WO1996035757A2

WO1996035757A2 - Thickening of print pastes

Info

Publication number: WO1996035757A2
Application number: PCT/GB1996/000954
Authority: WO
Inventors: Norman Stewart Batty; Neil Anthony Barrett; Neil Harris
Original assignee: Allied Colloids Limited
Priority date: 1995-04-24
Filing date: 1996-04-19
Publication date: 1996-11-14
Also published as: AU5342796A; ZA963275B; GB9508242D0; WO1996035757A3

Abstract

An aqueous print paste is provided which is thickened by a neutralised product of an acidic polymer-in-water emulsion having a larger than usual particle size for polymer-in-water emulsions. The particle size is at least 200nm, preferably above 250nm. The increased particle size is found surprisingly to lead to improved colour yield.

Description

Thickening of Print Pastes

A print paste is a blend of one or more dyes or pigments, an aqueous carrier, a thickening polymer for controlling the viscosity and rheology of the print paste, and various other components generally including binder and ammonia or other alkaline agent.

The polymeric thickener is included in order to impart to the paste viscosity and rheology appropriate for printing of the paste. Because the paste often has a significant electrolyte content (for instance due to incorporation of electrolyte with the pigment and/or due to the alkaline conditions in the paste) it is necessary to select polymers that will give adequate viscosity and rheology despite the electrolyte. In addition to giving the desired rheology and viscosity, it is also necessary that the polymeric thickener should promote, or at least not detract from, the colour printing properties of the print paste. For instance it is well established that some polymers which can give good rheology and viscosity properties result in the print having a rather weak colour. This is referred to as a low "colour yield". It is therefore necessary to select a polymer which is a good thickener in the electrolyte-containing print paste and which gives good colour yield.

One class of polymer which has proved particularly successful is formed from water soluble monomer or monomer blend including an ethylenically unsaturated carboxylic monomer and which is in cross-linked, particulate, form. The particle size is small (typically of the order of 1 to 2μm) . The monomer or monomer blend is such that, when the particles are in neutralised or part-neutralised form in the aqueous alkaline print paste, the particles swell to provide microgel latex thickening. Such polymers typically are cross-linked acrylic acid or acrylic acid-acrylamide polymers made by reverse phase polymerisation as an emulsion in a non-aqueous liquid. The particles are generally supplied to the print paste manufacturer as a liquid dispersion in a hydrocarbon liquid or other non-aqueous continuous matrix. Examples are volatile hydrocarbons, high boiling and relatively non- volatile mineral oils, vegetable oils, fatty acid esters and polyalkylene oxides. These materials are inevitably carried into the print paste with the polymer particles and this can be undesirable. For instance hydrocarbon may evaporate into the atmosphere and print obtained from such print pastes may release hydrocarbon or other material into the environment, for instance during washing of the printed textile or other substrate.

Supplying the cross-linked polymer particles as dry powder or agglomerated powder has not proved entirely satisfactory for a number of reasons. The powder may itself be contaminated by residues of the hydrocarbon or other non-aqueous carrier. Because the powder necessarily is very fine, there can be dust inhalation, respiratory and other handling problems even if it is agglomerated. It is difficult to meter, pump and measure the powders for automatic make-up systems and the admixing of the powders into the print paste incurs the risk of the formation of lumps and gels with consequential blockage of filters or the screen, and streaky printing. It is known that microgel thickening depends at least in part upon interaction between adjacent particles and that normally viscosification will increase as the particle size decreases. Accordingly it might be expected that improved results would be obtained by reducing the particle size. However the manufacture of reverse phase polymer emulsions having a particle size significantly below lμ is accompanied by associated difficulties, such as the need to use large amounts of surfactant, which is undesirable as the surfactant will be carried into the print paste. A product which is a stable dispersion (i.e., an anhydrous emulsion) in hydrocarbon of cross-linked acrylic acid polymer, optionally with acrylamide, made by reverse phase emulsion polymerisation has proved very successful and is sold by Allied Colloids Limited under the trade name Alcoprint PTF. In addition to giving a satisfactory rheology and viscosity at a reasonably low dosage even in pastes having quite high electrolyte content, it also gives good colour yield. Nevertheless it would be desirable to be able to provide a thickener which provides better properties in the presence of high electrolyte contents. Various other print-paste thickeners have been proposed, including polymers designed to be particularly resistant to viscosity-degradation due to the electrolyte in the print paste. However none of them so far seem to have provided a combination of viscosification and colour yield as satisfactory as the reverse-phase polymerised products such as Alcoprint PTF.

For instance in EP-A-216479 we describe print-paste thickeners of various types. One type is a cross-linked, reverse phase polymerised, particulate polymer having a size below 4μm emulsified in oil and made by the same general technique as discussed above except that the aqueous monomer blend includes a small amount of an associative monomer which can have the formula ABR, where A is an allyl ether group, B is a polyethoxy linkage and R is a hydrophobic alkyl or other long hydrocarbon group. Another type is an acidic polymer-in-water emulsion that includes the associative monomer groups. This polymer is made by emulsion polymerisation of a water-insoluble monomer blend which includes ethylenically unsaturated carboxylic monomer such as acrylic acid or methacrylic acid, ethylenically unsaturated non-ionic, water insoluble, monomer such as ethyl acrylate, optionally a cross-linking agent, and the associative monomer. This type of polymer- in-water emulsion is frequently referred to as an "associative thickener" and it is known to be effective despite the presence of electrolyte. Such thickeners made using the allyl ether monomer ABR are commercially available from Allied Colloids Limited under the trade name Rheovis for various purposes, such as viscosifying emulsion paints. When the polymer-in-water emulsion is added to the alkaline paint or other aqueous medium, the polymer particles become wholly or partly neutralised and swell significantly to provide viscosification.

It is conventional to make polymer-in-water emulsions to a smaller particle size than reverse phase emulsions, and this would be expected to improve viscosification because of the resultant increase in the number of microgel particles per gram polymer. For instance Rheovis products typically have an average particle size of the order of lOOnm (O.lμm) .

Other associative polymer-in-water emulsions have been proposed in the literature. For instance U.S. 4,384,096 describes such polymers where the associative monomer is an acrylic ester rather than an allyl ether. This mentions conventional thickening uses for associative thickeners, such as in paints and cosmetics, but does not mention print pastes. It confirms the small particle size of such emulsions and states that the polymer particles have average particle diameters of 50 to 300nm, preferably 100 to 175nm, as measured by light diffraction. Products which are apparently similar to those described in U.S. 4,384,096 are available commercially from Rohm & Haas under the trade name Primal and appear to have an average particle size within the preferred range, of up to 175nm as measured by light diffraction.

We have now found that although satisfactory viscosification of a print paste can be achieved using associative polymer-in-water emulsions having these preferred sizes, the print quality is not as good in most instances as is obtained using a conventional material made from a water-soluble monomer blend, such as Alcoprint PTF. In particular, the colour yield is worse. It would be desirable to be able to obtain good viscosification.and good colour yield by neutralisation of an acidic polymer made from a water-insoluble monomer blend by polymer-in-water emulsion polymerisation, thereby avoiding the problems of contamination with hydrocarbon or other non-aqueous carrier. It would also be desirable to be able to obtain this in a wide range of print pastes, including those having a high electrolyte concentration.

We have now surprisingly found that colour yield is improved, while thickening is substantially maintained, if the acidic polymer-in-water emulsion has particle size which is larger than the usual size for polymer-in-water emulsions. This is despite the fact that increasing the particle size would be expected to reduce the microgel thickening effect, so that the polymer might be less effective as viscosifier. In particular, we find that there tends to be a very large increase in colour yield as the particle size of the emulsion increases above the conventional values. This is surprising and we do not know the reason. The benefit arises in particular when the particle size increases above 200nm up to above 250 or above 300nm. In this specification, when we refer to particle size we mean, unless otherwise specified, the average particle size, and the best way of measuring this average particle size is by determining the z-average particle size by the technique described in Test Methods below. In particular, an aqueous print paste according to the invention is thickened by a neutralised product of an acidic polymer-in-water emulsion which is the emulsion polymer of a water-insoluble monomer blend consisting of, by weight, (a) 10 to 60% ethylenically unsaturated carboxylic acid

(b) 10 to 90% alkyl ester of ethylenically unsaturated carboxylic acid

(c) 0 to 60% ethylenically unsaturated monomer having the group ABR where A is an ethylenically unsaturated moiety, B is a polyethoxy chain of at least two ethoxy groups and R is a hydrophobic aliphatic or aromatic group of at least 8 carbon atoms,

(d) 0 to 5% polyethylenically unsaturated cross linking agent (e) 0 to 40% other ethylenically unsaturated monomer, and wherein the particle size of the emulsion is above 200nm.

The invention also includes the use of a polymer for thickening an aqueous pigmented print paste in which the polymer is provided as the defined acidic polymer-in-water emulsion.

The invention also includes a method of making a print paste by blending aqueous carrier, pigment and polymer and alkali, in which the polymer is provided as the defined acidic polymer-in-water emulsion.

The average particle size of the acidic polymer-in- water emulsion in the invention is always above 200nm and should be as large as is necessary to obtain a high colour yield, for instance approximately as high as is obtainable with Alcoprint PTF, or higher. Generally it is at least 220nm or 250nm and frequently above 300nm.

It is necessary that the size should not be more than about lOμm because of the need to ensure that the swollen polymer particles in use do not lead to blockages during printing. Generally the z-average particle size of the acidic polymer emulsion is below lμm, preferably below 750nm.

A range of polymers that differ substantially only in particle size can be made using different emulsification conditions from an otherwise similar polymerisation mixture of monomer blend and initiator. We find that the performance of such polymers in any particular print paste depends on the particle size. In particular, we find that colour yield increases significantly, without any significant decrease in viscosification performance, as the particle size increases up to a threshold value. Further increase in the particle size above the threshold value gives little or no further increase in colour yield. In the invention, the particle size should preferably not only be above 200nm, preferably above 300nm, but should also be above the threshold value of the particle size. The threshold value for this purpose is defined as the particle size at which the colour yield is at least 80%, and preferably at least 90%, of the optimum colour yield obtainable in that paste with that range of polymers.

It is usual for there to be a spread of particle sizes and in the invention it is preferred that this spread should be low, as indicated by polydispersity, calculated by the Test Method described below. In this test, the polydispersity indicates the slope of the leading edge of the distribution curve, with the result that as the slope approaches the vertical (indicating a narrow particle size distribution) the polydispersity approaches zero.

Preferably polydispersity is below 0.2, most preferably below 0.1.

The acidic polymer-in-water emulsion is made by polymerising an emulsion of the water-insoluble monomer blend, with monomer (a) in the form of free acid, in conventional manner under conditions that will yield the desired particle size. These conditions generally consist of conventional oil-in-water emulsion polymerisation conditions modified by selection of the emulsification method and the nature and the amount of emulsifier so as to give the desired particle size in the final polymer emulsion.

Suitable emulsifiers are surface-active materials for example non-ionic types such as ethoxylated nonyl phenols or ethoxylated alcohols and anionic types such as ethoxylated alcohol sulphates, ethoxylated nonyl phenol sulphates, ethoxylated alcohol phosphates, sodium alkyl sulphates or sulphonates. The preferred types are the ethoxylated alcohol phosphates. The alcohol may be saturated or unsaturated, C₁₂-C₁₈ linear or branched aliphatic, cycloaliphatic or araliphatic and the extent of ethoxylation may be from 2 to 50 moles or ethylene oxide per mole of alcohol.

In addition to selecting ethoxylated aliphatic alcohol phosphate or other suitable emulsifier, it is also necessary to select the amount so as to obtain the desired particle size. Generally it is in the range 1 to 5%, preferably 1 to 3%, based on the weight of monomers.

It should be noted that in U.S. 4,384,096 about 11% of a mixture of proprietary ethoxylated phenol phosphate, sulphonate and non-ionic surfactant is used while in EP-A-

216479 3.75% Perlankrol ESD was used. This is an ethoxylated alcohol sulphate emulsifier. Both these systems seem to give very small particle size, below 175nm.

The ethylenically unsaturated carboxylic acid (a) can be, for example, methacrylic acid, acrylic acid, itaconic acid, maleic acid, or mixtures of these acids. Methacrylic acid is preferred.

The alkyl ester monomer (b) can be an alkyl ester of any suitable ethylenically unsaturated carboxylic acid such as methacrylic acid or, more usually, acrylic acid. The alkyl group can be substituted but is usually unsubstituted. Suitable esters are, for example, ethyl acrylate, methyl acrylate, butyl acrylate, 2-ethyl hexyl aer late, or mixtures of these. Ethyl acrylate is preferred.

The associative monomer (c) is optional but is preferably included. For instance it improves viscosity and rheology, especially in the presence of electrolyte. It can be any appropriate ethylenically unsaturated monomer that carries a polyethoxy chain terminated in the hydrophobic group of at least 8 carbon atoms. The ethylenically unsaturated monomer can be, for instance, an associative acrylic or other carboxylic ester, such as described in U.S. 4,384,096, or an acrylamide derivative such as described in U.S. 4,423,199, or a vinyl ether such as described in JP-A-60-235815, but is preferably an allyl ether as described in EP-A-216479. Thus monomer ABR (c) is preferably included and A can be a methallyl group but is preferably allyl, B is a polyethoxy chain and R is a hydrophobic aliphatic or aromatic group of at least 8 carbon atoms. The polyethoxy group can be interrupted by propoxy groups but preferably consists solely of ethoxy groups. There must be at least two and generally at least five ethoxy groups. There can be up to, for instance, 100 but generally there are 10 to 20 ethoxy groups in the linking group B.

R is generally selected from alkyl, aralkyl, alkaryl, aryl and cycloalkyl and usually contains 8 to 30, preferably 10 to 24, carbon atoms. Preferably R is alkyl, especially stearyl or other hydrocarbon residue of a fatty alcohol.

A preferred associative monomer (c) is the allyl ether of ethoxylated stearyl or other fatty alcohol with 5 to 30, preferably about 10 to 20, moles ethylene oxide.

The polyethylenically unsaturated cross-linking agent (d) is optional and can be any conventional polyfunctional cross-linking monomer, for example, diallyl phthalate, divinyl benzene, tetraallyl oxyethane, triallyla ine, trisacryloyl hexahydro-l,3,5-triazine, preferably diallyl phthalate. The monomer blend can include other monomer (e) provided it does not interfere with the formation of the acidic insoluble monomer blend and the acidic polymer-in- water emulsion by emulsion polymerisation. Such other monomer can include water-soluble monomer such as acrylamide but, if present at all, it is generally a water insoluble monomer such as styrene or a substituted styrene, (meth)acrylonitrile, vinyl acetate or other alkanoate or vinyl or vinylidene chloride or other halide. The amount of any such insoluble monomer is usually less than the amount of alkyl ester (b) and usually monomer (e) is omitted but it can be present in an amount of up to, for instance, 20%. The amount of monomer (a) is generally, by weight of total monomer, 10 to 50%, preferably 25 to 45% and most preferably from 30 to 40%.

The amount of monomer (b) must be such that, with the other monomers, the blend can be polymerised by oil-in- water polymerisation and is usually in the range 40 to 90%, preferably 45 to 75% and most preferably from 45 to 60%.

Polymer emulsions formed by copolymerising monomers (a) and (b) and optionally (d) , in the absence of (c) , are useful and can give improved colour yield provided they have the defined particle size. They can also give adequate viscosification and rheology properties.

However best results, both in terms of viscosification and colour yield, especially in the presence of electrolyte, are obtained when the monomers include at least 2% by weight of monomer (c) . The presence of monomer (c) in the polymer gives particular improvement with respect to colour yield and performance when the print paste has a relatively high electrolyte concentration. Preferably the amount of the associative monomer (c) is in the range 2 to 40%, preferably 5 to 20%, with best results generally being obtained with about 10 or 15% by weight of the associative monomer, based on the weight of the monomer blend. In order that optimum microgel thickening occurs it is desirable that the polymer should remain in swollen particulate form in the print paste and accordingly the monomer blend should be such that the particles do not dissolve fully in the print paste. The particles will retain their particulate structure if the monomer blend contains sufficient water-insoluble monomer (b) , (c) and (e) relative to the amount of potentially soluble monomer (a) , especially when polymerisation is conducted under conditions that lead to very high molecular weight. It is therefore possible to perform the invention using a polymer which is not deliberately cross-linked and in which the amount of monomer (d) is therefore zero. However it is generally preferred that the monomer blend should include cross linking monomer (d) , generally in an amount of at least 0.01% and preferably at least 0.05% (500ppm) . It is usually unnecessary for the amount to be more than 2% and amounts of from 0.05 to 0.15 or 0.2% are generally preferred.

Emulsification of the monomer blend, and the emulsion polymerisation, may be conducted in conventional manner except for the described modification of the emulsification and the particle size.

The acidic polymer-in-water emulsion should be sufficiently storage-stable that it does not significantly and deleteriously settle out upon storage prior to use. If the particle size is sufficiently small, for instance sufficiently below 500nm, the emulsifier used to assist in the formation of emulsion will usually be sufficient to ensure adequate storage stability. However if the emulsion is not sufficiently storage-stable, and particularly if the emulsion has a large particle size(for instance above 750nm) , it may be desirable to stabilise the emulsion. This can be achieved by subjecting the acidic polymer to a small degree of neutralisation sufficient to cause the emulsion to swell and viscosity itself slightly, but insufficient to achieve full viscosification of the emulsion. Preferably, however, an acid-stable stabiliser is added, such as guar gum.

The acidic polymer-in-water emulsion is acidic in the sense that the carboxylic groups are either wholly in the acidic form or are sufficiently in the acidic form that the emulsion has low viscosity and can easily be mixed in with the other components of the print paste.

In order to develop viscosity, it is necessary to fully or partially neutralise the acid groups. This can be done prior to mixing with the other components of the print paste but generally the neutralisation is conducted when the polymer is mixed with the remainder of the print paste components, in conventional manner. These components generally include an alkali, and this will cause full or partial neutralisation and the development of viscosity.

The paste can contain one or more pigments and/or dyes, such as disperse dye or reactive dye, typically in an amount of 1 to 10%, together with alkali such as alkali- metal hydroxide and/or ammonia in an amount sufficient to provide a pH of at least 6.5, often at least 7. The paste may also contain binder and other conventional additives. The amount of polymer which is added to the paste is selected to give the desired viscosity and is typically in the range 0.5 to 5%, often around 1 to 2 or 3%, dry weight of polymer based on the total weight of the paste.

The paste can be used for printing textiles or other substrates by techniques such as rotary or flat bed screen printing. The substrate can typically be upholstery, sheeting, carpeting or clothing. Test Methods Average Particle Size and Polydispersity

The particle size measurements in the examples are z- average particle size measured with a Malvern System 4700 Photon Correlation Spectrometer, with a helium-neon laser at 628nm and a scattering angle of 90°, at 20.0°, with the viscosity set at 0.8900Cp and the refractive index (liquid) set at 1.3300. 10ml of deionised water that has been filtered through a 0.2μ filter is poured into a 20ml vial and approximately 0.03ml of the emulsion is added from a pipette. The vial is capped and shaken gently. It is then put into the cell compartment of the instrument. It is left for 10 minutes to equilibrate to temperature before being tested. If the track of the laser through the liquid appears fuzzy, the sample is removed and diluted further. All the samples have a slight iridescence when they are tested. If they appear optically clear they are too dilute and are not used.

The scattered light is measured at a series of time intervals and the z-average particle size and the polydispersity calculated in accordance with the instructions in the Series 4700 Instruction Manual, IM 040,

Issue 2, published by Malvern Instruments Ltd., March 1990.

Since the emulsion particles are substantially spherical, similar numerical values for average particle size should be obtainable by other techniques, especially other Photon Correlation Spectroscopy techniques, if the

Malvern System 4700 is not available. Additionally, proprietary standard emulsion latices are available (such as the "Nanosphere" polystyrene latices from Duke

Scientific Corporation California) and in the absence of a

Malvern System 4700 an appropriate indication of whether or not any particular emulsion has a z-average particle size above a chosen value of, for instance, 200, 220 or 250nm can be made by comparison with such a standard using any suitable measuring technique.

Make-Up of Print Pastes

A pigment stock is made up from: 40.Og Imperon Blue KRR (Hoechst) 120.Og Alcoprint PBA 10.Og .880 Ammonia 750g Deionised Water

147.20g of the stock is weighed into a 250ml plastic beaker and stirred gently with a higher shear stirrer. A disposable syringe is filled with the thickener emulsion and weighed. The thickener is injected carefully into the vortex of the stock stirring in the beaker until the paste becomes thick. The stirrer speed is increased slowly to its maximum and the paste is stirred for 1 minute.

The viscosity is measured with a Brookfield RVT rotary viscometer, spindle #6, at lOrpm.

More thickener is added and stirred in until the viscosity is 20000 ± 2000cP Deionised water is added to make the total weight (stock + thickener + water) 160.OOg and is thoroughly stirred in. The viscosity is measured again.

The syringe is reweighed to find the weight of thickener added.

A paste is made in the same way with a standard thickener (Alcoprint PTF) and is used as a comparison for all the test prints. Printing of Print Pastes

A piece of the 50/50 polyester-cotton fabric about 35x50cm is cut and laid flat on the table of a Zimmer MDF- 240 laboratory printing machine.

A screen with an open blotch area 25x40cm is carefully placed over the fabric so that all of the blotch area is over fabric. A number 4 magnetic bar is put in the screen so that there is a space of l-2cm between the bar and the edge of the blotch area.

The magnet is moved so that it is under the bar and is then switched on at power 2.

About 20g of each paste to be tested is spread side by side in the area between the bar and the edge of the blotch.

The magnet is moved across the screen at speed 5 so that it pushes the paste across the blotch in front of it and all the printed areas are continuous, i.e., there are no spaces between the printed marks. The magnet is switched off and the screen carefully lifted away from the fabric.

The fabric is dried in a Benz drier for 1 minute at 110°C.

Colour Yield of Print Paste A standard scale is prepared by making and printing pastes thickened with a standard, for instance Alcoprint PTF. A paste with 4% (40g/l) Imperon Blue KRR is prepared as described above. Similar pastes are prepared with amounts of Imperon Blue KRR in the stock at 4g intervals (36,32 etc) instead of the 40g, down to zero. Water is added so that the total weight is the same in every case. The print with 4% Imperon Blue KRR is then 100% colour depth and the others 90%, 80%, etc., respectively. The colour yield is then assessed by comparison with samples on this scale and can be quoted as a percentage of the standard. Alternatively the colour yield can be expressed as a percentage of the best colour yield obtained by any of the test polymers.

Example 1

18Og of deionised water and l.Og of a phosphate ester of the reaction product of oleyl alcohol with 3 moles of ethylene oxide were weighed into a 700ml resin pot and stirred and heated to 85°C on a water bath. Oxygen was removed by passing nitrogen through the solution for 30 minutes.

An aqueous feed was made up by weighing 198.5g of deionised water and 3.0g of a phosphate ester of the reaction product of oleyl alcohol with 3 moles of ethylene oxide into a beaker and stirring.

A monomer feed was made up by stirring 79.4g of methacrylic acid, lOOg of ethyl acrylate, 19.9g of the allyl ether of the reaction product of stearyl alcohol with

10 moles of ethylene oxide and 0.50g of tetraallyl oxyethane in a beaker.

The aqueous feed was stirred with a high shear mixer and the monomer feed was poured slowly into it so that a stable monomer emulsion was formed.

The nitrogen bubbler was lifted into the air space above the liquid in the resin pot. A gentle flow of nitrogen through the pot was continued throughout the reaction. Solutions of ammonium peroxydisulphate were made up:

0.15g in lOg of deionised water for the charge and 0.45g in

20g of deionised water for the feed. The ammonium peroxydisulphate for the charge was added to the resin pot from a syringe through a Subaseal (Trade Mark) . The peroxydisulphate feed and the monomer emulsion were fed into the reaction mixture in the resin pot at 85°C over 2 hours. The reaction was left stirring under nitrogen for 1 hour after the feeds had finished and then cooled to about 30°C and poured out through a filter cloth with a 50μm mesh. The polymer emulsion so produced had an active content of 32.05% by dry weight.

The z-average particle size was measured as 186nm and the polydispersity was .029.

A printing paste was made up with 2.41g of dry polymer per lOOg of paste. It was a smooth paste with a viscosity of 20100CP.

The print was bright and level and the colour yield was rated at 100% (relative to Alcoprint PTF) . Example 2 (Comparative) An emulsion polymer was made in exactly the same way as in Example 1, except that the emulsifier was sodium lauryl sulphate instead of the phosphate ester of the reaction product of oleyl alcohol with 3 moles of ethylene oxide. The dry weight of the product was 31.91%.

The z-average particle size of the polymer emulsion was found to be 130nm and the polydispersity was 0.089.

A printing paste was made with 1.71g of dry polymer per lOOg of paste. It was a smooth paste with a viscosity Of 19600CP.

The print made was level and the depth of colour was rated at only 50%. Example 3

A polymer emulsion was prepared as described above in Example 1 but the monomer solution was made with

69.65g methacrylic acid,

23.88g of the allyl ether of the reaction product of stearyl alcohol with 10 moles of ethylene oxide,

105.5g of ethyl acrylate and 0.36g of diallyl phthalate.

The polymer emulsion obtained was found to be 30.03% active. The z-average particle size was 252nm and the polydispersity was 0.062.

A printing paste was made with 1.72g of dry polymer per lOOg of paste. It was a smooth paste with a viscosity of 20700cP.

The print was level and the colour yield was rated at 100%. Example 4

A polymer emulsion was prepared as described above in Example 3 but the reaction was carried out at 90°C instead of at 85°C.

The polymer emulsion was found to be 29.97% active.

The z-average particle size was 203nm and the polydispersity was 0.060. A printing paste was made with 1.59g of dry polymer per lOOg of paste. It was a smooth paste with a viscosity of 19400cP.

The print was level but the depth of colour yield of the print was 80% of the standard. Example 5 (Comparative)

A printing paste was made up as described below with Rheovis CRX (Allied Colloids) , a commercial associative polymer emulsion thickener (3.03% w/w of the emulsion). The viscosity was 19900cP. The print made as described below. The depth of colour was poor and was estimated to be only 50% of that of the standard.

The z-average particle size of the Rheovis CRX was found to be 85nm and its polydispersity was 0.227. Example 6 (Comparative) A printing paste was made up as described below with Primal TT615 (Rohm and Haas) , a commercial associative polymer emulsion thickener. 1.87%w/w of emulsion was used. The viscosity was 21000cP. It was printed as described below. The colour yield was poor and was estimated to be only 55% of the standard.

The z-average particle size of the emulsion thickener was found to be 164nm and the polydispersity was 0.073. Example 7

Emulsion polymers prepared by the method of Example 1 but using various stabilising emulsifiers to achieve a range of particle sizes were tested as pigment print thickeners. Colour yield was compared to a standard using Alcoprint PTF.

Emulsifier Particle Colour Yield Size (n )

Alkyl ether sulphate 130 50%

Sodium lauryl sulphate 153 55% do. 203 60%

Alkyl ether phosphate 215 80% do. 222 90% do. 222 95% do. 230 95% do. 242 95% do. 244 95% do. 279 100% do. 283 95% do. 286 95% do. 694 100%

From these results it is apparent that all the polymers in this series having a size of 215nm or more give a colour yield that is at least 80% of the optimum values (obtained with sizes of 279 and 694nm) . Hence the threshold value for this polymer is about 215nm. Example 8

A print paste was formulated as follows: 3515g of water was measured out and 300g of emulsion added with low speed stirring. 20.Og of antifoam (Burst 100) was dispersed in the solution and then 15.Og of sodium hydroxide (flake) were added and stirring continued for 5 minutes to ensure dissolution. pH was checked at this point and found to be 6.90. Maintaining low speed stirring, further additions of 100.Og sodium carbonate, 1000.Og of urea and 50.Og Ludigol (sodium-m-nitrobenzene sulphonate) were made, followed by stirring under high shear for 10 minutes to ensure complete dissolution of these components. During this period the viscosity of the paste increased to a final value of 30dPaS (Haake VT-02 viscometer, spindle no.l, measured at 20°C) . The final pH of the paste was 8.90.

250.Og of Remazol Black B were added to the above paste followed by stirring for 5 mins. under low shear to ensure complete mixing of colour. The final paste viscosity was measured at 26dPaS.

The paste was printed on to 100% plain woven cotton fabric (HO.Og/m) and 100% plain woven staple viscose fabric (132.0g/m²) on a Stork RD-DD machine through a 195 Nova Screen. The printed fabric was dried at 140°C for 50 seconds. Fixation of colour was effected by steaming the fabrics at 102°C for 8 minutes followed by washing off on a continuous 8 bath counterflow washing range utilising a cold (20°C) rinse with water only in the first bath, a hot wash (95°C +) with 2.0g/l Alcosperse AD in the 2nd bath and then sequential rinses with water only ranging from 80°C to 20°C in the remaining 6 baths. The fabrics were then stentered dry at 105°C for 2 minutes.

Excellent colour yield, definition and penetration were obtained on both fabric qualities indicating that the emulsion is an excellent thickener for use in printing cellulosic fibres with reactive dyestuffs. Example 9

A paste was formulated as follows: 4380g of water was measured out and 20.Og of antifoam (Burst 100) was added with low speed stirring. 250.Og of the emulsion was added to this solution followed by 350.Og of ammonia solution (0.880 SG) . Speed of stirring was increased and maintained at maximum for 5 minutes after which the paste viscosity was measured as lOOdPaS (Haake VT-02 viscometer, spindle no.l, measured at 20°C) . 50.Og of Terasil Blue XBGE liquid was added to the paste and stirred for 5 mins. at low speed to ensure complete mixing. Viscosity was the same at 100 dPaS.

The paste was printed on to a knitted polyester fabric (150.0g/m) on a Stork RD-DD machine through a 125 mesh penta screen. The printed fabric was dried at 140°C for 50 seconds. Fixation of colour was effected by steaming at 140°C for 45 minutes followed by a washing treatment in a winch machine consisting of a cold (20°C) rinse, a hot scour at 90°C in a solution containing 2g/l Sapolib DCR plus lg/1 caustic soda flake and subsequent cold rinsing until clear. Finally the fabric was stentered dry.

Excellent definition, coverage and colour yield was obtained. After washing there was no evidence of residual thickener on the fabric, a very soft handle was apparent. Accordingly the polymer of Example 1 is an excellent thickener for disperse dye printing of polyester.

Claims

1. An aqueous print paste thickened by a wholly or partially neutralised product of an acidic polymer-in-water emulsion which is the emulsion polymer of a blend consisting of, by weight,

(a) 10 to 60% ethylenically unsaturated carboxylic acid

(b) 10 to 90% by weight alkyl ester of ethylenically unsaturated carboxylic acid (c) 0 to 60% by weight ethylenically unsaturated monomer ABR where A is an ethylenically unsaturated moiety, B is a polyethoxy chain of at least two ethoxy groups and R is a hydrophobic aliphatic or aromatic group of at least 8 carbon atoms (d) 0 to 5% polyethylenically unsaturated cross- linking agent

(e) 0 to 40% other ethylenically unsaturated monomer, characterised in that the acidic polymer-in-water emulsion has a particle size of at least 200nm.

2. A paste according to claim 1 in which the average particle size is at least 250nm.

3. A paste according to claim 1 or claim 2 in which the polydispersity of the emulsion particles is below 0.1.

4. A paste according to any preceding claim in which monomer (c) is present in an amount of at least 5% by weight.

5. A paste according to claim 4 in which A is an allyl ether group, B is polyethoxy of 5 to 100 ethoxy groups and R is alkyl, aralkyl, alkaryl, aryl or cycloalkyl of 10 to 24 carbon atoms.

6. A paste according to any preceding claim in which monomer (d) is present in an amount of at least 0.01%.

7. A paste according to any preceding claim in which the amount of monomer (a) is 25 to 45%, monomer (b) 45 to 75%, monomer (c) 5 to 20%, monomer (d) 0.01 to 2%, and monomer (e) is 0 to 20%.

8. A paste according to any preceding claim in which monomer (a) is methacrylic acid, monomer (b) is ethyl acrylate and monomer (c) is an allyl ether of a polyethoxylated fatty alcohol.

9. A paste according to any preceding claim in which the particle size of the polymer is above the threshold value of the particle size where the threshold value is the particle size at which the colour yield is at least 80% of the optimum colour yield obtainable in that paste with the same polymer composition but at other particle sizes.

10. A paste according to any of claims 1 to 9 in which the emulsion contains emulsifier which comprises an ethoxylated alcohol phosphate.

11. Use as a print paste thickener of a wholly or partially neutralised product of an acidic polymer-in-water emulsion as defined in any of claims 1 to 10.

12. A method of making a print paste comprising blending aqueous carrier, pigment, alkali and polymer, wherein the polymer is provided as an acidic polymer-in-water emulsion as defined in any of claims 1 to 10.