US2370268A - Paper-coating composition - Google Patents

Paper-coating composition Download PDF

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US2370268A
US2370268A US502198A US50219843A US2370268A US 2370268 A US2370268 A US 2370268A US 502198 A US502198 A US 502198A US 50219843 A US50219843 A US 50219843A US 2370268 A US2370268 A US 2370268A
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zein
clay
water
coating
paper
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US502198A
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Charles W Stewart
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Corn Products Refining Co
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Corn Products Refining Co
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    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/46Non-macromolecular organic compounds
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/50Proteins

Definitions

  • This invention relates to the coating or filling of paper or like material with china clay, precipitated chalk, precipitated barium sulfate (blanc fixe) talc, titanium pigment, or other inert, argillaceous or mineral substance used for closing the pores of the paper so as to give thepaper a glossy surface and make it suitable; for example, for printing.
  • inert filling material is intended to include any and all materials used for this purpose; and when the term clay is used in the description, it will be understood that in place of clay any other suitable inert filling material may be employed as an equivalent.
  • casein as an adhesive or binder for the clay in compounds of this type; the coating consisting in such case, essentially, of clay, or other inert filling material, casein dissolved by an alkali or alkalinesalt such as borax or soda ash, and water.
  • the compound is ordinarily applied to the paper either by a roll coating machine or by a brush coating machine, after which the coated paper web is tightly drawn over a moving rubber apron or revolving drum. It is then dried in suitable drying apparatus, for example, in a festoon drier, through which the paper, webs, hung in loops from supports are moved'in an atmosphere controlled as to temperature and humidity. Finally, the coated paper is subjected to pressure between weighted calender rolls.
  • the present invention is based u on the discovery that it is possible, and mo eover prac tically feasible, to substitute for casein in' paper coating compounds zein, the alcohol soluble constituent of corn (maize) protein, provided the zein be dissolved or dispersed by the use of suitable dispersing agents as hereinafter described; and further, that by this substitution several very important and unexpected advantages are obtained namely:
  • casein-clay paper coating compound To prepare a casein-clay paper coating compound, the casein must be soaked in water for two to three hours and then dissolved with an alkali, oralkaline salt, soda ash, for example,
  • the coating material will be non-uniform and lumpy so as to interfere with proper printing.
  • the amount of zein required to fix a given quantity of clay is less than the amount of casein required.
  • zein-clay compound can be produced bymerely mixing together in water, and at room temperature, the clay, the zein and the zein dispersing agent; the operation. requiring only from about one-half hour to one hour depending on the character of the ingredients.-
  • One may also prepare paper about 10 to 12 parts. ofcasein per parts of clay, by weight, is required to give adequate adhesion. Equivalent results are obtained with 5 to 8 parts of zein.
  • larger amountsof clay will be required and proportionately larger amounts of the protein binder. Under these circumstances the advantage of using zein lnlplace of casein is enhanced.
  • zein-clay coating for paper to be used for half-tone printing.
  • the printing ink used for the half-tone background consists of a dispersion of pigment in oil; and the background consists of scattered ink dots on the spots where the oily ink is able to overcome the oil resistance of the protein.
  • Both casein and zein are-oil resistant to a greater or less extent. Therefore. the smaller the ratio of protein to clayfthe better will be the uniformity of the half-tone background.
  • the ink dots are larger and less uniform than when the protein content is lower, Moreover, it frequently happens that a small protein surface is so ink resistant that it does not 4 contact, a larger ink spot than was intended.
  • the zein-clay compound by separately dlssolving the zein in a mixture of water and dispersing agent and then combining the zein solution or the uniformity
  • a ratio. of protein to clay as may be done with the substitution or zein for casein, oi theahali-tone background is dispersion with the clay properly dlspersedln ll much improved.
  • a coating compound containing a given amount of casein will have a higher viscosity than one containing an equal quantity of zein. This difference is of considerable importance, particularly in the application of the coating to paper by means of a roll coating machine.
  • casein in order to obtain the proper viscosity for the roll coating machine, it is necessary to dilute the casein-clay dispersion-suspension to about 35% solids and 65% water. At this dilution the coating compound deposits only a thin coating on the paper, for example, about 6 pounds of the coating per ream of paper.
  • casein-clay coated paper when dried in a festoon drier of ordinary length, it may re uire a drying temperature between 120 and 130 F. with the zein-clay coating compound it has been found possible to do away entirely with artificial heating of the air. Or instead of this, the length of the drier, which is ordinarily very considerable, may be considerably reduced. Or the movement of the paper through the drier may be speeded up. In any case, the drying cost of the zein-clay coating is considerably reduced through increased capacity of the drying apparatus per unit of time or length of the drier, or through a reduction of temperature. or elimination of the heating apparatus and of temperature and humidity controls.
  • thermoplasticity of zein is substantially non-thermoplastic, that is. they retain their original rigidity when heated. Zein, on the contrary, becomes flexible under heat, or in other words, is-thermoplastic.
  • This advantage of zein resulting from its thermoplasticity is particularly important where a zein-clay coated paper is used for embossing. In the embossing of clay coated paper the paper is subjected to an embossing roll, which roll, by pressure and friction, heats the coating.
  • a zeinclay coating because of its thermoplasticity, can be given the embossed design without substantial distortion of the paper itself. That is, the design can be raised on the coated side of the paper without correspondingly recessing or indenting the reverse side of the paper. This is not possible with a casein-clay coating.
  • the coating compound of the present invention consists essentially of a dispersion, preferably a water dispersion, of zein in which the zein is dispersed or dissolved by means of a suitable dispersing agent or agents, and clay or other filling substance carried in suspension in said zein dispersion.
  • Foam inhibitors are commonly used in connection with casein-clay coating compounds, and may be desirable in some instances in the case of the zein-clay compounds of the present invention.
  • Suitable foam inhibiting substances are: pine oil; mixtures of pine oil and octyl alcohol; butyl alcohol; butyl stearate; amyl alcohol; lecithin; kerosene; and alum.
  • foam inhibitors are not required or at least their use minimized, as will be hereinafter described.
  • the zein dispersing agent may consist of, or contain the following substances: rosin size, for example the sodium soap of rosin containing, for instance about 60% dry substance and 40% water, or other soaps of abietic acid containin substances such as the potassium, ammonium or amine soaps of common rosins. hydrogenated rosins and ester gums; the sulfonated vegetable oils of the common vegetable oils, such as the castor oil; the soap of tall oil, which oil is a fatty acid mixture, that is the by-product of the wood pulp industry; the sulfonated mineral oils and-a preferred dispersing agent, as will be hereinafter described-sulfonated tall 011.
  • rosin size for example the sodium soap of rosin containing, for instance about 60% dry substance and 40% water, or other soaps of abietic acid containin substances such as the potassium, ammonium or amine soaps of common rosins. hydrogenated rosins and ester gums; the sulfonated vegetable oils
  • the soaps of abietic acid containing substances, the soaps of other oils such as tall oils, and the sulfonated oils may be used either singly or together.
  • any solvent or dispersant of zein, or solvent or dispersant mixture of zein which will give a zein solution or dispersion of sufllcient viscosity to hold the required amount of clay or other inert filling material in suspension, may be employed in this connection; and the term zein dispersing agent, as used herein, is intended to cover all such substances and compounds.
  • zein dispersing agent as used herein, is intended to cover all such substances and compounds.
  • the primary dispersing agent is a sulfonated oil or is an oil soap, it is preferable, but
  • the alkali is not used as a primary dispersing agent. -The amounts used are too small for this purpose.
  • the alkali does not form a reaction product with the zein as in the case when zein, as has been customary, is dissolved in strong, highly caustic solutions.
  • urea prevents the precipitation of the zein in aqueous dispersions where dispersing agents are used of such character as to reduce hydrogen ion concentration.
  • dispersing agents are used of such character as to reduce hydrogen ion concentration.
  • some of the sulfonated c'astor oils produce zein dispersions having pHs betwein 7 and 8. At this pH range the zein has a tendency to precipitate. The presence of urea retards this tendency.
  • a zein-clay dispersion will dry more quickly than a casein-clay dispersion. This may constitute an advantage, as indicated above; but in som cases it may be a detriment. ple, in the application of clay coatings with a brush coating machine, it is essential thatthe zein-clay coating should not dry or set so rapidly that the oscillating fiat brushes, which follow the revolving cylindrical brush, will gve an uneven or scratched surface to the coated paper.
  • the penetrating power of the dissolved protein element of a zein-clay dispersion is greater than the penetrating power of the protein in a caseinclay dispersion.
  • drying and penetration retarding agents agents which thicken the d spersion and which may be designated as "drying and penetration retarding agents.”
  • drying and penetration retarding agents are all, generally speaking, of a colloidal or mucillaginous character, such as thick boiling starch pastes, that is, ordinary commercial, non-modified corn or other starches in a pasted condition; acid hydrolyzed, thin boiling starches; heat gelatinized or cold water swelling starches; thin boiling gelatinized or cold water swelling starches; viscous chlorinated starches; oxid zed, thin boiling starches; and non-starch substances such asani mal glue, soya bean protein, blood albumin, algin. casein, and methylcellulose.
  • starch products are preferred for the purpose of retarding drying and pen tration; and experience with the several starch products, re-
  • starch in a zein-clay dispersion also appears to give a smoother surface to the finished coating.
  • Example 1 This compound is intended particularly for the roll type ofcoat ng machine.
  • the compound consists of the following substances in quantities, by weight, as follows. (In all examples the quantities are by weight unless otherwise specifled) Parts Zein 100 60% rosin size 170 Water 1,115 China clay 1,400 I The rosin size consists of 60% dry substance sodiumrosin soap and 40% water. The dry substance in the rosin size may vary between 10% and 100%. The ratio of zein to rosin size. dry substance basis, may vary between 1 to l and 10 to 4.
  • a festoon or other may vary between 20% and 65%.
  • the amount of rosin size must be suflicient to disperse the zein.
  • the product composed of the ingredients in the proportions given above, specifically, will have the right consistency for use in connection with a roll coating machine.
  • the paper after being coated is passed through drier which need not be beated, although the use of heat is not excluded.
  • coated paper may also be passed over heated drums, or it may be dried by a combination of heated drums and festoon driers, or through a heated tunnel where the paper, suitably suspended or supported is subjected to a blast of air. Or the drying may be accomplished by any combination of heated drums, heated tunnels and festoon driers. require as much heat as in the case of caseinclay coated papers.
  • the dried paper is then passed between the rolls of a series of pairs of calender rolls, which rolls, however, need not be weighted, or at least may have lighter weights than have been used heretofore.
  • this coating will be very strong, but the coating compound may have a tendency to foam so as to make advisable the use of foam inhibitors as described above.
  • Example 2 This compound is intended particularly for use in connection with a brush coating machine. It consists of the following substances in quantities, by weight, as follows, possible variations being indicated in parentheses:
  • Example 3 The coating compound consists of the following substances in quantities, by weight as follows:
  • 85% sulfonated castor oil is intended a sulfonated castor oil having a water content of about 15%.
  • the above described clay coating compound may be used either on a roll or brush coating machine, after proper adjustment of viscosity and dry substance content.
  • the resulting coating has been found to be superior in respect to water resistance and color to the coatingsproduced in accordance with Examples 1 and 2. It is believed that the ammonium rosin size contributes to improved color and improved water resistance.
  • Zein 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Sodium aluminate 0.4 (0.3 to 1.0) Urea 4 (1 to 8) Water 85 to 100) China clay 100
  • the zein is dispersed in the sulfonated castor oil and 25 parts (20 to 40 parts) of the water, and to this is added the mixture of urea and sodium aluminate.
  • the clay is puddled with the rest of the water until all lumps are removed and the .zein, dispersion is then mixed with the clay suspension. With the preferred amounts indicated above, this will give a clay coating compound containing about 57.5% dry substance.
  • Example 6 The coating compound consists of the following ingredients in quantities, by weight, as follows:
  • Example 7 The coating compound consists of the following substances in quantities,by weight, as follows:
  • Example 9 The compound consists of the following substances in quantities, by weight, as follows:
  • Example 12 The compound consists of the following substances in quantities, by weight, as follows: 1
  • Algin 0.4 (0 to 1) Algin, used herein as a drying and penetration retarding agent, is a by-product obtained during the extraction of iodine from sea kelp.
  • Example 14 The coating compound consists boiling starch
  • the sodium peroxide modified thin boiling starch which may have a fluidity of about 80, is used as a drying and penetration retarding agent.
  • the oxidized starch should be added in the pasted state. This is preferably accomplished by cooking the 2.5 parts of starch with 6 parts of water. Other oxidized starches might be used.
  • Example 15 The compound consists of the following substances in quantities, by weight, as follows:
  • the gelatinized tapioca starch is dissolved in 40 parts of the water, which may be cold.
  • the china clay mixed with the rest 01' the water is added to the starch suspension.
  • the zeinsulfonated castor oil-caustic soda mixture is mixed thoroughly with the clay-starch suspension. It appears to be desirable, if not necessary, to add the starch to the clay mix before compounding with the zein mix in order to obtain a smooth, non-lumpy and uniform mixture of all ingredients.
  • Example 16 The compound consists of the following substances in quantities, by weight, a
  • Example 17 The formula here isthe same as in Example 16 except that animal glue is used in place of starch paste. 2 parts of animal glue are mixed with 4 parts of the specified amount of water and heated to a paste. 10 parts more of the water is added to the paste and the ingredients mixed as in Example 16.
  • Example 18 The compound consists of the following substances in quantities, by weight, as-
  • the methylcellulose acts as a drying and penetration retarder.
  • the zein, sulfonated castor oil, caustic soda solution and 27.5% of the water are mixed together to form a zein dispersion.
  • 0.3 part of the caustic soda is used in making the zein-sulfonated tall oil dispersion.
  • 0.1 part of the caustic soda is used in puddling the clay and the rest of the water in order to obtain a better dispersion of the clay.
  • This expedient of using a small amount of an alkaline substance, particularly a caustic alkali, to improve the dispersion of the clay in the water, may be employed in any of the examples given above.
  • the zein-clay coating compound of this example has certain definite advantages as follows: (a) The zein is dispersed more quickly. With most, of the zein dispersions made from sulfonated castor oil or rosin size, it is necessary to mix the ingredients for about an hour, whereas,
  • the dispersion may be follows:
  • dispersing agents suitable for the purposes of the present invention include the following water soluble, highly ionized, compounds containing 8 or more carbon atoms: (1) the alkali metal, ammonia and amine soaps; (2) the sulfonated vegetable oils; (3) the sulfated and sulfonated fatty acids and alkali metal, ammonia and amine and other water soluble salts of said sulfated and sulfonated fatty acids; (4) the sulfated and sulfonated fattyalcohols and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty alcohols; (5) the alkali metal, ammonia, amine and other water soluble salts of alkyl, aryl, alkyl aryl, and heterocyclic sulfonic acids; (6) the salts of aryl carboxy-lic acid; and ('7) derivatives of
  • rosin soap formed by combining rosin with caustic soda may employ the following: rosin soap formed by combining rosin with caustic soda; amine iaurate soap formed by combining lauric acid with triethanolamine; amine soap formed by combining lauric acid with monomethylamine; ammonium soap of rosin; ammonium soap of linseed oil fatty acids; .rosin soap composed of rosin and morpholine; sodium stearate; sulfated stearyl alcohol (Avitex S. F.); sodium salt of alkyl naphthalene sulfonic acid (Nekal B. X); oleyl ethane sulfonic acid salt derived by extraction with alcohol from the commercial product Igepon A, P.
  • alco hol is preferably absent, as follows: (1) the alkali metal, ammonia, and amine soaps; (2) the sulfonated vegetable oils; (3) the sulfated and sulfonated fatty acids and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty acids; (4) the sulfated and sulfonated fatty alcohols and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty alcohols; (5) the alkali metal, ammonia, amine, and other water soluble salts of the alkyl, aryl, alkyl aryl, and heterocyclic sulfonic acids; (6) the salts of aryl carboxylic acid; and (7) derivatives of
  • Iclaim Composition of matter suitable for coating paper comprising the following substances in ztoloparts.

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Description

Patented Feb. 27, 1945 Q PAPER-COATING oomosmoN Charles W. Stewart, River Forest, 111., minor to I Corn Products Refining Company, New
N. Y., a corporation of New Jersey Original application October 1, No. 413,128. Divided and this ap- No Drawing.
1941, Serial York,
plication September 13, 1943, Serial No. 502,198
1 Claim. (Cl. 106150) This invention relates to the coating or filling of paper or like material with china clay, precipitated chalk, precipitated barium sulfate (blanc fixe) talc, titanium pigment, or other inert, argillaceous or mineral substance used for closing the pores of the paper so as to give thepaper a glossy surface and make it suitable; for example, for printing. The term inert filling material, as used herein, is intended to include any and all materials used for this purpose; and when the term clay is used in the description, it will be understood that in place of clay any other suitable inert filling material may be employed as an equivalent. I
This application is a division of application Serial No. 413,128, filed October 1, 1941.
It has been customary heretofore to use casein as an adhesive or binder for the clay in compounds of this type; the coating consisting in such case, essentially, of clay, or other inert filling material, casein dissolved by an alkali or alkalinesalt such as borax or soda ash, and water. The compound is ordinarily applied to the paper either by a roll coating machine or by a brush coating machine, after which the coated paper web is tightly drawn over a moving rubber apron or revolving drum. It is then dried in suitable drying apparatus, for example, in a festoon drier, through which the paper, webs, hung in loops from supports are moved'in an atmosphere controlled as to temperature and humidity. Finally, the coated paper is subjected to pressure between weighted calender rolls.
The present invention is based u on the discovery that it is possible, and mo eover prac tically feasible, to substitute for casein in' paper coating compounds zein, the alcohol soluble constituent of corn (maize) protein, provided the zein be dissolved or dispersed by the use of suitable dispersing agents as hereinafter described; and further, that by this substitution several very important and unexpected advantages are obtained namely:
(1) The preparation and mixing of the ingredients is simplified and made less costly. The
water. To prepare a casein-clay paper coating compound, the casein must be soaked in water for two to three hours and then dissolved with an alkali, oralkaline salt, soda ash, for example,
at an elevated temperature, for instance at about 150 F., otherwise the coating material will be non-uniform and lumpy so as to interfere with proper printing.
(2) The amount of zein required to fix a given quantity of clay is less than the amount of casein required. For example, for ordinary printing zein-clay compound can be produced bymerely mixing together in water, and at room temperature, the clay, the zein and the zein dispersing agent; the operation. requiring only from about one-half hour to one hour depending on the character of the ingredients.- One may also prepare paper about 10 to 12 parts. ofcasein per parts of clay, by weight, is required to give adequate adhesion. Equivalent results are obtained with 5 to 8 parts of zein. For higher gloss papers (referring to the gloss of the paper before printmg) ,larger amountsof clay will be required and proportionately larger amounts of the protein binder. Under these circumstances the advantage of using zein lnlplace of casein is enhanced.
(3) For gloss printing where a' high gloss or varnish-like printed surface is required, it is ordinarily necessaryto use between 16 and 20 parts of casein per 100 parts of clay. Equivalent results in respect to the gloss of the printed surface may be obtained by using 10 to 12 parts of zein per 100 parts of clay.
It will be understood that the comparative fi uresgiven in the preceding numbered paragraphs are approximate and typical. They are not intended to be exact for all operations.
(4) There is a special advantage in the use of a zein-clay coating for paper to be used for half-tone printing. The printing ink used for the half-tone background consists of a dispersion of pigment in oil; and the background consists of scattered ink dots on the spots where the oily ink is able to overcome the oil resistance of the protein. Both casein and zein are-oil resistant to a greater or less extent. Therefore. the smaller the ratio of protein to clayfthe better will be the uniformity of the half-tone background. Where the protein content of the clay coating is high, the ink dots are larger and less uniform than when the protein content is lower, Moreover, it frequently happens that a small protein surface is so ink resistant that it does not 4 contact, a larger ink spot than was intended.
the zein-clay compound by separately dlssolving the zein in a mixture of water and dispersing agent and then combining the zein solution or the uniformity By reducing the ratio. of protein to clay, as may be done with the substitution or zein for casein, oi theahali-tone background is dispersion with the clay properly dlspersedln ll much improved. a
A coating compound containing a given amount of casein will have a higher viscosity than one containing an equal quantity of zein. This difference is of considerable importance, particularly in the application of the coating to paper by means of a roll coating machine. With casein, in order to obtain the proper viscosity for the roll coating machine, it is necessary to dilute the casein-clay dispersion-suspension to about 35% solids and 65% water. At this dilution the coating compound deposits only a thin coating on the paper, for example, about 6 pounds of the coating per ream of paper. Therefore, in the case of roll coating machine operations, it has usually been found necessary, where the binder consists of casein, to give the paper two coatings in order that the necessary amount, say 12 pounds, of clay coating per ream may be deposited on the paper. Because of the lower viscosity of zeinclay dispersions of the same dry substance protein content, it is possible to increase the dry substance protein in the zein-clay coating compound and yet have the viscosity suiilciently low so as to make the compound workable on the roll coating machine. For example, experience has proven that zein-clay dispersions containing about 60% of solids and 40% of water may be used on the roll coating machine to deposit, in a single coating, about 12 pounds of clay coating per ream of paper.
(6) The cost of drying a zein-clay coating is less than the cost of drying a casein-clay coating. This appears to be due to two factors: lower viscosity, which makes possible higher concentration in the case of zein-clay coating compounds, so that there is less water to be dried out; and the fact that in the casein-clay compound the water is more closely held than in the zein-clay compound so that the moisture is less easily driven off.
For example, when the casein-clay coated paper is dried in a festoon drier of ordinary length, it may re uire a drying temperature between 120 and 130 F. with the zein-clay coating compound it has been found possible to do away entirely with artificial heating of the air. Or instead of this, the length of the drier, which is ordinarily very considerable, may be considerably reduced. Or the movement of the paper through the drier may be speeded up. In any case, the drying cost of the zein-clay coating is considerably reduced through increased capacity of the drying apparatus per unit of time or length of the drier, or through a reduction of temperature. or elimination of the heating apparatus and of temperature and humidity controls.
(7) The cost of the operation of the calender rolls. in the case 'of zein-clay coatings, is reduced. Zein has the property of producing a betat all. or the weights may be lighter, and this results in a saving of power.
(8) Another advantage follows from the thermoplasticity of zein. Casein containing coatings are substantially non-thermoplastic, that is. they retain their original rigidity when heated. Zein, on the contrary, becomes flexible under heat, or in other words, is-thermoplastic. This advantage of zein resulting from its thermoplasticity is particularly important where a zein-clay coated paper is used for embossing. In the embossing of clay coated paper the paper is subjected to an embossing roll, which roll, by pressure and friction, heats the coating. A zeinclay coating, because of its thermoplasticity, can be given the embossed design without substantial distortion of the paper itself. That is, the design can be raised on the coated side of the paper without correspondingly recessing or indenting the reverse side of the paper. This is not possible with a casein-clay coating.
The coating compound of the present invention consists essentially of a dispersion, preferably a water dispersion, of zein in which the zein is dispersed or dissolved by means of a suitable dispersing agent or agents, and clay or other filling substance carried in suspension in said zein dispersion.
Foam inhibitors are commonly used in connection with casein-clay coating compounds, and may be desirable in some instances in the case of the zein-clay compounds of the present invention. Suitable foam inhibiting substances are: pine oil; mixtures of pine oil and octyl alcohol; butyl alcohol; butyl stearate; amyl alcohol; lecithin; kerosene; and alum.
When certain zein dispersing agents are used, in accordance with the present invention, the use of foam inhibitors is not required or at least their use minimized, as will be hereinafter described.
The zein dispersing agent may consist of, or contain the following substances: rosin size, for example the sodium soap of rosin containing, for instance about 60% dry substance and 40% water, or other soaps of abietic acid containin substances such as the potassium, ammonium or amine soaps of common rosins. hydrogenated rosins and ester gums; the sulfonated vegetable oils of the common vegetable oils, such as the castor oil; the soap of tall oil, which oil is a fatty acid mixture, that is the by-product of the wood pulp industry; the sulfonated mineral oils and-a preferred dispersing agent, as will be hereinafter described-sulfonated tall 011. The soaps of abietic acid containing substances, the soaps of other oils such as tall oils, and the sulfonated oils may be used either singly or together. In fact, any solvent or dispersant of zein, or solvent or dispersant mixture of zein, which will give a zein solution or dispersion of sufllcient viscosity to hold the required amount of clay or other inert filling material in suspension, may be employed in this connection; and the term zein dispersing agent, as used herein, is intended to cover all such substances and compounds. One may. for example, employ in this connection any of the zein dispersing agents described in applicant's copending application, Serial No. 349,288, filed August 1, 1940, for "Zein dispersions and process of making the same, or any of the zein dispersing a ents disclosed in the pending application of Albert Luther James, Serial No. 351,274, filed August 3, 1940, for Zein dispersons'and processes of making same.
However, the present specification will give certain preferred dispersing agents and the methods of compounding the same with the clay to form zein-clay dispersions suitable for carrying out the present invention by processes which have been found desirable and expedient.
when the primary dispersing agent is a sulfonated oil or is an oil soap, it is preferable, but
' tion is to aid the primary dispersing agent. in
bringing about a complete dispersion of the zein. In such case the alkali is not used as a primary dispersing agent. -The amounts used are too small for this purpose. The alkali does not form a reaction product with the zein as in the case when zein, as has been customary, is dissolved in strong, highly caustic solutions.
It is also preferable to mix a small amount of caustic alkali with the clay to facilitate its dispersion. 0.1 of the clay, dry substance basis.
It is advantageous but not essential to incorporate urea with the other substances constituting the dispersing agent. It has been found that the addition of urea to a zein-clay coating compound increases the solubility of the zein and gives a lower viscosity for the same dry substance content, and thereby improves workability in the coating machines. Finally, the urea prevents the precipitation of the zein in aqueous dispersions where dispersing agents are used of such character as to reduce hydrogen ion concentration. For example, some of the sulfonated c'astor oils produce zein dispersions having pHs betwein 7 and 8. At this pH range the zein has a tendency to precipitate. The presence of urea retards this tendency.
A zein-clay dispersion will dry more quickly than a casein-clay dispersion. This may constitute an advantage, as indicated above; but in som cases it may be a detriment. ple, in the application of clay coatings with a brush coating machine, it is essential thatthe zein-clay coating should not dry or set so rapidly that the oscillating fiat brushes, which follow the revolving cylindrical brush, will gve an uneven or scratched surface to the coated paper.
The penetrating power of the dissolved protein element of a zein-clay dispersion is greater than the penetrating power of the protein in a caseinclay dispersion. The degree of penetration-will naturally depend upon the fibrous character of the paper. When zein penetrates into the paper, separation necessarily takes place between the dissolved zein and the clay which latter is not capable of penetrating; the paper to the same extent. This may result in lack of adhesion of the clay.
The too rapid drying of the zein solution and the tendency of the dissolved zein to penetrate the paper excessively may be counteracted, in accordance with the present invention by the addition of agents which thicken the d spersion and which may be designated as "drying and penetration retarding agents." These agents are all, generally speaking, of a colloidal or mucillaginous character, such as thick boiling starch pastes, that is, ordinary commercial, non-modified corn or other starches in a pasted condition; acid hydrolyzed, thin boiling starches; heat gelatinized or cold water swelling starches; thin boiling gelatinized or cold water swelling starches; viscous chlorinated starches; oxid zed, thin boiling starches; and non-starch substances such asani mal glue, soya bean protein, blood albumin, algin. casein, and methylcellulose. I
For the purpose of retarding drying and pen tration, the starch products are preferred; and experience with the several starch products, re-
- ferred to above, indicate that a heat gelatinized The amount used is preferably about For examor cold swelling tapioca starch gives the best results. In comparison with the other starch products referred to a lesser quantity is required to give the same viscosity; it has greater capacity for retarding the drying of the zein. clay coating. It assists in giving a better bond of the clay to the paper; it produces a finer colloidal dispersion and, for that reason, is able to reta'rd the penetration of the zein into the interiorof the paper sheet; and, beinga cold water swelling or pasting product, it does not require cooking in order to paste it. However, any thickening colloidal or mucillaginous material can be usedand will be effective to a certain extent. In general, one should use only the amount of starch or other agent which will retard drying and retard zein penetration to the desiredextent without giving the zein-clay dispersion too high a viscosity for working conditions.
The use of starch in a zein-clay dispersion also appears to give a smoother surface to the finished coating.
The following are specific examples illustrating the reduction of the present invention to practice. It will be understood, however, that these examples are purely illustrative and typical and are not to be considered as limiting the invention to the particular data given therein. The intention is to cover all equivalents and also all modifications within the scope of the hereto appended claims.
Example 1.-This compound is intended particularly for the roll type ofcoat ng machine. The compound consists of the following substances in quantities, by weight, as follows. (In all examples the quantities are by weight unless otherwise specifled) Parts Zein 100 60% rosin size 170 Water 1,115 China clay 1,400 I The rosin size consists of 60% dry substance sodiumrosin soap and 40% water. The dry substance in the rosin size may vary between 10% and 100%. The ratio of zein to rosin size. dry substance basis, may vary between 1 to l and 10 to 4.
a festoon or other may vary between 20% and 65%.
.the desired coating in respect to adhesiveness,
gloss of coating and gloss of the printed surface. In any case, the amount of rosin size must be suflicient to disperse the zein.
The product composed of the ingredients in the proportions given above, specifically, will have the right consistency for use in connection with a roll coating machine.
The paper after being coated is passed through drier which need not be beated, although the use of heat is not excluded. The
coated paper may also be passed over heated drums, or it may be dried by a combination of heated drums and festoon driers, or through a heated tunnel where the paper, suitably suspended or supported is subjected to a blast of air. Or the drying may be accomplished by any combination of heated drums, heated tunnels and festoon driers. require as much heat as in the case of caseinclay coated papers. The dried paper is then passed between the rolls of a series of pairs of calender rolls, which rolls, however, need not be weighted, or at least may have lighter weights than have been used heretofore.
The bond of this coating will be very strong, but the coating compound may have a tendency to foam so as to make advisable the use of foam inhibitors as described above.
Example 2.This compound is intended particularly for use in connection with a brush coating machine. It consists of the following substances in quantities, by weight, as follows, possible variations being indicated in parentheses:
In any case the drying will not Parts Zein 10 (6 to 12) Sulfonated castor oil 4 (1 to 12) Caustic soda 0.4 (0.2 to 0.6) Water 125 (80 to 150) China clay 100 generally speaking, a change in the quantity of one ingredient from the specified preferred amount should be accompanied by a correspondingchange in the quantities of the other ingredients in order to obtain the best results.
Example 3.--The coating compound consists of the following substances in quantities, by weight as follows:
Parts Zein 8 (6 to 12) 85% sulfonated castor oil 3 (3 to 5) Ammonium rosin(Staybelite size) 5 (3 to 8) Water 90 (85 to 150)' China clay 100 By 85% sulfonated castor oil" is intended a sulfonated castor oil having a water content of about 15%.
Approximately one-third of the water (not counting that in the sulfonated castor oil) is mixed with the sulfonated castor oil and the ammonium rosin size, and the zein dispersed in this mixture. Into the zein dispersion, thus formed, is mixed the clay and the rest of the water, and the mixture is puddled until all lumps are removed.
The above described clay coating compound may be used either on a roll or brush coating machine, after proper adjustment of viscosity and dry substance content. The resulting coating has been found to be superior in respect to water resistance and color to the coatingsproduced in accordance with Examples 1 and 2. It is believed that the ammonium rosin size contributes to improved color and improved water resistance.
as'raees Parts Zein 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Sodium aluminate 0.4 (0.3 to 1.0) Urea 4 (1 to 8) Water 85 to 100) China clay 100 The zein is dispersed in the sulfonated castor oil and 25 parts (20 to 40 parts) of the water, and to this is added the mixture of urea and sodium aluminate. The clay is puddled with the rest of the water until all lumps are removed and the .zein, dispersion is then mixed with the clay suspension. With the preferred amounts indicated above, this will give a clay coating compound containing about 57.5% dry substance.
Example 6.The coating compound consists of the following ingredients in quantities, by weight, as follows:
Parts Zein 8 (6 to 12) sulfonated castor oil 4 (3 to '8) Urea 4 (3 to 8) Water 85 (80 to China clay 100 It will be noted that in this example the alkaline sodium aluminate of Example 4 is omitted.
Example 7.-The coating compound consists of the following substances in quantities,by weight, as follows:
Parts Zein 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Bor 1 (0.8 to 2) Urea 4 (1 to 8) Water 85 (80 to 100) China clay 100 Example 8.The compound consists of the following substances in quantities, by -weight, as follows:
, Parts Zein. 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Concentrated ammonium hydroxide solution, 28% concentration 1 Urea 4 (1 to 8) Water 85 (80 to 100) China clay 100 I Example 9.The compound consists of the following substances in quantities, by weight, as follows:
China clay Example lit-The compound consists of the iollowing substances in quantities, by weight. as follows:
Parts Zein I I 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Trisodium phosphate 0.5 Urea 4 (1 to 8) Water 85 (80 to 100) China clay 100 Example 11.The compound consists of the followingsubstances in quantities, by weight, as follows:
Ewample 12.The compound consists of the following substances in quantities, by weight, as follows: 1
Parts Zein 8 (6 to 12) Sulfonated mineral oil 4 (3 to 6) Concentrated ammonium hydroxmp 2 (1.5 to 3) Urea 4 (1 to 8) Water 85 (80 to 100) China clay Example 13.--The compound consists of the following substances in quantities, by weight, as
follows:
Parts Zein 8 (6 to 12) 85% sulfonated castor oil 3 (2 to 8) Sodium aluminate 0.4 (0.3 to 1) Urea 4 (1 to 8) Water 85 (80 to 100) China clay 100 Algin 0.4 (0 to 1) Algin, used herein as a drying and penetration retarding agent, is a by-product obtained during the extraction of iodine from sea kelp.
Example 14.The coating compound consists boiling starch The sodium peroxide modified thin boiling starch, which may have a fluidity of about 80, is used as a drying and penetration retarding agent. The oxidized starch should be added in the pasted state. This is preferably accomplished by cooking the 2.5 parts of starch with 6 parts of water. Other oxidized starches might be used.
Example 15.--The compound consists of the following substances in quantities, by weight, as follows:
Parts Zein 8 sulfonated castor oil 8 Water China clay 100 Heat gelatinized or cold swelling tapi-v oca starch 3 (3 to 5).
The gelatinized tapioca starch is dissolved in 40 parts of the water, which may be cold. The china clay mixed with the rest 01' the water is added to the starch suspension. Finally, the zeinsulfonated castor oil-caustic soda mixture is mixed thoroughly with the clay-starch suspension. It appears to be desirable, if not necessary, to add the starch to the clay mix before compounding with the zein mix in order to obtain a smooth, non-lumpy and uniform mixture of all ingredients.
' Example 16.-The compound consists of the following substances in quantities, by weight, a
follows:
Parts Zein 6 85% sulfonated castor oil 8 Sodium aluminate 0.3 Water 100 China clay 100 Thin boiling chlorinated starch 6 A paste is ,made by cooking the thin boiling chlorinated starch in 40 parts 0! the water. The clayis puddled in the rest of the water. The paste is cooled and all of the ingredients mixed together, namely: the clay-water dispersion, the zein-sulfonated cil dispersion, and the cold starch paste.
Example 17.The formula here isthe same as in Example 16 except that animal glue is used in place of starch paste. 2 parts of animal glue are mixed with 4 parts of the specified amount of water and heated to a paste. 10 parts more of the water is added to the paste and the ingredients mixed as in Example 16.
Example 18.-The compound consists of the following substances in quantities, by weight, as-
The methylcellulose acts as a drying and penetration retarder.
The zein, sulfonated castor oil, caustic soda solution and 27.5% of the water are mixed together to form a zein dispersion. The clay, the
rest of the water and the methylcellulose are mixed together and the two mixtures combined.
Example '19.--The compound consists of the following substances in quantities; by weight, as follows:
Parts Zein 8 (6 to 16) Tall oil 4 (4 to 12) Urea 4 (2 to 8) Ammonium hydroxide 2 (2 to 6) Water ..l 85 (60 to 200) China clay Example 20.'I'he compound consists of the following substances in quantities, by weight, as follows:
, 'Parts Zein 8 (6 to 16) 63% sulfonated tall oil (2 to 8) Caustic soda 0.4 (0.3 to 0.5) Water 100 (60 to 200) China clay 100 63% sulfonated tall oil has a water content of 37% not included in the specified 100 parts.
0.3 part of the caustic soda is used in making the zein-sulfonated tall oil dispersion. 0.1 part of the caustic soda is used in puddling the clay and the rest of the water in order to obtain a better dispersion of the clay.
This expedient of using a small amount of an alkaline substance, particularly a caustic alkali, to improve the dispersion of the clay in the water, may be employed in any of the examples given above.
The zein-clay coating compound of this example has certain definite advantages as follows: (a) The zein is dispersed more quickly. With most, of the zein dispersions made from sulfonated castor oil or rosin size, it is necessary to mix the ingredients for about an hour, whereas,
by the use of this formula the dispersion may be follows:
Parts Zein 16 (12 to 32) 63% sulfonated tall oil 5 (4 to 12) Potassium rosin size made from hydrogenated rosin (Staybelite) --L. 10 (4 to 20)- Sodium hydroxide 0.4 (0.3 to 0.75) Water 200 (150 to 400) China clay 200 Heat gelatinized tapioca starch. 6 (2 to 10) The sodium hydroxide is dissolved in 2.5 parts of the water and the gelatinized tapioca starch in the rest of the water. The china clay is mixed with the water mixture of the starch and this mixture is combined with the zein, sulfonated tall oil, rosin and sodium hydroxide dispersion. About 0.1 part of the caustic soda is introduced into the clay suspension before this suspension is added to the zein dispersion.
In both Examples 20 and 21 in which sulfonated tall oil is used, it appears to be important, if the best results are to be obtained, to introduce into the compound a small quantity of an alkaline substance, particularly caustic soda or caustic potash. It also appears to be important to introduce into the clay a small quantity of the caustic when the clay is puddled with the water or diluted starch paste.
In place of the zein dispersing agents men- -tioned in the foregoing examples one may use any of the zein dispersing agents disclosed in the application of Stewart, Serial No: 349,288, which,
in all cases, involve a certain amount of alcohol, aqueous ethyl, methyl, isopropyl, or high boiling point organic zein solvent,'-but with water also present in such large quantity that, except for the dispersing agent, the zein would be precipitated. As set forth in the Stewart application, dispersing agents suitable for the purposes of the present invention include the following water soluble, highly ionized, compounds containing 8 or more carbon atoms: (1) the alkali metal, ammonia and amine soaps; (2) the sulfonated vegetable oils; (3) the sulfated and sulfonated fatty acids and alkali metal, ammonia and amine and other water soluble salts of said sulfated and sulfonated fatty acids; (4) the sulfated and sulfonated fattyalcohols and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty alcohols; (5) the alkali metal, ammonia, amine and other water soluble salts of alkyl, aryl, alkyl aryl, and heterocyclic sulfonic acids; (6) the salts of aryl carboxy-lic acid; and ('7) derivatives of any of these groups which contain at least eight carbon atoms in the organic radical and substituent group taken together.
As specific examples of the groups just mentioned one may employ the following: rosin soap formed by combining rosin with caustic soda; amine iaurate soap formed by combining lauric acid with triethanolamine; amine soap formed by combining lauric acid with monomethylamine; ammonium soap of rosin; ammonium soap of linseed oil fatty acids; .rosin soap composed of rosin and morpholine; sodium stearate; sulfated stearyl alcohol (Avitex S. F.); sodium salt of alkyl naphthalene sulfonic acid (Nekal B. X); oleyl ethane sulfonic acid salt derived by extraction with alcohol from the commercial product Igepon A, P.
One may also use any of the zein dispersing agents disclosed in said application of Albert Luther James, Serial No. 251,274, in which alco hol is preferably absent, as follows: (1) the alkali metal, ammonia, and amine soaps; (2) the sulfonated vegetable oils; (3) the sulfated and sulfonated fatty acids and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty acids; (4) the sulfated and sulfonated fatty alcohols and the alkali metal, ammonia, amine and other water soluble salts of said sulfated and sulfonated fatty alcohols; (5) the alkali metal, ammonia, amine, and other water soluble salts of the alkyl, aryl, alkyl aryl, and heterocyclic sulfonic acids; (6) the salts of aryl carboxylic acid; and (7) derivatives of any of these groups which contain at least eight carbon atoms in the organic radical and substit-,
-' triethanolamine cleate; triethanolamine palmitate; ammonium naphthenate; sodium soap produced by the reaction of stearic acid with sodium hydroxide; Avitex S. F.; Nekal B. X; Triton zein 12 to 32 parts; sulionatcd tall oil 4 to 12 parts; potassium rosin size made from hydrogenated rosin 4 to 20 parts; sodium hydroxide 0.3 to 0.75 part; water 150 to 400parts; china 5 clay 200 parts; heat zelatinized tapioca starch 1-18, a reaction produced of a fatty acid with an aryl alkylatcd amine; Decersol O. T., a sodium salt of a sulfate 01 dicarboxylic acid ester; Igepon A. P.
Iclaim: Composition of matter suitable for coating paper comprising the following substances in ztoloparts.
ems w. s'mwm'r.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2736663A (en) * 1951-03-09 1956-02-28 Sherwin Williams Co Production of nonallergen reacting protein coatings from allergen-containing pomaces

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2736663A (en) * 1951-03-09 1956-02-28 Sherwin Williams Co Production of nonallergen reacting protein coatings from allergen-containing pomaces

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