce at temperatures of not less than about F., the average particle size of said discrete thermoplastic particles being less than about 30 microns,

B. about 75 to about 15 percent opaque pigment particles of an average particle size in the range from about 0.2 to about 5 microns, and

C. about 5 to about 20 binder which is film-forming between about room temperature and a temperature below about 140 F. for binding said thermoplastic particles and pigment particles together and to said paper,

said percentages being based on the total dry weight of the above listed components A, B and C, and thereafter removing the inert vehicle therefrom.

19. Method of manufacturing a paper article as claimed in claim 17 comprising contacting the coated surfaces of a plurality of sheets of coated paper as claimed in claim 1 with each other in the area desired to be bonded and compressing said sheets together in said area at a pressure of at least about 30 p.s.i. while heating the contacted coated surfaces in said area to a temperature sufficient under the applied pressure to cause the thermoplastic particles in the coating to coalesce and cooling to bond said sheets together.

20. Method as claimed in claim 19 wherein printing is applied to the coated surface of said sheets.

Claims (19)

1. 2. Coated paper as claimed in claim 1 wherein said thermoplastic particles coalesce at about 140* to about 400* F.
2. 3. Coated paper as claimed in claim 1 wherein said pigment particles are calcium carbonate particles.
3. 4. Coated paper as claimed in claim 1 wherein said pigment particles are titanium dioxide particles.
4. 5. Coated paper as claimed in claim 1 wherein said pigment particles are clay particles.
5. 6. Coated paper as claimed in claim 1 wherein said thermoplastic particles are poly(vinyl chloride) particles.
6. 7. Coated paper as claimed in claim 1 wherein said thermoplastic particles are styrene-butadiene copolymer particles.
7. 8. Coated paper as Claimed in claim 1 wherein said discrete thermoplastic particles are styrene-butadiene-acrylonitrile terpolymer particles.
8. 9. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are vinyl chloride-vinyl acetate copolymer particles.
9. 10. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are polystyrene particles.
10. 11. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are polymerized rosin glyceride particles.
11. 12. Coated paper as claimed in claim 1 wherein said discrete thermoplastic particles are polyethylene particles.
12. 13. Coated paper as claimed in claim 1 wherein said binder is poly(vinyl alcohol) which is film forming at a temperature below about 140* F.
13. 14. Coated paper as claimed in claim 1 wherein said binder is hydroxyethyl ether substituted starch which is film forming at a temperature below about 140* F.
14. 15. Coated paper as claimed in claim 1 wherein said binder is styrene-butadiene copolymer which is film forming at a temperature below about 140* F.
15. 16. Coated paper as claimed in claim 1 wherein said binder is protein which is film forming at a temperature below about 140* F.
16. 17. A paper article comprising a plurality of sheets of coated paper as claimed in claim 1, the thermoplastic particles of the coating of one of said sheets being coalesced with the thermoplastic particles of another of said sheets.
17. 18. Method of manufacturing coated paper which is printable and bondable by heat and pressure comprising the steps of applying to paper a composition comprising in an inert vehicle a mixture containing A. about 20 to about 65 percent discrete thermoplastic particles which are capable of forming an opaque coating from a dispersion thereof and remain discrete when dried at temperatures below about 140* F. and which coalesce at temperatures of not less than about 140* F., the average particle size of said discrete thermoplastic particles being less than about 30 microns, B. about 75 to about 15 percent opaque pigment particles of an average particle size in the range from about 0.2 to about 5 microns, and C. about 5 to about 20 binder which is film-forming between about room temperature and a temperature below about 140* F. for binding said thermoplastic particles and pigment particles together and to said paper, said percentages being based on the total dry weight of the above listed components A, B and C, and thereafter removing the inert vehicle therefrom.
18. 19. Method of manufacturing a paper article as claimed in claim 17 comprising contacting the coated surfaces of a plurality of sheets of coated paper as claimed in claim 1 with each other in the area desired to be bonded and compressing said sheets together in said area at a pressure of at least about 30 p.s.i. while heating the contacted coated surfaces in said area to a temperature sufficient under the applied pressure to cause the thermoplastic particles in the coating to coalesce and cooling to bond said sheets together.
19. 20. Method as claimed in claim 19 wherein printing is applied to the coated surface of said sheets.

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