TW201714981A - Process, dispersions and use - Google Patents

Abstract

A process for preparing an encapsulated pigment dispersion suitable for use in an ink jet printing ink comprising the following steps in the order (I) followed by (II): (I) providing a dispersion comprising a pigment, a liquid medium and a dispersant having a WAMW of up to 50,000 Daltons obtained by copolymerising a monomer composition comprising components (a) and (b): (a) from 75 to 97 parts of one or more hydrophobic ethylenically unsaturated monomers comprising at least 50 parts benzyl (meth) acrylate; and (b) from 3 to 25 parts one or more hydrophilic ethylenically unsaturated monomers having one or more ionic group(s); wherein the parts are by weight and the sum of the parts (a) and (b) add up to 100; (II) cross-linking the dispersant in the presence of the pigment and the liquid medium.

Description

Method, dispersion and use

The present invention relates to a method for preparing an encapsulated pigment dispersion, an encapsulated pigment dispersion obtainable by the method, an inkjet printing ink containing the dispersion, and a method for preparing an inkjet printing ink Use.

The ink used for inkjet printing is divided into two main categories depending on the type of colorant it contains. Dye-based inks typically comprise a dye dissolved in a liquid medium. Pigment-based inks typically comprise a pigment dispersed in a liquid medium. Pigment-based inks generally have better ozone and lightfastness than dye-based inks. However, because the pigment is in the form of a particle dispersion, the pigment particles have a tendency to coalesce or flocculate when the ink is stored and/or when the ink is used (eg, printed). Such coalescence or flocculation is highly undesirable, especially when the ink is intended to be used in printers having very small nozzles susceptible to any clogging of excessive particulate matter. Therefore, much effort has been spent in the field of inkjet to attempt to increase the stability of pigment dispersions. It is especially difficult to provide pigment inks with good stability when the liquid medium contains a large amount of water-miscible organic solvent and a relatively small amount of water.

It is also desirable to provide pigment inks that provide high optical density (OD), especially when printed onto blank paper.

EP 2,342,005 describes a process for the preparation of pigment dispersions from dispersants having a weight average molecular weight of more than 82,000. The present invention seeks to provide a method of producing a pigment dispersion that has good performance in ink jet printing (e.g., good storage stability even when stored at elevated temperatures).

According to a first aspect of the invention, there is provided a process for the preparation of an encapsulated pigment dispersion suitable for use in ink jet printing inks, the process comprising the following steps in the order of I) followed by II): I) providing a dispersion, It comprises a pigment, a liquid medium and a dispersant having a weight average molecular weight ("WAMW") of up to 50,000 Daltons (Da) by copolymerizing a monomer composition comprising components a) and b) And obtaining: and a) 75 to 97 parts comprising at least 50 parts of one or more hydrophobic ethylenically unsaturated monomers of benzyl (meth) acrylate; and b) 3 to 25 parts having one or more ionic groups Or one or more hydrophilic ethylenically unsaturated monomers; wherein the aliquots are by weight, and the sum of the aliquots of a) and b) is up to 100; II) in the presence of pigments and liquid media The dispersant is crosslinked.

In this specification, the words "a" and "an" mean one or more unless otherwise indicated. Thus, for example, "a (a)" pigment includes the possibility of the presence of more than one pigment, and similarly, "a (a)" dispersant includes the possibility of the presence of more than one dispersant.

The dispersant used in step I) preferably has a WAMW of from 1,000 to 50,000 Daltons, more preferably from 5,000 to 45,000, and especially from 10,000 to 38,000.

The WAMW of the dispersant can be determined by gel permeation chromatography ("GPC"), preferably by comparison to a polymer of known WAMW. Preferably, GPC uses N,N-dimethylformamide (DMF) as the leaching agent. For convenience, two Plgel "mixed D" columns and a single detector (Refractive Index) for sequential connection of GPCs can be used.

In one embodiment, the dispersion in step I) can be provided by dispersing the pigment in a liquid medium in the presence of a dispersant having the above composition. Dispersion can be carried out by any suitable method including, for example, bead milling, bead shaking, ultrasonic treatment, homogenization, and/or microfluidization. A preferred method for dispersing a pigment in a liquid medium comprises Bead mill. Generally, bead milling is carried out using a composition comprising abrasive beads, a dispersing agent, a liquid medium, and a relatively high proportion of pigment, often from about 15% to about 45% by weight relative to the weight of the liquid medium. After grinding, the beads are typically removed by filtration. The milled dispersion (yield) may be diluted with a majority of the liquid medium, optionally containing additional dispersing agents, which may be the same or different than the dispersing agents included in the foregoing compositions.

The pigment may comprise and preferably be an inorganic or organic pigment material or a mixture thereof that is insoluble in the liquid medium.

Preferred organic pigments include, for example, any of the pigments described in Colour Index International, Third Edition, (1971) and subsequent revisions and supplements thereof, entitled "Pigments". Examples of organic pigments include those derived from azo (including disazo and condensed azo), thioindigo, hydrazine, isoindole, ruthenium, osmium, isobenzophenone, and triphenyl dioxin. The pigments of the azine, quinacridone and phthalocyanine series, especially copper phthalocyanine and its nuclear halogenated derivatives, also lack acidic, basic and mordant dyes. Preferred organic pigments include phthalocyanine (especially copper phthalocyanine) pigments, azo pigments, anthraquinone, anthraquinone and quinacridone pigments.

Preferred inorganic pigments include carbon black, titanium dioxide, aluminum oxide, iron oxide, and cerium oxide.

In the case of carbon black pigments, such pigments can be prepared in such a manner that a part of the carbon black surface has an oxidizing group (for example, a carboxylic acid and/or a hydroxyl group). However, the amount of such groups is preferably not so high that the carbon black can be dispersed in the water without the aid of a dispersing agent.

Preferably, the pigment is a cyan, magenta, yellow, orange, violet, green or black pigment.

The pigment may be a single chemical or a mixture comprising two or more than two chemicals (eg, a mixture comprising two or more different pigments). In other words, two or more than two different pigments can be used in the process of the invention. Where two or more pigments are used, such pigments may have the same color or hue or they may have Different colors or shades.

Preferably, the pigment is not dispersible in the aqueous liquid medium with the aid of a dispersing agent, i.e., a dispersing agent is present to facilitate dispersion. Preferably, pigments without chemical surface treatment, e.g., a pigment is preferably free of covalently bonded ionic group to the surface (e.g., free -CO ₂ H group and a -SO ₃ H group).

Preferably, the liquid medium is aqueous, that is, it is or contains water. The aqueous liquid medium may optionally contain one or more water-miscible organic solvents.

When the liquid medium comprises a mixture of water and one or more water-miscible organic solvents, the total amount of water and water-miscible organic solvent is preferably from 1:1 to 100:1, more preferably from 2 : 1 to 50:1 and especially from 3:1 to 20:1.

Preferred liquid medium comprises: (a) 50 to 100 parts, more preferably 75 to 100 parts of water; and (b) 0 to 50 parts in total, more preferably 0 to 25 parts or more of water miscible An organic solvent; wherein the aliquots are by weight, and the sum of the parts (a) and (b) = 100.

In one embodiment, the only liquid in the liquid medium is water.

In addition to the water and water miscible organic solvent, the liquid medium may further contain additional components such as biocides, surfactants, water-immiscible organic solvents, and additional dispersants.

A water-miscible organic solvent can be used to increase the solubility of the dispersant in the aqueous liquid medium.

Preferably, the liquid medium has a viscosity of less than 100 mPa.s, more preferably less than 50 mPa.s, when measured at 25 °C.

Although the number of parts a) and b) is 100 in total, this only determines the amount of each of component a) and component b) relative to each other and does not exclude the presence of a) in the composition. An additional component other than b), for example, one or more hydrophilic olefinic groups having a hydrophilic nonionic group Saturated monomers can be present as component c).

The dispersant preferably has a WAMW of from 1000 to 50,000 Da, more preferably from 5,000 to 45,000 Da, especially from 10,000 to 38,000 Da.

Preferably, the dispersant is obtained by copolymerizing a monomer composition comprising component a) to component c): a) 75 to 97 parts comprising at least 50 parts of benzyl (meth) acrylate or a plurality of hydrophobic ethylenically unsaturated monomers; b) from 3 to 25 parts of one or more hydrophilic ethylenically unsaturated monomers having one or more ionic groups; and c) from 0 to 2 parts having hydrophilicity One or more hydrophilic ethylenically unsaturated monomers; and wherein the aliquots are by weight and the sum of the parts a) to c) is 100 in total.

By copolymerizing c) from 0 to 2 parts of a monomer composition having one or more hydrophilic unsaturated monomers having a hydrophilic nonionic group, a preferred dispersant will be obtained; the dispersant may alternatively be represented as The hydrophilic ethylenically unsaturated monomer composition having a hydrophilic nonionic group is not contained, or is represented by a total of up to 2 parts of a hydrophilic ethylenically unsaturated monomer composition having a hydrophilic nonionic group.

Preferred dispersants have a graft, comb or star structure, more preferably a linear structure.

The dispersant is a copolymer. A preferred copolymer is a block copolymer (for example, a monomer unit thereof is distributed throughout the copolymer such as AAAA-BBBB), and more preferably, the dispersant is a random copolymer (for example, a monomer unit thereof Random/statistical means throughout the copolymer distribution).

The dispersion referred to in step I) of the process of the invention optionally comprises two or more than two dispersants, wherein one or all of such dispersants are as defined above. It is possible to utilize one or more of the dispersing agents defined in the above description of the invention and one or more additional dispersing agents not as defined in the above description of the invention. Preferably used in the step I) There are dispersants as defined in the above description of the invention.

The dispersing agent used in the method according to the first aspect of the present invention can be produced by any suitable means. A preferred method is free radical polymerization. Suitable free radical polymerization methods include suspension polymerization, emulsion polymerization, dispersion polymerization, and preferably solution polymerization. Preferably, the dispersing agent is prepared by solution polymerization of a monomer composition comprising components a), b) and c) (when present) in the presence of an aqueous or organic liquid carrier.

The term hydrophobic means to be more hydrophobic than the hydrophilic monomers of components b) and c) when present. Preferably, the hydrophobic monomer does not have a hydrophilic group, for example, the hydrophobic ethylenically unsaturated monomer does not contain an ionic or nonionic water-dispersing group. For example, the hydrophobic ethylenically unsaturated monomer preferably contains no acidic groups and no polyvinyloxy groups.

Preferably, the hydrophobic ethylenically unsaturated monomer has a calculated Log P value of at least 1, more preferably from 1 to 6, especially from 2 to 6.

A review of Mannhold, R. and Dross, K. (Quant. Struct-Act. Relat. 15, 403-409, 1996) describes 14 methods for calculating the Log P value of a compound, and in particular a drug. Since then, we have preferred the "fragmentation method" and especially the fragmentation method implemented by ACD Lab Software. Commercially available computer software can be used (for example, using Log P DB software version 7.04 or a later version of this software (available from Advanced Chemistry Development Inc) to calculate the calculated Log P for the monomer. Any ion The group or ionizable group is calculated in a neutralized (non-ionized) form. Higher log P values correspond to higher hydrophobic monomers. We have found that the inclusion of such monomers helps to adsorb the dispersant Up to the surface of the pigment and to help provide an encapsulated pigment dispersion with good optical density when printed onto a blank sheet.

Preferred hydrophobic ethylenically unsaturated monomers include styrenic monomers (e.g., styrene, alpha methyl styrene), aromatic (meth) acrylates (especially benzyl (meth) acrylate), C _1-30 - (meth)acrylic acid alkyl ester, butadiene, (meth) acrylate containing poly(C _3-4 ) alkylene oxide group, containing alkyl oxa oxide or fluorinated alkyl ( Methyl) acrylate and vinyl naphthalene.

Preferably, the amount of the hydrophobic ethylenically unsaturated monomer comprising at least 50 parts of benzyl (meth) acrylate for producing a dispersant is from 75 to 97 parts by weight, more preferably from 77 to 97 parts by weight. It is especially from 80 to 93 parts and most especially from 82 to 91 parts.

A dispersant having a defined WAMW and comprising at least 50 parts of benzyl (meth) acrylate per 100 parts of monomer (ie, a dispersant containing at least 50% by weight of benzyl (meth) acrylate) is provided on a blank sheet of paper An encapsulated pigment dispersion with good stability and good OD.

Component a) preferably comprises at least 60 parts by weight, more preferably at least 70 parts by weight and particularly preferably at least 80 parts by weight of benzyl (meth)acrylate. The remainder required to obtain an overall preferred amount of hydrophobic monomer can be provided by removing one or more hydrophobic monomers other than benzyl (meth) acrylate (eg, selected from the above hydrophobic ethylenically unsaturated monomers) Things. Preferably, benzyl (meth)acrylate is benzyl methacrylate (rather than benzyl acrylate).

In a preferred embodiment, the hydrophobic ethylenically unsaturated monomer used as component a) consists of benzyl (meth)acrylate, more preferably consists of benzyl methacrylate.

Preferably, the hydrophilic ethylenically unsaturated monomer used as component b) has a calculated Log P value of less than 1 when calculated as a non-neutralized (e.g., free acid) form, more preferably 0.99 to 2 , especially from 0.99 to 0 and most especially from 0.99 to 0.5.

Preferably, the ionic group present in the monomer in component b) is a cationic group, or more preferably an anionic group.

Preferably, the hydrophilic ethylenically unsaturated monomers of component b) each have one or more anionic groups, more preferably one or more acidic anionic groups.

Preferred acidic anionic groups include sulfonic acids, phosphonic acids and especially carboxylic acids. Acidic sulfates, phosphates and polyphosphates can also be used as acidic anionic groups.

Thus, component b) preferably comprises one or more hydrophilic ethylenically unsaturated monomers having one or more carboxylic acid groups.

Preferred hydrophilic ethylenically unsaturated monomers having one or more carboxylic acid groups (as ionic groups) include beta carboxyethyl acrylate, itaconic acid, maleic acid, fumaric acid, Butenoic acid, more preferably includes acrylic acid and especially includes methacrylic acid. Preferably, such ethylenically unsaturated monomers having ionic groups provide all of the ionic groups present in the dispersant when polymerized.

In a preferred embodiment, component b) is or comprises methacrylic acid. Preferably, the amount of hydrophilic ethylenically unsaturated monomer having one or more ionic groups used to make the dispersant is from 3 to 25 parts by weight, more preferably from 3 to 23 parts by weight, especially from 7 to 22 parts and most especially 9 to 18 parts. This is especially true when component b) comprises or more preferably methacrylic acid.

For the purposes of the present invention, monomers having both ionic and nonionic hydrophilic groups are considered to belong to component c). Thus, all ethylenically unsaturated monomers in component b) are free of hydrophilic nonionic groups.

The dispersing agent is preferably obtained by copolymerizing the above components a) and b) and 0% by weight to 2% by weight of the hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group in a specified amount.

Preferably, in the presence of d) one or more chain transfer agents ("CTA"), especially in the case where at least one CTA has one or more hydrophilic groups, by polymerizing comprises components a), b) And the aforementioned monomer composition of c), as the case may be, to obtain a dispersant.

The use of CTA during free radical polymerization is known in the art and is described, for example, in the textbook "Handbook of Free-Radical Polymerization" by Davis and Matyjaszewski (Wiley Interscience 2002, ISBN 0-471-39274-X). Chapter 12 ("Control of Free-Radical Polymerization by Chain Transfer Methods" by Chiariri and Rizzardo; pages 639 to 690).

One function of CTA is to allow control of the chain length during synthesis, which results in a decrease in the molecular weight of the polymer obtained when compared to a polymer made in the absence of CTA.

Preferred CTAs contain one or more sulfur atoms. Such CTAs include thiols (including difunctional thiols and higher functional thiols), polysulfides (especially disulfides), and thioethers, thioesters, and thiocarbamates.

Preferably, the CTA has at least one, more preferably only one -SH (thiol) group.

Preferred CTA has only one hydrophilic group. For CTA, the hydrophilic group is different from the chain transfer group. Thus, for example, -SH is not considered to be a hydrophilic group for CTA.

The CTA preferably has one or more hydrophilic groups selected from the group consisting of a nonionic group, a cationic group, and especially an anionic group. Possible hydrophilic groups are as previously described for the monomers.

Preferred hydrophilic anionic groups on CTA include sulfonic acid groups, phosphonic acid groups, and especially carboxylic acid groups.

Preferred hydrophilic nonionic groups on CTA include hydroxyl groups and polyvinyloxy groups.

Preferred CTAs having one or more hydrophilic groups include: i) mercapto acid, preferably thioglycolic acid, mercapto undecanoic acid, thiolactic acid, thiobutyric acid, thiomalic acid, sulfur Malonate, thioadipate, 2-mercaptoethanesulfonic acid and especially 3-mercaptopropionic acid; ii) mercapto alcohol, preferably 2-mercaptoethanol, mercaptopropanol, mercaptobutanol, 3 - mercapto-1,2-propanediol, thioglycerol, ethylene glycol monothioglycolate; iii) mercaptoamine and especially cysteine.

In all of the above, a preferred CTA having one or more hydrophilic groups is 3-mercaptopropionic acid.

Preferably, the CTA is not acrolein or (meth)acrolein.

In some cases, component d) (CTA) may contain one or more CTAs that do not have a hydrophilic group (except of course the chain transfer group itself). These CTAs may be referred to simply as hydrophobic CTAs. When present, preferred "hydrophobic" CTA includes thiols such as octyl mercaptan, n-dodecyl mercaptan, tri-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan And a third-tetradecyl mercaptan, butyl 3-mercaptopropionate; a disulfide di-orthoester such as dimethyl disulfide xanthate, diethyl disulfide xanthate and diisopropyl Disulfide disulfide; dimethylthiocarbonylamine disulfide, for example, tetramethyldimethylthiocarbazone disulfide, disulfide tetrasulfide Ethyl bis-methyl carbonyl hydrazide and tetrabutyl bis thiocarbonyl decyl amine; halogenated hydrocarbons, for example, carbon tetrachloride and ethylene bromide; hydrocarbons, for example, pentaphenylethane; unsaturated cyclic hydrocarbon compounds For example, 2-ethylhexyl hydrogen thioacetate, terpinolene, alpha terpinene, gamma terpinene, diterpene, alpha methyl styrene dimer, 9,10-indane, 1 , 4-dihydronaphthalene, anthracene and 1,4-cyclohexadiene; unsaturated heterocyclic compounds such as dibenzopyran and 2,5-dihydrofuran; certain transition metal chelating compounds, for example, Low-spin bis(ethylenedidecyl)cobalt (II) complex; and analogs thereof. These hydrophobic CTAs can be used singly or in the form of at least two types of hybrids.

Preferably, in component d), the ratio of the total number of moles of CTA having one or more hydrophilic groups to the total number of moles of all CTAs having no hydrophilic group is 1:1, Preferably, the ratio is 5:1, especially 10:1, and particularly preferred, component d) comprises only CTA having one or more hydrophilic groups. In this way, all CTA bound to the copolymer provides a CTA group with a hydrophilic group. Also, the chain transfer group is not regarded as a hydrophilic group.

The optimum total amount of CTA to be used in the composition will depend on the amount of molecular weight desired, the chemical structure of the CTA used, and its reactivity with respect to the monomers present in the composition. The optimum total amount of CTA to be used experimentally can be determined, for example, by first polymerizing a composition in which no CTA is present, followed by repeating polymerization using increasing amounts of CTA to obtain a polymer having the desired WAMW. The WAMW of each polymer can then be measured and the data of the (x,y) curve used to generate the CTA is used in comparison to the obtained WAMW: the resulting line can then be used to determine how many CTAs are needed to obtain A polymer having a specific value of WAMW.

The CTA d) optionally present may be present in an amount to form a dispersant in an amount of from 0.1% by weight to 15% by weight, based on the total weight of the polymerizable component present in the composition, especially It is from 1% by weight to 10% by weight and most especially from 1% by weight to 5% by weight.

Preferably, the monomer composition further comprises e) an initiator, especially a free radical initiator. Preferably, the initiator is thermally activated, that is, a thermal initiator.

Examples of the radical initiator include an azo compound such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis-(2-methyl)butyronitrile, 4,4'- Azobis(4-cyanovaleric acid), 2-(t-butylazo)-2-cyanopropane and 2,2'-azobis[2-methyl-N-hydroxyethyl)] - Propylamine. Other soluble free radical initiators may also be used, examples of which include peroxy compounds such as benzamidine peroxide, lauric acid peroxide, hydrogen peroxide and sodium persulfate, potassium persulfate and ammonium persulfate. Redox initiator systems can also be used, examples of which include redox couples such as ammonium persulfate and sodium metabisulfite.

The initiator e) may be present in an amount to form a dispersant in an amount of from 0.1% by weight to 15% by weight, especially 1% by weight based on the total weight of the polymerizable component present in the composition. From about 10% by weight and most especially from 1% to 7% by weight. When a dispersant is obtained from a composition containing a large amount of CTA, it is sometimes advantageous to also increase the content of the initiator.

Preferably, one or more of the monomers in component c), as the case may be, have a calculated Log P value of less than 1, more preferably from 0.99 to 2.

The presence of 2 parts or less (2 wt% or less) of the monomer as defined in component c) produces a modified OD when the ink derived from the dispersant is printed onto a blank sheet.

Preferably, the monomer composition comprises less than 1 part, more preferably less than 0.5 part, especially less than 0.1 part, and most especially 0 parts of hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group. .

Examples of hydrophilic nonionic groups include polyvinyloxy, polyacrylamide, polyvinylpyrrolidone, hydroxy functional cellulose, and polyvinyl alcohol. The most common ethylenically unsaturated monomer having a hydrophilic nonionic group is polyvinyloxy (meth) acrylate.

In the embodiment, in the case where the residue of component c) (for example, 2 parts by weight of component c) is present in the dispersant, in one embodiment, from the preferred amount of component a) Subtract the amount of component c). In this way, the amounts of all components a) to c) still total 100. Thus, for the case where 2 parts by weight of component c) are present, the preferred amount of component a) indicated above will become 73 to 95 parts by weight (i.e., 75-2 to 97-2) component a) More preferably 75 to 95 (ie 77-2 to 97-) 2), especially 78 to 91 (i.e., 80-2 to 93-2) and most especially 80 to 89 (i.e., 82-2 to 91-2). In another embodiment, it is possible to subtract the amount of component c) from the preferred amount of component b) such that the sum of the amounts of components a) to c) again amounts to 100 parts by weight.

In view of the foregoing, a preferred dispersant is obtained by copolymerizing a monomer composition comprising ethylenically unsaturated monomers a) to c): a) 75 to 97 parts comprising at least 50 parts of benzyl methacrylate Or a plurality of hydrophobic ethylenically unsaturated monomers; b) 3 to 25 parts of methacrylic acid; and c) 0 parts of a hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group; wherein the number of parts is The total of the parts by weight and the sum of a) to c) is 100.

When the component used to make the dispersant comprises CTA, the dispersant will typically comprise a residue of CTA.

Preferably, only the hydrophobic ethylenically unsaturated monomer in component a) is benzyl methacrylate.

More preferably, the dispersant is obtained by copolymerizing a monomer composition comprising ethylenically unsaturated monomers a) to c): a) 80 to 93 parts of one or more of at least 50 parts of benzyl methacrylate a hydrophobic ethylenically unsaturated monomer; b) 7 to 22 parts of methacrylic acid; c) 0 part of a hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group, wherein the parts are by weight, and The sum of the parts of a) to c) is 100 in total.

Preferably, the dispersant has at least 0.35 mmole, more preferably at least 0.9 mmole, even more preferably at least 1.15 mmole and especially at least 1.3 mmole per gram of dispersant.

Preferably, the dispersing agent has an order of increasing preference of no more than 2.65 mmole, 2.3 mmole, 2.15 mmole, 2.0 mmole, 1.75 mmole and 1.40 per g of dispersing agent. The ionic group of mmole. In one embodiment, the dispersant comprises from 1.2 to 2.0 mmole, more preferably from 1.3 to 1.7 mmole, of ionic groups per gram of dispersant.

Preferred dispersants have, for example, from 0.9 to 2.65 mmole, especially from 1.0 to 2.3 mmole and most preferably from 1.0 to 2.0 mmole per gram of dispersant. These dispersants work particularly well in the present invention and can be used to provide pigment inks which provide particularly good optical density on blank paper and which have good stability.

The amount of ionic groups can be determined by any suitable method, preferably by titration, such as acid/base titration.

Preferably, all of the ionic groups present in the dispersant are anionic (especially acidic). More preferably, all of the ionic groups present in the dispersant are selected from the group consisting of -CO ₂ H, -SO ₃ H and -PO ₃ H ₂ groups and salts thereof. Most preferably, the dispersant is present in all the ionic groups are -CO ₂ H group or a salt thereof. When all of the ionic groups are -CO ₂ H groups or salts thereof, the dispersant can be used to prepare inks having particularly good optical densities on blank paper. Therefore, it is preferred that the amount of mmole of the ionic group directly corresponds to the preferred amount of mmole of the carboxylic acid group present in the dispersant.

The dispersing agent optionally contains a dispersing agent capable of self-crosslinking one or more groups in step II).

In one embodiment, the dispersing agent comprises an ethylenically unsaturated group, especially a vinyl group. These groups enable the dispersant to self-crosslink in step II), for example in the presence of an initiator, especially a free radical initiator.

In another embodiment, the dispersant can be self-crosslinked using one or more ionic groups (as described in component b) and cross-linking one or more groups with the ionic group. For example, the dispersant can comprise a carboxylic acid ionic group and an epoxy group to produce a self-crosslinkable dispersant.

The self-crosslinking reaction is preferably carried out by heating the dispersion.

When step II) is carried out, the dispersant is preferably adsorbed onto the pigment.

Although it is possible for the dispersant to chemically bond to the surface of the pigment, this is not preferred.

Preferably, the method further comprises the step of preparing a dispersant by copolymerizing the monomer composition in the absence of the pigment (i.e., preferably, the monomer composition is free of pigment).

Preferably, the dispersion in step I) has no more than 2.0M, no more than 1.8M, no more than 1.6M, no more than 1.4M, no more than 1.2M, no more than 1.0M and no more than 0.8 in order of increasing preference. The critical coagulation concentration of sodium chloride (CCC) of M.

Preferably, the dispersion in step I) has a CCC of at least 0.1 M, more preferably at least 0.25 M and especially at least 0.35 M.

In a preferred embodiment, the dispersion in step I) has a CCC of from 0.1 M to 2.0 M, more preferably from 0.10 M to 1.8 M, even more preferably from 0.20 M to 1.6 M and especially from 0.30 M to 0.8. M.

The CCC is preferably measured by the following steps in the order of i) to v): i) adjusting the concentration of the pigment in the dispersion mentioned in step I) to 10% by weight by addition or removal of water ;ii) preparing a test sample by mixing two drops of the adjusted dispersion prepared in step i) with 1.5 g of a sodium chloride solution having a molar concentration of 0.5 M in water; iii) at 25 Store the test sample prepared in step ii) for 24 hours at a temperature of °C; iv) visually evaluate the test sample to see if there is significant precipitation at the bottom of the sample; v) use higher or lower molar concentration of chlorination The sodium solution is repeated steps i) to iv) until the lowest molar concentration of the sodium chloride solution is determined, at which the visual assessment mentioned in step iv) reveals a significant precipitate at the bottom of the sample, This molar concentration is CCC.

Significant precipitation means that most or all of the pigment originally present in the test sample has precipitated. Only a small amount of precipitated pigment is not considered to be a distinct precipitate. By using the heavy force measurement or light transmittance method, it is possible to measure the degree of precipitation more accurately, however, for most purposes In other words, visual assessment is sufficiently accurate and reliable.

It has been found in step v) that depending on the accuracy required, a sodium chloride solution using a higher or lower molar concentration (to the extent of, for example, 0.05 M or 0.1 M) will generally be suitable.

Experimentally, in order to quickly determine CCC, it is often advantageous to simply prepare a large number of samples each having a different concentration of sodium chloride.

It has been found that dispersions having the above CCC values tend to provide prints on blank paper having good optical density.

The pigments in the dispersions mentioned in step I) are preferably in the form of particles having an average particle size of not more than 1 micron, more preferably from 10 nm to 1000 nm, especially from 50 nm to 500 nm and most especially from 50 nm to 300nm. The average particle size is preferably measured by light scattering techniques. Preferably, the average particle diameter is a Z average particle diameter or a volume average particle diameter.

Preferably, the pH of the dispersion in step I) is from 5 to 12, more preferably from 7 to 11.

In step II), the dispersant may be crosslinked by self crosslinking, crosslinking with a crosslinking agent or a combination of self crosslinking and crosslinking. In any case, preferably, the crosslinking reaction connects the dispersant molecules by a covalent bond.

The crosslinking reaction utilizes any of those described in PCT Patent Publication No. WO 2005/061087, page 6, Table 1 (wherein the "reactive group in the compound" of the second row can be read as a reactive group in the crosslinking agent) The right group.

Preferred crosslinking agents include those having isocyanate, aziridine, n-hydroxymethyl, carbodiimide, oxetane, oxazoline and especially having an epoxy group. These reactive groups are particularly suitable for crosslinking dispersants comprising one or more carboxylic acid groups. Preferred crosslinking agents have an epoxy group (preferably as a separate crosslinkable group) without other crosslinking groups.

In a preferred embodiment, the crosslinking in step II) is achieved by an epoxy crosslinking agent and component b) is or comprises one or more hydrophilic ethylenic unsaturation having one or more carboxylic acid groups monomer.

Preferably, by including a heated dispersion, preferably in the presence of a crosslinking agent, preferably Crosslinking in step II) is carried out by heating to a temperature in the range of from 40 ° C to 100 ° C. In order to accelerate or promote the crosslinking reaction, it is sometimes suitable for crosslinking in the presence of a catalyst.

The pH of the dispersion used in step II) is preferably from 5 to 13, especially from 7 to 12.

When the crosslinking in the step II) is carried out in the presence of a crosslinking agent in which an epoxy group is present, crosslinking is preferably carried out in the presence of a borate and/or a boric acid.

Preferably, the crosslinking in step II) is carried out by a method comprising mixing a composition comprising the following components in a specific ratio: (a) 30 parts to 99.7 parts, preferably 50 parts to 97 parts a liquid medium; (b) 0.1 part to 50 parts, preferably 1 part to 30 parts by weight of the pigment; (c) 0.1 part to 30 parts, preferably 1 part to 30 parts, of a dispersing agent; and (d) From 0.001 parts to 30 parts, preferably from 0.01 part to 10 parts, of the crosslinking agent; wherein the parts are by weight.

Preferably, the encapsulated pigment dispersion produced in the process of the invention has a CCC of no more than 2.0M. The CCC of the encapsulated pigment dispersion produced in the process of the invention is preferably from 0.1 M to 2.0 M, more preferably from 0.10 M to 1.8 M, especially from 0.20 M to 1.6 M and most preferably from 0.30 M to 1.0 M.

The method according to the first aspect of the invention may additionally comprise the step of removing some or all of the liquid medium from the pigment dispersion produced. The liquid medium can be removed by methods such as evaporation and filtration. In this way, the pigment dispersion can be concentrated or converted to a dry solid form. When the liquid medium comprises a mixture of water and a water-miscible organic solvent, it may be desirable to selectively remove the water-miscible organic solvent. This can be done, for example, by distillation or by membrane treatment.

Preferably, the method according to the first aspect of the invention further comprises the step of purifying the encapsulated pigment dispersion. Preferably, the purification process is carried out after step II). Purification can be carried out by any suitable method including microfiltration, deionized resin, centrifugation followed by decantation and washing. A preferred purification method is membrane filtration, especially ultrafiltration using ultrafiltration membranes. Better super The filter membrane has a pore size of about 0.1 microns. Preferably, the dispersion after step II) is washed with from 5 to 50 volumes of purified water based on the volume of the dispersion. Preferably, the water used in the ultrafiltration process is deionized, distilled or has been purified by reverse osmosis. When the dispersion has been sufficiently purified, the preferred method of evaluation is to measure the conductivity of the permeate stream from the ultrafiltration stage and continue to add other volumes of pure water until the permeate stream has a conductivity of less than 100 [mu]S/cm, more preferably Less than 50 μS/cm. Preferably, the dispersion having from 10% to 15% by weight of the pigment in the dispersion is subjected to ultrafiltration. We have found that purification can provide a final dispersion in some cases and a further improved OD ink when printed onto a blank sheet.

Preferably, the method of the present invention further comprises adding one or more additives to the encapsulated pigment dispersion, the one or more additives preferably being selected from the group consisting of viscosity modifiers, pH buffers, metal chelators, surfactants, Corrosion inhibitors, biocides, dyes, water-miscible organic solvents and/or scale reducing additives. Preferably, any additives are added after step II).

According to a second aspect of the invention, there is provided a dispersion comprising an encapsulating pigment obtained by or by a method according to the first aspect of the invention.

Preferably, the dispersion comprises water and from 5 wt% to 60 wt%, more preferably from 10 wt% to 40 wt%, especially from 12 wt% to 30 wt% of the encapsulated pigment, by or according to the invention Obtained by the method of the first aspect.

The encapsulated pigment dispersion according to the second aspect of the invention and the method according to the first aspect of the invention can be used to prepare inks, especially ink jet printing inks. Accordingly, a third aspect of the invention provides an ink jet printing ink comprising an encapsulated pigment dispersion in accordance with a second aspect of the invention. Preferably, the dispersion according to the second aspect of the invention and/or the ink according to the third aspect of the invention has a lower than 50 mPa.s, more preferably when measured at a temperature of 25 °C. Viscosity at 30 mPa.s and especially below 15 mPa.s.

Preferably, the ink has a surface tension of from 20 dynes/cm to 65 dynes/cm, more preferably from 30 dynes/cm to 60 dynes/cm, when measured at a temperature of 25 °C.

The pH of the ink is preferably from 4 to 11, more preferably from 7 to 10.

When the ink is used in ink jet printing, the ink preferably has a concentration of less than 500 parts per million of halide ions, more preferably less than 100 parts per million. More preferably, the ink has less than 100 parts per million, more preferably less than 50 parts per million of divalent and trivalent metals. Each of the above uses is used in parts by weight relative to the total weight of the ink. These low concentrations of ions in the resulting ink can be achieved by the above purification steps.

Preferably, the method for making the ink comprises the step of removing particles of any particulate material having a diameter of more than 1 micron, for example, by filtration or centrifugation from the dispersion or ink. The particles present in the dispersion or in the ink are preferably less than 10% by weight, more preferably less than 2% by weight, and especially less than 1% by weight, and the particles have a diameter greater than 1 micron.

Preferably, the amount of pigment in the ink is from 0.1% by weight to 15% by weight, more preferably from 1% by weight to 10% by weight and especially from 3% by weight to 10% by weight, based on the total weight of the ink.

The weight of water and organic solvent contained in the ink is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 70:30.

Preferred organic solvents are water-miscible organic solvents and mixtures of such solvents. Preferred water-miscible organic solvents include: C _1-6 alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, second butanol, third butanol, n-pentyl Alcohol, cyclopentanol and cyclohexanol; linear decylamine, preferably dimethylformamide or dimethylacetamide; ketone and ketol, preferably acetone, methyl ether ketone, cyclohexane a ketone and diacetone alcohol; a water-miscible ether, preferably tetrahydrofuran and dioxane; a diol, preferably a diol having 2 to 12 carbon atoms, such as pentane-1,5-diol, Ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol and thiodiglycol and oligomeric alkanediol and polyalkylene glycol, preferably diethylene glycol, triethylene glycol, poly Ethylene glycol and polypropylene glycol; triol, preferably glycerol and 1,2,6-hexanetriol; mono-C _1-4 alkyl ether of diol, preferably having 2 to 12 the diol -C _1-4 carbon atoms mono alkyl ethers, especially 2-methoxyethanol, 2- (2-methoxyethoxy) ethanol, 2- (2-ethoxyethoxy )-Ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethylene Monoallyl ether; cyclodecylamine, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3 - dimethylimidazolidinone; a cyclic ester, preferably caprolactone; an anthracene, preferably a dimethyl hydrazine and a cyclobutyl hydrazine. Preferably, the liquid medium comprises water and two or more than two (especially two to eight) water-miscible organic solvents.

Particularly preferred water-miscible organic solvents for use in the ink are cyclic guanamines, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1 , 5-pentane diol, ethyleneglycol, thiodiglycol, diethylene glycol and triethylene glycol; and mono glycols of -C _1-4 - alkyl ethers and two -C _1-4 - alkyl The alkyl ether is more preferably a mono-C _1-4 -alkyl ether of a diol having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.

Examples of other suitable ink media comprising a mixture of water and one or more organic solvents are described in US 4,963,189, US 4,703,113, US 4,626,284, and EP 4,251, 50A.

Ink jet printing inks can be included in the chamber of the ink jet printer ink cartridge to provide an ink jet printer ink cartridge containing the ink of the present invention.

The method of the present invention can be used to prepare encapsulated pigment dispersions that are particularly useful for ink jet printing inks. In addition, encapsulated pigment dispersions can be used in other inks, coatings, stains, cosmetics, thermoplastics, and thermosets.

According to a fourth aspect of the invention, there is provided the use of a method according to the first aspect of the invention for the preparation of an ink jet printing ink. Preferably, this use is for the purpose of providing ink jet printing inks having good and/or improved storage stability (e.g., inkjet printing inks that demonstrate no deposition when stored at 60 ° C for 4 weeks). Storage stability can be determined by, for example, measuring how the viscosity of the ink changes over time at elevated temperatures. Low viscosity changes indicate high storage stability. Furthermore, a slow increase or no increase in the average particle size over time also indicates good storage stability.

In some embodiments, the encapsulated pigments are prepared by the method of the present invention. Dispersion inkjet printing inks can be used with papers that contain fixatives to improve, for example, wet fastness, optical density, or reduced bleeding. In another embodiment, an inkjet printing ink containing an encapsulated pigment dispersion prepared by the process of the present invention can be used with a jettable fixative. For example, an inkjet printer ink cartridge can contain an ink as described above in one chamber and a fixative-containing liquid in another chamber. In this way, an inkjet printer can apply ink and fixative to the substrate.

Fixing agents are well known in the art and include materials such as metal salts, acids, and cationic materials.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated. "Parts" and "parts" mean the number of copies of the relevant components.

Instance WAMW measurement

Use a 2695 Separation Module, 2414 Refractive Index Detector unit and two x Plgel Hybrid D 5 micron 300mm x 7.5mm columns fitted with a guard column (PLgel 5μm Guard 50 x 7.5mm) Waters GPC equipment obtained by Agilent Technologies, using a dispersant containing 1 wt% of acetic acid and triethylamine (DMF (GPC grade) to measure WAMW. The flow rate used was 1.0 mL/min and the injection volume was micro Liters. Samples were prepared directly from the polymer solution as follows: (on a four-point analytical balance) approximately 50 mg of the polymer solution under evaluation was accurately weighed into a suitable glass vial (according to the polymer concentration in the solution) The weight is such that the weight of the polymer in the sample is about 20 mg. The freshly prepared eliminator is added as a solvent (10 ml, having the above composition), and the vial is kept at least 6 at ambient temperature (18 ° C to 25 ° C). hours to allow complete dissolution of the sample, thereby providing for analysis of the polymer having a solvent concentration of about 2.0mg per mL of the polymer solution. once dissolved, the solution was analyzed using the sample through a 0.2 micron PFTE Autovial ^TM disposable non-injected The filter unit (available from GE Healthcare) was placed in a 2 mL sample vial that was sealed (crimped cap) immediately after filling. The sample was repeatedly tested using a flow rate of 1.0 mL/min and a column oven temperature of 50 °C (100 μl injection) For each sample, repeat injections were directly and continuously used for comparison. At the beginning and end of each sample test set, the EasiCal® PS-2 standard (obtained from Agilent Technologies) was injected (range 0.58 kDa to 400 kDa; A And the B polystyrene sample mixture is injected once), that is, the first and last samples in any set of analyses are injections from reference standard samples of known WAMW and narrow polydispersity. Treatment with Waters Empower 2 software package / Manipulate the original data.

Particle size measurement

The Z average particle size of the dispersion at the end of the milling was determined by dynamic light scattering using a Malvern ZS90 Zetasizer instrument. The dispersion was diluted with HPLC grade water to a pigment concentration of approximately 0.0005 wt% and subsequently added to a disposable analytical cuvette. The instrument settings are as follows: measurement type = size

Material = type of pigment used

Dispersant = water

General Options - Preset (Mark-Houwink)

Temperature = 25 ° C at 2 minutes equilibration time

Unit = DT0012

Measurement = automatic measurement number = 3

Data Processing Model - General (Common Resolution)

For each of the two samples and Dispersion measurements performed using each set of the standard samples (Nanosphere ^TM Size Standards, 200nm; available from Fisher) of the test.

Viscosity measurement

The viscosity measurements described in Table 2 below were measured using a Brookfield LV-DVII viscometer and a Brookfield viscosity standard of ~5cP. Measure the viscosity of the ink "as is". Instrument setting Set as follows: Temperature = 25 ° C +/- 1 ° C at 30 minutes equilibration time.

Ultra Low Adapter (ULA) Shaft

The shaft was spun at 60 rpm for 15 minutes and then the viscosity was measured at the same rotational speed.

The measured torque ranged from 10% to 100% and was measured twice. The average of 2 readings within +/- 0.2 cP is included in Table 2.

Deposition test

The deposition tests mentioned in Table 3 below were carried out as follows: Each ink under evaluation was sealed in a clear, plastic flat bottom bottle and stored in an oven at 60 ° C for 4 weeks. The bottle is then removed from the oven and inverted, with the bottle cap facing down. After cooling overnight, the bottles were then turned up and the caps were immediately removed, followed by visual inspection to determine if there were any deposits indicating instability of the ink formulation. If the deposit is present, the ink is judged as "yes" (poor storage stability). If there is no deposit, the ink is judged as "No" (good storage stability).

The following chemical abbreviations are used in the following: TRB2 is C.I. Pigment Blue 15:3 from Dainichiseika.

Nipex 170 is C.I. Pigment Black 7 from Orion.

Yellow 7413 is C.I. Pigment Yellow 74 from Sanyo.

EX-321 is from Nagase Denacol ^TM EX-321 ChemteX the obtained having a weight per epoxy group of 140.

1. Preparation of dispersant Dispersant (1) (WAMW 26, 209Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (612.3 parts), methacrylic acid (167.7 parts), 3-mercaptopropionic acid (15.6 parts), and dipropylene glycol (288.8 parts).

By 2-tert-butylperoxyethylhexanoate (13.8 parts) and dipropylene glycol (172.5 parts) Mix to prepare an initiator feed composition. Dipropylene glycol (752.7 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a dispersant (1) and has the following characteristics: - 16, 910 Da number average molecular weight ("NAMW"); - 26,209 Da WAMW; - 1.55 polydispersity; - corresponding to dispersant An acid value of about 2.59 mmole of acid groups per gram; and - benzyl methacrylate and methacrylic acid in a ratio of 78.5:21.5 by weight relative to each other.

Dispersant (2) (WAMW 31, 625Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (572.2 parts), methacrylic acid (84.8 parts), n-butyl 3-mercaptopropionate (15.3 parts), and dipropylene glycol (243.7 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (10.8 parts) with dipropylene glycol (145.6 parts).

Dipropylene glycol (635.2 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a dispersant (2) and has the following characteristics: - NAMW of 19,709 Da; - WAMW of 31,625 Da; - dispersibility of 1.60; - acid value of acid group / g corresponding to about 1.44 mmole of dispersant; and - ratio of 87.1 by weight relative to each other: 12.9 benzyl methacrylate and methacrylic acid.

Dispersant (3) (WAMW 22,078Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (544 parts), methacrylic acid (113 parts), n-butyl 3-mercaptopropionate (21.6 parts), and dipropylene glycol (246.2 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (11.2 parts) with dipropylene glycol (147 parts).

Dipropylene glycol (641.5 parts) was heated to 85 ° C in a reactor vessel, stirred constantly and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as dispersant (3) and has the following characteristics: - 14,664 Da of NAMW; - 22,078 Da of WAMW; - 1.51 of polydispersity; - corresponding to the dispersant of about 1.90 mmole of acid groups / The acid value of g; and - the ratio of butyl methacrylate to methacrylic acid in a ratio of 82.8:17.2 by weight relative to each other.

Dispersant (4) (WAMW 35, 659Da)

By benzyl methacrylate (368.28 parts), methacrylic acid (54.54 parts), 3-巯 The propionic acid (7.61 parts) and dipropylene glycol (171.08 parts) were mixed to prepare a monomer feed composition.

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (6.93 parts) with dipropylene glycol (103.22 parts).

Dipropylene glycol (401.75 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as dispersant (4) and has the following characteristics: - 23,150 Da of NAMW; - 35,659 Da of WAMW; - 1.54 of polydispersity; - corresponding to the dispersant of about 1.61 mmole of acid groups / The acid value of g; and - benzyl methacrylate and methacrylic acid in a ratio of 87.1:12.9 by weight relative to each other.

Dispersant (5) (WAMW 10,336Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (202.25 parts), methacrylic acid (47.75 parts), 3-mercaptopropionic acid (15.06 parts), and dipropylene glycol (96.1 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (4.33 parts) with dipropylene glycol (28.1 parts).

Dipropylene glycol (250.5 parts) was heated to 95 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 95 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. Keep the contents of the reactor vessel at 95 ° C while adding the feed, and then This temperature was maintained for an additional 2 hours and then cooled to 25 °C.

The resulting polymer is represented as dispersant (5) and has the following characteristics: - NAMW of 7,279 Da; - WAMW of -10,336 Da; - polydispersity of 1.42; - acid group of about 2.59 mmole corresponding to dispersant / Acid value of g; and - benzyl methacrylate and methacrylic acid in a ratio of 80.9:19.1 by weight relative to each other.

Dispersant (6) (WAMW 40, 597Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (679.4 parts), methacrylic acid (100.6 parts), 3-mercaptopropionic acid (14 parts), and dipropylene glycol (287.9 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (12.8 parts) with dipropylene glycol (172 parts).

Dipropylene glycol (750.3 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as dispersant (6) and has the following characteristics: - NAMW of 25,701 Da; - WAMW of -40,597 Da; - polydispersity of 1.58; - acid group of about 1.61 mmole corresponding to dispersant / The acid value of g; and - benzyl methacrylate and methacrylic acid in a ratio of 87.1:12.9 by weight relative to each other.

Comparative Dispersant (1) (WAMW 82, 400Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (672.2 parts), methacrylic acid (184.3 parts), butyl 3-mercaptopropionate (5.55 parts), and dipropylene glycol (327.4 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (15.1 parts) with dipropylene glycol (197.1 parts).

Dipropylene glycol (811.1 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a comparative dispersant (1) and has the following characteristics: - NAMW of 47,535 Da; - WAMW of -82,400 Da; - polydispersity of 1.73; - acid group of about 2.50 mmole corresponding to dispersant Acid value of /g; and - benzyl methacrylate and methacrylic acid in a ratio of 78.5:21.5 by weight relative to each other.

Comparative Dispersant (2) (WAMW 68, 105Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (723 parts), methacrylic acid (150.6 parts), butyl 3-mercaptopropionate (5.76 parts), and dipropylene glycol (318.6 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (14.88 parts) with dipropylene glycol (190.2 parts).

Dipropylene glycol (830.4 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. with Both the monomer feed and the initiator feed were started, but they were separately fed to the reactor over a period of 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a comparative dispersant (2) and has the following characteristics: - a NAMW of 40,067 Da; - a WAMW of -68,105 Da; - a polydispersity of - 1.70; - an acid group of about 2.00 mmole corresponding to a dispersing agent Acid value of /g; and - benzyl methacrylate and methacrylic acid in a ratio of 82.8:17.2 by weight relative to each other.

Comparative Dispersant (3) (WAMW 67, 177Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (215.5 parts), methacrylic acid (34.5 parts), 3-mercaptopropionic acid (0.99 parts), and dipropylene glycol (91.0 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (4.13 parts) with dipropylene glycol (54.4 parts).

Dipropylene glycol (237.3 parts) was heated to 95 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 95 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The reactor vessel contents were maintained at 95 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a comparative dispersant (3) and has the following characteristics: - NAMW of 37,324 Da; - WAMW of -67,177 Da; - polydispersity of 1.80; - acid group of about 1.61 mmole corresponding to dispersant Acid value of /g; and - Benzyl methacrylate and methacrylic acid in a ratio of 86.2:13.8 by weight relative to each other.

Comparative Dispersant (4) (WAMW 97, 718Da)

A monomer feed composition was prepared by mixing benzyl methacrylate (215.5 parts), methacrylic acid (34.5 parts), 3-mercaptopropionic acid (0.99 parts), and dipropylene glycol (91.0 parts).

An initiator feed composition was prepared by mixing 2-tert-butylperoxyethylhexanoate (4.13 parts) with dipropylene glycol (54.4 parts).

Dipropylene glycol (237.3 parts) was heated to 85 ° C in a reactor vessel, continuously stirred and purged under a nitrogen atmosphere. The monomer feed composition and initiator feed composition were slowly fed into the reactor vessel while the contents were stirred, maintaining the temperature at 85 ° C and maintaining a nitrogen atmosphere. Both the monomer feed and the initiator feed were started at the same time, but they were separately fed to the reactor in 4 and 5 hours. The contents of the reactor vessel were maintained at 85 ° C while the feed was added and then held at this temperature for an additional 2 hours, followed by cooling to 25 °C.

The resulting polymer is represented as a comparative dispersant (4) and has the following characteristics: - NAMW of 52,445 Da; - WAMW of - 97,718 Da; - polydispersity of 1.86; - acid group of about 1.61 mmole corresponding to dispersant Acid value of /g; and - benzyl methacrylate and methacrylic acid in a ratio of 86.2:13.8 by weight relative to each other.

2. Preparation of dispersant solution

Diluting the above dispersing agents (1) to (6) and comparing dispersing agents (1) to (4) in an amount of 300 parts by weight, respectively, with dipropylene glycol (about 150 parts), and using 50% by weight The aqueous potassium hydroxide solution neutralizes the resulting solution separately to provide a homogeneous aqueous solution having a pH in the range of 8 to 9 and the resulting solution consists of water in which a total of 1000 parts of the dispersant solution is required to be produced. This produces approximately 300 parts each (approximately 30% by weight) Dispersant solutions (1) to (6) of the relevant dispersant and comparative dispersant solutions (1) to (4).

3. Preparation of color paste and comparative color paste

The pigment powder and related dispersant solutions were mixed together in the amounts shown in Table 1 to form a pre-mix. Water (providing a suitable viscosity for mixing and grinding) was added to each premix as needed to achieve the abrasive strength (wt% pigment) indicated in Table 1.

The resulting mixture was mixed for 90 minutes using a high shear mixer. After mixing, the mixture was transferred to a horizontal bead mill containing 1 mm beads. The mixture is then milled until the particles present in the dispersion have the desired Z average particle size. (In Table 1, the comparative color paste 4 has a high Z average value and a high grinding specific energy. This reflects the fact that it is impossible to reduce the particle diameter to a particle diameter similar to other examples after extensive grinding. Comparative color paste CMB4 The higher particle size of the pigment in the middle indicates that the comparative dispersant solution 4 is not able to completely stabilize the pigment dispersion).

The grinding specific energy referred to in Table 1 represents the total energy (kW.h/kg) consumed per 100% of the pigment during the process of grinding the pigment to the desired particle size; it is defined as the electric power taken by the grinding motor ( kW) multiplied by the total time (h) of the abrasive pigment, divided by the mass (kg) of the 100% pigment that was ground at that time.

The colorants MB1 to MB4 and the comparative color pastes CMB1 to CMB4 produced are discharged from the grinder.

4. Crosslinking dispersant to prepare encapsulated pigment dispersion

The above colorants MB1 to MB4 and comparative colorants CMB1 to CMB4 were adjusted to a pigment content of about 10% by weight by adding water and a boric acid solution (3 wt% in water). The boric acid solution acts as a pH buffer.

Each followed by at trimethylolpropane polyglycidyl ether (Denacol ^TM EX-321) was heated at 70 ℃ 6 hours the paste MB1 to MB4 to CMB4 CMB1 and Comparative paste in the dispersant of the Cross-linking. This crosslinks the carboxylic acid groups in the dispersant and thereby encapsulates the pigment.

Crosslinking of colorants MB1 to MB4 and comparative colorants CMB1 to CMB4 respectively produces encapsulated pigment dispersions 1 to 4 ("ECPD1" to "ECPD4") and comparative encapsulated pigment dispersions 1 To 4 ("Compare ECPD1" to "Compare ECPD4").

5. Purification of ECPD1 to EPCD4 by ultrafiltration to compare ECPD1 to compare EPCD4

ECPD1 to EPCD4 and comparative ECPD1 to comparative EPCD4 were purified by ultrafiltration using a membrane with a 0.1 micron pore size. The pigment dispersion is diafiltered by diafiltration of approximately 10 to 40 wash volumes of pure deionized water per 1 volume of encapsulated pigment dispersion. The ultrafiltration membrane is then used to concentrate the encapsulated pigment dispersion back to a pigment content of about 10% to 15% by weight to obtain purified ECPD1 to EPCD4 and purified comparative ECPD1 to a purified comparative EPCD4, as indicated in Table 1 below:

6. Preparation and stability results of Inks 1 and 2 and Comparative Inks 1 and 2

Inks 1 and 2 and comparative inks 1 and 2 were prepared by mixing the components shown in Table 2 below in the indicated parts. Table 2 provides the viscosity of the ink at initial (0 weeks) and after 4 weeks at 60 °C. Large changes in viscosity indicate poor storage stability, while zero or small changes indicate good storage stability:

The results in Table 2 show that Inks 1 and 2 have improved storage stability over Comparative Inks 1 and 2.

7. Preparation and testing of high strength inks 3 and 4 and high intensity comparison inks 3 and 4.

High strength inks 3 and 4 and high intensity comparative inks 3 and 4 were prepared by mixing the ingredients shown in Table 3 below in the indicated parts. The resulting ink contained approximately 10.0% by weight pigment.

As can be seen from Table 3 above, the inks 3 and 4 derived from the low WAMW dispersant according to the present invention have better storage stability than the comparative inks derived from the higher WAMW dispersant.

8. Effect of WAMW on dispersion stability

The purified dispersion ECPD 2 and the purified ECPD 2 were measured before storage (0 weeks) and after 4 weeks of storage at 60 ° C and the results are shown in Table 4 below. Large changes in viscosity indicate poor storage stability, while zero or small changes indicate good storage stability:

As can be seen from Table 4 above, the viscosity of the purified ECPD2 derived from the dispersant having a WAMW of 10,336 was much less than the viscosity of the comparative dispersion derived from the dispersant having a WAMW of 68,105. Therefore, purification of ECPD2 has better storage stability than ECPD2 compared to purification.

9. Other inks

Other inks described in Tables A and B can also be prepared. The purified encapsulated pigment dispersion derived from the dispersant (2), the dispersant (3) and the dispersant (4) in the same manner can also be used in place of the PECPD1 used in Tables A and B. The number quoted in the third row above refers to the number of parts of the relevant ink component. All parts are by weight. The ink can be applied to the paper by thermal, piezoelectric or Memjet inkjet printing.

The following abbreviations are used in Tables A and B: PECPD1 = purified ECPD1 derived from dispersant (3) with WAMW of 22,078 Da

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methylpyrrolidone

DMK=dimethyl ketone

IPA = isopropanol

MEOH = methanol

2P=2-pyrrolidone

MIBK=Methyl Isobutyl Ketone

P12=propane-1,2-diol

BDL=butane-2,3-diol

Surf=Surfynol ^TM 465 from Airproducts

PHO=Na ₂ HPO ₄ and

TBT = third butanol

TDG=thiodiglycol

GLY = glycerol

nBDPG = mono-n-butyl ether of dipropylene glycol

nBDEG=di-n-butyl ether of diethylene glycol

nBTEG=Triethylene glycol mono-n-butyl ether

Claims (24)

A method for preparing an encapsulated pigment dispersion suitable for use in ink jet printing inks, the method comprising the following steps in the order of I) followed by II): I) providing a dispersion comprising a pigment, a liquid medium and having up to 50,000 Dalton's WAMW dispersant obtained by copolymerizing a monomer composition comprising components a) and b): a) 75 to 97 parts comprising at least 50 parts of benzyl (meth)acrylate One or more hydrophobic ethylenically unsaturated monomers; and b) from 3 to 25 parts of one or more hydrophilic ethylenically unsaturated monomers having one or more ionic groups; wherein the aliquots are By weight, and the sum of the parts of a) and b) is 100 in total; II) crosslinking the dispersant in the presence of the pigment and the liquid medium. The method of claim 1, wherein the dispersing agent is obtained by copolymerizing a monomer composition comprising components a) to c): a) 75 to 97 parts comprising at least 50 parts of benzyl (meth) acrylate One or more hydrophobic ethylenically unsaturated monomers; b) from 3 to 25 parts of one or more hydrophilic ethylenically unsaturated monomers having one or more ionic groups; c) from 0 to 2 parts having hydrophilicity One or more hydrophilic ethylenically unsaturated monomers; and wherein the aliquots are by weight and the sum of the aliquots a) to c) is 100 in total. The method of claim 1 or 2, wherein the dispersant has a WAMW of 10,000 to 38,000. The method of claim 1 or 2, wherein component a) comprises at least 70 parts of benzyl (meth)acrylate. The method of claim 1 or 2, wherein component a) consists of benzyl (meth)acrylate. The method of claim 1 or 2 wherein component a) consists of benzyl methacrylate. The method of claim 1 or 2, wherein the one or more hydrophilic ethylenically unsaturated monomers having one or more ionic groups comprise one or more hydrophilic olefinic groups having one or more carboxylic acid groups. Saturated monomer. The method of claim 1 or 2, wherein component b) comprises methacrylic acid. The method of claim 1 or 2 wherein component b) consists of methacrylic acid. The method of claim 1 or 2, wherein the monomer composition does not contain a hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group. The method of claim 1, wherein the dispersing agent is obtained by copolymerizing a monomer composition comprising components a) to c): a) 80 to 93 parts comprising at least 50 parts of benzyl methacrylate or a plurality of hydrophobic monomers; b) 7 to 22 parts of methacrylic acid; c) 0 parts of a hydrophilic ethylenically unsaturated monomer having a hydrophilic nonionic group; wherein the aliquot is by weight, and The sum of the parts of a) to c) is 100 in total. The method of claim 1 or 2, wherein the crosslinking in step II) is achieved by an epoxy crosslinking agent, and component b) is or comprises one or more of one or more carboxylic acid groups body. The method of claim 1 or 2, wherein the liquid medium is or comprises water. The method of claim 1 or 2, wherein the dispersion provided in step I) has a critical concentration of sodium chloride of no more than 2.0M. The method of claim 1 or 2, wherein the resulting encapsulated pigment dispersion has no more than 2.0M sodium chloride critical agglomeration concentration. The method of claim 14, wherein the resulting encapsulated pigment dispersion has a critical concentration of sodium chloride of from 0.2 M to 1.6 M. The method of claim 1 or 2, further comprising the step of purifying the encapsulated pigment dispersion. The method of claim 1 or 2, further comprising adding one or more additives to the encapsulated pigment dispersion, the additives being selected from the group consisting of viscosity modifiers, pH buffers, metal chelators, surfactants, corrosion inhibitors , biocides, dyes, water-miscible organic solvents and scale-reducing additives. The method of claim 1 or 2, wherein the monomer composition further comprises d) from 0.1% by weight to 15% by weight, based on the total weight of the polymerizable component present in the composition, of a chain transfer agent. An encapsulated pigment dispersion obtained by or by the method of claim 1 or 2. An ink jet printing ink comprising the encapsulated pigment dispersion of claim 20, or prepared by the method of claim 1 or 2. An ink jet printer ink cartridge comprising a chamber and an inkjet printing ink, wherein the inkjet printing ink is present in the chamber and is as claimed in claim 21. Use of the method of claim 1 or 2 for the preparation of an ink jet printing ink. The use of claim 23 for the technical purpose of providing ink jet printing inks having good and/or improved storage stability.