CA2237071A1 - Permanent aqueous marker inks including silicone - Google Patents

Abstract

Permanent aqueous marker inks are provided which include a silicone surfactant, a pigment, a film-forming polymer and water. Fluorocarbon surfactants and/or hydrocarbon surfactants may also be included in the ink. The aqueous inks according to the invention can be used to mark paper, plastics, glass and metal and provide an alternative to solvent-based inks.

Description

PERMANENT AQUEOUS MARKER INKS INCLUDING SILICONE
This application is a divisional of Application Serial No. 2,140,652 filed July 13, 1993.
Back~round of the Invention This invention relates to m~rking compositions.
Traditionally, permanent inks for use in markers have been provided in liquid form, as solvent-based or aqueous solutions. Solvent-based inks generally provide good adhesion and wetting on a wide variety of smooth, difflcult to wet substrates, e.g., glass, plastic and metal. However, there is an increasing desire in the field to reduce or 10 elimin~te solvent use, due to environmental and safety concerns, and secondarily, to avoid the unpleasant odour of solvent-based inks. Aqueous inks, form~ tecl to replace solvent based inks, generally do not wet all substrates, particularly plastics, glass and metal, and are often not water-fast.
The invention features permanent aqueous marker inks that can be used to 15 mark, e.g., paper, plastics, glass, and metal.
One aspect of the invention features an aqueous marker ink which includes a silicone surfactant, a film-forming polymer, a pigment, and water. In preferred compositions, the silicone surfactant is a siloxane or silane surfactant and the silicone ~ulrac~lll is fluorinated. The compositions may further include a fluorocarbon and/or a 20 hydrocarbon surfactant.
Preferred inks include, by weight, about 0.1 to 1, more preferably 0.2 to 0.6 percent of the surfactant(s), about 10 to 40, more preferably 20 to 30 percent of the film-forming polymer, about 2 to 8 percent pigment, and sufficient water to provide a viscosity of less than about 20 cps. The ink may also include a small quantity (preferably 1-10%) of a low (less than 5) carbon alcohol.
The invention also features a method of m~rking a substrate, e.g., glass, plastic or metal. The method includes the steps of providing a marker having a reservoir, 5 the reservoir cont~ining one of the featured inks, and making a mark with the marker on the substrate.
Preferred marker inks advantageously do not include any solvent. The term "solvent", as used herein, refers to liquids which are defined as Volatile Organic Compounds (VOCs). Further, they are permanent, i.e., water-fast and fade resistant, and 10 write well on a wide variety of substrates, including difficult to wet substrates such as glass, metal, and plastics, e.g., poly~ropylene, polyethylene and PVC film (SARAN~
film). Preferred inks have a surface tension of from about 18 to 34 dynes/cm.
Other features and advantages of the invention will be apparent from the description of the plefclled embodiments thereof, and from the claims.
Prefcll~d marker inks include a surfactant, or combination of surfactants, to reduce the surface tension of the ink composition to less than about 35 dynes/cm, an acrylic film-forming polymer, a water-dispersible pigment, a humectant, and water.
The surfactant(s) can be either: (a) a silicone surfactant, or (b) a combination of a silicone surfactant and a fluorocarbon surfactant and/or a hydrocarbon surfactant.
20 The total amount of the surfactant in the composition is preferably from about 0.1 to 1, more preferably 0.2 to 0.6 percent by weight. It is plcfelled that the amount of the surfactant(s) included, and the ratio of surfact~nt~, if a combination is used, be selected so as to provide a composition having a surface tension between about 18 and 34 dynes/cm. Too little surfactant(s) may prevent the composition from properly wetting difficult substrates, while too much may cause the ink to "soak through" when used on paper.
In the embo~iment~ in which a combination of fluorocarbon and hydrocarbon 5 surf~ct~nt~ is used, the ratio of fluorocarbon surfactant to hydrocarbon surfactant is preferably about 1:1.
Suitable fluorocarbon surfact~nt~ include at least one aliphatic fluorocarbon group. Preferred fluorocarbon surfactants include ZONYL~ FSA and FSN
fluorosurfactants, available from Dupont, which contain, respectively, lithium 3, [(lH, lH, 10 2H, 2H-fluoroalkyl) thio] proprionate and telomer B monoether with polyethylene glycol (CAS No. 65545-80-4). Other suitable surf~ct~nt~ are fluorinated alkyl alkoxylates, available from 3M under the tradename FLUORAD~, e.g., FLUORADTM FC-171 surfactant.
Hydrocarbon surf~ct~nt~ include at least one aliphatic group. Suitable 15 hydrocarbon surfactants include alkylphenol ethoxylates in which the alkyl group has between 6 and 12 carbons. The plefel,ed alkylphenyl ethoxylate is octylphenol ethoxylate, e.g., TRITONsM X-100 non-ionic surfactant, available from Union Carbide, Danbury, CT.
Suitable silicone surfactants include silanes and siloxanes. Examples are 20 polyoxyethylene modified polydimethylsiloxanes (referred to in the art as "silicone glycol copolymers"), e.g., DOW CORNING~ Q2-5211 and Q2-5212 super-wetting agents, available from Dow Corning Corp., Mi~ n~1, MI. Also preferred are fluorinated silicone surf~ct~nt.c, e.g., fluorinated polysilanes, available from Ecology Chemical Co., Watertown, M~s~chllsett~, under the tradename LEVELENED' 100.
The choice of surfactant will depend upon the properties desired from the ink, and cost and stability factors. Typically, the silicone surfactant provides good wetting 5 and allows the use of a single surfactant. Addition of the hydrocarbon/fluorocarbon combination provides wetting properties that are stable over a long storage period.
Enough pigment should be included in the ink to provide an adequate colour intellsily, but not so much that viscosity becomes excessively high. The pre~elled inks include between approximately 2% and 8 % pigment by weight, more preferably between 10 approximately 5% and 7%. Pigments that may be used in the invention include water dispersible pigments, and preferably the pigment is provided in the form of an aqueous dispersion, for accurate measurement and uniform mixing. Suitable dispersions include those available from Hoechst Celanese under the tradename FLEXONYL~ or HOSTAFINE~ those available from KVK U.S.A. Inc. under the tradename 15 PREDISOL~, those available from Heucotech Ltd. under the tradename HEUCOSPERSE~, those available from Nippon Keiko K~g~ , Ltd. under the tradename LUMIKOL~, and those available from Mikuni Colour Works, Inc. under the tradename TITICACATM. The total amount of the pigment dispersion to be added will depend upon the solids level of the dispersion, and will be selected to give an effective 20 amount of the pigment, as described above. It is preferred that the pigment have a relatively small particle size, preferably less than 0.5 micron, to prevent settling. The small particle size also is more suitable for use in capillary feed markers.

The acrylic polymer is preferably provided in the form of an emulsion.
However, if desired, a water soluble acrylic may be used. Preferred acrylic polymers include thermoplastic acrylics, e.g., polymethacrylates, such as polymethyl methacrylate and other methyl acrylates. A p~felled acrylic emulsion is RHOPLEX~ AC-261 5 emulsion, available from Rohm and Haas Co., Philadelphia, PA. Rhoplex AC-261 is an all-acrylic co-polymer combination, a butyl acrylate/methyl methacrylate blend having a low acid content, a molecular weight of around 1,000,000 and a glass transition lelllpeld~ulc of between 15 and 20. The resin is thermoplastic and in use forms a film on the substrate by coalescence after the correction fluid is applied. Preferred compositions 10 contain from about 20 to 30 weight percent of the acrylic polymer. Too much of the acrylic may result in undesirably high viscosity at an effective level of pigment, while too little may result in an ink having poor water re~ t~nre when dry.
Preferred hllm~ct~nt~ are glycols, such as diethylene or di~ro~ylene glycol or glycerol. A more preferred humectant is propylene glycol. The humectant prevents 15 dry-out of the marker when the cap is left off. Accordingly, too much may cause the ink to dry too slowly, while too little may not prevent drying out of the marker. Preferred compositions include from 1 to 25 weight percent of the humectant, preferably from about 5 to 15 weight percent.
Other conventional ingredients may be included in the composition, e.g., 20 biocides.
Sufficient water should be included in the ink so that its Brookfield viscosity at 25~C is less than about 20 cps, more preferably between about 2 cps and 10 cps. If the viscosity is too low, the composition may not contain effective amounts of the active ingredients. If the viscosity is too high, the ink may be too thick for practical use, particularly in capillary feed systems.
A preferred procedure for preparing the compositions of the invention is to provide the pigment in the form of a dispersion, add to this dispersion the super-wetting 5 surfactant (if a blend of surfact~ntc is used, these are preferably mixed prior to addition to the pigment dispersion), then add the humectant, the water, and, finally, the acrylic emulsion, mixing between each addition. The ingredients can be mixed using any conventional mixer, under conditions of relatively low shear.
The following examples illustrate the invention.

A series of ink compositions were prepared using the pl~efelled procedure described above. The formulations for these compositions are given in Table 1. Each ink was tested by forming a line on a series of substrates (PVC film (SARANTM wrap), polyethylene, polypropylene, metal, glass and cellophane tape) and observing whether the 15 line dried without shrinkage and/or beading. Each ink formed a uniform line, without beading or shrinkage, on each of the test substrates.

Ingredient Sample 1 Sample 2 Sample 3 Sample 4 Pigment dispersion FLEXONYL~ ACB 10 10 Pigment dispersion FLEXONYL~ AB26 10 Pigment dispersion Propylene Glycol 10 10 10 10 TRITONn' X-100 0.5 hydrocarbon surf.
ZONYL~ FSA 0.25 fluorocarbon surf.
SUPER~ KSx 0.5 Q2-5212 silicone LEVELENE~ 100 1 0.5 0.5 hydrocarbon surf.
bacteriocide 0.1 0.1 0.1 0.1 RHOPLEX~ AC261 50 50 50 50 acrylic polymer water 24 29 29 29 ~ CA 02237071 1998-06-26 Other Embo(1imentc Other embodiments are within the claim. For example, a small amount (less than 10%) of 2-propanol may be added to the ink to decrease the drying time.

Claims (11)

1. An aqueous marker ink comprising a silicone surfactant, a film-forming polymer, a pigment, and water.

2. A marker ink of claim 1, wherein said silicone surfactant is selected from the group consisting of siloxane surfactants and silane surfactants.

3. A marker ink of claim 1, wherein said silicone surfactant is fluorinated.

4. A marker ink of claim 1, wherein said silicone surfactant is a polydimethylsiloxane comprising polyoxyethylene.

5. A marker ink of claim 1, wherein said film-forming polymer is an acrylic polymer.

6. A marker ink of claim 1, wherein said ink further comprises a surfactant selected from the group consisting of fluorocarbon surfactants, hydrocarbon surfactants including at least 1 aliphatic group and mixtures thereof.

7. A marker ink of claim 1, wherein said ink comprises, by weight, about 0.1 to 1 percent of the silicone surfactant, about 20 to 30 percent of the film-forming polymer, about 2 to 8 percent pigment, and sufficient water to provide a viscosity of less than about 20 cps.

8. A marker ink of claim 1, wherein said ink further comprises a humectant.

9. A marker ink of claim 1, wherein said ink has a surface tension of less than about 35 dynes/cm.

10. A method of marking a substrate including the steps of providing a marker having a reservoir, the reservoir containing an ink comprising a silicone surfactant, a pigment, a film-forming polymer, and water, and making a mark with said marker on the substrate.

11. A marker comprising a hollow tubular body defining an ink reservoir, the reservoir containing an ink comprising a silicone surfactant, a pigment, a film-forming polymer and water and a tip in fluid communication with said reservoir for delivering said ink to a substrate by capillary action.