WO2000022055A1

WO2000022055A1 - Reactive jet ink composition

Info

Publication number: WO2000022055A1
Application number: PCT/GB1999/003301
Authority: WO
Inventors: Wan Kang Zou; Fengfei Xiao; Carrie Woodcock; Shannon Falk; Qiao Qiao Dong
Original assignee: General Electric Company PLC; Marconi Data Systems Inc
Current assignee: General Electric Company PLC; Videojet Technologies Inc
Priority date: 1998-10-09
Filing date: 1999-10-05
Publication date: 2000-04-20
Anticipated expiration: 2001-04-09
Also published as: EP1123357B1; ATE312882T1; EP1123357A1; AU6214799A; DE69928957T2; US6140391A; DE69928957D1

Abstract

The present invention provides a jet ink composition suitable for application onto a substrate comprising an ink carrier, a colorant, a polyol, an aldehyde-based cross-linking agent, and a catalyst that promotes a reaction between the cross-linking agent, the polyol, and the substrate. Examples of preferred cross-linking agents are modified melamine formaldehyde resin and modified urea formaldehyde resin. The substrates preferably possess carboxyl, hydroxyl, amide, or sulfhydryl groups. An example of a preferred substrate is cellulose. The cross-linking reaction is carried out at relatively moderate temperatures and at high speeds. The printed image has excellent adhesion to substrates, abrasion resistance, crinkling resistance, water resistance, and heat resistance.

Description

REACTIVE JET INK COMPOSITION

The present invention generally relates to an ink jet ink composition, and particularly to a

reactive ink jet ink composition suitable for printing images on substrates having hydroxyl, carboxyl,

amide, or sulfhydryl groups with improved adhesion.

Inkjet printing is a well-known technique by which printing is accomplished without contact

between the printing device and the substrate on which the printed characters are deposited. Briefly

described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface

and controlling the direction of the stream, e.g., electronically, so that the droplets are caused to form

the desired printed image on that surface. This technique of noncontact printing is well suited for

application of characters onto a variety of surfaces including porous and non-porous surfaces. Ink

jet printing can be accomplished in a continuous mode as well as in a drop-on-demand mode.

Reviews of various aspects of ink jet printing can be found in these publications: Kuhn et al.,

Scientific American, April, 1979, 162-178; and Keeling, Phys. Technol, 12(5), 196-303 (1981).

Various ink jet apparatuses are described in the following U.S. patents: 3,060,429, 3,298,030,

3,373,437, 3,416,153, and 3,673,601.

In general, an ink jet ink composition must meet one or more rigid requirements to be useful

in ink jet printing operations. These relate to viscosity, resistivity, solubility, compatibility of

components, and wettability of the substrate. Further, the ink must be quick-drying and smear

resistant, must be capable of passing through the ink jet nozzle without clogging, and must permit

rapid cleanup of the machine components with minimum effort.

In addition, the printed image should be robust and have good adhesion to the substrate. The

printed image should have rub or abrasion resistance. Attempts have been made in the industry to

improve these qualities by providing inks that are reactive. In many of these attempts, a reactive ink is provided which cures upon exposure to heat or UV light to provide a durable image. In these

systems, the curing results in the formation of cross-links among the components of the ink. They

often fail to disclose a system in which a reactive component forms a covalent bond with the printed

substrate, as discussed below. For example, U.S. Patent 4,978,969, discloses a method of ink jet

printing using an UV curable ink composition. The ink contains an UV curable adhesive such as

an urethane oligomer. The ink is jet printed onto a substrate which is then exposed to UV light to

effect the curing. It is worth noting that the aforesaid UV exposure is carried out for a significantly

long period of time, i.e., for about 0.5-10 minutes.

U.S. Patent 5,230,733 discloses an ink composition containing a water soluble polymer-

bound dye, such as a dye bound to a polymer having hydroxyl and carboxyl pendant groups, which

loses water and becomes insoluble upon exposure to heat. U.S. Patent 5,380,769 discloses a two-

component system involving a base ink component containing a cross-linkable agent and a curing

component containing a cross-linking agent. The components are applied to the receiving substrate

separately. An example of a cross-linkable agent is an ethylene-acrylic acid copolymer, and an

example of cross-linking agent is an amine such as diethylenetriamine. The printed image contains

a product of the reaction between the cross-linkable agent and the cross-linking agent.

U.S. Patent 5,738,013 discloses a method of making a lithographic plate which employs a

water- insoluble printed image made by using an ink jet ink composition. The ink composition

contains a liquid carrier and an organic reactive component such as a blocked isocyanate. The ink

is printed on a hydrophilic receiving layer that contains a hydrophilic coating, such as a coating of

polyvinyl alcohol. Upon subsequent exposure to an energy source, such as heat, a water-insoluble

pattern is formed on the hydrophilic receiving layer. The printed image is then transferred to a

lithographic plate. It is again worth noting that the formation of the pattern is effected under rather

harsh conditions, i.e., by heating the receiving layer with a hot air gun set at 900°F and held at 18 inches from the layer for about 5 minutes.

European Patent Application 0 672 538 discloses an ink/support medium set. The ink

contains an aqueous carrier and a dye or pigment dispersion as the colorant. The support medium

contains a plastic support sheet and a coating layer that contains a hydrophilic polymer, for example,

polyvinyl alcohol, and a reactive component, for example, one that contains acid groups. After ink

jet printing, the printed medium is exposed to an energy source, such as heat or UV, and as a result

of which, the hydrophilic polymer undergoes a cross-linking reaction.

U.S. Patent 4,694,302 discloses a two-part ink jet printing system, for example, wherein one

part of the system contains carboxymethylcellulose, which is a known reactive polymer. The second

part contains an aluminum salt. The dye can be present in either part. When the two parts are

deposited on a substrate, the reaction between the carboxymethylcellulose and the aluminum salt

leads to the formation of a polymer lattice which binds the dye therein, thereby forming a water-fast

ink. US-4,694,302 also discloses a one-part ink jet printing system, for example, wherein the ink

contains a colloidal suspension of carbon black in diglyme solvent and a reactive species such as

sebacyl chloride. Upon deposition of the ink on a cellulose-containing substrate such as paper, the

sebacyl chloride reacts with the cellulose to form a cellulosic polymer.

Thus, there exists a need for a jet ink composition containing a component that is reactive

to and forms a covalent bond with the receiving substrate.

Further, as discussed above, many reactive ink jet ink compositions require long curing times

and/or high temperatures to complete curing. Thus, there exists a need for a jet ink composition that

cures relatively fast. There also exists a need for a jet ink composition that cures at relatively low or moderate temperatures.

According to the present invention there is provided a jet ink composition suitable for

application onto a substrate comprising an ink carrier, a colorant, a polyol, an aldehyde-based cross- linking agent, and a catalyst that promotes a reaction between the cross-linking agent, the polyol, and

the substrate.

The present invention further provides a process of jet ink printing onto a substrate

comprising projecting a stream of ink droplets to the substrate, controlling the direction of the

droplets so that the droplets form the desired printed image on the substrate, and heating the image

to obtain a cured printed image, wherein the ink droplets are formed from a jet ink composition

according to the preceding paragraph.

Preferred embodiments of the present invention will now be described.

The jet ink composition contains at least one cross-linking agent which reacts with the

receiving substrate to form a covalent bond thereto, and preferably, the cross-linking agent reacts

with the substrate and the polyol to form covalent bonds. Thus, in a preferred embodiment, the

polyol and the substrate are covalently linked through the cross-linking agent. Further, one or more

of the ingredients of the jet ink composition are also capable of undergoing condensation or reaction

with themselves. Thus, for example, a polyol molecule can link with one or more polyol molecules,

the hydroxyl groups being linked through the cross-linking agent.

It has been found that the ink composition of the present invention provides printed images

which incorporate tough, flexible, durable, abrasion resistant, water resistant, and chemical resistant

high molecular weight structures. The jet ink composition is preferably a one-part system and can

be printed using an inkjet printer onto a variety of substrates, preferably those containing hydroxyl,

carboxyl, amide, or sulfhydryl groups. Examples of suitable substrates include polymeric substrates,

preferably plastics such as cellulose, nylon, polycarbonate, and acrylics, and more preferably

cellulose. The jet ink composition of the present invention can also be printed on metal and glass

substrates with good print adhesion qualities.

One of the advantages of the jet ink composition of the present invention is that the cross- linking reaction can be completed in a relatively short period of time following jet printing, for

example, in a period of from about 5 seconds to about 120 seconds, preferably in less than or equal

to about 60 seconds, and more preferably in less than or equal to about 30 seconds. The cross-

linking reaction is carried out under relatively low or moderate temperatures, e.g., at a temperature

of from about 100°F to about 400°F, preferably, less than about 350°F, and more preferably, less

than about 300°F.

It has been found that the jet ink composition of the present invention is particularly useful

in the printing of identification marks on cellulose-based casings such as sausage casings. A

continuous ink jet printer can be installed in-line in the sausage casing production line. Such a

method is advantageous over the traditional flexographic printing method using a two-component

reactive ink system which is generally carried out off-line. The in-line printing method using an ink

jet printer allows variable information to be placed on the substrate readily. This is not feasible

readily with the off-line method. The inkjet printing also can be accomplished without harm to the contents of the cellulose casings.

The jet ink composition of the present invention can be used in continuous ink jet printers

as well as in drop-on-demand inkjet printers. For use in continuous inkjet printing systems, the jet

ink composition should have the following characteristics: (1) a viscosity of from about 1.6 to about

7.0 centipoises (cps) at 25 °C; (2) an electrical resistivity of from about 50 to about 2000 ohm-cm;

and (3) a sonic velocity of from about 1100 to about 1700 meters/second. For example, a typical ink

composition for continuous printing has the following properties: a viscosity of 3.8 cps, an electrical

resistivity of 1050 ohm-cm, a pH of 2.5, a specific gravity of 0.930 g/cc, and a sonic velocity of 1300

meters/second. For use in drop-on-demand systems, the ink composition preferably has a viscosity of from about 3 cps to about 50 cps.

A detailed discussion of the ingredients and the characteristics of the inventive jet ink composition is set forth below.

INK CARRIER

Any suitable ink carrier can be employed to prepare the ink composition of the present

invention. Preferably an organic solvent is used as the ink carrier. Suitable organic solvents include

alcohols, esters, ketones, amides, ethers, and halides. Alcohols and ketones are preferred solvents.

Particular examples of alcohols include ethanol and l-methoxy-2-propanol. A particular example

of a ketone is acetone.

Typically the carrier is present in an amount of from about 40% by weight to about 90% by

weight, and preferably from about 60% by weight to about 85% by weight of the jet ink composition.

A mixture of solvents can also be used. For example, a mixture of ethanol and l-methoxy-2-

propanol can be used. Ethanol and l-methoxy-2 -propanol can be present in any suitable ratio. Thus,

if a mixture of ethanol and l-methoxy-2 -propanol is used, preferably, ethanol is used in an amount

of from about 20% by weight to about 70% by weight of the jet ink composition and l-methoxy-2 -

propanol is used in an amount of from about 20%) by weight to about 60% by weight of the jet ink

composition. In certain embodiments of the present invention, the ink carrier is a mixture of

acetone, ethanol, and l-methoxy-2 -propanol. When such a mixture is used, acetone is preferably

present in an amount of up to about 40% by weight of the jet ink composition, and ethanol and 1-

methoxy-2 -propanol can be present in any suitable ratio.

In certain embodiments, such as a jet ink composition for use in drop-on-demand printers,

the ink carrier includes a non/low volatile organic solvent to prevent the ink from drying and

clogging the jet nozzle openings. An example of such as solvent is propylene glycol. The non/low

volatile organic solvent can be present in any suitable amount, for example, in an amount of up to

about 70%) by weight of the ink composition. COLORANT

The ink composition comprises one or more colorants that impart the desired color to the

printed message. Any dye, pigment, or lake that may be dissolved or dispersed in the ink

composition can be used. Dyes are particularly preferred.

Examples of dyes suitable for use in the preparation of the jet ink composition include, but

are not limited to, C.I, Solvent Black 29 and C.I. Solvent Black 7 (both from Orient Chemical), C.I.

Solvent Blue 70 (Orasol Blue GL, Ciba), and C.I. Solvent Red (Keyfast Spirit Red 3 BLS, Keystone

Aniline). The colorant can be employed in any suitable amount, for example, in an amount of from about 0.5% to about 15% by weight of the jet ink composition, preferably in an amount of from

about 3% by weight to about 8% by weight of the jet ink composition.

POLYOL

The jet ink composition of the present invention comprises a polyol. Any suitable polyol -

diol, triol, or higher alcohol, can be employed. The polyol has an hydroxyl number of from about

50 to about 400, preferably from about 90 to about 300. It is believed that the polyol provides the

following one or more advantageous properties to the printed image. The polyol provides flexibility

to the film that forms when the ink cures on the printed substrate. The polyol participates in the

cross-linking reaction. The polyol improves the robustness of the image as well as adhesion of the

image to the substrate. Examples of polyols include polyester polyol, polyether polyol, polyester

urethane triol resin, and oxidized castor oil. Examples of suitable polyester polyols include polyester

polyols such as low molecular weight linear, saturated, aliphatic structures with hydroxyl groups.

The aliphatic structures can include polyester, urethane, or combinations thereof. K-FLEX™ 188

polyester polyol, available from King Industries, Inc. in Norwalk, CT, is a preferred polyol and has

an hydroxyl number of 230. K-FLEX XM 3322 polyester urethane triol resin, also available from King Industries, Inc., is another preferred polyol, and has an hydroxyl number of 95. Castor oil

derived polyols also can be used. For example, oxidized castor oil polymers available from Siid-

Chemie Rheologicals in Louisville, KY, oxygenated (blown) castor oils available from The Degen

Co. in Jersey City, NJ, and CASPOL™ polyols available from CasChem Inc. in Bayonne, NJ, can

be used.

The polyol can be used in any suitable amount. For example, the polyol can be used in an

amount of from about 0.5% to about 30%> by weight of the jet ink composition, preferably in an

amount of from about 1% to about 10% by weight of the jet ink composition.

CROSS-LINKING AGENT

The jet ink composition of the present invention comprises at least one cross-linking agent,

preferably one that reacts with polar groups such as hydroxyl, carboxyl, sulfhydryl, or amido. The

cross-linking agent preferably is aldehyde-based, or more preferably, formaldehyde-based.

Examples of suitable formaldehyde-based cross-linking agent include alkylated melamine

formaldehyde resins and alkylated urea formaldehyde resins. An example of an alkylated melamine

formaldehyde resin is the methylated melamine formaldehyde resin such as the

hexamethoxymethylmelamine resin available as CYMEL™303 resin from Cytec Industries, Inc. in

West Paterson, NJ. An example of an alkylated urea formaldehyde resin is the methylated urea

formaldehyde resin such as the RESIMENE™ 975 resin available from Solutia Inc. in St. Louis,

MO. BEETLE™ 65, a methylated urea formaldehyde resin available from Cytec Industries, Inc.,

also can be used. In addition, other alkylated melamine formaldehyde resins and alkylated urea

formaldehyde resins, for example, butylated melamine formaldehyde and butylated urea formaldehyde, can be used as the cross-linking agent.

The cross-linking agent can be used in any suitable amount. For example, the cross-linking agent can be used in an amount of from about 0.5% to about 30% by weight of the jet ink

composition, preferably in an amount of from about 2% to about 15% by weight of the jet ink

composition. In certain embodiments of the ink composition of the present invention, the cross-

linking agent is present in an amount of from about 2% to about 5%o by weight, and some other

embodiments, the cross-linking agent is present in an amount of from about 5% to about 11% by

weight of the jet ink composition.

The jet ink composition can further include a higher alcohol, e.g., n-butyl alcohol, which acts

as a stabilizer for the alkylated formaldehyde resins, up to about 10% by weight of the ink composition, preferably in an amount of from about 2% by weight to about 3% by weight. It is to

be noted that when a higher alcohol such as butyl alcohol is used as the ink carrier, the amount of

this alcohol used to prepare the ink composition will be higher than the above-mentioned stabilizing

amounts.

CATALYST

The jet ink composition of the present invention comprises a catalyst that promotes a reaction

of the cross-linking agent with the substrate and the polyol. The reaction leads to covalent bond

formation. Any suitable catalyst can be used, preferably an acid catalyst, and more preferably a

strong acid catalyst. Examples of strong acid catalysts include sulfonic acid catalysts. Aromatic

sulfonic acid catalysts are preferred. Preferred examples of sulfonic acid catalysts include

dinonylnaphthalene disulfonic acid, available as NACURE™ 155 and dodecylbenzene sulfonic acid,

available as NACURE 5076, from King Industries, Inc., and toluene sulfonic acid and the aromatic

sulfonic acid catalyst, available as CYCAT™ 4040 and CYCAT 600, respectively, from Cytec

Industries, Inc.

The catalyst can be present in the ink composition in an amount of up to about 10% by weight of the ink composition, preferably in an amount of from about 0.5% by weight to about 3% by weight of the ink composition.

SURFACE ACTIVE AGENT

The jet ink composition of the present invention preferably includes a surface active agent.

Those of ordinary skill in the art know that surface active agents improve the performance of the ink

composition. For example, the surface active agent provides improved dot definition. Any suitable

surface active agent, including silicones and fluoroaliphatic polyesters, can be employed. A

particular example of a surface active agent is the polyester modified polydimethylsiloxane available

as BYK™ 370 from BYK-Chemie USA in Wallingford, CT. In addition to shaping the ink droplets,

the hydroxyl group at the end of the polyester pendant groups participate in the cross-linking reaction and provides improved adhesion and surface properties.

The surface active agent can be present in the ink composition in an amount of up to about

5%> by weight of the ink composition, preferably in an amount of from about 0.05% by weight to

about 2% by weight of the ink composition, and more preferably in an amount of from about 0.1 % by weight to about 0.5% by weight of the ink composition.

CONDUCTIVITY AGENT

Jet printing ink compositions for use in continuous inkjet printers should have a low specific

resistivity, such as within the range of about 20 to about 2000 ohm-cm. The desired conductivity

can be achieved by the addition of an ionizable material. Examples of such ionizable materials

include ammonium, alkali, and alkaline earth metal salts such as ammonium hydroxide, lithium

nitrate, lithium chloride, lithium thiocyanate, lithium trifluoromethane sulfonate,

tetraethylammonium toluene sulfonate, sodium chloride, potassium chloride, potassium bromide, calcium chloride, and the like, dimethylamine hydrochloride, and hydroxylamine hydrochloride.

Any suitable amount of the ionizable material can be used. Normally, an ionizable material content

of up to about 5% by weight of the ink composition provides the desired conductivity.

The following examples further illustrate the present invention.

EXAMPLE 1

This Example illustrates the preparation of a black reactive jet ink composition of the present

invention which is suitable for use in a continuous inkjet printer. The following ingredients were

combined in the order listed and mixed for a period of 90 minutes. The resulting mixture was

filtered to remove any particulates and the ink composition was recovered.

Ingredients % by wt.

Ethyl Alcohol(SDA 23 A 190 proof, Quantum Chemical) 30.9 l-Methoxy-2-Propanol (Ashland) 46.4

Lithium Nitrate (FMC Corp.) 1.5

Solvent Black 29 (Orient Chemical) 5.6

Butyl Alcohol (Ashland Chemical) 3.0

Polyester Modified Polydimethylsiloxane (BYK370, BYK- 0.1 Chemie USA)

Modified Melamine-Formaldehyde Resin (CYMEL 303, 2.0

Cytec Ind.)

Polyester Urethane Triol Resin (K-FLEX XM 3322, King 9.0

Ind.) Dinonylnaphthalene Disulfonic Acid (NACURE 155, King 1.5

Ind.)

100.0

The ink composition was printed on a cellulose sausage casing provided by Viskase

Corporation in Chicago, Illinois. The printed image was cured at a temperature of 257 °F for 30 seconds. The image had excellent water resistance and abrasion resistance. The image also had both

dry and wet crinkling resistance and ink film flexibility. The wet crinkling resistance was measured

after soaking the printed cellulose casing in water at about 20 °C for a period of at least 10 minutes.

EXAMPLE 2

This Example illustrates the preparation of another black reactive jet ink composition of the

present invention which is suitable for use in a continuous inkjet printer. The ink composition was

prepared using the following ingredients and tested as in Example 1. The image had excellent water

resistance and abrasion resistance. The image also had dry and wet crinkling resistance and ink film

flexibility.

Ingredients % by wt.

Ethyl Alcohol (SDA 23 A 190 proof) 30.0 l-Methoxy-2-Propanol 46.15 Lithium Nitrate 1.5

Solvent Black 29 5.7

Butyl Alcohol 2.0

Polyester Modified Polydimethylsiloxane (BYK 370) 0.15

Modified Melamine-Formaldehyde Resin (CYMEL 303) 10.5 Oxidized Castor Oil (Sϋd-Chemie) 3.0

Dodecylbenzene Sulfonic Acid (NACURE 5076) L0

100.0

EXAMPLE 3

This Example illustrates the preparation of yet another black reactive jet ink composition of

the present invention which is suitable for use in a continuous inkjet printer. The ink composition

was prepared using the ingredients listed below and tested as in Example 1. The image had excellent water resistance and abrasion resistance. The image also had dry and wet crinkling resistance and ink film flexibility.

Ingredients % by wt.

Ethyl Alcohol (SDA 23 A 190 proof) 32.9 l-Methoxy-2-Propanol 46.8 Lithium Nitrate 1.2

Solvent Black 29 5.6

Butyl Alcohol 2.0 Polyester Modified Polydimethylsiloxane (BYK 370) 0.2

Methylated Urea-Formaldehyde Resin (RESIMENE 975) 3.0

Polyester Urethane Triol Resin (K-FLEX XM 3322) 6.0 Dinonylnaphthalene Disulfonic Acid (NACURE 155) L5

100.0

EXAMPLE 4

This Example illustrates the preparation of a blue reactive jet ink composition of the present

invention which is suitable for use in a continuous inkjet printer. The ink composition was prepared

using the ingredients listed below and tested as in Example 1. The image had excellent water

resistance and abrasion resistance. The image also had dry and wet crinkling resistance and ink film flexibility. Ingredients % by wt.

Ethyl Alcohol 50.6 l-Methoxy-2-Propanol 25.0 Lithium Nitrate 1.2

Orasol Blue GL (Ciba) 6.0

Butyl Alcohol 2.0

Polyester Modified Polydimethylsiloxane (BYK 370, BYK- 0.2

Chemie USA) Methylated Urea-Formaldehyde Resin (BEETLE 65, Cytec 6.0

Ind.)

Modified Melamine-Formaldehyde Resin (CYMEL 303, 5.0

Cytec Ind.)

Polyester Polyols (K-FLEX 188, King Ind.) 3.0 Toluene Sulfonic Acid (CYCAT 4040, Cytec Ind.) L0

100.0

EXAMPLE 5

This Example illustrates the preparation of a red reactive jet ink composition of the present

flexibility. Ingredients % by wt.

Ethyl Alcohol (SDA 23 A 190 proof) 49.0 l-Methoxy-2-Propanol 25.0 Lithium Nitrate 1.2

Keyfast Spirit Red 3 BLS (Keystone Aniline) 6.0

Butyl Alcohol 2.0

Polyester Modified Polydimethylsiloxane (BYK 370) 0.2

Modified Melamine-Formaldehyde Resin (CYMEL 303) 11.0 Oxidized Castor Oil 3.0

Dinonylnaphthalene Disulfonic Acid (NACURE 155) 2,5

100.0

EXAMPLE 6 This Example illustrates the preparation of a black reactive jet ink composition of the present invention which is suitable for use in a drop-on-demand inkjet printer. The ink composition was prepared using the following ingredients. The ink composition was printed on a cellulose sausage casing provided by Viskase Corporation in Chicago, Illinois. The printed image was cured at a temperature of 257°F for 30 seconds. The image had excellent water resistance and abrasion resistance. The image also had dry and wet crinkling resistance and ink film flexibility.

Ingredients % by wt.

l-Methoxy-2-Propanol 30.0 Propylene Glycol (Ashland Chemical) 47.3

Solvent Black 29 4.0

Butyl Alcohol (Ashland Chemical) 4.0

Polyester Modified Polydimethylsiloxane (BYK 370) 0.2

Modified Melamine-Formaldehyde Resin (CYMEL 303) 5.0 Polyester Urethane Triol Resin 8.5

Dinonylnaphthalene Disulfonic Acid (NACURE 155) 1.0

100.0 The jet ink composition of the present invention has one or more of the following advantages. The ink is a reactive ink. The ink is a one-pack or one-component system which permits ease of handling during printing operations. The ink is stable under normal storage and shipping conditions. The ink cures at high speeds at relatively moderate temperatures. The printed image covalently bonds to the substrate thereby providing superior water resistance, abrasion resistance, crinkling resistance, and superior ink film flexibility. The substrate with the printed image can therefore be subjected to mechanical manipulations without degrading the print quality.

The printed image is stable to heat. The printed image is resistant to smoke cooking and hot- cold water cycling. Thus, for example, the printed substrate can be soaked in tap water for at least 10 minutes and the images can be rubbed firmly, and, in addition, the substrate can be crinkled vigorously, without degrading the image. The printed substrate can be subjected to hot water and steam cooking conditions followed by exposure to cold tap water.

The ink has good stability with a relatively long shelf life. The ink provides superior print quality with no color off-setting, migration, or penetration. The inkjet printing method using the ink composition of the present invention provides high speed in-line printing during production.

Claims

CLAIMS:

1. A jet ink composition suitable for application onto a substrate comprising an ink

carrier, a colorant, a polyol, an aldehyde-based cross-linking agent, and a catalyst that promotes a

reaction between said cross-linking agent, the polyol, and the substrate.

2. A jet ink composition according to claim 1, wherein said aldehyde-based cross-

linking agent comprises one or more modified formaldehyde resins.

3. A jet ink composition according to claim 2, wherein said cross-linking agent

comprises an alkylated melamine formaldehyde resin and/or an alkylated urea formaldehyde resin.

4. A jet ink composition according to claim 3, wherein said alkylated melamine

formaldehyde resin is a methylated melamine formaldehyde resin and said alkylated urea

formaldehyde resin is a methylated urea formaldehyde resin.

5. A jet ink composition according to any one of the preceding claims, wherein said

polyol is selected from the group consisting of a polyester polyol, polyether polyol, polyester

urethane triol resin, and oxidized castor oil.

6. A jet ink composition according to any one of the preceding claims, wherein said catalyst is an acid catalyst.

7. A jet ink composition according to claim 6, wherein said acid catalyst is a sulfonic

acid catalyst.

8. A jet ink composition according to claim 7, wherein said sulfonic acid catalyst is an

aromatic sulfonic acid catalyst.

9. A jet ink composition according to claim 8, wherein said aromatic sulfonic acid

catalyst is selected from the group consisting of dinonylnaphthalene disulfonic acid, dodecylbenzene

sulfonic acid, and toluene sulfonic acid.

10. A jet ink composition according to any one of the preceding claims, wherein said ink

carrier comprises one or more alcohols.

11. A jet ink composition according to claim 10, wherein said alcohol is selected from

the group consisting of acetone, ethanol, and l-methoxy-2 -propanol.

12. A jet ink composition according to any one of the preceding claims, wherein said

colorant is selected from the group consisting of Solvent Black 29, C.I. Solvent Black 7, C.I. Solvent

Blue 70, and C.I. Solvent Red 91.

13. A jet ink composition according to any one of the preceding claims, wherein said

composition further includes a surface active agent.

14. A jet ink composition according to claim 13, wherein said surface active agent is a

siloxane polymer such as polyester modified polydimethylsiloxane.

15. A j et ink composition according to any one of the preceding claims, wherein said j et ink composition is suitable for use in continuous inkjet printing and has a Brookfield viscosity at

25 °C of from 1.6 centipoise (cps) to 7.0 cps, an electrical resistivity of from 50 ohm-cm to 2000

ohm-cm, and a sonic velocity of from 1100 meters/second to 1700 meters/second.

16. A jet ink composition according to any one of claims 1 to 14, wherein said jet ink

composition is suitable for use in drop-on-demand printing and has a Brookfield viscosity of from

3 cps to 50 cps at 25 °C.

17. A process of jet ink printing onto a substrate comprising projecting a stream of ink

droplets to said substrate, controlling the direction of said droplets so that the droplets form the

desired printed image on the substrate, and heating the image to obtain a cured printed image,

wherein said ink droplets are formed from a jet ink composition according to any one of the

preceding claims.

18. A process according to claim 17, wherein said substrate is a polymeric substrate.

19. A process according to claim 18, wherein said polymeric substrate has a functional

group selected from the group consisting of hydroxyl, carboxyl, sulfhydryl, and amide.

20. A process according to claim 18, wherein said polymeric substrate is cellulose.