MXPA01007490A - Aqueous polymeric emulsion compositions and their use for the sizing of paper - Google Patents

Abstract

A method of sizing paper by applying a composition comprising an aqueous dispersion of polymeric particles of particle size up to 1 micron, preferably 80-200 nm, wherein the polymeric particles comprise a water insoluble polymer matrix, preferably formed from styrene and 2-ethylhexyl acrylate, characterised in that an oligomer formed from a monomer blend comprising, (a) (meth)acrylamide, and (b) organic mercaptan or an organic sulphone, preferably dodecyl mercaptan or dodecyl sulphone is located at the surface of the particles. Compositions where the oligomer further comprises an ethylenically unsaturated monomer comprising either a tertiary amine group or a quaternary ammonium group, preferably dimethylaminoethymethacrylate are novel. Advantages of the composition when applied to the surface of paper, include improved water resistance, brightness and printability properties of the treated paper.

Description

COMPOSITIONS OF AQUEOUS POLYMERIC EMULSIONS AND THEIR APPLICATION FOR PAPER APPLICATION FIELD OF THE INVENTION The present invention relates to novel compositions comprising an aqueous dispersion of water-insoluble polymer particles, wherein the polymer particles further comprise on their surface an oligomeric compound. The invention also encompasses a method for sizing paper and a method for improving paper printability.

BACKGROUND OF THE INVENTION It is known to produce dispersions of polymer particles insoluble in water by emulsion polymerization or by suspension polymerization. In such processes it would be usual to disperse a water-insoluble monomer or mixture of monomers in a continuous aqueous phase to form monomer drops. In aqueous emulsion polymerization or aqueous suspension polymerization it is standard practice to use surface active ingredients such as emulsifiers, surfactants or polymerization stabilizers. Typically such compounds would have a high hydrophilic and lipophilic (HLB) balance, so that the compound would preferably be partitioned into the continuous aqueous phase.

It is known to use oligomeric compounds as emulsifiers or polymerization stabilizers in the emulsion polymerization of water insoluble monomers such as styrene, acrylonitrile, ethyl acetate and butyl acetate and the like. Such compositions have been produced as rubber or plastic latex from which the solid polymer could be obtained. Generally, such compositions were produced to provide products that exhibited low viscosity and reduced foaming characteristics and were able to form suitable solid rubber or plastic materials. It is a standard practice in the field of paper and cardboard manufacturing to print paper both internally and externally. The sizing agents impart hydrophobicity to paper or cardboard and improve the resistance to penetration by liquids, especially water. Internal sizing is usually achieved by incorporating a sizing agent into the paper when making the paste before draining over the mesh of the machine. The sizing agent may be a non-reactive sizing such as the rosin resin, but more commonly it is a reactive sizing such as alkenyl succinic anhydride (ASA). The ASA would easily disperse through the cellulosic slurry and react chemically with cellulose and is therefore generally considered a very efficient sizing agent. However, due to the reactivity of ASA sizing, and the ease with which aqueous sizing emulsions are hydrolyzed, they are usually made with it. If the hydrolysis of the ASA anhydrous groups takes place to any significant degree prior to application, this would result in gummy deposits which would damage the formation of paper and in severe cases would stop the production of paper. Therefore care must be taken when applying a reactive sizing. It is known to use various hydrophobic materials such as waxes and water-insoluble polymers and reactive sizing such as compositions for sizing paper surfaces such as ASA. In general, such compositions are prepared as aqueous dispersions or emulsions and mixed with other materials such as starch before being applied to the paper sheet in the sizing press. It is important to impart the correct degree of hydrophobicity and thus water resistance without damaging the brightness of the paper. It is often the case that a product that imparts optimum hydrophobicity significantly reduces brilliance. It is often necessary to establish a compromise between hydrophobicity and brilliance and the product chosen should not damage the brilliance in a very significant way and still provide adequate resistance to water. Where products provide maximum water resistance to paper, the resolution of images during printing would normally improve. However, any significant reduction in the brightness of the paper would mean that there would also be a poor contrast between the paper and the image. It will therefore be desirable to provide a paper dressing composition that imparts significantly improved hydrophobicity and printability characteristics and that does not significantly reduce the brightness of the paper or paperboard.

BRIEF DESCRIPTION OF THE INVENTION In this way a method is provided for preparing paper or cardboard, where a composition (A) is applied to at least one of, i) the surface of a sheet of paper or cardboard formed, ii) a cellulose suspension for making paper or cardboard before draining, wherein the composition (A) comprises an aqueous dispersion of polymer particles with a particle size of up to 1 micron, wherein the polymer particles comprise a polymeric polymer insoluble in water, characterized in that it comprises an oligomer formed of a monomer mixture comprised of ethylenically unsaturated monomers or a mixture of ethylenically unsaturated monomers, (a) (meth) acrylamide and (b) an organic mercaptan or organic sulfone, is located on the surface of the polymer particles. It has been found that the application of the composition (A) to a pulp to make paper before draining on the mesh of the machine produces internally effective sized paper. The composition (A) can be applied to the polymer dispersion as a single addition to the papermaking paste or can be combined with for example retention aids, drainage or reinforcement aids. It is often preferred to apply the composition as a precooked starch formulation. Typically the formulation would comprise 90-99.5% by weight of starch and 0.5-10% by weight of polymer particles, preferably 92.5-97.5% by weight of starch and 2.5-7.5% by weight of polymer particles, more preferably. preferably 95-97.5% by weight of starch and 2.5-5% by weight of polymer particles, based on the total dry weight of the starch and the polymer particles. It has surprisingly been found that the composition can be used to form internally sized paper with superior properties. The composition (A) is particularly suitable for sizing the paper surface and provides unique properties to the paper. Incorporated in the method for preparing paper or cardboard the composition (A) is applied to the surface of a sheet of paper or cardboard. It is often preferred to apply the composition as a precooked starch formulation. Typically the formulation will comprise 90-99.5% by weight of starch and 0.5-10% by weight of polymer particles, preferably 92.5-97.5% by weight of starch and 2.5-7.5% by weight of polymer particles, in a further manner. preferably 95-97.5% by weight of starch and 2.5-5% by weight of polymer particles, based on the total weight of the starch and polymer particles. Although the composition (A) would be desirably applied as a mixture with starch it can also be applied as a pure aqueous dispersion of polymer particles. In addition to combining the composition (A) with starch it may also be desirable to combine other ingredients normally applied during surface sizing, for example optical brightening agents.

(OBA) Normally the pure composition is applied in the sizing press to achieve the maximum benefits of the sizing method described here.

DETAILED DESCRIPTION OF THE INVENTION Preferably, in the method for sizing paper and board the composition comprises an aqueous dispersion of polymer particles with a particle size of up to 1 micron, where the polymer particles comprise a polymer matrix insoluble in water and in the surface an oligomer formed from a mixture of monomers comprising, (a) (meth) acrylamide, (b) an organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising an aminotercial group or an amino-quaternary group and ( d) optionally other monomers. The oligomer comprised in the composition used in the paper sizing method can incorporate any organic mercaptan or organic sulfone, but is preferably optionally substituted C 1-20 alkylmercaptan, optionally substituted C 1 -C 2 alkylsulfones, C 5-7 cycloalkylmercaptans optionally replacedoptionally substituted aromatic mercaptans, optionally substituted Cs_7 cycloalkylsulfones or optionally substituted aromatic sulfones are preferred. More preferred are alkyl mercaptans of Cd-20 / -cycloalkyl mercaptans of C5-7, aromatic mercaptans, Cs-2o alkylsulfones, C5-7 cycloalkylsulfones or aromatic sulfones. Particularly preferred is either dodecyl mercaptan or dodecyl sulfone. Suitable substituted alkyl mercaptans include 3-mercaptopropanoic acid, 2-mercaptoethanol, although 2-sulfonylethanol and 3-sulfonyl-propanoic acid are suitable substituted alkylsulfones.

The amount of organic mercaptan or organic sulfone used in the oligomer is usually up to 10 mol%. It may be possible to use more than one organic mercaptan and / or organic sulfone in the preparation of the oligomer, although the combined molar portions of the organic mercaptans and / or organic sulfones is generally up to 10 mol%. Preferably the level of organic mercaptan or organic sulfone compounds is in the range of 2.5-5 mol%. In the method for sizing paper or paperboard the oligomer comprises any of the tertiary amine or quaternary ammonium ethylenically unsaturated compounds in the oligomer, although the compounds represented by the compounds of formula (1) CH2 = CR-Q (1) are preferred where Q is -C (0) - ZA, -CH2-N + R? R3CH2CR = CH2 X "or -CH2NR? CH2CR = CH2 Z is -0- or -NH-, A is -CnH2n-B, n is a number integer from 1 to 4, B is -NRXR2 or -N + R? R2R3 X ", R is -H or -CH3 Ri is C? _4 alkyl, R2 is C1-4 alkyl, R3 is -H or alkyl Ci-β, cycloalkyl of C7-7 or benzyl, and X ~ is an anion, preferably halide, more preferably chlorine. Preferred ethylenically unsaturated tertiary amine or quaternary ethylenically unsaturated ammonium compounds include, for example, dimethylaminoethyl (meth) acrylate, acid addition salt or quaternary ammonium salt thereof, preferably dimethylaminoethyl (meth) acrylate, quaternary ammonium methyl chloride or dimethylaminoethyl (meth) acrylate, quaternary ammonium salt of benzyl chloride. Normally the level of ethylenically unsaturated tertiary amine or ethylenically unsaturated quaternary ammonium compounds to be incorporated in oligomer is up to 10 mol%. Preferably those compounds are present in the oligomer in amounts in the range of 2.5-5 mol%. The oligomeric compound usually contains higher levels of acrylamide or methacrylamide components. For example, the molar portion of (meth) acrylamide is usually at least 85 mol% and is preferably at least 90 mol%. Typically the molar portion of the (meth) acrylamide is between 90 and 97.5 mol%, preferably 92.5-95 mol%.

It is also possible to incorporate other ethylenically unsaturated monomers into the oligomer. In particular it is possible to incorporate up to 10 mol% of ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic anhydride. This can be, for example, acrylic acid or maleic anhydride, preferably used in an amount of between 2.5 and 5 mol%. In the method for sizing paper the composition applied to the surface of the paper or cardboard sheet further comprises polymeric particles comprised of ethylenically unsaturated monomers or mixtures of ethylenically unsaturated monomers, monomers or monomer mixtures which are substantially insoluble in water at room temperature . The monomers polymerize to provide polymers that are substantially insoluble in water at room temperature. Desirably the monomer or mixture of monomers has a solubility in water at 25 ° C of less than 5%. The monomers can be an ester of an ethylenically unsaturated carboxylic acid, styrene, alkylstyrene, (meth) acrylonitrile, vinyl carboxylate, etc. Typically, the matrix of the polymeric particles is formed from a monomer or a mixture of monomers comprising monomers selected from the group consisting of styrene, C? _2 alkyl (meth) acrylate, vinyl acetate, acrylonitrile. Preferably, the matrix of the polymeric particles is formed from 25-75% by weight of monomer or mixture of monomers selected from any of the styrene, acrylonitrile, vinyl acetate or alkyl (meth) acrylate of C? _2, preferably styrene, acrylonitrile, methyl methacrylate, methyl acrylate, ethyl methacrylate, vinyl acetate and 25-75% by weight of monomer or mixture of monomers selected from any of the C3- (C3) alkyl (meth) acrylates? 2, preferably butyl acrylate, n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. More preferably, the matrix in the polymeric particles is formed from 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight styrene and 25- / 5% by weight , preferably 35-65% by weight, more preferably 50% by weight of 2-ethylhexyl acrylate. In another preferred aspect the polymer particles have a minimum film which is formed at a temperature between -5 and 55 ° C, preferably between 25 and 45 ° C, more preferably at about 35 ° C. It may also be desirable to combine crosslinking monomer in the monomer mixture. The crosslinking monomer can be any polyethylenically unsaturated monomer, for example divinylbenzene, ethylene glycol dimethacrylate or triethylamine. Typically the amount of crosslinking monomer used is less than 1% by weight based on the total weight of the monomer, for example in the range of 0.25-50% by weight. In general, the composition used in the paper or cardboard preparation method comprises polymer particles which have a particle size in the range of 80-200 nm, preferably 100-120 nm. In the method for sizing paper the mixture of starch and polymeric particles would be applied to the surface of the sheet formed of paper at a dose of up to 20 g / m2, preferably up to 10 g / m2, typically around 3 g / m2 . The method for sizing paper or paperboard provides paper with good water resistance properties in combination with surprisingly high levels of paper gloss. In addition, sizing can be conveniently applied in pH sizing formulations as low as 1 to high as 12 and still provide acceptable results. A further aspect of the invention includes a method for improving the printability of a sheet of paper by applying the surface of the sheet formed of paper a composition comprising an oligomer formed from a mixture of monomers comprising, (a) ( met) acrylamide, (b) organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group, a quaternary ammonium group, and (d) optionally other monomers. In the method of providing printing ability to the paper the oligomer would be applied directly to the sheet formed of paper at a dose of up to 20 g / m2, preferably up to 10 g / m2, typically around 3 g / m2. In the method of improving the printability of a sheet of paper, the oligomer, comprised in the composition may comprise any organic mercaptan or organic sulfone, generally optionally substituted alkyl mercaptans of C? _2o, optionally substituted alkyl sulfones of C3.-20 optionally substituted C5-7 cycloalkyl mercaptans, optionally substituted aromatic mercaptans, optionally substituted C5-7 cycloalkylsulfones or optionally substituted aromatic sulfonates are preferred. Most preferred are C8_2o alkyl mercaptans, C5_7 cycloalkyl mercaptans, aromatic mercaptans, Cs-20 alkyl sulfones, C5_7 cycloalkylsulfones, or aromatic sulfones. Particular preference is given to dodecyl mercaptan or dodecyl sulfone. In the method for improving the printing capacity the organic mercaptan or organic sulfone capacity used in the oligomer used in the composition is usually up to 10 mol%. It may be possible to use more than one organic mercaptan and / or organic sulfone in the preparation of the oligomer, although the combined molar proportions of organic mercaptans and / or organic sulfones is generally up to 10 mol%. Preferably, the level of organic mercaptan or organic sulfone compounds is in the range of 2.5-5 mol%. Preferably the oligomer used in the paper-sizing composition comprises alkylmercaptans of Ce-20f C5-7 cycloalkyl mercaptans, aromatic mercaptans, Cs-20 alkyl sulfones, C5_7 cycloalkyl mercaptans or aromatic sulfones. Suitable substituted alkyl mercaptans include 3-mercaptopropanoic acid, 2-mercaptoethanol although 2-sulfonylethanol and 3-sulfonylpropanoic acid are suitable substituted alkylsulfones. Most preferably, the paper dressing composition comprises an oligomer comprising dodecyl mercaptan or dodecyl sulfone. The oligomer incorporated in the paper sizing composition comprises the organic mercaptan or organic sulfone in an amount of up to 10 mol%, preferably 2.5-5 mol%. In the method for improving the paper or paperboard printing ability the oligomer comprises ethylenically unsaturated tertiary or quaternary amine compounds in the oligomer, although the preferred compounds are represented by the compounds of formula (1) given above in the specification and where the same preferences apply. The ethylenically unsaturated tertiary amine or ethylenically unsaturated quaternary ammonium compounds comprise, for example, dimethylaminoethyl (meth) acrylate, acid addition salt or quaternary ammonium salt thereof, preferably dimethylaminoethyl (meth) acrylate, quaternary ammonium salt of methyl chloride or dimethylaminoethyl (meth) acrylate, quaternary ammonium salt of benzyl chloride. In the method for improving paper printability the oligomer would preferably comprise ethylenically unsaturated tertiary amine or ethylenically unsaturated quaternary ammonium compounds to be incorporated in the oligomer up to 10 mol%. Preferably those compounds are present in the oligomer in amounts in the range of 2.5-5 mol%. The oligomeric compound usually contains the levels of acrylamide or methacrylamide components. For example, the molar ratio of the (meth) acrylamide is usually at least 85 mol% and preferably at least 90 mol%. It is also possible to incorporate other ethylenically unsaturated monomers into the oligomer. In particular it is possible to incorporate up to 10 mol% of other ethylenically unsaturated monomers in the oligomer. In particular it is possible to incorporate up to 10 mol% of ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic anhydride. This can be, for example, acrylic acid or maleic anhydride, preferably used in an amount between 2.5 and 5 mol%. In a particularly preferred method for improving the printability of paper, the oligomer is comprised in an aqueous dispersion of polymer particles. The oligomer would be present on the surface of the polymeric particles where the matrix of the polymeric particles are derived from ethylenically unsaturated monomer or mixture of ethylenically unsaturated monomers, monomer or mixture of monomers which are substantially insoluble in water at room temperature. The monomers polymerize to provide polymerics that are substantially insoluble in water at room temperature. Typically the matrix of the polymer particles is formed from a monomer or mixture of monomers comprising monomers selected from the group consisting of styrene (C 1 -C 2) alkyl (meth) acrylate, vinyl acetate, acrylonitrile. Preferably, the polymeric particle matrix is formed from 25-75% by weight of monomer or mixture of monomers selected from any of the styrene, acrylonitrile, vinyl acetate or C? _2 alkyl (meth) acrylates, preferably styrene, acrylonitrile, methyl methacrylate, methyl acrylate, ethyl methacrylate, vinyl acetate and 25-75% by weight of monomer or mixture of monomers selected from any of the C3-? 2 alkyl (meth) acrylates, preferably n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. More preferably, the matrix of the polymeric particles is formed from 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight styrene and 25-75% by weight, preferably 35-75% by weight, more preferably 50% by weight of 2-ethylhexyl acrylate. In another preferred aspect the polymer particles have a minimum film that is formed at a temperature of -5 and 55 ° C, preferably between 25 and 45 ° C, more preferably at about 35 ° C. In general, the composition used in the paper or paperboarding method comprises polymer particles which have a particle size in the range of 80 to 200 nm, preferably 100-120 nm. In a preferred method for improving the printing ability of the paper is a mixture of starch and an aqueous dispersion of polymer particles with a particle size of up to 1 micron, preferably 80-200 nm, more preferably 100-120 nm, wherein the polymeric particles comprise a water-insoluble polymer matrix is characterized in that an oligomer is formed from a monomer mixture comprising, (a) (meth) acrylamide, (b) an organic mercaptan or an organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group and (d) optionally other monomers and an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group comprising one or more compounds of formula ( 1) given earlier in the specification and where the same preferences apply. Typically in the method for improving paper printability the oligomer comprised in the composition applied to the surface of the sheet formed of paper comprises the compound of formula (1) in an amount of up to 10 mol%, preferably 2.5- 5 mol%. Ideally the oligomers are formed from a mixture of monomers comprising, one or more compounds selected from the list comprising dimethylaminoethyl (meth) acrylate, acid addition salt or quaternary ammonium salt thereof and preferably (meth) ) dimethylaminoethyl acrylate, quaternary ammonium salt of methyl chloride or dimethylaminoethyl (meth) acrylate, quaternary ammonium salt of benzyl chloride. Preferably, the oligomer formed from a mixture of monomers comprises acrylamide or methacrylamide in an amount of at least 85 moles, preferably at least 90 mol%. The oligomer incorporated in the paper sizing composition may comprise an additional ethylenically unsaturated monomer. In particular it is possible to incorporate up to 10 mol% of ethylenically unsaturated carboxylic acid or an ethylenically unsaturated carboxylic anhydride. This may be, for example, acrylic acid or maleic anhydride, preferably used in an amount of between 2.5 and 5 mol%. The invention relates to a method for improving the printability of paper by applying to the surface of the paper a mixture comprising starch, optionally optical brighteners and an aqueous dispersion of the polymer particles which were formed from a monomer or a mixture of monomers comprising monomers selected from the group consisting of styrene, C 1 -X 2 alkyl (meth) acrylate, vinyl acetate and acrylonitrile. Preferably the matrix of the polymer particles is formed from 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight, of monomer or mixture of monomers selected from the group consists of styrene, acrylonitrile, vinyl acetate and C? ~ 2 alkyl (meth) acrylate, preferably styrene, acrylonitrile, methyl (meth) acrylate, methyl acrylate, ethyl methacrylate, vinyl acetate and 25- 75% by weight, preferably 35-65% by weight, more preferably approximately 50% by weight, monomer or mixture of monomers selected from any of the C3-I2 alkyl (meth) acrylates, preferably acrylate of n-butyl, n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. More preferably the matrix of the polymer particles is formed of 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight of styrene and 25-75% by weight, so preferably 35-65% by weight, and more preferably about 50% by weight of 2-ethylhexyl acrylate. The method for improving the printing capacity of paper desirably involves applying to the surface of a paper sheet a mixture of starch and polymer particles having a minimum film-forming temperature of between -5 and 55 ° C, preferably between 25 and 45 ° C, more preferably about 35 ° C. The polymeric particles comprised in the paper sizing composition desirably have a particle size of less than 1 micron, preferably in the range of 80 to 200 mm, more preferably 100-120 nm. Ideally, the mixture of starch and polymer particles comprises 0.5 to 10% by weight of polymer particles and 90 to 99.5% by weight of starch, based on the dry weight of the starch. In the method for improving the printing capacity the mixture of starch and polymer particles would be applied to the surface of the sheet formed of paper at a dose of up to 20 g / m2, preferably up to 10 g / m2, typically around of 3 g / m2. In the method for improving the paper's printing ability, it has been found surprisingly that the paper treated by this method has an acceptable level of water resistance in combination with a high degree of glossiness of the paper and when used in, for For example, printing without impact, provides superior printing properties. In addition, sizing can be conveniently applied in formulations for tightening of pH as low as 1 up to as high as 12 and still provide acceptable results. One aspect of the invention encompasses a novel composition comprising an aqueous dispersion of polymer particles with a particle size of up to 1 micron, wherein the polymer particles comprise a polymer matrix insoluble in water and on the surface an oligomer formed from a mixture of monomers comprising, (a) (meth) acrylamide, (b) an organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group and (d) optionally other monomers. Although any organic mercaptan or organic sulfone may be present in the oligomer, optionally substituted alkylmercaptans of optionally substituted C? -20 alkylsulfones of C? -20, optionally substituted C5-7 cycloalkyl mercaptans, optionally substituted aromatic mercaptans, C5 cycloalkylsulfones are preferred. -7 optionally substituted or optionally substituted aromatic sulfones. Suitable substituted alkyl mercaptans include 3-mercaptopropanoic acid, 2-mercaptoethanol, while 2-sulfonylethanol and 3-sulfonylpropanoic acid are suitable substituted alkylsulfones. Most preferred are alkylmercaptans of Cs-20r C5-7 cycloalkylmercaptans, aromatic mercaptans, C8-2 alkyl cycloalkyl sulfones, or aromatic sulfones. Particularly preferred is dodecyl mercaptan or dodecyl suclone. The amount of organic mercaptan or organic sulfone used in the oligomer is usually up to 10 mol%. It may be possible to use more than one organic mercaptan and / or organic sulfone in the preparation of the oligomer, although the combined molar portions of organic mercaptans and / or organic sulfones is generally up to 10 mol%. Preferably the level of organic mercaptan or organic sulfone compounds is in the range of 2.5 to 5 mol%. It would be impossible to incorporate any number of ethylenically unsaturated tertiary amine or ethylenically unsaturated quaternary amine compounds in the oligomer, but the preferred compounds are represented by the compounds of formula (1) given above in the specification and where the same preferences apply. Preferred ethylenically unsaturated tertiary amine and ethylenically unsaturated quaternary ammonium compounds include, for example, dimethylaminoethyl (meth) acrylate, acid addition salt or quaternary ammonium salt thereof, preferably dimethylaminoethyl (meth) acrylate, ammonium salt quaternary of methyl chloride or dimethylaminoethyl (meth) acrylate, quaternary ammonium salt of benzyl chloride. Normally, the level of ethylenically unsaturated tertiary amine or ethylenically unsaturated quaternary ammonium compounds to be incorporated in the oligomer is up to 10 mol%. Preferably those compounds are present in the oligomer in amounts in the range of 2.5 to 5 mol%. The oligomeric compound usually contains higher levels of acrylamide or methacrylamide components. For example, the molar ratio of (meth) acrylamide is usually at least 85 mol% and is preferably between 90 mol% and 97.5 mol%, preferably 92.5 mol% to 95 mol%. It is also possible to incorporate other ethylenically unsaturated monomers into the oligomer. In particular it is possible to incorporate up to 10 mol% of ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic anhydride. This can be, for example, acrylic acid or maleic anhydride, preferably used in an amount of between 2.5 and 5 mol%. Generally speaking, the matrix of the polymer particles is comprised of ethylenically unsaturated monomer or mixture of ethylenically unsaturated monomers, monomers or mixture of monomers which are substantially insoluble in water at room temperature. The monomers polymerize to provide polymers that are substantially insoluble in water at room temperature. Typically, the matrix of the polymeric particles is formed from a monomer or a mixture of monomers comprising monomers selected from the group consisting of styrene, C? ~ 2 alkyl (meth) acrylate, vinyl acetate, acrylonitrile. Preferably, the matrix of the polymeric particles is formed from 25-75% by weight of monomer or mixture of monomers selected from any of the styrene, acrylonitrile, vinyl acetate or alkyl (meth) acrylates of C? -2, especially styrene, acrylonitrile, methyl methacrylate, methyl acrylate, ethyl methacrylate and vinyl acetate and 25-75% by weight of monomer or mixture of monomers selected from any of C3_2 alkyl (meth) acrylates, especially butyl acrylate , n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. More preferably the matrix of the polymeric particles is formed of 25-75% by weight, preferably 35-65% by weight, more preferably about 50% by weight of styrene and 25-75% by weight, of preferably 35-65% by weight, more preferably about 50% by weight of 2-ethylhexyl acrylate. In another preferred aspect the polymer particles have a minimum film-forming temperature of between -5 and 55 ° C, preferably between 25 and 45 ° C, more preferably about 35 ° C. In general, the composition comprises a dispersion of polymer particles having a particle size in the range of 80-200 nm, preferably 100-120 nm.

Thus, the invention encompasses an aqueous dispersion of polymer particles, wherein the polymer particles have a particle size in the range of 80-200 mm, more preferably 100-120 nm and comprising a polymer matrix insoluble in water, preferably formed from ethylenically unsaturated water-insoluble monomers, more preferably formed from 25-75% by weight, usually about 50% by weight, of one or more monomers selected from styrene, acrylonitrile, methyl methacrylate, acetate of vinyl, especially styrene and 25-75% by weight, usually about 50% by weight of one or more monomers selected from butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate and n-octyl acrylate, especially 2-ethylhexyl acrylate, characterized in that the polymer particles also comprise on their surface an oligomer of acrylamide or methacrylamide which additionally comprises a mercaptan or organic or organic sulfone, more preferably a C8-2o methylamercaptane or C8_2o alkyl sulfone, more preferably dodecyl mercaptan or dodecyl sulfone. Preferably, the oligomer also comprises components based on ethylenically unsaturated tertiary amines or ethylenically unsaturated quaternary ammonium compounds, for example quaternized dimethylaminoethyl trimethylmethacrylate or dimethylaminoethyl quaternized dimethylaminoethyl dimethacrylate benzyl chloride. It is also possible to incorporate other ethylenically unsaturated monomers into the oligomer. In particular, it is possible to incorporate up to 10 mol% of ethylenically unsaturated carboxylic acid or ethylenically unsaturated carboxylic anhydride. This can be, for example, acrylic acid or maleic anhydride, preferably used in an amount of between 2.5 and 5 mol%. The novel composition could be used in the coating of various substrates, but the compositions are desirably agents for sizing paper and paperboard or coating paper coating materials that can improve water resistance and / or paper printability. In general, the novel compositions are mixed with other materials such as solutions of water-swellable polymers or natural or synthetic water-soluble to form sizing or coating formulations. The oligomers are made by mixing the components together with water and optionally other solvents for example alcohols such as ethanol or carboxylic acids such as acetic acid, where the components comprise at least (a) (meth) acrylamide and (b) an organic mercaptan or organic sulfone and effect the oligomerization in a usual manner.

A preferred form of the oligomer comprises the components (a) (meth) acrylamide, (b) an organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group and (d) optionally other monomers are mixed with sufficient water and optionally an alcohol, for example ethanol, and optionally a carboxylic acid, such as acetic acid, to provide an aqueous solution of the monomer mixture. The oligomerization is effected by the use of suitable initiators in the usual manner. Oligomers formed from any of the organic mercaptans can be treated with a suitable oxidizing agent, for example a peroxide, especially hydrogen peroxide, to convert some or all of the mercapto groups to sulfone groups. The preparation of the aqueous dispersion of polymer particles according to the invention can be carried out in a desirable manner by suspension polymerization or emulsion polymerization. In a preferred process, the water-insoluble monomers are emulsified in an aqueous medium comprising the oligomer in an amount of up to 30% by weight, preferably between 10 and 20% by weight. The polymerization is carried out in the usual way, but for example redox initiators, thermal initiators, UV radiation or combinations of these can be used. The compositions formed will comprise an aqueous dispersion of polymer particles of a particle size of up to 1 micron, preferably in the range of 80-200 nm, more preferably in the range of 100-120 nm, where the polymer particles comprise a water-insoluble polymer matrix wherein the polymer particles comprise a polymer matrix insoluble in water and on the surface an oligomer formed from a mixture of monomers comprising, (a) (meth) acrylamide, and (b) an organic mercaptan or organic sulfone In a preferred form of the composition the oligomer is formed from a mixture of monomers comprising, (a) (meth) acrylamide (b) an organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group; and (d) optionally other monomers. The following are examples of the invention.

Example 1 Preparation of Polymer A 45 parts by weight of styrene and 45 parts by weight of 2-ethylhexyl acrylate are emulsified in 125 parts by weight of water with a content of 10 parts by weight of an oligomer formed from 20 molar parts of acrylamide and 1 mole part of dodecyl mercaptan and oligomerized in 50/50 weight / weight water / ethanol medium. The emulsion polymerization is carried out in the usual manner using redox initiators and a thermal initiator to form a stable dispersion of polymer particles.

Preparation of Polymer B The process for preparing polymer A is repeated except that the polymer used comprises 19 parts per mole of acrylamide, 1 part per mole of dodecyl mercaptan and 1 part per mole of quaternary ammonium salt of methyl chloride of methacrylate. dimethylaminoethyl.

Preparation of Polymer C The process for preparing polymer A is repeated except that the polymer used comprises 19 parts per mole of acrylamide, 1 part per mole of dodecyl mercaptan and 1 part per mole of quaternary ammonium salt of methyl chloride of methacrylate of dimethylaminoethyl.

Preparation of Polymer D The process for preparing polymer A is repeated except that the oligomer is prepared in a water / acetic acid solvent 50/50 w / w.

Preparation of Polymer E The process for preparing polymer D is repeated except that the oligomer used comprises 90 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan and 5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer F The process for preparing polymer D is repeated except that the oligomer used comprises 92.5 parts per mole of acrylamide, 2.5 parts per mole of dodecyl mercaptan and 5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer G The process for preparing polymer D is repeated except that the oligomer used comprises 85 parts per mole of acrylamide, 10 parts per mole of dodecyl mercaptan and 5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer H The process for preparing polymer D is repeated except that the oligomer used comprises 93.5 parts per mole of acrylamide, 1.5 parts per mole of dodecyl mercaptan and 5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer I The process for preparing polymer D is repeated except that the oligomer used comprises 92.5 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan and 2.5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer J The process for preparing polymer D is repeated except that the oligomer used comprises 95 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan.

Preparation of Polymer K The process for preparing polymer D is repeated except that the oligomer used comprises 80 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan and 15 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer L The process for preparing polymer D is repeated except that the oligomer used comprises 85 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan and 10 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer M The process for preparing polymer D is repeated except that the oligomer used comprises 90 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan and 5 parts per mole of dimethylaminoethyl methacrylate.

Preparation of Polymer N The process for preparing polymer D is repeated except that the oligomer used comprises 85 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan, 5 parts per mole of dimethylaminoethyl methacrylate and 5 parts per mole of acrylic acid .

Preparation of Polymer O The process for preparing polymer D is repeated except that the oligomer used comprises 82.5 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan, 5 parts per mole of dimethylaminoethyl methacrylate and 7.5 parts per mole of acrylic acid .

Preparation of Polymer P The process for preparing polymer D is repeated except that the oligomer used comprises 87.5 parts per mole of acrylamide, 5 parts per mole of dodecyl mercaptan, 5 parts per mole of dimethylaminoethyl methacrylate and 2.5 parts per mole of acrylic acid. .

Preparation of the Polymer The process for preparing the polymer N is repeated except that the monomer mixture comprises 63 parts by weight of styrene and 27 parts by weight of 2-ethylhexyl acrylate.

Preparation of Polymer R The process for preparing polymer Q is repeated except that 20% by weight of the oligomer is used.

Preparation of Polymer S The process for preparing polymer R is repeated except that 0.25% by weight of ethylene glycol dimethacrylate is combined with the monomeric mixture of styrene / 2-ethylhexyl acrylate.

Preparation of Polymer T The process for preparing polymer R is repeated except that 0.50% by weight of ethylene glycol dimethacrylate is combined with the monomeric mixture of styrene / 2-ethylhexyl acrylate.

Preparation of Polymer U The process for preparing polymer R is repeated except that 0.25% by weight of divinylbenzene is combined with the monomeric mixture of styrene / 2-ethylhexyl acrylate.

Preparation of Polymer V The process for preparing polymer Q is repeated except that the oligomer used is prepared using 5 parts per mole of maleic anhydride in place of acrylic acid.

Example 2 The polymers of Example 2 are mixed with an aqueous suspension of 6% precooked starch at a starch / polymer ratio of 40: 1 to provide a sizing formulation. Dressing formulations are applied to the paperboard surface for standard paperless sizing using a sizing press with a No. 7 K-bar to give a coating of 5 gm-2 and drying for 30 minutes at 110 ° C in a oven, made by mixing each of the polymers of Example 1 with a precooked starch solution to provide a mixture comprising a 40: 1 ratio of starch: polymer. The leaves are evaluated for 60 seconds in a Cobb test and the results are shown in Table 1.

Table 1 As can be seen from the results, all the products gave resistance to water acceptable to the leaves. Particularly good results were obtained for formulations comprising polymers B, I, J, M, Q, R, S, T, U and V.

Example 3 The polymers of example 1 are mixed with an aqueous suspension of 6% starch at a ratio of 20: 1 starch / polymer. The mixtures are coated on sheets of UMIST paper at a dose of 5 gm "" 2. The print capacity tests were obtained using a Deskjet 560C printer from Hewlett Packard. The Optical Density of the Black and the Color Density were measured on coated paper using the respective products. The results are presented in Table 2. OD-DC Optical Density-Color Density. Deskjet is a trademark of Hewlett Packard.

Table 2 Table 2 (Continued) As can be seen, all polymers give acceptable results.

Example 4 The 20: 1 starch / polymer formulations of Example 3 are coated on standard UMIST paper sheets and standard brightness tests were carried out. The results of the tests are shown in Table 3.

Table 3 Table 3 (Continued) Surface Sizing Brilliance Starch + OBA + Polymer B 82.06 Starch + OBA + Polymer C 82.62 Starch + OBA + Polymer D 82.63 Starch + OBA + Polymer I 81.0 Starch + OBA + Polymer J 80.6 Starch + OBA + Polymer K 81.1 Starch + OBA + Polymer L 81.3 Starch + OBA + Polymer M 81.5 Starch + OBA + Polymer N 83.39 The polymers of the present invention give a high degree of brilliance. Better results were obtained using polymers A, B, C, D and N.

EXAMPLE 5 Polymers D and Q of Example 1 are mixed with an aqueous suspension of 6% precooked starch in a starch / polymer ratio of 40: 1 to provide various formulations for sizing at different pH. The sizing formulations are applied to the surface of the standard coated paperboard as in example 2. The water resistance of the sized paper is measured using the 60 second Cobb test. The results are shown in Tables 4 and 5.

Table 4 Table 5 The results of this test show that the polymers provide the paper with good resistance to water at acid, neutral or alkaline pH.

Example 6 Polymer Q was added as the aqueous emulsion directly to two types of pulp to make paper and the formed paper sheets were tested for water resistance.

As can be seen, the use of the polymers of the invention as internal sizing agents shows properties of good water resistance on two different types of pulp. The results of all these modalities clearly demonstrate that the products of the invention provide good water resistance, printability and brightness to paper.

Claims (2)

CLAIMS 1. A method for preparing paper or cardboard by applying a composition (A) to at least one of, i) the surface of a formed sheet of paper or cardboard, ii) a cellulosic suspension for making paper or cardboard before draining, where the composition (A) comprises an aqueous dispersion of polymer particles with a particle size of up to 1 micron, wherein the polymer particles comprise a polymeric polymer insoluble in water, comprised of ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers, characterized in that a oligomer formed from a mixture of monomers comprises (a) (meth) acrylamide and (b) an organic mercaptan or organic sulfone, located on the surface of the polymer particles. 2. A method according to claim 1, characterized in that component (b) is selected from the group consisting of C8-2o alkyl mercaptans, C5-7 cycloalkyl mercaptans, aromatic mercaptans, Cs-20 alkyl sulfones, cycloalkylsulfones, C5_7, and aromatic sulfones, preferably dodecyl mercaptan or dodecyl sulfone. 3. The method according to claim 1 or claim 2, characterized in that the oligomer further comprises component (c) which has a compound of formula (1) CH2 = CR-Q (1) where Q is - C (0) -Z -A, -CH2-N + R1R3CH2CR = CH2 X "or -CH2NR? CH2CR = CH2 Z is -0- or -NH-, A is -CnH2r -B, n is an integer of 1 to 4, B is -NR] R2 or -N + R? R2R3 X ", R is -H or -CH3 Ri is C? _4 alkyl, R2 is C? _4 alkyl, R3 is -H or C alkyl? ? 8, cycloalkyl of C? -7 or benzyl, and
1. X ~ is an anion, preferably halide, more preferably chlorine. The method according to any of claims 1 to 3, characterized in that component (c) is dimethylaminoethyl (meth) acrylate, acid addition salt or quaternary ammonium salt thereof, preferably (meth) acrylate of dimethylaminoethyl, quaternary ammonium salt of methyl chloride or dimethylaminoethyl (meth) acrylate or quaternary ammonium salt of benzyl chloride. The method according to any of claims 1 to 4, characterized in that the oligomer comprises at least 85 mol% of component (a), preferably, at least 90 mol%. The method according to any of claims 1 to 5, characterized in that the oligomer comprises the component (b) in an amount of up to 10 mol%, preferably 2.5-5 mol%. The method according to any of claims 1 to 6, characterized in that the oligomer comprises the component (c) in an amount of up to 10 mol%, preferably 2.5-5 mol%. The method according to any of claims 1 to 7, characterized in that the oligomer further comprises component (d), which is an ethylenically unsaturated carboxylic acid or an ethylenically unsaturated carboxylic anhydride in an amount of up to 10 mol %. The method according to claim 8, characterized in that the component (d) is acrylic acid or maleic anhydride and is present in an amount between 2.5 and 5 mol%. The method according to any of claims 1 to 9, characterized in that the matrix of the polymeric particles are formed from a monomer or a mixture of monomers comprising monomers selected from the group consisting of styrene, (meth) acrylate of alkyl of C? _? 2, vinyl acetate and acrylonitrile. The method according to any of claims 1 to 10, characterized in that the matrix of the polymeric particles is formed of 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight. weight, of monomers or mixture of monomers selected from any of the styrene, acrylonitrile, vinyl acetate and C? _2 alkyl (meth) acrylate, preferably styrene, acrylonitrile, methyl methacrylate, methyl acrylate, ethyl methacrylate, vinyl acetate and 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight of monomer or mixture of monomers selected from any of ) C3_8 alkyl acrylates, preferably butyl acrylate, n-hexyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate. The method according to any of claims 1 to 11, characterized in that the matrix of the polymeric particles is formed of 25-75% by weight, preferably 35-65% by weight, more preferably 50% by weight. weight of styrene, and 25-75% by weight, preferably 35-75% by weight, more preferably 50% by weight of 2-ethylhexyl acrylate. The method according to any of claims 1 to 12, characterized in that the polymer particles are formed from a monomer mixture comprising crosslinking monomers. The method according to any of claims 1 to 13, characterized in that the polymer particles have a minimum film-forming temperature between -5 and 55 ° C, preferably between 25 and 45 ° C, preferably about 35 ° C. The method according to any of claims 1 to 14, characterized in that the polymer particles have a particle size in the range of 80-200 nm, preferably 100-120 nm. The method according to any of claims 1 to 15, characterized in that the composition (A) comprises 0.5 to 10% by weight, preferably 2.5 to 5% by weight, of polymer particles and 90 to 99% by weight , preferably 95 to 97.5% by weight, of starch on the basis of the total dry weight of the polymeric particles and the starch. 17. A method for improving the printability of a sheet of paper by applying to the surface of the formed sheet of paper a sheet of paper comprising an oligomer formed from a mixture of monomers comprising, a) (meth) acrylamide , (b) an organic mercaptan or organic sulfone, (c) an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary ammonium group and (d) optionally other monomers. 18. The method of compliance with the claim 17, characterized in that the composition comprises an aqueous dispersion of polymer particles with a particle size of up to 1 micron, preferably 80-200 nm, wherein the polymer particles comprise a water-insoluble polymer matrix, preferably formed of styrene and acrylate. 2-ethylhexyl, and the oligomer is located on the surface of the polymer particles. The method according to claim 17 or 18, characterized in that the oligomer is formed of a mixture of monomers comprising, (a) 85-95% (meth) acrylamide, (b) 2.5-10 mol% of a organic mercaptan or an organic sulfone, preferably dodecyl mercaptan or dodecyl sulfone, (c) 2.5-10 mol% of an ethylenically unsaturated monomer comprising a tertiary amine group or a quaternary amino group, preferably dimethylaminoethyl methacrylate, and (d) 0-10 mol% of other ethylenically unsaturated monomers, preferably acrylic acid or maleic anhydride. The method according to any of claims 17 to 19, characterized in that the composition comprises from 0.5 to 10% by weight, preferably from 2.5 to 5% by weight, of polymer particles and from 90 to 99% by weight , preferably from 95 to 97.5% by weight, of starch on the basis of the total dry weight of the polymeric particles and the starch. 21. The method according to any of claims 17 to 20, characterized in that the composition comprises optical brightening aid. 22. A composition comprising an aqueous dispersion of polymer particles with a particle size of up to 1 micron, wherein the polymer particles comprise a water-insoluble polymer matrix, preferably formed of styrene and 2-ethylhexyl acrylate, characterized in that an oligomer formed of a monomer mixture comprises, (a) 85-95% (meth) acrylamide, and (b) 2.5-10 mole% of an organic mercaptan or an organic sulfone, and (c) 2.5-10 mole% of a monomer ethylenically unsaturated comprising a tertiary amine group or a quaternary ammonium group; and (d) 0-10 mol% of other ethylenically unsaturated monomers, preferably acrylic acid or maleic anhydride, located on the surface of the polymeric particles. 23. The composition according to claim 22, characterized in that the polymer particles have a particle size of 80-200 nm. The composition according to claim 22 or claim 23, characterized in that component (b) is dodecyl mercaptan or dodecyl sulfone, present in an amount of 2.5-5 mol% based on the total oligomer. 25. The composition according to any of claims 22 to 24, characterized in that component (c) is dimethylaminoethyl methacrylate, present in an amount of 2.5-5 mol% based on the total oligomer. 26. The composition according to any of claims 22 to 25, characterized in that the component (d) is acrylic acid or maleic anhydride, present in an amount of
2. 2.5-5 mol% based on the total oligomer.