GB2284829A

GB2284829A - Filler and coating composition for paper

Info

Publication number: GB2284829A
Application number: GB9418957A
Authority: GB
Inventors: Dieter Naumann; Alfred Hoehener
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1993-12-15
Filing date: 1994-09-21
Publication date: 1995-06-21
Also published as: GB9418957D0

Abstract

A filler composition for use in paper coating comprises: A) a highly dispersed, solid, water-insoluble organic polymer, preferably a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2, preferably 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, having a mean particle diameter of 1 to 20, preferably 2 to 10, especially 3 to 7 microns and having a specific BET surface of 5 to 100, preferably 15 to 60 8 m<2>/g; and B) 0.01 to 10, preferably 0.05 to 5 weight%, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent. The filler composition of the present invention is useful, e.g., as a white pigment in dispersion inks and, in particular, as a filler in pulp used to make paper. It is also valuable as a filler in a coating composition for paper.

Description

Filler and Coating Composition for Paper The present invention relates to a filler having a high whiteness value and containing a fluorescent whitening agent; to a paper containing this filler; to a process for the production of paper, by treating pulp, in the mass, with this filler to produce whitened paper having a high whiteness value; to a coating composition for paper comprising a polymeric binder, an inorganic pigment and the said filler; to a process for coating paper using this coating composition; and to coated paper so produced and having a high whiteness value.

Conventional papers contain large amounts of inorganic pigments such as talcum, kaolin, calcium carbonate, zinc sulphide, alumina or titanium dioxide. These pigments act as fillers and may also impart improvements to various properties of paper treated with such pigments.

Such pigments, however, are only poorly retained by the paper and they also tend to impair the strength of paper which contains them.

In DE-B-2 100 907, there is described paper comprising cellulose and, as a filler, 0.5 to 80% by weight, based on the weight of the dry cellulose, of an insoluble, infusible, non-porous, particulate urea-formaldehyde resin having a mole ratio of urea to formaldehyde ranging from 1:1.3 to 1:1.8 and a BET surface ranging from 5 to 100 m2/g.

In DE-A-2 556 017, there is described a coating composition for paper comprising an aqueous composition containing a polymeric binder; an inorganic pigment; and a water-insoluble urea-formaldehyde polycondensation product of 1 mole of urea with 1.3 to 2 moles of formaldehyde, which is present in highly dispersed form and which has a mean particle diameter of 3 to 6 microns and a specific surface of 3 to 12 m2/g. In Example 1 of DE-A-2 556017 a coating composition for paper is disclosed which also contains an optical whitener.

Although the incorporation of the urea-formaldehyde resin overcomes the filler retention and paper strength problems associated with the use of conventional fillers, the whiteness level of paper filled with urea-formaldehyde resin is not entirely satisfactory, even when an optical whitener is incorporated as a separate component of the coating composition.

JP 61-119799 describes paper having improved whiteness and opaqueness comprising 0.3-100 parts by weight of associated particles of a urea-formaldehyde polymer and 0.001-3 parts by weight of a fluorescent whitening agent, each per 100 parts of dry pulp in the paper. The urea-formaldehyde polymer and the fluorescent whitening agent, however, are added separately to the paper. There is no suggestion in JP 61-119799 that the urea-formaldehyde polymer and the fluorescent whitening agent should be combined prior to their addition to the paper.

Surprisingly, it has now been found that a highly dispersed, solid water-insoluble organic polymer, in particular a urea-formaldehyde resin, is first combined with a water-soluble fluorescent whitening agent, as a filler in the production of paper in the mass, or in a paper coating composition, a paper is obtained having a high whiteness value, improved opacity and a better printability. This is true even when a water-soluble fluorescent whitening agent is used which cannot be used successfully, per se, for the fluorescent whitening of paper in the mass.

Accordingly, the present invention provides, as a first aspect, a filler composition comprising: A) a highly dispersed, solid, water-insoluble organic polymer, preferably a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2, preferably 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, having a mean particle diameter of 1 to 20, preferably 2 to 10, especially 3 to 7 microns and having a specific BET surface of 5 to 100, preferably 15 to 60 m2/g; and B) 0.01 to 10, preferably 0.05 to 5 weight%, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

As a second aspect, the present invention provides a coating composition for paper comprising: I) a polymeric binder; II) an inorganic pigment; and III) a previously-prepared combination of: a) a highly dispersed, solid, water-insoluble organic polymer, preferably a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2, preferably 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, having a mean particle diameter of 1 to 10, preferably 3 to 7, especially 4 to 5 microns and having a specific BET surface of 1 to 30, preferably 5 to 20, especially 8 to 12 m2/g; and b) 0.01 to 10, preferably 0.05 to 5% by weight, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

The solids content of the coating composition according to the present invention preferably ranges from 40 to 70, especially from 50 to 60% by weight. The viscosity of the coating composition according to the present invention preferably ranges from 1000 to 1600, particularly from 1200 to 1500 centipoise, when determined by the Brooldield method at 100 revolutions per minute and at 250C.

The coating composition according to the present invention preferably contains, based on the total weight of the composition, 5 to 30, preferably 5 to 15% by weight of component I); 60 to 95, preferably 70 to 90% by weight of component II); and 1 to 25, preferably 5 to 15% by weight of component m). Component III) preferably comprises 0.1 to 15, preferably 0.5 to 10% by weight of component b), based on the total weight of component Ill).

Component I) of the coating composition according to the present invention may be any conventional polymeric binder system used for coating compositions for paper. Examples include modified starches, e.g. oxidised, hydrolysed or hydroxyethylated starches. Other polymeric binder systems, which may be used alone or in combination with a modified starch, include casein, soya protein, polyvinyl alcohol and latex types such as polyvinyl acetate, preferably styrene-butadiene copolymers and acrylic polymers such as polyacrylic acid, polyethyl acrylate and polymethyl methacrylate.

Component II) of the coating composition according to the present invention may be any inorganic pigment which is conventionally used in paper coating compositions. Examples include talcum, titanium dioxide, extended titanium dioxide compositions, aluminium oxide, barium sulphate, calcium sulphate, satin white, zinc oxide, silicon dioxide or, especially, precipitated or ground calcium carbonate and/or china clays. Fine china clays, that is those having a mean particle size such that preferably 80% of the particles are below 2 microns, are preferred, in particular the so-called coating china clays.

Components A) or IIIa) of the respective filler and coating compositions of the present invention, may be, e.g., a highly dispersed solid polymer formed by polymerisation, polycondensation or polyaddition reactions or by a combination thereof. Such polymers are described in GB-B-1 323 890 and include polycondensation products, especially polycondensed aminoplasts such as urea/formaldehyde and melamine/formaldehyde polymers, as well as vinyl polymers such as polyacrylonitrile.

The specific BET surface of the preferred water-insoluble urea-formaldehyde resin is determined according to the method of Brunauer, Emmett and Teller [c.f.

J.Am.Chem.Soc. 60, 309-319 (1938), Chemie-Ing.Techn. 32, 349-354 (1960) and 35 568-589 (1963)].

The preferred water-insoluble urea-formaldehyde resin components A) or alia) and their production are known and have been described, e.g., by A.Renner: Makromolekulare Chemie 149, 1-27 (1971).

The preferred components A) or IIIa) are readily produced by reacting formaldehyde with urea in aqueous solution in the above-mentioned ratios. The reaction is preferably conducted in two stages. In the first step, the urea and formaldehyde may be reacted normally, according to the conventional condensation mechanism, to form a low molecular, water-soluble pre-condensate. In the second stage, an acidic crosslinking catalyst may be introduced, to accelerate the reaction and the crosslinking, and produce an insoluble, finely-divided solid.

The amount of water in the reaction solution should never be substantially lower than the total weight of the organic reactants present in it, and should be present in substantial excess over the total weight of all other components of the reaction mixture during the actual formation and precipitation of the insoluble polymer particles.

The reaction temperature in the first step is generally in the range of from 20 to 100"C., preferably from 40 to 850C, and especially from 60 to 800C. The pH value may be adjusted to 6 to 9, preferably to 6.5 to 7.5, by adding an aqueous inorganic strong base, e.g. a sodium hydroxide solution.

It can be advantageous to perform the production of the pre-condensate in the presence of a surfactant, e.g. a cationic quaternary ammonium base, an anionic fatty alcohol sulphonate, a nonionic polyethylene ether, preferably a salt of a sulphosuccinic acid ester, in particular sodium dodecylbenzene sulphonate. The amount of surfactant used may range, e.g., from 0.5 to 5% by weight, based on the total weight of the urea and formaldehyde. Ionic surfactants effect an increase in the specific surface of the urea-formaldehyde polymer product, whereas non-ionic surfactants have the reverse effect.

The presence of a macromolecular, water-soluble protective colloid having polyelectrolyte characteristics during the first reaction step may also prove useful. Examples of such colloids include gelatine, tragacanth, agar and polyvinyl pyrrolidone, especially homo- or copolymers of acrylic- or methacrylic acids, in particular polymethacrylic acid. The amount of colloid used may range, e.g., from 0.5 to 5% by weight, based on the total weight of the urea and formaldehyde. Neither polyvinyl pyrrolidone nor polymethacrylic acid effects an increase in the specific surface of the water-insoluble urea-formaldehyde resin, component A) or alia).

One of the most important conditions for the successful production of infusible, insoluble and finely-divided urea-formaldehyde polymers of adequate quality for use in the present invention is the use, in the second step of the reaction, of a suitable gelation catalyst.

Suitable catalysts include, e.g., the relatively strong inorganic and/or organic acids such as sulphuric acid, sulphurous acid, sulphamic acid, phosphoric acid, hydrochloric acid, chloracetic acid, maleic acid or its anhydride. Generally, these gelation catalysts should have an ionisation constant of more than 104. Sulphuric acid and its acidic ammonium- or amine salts such as ammonium-, methylamine- or ethanolamine-hydrogen sulphate, are preferred.

The acids are usually employed as 1 to 15% by weight aqueous solutions.

As a rule, 20 to 100 millimoles of cross-linking catalyst are used per mole of added urea.

This effects a lowering of the pH value of the reaction mixture to 1.5 to 3.0 in the second step, i.e. during the formation of the polymer.

If sulphamic acid is used, generally water-insoluble urea-formaldehyde resins of relatively high specific surface are obtained, whereas the other acids mentioned above, in particular sulphuric acid and its ammonium- or amine salts have the opposite effect.

The reaction temperatures used in the second, resin formation reaction, generally range from 20 to 1000C., preferably from 400C. to 850C., especially from 40 to 650C. Large temperature fluctuations in the reaction mixture should be avoided while adding the catalyst. It is therefore desirable, prior to adding the aqueous catalyst solution, to pre-heat it to the temperature of the reaction mixture. Generally, a white gel is obtained after only 15 to 30 seconds. The cross-linking reaction is usually complete after a time ranging from 30 minutes to 3 hours.

The insoluble polymer, obtained as a white gel, may be mechanically comminuted, treated with an approximately equal amount of water, adjusted to pH 6 to 9, preferably to pH 6.5 with alkali or ammonia, in particular with sodium hydroxide solution, and then separated from the aqueous liquid, e.g., by filtration, centrifuging or evaporation. Drying can be conducted, e.g., by spray drying or by convection drying. Although the final product basically comprises fine particles, it is nevertheless desirable to submit the solid product to comminution or de-agglomeration, to reduce the mean agglomerate size and to increase the absorption value for inks and other liquids.

The water-soluble fluorescent whitening agent, component B) or IIlb) of the respective filler or coating composition of the present invention, may be, e.g., a triazinyl-diaminostilbene disulphonic acid; an aminocoumarin such as 7-diethylamino-4-methylcoumarin; a carbostyryl such as 1 -ethyl-3-phenyl-7-dimethylamino-carbostyryl; a pyrazoline such as p-[3-(p-chlorophenyl)-2-pyrazolin- 1 -yl]-benzenesulphonamide; a stilbyl naphthotriazole; a stilbene oxotriazole such as 4,4'-bis-[1,2,3-triazolyl-(2)1-stilbene-2,2'-disulphonic acid di-potassium salt; a distyryl benzene such as 1 ,4-bis-[2- 2-(N-ethyl-N-carboxylatomethyl-ammonio)-ethoxy } styryl] benzene; a distyrylstilbene; or a benzoxazole such as 2,5-bis(benzoxazol-2-yl)thiophene or the compound having the formula:

Preferred water-soluble fluorescent whitening agents are those having the formula:

in which R1 is aniline, aniline-3-sulphonic acid, aniline-4-sulphonic acid or diethanolamine and R2 is amino, methoxy, methylamine, ethylamine, ethanolamine, diethanolamine, N-methylethanolamine, ethanolaminopropionamide, aniline, aniline-4-sulphonic acid or morpholine.

Other preferred water-soluble fluorescent whitening agents are those having the formula:

in which n isO or 1.

Most preferred water-soluble fluorescent whitening agents are those having the formula:

or the formula:

The compound of formula (4) is especially preferred.

As a further optional component, the filler composition of the present invention may contain a colourant such as a dye or pigment, in particular a cationic direct dye or a suitable reactive dye.

The filler composition of the present invention may be produced, e.g., by mixing components A) and B), preferably in the presence of a solvent, especially water. After the mixing, any solvent may be removed, if desired.

The filler composition of the present invention is useful, e.g., as a white pigment in dispersion inks and, in particular, as a filler in pulp used to make paper.

The present invention therefore also provides a paper comprising cellulose and 0.5 to 80%, preferably 5 to 20% by weight, based on the weight of the dry cellulose, of a filler composition comprising: A) a highly dispersed, solid, water-insoluble organic polymer, preferably a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2, preferably 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, has a mean particle diameter of 1 to 20, preferably 2 to 10, especially 3 to 7 microns and has a specific BET surface of 5 to 100, preferably 15 to 60 m2/g; and B) 0.01 to 10, preferably 0.05 to 5 weight%, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

The filler composition of the present invention may be used alone or in combination with a conventional paper filler, in particular calcium carbonate. When a conventional paper filler is also present, it preferably makes up 10 to 90%, especially 20 to 80% of the total amount of the filler.

It is often desirable that the paper, in addition to the filler, also contains 0.1 to 25, more preferably 0.2 to 15% by weight of a water-soluble polymer which improves the dry strength and/or the wet strength of the paper.

Preferred soluble polymers include anionic or cationic urea/formaldehyde resins; cationic or nonionic melamine/formaldehyde resins; anionic, cationic or nonionic starches; an alginate; or combinations of these polymers. Particularly useful are a nonionic starches having a high content of amylose and/or carboxymethylcellulose.

The cellulose component of the paper of the present invention may be any conventional pulp which is used to produce paper sheets. The cellulose used may be a chemically treated cellulose, such as a sulphite pulp, a soda pulp or a kraft pulp; a semi-chemical pulp; mechanical wood pulp; or mixtures of these. Cellulose from plants or rags may also be employed. In some cases, it may not prove necessary to employ pulp, rather used paper may be utilised, either alone or in combination with pulp. Shredded used paper may be added to the pulp either in dry form or as an aqueous suspension.

The paper of the present invention preferably contains a protective colloid which serves to strongly increase the viscosity of aqueous solutions. As previously indicated, the protective colloid may have been already introduced during the production of the water-insoluble urea-formaldehyde resin.

Other materials which may usefully added to the pulp include conventional neutral paper sizes, such as ketene dimers or succinic anhydride derivatives; acidic paper sizes, such as pine rosin or its sodium salt; and precipitation agents for the size, such as aluminium salts e.g. alum or aluminium sulphate.

A fourth aspect of the present invention is a process for the production of paper comprising adding to the pulp, in the mass, 0.5 to 80%, preferably 5 to 20% by weight, based on the weight of the dry pulp, of a filler composition comprising: A) a highly dispersed, solid, water-insoluble organic polymer, preferably a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2, preferably 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, has a mean particle diameter of 1 to 20, preferably 2 to 10, especially 3 to 7 microns and has a specific BET surface of 5 to 100, preferably 15 to 60 m2/g; and B) 0.01 to 10, preferably 0.05 to 5 weight%, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

The composition comprising components A) and B) may be added either in dry form or as a slurry and is then intimately mixed with the pulp slurry. Finally, a paper is formed on a wire screen of a conventional paper machine such as a Fourdrinier machine; dewatered; dried; and calendered.

The composition of the present invention may be added at any stage prior to the formation of the paper sheets.

Preferably, the composition of the present invention is comminuted and dispersed, prior addition to the pulp. The pulp containing the composition of the present invention may then be brought into a suitable state of fineness by grinding it, before it is processed to paper on a paper-making machine.

The paper so obtained has improved whiteness, opacity and printability.

Prior to use in the coating composition according to the present invention, the component Ill) may be produced by adding a dilute aqueous solution of the water-soluble fluorescent whitening agent to the solid water-insoluble organic polymer, in particular a urea-formaldehyde resin, e.g., in powder form or dispersed in a solvent, especially water.

The water-soluble fluorescent whitening agent is quantitatively adsorbed by the water-insoluble organic polymer. The mixture may then be homogenised, e.g., by stirring, rolling or shaking, and optionally dried and sieved.

In addition to components I), II) and III), the coating composition according to the present invention may also contain additives which are conventionally present in a coating composition for paper. Examples include waxes, dispersing agents, wetting agents, viscosity regulators, foam inhibitors, lubricants, plasticisers and stabilisers.

A fifth aspect of the present invention is a process for the production of a coating composition for paper comprising: a) firstly forming a solution or dispersion of component I) in water; b) adding component II) to the solution or dispersion obtained in step a); and c) adding component III) to the mixture obtained in step b).

With respect to step a), especially if starch is used as binder, complete dissolution may often be accelerated by heating or boiling the aqueous mixture.

If desired, component II) may be predispersed to form a concentrated aqueous dispersion, prior its addition to the solution or dispersion of the binder obtained in step a).

The sequence of the steps in the process for the production of a coating composition for paper may be modified, if desired, e.g. by adding component III) to the mixture obtained in step a), prior to conducting step b).

Finally, the coating composition may be diluted with water to the desired solids content.

The coating composition according to the present invention, when applied to intaglio or offset paper substrates, is effective at a low total coating weight per unit area, thus enabling the production of coated publication papers, especially papers for four colour-, intaglio- or offset printing, having low weight after finishing.

The coating composition according to the present invention may be used to produce coated papers by applying the composition to at least one side of the raw paper, followed by drying and, optionally, calendering.

Preferably, the raw paper is coated on both sides with the coating composition according to the present invention, desirably in a single operation. The raw paper used preferably has a weight of 30 to 120, more preferably 30 to 80, especially 50 to 70 g/m2.

The paper coating operation is desirably so conducted that the adherent coating has a weight of 5 to 20g/m2. Depending on the paper used, the coating composition used and the amount of the coating composition used, the finished, coated paper generally has a weight of 35 to 160, preferably 35 to 120, especially 50 to 80g/m2.

In contrast to known coated papers, papers coated according to the present invention have an increased whiteness level, improved opacity and smoothness and, in particular, improved printability. The improved printability is illustrated in that the uptake of printing ink is increased in intaglio printing, the printed images are more brilliant, the printing ink "stands" better and the print has less missing dots. Moreover, paper coated according to the present invention provides the absorptive capacity which is required for prints etched with laser beams.

The following Examples further illustrate the present invention. Parts and percentages are by weight unless otherwise stated.

The water-soluble fluorescent whitening agents (fwas) used in the following Examples are: a) The fwa compound of formula (3); b) The fwa compound of formula (4); c) The fwa compound of formula (1) in which R1 is aniline and R2 is morpholine; d) The fwa compound of formula (1) in which R1 is aniline and R2 is diethanolamine; e) The fwa compound of formula (1) in which R1 is aniline and R2 is N-methylethanolamine; f) The fwa compound of formula (1) in which R1 is aniline and R2 is methylamine; g) The fwa compound of formula (1) in which R1 is aniline-3-sulphonic acid and R2 is diethanolamine; and h) The fwa compound 4,4'-bis-[1,2,3-triazolyl-(2)]-stilbene-2,2'-disulphonic acid di-potassium salt.

Examples 1 to 8 20 grams (based on dry weight) of a commercially-available urea/formaldehyde condensation product (PergopackM2) are weighed into a flask and stirred into a paste with 200 mls. of deionised water.

The urea/formaldehyde condensation product has the following characteristics: diameter of the primary particles: 0.1 micron diameter of the agglomerates of these particles: 3-7 microns specific surface area of the particles: 20 m2/g specific weight: 1.45 g/cm3.

To the paste so obtained there are then added 20mg (0.1 % by weight), based on the weight of the urea/formaldehyde condensation product, of the water-soluble fluorescent whitening agent b), the compound of formula (4), dissolved in a little deionised water. The fluorescent whitening agent of formula (4) is quantitatively adsorbed by the urea/formaldehyde condensation product. The mixture is heated on a water bath for 5 minutes at 800C. and at pH 7.

The product so obtained is filtered through a glass fibre filter and the filtrate is subjected to UV spectral analysis to determine the amount of the water-soluble fluorescent whitening agent b) in the filtrate.

The solid material retained on the filter is dried under vacuum at 40"C, comminuted and sieved through a 0.5 mm mesh screen. The Ganz whiteness of a sample of the powder is determined.

The procedure is repeated using 0.2 or 0.5% by weight of the water-soluble fluorescent whitening agent of formula (4), otherwise designated above as water-soluble fluorescent whitening agent b), or using the other water-soluble fluorescent whitening agents designated a) and c) to i) above.

The whiteness value and the level of uptake of the respective water-soluble fluorescent whitening agents by the urea/formaldehyde condensation product are shown in the following Table 1: Table 1

% by weight Ganz %Active F.W.A.

Example Active F.W.A.

Active F.W.A. Whiteness on U/F Resin in residual water ~ none 0 97 0 0.1 200 87 13 1 F.W.A.b) 0.2 216 82 18 0.5 228 75 25 0.1 186 99 1 2 F.W.A. a) 0.2 149 99 1 0.1 197 95 5 3 F.W.A. c) 0.2 196 93 7 0.5 211 81 19 0.1 179 83 17 4 F.W.A. d) 0.2 205 77 23 0.1 195 96 4 5 F.W.A. e) 0.2 201 96 4 6 F.W.A. f) 0.1 189 95 5 0.2 204 95 5 0.1 195 95 5 7 F.W.A. g) 0.2 217 95 5 8 F.W.A. h) 0.1 169 74 26 The Ganz whiteness is determined according to the method described in detail in the Ciba-Geigy Review, 1973/1, and also in the Article "Whiteness Measurement", ISCC Conference on Fluorescence and the Colorimetry of Fluorescent Marerials, Williamsburg, February 1972, published in the Journal of Color and Appearance, 1, No. 5 (1972).

It is clear from the results in Table 1 that the compositions of the present invention have a substantially higher whiteness value relative to the base urea/formaldehyde resin and that the percentage retention of the respective water-soluble fluorescent whitening agents by the urea/formaldehyde resin is very high.

Example 9 Samples of a neutral sized paper are produced using a commercially available size with or without a filler. When a filler is present, it comprises calcium carbonate containing 1,3 or 5% by weight of a composition of the invention containing the base urea/formaldehyde resin and the water-soluble fluorescent whitening agent of formula (4).

Firstly, 5g of 100% bleached cellulose are adjusted to a solids content of 3.3% using 150 ml of water having a pH of 7.5 and 10 degrees of hardness.

7.5 ml of a 10 volume % aqueous solution of calcium carbonate, are then added to the cellulose suspension.

To the mixture so obtained is then added either i) 1, 3 or 5% by weight of the base urea/formaldehyde resin described in Examples 1 to 8, or ii) 1, 3 or 5% by weight of a combination of the base urea/formaldehyde resin and the water-soluble fluorescent whitening agent of formula (4).

There are then added 3.0 mls of a 2.5% solution of the size and 10 mls of a 0.05% solution of a commercially available retention aid, to improve the retention of the filler.

After appropriate periods have elapsed for the filler, size and retention aid to exhaust on to the fibre, the suspension is diluted and a paper sheet is formed using a Rapid-Köthen sheet-forming apparatus.

The Ganz whiteness values of the respective paper samples are then determined and the resul Table 2

Example Filler Resin % by weight of Filler Resin Ganz Whiteness none 75 1 1 76 3 resin 3 78 5 80 1 99 U/F resin and 3 120 9 F.W.A. b) 5 130 The results in Table 2 demonstrate that a substantial increase in whiteness of paper is obtained when the paper is filled with a filler comprising a composition of the present invention. The results are surprising since the water-soluble fluorescent whitening agent of formula (4), per se, cannot be used successfully for fluorescent whitening of paper in the mass.

Examples 10 to 12 A) Preparation of the Filler Using the procedure described in Examples 1 to 8, 20 grams (based on dry weight) of a commercially-available ureafforrnaldehyde condensation product (pergopackM2) are weighed into a flask and stirred into a paste with 200 mls. of deionised water The urea/formaldehyde condensation product has the following characteristics: diameter of the primary particles: 0.1 micron diameter of the agglomerates of these particles: 3-7 microns specific surface area of the particles: 20 m2/g specific weight: 1.45 g/cm3.

To the paste so obtained there are then added 40mg (0.2% by weight), based on the weight of the urea/formaldehyde condensation product, of the water-soluble fluorescent whitening agent g), having the formula:

dissolved in a little deionised water. The fluorescent whitening agent g) is quantitatively adsorbed by the urea/formaldehyde condensation product. The mixture is heated on a water bath for 5 minutes at 80"C. and at pH 7.

The product so obtained is filtered through a glass fibre filter. The solid material retained on the filter is dried under vacuum at 400C, comminuted and sieved through a 0.5 mm mesh screen.

The procedure is repeated using 0.4 or 0.8% by weight of the water-soluble fluorescent whitening agent g) or using the other water-soluble fluorescent whitening agents designated a) to f) and h) above.

B) Preparation of the Base Coating Composition The following base coating composition is made up: 20 parts of a commercial clay; 80 parts of a commercial calcium carbonate; 18 parts of a commercial 50% dispersion of a styrene/butadiene copolymer latex; 0.5 part of a commercial polyvinyl alcohol; 0.5 part of carboxymethylcellulose; and 0.5 part of a commercial 65% melamine/formaldehyde precondensate.

To two separate samples of the base coating composition there are added, respectively: i) 10 parts of a commercially-available urea/formaldehyde condensation product (PergopackM2); or ii) 10 parts of a commercially-available urea/formaldehyde condensation product (Pergopack8M2) containing 0.2, 0.4 or 0.8% by weight, based on the total weight of the base coating composition, of the water-soluble fluorescent whitening agent of formula (5), produced according to part A).

C) Application of the Coating Composition to Wood-free, Base-coated Paper Separate samples of commercial wood-free base coated paper, having a weight per unit area of 83g/m2, are coated with a coating composition described in part B).

The coating is conducted using a Dow laboratory coater. The drying is effected with hot air at a temperature of 195-2000C. until the moisture content is constant at 7% by weight, under standard conditions. The coating weight, after acclimatisation (230C., 50% relative humidity), is 12.5 plus or minus 0.5g/m2.

The Ganz whiteness of each of the paper samples so coated is then determined according to the method described in detail in the Ciba-Geigy Review, 1973/1, and also in the Article "Whiteness Measurement", ISCC Conference on Fluorescence and the Colorimetry of Fluorescent Marerials, Williamsburg, February 1972, published in the Journal of Color and Appearance, 1, No. 5 (1972). The results are shown in the following Table 3: Table 3

Example Amount of fwa in Ganz Whiteness coating composition none 84 10 0.2% 102 11 OA% 108 12 0.8% 116 Similar results are obtained when the water-soluble fluorescent whitening agent of formula (5) is replaced by a water-soluble fluorescent whitening agent designated a) to f) or h) above.

Examples 13 to 15 A) Preparation of the Filler The procedure described in step A) of Examples 10 to 12 is repeated.

B) Preparation of the Base Coating Composition The procedure described in step B) of Examples 10 to 12 is repeated.

C) Application of the Coating Composition to Wood-containing, Base-coated Paper Separate samples of commercial wood-containing base coated paper, having a weight per unit area of 77g/m2, are coated with a coating composition described in part B) and are coated in the manner described in part B).

The Ganz whiteness of each of the paper samples so coated is then determined and the results are shown in the following Table 4: Table 4

Example Amount of fwa in Ganz Whiteness coating composition none 61 13 0.2% 76 14 0.4% 86 15 0.8% 94 Similar results are obtained when the water-soluble fluorescent whitening agent of formula (5) is replaced by a water-soluble fluorescent whitening agent designated a) to f) or h) above.

Examples 16 to 18 A) Preparation of the Filler 20 grams (based on dry weight) of a commercially-available urea/formaldehyde condensation product (Pergopack84210) are weighed into a flask and stirred into a paste with 200 mls. of deionised water.

The urea/formaldehyde condensation product has the following characteristics: diameter of the primary particles: 0.3 micron; diameter of the agglomerates of these particles: 4-5 microns; specific surface area of the particles: 8-12 m2/g; specific weight: 60-90 g/cm3.

To the paste so obtained there are then added 40mg (0.2% by weight), based on the weight of the urea/formaldehyde condensation product, of the water-soluble fluorescent whitening agent gj, having the formula (5), dissolved in a little deionised water. The fluorescent whitening agent g) is quantitatively adsorbed by the urea/formaldehyde condensation product. The mixture is heated on a water bath for 5 minutes at 800C. and at pH 7.

C) Application of the Coating Compositions to Wood-free, Base-coated Paper The procedure described in step C) of Examples 10 to 12 is repeated. The results are shown in the following Table 5: Table 5

Example Amount of fwa in Ganz Whiteness coating composition none 103 16 0.2% 111 17 0.4% 115 18 0.8% 121 Similar results are obtained when the water-soluble fluorescent whitening agent of formula (5) is replaced by a water-soluble fluorescent whitening agent designated a) to f) or h) above.

Examples 19 to 21 A) Preparation of the Filler The procedure described in step A) of Examples 16 to 18 is repeated.

B) Prenaration of the Base Coating Composition The procedure described in step B) of Examples 10 to 12 is repeated.

C) Application of the Coating Compositions to Wood-containinzz Base-coated Paper The procedure described in step C) of Examples 13 to 15 is repeated. The results are shown in the following Table 6: Table 6

Example Amount of fwa in Ganz Whiteness coating composition none 76 19 0.2% 87 20 0.4% 93 21 0.8% 99 Similar results are obtained when the water-soluble fluorescent whitening agent of formula (5) is replaced by a water-soluble fluorescent whitening agent designated a) to f) or h) above.

Claims

1. A filler composition comprising: A) a highly dispersed, solid, water-insoluble organic polymer; and B) 0.01 to 10 weight%, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

2. A coating composition for paper comprising: I) a polymeric binder; II) an inorganic pigment; and III) a previously-prepared combination of: a) a highly dispersed, solid, water-insoluble organic polymer; and b) 0.01 to 10% by weight, based on the weight of the water-insoluble polymer, of a water-soluble fluorescent whitening agent.

3. A filler or coating composition, respectively, according to claim 1 or 2, in which component A) or IIIa), respectively, is a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 2 moles of formaldehyde, which is present in highly disperse form, has a mean particle diameter of 1 to 20 microns and has a specific BET surface of 5 to 100 m2/g.

4. A composition according to claim 3 in which component A) or IIIa), respectively, is a water-insoluble urea-formaldehyde resin comprising 1 mole of urea and 1.3 to 1.8 moles of formaldehyde, which is present in highly disperse form, has a mean particle diameter of 2 to 10 microns and has a specific BET surface of 15 to 60 m2/g.

5. A composition according to any of the preceding claims in which the fluorescent whitening agent, component B) or IIIb), respectively, is a triazinyl-diaminostilbene disulphonic acid; an aminocoumarin; a carbostyryl ; a pyrazoline; a stilbyl naphthotriazole; a stilbene oxotriazole; a distyryl benzene; a distyrylstilbene; or a benzoxazole.

6. A composition according to claim 5 in which the fluorescent whitening agent is 7-diethylamino-4-methylcoumarin; 1-ethyl-3-phenyl-7-dimethylamino-carbostyryl; p-[3-(p-chlorophenyl)-2-pyrazolin- l-yl]-benzenesulphonamide; 4,4'-bis-[ 1,2,3-triazolyl- (2)] -stilbene-2,2'-disulphonic acid di-potassium salt; 1,4-bis-[2-{2-(N-ethyl-N-carboxylatomethyl-ammonio)-ethoxyXst yryl]ben ne; 2,5-bis(benzoxazol-2-yl)thiophene; or the compound having the formula:

7. A composition according to claim 5 in which the fluorescent whitening agent is one having the formula:

in which R1 is aniline, aniline-3-sulphonic acid, aniline-4-sulphonic acid or diethanolamine and R2 is amino, methoxy, methylamifle, ethylamine, ethanolamine, diethanolamine, N-methylethanolamine, ethanolaminopropionamide, aniline, aniline-4-sulphonic acid or morpholine.

8. A composition according to claim 5 in which the fluorescent whitening agent is one having the formula:

in which n is O or 1.

9. A composition according to claim 5 in which the fluorescent whitening agent is one having the formula:

or the formula:

10. A composition according to claim 9 in which the fluorescent whitening agent is one having the formula (4).

11. A filler composition according to any of claims 1 and 3 to 10 in which a colourant is also present.

12. A filler composition according to claim 11 in which the colourant is a cationic direct dye or a reactive dye.

13. A paper comprising cellulose and 0.5 to 80% by weight, based on the weight of the dry cellulose, of a filler composition according to claim 1, 3 or 4.

14. A paper according to claim 13 comprising cellulose and, 0.5 to 20% by weight, based on the weight of the dry cellulose, of a filler composition according to claim 1, 3 or 4.

15. A paper according to claim 13 or 14 comprising, as filler, a combination of a filler composition according to claim 1, 3 or 4, together with a conventional paper filler.

16. A paper according to claim 15 in which the conventional paper filler is calcium carbonate.

17. A paper according to claim 15 or 16 in which the conventional paper filler makes up 20 to 80% by weight of the total weight of the filler.

18. A paper according to any of claims 13 to 17 comprising, in addition to the filler, 0.1 to 25% by weight of a water-soluble polymer which improves the dry strength and/or the wet strength of the paper.

19. A paper according to claim 18 in which the polymer is an anionic or cationic urea/formaldehyde resin; a cationic or nonionic melamine/formaldehyde resin; an anionic, cationic or nonionic starch; an alginate; or a combination of these polymers.

20. A paper according to claim 19 in which the polymer is a a nonionic starch having a high content of amylose and/or carboxymethylcellulose.

21. A paper according to any of claims 13 to 20 in which the cellulose component is any conventional pulp which is used to produce paper sheets.

22. A paper according to claim 21 in which the cellulose component is a chemically treated cellulose; a semi-chemical pulp; mechanical wood pulp; or a mixture of these.

23. A paper according to claim 22 in which the chemically treated cellulose is a sulphite pulp, a soda pulp or a kraft pulp.

24. A paper according to claim 22 in which the cellulose used is obtained from plants or rags.

25. A paper according to claim 22 in which the cellulose used is used paper, either alone or in combination with pulp.

26. A paper according to any of claims 13 to 25 in which a protective colloid is present.

27. A paper according to any of claims 13 to 26 in which there is also present a conventional neutral paper size; an acidic paper size; a precipitation agent for the size; or a mixture of these.

28. A paper according to claim 27 in which the conventional neutral paper size is a ketene dimer or succinic anhydride derivative; the acidic paper size is pine rosin or its sodium salt; and the precipitation agent for the size is an aluminium salt.

29. A paper according to claim 28 in which the aluminium salt is alum or aluminium sulphate.

30. A process for the production of paper comprising adding to pulp, in the mass, 0.5 to 80% by weight, based on the weight of the dry pulp, of a filler composition according to claim 1, 3 or 4.

31. A process according to claim 30 comprising adding to pulp, in the mass, 0.5 to 20% by weight, based on the weight of the dry cellulose, of a filler composition according to claim 1, 3 or 4.

32. A coating composition according to any of claims 2 to 12 in which the solids content of the coating composition ranges from 40 to 70% by weight.

33. A composition according to any of claims 2 to 12 and 32 in which the viscosity of the coating composition ranges from 1000 to 1600 centipoise, when determined by the Brookfield method at 100 revolutions per minute and at 250C.

34. A composition according to any of claims 2 to 12, 32 and 33 containing, based on the total weight of the composition, 5 to 30% by weight of component I); 60 to 95% by weight of component II); and 1 to 25% by weight of component III).

35. A composition according to claim 34 containing, based on the total weight of the composition, 5 to 15% by weight of component I); 70 to 90% by weight of component II); and 5 to 15% by weight of component III).

36. A composition according to any of claims 2 to 12 and 32 to 35 in which component III) comprises 0.1 to 15% by weight of component a), based on the total weight of component IH).

37. A composition according to any of claims 2 to 12 and 32 to 36 in which component I) is a modified starch, casein, soya protein, polyvinyl alcohol, polyvinyl acetate, a styrene-butadiene copolymer, polyacrylic acid, polyethyl acrylate or polymethyl methacrylate.

38. A composition according to any of claims 2 to 12 and 32 to 37 in which component II) is talcum, titanium dioxide, an extended titanium dioxide composition, aluminium oxide, barium sulphate, calcium sulphate, satin white, zinc oxide, silicon dioxide, a precipitated or ground calcium carbonate or a china clay.

39.A composition according to claim 38 in which component II) is a coating china clay.

40. A composition according to any of claims 2 to 12 and 32 to 39 in which, in addition to components I), II) and m), the coating composition also contains one or more of a wax, a dispersing agent, a wetting agent, a viscosity regulator, a foam inhibitor, a lubricant, a plasticiser and a stabiliser.

41. A process for the production of a coating composition for paper, as defined in claim 2, comprising: a) firstly forming a solution or dispersion of component I) in water; b) adding component II) to the solution or dispersion obtained in step a); and c) adding component m) to the mixture obtained in step b).

42. A process for the production of a coated paper comprising applying a coating composition, as claimed in any of claims 2 to 12 and 32 to 40, to at least one side of a raw paper; followed by drying; and, optionally, calendering.

43. A process according to claim 42 in which the raw paper is coated on both sides with the coating composition, according to the present invention, desirably in a single operation.

44. A process according to claim 43 in which the raw paper used has a weight of 30 to 120 g/m2.

45. A process according to claim 44 in which the raw paper used has a weight of 30 to 80 glum2.

46. A process according to any of claims 41 to 45 in which the paper coating operation is so conducted that the adherent coating so obtained has a weight of 5 to 20g/m2.

47. A process according to any of claims 41 to 46 in which the finished, coated paper has a weight of 35 to 160g/m2.

48. A process according to claim 47 in which the finished, coated paper has a weight of 50 to 80g/m2.