Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/58—Polymers or oligomers of diolefins, aromatic vinyl monomers or unsaturated acids or derivatives thereof

Definitions

• the present invention relates to paper coating compounds. More particularly, the present invention relates to high solids paper coating compounds having good rheology which provide coated paper with a good balance of properties; particularly good gloss and pick characteristics.
• Carboxylated styrene-butadiene latices have been offered to the paper coating industry since at least as early as the early 1960's. Typical of the latices sold at that time was K-55E, sold by ARCO, a styrene-butadiene latex containing from 1 to 2% carboxylation.
• U.S. Patent 3,399,080 issued August 27, 1968 to the Dow Chemical Company disclosed the use of a latex polymer comprising 2 to 10 weight percent of a carboxylic acid; 30 to 50 weight percent of a C4 ⁇ 9 conjugated diolefin and 48 to 68 weight percent of a monomer composition comprising 10 to 100 weight percent of an alkenyl mononuclear aromatic monomer and the balance acrylonitrile.
• the above latices were used in medium solids paper coating compounds and were suitable for use in the paper coating process of the mid 1960's to mid 1970.
• the paper coating compounds of the present invention have a higher solids than the 60% solids level taught in the examples in U.S. Patent 3,399,080.
• Chemical Abstract 97:111522u of Japanese Patent 82 66,195 discloses a high solids paper coating compound.
• the compound uses as a binder a latex comprising mixed ethylenically unsaturated carboxylic acids; butadiene; styrene and methyl methacrylate.
• the polymer composition of the present invention does not include alkyl (meth)acrylates.
• the present invention seeks to provide a simple high solids paper coating compound which has a good rheology, good stability to multi-valent, preferably bi-valent, ions, and provides coated paper having a good balance of properties including high gloss and pick strength.
• the present invention provides a paper coating composition having a solids content of from 65 to 75 weight percent and a viscosity as measured on a Hercules Hi Shear viscometer with an E bob and a 400,000 dynes cm/cm spring at 4400 rpm and 105°F of less than 80 centipoise, which comprises from 95 to 85 weight percent by dry weight of a composition comprising 100 to 40 weight percent of clay; and 0 to 60 weight percent of one or more members selected from the group consisting of calcium carbonate, aluminium trihydrate, titanium dioxide, and barium sulfate; from 5 to 15 weight percent by dry weight of a latex which produces less than 0.5 weight percent coagulum on exposure to 10%
• CaCl2 comprising an interpolymer of from 55 to 65 weight percent of a C8 ⁇ 12 vinyl aromatic monomer which is unsubstituted or substituted by a C1 ⁇ 4 alkyl radial or a chlorine atom; form 30 to 40 weight percent of a branched or
• the present invention also provides paper coated with the above composition at a weight of 8 to 15 lb dry per 3300 ft2 (ream) (9 to 17 g/m2). Paper coated in accordance with the present invention has a good balance of properties including sheet gloss, ink holdout characteristics, brightness, with IGT binding strengths of at least 400 m/sec (#4 tack ink).
• the paper coatings of the present invention comprise a major amount, from 95 to 85 weight percent of a pigment.
• the pigment may be all clay or the pigment may comprise from 100 to 40, preferably more than 70 weight percent clay and up to 60, preferably less than 30 weight percent of calcium carbonate.
• a preferred pigment composition comprises from 70 to 80 weight percent of clay and from 30 to 20 weight percent of calcium carbonate.
• the clay used in paper coating compounds have an average particle size of less than 5 microns. Most preferably, the clay has a size of less than about 2 microns. When calcium carbonate is used in the coating compounds of the present invention, the average particle size should be less than 2 microns.
• the latex binder used in accordance with the present invention comprises from 55 to 65, preferably 58 to 62 weight percent of a C8 ⁇ 12 vinyl aromatic monomer which is unsubstituted or substituted by a C1 ⁇ 4 alkyl radical or a chlorine atom; from 30 to 40, preferably from 32 to 36 weight percent of a branched or straight chained C4 ⁇ 6 conjugated diolefin which is unsubstituted or substituted by a chlorine atom; and from 4 to 10, preferably 5 to 7 weight percent of one or more C3 ⁇ 6 ehtylenically unsaturated carboxylic acids.
• the polymer may optionally contain a minor amount, less than 5, preferably less than 2 weight percent of an additional functional monomer selected from the group consisting of amides of a C3 ⁇ 6 ethylenically unsaturated carboxylic acids which amides are unsubstituted or substituted at the nitrogen atom by up to two radials selected from the group consisting of C1 ⁇ 4 alkyl and hydroxyalkyl radicals, and C3 ⁇ 6 ethylenically unsaturated aldehydes.
• an additional functional monomer selected from the group consisting of amides of a C3 ⁇ 6 ethylenically unsaturated carboxylic acids which amides are unsubstituted or substituted at the nitrogen atom by up to two radials selected from the group consisting of C1 ⁇ 4 alkyl and hydroxyalkyl radicals, and C3 ⁇ 6 ethylenically unsaturated aldehydes.
• Suitable C8 ⁇ 18 vinyl aromatic monomers include styrene and alpha methyl styrene.
• Useful C4 ⁇ 6 conjugated diolefins include butadiene, isoprene and chloroprene.
• Suitable C3 ⁇ 6 ethylenically unsaturated carboxylic include both mono- and di-carboxylic acids; such as acrylic, methacrylic, fumaric and itaconic acids and mixtures thereof. Particularly useful results are obtained when the polymer contains mixed mono- and di-carboxylic acids. If mixed mono- and di-carboxylic acid monomers are used they may be used in a weight ratio of 10:1 to 1:10. Peferably the weight ratio of mono- to di-carboxylic acid monomer is from about 2:1 to 8:1, most preferably from about 4:1 to 6:1.
• the polymer In preparing the polymer, conventional techniques are used. Generally the latex will contain from 45 to 55 weight percent solids. Preferably, the polymer is prepared in the presence of from 0.5 to 2, most preferably about 1 part by weight of a chain transfer agent.
• chain transfer agents are the C8 ⁇ 12 alkyl mercaptans. Chloroform and bromoform are also suitable chain transfer agents.
• the polymers of the present invention have a high stability of multi-valent ions, particularly calcium ions. In the presence of 10% CaCl2 solution for 14 days there should be only a trace (less than 0.5%) of coagulum.
• a dispersant may be added to the pigments.
• a thickener and/or opacifying agent(s) may be added to the coating compound and dilution made with water to the required solids contact.
• Useful dispersants and thickeners are listed in trade catalogues such as McCutcheon's Functional Materials (either the North American edition or the International edition), published annually by McCutcheon's Division, The Manufacturing Confectioner Publishing Co. The selection of any specific functional material will depend on the specific properties desired in the coating.
• the compound at a solids content of from 65 to 70 weight percent should have a viscosity of less than 80, preferably from 20 to 70 centipoise, as measured on a Hercules Hi Shear viscometer with an E bob, a 400,000 dyne cm/cm spring at 4400 rpm at 105°F.
• Paper may be coated with the coating compounds of the present invention using conventional techniques and where required calendered under appropriate conditions.
• the resulting paper should have a dry pick of at least 400 m/sec.
• a base latex was prepared by emulsion polymerization of approximately 60 parts stryene, 33 parts butadiene, 7 parts of mixture of acrylic and itaconic acid in the presence of 1 part of a chain transfer agent.
• the latex had a 50 weight percent solids level after stripping.
• a base compound was prepared comprising Clay 70 CaCl3 30 Latex 12 Starch 2 Water to about - 65% solids
• the viscosity of the compound was measured with a Hercules Hi Shear viscometer with an E bob, a 400,000 dyne cm/cm spring at 4400 rpm and 105°F.
• the coating compound was coated on paper at a dry weight of 9.5 lb per ream and calendered to simulate mill conditions.
• the coated paper was conditioned overnight at 73°F and 50% relative humidity.
• Example 1 The control and experimental latex of Example 1 were compounded as follows: Clay 60 Calcium Carbonate 40 Latex 13 Starch 3 Lubricant 1
• the compounds were diluted with water to a solids level of 63, 67 and 70 weight percent.
• Example 2 The latex was tested as in Example 1. Paper was coated on a laboratory coater at 9.5 lb (dry) per ream. The paper was calendered and tested as in Example 1. The results are set forth in Table II. TABLE II Control Latex Experimental Latex Compound Solids % 63 67 70 63 67 70 Hercules Viscosity 19 43 Break 17 38 70 Centipoise at 4400 rpm (4000rpm) Sheet Gloss at 75°F 65 69 -- 65 69 74 Print Gloss 77 81 -- 80 83 87 Brightness 82.4 81.9 -- 84.1 84.5 85.5 IGT Dry Pick (#4 ink/4 m/sec 35 kgf) 600 580 -- 625 600 575 Note: Test results on paper coated at 70% solids with the control latex were not taken as the paper could not be coated under conventional coating conditions. This shows the improvement in high shear rheology, print gloss and dry pick obtainable in accordance with the present invention.
• Example 1 The experimental latex of Example 1 was tested for calcium ion stability.

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• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

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• 1989
  • 1989-05-05 EP EP19890108130 patent/EP0341598A3/fr not_active Withdrawn
  • 1989-05-10 FI FI892260A patent/FI892260A7/fi not_active Application Discontinuation
  • 1989-05-12 AU AU34718/89A patent/AU3471889A/en not_active Abandoned
  • 1989-05-12 JP JP1117653A patent/JPH026693A/ja active Pending

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