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 an aqueous composition for coating paper comprising an alkalinating latex substantially insoluble in water.
• composition for coating of paper one generally indicates an aqueous coating composition essentially containing a filler (pigment), a binder and possibly various adjuvants.
• Such a composition is applied to paper in order to modify the surface properties, in particular the whiteness, the gloss, the printability, etc.
• a hydrocolloid or a natural thickening agent such as carboxymethylcellulose, or synthetic such as polyvinyl alcohol and alkali-soluble latexes is usually used.
• Water retention of a paper coating composition is defined as the ability of the composition to resist this transfer of water.
• alkaline swelling latex is meant according to the invention, a swelling latex with alkalis (in particular, soda, potash, ammonia) contained or added in the aqueous emulsion.
• alkalis in particular, soda, potash, ammonia
• These latexes allow producing coating compositions whose viscosities increase with the pH in the alkaline range.
• alkalinating latex improves the water retention and the rheological properties of the coating composition.
• Such insoluble alkali-swelling latexes are for example described by FR-A 2,444,114 from a styrene / butadiene / acrylic acid copolymer whose viscosity of the coating bath is stabilized by addition of a polyalkylene glycol as well as in the patent.
• US-A 3,793,244 where acrylic acid is replaced by itaconic acid.
• 1,3-butadiene is very hydrophobic, which requires the use of large quantities of acidic monomers which are the cause of the passage into polymer solution, which has the consequence of greatly increasing the viscosity of the bath and of degrading. the binding power.
• this patent teaches neither the size of the latex particles nor the fact that the pigment must necessarily contain at least 40% CaCO3.
• the present invention aims to provide a coating composition for paper having better water retention and better machinability.
• composition of the above type the pigment of which comprises at least 40% CaCO3, having acceptable gloss while exhibiting suitable water retention and a high dry extract.
• composition of the above type the binder part of which is a mixture of two water-insoluble latexes, one of which is alkaline, said mixture being stable on storage at a neutral or slightly acidic pH.
• the ratio ⁇ A / ⁇ B measured at a pH between 2 and 4 is between 1.4 and 6, preferably between 1.8 and 3.0 even more preferably this ratio is close to 2.
• Latex A is a film-forming latex which is substantially insoluble and non-alkalinizing in alkaline solutions with a pH greater than 8, preferably greater than 9 and less than 13.
• Latex A can in fact be an organic polymer latex used usually for coating paper, insofar as it is a film-forming latex, substantially insoluble and non-alkalinizing, the diameter ⁇ A of the polymer particles of which is between 60 and 300 nm.
• Latex A is preferably a copolymer based on styrene / 1,3-butadiene. More particularly suitable are copolymers based on 25 to 60% by weight of butadiene, 40 to 75% by weight of styrene and 0 to 6% of ethylenically unsaturated monomers comprising at least one carboxylic acid function and their monoesters with an alkanol in C1 - C8.
• Examples of monomeric carboxylic acids which can be used are acrylic acid, methacrylic acid or its dimer, fumaric acid, crotonic acid, itaconic acid, maleic acid and also the monoesters of the above acids. with C1 -C8 alkanols, such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethyl hexyl acrylate, methacrylate methyl, ethyl methacrylate and n-butyl methacrylate.
• C1 -C8 alkanols such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethyl hexyl acrylate, methacrylate methyl, ethyl methacrylate and n-butyl methacrylate.
• Latex B is preferably a copolymer: monoester of ethylenically unsaturated carboxylic acid / ethylenically unsaturated carboxylic acid / vinylaromatic and / or vinyl nitrile.
• ethylenically unsaturated carboxylic acid monoester it is recommended to use the acrylates, methacrylates, fumarates and maleates of methyl, ethyl, isopropionic, propionic, isobutyl, n-butyl, tert-butyl and 2-ethylhexyl alcohol. .
• an acid or a mixture of acids mentioned above can be used for latex A, namely preferably acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid.
• Latex B further comprises a third monomer chosen from a vinyl aromatic monomer such as styrene and methylstyrene and / or a vinyl nitrile such as acrylonitrile and methacrylonitrile.
• a vinyl aromatic monomer such as styrene and methylstyrene
• a vinyl nitrile such as acrylonitrile and methacrylonitrile.
• Latex B also comprises a monomer comprising at least 2 ethylenic unsaturations and playing the role of crosslinking agent incorporated during the polymerization of the monomers.
• This crosslinking agent can in particular be chosen from ethylene glycol di (meth) acrylate, tripolypropylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, diallyl maleate, triallyl cyanurate, divinylbenzene and methylene-bis acrylamide.
• crosslinking agents are used, preferably in an amount of 0.1 to 5%, preferably from 0.2 to 1% by weight relative to the total weight of monomer, the preferred crosslinking agents being ethylene glycol dimethacrylate and divinylbenzene .
• a latex B which is more particularly suitable is a copolymer comprising 55 to 65% by weight of unsaturated carboxylic acid ester, preferably ethyl acrylate, 10 to 20% by weight of unsaturated carboxylic acid, preferably methacrylic acid, 20 to 32% by weight of styrene and 0.1 to 5% by weight of crosslinking agent.
• a particularly suitable monomer mixture comprises 58 to 60% by weight of ethyl acrylate, 14 to 16% by weight of methacrylic acid and 25 to 27% by weight of styrene and 0.2% to 1% by weight of crosslinking agent.
• the polymerization of latex B is carried out, in a manner known per se, in one or more stages.
• the monomers can be preemulsified with water in the presence of an anionic or nonionic emulsifying agent, which usually uses about 0.01 to 10%, calculated based on the weight of total monomers.
• a free radical generator type polymerization initiator such as ammonium or potassium persulfate, can be used alone or in combination with an accelerator, such as sodium metabisulfite or sodium thiosulfate, sodium formaldehyde sulphoxylate as well as metal ions (iron, cobalt, copper ).
• free radical generators such as azo (2,2'-azobisisobutyronitrile, 4,4'-azobis (4-cyanopentanoic acid) ...) or peroxides such as hydrogen peroxide or tert-butyl hydroperoxide or cumene hydroperoxide in combination with a reducing agent.
• the initiator and the accelerator constituting jointly what is usually called catalyst, can be used in an amount of 0.1 to 2% each based on the weight of monomers to be copolymerized.
• the polymerization temperature can be between 30 ° C and 100 ° C, more favorably between 50 ° C and 90 ° C.
• cross-linking agents which are monomers having several, that is to say at least 2 ethylenic unsaturations, are incorporated during the polymerization, in an amount ranging from 0.1 to 5%.
• monomers include ethylene glycol di (meth) acrylate, tripopylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, diallyl maleate, triallylcyanurate, divinylbenzene, methylene-bis acrylamide.
• latex B can be adjusted to a neutral or slightly acidic pH of between 4 and 7 using one or more bases such as alkali hydroxides, ammonia or water-soluble organic amines such as 2-amino 2-methylpropanol, diethylaminoethanol or alternatively quaternary ammoniums such as tetrabutylammonium hydroxide.
• bases such as alkali hydroxides, ammonia or water-soluble organic amines such as 2-amino 2-methylpropanol, diethylaminoethanol or alternatively quaternary ammoniums such as tetrabutylammonium hydroxide.
• the aqueous coating composition has a concentration of dry extracts, that is to say of solid materials (pigment plus latex particles A and B) preferably between 60 and 80% by weight, preferably between 65 and 75%.
• Latex A can have a dry extract of 40 to 60% by weight, preferably between 50 and 55%.
• Latex B advantageously has a dry extract of between 30 and 50% and preferably between 40 and 45% by weight.
• pigment for 100 parts by weight of pigment, there are 5 to 20 parts of dry extracts of latex A and 8, preferably between 7 and 15 parts.
• At least 40% by weight of the pigment consists of CaCO3, the rest being chosen from the mineral pigments usually chosen for coating paper such as natural or calcined clay, kaolin, barium sulphate, titanium oxide , talc, hydrated alumina, bentonite and calcium sulfoaluminate (satin white).
• the pigment is constituted by ground CaCO3 and / or precipitation optionally treated with a fatty acid ester such as calcium stearate.
• At least 50% by weight of the pigment has a particle size of less than 2 ⁇ m, preferably less than 1 ⁇ m, the rest having a particle size between 2 and 10 ⁇ m.
• the fine-grained pigments can advantageously consist of precipitation CaCO3, kaolin, calcined clay or hydrated alumina, the coarser particle-size pigments generally consist of CaCO3 and baryte (crushed natural barium sulfate) .
• the coating compositions according to the invention have, before the addition of alkali (preferably NH4 OH or NaOH so as to reach a pH between 8 and 13 preferably between 9 and 10), have an apparent viscosity between 50 and 1000 mPa.s at 25 ° C.
• alkali preferably NH4 OH or NaOH
• compositions after addition of alkali have an apparent viscosity generally between 4000 and 25000 mPas at 25 ° C. preferably between 5000 and 10000 mPa.s. (Brookfield 10 rpm).
• the latex emulsion A the latex emulsion B are prepared and it is recommended to add, by homogenizing the latex emulsion B into the latex emulsion A, having first adjusted the pH of the latex A between 4 and 7, preferably between 5.5 and 6.5.
• the mixture of latexes A and B is stable on storage at a pH preferably between 5 and 7 for at least several months.
• stable on storage means mainly according to the invention that no appreciable change in the viscosity, the particle size of the emulsions and the pH of the mixture is observed.
• a pigment mixture based on CaCO3 defined above is incorporated into this latex mixture by simple mixing and without particular precautions.
• the pH is adjusted between 8 and 13 and preferably between 9 and 10 and the coating composition is ready for use.
• the coating compositions according to the invention can be used as such without the addition of conventional natural binders such as casein, starch, carboxymethylcellulose or synthetic thickeners such as polyvinyl alcohol and alkali-soluble latexes as for example described by US-A 4,397,984; they are more particularly recommended for coated papers and are used more particularly for printing in roto offset, offset and lithography.
• conventional natural binders such as casein, starch, carboxymethylcellulose or synthetic thickeners such as polyvinyl alcohol and alkali-soluble latexes as for example described by US-A 4,397,984; they are more particularly recommended for coated papers and are used more particularly for printing in roto offset, offset and lithography.
• compositions according to the invention can be used in an amount of 5 to 30 g, preferably 10 to 20 g of composition per m2 (1 side) of paper.
• the viscosities are Brookfield viscosities measured at 23 ° C. In addition, unless otherwise indicated, all% and parts are by weight.
• the temperature of the reaction medium is kept constant at 82 ° C throughout the duration of the polymerization.
• the latex B obtained in Example 1 is neutralized with dilute ammonia (2%).
• the evolution of the particle size as a function of the pH is measured by diffusion of quasielastic light using a NANO-SIZER® from the company COULTER.
• buffer solutions In order to keep the pH of the latex constant, it is diluted in buffer solutions whose pH is identical to that of the latex. Buffer solutions are prepared according to the HANDBOOK OF CHEMISTRY AND PHYSICS Section D.
• C1 and C2 are used in aqueous slip at 70% by weight of carbonate.
• C1 has 90% of particles having a particle size less than 2 ⁇ m and 60% of particles having a particle size less than 1 ⁇ m.
• C2 has 95% of particles having a particle size less than 2 ⁇ m and 78% of particles having a particle size less than 1 ⁇ m.
• Carboxymethylcellulose : CMC is used in Comparative Examples 4 and 6 in place of latex B.
• Dispex N40® sodium salt of a low molecular weight polyacrylate.
• Example 3 To produce the coating composition of Example 3, the ingredients below are mixed, the parts by weight of which are calculated on a dry basis.
• C1 is dispersed in water in a high speed mixer in the presence of D1 which serves as a dispersing agent for C1 and the mixture of latex A and latex B is added having previously adjusted the pH of latex A between 6 and 6.5.
• the solid content is adjusted to 73.50% by weight, then the pH of the mixture is brought to 9-10 by addition of an ammonia solution and the viscosity and water retention of the mixture are measured.
• Water retention is evaluated by conductimetric measurement of the speed of passage of a blotting paper by the water released by the coating bath. This test known as the Warren test is described in the review TAPPI, Volume 41, No. 2, page 77 of February 1958.
• Paper is coated on a Bachofen® pilot machine which is a high speed doctor blade coating machine; the angle of the blade is 45 ° C; the coating speed is 300 m / min, the speed of the ink roller is 70 m / min, drying in dry air is carried out at 185 ° C; 11 g / m2 of dry matter are deposited.
• the humidity relative to the coated paper is 4.5%.
• the gloss of the paper (75 °) and the gloss of the ink (75 °) are measured using an ERICHSEN® glossmeter and a PRUFBAU® press, the printing force is set to 800 N.
• LORILLEUX® 3805 or 3808 ink is used for this using an electric IGT press, the final speed of which is set at 2 m / s.
• Resistance to wet peeling is done with LORILLEUX® 3801 ink on a PRUFBAU® press under a printing force of 800N at a speed of 0.5 m / s.
• the optical density (OD) of the wet black inked area and the optical density (OD) of the torn off wet area are measured.
• the wet tearing score is given by the ratio of the DO of the wet part to the OD of the dry part.
• the ink refusal makes it possible to appreciate the repulsion of the ink by water during the offset printing of a wet coated paper.
• a PRUFBAU® press fitted with a wetting device and HUBER® n ° 1 ink at a printing force of 800 N.
• the OD of the inked non-wet area and the OD of the wet area are measured.
• the ink refusal is then the ratio of the average optical density of the dry part to the average of the optical density of the wet part.
• Example 5 To produce the coating compositions of Comparative Examples 4 and and of Example 5, the procedure is exactly as in Example 3 except that the coating composition is modified in accordance with the indications in Table 2. The results obtained are collated in the table 2 below.
• a gain in gloss of the paper and ink is also obtained, in particular in the case of C1. Furthermore, the binding power of the coating composition is, in the case of Examples 3 and 5 at least equivalent if not greater (dry stripping) than that of the compositions of Comparative Examples 4 and 6 comprising CMC instead latex B.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Glass Compositions (AREA)
• Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Paints Or Removers (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9411825

Family Applications (1)

Country Status (7)

Cited By (10)

Families Citing this family (16)

Citations (4)

Family Cites Families (3)

• 1991
  • 1991-04-15 FR FR9104565A patent/FR2675165B1/fr not_active Expired - Lifetime
• 1992
  • 1992-04-07 AT AT92400961T patent/ATE167909T1/de not_active IP Right Cessation
  • 1992-04-07 ES ES92400961T patent/ES2121831T3/es not_active Expired - Lifetime
  • 1992-04-07 EP EP92400961A patent/EP0509878B1/de not_active Expired - Lifetime
  • 1992-04-13 BR BR929201346A patent/BR9201346A/pt not_active IP Right Cessation
  • 1992-04-14 FI FI921674A patent/FI110386B/fi active
• 1994
  • 1994-08-18 US US08/292,313 patent/US5563201A/en not_active Expired - Fee Related

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events