Source: http://www.google.de/patents/US3968319?hl=de
Timestamp: 2013-12-11 22:25:02
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Patent US3968319 - Plastic pigments for paper coatings - Google PatenteSuche Bilder Maps Play YouTube News Gmail Drive Mehr » Erweiterte Patentsuche | Anmelden Erweiterte Patentsuche PatentePaper coatings exhibiting improved pick resistance at lower binder levels are provided by incorporating into a conventional binder a pigment comprising a copolymer of an ethylenically unsaturated hard monomer such as styrene and an ethylenically unsaturated amide such as acrylamide in the form of non-film...http://www.google.de/patents/US3968319?utm_source=gb-gplus-sharePatent US3968319 - Plastic pigments for paper coatings Ver�ffentlichungsnummerUS3968319 APublikationstypErteilung AnmeldenummerUS 05/478,125 Ver�ffentlichungsdatum6. Juli 1976Eingetragen10. Juni 1974 Priorit�tsdatum10. Juni 1974Auch ver�ffentlicht unterCA1035900A1 Ver�ffentlichungsnummer05478125, 478125, US 3968319 A, US 3968319A, US-A-3968319, US3968319 A, US3968319A ErfinderInder Mani, Alexander ShandUrspr�nglich Bevollm�chtigterThe Dow Chemical CompanyZitat exportierenBiBTeX, EndNote, RefManPatentzitate (3), Referenziert von (24), Klassifizierungen (21) Externe Links: USPTO, USPTO-Zuordnung, EspacenetPlastic pigments for paper coatingsUS 3968319 A Zusammenfassung Paper coatings exhibiting improved pick resistance at lower binder levels are provided by incorporating into a conventional binder a pigment comprising a copolymer of an ethylenically unsaturated hard monomer such as styrene and an ethylenically unsaturated amide such as acrylamide in the form of non-film forming discrete particles having an average particle diameter in the range from about 0.25 to about 1 micrometer.
What is claimed is: 1. A coated paper comprising a paper substrate having adhered thereto a coating composition comprising a binding amount of from about 1.3 to about 11.5 dry volume parts of a binder and an opacifying amount of 38.8 dry volume parts of a pigment, provided that at least a portion of said pigment is in the form of an amide pigment comprising a water-insoluble copolymer of an emulsion polymerizable, α,β-ethylenically unsaturated hard monomer and at least about 1 weight percent of an emulsion polymerizable, α,β-ethylenically unsaturated amide in the form of non-film forming discrete particles having an average particle diameter in the range from about 0.25 to about 1 micrometer with no more than 10 weight percent of said particles having diameters outside said range, said unsaturated amide being selected from the group consisting of acrylamide, methacrylamide, amides of fumaric acid, maleic acid, itaconic acid and citraconic acid, N-isopropylacrylamide, and N-(2-hydroxyethyl)acrylamide, said portion of amide pigment being sufficient to impart improved pick resistance as compared to a coating containing only inorganic pigment.
BACKGROUND OF THE INVENTION This invention relates to plastic pigments for paper coatings having excellent opacity, visual gloss and improved pick resistance.
SUMMARY OF THE INVENTION In one aspect, the present invention is a novel plastic pigment comprising a water-insoluble, copolymer of an ethylenically unsaturated hard monomer and at least about 1 weight percent of ethylenically unsaturated amide in the form of non-film forming discrete particles having an average diameter in the range from about 0.25 to about 1 micrometer with no more than about 10 weight percent of said particles having diameters outside said range. Hereinafter the foregoing pigment will be referred to as an amide pigment.
DETAILED DESCRIPTION OF EMBODIMENTS The discrete particles of the amide pigment are composed of non-film forming copolymer of a hard monomer and α,β-ethylenically unsaturated amide. The copolymer is water-insoluble and is insoluble in the particular binder to be used in the paper coating composition.
By "non-film forming" it is meant that the amide pigment does not coalesce to form a film at ambient temperature and at temperatures that the amide pigment attains during drying and finishing, e.g., supercalendering, of the coated paper. While such temperature requirement varies with the type of finishing method used, it is preferred that the polymer of the amide pigment not be film forming at temperatures of 140 particularly if the coated surface is to be finished by processes such as calendering or supercalendering. If the discrete particles of the amide pigment are permitted to fuse or coalesce throughout the coating during the coating and finishing process, the light scattering properties (opacity) of the coated surface will be reduced substantially. Accordingly, preferred copolymers of the amide pigment have Vicat Softening Points, as determined by ASTM D-1525-65T, greater than about 140 copolymer of the amide pigment be insoluble in water and in the binder of the coating.
In addition to being composed of discrete particles of non-film forming copolymer as set forth hereinbefore, the amide pigment should be in the form of particles having an average diameter in the range from about 0.25 to about 1.0 micrometer, with no more than about 10 weight percent of the particles based on total weight of particles forming the amide pigment having diameters outside said range, preferably not more than 4 weight percent. It is found that an amide pigment which contains an excessive number (&gt;10 weight percent) of particles having diameters less than 0.22 micrometer does not possess the desired binding and opacifying characteristics. Preferably, the average particle diameter of the amide pigment is in the range from about 0.3 to about 0.8 micrometer.
In one preferred method, the polymerization zone is purged with inert gas and then charged with water-soluble catalyst, water, surfactant and monomer. The resulting reaction mixture is brought to a suitable reaction temperature usually from about 30 reaction is allowed to go to completion. In the practice of this preferred embodiment, it is sometimes advantageous to add a buffer such as sodium bicarbonate to the reaction mixture prior to polymerization and to add catalyst during later stages of polymerization to force the polymerization to completion. In an especially preferred batchwise method, it is desirable to use the amide pigment prepared in the foregoing manner as a seed latex to prepare an amide pigment of a larger and more desirable particle size. In such instance, the seed latex is added to the polymerization zone or formed therein insitu before polymerization of remaining monomer. Polymerization of remaining monomer is effected as described hereinbefore, preferably in a batchwise manner.
Alternatively, the monomers may be added continuously or intermittently during polymerization provided that amide monomer is present in the aqueous phase during polymerization and the surfactant is always present in the aforementioned amounts less than the CMC for the surfactant. In the practice of these alternative embodiments, it is desirable to maintain the temperature of polymerization below 80 method, it is understood that catalyst and surfactant may be added to the polymerization zone prior to polymerization and/or during polymerization in continuous or intermittent fashion. In the case of the surfactant, however, it should be present in the reaction mixture prior to as well as during polymerization.
Surfactants suitable for the purposes of this invention are the water-soluble anionic surfactants and mixtures thereof with nonionic surfactants with the anionic surfactants being preferred. In instances wherein a mixture of anionic and nonionic surfactants is to be employed, it is desirable that the major amount be anionic. Anionic surfactants include water soluble soaps of soap-forming monocarboxylic acids, e.g., alkali metal salts of linoleic acid dimer; and sulfated and sulfonated compounds having the general formula R -- OSO.sub.3 M and R -- SO.sub.3 M, wherein R represents an organic radical having from 9 to 23 carbon atoms and M represents an alkali metal, an ammonium or amine group. Examples of the sulfonate and sulfate emulsifiers include sodium dodecyl benzene sulfonate, sodium oleyl sulfate, ammonium dodecyl benzene sulfonate, potassium lauryl sulfate, sodium dodecyl diphenyl oxide disulfonate, dioctyl potassium sulfosuccinate, dihexyl sodium sulfosuccinate, the aryl sulfonate-formaldehyde condensation products and other anionic emulsifiers as set forth in McCutcheon's Detergents and Emulsifiers Annual, John W. McCutcheon, Inc., Morristown, N.J. (1970). Nonionic surfactants which are suitable include the polyoxyalkylene agents, e.g., polyethyleneoxyethanol derivatives of methylene linked alkyl phenols, the ethylene glycol polyethers, the alkyl phenoxy polyethyleneoxyethanols having alkyl groups of 7 to 12 carbon atoms such as nonylphenoxy-poly(ethyleneoxy)ethanols and condensation products of ethylene oxide with high alkyl mercaptans having alkyl groups of about 9 carbon atoms, and condensation products of ethylene oxide with alkyl thiophenols having alkyl groups of 6 to 15 carbon atoms; ethylene nonyl phenol polyethers; the fatty acid esters of polyhydric alcohols e.g., propylene glycol fatty acid ester; and others set forth in McCutcheon, supra. Of the foregoing emulsifiers, dihexyl sodium sulfosuccinate is preferred.
EXAMPLE 1 Step 1 To 10 oz. citrate bottle are added the following ingredients:
The bottle is purged with nitrogen, sealed and rotated in a water bath at 65 particles (latex) is cooled, filtered and determined to be a stable, highly monodisperse latex having an average particle diameter of 0.37 micrometer with less than 1 percent of the particles having diameters outside the range of 0.3 to 0.8 micrometer.
Step 2 Using the latex of Step 1 as a seed latex, the following ingredients:
A coating composition is prepared by mixing 100 parts (dry basis) of the amide pigment with 26 parts (dry basis) of cooked ethylated starch. The solids of the composition are adjusted to 30 percent and pH to 7.9 by addition of aqueous ammonia. Enough of the composition is applied by a Meyer rod to a paper substrate to obtain 5 pounds of dried coating per book ream of paper. The coated paper is cut to a width of 7 inches and passed through the nip of a laboratory supercalender at 1200 pounds per linear inch and different temperatures beginning at 150 degree of sticking to the steel roll of the supercalender is evaluated qualitatively by sound of paper sticking to roll, the degree of curl of the paper and the effect the supercalendering has on the resultant finished paper. It is observed that the coated paper containing the amide pigment can be supercalendered at temperatures from 20 higher before sticking and curling of the paper than can similar coated papers containing conventional styrene/acrylic acid (97/3 ) copolymer pigment.
Four sheets of paper coated with the composition containing the amide pigment and four sheets coated with another composition similar in all respects to said composition except containing conventional styrene/acrylic acid (97/3) copolymer pigment instead of the amide pigment are supercalendered 4 nips at 1200 pounds per linear inch and 150 finished papers are tested for gloss, brightness, opacity, ink receptivity and pick resistance. The results are recorded in Table I.
TABLE I______________________________________Sample No.           1         C*______________________________________Pigment, dry parts Styrene/Acrylamide, dry parts                100 Styrene/Acrylic Acid, dry parts                          100Starch Binder, dry parts                26        26Sodium alginate, dry parts                0.5       NonePercent Solids       30        30pH                   7.9       7.6Brookfield Viscosity .sup.(1), cps  20 rpm             330       370 100 rpm             210       16075                66        74Percent Brightness.sup.(3)                79.4      78.9TAPPI Opacity.sup.(4)                87.8      87.2K&amp;N Ink Receptivity.sup.(5), % Drop                31.0      32.1IGT Pick Resistance.sup.(6), ft/min                **285.sup.(8)                          270.sup.(6)______________________________________ *Not an example of the invention. **Fiber lifting or blistering occurs at this value before any evidence of coating pick. .sup.(1) Viscosity in centipoise using a No. 4 spindle at 23 .sup.(2) TAPPI Standard Method T 480 os-72. .sup.(3) TAPPI Standard Method T 452 os-58. .sup.(4) TAPPI Standard Method T 425 os-60. .sup.(5) TAPPI Useful Method 553. .sup.(6) TAPPI Suggested Method T 499 su-64 wherein "B" tension and 50 kilograms printing pressure is employed. Ink number is given in ().
EXAMPLE 2 Step 1 Into a 2-liter, 3-necked flask equipped with a stirrer, N.sub.2 inlet tube and condenser are added the following ingredients:
The reaction mixture in the flask is stirred, and the flask is purged with N.sub.2 for 10-20 minutes. The temperature of the reaction mixture is brought to 65 N.sub.2 for 6 hours. The resulting 40.4 percent solids latex is cooled and filtered for use in Step 2.
TABLE II__________________________________________________________________________Sample No.      1      2      3      4      C*__________________________________________________________________________Pigment, dry parts Styrene/acrylamide           100    100    100    100 Styrene/acrylic acid                       100Starch Binder, dry parts           26     13     5.2    2.6    26Sodium Alginate, dry parts    0.5    1.0Percent Solids  40     40     40     40     40pH              7.1    7.0    7.4    7.6    7.2Brookfield Viscosity.sup.(1), cps  20 rpm        1230   640    120    30     3000 100 rpm        745    360    90     40     114075           56     59     73     72     57Percent Brightness.sup.(3)           80.2   80.0   80.5   80.3   80.6TAPPI Opacity.sup.(4)           88.2   88.5   88.7   88.4   88.5K&amp;N Ink Receptivity.sup.(5) % Drop           24.8   25.0   39.6   40.7   28.5IGT Pick Resistance.sup.(6) ft/min           NP**   NP**   80.sup.(6)                                75.sup.(4)                                       165.sup.(7)__________________________________________________________________________ *Not an example of the invention. **NP - No pick with a No. 8 ink. .sup.(1) -.sup.(6) Same as in Table I.
EXAMPLE 3 Step 1 Into a 20 gallon reactor equipped with a stirrer, an N.sub.2 inlet tube and a condenser are added the following ingredients at 30
The reactor is purged with N.sub.2 for 20 minutes. A 57.6 part portion of styrene is then added. The reactor is heated to 65 at such temperature for 7 hours under N.sub.2 atmosphere. The resulting latex is cooled and filtered for use in Step 2.
are charged into the 20 gallon reactor as in Step 1 and heated to 65 latex of amide pigment having an average particle size of 0.52 micrometer with less than 1 percent of the particles having diameters outside the range of 0.3 to 0.8 micrometer. Based on total polymer it is found that 96.4 percent exists as water-insoluble copolymer particles of the latex and 3.6 percent exists as water-soluble styrene/acrylamide copolymer containing more than 50 percent polymerized acrylamide.
For purposes of comparison, a plastic pigment (Sample No. A.sub.1) is prepared by the procedure of Example 1 of U.S. Pat. No. 3,595,823 to Huang. A second comparative pigment (Sample No. A.sub.2) is similarly prepared except that the monomer composition of the pigment is varied. As a control (Sample No. C), a pigment is prepared of styrene/acrylic acid in the manner described in U.S. application Ser. No. 177,431 to Loeffler et al filed Sept. 2, 1971.
TABLE III__________________________________________________________________________Sample No.      1      A.sub.1 *                         A.sub.2 *                                C*__________________________________________________________________________Pigment.sup.(a), dry parts Sty/AAM (96/4) 100 Sty/VCN/AAM (81/18/1) 100 Sty/VCN/AAM (78/18/4)        100 Sty/AA (97/3)                       100Starch Binder, dry parts           15     15     15     15Percent Solids  40     40     40     40pH              7.3    7.4    7.6    7.4Brookfield Viscosity.sup.(1), cps  20 rpm        5080   4450   4070   1660 100 rpm        1840   1470   1540   655Coat Weight, lbs/book ream           5.4    5.5    5.2    6.175           56.6   64.5   54.3   57.0Percent Brightness.sup.(3)           84.8   81.2   79.4   84.4TAPPI Opacity.sup.(4)           91.7   89.4   88.4   91.9K&amp;N Ink Receptivity.sup.(5) % Drop           48.9   36.7   35.0   50.4IGT Pick, Resistance.sup.(6) ft/min           590.sup.(6)                  O.sup. (2)                         140.sup.(2)                                350.sup.(3)__________________________________________________________________________ *Not an example of the invention. .sup.(a) Sty-styrene, AAM-acrylamide, VCN-acrylonitrile and AA-acrylic acid. .sup.(1).sup.- (6) Same as in Table I.
EXAMPLE 4 Using the amide pigments (Sample No. 1) of Example 3, several coating compositions are prepared by combining the pigment with coating compositions comprising varying amounts of kaolin clay and binder which is a mixture of styrene/butadiene copolymer latex and starch. Using the paper coating procedure of Example 1 except that supercalendering is carried out using 800 pounds per linear inch at 125 are prepared and tested as in Example 1. The results are recorded in Table IV.
TABLE IV__________________________________________________________________________Sample No.     1     2     3     4     5     A.sub.1 *                                              A.sub.2 *                                                    C*__________________________________________________________________________Pigment, dry parts Styrene/Acrylamide          5     10    15    20    25 Clay, No. 1   95    90    85    80    75    95    75    100 Styrene/Acrylic Acid                        5     25Binder, dry parts S/B latex     8     8     8     8     8     8     8     8 Starch        4     4     4     4     4     4     4     4Percent Solids 51.5  51.5  51.4  51.3  51.5  51.5  51.5  51.4pH             8.3   8.3   8.3   8.3   8.3   8.3   8.3   8.3Brookfield Viscosity.sup.(1), cps  20 rpm       3960  3530  3680  3580  3650  3400  3580  3420 100 rpm       1200  1100  1110  1170  1400  980   1040  1020Coat Weight, lb/book ream          9.0   9.9   9.5   8.6   9.7   10.2  9.4   8.875          57    61    61    64    70    62    71    57Percent Brightness.sup.(3)          78.0  79.2  78.7  79.7  80.0  77.3  79.4  77.1TAPPI Opacity.sup.(4)          91.6  92.2  90.5  90.9  91.5  91.7  91.7  90.9K&amp;N Ink Receptivity.sup.(5)  % Drop          31.6  35.5  35.6  36.0  39.7  31.6  35.2  25.7IGT Pick Resistance.sup.(6) ft/min          400.sup.(5)                410.sup.(5)                      410.sup.(5)                            440.sup.(5)                                  460.sup.(5)                                        320.sup.(5)                                              230.sup.(5)                                                    &amp;lt;50.sup.(5)__________________________________________________________________________ *Not an example of the invention. .sup.(1) -.sup.(6) Same as in Table I.
EXAMPLE 5 Into a 2-liter, 3-necked flask equipped with a stirrer, N.sub.2 inlet tube and condenser are added the following ingredients:
The contents of the flask are stirred at 200 rpm and the flask is purged with N.sub.2 for 20 minutes. The temperature of the reaction mixture is brought to 70 N.sub.2 until an exotherm is observed after about 2.5 hours. Heating is continued for an additional hour until the exotherm subsides, and the resulting 44.5 percent solids latex is filtered and cooled. The resulting latex has an average particle size of 0.65 micrometer with a standard particle size deviation less than 1 percent. The pigmenting characteristics of the latex in coated paper are comparable to those of Example 3.
EXAMPLE 6 Following the procedure of Example 5 except that 246 parts of methyl methacrylate is added continuously over the first 2 hours of polymerization wherein the polymerization temperature is 60 latex is prepared using the following ingredients:
EXAMPLE 7 Step 1 Following the procedure of Example 2, an amide pigment is formed from the following ingredients:
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