GB2330586A

GB2330586A - Aqueous pigment printing paste composition

Info

Publication number: GB2330586A
Application number: GB9722665A
Authority: GB
Inventors: Arshad-Ul-Haq Chaudhry; Johanna Nichols; Peter Edward Berrill
Original assignee: Scott Bader Co Ltd
Current assignee: Scott Bader Co Ltd
Priority date: 1997-10-27
Filing date: 1997-10-27
Publication date: 1999-04-28
Anticipated expiration: 2017-10-27
Also published as: GB2330586B; GB9722665D0

Abstract

A printing paste composition comprises (1) a pigment; (2) an aqueous medium; (3) as a thickener for the aqueous medium, an acrylamide/acrylic copolymer; (4) as a binder for the pigment, a water-insoluble vinyl addition polymer having a glass transition temperature of from -40‹C to +65‹C and incapable of self-crosslinking; and (5) as a crosslinking agent, a component having at least two blocked isocyanate groups capable, on heating, of decomposing to provide respective isocyanate groups capable of cross-linking with hydroxyl groups present on at least one of the binder, the thickener and any cellulosic material to be printed; and (6) the printing paste composition has a pH of # 8.

Description

AQUEOUS PIGMENT PRINTING PASTE : COMPOSITION This invention relates to an aqueous pigment printing paste composition.

World-wide, pigments are the most important colouring system used for textile printing. Pigment printing is not only the oldest but also the easiest printing method, as far as the simplicity of application is concerned. In pigment printing, insoluble pigments, which have no affinity for the fibre, are fixed onto the textile with binding agents in the pattern required. This principle is applicable to almost any textile material. After printing and drying, only a fixation process at elevated temperatures is required. Additional steps of washing off and drying the fabrics, essential in all dye printing applications, are avoided. In this way pigments differ fundamentally from the normal colorants (dyestuffs) used in textile printing.

The beginning of the "modern" textile pigment printing can be traced back to 1937. Earlier recommendations were based on emulsion print pastes, which utilised white spirit emulsions in water as the thickening systems. During drying and fixation water and volatile solvents were removed by evaporation and pigment prints could be produced which met an acceptable standard in respect of colour yield, clarity of shade, softness of handle and reasonable fastness properties.

During the 1970's in Western Europe and North America, emulsion pastes became less acceptable for both safety and environmental reasons. Currently, all-aqueous pigment printing systems are in use not only in the industrialised world but also in other parts of the world.

Successful conventional all-aqueous pigment printing systems are based upon: 1. Pigment dispersions.

2. Binders.

3. Cross-linking/fixing agents.

4. Thickeners.

5. Auxiliaries, for example, for rheology modification and runnability.

Most of the pigments currently used in textile printing are synthetic organic materials, except for carbon black, for blacks, titanium dioxide for whites and copper and aluminum alloys for metallic bronze pigments which are sometimes also used.

The binder is a film forming substance made up of longchain macromolecules which, when applied to the textile, together with the pigment during a suitable fixation process, produces a three-dimensionally linked network. The binders employed in pigment printing of textiles are polymers, preferably co-polymers, of unsaturated monomers such as ethyl acrylate, butyl acrylate, styrene, acrylonitrile, vinyl acetate and butadiene. The polymer composition may be selected in dependence upon application requirements.

The abovementioned crosslinking of the binder serves to provide elasticity and improved adhesion of the binder film containing the pigment. The crosslinking reaction must produce covalent bonds which are insensitive to hydrolysing agents such as detergents, body sweat and industrial atmospheres.

External crosslinking agents, known in the textile industry as fixing agents, are used especially when printing hydrophobic materials. Fixing agents are normally poly nmethylol compounds. Preferred fixing agents are water soluble methyl ethers of tetra or hexa-methylolmelamines.

Self crosslinking binders (binders having a crosslinking capability within the binder molecule) contain copolymerised n-methylolacrylamide or n-methylolmethacrylamide or more stable methyl ethers of these compounds.

More particularly, a conventional all-aqueous pigment printing system consists of: 1. Water xg 2. Flow moderator 0-5g 3. Softener 5-20g 4. Defoamer 2-3g 5. Emulsifier 2-5g 6. Synthetic thickener 25-30g 7. Binder 80g 8. Cross-linking agent 0-lOg However, it is generally recognised that: 1. Pigment print paste pH during preparation, storage and application must at least be 8 and, in general, about 8-9 (see EP-A-0161038). A pH of 8-9 is normally achieved with the addition of volatile alkalis, such as ammonia or amines such as mono, di or triethanolamine to the print paste.

2. The use of methylol based crosslinking binders and melamine based fixing agents produces prints with formaldehyde. The level of formaldehyde in the print depends upon the type of binder and fixing agents used. In Europe Oko-Tex Standard 100 sets out specification limits for the presence of formaldehyde allowed in fabrics for various applications e.g.

OKO-TEX STANDARD 100 FORMALDEHYDE SPECIFICATIONS (TEST ACCORDING TO JAPANESE lAW 112)

Fabric/Application Test Standard Formaldehyde Specification (ppm) 1. Fabrics for 104 #20 babywear 2. Accessories for 105 #20 babywear 3. Babywear 106 #20 It is known to use formaldehyde scavengers, such as urea, in printing pastes to reduce the level of formaldehyde in the pigment prints. However, the use of formaldehyde scavengers such as urea has an adverse effect on the printing quality. Rub fastness, particularly wet rub fastness is impaired as is the handle of the printed fabric.

Thus, it would be a significant innovation if an aqueous, especially an all-aqueous, pigment printing system could be designed which could be used for pigment printing textiles and other suitable materials, using existing printing techniques (and apparatus) e.g silk screens, roller, flat-bed, rotary screens and ink-jets and if the resultant print pastes: 1. did not require pH adjustment and control, during preparation, storage and application; 2. did not involve the use of irritants such as ammonia or other less volatile and less safe alkalis, such as amines; 3. provided exceptional print paste stability over wide pH and temperature ranges; 4. enabled printers to produce prints which met all established specifications in terms of formaldehyde content, without the use of formyl based fixing agents and without the use of formaldehyde scavengers; 5. produced prints of equivalent or superior quality in comparison to prior art all-aqueous systems; 6. produced prints of acceptable crock and wash fastness; 7. did not produce any undesirable odours during preparation, storage and application of print pastes; and 8. allowed processing of prints using established techniques and conditions.

Surprisingly we have now found that an aqueous, preferably all-aqueous, pigment printing composition, which need not have any formyl groups in it, not only provides prints which meet established OKO-Tex Standard 100 requirements but does not require pH control during preparation, storage or application of the print paste.

Resultant print paste pH is always less than 8, preferably 5 7 but more preferably 2 4, still more preferably 2 5, thus avoiding the use of irritants such as ammonia and/or expensive but less safe amines. In addition a preferred pigment printing composition is capable of providing all the desired benefits 1-8 listed above.

Thus, according to the invention, there is provided a printing paste composition comprising (1) a pigment; (2) an aqueous medium; (3) as a thickener for the aqueous medium, an acrylamide/acrylic copolymer; (4) as a binder for the pigment, a water-insoluble vinyl addition polymer having a glass transition temperature of from -400C to +650C and incapable of self-crosslinking; (5) as a crosslinking agent, a component having at least two blocked isocyanate groups capable, on heating, of decomposing to provide respective isocyanate groups capable of crosslinking with hydroxyl groups present on at least one of the binder, the thickener and any cellulosic material to be printed; and (6) which printing paste has a pH of s 8.

Preferred components of the above printing paste composition will now be described: (1) Pigment This may be any compound which is substantially insoluble in the aqueous medium and may be an inorganic or organic material. Typical inorganic pigments are carbon black, titanium dioxide and copper and aluminum alloys.

However, more preferably, the pigment is a synthetic organic material, still more preferably any of the pigments given in the Colour Index and referred to as CI Pigments, for example, a CI Pigment Red, Orange, Yellow, Green, Blue, Violet or Black. A typical such pigment is CI Blue 15:2 available commercially as Aquarine Blue 3GW.

(2) Aqueous Medium This has a pH of s 8, preferably s 7, which level of pH is achievable without the addition of volatile alkaline materials such as ammonia or amines. More preferably, however, the pH 2 4, still more preferable 2 5, thus, avoiding use of an excessively corrosive medium.

The aqueous medium allow dissolution in it of the thickening component to achieve the desired viscosity of printing paste, which is preferably between about 12,000 and 14,000 cps.

(3) Thickener The thickener is an acrylamide/acrylic copolymer and the acrylic component may be acrylic acid, methacrylic acid, 2acrylamido-2-methyl propanesulphonic acid, 2-sulphoethyl methacrylate and their water soluble, especially alkaline metal, salts. However, more preferably, the thickener is an acrylamide/acrylic acid copolymer in which the acrylic acid component is at least partially (but which may be wholly) neutralised with an alkali capable of forming a water soluble salt, for example, an alkaline metal or ammonium salt, with acrylic acid. Partial neutralisation, especially with an ammonium salt, but so as to provide no free ammonia, is especially preferred.

Still more preferably, the acrylamide/acrylic copolymer is lightly crosslinked (ie no more than about 3 equivalents per mole of monomer mix and in any event no more than about 0.5 weight % by weight of total weight of monomer) with a polyfunctional monomer, for example, diallylurea, methylene bis acrylamide, allylmethacrylate, diallylphthalate, glycol di (methyl) acrylate, triallyl cyanurate, triallyl isocyanurate and polyfunctional poly(alkylene ethers).

A thickener may be incorporated in a composition in the form of a powder, solution or dispersion, but is most preferably added in the form of an inverse emulsion. Details of such inverse emulsions, their methods of preparation and additives incorporated in them, as well as examples of acrylamide/acrylic copolymers are given in EP-A-0186361.

A preferred thickener is a high molecular weight polymer having a number average molecular weight between 1 x 106 and 6 x 106.

Thus, although many conventional thickeners (eg polyacrylic acids ) require pH adjustment before they become effective, thickeners may be chosen from those mentioned above which have a pH c 7 and preferably > 4 and which do not require any such pH modification during preparation of the composition, storage or application. For example, when the thickener is an acrylamide/acrylic acid copolymer, it can be neutralised to an extent such as to provide a composition which does not require subsequent pH modification. When formulated into the resulting print paste, they can provide a pH within a range of 4-8, more preferably 5-7 as indicated above.

Moreover, such thickeners conform to the requirements of the Oko-Tex.

The thickener is added in an amount such as to provide the final printing paste composition with the desired viscosity, which is preferably about 12,000 to 14,000 cps.

When the thickener is in the form of a water-in-oil emulsion of a high molecular weight copolymer, this amount may be between 2-8% of emulsion (preferably containing about 0.05 to 4, more preferably 0.1 to 2, wt% solid polymer by weight of total emulsion) by weight of total composition.

(4) Binder The binder is a water-insoluble vinyl addition polymer having a glass transition temperature of from -40"C to +650C, thereby having excellent film formation properties.

Preferably, the binder contains ionic groups, for example, carboxyl, nitrile, amide and hydroxyl.

In dependence upon the exact property profile required for the final print quality, for example, softness, adhesion, elasticity, solvent resistance and weatherability, desirable for a particular application, then the polymer content of the vinyl addition copolymer can be selected accordingly.

Examples of such vinyl monomers, ie monomers having a terminal ethylenic unsaturation, are acrylic or methacrylic (hereinafter " (meth) acrylic") compounds are Cis alkyl, especially C24 alkyl, (meth) acrylates, (meth) acrylonitrile, (meth) acrylamide, ethylenically unsaturated mono and dicarboxylic acids, their half esters or full esters derived from polyhydric alcohols, for example, hydroxyethyl/propyl (meth)acrylate, vinyl or vinylidene chloride, mono or polyethylenically unsaturated hydrocarbons (e.g. ethylene, propylene, butylene, 4-methyl-l-lpentene, styrene-butadiene, isoprene and chloroprene), vinyl esters and vinylsulfonic acid.

Typically, the binder may be a copolymer of an alkyl (preferably C14 alkyl) (meth) acrylate and a hydroxyalkyl (preferably C14 alkyl) (meth) acrylate, for example, a copolymer of ethyl (meth) acrylate and hydroxyethyl (meth) acrylate, in which the molar proportion of the hydroxylalkyl (meth) acrylate is about 2-7, preferably 3-6, more preferably 3.5-5.5 mole%.

Especially if the thickening material is not provided with hydroxyl groups, then this binder may be a vinyl addition copolymer containing hydroxyl group capable of reaction with the cross linking agent or a cellulosic fibre.

Typical monomer components of the binder providing such hydroxyl groups are hydroxyethyl acrylate and methacrylate.

Again, the above choice of binder allows the above mentioned Oko-Tex Standard 100 requirements to be met.

The amount of the binder added should be such as to provide a print with a rub fastness of 3-4. The binder may be present in an amount of 1-20, preferably about 2-10 wt, typically about 3-6 wt solid polymer by weight of the total composition. Usually the binder is added in the form of a commercially available emulsion containing about 30-60 wt% solid polymer and the binder emulsion may be present in an amount of 5-30wtE, typically about 10wog of emulsion by weight of the total composition.

(5) Crosslinkins Aqent This is a component having at least two blocked isocyanate groups, ie, groups which on heating are capable of decomposing to provide respective isocyanate groups, which isocyanate groups are capable of crosslinking with hydroxyl groups present on at least one of the binder, the thickener and any cellulosic material to be printed.

The crosslinking agent may be added, for example, as an aqueous dispersion of a blocked isocyanate. In particular, it may be admixed firstly with the binder component in respective predetermined quantities and supplied as a single product to be used as the bonding system, this replacing two component systems of binder and fixing agent conventionally used in pigment printing paste. However, alternatively, the binder and the crosslinking agent can be added as two separate products. Whichever method is adopted, adjustment and control of pH is not necessary.

Yet again, use of such a crosslinking agent allows avoidance of the presence of any formyl or any other group capable of undergoing crosslinking as a consequence of pH changes and/or storage. Thus, the prepared printing paste, including the crosslinking agent, can show excellent print paste stability over a wide pH and storage temperature range.

Moreover, the crosslinking agent is capable of crosslinking with the binder and/or thickener present in the print base and/or fabric during normal fixing conditions, ie, at a temperature 21400C.

Yet again, the above mentioned choice of crosslinking agent allows the Oko-Tex Standard 100 requirements to be met.

The crosslinking agent may be present in an amount of about 1-25wt%, typically 2-12wt%, by weight of the total composition. When added in the form of a 45 wt% solid polymer emulsion (in which some crosslinking agents are commercially available) it may be present in an amount of about 2-35wt%, typically about 20wt% of emulsion by weight of total composition.

Preferred embodiments of the abovementioned will now be described with reference to the accompanying drawings and examples in which: Fig 1 is a graphical representation of a relationship between viscosity (cPs) and storage time (hrs) at 400C of a conventional printing paste composition containing melamine and having the composition given in Example 1; Fig 2 is a graphical representation of the variation of pH with storage time (hrs) at 400C for the conventional printing paste of Example 1; Fig 3 is a graphical representation of the variation in viscosity (cPs) with storage time (hrs) at 4 OOC of the composition of Example 2, in accordance with the invention; and Fig 4 is a graphical representation of pH against storage time of the composition of Example 2.

Example 1 The following, conventional, printing paste composition was prepared Water 825 Texipol 36-506l 35 Texicryl 13-2112 100 Pigment blue 30 Melamine 10 (Parts by weight) 1000 1 Texipol 63-506 is an inverse emulsion thickener designed to produce a printing paste having a pH of 2 8.0, as is conventional. It has a viscosity s 3,500 (measured with a Brookfield RVT, spindle 3, speed 20 at 250C) and when present in an amount of 3 wt emulsion, thickens distilled water to a viscosity 2 100,000 cps (measured using a Brookfield RVT, spindle 6, speed 5 at 200C).

2 Texicryl 13-211 is a conventional acrylic co-polymer binder emulsion having a solid polymer content of 45 t 1% and containing n-methylolacrylamide for use in a pigment printing paste without an external cross linking agent. It has the composition: Wt% Ethyl acrylate 85.93 Butyl acrylate 9.99 Acrylamide 1.66 Methylol acrylamide 2.47 100.00 The viscosity of the printing paste was 14,000 cps at 25"C, as measured with a Brookfield RVT viscometer spindle 6, speed 20. The pH of the composition was 8.5. The printing paste was left in storage at 400C for 336 hours and, during this period, various viscosity measurements were taken. The results are shown in Fig. 1, from which it can be seen that this viscosity was not stable over this period.

Similarly, the pH of the printing paste was monitored over this period, measurements initially being taken on a 2% print paste dissolved in distilled water. After about 72 hours, the print paste gelled and pH measurements were taken on the gel. The results are shown in Fig. 2 Yet again, these results showed a considerable drop in pH from 8.5 down to 6.3 over the first 120 hours, indicating poor pH stability.

In addition to the above mentioned measurement of viscosity at 40 C, viscosity measurements were also taken with various samples of the above mentioned composition adjusted to a respective pH of 6, 7, 8 or 9 and stored at 25 or 400C respectively.

The results are shown below.

SAMPLE 1 pH 6

STORAGE TIME Storage temp C Initial 24 hrs 168 hrs 336 hrs Vise. Visc visc. Visc.

25 14300 15900 Gelled - 40 - 16500 Gelled - SAMPLE 2 pH 7

STORAGE TIME Storage temp C Initial 24 hrs 168 hrs 336 hrs Visc. Visc. Visc. Visc.

25 15000 16700 29200 Gelled 40 - 19100 Gelled - SAMPLE 3 pH 8

STORAGE TIME Storage temp C Initial 24hrs 168 hrs 336 hrs Visc. Visc. Visc. Visc.

25 14100 14400 14700 15100 40 - 14900 24200 Gelled SAMPLE 4 pH 9

STORAGE TIME Storage temp C Initial 24hrs 168hrs 336hrs Visc. Visc. Visc. Visc.

25 14000 14100 14400 14100 40 - 14600 16200 21600 Example 2 The following print paste was prepared: Water 818 Texipol 67-50383 32 Texicryl 13-1154 80 Pigment blue 30 Acrafix CA 460725 20 (Parts by weight) 1000 3 Texipol 67-5038 is an inverse emulsion thickener having a viscosity (Brookfield RVT, spindle 3, speed 20 at 25"C) of < 3,000 cps and which when present in an amount of 3wt% of emulsion in distilled water provides a viscosity > 50,000 cps (Brookfield RVT, spindle 6, speed 5 at 250C).

4 Texicryl 13-115 is an emulsion polymer binder (50 + 1 wt% solid polymer, viscosity 0.1-2 poise, pH 6-7, MFFT* < 20C), having the composition: Wt%- Ethyl acrylate 95.00 Hydroxyethyl methacrylate 5.00 100. 00 Thus, this binder, does not contain a self cross-linking moiety such as N-methylol acrylamide present in some binders.

It does, however, contain hydroxyl groups capable of crosslinking with the isocyante cross-linking agent.

* Minimum Film Formation Temperature, determined using a Rhopoint MFFT bar.

5 Acrafix ix CA 46072 is a polyurethane emulsion having blocked isocyanate groups. It has a pH of 6-8 (undiluted).

The viscosity, measured as in Example 1 above, of the printing paste was 12,200 cps at 250C and the pH was 7. As in Example 1, a variation of both viscosity and pH with storage time at 400C over a period as long as 325 hours at 400C was measured and the results are shown in Figs. 3 and 4.

As can be seen, the viscosity was practically stable over this long period of time and there was no variation in pH whatsoever.

In addition, as in Example 1, samples of the paste were adjusted to pH 6, 7, 8 or 9 and stored for 336 hours at 25 and 40"C and the viscosity measured at various intervals over this period.

The results are shown below.

SAMPLE 1 pH 6

25 12800 12500 12800 12600 40 - 11200 11300 11100 SAMPLE 2 pH 7

25 12200 12300 11900 12000 40 - 11500 11100 11200 SAMPLE 3 pH 8

STORAGE TIME Storage temp C Initial 24hrs 168 hrs 336 hrs Vise @ Visc. Vise Visc.

25 11300 11400 11700 11600 40 @ 10800 10400 10600 SAMPLE 4 pH 9

STORAGE TIME Storage temp C Initial 24hrs 168hrs 336hrs Visc. Visc. Visc. Visc.

25 10400 9700 10100 9500 40 @ 10300 9600 7800 Again, these demonstrate the usefulness of printing paste embodying the invention without the need to control pH to a value greater than 8.

Example 3 A comparison of the printing performance of the conventional composition (A) of Example 1 and the composition (B) of Example 2 embodying the invention was made.

For comparison, these compositions are set out below, as are the printing conditions.

Print Pastes A B Water 825 818 Texipol 63-506 35 Texipol 67-5038 32 Texicryl 13-211 100 Texicryl 13-115 80 Melamine 10 Acrafix CA46072 20 (Parts by weight) 1000 1000 pH 8.5 6.2 Viscosity (cps) 14000 12800 Printing conditions Zimmer table - mini MDF Bar 8 mm diameter Pressure setting 1 Speed 5 The prints were dried out at room temperature and fixed at 1480C for 4 minutes.

The Crock fastness11, a well known measure of abrasion/scrub resistance, was measured after 25 cycles and assessed according to the grey scale.

Test were carried out on 100% cotton fabric and 50:50 polyester/cotton fabric.

The results are shown below: Fabric 100% cotton Performance Comparisons Print Pastes Print Qualities A B Colour value Standard Similar to standard Definition Standard Similar to standard Levelness Standard Similar to standard Brilliancy Standard Similar to standard Handle Standard Softer Dry crock 3 3 Wet crock 3 3 Wash fastness 2/3 2/3 Formaldehyde (ppm) Free 160 9 Released 550 15 Fabric (50 : 50) Polyester/cotton Print Qualities Colour value Standard Similar to standard Definition Standard Similar to standard Levelness Standard Similar to standard Brilliancy Standard Similar to standard Handle Standard Similar to standard Dry crock 3 3 Wet crock 3/4 3/4 Wash fastness 3 3 Formaldehyde (ppm) Free 170 7 Released 890 15 The above results demonstrate that in addition to meeting all current requirements in respect of free and released formaldehyde, the printing paste embodying the invention gave printing pastes equally as good having regard to the standard of colour, dry crock, wet crock and wash fastness while providing an improved handle.

Example 4 The following printing pastes were prepared.

Print Pastes C D Water 818 818 Texipol 67-5038 32 32 Texicryl 13-115 100 Pre-Mix' 20 Pigment Blue 30 30 Acrafix CA 46072 20 (Parts by weight) 1000 1000 pH 6.2 6.2 Viscosity (cps) 14000 14000 * The pre-mix consisted of 80 parts Texicryl 13-115 and 20 parts Acrafix.

These pastes were printed and fixed as described in Example 3.

The results obtained when printing each of pastes C and D were similar to one another, showing that printing was reproducible irrespective of whether or not the binder and crosslinking agent were added as a pre-mix or as separate components.

Example 5 The performance of print paste C given in Example 4 and below was compared with that of print paste E containing, in place of the Acrafix CA 46072, an equal amount of Vestanat EP-DS 1205, a blocked polyisocyanate emulsion.

Print Pastes C E Water 818 818 Texipol 67-5038 32 32 Texicryl 13-115 100 100 Pigment Blue 30 30 Acrafix CA 46072 20 Vestanat EP-DS 12056 20 (Parts by weight) 1000 1000 pH 6.2 6.2 Viscosity (cps) 14000 14000 6 Vestanat EP-DS 1205 is a blocked polyisocyanate emulsion having a solid polymer content of about 45 wits, a pH of 8.9 t 0.5, a blocked isocyanate content (resin) of 11.0 and a viscosity at 230C (D=200 s-l) of 40-80 mPa.s . It can be de-blocked at temperatures 2 1450C.

The printing and fixing conditions were as in Example 3 and the results obtained were similar for both composition C and E.

Claims

CLAIMS 1. A printing paste composition comprising (1) a pigment; (2) an aqueous medium; (3) as a thickener for the aqueous medium, an acrylamide/acrylic copolymer; (4) as a binder for the pigment, a water-insoluble vinyl addition polymer having a glass transition temperature of from -400C to +650C and incapable of self-crosslinking; (5) as a crosslinking agent, a component having at least two blocked isocyanate groups capable, on heating, of decomposing to provide respective isocyanate groups capable of cross-linking with hydroxyl groups present on at least one of the binder, the thickener and any cellulosic material to be printed; and (6) which printing paste composition has a pH of 5 8.
2. A printing paste composition according to claim 1, which has a pH of 5 7.
3. A printing paste composition according to claim 1 or claim 2, which has a pH 2 4.
4. A printing paste according to any preceding claim, wherein the thickener is an acrylamide/acrylic acid component in which the acrylic acid component is at least partially neutralised.
5. A printing paste according to any preceding claim, wherein the binder is a copolymer of an alkyl (meth) acrylate and a hyroxyalkyl (meth) acrylate.
6. A printing paste according to any preceding claim, wherein the crosslinking agent is a polyurethane or a polyisocyanate, which polyurethane or polyisocyanate has blocked isocyanate groups.