Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-11-19
2004-04-27
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S161000, C524S558000
Reexamination Certificate
active
06727296
ABSTRACT:
This invention relates to coloured water-dissipatable polymers, to inks containing the coloured water-dissipatable polymers and to their use in ink jet printing.
Ink jet printing methods involve a non-impact printing technique for printing an image onto a substrate using ink droplets ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
There are many demanding performance requirements for colorants and inks used in ink jet printing. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle. The most popular ink jet printers are thermal and piezoelectric ink jet printers.
There is a need for inks which are suitable for both thermal and piezo ink jet printers, have high colour strength and produce images having a high light-fastness and water-fastness when printed on a substrate.
We have surprisingly found that the coloration of water-dissipatable polymers having hydroxy functional groups by reacting the hydroxy functional groups with a colorant, a bridging group for a colorant or a colorant precursor and further reaction of the bridging compound with a colorant or colorant precursor and subsequent conversion of the colorant precursor to a colorant, gives a coloured water-dissipatable polymer which is suitable for use in inks for thermal and piezo ink jet printers.
According to a first aspect of the present invention there is provided a water-dissipatable polymer having colorant attached thereto through a covalent —O-link.
A —O-link may be exemplified by but is not limited to the following links such as an ether link (R
1
—O—R
2
, an ester link (R
1
—O—C(O)—R
2
) and a phosphate ester link (R
1
—O—P(O)(OH)—R
2
), where R
1
represents the water-dissipatable polymer and R
2
represents the colorant.
A water-dissipatable polymer of the invention is obtainable by attaching a colorant to a water-dissipatable polymer having hydroxy functional groups by means of a reaction between the hydroxy functional groups on the polymer with a colorant having a functional group capable of reacting with the hydroxy functional group.
The colorant may also be attached to the water-dissipatable polymer by means of a reaction between a hydroxy group on the polymer with a colorant precursor thereby forming a covalent bond therebetween and subsequently converting the colorant precursor to a colorant.
Alternatively, colorants may be grafted to the water-dissipatable polymer via a bridging compound. For example, colorant may be attached to the water-dissipatable polymer by means of a reaction between the hydroxy functional group on the water-dissipatable polymer with a bridging compound thereby forming a covalent bond therebetween and subsequently reading the bridging compound with a colorant or colorant precursor. The bridging agent may be a di-, tri-, tetra- or polyfunctional structure, and examples include, but are not limited to bis alkyl halides, tris dialkyl halides, bis acid chlorides, tris dia chlorides, bis vinyl sulphones, tris divinyl sulphones, mixtures of alkyl halides and acid chlorides, michael acceptors, cyanuric chloride and related reactive 1,3,5-triazines, other reactive heterocyclic halides and aromatic halides. Most preferably cyanuric chloride is used.
The water-dissipatable polymer of the invention is preferably prepared by condensing a water-dissipatable polymer having hydroxy functional groups with a colorant having a functional group reactive towards the hydroxy functional groups. Such functional groups are described above. Up to 100%, preferably at least 95%, more preferably at least 90%, most preferably at least 85% of the hydroxy functional groups are reacted with the colorant. The condensation is performed by preparing a solution or suspension of a water-dissipatable polymer having hydroxy functional groups in an aqueous and/or non-aqueous solvent. Preferably the condensation is performed at a pH of 5 to 14, more preferably of 6 to 13, especially of 7 to 12. The condensation is preferably performed in the presence of an inorganic or organic base. Preferred inorganic bases are NaOH, KOH, Na
2
CO
3
, K
2
CO
3
. Preferred organic bases are trialkyl amines, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Subsequently an aqueous solution of a colorant is added to the suspension and the mixture is stirred until the reaction is complete.
Alternatively a non-aqueous grafting reaction can be used to react the water-dissipatable polymer having hydroxy functional groups with a colorant. The colorant and polymer are stirred in a non-aqueous solvent with a base (either homogeneous or heterogeneous) and heated as required to complete the reaction. In the case of ester formation, for example reacting an acid functionalised colorant (e.g. phosphoric acid functionalised) and the water-dissipatable polymer having hydroxy functional groups, conditions are required to remove the generated water either physically (e.g. by azeotroping, molecular sieves) or chemically using a dehydrating agent such as dicyclohexylcarbodiimide or dicyandiamide. Acid catalysts such as p-toluenesulphonic acid or sulphuric acid may also be employed.
The water-dissipatable polymer of the invention may be isolated from the aqueous system by either acidification and filtration; dilution with a water miscible solvent and filtration, salting out with organic salts or solutions of organic salts or combinations of these methods. Suitable salts include sodium chloride, ammonium chloride, sodium sulphate and lithium chloride. Alternatively the mixture is acidified until the water-dissipatable polymer of the invention precipitates out or the solvent is evaporated or the solvent is diluted with water until the water-dissipatable polymer of the invention precipitates out.
Alternatively the water-dissipatable polymer of the present invention may be purified by ion-exchange methods on cationic resins. Other options include the removal of low molecular weight materials such as co-solvents used for the polymerisation, low molecular weight salts, impurities and free monomers by ultra-filtration, osmosis, reverse osmosis, dialysis, ultra-filtration or a combination thereof, followed by evaporation of the water.
Preferably the number average molecular weight (Mn) of the water-dissipatable polymer used to make the polymer of the invention is less than 25,000, more preferably is less than 20,000, especially less than 15,000. The Mn of the polymer may be measured by gel permeation chromatography (“gpc”).
The gpc method used for determining Mn preferably comprises applying the polymer to a chromatography column parked with cross-linked polystyrene/divinyl benzene, eluting the column with tetrahydrofuran at a temperature of 40° C. and assessing the Mn of the polymer compared to a number of a polystyrene standards of a known Mn. Suitable cross-linked polystyrene/divinyl benzene chromatography columns are commercially available from Polymer Laboratories.
As an alternative to the gpc method for determining Mn, the Mn may be determined using for example by multi-angle light scattering (MALLS).
The water-dissipatable polymer may be a copolymer, for example a random, alternating or block copolymer, preferably a random copolymer.
The water-dissipatable polymer may be a polyurethane, polyester or an olefinic polymer. Preferably the water-dissipatable polymer is an olefinic polymer. An olefinic polymer is a polymer obtainable from the polymerisation of one or more olefinically unsaturated monomers.
The water-dissipatable olefinic polymer is preferably obtainable from the polymerisaton of one
Double Philip John
Gregory Peter
James Mark Robert
Padget John Christopher
Pears David Alan
Avecia Limited
Pillsbury & Winthrop LLP
Shosho Callie
LandOfFree
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