IE83751B1 - A phase change ink composition - Google Patents
A phase change ink composition Download PDFInfo
- Publication number
- IE83751B1 IE83751B1 IE2002/0020A IE20020020A IE83751B1 IE 83751 B1 IE83751 B1 IE 83751B1 IE 2002/0020 A IE2002/0020 A IE 2002/0020A IE 20020020 A IE20020020 A IE 20020020A IE 83751 B1 IE83751 B1 IE 83751B1
- Authority
- IE
- Ireland
- Prior art keywords
- ink
- dispersant
- particles
- pigment
- carrier
- Prior art date
Links
- 239000000203 mixture Substances 0.000 title claims description 23
- 239000002270 dispersing agent Substances 0.000 claims description 87
- 239000000049 pigment Substances 0.000 claims description 72
- 239000002245 particle Substances 0.000 claims description 71
- 239000000919 ceramic Substances 0.000 claims description 67
- 239000000843 powder Substances 0.000 claims description 53
- 239000000969 carrier Substances 0.000 claims description 41
- 239000000463 material Substances 0.000 claims description 36
- 239000000758 substrate Substances 0.000 claims description 36
- 239000002904 solvent Substances 0.000 claims description 29
- YXFVVABEGXRONW-UHFFFAOYSA-N toluene Substances CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 21
- 239000003795 chemical substances by application Substances 0.000 claims description 19
- QIQXTHQIDYTFRH-UHFFFAOYSA-N Stearic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 16
- 238000003801 milling Methods 0.000 claims description 14
- 238000007639 printing Methods 0.000 claims description 13
- 238000002844 melting Methods 0.000 claims description 12
- 238000010304 firing Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 11
- 238000007641 inkjet printing Methods 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 9
- 235000021355 Stearic acid Nutrition 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 8
- 239000008117 stearic acid Substances 0.000 claims description 8
- DKPFZGUDAPQIHT-UHFFFAOYSA-N Butyl acetate Natural products CCCCOC(C)=O DKPFZGUDAPQIHT-UHFFFAOYSA-N 0.000 claims description 6
- ULQISTXYYBZJSJ-UHFFFAOYSA-N 12-hydroxyoctadecanoic acid Chemical group CCCCCCC(O)CCCCCCCCCCC(O)=O ULQISTXYYBZJSJ-UHFFFAOYSA-N 0.000 claims description 4
- 229940114072 12-hydroxystearic acid Drugs 0.000 claims description 4
- 235000014113 dietary fatty acids Nutrition 0.000 claims description 4
- 239000000194 fatty acid Substances 0.000 claims description 4
- 238000000498 ball milling Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 150000004665 fatty acids Chemical class 0.000 claims description 3
- 125000002524 organometallic group Chemical group 0.000 claims description 3
- 229920000058 polyacrylate Polymers 0.000 claims description 3
- FJKROLUGYXJWQN-UHFFFAOYSA-N 4-Hydroxybenzoic acid Chemical compound OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 claims description 2
- UKMSUNONTOPOIO-UHFFFAOYSA-N Behenic acid Chemical compound CCCCCCCCCCCCCCCCCCCCCC(O)=O UKMSUNONTOPOIO-UHFFFAOYSA-N 0.000 claims description 2
- 235000021357 Behenic acid Nutrition 0.000 claims description 2
- POULHZVOKOAJMA-UHFFFAOYSA-N Lauric acid Natural products CCCCCCCCCCCC(O)=O POULHZVOKOAJMA-UHFFFAOYSA-N 0.000 claims description 2
- FEWJPZIEWOKRBE-XIXRPRMCSA-N Mesotartaric acid Chemical compound OC(=O)[C@@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-XIXRPRMCSA-N 0.000 claims description 2
- 229960004274 Stearic acid Drugs 0.000 claims description 2
- 229950008690 docosanoic acid Drugs 0.000 claims description 2
- 229960001367 tartaric acid Drugs 0.000 claims description 2
- 235000002906 tartaric acid Nutrition 0.000 claims description 2
- 239000011975 tartaric acid Substances 0.000 claims description 2
- 125000003944 tolyl group Chemical group 0.000 claims 1
- 239000000976 ink Substances 0.000 description 86
- 239000001993 wax Substances 0.000 description 13
- 238000000034 method Methods 0.000 description 12
- 239000011521 glass Substances 0.000 description 11
- 239000012071 phase Substances 0.000 description 9
- 239000006185 dispersion Substances 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 239000000470 constituent Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000012188 paraffin wax Substances 0.000 description 6
- 238000003860 storage Methods 0.000 description 5
- 230000004580 weight loss Effects 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 239000011324 bead Substances 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000004062 sedimentation Methods 0.000 description 4
- KIHBGTRZFAVZRV-UHFFFAOYSA-N 2-hydroxystearic acid Chemical compound CCCCCCCCCCCCCCCCC(O)C(O)=O KIHBGTRZFAVZRV-UHFFFAOYSA-N 0.000 description 3
- 238000010928 TGA analysis Methods 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 239000000975 dye Substances 0.000 description 3
- 239000004615 ingredient Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 238000002411 thermogravimetry Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 239000003086 colorant Substances 0.000 description 2
- 239000005357 flat glass Substances 0.000 description 2
- 238000005189 flocculation Methods 0.000 description 2
- 230000016615 flocculation Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 239000011368 organic material Substances 0.000 description 2
- 238000003921 particle size analysis Methods 0.000 description 2
- 238000007650 screen-printing Methods 0.000 description 2
- 238000010023 transfer printing Methods 0.000 description 2
- KHPFIDDXCRYEHS-UHFFFAOYSA-N 2-butyloctadecanoic acid Chemical compound CCCCCCCCCCCCCCCCC(C(O)=O)CCCC KHPFIDDXCRYEHS-UHFFFAOYSA-N 0.000 description 1
- BXHGDCLMSZGPOH-UHFFFAOYSA-N C(C(O)C(O)C(=O)O)(=O)O.C1(=CC=CC=C1)C Chemical compound C(C(O)C(O)C(=O)O)(=O)O.C1(=CC=CC=C1)C BXHGDCLMSZGPOH-UHFFFAOYSA-N 0.000 description 1
- ICOXKGOOBYUTJV-UHFFFAOYSA-N C1(=CC=CC=C1)C.C(CCCCCCCCCCCCCCCCCCCCC)(=O)O Chemical compound C1(=CC=CC=C1)C.C(CCCCCCCCCCCCCCCCCCCCC)(=O)O ICOXKGOOBYUTJV-UHFFFAOYSA-N 0.000 description 1
- 235000010919 Copernicia prunifera Nutrition 0.000 description 1
- 240000003412 Copernicia prunifera Species 0.000 description 1
- 210000003298 Dental Enamel Anatomy 0.000 description 1
- 235000009134 Myrica cerifera Nutrition 0.000 description 1
- 235000012851 Myrica pensylvanica Nutrition 0.000 description 1
- -1 Polyethylene Polymers 0.000 description 1
- 239000004698 Polyethylene (PE) Substances 0.000 description 1
- 235000002594 Solanum nigrum Nutrition 0.000 description 1
- 240000006258 Solanum nigrum Species 0.000 description 1
- 238000003854 Surface Print Methods 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 230000000111 anti-oxidant Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 238000010296 bead milling Methods 0.000 description 1
- 235000013871 bee wax Nutrition 0.000 description 1
- 239000012166 beeswax Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000003115 biocidal Effects 0.000 description 1
- 239000003139 biocide Substances 0.000 description 1
- 239000005388 borosilicate glass Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 125000005313 fatty acid group Chemical group 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000012182 japan wax Substances 0.000 description 1
- 238000002372 labelling Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000011068 load Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- BJMNMDAUEMUSRJ-UHFFFAOYSA-N octadecanoic acid;toluene Chemical compound CC1=CC=CC=C1.CCCCCCCCCCCCCCCCCC(O)=O BJMNMDAUEMUSRJ-UHFFFAOYSA-N 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000012254 powdered material Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000003134 recirculating Effects 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 230000003678 scratch resistant Effects 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 230000003019 stabilising Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 235000013311 vegetables Nutrition 0.000 description 1
- 238000000196 viscometry Methods 0.000 description 1
- 239000004034 viscosity adjusting agent Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/30—Inkjet printing inks
- C09D11/34—Hot-melt inks
Description
The invention relates to inks for application to a heat resistant substrate such as glass,
metal, or ceramic and subsequently firing to fuse the ink to the substrate.
Prior Art Izjscussion
US4390565 and US5212212 describe inks based on a UV curable ink system and are
designed to be applied by a screen printing process. The ceramic ink formulations
described are in liquid form and the solid constituents of the inks tend to sediment as a
function of time in storage. Therefore the ink must be constantly mixed while not in use.
This also applies to other types of liquid ink such as solvent or oil based ink.
EP0l05994 (Corning Glass) describes a thermoplastic hot melt ink, the viscosity of
which has a tacky paste consistency for application by elastomeric transfer printing to a
substrate.
While such inks may adhere well to substrates such as ceramics, the printing methods
involved suffer from the following disadvantages:—
need for storage of screens or transfer members,
— high cost for low volume printing and lack of versatility generally,
- limitations in substrate surface printing coverage, in which edge—to—edge printing
is often not possible, and
— requirement for an even substrate surface.
The invention is therefore directed towards providing an ink for application to a heat
resistant substrate to overcome at least some of the above problems.
N
According to the invention there is provided an ink suitable for application to a heat
resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for
ink jet printing and comprising:-
a carrier material;
a pigment comprising ceramic pigment particles of less than 10 microns in size;
a fusible vitreous agent comprising particles of less than 10 microns in size, and
the carrier having a melting point for phase change of the ink.
Preferably the concentration of ceramic pigment in the ink is in the range of 10% to 60%
by weight, preferably 20% to 50% by weight.
In another embodiment of the invention the pigment and fusible vitreous agent are
combined in the form of ceramic pigment particles. Preferably the ceramic pigment
particles are less than 5 microns in size.
In one embodiment of the invention the ink comprises a dispersant. Preferably the
particles are coated with the dispersant.
Most preferably the dispersant is chemisorbed onto the particles.
The dispersant may be chemisorbed onto the particles by drying in an oven for up to 24
hours wherein the temperature of the oven is at least 120‘-’C.
Preferably the dispersant is selected from a modified polyacrylate and fatty acid, most
preferably the dispersant is selected from 12-hydroxystearic acid, stearic acid, tartaric
acid, hydroxybenzoic acid and docosanoic acid. Ideally the dispersant comprises stearic
acid.
In one embodiment of the invention the dispersant is present in a concentration by weight
of the ceramic pigment from 2 to 5%, preferably approximately 4%.
Preferably the particles are coated with a dispersant in the presence of a solvent. Most
preferably the dispersant is soluble in the solvent. The solvent may be toluene or butyl
acetate.
The particles may be coated with a dispersant by ball milling or using a rotary dissolver.
Preferably the carrier material comprises a wax material. Most preferably the carrier
material has a melting point of from 20 to 1509C, preferably 50 to 1009C.
In another embodiment of the invention the pigment comprises organometallic particles
and metallic components.
The invention provides an ink suitable for application to a heat resistant substrate and
firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and
comprising;—
ceramic pigment particles of less than 10 microns in size;
fusible vitreous particles of less than 10 microns in size; and
a carrier having a melting point for phase change of the ink.
Preferably the particles are coated with a dispersant.
The invention also provides an ink suitable for application to a heat resistant substrate
and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and
comprising;-
a carrier having a melting point for phase change of the ink;
ceramic pigment particles of less than 10 microns in size;
fusible vitreous particles of less then 10 microns in size; and
a dispersant which is chemisorbed onto the particles.
The invention further provides a method of producing an ink in a form for ink jet printing
comprising the steps of:—
milling a fusible vitreous agent to provide a powder having a particle size less
than 10pm;
providing a pigment for the ink;
heating a phase change carrier, and mixing the powder with the molten carrier;
and
allowing the carrier to cool to provide solid ink.
Preferably the pigment is combined with the fusible vitreous agent as ceramic pigment
particles.
The invention also provides a method of producing an ink comprising the steps of:-
milling a fusible vitreous agent to provide a powder having a particle size less
than 10pm;
providing a pigment for the ink;
mixing the milled particles with a dispersant, and a solvent;
removing the solvent;
heating the mixture to a temperature in excess of 1209C whereby the dispersant is
chemisorbed onto the milled particles;
heating a phase change carrier, and mixing the powder mixture with the molten
carrier; and
allowing the carrier to cool to provide solid ink.
Preferably the pigment is combined with the fusible vitreous agent as ceramic pigment
particles.
D HNVEI
The invention will be more clearly understood from the following description of some
embodiments thereof, given by way of example only with reference to Fig. 1 which is a
graph showing dispersant adsorption.
The invention provides an improved phase change ink suitable for application to heat
resistant substrates by ink jet printing.
The advantages of using an inkjet printing method over a screen printing method or
elastomeric transfer printing include the following; 1). Images and patterns are produced
and stored digitally, and therefore there is no requirement for storage of a large number of
printing screens; 2) it is equally feasible to print images in small numbers as it is to print
in large numbers; 3) the printer can change from printing one image to printing another
without shutting down; 4) each image printed can be different from the previous one: 5)
edge to edge printing is possible; 6) any size of image is possible; 7) process colours are
possible; 8) it is possible to print onto uneven surfaces; 9) it is possible to print onto three
dimensional shapes e.g. table ware and ornamental ware; 10) it offers greater flexibility
in terms of the types of images that can be printed as well as the types of substrates that
can be printed onto; 11) a smaller number of ink colours are required.
The ink of the invention in a form for ink jet printing comprises the following:—
(a) a carrier material, preferably a wax having a melting point of from 20 to 150°C,
preferably from 50 to 100°C, suitable for solid/liquid phase change of the ink.
(b) pigment particles of less than 10 microns in size;
(c) fusible vitreous particles of less than 10 microns in size; and
(d) a dispersant.
The ink is a phase change ink. In other words the ink remains in a solid form while in
storage and when the temperature of the printer is lower than the melting point of the ink
carrier material, for example when the printer is switched off. When the printer is
operating the ink is heated to a temperature which is higher than the melting point of the
carrier material, the carrier material melts, and the ink becomes liquid. In this way no
sedimentation of the ceramic particles occurs while the ink is in storage thus effectively
and significantly increasing the shelf life of the ink. The ink can be inkjet printed onto
ceramic, glass, metal and other heat-resistant materials. The print is subsequently fired to
remove the organic constituents of the ink and to fuse the pigment constituents to the
substrate.
The carrier material is a wax material such as paraffin wax, an example of which is,
Paraflint C77®, produced by Schuman Sasol GmbH, Hamburg, Germany. However, any
other suitable wax or wax—like material such as, but not limited to, those outlined in Table
below may be used (mp = melting point).
Table 1
Animal Vegetable Mineral Synthetic
Beeswax Candelillia Montan Fischer—Tropsch waxes
(mp 62—65°C) (mp 68.5-72.5°C) (mp 83-93°C) eg. paraffin (mp 44-
°C)
Carnauba
(mp 83-86°C)
Bayberry
(mp 38-49 °C)
Polyethylene
(mp 90—120°C)
Japan wax
(mp 50°C)
Fatty acids e.g. stearic
acid (mp 69°C),
hydroxystearic acid (mp
75°C)
The pigment may be any material capable of providing a colour. Preferably the pigment
is a ceramic pigment material.
The term “ceramic” means the inorganic constituents of the ink. These may include
crystalline or amorphous (glass) inorganic materials. The ceramic constituents form the
pigment in the ink and not only produce the colour in the ink but also fuse to the substrate
during the firing process. The ceramic may be one or more discrete materials, however,
they are referred to collectively as the “ceramic pigment”.
The ceramic pigment may comprise one or more metal oxides, which have characteristic
crystalline structures, which impart colour to materials.
Preferably the ceramic pigment material is a powdered pigmented vitreous material
comprising a combination of a ceramic pigment and a fusible vitreous agent.
The pigment may be an organometallic material, wherein on firing, the organic
constituent burns off and the metallic constituents oxidise to form a metal oxide.
Alternatively, the colour may be produced by using compounds which contain metallic
elements and are soluble in the carrier material. On firing, the metallic elements oxidise
to form coloured metal oxides. The resultant inks may be of any colour, but will
preferably be black, cyan, magenta, yellow, or white or variations of these.
The vitreous agent provides the means for fusing the pigment material to the substrate
during firing at temperatures in the range of approximately 700 to 1300°C. The fusible
vitreous agent may be a lead-boro-silicate glass material or any other suitable glass
material. The pigment and fusible vitreous agent are preferably combined/incorporated in
the form of ceramic pigment particles.
The dispersant assists in stabilising the dispersion of the pigment particles in the ink by
creating repulsive forces between the particles, thereby inhibiting agglomeration or
flocculation in the ink. The proportion of dispersant added to the ink composition is in
the range of from 0.5-20% of the weight of the ceramic powder. However, the amount of
dispersant added is preferably from 2 to 5% of the weight of the ceramic powder.
Preferably the dispersant is a modified polyacrylate, such as EFKA 4401®, produced by
EFKA Additives B.V., Netherlands. Alternatively the dispersant is a fatty acid material
such as l2—hydroxystearic acid or stearic acid, or any other suitable dispersant.
The ceramic pigment of the invention is in the form of a very fine powder with a particle
size less than l0p.m, most preferably less than Sum in size. The viscosity of the ink is in
the range of from 10 to 40cP, and preferably from 10 to 25cP.
The powdered materials with the desired particle size distribution may be produced by
milling, sol—gel, or any other suitable powder production method. Preferably the desired
particle size distribution is obtained by bead milling commercially available pigments in
the presence of a liquid. A quantity of the commercially available ceramic pigment
powder is placed into a ceramic vessel with a quantity of ceramic beads. To this water is
added and the contents are stirred at high speed with a ceramic stirrer. At different time
intervals samples of the powder/water mixture (slurry) are extracted and the particle size
distribution is determined by a laser diffraction technique. After milling is complete the
liquid is removed by filtration, evaporation or any other suitable method and the milled
powder is dried thoroughly in an oven.
The pre-milled pigment(s), with the desired particle size distribution, are prepared for
dispersion in a carrier material by coating the particles with the dispersant. The powder
(milled pigment) is mixed with a suitable solvent and the dispersant is added to the
mixture. Preferably the dispersant is soluble in the solvent. The solvent may be selected
from any one or more of toluene or butyl acetate. The dispersant helps to stabilise the
dispersion of the pigment particles in the ink by creating repulsive forces between the
particles, thereby inhibiting agglomeration or flocculation in the ink. The proportions of
powder and solvent are approximately 5g powder per 100ml toluene. The proportion of
dispersant added is in the range of from 0.520% of the weight of the ceramic powder.
However, the amount of dispersant added is preferably from 2 to 5% of the weight of the
ceramic powder.
The mixture is combined thoroughly by a dispersion process such as ball milling or
employing a rotary dissolver, which breaks up agglomerates and floccs thereby reducing
the powder to the primary particles. The process coats the particles with the dispersant.
After mixing, the solvent is removed by filtration, evaporation, or any other suitable
means. In this way the powder is coated with dispersant. However, the dispersant is only
relatively weakly bonded (physisorbed) to the surface of the particles. In order to form a
stronger bond the dispersant coated powder is dried in an oven for up to 24 hours at a
temperature of 120°C. This removes any remaining toluene and forms a stronger bond
(chemisorbed) between the dispersant molecules and the surface of the powder particles.
After the chemisorption process the powder may be passed through a l50um sieve to
break down large agglomerates. The powder is then ready to be dispersed in the carrier
material.
In order to optimise the amount of dispersant required to coat the ceramic particles an
adsorption test was conducted for each type of dispersant used. The adsorption test
involves varying the amount of dispersant added to the powder and combining, as
described above the dispersant and powder in the proportions as outlined in Table 2
below. The ceramic powder and dispersant contents are expressed in terms of weight
percent of the total solids content. The adsorption test in this case was conducted using
12—hydroxystearic acid and WHITE 45T4l pigment powder [from Johnson Matthey plc,
UK]
-1]-
Table 2
Sample Toluene (ml) Powder Wt % Dispersant Wt %
A001 65 100 0
A002 65 99 1
A003 65 98 2
A004 65 97 3
A005 65 96 4
A006 65 95 5
A007 65 94 6
A008 65 93 7
A009 65 90 10
A010 65 88 12
A012 65 86 14
A013 65 80 20
The solvent is removed by filtration and the powder is washed by more solvent to remove
the excess dispersant. The dispersant—coated powder is then dried in an oven at a
temperature of at least 120°C.
Samples of the dispersant—coated powders were analysed by thermogravimetric analysis
to determine the amount of adsorbed dispersant on the powder in each sample.
Thermogravimetric analysis involves controlled heating of a small amount of the sample
in a highly sensitive balance. As the organic material, i.e. the dispersant, is burned off,
the balance detects a weight loss and the temperature at which it occurs. The aim is to
achieve the maximum weight loss as this represents the maximum amount of adsorbed
dispersant. The thermogravimetric analysis results of the samples are presented in Table
below.
Table 3
Sample Weight Loss (%) % Dispersant Adsorbed
A001 0 0
A002 0.38 36
A003 1.62 81
A004 2.79 93
A005 3.04 76
A006 3.51 70.2
A007 4.19 69.83
A008 4.7 67.14
A009 5.77 57.7
A010 7.32 61
A012 9.46 67.57
A013 11.83 59.15
By plotting the weight loss results as a percentage of the weight of the dispersant added,
as shown in Fig. 1, it can be seen that the amount of adsorbed dispersant increases rapidly
up to approximately 2.8% weight loss which corresponds to a powder to dispersant ratio
of 97:3 by weight. The results indicate that the minimum amount of the dispersant
required to coat the powder is 2%, by weight, of the total amount of ceramic pigment.
Preferably, 4% dispersant is used in the production of inks in order to ensure complete
coverage of the pigment particles with dispersant molecules. The ceramic pigment
material may alternatively be milled in the presence of a solvent. In this case the
dispersant is added during the milling step of the process. After milling the solvent is
removed and the dispersant chemisorbed to the powder as described previously.
The dispersant coated pigment powder is mixed with the carrier material by first wetting
the powder with a small amount of solvent (approximately 1 part of solvent to 20 parts of
pigment by weight) in a heating vessel with accurate temperature control. The carrier
material is then added and the mixture is heated, to approximately 110°C. At this
temperature the carrier material melts and the solvent is removed. The dispersant coated
pigment particles are dispersed in the molten carrier material by any suitable dispersion
technique such as a rotary dissolver or a three roll mill. The mixture may be maintained
inside a partial vacuum during mixing in order to minimise the amount of dissolved air in
the ink. After mixing, the mixture is allowed to cool so that it solidifies. The solidified
material is ready for use as an ink.
The properties of the ink composition of the invention are suitable for printing using a
piezoelectric drop—on-demand inkjet printer. The viscosity is in the range of from 10 to
40cP, and preferably from 10 to 25cP. The printing process or printer may comprise
any of the following features: an ink reservoir with suitable heating capability which can
be employed to melt the ink as required. An ink umbilical which may be heated in order
to transport the ink from the reservoir to the printhead without allowing the ink to
solidify; a piezoelectric drop—on-demand inkjet printhead with inbuilt heating capability
which can maintain the ink in liquid form during printing. The heating capability of the
printhead may control the temperature of the ink so as to optimise the viscosity of the ink.
Other additives to the ink composition may include binders, plasticisers, dyes, biocides,
antioxidants, viscosity modifiers, defoamers or any other additives as appropriate. These
ingredients may be added at the milling stage or at the dispersion stage of the production
process, as appropriate.
The ink may be printed onto a variety of substrates including glass, ceramic and metal
substrates. An advantage of phase change inks is that the ink droplets solidify the instant
they strike the substrate. This makes substrate handling more convenient. After printing
the printed ink and substrate may by fired typically at temperatures of from 700°C to
1300°C, preferably glass articles will be fired at a temperature of from 700°C to 800°C
and ceramic articles will be fired at temperatures of from 900°C to 1200°C, in order to
remove the carrier material and other organic ingredients and to fuse the vitreous ceramic
material, from the ink, to the substrate. The ink composition of the invention has many
industrial applications. The ink may be used for decorating ceramic tiles, decorating
glass articles, decorating ceramic and glass tableware, decorating ceramic and glass
ornamental ware, temperature resistant marking and labelling, and decorating metal
articles.
The invention will be more fully understood from the following examples.
E I I M“.
g of white ceramic pigment powder (Johnson Matthey plc., UK (product code WHITE
45T41)), was placed in a ceramic pot with 400ml of water and 600g of ceramic beads.
The contents were stirred with a ceramic stirrer at a speed of 1000 r.p.m. The results of
the particle size analysis of samples of powder after milling for 1, 3, 5 and 7 hours, under
these conditions, are presented in Table 4 below.
Table 4
Milling time Max. particle size (um) Min. particle size (um)
Before milling 50 0.2
Hour 45 0.2
.5 Hours 20 0.15
Hours 2.5 0.15
Hours 1.5 0.1
The milled powder is dried by freeze-drying. This helps to minimise the amount of
agglomeration. The powder is then placed in an oven at 100°C to complete the drying
process.
The results of the particle size analysis are confirmed by scanning electron microscopy.
g of milled ceramic pigment powder was placed in a container. 50g of ceramic pellets,
65ml of toluene solvent and 0.12g of 12—hydroxystearic acid (dispersant) were added and
the container was sealed. The contents were ball milled for 24 hours. The resultant slurry
was removed from the container and the solvent extracted by filtration, leaving dispersant
coated powder. The powder was dried in an oven at 120°C for 24 hours, to allow
chemisorbtion of the dispersant onto the powder particles.
The dispersant coated powder and a solid wax, in the form of beads, were placed in a
dispersion vessel. 20ml of toluene was added to wet the powder and the mixture was
stirred. The mixture was heated to 80°C to melt the wax. The resultant liquid mixture
was then dispersed using a rotary dissolver and the temperature was raised to 110°C to
evaporate the toluene. The dispersion was continued for 1 hour. The ink was then cooled
until it solidified.
In Example 1 and 2 the vitreous agent and the pigment are combined or incorporated in
the ceramic pigment particles. However the pigment may alternatively be provided as a
chemical dye. In the latter case the vitreous agent particles are milled as described above
for the ceramic pigment particles, and the dye is dissolved in a solvent and mixed with
liquid wax before addition to the milled vitreous agent particles.
Di r i ' 't
ml samples of each phase change ink were placed in 5ml graduated cylinders. Stoppers
were placed on the cylinders to avoid evaporation. The cylinders were placed in an oven
at 120°C.
The cylinders were then allowed to stand at 120°C for 72 hours. The sedimentation
volume was recorded at times of 1, 2, 4, 8, 12, 24, 48 and 72 hours.
Table 5 shows the sedimentation results, at 120°C, obtained for inks containing ceramic
pigment (20% by weight), hydroxystearic acid (0.8% by weight) as the dispersant and
hydroxystearic acid (79.2% by weight) as the wax carrier.
Table 5
Time (hrs) Sedimentation Volume (ml)
1 0
.1
.3
.5
D' r 1 1
litres of solvent, 100g of unmilled ceramic pigment and 4g of dispersant were placed in
the milling chamber of an enclosed, recirculating bead mill. The contents were milled for
hours. The slurry was then removed from the mill and the solvent extracted by
evaporation, yielding the milled dispersant-coated powder. The dispersant was
chemisorbed and the powder dispersed in the wax carrier material as described in
Example 2. The advantage of this method is that the milling and dispersant addition are
completed in a single step process, thereby simplifying the overall process.
Ink formulations with varying pigment loading, as outlined in Table 6, were produced by
the methods described in Examples 2 and 3.
Table 6
Sample Wax Wt % Ceramic Pigment Wt %
P1001 90 10
P1002 80 20
P1003 70 30
P1004 60 40
P1005 50 50
P1006 40 60
'n ' r
An ink was produced as described in Example 3 comprising 70% by weight stearic acid
as a carrier, 28.8% by weight WHITE 45T41 ceramic pigment and 1.2% by weight
EFKA 4401® dispersant. The ink was heated to 120°C in a piezoelectric drop-on-
demand inkjet printhead and printed in straight lines 1cm wide, via the printhead, onto a
flat glass substrate. The substrate with print applied were then passed through a kiln and
fired at a temperature of 745°C, which burned off the organic materials and fused the
inorganic (ceramic) materials to the glass substrate. This yielded a white enamel print of
white lines on a glass substrate. It was found that the print was fused completely and was
highly scratch resistant.
While the example describes printing onto a flat glass substrate the substrate may be of
any desired shape.
Examples of possible combinations of ingredient that may be used to produce inks, as
described above, are presented in Table 7.
Table 7
Ink Formulation Ceramic Dispersant Solvent Wax
Powder
WHITE 12—Hydroxystearic Toluene 12-Hydroxystearic
45T41 acid acid
WHITE Stearic acid Toluene Paraffin
45T41
WHITE EFKA 4401 Butyl Stearic acid
45T41 acetate
WHITE Tartaric acid Toluene Paraffin
45T41
WHITE Hydroxybenzoic Toluene Paraffin
45T41 acid
WHITE Docosanoic acid Toluene Paraffin
45T41
Viscosity
The viscosity of the ink was determined by cone and plate rotational viscometry
employing a Haake RV-1 rotational viscometer with temperature control attachments.
The test involves placing the sample between a cone and a plate of standard geometry.
The cone is rotated at a preset speed. The torque required to maintain the rotational
speed is related to the viscosity. The viscosity is calculated from the torque required.
The set speed and the geometry factors, shear force and shear rate are also calculated.
The viscosity and shear force were determined for each sample at varying shear rate.
As an example the viscosity (11 (CP) @ 1209C, 300034) obtained by varying the ceramic
content in inks using EFKA 4401 as the dispersant (4% by weight) and stearic acid as the
wax carrier are presented in Table 8.
Table 8
% Dispersant Ceramic Powder % Wax Viscosity fi
90 4
80 5
70 12
40 60 15
50 50 23
The invention is not limited to the embodiments described but may be varied in
construction and detail.
Claims (31)
1. An ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising:- a carrier material; a pigment comprising ceramic pigment particles of less than 10 microns in size; a fusible vitreous agent comprising particles of less than 10 microns in size, and the carrier having a melting point for phase change of the ink.
2. An ink as claimed in claim 1 wherein the concentration of ceramic pigment in the ink is in the range of 10% to 60% by weight.
3. An ink as claimed in claims 1 or 2 wherein the concentration of ceramic pigment in the ink is in the range of 20% to 50% by weight.
4. An ink as claimed in any preceding claim wherein the pigment and fusible vitreous agent are combined in the form of ceramic pigment particles.
5. An ink as claimed in any preceding claim wherein the particles are less than 5 microns in size.
6. An ink as claimed in any preceding claim wherein the ink comprises a dispersant.
7. An ink as claimed in claim 6 wherein the particles are coated with the dispersant.
An ink as claimed in claim 6 or 7 wherein the dispersant is chemisorbed onto the particles.
An ink as claimed in claim 8 wherein the dispersant is chemisorbed onto the particles by drying in an oven for up to 24 hours.
An ink as claimed in claim 9 wherein the temperature of the oven is at least 120°C.
An ink as claimed in any of claims 6 to 10 wherein the dispersant is selected from a modified polyacrylate and fatty acid.
An ink as claimed in any of claims 6 to 11 wherein the dispersant is selected from 12—hydroxystearic acid, stearic acid, tartaric acid, hydroxybenzoic acid and docosanoic acid.
An ink as claimed in any of claims 6 to 12 wherein the dispersant comprises stearic acid.
An ink as claimed in any of claims 6 to 13 wherein the dispersant is present in a concentration by weight of the ceramic pigment from 2 to 5%.
An ink as claimed in any of claims 6 to 14 wherein the dispersant is present in a concentration by weight of the ceramic pigment of approximately 4%.
An ink as claimed in any of claims 6 to 15 wherein the particles are coated with a dispersant in the presence of a solvent.
An ink as claimed in claim 16 wherein the dispersant is soluble in the solvent.
An ink as claimed in claim 17 wherein the solvent is toluene or butyl acetate.
An ink as claimed in any of claims 6 to 18 wherein the particles are coated with a dispersant by ball milling or using a rotary dissolver.
An ink as claimed in any preceding claim wherein the carrier comprises a wax material.
An ink as claimed in any preceding claim wherein the carrier has a melting point of from 20 to 150°C, preferably 50 to 100°C.
An ink as claimed in any preceding claim wherein the pigment comprises organometallic particles and metallic components.
An ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising:— ceramic pigment particles of less than 10 microns in size; fusible vitreous particles of less than 10 microns in size; and a carrier having a melting point for phase change of the ink.
An ink claimed as in claim 23 wherein the particles are coated with a dispersant.
An ink suitable for application to a heat resistant substrate and firing to fuse the ink to the substrate, the ink being in a form for ink jet printing and comprising:- a carrier having a melting point for phase change of the ink; ceramic pigment particles of less than 10 microns in size; fusible vitreous particles of less than 10 microns in size; and a dispersant which is chemisorbed onto the particles.
26. A jet printing ink substantially as herein before described with reference to the examples.
27. A method of producing an ink in a form for ink jet printing comprising the steps of:- milling a fusible vitreous agent to provide a powder having a particle size less than 10pm; providing a pigment for the ink; heating a phase change carrier, and mixing the powder with the molten carrier; and allowing the carrier to cool to provide solid ink.
28. A method as claimed in claim 27, in which the pigment is combined with the fusible vitreous agent as ceramic pigment particles.
29. A method of producing an ink comprising the steps of:- milling a fusible vitreous agent to provide a powder having a particle size less than 10pm; 20 providing a pigment for the ink; mixing the milled particles with a dispersant, and a solvent, removing the solvent; heating the mixture to a temperature in excess of 120°C whereby the dispersant is chemisorbed onto the milled particles, heating a phase change carrier, and mixing the powder mixture with the molten carrier; and allowing the carrier to cool to provide solid ink.
30. A method as claimed in claim 29, wherein the pigment is combined with the fusible vitreous agent as ceramic pigment particles.
31. An ink whenever prepared by a method as claimed in claim 27 to 30. % dispersant adsorbed
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EPEUROPEANPATENTOFFICE(EPO)16/01/2 | |||
EP01650006 | 2001-01-16 |
Publications (2)
Publication Number | Publication Date |
---|---|
IE20020020A1 IE20020020A1 (en) | 2003-05-28 |
IE83751B1 true IE83751B1 (en) | 2005-01-12 |
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